Progress on Noble Metal-Based Catalysts Dedicated to the Selective Catalytic Ammonia Oxidation into Nitrogen and Water Vapor (NH3-SCO)

A recent development for selective ammonia oxidation into nitrogen and water vapor (NH₃-SCO) over noble metal-based catalysts is covered in the mini-review. As ammonia (NH₃) can harm human health and the environment, it led to stringent regulations by environmental agencies around the world. With the enforcement of the Euro VI emission standards, in which a limitation for NH₃ emissions is proposed, NH₃ emissions are becoming more and more of a concern. Noble metal-based catalysts (i.e., in the metallic form, noble metals supported on metal oxides or ion-exchanged zeolites, etc.) were rapidly found to possess high catalytic activity for NH₃ oxidation at low temperatures. Thus, a comprehensive discussion of property-activity correlations of the noble-based catalysts, including Pt-, Pd-, Ag- and Au-, Ru-based catalysts is given. Furthermore, due to the relatively narrow operating temperature window of full NH₃ conversion, high selectivity to N₂O and NO_x as well as high costs of noble metal-based catalysts, recent developments are aimed at combining the advantages of noble metals and transition metals. Thus, also a brief overview is provided about the design of the bifunctional catalysts (i.e., as dual-layer catalysts, mixed form (mechanical mixture), hybrid catalysts having dual-layer and mixed catalysts, core-shell structure, etc.). Finally, the general conclusions together with a discussion of promising research directions are provided.     

甲醛氧化催化剂及反应机理

甲醛具有致畸和致癌性,是主要的室内污染物。催化氧化法甲醛转化效率高,没有二次污染,相关研究日益受到关注。本文详细介绍了贵金属和非贵金属两类主要的甲醛氧化催化剂,探讨了活性组分、载体、催化剂助剂等催化剂组成对于其理化性质和反应性能的影响规律,讨论了制备方法、反应物中的水含量等因素对于催化反应的影响,分析了催化剂失活的主要因素。研究表明,催化剂表面活性氧、表面羟基、氧空位数量以及对反应物的吸脱附和存储能力是影响催化活性的关键因素。贵金属催化剂,特别是Pt催化剂具有较好的催化性能,可在较低温度实现甲醛充分转化;非贵金属催化剂具有可变价态,通过催化剂的合理设计可以具有足够的催化活性,其原料资源丰富,价廉易得,应用前景广阔。     

二氧化钛载Ir催化剂对氨氧化的电催化性能

用同一方法制备了Ir含量相同而载体TiO2-晶体结构不同的TiO2-载Ir（Ir/TiO2）催化剂,研究了TiO2-晶体结构对Ir/TiO2催化剂对氨氧化的电催化性能的影响,发现具有金红石结构的TiO2-载Ir（Ir/TiO2-R）催化剂对氨氧化的电催化性能远好于具有锐钛矿型结构的TiO2-载Ir（Ir/TiO2-A）催化剂。 物理化学和电化学的表征揭示了Ir/TiO2-R催化剂对氨氧化的电催化性能好的可能原因归结于Ir纳米粒子在TiO2-R上的均匀分布。     

非贵金属催化剂上CO氧化的研究与进展

非贵金属催化剂催化CO氧化反应研究,不仅拓展了非贵金属的应用,而且为探求可替代贵金属催化CO氧化反应的催化剂提供了新机遇,成为当前催化研究中的热点课题之一。本文综述了近年来铜、钴等非贵金属催化剂体系催化CO氧化反应的研究进展。     

非贵金属催化剂上CO氧化的研究与进展

非贵金属催化剂催化CO氧化反应研究,不仅拓展了非贵金属的应用,而且为探求可替代贵金属催化CO氧化反应的催化剂提供了新机遇,成为当前催化研究中的热点课题之一。本文综述了近年来铜、钴等非贵金属催化剂体系催化CO氧化反应的研究进展。     

铁铜双金属催化剂选择性催化氧化氨为氮气(英文)

固定铜铁的总质量不变,采用共浸渍法制备铜铁双金属催化剂.为了更好地了解催化剂的性质,分别用N2吸附-脱附、H2-程序升温还原(H2-TPR)、NH3-程序升温脱附(NH3-TPD)、X射线衍射(XRD)和X射线光电子能谱(XPS)方法对制备的催化剂进行表征.研究发现在100000 h-1空速下,铜铁双金属催化剂呈现出好的活性和氮气选择性.在低温区,随着铜含量的增加,活性和氮气的选择性增加,然而在高温区氮气的选择性直接和铁的含量相关.其中催化剂Fe0.25Cu0.75/ZSM-5,在350°C氨的转化率达到最高,在300°C氮气的选择性上升到97%.Fe0.75Cu0.25/ZSM-5在500°C有很高的氮气选择性甚至可以达到98%.并且所有的催化剂均产生很少的N2O副产物.表征结果显示催化剂的酸量和铜物种的含量可以影响催化剂的活性,并且高的还原能力和铁含量有助于高温氮气选择性的提高.     

酸化膨润土负载金催化剂用于CO氧化

用盐酸和硫酸对膨润土（Ben）进行改性处理,采用浸渍法（IMP）、沉积-沉淀法（DP）和阳离子吸附法(CA)制备改性膨润土负载的金催化剂,以CO氧化作为探针反应对催化剂的催化性能进行了研究,采用BET、XRD、TEM和TPD等对催化剂进行表征。 结果表明,经过简单的酸处理后的膨润土比表面积和孔体积有了大幅度的提高,硫酸酸化的膨润土作为载体较之盐酸酸化土更容易得到活性较高的金催化剂,XRD粒径计算结果和TEM观察结果证明,硫酸酸化的膨润土作为载体相比盐酸酸化土可以得到Au颗粒度更小的催化剂。 不同制备方法中,阳离子吸附法能较好的将Au负载于膨润土载体上,得到小颗粒的金催化剂,且在吸附48 h、450 ℃焙烧、150 ℃下H2还原的预处理条件下得到的催化剂活性最好。     

Oxidation of Carbon Monoxide over Cu/CeO_2 Catalysts Prepared by SMAI

Introduction Carbon monoxide is ubiquitous air pollutants emitted by many sources. Total oxidation of carbon monoxide to carbon dioxide is employed to meet environmental regulations in an economic way. Precious metals (Pt, Pd) are well-known oxidation catalysts with high activity and stability, and are widely used for exhaust gas emission control. However, the high cost of precious metals and their sensitivity to sulfur poisoning have long motivated the search for substitute catalysts. …     

变换催化剂研究进展

烃类化合物的水蒸汽重整与水煤气变换反应(简称变换反应)组合是廉价制取氢气的主要方式.经过80多年的研究和实践,工业化的变换催化剂已基本定型.近年来由于燃料电池技术的飞速发展,有关变换催化剂的研究与开发又重新引起人们的兴趣与关注.本文在总结传统变换催化剂研究进展情况的基础上,重点介绍了以燃料电池应用为目的变换催化剂的研究进展.总结表明,"(贵)金属/载体" 型双功能催化剂已经成为变换催化剂的主要研究方向.(贵)金属和载体种类、制备方法和条件等对催化剂粒径分布、体相织构、表面性质和活性等都有很大影响.虽然与传统变换催化剂相比,"(贵)金属/载体" 型双功能变换催化剂体现了更优良的性能,但与燃料电池商业化应用的要求还有一定的差距.     

Selective Oxidation of Propylene to Acetone over Supported Vanadia Catalysts

A 10%V₂O₅/TiO₂ catalyst showed a pronounced catalytic activity for the selective oxidation of propylene to acetone and the formation of isopropoxy species from the adsorption of propylene was found to be the rate-limiting step.     

氧化铈气凝胶担载氧化铜催化剂上的一氧化碳氧化

 以一氧化碳氧化为探针反应,考察了氧化铈气凝胶担载氧化铜催化剂的催化活性,研究了催化剂中氧化铜的含量、载体及催化剂的焙烧温度对催化剂活性的影响．结果表明,氧化铈气凝胶担载的氧化铜催化剂对一氧化碳氧化反应呈现出高催化活性,适当温度下焙烧载体及催化剂有利于提高催化剂的催化活性;随着催化剂中氧化铜含量的增加,一氧化碳完全转化的温度降低,但当w（CuO）＞12％时,过量的氧化铜以体相形式而不是以高分散形式存在,对催化剂活性的影响很小．     

Partial Oxidation of Butane to Syngas over Nickel Supported Catalysts Modified by Alkali Metal Oxide and Rare-Earth Metal Oxide

There are abundant supplies of mixture gases containing CH4, C2H6, C3H8 and C4H10, etc. from FCC (Fluidized Catalytic Cracking) tail gas, refinery gas, etc. Commonly, the mixture gases are primarily combusted to carbon dioxide because the complete separation of CH4, C2H6, C3H8 and C4H10, respectively, from the mixture gases may not be economical. Provided that syngas (CO+H2) could be produced from the mixture gases over nickel supported catalysts with high selectivity and conversion,…     

在复合金属氧化物催化剂上丙烷直接氧化制丙烯酸

丙烷直接氧化制丙烯酸是近年来催化氧化的热点课题。MoVTe(Sb)NbO复合金属氧化物催化剂是该反应最重要的一类催化剂。本文对该类催化剂的制备化学包括活化方式以及决定催化性能的主要活性相结构等方面的新近认识进行了系统评述;依据丙烷催化转化的反应途径,总结了有关催化剂元素组分在反应中的作用与功能的最新进展,调变催化剂的粒子尺寸与形貌、晶相组成与结构、表面酸碱性与氧化还原性是获得优良催化性能的关键因素。     

Nanostructured Vanadium Oxide Model Catalysts for Selective Oxidation Reactions

Controlled synthesis based on spectroscopic characterization, structure, and catalytic performance of mesoporous silica SBA‐15‐supported vanadium oxide model catalysts (see TEM image) are reviewed. The effect of water on the structure and dispersion of highly dispersed vanadium oxide is discussed in the light of recent results in multiple in situ spectroscopy.

     

Revealing the Active Species for Aerobic Alcohol Oxidation by Using Uniform Supported Palladium Catalysts

The active species in supported metal catalysts are elusive to identify, and large quantities of inert species can cause significant waste. Herein, using a stoichiometrically precise synthetic method, we prepare atomically dispersed palladium–cerium oxide (Pd₁/CeO₂) and hexapalladium cluster–cerium oxide (Pd₆/CeO₂), as confirmed by spherical‐aberration‐corrected transmission electron microscopy and X‐ray absorption fine structure spectroscopy. For aerobic alcohol oxidation, Pd₁/CeO₂ shows extremely high catalytic activity with a TOF of 6739 h^?1 and satisfactory selectivity (almost 100 % for benzaldehyde), while Pd₆/CeO₂ is inactive, indicating that the true active species are single Pd atoms. Theoretical simulations reveal that the bulkier Pd₆ clusters hinder the interactions between hydroxy groups and the CeO₂ surface, thus suppressing synergy of Pd‐Ce perimeter.     

Characteristics of Active Site Formation in Co-Containing Catalysts for CO Oxidation on Chemically Different Supports

We have studied the catalytic activity in CO oxidation for cobalt-containing (1.2 mass % Co) catalysts on different supports: ZSM-5, Al₂O₃, SiO₂, and ERI. Using X-ray photoelectron spectroscopy (XPS), diffuse reflection electronic spectroscopy, and thermal programmed reduction we have established that the differences in the activity of Co-containing catalysts are due to different localization of the cobalt cations, the nature of their distribution in the surface layer of the catalyst, and the presence of cobalt ions Co_Oh in an environment of intralattice oxygen which have high reducibility.     

BiMo基复合氧化物催化剂丙烷直接氧化至丙烯醛研究

The effects of the available zoon above the catalyst bed on the performance of the catalyst were investigated. It has been suggested that propylene is an intermediate species in the reaction of propane to acrolein， and a two-step reaction scheme is proposed， the first step is oxidative dehydrogenation of propane to propylene in the gas phase then followed by the second step， the selective oxidation of propylene to acrolein on the surface of the catalyst. The performance of the catalyst depends on both the oxidative dehydrogenation of propane to propylene in the gas phase and the selective oxidation of propylene to acrolein on the catalyst surface. The thermal cracking， homogeneous oxidative dehydrogenation and heterogeneous catalytic dehydrogenation of propane as well as the selective catalytic oxidation of propane to acrolein over BiMoO based mixed oxides catalysts were studied. Under the optimum reaction conditions of propane dehydrogenation and selective oxidation of propylene， the selectivity and the yield of acrolein approached to 45mol% and 14mol%， respectively under about 30mol% propane conversion.     

贵金属催化剂上氢气选择性催化还原NOx

NO_x的控制对于改善大气环境质量具有重要意义,而氢气选择性催化还原(H₂-SCR)NO_x作为一种高效环保的脱硝技术而备受关注。本文总结概述了近年来贵金属催化剂在H₂-SCR脱硝反应中的研究进展,首先介绍了H₂-SCR反应机理,在此基础上分别论述了影响贵金属催化剂性能的因素(如活性组分、载体类型、助剂添加及组分存在形式等)及催化剂结构与性能的构效关系。最后,针对目前存在的问题展望了H₂-SCR脱硝未来的发展方向。     

Cu/Fe催化剂催化甲醇部分氧化制氢

采用共沉淀法制备的Cu/Fe催化剂催化甲醇部分氧化制氢结果表明，Fe的引入，有利于降低CO选择性，Cu/Fe比对催化性能有明显影响，当Cu/Fe比为2：8时，甲醇转化率最高，与其它的Cu基催化剂相比，在较宽的Cu/Fe比范围内，CO的选择性均保持在较低的水平，利用XRD，XPS等方法，对Cu/Fe催化剂进行表征，结果表明，Fe的引入，有利于活性组分Cu在催化剂表面上的分散，在反应过程中Cu组分向表面富集，因而可使得催化剂表面的Cu物种不因Fe的引入而减少。