- Stable and selective electrochemical reduction of carbon dioxide to ethylene on copper mesocrystals
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Stable and selective electrochemical reduction of carbon dioxide to ethylene was achieved using copper mesocrystal catalysts in 0.1 M KHCO3. The Cu mesocrystal catalysts were facilely derived by the in situ reduction of a thin CuCl film during the first 200 seconds of the CO2 electroreduction process. At -0.99 V vs. RHE, the Faradaic efficiency of ethylene formation using these Cu mesocrystals was ～18× larger than that of methane and forms up to 81% of the total carbonaceous products. Control CO2 reduction experiments show that this selectivity towards C2H4 formation could not be replicated by using regular copper nanoparticles formed by pulse electrodeposition. High resolution transmission electron microscopy reveals the presence of both (100)Cu facets and atomic steps in the Cu mesocrystals which we assign as active sites in catalyzing the reduction of CO2 to C2H4. CO adsorption measurements suggest that the remarkable C2H4 selectivity could be attributed to the greater propensity of CO adsorption on Cu mesocrystals than on other types of Cu surfaces. The Cu mesocrystals remained active and selective towards C2H4 formation for longer than six hours. This is an important and industrially relevant feature missing from many reported Cu-based CO2 reduction catalysts.
- Chen, Chung Shou,Handoko, Albertus D.,Wan, Jane Hui,Ma, Liang,Ren, Dan,Yeo, Boon Siang
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- Effects of thickness extension mode resonance oscillation of acoustic waves on catalytic and surface properties. IV. Activation of a Ag catalyst for ethanol decomposition by overtone resonance frequencies
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The effects of resonance frequencies of acoustic waves on catalytic and surface properties were studied. The overtone resonance frequencies of 3.5, 10.8, and 17.9 MHz were applied to a 100 nm thick Ag catalyst deposited on a ferroelectric z-cut LiNbO3 crystal which generated thickness extension mode resonance oscillation (TERO). For ethanol decomposition, the TERO enhanced ethylene production without significant changes in acetaldehyde production for all the frequencies. The extent of catalyst activation strongly depended on the resonance frequency. In a low power region (1.0 W), it increased in the order 3.5 > 10.8 > 17.9 MHz. The activation energy for ethylene production decreased remarkably in the presence of TERO, the extent of which strongly depended on the frequency. Laser Doppler measurements showed that with increasing resonance frequency, the number of standing waves increased markedly, whereas the amplitudes of the wave decreased considerably. The specific catalytic activity, defined as the activity enhancement per the density of wave, increased in a nonlinear manner with lattice displacement. The resonance frequency effects of TERO on catalyst activation are discussed.
- Saito,Inoue
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- Role of Exposed Surfaces on Zinc Oxide Nanostructures in the Catalytic Ethanol Transformation
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For a series of nanometric ZnO materials, the relationship between their morphological and surface functionalities and their catalytic properties in the selective decomposition of ethanol to yield acetaldehyde was explored. Six ZnO solids were prepared by a microemulsion-precipitation method and the thermal decomposition of different precursors and compared with a commercial sample. All these materials were characterized intensively by XRD and SEM to obtain their morphological specificities. Additionally, surface area determinations and IR spectroscopy were used to detect differences in the surface properties. The density of acid surface sites was determined quantitatively using an isopropanol dehydration test. Based on these characterization studies and on the results of the catalytic tests, it has been established that ZnO basal surfaces seem to be responsible for the production of ethylene as a minor product as well as for secondary reactions that yield acetyl acetate. Furthermore, one specific type of exposed hydroxyl groups appears to govern the surface catalytic properties.
- Morales, María V.,Asedegbega-Nieto, Esther,Iglesias-Juez, Ana,Rodríguez-Ramos, Inmaculada,Guerrero-Ruiz, Antonio
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- Reaction of the ethyl radical with oxygen at millitorr pressures at 243-368 K and a study of the Cl + HO2, ethyl + HO2, and HO2 + HO2 reactions
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Ethyl radicals formed in the reaction of C2H6 + Cl are allowed to react with molecular oxygen in a very low pressure reactor (VLPR) experimental flow system over the temperature range of 243-368 K. Mass spectrometric analysis of reactants and products made possible the determination of rate constants (cm3/(molecule·-s)) of all major reaction steps. Mass balances for C, H, and Cl are good to ±4% on average. The elementary steps are the following: C2H5 + O2 → HO2 + C2H4, k6 = (1.42 ± 0.38) × 10-17 exp[(5064 ± 154)/RT], measured independently from recording C2H5 consumption or C2H4 formation rates; 2HO2 → H2O2, k7 = (4.50 ± 0.56) × 10-13 exp[(1064 ± 77)/RT]; C2H5 + HO2 → H2O2 + C2H4, k8a = (2.98 ± 0.11) × 10-12; Cl + HO2 → HCl + O2, k9 = (4.45 ± 0.06) × 10-11. Activation energies are given in cal/mol. Reactions 8a and 9 show no change in the temperature range of measurements, while reactions 6 and 7 both have negative temperature dependence. The radical oxidation reaction 6 is suggested to occur via excited ethylperoxy and 2-hydroperoxyethyl radical formations as consecutive reversible steps.
- Dobis, Otto,Benson, Sidney W.
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- NEW PATHWAYS IN LASER INDUCED THERMAL GAS-PHASE CHEMISTRY
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Various cw CO2 laser-induced reactions in the presence of energy conveying SF6 are shown to proceed in a specific way due to the absence of heterogeneous stages that are very difficult to avoid in normal hot wall reactors.Truly homogeneous courses are reported for some dehydrochlorinations, oxidations of perhaloalkenes with molecular oxygen, and decomposition of representatives of amines, nitroalkanes and perfluorinated, bridged and unsaturated derivatives of carboxylic acids.
- Pola, J.
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- High selectivity for ethylene from carbon dioxide reduction over copper nanocube electrocatalysts
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Nanostructured surfaces have been shown to greatly enhance the activity and selectivity of many different catalysts. Here we report a nanostructured copper surface that gives high selectivity for ethylene formation from electrocatalytic CO2 reduction. The nanostructured copper is easily formed in situ during the CO2 reduction reaction, and scanning electron microscopy (SEM) shows the surface to be dominated by cubic structures. Using online electrochemical mass spectrometry (OLEMS), the onset potentials and relative selectivity toward the volatile products (ethylene and methane) were measured for several different copper surfaces and single crystals, relating the cubic shape of the copper surface to the greatly enhanced ethylene selectivity. The ability of the cubic nanostructure to so strongly favor multicarbon product formation from CO2 reduction, and in particular ethylene over methane, is unique to this surface and is an important step toward developing a catalyst that has exclusive selectivity for multicarbon products. Cubic nanostructures formed on a polycrystalline copper surface give high selectivity for ethylene formation from carbon dioxide electroreduction. The nanocubes are easily synthesized in situ, and online electrochemical mass spectrometry is used to compare the reactivity to other copper single-crystal surfaces.
- Roberts, F. Sloan,Kuhl, Kendra P.,Nilsson, Anders
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- Cross-metathesis vs. silylative coupling of vinyl alkyl ethers with vinylsilanes catalyzed by a ruthenium-carbene complex (Grubbs catalyst)
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Grubbs complex, (PCy3)2Cl2Ru=CHPh (I) is a very effective catalyst of the cross-disproportionation of vinyl-trisubstituted silanes H2C=CHSiR3 [where R3 = Me3, PhMe2, (OEt)3] with vinyl alkyl ethers H2C=CHOR' [where R' = ethyl, propyl, butyl, t-butyl, t-pentyl, 2-(ethyl)hexyl, cyclohexyl, trimethylsilyl] to yield a mixture of (E + Z) 1-silyl-2-alkoxyethenes. The reaction occurs quantitatively under milder conditions (60 °C) than the analogous one catalyzed by Ru-H and/or Ru-Si complexes reported previously (80 °C). The stoichiometric reaction of (I) and (PCy3)2Cl2Ru=CH2 (III) with vinyl ethyl ether leads to the formation of (PCy3)2Cl2Ru=CH(OEt) (II), inactive in the stoichiometric reaction with vinylsilanes but very active in the catalytic process. Experiments with the use of deuterated vinylsilanes indicate the non-metallacarbene mechanism of the reaction and provide evidence for the initiation of Ru-H bond formation via the hydrovinylation with vinylsilanes.
- Marciniec,Kujawa,Pietraszuk
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- Identification and active site analysis of the 1-aminocyclopropane-1- carboxylic acid oxidase catalysing the synthesis of ethylene in Agaricus bisporus
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Background 1-Aminocyclopropane-1-carboxylate oxidase (ACO) is a key enzyme that catalyses the final step in the biosynthesis of the plant hormone ethylene. Recently, the first ACO homologue gene was isolated in Agaricus bisporus, whereas information concerning the nature of the ethylene-forming activity of this mushroom ACO is currently lacking. Methods Recombinant ACO from A. bisporus (Ab-ACO) was purified and characterised for the first time. Molecular modelling combined with site-directed mutagenesis and kinetic and spectral analysis were used to investigate the property of Ab-ACO. Results Ab-ACO has eight amino acid residues that are conserved in the Fe (II) ascorbate family of dioxygenases, including four catalytic residues in the active site, but Ab-ACO lacks a key residue, S289. In comparison to plant ACOs, Ab-ACO requires ACC and Fe (II) but does not require ascorbate. In addition, Ab-ACO had relatively low activity and was completely dependent on bicarbonate, which could be ascribed to the replacement of S289 by G289. Moreover, the ferrous ion could induce a change in the tertiary, but not the secondary, structure of Ab-ACO. Conclusions These results provide crucial experimental support for the ability of Ab-ACO to catalyse ethylene formation in a similar manner to that of plant ACOs, but there are differences between the biochemical and catalytic characteristics of Ab-ACO and plant ACOs. General significance This work enhances the understanding of the ethylene biosynthesis pathways in fungi and could promote profound physiological research of the role of ethylene in the regulation of mushroom growth and development.
- Meng, Demei,Shen, Lin,Yang, Rui,Zhang, Xinhua,Sheng, Jiping
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- Methane conversion to ethylene over GaN catalysts. Effect of catalyst nitridation
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Vast availability of natural and shale gases makes methane a reliable source for synthesizing valuable chemical building blocks such as ethylene. A new stable supported GaN/SBA15 catalyst from an emerging class of nitride catalysts was reported for the direct non-oxidative methane coupling to ethylene. The effect of nitridation on the catalyst properties and activity was investigated. The optimum nitridation temperatures were 700 °C and 750 °C for the GaN/SBA15 and the unsupported GaN catalyst, respectively. Supported catalysts were more stable and had 5–10 times higher product (ethylene) formation rates per gram of gallium than the unsupported catalysts due to the higher surface area (>320 vs. 2 g?1) and Ga-dispersion inside the pores. Compared to the oxide precursors, the nitrides exhibited a higher atom conversion efficiency for the CH4 carbon leading to higher ethylene selectivity (71 % for GaN/SBA15, 2O3/SBA15) and lower coke selectivity (27 % for GaN/SBA15, 40 % for Ga2O3/SBA15).
- Dutta, Kanchan,Chaudhari, Vishnu,Li, Chao-Jun,Kopyscinski, Jan
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- Calorimetric Study of Vanadium Pentoxide Catalysts Used in the Reaction of Ethane Oxidative Dehydrogenation
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Vanadium pentoxide catalysts have been studied in the partial oxidation reaction of ethane in the 723-843 K temperature range.The relationship between the acid-base properties and the catalytic behavior was investigated.The number and character of acidic sites of V2O5 catalysts were determined by studying the adsorption of a basic molecule using microcalorimetry.The reducibility level and the evolution of the surface state, as well as the heat evolved, were studied by using a pulse method with pure ethane only.The reaction of ethane oxidative dehydrogenation was studied by a continuous flow method and the activation energies for the formation of C2H4 and CO were calculated.The selectivity of the catalyst was interpreted in connection with the acid-base properties.The strong sites were observed to decrease rapidly with time on stream, although the catalysts were still active.Temperature-programmed reduction of V2O5 using a TG-DSC coupling was also investigated with hydrogen, ethylene, or ethane as reducers.The different heats of reduction are given.It was observed that C2H4 is a much more efficient reducing agent than H2 and C2H6.Following each reduction, reoxidation studies by oxygen were performed in the same equipment showing clearly different steps in the reoxidation process.
- Le Bars, J.,Vedrine, J. C.,Auroux, A.,Pommier, B.,Pajonk, G. M.
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- Rate Constant and Product Branching for the Vinyl Radical Self Reaction at T = 298 K
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The rate constant and product branching for the self reaction of C2H3 has been measured using the discharge-flow kinetic technique coupled to mass spectrometric detection at T = 298 K and 1 Torr nominal pressure (He).C2H3 is produced by the reaction of F with C2H4, which also forms C2H3F + H.In addition to the C2H3 self reaction, C2H3 also decays by reaction with H and by wall loss processes.The result obtained by parameter fitting the C2H3 decay curves was k(C2H3 + C2H3) = (1.41 +/- 0.60)E-10 cm3 molecule-1 s-1, where k is defined by d/dt = 2k2.Results from the product studies showed that the recombination product 1,3-butadiene was not observed at 1 Torr and that the ratio product formed/0 was 0.65 +/- 0.14 for the combined C2H3 + C2H3 and C2H3 + H reactions.Both observations are consistent with C2H2 + C2H4 being the exclusive C2H3 + C2H3 products, since the maximum yield of C2H2 from the combined C2H3 + C2H3 and C2H3 + H reactions is 0.59.The experimental observations that k1 is independent of pressure and that no 1,3-butadiene (product of C2H3 combination) is observed at 1 Torr pressure requires a mechanism in which the chemically activated 1,3-butadiene undergoes a unimolecular reaction.It is postulated that the 1,3-butadiene first isomerizes to cyclobutene, which then unimolecularly decomposes to C2H2 and C2H4.Although the former reaction is well documented, the latter reaction has not been previously reported.RRKM calculations predict a pressure dependence similar to what is experimentally observed.
- Thorn, R. P.,Payne, W. A.,Stief, L. J.,Tardy, D. C.
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- [Li2{CH2S(O)Ph}2(TMEDA)2] - An α-sulfinyl-functionalized methyllithium carbenoid Dedicated to Professor Manfred Scheer on the occasion of his 60th birthday.
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The aggregation state of the α-sulfinyl-functionalized methyllithium compound [Li2{CH2S(O)Ph}2(TMEDA)2] (1) in solution and its carbenoid reactivity is presented. Temperature dependent NMR measurements of 1 in THF-d8 revealed the presence of an intermolecular dynamic process (dimer-monomer-dimer equilibrium) with a Gibbs free energy of activation of about 45 kJ/mol. 1H DOSY NMR measurements exhibited that in THF-d8 solution the coligand TMEDA is partially cleaved off. Furthermore, the decomposition of 1 in THF-d8 (room temperature, 96 h) led to the formation of ethylene and PhSSPh. In refluxing toluene 1 decomposed with formation of ethylene, PhSSPh, xylenes, ethylbenzene, n-propylbenzene and isopropylbenzene. The dimerizing α-elimination yielding ethylene and the C-H insertion reactions observed in boiling toluene give proof of a carbenoid reactivity of 1.
- Ludwig, Gerd,Str?hl, Dieter,Schmidt, Harry,Steinborn, Dirk
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- Boron-doped CuO nanobundles for electroreduction of carbon dioxide to ethylene
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Novel boron-doped CuO nanobundles are designed for CO2 reduction to the single multi-carbon product of ethylene, and their faradaic efficiency can reach 58.4% with a current density of 18.2 mA cm-2. This active, selective and simply prepared electrocatalyst provides a promising electrocatalyst candidate for CO2 reduction to ethylene.
- Wan, Qiang,Zhang, Jianling,Zhang, Bingxing,Tan, Dongxing,Yao, Lei,Zheng, Lirong,Zhang, Fanyu,Liu, Lifei,Cheng, Xiuyan,Han, Buxing
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- Kinetics of the CH2CH2Cl ? C2H4 + Cl reaction
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The kinetics of the unimolecular decomposition of the CH2CH2Cl radical has been studied experimentally in a heated tubular flow reactor coupled to a photoionization mass spectrometer. Rate constants for the decomposition were determined in time-resolved experiments as a function of temperature (400-480 K) and bath gas density ([He] = (3-24) × 1016 atoms cm-3). The rate constants are close to the low-pressure limit under the conditions of the experiments. Ab initio and master equation modeling are applied to analyze both the experimental data and literature data on the reverse reaction: the addition of Cl atom to ethylene. On the basis of the results of this modeling, parametrized expressions for the temperature and pressure dependencies of the rate constants for both the direct and the reverse reactions are provided.
- Knyazev, Vadim D.
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- Ag-Ni bimetallic SiBEA zeolite as an efficient catalyst of hydrodechlorination of 1,2-dichloroethane towards ethylene
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Dealuminated form of BEA zeolite with Si/Al ratio of 1500 was used for the synthesis of Ag2.0SiBEA, Ni2.0SiBEA and Ag2.0Ni2.0SiBEA by two-step postsynthesis method. The calcination of zeolite samples led to the formation of well dispersed isolated mononuclear Ag(I) and Agnδ + clusters and a pseudo-tetrahedral Ni(II), incorporated in BEA framework as evidenced by DR UV-vis investigations. The treatment of samples in flowing 10% H2/Ar stream gave small (average 3.1 nm) and well dispersed metal nanoparticles. Reduced catalysts were investigated in 1,2-dichloroethane hydrodechlorination at atmospheric pressure, at low reaction temperature (523 K) with ～ 100% of selectivity to ethylene, desired product of the reaction.
- ?r?bowata,Zielińska,Baran,S?owik,Dzwigaj
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- Weak Collision Effects in the Reaction C2H5 C2H4 + H
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The unimolecular decomposition of C2H5 in helium has been investigated near the low-pressure limit (T = 876 - 1094 K; P = 0.8 - 14.3 Torr).Rate constants (k1) have been determined as a function of temperature and pressure in the indicated ranges in time-resolved experiments.The reaction was isolated for quantitative study in a heated tubular reactor coupled to a photoionization mass spectrometer.Weak collision effects (fall-off behavior) were analyzed using a master equation analysis.Values of (ΔE)down for the exponential down energyloss probability were obtained for each experiment performed.The microcanonical rate constants, k1(E), needed to solve the master equation were obtained from a transition state model for the reaction which is described.The temperature dependence of these (ΔE)down determination was apparent and fits the expression (ΔE)down = 0.255T1.0(+/-0.1) cm-1.It is shown that this expression (derived from experiments conducted between 876 and 1094 K) provides a reasonable representation of observed weak collison effects in helium down to 285 K.Values for (ΔE)down for C2H5 decomposition in other bath gases were obtained by reexamining published data on the fall-off of the C2H5 unimolecular rate constant in N2, SF6, and C2H6.The experimental results and data simulations were used to obtain a parametrized expression for k1(T,M), the low-pressure limit rate constant for C2H5 decomposition in helium (200 - 1100 K); k10 = 6.63 x 109T-4.99 exp(-20,130 K/T) cm3 molecule-1 s-1.Prior published experiments on both the forward and reverse reactions (C2H5 + (M) C2H4 + H + (M)) in the fall-off region were reevaluated and used in conjunction with an RRKM model of the transition state to obtain a new recommended expression for the high-pressure limit rate constant for the temperature range 200 - 1100 K, k1 = 1.11 x 1010T1.037 exp(-18,504/T)s-1.Parametrization of the density and temperature dependence of k1 in helium according to the modified Hinshelwood expression introduced by Gilbert et al. is provided.
- Feng, Y.,Niiranen, J. T.,Bencsura, A.,Knyazev, V. D.,Gutman, D.,Tsang, W.
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- Methyl vinyl glycolate as a diverse platform molecule
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Methyl vinyl glycolate (methyl 2-hydroxybut-3-enoate, MVG) is available by zeolite catalyzed degradation of mono- and disaccharides and has the potential to become a renewable platform molecule for commercially relevant catalytic transformations. This is further illustrated here by the development of four reactions to afford industrially promising structures. Catalytic homo metathesis of MVG using Grubbs-type catalysts affords the crystalline dimer dimethyl (E)-2,5-dihydroxyhex-3-enedioate in excellent yield and with meso stereochemical configuration. Cross metathesis reactions between MVG and various long-chain terminal olefins give unsaturated α-hydroxy fatty acid methyl esters in good yields. [3,3]-Sigmatropic rearrangements of MVG also proceed in good yields to give unsaturated adipic acid derivatives. Finally, rearrangement of the allylic acetate of MVG proceeds in acceptable yield to afford methyl 4-acetoxycrotonate.
- S?lvh?j, Amanda,Taarning, Esben,Madsen, Robert
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- From vanadia nanoclusters to ultrathin films on TiO2(110): Evolution of the yield and selectivity in the ethanol oxidation reaction
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Oxide-on-oxide systems are becoming increasingly important in nanocatalysis and surface engineering, because of the creation of hybridized interfaces holding high reactivity and selectivity toward oxidation reactions. Here we report on the results of a multitechnique surface science study conducted on an oxide/oxide model system. By depositing increasing amounts of vanadium oxide (VOx) on a titanium dioxide-rutile(110) substrate, we were able to follow the morphology and oxidation state of the overlayer. Three growth modes were detected: nanoclusters at low coverage (0.3 and 0.5 monolayer), one-dimensional strands aligned along the substrate [001] direction at monolayer coverage, and three-dimensional nanoislands at higher coverage (2.0 and 5.0 monolayers). All these structures share the same oxidation state (V2O3). We studied the reactivity and selectivity of these model catalysts toward partial oxidation of ethanol, finding that both of them depend on the VOx thickness. Nanoclusters can yield acetaldehyde through low-temperature oxidative dehydrogenation but show a scarce selectivity in the investigated temperature range. The monolayer coverage is the most reactive toward ethanol dehydration to ethylene, showing also good selectivity. Similar results are found at high coverage, although the overall reactivity of the systems toward alcohol oxidation decreases.
- Artiglia, Luca,Agnoli, Stefano,Savio, Letizia,Pal, Jagriti,Celasco, Edvige,Rocca, Mario,Bondino, Federica,Magnano, Elena,Castellarin-Cudia, Carla,Netzer, Falko P.,Granozzi, Gaetano
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- Ring opening reaction dynamics in the reaction of hydrogen atoms with ethylene oxide
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Ethylene oxide, C2H4O, is a three-membered ring with a single oxygen atom bridging the two carbons.Reactions of H and D atoms with ethylene oxide have been studied in the gas phase to provide insight into the dynamics of three-membered ring opening.H atoms were produced by photolyzing HI in the wavelength range 240-266 nm.The channel leading to OH+C2H4 was monitored via laser-induced fluorescence (LIF) of the OH A 2Σ 2Π system.The D atom reaction yields OD with no hydrogen scrambling.With an available energy of 23 000 cm-1, the average OH D rotational energy is ca. 350 cm-1 for OH(ν=0) and OD(ν=0) and ca. 250 cm-1 for OD(ν=1).OH(ν=1) was not observed, while the OD(ν=1) population was about one-tenth that of OD(ν=0).There was no apparent bias in populations between Λ doublets in each of the spin-orbit states for both OH and OD.Doppler broadening of OH(ν=0) rotational lines was measured to evaluate the average center-of-mass (c.m.) translational energy, which was found to be ca. 2300 cm-1.On average, the ring opening process deposits ca. 10percent of the available energy into c.m. translation, ca. 2percent into OH rotation, and ca. 88percent into ethylene internal energy.Comparison with CH2CH2OH unimolecular dissociation dynamics and theoretical transition state calculations leads to a likely mechanism in which hydrogen abstracts oxygen via sequential C-O bond fission without involving a long-lived CH2CH2OH intermediate.
- Shin, S. K.,Jarek, R. L.,Boehmer, E.,Wittig, C.
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- Oxidative coupling of methane to form ethylene: Effect of the preparation method on the phase composition and catalytic properties of Li-W-Mn-O-SiO2 composite materials
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Production of ethylene by oxidative coupling of methane (OCM) is a promising direct path from methane to ethylene. Li-W-Mn-O-SiO2 composite materials prepared by various methods - solid-phase synthesis, silica impregnation, sol-gel synthesis - are used as OCM catalysts. The phase states of these composite materials prepared by the different methods has been studied before and after use in the OCM reaction; the study has unexpectedly revealed the effect of the preparation technique on the phase composition of the material and the specific features of its catalytic behavior in OCM. Optimum catalysts provide an ethylene yield of 15% in terms of passed methane.
- Dedov,Loktev,Nipan,Dorokhov,Golikov,Spesivtsev,Moiseev
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- METATHESIS OF VINYLTRIALKOXYSILANES
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Ruthenium(II) and ruthenium(III) complexes have been found to be the first efficient catalysts for the metathesis of organosilicon olefins. trans-1,2-Bis(triethoxysilyl)ethene is prepared via metathesis of vinyltriethoxysilane catalyzed by ruthenium complexes with a yield above 80percent.
- Marciniec, Bogdan,Gulinski, Jacek
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- FACTORS AFFECTING GAS-PHASE CONTINUOUS WAVE INFRARED LASER SENSITIZED PYROLYSIS.
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A model is developed for predicting temperature profiles in a gas cell containing an absorbing gas when irradiated by a CW laser beam with well-defined parameters. The model takes into account the explicit temperature dependence of heat capacities, thermal conductivities, molar absorptivities, and gas densities. The predicted transmittance of the laser beam as a function of incident power agrees with experimental values. The model is further used to predict rate parameters of a standard homogeneous pyrolysis reaction that is sensitized by the heated gas. The results provide insight into the comparison between the traditional thermal processes and CW laser sensitized pyrolysis.
- Zhu,Yeung
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- Kinetic and process study of ethanol steam reforming over Ni/Mg(Al)O catalysts: The initial steps
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In this work, a 2 wt.% Ni/Mg(Al)O catalyst was subjected to kinetic studies for the ethanol steam reforming (ESR) reaction at 500 °C, with space-time ranging from 0.03 to 0.50 mg min/ml and with PC2H5OH:PH2O:PInert = 0.0163:0.0500:0.93 (atm) as standard conditions. The results indicate that dehydrogenation and dehydration of ethanol were the predominant reactions. CH3CHO and C2H4 were primary products and formed in parallel on different active sites. H2O and C2H5OH competed for the same active sites on the catalyst surface and the reaction order with respect to H2O was negative. The apparent activation energy for ethanol conversion was 110 kJ/mol. Furthermore, temperature-programmed desorption experiments confirmed the competing adsorption of C2H5OH and H2O. Temperature-programmed deuteration of used catalyst showed that the catalyst contained C2H4, CHx, acetate and carbonate species during ESR reaction.
- Zeng, Guangming,Li, Yongdan,Olsbye, Unni
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- Control of Surface Barriers in Mass Transfer to Modulate Methanol-to-Olefins Reaction over SAPO-34 Zeolites
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Mass transfer of guest molecules has a significant impact on the applications of nanoporous crystalline materials and particularly shape-selective catalysis over zeolites. Control of mass transfer to alter reaction over zeolites, however, remains an open challenge. Recent studies show that, in addition to intracrystalline diffusion, surface barriers represent another transport mechanism that may dominate the overall mass transport rate in zeolites. We demonstrate that the methanol-to-olefins (MTO) reaction can be modulated by regulating surface permeability in SAPO-34 zeolites with improved chemical liquid deposition and acid etching. Our results explicitly show that the reduction of surface barriers can prolong catalyst lifetime and promote light olefins selectivity, which opens a potential avenue for improving reaction performance by controlling the mass transport of guest molecules in zeolite catalysis.
- Gao, Mingbin,Li, Hua,Liu, Zhongmin,Peng, Shichao,Yang, Miao,Ye, Mao
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- The Gas-phase Amino-Claisen Rearrangement of Protonated N-Allylaniline
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Metastable molecular protonated ions of N-allylaniline dissociate with significant losses of ethene and ammonia in the flight path of a mass spectrometer.The structures of the daughter ions formed on the loss of ethene have been elucidated using collision-induced dissociation and it is postulated that two isomeric structures are formed, one corresponding to molecular protonated ions which have undergone an amino-Claisen rearrangement.The relative proportion of this rearranged species is dependent on the exothermicity of the proton-transfer reaction between the sample molecule and the chemical ionization reagent gas ion.It is proposed that the two isomeric parent species differ in the site of protonation.
- Kingston, Eric E.,Beynon, John H.,Vandezonneville, Alexandra,Flammang, Robert,Maquestiau, Andre
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- Ammoxidation of Ethane to Acetonitrile over Metal-Zeolite Catalysts
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Ammoxidation of ethane to acetonitrile was studied over a variety of metal ion exchanged zeolite catalysts. We discovered that ethane can be efficiently converted to acetonitrile over some Cozeolite catalysts. The type of zeolite is very important. In this regard, ZSM-5, beta, and NU-87 are superior to others. Among various transition metal cations, Co2+ is most active for acetonitrile formation. Kinetic studies on Co-ZSM-5 show that the nitrile formation rate is first order in NH3, 0.5 order in C2H6, and 0.8 order in O2. In the absence of O2, no reaction occurs. A reaction scheme is proposed, whereby C2H4, a reactive intermediate, is thought to add to a strongly adsorbed NH3 forming an adsorbed ethylamine, which is subsequently dehydrogenated to form C2H3N.
- Li, Yuejin,Armor, John N.
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- A Laser Flash Photolysis, Time-Resolved Fourier Transform Infrared Emission Study of the Reaction Cl + C2H5 -> HCl(υ) + C2H4
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The atom-radical reaction Cl + C2H5 -> HCl(υ) + C2H4 is studied using laser flash photolysis, time-resolved Fourier transform infrared emission spectroscopy and broad band infrared chemiluminescence.The Cl atoms and ethyl radicals are produced from a number of different precursors using one or two lasers.The initial HCl vibrational distribution is determined to be HCl (υ=1/2/3/4=0.39+/-0.04/0.29+/-0.03/0.22+/-0.02/0.10+/-0.02).The vibrational distribution is characteristic of an addition-elimination mechanism and can be reproduced using modified statistical theories of energy partitioning within the (excit.) intermediate.The time evolution of the HCl(υ=4) emission is used to estimate a rate coefficient for this reaction of (3.0+/-1.0)*10-10 cm3 molecule-1 s-1.
- Seakins, Paul W.,Woodbridge, Eric L.,Leone, Stephen R.
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- Gas-Phase Ion Chemistry of TiCl4 and CH3TiCl3. Reaction of CH3TiCl2+ with Ethylene
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TiCl4+ and TiCl3+ are the principal ions produced by electron-impact ionization of TiCl4.Both react with TiCl4 to give Ti2Cl7+.Reactions of this and other species of the form TiCl3(ligand)+ allow the determination of an order of relative ligand binding energies to TiCl3+ of MeF+ than TiCl4.Study of halide-transfer and proton-transfer reactions leads to determination of the thermochemical results: D(TiCl3+-Cl-) = 217+/-11 kcal/mol, D(TiCl3+-F-) = 254+/-4 kcal/mol, and PA(TiCl4) = D(TiCl4-H+) = 157+/-11 kcal/mol.Chloride transfer from CH3TiCl3 to TiCl3+ yields CH3TiCl2+ as the major ion at intermediate times in the ion chemistry of CH3TiCl3.CH3TiCl2+ reacts with C2H4 to give C3H5TiCl2+ with H2 elimination.C3H5TiCl2+ does not react further with ethylene.With C2D4, HD elimination predominates (>85percent).A mechanism involving insertion of C2D4 into the Ti,C bond in CH3TiCl2+ followed by 1,2-elimination of HD at the β- and γ-carbons is inferred.This demonstrates carbon-carbon bond formation and chain growth in a Zigler-Natta catalyst site model system, but this gas-phase bimolecular process does not lead to continued polymerization because disposal of the excess internal energy of the complex results in chain termination by unimolecular decomposition.
- Uppal, Jack S.,Johnson, Douglas E.,Staley, Ralph H.
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- Reaction of Dichloroethane and Oxygen on a Rough Silver Surface
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Electron energy loss spectroscopy (EELS) results indicate that dichloroethane physisorbs at 55 K on rough, coldly deposited silver.By contrast surface-enhanced Raman scattering (SERS) spectroscpoy reveals that a large fraction of the adsorbed dichloroethane decomposes into ethylene and chlorine on the same type of surface at 55 K and above.With postadsorption of oxygen, dichloroethane or its decomposition products oxidize at temperatures equal to or greater than 140 K, forming products that include a species with a carbonyl group that is either bonded directly to chlorine, as in phosgene or oxalyl chloride, or to a metal atom with chlorine nearby.No hydrogen is bonded sufficiently closely to the CO group in the species to cause a deuterium shift.A second oxidation product is also detected containing an OH group.These reactions occur exclusively at the SERS-active sites and are undetected by EELS.We therefore conclude that SERS and EELS probe different surface sites.EELS seems to be the more globally sensitive technique, and SERS appears to be sensitive to fewer but chemically more reactive sites.This may be due either to the fact that these chemically reactive sites are located at "interior" portions of the surface, i.e., in valleys and pits located among surface features where, it has been suggested, the electromagnetic enhancement is unusually large, or to the extra enhancement that sometimes accompanies chemisorption resulting from the increase of the Raman polarizability of the surface complex, or perhaps to both effects.Whatever the reason, it appears that SERS is uniquely sensitive to those sites where the most interesting chemistry occurs on silver.These may also be the catalytically most important sites.
- Gu, X. J.,Akers, K. L.,Moskovits, M.
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- Unravelling the Enigma of Nonoxidative Conversion of Methane on Iron Single-Atom Catalysts
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The direct, nonoxidative conversion of methane on a silica-confined single-atom iron catalyst is a landmark discovery in catalysis, but the proposed gas-phase reaction mechanism is still open to discussion. Here, we report a surface reaction mechanism by computational modeling and simulations. The activation of methane occurs at the single iron site, whereas the dissociated methyl disfavors desorption into gas phase under the reactive conditions. In contrast, the dissociated methyl prefers transferring to adjacent carbon sites of the active center (Fe1SiC2), followed by C?C coupling and hydrogen transfer to produce the main product (ethylene) via a key ?CH?CH2 intermediate. We find a quasi Mars–van Krevelen (quasi-MvK) surface reaction mechanism involving extracting and refilling the surface carbon atoms for the nonoxidative conversion of methane on Fe1SiO2 and this surface process is identified to be more plausible than the alternative gas-phase reaction mechanism.
- Chang, Chun-Ran,Duan, Zeng-Hui,Li, Jun,Li, Teng-Hao,Li, Wan-Lu,Liu, Jin-Cheng,Liu, Yuan,Wang, Yang-Gang,Xiao, Hai,Yan, Ming,Zhang, Tian-Yu
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- Infrared-induced reaction on MoO3 using a tunable infrared free electron laser
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We observed the IR-induced reaction of C2H5OH on MoO3 using a pulsed and tunable infrared free electron laser (IR-FEL). The IR-FEL-induced reaction showed wavelength dependency and requires light stronger than a certain threshold level. The C2H5OH was converted mainly to C2H4 only when the MoO3 was irradiated with focused IR-FEL at 967 and 814 cm-1 corresponding to Mo=O stretching modes, whereas IR light at 1200 cm-1 induced no reaction. The origin of this IR-FEL-induced reaction is discussed.
- Moula, Golam,Sato, Shinsuke,Irokawa, Katsumi,Niimi, Hironobu,Suzuki, Shushi,Asakura, Kiyotaka,Kuroda, Haruo
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- Photochemical reactions in alkali halide matrix, decarboxylation of maleic acid into ethylene by uranyl nitrate in a pressed potassium bromide disk
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The feasibility of quantitative photochemical reactions of organic compounds in the solid alkali halide disk, usually used for the study of infrared spectroscopy has been explored.The disks were prepared by mixing maleic acid, uranyl nitrate and potassium bromide.Ultraviolet light was used for the irradiation of disk and the products were identified by infrared spectroscopy.It has been observed that the rate of reaction increases with time of irradiation.The results indicate that the ethylene and uranyl (VI) complex of carboxylate are formed with the decarboxylation of maleic acid, sensitized by uranyl nitrate.
- Mehta, B. K.,Dubey, Avinash,Gupta, K. C.,Bokadia, M. M.
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- C?C Coupling Is Unlikely to Be the Rate-Determining Step in the Formation of C2+ Products in the Copper-Catalyzed Electrochemical Reduction of CO
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The identity of the rate-determining step (RDS) in the electrochemical CO reduction reaction (CORR) on Cu catalysts remains unresolved because: 1) the presence of mass transport limitation of CO; and 2) the absence of quantitative correlation between CO partial pressure (pCO) and surface CO coverage. In this work, we determined CO adsorption isotherms on Cu in a broad pH range of 7.2–12.9. Together with electrokinetic data, we demonstrate that the reaction orders of adsorbed CO at pCO 0.6 atm are 1st and 0th, respectively, for multi-carbon (C2+) products on three Cu catalysts. These results indicate that the C?C coupling is unlikely to be the RDS in the formation of C2+ products in the CORR. We propose that the hydrogenation of CO with adsorbed water is the RDS, and the site competition between CO and water leads to the observed transition of the CO reaction order.
- Chang, Xiaoxia,Li, Jing,Lu, Qi,Xiao, Hai,Xiong, Haocheng,Xu, Bingjun,Xu, Yifei,Zhang, Haochen
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supporting information
(2021/12/03)
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- Investigation on the Thermal Cracking and Interaction of Binary Mixture of N-Decane and Cyclohexane
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Abstract: The investigation about the thermal cracking performance and interaction of different components in hydrocarbon fuels is of great significance for optimizing the formulation of high-performance hydrocarbon fuels. In this work, thermal cracking of n-decane, cyclohexane and their binary mixture were studied in a tubular reactor under different temperatures and pressures. The gas and liquid products were analyzed in detail with different gas chromatography. The main gas products of pure n-decane and cyclohexane are similar, and there is a certain difference in the main liquid products. For binary mixture, the overall conversion rate and gas yield are lower than their theoretical value. The cracking conversion rate of n-decane in binary mixture is lower than that in pure n-decane, but the opposite change occurs for cyclohexane, and the effect become more obvious as the increase of the reaction pressure. These experimental phenomena can be explained by bond dissociation energy and free radical reaction mechanism. The pressure affects the free radical reaction path, and high pressure is more conducive to bimolecular hydrogen abstraction reaction, which will lead to different product content. A law of interaction between the n-decane and cyclohexane was observed according to the experimental results. [Figure not available: see fulltext.]
- Chen, Xuejiao,Pang, Weiqiang,Wang, Bo,Zhang, Ziduan,Zhou, Lingxiao,Zhu, Quan
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- Efficient Polyester Hydrogenolytic Deconstruction via Tandem Catalysis
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Using a mechanism-based solvent-free tandem catalytic approach, commodity polyester plastics such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN) are rapidly and selectively deconstructed by combining the two air- and moisture-stable catalysts, Hf(OTf)4 and Pd/C, under 1 atm H2, affording terephthalic acid (or naphthalene dicarboxylic acid for PEN) and ethane (or butane for PBT) in essentially quantitative yield. This process is effective for both laboratory grade and waste plastics, and comingled polypropylene remains unchanged. Combined experimental and DFT mechanistic analyses indicate that Hf(OTf)4 catalyzes a mildly exergonic retro-hydroalkoxylation reaction in which an alkoxy C?O bond is first cleaved, yielding a carboxylic acid and alkene, and this process is closely coupled to an exergonic olefin hydrogenation step, driving the overall reaction forward.
- Kratish, Yosi,Marks, Tobin J.
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supporting information
(2021/12/22)
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- Nanoconfinement Engineering over Hollow Multi-Shell Structured Copper towards Efficient Electrocatalytical C?C coupling
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Nanoconfinement provides a promising solution to promote electrocatalytic C?C coupling, by dramatically altering the diffusion kinetics to ensure a high local concentration of C1 intermediates for carbon dimerization. Herein, under the guidance of finite-element method simulations results, a series of Cu2O hollow multi-shell structures (HoMSs) with tunable shell numbers were synthesized via Ostwald ripening. When applied in CO2 electroreduction (CO2RR), the in situ formed Cu HoMSs showed a positive correlation between shell numbers and selectivity for C2+ products, reaching a maximum C2+ Faradaic efficiency of 77.0±0.3 % at a conversion rate of 513.7±0.7 mA cm?2 in a neutral electrolyte. Mechanistic studies clarified the confinement effect of HoMSs that superposition of Cu shells leads to a higher coverage of localized CO adsorbate inside the cavity for enhanced dimerization. This work provides valuable insights for the delicate design of efficient C?C coupling catalysts.
- Li, Jiawei,Liu, Chunxiao,Xia, Chuan,Xue, Weiqing,Zeng, Jie,Zhang, Menglu,Zheng, Tingting
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supporting information
(2021/12/06)
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- Impact of composition and structural parameters on the catalytic activity of MFI type titanosilicalites
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Titanosilicalite of the MFI type was obtained via a hydrothermal method. Its initial and annealed at 75 °C (TS-1P(75)) and 500 °C (TS-1P(500)) forms were studied by X-ray powder diffraction (PXRD), X-ray absorption spectroscopy (XAS-method), Fourier-transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), temperature-programmed ammonia desorption (TPD NH3), and pyridine adsorption (Py). The full-profile Rietveld method allowed us to observe the presence of the organic template tetrapropylammonium hydroxide (TPAOH) in the framework voids, as well as to determine the silicate module (Si/Ti = 73.5) and the distribution of Ti4+ ions over the MFI-type structure sites (Ti atoms replace Si ones in two positions: T1 and T6). The coordination numbers of titanium (CNTi = 4.6 for TS-1P and TS-1P(75), CNTi = 3.8 for TS-1P(500)) were established by the XAS-method. The catalytic activity of titanosilicalites was found in the reactions of nitrous oxide decomposition (the maximal decomposition rate is demonstrated for the TS-1P(75) sample), allyl chloride epoxidation to epichlorohydrin (the best combination of all indicators was exhibited for the TS-1P sample) and propane conversion (maximum propane conversion, and butadiene and propylene selectivity were observed in both TS-1P(75) and TS-1P(500) samples). Mechanisms for the catalytic processes are proposed. The relationship between the catalytic properties and the composition (Si/Ti), Ti4+ ion distribution over the MFI-type structure sites, the local environment of titanium ions, and the number of acid sites in the titanosilicalites are discussed.
- Bruk, Lev,Chernyshev, Vladimir,Khramov, Evgeny,Kravchenko, Galina,Kustov, Aleksander,Kustov, Leonid,Kuz'Micheva, Galina,Markova, Ekaterina,Pastukhova, Zhanna,Pirutko, Larisa
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p. 3439 - 3451
(2022/03/14)
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- Vanadium Imido NHC Complexes for Ring-Closing Olefin Metathesis Reactions
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Vanadium bis-phosphine imido and oxo chloride alkylidenes have been extensively applied in the ring-closing metathesis of various acyclic olefins. However, their reactions involving ethylene have shown limited productivity due to rapid decomposition. The
- Belov, Dmitry S.,Bukhryakov, Konstantin V.,Fenoll, Didac A.,Rue, Kelly L.,Solans-Monfort, Xavier,Tejeda, Gabriela,Tsay, Charlene
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supporting information
p. 361 - 365
(2022/02/23)
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- Understanding the origin of selective oxidative dehydrogenation of propane on boron-based catalysts
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Boron-based catalysts have been reported to exhibit high selectivity to olefins in oxidative dehydrogenation of propane (ODHP). However, the origin of their superior ODHP selectivity to conventional vanadium-based catalysts is still under debate. In this work, we proposed that oxidized boron species is the active site for highly selective olefin formation in ODHP on boron-based catalysts. Combined isotopic and kinetic experiments suggested that O2 weakly bonds to the electron-deficient B center to form non-dissociative >B–O-O–BB–O-O–B sites. These findings offer in-depth knowledge of ODHP on boron-based catalysts.
- Li, Jiwei,Lin, Jingdong,Qian, Shuya,Tian, Jinshu,Wan, Shaolong,Wang, Shuai,Wang, Yong,Zhang, Zhaoxia
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- STABLE, HIGH SELECTIVITY CATALYSTS AND CATALYST SYSTEMS, AND PROCESSES FOR THEIR USE
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The present invention relates to catalysts, catalyst systems, and processes for the production of valuable light olefins, such as C2-C4 olefins (ethylene, propylene, and/or butenes) from paraffinic hydrocarbons, such as propane, through dehydrogenation and metathesis. Some particular aspects relate to the discovery of non-precious metal catalysts and catalyst systems utilizing such catalysts, for example in the case of being in an admixture with a metathesis catalyst, which advantageously exhibit high performance in terms of activity, selectivity, and stability. Other advantages can include a reduced production of byproducts (e.g., methane and ethane) that result from undesired side reactions, in addition to benefits that may be attained through the addition of a sulfur-bearing compound (e.g., H2S).
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Paragraph 84-87; 92; 93; 96
(2021/08/06)
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- Catalytic activity of heteropoly tungstate catalysts for ethanol dehydration reaction: Deactivation and regeneration
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The pure and palladium doped 12-tungstophosphoric acid - H3PW12O40 (HPW) and its cesium salts CsxH3-xPW12O40 (x = 1, 2, 2.25 and 2.5) were prepared and characterized by thermal analysis, FTIR, XRD, BET and XPS methods. In this paper were determined the optimal reaction temperature and the effect of palladium on the coke content during the dehydration of ethanol in the temperature range of 200?350 °C. Above 300 °C, a strong deactivation of the catalysts was caused by coke formation. The catalytic tests demonstrate that by supporting the HPW and PdyPW (y = 0.15, 0.2 and 0.25) on mesoporous molecular sieve SBA-15 the catalytic activity in ethanol dehydration reaction was improved. Palladium doping of HPW/SBA-15 significantly decreases the formation of coke deposit. The formation of coke during the ethanol dehydration does not affect the Keggin structure which led us to conclude that such catalysts can be regenerated in air and regain their catalytic activity for a short time.
- Verdes, Orsina,Sasca, Viorel,Popa, Alexandru,Suba, Mariana,Borcanescu, Silvana
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p. 123 - 132
(2020/01/03)
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- Selective Preparation of Olefins through Conversion of C2 and C3 Alcohols on NASICON-Type Phosphates
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Abstract—: We have studied the catalytic activity of LiZr2(PO4)3-based NASICON-type phosphates for conversion of C2 and C3 aliphatic alcohols with the aim of selectively preparing C2–C4 olefins. Selectivity has been controlled via partial heterovalent substitutions of In3+ or Nb5+ for Zr4+ or Mo for phosphorus. We have investigated the structure and morphology of the synthesized catalysts. The nature of the dopants has been shown to play a key role in determining the selectivity of the catalysts studied. Partial In3+ substitution for Zr4+ improves the dehydrogenating properties of the materials, whereas partial substitutions of Nb5+ for Zr4+ and Mo6+ for P5+ improve their dehydrating properties. We have demonstrated the possibility of highly selective preparation of ethylene and butylenes from ethanol and of propylene from propanol-1 and propanol-2.
- Ermilova, M. M.,Il’in, A. B.,Orekhova, N. V.,Yaroslavtsev, A. B.
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p. 693 - 700
(2021/07/26)
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- Selective Butene Formation in Direct Ethanol-to-C3+-Olefin Valorization over Zn-Y/Beta and Single-Atom Alloy Composite Catalysts Using in Situ-Generated Hydrogen
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The selective production of C3+olefins from renewable feedstocks, especially via C1and C2platform chemicals, is a critical challenge for obtaining economically viable low-carbon middle-distillate transportation fuels (i.e., jet and diesel). Here, we report a multifunctional catalyst system composed of Zn-Y/Beta and “single-atom” alloy (SAA) Pt-Cu/Al2O3, which selectively catalyzes ethanol-to-olefin (C3+, ETO) valorization in the absence of cofed hydrogen, forming butenes as the primary olefin products. Beta zeolites containing predominately isolated Zn and Y metal sites catalyze ethanol upgrading steps (588 K, 3.1 kPa ethanol, ambient pressure) regardless of cofed hydrogen partial pressure (0-98.3 kPa H2), forming butadiene as the primary product (60% selectivity at an 87% conversion). The Zn-Y/Beta catalyst possesses site-isolated Zn and Y Lewis acid sites (at ～7 wt % Y) and Br?nsted acidic Y sites, the latter of which have been previously uncharacterized. A secondary bed of SAA Pt-Cu/Al2O3selectively hydrogenates butadiene to butene isomers at a consistent reaction temperature using hydrogen generatedin situfrom ethanol to butadiene (ETB) conversion. This unique hydrogenation reactivity at near-stoichiometric hydrogen and butadiene partial pressures is not observed over monometallic Pt or Cu catalysts, highlighting these operating conditions as a critical SAA catalyst application area for conjugated diene selective hydrogenation at high reaction temperatures (>573 K) and low H2/diene ratios (e.g., 1:1). Single-bed steady-state selective hydrogenation rates, associated apparent hydrogen and butadiene reaction orders, and density functional theory (DFT) calculations of the Horiuti-Polanyi reaction mechanisms indicate that the unique butadiene selective hydrogenation reactivity over SAA Pt-Cu/Al2O3reflects lower hydrogen scission barriers relative to monometallic Cu surfaces and limited butene binding energies relative to monometallic Pt surfaces. DFT calculations further indicate the preferential desorption of butene isomers over SAA Pt-Cu(111) and Cu(111) surfaces, while Pt(111) surfaces favor subsequent butene hydrogenation reactions to form butane over butene desorption events. Under operating conditions without hydrogen cofeeding, this combination of Zn-Y/Beta and SAA Pt-Cu catalysts can selectively form butenes (65% butenes, 78% C3+selectivity at 94% conversion) and avoid butane formation using onlyin situ-generated hydrogen, avoiding costly hydrogen cofeeding requirements that hinder many renewable energy processes.
- Allard, Lawrence F.,Assary, Rajeev S.,Cordon, Michael J.,Krause, Theodore R.,Kropf, A. Jeremy,Li, Zhenglong,Lin, Fan,Liu, Dongxia,Miller, Jeffrey T.,Purdy, Stephen C.,Unocic, Kinga A.,Wang, Huamin,Wegener, Evan C.,Yang, Ce,Zhang, Junyan,Zhou, Mingxia
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p. 7193 - 7209
(2021/06/30)
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- CATALYTIC CONVERSION OF ETHANOL TO 1-/2-BUTENES
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Simple and economical conversion of aqueous ethanol feed streams into butenes by a single step method using transition metal oxides on a silica supports under preselected processing conditions. By directly producing a C4-rich olefin mixture from an ethanol containing stream various advantages are presented including, but not limited to, significant cost reduction in capital expenses and operational expenses.
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Paragraph 0013-0022; 0026-0046
(2021/06/11)
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- The enhancement effects of BaX2 (X?=?F, Cl, Br) on SnO2-based catalysts for the oxidative coupling of methane (OCM)
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In this study, the promotional effects of different barium halides (BaF2, BaCl2 and BaBr2) on SnO2 for OCM reaction have been investigated. It is observed that the addition of all the barium halides can improve the reaction performance of SnO2, following the sequence of BaBr2 > BaCl2 > BaF2. Raman and XRD results have substantiated that adding barium halides to SnO2 can increase the amount of surface vacancies/defects, hence creating more abundant surface OCM reactive oxygen sites by anion substitution. At the same time, the amount of the moderate basic sites contributing to OCM reaction is also improved. During OCM reaction, the amount of the OCM reactive oxygen species as well as the moderate basic sites can be further increased. As proved by In situ Raman and XPS results, on BaF2:SnO2 = 1:1 and BaCl2:SnO2 = 1:1, O2? is the OCM reactive oxygen sites. In contrast, on BaBr2:SnO2 = 1:1, O22- is the OCM reactive oxygen sites, which is induced by the formation of BaSnO3 perovskite phase. Moreover, O22- anions are reported to be favourable for the direct formation of C2H4 through carbene mechanism, which explains the high ethylene selectivity on BaBr2-modified catalyst. The amount and properties of the surface active oxygen species and basic sites are of great importance for OCM reaction, and their concerted interaction determines the reaction performance of BaX2/SnO2 catalysts. BaBr2:SnO2 = 1:1 contains the apporiate amount of both types of active sites, hence displaying the best OCM performance among all the catalysts.
- Xi, Rong,Xu, Junwei,Zhang, Yan,Zhang, Zhixuan,Xu, Xianglan,Fang, Xiuzhong,Wang, Xiang
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- CONVERSION OF METHANE INTO ETHYLENE USING ISOMORPHOUS METAL-SUBSTITUTED ZEOLITE FRAMEWORK CATALYST
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Process for the conversion of non-oxidative coupling of methane to ethylene, under non- oxidative conditions, comprising: providing a first stream containing at least 50 vol.% of methane based on the total volume of said first stream; providing a catalyst; putting in contact said first stream with said catalyst at a weight hour space velocity ranging from 0.5 to 100 h-1, a temperature ranging from 500°C to 1100°C and a pressure ranging from 0.1 MPa to 5Mpa in the absence of oxygen; recovering a second stream containing unconverted methane if any, ethylene and hydrocarbons having at least 2 carbon atoms. Said process is remarkable in that said catalyst is a synthetic zeolite material, containing at least one metal M with silicon to metal M molar ratio Si/M as determined by inductively coupled plasma optical emission spectrometry ranging from 100 to 65440 and in that said metal M is incorporated inside of the zeolite tetrahedral sites.
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Page/Page column 48-49
(2021/05/07)
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- Transformation synthesis of SSZ-13 zeolite from ZSM-35 zeolite
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Interzeolite conversion as a promising alternative strategy for zeolite synthesis has received extensive attention. It is of great significance to understand the potential rules of conversion between zeolites with different topologies for effective regulation of zeolite synthesis. Hydrothermal conversion of ZSM-35 (FER-type) zeolite containing the mor composite building units into SSZ-13 zeolite (CHA-type) using N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as template was performed for the first time. The effects of TMAdaOH/SiO2 ratio, Na2O/SiO2 ratio, the additional starting zeolite and crystallization time on the interzeolite conversion of ZSM-35 into SSZ-13 were investigated. The interzeolite conversion mechanism concerning the synthesis of SSZ-13 from ZSM-35 zeolite was proposed and verified by DFT calculation. The results of DFT calculations suggested that ZSM-35 zeolite with mor composite building unit had the potential to decompose into 6-Membered Rings, and further transform into CHA-type zeolite containing d6r composite building unit. Therefore, zeolites containing mor structure have the potential to be converted into zeolites containing d6r structure.
- Bing, Liancheng,Cong, Wenwen,Han, Dezhi,Li, Kexu,Li, Qiang,Wang, Fang,Wang, Guangjian,Xu, Changyou
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- Oxidative Cracking of Propane in the Presence of Hydrogen
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The effect of H2 additions to the initial mixture on the parameters of the oxidative cracking of propane at atmospheric pressure, temperatures of 500°C–750°C, reaction time of 2 s, and С3H8/О2 initial ratio ~2 was experimentally evaluated. Results revealed that small amounts of H2 promoted the process due to the formation of additional active radicals OH? and H?. Performance of the oxidative cracking of propane in a large excess of H2 led to an increase in the yield of methane and ethane, while the yield of ethylene, the target product of the process, decreased.
- Arutyunov, V. S.,Nikitin, A. V.,Ozerskii, A. V.,Sedov, I. V.,Timofeev, K. A.,Zimin, Ya. S.
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p. 787 - 792
(2021/08/13)
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- Insight into Carbocation-Induced Noncovalent Interactions in the Methanol-to-Olefins Reaction over ZSM-5 Zeolite by Solid-State NMR Spectroscopy
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Carbocations such as cyclic carbenium ions are important intermediates in the zeolite-catalyzed methanol-to-olefins (MTO) reaction. The MTO reaction propagates through a complex hydrocarbon pool process. Understanding the carbocation-involved hydrocarbon pool reaction on a molecular level still remains challenging. Here we show that electron-deficient cyclopentenyl cations stabilized in ZSM-5 zeolite are able to capture the alkanes, methanol, and olefins produced during MTO reaction via noncovalent interactions. Intermolecular spatial proximities/interactions are identified by using two-dimensional 13C–13C correlation solid-state NMR spectroscopy. Combined NMR experiments and theoretical analysis suggests that in addition to the dispersion and CH/π interactions, the multiple functional groups in the cyclopentenyl cations produce strong attractive force via cation-induced dipole, cation–dipole and cation–π interactions. These carbocation-induced noncovalent interactions modulate the product selectivity of hydrocarbon pool reaction.
- Cai, Wenjin,Chu, Yueying,Deng, Feng,Hu, Min,Li, Shenhui,Qi, Guodong,Wang, Chao,Wang, Qiang,Xu, Jun
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supporting information
p. 26847 - 26854
(2021/11/17)
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- Dehydrogenation of Propane in the Presence of CO2 on Supported Monometallic MOy/SiO2 and CrOxMOy/SiO2 (M = Fe, Co, and Ni) Bimetallic Catalysts
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Abstract: An analysis is performed of the physicochemical properties of M/SiO2 (M = Fe, Co, and Ni) oxide monometallic and CrM/SiO2 (M = Fe, Co, and Ni) bimetallic catalysts supported on amorphous silica. The catalysts are characterized via TGA, XRD, UV–Vis diffuse reflectance spectroscopy, and SEM. Adding 1?wt?% of a second transition metal (Fe, Ni, and Co) to the 3% CrOx/SiO2 chromium oxide catalyst substantially raises the conversion of propane to 64% with a drop in the selectivity towards propylene and formation of methane as a main by-product in the case of nickel. Introducing iron and cobalt raises the selectivity towards propylene to 72% with a drop in the conversion of propane.
- Tedeeva,Kustov,Pribytkov,Strekalova,Kalmykov,Dunaev,Kustov
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- Selectivity Map for the Late Stages of CO and CO2 Reduction to C2 Species on Copper Electrodes
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The electrochemical CO and CO2 reduction reactions (CORR and CO2RR) using copper catalysts and renewable electricity hold promise as a carbon-neutral route to produce commodity chemicals and fuels. However, the exact mechanisms and structure sensitivity of Cu electrodes toward C2 products are still under debate. Herein, we investigate ethylene oxide reduction (EOR) as a proxy to the late stages of CORR to ethylene, and the results are compared to those of acetaldehyde reduction to ethanol. Density functional theory (DFT) calculations show that ethylene oxide undergoes ring opening before exclusively reducing to ethylene via *OH formation. Based on generalized coordination numbers (CN), a selectivity map for the late stages of CORR and CO2RR shows that sites with moderate coordination (5.9 CN 7.5) are efficient for ethylene production, with pristine Cu(100) being more active than defective surfaces such as Cu(311). In contrast, kinks and edges are more active for ethanol production, while (111) terraces are relatively inert.
- Piqué, Oriol,Low, Qi Hang,Handoko, Albertus D.,Yeo, Boon Siang,Calle-Vallejo, Federico
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supporting information
p. 10784 - 10790
(2021/04/15)
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- Bidirectional Synthesis, Photophysical and Electrochemical Characterization of Polycyclic Quinones Using Benzocyclobutenes and Benzodicyclobutenes as Precursors
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Quinones have widespread applications in view of their interesting chemical and photophysical features. On the other hand, benzocyclobutenes (BCBs) are generally masked reactive dienes suitable for the [4+2] cycloaddition reactions. Here, benzocyclobutenes and benzodicyclobutenes (BDCBs) were prepared and further reacted with benzoquinone and naphthoquinone in order to obtain some new polycyclic quinones with highly extended π systems, namely, 6-bromo-5,8-dimethoxyanthracene-1,4-dione, 2,9-dibromo-1,4,8,11-tetramethoxypentacene-6,13-dione, 9-bromo-7,10-dimethoxytetracene-5,12-dione, 3,10-dimethoxycyclobuta[b]anthracene-1,5,8(2H)-trione, 6,10,17,21-tetramethoxynonacene-1,4,8,12,15,19-hexaone, and 3,12-dimethoxycyclobuta[b]tetracene-1,5,10(2H)-trione. In addition to their spectroscopic characterization the new compounds are investigated by UV and fluorescence spectroscopy, cyclic voltammetry, and DFT calculations.
- Mohamed Abdelmoniem, Amr,Abdelshafy Abdelhamid, Ismail,Butensch?n, Holger
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p. 6319 - 6333
(2021/09/25)
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- Study of Cu modified Zr and Al mixed oxides in ethanol conversion: The structure-catalytic activity relationship
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Here, we study the influence of the Cu modified (Zr + Ce)O2-Al2O3 systems composition and synthesis conditions on their catalytic properties in the ethanol conversion. First, we obtained varios ratios mixed Al-Zr supports at different synthesis temperatures using a sol-gel method. Then we modified the surface of the oxides by Cu, reduced in hydrogen flow. All obtained systems demonstrated а high alcohol conversion and selectivity to acetaldehyde. The surface area (SBET), the pore volume, and the pore distribution were measured by the nitrogen adsorption method. The structure of the samples have been investigated by XRD and XAS-spectroscopy. A correlation between the synthesis temperature and contents of mixed oxide support and textural properties were observed. The results show that Al-Zr mixed oxide support structure plays a crucial role in forming a Cu active site for ethanol dehydrogenation to acetaldehyde.
- Zhukova,Chuklina,Maslenkova
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p. 159 - 165
(2021/03/17)
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- Catalytic properties of the framework-structured zirconium-containing phosphates in ethanol conversion
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Aliphatic alcohols C1–C4 can serve as raw material for the production of essential organic products, such as olefins, aldehydes, ketones and ethers. For the development of catalysts of alcohols’ conversion, the authors considered two families of framework phosphate compounds with significant chemical, thermal and phase stability: NaZr2(PO4)3 (NZP/NASICON) and Sc2(WO4)3 (SW). Variation in the composition of zirconium-containing NZP- and SW-complex phosphates allows one to vary the number and strength of Lewis acid centers and incorporate oxidative-reducing centers (such as d-transition metals) into the structure. The phosphates M0.5+xNixZr2 ? x(PO4)3 (where M are Mn and Ca) were studied in the reactions of ethanol conversion. From the results of complex investigation, the compounds with M–Mn (x = 0, 0.3 and 0.5) were crystallized in the SW-type (monoclinic symmetry), while the phosphates with M–Ca (x = 0, 0.2 and 0.4) were characterized as the NZP-structured compounds (trigonal symmetry). The surface areas and pore volumes of synthesized catalysts varied, with different compositions, from 14 to 32?m2/g and 0.03 to 0.12?mL/g, respectively. From the catalytic experiments, the main direction of conversion on all the studied catalysts was ethanol dehydrogenization with acetaldehyde formation. The other conversion products—diethyl ether and ethylene—were produced with small yields. Based on the results obtained, the NZP-sample Ca0.5Zr2(PO4)3 can be considered as a selective catalyst for producing acetaldehyde at 400?°C with a yield of 55% from its theoretical amount.
- Mayorov, Pavel,Asabina, Elena,Zhukova, Anna,Osaulenko, Diana,Pet’kov, Vladimir,Lavrenov, Dmitry,Kovalskii, Andrey,Fionov, Alexander
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p. 3645 - 3659
(2021/06/02)
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- Reactivity of vanadyl pyrophosphate catalyst in ethanol ammoxidation and β-picoline oxidation: Advantages and limitations of bi-functionality
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This study investigates the catalytic activity of vanadyl pyrophosphate (VPP) for both gas-phase ethanol ammoxidation to acetonitrile and β-picoline oxidation to nicotinic acid. Both reactions may be alternative processes to the industrial technologies used to produce these two chemicals. The reaction networks were investigated, also by feeding possible intermediates; in-situ DRIFT spectroscopy was used to monitor the interaction of ethanol and ammonia with the catalyst. VPP bi-functionality features played an important role in the two reactions; specifically, acidity was detrimental either because it catalyzed undesired reactions, such as ethanol dehydration to ethylene during ethanol ammoxidation, or because it caused a strong interaction with reactants – especially those containing N atoms, ammonia and β-picoline – thus giving rise to some surface saturation phenomena which inhibited the consecutive reactions leading to the final desired compounds, acetonitrile and nicotinic acid. The co-feeding of steam helped product desorption, thus enhancing selectivity in β-picoline oxidation.
- Tabanelli, Tommaso,Mari, Massimiliano,Folco, Federico,Tanganelli, Federico,Puzzo, Francesco,Setti, Laura,Cavani, Fabrizio
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- Enhanced Catalytic Performance of Fe-containing HZSM-5 for Ethane Non-Oxidative Dehydrogenation via Hydrothermal Post-Treatment
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A facile strategy is applied to construct Fe supported ZSM-5 (Fe/HZ5-HTS) via hydrothermal post-treatment and applied to ethane non-oxidative dehydrogenation. Compared with Fe/HZ5-IWI prepared by incipient wetness impregnation, Fe/HZ5-HTS exhibits superior catalytic activity and long catalyst stability with 6000 minutes time-on-stream. An obvious volcanic curve is observed between the ethylene generation rate and Fe content, and 1.0Fe/HZ5-HTS exhibits the highest ethylene generation rate with 0.166 mmol C2H4 s?1 gFe?1 over different Fe loading, which is twice as much as that of 1.0Fe/HZ5-IWI. According to various characterizations, isolated Fe3+ species and carburized Fe species are active sites, and the better catalytic performance over 1.0Fe/HZ5-HTS is ascribed to more disperse Fe species and exposing more Fe species in the surface. Besides, the lower ethylene desorption temperature and higher ethane desorption temperature over Fe/HZ5-HTS could suppress the overreaction of the ethylene to generate coke and increase ethane residence reaction time, resulting in less coke deposition and facilitating the catalytic performance.
- Wu, Lizhi,Fu, Zhiyuan,Ren, Zhuangzhuang,Wei, Jinhe,Gao, Xinhua,Tan, Li,Tang, Yu
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p. 4019 - 4028
(2021/08/03)
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- Nb?V Mixed Oxide with a Random Assembly of Pentagonal Units: A Catalyst for Oxidative Dehydrogenation of Ethane and Propane
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High-dimensionally structured (HDS) mixed oxides of vanadium with metals (M) (e. g., Nb, Mo, and W; denoted as HDS-MVO) were constructed by {M6O21}12? pentagonal units and {MO6} (M=Nb, Mo, W, or V) octahedra as linkers. The materials were synthesized using a hydrothermal method and rod-shaped solids. The random assembly of the pentagonal units and octahedra in the cross-sectional plane of the rods facilitated the formation of micropore channels along the long axis of the rods. Micropore formation was directly observed in the cross-section by HAADF-STEM. These structural features are common to HDS-NbVO, HDS-MoVO, and HDS-WVO. The catalytic activity of these three HDS-MVOs with V/Mo ratios in the range 0.35–0.39 was tested for the oxidative dehydrogenation of ethane and propane. The reaction rates per surface area for ethane oxidation and propane oxidation over the HDS-MoVO and HDS-WVO catalysts were comparable, whereas the HDS-NbVO catalyst showed an appreciable difference between the two reaction rates. Both HDS-MoVO and HDS-WVO exhibited higher selectivity for olefin formation during ethane oxidation than propane oxidation. Interestingly, the olefin selectivity over the HDS-NbVO catalyst was found to be almost independent of the alkane substrate. These catalytic features were discussed on the basis of V?O?V or V?O?Mo redox coupling and pore structure effects in HDS-MoVO and HDS-WVO and also of isolated and valence stable surface V in HDS-NbVO.
- Shimoda, Kosuke,Ishikawa, Satoshi,Matsumoto, Katsuya,Miyasawa, Mai,Takebe, Marino,Matsumoto, Riku,Lee, Syutoku,Ueda, Wataru
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p. 3132 - 3139
(2021/05/29)
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- Synergistic effect of Fe and Ga incorporation into ZSM-5 to increase propylene production in the cracking ofn-hexane utilizing a microchannel reactor
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In the present study, the effect of various amounts of Fe and Ga in the catalytic cracking ofn-hexane in a microchannel reactor was investigated using experimental design by the D-optimal method. Nano zeolites incorporated with Fe and Ga metals were synthesized in a fluorine environment to investigate the synergistic effect of the metals on the textural and acidic properties of the catalysts, which ultimately improved the performance of the synthesized catalysts in the efficient production of light olefins, in particular propylene. Three synthesis parameters including the Si/Al, Si/Fe and Si/Ga ratios were considered as the main factors to determine the optimal conditions for obtaining the maximum conversion ofn-hexane, yield of light olefins, and P/E ratio and minimum yield of alkanes as the responses. In sample FeGa-1, the P/E ratio reached 3.97, indicating the significant effect of the substituted metals in improving the desirable routes for propylene production. According to the results of the acidic properties, Fe, Al and Ga increased the number of total acid sites and the strengths of strong and weak acid sites, respectively. In addition, according to the results obtained from sample FeGa-7, the synergistic effect of Fe and Ga increased the number of weak acid sites.
- Halimitabrizi, Parya,Rashidzadeh, Mehdi,Sakha, Mohsen Rostami,Salari, Darush,Soltanali, Saeed
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p. 13833 - 13846
(2021/08/16)
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- The effect of oxygen vacancy of alkaline-earth metal Sr doped Sm2Zr2O7 catalysts in the oxidative coupling of methane
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A series of the Sr/Sm2Zr2O7 catalysts with different Sr contents prepared by the coprecipitation method were used for OCM. The results revealed that the basicity and oxygen vacancies concentration on the surface of the Sm2Zr2O7 catalyst were notably increased because of the addition of Sr. Activation of O2 by the oxygen vacancies was responsible for the formation of C2. Specifically, the 7.6% Sr/Sm2Zr2O7 catalyst possessed 18.4% C2 yield at 750 °C due to the presence of moderate basicity and the highest ratio of the oxygen species O2– to lattice oxygen O2–. More importantly, the 7.6%Sr/Sm2Zr2O7 catalyst possessed high stability.
- Hao, Jie,Cai, Fufeng,Wang, Jiyang,Fu, Yu,Zhang, Jun,Sun, Yuhan
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- Unexpected activity of MgO catalysts in oxidative coupling of methane: Effects of Ca-promoter
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Unexpectedly, we founded very different catalytic activities of MgO in oxidative coupling of methane (OCM) depending on company that supplied the precursors, which was due to the Ca-related impurities. Accordingly, we investigated the effects of Ca-promoter on the catalytic activity of MgO catalysts. Substituting Ca into the MgO catalysts strongly influenced both the formation of oxygen vacancies and the base properties of surface lattice oxygen (Olat), which are key factors in this reaction. The formed oxygen vacancies resulted in high methane conversion through the facile conversion of methane to methyl radical, whereas Olat with medium basicity played an important role in producing ethylene through the facile dehydrogenation of ethane.
- An, Suna,Cho, JeongHyun,Jung, Ji Chul,Kwon, Dahye,Yang, Inchan
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- THERMAL OXIDATIVE COUPLING OF METHANE PROCESS USING RENEWABLE ENERGY WITH POSSIBLE CO-PRODUCTION OF HYDROGEN
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The disclosure relates in its first aspect to a process for converting methane into chemicals. The process comprises the steps of (a) providing a first stream (1; 7) comprising methane; (b) providing a second stream (13) which is an oxygen-rich stream; (c) contacting said first stream (1; 7) with said second stream (13) under oxidation reaction conditions to obtain a third stream (15) comprising chemicals and water; (d) performing at least one separation step on said third stream (15) to recover a water stream (21) and a fourth stream (39) comprising chemicals; (e) subjecting said water stream (21) to an oxidation reaction under first reaction conditions to produce at least an oxygen stream (29), wherein the oxygen stream (29) is recycled into the second stream (13). In its second aspect, the disclosure relates to an installation for working the process of the first aspect.
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Page/Page column 20
(2021/12/30)
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- Oxidative coupling of methane over Mo-Sn catalysts
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A novel Mo-Sn catalyst for the oxidative coupling of methane was designed using a hydrothermal method. At 650 °C, the conversion of methane was 8.6% and the selectivity of the C2 hydrocarbons reached as high as 98.1% over the Mo1Sn3 catalyst, with a CO2 selectivity of only 0.8%. We demonstrated that the deep oxidation of methane to CO2 was further inhibited due to the synergistic effects of moderately strong basic sites and reactive oxygen species on the catalyst surface. This journal is
- Gao, Xiujuan,Han, Yizhuo,Liu, Xiaoyan,Meng, Xianghai,Song, Faen,Tan, Yisheng,Wang, Xiaoxing,Yan, Lina,Zhang, Junfeng,Zhang, Qingde,Zhang, Tao
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supporting information
p. 13297 - 13300
(2021/12/17)
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- Morphology Effects of Nanoscale Er2O3 and Sr-Er2O3 Catalysts for Oxidative Coupling of Methane
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Abstract: Er2O3 nanorods were prepared by a hydrothermal method, and Sr-modified Er2O3 nanorods (Sr-Er2O3) were synthesized using an impregnation method. Their catalytic performance for oxidative coupling of methane was investigated. The catalysts were characterized by several techniques such as XRD, N2 adsorption, TEM, XPS, O2-TPD and CO2-TPD. Compared with Er2O3 and Sr-Er2O3 nanoparticles, Er2O3 and Sr-Er2O3 nanorods exhibit higher CH4 conversion and C2–C3 selectivity. This is caused by higher (O? + O2?)/O2? ratio, a higher number of chemisorbed oxygen species and moderate basic sites achieved on the nanorods catalysts. The Sr-Er2O3 nanorods afford a 23.2% conversion of CH4 with 50.3% selectivity to C2–C3 at 650?°C. Graphic Abstract: [Figure not available: see fulltext.]
- Fan, Yuqiao,Sun, Mingxing,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
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p. 2197 - 2206
(2021/01/04)
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- New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na2WO4/SiO2 Catalysts
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The complex structure of the catalytic active phase, and surface-gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na2WO4/SiO2 catalysts. The present study demonstrates, with the aid of in situ Raman spectroscopy and chemical probe (H2-TPR, TAP and steady-state kinetics) experiments, that the long speculated crystalline Na2WO4 active phase is unstable and melts under OCM reaction conditions, partially transforming to thermally stable surface Na-WOx sites. Kinetic analysis via temporal analysis of products (TAP) and steady-state OCM reaction studies demonstrate that (i) surface Na-WOx sites are responsible for selectively activating CH4 to C2Hx and over-oxidizing CHy to CO and (ii) molten Na2WO4 phase is mainly responsible for over-oxidation of CH4 to CO2 and also assists in oxidative dehydrogenation of C2H6 to C2H4. These new insights reveal the nature of catalytic active sites and resolve the OCM reaction mechanism over supported Na2WO4/SiO2 catalysts.
- Baltrusaitis, Jonas,Fushimi, Rebecca R.,Kiani, Daniyal,Sourav, Sagar,Wachs, Israel E.,Wang, Yixiao
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p. 21502 - 21511
(2021/08/25)
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- Controlling the Surface Oxidation of Cu Nanowires Improves Their Catalytic Selectivity and Stability toward C2+ Products in CO2 Reduction
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Copper nanostructures are promising catalysts for the electrochemical reduction of CO2 because of their unique ability to produce a large proportion of multi-carbon products. Despite great progress, the selectivity and stability of such catalysts still need to be substantially improved. Here, we demonstrate that controlling the surface oxidation of Cu nanowires (CuNWs) can greatly improve their C2+ selectivity and stability. Specifically, we achieve a faradaic efficiency as high as 57.7 and 52.0 % for ethylene when the CuNWs are oxidized by the O2 from air and aqueous H2O2, respectively, and both of them show hydrogen selectivity below 12 %. The high yields of C2+ products can be mainly attributed to the increase in surface roughness and the generation of defects and cavities during the electrochemical reduction of the oxide layer. Our results also indicate that the formation of a relatively thick, smooth oxide sheath can improve the catalytic stability by mitigating the fragmentation issue.
- Lyu, Zhiheng,Zhu, Shangqian,Xie, Minghao,Zhang, Yu,Chen, Zitao,Chen, Ruhui,Tian, Mengkun,Chi, Miaofang,Shao, Minhua,Xia, Younan
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supporting information
p. 1909 - 1915
(2020/12/07)
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- Multiple Cuprous Centers Supported on a Titanium-Based Metal-Organic Framework Catalyze CO2Hydrogenation to Ethylene
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Hydrogenation of carbon dioxide (CO2) to ethylene (C2H4) can be achieved in two routes via tandem reactions: (1) CO2hydrogenation to methanol (CH3OH) followed by methanol-to-olefin conversion and (2) reverse water-gas shift reaction followed by Fischer-Tropsch synthesis. Here we present another tandem route for CO2-to-C2H4conversion via (3) CO2hydrogenation to ethanol (C2H5OH) followed by C2H5OH dehydration. Multiple cuprous (CuI) centers were loaded onto the Ti8(μ2-O)8(μ2-OH)4secondary building units of a Ti-based metal-organic framework (MOF), MIL-125-NH2, via deprotonation and ion exchange of the μ2-OH groups. These multiple CuIcenters catalyzed CO2hydrogenation to C2H5OH, while the Ti2-μ2-O-M+(M+= H+, Li+) sites converted C2H5OH to C2H4. The MOF achieved CO2-to-C2H4generation rates of up to 2598 μmol gCat-1h-1in supercritical CO2(CO230 MPa, H25 MPa) at 85 °C and 514 μmol gCat-1h-1in the gas phase at 5 MPa (H2:CO2= 3) and 100 °C, respectively. This work opens another path to selectively producing C2H4via the hydrogenation of CO2
- An, Bing,Cao, Yonghua,Dai, Yiheng,Li, Han,Li, Zhe,Lin, Wenbin,Wang, Cheng,Wang, Yongke,Zeng, Lingzhen,Zhang, Jingzheng,Zhou, Yang
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p. 11696 - 11705
(2021/09/28)
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- Facet-Selective Deposition of Ultrathin Al2O3 on Copper Nanocrystals for Highly Stable CO2 Electroreduction to Ethylene
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Catalysts based on Cu nanocrystals (NCs) for electrochemical CO2-to-C2+ conversion with high activity have been a subject of considerable interest, but poor stability and low selectivity for a single C2+ product remain obstacles for realizing sustainable carbon-neutral cycles. Here, we used the facet-selective atomic layer deposition (FS-ALD) technique to selectively cover the (111) surface of Cu NCs with ultrathin Al2O3 to increase the exposed facet ratio of (100)/(111), resulting in a faradaic efficiency ratio of C2H4/CH4 for overcoated Cu NCs 22 times higher than that for pure Cu NCs. Peak performance of the overcoated catalyst (Cu NCs/Al2O3-10C) reaches a C2H4 faradaic efficiency of 60.4 % at a current density of 300 mA cm?2 in 5 M KOH electrolyte, when using a gas diffusion electrode flow cell. Moreover, the Al2O3 overcoating effectively suppresses the dynamic mobility and the aggregation of Cu NCs, which explains the negligible activity loss and selectivity degradations of Cu NCs/Al2O3-10C shown in stability tests.
- Li, Hui,Yu, Peiping,Lei, Renbo,Yang, Feipeng,Wen, Peng,Ma, Xiao,Zeng, Guosong,Guo, Jinghua,Toma, Francesca M.,Qiu, Yejun,Geyer, Scott M.,Wang, Xinwei,Cheng, Tao,Drisdell, Walter S.
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supporting information
p. 24838 - 24843
(2021/10/15)
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- Synthesis of Vanadium Oxo Alkylidene Complex and Its Reactivity in Ring-Closing Olefin Metathesis Reactions
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V imido alkylidenes have been applied for the ring-opening metathesis polymerization involving cyclic olefins. However, those complexes found limited application in reactions with acyclic terminal olefins due to instability toward ethylene. Experimental and theoretical studies show that the β-hydride elimination from unsubstituted metallacyclobutene is the primary decomposition pathway in those systems. Herein, we report the synthesis of the first catalytically active V oxo alkylidene, VO(CHSiMe3)(PEt3)2Cl, which exhibits the highest reported productivity with various terminal olefins in ring-closing metathesis reactions among known V catalysts. Presented DFT studies indicate that β-hydride elimination is significantly disfavored for V oxo species.
- Belov, Dmitry S.,Bukhryakov, Konstantin V.,Chakraborty, Indranil,Fenoll, Didac A.,Solans-Monfort, Xavier
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supporting information
p. 2939 - 2944
(2021/09/13)
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- Pd-Modified ZnO-Au Enabling Alkoxy Intermediates Formation and Dehydrogenation for Photocatalytic Conversion of Methane to Ethylene
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Photocatalysis provides an intriguing approach for the conversion of methane to multicarbon (C2+) compounds under mild conditions; however, with methyl radicals as the sole reaction intermediate, the current C2+ products are dominated by ethane, with a negligible selectivity toward ethylene, which, as a key chemical feedstock, possesses higher added value than ethane. Herein, we report a direct photocatalytic methane-to-ethylene conversion pathway involving the formation and dehydrogenation of alkoxy (i.e., methoxy and ethoxy) intermediates over a Pd-modified ZnO-Au hybrid catalyst. On the basis of various in situ characterizations, it is revealed that the Pd-induced dehydrogenation capability of the catalyst holds the key to turning on the pathway. During the reaction, methane molecules are first dissociated into methoxy on the surface of ZnO under the assistance of Pd. Then these methoxy intermediates are further dehydrogenated and coupled with methyl radical into ethoxy, which can be subsequently converted into ethylene through dehydrogenation. As a result, the optimized ZnO-AuPd hybrid with atomically dispersed Pd sites in the Au lattice achieves a methane conversion of 536.0 μmol g-1 with a C2+ compound selectivity of 96.0% (39.7% C2H4 and 54.9% C2H6 in total produced C2+ compounds) after 8 h of light irradiation. This work provides fresh insight into the methane conversion pathway under mild conditions and highlights the significance of dehydrogenation for enhanced photocatalytic activity and unsaturated hydrocarbon product selectivity.
- Jiang, Wenbin,Low, Jingxiang,Mao, Keke,Duan, Delong,Chen, Shuangming,Liu, Wei,Pao, Chih-Wen,Ma, Jun,Sang, Shuaikang,Shu, Chang,Zhan, Xiaoyi,Qi, Zeming,Zhang, Hui,Liu, Zhi,Wu, Xiaojun,Long, Ran,Song, Li,Xiong, Yujie
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supporting information
p. 269 - 278
(2021/01/12)
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- Steric effect induces CO electroreduction to CH4on Cu-Au alloys
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The electrocatalytic reduction of carbon monoxide (CO) is an emerging direction with new catalyst structures, among which the bimetallic component catalysts feature both functional diversity and high-density of active sites. In this work, we demonstrate that the fine tuning of adjacent bimetallic sites can allow us to select different reaction pathways toward C1or C2products in the electroreduction of CO. Cu and Cu-Au alloy catalysts with different atomic ratios were fabricated and investigated for appropriate molecular distances. The pure Cu catalyst was found to be active for electroreducing CO to C2H4, as the adjacent Cu sites were beneficial for adsorbing multiple CO molecules and subsequent C-C coupling. On the other hand, alloying Cu with Au introduced steric hindrance and a larger intermolecular distance between adjacent adsorbed *CO intermediates, thus leading to a decrease of C2H4selectivity but an enhanced CH4pathway. Our work revealed the importance of spacing between active sites for CO electroreduction, which can benefit the catalyst design to further improve activities and selectivities in electrocatalytic CO reduction.
- Guan, Anxiang,Ji, Yali,Li, Si,Qian, Linping,Wang, Qihao,Wu, Limin,Yang, Chao,Zhang, Lijuan,Zheng, Gengfeng
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supporting information
p. 21779 - 21784
(2021/10/12)
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- Machine-Learning-Guided Discovery and Optimization of Additives in Preparing Cu Catalysts for CO2Reduction
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Discovery and optimization of new catalysts can be potentially accelerated by efficient data analysis using machine-learning (ML). In this paper, we record the process of searching for additives in the electrochemical deposition of Cu catalysts for CO2 reduction (CO2RR) using ML, which includes three iterative cycles: "experimental test; ML analysis; prediction and redesign". Cu catalysts are known for CO2RR to obtain a range of products including C1 (CO, HCOOH, CH4, CH3OH) and C2+ (C2H4, C2H6, C2H5OH, C3H7OH). Subtle changes in morphology and surface structure of the catalysts caused by additives in catalyst preparation can lead to dramatic shifts in CO2RR selectivity. After several ML cycles, we obtained catalysts selective for CO, HCOOH, and C2+ products. This catalyst discovery process highlights the potential of ML to accelerate material development by efficiently extracting information from a limited number of experimental data.
- Guo, Ying,He, Xinru,Su, Yuming,Dai, Yiheng,Xie, Mingcan,Yang, Shuangli,Chen, Jiawei,Wang, Kun,Zhou, Da,Wang, Cheng
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supporting information
p. 5755 - 5762
(2021/05/07)
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- CuAg nanoparticle/carbon aerogel for electrochemical CO2reduction
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The electrochemical carbon dioxide reduction reaction (eCO2RR) is a promising technology that uses electrical energy to catalytically reduce greenhouse gas-CO2, converting CO2into high value-added products such as hydrocarbons and alcohols. However, due to the complexity of the eCO2RR, the activity and selectivity of the eCO2RR is highly dependent on the intrinsic catalytic activity of a catalyst with mass transportation-favorable morphology. Herein, silk fibroin-derived carbon aerogels (CAs) loaded with small amounts of Cu and Ag nanoparticles were synthesized. Based on the molar content of Cu, the catalysts were labeled SF-CuAg/CA-N(N= 20%, 40%, 60%, 80%). Among them, SF-CuAg/CA-40% showed a good FECOof 71% at ?1.26 Vvs.a reversible hydrogen electrode (RHE), and a significant current density of ?15.77 mA cm?2towards CO at ?1.06 Vvs.RHE, which is close to 2.6, 2.53 and 2.71 times those of SF-CuAg/CA-20% (?6.02 mA cm?2), SF-CuAg/CA-60% (?6.24 mA cm?2) and SF-CuAg/CA-80% (?5.82 mA cm?2). The SF-CuAg/CA-Ncomposite materials prepared in this study provide new ideas for the design of highly efficient electrocatalysts for the eCO2RR.
- Gong, Shanhe,Liu, Bin,Lu, Runqing,Lv, Xiaomeng,Sam, Daniel Kobina,Wang, Wenbo,Xiao, Xinxin
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p. 18290 - 18295
(2021/10/19)
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- PROCESS FOR CONVERTING ONE OR MORE METHYL HALIDES INTO ETHYLENE AND PROPYLENE
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The present disclosure concerns a process for converting methyl halides to ethylene and propylene, said process comprising the steps of (a) providing a feedstream comprising methyl halides; (b) providing a first and second catalyst composition, said second catalyst composition comprising a cracking catalyst; (c) contacting said feedstream with said first catalyst composition in a first reaction zone under first reaction conditions to provide a first product stream; and (d) subjecting at least a part of said first product stream to an Olefin Catalytic Cracking with said second catalyst composition in a second reaction zone under second reaction conditions to provide a second product steam. The process is remarkable in that said step (c) is performed under 400°C, and in that said first catalyst composition comprises molecular sieves with a Si/Al atomic between 2 and 18 and with a plurality of pores with a shape of an 8-membered ring or less.
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Page/Page column 29
(2021/05/29)
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- PROCESS FOR CONVERTING ONE OR MORE METHYL HALIDES INTO C3-C5 ALPHA OLEFINS
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The present disclosure relates to a process for converting methyl halides to C3-C5 α-olefins, said process comprising the steps of (a) providing a feedstream comprising methyl halides; (b) providing a first and second catalyst composition, said second catalyst composition comprising a metathesis catalyst; (c) contacting said feedstream with said first catalyst composition in a first reaction zone under first reaction conditions to provide a first product stream, and (d) contacting said first product stream with an olefin stream and with said second catalyst composition in a second reaction zone under second reaction conditions to provide a second product steam. The process is remarkable in that said step (c) is performed under 400°C, and in that said first catalyst composition comprises molecular sieves with a Si/Al atomic ratio between 2 and 18 and with a plurality of pores with a shape of an 8-membered ring or less.
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Page/Page column 27-29
(2021/05/29)
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- Rational construction of hierarchical SAPO-34 with enhanced MTO performance without an additional meso/macropore template
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A relatively facile strategy was rationally developed for the synthesis of hierarchical SAPO-34 using aluminum phosphate spheres as the nutrient and mesoporogen, without utilizing any additional meso/macropore-directing agents. The simple synthesis resulted in SAPO-34 (CHA) with classical rhombohedral morphology with dimensions between 2 and 3 μm and intracrystalline meso/macropores. It was demonstrated that the employment of spherical aluminum phosphate particles and the regulation of synthesis conditions to carry out the dissolution of aluminum phosphate spheres parallel to the crystallization process of the CHA phase were crucial factors leading to successful synthesis. The crystallization process of the hierarchical SAPO-34 was investigated and a possible crystallization model was proposed. The catalytic performances of the synthesized SAPO-34s in the MTO reaction were evaluated. The SAPO-34 with a hierarchical porous structure exhibited an improved catalytic lifespan and higher selectivity for light olefins. This work not only provides a new facile method to synthesize hierarchical SAPO-34 but also holds great promise for offering useful guidance for the synthesis of other aluminophosphate zeolites with hierarchical structures.
- Liang, Yafei,Gao, Beibei,Zhou, Lipeng,Yang, Xiaomei,Lu, Tianliang,Yao, Hongchang,Su, Yunlai
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p. 1859 - 1867
(2021/02/03)
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- CATALYST COMPOSITIONS AND METHODS OF PREPARATION AND USE THEREOF
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Disclosed are catalyst compositions containing a hydrogen/copper-chabazite (H/Cu- CHA) zeolite with silica (SiO2) and alumina (AI2O3) at a silica-alumina ratio (SAR) of about 5:1 to about 50:1 and about 0.1 wt% to about 5.0 wt% of a copper oxide. Also disclosed are methods of preparation and methods of use thereof.
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Paragraph 0006-0010; 0017-0018; 0056-0059; 0069-0070
(2021/03/05)
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- Investigation of the Effect of Crystallization Temperature and Time in Synthesis of SAPO-34 Catalyst for the Production of Light Olefins
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Abstract: In this paper, the effect of variation of crystallization temperatures and times on the synthesis of SAPO-34 catalysts for conversion of methanol to light olefins has been investigated. These are two of the very effective parameters in the synthesis of SAPO-34 which affect phase purity, crystallinity, acidic properties, and finally the performance of catalysts. For this purpose, 9 samples have been synthesized by varying of temperature and time of crystallization in the range of 170–210°C, 12–36 h, respectively and the molar ratio of 1Al2O3 : 1P2O5 : 0.4 SiO2: 0.5 TEAOH : 1.5 MOR : 70 H2O and characterized by XRD, SEM, FTIR, BET, and NH3–TPD techniques. Finally, performance of catalysts was investigated in the process of conversion of methanol to light olefins in a fixed-bed reactor 410°C. The results show that crystallinity, phase purity, size, and distribution of particles, surface area, and acidic properties have great effects on performance and selectivity of ethylene and propylene and these properties themselves severely depend on Crystallization temperature and time. The results of characterized of catalysts show that high characterized temperature, reduces the phase purity and increases size in particles. The catalysts that have been synthesized at 190°C and 24 h have the highest crystallinity, suitable size, and distribution of particles, high surface area, and suitable acidic sites, so it has the highest selectivity of light olefins at MTO process.
- Kianfar
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p. 527 - 537
(2021/04/09)
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- High-efficient hierarchical [B]-ZSM-5 catalyst by simultaneously using of CTAB surfactant and boron promoter for methanol to olefins reaction
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In this work, a one-pot hydrothermal route was applied to prepare the hierarchical high-silica ZSM-5 catalyst (Si/Al = 200), including boron promoter in the structure and CTAB surfactant. XRD, FE-SEM, BET, NH3-TPD, and FT-IR techniques were applied to evaluate the physical and chemical properties. The effect of different amounts of secondary template (CTAB) and different operating conditions was studied on the ZSM-5 catalyst preparation and performance in methanol to olefins reaction. The results showed the high surface area (391.8?m2g?1), mesoporous structure, high crystallinity, and well-adjusted acidity for the modified catalyst. The prepared catalyst with CTAB/TPABr molar ratio of 1 led to the highest propylene selectivity (48.56%), the highest P/E ratio of 6.3, and the highest light olefin selectivity (71%). This improved performance can be assigned to the high surface area, short diffusion path length by mesopore structure, and optimum acidity. It was found that the optimum temperature and weight hourly space velocity were 480?°C and 7.2?h?1, respectively.
- Dalirian, Fereshte,Rostamizadeh, Mohammad,Alizadeh, Reza
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p. 3201 - 3215
(2021/04/26)
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- The hydrothermal synthesis of hierarchical SAPO-34 with improved MTO performance
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The fabrication of intracrystalline secondary pores is an important approach to improve the catalytic performance of microporous zeolites. Herein, a two-step crystallization process using only TEAOH/TEA has been developed for the hydrothermal synthesis of hierarchical SAPO-34. When crystalline AlPO4characterized with four-coordinated aluminum and phosphorus atoms was applied, hierarchical SAPO-34 could hydrothermally be synthesized under thenH2O?:?nAl2O3> 20 condition, and the crystallization process was analyzed. The crystalline AlPO4is beneficial for the SAPO-34 synthesis, and hierarchical SAPO-34 with abundant intracrystalline secondary porosity can be efficiently synthesized in 2 h. Although both the distribution range and volume of the mesopores decrease with time, the mesopore volume of hierarchical SAPO-34-31 achieved 0.069 cm3g?1. Furthermore, the silicon atoms in hierarchical SAPO-34-31 are mainly in the Si(OAl)4and Si(OSi)(OAl)3states, and the accessibility would be improved by the intracrystalline mesopores (16-20.3 nm). SAPO-34-31 exhibited more excellent MTO activity than the nano-sized SAPO-34, and the selectivity of ethylene and propylene achieved more than 80%, while thenC2H4?:?nC3H6is always about 0.8.
- Rui, Peixin,Wang, Baorong,Chen, Feibiao,Xiang, Yanjuan,Yang, Jianming,Guo, Tao,Wu, Zheng,Liao, Weilin,Shu, Xingtian
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p. 11093 - 11100
(2021/07/06)
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- Embryonic zeolite-assisted synthesis of SSZ-13 with superior efficiency and their excellent catalytic performance
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An X-ray amorphous material with a CHA-like structure, named embryonic CHA zeolite, has been designed and employed for the synthesis of SSZ-13, which leads to ultra-fast crystallization (1.5-12 h), wide product SiO2/Al2O3ratio (SAR = 22-100) and high yield (82.8-92.9%). The usage ofN,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) for the synthesis can be controlled at unprecedentedly low amounts (TMAdaOH/SiO2= 0.035-0.050). Characterization results reveal that the embryonic zeolite has a small particle size of 10-20 nm, large micro/mesopore volume and abundant double 6-ring units (subunits of the CHA structure). It provides ample active surface and subunits for the formation of the CHA structure and promotes the fast synthesis of SSZ-13 with a wide phase region. The resultant material (SAR = 23.2), after Cu2+exchange, exhibits superior NH3-SCR activity and extraordinary hydrothermal stability (steaming at 800 °C for 16 h), implying its promising application for NOxremoval. In addition, high-silica SSZ-13 shows good catalytic performance for the MTO reaction. It is anticipated that the embryonic zeolite-assisted strategy will benefit the synthesis of more industrially important zeolites.
- Cui, Wenhao,Fan, Dong,Han, Jingfeng,Li, Bing,Liu, Zhongmin,Tian, Peng,Wang, Juan,Wang, Linying,Zhu, Dali
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p. 15238 - 15245
(2021/07/21)
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- Generating Assembled MFI Nanocrystals with Reduced b-Axis through Structure-Directing Agent Exchange Induced Recrystallization
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Controlling crystal size and shape of zeolitic materials is an effective way to promote their mass transport and catalytic properties. Herein, we report a single step, Na+- and porogen- free crystallization of MFI hierarchical architecture made up of aligned nanocrystals with reduced b-axis thickness (5–23 nm) and adjustable Si/Al ratios between 35 to 120, employing the commonly used tetrapropylammonium hydroxide (TPAOH) and tetrabutylammonium hydroxide (TBAOH) as structure-directing agents (SDAs). Homogeneous nucleation driven by both SDAs and subsequent SDA-exchange induced dissolution-recrystallization are responsible for the formation of such structure. The enhanced textural and diffusion properties account for a notable exaggeration of propene selectivity and catalyst lifetime in dimethyl ether-to-olefins (DTO) conversion. This protocol is extendable to the rational synthesis of other hierarchical zeolites through crystallization process control.
- Zhao, Xiaoling,Zeng, Shu,Zhang, Xueliang,Deng, Quanzheng,Li, Xiujie,Yu, Wenguang,Zhu, Kake,Xu, Shutao,Liu, Jichang,Han, Lu
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supporting information
p. 13959 - 13968
(2021/05/19)
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- CATALYST, AND METHOD FOR DIRECT CONVERSION OF SYNGAS TO PREPARE LIGHT OLEFINS
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A process for direct synthesis of light olefins uses syngas as the feed raw material. This catalytic conversion process is conducted in a fixed bed or a moving bed using a composite catalyst containing components A and B (A+B). The active ingredient of catalyst A is metal oxide; and catalyst B is an oxide supported zeolite. A carrier is one or more of Al2O3, SiO2, TiO2, ZrO2, CeO2, MgO and Ga2O3 having hierarchical pores; the zeolite is one or more of CHA and AEI structures. The loading of the zeolite is 4%-45% wt. A weight ratio of the active ingredients in the catalyst A and the catalyst B is within a range of 0.1-20, and preferably 0.3-5. The total selectivity of the light olefins comprising ethylene, propylene and butylene can reach 50-90%, while the selectivity of a methane byproduct is less than 15%.
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Paragraph 0064-0067
(2021/01/26)
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