氧化物负载型亚纳米金属催化剂的制备及其在有机催化中的应用

近几年来，亚纳米金属催化剂(单原子催化剂和团簇催化剂)由于具有高的催化活性和金属原子利用率，在各个领域里具有重要研究意义，尤其是在有机催化反应中表现出优异的催化性能。氧化物因其具有丰富的缺陷位点、表面酸碱位点和高温稳定性等多种优势，作为负载型亚纳米金属催化剂的载体材料。主要综述了氧化物载体负载型亚纳米金属催化剂的几种合成方法及其在氧化反应、加氢反应及偶联反应等有机催化中的应用。     

负载型磷钨酸催化剂研究进展

介绍了负载型磷钨酸催化剂的制备方法,重点综述了不同种类载体负载的磷钨酸催化剂在催化反应中的研究和应用情况。讨论了载体的结构及其性质对催化性能的影响,并对负载磷钨酸催化剂发展前景进行了展望。     

挥发性有机化合物催化燃烧用铂基催化剂的研究进展

负载型Pt催化剂由于具有高活性和良好的稳定性,被广泛应用于挥发性有机化合物(VOCs)的催化完全氧化反应中。系统阐述了载体种类、第二金属组分、催化剂预处理、颗粒尺寸等对催化剂反应活性和稳定性的影响,还概述了Pt催化剂对VOCs完全氧化的催化机理及动力学模型。最后,指出了负载型Pt催化剂今后的发展方向。     

黏土负载型类Fenton催化剂的研究进展

黏土负载型类Fenton催化剂是将活性金属固定在黏土上,用以催化活化H₂O₂产生羟基自由基去除难降解有机污染物,克服了均相Fenton氧化适用pH范围窄、易产生铁泥沉淀等缺点。本文从黏土的类型和结构特点出发,简述了层状与非层状黏土负载活性金属的特点及其催化性能;分析了柱撑、浸渍、沉积-沉淀等活性金属负载方法和黏土的改性手段;阐述了负载活性金属类型及其对催化性能的影响。针对黏土负载型类Fenton催化剂的特点和现阶段存在的问题,从黏土负载型催化剂的活性金属负载形式、负载方法和高效稳定催化性能的需求等角度指出了今后的研究方向。     

负载型金属纳米催化剂对催化反应性能影响的研究进展

负载型金属纳米催化剂是由活性金属纳米粒子和载体组成的。金属纳米粒子是各种纳米技术应用中的关键功能部件,因为它们的尺寸、形状和组成具有独特的性质,且具有比表面积大的优点。对于相同质量的金属和纳米金属粒子而言,纳米金属表面积是普通金属表面积的千百倍,这个优点使其吸附作用非常强。纳术金属广泛的被应用于光学器件、电子器件、信息储存、生物传感等领域。多年来,金属纳米粒子催化剂的催化活性备受关注,金属的尺寸大小、掺杂、构成、种类和负载量均对催化反应的催化性能有一定的影响。     

烯烃聚合后过渡金属催化剂负载化研究进展

综述了后过渡金属催化剂负载化方式和载体的种类及其催化特性,该催化剂载体包括无机载体、聚合物载体、自固载和介孔分子筛等。通过与均相催化剂性能的比较,进一步阐述了负载的目的和必要性。随着这一领域研究深入,将对后过渡金属催化剂工业化发展具有重要的意义。     

负载固相的铑基催化剂应用于烯烃氢甲酰化反应的研究进展

负载固相的催化剂因其简便的分离循环操作以及可观的催化性能而广受关注,但存在反应活性较差、金属流失量较大、催化剂制备成本较高等问题。本文首先从不同负载材料的角度综述了近年来该类催化剂最新的研究进展,主要探讨了载体的表面性质、催化剂的制备方法、膦配体等对催化性能的影响;最后介绍了新型的单原子催化剂所取得的突破性进展。分析表明：具有"类均相"特点的多孔有机聚合物的催化活性很好,而超支化聚合物功能化的磁性纳米催化剂的稳定性更佳。另外还对负载型铑催化剂未来的研究方向进行了展望：需要进一步加深对多孔有机聚合物的化学结构的理解,以便对其更好地表征;借助一些先进的表征技术如高角环状暗场扫描透射电镜和密度泛函理论的计算来深入研究载体结构对单原子催化剂的催化性能的影响。     

天然气催化燃烧催化剂的研究(Ⅱ）

介绍了天然气催化燃烧钙钛矿型氧化物催化剂、六铝酸盐型催化剂以及负载型非贵金属催化剂的研究现状。对于钙钛矿型氧化物催化剂,利用A位取代或调整B位元素的种类及配比、新的技术和方法制备高比表面积或具有纳米结构的钙钛矿型氧化物,是提高其甲烷催化燃烧活性的重要手段。六铝酸盐型催化剂具有很高的热稳定性和甲烷燃烧活性,但起燃温度较高,通过采用将金属Pd负载到六铝酸盐上或改变制备方法,提高其比表面积,以提高其低温反应活性。负载型非贵金属催化剂研究最多的是过渡族金属,其氧化活性、抗毒性能和耐久性都存在问题,需进一步研究。     

杂多酸催化剂的组成对烷烃异构化性能影响规律分析

含固体杂多酸双功能催化剂表现出优异的催化活性,并具有催化反应条件温和、不腐蚀设备、不污染环境等优点.此外,杂多酸基催化剂具有广阔的应用前景,已成为烷烃异构化催化剂领域研究热点.该文综述了杂多酸用于轻质烷烃异构化研究进展,详细论述了负载型杂多酸的载体种类、金属活性组分种类和混合方式等对异构化性能的影响规律.分析了杂多酸基催化剂结构与异构化性能之间的构效关系.提出了今后杂多酸基异构化催化剂的研究方向.     

Al2O3负载Pd基催化剂的研究进展

氧化铝的化学性质稳定，并具有丰富的孔道结构，常被用为催化剂载体来分散金属活性组分，起到提高催化剂的催化活性和稳定性的作用，已被广泛地应用于化学工业中。负载型纳米Pd基催化剂具有优异的反应活性和产品选择性，己被广泛应用于催化加氢、脱氢、碳-碳耦合等反应中。综述了近年来Al₂O₃负载Pd基催化剂的研究进展。     

Surrounded catalysts: concept,design and catalytic performance

Supported catalysts are widely used in heterogeneous catalysis processes, in which the interfacial interaction between the active phase and the support and the influence of the interfacial density on the catalytic reaction mechanism and performance have always attracted attention. The main preparation method for traditional supported catalysts is impregnation method, in which a metal precursor is deposited onto the outer surface of support, normally rendering limited contact area and relatively weak interface interaction between the active species and the support. We use the reverse design idea to construct the surrounding catalyst, and develop a simple and universal preparation method, namely the ion exchange reverse loading method, so that the metal ions of the carrier precursor can replace the metal ions of the active metal hydroxide precursor through the ion exchange reaction. After calcination and reduction, a catalyst with an active core surrounded by a carrier is formed. The unique surrounded structure presents not only high interface density and mutually changed interface, but also high stability due to the physical isolation of active phase, revealing superior catalytic performance to the traditional supported catalyst, suggesting the great potential of this new surrounded catalyst as the upgrade of supported catalyst.     

负载型金属催化剂制备新技术研究进展

负载型金属催化剂因为其独特的催化性能在众多领域得到广泛应用。传统的催化剂制备方法有浸渍法,沉淀法,离子交换法和熔融法等。文章综述了溶剂化金属原子浸渍法,超临界技术和微波技术在负载型金属催化剂制备中的应用。     

Progress of immobilized catalysts for ethylene oligomerization to α-olefin

综述了乙烯齐聚制a-烯烃固载化催化剂的研究新进展。通过讨论固载化催化剂的载体结构和性质、固载化方法、助催化剂以及主催化剂与载体的相互作用等对乙烯齐聚反应的影响,指出固载化催化剂由于载体与活性金属中心的相互作用改变了原均相催化剂活性中心的有规立构及定向性,使其活性金属中心的电子密度发生变化是导致固载化催化剂的活性与原均相催化剂不同的重要原因,且多数固载化催化剂的活性有所降低。另外,对固载化催化剂活性中心及反应中间物种形成的催化反应机理进行了简单阐述。最后指出开发新型载体及更为简单有效的固载化方法,明晰主客体之间的相互关系是今后乙烯齐聚固载化催化剂研究的重要任务。     

Methanation of carbon monoxide catalyzed by nickel/zeolite y and nickel/ η-alumina; effect of reduction time

The catalytic behavior of three nickel catalysts, viz. nickel supported on η-alumina and nickel supported on zeolite Y (prepared by impregnation and ion exchange methods) were investigated for the methanation reaction. All the catalysts were reduced in flowing hydrogen at 723 K for times varying from 6 h to 24 h. The catalytic activities of these catalysts were determined using a differential flow reactor. The catalysts were characterized using the techniques of hydrogen chemisorption and x-ray diffraction. Nickel metal areas were found to increase with reduction time for all catalysts. X-ray diffraction studies showed that crystallite size varied with reduction time in the case of Ni/zeolite Y catalyst (both impregnated and ion exchanged). Turnover numbers were found to vary with crystallite size and the maximum values of the turnover number were obtained for the catalysts having crystallite sizes of 14-16 nm. There appears to be strong evidence that reduction time can have an effect on catalytic activity; possibly by its effect on crystallite size. The effect of support on catalytic activity was more complicated as there appeared to be an interaction with reduction time. However, nickel/η-alumina appeared to be a more active catalyst than nickel/zeolite Y.     

Catalytic Hydrogen Production from Methane Partial Oxidation: Mechanism and Kinetic Study

The multifunctional potential of a transition and noble metal catalyst supported on either a single support or combined oxide support in the catalytic partial oxidation of methane (CPOM) is reviewed. The close interaction and interfacial area between the metal, reducible oxide, and acidic support are highlighted, which are crucial for low-temperature CPOM. The effects of the catalyst components and their preparation methods are considered. Their impact on the catalytic performance and stability on the CPOM reaction is evaluated. The two main mechanisms of CPOM, namely, direct partial oxidation and combustion and reforming reaction, are also covered along with the most recent kinetic studies. Finally, the deactivation of the CPOM catalysts is evaluated in terms of coke and carbon deposition along with CO poisoning.     

High utilization platinum deposition on single-walled carbon nanotubes as catalysts for direct methanol fuel cell

This research aims to enhance the activity of Pt catalysts, thus to lower the loading of Pt metal in fuel cell. Highly dispersed platinum supported on single-walled carbon nanotubes (SWNTs) as catalyst was prepared by ion exchange method. The homemade Pt/SWNTs underwent a repetition of ion exchange and reduction process in order to achieve an increase of the metal loading. For comparison, the similar loading of Pt catalyst supported on carbon nanotubes was prepared by borohydride reduction method. The catalysts were characterized by using energy dispersive analysis of X-ray (EDAX), transmission electron micrograph (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectrum (XPS). Compared with the Pt/SWNTs catalyst prepared by borohydride method, higher Pt utilization was achieved on the SWNTs by ion exchange method. Furthermore, in comparison to the E-TEK 20 wt.% Pt/C catalyst with the support of carbon black, the results from electrochemical measurement indicated that the Pt/SWNTs prepared by ion exchange method displayed a higher catalytic activity for methanol oxidation and higher Pt utilization, while no significant increasing in the catalytic activity of the Pt/SWNTs catalyst obtained by borohydride method.     

酯交换合成碳酸二甲酯催化剂研究进展

综述了近年来国内外碳酸乙烯酯或碳酸丙烯酯与甲醇酯交换合成碳酸二甲酯催化剂的研究进展，重点对金属氧化物催化剂、离子交换树脂和负载型催化剂等多相催化剂的制备和催化性能作了介绍。金属氧化物催化剂在使用过程中可能发生化学变化，催化寿命较短；离子交换树脂对热稳定性较差，不能在高温下长期使用；负载型催化剂活性组分的流失有待解决。尽管存在这些不足，但多相催化剂分离简单，容易实现反应 分离一体化，是今后研究开发的主要方向。     

加氢脱氮催化剂研究进展

对加氢脱氮催化剂进行论述,从催化剂活性组分、助剂和载体方面介绍了国内外载体的发展趋势。加氢活性组分的过渡金属碳化物、过渡金属氮化物和过渡金属磷化物成为研究热点,特殊功能的助剂加入到催化剂中,提高了催化剂酸性或活性组分分散度。新型催化材料用于催化剂载体,改性Al_2O_3、TiO_2复合载体和纳米材料复合载体有望替代传统载体。     

Fischer-Tropsch synthesis on ruthenium supported ETS-10 titanium silicate catalysts

Titanium silicate ETS-10 was found to be a suitable metal catalyst support, having high surface area, high ion exchange capacity and no acidic functions. In this work, ETS-10 was used as a support in preparing ruthenium supported catalyst for Fischer-Tropsch synthesis. Ru/METS-10 catalytic systems (M standing for Na or K) showed some important characteristics, as good metal dispersion and shape selectivity. Moreover, no side reactions due to acidic functions were evidenced; indeed readsorption of olefins on active metal centers was found to control the activity of the catalysts.In part presented at 10th IZC, Garmisch-Partenkirchen, July 1994.     

Rational approach to polymer-supported catalysts: synergy between catalytic reaction mechanism and polymer design

Supported catalysis is emerging as a cornerstone of transition metal catalysis, as environmental awareness necessitates "green" methodologies and transition metal resources become scarcer and more expensive. Although these supported systems are quite useful, especially in their capacity for transition metal catalyst recycling and recovery, higher activity and selectivity have been elusive compared with nonsupported catalysts. This Account describes recent developments in polymer-supported metal-salen complexes, which often surpass nonsupported analogues in catalytic activity and selectivity, demonstrating the effectiveness of a systematic, logical approach to designing supported catalysts from a detailed understanding of the catalytic reaction mechanism. Over the past few decades, a large number of transition metal complex catalysts have been supported on a variety of materials ranging from polymers to mesoporous silica. In particular, soluble polymer supports are advantageous because of the development of controlled and living polymerization methods that are tolerant to a wide variety of functional groups, including controlled radical polymerizations and ring-opening metathesis polymerization. These methods allow for tuning the density and structure of the catalyst sites along the polymer chain, thereby enabling the development of structure-property relationships between a catalyst and its polymer support. The fine-tuning of the catalyst-support interface, in combination with a detailed understanding of catalytic reaction mechanisms, not only permits the generation of reusable and recyclable polymer-supported catalysts but also facilitates the design and realization of supported catalysts that are significantly more active and selective than their nonsupported counterparts. These superior supported catalysts are accessible through the optimization of four basic variables in their design: (i) polymer backbone rigidity, (ii) the nature of the linker, (iii) catalyst site density, and (iv) the nature of the catalyst attachment. Herein, we describe the design of polymer supports tuned to enhance the catalytic activity or decrease, or even eliminate, decomposition pathways of salen-based transition metal catalysts that follow either a monometallic or a bimetallic reaction mechanism. These findings result in the creation of some of the most active and selective salen catalysts in the literature.