负载型Pt/Al2O3催化剂中铂的测定

利用Pt（Ⅳ）在盐酸介质中与过量的氯化亚锡形成黄色的氯铂酸锡络合物，采用紫外-可见分光光度计在403 nm处测定该络合物显色液的吸光度，然后通过换算因子计算出负载型Pt/Al₂O₃催化剂中的铂含量。方法简单、快捷、准确，回收率在97％以上，相对标准偏差在2.0％以内 。在选定的试验条件下，负载型Pt/Al₂O₃催化剂中的常见元素对测定铂含量无干扰，但NO^－₃的存在对测定有影响。     

铂催化硅氢加成反应研究进展

硅氢加成反应是合成有机硅材料最重要的途径之一,铂催化剂作为其应用最广的催化剂,具有重要的意义。本文首先介绍了硅氢加成反应机理的研究现状;分析了聚合物长链段铂配合物、含多个铂原子铂簇化合物及N-杂环卡宾铂配合物均相铂催化剂的研究进展,致力于改善均相催化剂催化选择性差、催化活性难以控制等缺点;分别阐述了不同铂催化剂载体如无机二氧化硅、炭载体、金属氧化物、有机高分子、固载液等作为铂催化剂载体的优点,负载铂催化剂具有可回收、产物选择性好的优点,有效解决了工业上铂损失的问题;最后对铂催化硅氢加成反应的发展趋势进行了展望分析,铂负载能力的提高、铂负载催化剂的分离、硅氢加成反应的原理、催化范围的扩大等均是今后研究的重要方向。     

碳纳米管、碳化钨在直接法合成过氧化氢中的应用

选用新型纳米材料——碳纳米管（CNTs）作为催化剂载体,用沉积沉淀法制备负载型钯-铂合金催化剂。同时选用过渡金属碳化物材料（碳化钨）为催化剂,其具有类似于Pt的表面电子结构,有望替代贵金属催化剂。探讨了Pd-Pt/CNTs及碳化钨在氢氧直接合成过氧化氢反应中的催化性能。     

NCH1-1型铂系苯加氢催化剂侧流试验

在实验室模拟装置和南京帝斯曼东方化工有限公司现场侧流试验装置上,分别进行了NCH11型铂系苯加氢催化剂的性能评价。结果表明,NCH11型铂系苯加氢催化剂性能已达到甚至部分超过进口催化剂的水平,尤其是催化剂使用强度较好,可替代进口催化剂产品。     

铂纳米微粒制备方法的研究

分散型铂纳米微粒和负载型铂纳米微粒都是重要的催化剂。制备尺度可控、粒度分布均一的铂纳米微粒,对提高其催化活性和选择性,以及延长其使用寿命具有重要的意义。本文介绍了分散型和负载型铂纳米微粒常用的制备方法,讨论了各方法的制备原理及其优缺点。     

多相贵金属催化剂对芳香化合物催化加氢研究进展

综述了近年来多相贵金属催化剂对芳香化合物加氢的研究；揭示了负载型铂、钯、钌、铑以及二元金属催化剂各自在加氢反应中的特点，以及载体、助催化剂对其活性和选择性的重要作用；同时介绍了TCSM和Raney型贵金属催化剂的概况。     

用负载型铂胶体催化剂合成三氟丙基甲基二氯硅烷

三氟丙基甲基二氯硅烷是合成氟硅橡胶和氟硅油等氟硅产品的重要单体。氟硅橡胶具有优良的耐油、耐溶剂、耐化学药品性能及良好的耐寒和耐热性，兼具硅橡胶和氟橡胶的优异性能，是目前惟一能在68—230℃的润滑油和燃油介质中使用的橡胶材料，广泛用于飞机、火箭、导弹、宇宙飞船及石油化工等领域。氟硅油具有优异的耐溶剂和耐化学试剂，以及润滑、脱模、消泡及抗污性能，广泛应用于织物的憎水、憎油、防污。整理及化妆品、耐溶剂、高效消泡剂等方面。工业上用3，3，3-三氟丙烯与甲基二氯硅烷在均相铂系催化剂作用下制得3，3，3一三氟丙基甲基二氯硅烷。早期采用的氯铂酸异丙醇催化体系反应活性不高，诱导期不易控制，难以从反应体系中分离回收，应用受到了一定的限制。近年来，对各种配位催化剂，特别是负载型配位催化剂的研究日趋活跃，其兼备均相和非均相催化剂的优点，如活性高、选择性好、易从反应体系中分离及可重复使用等。用102白色担体负载的聚三氟丙基乙烯基甲基硅氧烷铂胶体催化剂，催化合成了三氟丙基甲基二氯硅烷，其反应条件相对温和，产物收率高、选择性好。     

Pt-CS负载物催化硅氢加成反应的研究

通过壳聚糖负载铂制备了一种硅氢加成反应用多相催化剂(Pt-CS);并采用聚醚F-6与低含氢硅油的硅氢加成反应体系,比较了不同铂含量的Pt-CS负载物与氯铂酸异丙醇溶液的催化活性。结果表明,当Pt-CS负载物中的铂含量与均相催化剂相当时,其催化活性不如均相催化剂;Pt-CS负载物中的铂含量约为均相催化剂的12倍时,反应达到平衡所需的时间比采用均相催化剂时缩短了1 h;其催化活性与均相催化剂接近,重复使用13次后,催化活性没有明显下降。     

有机硅匀泡剂合成中铂系催化剂性能的研究

研究了氯铂酸催化剂体系的制备及Si-C型有机硅匀泡剂合成中硅氢加成反应工艺。在氯铂酸催化剂作用下,使含有Si-H的聚硅氧烷和烯丙基聚醚进行加成反应,温度控制在110±5 ℃为宜;制备了氯铂酸-异丙醇催化剂和氯铂酸-二乙基聚硅氧烷络合型催化剂,比较了在硅氢加成反应中的催化活性。结果表明,使用络合型Karstedt催化剂后,铂用量减少(<10 μg-Pt·g-1),产品质量指标提高。     

埃洛石固载铂催化合成硅骨架环氧树脂

以天然纳米管状埃洛石为载体,负载氯铂酸制得埃洛石固载铂催化剂,催化1,1,3,3-四甲基二硅氧烷和甲基丙烯酸缩水甘油酯的硅氢加成反应,合成一种硅骨架环氧树脂,产率达到93.26%。利用SEM和TEM表征了埃洛石固载铂催化剂的形貌。结果显示,纯化后的埃洛石呈纳米管状结构,管长为0.5~1.5μm,管外径为50~190nm,管内径为10~20nm,管体清晰,表面干净规整,固载铂催化剂后,催化剂颗粒在埃洛石表面均匀分布。利用红外光谱和氢核磁共振谱对硅骨架环氧树脂结构进行了表征。     

Carbon‐Carbon Double Bond versus Carbonyl Group Hydrogenation: Controlling the Intramolecular Selectivity with Polyaniline‐Supported Platinum Catalysts

The use of polyaniline (PANI) as catalyst support for heterogeneous catalysts and their application in chemical catalysis is hitherto rather poorly known. We report the successful synthesis of highly dispersed PANI‐supported platinum catalysts (particle sizes between 1.7 and 3.7 nm as revealed by transmission electron microscopy, TEM) choosing two different approaches, namely (i) deposition‐precipitation of H₂PtCl₆ onto polyaniline, suspended in basic medium (DP method) and, (ii) immobilization of a preformed nanoscale platinum colloid on polyaniline (sol‐method). The PANI‐supported platinum catalysts were applied in the selective hydrogenation of the α,β‐unsaturated aldehyde citral. In order to benchmark their catalytic performance, citral hydrogenation was also carried out by using platinum supported on the classical support materials silica (SiO₂), alumina (Al₂O₃), active carbon and graphite. The relations of the structural characteristics and surface state of the catalysts with respect to their hydrogenation properties have been probed by EXAFS and XPS. It is found that the DP method yields chemically prepared PtO₂ on polyaniline and, thus, produces a highly dispersed and immobilized Adams catalyst (in the β‐PtO₂ form) which is able to efficiently hydrogenate the conjugated CC bond of citral (selectivity to citronellal=87%), whereas reduction of the CO group occurs with polyaniline‐supported platinum (selectivity to geraniol/nerol=78%) prepared via the sol‐method. The complete reversal of the selectivity between the preferred hydrogenation of the conjugated CC or CO group is not only particularly useful for the selective hydrogenation of α,β‐unsaturated aldehydes but also unveils the great potential of conducting polymer‐supported precious metals in the field of hitherto barely investigated chemical catalysis.     

凹凸棒土负载Pt催化剂的氯代硝基苯选择性加氢性能

以3 mol·L-1的HCl酸化凹凸棒土为载体,200℃还原制备负载型纳米Pt催化剂,并应用于氯代硝基苯选择加氢反应。在反应温度60℃和反应压力2.0 MPa条件下,催化剂显示出优异的加氢活性和选择性,在氯代硝基苯完全转化情况下,氯代苯胺选择性达100%,制备的催化剂具有很高的金属分散度,Pt纳米粒子粒径约2 nm,凹凸棒土载体对提高Pt分散度发挥了关键的作用,高分散纳米Pt粒子显著提高催化剂的加氢活性与氯代苯胺选择性,完全抑制了脱氯现象。     

Surface Characterization of Supported and Nonsupported Hydrogenation Catalysts

In this review we report on some methods for characterizing the metallic component in heterogeneous hydrogenation catalysts, and metals like nickel, palladium, platinum, rhodium, copper, and iridium, supported or nonsupported, will be reviewed. The review is intended especially for organic chemists who make use of supported-metal hydrogenation catalysts, and who are unfamiliar with surface characterization techniques.     

钯、铂催化剂在硝基苯催化加氢合成对氨基苯酚反应中的比较

制备了一系列不同金属粒径的活性炭负载钯、铂催化剂,用于硝基苯液相催化加氢合成对氨基苯酚反应.采用N2-物理吸附、联碱滴定和TEM等表征手段对活性炭载体及其负载钯、铂催化剂进行表征.结果表明,对氨基苯酚选择性与钯、铂活性组分的金属粒径存在紧密的内在联系,说明活性炭负载钯、铂催化剂对于硝基苯液相催化加氢合成对氨基苯酚的反应...     

On the effects of confinement within a catalyst consisting of platinum embedded within nanoporous carbon for the hydrogenation of alkenes

In heterogeneous catalysis, pore size exerts an influence on reaction pathway, selectivity, equilibrium and adsorption constants. This effect can in principle cause noticeable changes in selectivity. Here, we present an analysis of a diffusion–reaction process in the pores of a catalyst comprised of platinum nanoparticles embedded within a molecular sieving carbon. When the alkenes are hydrogenated over this catalyst, the reaction takes place within the ultramicropores of the carbon. Experimental data for the liquid phase hydrogenation of different alkenes over platinum supported on the carbon versus platinum embedded within the same carbon were collected. From these data kinetic parameters and diffusion coefficients for reactions were evaluated. The forward rate constant for 2-methyl-1-pentene hydrogenation was found to be almost one order of magnitude larger within the embedded platinum catalyst versus the supported platinum catalyst. The variation in pore size and reactant molecule dimension, were also found to affect the adsorption equilibrium constants and diffusion coefficients. For 2-methyl-1-pentene molecule with the highest steric hindrance, K increased to 500 g/mol in embedded catalyst compared to 100 g/mol on supported catalyst. At the same time the diffusion coefficient for 2-methyl-1-pentene was one order of magnitude smaller than 1-hexene.     

2-乙基蒽醌加氢催化剂的研究进展

高活性和高选择性的催化剂是解决蒽醌法生产过氧化氢过程中瓶颈问题的根本途径。综述了近年来高活性和高选择性镍、钯、铂系催化剂制备的进展。指出负载型镍系非晶态合金和钯系高分子催化剂应是今后蒽醌加氢催化剂研究的方向。     

Characteristics of Al-MCM-41 supported Pt catalysts: effect of Al distribution in Al-MCM-41 on its catalytic activity in naphthalene hydrogenation

Naphthalene hydrogenation was carried out in a high-pressure batch reactor over platinum catalysts supported on Al-MCM-41 where aluminum was incorporated through two different methods: a direct sol–gel method (Pre) and post-synthetic grafting method (Post). The catalytic reaction was also performed in the presence of dibenzothiophene to investigate the sulfur tolerance. The hydrogenation activity, selectivity and the sulfur tolerance strongly depended on the acidic nature of Al-MCM-41 support. It was suggested that the acid sites of Al-MCM-41-Post be more accessible than those of Al-MCM-Pre due to different aluminum distribution within the pore wall. The naphthalene and tetralin conversion increased with the acid amount of the supports in Pt/Al-MCM-41 catalysts. The acid sites in bifunctional catalysts seemed to contribute to alternative pathway by the spillover hydrogen in the acid–metal interfacial region for naphthalene hydrogenation, since the metal dispersions were kept constant for Pt/Al-MCM-41 catalysts. The trans-decalin selectivity generally increased with temperature or acid amount. The acid sites seemed to enhance the sulfur tolerance of supported platinum catalysts due to the electron-deficient state of metal.     

Supported nanometric platinum–nickel catalysts for solvent-free hydrogenation of tetralin

This paper aims to report a method of synthesizing alloyed platinum-nickel nanoclusters on activated carbon to enhance its hydrogenation performance of tetralin without adding solvents. The activated carbon provides a high surface area, while the highly-dispersed platinum acts as the hydrogen adsorption and dissociation site, in addition the Ni can alloy with Pt to induce more electron deficiency. Due to such favorable conditions, the bimetallic Pt–Ni/AC catalysts show good conversion and selectivity for hydrogenation of tetralin within a very short time. Furthermore, after six consecutive cycles, no prominent fluctuations in activity and selectivity are observed. Thus, the supported platinum–nickel nanocatalysts with excellent efficiency and prolonged lifetime for tetralin hydrogenation harbors great significance for future nanocatalyst design.     

Origin of the cluster-size effect in the hydrogenation of cinnamaldehyde over supported Au catalysts

Gold nanoclusters supported on γ-Al₂O₃ were more active and selective than platinum nanoclusters in the high-pressure liquid-phase hydrogenation of cinnamaldehyde to cinnamylalcohol, while in the hydrogenation of cyclohexene gold was less active than platinum. The differences in catalytic performance are ascribed to the weaker interaction of gold with the reactants and products compared to platinum. Gold clusters with a diameter below 2 nm are essential to obtain a high activity and selectivity in the hydrogenation of cinnamaldehyde. The size dependence of the selectivity originates from the stronger dependence of the CO hydrogenation rate on cluster size compared to the CC hydrogenation rate. Small clusters exhibit an enhanced π backbonding, which favors CO adsorption over CC adsorption.     

Platinum Nanoparticles Supported on Ionic Liquid‐Modified Magnetic Nanoparticles: Selective Hydrogenation Catalysts

A method for supporting platinum nanoparticles on magnetite nanoparticles is described. The method requires modification of the surface of the magnetic nanoparticles with ionic liquid groups. Before modification, the magnetic nanoparticles are not stable and easily aggregate and, after modification, the magnetite nanoparticles become highly stable and soluble in polar or non‐polar organic solvents depending on the alkyl group of the linked ionic liquids. The supporting of platinum nanoparticles on the modified magnetic nanoparticles was achieved by adsorbing platinum salts (K₂PtCl₄) on the surface of the magnetite nanoparticles via ion exchange with the linked ionic liquid groups and then reducing them by hydrazine. The supported platinum nanoparticles were applied in the catalytic hydrogenation of alkynes in which cis‐alkenes were selectively produced, and in the hydrogenation of α,β‐unsaturated aldehydes where the allyl alcohols were obtained as the exclusive products. The new catalyst can be easily separated from the reaction mixtures by applying an external magnetic field and recycled.