Reaction routes for hydrogenation of acetylene-ethylene mixtures using a double labelling method

Hydrogenation of C₂H₂:C₂H₄ mixtures using a double labelling method has been studied. Both in the presence and absence of ethylene the rate of acetylene hydrogenation on its partial pressure proceeds through a maximum and the rate is higher when ethylene is added. Using¹⁴C–C₂H₂ it was demonstrated that at low acetylene partial pressures the main route of acetylene hydrogenation was the formation of ethane and C₄ hydrocarbons. Using¹⁴C–C₂H₄ it was also shown that at certain acetylene partial pressures the formation of ethane from ethylene completely ceased. Different surface species are suggested and a reaction mechanism is proposed.

---

C₂H₂:C₂H₄, . , , . C¹⁴–C₂H₂, , C₄. C¹⁴–C₂H₄, , . .

     

钯/石墨烯催化苯醌加氢制备氢醌

采用微波辅助加热还原法合成了钯/石墨烯(Pd/G)、钯/活性炭(Pd/AC)、钯/石墨(Pd/Graphite)和钯/二氧化硅(Pd/SiO2),并使用透射电子显微镜观测了钯的形貌及在载体上的分散性.将负载型钯催化剂用于苯醌加氢反应,结果显示,Pd/G催化剂的活性最高,苯醌的转化率达到99%,氢醌的选择性为100%,并且循环7次后催化剂仍保持着较高的转化率和选择性。结构表征表明,石墨烯担载的钯纳米粒子的粒径约为5nm,无明显团聚.实验进一步考察了反应溶剂(甲醇、乙醇、丙酮、正丙醇、异丙醇、正丁醇)对Pd/G催化苯醌加氢反应的影响,结果表明该反应对溶剂较为敏感,其中甲醇和丙酮较适宜作为反应溶剂.当以甲醇作为溶剂时,苯醌的转化率为98%,氢醌选择性为99%;以丙酮为溶剂时,苯醌转化率为98%,氢醌选择性为90%.研究工作表明,作为载体,石墨烯对钯催化剂的催化效果起着稳定和增强作用.     

Effect of Pd nanoparticle size on the catalytic hydrogenation of allyl alcohol

We report a particle size dependence for the rate of hydrogenation of allyl alcohol using 1.3-1.9 nm Pd dendrimer-encapsulated nanoparticle (DEN) catalysts. For particles with diameters of <1.5 nm and containing <147 Pd atoms, the modulation in catalytic activity is due to the electronic properties of the particle. For the larger particles, 1.5-1.9 nm in diameter and containing an average of 147-250 Pd atoms, the size effect is a result of geometrical constraints. Specifically, the hydrogenation reaction is shown to occur preferentially on the face atoms of the larger nanoparticles.     

Preparation and catalytic performance of monolayer-dispersed Pd/Ni bimetallic catalysts for hydrogenation

Pd/Ni bimetallic catalysts were prepared by replacement reactions, characterized by X-ray diffraction, CO chemisorption and H₂ temperature-programmed desorption, and evaluated for hydrogenation of cyclohexene, styrene and acetone. The results show that Pd atoms are monolayer-dispersed on the Ni surface in these Pd/Ni catalysts. Consequently, Pd/Ni catalysts are much more active than Pd/Ni and Pd/c-Al₂O₃ with the same Pd loading prepared by the conventional impregnation method. __________ Translated from Chinese Journal of Catalysis, 2007, 28(8): 676–680 [译自: 催化学报]     

Preparation of microporous polymer-encapsulated Pd nanoparticles and their catalytic performance for hydrogenation and oxidation

Palladium nanoparticles (Pd NPs) encapsulated by conjugated microporous polymers (CMPs) were prepared by the Pd-catalyzed polymerization followed by a thermal treatment with N₂ or H₂. The Pd catalysts were embedded in the porous network during polymerization and used as a precursor for the generation of Pd NPs in CMP. Although no Pd NPs were formed in the as-synthesized Pd/CMPs, Pd NPs with 1.6–3.5 nm size were formed after the thermal treatment. The obtained Pd/CMP-N₂ and -H₂ catalysts were highly selective in the hydrogenation of 4-nitrostyrene to 4-ethylnitrobenzene, whereas Pd NPs supported on carbon (Ketjen black) gave a fully reduced product, 4-ethylaniline. Substituents in CMP framework could change the catalytic activity of Pd NPs; hydroxy-substituted CMP encapsulated Pd NPs showed higher catalytic activity than Pd/CMP-H₂ for benzyl alcohol oxidation.     

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     

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.     

Triangular Ag/Pd nanoplates with sawtooth edges: Displacement synthesis and optical and catalytic properties

Ag/Pd nanoplates with sawtooth edges were prepared via a galvanic displacement reaction in which added Pd(OAc)₂ slowly reacted with Ag nanoplates containing adsorbed hexadecyltrimethylammonium bromide. Control over the optical properties and catalytic activity of the Ag/Pd nanoplates for electroless copper deposition could be achieved by varying the Ag/Pd alloying ratio.     

New catalytic system for the hydrogenation of ketones

Alcohols are produced in high yield by hydrogenation of several aliphatic and aromatic ketones with rhodium complexes as catalysts in the presence of strong alkali.     

Ag和Pd及其离子对TiO2光催化分解CH3CHO的影响

当用能量大于其禁带宽度的光照射通有氧气的TiO₂悬浮液时,在TiO₂微粒表面会产生反应活性很高的空穴和O₂^-、H₂O₂等多种活性氧.在上一篇文章中^[1]我们已报道了在通氧气和紫外光照的条件下,向TiO₂悬浮液中加入少量Ag⁺或Pd²⁺,将会大幅度提高体系中H₂O₂的生成量.另外,蔡汝雄等人也曾通过向TiO₂悬浮液中加入SOD的方法来提高其中H₂O₂的生成量^[2],而且证明了H₂O₂生成量的增多有助于杀死子宫癌细胞^[3].另一方面,利用TiO₂光催化来分解处理工业废水中的有机物已多见报道^[4～7].因此,为考察H₂O₂含量的增加是否有助于TiO₂催化分解有机物,我们以CH₃CHO为氧化对象,测定了经Ag和Pd表面修饰以及直接向悬浮体系添加Ag⁺或Pd²⁺离子前后,TiO₂光催化氧化分解CH₃CHO效率的变化,并对氮气和氧气气氛的实验结果进行了测定和比较.     

Electroless Pd and Ag deposition kinetics of the composite Pd and Pd/Ag membranes synthesized from agitated plating baths

The atomic absorption spectroscopy (AAS) has been successfully utilized for the measurement of the Pd and Ag ion concentrations in the plating baths and to elucidate the effects of temperature, initial metal ion and reducing agent concentrations and agitation on the electroless plating kinetics of Pd and Ag metals. The initial metal ion concentrations for Pd and Ag were varied over a range of 8.2–24.5 mM and 3.1–12.5 mM, respectively. The plating reactions were conducted in a constant temperature electroless plating bath over a temperature range of 20–60 °C and an initial hydrazine concentration range of 1.8–5.4 mM. It was found that the electroless plating of both Pd and Ag were strongly affected by the external mass transfer in the absence of bath agitation. The external mass transfer limitations for both Pd and Ag deposition have been minimized at or above an agitation rate of 400 rpm, resulting in a maximum conversion of the plating reaction at 60 °C and dramatically shortened plating times with the added advantage of uniform deposition morphology. The derivation of the differential rate laws and the estimation of the reaction orders and the activation energies for the electroless Pd and Ag kinetics were conducted via non-linear regression analysis based on the method of initial rates. For a constant-volume batch reactor, the integrated rate law was solved to calculate the conversion and the reactant concentrations as a function of plating time. The model fits were in good agreement with the experimental data. Furthermore, the bath agitation and the plating conditions used in the kinetics study were adopted for the synthesis of 16–20 μm thick composite Pd/Ag membranes (10–12 wt% Ag) and a pure-Pd membrane with a hydrogen selective dense Pd layer as thin as 4.7 μm. While hydrogen permeance of the Pd/Ag membranes A and B at 450 °C were 28 and 32 m³/m²-h-atm^0.5, the H₂ permeance for the 4.7 μm thick pure-Pd membrane at 400 °C was as high as 63 m³/m²-h-atm^0.5_. The long-term permeance testing of all the membranes synthesized from agitated plating baths resulted in a relatively slow leak growth due primarily to the improved morphology obtained via the bath agitation and modified plating conditions.     

An efficient catalytic system for the hydrogenation of quinolines

A new catalytic system ([Ru(p-cymene)Cl₂]₂/I₂) has been developed for the hydrogenation of quinoline derivatives with high reactivity. For the 2-methyl-quinoline, the hydrogenation reaction can proceed smoothly at an S/C of 20,000/1 with complete conversion. The iodine additive is important for the reactivity.     

胶原纤维接枝多酚负载纳米钯的制备及其对硝基苯加氢的催化特性

以胶原纤维(CF)接枝表棓儿茶素棓酸脂(EGCG)为载体,制备了新型非均相钯(Pd)纳米催化剂(CF-EGCG-Pd).EGCG作为"桥分子"不仅对Pd纳米颗粒具有锚定作用,而且能控制Pd纳米颗粒的大小及分布.通过SEM、TEM、XRD、XPS对该催化剂的形貌和物理特性能进行了表征,发现该催化剂具有规整的纤维结构,在胶原纤维的外表面形成了高分散的平均粒径在3.8 nm的Pd纳米颗粒.将该催化剂用于硝基苯液相催化加氢反应,结果表明在308 K和1.0 MPa氢压下,硝基苯转化速率(TOF)达到34.13 mol·mol-1·min-1,苯胺选择性为100%,催化剂重复使用3次其催化活性基本不变.     

Synthesis of novel serotonergics and other N-alkylamines using simple reductive amination using catalytic hydrogenation with Pd/C

Formation of N-alkylated α-methyltryptamine derivatives (2) was accomplished by simple reductive amination of amine (1) with ketones using catalytic hydrogenation conditions (3 atm H₂ and 10% Pd on carbon). This method was also applied to other primary and secondary amines using ketones and aldehydes.     

Amine groups functionalized gel-type resin supported Pd catalysts: Physicochemical and catalytic properties in hydrogenation of alkynes

Palladium catalysts (0.125–0.5 wt.% Pd) supported by amine groups—functionalized gel-type resin (FCN) were studied in the hydrogenation of alkynes reagents, 2-butyne-1,4-diol and phenylacetylene. The catalysts were prepared by two routes. The first, “OAc” is based on the immobilization of Pd-precursor in the pre-swollen resin from THF solution of Pd(OAc)₂, followed by chemical reduction of the Pd-centers. This method produces Pd particles of size in nano-scale. The second procedure, “aq” implies the deposition of Pd-species on dry resin beads using aqueous solution of PdCl₂. Reduction of these Pd-species gives relatively large Pd particles, dominating are 30–50 nm in size. The SEM studies performed over the cross-section of catalysts grains showed location of Pd in outer shell of polymer beads in both “OAc” and “aq” catalysts; however, thinner layer of Pd appears in “aq” series catalysts. In the presence of all catalysts, prepared by “OAc” and “aq” methods the selectivity towards alkenes is high, above 90%. The catalysts of “aq’ series are much more active and more selective than “OAc” analogues giving selectivity to alkene ca. 94% at almost complete conversion of alkynes. Moreover, catalytic performance of “aq’ series catalyst is unchanged under recycling use. The catalyst was recovered and reused 4 times, maintaining its catalytic efficiency.     

Co-ligand effects in the catalytic activity of Pd(II)-NHC complexes

Three cis-chelating di-N-heterocyclic carbene palladium(II) complexes [PdX₂(diNHC)] (X = I, 1; X = SCN, 2; X = CF₃CO₂, 3) bearing different anionic co-ligands were synthesized and fully characterized. A comparison of their catalytic activities in the Mizoroki-Heck reaction and conjugate addition of arylboronic acids to cyclic enones revealed increasing efficiency in the order SCN⁻ < I⁻ < CF₃CO₂⁻. The di(trifluoroacetato) complex 3 showed the best activity in both transformations highlighting the importance of co-ligands effects in catalysis. In addition, the molecular structure of an unusual poly-heteronuclear complex salt 4 is reported, which has been isolated as a byproduct in the synthesis of complex 3.     

Structure effects of palladium complexes with phosphinated polystyrene on their catalytic properties in phenylacetylene hydrogenation

The structure of palladium acetate complexes with phosphinated polystyrene has been studied by IR and UV spectroscopy. The results indicate that on polystyrene both mono- and dinuclear palladium complexes are formed. The comparison of the catalytic properties of palladium complexes on phosphinated polystyrene with those of mono- and dinuclear complexes supported on silica confirmed the formation of dinuclear palladium complexes on polystyrene surface.

---

- - . , . - , , .

     

Ionic liquid-phase asymmetric catalytic hydrogenation: hydrogen concentration effects on enantioselectivity

Molecular hydrogen is almost four times more soluble in the ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI·BF₄) than in its hexafluorophosphate (BMI·PF₆) analogue at the same pressure. The Henry coefficient solubility constant for the solution BMI·BF₄/H₂ is K=3.0×10⁻³ mol L⁻¹ atm⁻¹ and 8.8×10⁻⁴ mol L⁻¹ atm⁻¹ for BMI·PF₆/H₂, at room temperature. The asymmetric hydrogenation of (Z)-α-acetamido cinnamic acid and kinetic resolution of (±)-methyl-3-hydroxy-2-methylenebutanoate by (−)-1,2-bis((2R,5R)-2,5-diethylphospholano)benzene(cyclooctadiene)rhodium(I) trifluoromethanesulfonate and dichloro[(S)-(−)-2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl]ruthenium(II) complexes immobilised in BMI·PF₆ and BMI·BF₄ were investigated. Remarkable effects in the conversion and enantioselectivity of these reactions were observed as a function of molecular hydrogen concentration in the ionic phase rather than pressure in the gas phase.     

Highly efficient solvent-free catalytic hydrogenation of solid alkenes and nitro-aromatics using Pd nanoparticles entrapped in aluminum oxy-hydroxide

Solid alkenes and aromatic nitro compounds are readily hydrogenated to the corresponding alkanes without further reduction of other functional group and amino compounds in nearly quantitative yields in the presence of Pd nanoparticles entrapped in aluminum oxy-hydroxide under the solvent-free condition.     

硝基苯催化加氢制对氨基苯酚的合成工艺研究进展

介绍了硝基苯在酸性介质中一步加氢重排的反应机理及模型。以提高对氨基苯酚产率和纯度为宗旨，在大量文献调研的基础上提出了控制副反应的几种方法，并讨论了改进对氨基苯酚产量和纯度的可能途径。引用文献22篇。