Selective hydrogenation of styrene/1-octene mixtures over a monolithic Pd catalyst

Mixtures of styrene and 1-octene in toluene were hydrogenated over a monolithic Pd catalyst in the three-phase regime. Styrene was preferably hydrogenated to ethylbenzene, while a major part of the initial quantity of 1-octene was isomerized to internal olefins. Formation of alkylcyclohexanes was negligible. Observed rates of styrene hydrogenation were high compared to the values listed in literature.     

以Pd/C为催化剂的松香加氢反应机理

松香是由松树分泌的松脂经蒸馏而得,其主要成分为枞酸型树脂酸(C19H29COOH)[1]。由于枞酸型树脂酸含有共轭双键,易与大气中的氧作用,使松香的颜色加深、质变脆、热稳定性差、品级下降。松香经催化加氢反应,改变了枞酸型树脂酸的双键结构,使其趋于脂环的稳定结构,消除了松香因共     

Chemoselective hydrogenation method catalyzed by Pd/C using diphenylsulfide as a reasonable catalyst poison

While Pd/C is one of the most useful catalysts for hydrogenation, the high catalyst activity of Pd/C causes difficulty in its application to chemoselective hydrogenation between different types of reducible functionalities. In order to achieve chemoselective hydrogenation using Pd/C, we investigated catalyst poison as a controller of the catalyst activity. We found that the addition of Ph₂S (diphenylsulfide) to the Pd/C-catalyzed hydrogenation reaction mixture led to reasonable deactivation of Pd/C. By the use of the Pd/C-Ph₂S catalytic system, olefins, acetylenes, and azides can be selectively reduced in the coexistence of aromatic carbonyls, aromatic halides, cyano groups, benzyl esters, and N-Cbz (benzyloxycarbonyl) protecting groups. The present method is promising as a general and practical chemoselective hydrogenation process in synthetic organic chemistry.     

Acetophenone hydrogenation over a Pd catalyst in the presence of H2O and CO2

The addition of carbon dioxide and water enhances acetophenone hydrogenation activity over an activated carbon-supported palladium catalyst, and 1-phenylethanol can be easily recovered without distillation and neutralization. Two liquid phases (water and acetophenone) are indispensable for enhancement of the hydrogenation rate.     

Synthesis of carbon-supported Pd/SnO_2 catalyst for highly selective hydrogenation of 2,4-difluoronitrobenzene

Halogenated anilines have a wide range of applications in the production of pharmaceuticals and agrochemical substances, and thus it is of great importance to develop highly active and selective catalysts for the hydrogenation of halogenated nitrobenzenes. We approach this challenge by probing noble metal/non-noble metal oxide nanoparticles(NPs) catalysts. Carbon-supported Pd/SnO2catalysts were synthesized by the chemical reduction method, and their catalytic activity was evaluated by the hydrogenation reaction of 2,4-difluoronitrobenzene(DFNB) to the corresponding 2,4-difluoroaniline(DFAN), showing a remarkable synergistic effect of the Pd and SnO2 NPs. The as-prepared Pd/SnO2/C catalysts were characterized using TEM, XRD, H2 TPD and XPS techniques. Modifications to the electronic structure of the Pd atoms through the use of SnO2 led to the suppression of the hydrogenolysis of the C–F bond and the acceleration of nitrosobenzene(DFNSB) conversion and consequently, resulted in the inhibition of the formation of reactive by-products and may be responsible for the enhancements observed in selectivity.     

Solvent effect on the rate and direction of furfural transformations during hydrogenation over the Pd/C catalyst

Russian Chemical Bulletin - The rate and directions of transformations during the liquid-phase hydrogenation of furfural with molecular hydrogen in the presence of the 5%Pd/C catalyst (at 423 K, 3...     

Behavior of adsorbed diphenyl-sulfide on the Pd/C catalyst for o-chloronitrobenzene hydrogenation

A series of diphenyl-sulfide（Ph₂S）-immobilized Pd/C catalysts(Pd-Ph₂S_（X）/C) were prepared using the wetness-impregnation and immobilization method.Pd-Ph₂S_（x）w/C catalysts employed for the hydrogenation of o-chloronitrobenzene showed very high selectivity.The structure of Pd-Ph₂S_（x）/C with different molar ratio of ligand（x-values） was characterized by XPS and TG-DSC-MS.The results suggest a "saturated" surface ratio of Ph₂S/Pd（about 0.3） was formed on the Pd-Ph₂S_（x）/C catalysts surface.The Ph₂S immobilized on the Pd particle is quite stable,and the desorption of Ph₂S or dissociative loss of phenyl group was only found at temperatures above 500 K.The possible catalytic mechanism of the Pd-Ph₂S_（x）/C catalyst was also discussed.     

Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst

Selective hydrogenation of α, β-unsaturated aldehydes with modified Pd/C catalyst was developed.The reduction of C=O bond could be efficiently inhibited by the addition of carbonates,and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions.This protocol provides an alternative for efficient preparation of saturated aldehydes.     

Selective aqueous-phase hydrogenation of furfural to cyclopentanol over PdRu/C catalyst

The bimetallic PdRu catalyst supported on carbon nanotubes were found ot provide an efficient synthesis of cyclopentanol in aqueous-phase hydrogenation of furfural. Under the chosen reaction conditions (temperature of 473 K, total pressure of 8 MPa), the selectivity towards cyclopentanol reaches 77% at a complete conversion of furfural. A high activity of this catalyst can be associated with changes in the electronic state and dispersion of the supported metals caused by their mutual interaction and formation of PdRu alloy.     

Synthesis of Pd particles with various shapes by ionic liquids for HFP hydrogenation catalyst

Palladium particles were simply synthesized using various ionic liquids. The morphology of the particles was significantly affected by the anion parts of the ionic liquids. Among the ionic liquids, hexafluorophosphate as an anion part was more effective in forming the palladium particles with relatively small and narrow size distribution. However, irregularly shaped palladium particles were synthesized without ionic liquid assistance. For a hexafluoropropylene hydrogenation to produce hydrofluorocarbons, palladium was impregnated on a carbon powder as a catalyst. During the preparation of the catalyst, ionic liquids were added to control the shape of the palladium on the support. After calcinations at 500 °C, all catalysts possessed the comparable crystal structure. Under identical reaction conditions, the catalyst prepared using 1-hexyl-3-methylimidazolium hexafluorophosphate was the most effective in this reaction. Hence, catalytic activity was mainly determined by the size of the palladium particles.     

Selective hydrogenation of maleic anhydride to gamma-butyrolactone over Pd/Al2O3 catalyst using supercritical CO2 as solvent

A selective hydrogenation of maleic anhydride to either gamma-butyrolactone or succinic anhydride over simple Pd/Al2O3 catalyst under supercritical CO2 medium is described for the first time which has considerable promise for both lab-scale as well as industrial selective hydrogenations of low vapor pressure compounds without employing environmentally harmful organic solvents.     

Inhibiting effect of tungstic compounds on glucose hydrogenation over Ru/C catalyst

The effect of acid component including various conventional acids and tungstic compounds on glucose hydrogenation over a series of binary catalyst system containing Ru/C catalyst was investigated. The results showed that HCl, H2SO4, H3BO3, H3PO4, and HNO3 had negligible effect, while all the tungstic compounds imposed inhibiting effects on the hydrogenation of glucose over Ru/C catalyst, and the suppressing effect followed the order of H2WO4>HPW>WO3>AMT>HSi W. This order is the same as the order of ethylene glycol(EG) yields in the one-pot conversion of glucose to EG, suggesting the important role of competition between glucose hydrogenation and retro-aldol condensation in controlling the selectivity of EG.     

Pd/CuO-Ce_(0.5)Mn_(0.5)O_2催化氧化合成葡萄糖醛酸及其内酯

用柠檬酸络合法制备了掺杂铈锰复合金属氧化物载体,采用沉淀法负载活性组分钯得到催化剂Pd/CuO-Ce0.5Mn0.5O2,用XRD、SEM和XPS对催化剂结构进行了表征分析,考察了不同CuO掺入量对葡甲苷的伯羟基选择氧化合成葡萄糖醛酸及其内酯的催化活性的影响。结果表明,CuO的掺入对载体的孔结构及活性组分在载体表面的分散都得到了不同程度的改善;Ce-Cu-Mn的协同作用有利于提高Pd的氧化还原性能。当CuO添加量为9%及Pd负载量为0.5%时,葡萄糖醛酸及其内酯的总收率可达70%。     

Pd/C modified with Sn catalyst for liquid-phase selective hydrogenation of maleic anhydride to gamma-butyrolactone

Pd catalysts suffered from poor selectivity and stability for liquid-phase hydrogenation of maleic anhydride (MA) to gamma-butyrolactone (GBL). Thus, Pd/C catalysts modified with different Sn loadings were synthesized, and characterized by XRD, XPS, TEM and elemental mapping. The types of alloy phase and the amounts of the surface Pd-SnOx sites altered along with Sn/Pd mass ratios from 0-1.0 synthesized in the process of preparation. The maximum reaction rate was 0.57 mol-GBL/(mol-Pd min) and selectivity was 95.94% when the Sn/Pd mass ratio was 0.6. It might be attributed to the formation of Pd₂Sn alloy and less amounts of Pd-SnOx sites.     

Inhibition of the adsorption of cyclohexene over a Pd/sepiolite catalyst by acrylamide

Cyclohexene acts as a powerful hydrogen donor over supported Pd catalysts. On the basis of the theory of competitive hydrogenations, this paper aims at accounting for the fact that acrylamide cannot be reduced by hydrogen transfer using cyclohexene as donor, whereas methacrylamide can.

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An unusual reduction route of 2,4,6-trinitrobenzoic acid under conditions of aqueous-phase hydrogenation over Pd/Sibunit catalyst

For the first time it was established that the catalytic hydrogenation of 2,4,6-trinitrobenzoic acid to 1,3,5-triaminobenzene can proceed via the formation of aromatic hydroxyamines and cyclohexane-1,3,5-trione trioxime. As a result of aqueous-phase hydrogenation of sodium salt of 2,4,6-trinitrobenzoic acid in the presence of 5%Pd/Sibunit catalyst at a temperature of 323 K and pressure of 0.5 MPa, a trioxime in high yield (about 70 %) was obtained. Due to high selectivity to cyclohexane-1,3,5-trione trioxime the catalytic hydrogenation of sodium salt of 2,4,6-trinitrobenzoic acid can be considered as a new method for its synthesis.     

Chemoselective hydrogenation of 3-nitrostyrene over Ag/TiO2-SiO2 catalyst in a flow reactor

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光照对Pt/Al2O3光热CO2加氢反应的增强作用（英文）

在传统热催化材料的研究领域中,光照技术已经得到了广泛的应用,从而使传统热催化剂的催化反应活性和选择性得到优化.然而,在光热协同催化反应过程中,光照因素对催化反应过程的影响尚未得到很好地研究和理解.本文通过浸渍法制得Pt/Al2O3催化剂,并应用于光热协同催化CO2加氢反应.结果证明,在光热协同CO2加氢催化反应中, Pt/Al2O3催化剂表现出光热协同效应.本文结合原位漫反射红外光谱(operandoDRIFTS)和密度泛函理论计算(DFT)对光照因素对该催化反应过程的作用机制进行了进一步深入研究.结果表明, CO气体分子从Pt纳米颗粒上的脱附过程为CO2加氢反应的重要步骤;CO气体分子在Pt纳米颗粒上脱附的位置包含台阶位置(Ptstep)和平台位置(Ptterrace).结果表明,反应过程中CO气体分子从Pt表面的脱附有利于催化剂暴露出Pt反应活性位点.值得注意的是,在光热协同催化CO2加氢反应过程中,光照和温度因素对CO气体分子的脱附过程具有不同影响.吸附能的计算结果证明, CO气体分子吸附在Ptstep和Ptterrace上的吸附能分别为-1.24和-1.43eV.由此可见, CO气体分子与Pt纳米颗粒上的Ptstep吸附位点之间相互作用更强.在无光照作用的条件下对催化剂进行加热, CO气体分子更容易从Ptterrace吸附位点发生脱附;但是在对应的温度下加入光照作用后,吸附在Ptstep位点上的CO气体分子会先转移到Ptterrace吸附位点上,随后脱附,从而促进CO2加氢反应的进行.     

Gas-phase hydrogenation of styrenes by transfer over Pd/AlPO4 catalysts

This paper reports the results obtained in the hydrogenation of styrene and -methylstyrene by transfer over Pd catalysts supported on AlPO₄, using cyclohexene as donor. The catalysts were activated in the pulse reactor itself and retained hydrogen which was subsequently used to reduce the olefins. The amount of ethylbenzene yielded from styrene can be accounted for on the basis of hydrogen transferred in a concerted fashion by cyclohexene and hydrogen stored over the catalyst surface during treatment with cyclohexene intended to reduce the impregnating metal salt.

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Reduction of alkenes by hydrogen transfer over a Pd/sepiolite catalyst. Compensation effect

This paper shows the occurrence of a linear relationship between the activation energy (E_A) and the logarithm of the pre-exponential factor (ln A) in the Arrhenius equation, and between the enthalpy increment (H) and the entropy increment (S) in the Eyring equation for the reduction of olefinic double bonds by hydrogen transfer over a Pd/sepiolite catalyst. Such a relationship is known as the compensation effect or isokinetic relationship.

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Pd/ (E_a) (ln A) (H) (S) . .