- Reductive dehydration of butanone to butane over Pt/γ-Al 2O3 and HZSM-5
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We show that butanone can be reacted to form n-butane in an isothermal reactor containing a 1 wt.% Pt/γ-Al2O3 and an HZSM-5 catalyst (total mass of 12-400 mg, Si/Al = 11.5) below 160 C with up to 99% selectivity and 67% yield. The catalyst loading (12-400 mg) and temperature (100-250 C) were varied to obtain primary products whose selectivities decreased with conversion and secondary/tertiary products whose selectivities increased with conversion. As conversion increased, the selectivities of butanol and butene decreased, showing the formation of butane from butanone through a series reaction pathway: butanone → 2-butanol → butene → butane. Butane selectivity increased as the temperature was increased from 100 to 200 C when compared at similar conversions due to higher dehydration rates over the zeolite. Processing ketones at low temperatures over bifunctional catalysts may be an efficient means of obtaining high yields of stable paraffins from reactive oxygenates.
- Blass, Samuel D.,Rosenthal, Corey,Bhan, Aditya,Schmidt, Lanny D.
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- Deceptive Similarities in the Reactions of Fe+ and Co+ with Linear Nitriles in the Gas Phase
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The gas-phase reactions of the transition-metal ions Fe+ and Co+ with linear C(4)-C(12) nitriles are reported.In spite of an overall similar reactivity pattern, a more detailed analysis, based on the study of labeled nitriles, reveals distinct differences with regard to the mechanisms of elimination of alkenes and alkanes.For both metal ions, hydrogen and alkenes are generated from linear C(4)-C(12) nitriles, and the intermediates are formed via oxidative addition to terminal and internal C-H bonds.For the RCN/Fe+ system insertion in an internal C-H bond commences at position C(8) of the nitrile; for the analogous RCN/Co+ system, the oxidative addition to an internal C-H bond starts at position C(7) of the nitrile.Similarly, alkane formation is different for the two transition-metal ions.For RCN/Fe+ the generation of alkanes is observed for nitriles having at least eight carbon atoms; in contrast, the elimination of alkanes from RCN/Co+ is already observed for C(6) nitriles.Alkane elimination seems to follow the conventional mechanism (i.e., oxidative addition to a C-C bond, β-hydrogen transfer, and reductive elimination) for the RCN/Co+ system, whereas for the RCN/Fe+ complex there exists an additional mechanism.This mechanism corresponds to the loss of H2 from an internal position of the alkyl chain followed by the elimination of an alkene.Some possible origins of the different behavior of Fe+ vs.Co+ are discussed.
- Lebrilla, Carlito B.,Drewello, Thomas,Schwarz, Helmut
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- Cobalt-Iron-Manganese Catalysts for the Conversion of End-of-Life-Tire-Derived Syngas into Light Terminal Olefins
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Co-Fe-Mn/γ-Al2O3 Fischer–Tropsch synthesis (FTS) catalysts were synthesized, characterized and tested for CO hydrogenation, mimicking end-of-life-tire (ELT)-derived syngas. It was found that an increase of C2-C4 olefin selectivities to 49 % could be reached for 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn/γ-Al2O3 with Na at ambient pressure. Furthermore, by using a 5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3 catalyst the selectivity towards the fractions of C5+ and CH4 could be reduced, whereas the selectivity towards the fraction of C4 olefins could be improved to 12.6 % at 10 bar. Moreover, the Na/S ratio influences the ratio of terminal to internal olefins observed as products, that is, a high Na loading prevents the isomerization of primary olefins, which is unwanted if 1,3-butadiene is the target product. Thus, by fine-tuning the addition of promoter elements the volume of waste streams that need to be recycled, treated or upgraded during ELT syngas processing could be reduced. The most promising catalyst (5 wt % Co, 5 wt % Fe, 2.5 wt % Mn, 1.2 wt % Na, 0.03 wt % S/γ-Al2O3) has been investigated using operando transmission X-ray microscopy (TXM) and X-ray diffraction (XRD). It was found that a cobalt-iron alloy was formed, whereas manganese remained in its oxidic phase.
- Falkenhagen, Jan P.,Maisonneuve, Lise,Paalanen, Pasi P.,Coste, Nathalie,Malicki, Nicolas,Weckhuysen, Bert M.
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- Catalytic: N -pentane conversion on H-ZSM-5 at high pressure
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The effect of temperature (633-723 K), pressure (10-60 bar) and weight hourly space velocity (WHSV) (400-1500 gC5 gcat-1 h-1) on the conversion of n-pentane on H-[Al]ZSM-5 type catalysts has been investigated. Catalyst properties were tested using a packed-bed laboratory microreactor and reaction products were analyzed via online gas chromatography. 5-25% pentane conversion was observed at a pressure of 40 bar and temperatures in the range of 633-723 K. Reactant consumption rate approached saturation kinetics at pressures above 30 bar (～14% conversion, 673 K). At 40 bar and 673 K, increasing WHSV (400-1500 gC5 gcat-1 h-1) resulted in a reduction in pentane conversion (26-10%). In all cases, propane and butane were the major products, followed by heavier C6+ compounds and other lighter products (C1-C4 paraffins and olefins). Propane carbon selectivity increased from 24% at 633 K to 34% at 723 K, while butane carbon selectivity (～40%) was nearly constant. An inverse relationship between the production of C6+ and light products was observed with changes in reaction conditions. The carbon selectivity to C6+ compounds increased from 20% at 10 bar to 27% at 60 bar and decreased from 28% at 633 K to 18% at 723 K. At all reaction conditions, the observed product distribution can be explained as the result of fast bimolecular reactions, including hydride transfer and alkylation.
- Schreiner, Edward P.,Teketel, Shewangizaw,Lobo, Raul F.
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- Hyrogenation of Carbon Monoxide, Aldehydes, and Unsaturated Hydrocarbons on Titania-Supported Palladium Catalysts
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Pd/TiO2 catalysts prepared by different methods showed quite different catalytic activities in the hydrogenation of CO and other unsaturated compouds.The catalyst prepared by coprecipitation od Pd acetate and titanium tetraisopropoxide contained smaller Pd particles than those in catalysts prepared by impregnation methods.In the hydrogenation of CO, activities of the catalysts increased with increase in the Pd dispersion.The coprecipitated catalyst was much more active for this reaction than the other catalysts and showed high activity for methanol formation under normal pressure.In the hydrogenation of propionaldehyde to 1-propanol, the catalysts showed similar behavior to that in the CO/H2 reaction.However, in hydrogenation of C=C double bonds, the activity order of the catalysts was reverse.Higher activity was obtained on the impregnated catalysts with larger Pd particle size and this trend was stronger in hydrogenation of the conjungated butadiene and C=C bond in acrylaldehyde than in the hydrogenation of ethylene.
- Wu, Jihong,Funakoshi, Masaki,Nagamoto, Hidetoshi,Komiyama, Hiroshi,Inoue, Hakuai
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- Role of Ga3+promoter in the direct synthesis of iso-butanolviasyngas over a K-ZnO/ZnCr2O4catalyst
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The direct synthesis of iso-butanol is an important reaction in syngas (composed of CO and H2) conversion. K-ZnO/ZnCr2O4(K-ZnCr) is a commonly used catalyst. Here, Ga3+is used as an effective promoter to boost the efficiency of the catalyst and retard the production of CO2. X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflection spectroscopy and electron microscopy were used to characterize the structural variations with different amounts of Ga3+, the results showed that the particle size of the catalyst decreases with the addition of Ga3+. The temperature-programmed desorption of NH3and CO2, and diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTs) analysis of the CO adsorption revealed that the acidity and basicity were altered owing to the different forms of Ga3+adoption. X-ray photoelectron spectroscopy and density functional theory (DFT) calculations revealed that the formation of Ga clusters that are coordinated on the exposed surfaces of ZnCr2O4, and undergo a tetra-coordinated Ga3+exchange with one of the Zn in ZnCr2O4(ZG) and ZnGa2O4, probably depends on the amount of Ga added. The structural evolution of the Ga3+promoted K-ZnO/ZnCr2O4catalysts can be described as follows: (i) the main forms are ZG and Ga coordinated ZnCr2O4, in which the amount of Ga3+is below 1.10 wt%; and (ii) the Ga3+containing compound is gradually changed from ZG to ZnGa2O4and the amount of gallium clusters increased when the amount of Ga3+was higher than 1.10 wt%. The catalytic performance evaluation results show that K-Ga1.10ZnCr exhibits the highest space time yield and selectivity of alcohols, in which the three compounds play different roles in syngas conversion: ZG is the main active site that boosts the efficiency of the catalysts, owing to the intensified CO adsorption and decreased activation energy of CHO formation through CO hydrogenation; ZnGa2O4only modifies the surface basicity and acidity on the catalyst, thereby impacting the carbon chain growth after the CO is adsorbed. The effects of Ga coordinated with ZnCr2O4shows little impact on the CO adsorption owing to the weak electron donating effects of Ga.
- Zhang, Tao,Zeng, Chunyang,Wu, Yingquan,Gong, Nana,Yang, Jiaqian,Yang, Guohui,Tsubaki, Noritatsu,Tan, Yisheng
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- Enzymatic Electrosynthesis of Alkanes by Bioelectrocatalytic Decarbonylation of Fatty Aldehydes
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An enzymatic electrosynthesis system was created by combining an aldehyde deformylating oxygenase (ADO) from cyanobacteria that catalyzes the decarbonylation of fatty aldehydes to alkanes and formic acid with an electrochemical interface. This system is able to produce a range of alkanes (octane to propane) from aldehydes and alcohols. The combination of this bioelectrochemical system with a hydrogenase bioanode yields a H2/heptanal enzymatic fuel cell (EFC) able to simultaneously generate electrical energy with a maximum current density of 25 μA cm?2 at 0.6 V and produce hexane with a faradaic efficiency of 24 %.
- Abdellaoui, Sofiene,Macazo, Florika C.,Cai, Rong,De Lacey, Antonio L.,Pita, Marcos,Minteer, Shelley D.
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- Influence of Strong Metal-Support Interaction on Exchange with Deuterium and other Reactions of Hydrocarbons. Part 1. - Studies with Rh/TiO2 and Rh/SiO2
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The changes in the catalytic properties of Rh/TiO2 caused by raising the reduction temperature from 473 to 773 K have been investigated for four reactions, the exchange with deuterium of methane and cyclopentane, and the hydrogenolysis of 2,2-dimethylpropane and methylcyclopentane.The so-called strong metal-support interaction (SMSI) brought about by the high-temperature reduction had least effect on the exchange of methane but reduced the rate of hydrogenolysis of 2,2-dimethylpropane by factors of 1E4 or 1E5.The SMSI was reversible and its influence on each of the reactions was eliminated by oxidation of the catalyst followed by low-temperature reduction.No marked changes in the catalytic behaviour of Rh/SiO2 resulted from increasing the reduction temperature.The results provide further evidence for the existence of a number of kinds of catalytic sites on Rh/TiO2.The sites for the more structure-sensitive reactions tend to be more seriously affected by SMSI and probably involve more metal atoms than the sites responsible for methane exchange.
- Costa Faro, Arnaldo da,Kemball, Charles
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- Skeletal Rearrangement of Alkanes over Ir/Al2O3. Transformation of n-Pentane, 2-Methylbutane and 2,2-Dimethylbutane
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Transformation of n-pentane, 2-methylbutane and 2,2-dimethylbutane has been investigated as a function of the H2/hydrocarbon ratio over a 10 wtpercent Ir/Al2O3 catalyst of 14 percent dispersion.The selectivity of isomer formation has been observed to decrease with the increase of the H2/hydrocarbon ratio and follow the sequence n-pentane > 2-methylbutane >> 2,2-dimethylbutane.The effect of the experimental conditions on the product selectivity has been interpreted considering the actual surface state of the working catalyst.
- Sarkany, Antal
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- On the Active Species of Aluminium(III) Bromide-Copper(II) Bromide Mixtures as Catalysts for the Isomerization of Pentane
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Mixtures of AlBr3 and CuSO4 have high catalytic activity and selectivity for the isomerization of pentane at room temperature.The isomerization obeys the first-order kinetics with respect to pentane and proceeds both in the liquid phase and on the surface of copper(II) sulphate.The complex formed from the two substances seems responsible for the catalytic activity.
- Kitajima, Nobumasa,Sakuma, Shigeharu,Ono, Yoshio
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- Catalytic behavior of graphite nanofiber supported nickel particles. 3. The effect of chemical blocking on the performance of the system
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Graphite nanofibers are a newly developed type of material produced by the catalytic decomposition of carbon containing gases at high temperatures. The individual components of these conformations, small-sized graphite crystallites, are arranged in such a manner that only the edge regions are exposed. The carbon atoms at these sites that are arranged in two conformations, `armchair' or `zigzag', act as templates for the nucleation of metal crystallites. Treatment of graphite with certain phosphorus compounds is a process that is known to result in preferential blocking of the `armchair' faces, whereas boron oxide selectively substitutes into the `zigzag' faces. In the current investigation pretreatment in phosphorus oxide was found to exert little or no effect on the subsequent catalytic performance of graphite nanofiber supported nickel with respect to hydrogenation of ethylene and 1-butene. In contrast, incorporation of boron into the carbonaceous support, which resulted in blockage of the `zigzag' sites of the graphite nanofibers rendered the supported metal system virtually inactive toward hydrogenation of either of the olefins. These results suggest that the active state of nickel is one where the particles are preferentially located on the `zigzag' faces of the nanofiber structures. Under these conditions the metal particles adopt a crystallographic arrangement that is favorable toward reaction with both reactant molecules. It is evident that one can control the catalytic behavior of a given metal by careful tailoring the support structure at the atomic level.
- Park, Colin,Baker, R. Terry K.
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- Cleavage of Unactivated Si?C(sp3) Bonds with Reed's Carborane Acids: Formation of Known and Unknown Silylium Ions
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An efficient method for the benzenium-ion-mediated cleavage of inert Si?C(sp3) bonds is reported. Various tetraalkylsilanes can thus be converted into the corresponding counteranion-stabilized silylium ions. The reaction is chemoselective in the case of hexamethyldisilane. Computations reveal a mechanism with backside attack of the proton at one of the alkyl groups. Several activated Si?C(spn) bonds (n=3–1) react equally well, and the procedure can be extended to the generation of stannylium ions.
- Wu, Qian,Qu, Zheng-Wang,Omann, Lukas,Irran, Elisabeth,Klare, Hendrik F. T.,Oestreich, Martin
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- A robust platinum carbonyl cluster anion [Pt3(CO)6]52- encapsulated in an ordered mesoporous channel of FSM-16: FTIR/EXAFS/TEM characterization and catalytic performance in the hydrogenation of ethene and 1,3-butadiene
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A robust trigonal prismatic cluster anion [Pt3(CO)6]52- (vCO = 2078, 1878 cm-1; ??max = 405 and 702 nm; R1(Pt - Pt) = 2.68 Aì? (CN = 2.0); R2(Pt - Pt) = 3.08 Aì? (CN = 1.5)) is selectively synthesized in the ordered hexagonal channel of FSM-16 by the reductive carbonylation of H2PtCl6TNR4+/FSM-16 under a CO + H2O atmosphere at 323 K. The Pt cluster anion extracted in THF solution by cation metathesis was identified as [Pt3(CO)6]52- by FTIR and UV - vis spectroscopic data. TEM observation showed that [Pt3(CO)6]52- was uniformly dispersed and aligned in the mesoporous channels of FSM-16. The Pt15 cluster anions formed in FSM-16 were relatively stabilized by the coimpregnated quaternary alkylammonium cations as NR4+ in the following order for the alkyl groups: butyl > ethyl > methyl, methyl viologen (MV) > hexyl a?? no countercations. The EXAFS and FTIR studies demonstrated that [Pt3(CO)6]52- in FSM-16 was transformed by the controlled removal of CO at 300-343 K into the partially decarbonylated Pt15 cluster (R1(Pt - Pt) = 2.69 Aì?, CN = 2.2; R2(Pt - Pt) = 3.10 Aì?, CN = 1.4). This sample showed IR spectra indicating a linear CO (vCO = 2062 cm-1) without a bridged one. The Pt carbonyl cluster was eventually converted by thermal evacuation exceeding 463 K to naked Pt particles (15 Aì? diameter; R(Pt - Pt) = 2.76 Aì?, CN = 7.8). The controlled removal of CO from [Pt3(CO)6-x]52- in FSM-16 by thermal evacuation at 300-423 K yields samples with marked catalaytic activities for hydrogenation of ethene and 1,3-butadiene at 300 K. 1,3-Butadiene is selectively hydrogenated to 1-butene on the partially decarbonylated Pt carbonyl clusters in FSM-16, whereas it is preferentially converted to n-butane on the naked Pt particles in FSM-16.
- Yamamoto, Takashi,Shido, Takafumi,Inagaki, Shinji,Fukushima, Yoshiaki,Ichikawa, Masaru
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- THIOPHENE HYDRODESULFURIZATION OVER RHENIUM SURFACES: THE EFFECTS OF STRUCTURE AND ADSORBATES (C AND S)
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Thiophene hydrodesulfurization (HDS) has been investigated over rhenium single crystals and polycrystalline foils and was found to be a structure-sensitive reaction over these surfaces.Rhenium single crystals are 1-6 times more active than molybdenum single crystals, which is in agreement with prevoius studies using rhenium disulfide and molybdenum disulfide catalysts.Adsorbed carbon and sulfur overlayers decrease the activity of the rhenium single crystals, suggesting that the catalyst surfaces remain free of strongly bound deposits of carbon and/or sulfur.The trend in HDS activity measured for the Re catalysts can be explained by considering the difference in coordination of the top layer rhenium atoms in the single-crystal surfaces.
- Bussell, Mark E.,Somorjai, Gabor A.
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- Selective hydrogenation of 1,3-butadiene on PdNi bimetallic catalyst: From model surfaces to supported catalysts
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The selective hydrogenation of 1,3-butadiene serves as a means to purify the butene stream generated from cracking naphtha or gas oil. To identify selective hydrogenation catalysts, 1,3-butadiene was studied on single crystal Ni/Pd(1 1 1) bimetallic surfaces, utilizing density functional theory (DFT) calculations and temperature-programmed desorption (TPD). DFT calculations predicted that the Pd-terminated bimetallic surface should be more active and selective to produce 1-butene, which were verified experimentally using TPD. The promising results on model surfaces were extended to γ-Al 2O3-supported catalysts using both batch and flow reactors. Extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) confirmed the formation of bimetallic nanoparticles. The PdNi bimetallic catalyst showed higher hydrogenation activity and 1-butene selectivity than the monometallic catalysts. The excellent correlation between model surfaces and supported catalysts demonstrates the feasibility of designing effective bimetallic catalysts for selective hydrogenation reactions.
- Hou, Ruijun,Yu, Weiting,Porosoff, Marc D.,Chen, Jingguang G.,Wang, Tiefeng
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- In Situ Fourier Transform Infrared Study of Crotyl Alcohol, Maleic Acid, Crotonic Acid, and Maleic Anhydride Oxidation on a V-P-O industrial Catalyst
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Crotyl alcohol, maleic acid, crotonic(2-butenoic) acid, and maleic anhydride were fed to an in situ infrared cell at 300 deg C containing a P/V = 1.1 vanadium-phosphorus-oxide (V-P-O) catalyst used for the selective oxidation of n-butane.Crotyl alcohol was used as a mechanistic probe for the formation of reactive olefin species observed during previous n-butane and 1-butene studies.Crotonic acid, maleic acid, and maleic anhydride were fed as probes for the existence of other possible adsorbed intermediates.Olefin species and maleic acid are proposed as possible reaction intermediates in n-butane selective oxidation to maleic anhydride.The involvement of peroxide species in the oxidation of butadiene to maleic acid is also discussed.
- Wenig, Robert W.,Schrader, Glenn L.
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- Production of high-calorie synthetic natural gas using copper-impregnated iron catalysts
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Fe-Cu catalysts were applied in the production of high-calorie synthetic natural gas (HC-SNG), wherein a proper level of C2–C4 hydrocarbon selectivity must be secured. The Fe-Cu catalysts were activated by reduction under diluted CO gas before the reaction, and their catalytically active Fe phases changed according to the reduction temperature: Fe3O4 formed when reduced at 300 °C, carbon-deficient FeCx at 400 °C and Fe3C at 500 °C. Iron carbide catalysts achieved stronger CO adsorption and higher BET surface area than Fe3O4 catalysts, which resulted in higher CO conversion. The carbon-deficient FeCx was metal-like in its electron structure due to the low number of bonded carbons, and it was attributed to the highest CO and H2 conversion of FC15-400R by providing H2 activation ability. The Cn (n ≥ 2) selectivity or carbon chain growth of the hydrocarbons increased as the carburization degree of the active Fe phase increased, which was associated with an increase in the CO chemisorption strength. The impregnated Cu exerted little influence on the product selectivity, but it promoted hydrogen adsorption, thereby improving the paraffin-to-olefin ratio of the produced hydrocarbons.
- Lee, Yong Hee,Lee, Dae-Won,Lee, Kwan-Young
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- Parahydrogen-induced polarization (PHIP) in heterogeneous hydrogenation over bulk metals and metal oxides
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The results show that, in general, observation of PHIP effects on metals does not require the presence of a support. In addition, certain metal oxides can produce PHIP effects in the absence of a supported metal. The new promising catalysts for producing PHIP heterogeneously have been identified. The Royal Society of Chemistry.
- Kovtunov, Kirill V.,Barskiy, Danila A.,Salnikov, Oleg G.,Khudorozhkov, Alexander K.,Bukhtiyarov, Valery I.,Prosvirin, Igor P.,Koptyug, Igor V.
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- Ethane conversion in the presence of iron- and manganese-promoted sulfated zirconium dioxide: Evidence of autocatalysis and oligocondensation chemistry
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Ethane reacts in the presence of Fe- and Mn-promoted sulfated ZrO2 to form butane, ethene, methane and H2 at temperatures ≥473 K; the data indicate autocatalysis with carbocation intermediates as in superacid solution chemistry.
- Cheung, Tsz-Keung,Gates, Bruce C.
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- Quantitative determination of volatile products formed in electrolyses of organic compounds
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A straightforward and accurate procedure has been developed for the quantitation of volatile products that are formed from electrolyses of organic compounds. This methodology, which eliminates the need for external cold traps, utilizes an internal standard that is present in both the solution and gas phases of a gas-tight electrochemical cell. By sampling the gas and solution phases of the cell at the end of an electrolysis and by using gas chromatography to determine the quantities of the various volatile products in each phase with respect to the internal standard, one can ascertain the absolute yield of each product derived from the electrolysis of the starting material. In this paper, we present the theoretical background for this technique, including the formulation and use of experimentally measured gas chromatographic response factors, and we demonstrate the applicability of the approach for the quantitation of seven volatile products that are formed by the electrolytic reduction of 1,4-dibromobutane at a reticulated vitreous carbon cathode in dimethylformamide containing tetramethylammonium perchlorate. This method can be readily adapted to any compound whose electrolysis gives rise to volatile products.
- Pritts, Wayne A.,Vieira, Kenneth L.,Peters, Dennis G.
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- Rate coefficients and products of ethyl and vinyl cross-radical reactions
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Rate constants and products for cross-radical reactions of vinyl (C2H3) and ethyl (C2H5) radicals have been determined at T = 298 K and a total pressure (predominately helium) of 93.3 kPa (700 Torr). C2H3 and C2H5 were produced simultaneously through the 193-nm excimer laser photolysis of dilute mixtures of C2H5COC2H3 (EVK)/He. This is the first report of direct rate determination for the C2H5 + C2H5 reaction and using the photolysis of EVK as a precursor for producing a nearly 1:1 ratio of C2H5/C2H3. Time-resolved UV absorption spectroscopy and gas chromatographic/mass spectroscopic (GC/MS) product analysis methods were employed for kinetics and product studies. Major reaction products consisted of n-butane, 1,3-butadiene, and 1-butene which are formed, respectively, through the combination reactions: C2H5 + C2H5 → n-butane (1c), C2H3 + C2H3 → 1,3-butadiene (2c,) and C2H5 + C2H3 → 1-butene (3c). Minor products, ethane, ethylene, and acetylene, result from disproportionation reactions. Analysis of the temporal absorptions at 230 and 235 nm through kinetic modeling of the reaction system resulted in an overall rate constant of k3 = 9.6 × 10-11 cm3 molecule-1 s-1 for the C2H5 + C2H3 cross-radical reaction. A detailed error analysis with estimates of both random error and systematic errors for each parameter in the model was performed; the resulting combined uncertainty on the rate constant k3 is ±1.9 × 10-11 cm3 molecular-1 s-1. Using previously published rate constants for the combination reactions 1c and 2c [2.0 × 10-11 and 9.3 × 10-11 cm3 molecule-1 s-1, respectively], and relative yields of the combination products the rate constant for the cross-combination reaction k3c [C2H3 + C2H5] c alculated to be (6.5 ± 1) × 10-11 cm3 molecule-1 s-1.
- Fahr, Askar,Tardy, Dwight C.
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- SPIROANNELATION VIA GEM-DIHALOCYCLOPROPANE SUBSTRATES AND A CYCLOCUPRATE SPECIES
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The dialkylation of gem-dibromocyclopropanes with a new 'cyclocuprate' species to yield spiro compounds is possible if the reaction is performed in the presence of a lithium acetylide.
- Scott, Frederick,Mafunda, Brownlee G,Normant, Jean F.,Alexakis, Alexandre
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- Catalytic Properties of Low-valent Lanthanide Species introduced into Y-Zeolite
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Low-valent ytterbium or europium species were introduced into Y-zeolites by impregnation from ytterbium or europium metal dissolved in liquid ammonia.The zeolites thus loaded with ytterbium or europium have a high catalytic activity for the isomerization of but-1-ene at 273 K, when they were heated under vacuum at ca. 500 K.Their catalytic activities are strongly influenced by the alkali-metal cations present in the Y-zeolite.The isomerization proceeds via an allylic carbanion-type intermediate.On the other hand, the zeolites heated under vacuum around 900 K areactive for the hydrogenation of ethene at 273 K, and buta-1,3-diene at 323 K.The photoluminescence of europium supported on zeolites and temperature-programmed desorption spectra of gases desorbed from zeolites loaded with europium or ytterbium suggest that metal imides such as EuNH, and metal-like species may be formed by the zeolites under vacuum at ca. 500 and 900 K, respectively.
- Baba, Toshida,Kim, Geon Joong,Ono, Yoshio
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- Effect of hydrogen on the cracking mechanisms of cycloalkanes over zeolites
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Hydrocracking of secondary interest refinery streams (high aromatic content) can yield valuable products for transportation and petrochemical industry. In order to promote the hydrogenation and cracking steps, a bifunctional catalyst (metal + acid function) is required. We have studied the effect of the operating conditions on cycloalkane (product of aromatic hydrogenation) ring opening over a monofunctional HZSM-5 zeolite, by focusing on the effect of hydrogen in the cracking mechanisms. Methylcyclohexane has been selected as the test reactant and the conditions used corresponds to temperature, 250-450 °C; space velocity, 0.7-1.1 h-1; pressure, 2-80 bar; hydrogen/methylcyclohexane molar ratio, 1-79; conversion, 0-100% (integral reactor). At these conditions the zeolite catalyses hydrogenation as well as cracking (bifunctional capabilities), thus the cracking mechanisms are directly affected by hydrogen as products (alkenes) and intermediates (carbenium ions) are saturated. The overall effect of rising hydrogen partial pressure is an enhancement of (hydro)isomerization and monomolecular cracking, that is, an increase of the yield/selectivity of methane, ethane, penthane and isoalkanes.
- Casta?o, Pedro,Arandes, José M.,Olazar, Martin,Bilbao, Javier,Pawelec, Bárbara,Sedrán, Ulises
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- Bimetallic Au-Pd alloy nanoparticles supported on MIL-101(Cr) as highly efficient catalysts for selective hydrogenation of 1,3-butadiene
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Gold-palladium (Au-Pd) bimetallic nanoparticle (NP) catalysts supported on MIL-101(Cr) with Au : Pd mole ratios ranging from 1 : 3 to 3 : 1 were prepared through coimpregnation and H2reduction. Au-Pd NPs were homogeneously distributed on the MIL-101(Cr) with mean particle sizes of 5.6 nm. EDS and XPS analyses showed that bimetallic Au-Pd alloys were formed in the Au(2)Pd(1)/MIL-101(Cr). The catalytic performance of the catalysts was explored in the selective 1,3-butadiene hydrogenation at 30-80 °C on a continuous fixed bed flow quartz reactor. The bimetallic Au-Pd alloy particles stabilized by MIL-101(Cr) presented improved catalytic performance. The as-synthesized bimetallic Au(2)Pd(1)/MIL-101(Cr) with 2 : 1 Au : Pd mole ratio showed the best balance between the activity and butene selectivity in the selective 1,3-butadiene hydrogenation. The Au-Pd bimetallic-supported catalysts can be reused in at least three runs. The work affords a reference on the utilization of a MOF and alloy nanoparticles to develop high-efficiency catalysts.
- Guo, Luxia,Jiang, Shuai,Li, Yingjie,Liu, Lili,Tai, Xishi,Yan, Shijuan,Zhou, Xiaojing
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- UV-induced photolysis of diethyl selenium and diethyl tellurium: extrusion of selenium and tellurium via molecular elimination of ethene
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KrF laser-induced photolysis of gaseous (C2H5)2M (M = Se, Te) compounds is shown to be a one-photon process controlled by the cleavage of both C-M bonds. It is dominated by the molecular elimination of ethene and yields elemental selenium and tellurium.
- Pola, Josef,Ouchi, Akihiko
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- Kinetic and Mechanistic Assessment of Alkanol/Alkanal Decarbonylation and Deoxygenation Pathways on Metal Catalysts
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This study combines theory and experiment to determine the kinetically relevant steps and site requirements for deoxygenation of alkanols and alkanals. These reactants deoxygenate predominantly via decarbonylation (C-C cleavage) instead of C-O hydrogenolysis on Ir, Pt, and Ru, leading to strong inhibition effects by chemisorbed CO (CO?). C-C cleavage occurs via unsaturated species formed in sequential quasi-equilibrated dehydrogenation steps, which replace C-H with C-metal bonds, resulting in strong inhibition by H2, also observed in alkane hydrogenolysis. C-C cleavage occurs in oxygenates only at locations vicinal to the C=O group in RCCO? intermediates, because such adjacency weakens C-C bonds, which also leads to much lower activation enthalpies for oxygenates than hydrocarbons. C-O hydrogenolysis rates are independent of H2 pressure and limited by H?-assisted C-O cleavage in RCHOH? intermediates on surfaces with significant coverages of CO? formed in decarbonylation events. The ratio of C-O hydrogenolysis to decarbonylation rates increased almost 100-fold as the Ir cluster size increased from 0.7 to 7 nm; these trends reflect C-O hydrogenolysis reactions favored on terrace sites, while C-C hydrogenolysis prefers sites with lower coordination, because of the relative size of their transition states and the crowded nature of CO?-covered surfaces. C-O hydrogenolysis becomes the preferred deoxygenation route on Cu-based catalysts, thus avoiding CO inhibition effects. The relative rates of C-O and C-C cleavage on these metals depend on their relative ability to bind C atoms, because C-C cleavage transitions states require an additional M-C attachment.
- Gürbüz, Elif I.,Hibbitts, David D.,Iglesia, Enrique
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- Evidence for Surface Phosphinidene Intermediates Mg> in the Heterogeneous Dechlorination of Alkyldichlorophosphanes RPCl2 by Mg Metal
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The heterogeneous dechlorination of alkyldichlorophosphanes by Mg metal at 600 K yields chemisorbed products which include penta-alkylcyclopentaphosphanes (RP)5, in addition to RnPH(3-n), R2P-PR2, P4, RH, and R-R, and thus provides evidence for surface phosphinidene intermediates Mg>.
- Bock, Hans,Bankmann, Martin
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- Effects of the proton content of ZSM-5 and the amount of Pt on the hydrodesulfurization activity of Pt/ZSM-5
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The effects of the proton content of ZSM-5 and the amount of Pt on the hydrodesulfurization (HDS) activity of Pt/ ZSM-5 were studied. The extent of proton exchange was shown to affect the reaction selectivity, the formation of aromatics, the cracking of hydrocarbons, and the dispersion of Pt. The HDS activity depended on the surface area of loaded Pt. A catalyst consisting of 5 wt% Pt supported on a 50% cation exchanged ZSM-5 gave a higher HDS activity than other tested catalysts and a small amount of cracking products.
- Kurosaka, Tadahiro,Sugioka, Masatoshi,Matsuhashi, Hiromi
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- Al13Fe4 selectively catalyzes the hydrogenation of butadiene at room temperature
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The hydrogenation of butadiene has been investigated for the first time on Al13Fe4. The model (010) surface of this non-noble metal combination appears to be both active and selective under mild reaction conditions. The performances of Al13Fe4 for CC bond hydrogenation are compared with those of the reference noble metal, palladium.
- Piccolo, Laurent
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- Catalytic reduction of iodoethane and 2-iodopropane at carbon electrodes coated with anodically polymerized films of nickel(II) salen
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In acetonitrile containing tetramethylammonium tetrafluoroborate, nickel(II) salen undergoes anodic polymerization onto a carbon electrode. Nickel(II) in the polymer film exhibits reversible one-electron reduction to form nickel(I), which can catalytically reduce iodoethane or 2-iodopropane to form an ethyl or 2-propyl radical, respectively, and to regenerate nickel-(II). Kinetics studies with the aid of hydrodynamic voltammetry indicate that the catalytic reduction of iodoethane belongs to the ER regime of Saveant and co-workers, whereas catalytic reduction of 2-iodopropane is of the S classification. Controlled-potential electrolyses of iodoethane and 2-iodopropane at nickel-(II) salen-coated reticulated vitreous carbon cathodes give product distributions in accord with the relative importance of radical coupling and disproportionation. Direct reduction of iodoethane at a bare cathode generates products via a carbanion mechanism. Products obtained from direct reduction of 2-iodopropane depend on the potential employed; at a potential corresponding to the first voltammetric wave, product distributions are nearly identical with those obtained from the catalytic reduction, whereas at a potential after the second voltammetric wave, the products are derived from the 2-propyl carbanion.
- Dahm, Christopher E.,Peters, Dennis G.
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- ATP-independent substrate reduction by nitrogenase P-cluster variant
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The P-cluster of nitrogenase is largely known for its function to mediate electron transfer to the active cofactor site during catalysis. Here, we show that a P-cluster variant (designated P*-cluster), which consists of paired [Fe4S4]-like clusters, can catalyze ATP-independent substrate reduction in the presence of a strong reductant, europium (II) diethylenetriaminepentaacetate [Eu(II)-DTPA]. The observation of a decrease of activity in the rank ΔnifH, ΔnifBΔnifZ, and ΔnifB MoFe protein, which corresponds to a decrease of the amount of P*-clusters in these cofactor-deficient proteins, firmly establishes P*-cluster as a catalytically active metal center in Eu(II)-DTPA-driven reactions. More excitingly, the fact that P*-cluster is not only capable of catalyzing the two-electron reduction of proton, acetylene, ethylene, and hydrazine, but also capable of reducing cyanide, carbon monoxide, and carbon dioxide to alkanes and alkenes, points to a possibility of developing biomimetic catalysts for hydrocarbon production under ambient conditions.
- Lee, Chi Chung,Hu, Yilin,Ribbe, Markus W.
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- Infrared Spectra of Gas-Phase 1- and 2-Propenol Isomers
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Fourier transform infrared spectra of isolated 1-propenol and 2-propenol in the gas-phase have been collected in the range of 900-3800 cm-1, and the absolute infrared absorption cross sections reported for the first time. Both cis and trans isomers of 1-propenol were observed with the trans isomer in greater abundance. Syn and anti conformers of both 1- and 2-propenol were also observed, with abundance consistent with thermal population. The FTIR spectrum of the smaller ethenol (vinyl alcohol) was used as a benchmark for our computational results. As a consequence, its spectrum has been partially reassigned resulting in the first report of the anti-ethenol conformer. Electronic structure calculations were used to support our experimental results and assign vibrational modes for the most abundant isomers, syn-trans-1-propenol and syn-2-propenol.
- Shaw, Miranda F.,Osborn, David L.,Jordan, Meredith J. T.,Kable, Scott H.
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- Selective Lanthanide-catalysed Reactions. Catalytic Properties of Sm and Yb Metal Vapour Deposition Products
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The characteristics of lanthanide catalysts obtained when Sm and Yb were vaporized into a frozen organic (tetrahydrofuran, benzene and methylcyclohexane) matrix (77 K) were investigated.These low-valent, highly dispersed lanthanide particles (indicated as Sm/THF, Sm/benzene, Yb/THF, Yb/benzene etc.) were catalytically active and selective for hydrogenation and isomerization.Samarium usually showed a greater activity than ytterbium.Olefin hydrogenation obeyed the rate law v=kPH, suggesting that the reaction is controlled by catalytic activation of hydrogen.The molecular isotopic identity of hydrogen was conserved during the hydrogenation.Yb/THF and Yb/benzene were active for partial hydrogenation of benzene to cyclohexene.For the hydrogenation of olefins and acetylenes the substrate specificity was high; thus C-C double bonds were more readily reduced than triple bonds.The samarium and ytterbium catalysts discriminate between terminal and internal C-C triple bonds, only internal CC bonds (but-2-yne and pent-2-yne) being reduced very selectively in contrast to acetylene, methylacetylene and but-1-yne.Solid base character of the lanthanide provides a cause for these differences in catalytic properties.
- Imamura, Hayao,Kitajima, Keiji,Tsuchiya, Susumu
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- Considerable Reduction in Crystallization Time in the Preparation of a New Type of Zeolite Catalyst for Olefin Synthesis from Methanol
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A new type of zeolite catalyst for a highly selective (ca. 77 percent) synthesis of C2-C4 olefins from methanol has been prepared; the crystallization time at 187 deg C may be made very short (2 h) using tetramethylammonium hydroxide as the modifier.
- Inui, Tomoyuki,Ishihara, Takayuki,Takegami, Yoshinobu
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- Tuning crystal phase of molybdenum carbide catalyst to induce the different selective hydrogenation performance
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α-MoC, β-Mo2C, and MoC-Mo2C were synthesized and investigated in the selective hydrogenation of 1,3-butadiene to understand the effect of crystal phases. The catalysts were characterized by XRD, N2-physisorption, SEM, TEM, XPS and chemisorptions. The adsorption properties and electronic properties over MoC(001) and Mo2C(001) were investigated by DFT calculations. The catalysts were evaluated at low and high temperatures in a fixed-bed reactor. β-Mo2C exhibits high activity and low butenes selectivity, due to the high concentration of hydrogen at each active site as well as the stronger adsorption and higher capacity of alkene; MoC-Mo2C shows better stability due to synergetic effect. At high temperature, the reaction rate is more dependent on the PH2 than PC4H6. Increasing PH2 could promote the activity and reduce oligomers formation. β-Mo2C exhibits the best performance at high temperatures concerning its high activity and the inhibition of oligomerization. This work is valuable for the non-precious metal catalyst development.
- Ding, Ziluo,Hou, Ruijun,Sun, Kening,Xu, Yamei,Yang, Qiuchen
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- Ga+-catalyzed hydrosilylation? about the surprising system Ga+/HSiR3/olefin, proof of oxidation with subvalent Ga+and silylium catalysis with perfluoroalkoxyaluminate anions
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Already 1 mol% of subvalent [Ga(PhF)2]+[pf]- ([pf]- = [Al(ORF)4]-, RF = C(CF3)3) initiates the hydrosilylation of olefinic double bonds under mild conditions. Reactions with HSiMe3 and HSiEt3 as substrates efficiently yield anti-Markovnikov and anti-addit
- Barthélemy, Antoine,Glootz, Kim,Hanske, Annaleah,Krossing, Ingo,Scherer, Harald
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p. 439 - 453
(2022/01/22)
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- Conversion of Phenol and Lignin as Components of Renewable Raw Materials on Pt and Ru-Supported Catalysts
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Hydrogenation of phenol in aqueous solutions on Pt-Ni/SiO2, Pt-Ni-Cr/Al2 O3, Pt/C, and Ru/C catalysts was studied at temperatures of 150–250? C and pressures of 40–80 bar. The possibility of hydrogenation of hydrolysis lignin in an aqueous medium in the presence of a Ru/C catalyst is shown. The conversion of hydrolysis lignin and water-soluble sodium lignosulfonate occurs with the formation of a complex mixture of monomeric products: a number of phenols, products of their catalytic hydrogenation (cyclohexanol and cyclohexanone), and hydrogenolysis products (cyclic and aliphatic C2 –C7 hydrocarbons).
- Bobrova, Nataliia A.,Bogdan, Tatiana V.,Bogdan, Viktor I.,Koklin, Aleksey E.,Mishanin, Igor I.
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- Tandem catalysts for the selective hydrogenation of butadiene with hydrogen generated from the decomposition of formic acid
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We report for the first time the selective hydrogenation of 1,3-butadiene to butene using formic acid as the hydrogen source with 1 wt% Pd/carbon in a continuous flow reactor. The catalytic results show that the selectivity is even higher when formic acid is used compared to gas hydrogen.
- Carrales-Alvarado, D. H.,Dongil, A. B.,Guerrero-Ruiz, A.,Rodríguez-Ramos, I.
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supporting information
p. 6479 - 6482
(2021/07/07)
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- A selective and stable Fe/TiO2catalyst for selective hydrogenation of butadiene in alkene-rich stream
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The replacement of precious metals by more abundant and therefore much less expensive metals remains a very important challenge in catalysis. A Fe/TiO2catalyst prepared by deposition-precipitation with urea showed very high selectivity to alkenes (>99%), even at high conversion (>90%), in selective hydrogenation of butadiene in an excess of propene. Its activity is very stable at 175 °C whereas the catalyst deactivates at 50 °C, although it is also initially very active. The presence of metallic iron seems to be necessary to ensure these excellent performances.
- Casale, Sandra,Delannoy, Laurent,Louis, Catherine,Méthivier, Christophe,Santander de Soto, Laura,Wang, Zhao
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supporting information
p. 7031 - 7034
(2021/07/21)
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- RED SLUDGE USED AS A CATALYST FOR OLEFIN ISOMERIZATION
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The invention relates to systems and a method for isomerizing a charge to form a stream of alpha-olefin product. An example of a process includes calcination of red mud, flow of an olefin feedstock onto red sludge in an isomerization reactor, and separation of alpha-olefin from reactor effluent.
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Paragraph 0035
(2021/12/31)
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- Oxidative Addition of Aryl and Alkyl Halides to a Reduced Iron Pincer Complex
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The two-electron oxidative addition of aryl and alkyl halides to a reduced iron dinitrogen complex with a strong-field tridentate pincer ligand has been demonstrated. Addition of iodobenzene or bromobenzene to (3,5-Me2MesCNC)Fe(N2)2 (3,5-Me2MesCNC = 2,6-(2,4,6-Me-C6H2-imidazol-2-ylidene)2-3,5-Me2-pyridine) resulted in rapid oxidative addition and formation of the diamagnetic, octahedral Fe(II) products (3,5-Me2MesCNC)Fe(Ph)(N2)(X), where X = I or Br. Competition experiments established the relative rate of oxidative addition of aryl halides as I > Br > Cl. A linear free energy of relative reaction rates of electronically differentiated aryl bromides (ρ = 1.5) was consistent with a concerted-type pathway. The oxidative addition of alkyl halides such as methyl-, isobutyl-, or neopentyl halides was also rapid at room temperature, but substrates with more accessible β-hydrogen positions (e.g., 1-bromobutane) underwent subsequent β-hydride elimination. Cyclization of an alkyl halide containing a radical clock and epimerization of neohexyl iodide-d2 upon oxidative addition to (3,5-Me2MesCNC)Fe(N2)2 are consistent with radical intermediates during C(sp3)-X bond cleavage. Importantly, while C(sp2)-X and C(sp3)-X oxidative addition produces net two-electron chemistry, the preferred pathway for obtaining the products is concerted and stepwise, respectively.
- Rummelt, Stephan M.,Peterson, Paul O.,Zhong, Hongyu,Chirik, Paul J.
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p. 5928 - 5936
(2021/05/06)
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- Light-Induced Nonoxidative Coupling of Methane Using Stable Solid Solutions
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Achieving efficient and direct conversion of methane under mild conditions is of great significance for innovations in the chemical industry. However, the efficiency and lifetime of most catalysts remain too far from practical requirements, since it is difficult to break the first C?H bond of methane as well as to suppress the following complete dehydrogenation (or overoxidation) and the resulting carbonaceous deposition (or CO2). Here, we report that wurtzite GaN:ZnO solid solutions exhibit unique and unprecedented photocatalytic performances for the nonoxidative coupling of methane at room temperature, exclusively generating ethane with nearly stoichiometric H2. High conversion rate (>330 μmol g?1 h?1), long-term stability (>70 h), and superior coke-resistance were achieved. At 293 K, the methane conversion exceeds 7 %, comparable to the equilibrium conversion of thermal catalysis at 910 K. Mechanistic studies revealed that the N-ZnGa-ON units and the absence of acid sites on the surface played crucial roles in reactivity and coke resistance, respectively.
- Li, Jiayang,Li, Lu,Mu, Xiaowei,Mu, Xiaoyue,Qian, Yumeng,Wang, Guangming,Zhan, Qingyun
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supporting information
p. 20760 - 20764
(2021/08/13)
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- Effect of Re and Al2O3 Promotion on the Working Stability of Cobalt Catalysts for the Fischer–Tropsch Synthesis
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Abstract: The results of the working stability studies of cobalt catalysts based on SiO2 and Al2O3 promoted with Re and Al2O3 in the synthesis of hydrocarbons from CO and H2 in continuous tests for 200–300 h are presented. The prepared catalysts were characterized by transmission electron spectroscopy, temperature-programmed reduction with hydrogen, temperature-programmed desorption of CO, and X-ray fluorescence spectroscopy and tested at a temperature 200°C, a pressure of 0.1 MPa, and a GHSV of 100 h–1. It was determined that a cobalt–silica catalyst promoted with Al2O3 had the highest activity. It was established that the addition of Al2O3 to a cobalt–silica catalyst increased the conversion of CO and selectivity for C5+ hydrocarbons and inhibited the agglomeration of Co particles under the action of a reaction atmosphere in the Fischer–Tropsch synthesis. It was found that the initial conversion of CO increased by a factor of 2 upon the introduction of 0.1 wt % rhenium into the Co/γ-Al2O3 catalyst; however, the rate of its deactivation increased in this case due to an almost twofold increase in the size of cobalt particles in the course of synthesis after operation for 300 h.
- Denisov, O. D.,Narochniy, G. B.,Papeta, O. P.,Savost’yanov, A. P.,Yakovenko, R. E.,Zubkov, I. N.
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p. 310 - 317
(2020/04/22)
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- Understanding the deactivation behavior of Pt/WO3/Al2O3 catalyst in the glycerol hydrogenolysis reaction
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The selective hydrogenolysis of glycerol to 1,3-propanediol is a highly important reaction for both improving the profitability of biodiesel and valorization of biomass. While intensive research efforts have been devoted to enhancing the catalytic activity and selectivity, little is focused on the stability although the latter is of paramount importance to practical applications. In this work, we investigated the stability of Pt/WO3/Al2O3 and observed a continuous deactivation trend during a 700 h time-on-stream run. Neither the leaching of active W nor the coking was responsible for the deactivation. Instead, XRD, HAADF-STEM and CO chemisorption results clearly showed the occurrence of significant aggregation of Pt particles, which caused a remarkable decrease of Pt-WOx interfacial sites. As a consequence, strong Br?nsted acid sites which were in situ formed by H2 dissociation at the Pt-WOx interfacial sites were reduced, leading to the deactivation of the catalyst.
- Lei, Nian,Liu, Fei,Miao, Zhili,Pan, Xiaoli,Wang, Aiqin,Wang, Hua,Zhang, Tao
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p. 1261 - 1267
(2020/03/13)
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- Intermetallic GaPd2 Thin Films for Selective Hydrogenation of Acetylene
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The preparation of single-phase and catalytically active GaPd2 coatings was accomplished via DC magnetron sputtering using an intermetallic sputter target. Thin and uniform layers were deposited on borosilicate glass, Si(111) and planar as well as micro-structured stainless steel foils. The specimens were examined regarding their phase composition, film morphology and microstructure. Thin films of different layer thickness were catalytically characterized in the semi-hydrogenation of acetylene, which was conducted at 473 K and a feed gas composition of 0.5 vol.percent C2H2, 5 vol.percent H2 as well as 50 vol.percent C2H4 in helium. Pre-reduction of the catalyst was found to be essential to enhance the catalytic selectivity. Sputtered GaPd2 showed a high selectivity of 73 percent for the hydrogenation to ethylene at conversion levels above 80 percent. The surface-specific activity was strongly increased to 8.97 molacetylene·(A0·h)–1 compared to bulk- or nanoscale GaPd2 (1.93 and 0.30 molacetylene·(A0·h)–1, respectively) caused by the high specific surface area of the thin films.
- Zimmermann, René R.,Siebert, Martin,Ibrahimkutty, Shyjumon,Dittmeyer, Roland,Armbrüster, Marc
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p. 1218 - 1226
(2020/06/09)
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- Synthesis and catalytic performance of zeolite-Y supported on silicon carbide in n-heptane cracking
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In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ～400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrostatically attracts negatively charged aluminosilicate seeds and promotes the growth of zeolite (ZY) particles over SiC, thus leading to the formation of stable ZY?SiC supported catalysts. The supported ZY catalysts with different weight ratio of ZY and SiC were synthesized and characterized by various techniques such as XRD, SEM, SEM-EDX, SEM-mapping, TEM, STEM, FT-IR, 27Al MAS NMR and N2 sorption. The characterization of the supported ZY catalysts suggests the uniform growth of ZY particles over SiC together with the creation of hierarchical micro-mesopores assembly. In the catalytic cracking of n-heptane, the catalyst ZY?SiC-50 displayed a remarkable improvement in reaction rate when compared to commercial zeolite-Y (CBV-600) amounting to 3.5 folds enhancement. Interestingly, the light olefins yield is also substantially improved. At WHSV of 8 h?1 and 475 °C, the highest light olefin yield (24–36 %) was achieved over ZY?SiC-50 whereas the reference catalyst, CBV-600 produced lower light olefins yield (7–17 %). Moreover, the supported ZY catalyst exhibited less deactivation rates. This improved performance is attributed to the hierarchical micro-mesopores assembly created by the homogeneous dispersion of zeolite crystals on SiC which offers fast diffusion pathways for the reactants and enhanced accessibility to active sites thus leading to higher observed reaction rates and fast diffusion of products thus minimizing the occurrence of side reactions.
- Alhassan, Saeed M.,Berthod, Mikael,Dabbawala, Aasif A.,Joseph, Tony,Khan, Shaihroz,Mittal, Hemant,Morin, Stephane,Singaravel, Gnana,Vaithilingam, Balasubramanian V.,Wahedi, Yasser Al
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- Non oxidative and oxidative dehydrogenation of: N -octane using FePO4: Effect of different FePO4phases on the product selectivity
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The activation of n-octane with O2 has been investigated over different phases of FePO4 which were formed under dehydrogenation and oxidative dehydrogenation (ODH) conditions. Catalytic reactions were done with the tridymite-like FePO4 catalyst which showed a high selectivity towards cracked products and carbon oxides. Under dehydrogenation conditions, tridymite phase FePO4 is transformed into the iron pyrophosphate phase (Fe2P2O7). Octenes, aromatics, C8 oxygenates, carbon oxides (COx) and cracked products were present in the product stream. The iron pyrophosphate phase, under oxidative dehydrogenation conditions, showed high selectivity towards cracked products and on regeneration (restoring of the catalytic activity) with molecular oxygen it transformed into the α-phase and quartz type phase. The regenerated catalyst (α-phase and quartz type phase) exhibited a higher selectivity to ODH products when compared to the fresh and deactivated (Fe2P2O7) catalysts. The transformation of both fresh and deactivated catalysts was evident at a temperature of 450 °C. Since the α-phase is the active phase under ODH conditions and transformations between the reduced and α-phase take place reversibly, this could explain the highest selectivity towards octenes within this temperature range. Fresh and regenerated catalysts showed steady state conversions with time under constant conditions, showing that phase transformations were mainly due to varying temperature and oxidative environment. Characterization results show that FePO4 contains fivefold coordinate Fe3+ in the regenerated and fresh catalysts, and this species is believed to be responsible for selective n-octane activation. The surface area, acidity and metal dispersion of the deactivated and regenerated catalyst showed lower values when compared to the fresh catalysts. The results obtained from M?ssbauer spectroscopy showed direct correlation with the XRD data as well as the TPR-TPO results in terms of the phase changes and oxidation state of the calcined, uncalcined, reduced and reoxidised catalyst. This journal is
- Bharuth-Ram, K.,Dasireddy, Venkata D. B. C.,Friedrich, Holger B.,Khan, Faiza B.,Singh, Sooboo
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p. 7591 - 7600
(2020/12/01)
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- METHOD FOR THE HYDRODEOXYGENATION OF OXYGENATED COMPOUNDS TO UNSATURATED PRODUCTS
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The invention relates to methods of hydrodeoxygenation of oxygenated compounds into compounds with unsaturated carbon-carbon bonds, comprising the steps of: a) providing a reaction mixture comprising, an oxygenated compound containing one or more of a hydroxyl, keto or aldehyde group, an ionic liquid, a homogeneous metal catalyst, and carbon monoxide or a carbon monoxide releasing compound, b) reacting said reaction mixture under a H2 atmosphere at acidic conditions at a temperature between 180 and 250 °C and a pressure between 10 and 200 bar.
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Page/Page column 11
(2021/01/23)
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- Syntheses and Molecular Structures of [(thf)4Li] [{(thf)Li}M(C4H8)3] (M = Zr, Hf) and Their Solution Behavior
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The reaction of MCl4(thf)2 (M = Zr, Hf) with 1,4-dilitiobutane in diethyl ether at –25 °C or at 0 °C with a molar ratio of 1 : 3 yields the homoleptic “ate” complexes [(thf)4Li] [{(thf)Li}M(C4H8)3] 1-Zr (M = Zr) and 1-Hf (M = Hf). The crystalline compounds form ion lattices with solvent-separated [(thf)4Li]+ cations and [{(thf)Li}M(C4H8)3]– anions. The NMR spectra at –20 °C show magnetic equivalence of the M–CH2 and of the β-CH2 groups of the butane-1,4-diide ligands on the NMR time scale. Analogous reactions of MCl4(thf)2 with 1,4-dilithiobutane with a molar ratio of 1 : 2 proceed unclear. However, single crystals of [Li(thf)4] [HfCl5(thf)] (2) can be isolated with the hafnium atom in a distorted octahedral coordination sphere of five chloro and one thf ligand. NMR spectra allow to elucidate the time-dependent degradation of 1-Hf and 1-Zr in THF and toluene at 25 °C via THF cleavage. Addition of tmeda to a solution of 1-Zr allows the isolation of intermediately formed [{(tmeda)Li}2Zr(nBu)2(C4H8)2] (3).
- Fischer, Reinald,Schmidt, Heiner,Younis, Fadi M.,G?rls, Helmar,Suxdorf, Regina,Westerhausen, Matthias
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p. 207 - 214
(2020/02/20)
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- Reversible oxidative-addition and reductive-elimination of thiophene from a titanium complex and its thermally-induced hydrodesulphurization chemistry
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The masked Ti(ii) synthon (Ketguan)(η6-ImDippN)Ti (1) oxidatively adds across thiophene to give ring-opened (Ketguan)(ImDippN)Ti[κ2-S(CH)3CH] (2). Complex 2 is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate 1-a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π?-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from 2. Finally, pressurizing solutions of 2 with H2 (150 psi) at 80 °C leads to the hydrodesulphurization of thiophene to give the Ti(iv) sulphide (Ketguan)(ImDippN)Ti(S) (3) and butane.
- Gómez-Torres, Alejandra,Aguilar-Calderón, J. Rolando,Saucedo, Carlos,Jordan, Aldo,Metta-Maga?a, Alejandro,Pinter, Balazs,Fortier, Skye
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p. 1545 - 1548
(2020/02/13)
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- Effect of Promoter Nature on Synthesis Gas Conversion to Alcohols over (K)MeMoS2/Al2O3 Catalysts
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The influence of the promoter nature and of a modifier in (K)(Me)MoS2/Al2O3 (Me=Fe, Co, Ni) catalysts on the conversion and selectivity of products of synthesis gas conversion to alcohols and jnl oxygenates was investigated. Relationships between promoter nature, hydrocarbon chain length and selectivity in the formed alcohols were established. Electronic structure of a promoter atom in an active site (AS) was found to strongly affect selectivity of alcohol formation. Promotion of the S-edge by Fe, Co or Ni suppressed hydrogen activation, which resulted in a lower synthesis gas conversion. Promotion of the M-edge by Fe, Co, or Ni entailed the formation of double vacancies which are active sites of synthesis gas conversion. Potassium affected the oxophilicity of Mo atoms and reduced Co/Ni-promoted MoS AS. It decreased the probability of C?O bond breaking in the adsorbed intermediate and shifted selectivity from the formation of alkyl towards alkoxide fragments over these catalysts.
- Maximov, Vladimir V.,Permyakov, Eugenii A.,Dorokhov, Viktor S.,Wang, Anjie,Kooyman, Patricia J.,Kogan, Victor M.
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p. 1443 - 1452
(2020/02/11)
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- C?C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM-5 Zeolite
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Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn2+-ion exchanged ZSM-5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO2) at 20 % CO conversion. NMR spectroscopy, X-ray absorption spectroscopy, and X-ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM-5. Quasi-in-situ solid-state NMR, obtained by quenching the reaction in liquid N2, detects C2 species such as acetyl (-COCH3) bonding with an oxygen, ethyl (-CH2CH3) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Br?nsted acid site of the catalyst, respectively. These species could provide insight into C?C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn2+-ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ-13, MCM-22, and ZSM-12) all give ethane predominantly. By contrast, a physical mixture of ZnO-ZSM-5 favors formation of hydrocarbons beyond C3+. These results provide an important guide for tuning the product selectivity in syngas conversion.
- Bao, Xinhe,Chen, Yuxiang,Gong, Ke,Hou, Guangjin,Jiao, Feng,Pan, Xiulian,Si, Rui
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supporting information
p. 6529 - 6534
(2020/03/04)
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- Impact of the Spatial Organization of Bifunctional Metal–Zeolite Catalysts on the Hydroisomerization of Light Alkanes
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Improving product selectivity by controlling the spatial organization of functional sites at the nanoscale is a critical challenge in bifunctional catalysis. We present a series of composite bifunctional catalysts consisting of one-dimensional zeolites (ZSM-22 and mordenite) and a γ-alumina binder, with platinum particles controllably deposited either on the alumina binder or inside the zeolite crystals. The hydroisomerization of n-heptane demonstrates that the catalysts with platinum particles on the binder, which separates platinum and acid sites at the nanoscale, leads to a higher yield of desired isomers than catalysts with platinum particles inside the zeolite crystals. Platinum particles within the zeolite crystals impose pronounced diffusion limitations on reaction intermediates, which leads to secondary cracking reactions, especially for catalysts with narrow micropores or large zeolite crystals. These findings extend the understanding of the ??intimacy criterion” for the rational design of bifunctional catalysts for the conversion of low-molecular-weight reactants.
- Cheng, Kang,Harmel, Justine,Oenema, Jogchum,Sunley, Glenn,Yoshida, Hideto,Ze?evi?, Jovana,Zhang, Zhaorong,de Jong, Krijn P.,van der Wal, Lars I.
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supporting information
p. 3592 - 3600
(2020/02/05)
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- CATALYST SYSTEMS THAT INCLUDE METAL OXIDE CO-CATALYSTS FOR THE PRODUCTION OF PROPYLENE
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Embodiments of methods of synthesizing a metathesis catalyst system, which include impregnating tungsten oxide on silica support in the presence of a precursor to produce a base catalyst; calcining the base catalyst; impregnating a metal oxide co-catalyst comprising a metal oxide onto the surface of the base catalyst to produce a doped catalyst; and calcining the doped catalyst to produce a metathesis catalyst system. Further embodiments of processes for the production of propylene, which include contacting a hydrocarbon feedstock comprising a mixture of 1-butene and 2-butene with embodiments of the metathesis catalyst system to produce, via metathesis conversion, a product stream comprising propylene.
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Paragraph 0069-0070
(2020/05/02)
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- Mechanistic Interrogation of Alkyne Hydroarylations Catalyzed by Highly Reduced, Single-Component Cobalt Complexes
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Highly reactive catalysts for ortho-hydroarylations of alkynes have previously been reported to result from activation of CoBr2 by Grignard reagents, but the operative mechanism and identity of the active cobalt species have been undefined. A mechanistic analysis of a related system, involving hydroarylations of a (N-aryl)aryl ethanimine with diphenylacetylene, was performed using isolable reduced Co complexes. Studies of the stoichiometric reaction of Co(I) or Co(II) precursors with CyMgCl implicated catalyst initiation via a β-H elimination/deprotonation pathway. The resulting single-component Co(-I) complex is proposed as the direct pre-catalyst. Michaelis-Menten enzyme kinetic studies provide mechanistic details regarding the catalytic dependence on substrate. The (N-aryl)aryl ethanimine substrate exhibited saturation-like behavior, whereas alkyne demonstrated a complex dependency; rate inhibition and promotion depend on the relative concentration of alkyne to imine. Activation of the aryl C-H bond occurred only in the presence of coordinated alkyne, which suggests operation of a concerted metalation-deprotonation (CMD) mechanism. Small primary isotope effects are consistent with a rate-determining C-H cleavage. Off-cycle olefin isomerization catalyzed by the same Co(-I) active species appears to be responsible for the observed Z-selectivity.
- Suslick, Benjamin A.,Tilley, T. Don
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supporting information
p. 11203 - 11218
(2020/07/08)
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- A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite
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There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.
- Chen, Wei,Corma, Avelino,De Baerdemaeker, Trees,De Vos, Dirk E.,Dong, Zhuoya,Kolb, Ute,Lei, Chi,Müller, Ulrich,Ma, Yanhang,Marler, Bernd,Martínez, Cristina,Martínez-Triguero, Joaquín,Meng, Xiangju,Parvulescu, Andrei-Nicolae,Wu, Qinming,Xiao, Feng-Shou,Yokoi, Toshiyuki,Zhang, Weiping,Zheng, Anmin
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supporting information
p. 15649 - 15655
(2020/07/04)
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- In situ structural study of manganese and iron oxide promoted rhodium catalysts for oxygenate synthesis
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In situ x-ray diffraction (XRD) and absorption spectroscopy (XAS) was used to characterize the structure and phase composition of a novel Mn and Fe double-promoted Rh-based catalyst for CO hydrogenation to oxygenates. Catalysts with different Mn:Rh molar ratios were prepared by combining Mn and Rh precursors with Fe2O3 powder, which were then calcined in air and reduced under hydrogen. The resulting MnRh/Fe2O3 catalysts are found to be highly selective for ethanol synthesis (～40 %) for CO hydrogenation under mild conditions (～1 bar, 240 °C). Comparison of the reactivity results with quantitative phase information from in situ XRD measurements suggest that reduced metal oxides, MnO and FeOx, and metallic Rh co-exist as active phases to promote oxygenate selectivity. The results of this work also highlight the importance of in situ characterization for extracting meaningful information on the active phases of such complex, ternary catalysts which can vary under reaction conditions.
- Carrillo, Pamela,Senanayake, Sanjaya D.,Shi, Rui,White, Michael G.
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- Ethylene Dehydroaromatization over Ga-ZSM-5 Catalysts: Nature and Role of Gallium Speciation
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Bifunctional catalysis in zeolites possessing both Br?nsted and Lewis acid sites offers unique opportunities to tailor shape selectivity and enhance catalyst performance. Here, we examine the impact of framework and extra-framework gallium species on enriched aromatics production in zeolite ZSM-5. We compare three distinct methods of preparing Ga-ZSM-5 and reveal direct (single step) synthesis leads to optimal catalysts compared to post-synthesis methods. Using a combination of state-of-the-art characterization, catalyst testing, and density functional theory calculations, we show that Ga Lewis acid sites strongly favor aromatization. Our findings also suggest Ga(framework)–Ga(extra-framework) pairings, which can only be achieved in materials prepared by direct synthesis, are the most energetically favorable sites for reaction pathways leading to aromatics. Calculated acid site exchange energies between extra-framework Ga at framework sites comprised of either Al or Ga reveal a site-specific preference for stabilizing Lewis acids, which is qualitatively consistent with experimental measurements. These findings indicate the possibility of tailoring Lewis acid siting by the placement of Ga heteroatoms at distinct tetrahedral sites in the zeolite framework, which can have a marked impact on catalyst performance relative to conventional H-ZSM-5.
- Frenkel, Anatoly I.,Grabow, Lars C.,Liu, Jing,Rimer, Jeffrey D.,Smith, Scott K.,Thirumalai, Hari,Whitmire, Kenton H.,Zhou, Yunwen
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supporting information
p. 19592 - 19601
(2020/09/17)
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- Grubbs Metathesis Enabled by a Light-Driven gem-Hydrogenation of Internal Alkynes
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[(NHC)(cymene)RuCl2] (NHC=N-heterocyclic carbene) complexes instigate a light-driven gem-hydrogenation of internal alkynes with concomitant formation of discrete Grubbs-type ruthenium carbene species. This unorthodox reactivity mode is harnessed in the form of a “hydrogenative metathesis” reaction, which converts an enyne substrate into a cyclic alkene. The intervention of ruthenium carbenes formed in the actual gem-hydrogenation step was proven by the isolation and crystallographic characterization of a rather unusual representative of this series carrying an unconfined alkyl group on a disubstituted carbene center.
- Biberger, Tobias,Fürstner, Alois,Zachmann, Raphael J.
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supporting information
p. 18423 - 18429
(2020/08/25)
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- Unraveling the Homologation Reaction Sequence of the Zeolite-Catalyzed Ethanol-to-Hydrocarbons Process
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Although industrialized, the mechanism for catalytic upgrading of bioethanol over solid-acid catalysts (that is, the ethanol-to-hydrocarbons (ETH) reaction) has not yet been fully resolved. Moreover, mechanistic understanding of the ETH reaction relies heavily on its well-known “sister-reaction” the methanol-to-hydrocarbons (MTH) process. However, the MTH process possesses a C1-entity reactant and cannot, therefore, shed any light on the homologation reaction sequence. The reaction and deactivation mechanism of the zeolite H-ZSM-5-catalyzed ETH process was elucidated using a combination of complementary solid-state NMR and operando UV/Vis diffuse reflectance spectroscopy, coupled with on-line mass spectrometry. This approach establishes the existence of a homologation reaction sequence through analysis of the pattern of the identified reactive and deactivated species. Furthermore, and in contrast to the MTH process, the deficiency of any olefinic-hydrocarbon pool species (that is, the olefin cycle) during the ETH process is also noted.
- Chowdhury, Abhishek Dutta,Lucini Paioni, Alessandra,Whiting, Gareth T.,Fu, Donglong,Baldus, Marc,Weckhuysen, Bert M.
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supporting information
p. 3908 - 3912
(2019/02/20)
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- Electrophilic Organoiridium(III) Pincer Complexes on Sulfated Zirconia for Hydrocarbon Activation and Functionalization
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Single-site supported organometallic catalysts bring together the favorable aspects of homogeneous and heterogeneous catalysis while offering opportunities to investigate the impact of metal-support interactions on reactivity. We report a (dmPhebox)Ir(III) (dmPhebox = 2,6-bis(4,4-dimethyloxazolinyl)-3,5-dimethylphenyl) complex chemisorbed on sulfated zirconia, the molecular precursor for which was previously applied to hydrocarbon functionalization. Spectroscopic methods such as diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS), dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) spectroscopy, and X-ray absorption spectroscopy (XAS) were used to characterize the supported species. Tetrabutylammonium acetate was found to remove the organometallic species from the surface, enabling solution-phase analytical techniques in conjunction with traditional surface methods. Cationic character was imparted to the iridium center by its grafting onto sulfated zirconia, imbuing high levels of activity in electrophilic C-H bond functionalization reactions such as the stoichiometric dehydrogenation of alkanes, with density functional theory (DFT) calculations showing a lower barrier for β-H elimination. Catalytic hydrogenation of olefins was also facilitated by the sulfated zirconia-supported (dmPhebox)Ir(III) complex, while the homologous complex on silica was inactive under comparable conditions.
- Syed, Zoha H.,Kaphan, David M.,Perras, Frédéric A.,Pruski, Marek,Ferrandon, Magali S.,Wegener, Evan C.,Celik, Gokhan,Wen, Jianguo,Liu, Cong,Dogan, Fulya,Goldberg, Karen I.,Delferro, Massimiliano
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supporting information
p. 6325 - 6337
(2019/04/25)
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- Plant-mediated synthesis of AgPd/γ-Al2O3 catalysts for selective hydrogenation of 1,3-butadiene at low temperature
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In this dissertation, silver-palladium (AgPd) bimetallic nanoparticles were synthesized by a green biosynthesis method using Cacumen platycladi leaf extract, which provided both reductive and protective agents. Then the supported AgPd/γ-Al2O3 catalysts were obtained by the sol-immobilization method, and the as-biosynthesized AgPd/γ-Al2O3 catalysts with different particle sizes and compositions were used for 1,3-butadiene hydrogenation. Optimization of the catalyst preparation and selective hydrogenation parameters was performed. Using the catalyst, a 1,3-butadiene conversion of 98.2% and a butene selectivity of 88.1% were achieved. The durability experiment of AgPd/γ-Al2O3 catalysts was carried out for 50 h, and the activity decreased slightly and the selectivity almost remains the same during the 50 h, indicating their remarkable stability. The results of TEM and TG analysis showed that the size of the AgPd nanoparticles was nearly the same before and after the durability experiment, and the existence of residual biomolecules on the catalyst surface helped to prevent agglomeration and modification of the surface properties of the catalyst, which would promote desorption of the product, and then avoid intensifying the level of further hydrogenation.
- Lu, Fenfen,Sun, Daohua,Jiang, Xia
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p. 13891 - 13898
(2019/09/16)
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- Hydrogenation of Carbon Dioxide to C2–C4 Hydrocarbons Catalyzed by Pd(PtBu3)2–FeCl2 with Ionic Liquid as Cocatalyst
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Direct hydrogenation of CO2 to C2+ hydrocarbons is very interesting, but achieving this transformation below 200 °C is challenging and seldom reported. Herein, a homogeneous catalytic system was developed composed of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]), Pd(PtBu3)2, FeCl2, and the ligand 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) for hydrogenation of CO2 under mild conditions, which resulted in C2–C4 hydrocarbons in selectivities up to 98.3 C-mol % at 180 °C. The combination of [BMIm][PF6]) with Xantphos endowed the Pd–Fe catalysts with the ability of activating CO2 and H2 simultaneously via [HPd(PtBu3)(BMIm-COO)(BMIm)(PF6)Fe]+ species, thus catalyzing the formation of C2–C4 hydrocarbons through CO2 hydrogenation. In addition, this catalytic system is stable and recyclable, which may have promising applications.
- Wang, Huan,Zhao, Yanfei,Wu, Yunyan,Li, Ruipeng,Zhang, Hongye,Yu, Bo,Zhang, Fengtao,Xiang, Junfeng,Wang, Zhenpeng,Liu, Zhimin
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p. 4390 - 4394
(2019/09/09)
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- Effective Hydrogenolysis of Glycerol to 1,3-Propanediol over Metal-Acid Concerted Pt/WOx/Al2O3 Catalysts
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Selective cleavage of secondary C?O bond is an important yet challenging strategy in glycerol valorization, and the product 1,3-propanediol (1,3-PDO) is of great value in polyester industry. Herein, we report a series of Pt/WOx/Al2O3 catalysts for selective hydrogenolysis of glycerol in a fixed-bed reactor and obtain the highest space-time yield of 1,3-PDO (191.7*10?3 g1,3-PDO h?1 g?1 cat.) to date. Both Pt and W have substantial effects on the 1,3-PDO yield with the optimum Pt/W atomic ratio of 1/2～1/4. Spectroscopy characterizations as well as chemisorption experiments reveal that at the medium domain size of WOx, hydrogen spillover can take place to the greatest extent due to the improved dispersion of Pt and the suitable reducibility of WOx. Dehydration/dehydrogenation tests of 2-butanol suggest that strong Br?nsted acid sites are created via hydrogen dissociation at the Pt?WOx interface and spillover to the neighboring oxygen atom. Such in situ formed protons are critical to the selective cleavage of secondary C?O bonds of polyols.
- Lei, Nian,Zhao, Xiaochen,Hou, Baolin,Yang, Man,Zhou, Maoxiang,Liu, Fei,Wang, Aiqin,Zhang, Tao
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p. 3903 - 3912
(2019/07/18)
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- Hydrocarbon Synthesis via Photoenzymatic Decarboxylation of Carboxylic Acids
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A recently discovered photodecarboxylase from Chlorella variabilis NC64A (CvFAP) bears the promise for the efficient and selective synthesis of hydrocarbons from carboxylic acids. CvFAP, however, exhibits a clear preference for long-chain fatty acids thereby limiting its broad applicability. In this contribution, we demonstrate that the decoy molecule approach enables conversion of a broad range of carboxylic acids by filling up the vacant substrate access channel of the photodecarboxylase. These results not only demonstrate a practical application of a unique, photoactivated enzyme but also pave the way to selective production of short-chain alkanes from waste carboxylic acids under mild reaction conditions.
- Zhang, Wuyuan,Ma, Ming,Huijbers, Mieke M. E.,Filonenko, Georgy A.,Pidko, Evgeny A.,Van Schie, Morten,De Boer, Sabrina,Burek, Bastien O.,Bloh, Jonathan Z.,Van Berkel, Willem J. H.,Smith, Wilson A.,Hollmann, Frank
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supporting information
p. 3116 - 3120
(2019/03/06)
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- Exploring C(sp3)–C(sp3) reductive elimination from an isolable iron metallacycle
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A six-coordinate iron metallacyclopentane, (phen)2Fe(CH2)4, supported by two 1,10-phenanthroline (phen) ligands, has been synthesized and structurally and spectroscopically characterized. The complex is diamagnetic and an idealized octahedral geometry was observed in the solid state. The electronic structure of (phen)2Fe(CH2)4 was determined by a combination of X-ray diffraction, M?ssbauer spectroscopy, and DFT analyses and is best described as a low-spin Fe(III) center antiferromagnetically coupled to a radical anion delocalized equally over both phen ligands. The reactivity of (phen)2Fe(CH2)4 under different conditions was explored. Thermolysis or photolysis promoted elimination reactions and mixtures of isomeric butenes and butane were observed. Reactions of (phen)2Fe(CH2)4 with ethylene and isoprene yielded 3% and 11% of reductive elimination product cyclobutane, respectively, along with butane and butene isomers. Addition of π-accepting ligands such as carbon monoxide, maleic anhydride, or 1,4-benzoquinone to (phen)2Fe(CH2)4 promoted C(sp3)-C(sp3) reductive elimination as judged by high selectivity for cyclobutane formation. Two electron oxidation of (phen)2Fe(CH2)4 with two equivalents of ferrocenium tetraphenylborate also exclusively yielded cyclobutane in 95% yield. The electronic structure and reactivity of related bis(bipyridine) iron dialkyl compounds previously isolated by Kochi and co-workers were also revisited and their electronic structures revised based on structural, spectroscopic and computational data.
- Joannou, Matthew V.,Darmon, Jonathan M.,Bezdek, Máté J.,Chirik, Paul J.
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p. 308 - 317
(2019/01/04)
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- Tungsten Catalyst Incorporating a Well-Defined Tetracoordinated Aluminum Surface Ligand for Selective Metathesis of Propane, [(≡Si?O?Si≡)(≡Si?O?)2Al?O?W(≡CtBu) (H)2]
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A well-defined aluminium-bound hydroxyl group on the surface of mesoporous SBA-15, [(≡Si?O?Si≡) (≡Si?O)2 Al?OH], 3 was obtained by reacting di-isopropyl aluminium hydride with SBA-15 treated at 700 °C. The resulting surface [(≡Si?O?Si≡) (≡Si?O) 2 Al (isobutyl) fragment undergoes β-H elimination at 400 °C leading to [(≡Si?O?Si≡)(≡Si?O?)2Al?O) Al?H]. Further oxidation of this Al-hydride with N2O leads to 3. This acidic support was used to create a well-defined surface organo-tungsten fragment [(≡Si?O?Si≡)(≡Si?O?)2Al?O?W(≡CtBu)(CH2tBu)2] by reacting 3 with W(≡C-tBu)(CH2-tBu)3. A further reaction with hydrogen under mild conditions afforded the tungsten carbyne bis-hydride [(≡Si?O?Si≡)(≡Si?O?)2Al?O?W(H)2(≡C-tBu)]. The performance of each of the W-supported catalysts was assessed for propane metathesis in a flow reactor at 150 °C. [(≡Si?O?Si≡)(≡Si?O?)2 Al?O?W(≡CtBu)(H)2] was found to be a single-site catalyst, giving the highest turnover number (TON=800) and the highest reported selectivity for butane (45 %) vs. ethane (32 %) known for oxide-supported tungsten complex catalysts (with the supports being silica, silica-alumina, and alumina). The results demonstrate that modification of the oxide ligands on silica via the creation of Al Lewis acid center as an anchoring site for organometallic complexes opens up new catalytic properties, markedly enhancing the catalytic performance of supported organo-tungsten species.
- Werghi, Baraa,Bendjeriou-Sedjerari, Anissa,Jedidi, Abdesslem,Morlanes, Natalia,Abou-Hamad, Edy,Bhatte, Kushal,Guan, Erjia,Ma, Tao,Aguilar-Tapia, Antonio,Ould-Chikh, Samy,Cavallo, Luigi,Gates, Bruce C.,Basset, Jean-Marie
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p. 614 - 620
(2019/01/04)
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- Highly selective aromatization and isomerization of N-alkanes from bimetallic Pt-Zn nanoparticles supported on a uniform aluminosilicate
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A bimetallic-support interaction through Pt-Zn nanoparticles and uniform compact cylindrical ZSM-5 particles shows selectivity over 90% towards BTX and i-octane at controlled 60% conversion with negligible coke formation when reforming n-octane. This is a significant improvement compared to alternative Pt-Zn on conventional ZSM-5, with a selectivity of less than 40%.
- Jarvis, Jack S.,Harrhy, Jonathan H.,He, Peng,Wang, Aiguo,Liu, Lijia,Song, Hua
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supporting information
p. 3355 - 3358
(2019/04/03)
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- Thermal Behavior Analysis of Two Synthesized Flavor Precursors of N-alkylpyrrole Derivatives
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To expand the library of pyrrole-containing flavor precursors, two new flavor precursors—methyl N-benzyl-2-methyl-5-formylpyrrole-3-carboxylate (NBMF) and methyl N-butyl-2-methyl-5-formylpyrrole-3-carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG-DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2-methylpyrrole, 1-methylpyrrole-2-carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives.
- Ai, Lvye,Liu, Mengzhen,Ji, Xiaoming,Lai, Miao,Zhao, Mingqin,Ren, Tianbao
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p. 2389 - 2397
(2019/08/01)
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- Method for preparing n-butane from levulinic acid
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The invention belongs to the field of chemical synthesis, and particularly relates to a method for preparing n-butane from levulinic acid. The method comprises the following steps of: adding levulinicacid and a metal catalyst into a high-temperature high-pressure reaction kettle according to a molar ratio of the metal catalyst to the levulinic acid being 1-1000, adding a certain amount of solvent, sealing the reaction kettle, charging 50-1000 psi of hydrogen or a mixed gas containing hydrogen, conducting heating to 100-300 DEG C under stirring, conducting reacting for 0.5-25 hours, conductingquenching to room temperature, and collecting an organic phase and gas to obtain n-butane. The reaction raw materials are derived from green and renewable materials; and the by-product amount is verysmall, and the yield of the product n-butane can be up to 99% at most. The product is easy to collect. The method has the advantages of high product selectivity, simple post-treatment and easiness inindustrialization; and a precious metal has good stability in a water phase, is easy to reuse, and has very important application value.
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Paragraph 0022-0023; 0031-0042
(2019/08/01)
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- Ethanol to Butanol Conversion over Bifunctional Zeotype Catalysts Containing Palladium and Zirconium
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Abstract: A study of the kinetics of ethanol conversion in the presence of Zr-containing zeolites BEA doped with palladium particles has revealed the order of formation of the main reaction products. It has been shown that the primary processes are ethanol dehydrogenation to acetaldehyde on Pd sites and ethanol dehydration to diethyl ether on the acid sites of the catalyst. After that, acetaldehyde undergoes the aldol–croton condensation reaction to form crotonal, which is hydrogenated to butanol on the metal sites. Butanol, in turn, is dehydrated into butenes, which undergo hydrogenation to butane. The presence of hydrogen in the gas phase leads to the displacement of ethanol from the metal surface and prevents the formation of surface carbonates and acetates. It has been found that hydrogen significantly accelerates ethanol dehydration owing to a decrease in the activation energy, which can be attributed to hydrogen spillover to the zeolite. The addition of water inhibits all acid-catalyzed reactions owing to competitive adsorption on acid sites and thereby decreases the butanol yield and the ethanol conversion.
- Kots,Zabilska,Grigor’ev, Yu. V.,Ivanova
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p. 925 - 934
(2019/08/20)
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- Forming pure shaped ZSM-5 zeolite bodies by a steam-Assisted method and their application in methanol to aromatic reactions
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For an industrial-scale catalytic process with a fixed or packed bed reactor, powder catalysts are not suitable because they may block the reaction pipe and increase the pressure of the reactor. Therefore, catalyst molding is essential for the industrial application of a catalyst. During the catalyst molding, binders are employed as indispensable additives that can achieve the mechanical strength requirements for industrial applications. However, the addition of binders may cover the activity sites of the catalyst and suppress the mass transfer of the reactants and products. So, traditional processes of catalyst molding significantly affect the catalytic performance. In this study, we proposed a vapor-phase-Treatment to synthesize a pure shaped ZSM-5 zeolite with the re-crystallization of the binder incorporated silica sol and aluminum nitrate, which were converted into a part of ZSM-5 on a commercial H-ZSM-5 zeolite substrate. Subsequently, the shaped ZSM-5 catalyst was evaluated using the catalytic conversion of methanol to an aromatic (MTA reaction). The results showed that compared to the EPHZ catalyst, the SPHZ catalyst exhibited a long lifetime with a relatively high shape selectivity for methanol and aromatics. To rationalize these results and establish a structure-Activity relationship, the zeolite catalysts were thoroughly characterized by XRD, NH3-TPD, FT-IR, N2 adsorption, TG, SEM, TEM, ICP and Al MAS-NMR. The results demonstrated that an interesting intra-particle pore structure was formed within the monoliths of the SPHZ catalyst. Moreover, the superior catalytic performance obtained for SPHZ may have also been due to the broad acid strength distribution and the conversion of the silicon aluminum adhesive agent to zeolite crystals.
- Wang, Junwen,Gao, Xiaofeng,Chen, Guoliang,Ding, Chuanmin
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p. 28451 - 28459
(2019/09/30)
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- Catalytic Activation of Unstrained, Nonactivated Ketones Mediated by Platinum(II): Multiple C-C Bond Cleavage and CO Extrusion
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The complexes [Pt(tolpy)Cl(L)] (tolpy = 2-(4-tolyl)pyridyl; L = dmso, dms, py, PPh3, CO) are precursors for the catalytic cleavage of C-C bonds and extrusion of CO from a series of unactivated ketones such as cyclohexanone; deuterium labeling experiments demonstrate the involvement of a transfer hydrogen step in the mechanism.
- Sarju, Julia P.,Dey, Debashish,Torroba, Javier,Whitwood, Adrian C.,Redeker, Kelly,Bruce, Duncan W.
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supporting information
p. 4539 - 4542
(2019/11/29)
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- Nanostructured Hydrotalcite-Supported RuBaK Catalyst for Direct Conversion of Ethylene to Propylene
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A novel nanostructured hydrotalcite-supported alkali-doped Ru-based catalyst (RuBaKT/HT) was applied for the direct gas-phase conversion of ethylene to propylene at 70°C and 1 atm. The maximum conversion of ca. 87% was achieved at the initial time on stream with a 65% selectivity to propylene and a 6% selectivity to butenes via consecutive reactions. The overall selectivity to propylene and butenes decreased to 32% after 24 min of operation, however, necessitating a reaction–regeneration cycle in a possible industrial practice.
- Ghashghaee, Mohammad,Farzaneh, Vahid
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p. 972 - 976
(2018/09/06)
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- Chemoselective Hydrogenation with Supported Organoplatinum(IV) Catalyst on Zn(II)-Modified Silica
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Well-defined organoplatinum(IV) sites were grafted on a Zn(II)-modified SiO2 support via surface organometallic chemistry in toluene at room temperature. Solid-state spectroscopies including XAS, DRIFTS, DRUV-vis, and solid-state (SS) NMR enhanced by dynamic nuclear polarization (DNP), as well as TPR-H2 and TEM techniques revealed highly dispersed (methylcyclopentadienyl)methylplatinum(IV) sites on the surface ((MeCp)PtMe/Zn/SiO2, 1). In addition, computational modeling suggests that the surface reaction of (MeCp)PtMe3 with Zn(II)-modified SiO2 support is thermodynamically favorable (ΔG = -12.4 kcal/mol), likely due to the increased acidity of the hydroxyl group, as indicated by NH3-TPD and DNP-enhanced 17O{1H} SSNMR. In situ DRIFTS and XAS hydrogenation experiments reveal the probable formation of a surface Pt(IV)-H upon hydrogenolysis of Pt-Me groups. The heterogenized organoplatinum(IV)-hydride sites catalyze the selective partial hydrogenation of 1,3-butadiene to butenes (up to 95%) and the reduction of nitrobenzene derivatives to anilines (up to 99%) with excellent tolerance of reduction-sensitive functional groups (olefin, carbonyl, nitrile, halogens) under mild reaction conditions.
- Camacho-Bunquin, Jeffrey,Ferrandon, Magali,Sohn, Hyuntae,Yang, Dali,Liu, Cong,Ignacio-De Leon, Patricia Anne,Perras, Frédéric A.,Pruski, Marek,Stair, Peter C.,Delferro, Massimiliano
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p. 3940 - 3951
(2018/03/29)
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- An ordinary nickel catalyst becomes completely selective for partial hydrogenation of 1,3-butadiene when coated with tributyl(methyl)phosphonium methyl sulfate
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Performance of an ordinary supported nickel catalyst was tuned to reach an almost complete selectivity for partial hydrogenation of 1,3-butadiene by coating it with a phosphonium-type ionic liquid (IL), tributyl(methyl)phosphonium methyl sulfate, [P4441][MeSO4]. Thanks to high chemical and thermal stability of [P4441][MeSO4], the reaction conditions could be pre-optimized for high partial hydrogenation performance before the deposition of the IL coating. When the catalyst was coated with IL, it provided a total butene selectivity of 99.5 ± 0.2%, a record high partial hydrogenation selectivity ever reported for a nickel-based catalyst. X-ray photoelectron spectroscopy results illustrated that the IL donates electrons to nickel sites and makes them selective for partial hydrogenation. The conductor like screening model for realistic solvents (COSMO-RS) calculations indicated that the IL coating also exerts a filter effect, which helps to maintain this high partial hydrogenation selectivity at all conversion levels.
- Jalal, Ahsan,Uzun, Alper
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p. 321 - 326
(2018/06/29)
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- MULTIMETALLIC CATALYSTS FOR SELECTIVE HYDROGENATION OF DIENES AND ACETYLENES, AND PURIFICATION OF OLEFIN FEEDSTOCKS
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A catalyst for hydrogenation reaction processes includes an oxide substrate surface, a MOx promoter, where M is a transition metal or main group elemental oxide, the promoter being deposited on the substrate, and a platinum group catalytic metal.
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Paragraph 0025-0026
(2018/10/30)
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- Encapsulation of Crabtree's Catalyst in Sulfonated MIL-101(Cr): Enhancement of Stability and Selectivity between Competing Reaction Pathways by the MOF Chemical Microenvironment
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Crabtree's catalyst was encapsulated inside the pores of the sulfonated MIL-101(Cr) metal–organic framework (MOF) by cation exchange. This hybrid catalyst is active for the heterogeneous hydrogenation of non-functionalized alkenes either in solution or in the gas phase. Moreover, encapsulation inside a well-defined hydrophilic microenvironment enhances catalyst stability and selectivity to hydrogenation over isomerization for substrates bearing ligating functionalities. Accordingly, the encapsulated catalyst significantly outperforms its homogeneous counterpart in the hydrogenation of olefinic alcohols in terms of overall conversion and selectivity, with the chemical microenvironment of the MOF host favouring one out of two competing reaction pathways.
- Grigoropoulos, Alexios,McKay, Alasdair I.,Katsoulidis, Alexandros P.,Davies, Robert P.,Haynes, Anthony,Brammer, Lee,Xiao, Jianliang,Weller, Andrew S.,Rosseinsky, Matthew J.
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supporting information
p. 4532 - 4537
(2018/03/26)
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- Reactions of the Ni(0) Compound Ni(PPh3)4 with Unactivated Alkyl Halides: Oxidative Addition Reactions Involving Radical Processes and Nickel(I) Intermediates
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Reactions of the nickel(0) compound NiL4 (L = PPh3) with alkyl halides RX involve initial inner-sphere halogen atom abstraction from the alkyl halides to form alkyl radicals R· and halonickel(I) metalloradical species NiX(PPh3)2,3. The radical pairs then undergo combination within the solvent cage to give the square planar nickel(II) compounds NiRX(PPh3)2. Radical intermediacy is demonstrated persuasively by observations that the relative rates vary in the orders tert-butyl > sec-butyl > n-butyl and RI > RBr > RCl, while density functional theory calculations indicate that the radical mechanism provides a lower energy pathway than do alternative, more conventional pathways. The product of the reaction of Ni(PPh3)4 with methyl iodide, NiMeI(PPh3)2, decomposes in solution to ethane and NiI(PPh3)2,3, but when RX = EtI, n-BuI, sec-BuI, tert-BuI, the alkyl-nickel products undergo rapid β-hydrogen elimination to give the hydride NiHI(PPh3)2 plus the corresponding alkene(s). Reactions also occur in which a portion of the alkyl radicals diffuses from the solvent cage and abstracts hydrogen from NiHI(PPh3)2 to form alkanes RH and Ni(I) species NiI(PPh3)2. As a result, NiHI(PPh3)2 is invariably a minor product while the major products are alkanes RH, alkenes R-H, and NiI(PPh3)2. Hydride NiHI(PPh3)2 is found to decompose to H2 and NiI(PPh3)2 but is stable at low temperatures where it exhibits unusual NMR behavior because of exchange involving free PPh3 and the bis- and trisphosphine species, NiHI(PPh3)2 and NiHI(PPh3)3. Present in all of the reactions are paramagnetic, substitution-labile Ni(I) metalloradical species. As a result, resonances of PPh3, ethylene, and the smaller iodoalkenes are generally broad and shifted because of exchange between free and coordinated ligands.
- Kehoe, Ryley,Mahadevan, Markshun,Manzoor, Adeela,McMurray, Gillian,Wienefeld, Patrick,Baird, Michael C.,Budzelaar, Peter H. M.
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supporting information
p. 2450 - 2467
(2018/08/21)
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- In Situ routes to catalytically active Ru(0) Species by reduction of readily available, air-stable precursors
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Cross-dimerization of a conjugated diene with a substituted alkene catalyzed by in situ reduction of an air-stable Ru(II) catalyst precursor has been achieved. Reaction of 2,3-dimethylbutadiene with styrene is catalyzed by [Ru(acac)2(η4-1,5-COD)] (2a) (5 mol %) with BuLi (10 mol %) at 50 °C for 6 h in hexane, giving the cross-dimers in 99% yield ((E)-4,5-dimethyl-1-phenylhexa-1,4-diene (3a)/(E)-4,5-dimethyl-1-phenylhexa-2,4-diene (3b)/isomers = 84/9/7). Because neither 2a nor BuLi separately catalyzes the cross-dimerization and reduction of 2a with BuLi in the presence of naphthalene produces [Ru(η6-naphthalene)(η4-1,5-COD)] (1a), the active species in this catalysis is considered to be a Ru(0) compound. Interestingly, this in situ reduction method of Ru(II) using BuLi can be applied to the cross-dimerization using an ester such as methyl acrylate. Alternatively, an air-stable Ru(II) complex having a labile arene ligand such as [RuCl2(η6-anisole)]2 (5c) (5 mol %) with Na2CO3 (40 mol %) in the presence of 1,5-COD (20 mol %) at 100 °C for 6 h in 2-butanol also catalyzes the same cross-dimerization in 62% yield. These protocols provide facile methods for production of unsaturated linear compounds by the cross-dimerization using air-stable Ru(II) catalyst precursors.
- Hirano, Masafumi,Kobayashi, Hideyuki,Ueda, Takao,Hiroi, Yuki,Abe, Ryota,Komine, Nobuyuki,Colebatch, Annie L.,Bennett, Martin A.
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p. 1092 - 1102
(2018/04/17)
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