2453-00-1Relevant academic research and scientific papers
Insights into the Major Reaction Pathways of Vapor-Phase Hydrodeoxygenation of m-Cresol on a Pt/HBeta Catalyst
Sun, Qianqian,Chen, Guanyi,Wang, Hua,Liu, Xiao,Han, Jinyu,Ge, Qingfeng,Zhu, Xinli
, p. 551 - 561 (2016/02/20)
Conversion of m-cresol was studied on a Pt/HBeta catalyst at 225-350°C and ambient hydrogen pressure. At 250°C, the reaction proceeds through two major reaction pathways: (1) direct deoxygenation to toluene (DDO path); (2) hydrogenation of m-cresol to methylcyclohexanone and methylcyclohexanol on Pt, followed by fast dehydration on Br?nsted acid sites (BAS) to methylcyclohexene, which is either hydrogenated to methylcyclohexane on Pt or ring-contracted to dimethylcyclopentanes and ethylcyclopentane on BAS (HYD path). The initial hydrogenation is the rate-determining step of the HYD path as its rate is significantly lower than those of subsequent steps. The apparent activation energy of the DDO path is 49.7 kJ mol-1 but the activation energy is negative for the HYD path. Therefore, higher temperatures lead to the DDO path becoming the dominant path to toluene, whereas the HYD path, followed by fast equilibration to toluene, is less dominant, owing to the inhibition of the initial hydrogenation of m-cresol.
PROCESS FOR SELECTIVE RING OPENING OF CYCLIC HYDROCARBONS
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Paragraph 0057; 0060-0067, (2020/04/29)
PURPOSE: A process for ring opening is provided to obtain improved conversion ratio and selectivity in comparison with the case of using hydrogen as a reducing agent. CONSTITUTION: A cyclic hydrocarbon and a reducing agent are provided as supplying materials. The supplying materials are transferred into a reactor (5) and reacted under the presence of a catalyst. A product is separated from the effusion of reaction zone. The catalyst is a heterogeneous catalyst having both acid site and metallic component. The product is obtained by evaporating and heating a mixture containing 100 parts by weight of porous molecular sieve and 0.01-20 parts by weight of water soluble metallic salt. The cyclic hydrocarbon is a naphthene group cyclic hydrocarbon which is pentagonal or hexagonal compound, or an alkyl derivative thereof selected from cyclopentane and cyclohexane. The alkyl derivative is methyl, ethyl, profile, butyl, isopropyl or an isobutyl derivative.
Direct production of naphthenes and paraffins from lignin
Kong, Jiechen,He, Mingyuan,Lercher, Johannes A.,Zhao, Chen
supporting information, p. 17580 - 17583 (2015/12/08)
The utilization of lignin as a fuel precursor has attracted attention, and a novel and facile process has been developed for one-pot conversion of lignin into cycloalkanes and alkanes with Ni catalysts under moderate conditions. This cascade hydrodeoxygenation approach may open the route to a new promising technique for direct liquefaction of lignin to hydrocarbons.
A new approach for bio-jet fuel generation from palm oil and limonene in the absence of hydrogen
Zhang, Jingjing,Zhao, Chen
supporting information, p. 17249 - 17252 (2015/12/08)
The traditional methodology includes a carbon-chain shortening strategy to produce bio-jet fuel from lipids via a two-stage process with hydrogen. Here, we propose a new solution using a carbon-chain filling strategy to convert C10 terpene and lipids to jet fuel ranged hydrocarbons with aromatic hydrocarbon ingredients in the absence of hydrogen.
Study of Ir/WO3/ZrO2-SiO2 ring-opening catalysts: Part II. Reaction network, kinetic studies and structure-activity correlation
Lecarpentier, Sebastien,van Gestel, Jacob,Thomas, Karine,Gilson, Jean-Pierre,Houalla, Marwan
, p. 49 - 63 (2008/09/17)
The present paper is the second part of a systematic study of the influence of W and Ir loading on the activity of Ir/WO3/ZrO2-SiO2 catalysts for the ring-opening reaction of naphthenic molecules using methylcyclohexane (MCH) as a model compound. A series of Si-stabilized tungstated zirconias, WOx/ZrO2-SiO2, containing up to 3.5 atom W/nm2, was prepared. Ir-based catalysts containing up to 1.2 wt% were obtained by impregnation of these solids. Characterization of the metal dispersion and catalyst acidity was described in a previous article. The objective of the present study was to determine the best metal/acid balance for optimal performance of Ir/WOx/ZrO2-SiO2 catalysts in the ring-opening reaction of MCH. Monofunctional (acid WOx/ZrO2-SiO2 or metal Ir/ZrO2-SiO2) and bifunctional (Ir/WO3/ZrO2-SiO2) catalysts were examined. Based on the analysis of the yields and products distributions, a reaction network was proposed, and kinetic data (e.g., activation energies, initial rates) were calculated. Correlations between characterization results obtained earlier (e.g., acidity, dispersion) and catalytic performance are also reported. The monofunctional acid catalysts WOx/ZrO2-SiO2 showed a low selectivity for ring opening. The ring-contraction activity developed for W surface density above a threshold value of 1 atom W/nm2. This was attributed to the appearance and the development of a relatively strong Broensted acidity monitored by infrared measurements. MCH ring contraction and C5 naphthene ring opening occur according to a classic acid mechanism. For low conversions, the monofunctional metal catalysts Ir/ZrO2-SiO2 exhibited significant selectivity for ring opening that decreased with increasing conversion. Because of the lack of ring-contraction products, the observed activity was attributed to the direct ring opening of the MCH. Ring opening and cracking occur according to a dicarbene mechanism. The study of MCH conversion on Ir/WOx/ZrO2-SiO2 catalysts indicated that MCH ring contraction to alkylcyclopentanes occurs before ring opening. The best yields for ring opening were obtained with the 1.2% Ir/WOx/ZrO2 (1.5 atom of W/nm2). Further increases in W surface density led to a decrease in the indirect ring-opening yield, attributed to a decrease in Ir dispersion. For bifunctional metal/acid catalysts, analysis of the mechanism is less straightforward. The activation energy for C6 ring contraction and indirect C6 ring opening is a function of the metal/acid ratio. For high ratios, indirect ring opening occurs essentially over metallic sites. A decrease in the metal/acid ratio enhances the contribution of acid mechanism.
A novel reduction of polycarboxylic acids into their corresponding alkanes using n-butylsilane or diethylsilane as the reducing agent
Nimmagadda, Rama D.,McRae, Christopher
, p. 3505 - 3508 (2007/10/03)
A convenient one-pot reaction has been developed for the reduction of polycarboxylic acids on aliphatic and aromatic systems to their corresponding alkanes. The reduction utilises either diethylsilane or n-butylsilane as the reducing agent in the presence of the Lewis acid catalyst tris(pentafluorophenyl)borane.
Salicylidene-imine-Zirconium(IV) Complexes in Combination with Methylalumoxane as Catalysts for the Conversion of Hexa-1,5-diene: Adjusting of the Catalytic Activity
Schweder, Bernd,Walther, Dirk,D?hler, Thomas,Klobes, Olaf,G?rls, Helmar
, p. 736 - 747 (2007/10/03)
A variety of substituted Schiff base complexes of the composition ("salen")ZrCl2(thf) (1-21) were synthesized, with methylalumoxane ("MAO") activated and used for a systematic study of their catalytic activity towards hexa-1,5-diene ("salen": substituted salicylidene-ethylene-iminato ligands). Main product of the catalytic cycle is methylenecyclopentane. Dimers are only formed in minor amounts. The catalytic activity and selectivity of the Ziegler-Natta systems strongly depend on the nature and the position of the peripheric substituents in the Schiff base ligands. Electron-withdrawing substituents in para-position to the phenolato oxygen (5-position) decrease the catalytic activity. Improved activity and selectivity were obtained with electron-donating substituents in 5-position. Altering the ethylene bridge causes a lowering of the activity or inactivation. According to the X-ray analysis the metal center in the related complex (L)ZrCl2 (22) (L: N′,N′-bis(ethylene)-N′-methyl-N,N″- bis(benzoylacetonatoimine) has a pentagonal-bipyramidal environment. The pentadentate Schiff base ligand lies in the plane, and both chloro groups occupy the axial positions. In contrast to the catalytically active salene complexes 22 can not rearrange to form a species in which the both chlorides are cis to each other. Consequently 22 is catalytically inactive.
Catalysis with Palladium Deposited on Rare Earth Oxides: Influence of the Support on Reforming and Syngas Activity and Selectivity
Normand, F. Le,Barrault, J.,Breault, R.,Hilaire, L.,Kiennemann, A.
, p. 257 - 269 (2007/10/02)
The influence of the support has been tested on the reactivity of Pd/rare earth oxides catalysts (La2O3, CeO2, Pr6O11, Nd2O3, Tb4O7).According to BET surface area, chemisorption, temperature-programmed reduction (TPR) and oxidation (TPO), X-ray diffraction (XRD) and X-ray photoemission (XPS) characterizations, these catalysts have been classified into threeclasses according to their ability to create anion vacancies: (i) oxides of the type Re2O3 which are unreducible, (ii) CeO2 where anion vacancies can be created extrinsically by the reduction process, and (iii) Pr6O11 and Tb4O7 where anion vacancies exist due to the nonstoichiometric nature of these oxides.We emphasize also the role of chlorine, coming from the palladium precursor salt, which reacts with the support to form a stable oxychloride phase surrounding the metallic particle and interacting with it.Concerning the catalytic activity, (i) the active site is purely metallic in methylcyclopentane hydrogenolysis, with small selectivity changes on fluorite oxides as compared to Pd/Al2O3 catalysts due to some electronic interaction with the support, but (ii) the mechanism is found to be partly bifunctional in 3-methylhexane aromatization with a large increase in aromatization on Pr6O11 and Tb4O7 supports, and (iii) in syngas conversion, production of high alcohols occurs at the metal-support interface and is favored by the presence of intrinsic anion vacancies on Pr6O11 and Tb4O7 supports.A correlation is found between the density of anion vacancies on these supports and the chain growth probability deduced from the Anderson-Schulz-Flory plot.
NIOBIUM SULFUR SYSTEM: INFLUENCE OF S2-- GROUPS ON THE CATALYTIC PROPERTIES IN HYDROGENATION REACTIONS
Vrinat, M.,Guillard, C.,Lacroix, M.,Breysse, M.,Kurdi, M.,Danot, M.
, p. 1017 - 1025 (2007/10/02)
Unsupported NbS3 was prepared by direct combination of the elements and "NbS2" or Nb1.12S2 were obtained by thermal decomposition of the former.These samples were characterized by XRD and XPS and their activity was measured in the hydrogenation of biphenyl under medium pressure conditions.Compared to WS2, all these samples present higher activity and a peculiar ability to perform cracking reaction.These differences have been explained by the active site occurrence probability which is higher in NbS3 due to the reducibility of S2-- pairs.Such properties of niobium sulfides have been also evidenced in other hydrogenation reactions and have shown the potentiality of niobium sulfur system as catalyst for reactions involving hydrogenation and C-C bond cleavage.
Mechanism of Isomerization of Hydrocarbons on Metals. Part 11.-Isomerization and Dehydrocyclization of (13)C-labelled 3-Methylhexanes on Pt-Al2O3 Catalysts
Amir-Ebrahimi, Valia,Gault, Francois G.
, p. 1735 - 1756 (2007/10/02)
The isomerization, dehydrocyclization and hydrogenolysis of 3-methylhexane have been studied at 320-380 deg C over a series of Pt-Al2O3 catalysts with a metal dispersion extending from 0.05 to 1.The use of five labelled compounds, 3-methyl(1-(13)C), (2-(13)C), (3-(13)C), (6-(13)C)hexanes and 3-methyl((13)C)hexane, alloved distinction between the various parallel pathways.On all catalysts the predominant reaction was the isomerization according to a cyclic mechanism involving either 1,3-dimethyl-, 1,2-dimethyl- or ethyl-cyclopentane intermediates with a relative contribution of 60, 40 and 20 percent, respectively.These results are consistent wiith a dehydrocyclization scheme involving a metallocarbene as precursor and dicarbene or dicarbyne recombination as the rate-determining step.
