- [B(C6F5)4]: An air stable, lewis acidic stibonium salt that activates strong element-fluorine bonds
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As part of our ongoing interest in main group Lewis acids for fluoride anion complexation and element-fluorine bond activation, we have synthesized the stibonium borate salt [Sb(C6F5)4][B(C 6F5)4] (3). The perfluorinated stibonium cation [Sb(C6F5)4]+ present in this salt is a potent Lewis acid which abstracts a fluoride anion from [SbF 6]- and [BF(C6F5)3] - indicating that it is a stronger Lewis acid than SbF5 and B(C6F5)3. The unusual Lewis acidic properties of 3 are further reflected by its ability to polymerize THF or to promote the hydrodefluorination of fluoroalkanes in the presence of Et 3SiH. While highly reactive in solution, 3 is a perfectly air stable salt, making it a convenient Lewis acidic reagent.
- Pan, Baofei,Gabba?, Fran?ois P.
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- Catalytic hydrogenation of phenol, cresol and guaiacol over physically mixed catalysts of Pd/C and zeolite solid acids
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Highly reactive phenolic compounds of pyrolysis bio-oil are recognized as a major cause of the unpleasant properties of this biofuel. Catalytic hydrodeoxygenation of phenolic compounds of bio-oil is an efficient technique for improving the quality of bio-oil. Dual function catalysts consisting of metal and acid sites are usually used for transformation of bio-oil/bio-oil model compounds to high value hydrocarbons. Metal and acid sites are generally involved in hydrogenation/hydrodeoxygenation and dehydration/hydrocracking/dealkylation/alkylation reaction mechanisms, respectively. In this work, the product selectivity of hydrogenation of phenol, o-cresol, m-cresol and guaiacol was investigated over combined catalysts of Pd/C with zeolite solid acids of HZSM-5 (Si/Al of 30, 50 and 80) and HY (Si/Al of 30 and 60). Catalytic activity and product distribution in the hydrogenation process were affected by the density and strength of zeolite acid sites. HZSM-5 (30) with only weak acid sites showed lower cyclohexane selectivity compared with HZSM-5 (50) and HZSM-5 (80) which had both weak and strong acid sites. HY (30) and HY (60) containing only strong acid sites favored production of cycloketones.
- Shafaghat, Hoda,Sirous Rezaei, Pouya,Daud, Wan Mohd Ashri Wan
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- UEBER DIE AUSWIRKUNG VON METHYLSUBSTITUENTEN AUF DIE THERMISCHE ISOMERISIERUNG VON 1,7-OCTADIEN-3-INEN
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The influence of methyl substituents on the 1,7-octadien-3-yne to methylene-vinylcyclopentene rearrangement has been investigated.Whereas methyl groups in the 6-position induce the formation of 1,4-cycloheptadienes, methyl substituents in the 1-position lead to aromatic compounds.
- Kirsch, Reinhard,Priebe, Hanno,Hopf, Henning
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- On the Mechanism of the Cyclooctatetraene Synthesis from Ethyne Employing Nickel Catalysts
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The mechanism of the Reppe cyclization to cyclooctatetraene was investigated by employing ethyne-1-13C as a substrate in the nickel-catalyzed reaction.The specific catalytic systems studied were nickel acetylacetonate-calcium carbide and nickel acetylacetonate-diethylaluminum ethoxide.In both cases, the label pattern in the cyclooctatetraene produced was consistent with either a stepwise coupling or concerted "zipper-type" mechanism of formation.These results preclude the possibility of cyclobutadiene or benzene intermediates or any carbon-carbon bond cleavage processes which do not leave the original connectivity in the alkyne intact.These conclusions were based upon analysis of the isotopic label in C4 fragments, obtained by chemical degradation of the cyclooctatetraene produced.
- Colborn, Robert E.,Vollhardt, K. Peter C.
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- Studies on organolanthanide complexes XXIII. Reaction of organic halides with tricyclopentadienyllanthanides/sodium hydride
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The reductive dehalogenation of aryl and vinyl halides with tricyclopentadienyllanthanide/sodium hydride systems affords, respectively, the corresponding aromatics and alkenes in excellent yields under mild conditions.However, the reaction with alkyl halides generates alkylated products, which yield alkyl cyclopentadienes after hydrolysis.The reaction mechanism has been briefly investigated.
- Qian, Changtao,Zhu, Dunming,Gu, Yongjie
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- Reactions of Triarylsulphonium Salt with Alkoxide Nucleophiles: Involvement of Radical Intermediates
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Tri-p-tolylsulphonium bromide reacts with sodium isopropoxide or potassium hydroxide to give toluene; solvent isotope labelling experiments clearly show involvement of the p-tolyl radical species rather than the corresponding anion in this reaction.
- Chung, Sung-Kee,Sasamoto, Kazumi
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- STUDY OF THE PROPERTIES OF PENTASIL-CONTAINING CATALYSTS IN REACTIONS OF TRANSFORMATION OF HYDROCARBONS. 3. KINETICS OF AROMATIZATION OF PROPANE AND PROPYLENE ON H AND Zn FORMS OF PENTASILS
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The kinetics of transformations of propane and propylene on pentasils modified with zinc, Zn/HTsVM, and the H form of zeolite were investigated.Quantitative data were obtained which revealed significant differences for HTsVM and Zn-containing catalysts in the selectivity of transformations of propane with different degrees of its conversion.The promoting effect of Zn in the Zn/HTsVM system not only on the stage of dehydrogenation of propane into propylene, but also on subsequent transformations of propylene into aromatic hydrocarbons, was demonstrated.The absence of internal diffusion inhibition of the reaction in the conditions studied was demonstrated experimentally.It was shown that aromatization of propane takes place in the kinetic region.
- Sitnik, V. P.,Nekrasov, N. V.,Vasina, T. V.,Yakerson, V. I.,Bragin, O. V.
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- Activation of C?F Bonds by Electrophilic Organosilicon Sites Supported on Sulfated Zirconia
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The reaction of allyltriisopropylsilane with partially dehydroxylated sulfated zirconium oxide (SZO) forms surface organosilicon species. Solid-state NMR studies of the organosilicon functionalized SZO shows that electrophilic [TIPS][SZO] sites are present on the surface, in addition to less reactive TIPS-Ox and SiOx species. The electrophilic [TIPS][SZO] sites are strong Lewis acids from solid-state 31P NMR analysis of triethylphosphine oxide (O=PEt3) contacted materials. [TIPS][SZO] is active in hydrodefluorination reactions in the presence of Et3SiH.
- Culver, Damien B.,Conley, Matthew P.
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- Hydrodeoxygenation of m-cresol with Pt supported over mild acid materials
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The deoxygenation of m-cresol was studied using Pt catalysts supported on different materials of various levels of acidity, such as gamma alumina, silica, and H-BEA zeolites. The reaction was carried out at atmospheric pressure and 300 °C in a fixed-bed reactor. The catalysts were characterized by XRD, BET, TPR, TEM, H2 and CO chemisorptions, pyridine-TPD and pyridine-IR. The (metal function/acid function) ratio and the reaction conditions were adjusted in order to have a high selectivity to toluene. The effects of acid sites density, strength and type, as well as the pore structure of the different supports on the deoxygenation activity, selectivity and stability were addressed. In order to avoid the production of heavy products and a fast deactivation, the concentration of Br?nsted acid sites must be very low. A high acid sites density is detrimental for catalyst stability, due to coke formation via condensation of precursors adsorbed on adjacent sites. Additionally, a mesoporous structure is better than a microporous structure regarding the stability. All the catalysts can be regenerated in air at relatively low temperature.
- Zanuttini,Dalla Costa,Querini,Peralta
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- Synthesis and functionalization of ordered mesoporous carbons supported Pt nanoparticles for hydroconversion of n-heptane
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A comprehensive study was performed on the spectroscopic and textural properties of ordered mesoporous carbon (OMC) of the CMK-3 type modified by acid oxidation using K2S2O8 as a benign oxidant and nitrogen-doping by the aid of the polymerization of ethylenediamine and carbon tetrachloride inside the pore channels of SBA-15 hard template. The pristine, nitrogen-doped, and oxidized-ordered mesoporous carbons were used as supports to prepare 10 wt% platinum nanoparticles-loaded catalysts using ethylene glycol as a reducing agent. The catalytic behavior, mechanism, and influence of the surface functionalization of the ordered mesoporous carbon bifunctional catalysts toward the hydroconversion of n-heptane using a fixed-bed flow system operated under atmospheric pressure were investigated. The synthesized samples were characterized by various analytical and spectroscopic techniques. The mesostructural regularity corresponding to the hexagonal P6mm symmetry of the OMC-CMK-3 type was well-reserved even after surface modifications replicated from an SBA-15 template. H2 pulse chemisorption and EDX mapping images confirmed differences in the Pt NPs contents and dispersion depending on the support composition. The catalytic activity results achieved were hand in hand with the proper balance between the acidity strength and Pt NPs dispersion degree.
- Said
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- Catalytic benzene mono-alkylation over three catalysts: improving activity and selectivity with M-Y catalyst
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Modified Y type catalyst (M-Y) shows great potential for the preparation of toluene attribute to catalyst topology and synergistic effect of Lewis acid and Br?nsted acid in the alkylation reaction. However, it still remains a big challenge to build a reaction mechanism. Thereby, based on the study of HZSM-5, H-beta and M-Y catalysts structure and physical properties, a plausible reaction mechanism was proposed. The samples were characterized by X-ray diffraction, N2 adsorption/desorption, Fourier transform infrared absorption spectra and Pyridine adsorption infrared. The activity of catalysts was tested in benzene alkylation with methanol and was found to be in the following increasing order: Na-Y (no effect) H-Y HZSM-5 H-beta M-Y.
- Dong, Peng,Li, Zeyu,Ji, Dong,Wang, Xiaorui,Yun, Hongfei,Du, Zhisong,Bian, Jie,Li, Guixian
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- Aromatization of n-hexane over Ga, Mo and Zn modified H-ZSM-5 zeolite catalysts
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n-Hexane aromatization was investigated at 500 °C on parent and metal (i.e. Ga, Mo and Zn) modified H-ZSM-5 zeolite catalysts. Conversion reached 88% over H-ZSM-5 and was stable. Addition of metal resulted in lower conversion ( 35%) and Zn/H-ZSM-5 (> 40%) while H-ZSM-5 and Mo/H-ZSM-5 showed higher cracking activity. Gallium and zinc favored aromatization. At 600 °C a decrease in activity with increasing TOS was observed. A decrease in aromatics selectivity was also observed. The aromatics selectivity with increase in TOS of Ga/H-ZSM-5 (43-27%) and Mo/H-ZSM-5 (35-27%) catalysts was higher than for Zn/H-ZSM-5 (46-7%).
- Tshabalala, Themba E.,Scurrell, Michael S.
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- Aromatization of dimethyl and diethyl ethers on Mo2C-promoted ZSM-5 catalysts
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The adsorption and reaction pathways of dimethyl and diethyl ethers have been investigated on pure and Mo2C-containing ZSM-5. The catalysts have been characterized by XPS and surface acidity measurements. FTIR spectroscopic measurements indicated that a fraction of both ethers dissociates on pure and Mo2C-promoted zeolites already at 180-200 K resulting in the formation of methoxy from dimethyl ether, and ethoxy from diethyl ether. TPD experiments following the adsorption at 300 K showed desorption profiles corresponding to starting compounds and their decomposition products (methane, ethene and propene). ZSM-5 effectively catalyzed the reaction of dimethyl and diethyl ether above 473 K to yield various olefins and aromatics. From dimethyl ether xylene and from diethyl ether toluene were the main aromatic compounds. Adding Mo2C to the zeolites greatly promoted the formation of aromatics very likely by catalyzing the aromatization of olefins formed in the reaction of ethers on zeolites.
- Kecskemeti, Anita,Barthos, Robert,Solymosi, Frigyes
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- The enhancement of the catalytic performance of CrOx/Al2O3 catalysts for ethylbenzene dehydrogenation through tailored coke deposition
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In previous work we have shown that ethylbenzene dehydrogenation over CrOx/Al2O3 catalysts proceeds sequentially via cracking and then dehydrogenation reactions. The present work reports how tailored coke deposition on the catalyst surface can suppress undesired reactions such as cracking to benzene and coke during ethylbenzene dehydrogenation. Additionally, this approach also provides insights into the precursor molecules involved in the formation of carbonaceous deposits, hence providing further understanding of coke formation. Pre-coked catalysts were prepared by adsorbing the products of the ethylbenzene reaction (i.e., benzene, toluene, styrene, ethylene) as single components, in a flowing system at 600 °C over the fresh catalyst. The resulting pre-coked catalysts were then evaluated in the ethylbenzene dehydrogenation reaction and their performance compared with that of the catalyst without exposure to pre-treatment. Characterisation of pre-coked catalysts by elemental analysis, temperature-programmed oxidation (TPO), temperature-programmed desorption (TPD), Raman spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) indicated that ethylene is the main coke precursor during ethylbenzene dehydrogenation and that ethylene-derived coke is associated with a reduction in selectivity to styrene as compared to the fresh catalyst. Coke deposited after pre-coking with aromatic molecules, and in particular with benzene, was beneficial for dehydrogenation activity, as shown by the increase in styrene selectivity relative to the fresh catalyst. This enhancement of dehydrogenation activity was correlated with deactivation of acid sites and the reduction of chromium from Cr(vi) to Cr(iii) (active species for dehydrogenation) as a result of the pre-coking procedure.
- Gomez Sanz, Sara,McMillan, Liam,McGregor, James,Zeitler, J. Axel,Al-Yassir, Nabil,Al-Khattaf, Sulaiman,Gladden, Lynn F.
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- Reducing coke formation in the catalytic fast pyrolysis of bio-derived furan with surface modified HZSM-5 catalysts
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In order to reduce coke yield during catalytic fast pyrolysis of biomass, MgO and 2,4-dimethylquinoline (2,4-DMQ) were selected to reduce the number of external acid sites of HZSM-5. Both MgO and 2,4-DMQ deposition could cause a reduction in total acid sites (both weak acid sites and strong acid sites) and external acid sites of HZSM-5. The modified catalysts were used for the catalytic conversion of bio-derived furan. For the MgO/HZSM-5 catalyst, the effects of amount of MgO deposited and deposition time were studied. The carbon yields of aromatics, C2-C5 olefins, total chemicals, CO2 and CO increased at first and then decreased slightly when the deposited amount increased, while the carbon yield of coke decreased first and then increased gradually. Furthermore, as the deposited time increased, the carbon yields of petrochemicals, CO2 and CO increased greatly, whereas that of coke decreased. For the 2,4-DMQ/HZSM-5 catalyst, the effects of 2,4-DMQ treatment amount and treatment time were investigated. The experimental results showed that an increase in 2,4-DMQ treatment amount or treatment time could retard the generation of the target products, CO2 and CO but promote coke formation.
- Zhang, Bo,Zhong, Zhaoping,Xie, Qinglong,Chen, Paul,Ruan, Roger
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- Isotope Effects and Hydrogen Exchange Mechanism in Compounds Having Labile Aliphatic C-H Bonds in Basic Liquid Ammonia Solutions
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Specific features of the stepwise hydrogen exchange mechanism and transition state structure in the systems acetophenone-liquid ammonia in the absence of foreign compounds and in the presence of bases and toluene-liquid ammonia in the presence of potassium amide were studied in terms of an approach based primary and secondary kinetic isotope effects of the substrate and the solvent. The mechanisms of reactions involving acetophenone and toluene were compared. In the first case, an elementary act of CH-acid ionization is contributed to a small extent by diffusion-controlled separation of the carbanion and ammonia molecule, hydrogen exchange in toluene is characterized by complete absence of the internal ion pair return effect. The ratio k dNH3/kTNH3 for hydrogen exchange in acetophenone tends to decrease on addition of bases (with simultaneous increase in its rate), which may be explained by formation of an adduct via interaction between the unshared electron pair on the heteroatom in the base molecule and the carbonyl carbon atom. The anomalous temperature dependence of k DNH3/kTNH3 for hydrogen exchange in toluene is interpreted as a result of contribution of side metalation of the C-H bond by potassium amide. The change in the solvent protophilicity due to replacement of the "light" solvent by deuterated one differently affects the kinetics and mechanism of hydrogen exchange in acetophenone and toluene. Measurements of the α-deuterium effect gave information on the mode of angular deformation of C-D bonds in the methyl group of toluene in the hydrogen exchange transition state.
- Tupitsyn,Zatsepina
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- Catalytic Decarbonylation of Aldehydes using Ruthenium(II) Porphyrin Systems
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Extremely efficient decarbonylation of aromatic and aliphatic aldehydes has been accomplished catalytically under ambient conditions using solutions of bis(triphenylphosphine) (tetraphenylporphyrinato)ruthenium(II).
- Domazetis, George,Tarpey, Blaithin,Dolphin, David,James, Brian R.
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- Highly efficient unsupported Co-doped nano-MoS2 catalysts for p-cresol hydrodeoxygenation
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To prepare catalyst with high activity, high selectivity and good stability remains the biggest challenge in the hydrodeoxygenation (HDO) of phenols by adopting MoS2-based sulfides as catalysts. Herein, we report a simple hydrothermal method to synthesize highly-dispersed nano-MoS2 with abundant defects and some curved slabs. All these advantages enable nano-MoS2 to provide a large number of coordination unsaturated sites to anchor Co atoms. The unsupported Co-doped catalyst with an optimal Co/(Co + Mo) molar ratio of 0.3 exhibited excellent performance in the HDO of p-cresol with conversion of 98.7 % and toluene selectivity of 98.9 % at 220 °C. Moreover, the optimized Co/MoS2-0.3 catalyst had a good stability after reaction of 72 h. The excellent HDO performance was attributed to the formation of abundant Co-Mo-S active sites which optimize the electrical structure of nano-MoS2 by Co promoter.
- Cao, Jing,Li, An,Zhang, Yicen,Mu, Linchao,Huang, Xi,Li, Yankun,Yang, Tao,Zhang, Cen,Zhou, Congshan
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- The catalytic effects of sulfur in ethane dehydroaromatization
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In this work, we investigated the catalytic effect of adding sulfur on Zn/ZSM-5 catalyst for direct conversion of ethane to aromatics. We show that the continuous addition of hydrogen sulfide (H2S) effectively stabilizes zinc, prevents coking and results in a highly selective and stable catalyst. Considering the high content of sulfur in shale gas resources, these results highlight the importance of investigating catalysts under realistic operating conditions.
- Goodarzi, Farnoosh,Hansen, Lars P.,Helveg, Stig,Mielby, Jerrik,Nguyen, Thoa T. M.,Joensen, Finn,Kegn?s, S?ren
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- Kinetic Isotope Effects in Hydrogen Atom Transfer Reactions between Benzylic Carbons
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The kinetic deuterium isotope effect for transfer of hydrogen from tetralin, dihydroanthracene, fluorene, diphenylmethane, triphenylmethane, and acenaphthene to the benzyl radical was measured at 170 deg C.The range of values for the effect was from 6.5 to 8.0.Activation energy parameters were obtained for five of the hydrogen donors.The apparent difference between activation energies for deuterium or hydrogen transfer was 2 kcal/mol for triphenylmethane, diphenylmethane, and tetralin.Applications of several tests indicate that a tunnel effect plays a significant role in these hydrogen transfers.
- Bockrath, Bradley C.,Bittner, Edward W.,Marecic, Thomas C.
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- Effect of Pressure on the Electron Mobility in Liquid Benzene and Toluene
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High pressure causes a decrease of the mobility of excess electrons in both benzene and toluene.These decreases are interpreted as a shift in the equilibrium e-s + A A- in favor of the anions (A-) at high pressure.These attachment reactions are favored at high pressure by large negative volume changes of between -100 and -180 cm3/mol, which are attributed to electrostriction of the solvent by the anion.Above 1.5 kbar the mobility becomes independent of pressure.Transport under these conditions involves electron hopping from the anion to a neighboring molecule.
- Itoh, Kengo,Holroyd, Richard
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- Electrochemical Initiation of Aromatic SRN1 Reactions Using Redox Catalysts
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Electrochemical reduction of benzonitrile in the presence of bromobenzene and tetra-N-butylammonium benzenethiolate in dimethyl sulfoxide (Me2SO) forms diphenyl sulfide (67percent) and benzene (38percent).The reaction consumes 0.37 faraday per mol of bromobenzene, indicating that an SRN1 chain reaction is occuring.Reaction in Me2SO-d6 gives a decreased yield of benzene (17percent), 57percent of which was monodeuterated, which along with coulometric data indicates that a major termination pathway is abstraction of hydrogen atoms from Me2SO by phenyl radicals.Photoinitiated reactions in the presence and absence of tetra-N-butylammonium ions indicate that they are also a significant source of hydrogen atoms in termination.Evidence from reactions of 4-bromotoluene with benzenethiolate ion indicates that fragmentation of the diaryl sulfide radical anion intermediate is an important reaction in these systems.The presence of benzonitrile suppresses that cleavage.
- Swartz, James E.,Stenzel, Timothy T.
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- Mechanistic insight to acidity effects of Ga/HZSM-5 on its activity for propane aromatization
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Ga-modified HZSM-5 precursors, containing 1 wt% Ga, were first prepared using the incipient wetness impregnation method, and then subjected to one or three-times consecutive treatment by cycles of reduction in hydrogen and re-oxidation in air. The resulting Ga/HZSM-5 catalysts were characterized by N2 physical adsorption, ICP-AES, DRIFT, Py-FTIR, NH3-TPD, H2-TPR, XPS, DRIFT-TPSR and MS-TPSR techniques to obtain clear mechanistic details that the acidity of these Ga/HZSM-5 catalysts affected their activity for propane aromatization. The characterization data suggested that the impregnated introduction of Ga to ZSM-5 zeolite and subsequent reduction-oxidation treatment led to a great decrease in the number of Bronsted acid sites (BAS) and promoted the formation of strong Lewis acid sites (LAS) attributed to highly dispersed Ga species. The formed strong LAS specifically promoted the dehydrogenation steps during propane aromatization, whereas the original BAS were responsible for the whole aromatization process. The TPSR results suggested that propane was converted to propylene through the dehydrogenation on BAS and strong LAS, and simultaneously converted to ethylene through the β-scission on BAS at a low temperature. With the elevation of temperature, the generated propylene and ethylene on the strong BAS and the strong LAS were further converted into BTX aromatics accompanied by hydrogen release. It was plausible that the highly efficient synergy between BAS and strong LAS could result in lower aromatization temperatures and more product of benzene (β state) over the Ga/HZSM-5 catalysts than that over the Ga-modified HZSM-5 precursors.
- Xiao, He,Zhang, Junfeng,Wang, Peng,Zhang, Zhenzhou,Zhang, Qingde,Xie, Hongjuan,Yang, Guohui,Han, Yizhuo,Tan, Yisheng
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- Nonoxidative Direct Conversion of Methane on Silica-Based Iron Catalysts: Effect of Catalytic Surface
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For a stable methane to olefins, aromatics, and hydrogen (MTOAH) reaction, 0.27-0.43 wt % Fe-containing silica catalysts were synthesized through various preparation methods and tested. The presence of Fe species in SiO2 mixtures increased the true and apparent densities of the catalysts during the melt-fusing process at 1700 °C. Several characterizations (i.e., H2-TPR, TEM, and XAS) revealed that partially reduced iron oxide (Fe3O4) predominantly existed in cristobalite (CRS) in the melt-fused catalysts. The FeCRS catalyst prepared from fayalite and quartz by the melt-fusing method showed a higher resistance to structural sintering and coke deposition than other Fe catalysts during MTOAH at 1020 °C. It also showed a 40% higher apparent activation energy for coke formation than for methane consumption in the temperature range of 1000 to 1040 °C. Increased CRS surfaces increased the coke selectivity, indicating that even the pure CRS surface acts as a chain reaction terminator to form coke. At the same space velocity (9400 h-1), the FeCRS catalyst was more selective in producing C2 (ethane, ethylene, and acetylene), C3-C5 olefins, and aromatics than pure CRS and other Fe catalysts. At a steady state, the FeCRS surface was most suitable for methane conversion, being 2.3 times more efficient than without a catalytic surface. The FeCRS catalyst exhibited a stable activity and low coke selectivity, even for 50 h, in the MTOAH reaction. EXAFS profiles showed that highly dispersed Fe carbide with Fe-Si coordination was formed in the FeCRS catalyst, and electronic structure calculations indicated that these confined Fe sites were more favorable for methyl radical formation and a high coke resistance than Fe3C clusters. By optimizing reaction parameters, the FeCRS catalyst exhibited 6.9-5.8% methane conversion and 86.2% C2 selectivity for 100 h with cofeeding of 50% H2 at 1080 °C.
- Han, Seung Ju,Lee, Sung Woo,Kim, Hyun Woo,Kim, Seok Ki,Kim, Yong Tae
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- The equilibrium constant for the methylcyclohexane-toluene system
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The hydrogenation-dehydrogenation of toluene and methylcyclohexane has been studied for seasonal hydrogen energy storage for mobile and stationary systems. The efficiency of the system is dependent on the kinetics of the endothermic, equilibrium-limited dehydrogenation reaction of methylcyclohexane to toluene. The equilibrium constant (Keq) for the methylcyclohexane-toluene system was determined experimentally because of the lack of fit appearing in kinetic evaluations when using published values for the Keq. The published value of Keq(T = 650 K) = 4.61 ± 0.04 × 109 kPa3 due to J. Akyurtlu and W.E. Stewart was redetermined to a value of Keq(T =650 K) 3.60 ± 0.05 × 109 kPa3 with isothermal experiments utilizing methylcyclohexane and toluene feeds separately.
- Schildhauer,Newson,Mueller, St.
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- Correlation of the catalytic performance with Nb2O5 surface properties in the hydrodeoxygenation of lignin model compound
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Production of aromatic hydrocarbons through lignin hydrodeoxygenation (HDO) is of significant importance. Previously, we found that Ru/Nb2O5 was an excellent catalyst for the conversion of lignin to arenes with relatively high selectivity (71%). Herein, we aim to clarify which properties of Nb2O5 influence the activity and selectivity. Four Ru/Nb2O5 catalysts with different Nb2O5 morphologies were used in the HDO of 4-methylphenol. Intensive studies show that layered Nb2O5 supported Ru has more Nb[dbnd]O groups (unsaturated NbOx sites) and highest Ru dispersion, which led to the highest activity and toluene selectivity, this was further confirmed by loading pre-synthesized Ru colloids in various Nb2O5. Finally, a Ru/Nb2O5 catalyst with more unsaturated Nb[dbnd]O groups was designed and it was found that even with enzymatic lignin as the feedstock, the selectivity to arenes can reach up to 94.8% with the yield of hydrocarbons of 99.6%. This study provides a promising strategy for catalyst design towards the selective production of aromatic hydrocarbons from lignin.
- Xin, Yu,Dong, Lin,Guo, Yong,Liu, Xiaohui,Hu, Yongfeng,Wang, Yanqin
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- DEHYDROCYCLIZATION OF HEXANE TO BENZENE CATALYZED BY REDUCED ZIRCONIUM OXIDE TREATED WITH SULFATE, SELENATE, AND TELLURATE IONS
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Dehydrocyclization catalysts for paraffinic hydrocarbons were obtained by exposing Zr(OH)4 to 0.5 M H2SO4, 0.05 M H2SeO4, or 0.05 M H2TeO4 followed by calcination in air at 600-700 deg C and reduction at 500-550 deg C.The catalytic properties were highly dependent on metal oxides used as supports; ZrO2 was most effective.The catalyst converted hexane into benzene with selectivity up to 84percent.
- Hino, Makoto,Arata, Kazushi
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- Pyrolytic hydrocarbon growth from cyclopentadiene
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Aromatic hydrocarbon growth from cyclopentadiene (CPD) was studied using a laminar flow reactor operating in the temperature range 550-950 °C without oxygen. Benzene, indene, and naphthalene were the major products, which is in agreement with the previous computational studies on the reaction pathways from CPD. A crossover of indene and naphthalene yields around 775 °C was also observed, which further supports the results of the computational studies. Although the specific intermediates in the proposed pathways from CPD were not detected, the high selectivity of products and the observation of other methylindene and dihydronaphthalene intermediates suggest that the recombination of two CPDs via radical-molecule and/or radical-radical pathways to form indene and naphthalene is the dominant formation pathway. In addition to the products from the CPD-CPD reactions, the products from the reactions of CPD with indene, naphthalene, and acenaphthylene were also observed, which demonstrate the importance of CPD in carbon growth.
- Kim, Do Hyong,Mulholland, James A.,Wang, Dong,Violi, Angela
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- The application of a supported palladium catalyst for the hydrogenation of aromatic nitriles
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The use of a Pd/C catalyst in the liquid phase hydrogenation of various aromatic nitriles (benzonitrile, benzyl cyanide, 3-phenyl propionitrile and cinnamonitrile) has been studied in order to assess the effectiveness of this type of catalyst for this class of reaction. On modifying the nitrile substituent and upon introducing conjugation, varying degrees of conversion are observed. For benzyl cyanide and 3-phenylpropionitrile, incomplete mass balance profiles are linked to spill-over to the carbon support. In the case of benzonitrile hydrogenation, a hydrogenolytic step leads to a loss of selectivity to the primary amine to yield toluene with, ultimately, complete selectivity. Co-hydrogenation measurements on mixtures of benzonitrile and benzylamine indicate the presence of site-selective chemistry. Co-hydrogenation studies on mixtures of benzonitrile and benzyl cyanide highlight the competitive nature of the reaction system and, indirectly, establish a contribution from adsorbed imine species.
- McMillan, Liam,Gilpin, Lauren F.,Baker, Justin,Brennan, Colin,Hall, Alan,Lundie, David T.,Lennon, David
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- Catalytic fast pyrolysis of cellulose in a microreactor system using hierarchical zsm-5 zeolites treated with various alkalis
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Hierarchical ZSM-5 catalysts were prepared by desilication using NaOH, Na2CO3 and TPAOH with different concentrations under the same treatment conditions. Their structures and acidities were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption and desorption (N2-BET) and ammonia temperature-programmed desorption (NH3-TPD). The catalytic fast pyrolysis (CFP) of cellulose to produce aromatics over the hierarchical ZSM-5 catalysts prepared using different alkali treatments was investigated. The alkali treatment by Na2CO3 (0.4 ～ 0.8 M) was much milder than treatment by NaOH, which allowed the desilication process to be highly controllable, resulting in an increase of both the amount and strength of the strong acid sites, and the formation of hierarchical structures combining micro- and mesoporosity. The organic hydroxide TPAOH did not change the pore structure of ZSM-5, but it greatly increased the relative crystallinity. The CFP of cellulose with HZSM-5 produced 35.5% liquid aromatic hydrocarbons and 32.7% coke. The yield of aromatics increased after Na2CO3 treatment but decreased after NaOH treatment. In addition, the yield of coke showed the opposite trend. The highest aromatic yield (38.2%) and lowest coke yield were obtained in the CFP of cellulose with the desilicated zeolite treated with 0.6 M Na2CO3. The increased acidity in hierarchical ZSM-5 treated with Na2CO3 increased the selectivity of highly valuable aromatics, such as benzene, toluene, and xylene, and decreased the selectivity of large aromatics. TPAOH-treated HZSM-5 showed a slightly increased yield of aromatics due to the repair effect of TPAOH, but this treatment did not form a mesoporous structure.
- Qiao, Kai,Shi, Xu,Zhou, Feng,Chen, Hao,Fu, Jie,Ma, Huixia,Huang, He
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- Non-oxidative reactions of propane on Zn/Na-ZSM5
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Propene formation rates during propane conversion at 773 K on Zn/Na-ZSM5 are about ten times higher than on Zn/H-ZSM5 catalysts with similar Zn content. The total rate of propane conversion is also higher on Zn/Na-ZSM5 by a factor of four. Propane reactions lead to high propene selectivities (> 50%) as protons are replaced by Na cations in Zn/H-ZSM5 catalysts. The titration of acid sites with Na+ cations decreases the rate of acid- catalyzed chain growth reactions and the selectivity to C6-C9 aromatics. X- ray absorption studies at the Zn-K edge showed that aqueous ion exchange of Na-ZSM5 with Zn cations leads to isolated (ZnOH)+ species located at cation exchange sites. Unlike Zn species in Zn/H-ZSM5 (+ species with neighboring zeolite OH groups are less likely to occur in Zn/Na-ZSM5 and most Zn species remain as (ZnOH)+. Temperature programmed reduction studies show that Zn species in Zn/Na-ZSM5 reduce at lower temperatures than the (O-Zn2+-O-) species present in Zn/H-ZSM5. D2 exchange with surface OH groups showed that some protons are formed during ion exchange. Higher deuterium contents in products of C3H8-D2 mixtures on Zn/Na-ZSM5 suggest that (ZnOH)+ species in Zn/Na- ZSM5 catalyze rate-determining hydrogen desorption steps during propane conversion more effectively than (O-Zn2+-O-) sites present in Zn/H-ZSM5. The presence of (ZnOH)+ species and a lower acid site density in Zn/Na-ZSM5 leads to much higher propane conversion rates than on Zn/H-ZSM5. As the acid site density decreases, propene aromatization rates decrease, which leads to less hydrogen to be disposed by a more efficient hydrogen recombinative desorption species (ZnOH)+.
- Biscardi, Joseph A.,Iglesia, Enrique
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- THERMAL TRANSFER FLUID: 1-PHENYL-1-TETRAHYDRONAPHTHYLETHANE.
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Naphthalene was selectively hydrogenated to tetralin, followed by reaction with styrene to give 1-phenyl-1-tetrahydronaphthylethane in 87% yield. Efficient catalysts for the reaction were 90% sulfuric acid or solid acids possessing acid sites of H//0 less than or equal to minus 5. 6. Purified 1-phenyl-1-tetrahydronaphthylethane has favored properties for a high boiling point thermal transfer fluid: boiling point, 342 C; pour point minus 37. 5 C; good thermal stability, etc. On severe heating, it decomposed to low fractions to some extent with little tendency to polymerization.
- Matsumoto,Furukawa,Tanaka,Yano,Kamita
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- Electron Attachment to Toluene and 2,2-Dimethylbutane at High Pressure
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The effect of dilute concentrations of toluene on the electron mobility in two isomeric hexanes was studied as a function of pressure from 1 bar to 3 kbar and at selected temperatures between 9 and 60 deg C.The effect of toluene on the mobility is small a
- Itoh, Kengo,Nishikawa, Masaru,Holroyd, Richard
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- Oxidative dehydrogenation of cyclohexane and cyclohexene over supported gold, palladium and gold-palladium catalysts
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Supported gold, palladium and gold-palladium catalysts have been used to oxidatively dehydrogenate cyclohexane and cyclohexenes to their aromatic counterpart. The supported metal nanoparticles decreased the activation temperature of the dehydrogenation reaction. We found that the order of reactivity was Pd ≥ Au-Pd > Au supported on TiO2. Attempts were made to lower the reaction temperature whilst retaining high selectivity. The space-time yield of benzene from cyclohexane at 473 K was determined to be 53.7 mol/kgcat/h rising to 87.3 mol/kgcat/h at 673 K for the Pd catalyst. Increasing the temperature in this case improved conversion at a detriment to the benzene selectivity. Oxidative dehydrogenation of cyclohexene over AuPd/TiO2 or Pd/TiO2 catalysts was found to be very effective (conversion >99% at 423 K). These results indicate that the first step in the reaction sequence of cyclohexane to cyclohexene is the slowest step. These initial results suggest that in a fixed-bed reactor the oxidative dehydrogenation in the presence of oxygen, palladium and gold-palladium catalysts are readily able to surpass current literature examples and with further modification should yield even higher performance.
- Dummer, Nicholas F.,Bawaked, Salem,Hayward, James,Jenkins, Robert,Hutchings, Graham J.
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- Metal-Free Photocatalytic Reductive Dehalogenation Using Visible-Light: A Time-Resolved Mechanistic Study
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The reductive dehalogenation of organic bromides has been achieved in the presence of riboflavin (RF) as photocatalyst under visible-light irradiation. Specifically, benzyl bromide (2) and α-bromoacetophenone (3) were quantitatively converted into toluene and acetophenone, respectively, by using amines as electron donors and iPrOH as hydrogen donor, whereas bromobenzene (1) did not react. The thermodynamics of the reduction of the radical anion of RF were evaluated by using the redox potentials of the species involved: The reaction was found to be thermodynamically exergonic for 2 and 3, but not expected to occur for bromobenzene (1). The viability of the different competing processes on the timescales of the corresponding singlet and triplet RF excited states (1RF* and 3RF*) was analyzed by time-resolved techniques. The quenching of 1RF* by amines was very efficient, and comparison of the transient absorption spectra recorded in the absence and presence of amines additionally confirmed the efficient redox process between 1RF* and the amines. Moreover, RF·– was quenched by bromides 2 and 3, but not by 1. Thus, a deeper understanding of the overall mechanism of the photocatalytic reductive reaction has been achieved, and the key role of the radical anion of the photocatalyst has been demonstrated.
- Martinez-Haya, Rebeca,Miranda, Miguel A.,Marin, M. Luisa
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- Efficient hydrogenolysis of aryl ethers over Ce-MOF supported Pd NPs under mild conditions: mechanistic insight using density functional theoretical calculations
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Selective hydrogenolysis of lignin-derived aryl ethers under mild temperature and pressure conditions is an important milestone to be achieved to fulfill the future fuel demands from abundantly available biomass resources. Selective hydrogenolysis requires precise modulation of surface active sites of the catalyst to obtain the desired activity and selectivity. In this study, the selective hydrogenolysis of benzyl phenyl ether to phenol and toluene is achieved in methanol and water medium at a very low temperature and low H2 pressure over a Pd nanoparticle decorated Ce-BTC metal-organic framework. The activity of the developed catalyst is two times higher than that of Pd decorated CeO2. The structure-activity relationship is established using catalytic measurements, X-ray photoelectron spectroscopy, and transmission electron microscopy. The mechanistic insight into the hydrogenolysis of aryl ethers and the reasons behind the superior activity of Pd/Ce-BTC to that of Pd/CeO2 are investigated using density functional theoretical (DFT) calculations. Spectroscopic measurements and DFT calculations suggest that the higher Pd0/Pd2+ ratio and higher adsorption of benzyl phenyl ether over Pd/Ce-BTC and the higher adsorption of phenol over Pd/CeO2 are factors responsible for the higher activity of Pd/Ce-BTC than that of Pd/CeO2. Efficient recyclability and hot filtration tests reveal that the catalyst exhibits no noteworthy loss in the activity after five consecutive cycles. The Pd/Ce-BTC catalyst displays a very high turnover frequency and low activation energy, which are very attractive from the industrial perspective and academic point of view. This journal is
- Kar, Ashish Kumar,Kaur, Surinder Pal,Kumar, T. J. Dhilip,Srivastava, Rajendra
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- Hydrogenolysis of lignosulfonate into phenols over heterogeneous nickel catalysts
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We report a strategy for the catalytic conversion of lignosulfonate into phenols over heterogeneous nickel catalysts. Aryl-alkyl bonds (C-O-C) and hydroxyl groups (-OH) are hydrogenated to phenols and alkanes, respectively, without disturbing the arenes. The catalyst is based on a naturally abundant element, and is recyclable and reusable. The Royal Society of Chemistry 2012.
- Song, Qi,Wang, Feng,Xu, Jie
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- One-Pass Conversion of Benzene and Syngas to Alkylbenzenes by Cu–ZnO–Al2O3 and ZSM-5 Relay
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Alkylbenzenes have a wide range of uses and are the most demanded aromatic chemicals. The finite petroleum resources compels the development of production of alkylbenzenes by non-petroleum routes. One-pass selective conversion of benzene and syngas to alkylbenzenes is a promising alternative coal chemical engineering route, yet it still faces challenge to industrialized applications owing to low conversion of benzene and syngas. Here we presented a Cu–ZnO–Al2O3/ZSM-5 bifunctional catalyst which realizes one-pass conversion of benzene and syngas to alkylbenzenes with high efficiency. This bifunctional catalyst exhibited high benzene conversion (benzene conversion of 50.7%), CO conversion (CO conversion of 55.0%) and C7&C8 aromatics total yield (C7&C8 total yield of 45.0%). Characterizations and catalytic performance evaluations revealed that ZSM-5 with well-regulated acidity, as a vital part of this Cu–ZnO–Al2O3/ZSM-5 bifunctional catalyst, substantially contributed to its performance for the alkylbenzenes one-pass synthesis from benzene and syngas due to depress methanol-to-olefins (MTO) reaction. Furthermore, matching of the mass ratio of two active components in the dual-function catalyst and the temperature of methanol synthesis with benzene alkylation reactions can effectively depress the formation of unwanted by-products and guarantee the high performance of tandem reactions. Graphic Abstract: [Figure not available: see fulltext.]
- Han, Tengfei,Xu, Hong,Liu, Jianchao,Zhou, Ligong,Li, Xuekuan,Dong, Jinxiang,Ge, Hui
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p. 467 - 479
(2021/05/21)
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- Selective catalytic synthesis of bio-based high value chemical of benzoic acid from xylan with Co2MnO4@MCM-41 catalyst
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The efficient synthesis of bio-based chemicals using renewable carbon resources is of great significance to promote sustainable chemistry and develop green economy. This work aims to demonstrate that benzoic acid, an important high added value chemical in petrochemical industry, can be selectively synthesized using xylan (a typical model compound of hemicellulose). This novel controllable transformation process was achieved by selective catalytic pyrolysis of xylan and subsequent catalytic oxidation. The highest benzoic acid selectivity of 88.3 % with 90.5 % conversion was obtained using the 10wt%Co2MnO4@MCM-41 catalyst under the optimized reaction conditions (80 °C, 4 h). Based on the study of the model compounds and catalyst's characterizations, the reaction pathways for the catalytic transformation of xylan to bio-based benzoic acid were proposed.
- Fan, Minghui,He, Yuting,Li, Quanxin,Luo, Yuehui,Yang, Mingyu,Zhang, Yanhua,Zhu, Lijuan
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- MOF-derived Ru@ZIF-8 catalyst with the extremely low metal Ru loading for selective hydrogenolysis of C–O bonds in lignin model compounds under mild conditions
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Lignin hydrogenolysis to produce chemicals and biofuels is a challenge due to the stable C–O ether bond structure. Metal–organic framework (MOF) materials with excellent structural and chemical versatility have received widespread attention. Herein, a highly dispersed Ru metal anchored in functionalised ZIF-8 was fabricated by a general host–guest and reduction strategy. The Ru@ZIF-8 catalyst with a high specific surface area could efficiently promote the C–O bond cleavage of a variety of lignin model compounds under mild conditions. Compared with previous studies, the extremely low metal Ru loading in the Ru@ZIF-8 catalyst achieved a relatively higher activity. The introduction of Ru metal not only improved the dispersion of Zn metal, but also enhanced the electron density on the Zn surface, suggesting a high catalytic performance. It was more conducive for the Ru@ZIF-8 catalyst to exhibit the C–O bond cleavage activity when in the presence of both H2 and isopropanol. An investigation of the mechanism revealed that the direct hydrogenolysis of benzyl phenyl ether was the main reaction pathway.
- Cao, Jing-Pei,Jiang, Wei,Xie, Jin-Xuan,Zhang, Chuang,Zhang, Jian-Li,Zhao, Liang,Zhao, Xiao-Yan,Zhao, Yun-Peng,Zhu, Chen
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p. 488 - 496
(2022/02/07)
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- H2O2-mediated room temperature synthesis of 2-arylacetophenones from arylhydrazines and vinyl azides in water
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An environmentally benign, cost-efficient and practical methodology for the room temperature synthesis of 2-arylacetophenones in water has been discovered. The facile and efficient transformation involves the oxidative radical addition of arylhydrazines with α-aryl vinyl azides in the presence of H2O2 (as a radical initiator) and PEG-800 (as a phase-transfer catalyst). From the viewpoint of green chemistry and organic synthesis, the present protocol is of great significance because of using cheap, non-toxic and readily available starting materials and reagents as well as amenability to gram-scale synthesis, which provides an attractive strategy to access 2-arylacetophenones.
- Luo, Mengqiang,Zhang, Yaohong,Fang, Ping,Li, Yan,Qi, Chenze,Li, Yong,Shen, Runpu,Cheng, Kai,Wang, Hai
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supporting information
p. 630 - 635
(2022/02/01)
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- Hydrodeoxygenation of lignin and its model compounds to hydrocarbon fuels over a bifunctional Ga-doped HZSM-5 supported metal Ru catalyst
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Hydrodeoxygenation (HDO) of lignin to value-added biofuels and chemicals has a great significance for the advanced utilization of renewable lignocelluloses and the future biobased economy but is always a big challenge. Herein, a Ga-doped HZSM-5 supported metal Ru catalyst (bifunctional Ru/Ga-HZSM-5) exhibited the excellent HDO performance for converting diphenyl ether (DPE) to produce the only product, i.e., cyclohexane, under extremely mild conditions (180 °C, 1 MPa H2 and 2 h). The oxygen-containing group in DPE was mainly removed through the cleavage of the C-O ether bond, followed by metal- and acid-catalyzed comprehensive hydrogenation and deoxygenation. Further characterization results confirmed that the doping of Ga remarkably enhanced the interaction between the metal Ru and the support. For the depolymerization of real lignin, Ru/Ga-HZSM-5 could not only significantly improve the total liquid yield of lignin, but also convert the oxygen-containing species into the aliphatic hydrocarbons.
- Cao, Jing-Pei,Jiang, Wei,Xie, Jin-Xuan,Yang, Zhen,Zhang, Chuang,Zhang, Jian-Li,Zhao, Liang,Zhao, Xiao-Yan,Zhao, Yun-Peng,Zhu, Chen
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- One-step conversion of lignin-derived alkylphenols to light arenes by co-breaking of C-O and C-C bonds
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The conversion of lignin-derived alkylphenols to light arenes by a one-step reaction is still a challenge. A 'shortcut' route to transform alkylphenols via the co-breaking of C-O and C-C bonds is presented in this paper. The catalytic transformation of 4-ethylphenol in the presence of H2 was used to test the breaking of C-O and C-C bonds. It was found that the conversion of 4-ethylphenol was nearly 100%, and the main products were light arenes (benzene and toluene) and ethylbenzene under the catalysis of Cr2O3/Al2O3. The conversion of 4-ethylphenol and the selectivity of the products were significantly influenced by the reaction temperature. The selectivity for light arenes reached 55.7% and the selectivity for overall arenes was as high as 84.0% under suitable reaction conditions. Such results confirmed that the co-breaking of the C-O and C-C bonds of 4-ethylphenol on a single catalyst by one step was achieved with high efficiency. The adsorption configuration of the 4-ethylphenol molecule on the catalyst played an important role in the breaking of the C-O and C-C bonds. Two special adsorption configurations of 4-ethylphenol, including a parallel adsorption and a vertical adsorption, might exist in the reaction process, as revealed by DFT calculations. They were related to the breaking of C-O and C-C bonds, respectively. A path for the hydrogenation reaction of 4-ethylphenol on Cr2O3/Al2O3 was proposed. Furthermore, the co-breaking of the C-O and C-C bonds was also achieved in the hydrogenation reactions of several alkylphenols. This journal is
- Di, Yali,Li, Guangyu,Li, Zhiqin,Liu, Weiwei,Qiu, Zegang,Ren, Xiaoxiong,Wang, Ying
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supporting information
p. 2710 - 2721
(2022/02/21)
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- Impact of oxygen vacancies in Ni supported mixed oxide catalysts on anisole hydrodeoxygenation
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The hydrodeoxygenation (HDO) activity of anisole has been investigated over Ni catalysts on mixed metal oxide supports containing Nb–Zr and Ti–Zr in 1:1 and 1:4 ratios. XRD patterns indicate the incorporation of Ti (or Nb) into the ZrO2 framewo
- Ali, Hadi,Kansal, Sushil Kumar,Lauwaert, Jeroen,Saravanamurugan, Shunmugavel,Thybaut, Joris W.,Vandevyvere, Tom
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- Selective aerobic oxidation of toluene to benzaldehyde catalyzed by covalently anchored N-hydroxyphthalimide and cobaltous ions
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Selective oxidation of toluene to benzaldehyde via dioxygen is of great significance industrially but suffers from a severely low selectivity due to a much higher reactivity of the desired product than the reactant. A combination of homogeneous N-hydroxyphthalimide (NHPI) and cobaltous ions was found active and selective for the transformation from toluene to benzaldehyde in the presence of hexafloropropan-2-ol. In this work, homogeneous NHPI was covalently anchored onto the surface of commercial mesoporous SiO2 to facilitate the separation and recovery of the catalyst, aiming at a possible industrial application. The grafting bonds were well confirmed by FT-IR, TGA and XP spectra, and the density of > N–OH groups anchored was up to 0.6 mmol/g in the immobilized NHPI catalysts. The resulting catalysts exhibited an excellent activity for selective oxidation of toluene to benzaldehyde, and there was no appreciable loss in catalytic activity observed after repeated evaluations, suggesting a promising prospect for its further investigation and possible application.
- Xu, Jinyang,Shi, Guojun,Liang, Yuxin,Lu, Qiuting,Ji, Lijun
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- Determining the active catalytic palladium species under hydrodeoxygenation conditions
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The molecular, homogeneous catalyst 2,6-bis(4-isopropyl-2-oxazolinyl)pyridine palladium(II) was examined for the ability to perform selective hydrodeoxygenation of benzyl alcohol. Reaction conditions and substrate were chosen to mimic conditions used to depolymerize lignin biomass and subsequently convert the lignin-derived monomers into useful biofuels. The molecular catalyst exhibited moderate catalytic activity in methanol solvent with complete selectivity towards hydrodeoxygenation (HDO) of benzyl alcohol under mild conditions, including room temperature. At elevated temperatures, the molecular catalyst decomposed into solid particles. These particles were characterized with XPS and contained metallic palladium, which also exhibited catalytic HDO activity. The particles also achieved complete selectivity towards hydrodeoxygenation over aromatic ring hydrogenation, but only at temperatures above 200 °C. Recycling the solid particle catalysts over multiple reaction cycles, led to the leaching of the catalytically active species back into solution and the eventual deactivation of the solid particles.
- Tillou, Jake G.,Vannucci, Aaron K.
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- Selective upgrading of biomass-derived benzylic ketones by (formic acid)–Pd/HPC–NH2 system with high efficiency under ambient conditions
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Upgrading biomass-derived phenolic compounds provides a valuable approach for the production of higher-value-added fuels and chemicals. However, most established catalytic systems display low hydrodeoxygenation (HDO) activities even under harsh reaction conditions. Here, we found that Pd supported on –NH2-modified hierarchically porous carbon (Pd/HPC–NH2) with formic acid (FA) as hydrogen source exhibits unprecedented performance for the selective HDO of benzylic ketones from crude lignin-derived oxygenates. Designed experiments and theoretical calculations reveal that the H+/H? species generated from FA decomposition accelerates nucleophilic attack on carbonyl carbon in benzylic ketones and the formate species formed via the esterification of intermediate alcohol with FA expedites the cleavage of C–O bonds, achieving a TOF of 152.5 h?1 at 30°C for vanillin upgrading, 15 times higher than that in traditional HDO processes (～10 h?1, 100°C–300°C). This work provides an intriguing green route to produce transportation fuels or valuable chemicals from only biomass under mild conditions.
- Chen, Yuzhuo,Chen, Zhirong,Gong, Yutong,Mao, Shanjun,Ning, Honghui,Wang, Yong,Wang, Zhenzhen
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p. 3069 - 3084
(2021/11/16)
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- Iodine-catalyzed alcohol disproportionation method
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The invention relates to the technical field of catalysis, in particular to an iodine-catalyzed alcohol disproportionation method which comprises the following steps: sequentially adding alcohol, iodine and a solvent into a high-temperature and high-pressure reaction kettle, introducing a certain amount of nitrogen, conducting reacting for a certain time, collecting an organic phase after the reaction is ended, and conducting fractionating to obtain corresponding alkane and aldehyde/ketone. Alcohol disproportionation is efficient and atom-economical conversion without any additional oxidizing agent and reducing agent, and hydrocarbon and aldehyde/ketone molecules which are easy to separate can be formed at the same time. Meanwhile, the method has wide functional group tolerance, various substrate samples including aryl alcohol derivatives, heterocyclic alcohol derivatives, allyl alcohol derivatives and dihydric alcohol are tested, and the result shows that most of the substrate samples show good or extremely good yield.
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Paragraph 0024-0025
(2021/06/13)
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- Radical induced disproportionation of alcohols assisted by iodide under acidic conditions
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The disproportionation of alcohols without an additional reductant and oxidant to simultaneously form alkanes and aldehydes/ketones represents an atom-economical transformation. However, only limited methodologies have been reported, and they suffer from a narrow substrate scope or harsh reaction conditions. Herein, we report that alcohol disproportionation can proceed with high efficiency catalyzed by iodide under acidic conditions. This method exhibits high functional group tolerance including aryl alcohol derivatives with both electron-withdrawing and electron-donating groups, furan ring alcohol derivatives, allyl alcohol derivatives, and dihydric alcohols. Under the optimized reaction conditions, a 49% yield of 5-methyl furfural and a 49% yield of 2,5-diformylfuran were obtained simultaneously from 5-hydroxymethylfurfural. An initial mechanistic study suggested that the hydrogen transfer during this redox disproportionation occurred through the inter-transformation of HI and I2. Radical intermediates were involved during this reaction.
- Huang, Yang,Jiang, Haiwei,Li, Teng,Peng, Yang,Rong, Nianxin,Shi, Hexian,Yang, Weiran
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supporting information
p. 8108 - 8115
(2021/10/29)
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- Direct Use of Benzylic Alcohols for Multicomponent Synthesis of 2-Aryl Quinazolinones Utilizing the π-Benzylpalladium(II) System in Water
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We demonstrate the direct use of benzylic alcohols for a multicomponent reaction of readily available isatoic anhydrides with amines in water, which is a synthetic route for the direct construction of a series of 2-aryl quinazolinones. This one-pot synthetic method involves the dehydrative N-benzylation of in situ generated anthranilamides followed by an amide-directed benzylic C?H amination process utilizing the π-benzylPd(II) system. Comparison of independent rate measurements using benzyl alcohol and its deuterated form gave a kinetic isotope effect of 3.5. Therefore, the benzylic C?H bond is cleaved in the rate-determining step. We successfully carried out a gram-scale reaction in 85% yield with simplified product isolation. (Figure presented.).
- Hikawa, Hidemasa,Nakayama, Taku,Takahashi, Makiko,Kikkawa, Shoko,Azumaya, Isao
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supporting information
p. 4075 - 4084
(2021/07/26)
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- Phenylacetylene hydrogenation coupled with benzyl alcohol dehydrogenation over Cu/CeO2: A consideration of Cu oxidation state
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We have examined the effect of copper oxidation state in the continuous gas phase coupled phenylacetylene hydrogenation (to styrene) with benzyl alcohol dehydrogenation (to benzaldehyde) over Cu/CeO2. Analysis by H2-TPR, XPS, XRD and
- Pischetola, Chiara,Francis, Stephen M.,Grillo, Federico,Baddeley, Christopher J.,Cárdenas-Lizana, Fernando
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p. 316 - 331
(2020/12/07)
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- Water-promoted dehydrative coupling of 2-aminopyridines in heptane: Via a borrowing hydrogen strategy
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A synthetic method for dehydrative N-benzylation promoted by water molecules in heptane using a π-benzylpalladium system has been developed. The presence of water significantly accelerates carbon-nitrogen bond formation, which is accomplished in an atom-economical process to afford the corresponding N-monobenzylated products. A crossover experiment afforded H/D scrambled products, which is consistent with a borrowing hydrogen mechanism. Kinetic isotope effect measurements revealed that benzylic carbon-hydrogen bond cleavage was the rate-determining step.
- Azumaya, Isao,Hikawa, Hidemasa,Kikkawa, Shoko,Nakayama, Taku
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p. 23144 - 23150
(2021/07/21)
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- Bipyridinium and Phenanthrolinium Dications for Metal-Free Hydrodefluorination: Distinctive Carbon-Based Reactivity
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The development of novel Lewis acids derived from bipyridinium and phenanthrolinium dications is reported. Calculations of Hydride Ion Affinity (HIA) values indicate high carbon-based Lewis acidity at the ortho and para positions. This arises in part from extensive LUMO delocalization across the aromatic backbones. Species [C10H6R2N2CH2CH2]2+ (R=H [1 a]2+, Me [1 f]2+, tBu [1 g]2+), and [C12H4R4N2CH2CH2]2+ (R=H [2 a]2+, Me [2 b]2+) were prepared and evaluated for use in the initiation of hydrodefluorination (HDF) catalysis. Compound [2 a]2+ proved highly effective towards generating catalytically active silylium cations via Lewis acid-mediated hydride abstraction from silane. This enabled the HDF of a range of aryl- and alkyl- substituted sp3(C?F) bonds under mild conditions. The protocol was also adapted to effect the deuterodefluorination of cis-2,4,6-(CF3)3C6H9. The dications are shown to act as hydride acceptors with the isolation of neutral species C16H14N2 (3 a) and C16H10Me4N2 (3 b) and monocationic species [C14H13N2]+ ([4 a]+) and [C18H21N2]+ ([4 b]+). Experimental and computational data provide further support that the dications are initiators in the generation of silylium cations.
- Burton, Katherine I.,Elser, Iris,Waked, Alexander E.,Wagener, Tobias,Andrews, Ryan J.,Glorius, Frank,Stephan, Douglas W.
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supporting information
p. 11730 - 11737
(2021/07/16)
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- Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds
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We report the formation and full characterization of weak adducts between Li+ and Na+ cations and a neutral iron(0) complex, [Fe(CO)3(PMe3)2] (1), supported by weakly coordinating [BArF20] anions, [1·M][BArF20] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)3(PMe3)2][BArF20], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S). Further, we utilize [1·M][BArF20] as a catalyst in a simple hydrodehalogenation reaction under mild conditions to showcase its potential use in catalytic reactions. Finally, the mechanism of activation is probed using DFT and kinetic experiments that reveal that the alkali metal and iron(0) center cooperate to cleave C-X via a mechanism closely related to intramolecular FLP activation.
- Tinnermann, Hendrik,Sung, Simon,Csókás, Dániel,Toh, Zhi Hao,Fraser, Craig,Young, Rowan D.
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supporting information
p. 10700 - 10708
(2021/07/31)
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- New insight into the electrochemical reduction of different aryldiazonium salts in aqueous solutions
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Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied in this work and it is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion. The results of this research indicate that the reduction of aryldiazonium salts takes place in two single-electron steps. Our data show that when the substituted group on the phenyl ring is H, Cl, OH, NO2, OCH3or SO3?, the corresponding diazonium salt shows poor adsorption characteristics, but when the substituted group is methyl, the corresponding diazonium salt shows strong adsorption characteristics. In the latter case, the voltammogram exhibits three cathodic peaks. In addition, the effect of various substitutions on the aryldiazonium reduction was studied by Hammett's method. The data are show that with increasing electron withdrawing capacity of the substituent, the reduction of corresponding diazonium salt becomes easier.
- Goljani, Hamed,Nematollahi, Davood,Sepehrmansourie, Hassan,Tavakkoli, Zahra,Zolfigol, Mohammad Ali
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p. 25811 - 25815
(2021/08/09)
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- Nanoparticle-catalyzed green chemistry synthesis of polybenzoxazole
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Enabling catalysts to promote multistep chemical reactions in a tandem fashion is an exciting new direction for the green chemistry synthesis of materials. Nanoparticle (NP) catalysts are particularly well suited for tandem reactions due to the diverse surface-active sites they offer. Here, we report that AuPd alloy NPs, especially 3.7 nm Au42Pd58 NPs, catalyze one-pot reactions of formic acid, diisopropoxy-dinitrobenzene, and terephthalaldehyde, yielding a very pure thermoplastic rigid-rod polymer, polybenzoxazole (PBO), with a molecular weight that is tunable from 5.8 to 19.1 kDa. The PBO films are more resistant to hydrolysis and possess thermal and mechanical properties that are superior to those of commercial PBO, Zylon. Cu NPs are also active in catalyzing tandem reactions to form PBO when formic acid is replaced with ammonia borane. Our work demonstrates a general approach to the green chemistry synthesis of rigid-rod polymers as lightweight structural materials for broad thermomechanical applications.
- Shen, Mengqi,Yu, Chao,Guan, Huanqin,Dong, Xiang,Harris, Cooro,Xiao, Zhen,Yin, Zhouyang,Muzzio, Michelle,Lin, Honghong,Robinson, Jerome R.,Colvin, Vicki L.,Sun, Shouheng
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supporting information
p. 2115 - 2122
(2021/02/16)
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- CIRCULAR ECONOMIC METHODS FOR FRAGRANCE INGREDIENTS
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Disclosed is a method for converting cymene generated from renewable low value terpene streams into renewable benzene, toluene, xylenes, and cymene isomers (ortho and meta) under flow disproportionation reaction conditions, which compounds are basic building blocks for fragrance materials. This technology has potential to replace high volume petrochemical-based feedstocks with plant-based building blocks that can fill the renewability gap for key fragrance ingredients.
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Page/Page column 9-10
(2021/02/05)
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- CATALYTIC COMPOSITIONS FOR THE OXIDATION OF SUBSTRATES
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Catalytic compositions and sequential catalytic methods are generally described. in some embodiments, a composition comprises a first catalyst comprising a Cu-modified zeolite, and a second catalyst capable of a coupling reaction between (a) an intermediate resulting from a reaction of a reactant at the first catalyst, and (b) a co-reagent, wherein a rate of diffusion of the co-reagent within one or more cages and/or pores of the first catalyst is lower than a rate of diffusion of the intermediate within the one or more cages and/or pores of the first catalyst.
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Paragraph 0015-0023; 0105-0113
(2021/11/13)
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- Hydroconversion of n-Heptane over Bifunctional Pt–Ti–MSU/Al–Ti–MSU Catalysts in a Micro Reactor
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Abstract: Cracking and isomerization of n-alkanes,employing bifunctional catalysts, are vital reactions in various refineryprocesses for producing different high-quality fuels. These catalysts consist ofa specific metal component and a specific acid function. The metal component isused for dehydrogenation and hydrogenation constituted from a specific noblemetal such as palladium and platinum. The acid function, on the other hand, isused for cracking and isomerization aims. In this work, a number of mesoporouscatalysts with different ratios of Si/Ti based on MSU containing Platinum weresynthesized and characterized with XRF, XRD, NH3–TPD, andBET tests. These catalysts were applied in n-heptane hydroconversion process in a fixed bed microreactor to seetheir performance in an actual process. In the microreactor, the pressure wasconstant (atmospheric), and the temperature varies in the range of 250–600°C.The performance of each of the catalysts was investigated in different ratios ofhydrogen to hydrocarbon (5, 10, 15, 20, and 25) and in two values of Weight HourSpace Velocity (WHSV) (1.5 and 2.5 h–1). Productsanalysis carried out to check out the activity and selectivity of each of thecatalysts. The result showed that all samples have a high surface area,favorable pore distribution, and high acidity. The outcome of the study showedthat the CAT-D catalyst has the highest activity for normal heptane conversion.This catalyst also has the highest selectivity for isomerization products atmoderate temperatures (350°C) and WHSV = 1.5h–1.
- Bahrami,Mahmoudi,Hamoule,Aghajani
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p. 455 - 464
(2021/04/09)
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- NiCu bimetallic catalysts derived from layered double hydroxides for hydroconversion of n-heptane
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Supported NiCu bimetallic catalysts have been produced in-situ on commercial Al2O3 by using layered double hydroxides as precursors. The resulting catalysts show a uniform Ni and Cu distribution, thus providing good activity and selectivity in the reforming reaction of n-heptane. The catalytic performance has been found to depend on the Cu/Ni ratio, revealing the synergic catalysis between homogeneously dispersed Ni and Cu sites. The good catalysis of NiCu bimetallic catalysts makes it possible to partly or even completely replace Pt with NiCu bimetallic catalysts.
- An, Zhe,He, Jing,Shu, Xin,Yang, Minghuan,Zhang, Jian,Zhang, Zhen,Zhu, Yanru
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supporting information
(2021/10/29)
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- CATALYTIC PROCESS
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A catalytic process for the deoxygenation of an organic substrate, such as a biomass or bio-oil, is described. The catalytic process is conducted in the presence of a gaseous mixture containing both hydrogen and nitrogen. The presence of nitrogen in the gaseous mixture gives rise inter-aliato increased catalytic activity and/or increased selectivity for aromatic reaction products.
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Paragraph 0244-0245; 0247; 0250-0253; 0259
(2021/12/03)
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- Metal-Free Photoredox-Catalyzed Hydrodefluorination of Fluoroarenes Utilizing Amide Solvent as Reductant
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A metal-free photoredox-catalyzed hydrodefluorination of fluoroarenes was achieved by using N,N,N’,N’-tetramethyl-para-phenylenediamine (1) as a strong photoreduction catalyst. This reaction was applicable not only to electron-rich monofluoroarenes but also to polyfluoroarenes to afford non-fluorinated arenes. The experimental mechanistic studies indicated that the amide solvent NMP plays an important role for regeneration of the photocatalyst, enabling additive-free photoreduction catalysis.
- Toriumi, Naoyuki,Yamashita, Kazuya,Iwasawa, Nobuharu
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supporting information
p. 12635 - 12641
(2021/08/03)
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- Towards the Circular Economy: Converting Aromatic Plastic Waste Back to Arenes over a Ru/Nb2O5 Catalyst
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The upgrading of plastic waste is one of the grand challenges for the 21st century owing to its disruptive impact on the environment. Here, we show the first example of the upgrading of various aromatic plastic wastes with C?O and/or C?C linkages to arenes (75–85 % yield) via catalytic hydrogenolysis over a Ru/Nb2O5 catalyst. This catalyst not only allows the selective conversion of single-component aromatic plastic, and more importantly, enables the simultaneous conversion of a mixture of aromatic plastic to arenes. The excellent performance is attributed to unique features including: (1) the small sized Ru clusters on Nb2O5, which prevent the adsorption of aromatic ring and its hydrogenation; (2) the strong oxygen affinity of NbOx species for C?O bond activation and Br?nsted acid sites for C?C bond activation. This study offers a catalytic path to integrate aromatic plastic waste back into the supply chain of plastic production under the context of circular economy.
- Jing, Yaxuan,Wang, Yanqin,Furukawa, Shinya,Xia, Jie,Sun, Chengyang,Hülsey, Max J.,Wang, Haifeng,Guo, Yong,Liu, Xiaohui,Yan, Ning
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supporting information
p. 5527 - 5535
(2021/02/05)
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- Photoredox-catalyzed reduction of halogenated arenes in water by amphiphilic polymeric nanoparticles
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The use of organic photoredox catalysts provides new ways to perform metal-free reactions controlled by light. While these reactions are usually performed in organic media, the application of these catalysts at ambient temperatures in aqueous media is of considerable interest. We here compare the activity of two established organic photoredox catalysts, one based on 10-phenylphenothiazine (PTH) and one based on an acridinium dye (ACR), in the light-activated dehalogenation of aromatic halides in pure water. Both PTH and ACR were covalently attached to amphiphilic polymers that are designed to form polymeric nanoparticles with hydrodynamic diameter DH ranging between 5 and 11 nm in aqueous solution. Due to the hydrophobic side groups that furnish the interior of these nanoparticles after hydrophobic collapse, water-insoluble reagents can gather within the nanoparticles at high local catalyst and substrate concentrations. We evaluated six different amphiphilic polymeric nanoparticles to assess the effect of polymer length, catalyst loading and nature of the catalyst (PTH or ACR) in the dechlorination of a range of aromatic chlorides. In addition, we investigate the selectivity of both catalysts for reducing different types of aryl-halogen bonds present in one molecule, as well as the activity of the catalysts for C-C cross-coupling reactions. We find that all polymer-based catalysts show high activity for the reduction of electron-poor aromatic compounds. For electron-rich compounds, the ACR-based catalyst is more effective than PTH. In the selective dehalogenation reactions, the order of bond stability is C-Cl > C-Br > C-I irrespective of the catalyst applied. All in all, both water-compatible systems show good activity in water, with ACR-based catalysts being slightly more efficient for more resilient substrates.
- Eisenreich, Fabian,Kuster, Tom H. R.,Palmans, Anja R. A.,van Krimpen, David
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supporting information
(2021/10/05)
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- Evaluation of the role of graphene-based Cu(i) catalysts in borylation reactions
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Carbon-supported catalysts have been considered as macromolecular ligands which modulate the activity of the metallic catalytic center. Understanding the properties and the factors that control the interactions between the metal and support allows a fine tuning of the catalyzed processes. Although huge effort has been devoted to comprehending binding energies and charge transfer for single atom noble metals, the interaction of graphenic surfaces with cheap and versatile Cu(i) salts has been scarcely studied. A methodical experimental and theoretical analysis of different carbon-based Cu(i) materials in the context of the development of an efficient, general, scalable, and sustainable borylation reaction of aliphatic and aromatic halides has been performed. We have also examined the effect of microwave (MW) radiation in the preparation of these type of materials using sustainable graphite nanoplatelets (GNP) as a support. A detailed analysis of all the possible species in solution revealed that the catalysis is mainly due to an interesting synergetic Cu2O/graphene performance, which has been corroborated by an extensive theoretical study. We demonstrated through DFT calculations at a high level of theory that graphene enhances the reactivity of the metal in Cu2O against the halide derivative favoring a radical departure from the halogen. Moreover, this material is able to stabilize radical intermediates providing unexpected pathways not observed using homogeneous Cu(i) catalysed reactions. Finally, we proved that other common carbon-based supports like carbon black, graphene oxide and reduced graphene oxide provided poorer results in the borylation process.
- Cid, M. B.,Díaz, Cristina,Franco, Mario,Lamsabhi, Al Mokhtar,Sainz, Raquel,Tortosa, Mariola
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p. 3501 - 3513
(2021/06/06)
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- Lewis Basic Salt-Promoted Organosilane Coupling Reactions with Aromatic Electrophiles
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Lewis basic salts promote benzyltrimethylsilane coupling with (hetero)aryl nitriles, sulfones, and chlorides as a new route to 1,1-diarylalkanes. This method combines the substrate modularity and selectivity characteristic of cross-coupling with the practicality of a base-promoted protocol. In addition, a Lewis base strategy enables a complementary scope to existing methods, employs stable and easily prepared organosilanes, and achieves selective arylation in the presence of acidic functional groups. The utility of this method is demonstrated by the synthesis of pharmaceutical analogues and its use in multicomponent reactions.
- Bandar, Jeffrey S.,Reidl, Tyler W.
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supporting information
p. 11939 - 11945
(2021/08/20)
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- Palladium-catalyzed synthesis of 4-cyclohexylmorpholines from reductive coupling of aryl ethers and lignin model compounds with morpholines
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This work describes the highly efficient Pd-catalyzed direct coupling of aryl ethers (including the typical lignin model compounds) and morpholines to produce 4-cyclohexylmorpholines, a useful class of fine chemicals. Without employing any acidic additives, various 4-cyclohexylmorpholines could be synthesized with good yields from a variety of aryl ethers using H2 as a hydrogen resource. A mechanism study revealed that the desired product was formed via the cleavage of the C(Ar)-O bonds to generate the corresponding cyclohexanones and subsequent reductive amination. This journal is
- Zheng, Bingxiao,Song, Jinliang,Wu, Haihong,Han, Shitao,Zhai, Jianxin,Zhang, Kaili,Wu, Wei,Xu, Caiyun,He, Mingyuan,Han, Buxing
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p. 268 - 273
(2021/01/28)
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- Aluminum Metal-Organic Framework-Ligated Single-Site Nickel(II)-Hydride for Heterogeneous Chemoselective Catalysis
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The development of chemoselective and heterogeneous earth-abundant metal catalysts is essential for environmentally friendly chemical synthesis. We report a highly efficient, chemoselective, and reusable single-site nickel(II) hydride catalyst based on robust and porous aluminum metal-organic frameworks (MOFs) (DUT-5) for hydrogenation of nitro and nitrile compounds to the corresponding amines and hydrogenolysis of aryl ethers under mild conditions. The nickel-hydride catalyst was prepared by the metalation of aluminum hydroxide secondary building units (SBUs) of DUT-5 having the formula of Al(μ2-OH)(bpdc) (bpdc = 4,4′-biphenyldicarboxylate) with NiBr2 followed by a reaction with NaEt3BH. DUT-5-NiH has a broad substrate scope with excellent functional group tolerance in the hydrogenation of aromatic and aliphatic nitro and nitrile compounds under 1 bar H2 and could be recycled and reused at least 10 times. By changing the reaction conditions of the hydrogenation of nitriles, symmetric or unsymmetric secondary amines were also afforded selectively. The experimental and computational studies suggested reversible nitrile coordination to nickel followed by 1,2-insertion of coordinated nitrile into the nickel-hydride bond occurring in the turnover-limiting step. In addition, DUT-5-NiH is also an active catalyst for chemoselective hydrogenolysis of carbon-oxygen bonds in aryl ethers to afford hydrocarbons under atmospheric hydrogen in the absence of any base, which is important for the generation of fuels from biomass. This work highlights the potential of MOF-based single-site earth-abundant metal catalysts for practical and eco-friendly production of chemical feedstocks and biofuels.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Dwivedi, Ashutosh,Manna, Kuntal
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p. 3943 - 3957
(2021/04/12)
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- Highly selective reductive catalytic fractionation at atmospheric pressure without hydrogen
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Reductive catalytic fractionation (RCF) is an efficient and selective way to produce phenolic monomers from lignin. However, this strategy is difficult to scale up due to its high operating pressure. In this work, we investigated RCF reaction at or near atmospheric pressure and without the use of hydrogen. The atmospheric RCF (ARCF) was conducted in acidified ethylene glycol in glass vessels at 185-195 °C catalyzed by 5% Ru/C. The products mainly include propylguaiacol and propylsyringyl (up to 95.6% among the lignin monomers) and do not contain propanolguaiacol, propanolsyringyl, or H monomers. Although the total yield of lignin monomers in ARCF is about one-quarter less than that of RCF, the operation of ARCF is much easier, milder, safer, and cheaper due to the atmospheric condition and the feasibility of the semi-continuous operation.
- Ren, Tianyu,You, Shengping,Zhang, Zhaofeng,Wang, Yuefei,Qi, Wei,Su, Rongxin,He, Zhimin
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supporting information
p. 1648 - 1657
(2021/03/09)
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- Eco-friendly preparation of ultrathin biomass-derived Ni3S2-doped carbon nanosheets for selective hydrogenolysis of lignin model compounds in the absence of hydrogen
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Lignin is an abundant source of aromatics, and the depolymerization of lignin provides significant potential for producing high-value chemicals. Selective hydrogenolysis of the C-O ether bond in lignin is an important strategy for the production of fuels and chemical feedstocks. In our study, catalytic hydrogenolysis of lignin model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) over Ni3S2-CS catalysts was investigated. Hence, an array of 2D carbon nanostructure Ni3S2-CSs-X-Yderived catalysts were produced using different compositions at different temperatures (X= 0 mg, 0.2 mg, 0.4 mg, 0.6 mg, and 0.8 mg; Y = 600 °C, 700 °C, 800 °C, and 900 °C) were prepared and applied for hydrogenolysis of lignin model compounds and depolymerization of alkaline lignin. The highest conversion of lignin model compounds (β-O-4 model compound) was up to 100% and the yield of the obtained corresponding ethylbenzene and phenol could achieve 92% and 86%, respectively, over the optimal Ni3S2-CSs-0.4-700 catalyst in iPrOH at 260 °C without external H2. The 2D carbon nanostructure catalysts performed a good dispersion on the surface of the carbon nanosheets, which facilitated the cleavage of the lignin ether bonds. The physicochemical characterization studies were carried out by means of XRD, SEM, TEM, H2-TPR, NH3-TPD, Raman and XPS analyses. Based on the optimal reaction conditions (260 °C, 4 h, 2.0 MPa N2), various model compounds (β-O-4, α-O-4 and 4-O-5 model compounds) could also be effectively hydrotreated to produce the corresponding aromatic products. Furthermore, the optimal Ni3S2-CSs-0.4-700 catalyst could be carried out in the next five consecutive cycle experiments with a slight decrease in the transformation of lignin model compounds.
- Chen, Changzhou,Jiang, Jianchun,Li, Jing,Liu, Peng,Wu, Dichao,Xia, Haihong,Zhou, Minghao
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p. 3090 - 3103
(2021/05/07)
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- Design and preparation of metal-based carbon nanosheets for C–O bond cleavage in the absence of external H2
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A facile yet sustainable approach for the production of Ni3S2-doped ultrathin carbon nanosheets in one-pot with very thin thickness of 30 nm was reported. Reaction of nickel nitrate hexahydrate, sodium lignosulfonate with boric acid could produce ultrathin carbon nanosheets. In comparison with the conventional method for the synthesis of Ni3S2-doped ultrathin carbon nanosheets, this reaction did not require second vulcanization step. Sodium lignosulfonate was used as carbon and sulfur source. Boric acid was used as 2D template and it could also be readily recycled for repeated use by simply evaporative crystallization. Ni3S2-doped ultrathin carbon nanosheets was expected to be an excellent catalyst for C–O bond cleavage under 260°C through catalytic transfer hydrogenation process. In addition, the optimal catalyst could also be recovered in the end.
- Chen, Changzhou,Zhou, Minghao,Jiang, Jianchun
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p. 1181 - 1185
(2021/06/23)
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- Method for preparing aromatic compound from lignin through visible light photocatalysis
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The invention relates to a method for preparing an aromatic compound from lignin through visible light photocatalysis. The method comprises the following steps: adding a lignin reaction substrate and a visible light photocatalyst into a solvent in a closed light-transmitting reactor to form a lignin cracking reaction system, and then stirring for cracking reaction under the protection of inert gas to obtain the aromatic compound, wherein the visible light photocatalyst is a supported metal-based catalyst, and the metal comprises transition metal and precious metal in the VIII group of the periodic table of elements. The cheap metal nickel is mainly used as the catalyst, the price is low, the preparation is simple, and the catalytic cracking process of the C-O aryl ether bond has the advantages of mild conditions, high selectivity and high conversion rate. Light driving is introduced so that the energy consumption of catalytic reaction is greatly reduced, and higher safety is achieved. Lignin is mainly formed by connecting C-O aryl ether bonds and is an important renewable resource, and catalytic cracking utilization of lignin has a wide prospect.
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Paragraph 0070-0074
(2021/06/09)
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- Environmentally-friendly and sustainable synthesis of bimetallic NiCo-based carbon nanosheets for catalytic cleavage of lignin dimers
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This paper reports on a study of 2D metal-based (Ni-, NiCo-) carbon nanosheet (CNs) material that were synthesized via a template method and the synthetic materials showed an ultra-thin lamellar structure. The structures were characterized using different analytical methods including XRD, SEM, EDX, TEM, XPS, NH3-TPD. The synthesized NiCo-based CNs are ultrathin sheet shape with good crystallinity and uniform particle distributions. In the synthetic route of NiCo-based CNs, sodium lignosulfonate was employed as carbon and sulfur source and boric acid was used as 2D template to form a perfect lamellar structure. It manifested an environmentally-friendly and sustainable concept for preparation of the 2D NiCo-CNs. Although simple CNs was a poor catalyst, after Ni and NiCo doping, it became highly active in cleavage of β-O-4 ether bond in lignin through a catalytic transfer hydrogenation process and led to very high product yields.
- Chen, Changzhou,Jiang, Jianchun,Liu, Peng,Ren, Jurong,Wu, Dichao,Xia, Haihong,Zhou, Minghao
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- Non-plasmonic Ni nanoparticles catalyzed visible light selective hydrogenolysis of aryl ethers in lignin under mild conditions
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Light-driven catalysis on catalytically versatile group VIII metals, which has been widely used in thermal catalysis, holds great potential in solar-to-chemical conversion. We report a novel photocatalysis process for the selective hydrogenolysis of aryl ethers in lignin on a heterogeneous catalyst of non-precious Ni nanoparticles supported on ZrO2. Three aryl ether bonds in lignin were successfully cleaved under mild conditions with excellent conversion and good to excellent selectivity under visible light irradiation. We also used solar irradiation to demonstrate a significant reduction in the total energy consumption. The light irradiation excited interband transitions in Ni nanoparticles and the resultant energetic electrons enhanced the activity of reductive cleavage of the aryl ethers. Its application potential was illustrated by the depolymerization of dealkaline lignin to give a total monomer yield of 9.84 wt% with vanillin, guaiacol, and apocynin as the three major products.
- Baeyens, Jan,Li, Peifeng,Ouyang, Yixuan,Sarina, Sarina,Su, Haijia,Xiao, Gang,Zhao, Yilin,Zhu, Huai-Yong
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supporting information
p. 7780 - 7789
(2021/10/12)
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- Investigation on the stoichiometry of carbon dioxide in isotope-exchange reactions with phenylacetic acids
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The functionalization of carbon dioxide (CO 2) as a C1 building block has attracted enormous attention. Carboxylation reactions, in particular, are of major interest for applications in isotope labeling. Due to the inexpensive nature of CO 2, information about its stoichiometric use is generally unavailable in the literature. Because of the rarity and limited availability of CO 2isotopomers, this parameter is of concern for applications in carbon-isotope labeling. We investigated the effects of the stoichiometry of labeled CO 2on carbon isotope exchange of phenyl? acetic acids. Both thermal and photocatalytic procedures were studied, providing insight into product outcome and isotope incorporation. Preliminary results on isotope-dilution effects of carbonate bases in photocatalytic carboxylation reactions have also been obtained.
- Audisio, Davide,Goudet, Amelie,Sallustrau, Antoine,Talbot, Alex,Taran, Frederic
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- Dehydrogenation of methylcyclohexane over Pt-based catalysts supported on functional granular activated carbon
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Herein, we developed the dehydrogenation of methylcyclohexane over Pt-based catalysts supported on functional granular activated carbon. Sulphuric acid, hydrogen peroxide, nitric acid and aminopropyl triethoxy silane were adopted to modify the granular activated carbon. The structural characterizations suggested that the carbon materials had a large surface area, abundant pore structure, and a high number of oxygen-containing functional groups, which influenced the Pt-based catalysts on the particle size, dispersion and dehydrogenation activity. The hydrogen temperature-programmed reduction technique was utilized to investigate the interaction between the active component Pt and the various functionalized granular activated carbon materials. The CO pulse technique revealed the particle sizes and dispersion of the as-prepared Pt-based catalysts. Finally, the Pt-based catalysts were successfully applied to study their catalytic activity in the dehydrogenation reaction of methylcyclohexane. The results showed that the Pt-based catalyst over granular activated carbon functionalized with sulphuric acid groups had a higher conversion of methylcyclohexane (63%) and a larger hydrogen evolution rate (741.1 mmol gPt?1min?1) than the other resulting Pt-based catalysts at 300 °C.
- Cai, You-Qiong,Liu, Shuang-Xi,Shi, Yong-Fu,Ye, Hong-Li,Zhang, Cui
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p. 29287 - 29297
(2021/10/08)
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- Comparison of Physicochemical Properties and Catalytic Activity in the m-Xylene Isomerization of Catalysts Based on ZSM-12 Zeolites Prepared at Hydrothermal Conditions and under the Action of Microwave Radiation
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The properties of ZSM-12 zeolites prepared under hydrothermal conditions and microwave radiation influence were investigated. The prepared zeolites were characterized by various physicochemical methods of analysis, e.g., X-ray diffraction analysis, low-temperature nitrogen adsorption/desorption, scanning electron microscopy, solid-state 27Al and 29Si NMR spectroscopy, IR spectroscopy, temperature-programmed desorption of ammonia, IR spectroscopy of adsorbed pyridine, and X-ray fluorescence elemental analysis. The calcined zeolites were impregnated with 0.5 wt.% Pt, which performed the hydrogenation function in the reaction under study. The obtained materials were evaluated in the m-xylene isomerization reaction under the following conditions: Т = 300°С–440°С, WHSV = 1/hr, Р(Н2) = 10 atm. On the ZSM-12 MW catalyst, due to its high acidity and fine particles, which promoted high mass transfer, it is possible to increase the yields of m-xylene isomers, in particular p-xylene, to 36%–65%.
- Tsaplin,Ostroumova,Kulikov,Naranov,Egazar’yants,Karakhanov
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p. 1292 - 1301
(2021/12/29)
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- Aromatization Catalyst And Preparation Process And Use Thereof
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An aromatization catalyst and preparation process and use thereof is set forth. The catalyst comprises an inorganic oxide and a modified Ga-ZSM-5 zeolite, which comprises a modified ZSM-5 zeolite with a hierarchical macro-meso-microporosity and gallium deposited in channels of and/or on surfaces of the modified ZSM-5 zeolite. The hierarchical porosity of the modified ZSM-5 zeolite in the catalyst can reduce diffusion resistance of products during the aromatization reaction, thereby retarding carbon depositing rate and substantially improving catalytic activity, aromatic hydrocarbon selectivity, stability and lifetime of the catalyst. When being used in aromatization of propane, the catalyst exhibits a high stability, a lifetime of more than 320 hours, and a selectivity to aromatic hydrocarbons of up to 73.3 wt. %.
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Paragraph 0091-0092
(2021/07/17)
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- H2-Free Selective Dehydroxymethylation of Primary Alcohols over Palladium Nanoparticle Catalysts
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The dehydroxymethylation of primary alcohols is a promising strategy to transform biomass-derived oxygenates into hydrocarbon fuels. In this study, a novel, highly efficient, and reusable heterogeneous catalyst system was established for the H2-free dehydroxymethylation of primary alcohol using cerium oxide-supported palladium nanoparticles (Pd/CeO2). A wide range of aliphatic and aromatic alcohols including biomass-derived alcohols were converted into the corresponding one-carbon shorter hydrocarbons in high yields in the absence of any additives, accompanied by the production of H2 and CO. Pd/CeO2 was easily recovered from the reaction mixture and reused, retaining its high activity, thus, providing a simple and sustainable methodology to produce hydrocarbon fuels from biomass-derived oxygenates.
- Yamaguchi, Sho,Kondo, Hiroki,Uesugi, Kohei,Sakoda, Katsumasa,Jitsukawa, Koichiro,Mitsudome, Takato,Mizugaki, Tomoo
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p. 1135 - 1139
(2020/12/29)
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- Dual Active Sites on Molybdenum/ZSM-5 Catalyst for Methane Dehydroaromatization: Insights from Solid-State NMR Spectroscopy
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Methane dehydroaromatization (MDA) on Mo/ZSM-5 zeolite catalyst is promising for direct transformation of natural gas. Understanding the nature of active sites on Mo/ZSM-5 is a challenge for applications. Herein, using 1H{95Mo} double-resonance solid-state NMR spectroscopy, we identify proximate dual active sites on Mo/ZSM-5 catalyst by direct observation of internuclear spatial interaction between Br?nsted acid site and Mo species in zeolite channels. The acidic proton–Mo spatial interaction is correlated with methane conversion and aromatics formation in the MDA process, an important factor in determining the catalyst activity and lifetime. The evolution of olefins and aromatics in Mo/ZSM-5 channels is monitored by detecting their host–guest interactions with both active Mo sites and Br?nsted acid sites via 1H{95Mo} double-resonance and two-dimensional 1H–1H correlation NMR spectroscopy, revealing the intermediate role of olefins in hydrocarbon pool process during the MDA reaction.
- Gao, Wei,Qi, Guodong,Wang, Qiang,Wang, Weiyu,Li, Shenhui,Hung, Ivan,Gan, Zhehong,Xu, Jun,Deng, Feng
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supporting information
p. 10709 - 10715
(2021/04/09)
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- Method for preparing p-xylene by efficiently catalyzing conversion of 4-methyl-3-cyclohexenecarboxaldehyde through ferronickel bimetallic catalyst
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The invention provides a method for preparing p-xylene by efficiently catalyzing conversion of 4-methyl-3-cyclohexenecarboxaldehyde through a ferronickel bimetallic catalyst. The catalyst is an alumina-loaded bimetallic catalyst, 4-methyl-3-cyclohexenecarboxaldehyde is subjected to dehydrogenation aromatization and hydrodeoxygenation reaction at 100-300 DEG C under the action of the ferronickel bimetallic catalyst, p-xylene is efficiently generated, the ferronickel bimetallic catalyst can be prepared by an impregnation method, the 4-methyl-3-cyclohexenecarboxaldehyde catalytic reaction is carried out in a fixed bed reactor. According to the method, n-hexane is taken as a solvent, and a 4-methyl-3-cyclohexene formaldehyde solution is pumped into a reaction tube by a high-pressure flow pump, or passes through a catalyst bed layer under the purging of carrier gas to obtain p-xylene. The reaction process is simple in procedure and high in yield, the yield of p-xylene can reach 93% or above, and the catalyst is easy to prepare, high in activity, low in price and easy to obtain.
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Paragraph 0028-0032
(2021/05/22)
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- Poisoning effect of N-containing compounds on performance of Raney nickel in transfer hydrogenation
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The effect of amines, imines and heterocycle compounds on conversion has been studied in transfer hydrogenation of camphor and 2-PrOH catalyzed by Raney nickel. Small amount (5 mol% to nickel) of N-containing compound significantly decreases catalyst activity. It has been shown that the poisoning effect mostly depends on molecular size of amines and heterocyclic compounds. For aniline and cyclohexylamine the dependence of camphor conversion on poison/nickel ratio was obtained. Additionally, benzaldehyde, cinnamaldehyde demonstrated higher reactivity compared corresponding imines under transfer hydrogenation conditions. Obtained data explain low activity of nickel-based catalysts when N-containing compounds are presented in reaction mixture.
- Martyanov, Oleg N.,Philippov, Alexey A.
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- Method for preparing methylbenzene by efficiently catalyzing conversion of 3-cyclohexenecarboxaldehyde through copper-based bimetallic catalyst
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The invention provides a method for preparing methylbenzene by efficiently catalyzing conversion of 3-cyclohexenecarboxaldehyde through a copper-based bimetallic catalyst. According to the method, 1, 3-cyclohexenecarboxaldehyde is subjected to dehydroaromatization and hydrodeoxygenation reaction at 100-300 DEG C under the action of a supported copper-based bimetallic catalyst, and toluene is efficiently generated. The catalytic reaction of 3-cyclohexenecarboxaldehyde is carried out in a fixed bed reactor, n-octane is used as a solvent, and a 3-cyclohexenecarboxaldehyde solution is pumped into a reaction tube by a high-pressure flow pump or passes through a catalyst bed layer under the purging of hydrogen gas to obtain toluene. The reaction process is simple, the target product selectivity is high, the substrate can be obtained by taking 1, 3-butadiene and acrolein from biomass resources as raw materials through a one-step reaction, and a novel method for directly preparing aromatic chemicals from biomass is provided.
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Paragraph 0040-0044; 0061-0062
(2021/05/22)
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- Chromium-catalyzed ligand-free amidation of esters with anilines
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Amides are important structural motifs in pharmaceutical and agrochemical chemistry because of the intriguing biological active properties. We report here the amidation of commercially available esters with anilines that was promoted by low-cost and air-stable chromium(III) pre-catalyst combined with magnesium, providing access to amides. This reaction occurs without the use of external ligands in a simple operation. Mechanistic studies indicate that a reactive aminated Cr species responsible for the amidation can be considered, which may be formed by reaction of low-valent Cr with aniline followed by reduction with hydrogen evolution.
- Chen, Changpeng,Ling, Liang,Luo, Meiming,Zeng, Xiaoming
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supporting information
p. 762 - 766
(2021/04/14)
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- Recovery of Arenes from Polyethylene Terephthalate (PET) over a Co/TiO2 Catalyst
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Upcycling of spent plastics has become a more emergent topic than ever before due to the rapid generation of plastic waste associated with the change of lifestyles of the human society. Polyethylene terephthalate (PET) is a major aromatic plastic and herein, the conversion of PET back into arenes was demonstrated in a one-pot reaction combining depolymerization and hydrodeoxygenation (HDO) over a Co/TiO2 catalyst. The effectiveness of the Co/TiO2 catalyst in HDO and the underlining reaction pathway were established using the PET monomer terephthalic acid (TPA) as the substrate. Quantitative TPA conversion together with 75.2 mol% xylene and toluene selectivity under 30 bar initial H2 pressure at 340 °C was achieved after 4 h reaction. More encouragingly, the catalyst induced both depolymerization and HDO reaction via C?O bond cleavage when PET was used as a substrate. 78.9 mol% arenes (toluene and xylene) was obtained under optimized conditions.
- Hongkailers, Surachet,Jing, Yaxuan,Wang, Yanqin,Hinchiranan, Napida,Yan, Ning
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p. 4330 - 4339
(2021/09/03)
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- Properties and Reactivities of Zwitterionic Platinum(II)-ate Complexes Generated by Transforming Coordination of an Alkyne-Bisphosphine Ligand
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Coordination of an alkyne-bisphosphine ligand with platinum(II) precursors produced a structural reorganization in the ligand backbone to form stable zwitterionic platinum(II) complexes bearing an anionic platinum center. The structural properties and reactivities of these complexes were investigated using X-ray crystallographic analyses, computational studies, and stoichiometric reactions involving oxidative addition and reductive elimination. These studies have shown that the enhanced nucleophilicity of the platinum center to alkyl halides promotes smooth oxidative addition and that the charge rebalance accelerates the dissociation of the halide anion from the platinum(IV) intermediate, which is essential in the carbon-carbon bond-forming step.
- Okamoto, Kazuhiro,Sasakura, Kohei,Funasaka, Satoshi,Watanabe, Hiiro,Suezaki, Masahiro,Ohe, Kouichi
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supporting information
p. 848 - 856
(2021/05/04)
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