原位红外光谱研究镧对负载钯催化剂上甲醇车尾气氧化机理的影响

在色谱微反装置上考察了负载Pd催化剂的甲醇深度氧化性能.结果表明,在γ氧化铝载体中,添加镧对负载Pd催化剂催化活性和选择性影响较大,甲醇氧化含氧中间物含量大大降低.利用insituFTIR技术测定了镧改性后的负载Pd催化剂表面的吸附物种和表面的程序升温反应,对负载Pd催化剂甲醇深度氧化反应机理进行了探讨.     

低碳烷烃选择氧化金属氧化物催化剂的结构与其催化性能的关系

基于金属氧化物催化剂的低碳烷烃选择氧化是催化研究的一个热点和难点, 而认识催化剂的结构与其催化性能之间的关系对于获得高效催化剂, 解决低碳烷烃选择氧化反应中存在的问题至关重要. 本文围绕催化剂的结构对其催化性能的影响, 概述了V-P-O、V-Sb-O、Mo-V-Te-Nb-O和V-Mg-O等几类典型的氧化物催化剂体系在这方面的研究进展. 结合我们开发的Re-Sb-O催化剂体系, 分析了多功能中心、活性位分离、两相协同效应等方面对金属氧化物催化剂的催化性能的影响. 这些认识将有助于设计合成性能优异的催化剂及实现低碳烷烃的选择氧化活化和定向转化.     

不同载体负载的Cu2(OH)3CI催化剂对甲醇氧化羰基化的催化性能

采用浆液浸渍法制备了小同载体负载的Cu2(OH)3Cl催化剂,考察了催化剂对甲醇氧化羰基化合成碳酸二甲酯(DMC)反应的催化性能.结果表明,各载体负载的Cu2(OH)3Cl催化剂活性均高于传统的负载CuCl2催化剂;以比表面积较大的活性炭(AC)为载体的催化剂活性最高.以Cu2(OH)3Cl/AC(w(Cu)=18.71%)为催化剂时,甲醇转化率、DMC选择性和DMC时宅收率可分别达到6.93%,67.3%和139.1mg/(g·h);其催化性能比较稳定,反应60h后其催化活性略有下降.通过CO程序升温脱附、X射线衍射、X射线光电子能谱和扫描电镜等技术对催化剂进行了表征.结果表明,在反应过程中催化剂的活性物种Cu2(OH)3Cl的晶粒逐渐团聚、长大,并且转化为CuCl2和CuO;同时,新鲜催化剂中唯一的CuⅡ物种部分转化为CuⅠ物种.     

直接甲醇燃料电池阳极催化剂研究进展

 甲醇氧化电催化剂是决定直接甲醇燃料电池性能、寿命和成本的关键材料之一. 近年来人们从提高阳极催化剂活性和降低催化剂成本两个方面出发进行了大量的研究, 有力推动了直接甲醇燃料电池的发展. 在简要介绍电催化剂上甲醇氧化反应机理的基础上, 综述了近年来直接甲醇燃料电池阳极催化剂的研究进展, 从铂基催化剂、非铂基催化剂和催化剂载体三个方面进行了详细的介绍 (附有 58 篇参考文献), 并展望了甲醇电催化剂的发展趋势     

TiO2负载Pt对光催化去除低浓度NO性能的影响

以溶胶-凝胶法以及湿式浸渍法制备了Pt/TiO2催化剂,采用了XRD、BET、UV-vis、TEM、XPS等方法进行表征,并进行了对NO的催化氧化性能测试.结果表明铂的负载能显著提高TiO2光催化剂对NO的氧化转化能力和去除率.0.5%Pt/TiO2对NO的氧化率与去除率分别为45.0%和38.1%,与纯锐钛矿TiO2(13.6%,10.7%)相比,氧化效率提高3.3倍,去除效率提高3.6倍.通过比较不同方法制备的负载Pt催化剂的活性,初步讨论了催化剂表面发生的反应机理:铂氧化物以及催化剂表面吸附的O2分子通过与光生电子和光生空穴结合,产生了强氧化性自由基,将NO氧化得到NO2.     

催化甘油脱水氧化连串反应制丙烯酸

本文综述了近年来单反应器中甘油脱水氧化连串反应制备丙烯酸的研究进展。文中简介了甘油来源及丙烯酸的需求背景;概括了当前对单反应器中的催化体系、反应温度、接触时间、氧气分压及甘油浓度等的研究状况;重点讨论了单、双床层气固相体系中复合氧化物型催化剂和分子筛负载型催化剂的催化性能及其影响因素,涉及的催化剂有V-P、Fe-P、W-V、Mo-V、CsPW-Nb、VMo-SiC等复合氧化物和V_2O_5/BEA、V_2O_5/MFI分子筛负载型催化剂等;总结了当前研究对气固相催化反应机理和可能发生的副反应的认识;评述了催化剂的失活现象与再生问题;此外,还讨论了液固相体系中Cu/SiO_2-MnO_2和POM/Al_2O_3催化剂的催化特点及反应机理。最后分析了单反应器中甘油脱水氧化连续反应制丙烯酸反应过程尚存的难题,从反应体系的选取、催化剂性能的改进以及催化剂积炭消除等方面展望了可能的解决途径和方向。     

非贵金属Co-N-C/MgO高效催化糠醛氧化酯化制糠酸甲酯（英文）

设计开发绿色、可持续的生物质资源高效转化制化学品催化过程具有重要的科学与应用研究价值.生物质基平台分子糠醛在分子氧存在下与甲醇发生氧化酯化,提供了一条糠酸甲酯的"非石油基"合成新路线.该反应采用贵金属/非贵金属催化体系,目前通常需要引入K_2CO_3或CH_3ONa等碱性添加剂,以提高催化氧化酯化反应活性和选择性;但是存在活性组分流失、生成副产物及污染环境等问题,阻碍了其进一步应用.探索高性能非贵金属催化剂,实现无碱条件下糠醛高效氧化酯化,对于提高该生物质路线竞争力与推动工业化进程具有重要意义.本文利用浸渍法将1,10-邻菲罗啉合钴(Ⅱ)负载到碱性载体氧化镁上,在氮气气氛下800 ℃热解,制备了非贵金属Co-N-C/MgO催化剂.在糠醛氧化酯化制糠酸甲酯反应中,Co-N-C/MgO催化剂表现出优异的性能,在0.5 MPa O_2,100 ℃条件下反应12 h,糠醛转化率达到93.0%,糠酸甲酯选择性达到98.5%,远超过相同方法制备的其他载体(活性炭、NaX、NaY和CaO)负载的钴基催化剂,实现了无碱性添加剂条件下糠醛高效氧化酯化制糠酸甲酯.X射线光电子能谱、X射线衍射、透射电镜、元素分析以及对比实验结果表明,Co-N-C/MgO催化剂上可能存在含钴的氮掺杂碳物种;该催化剂在糠醛氧化酯化中的高性能与其脱氢能力密切相关.并且在0.3–1.0 MPa氧气压力范围内,Co-N-C/MgO催化糠醛氧化酯化过程基本不受压力变化影响.糠醛与甲醇的氧化酯化反应和缩合反应为两个竞争路径,反应路径决定了反应的主要产物.我们使用盐酸处理Co-N-C/MgO催化剂,脱除MgO载体,制备了Co-N-C(HCl)催化剂.当使用该催化剂时,糠醛与甲醇主要发生缩合反应,得到缩醛产物2-(二甲氧基甲基)呋喃.如果在Co-N-C(HCl)催化反应体系中引入MgO添加剂,则主要发生糠醛氧化酯化反应,主产物为糠酸甲酯.为了验证-Cl是否对反应产生影响,使用NaCl溶液对Co-N-C/MgO进行浸渍、清洗处理,或直接使用NaCl为添加剂-;在这两种情况下,糠醛转化率与糠酸甲酯选择性均下降,表明Cl对糠醛氧化酯化反应具有负面作用.根据实验结果,阴离子-(Cl)可能与℃(Ⅱ)中心发生配位,从而影响了金属活性中心的催化性能.Co-N-C(HCl)加入氧化镁,使得糠醛主要遵循氧化酯化路径进行转化,降低-Cl对Co-N-C(HCl)催化活性中心的影响.以上研究可为生物质基醛类化合物氧化酯化转化过程以及高性能非贵金属催化剂的设计开发提供有益参考.     

异丁烷脱氢催化剂的研究

本文对异丁烷脱氢反应制异丁烯过程催化剂体系及其反应机理进行了述评,指出异丁烷脱氢依然是最有潜力的转化途径,但非贵金属高效催化剂的研制是其关键.详细总 结了不同载体和助剂对脱氢反应的影响,尤其是载体和助剂的酸碱性以及载体的孔结构.弱 酸中心有利于异丁烷脱氢反应的发生,较小的孔结构能提高反应的选择性.催化剂的抗积炭 性能研究表明: 载体表面的弱酸位和活性组分在表面的高分散度以及碱性助剂的加入,有 利于提高催化剂的抗积炭性能.对异丁烷的脱氢反应机理的研究进行了阐述.     

氧化铜修饰羟基磷灰石负载金对醇类需氧氧化的双金属协同催化

采用均匀沉积-沉淀法制备了氧化铜修饰羟基磷灰石负载金催化剂(Au/CuO-HAP),并用原子吸收光谱、N2吸附脱附、X射线粉末衍射、透射电镜和X射线光电子能谱等方法对催化剂结构和形貌进行了表征.考察了催化剂对醇类液相需氧氧化的催化性能.与单金属Au/HAP或CuO-HAP相比较,双金属Au/CuO-HAP对苯甲醇氧化的催化活性和苯甲醛的选择性有显著提高,120 oC反应1.5 h,苯甲醇的转化率和苯甲醛的选择性分别达到99.7%和98.4%.在Au/CuO-HAP的催化下,其它类型的芳香醇均可高选择性转化为相应的醛或酮. Au/CuO-HAP催化剂有很好的稳定性和可回收性,4次回收后,其催化活性没有明显变化.     

氧化铜修饰羟基磷灰石负载金对醇类需氧氧化的双金属协同催化（英文）

采用均匀沉积-沉淀法制备了氧化铜修饰羟基磷灰石负载金催化剂(Au/CuO-HAP),并用原子吸收光谱、N2吸附脱附、X射线粉末衍射、透射电镜和X射线光电子能谱等方法对催化剂结构和形貌进行了表征.考察了催化剂对醇类液相需氧氧化的催化性能.与单金属Au/HAP或CuO-HAP相比较,双金属Au/CuO-HAP对苯甲醇氧化的催化活性和苯甲醛的选择性有显著提高,120℃反应1.5h,苯甲醇的转化率和苯甲醛的选择性分别达到99.7%和98.4%.在Au/CuO-HAP的催化下,其它类型的芳香醇均可高选择性转化为相应的醛或酮.Au/CuO-HAP催化剂有很好的稳定性和可回收性,4次回收后,其催化活性没有明显变化.     

Molecular complexes in water oxidation: Pre-catalysts or real catalysts

Artificial photosynthesis is considered a promising method to produce clean and renewable energy by sunlight. To accomplish this aim, development of efficient and robust catalysts for water oxidation and hydrogen production is extremely important. Owing to the advantages of easily modified structures and traceable catalytic processes, molecular water oxidation catalysts (WOCs) attract much attention during the past decade. However, the transformation of molecular WOCs to metal oxides/hydroxides or metal ions may occur under the harsh catalytic conditions, making the identification of true active species difficult. In this article, recent progress on molecular complexes acting as real catalysts or precursors toward water oxidation was briefly reviewed. We summarized the commonly used physical techniques and chemical methods that enable to distinguish homogeneous catalysts from heterogeneous catalysts. The factors that affect the nature of WOCs, such as reaction conditions, transition metal centers, and supporting ligands were discussed as well.     

Effects of Cerium Oxides on the Catalytic Performance of Pd/CNT for Methanol Oxidation

The carbon nanotubes supported palladium(Pd/CNT)nanocatalysts were modified by cerium oxides/ hydroxides and their catalytic performances for methanol oxidation were evaluated.Electrochemical measurements indicate that the introduction of cerium remarkably improves the catalytic activity of Pd/CNT catalysts towards methanol oxidation.X-Ray photoelectron spectra results reveal an interaction between palladium and cerium oxides.It is also observed that cerium-modified catalysts have excellent poison resistances,which is attributed to the poison-removal ability of cerium oxides/hydroxides.The highly oxidized cerium oxides/hydroxides have a strong ability to inhibit the accumulation of carbonaceous intermediates on the active sites of Pd catalysts.     

ZrO_2晶相对MoO_x/ZrO_2催化剂结构及其甲醇选择氧化性能的影响

以纯的单斜氧化锆(m-ZrO2)和四方氧化锆(t-ZrO2)为载体,采用浸渍法分别合成了具有不同MoOx表面密度的MoOx/m-ZrO2和MoOx/t-ZrO2催化剂,并结合粉末X射线衍射,Raman光谱和H2程序升温还原等技术表征了不同ZrO2晶相对MoOx分散状态、结构以及甲醇氧化反应性能的影响.在低于锆表面MoOx的单层分散阈值(～5nm-2)时,m-ZrO2比t-ZrO2能够更有效地分散MoOx,形成高分散的孤立或二维结构的MoOx物种,避免了晶相MoO3的出现.当Mo表面密度超过单层分散阈值后,经过600℃焙烧,MoOx与ZrO2载体发生固相反应生成晶相ZrMo2O8,m-ZrO2比t-ZrO2更有利于ZrMo2O8的生成.提高Mo表面密度,催化剂表面的酸性随之增强,说明晶相ZrMo2O8比分散的MoOx物种具有更强的酸性.t-ZrO2与MoOx作用形成的强酸中心更有利于催化甲醇脱水生成二甲醚,但m-ZrO2使得MoOx具有更高的氧化还原能力和催化甲醇选择氧化反应的活性.ZrO2晶相对MoOx/ZrO2催化剂影响的研究结果将有助于研究VOx等其它金属氧化物催化剂以及发展酸性和氧化还原性双功能催化剂体系.     

Nanoscale Perovskites as Catalysts and Supports for Direct Methanol Fuel Cells

With the ultimate goal of simultaneously finding cost-effective, more earth-abundant, and high-performance alternatives to commercial Pt/Pd-based catalysts for electrocatalysis, this review article highlights advances in the use of perovskite metal oxides as both catalysts and catalyst supports towards the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) within a direct methanol fuel cell (DMFC) configuration. Specifically, perovskite metal oxides are promising as versatile functional replacements for conventional platinum-group metals, in part because of their excellent ionic conductivity, overall resistance to corrosion, good proton-transport properties, and potential for interesting acidic surface chemistry, all of which contribute to their high activity and reasonable stability, especially within an alkaline electrolytic environment.     

A general synthetic strategy for oxide-supported metal nanoparticle catalysts

Despite recent exciting progress in catalysis by supported gold nanoparticles, there remains the formidable challenge of preparing supported gold catalysts that collectively incorporate precise control over factors such as size and size-distribution of the gold nanoparticles, homogeneous dispersion of the particles on the support, and the ability to utilize a wide range of supports that profoundly affect catalytic performance. Here, we describe a synthetic methodology that achieves these goals. In this strategy, weak interface interactions evenly deposit presynthesized organic-capped metal nanoparticles on oxide supports. The homogeneous dispersion of nanoparticles on oxides is then locked in place, without aggregation, through careful calcination. The approach takes advantage of recent advances in the synthesis of metal and oxide nanomaterials and helps to bring together these two classes of materials for catalysis applications. An important feature is that the strategy allows metal nanoparticles to be well dispersed on a variety of oxides with few restrictions on their physical and chemical properties. Following this synthetic procedure, we have successfully developed efficient gold catalysts for green chemistry processes, such as the production of ethyl acetate from the selective oxidation of ethanol by oxygen at 100 degrees C.     

甘油的催化选择氧化

综述了近年来生物柴油主要副产物甘油的催化选择氧化的研究进展。分析了甘油的化学催化选择氧化的反应网络;介绍了催化甘油选择氧化反应主要的催化剂如负载型金属催化剂、多孔催化剂以及有机酰基-TEMPO催化剂的催化性能及其催化机理;评述了甘油催化氧化过程中各反应条件等对产物选择性和反应物转化率的影响;概括了甘油的电催化氧化、甘油催化氧化聚合生成新型聚合物-聚丙酮二酸盐（Polyketomalonate）等新催化反应及其机理,总结了甘油生物催化氧化的产物二羟基丙酮（DHA）的新进展。最后提出了甘油的催化氧化存在的一些问题,并展望了甘油催化氧化的研究和发展方向。     

多酸在电催化析氢反应中的应用研究进展

电催化水裂解是一种可持续用于生产可再生氢能源的技术。然而,开发高效稳定、低成本的析氢电催化剂仍是一项具有挑战性的任务。多金属氧酸盐(多酸)是一种离散的金属氧簇合物,通常由氧配体和高价的钒(V)、钼(VI)、钨(VI)金属构成。由于多酸含有丰富的氧化还原活性金属中心,因此,近几年来,多酸在水裂解应用研究方面备受关注。本综述将聚焦于多酸在电催化水裂解析氢的应用研究进展。本文还突出强调了电催化析氢目前面临的主要问题,以及对多酸基催化剂及作为催化剂前体在电催化析氢方面的应用及发展前景做了展望。     

Selective Oxidation of Methane into Methanol Under Mild Conditions

Selective oxidation of methane to methanol under mild conditions has been considered as a dream reaction but suffers from poor efficiency due to the strong C-H bond of methane and easy overoxidation of the methanol product. For overcoming these problems, a series of strategies has been developed for improving methanol productivity with oxidants of hydrogen peroxide and even a mixture of oxygen and hydrogen at mild temperatures. Significant achievements in these strategies using effective catalysts, such as supported metal nanoparticles, colloidal metal nanoparticles, and metal@zeolites are briefly concluded. Moreover, the current challenges, future perspectives for preparing active, selective, and stable catalysts, have been discussed. The zeolite fixed metal nanoparticle structure has been found to boost the reaction by benefiting the formation and enrichment of peroxide intermediates, which might guide the development of more efficient catalysts.     

The application of FTIR in situ spectroscopy combined with methanol adsorption to the study of mesoporous sieve SBA-15 with cerium-zirconium oxides modified with gold and copper species

The molecular sieves SBA-15 with ceria, zirconia and mixed cerium-zirconium oxides were synthesized and used as supports for gold and copper species. The materials were characterised using a FTIR in situ spectroscopy combined with the adsorption of methanol and oxygen as probe molecules, which allowed the monitoring of the changes on the surface, in particular the creation of the intermediates species on the active sites of materials. The presence of interactions between gold and copper in bimetallic catalysts was considered during the reaction of methanol oxidation. The goal of this work was studied the changes of intermediates adsorbed on the surface of catalysts during the oxidation of methanol after treatment at selected temperature. The monometallic gold and the bimetallic copper–gold catalysts were tested in the reaction of methanol oxidation in the gas phase in situ.     

MCM-41 Supported Rhenium Oxides:Characterization and Selective Methanol Oxidation

Re oxides have not widely been used as catalysts for selective oxidations owing to sublimation under pretreatment and reaction conditions^[1].Nevertheless, the property of Re species capable of adopting a variety of oxidation states that are illustrated in both binary and ternary oxides^[2,3],may provide rich and interesting chemistry. One of us reported a crystalline binary oxide compound SbRe₂O₆ for the selective methylal formation in the methanol oxidation^[4]. The selectivity reached 92.5% at a conversion of 6.5% at 573 K. The performance of SbRe₂O₆ was attributed to the Re-oxide octahedra connecting with Sb-O chains^[5]. However, the crystalline oxide SbRe₂O₆ has a very low surface area (1 m² g^-1),resulting in insufficient activity for the methylal production. Recently, we found the new catalytic property of supported Re oxides for the selective oxidation of methanol to methylal^[6]. Here, we report the characterization and catalytic property of MCM-41 supported Re oxides for the selective methanol oxidation.