聚合物固载Co-Pd 催化剂的结构与活性

采用溶剂化金属原子浸渍(SMAI)法制备了几种不同金属含量的Co Pd催化剂,用X射线衍射、X射线光电子能谱和磁测定对催化剂进行表征,并与普通浸渍法(CI)制得的相同金属含量的催化剂进行比较.结果表明SMAI法制备的催化剂金属粒度小于CI法制备的催化剂,且前者零价金属含量高于后者.SMAI法制备的催化剂Co在表面上富集,而CI法制备的催化剂Co在表面和体相的金属含量基本相同.在二丙酮醇加氢及电催化反应中, SMAI法催化剂比相同组成的CI法催化剂具有更高的催化活性.     

柴油加氢精制催化剂制备技术

柴油加氢精制催化剂制备技术的发展大致经历了3个阶段,由此形成了三代柴油加氢催化剂:单层分散的负载型金属硫化物催化剂,多层分散的负载型金属硫化物催化剂和非负载型金属硫化物催化剂。本文对金属硫化钼基柴油加氢精制催化剂的应用背景、制备思想及催化剂研究开发现状进行了系统的总结,对柴油加氢催化剂的发展方向进行了展望。     

柴油加氢精制催化剂制备技术

柴油加氢精制催化剂制备技术的发展大致经历了3个阶段,由此形成了三代柴油加氢催化剂:单层分散的负载型金属硫化物催化剂,多层分散的负载型金属硫化物催化剂和非负载型金属硫化物催化剂.本文对金属硫化钼基柴油加氢精制催化剂的应用背景、制备思想及催化剂研究开发现状进行了系统的总结,对柴油加氢催化剂的发展方向进行了展望.     

Study of Supported Bimetallic Pd-Pt Catalysts. Characterization and Catalytic Activity for Toluene Hydrogenation

Bimetallic Pd-Pt catalysts were prepared either by a surface redox reaction (RC catalysts) or by coimpregnation (CI catalysts). RC bimetallic catalysts show a higher sulfur resistance in the course of toluene hydrogenation in the presence of thiophene compared to monometallic palladium and CI bimetallic catalysts. A characterization of the RC catalysts by IR and EXAFS allows to propose a structure of the Pd-Pt crystallites which would explain these results.     

1-辛烯在Co/CNTs催化剂上的氢甲酰化研究： 钌的促进作用

采用等体积浸渍法制备了碳纳米管负载的钴及钴-钌双金属催化剂，并以1-辛烯的氢甲酰化反应为探针，研究了所制催化剂的催化性能；用TEM、XRD、TPR、TG技术对催化剂的形貌、物相结构、还原行为和热稳定性进行了研究。结果表明，金属钌能够促进金属钴在碳纳米管上的均匀担载，并有助于金属钴的还原，降低了催化剂的还原温度。1-辛烯的氢甲酰化反应结果表明，少量钌的加入，可明显提高反应的转化率和C9-醛的选择性；在双金属催化剂中，金属催化剂的粒径更小，分布更均匀，钌的加入对钴金属催化剂有促进作用。     

Hydrodechlorination of chlorobenzene over supported metal catalysts

The use of supported Pd catalysts, with low and high metal content, for the hydrodechlorination of chlorobenzene is presented in this article. Application of microwave irradiation during preparation of catalysts resulted in the synthesis of large Pd particles at moderate temperatures. The nature of the support played a key role in the formation of cationic Pd species. The extent of interaction of the Pd species with the support, the nature of metal precursor, particularly the residual chlorine on the surface were found to significantly affect the activity of the catalysts. In the case of bimetallic catalysts also microwave heating resulted in creation of bigger particles of Pd compared to those observed in conventionally heated catalysts. Besides, it minimized alloy formation as a result of which the activity of the catalysts in hydrodechlorination was found to be higher compared to that observed on conventionally prepared catalysts. Contrary to the general observation that low dispersed Pd catalysts are preferable for high stability, by means of the deposition-precipitation method adopted for catalyst preparation it was demonstrated that even highly dispersed (low Pd containing) catalysts can exhibit comparable activity and stability. An analysis of the nature of Pd species and its role in the stability of the catalysts is presented.IICT communication No. 051224     

Dehydrocyclization of Diphenylamine to Carbazole over Platinum-Based Bimetallic Catalysts

 Gas phase dehydrocyclization of diphenylamine (DPA) to carbazole over monometallic and bimetallic 0.4 wt% Pt-based catalysts in a fixed bed reactor was studied in the presence of hydrogen at a temperature of 550 ^oC. Alumina and carbon supported Pt catalysts showed very high initial activity (> 95%). The selectivity for carbazole over carbon supported Pt catalysts was slightly lower. Doping of the catalyst with potassium led to an increase in the selectivity for carbazole by 15%. Bimetallic Pt-Sn catalysts prepared by co-impregnation were less selective than catalysts prepared by successive impregnation. The selectivity for carbazole over bimetallic Pt-Sn catalysts prepared by successive impregnation was 75%, but their activity decreased with increased Sn loading. Highly active and reasonably selective catalysts were Ir-doped bimetallic Pt-based catalysts. The conversion of diphenylamine over Pt-Ir catalysts was above 98% and the selectivity for carbazole was nearly 55%, while the lifetime was much longer.     

柴油车排放碳黑颗粒消除催化剂的研究进展

 柴油车尾气排放的碳黑颗粒已引起严重的环境污染问题. 对于柴油车尾气碳黑颗粒的处理必须使用高活性的催化剂来加快碳黑颗粒在低温下的氧化速率. 本文总结了柴油车排放碳黑颗粒催化燃烧用几种不同类型的催化剂,即碱金属或碱土金属催化剂、贵金属催化剂、过渡金属催化剂以及复合型催化剂,归纳了它们的催化作用机理,比较了它们在松散接触与紧密接触时的不同催化活性,概括了这些催化剂的最新研究进展,并对它们在实际应用中存在的问题和应用前景进行了探讨.     

水热老化对不同方法制备的Fe-ZSM-5用于NH_3选择性催化还原NO_x的影响

采用液体离子交换、等体积浸渍和固相离子交换制备了一系列Fe-ZSM-5催化剂,并将其用于NH3选择性催化还原NOx(NH3-SCR)反应.运用X射线衍射、紫外-可见漫反射吸收光谱和原位漫反射傅里叶变换红外光谱对催化剂进行了表征.结果表明,Fe-ZSM-5催化剂表面Fe物种可分为孤立Fe3+物种、低聚Fe氧化物团簇和Fe2O3,各催化剂上NH3-SCR反应活性不同的根本原因是其表面Fe物种分布不同.水热老化后,Fe-ZSM-5催化剂上400oC以下反应时NOx转化率降低,而高温活性略有提高,各催化剂活性差异减小;同时NH3氧化活性和NO氧化活性均明显降低.这可归因于水热老化使Fe-ZSM-5催化剂表面的孤立Fe3+物种相对浓度降低,低聚Fe氧化物团簇和Fe2O3相对浓度增加,以及催化剂表面Br?nsted酸性位显著减少所致.     

Formation of supported size-controlled nanoparticles of sulfated zirconia

Methods of the preparation of catalysts for alkane skeletal isomerization based on uniform nanoparticles of sulfated zirconia anchored to different supports were investigated. These catalysts were characterized by using the ICP, HRTEM and BET techniques. The activities of the catalysts in the reaction of n-butane isomerization were measured and compared with those of bulk catalysts.     

修饰型多相手性催化剂在不对称合成中的应用

本文评述了修饰型多相手性催化剂在不对称合成中的应用。按照不同的制备方法及催化反应对一些多相催化体系进行了归类总结, 包括过渡金属手性配合物的固相化、修饰型手性固体催化剂、手性分子筛及嵌入型粘土手性催化剂。对酒石酸及金鸡纳碱修饰型金属催化剂的反应机理也进行了探讨。     

辛可宁季铵盐的合成及催化不对称烷基化研究

探索了辛可宁季铵盐的通用合成方法, 确定辛可宁与取代苄溴在四氢呋喃中回流为最优反应途径, 合成了11个羟基保留的辛可宁季铵盐, 收率57%~88%, 并合成了4种羟基保护季铵盐, 羟基成醚过程在生成季铵盐前后均可进行, 总收率62%~71%; 羟基酯化只能在生成季铵盐之后进行, 总收率78%. 本文共合成了15个季铵盐(Cn-1~Cn-15), 其中5个为新化合物, 另有4个的合成方法未见文献报道. 选用该类季铵盐催化剂催化二苯亚甲基甘氨酸叔丁酯的不对称苄基化反应, 结果发现, 催化剂苄基具有4-Br取代或羟基成醚均有助于提高反应产物的对映选择性. Cn-9可得到最优的反应结果, 产率93%, e.e.值91%.     

Thermal characterisation of alumina supported chromium and platinum–chromium catalysts

This study presented results on reduction of alumina supported chromium and platinum–chromium catalysts using temperature programmed reduction method (TPR). It has been shown that catalysts after earlier oxidation step but without calcinations one undergo reduction in lower temperature in comparison to calcined only catalysts. Moreover, addition platinum to Cr/Al₂O₃ catalysts also caused decrease of reduction temperature. It has been observed that over the examined catalysts oxidation CO to CO₂ and reduction CO to CH₄ occurs. However, on Pt–Cr catalysts both reactions proceed at lower temperature compare to Cr catalysts.     

树枝化聚合物催化剂的合成与应用

树枝化聚合物具有大量的分子内空腔、密集的表面官能团和纳米尺寸等特点,是均相催化剂的理想载体。树枝化聚合物催化剂结合了均相催化剂和多相催化剂的优点,能使反应在温和条件下达到高活性和高选择性。本文介绍了树枝化聚合物的合成,重点论述了树枝化聚合物催化剂的合成与催化作用,并展望了这类新型催化剂的发展前景。     

焙烧条件对金催化剂的结构及其催化CO氧化性能的影响

采用共沉淀法和金属有机配合物固载法,分别制备了负载型金催化剂,并考察了焙烧条件对其催化CO氧化性能的影响。实验结果表明,焙烧温度和时间对催化剂的结构和活性的影响显著,不同的金属氧化物负载的金催化剂具有不同的最佳焙烧温度。DTA-TG分析结果确定了催化剂稳定结构的形成温度;XRD测试结果显示,在最佳焙烧条件下得到的催化剂,其载体为具有一定结晶度的金属氧化物。     

单原子催化剂在电化学中的研究进展

目前单原子催化剂的研究呈现爆发式增长, 已然成为材料科学和催化领域的明星材料和研究热点. 前期报道的单原子催化剂研究主要针对某一个应用方向进行探讨, 较少研究催化剂的双功能或多功能应用. 近年来, 为了拓展单原子催化剂在更多领域和方向的应用, 具有双功能甚至多功能的单原子催化剂的设计开发备受关注. 本文综合评述了近年来具有双功能活性的单原子催化剂的研究进展, 重点介绍了其在电化学领域中的最新应用研究. 最后, 对具有双功能活性的单原子催化剂发展研究中存在的问题进行了简要分析, 并对未来发展前景进行了展望.     

稀土在机动车尾气催化净化中的应用与研究进展

随着我国机动车尾气排放法规日趋严格,对机动车尾气净化催化剂性能提出了更高的要求.稀土元素由于独特的4f电子层结构和储放氧性能等特性,在机动车尾气催化剂中得到广泛应用.本文综述了稀土元素在机动车尾气催化剂中的应用及相关机理研究现状,并依据京V排放法规要求探讨了最新排放限值对尾气净化催化剂性能的要求,分析了稀土在开发高性能催化剂中的作用,并对稀土在机动车尾气净化催化剂中的应用前景进行了展望.     

从工业催化角度看分子筛催化剂未来发展的若干思考

从工业催化的角度思考和探讨了分子筛催化剂合成、催化及应用方面存在的一些问题与挑战, 并从沸石分子筛的高效催化、新结构分子筛合成与催化应用、沸石分子筛的经济合成、分子筛在绿色环保领域的新应用等几个方面, 综述了国内外相关的最新研究进展, 探讨了分子筛催化剂未来的发展方向. 旨在引发人们对分子筛催化未来向经济、可控、高效催化、绿色环保和新应用等方面发展的思考与探索.     

Occlusion of grubbs' catalysts in active membranes of polydimethylsiloxane: catalysis in water and new functional group selectivities

The Grubbs' first and second generation catalysts were occluded into cross-linked slabs of polydimethylsiloxane with volumes from 1 mm3 to 1 cm3 by swelling the polymer with catalyst and methylene chloride. Methylene chloride was evaporated under vacuum to yield occluded catalysts where their solvent was polydimethylsiloxane. These occluded catalysts were reacted with alkenes dissolved in H2O or H2O/MeOH mixtures that diffused into the polydimethylsiloxane to react by ring-closing metathesis and cross metathesis. Control experiments revealed that the catalysts remained occluded and metathesis did not occur in the solvent. Occlusion of these catalysts allowed commercially available Grubbs' catalysts to be used with H2O as the solvent while isolating the H2O sensitive ruthenium methylidene from exposure to H2O. Functional group selective experiments were carried out where the polydimethylsiloxane was an "active" membrane to exclude salts. Polydimethylsiloxane is a hydrophobic polymer, so the deprotonated salt of diallylmalonic acid did not diffuse into it while a diallylether diffused into it and reacted by metathesis. Thus, by controlling the polarity of reagents their reactivity can be controlled owing to the properties of polydimethylsiloxane rather than those of the Grubbs' catalysts. Occlusion of catalysts in polydimethylsiloxane has been shown to add new selectivities to mature catalysts.     

Renaissance of immobilized catalysts. New types of polymer-supported catalysts, 'microencapsulated catalysts', which enable environmentally benign and powerful high-throughput organic synthesis

Immobilized catalysts have been reinvestigated from two aspects; as keys to environmentally benign chemical processes and high-throughput organic synthesis for combinatorial chemistry. While most known polymer-supported catalysts are less active than the corresponding original catalysts, new types of polymer-supported catalysts, microencapsulated catalysts, have been developed. The catalysts were immobilized on to polymers using physical envelopment by polymer backbones and interaction between pi electrons of benzene rings of the polystyrenes used as polymer backbones and vacant orbitals of the catalysts. Microencapsulated Sc, Os, Pd and Ru catalysts have been successfully prepared and high activities have been attained. In all cases, no leaching of the catalysts occurred, and the immobilized catalysts were recovered quantitatively by simple filtration and reused without loss of activity. It is noted that this method enables direct immobilization of metals onto polymers, and that normally unstable species such as Pd(0)(PPh3) can be kept stable by this immobilization technique. It is expected that other metal catalysts can be immobilized using this microencapsulation technique.