Catalytic and kinetic study of the liquid-phase hydrogenation of various organic substrates over a polymer-anchored Pd(II) catalyst

A polymer-anchored Pd(II) complex has been prepared and characterized using scanning electron microscopy, elemental analysis, atomic absorption spectroscopy and FTIR. The catalyst shows excellent catalytic activity in the liquid-phase hydrogenation of substituted nitrobenzenes at normal pressure of hydrogen gas at 25 °C in DMF medium. We have also studied the liquid-phase hydrogenation of other organic substrates such as alkenes, alkynes, aromatic aldehydes, etc. The influences of various parameters such as amount of catalyst, concentration of substrate, temperature and solvent have been studied. The catalyst can be used five times without much loss in activity.     

Pt- and Pd-containing nanodiamonds in hydrogenation and hydroamination reactions

The catalytic activity of platinum- and palladium-containing nanodiamonds has been investigated in liquid-phase nitrobenzene, allyl alcohol, and cyclohexene hydrogenation and propanal hydroamination with 4-aminobenzoic acid as model reactions. The catalysts suggested are significantly more active than commercial Pd/C. The catalysts with a low metal weight content are the most effective in liquid phase catalytic hydrogenation.     

Pd催化糠醛加氢反应中溶剂依赖效应的理论计算

糠醛催化加氢反应工艺主要分为气相、液相以及催化转移加氢等.相比于糠醛气相加氢,液相加氢为反应提供了更多的可持续性和自由度,但其中溶剂依赖现象对糠醛定向催化转化的影响机制尚不清晰.针对上述问题,本文选用3种溶剂(甲醇、水和环己烷)为研究对象,采用密度泛函方法,从理论计算角度探究了Pd催化糠醛加氢反应中溶剂效应对反应活性和选择性的重要作用.结果表明,在糠醛加氢反应过程中,溶剂一方面能够形成氢键网络促进质子穿梭,另一方面能够稳定反应物、中间体以及生成物,有效降低C=O加氢的能垒.自由能计算结果表明,在液态水、甲醇和环己烷中,随着溶剂极性的降低(水>甲醇>环己烷),第一步C=O氢化的能垒逐渐降低(0.70 eV>0.68 eV>0.44 eV).在水和甲醇介导的糠醛加氢反应过程中,第一步C=O加氢的反应势垒进一步降低为0.47和0.41 eV.差分电荷密度以及Bader电荷分析表明,反应过程中存在糠醛和Pd催化剂之间的电荷转移.分波态密度(PDOS)分析表明,溶剂的加入使d带中心向靠近费米能级的方向移动,表明Pd催化剂的催化活性得到提高.     

Homogeneous catalytic hydrogenation of liquid carboxylated nitrile rubber

Homogeneous catalytic hydrogenation of olefinic bonds in liquid carboxylated nitrile rubber (L-XNBR) has been carried out selectively in the presence of nitrile and carboxyl functionality using a six-membered cyclopalladate complex of 2-benzoyl pyridine as catalyst. The degree of hydrogenation has been calculated from IR and NMR spectroscopic studies. For example, 68% hydrogenation has been obtained for a sample (containing 0.057 carboxyl equivalent/100 g and 26.1% acrylonitrile) under 2.7 MPa hydrogenation pressure, 0.18 mmol/L catalyst, at 333 K for 1 h in acetone solution. The overall extent of hydrogenation depends on the catalyst-to-double-bond ratio. The kinetics of hydrogenation of L-XNBR has been investigated. The reaction exhibits a pseudo-first order dependence on the concentration of the substrate. The rate constant of the reaction is reduced by the increase in carboxyl and nitrile content of the polymer. The effect of temperature on reaction kinetics has also been studied and the activation energy of hydrogenation of L-XNBR is 20.2 kJ/mol. Intrinsic viscosity of the polymer remains unchanged during the reaction. A significant lowering of the glass transition temperature and improvement of thermal stability have been observed on hydrogenation. © 1992 John Wiley & Sons, Inc.     

Hydrogenolysis of benzylic alcohols on rhodium catalysts

Alumina-supported catalysts from various sources and with different rhodium dispersions predominantly yield the hydrogenation product perhydro-1-indanol in the liquid-phase hydrogenation of 1-indanol, while carbonsupported catalysts mainly give the C-O bond scission - hydrogenation product perhydroindane. Addition of organic or inorganic bases to the reaction mixture suppresses C-O bond scission. To distinguish between the two possible pathways for C-O bond scission of direct hydrogenolysis or dehydration followed by hydrogenation, deuteration studies have been carried out with carbon-supported catalysts. Not only 1-indanol but also indane and indene (the two possible mechanistic intermediates in the C-O bond scission routes) were deuterated. Information about the actual pathway has been obtained by determining the degree of deuteration and the positions at which deuterium is incorporated in the resulting perhydroindane product by means of mass spectrometry and 13C NMR spectroscopy. The results prove that C-O bond scission takes place primarily through the direct hydrogenolysis pathway on the carbon-supported catalysts. Direct hydrogenolysis occurs on the carbon support because of the formation of a better leaving group (OH2+) from the benzylic hydroxy group and its subsequent substitution by spillover hydrogen.     

Ionic liquid [BMIM]PF6 as a medium for the selective hydrogenation of 1,4-diacetoxybut-2-yne on the Pd-containing catalysts

A possibility of using a ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆), as a reaction medium in the liquid-phase hydrogenation of 1,4-diacetoxybut-2-yne was examined. Two types of catalysts were studied: Pd(10%)/C and the palladium-containing catalytic system based on the biopolymer chitosan supported on silica gel (Pd(1%)/chitosan/SiO2). The data obtained indicate high selectivity of hydrogenation of 1,4-diacetoxybut-2-yne to cis-1,4-diacetoxybut-2-ene under selected conditions.     

Texture and catalytic properties of palladium supported on thermally expanded natural graphite

Data about preparation and properties of palladium catalysts on porous supports prepared by intercalation and subsequent thermal expansion of natural graphite are presented. Some relations between the structure of the graphite support, the state of supported palladium and its catalytic properties in the model reaction of cyclohexene liquid-phase hydrogenation were established. This revised version was published online in June 2006 with corrections to the Cover Date.     

Tandem Catalysis of Ammonia Borane Dehydrogenation and Phenylacetylene Hydrogenation Catalyzed by CeO2 Nanotube/Pd@MIL-53(Al)

Heterogeneously catalyzed, selective hydrogenation in the liquid phase is widely used in industry for the synthesis of chemicals. However, it can be a challenge to prevent active nanoparticles (e.g., palladium) from aggregation/leaching and meanwhile achieve high conversion as well as selectivity, especially under mild conditions. To address these issues, a CeO₂ nanotube/Pd@MIL-53(Al) sandwich-structured catalyst has been prepared in which the MIL-53(Al) porous shell can efficiently stabilize the palladium nanoparticles. When this catalyst was used in a tandem catalytic reaction involving the dehydrogenation of ammonia borane and the hydrogenation of phenylacetylene, remarkably, the hydrogen released from the dehydrogenation of ammonia borane boosted the catalytic process, with 100 % conversion of phenylacetylene and a selectivity of 96.2 % for styrene, even at room temperature and atmospheric pressure, within 1 min. This work therefore provides an alternative strategy for balancing the conversion and selectivity of liquid-phase hydrogenation reactions.     

The composition of transformation products of 2,4,6-trinitrobenzoic acid in the aqueous-phase hydrogenation over Pd/C catalysts

Due to a detailed analysis of NMR spectra of the reaction solutions with different composition obtained by the aqueous-phase catalytic (Pd/C) hydrogenation of 2,4,6-trinitrobenzoic acid, the intermediate compounds were identified and a more substantiated mechanism was proposed for the formation of the main reaction products—1,3,5-triaminobenzene and cyclohexane-1,3,5-trione trioxime. The condensation of the 1,3,5-triaminobenzene molecules produced by a complete hydrogenation of 2,4,6-trinitrobenzoic acid was shown to result in the formation of a paramagnetic heterocyclic compound.     

Preparation, characterization and testing of nickel on alumina monolithic catalysts

A series of Ni on alumina washcoated monoliths has been prepared and characterized. The selective liquid-phase hydrogenation of benzaldehyde to benzyl alcohol in a Berty reactor has been used as a test reaction.     

均相苯乙酮加氢反应研究

合成了一种新的钌膦配合物[RuCl2(Dmpp)2en](Dmpp=4-(2，6-二甲氧吡啶基)二苯基膦，en=乙二胺)，对其结构进行了表征．系统研究了反应温度，氢气压力，底物和催化剂的比例，碱和催化剂的比例等反应条件对[RuCl2(Dmpp)2en]催化的芳香酮加氢反应活性的影响，证明其在苯乙酮加氢反应中具有很好的催化活性．     

YDHC-10催化剂用于不饱和植物油脂肪酸氢化工艺条件的研究

采用自制的催化剂YDHC-10对氢化工艺条件进行了研究。找出了植物油脂肪酸氢化时,氢化压力2MPa、氢化温度180-200℃、氢化时间60min以及催化剂浓度对植物油脂肪酸氢化的影响．     

去甲基构树宁B的合成

以1,3-二羟基苯和对羟基苯甲醛为起始原料,经赫氏酰化、羟基保护、克莱森 斯密特缩合及催化氢化反应首次合成天然产物去甲基构树宁B,总收率40.9%,其结构经¹H NMR, ¹³C NMR和HR-MS(ESI TOF)确证。     

High-Selective Catalyst Based on Intermetallic Rh1In1 Particles for Nitrobenzene Hydrogenation

Kinetics and Catalysis - The catalytic performance of a bimetallic RhIn/SiO2 catalyst was studied in the liquid-phase hydrogenation of nitrobenzene. The formation of intermetallic Rh1In1...     

法西多曲原料药的合成

以胡椒醛和丙二酸酯为原料,经Knoevenagel缩合、常压催化氢化、缩合、加成、酰化5步反应合成了法西多曲,其结构经元素分析、IR和1H NMR表征。总收率72．1％。     

三尖杉酯碱侧链酸的不对称合成及结构表征

以N-Boc苏氨醛为起始原料,经Wittig、Meisenheimer重排和催化氢化系列反应,不对称合成了天然产物三尖杉酯碱的侧链酸,中间体及目标产物结构经核磁共振(1 H NMR、13 C NMR)、红外光谱和质谱表征.结果表明,所用合成方法具有产率高、反应条件温和、操作简单等优点;目标化合物的总收率达30%.     

Liquid-phase hydrogenation of 1-alkenes over Rh/AlPO4 and Rh/sepiolite catalysts

The catalytic activity of Rh (1 wt.%) catalysts supported on AlPO₄ and sepiolite has been studied in the liquid-phase hydrogenation of linear 1-alkenes. The reaction orders with respect to 1-alkene concentration are negative but are first order with respect to hydrogen, indicating that 1-alkene adsorbs very strongly on Rh sites and alkene and H₂, compete for adsorption sites on the surface. The initial hydrogenation rates increase in the order 1-hexene < 1-heptene < 1-octene, and furthermore, on going from 1-hexene to 1-octene the steric effects (through ΔS^≠) are activating, while electronic effects (from ΔH^≠) deactivate the reaction process. A cis-concerted mechanism taking place in a single step on a Rh site with three coordinative unsaturations which can simultaneously adsorb hydrogen and a π-bonded alkene is suggested.     

四氯化碳液相催化加氢制氯仿多元金属催化剂的制备及其催化性能

以贵金属M(=Pd,Pt)为主要活性成分,掺加过渡金属Fe和Ni作为助剂,采取浸渍和氢气还原法制备了椰壳活性炭(ACcs)负载的单元金属(M/ACcs)、二元金属(M-Ni/ACcs、M-Fe/ACcs)和三元金属(M-Ni-Fe/ACcs)系列催化剂;通过CC_l4液相催化加氢制氯仿反应考察了这些催化剂的催化活性和选择性。结果表明,Pd基催化剂的催化活性明显高于Pt基催化剂,但后者对氯仿的选择性优于前者;在前5 h加氢反应时段,两系列催化剂的活性顺序为:Pd-Ni-Fe/ACcsPd-Fe/ACcsPd/ACcsPd-Ni/ACcs和Pt/ACcs≈Pt-Fe/ACcsPt-Ni/ACcsPt-Ni-Fe/ACcs;总体上,引入Fe对于催化性能的改善效果要优于Ni,Ni的单独引入则会不同程度地降低催化活性。综合考量成本、活性和选择性等因素,优选Pd-Ni-Fe/ACcs作为催化剂,在393 K下反应5 h,可实现CC_l497.6%的转化率以及接近100%氯仿的选择性。     

Platinum- and palladium-containing carbon nanomaterials as catalysts for hydrogenation and hydrogenating amination

The catalytic activity of the carbon nanomaterials containing platinum and palladium in the model reactions of liquid-phase hydrogenation of nitrobenzene and hydrogenating amination was investigated. The catalytic systems based on nanodiamonds are more efficient than platinum-containing fullerene black, multi-walled nanotubes, and carbon nanofibers.     

Liquid-phase hydrogenation of nitrobenzene and o-nitrochlorobenzene in the presence of phosphorus-containing palladium nanoparticles

Kinetics and Catalysis - The properties of phosphorus-modified palladium catalysts in the liquid-phase hydrogenation of nitrobenzene and o-nitrochlorobenzene have been investigated. A general...