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。     

活性炭纤维在催化领域中的应用

介绍了活性炭纤维(ACF)的表面化学结构、催化特性及其在催化中的研究与应用:脱硫反应,除 NO的反应,电极法处理废水;综述了ACF的载体功能:负载金属、金属氧化物、金属氢氧化物、杂多酸等催化 剂。指出需进一步研究氮含量在脱硫过程中所起的作用,以及作为ACF催化氧化活性位的官能团种类。进 一步研究负载物与载体间存在的相互作用,进而获得性能良好的ACF负载型催化剂。     

负载型贵金属低温催化氧化甲醛催化剂的研究

制备贵金属低温催化氧化甲醛催化剂,研究了催化剂结构特征及催化氧化甲醛机理,并考察了催化剂性能。采用沉积-沉淀法制备负载型贵金属低温催化氧化甲醛催化剂,优化组成及制备条件,采用XRD、FT-IR、H_2-TPR、拉曼等对催化剂进行表征分析。催化剂最佳制备条件:NaOH为沉淀剂,载体n(Cu)/n(Mn)摩尔比为1∶2,Pt负载量(质量分数)为1%,载体制备pH为9—10,贵金属负载pH为9.5。Pt_1/Cu_(0.5)Mn催化剂以非化学计量比Cu_(0.9)Mn_(1.8)O_4无定形态晶体特征峰存在,Pt金属在载体表面分布均匀,且贵金属与载体相互作用使催化剂表面氧缺位浓度增加,表面活性氧物种增多,催化剂在室温下表现出良好的稳定性和重复性。室温下甲醛和氧气在催化剂表面共吸附,甲醛首先被催化剂表面活性氧氧化为DOM,由于DOM很活跃,在催化剂上很快被表面氧氧化成甲酸根,甲酸根在催化剂表面氧和气相氧的共同作用下氧化生成CO,最终被完全氧化为CO_2。其中甲酸盐物种向CO转化步骤是整个反应的速控步骤。     

活性炭负载金属催化剂的研究进展

活性炭作为一种优良的催化剂载体被广泛应用于催化领域,其经酸碱预处理或氧化预处理后表面可负载一种或多种金属催化剂,是优化各种金属催化剂性能的有效方法之一。为给今后活性炭载体催化剂的研发提供一些参考和方向,从单一金属催化剂负载和复合金属催化剂负载的制备、催化活性及应用着手,对近年来新制备的活性炭负载金属催化剂进行综述。     

负载钒基催化剂在丙烷氧化脱氢反应中催化性能的研究进展

丙烷氧化脱氢(ODPH)制丙烯是一种利用廉价低碳烷烃制备高附加值烯烃的重要途径。对于该反应体系,负载型钒基催化剂是目前公认的具有良好催化活性的催化剂之一。介绍了钒基催化剂的相关研究及ODPH反应机理,综述了载体的表面酸碱性质、孔道结构和形貌特征以及三种不同类型的金属添加剂对负载型钒基催化剂的催化活性和选择性的影响,为从催化剂设计的角度改进钒基催化剂的催化性能提供了借鉴。     

Pt-Pd/Ce_xZr_(1-x)O/SiO_2-Al_2O_3催化剂上丙烷催化氧化反应研究

以蜂窝状堇青石为载体,采用改性氧化铝浆液涂覆载体,再负载活性组分Pt和Pd,制备了丙烷催化燃烧催化剂,优化了催化剂制备工艺条件。研究表明:Si与CexZr1-xO的添加明显提高了涂层的耐高温性能,CexZr1-xO/SiO2-Al2O3涂层在高温下保持了较高的比表面积;活性组分Pt和Pd在其表面分散均匀;本实验制备的催化剂在430℃和20 000 h-1空速条件下,对含丙烷废气的总烃去除率可以达到90%以上。     

负载型稀土臭氧氧化催化剂在水处理中的应用进展

非均相催化臭氧氧化技术是一种高效的水污染控制技术。负载型稀土臭氧氧化催化剂因稀土元素独特的电子构型,展现出优异的催化性能,不仅具有良好的稳定性和较长的使用寿命,还可有效解决催化剂流失及出水金属离子超标问题,被认为是最有前景的非均相臭氧氧化催化剂。本文着重从负载型稀土臭氧氧化催化剂的制备、催化反应机理以及单稀土、稀土-过渡金属、双稀土-过渡金属氧化物负载型臭氧氧化催化剂在近几年的污水处理领域中的应用进展进行概述与总结。多稀土复合型非均相臭氧氧化催化剂的开发,以及对催化氧化过程的作用机理的深入研究,是未来非均相催化臭氧氧化技术在水处理中的重点研究方向。     

挥发性有机化合物催化消除前沿技术及研究进展

挥发性有机化合物（VOCs）是可吸入有害物质形成的重要前体,是大气污染物的重要组成部分。催化氧化法作为末端技术是目前处理VOCs最有效的途径之一。本文讨论了VOCs的热催化氧化、光催化氧化和光热协同催化氧化的研究进展,重点研究常用VOCs的催化氧化机理以及相关催化剂的构筑。其中,热催化燃烧主要以贵金属（Pt、Pd、Au、Ag等）、过渡金属（Mn、Co、Cr等氧化物）及复合型催化剂研究展开;光催化氧化以TiO₂和C₃N₄为典型催化剂进行讨论;光热协同催化研究主要包括碳基催化剂、贵金属负载型以及过渡金属负载型催化剂的开发与应用。此外,本文对基于催化剂的热催化、光催化和光热催化去除VOCs的开发和研究提出了进一步的展望。     

催化氧化法去除甲醛最新研究进展

介绍了贵金属催化剂与过渡金属催化剂催化氧化去除甲醛的最新进展。详细讨论提高催化氧化法去除甲醛的方法,包括:常见载体负载贵金属、传统金属氧化物负载贵金属、特殊形貌负载贵金属以及过渡金属氧化物改性,并对催化氧化法去除甲醛提出展望。     

二氧化碳和甲醇直接合成碳酸二甲酯非均相体系的研究进展

本文综述了以甲醇和二氧化碳为原料直接合成碳酸二甲酯非均相催亿体系的研究.非均相催化体系的催化剂分为有机金属负载型催化剂、Cu-Ni合金负载型催化剂、半导体负载型催化剂、负载型铑催化剂、金属氧化物催化剂、杂多酸催化剂.文中对各催化反应历程进行了分析.在该反应体系中,同时具有酸碱活性位的催化剂可有效活化二氧化碳和甲醇,使二...     

Catalytic wall reactor: Catalytic coatings of stainless steel by VOx/TiO2 and Co/SiO2 catalysts

Catalytic wall (structured) reactors and structured supports are suitable to study the catalytic properties of nanosized materials. The coating of metallic (aluminum and stainless steel) plates by thin layers of active phase is presented in two cases, VO_x/TiO₂ and Co/SiO₂, catalysts used in the oxidative dehydrogenation (ODH) of propane and in Fischer–Tropsch synthesis (FTS) of clean fuels, respectively. The preparation of coated plates and their characterisation by various methods of physicochemical analysis are described. Both chemical and physical methods were used for coating. VO_x/TiO₂ layers were obtained by grafting of Ti (on Al or stainless-steel plates) and V (on TiO₂) alkoxides and use of sol–gel media or suspension. A silica primer was deposited (on stainless-steel plate) by plasma-assisted chemical vapour deposition (PACVD) onto which Co oxide and silica were coprecipitated from sol–gel. The catalytic experiments in the respective reactions were carried out in special plate reactors and compared with those of catalytic powders. The study shows that the coating of a metallic substrate by a catalyst is not straightforward and requires specific studies dealing with both chemistry (chemical affinity between substrate and catalytic layers) and catalytic engineering (catalytic performance in taylor-made reactors).     

助剂Ba对Pd/Al_2O_3和Pt/Al_2O_3催化剂的C1-C3烷烃催化燃烧性能的影响

通过浸渍法制备了Al_2O_3负载的Pd和Pt催化剂,考察催化剂的甲烷、乙烷和丙烷催化燃烧活性,以及助剂Ba对催化性能的影响。对于Pd/Al_2O_3催化剂,加入Ba使活性物种PdO颗粒变大和还原温度升高,形成更稳定的PdO活性物种,是Pd-Ba/Al_2O_3催化剂活性提升的主要原因。对于Pt/Al_2O_3催化剂,加入Ba助剂使活性物种Pt0含量降低,PtO_x与Al_2O_3载体相互作用增强,使PtO_x物种更难被还原为Pt~0,导致Pt-Ba/Al_2O_3催化剂活性降低。Pd和Pt催化剂催化烷烃氧化反应活性规律一致:丙烷乙烷甲烷。Pd/Al_2O_3催化剂有利于C—H键活化,Pt/Al_2O_3催化剂有利于C—C键活化。Pt/Al_2O_3催化剂对C1-C3烷烃氧化活性的差别明显大于Pd/Al_2O_3催化剂。Pt/Al_2O_3催化剂对碳比例高的烷烃活性更高。     

The effects of SO2 on the oxidation of CO and propane on supported Pt and Au catalysts

The catalytic activities of Pt and Au supported on TiO₂ were compared with respect to the oxidation of CO and propane. While the Au catalysts showed higher activities for CO oxidation, the Pt catalysts were more active for propane combustion. A strong de-activation of the CO oxidation activity by SO₂ was observed only over the TiO₂-supported Au catalyst, indicating that SO₂ can block the active sites for CO oxidation over Au catalysts. The results are consistent with a model in which the perimeter sites have a special role in the CO oxidation reaction over Au catalysts.     

用于丙烷催化燃烧的PdxPty-ZSM-5/Cordierite整体式催化剂

以ZSM-5分子筛、铝溶胶、硝酸钯、硝酸铂和水为原料制备分子筛浆料，采用真空抽提-一次涂覆法在堇青石蜂窝陶瓷载体表面制备出Pd_xPt_y-ZSM-5/Cordierite整体式催化剂，考察了Pd负载量、ZSM-5分子筛的硅铝比和Pd/Pt质量比对整体式催化剂的丙烷催化燃烧性能的影响，并用超声波振荡、SEM、XRD、H₂-TPR和C₃H₈-TPD等手段对整体式催化剂进行了表征。当球磨时间为60 min，分子筛浆料固含量为38%时，整体式催化剂的涂层上载量可达到178 g?L^-1，涂层脱落率低于0.5%。Pd₂Pt₃-ZSM-5/Cordierite整体式催化剂（贵金属总负载量为1.2 g?L^-1）对于丙烷的催化燃烧具有较好的催化活性（T₅₀=259℃，T₉₀=323℃）和稳定性，具有良好的工业应用前景，其中较低的ZSM-5分子筛硅铝比以及Pd和Pt之间的相互作用增加了对丙烷的吸附能力和表面活性氧物种的数量，从而提高了整体式催化剂的催化活性。     

Selective catalytic reduction of NOx with NH3 over a V2O5/TiO2 on silica catalyst

The catalytic properties of various supported and unsupported vanadium oxide based catalysts for the Selective Catalytic Reduction of NO_x with NH₃ (SCR) are investigated. It is concluded, that in order to achieve good selectivity in the SCR, the number of active sites favouring SCR has to be increased at the cost of sites favouring ammonia oxidation. This can be achieved by the application of the active vanadium oxide onto a suitable support. A specific catalyst preparation procedure is described which enables the application of vanadium oxide onto TiO₂-adlayered silica. The thus prepared catalyst is shown to exhibit the desired properties, that is, a high selectivity and good activity in the Selective Catalytic Reduction of NO_x with NH₃.     

Methane partial oxidation over NiO-MgO/Ce0.75Zr0.25O2 catalysts

Methane partial oxidation (MPO) is considered as an alternative method to produce hydrogen because it is an exothermic reaction to afford a suitable H₂/CO ratio of 2. However, carbon deposition on a catalyst is observed as a major cause of catalyst deactivation in MPO. In order to find suitable catalysts that prevent the carbon deposition, NiO-MgO/Ce_0.75Zr_0.25O₂ (CZO) supported catalysts were prepared via the co-impregnation (C) and sequential incipient wetness impregnation (S) methods. The amount of Ni loading was fixed at 15 wt-% whereas the amount of MgO loading was varied from 5 to 15 wt-%. The results revealed that the addition of MgO shifted the light-off temperatures to higher temperatures. This is because the Ni surface was partially covered with MgO, and the strong interaction between NiO and NiMgO₂ over CZO support led to the difficulty in reducing NiO to active Ni⁰ and thus less catalytic activity. However, among the catalysts tested, the 15Ni5Mg/CZO (S) catalyst exhibited the best catalytic stability for MPO after 18 h on stream at 750°C. Moreover, this catalyst had a better resistance to carbon deposition due to its high metallic Ni dispersion at high temperature.     

Design of catalysts for deNOx process using synergistic phenomenon

Investigation of the mechanism of the selective reduction of NO_x by propane over the individual samples of commercial catalysts NTK, STK, and Ni–Cr-oxide catalyst and over their binary mechanical mixtures has shown that the synergistic effect observed in the latter case is caused by the oxidative activation of propane on the STK and Ni–Cr-oxide surface which results in the formation of more effective reducing agents, propylene and hydrogen correspondingly. In the case of the Ni–Cr-oxide and NTK catalytic system, hydrogen forms over the former catalyst in propane oxidation, migrates through the gas phase to the latter catalyst, where NO_x is activated with the formation of nitrate structures which interact with the said hydrogen giving the products of the overall reaction, N₂ and H₂O. When the pair of NTK and STK is concerned, the interaction of C₃H₈ and O₂ over the latter catalyst gives stable products of partial propane oxidation and/or oxidative dehydrogenation which are transported due to interphase diffusion to NTK surface. The nature of observed synergistic enhancement of catalysis in the case of binary mixtures is proposed under the terms of “remote control” mechanism described in literature and can serve a useful purpose in the design of catalysts for this reaction.     

A comparative study of Ag/Al2O3 and Cu/Al2O3 catalysts for the selective catalytic reduction of NO by C3H6

The selective catalytic reduction (SCR) of NO by C₃H₆ in excess oxygen was evaluated and compared over Ag/Al₂O₃ and Cu/Al₂O₃ catalysts. Ag/Al₂O₃ showed a high activity for NO reduction. However, Cu/Al₂O₃ showed a high activity for C₃H₆ oxidation. The partial oxidation of C₃H₆ gave surface enolic species and acetate species on the Ag/Al₂O₃, but only an acetate species was clearly observed on the Cu/Al₂O₃. The enolic species is a more active intermediate towards NO + O₂ to yield—NCO species than the acetate species on the Ag/Al₂O₃ catalyst. The Ag and Cu metal loadings and phase changes on Al₂O₃ support can affect the activity and selectivity of Ag/Al₂O₃ and Cu/Al₂O₃ catalysts, but the formation of enolic species is the main reason why the activity of the Ag/Al₂O₃ catalyst for NO reduction is higher than that of the Cu/Al₂O₃ catalyst.     

Ce改性Pd基整体式催化剂的结构特征及其甲烷催化燃烧性能

分别以拟薄水铝石和添加Ce的拟薄水铝石制备铝溶胶,经过堇青石（Cord）表面涂覆和Pd溶液浸渍,得到浸渍法和溶胶法Ce改性的Pd/γ-Al₂O₃/Cord整体式催化剂。采用XRD、SEM和XPS等对催化剂进行表征,评价其甲烷催化燃烧反应性能,并考察Ce的不同添加方式对催化剂结构和反应性能的影响。结果表明,适量Ce的添加可提高Pd基整体式催化剂的甲烷催化燃烧性能,溶胶法优于浸渍法。随着Ce添加量的增加,浸渍法改性的Pd基催化剂催化性能有所降低,溶胶法则呈现先升高后降低的趋势。溶胶法中Ce的添加物与γ-Al₂O₃涂层充分融合,提高了涂层的热稳定性和活性组分的分散度,0.5Pd/γ-Al₂O₃(3.0Ce)/Cord催化剂催化性能最优。     

动物骨源羟磷灰石负载Co3O4用于N2O催化分解

通过焙烧猪骨和鸡骨获得羟磷灰石(nHAP)载体,并采用浸渍法制备Co3O4/nHAP催化剂。采用XRD、N2物理吸附-脱附、FT-IR和H2-TPR等对催化剂进行表征,在连续流动微反装置上考察催化剂催化分解N2O的性能。结果表明,相比于鸡骨源Co3O4/nHAP催化剂,以猪骨源HAP为载体的催化剂因其较大的比表面积以及较小的Co3O4粒径尺寸,提供了更多的活性位点。特别是猪骨源Co3O4/nHAP催化剂中适量的K、Na等元素促进了Co^3+到Co^2+的还原,削弱了Co-O键,使催化剂的催化活性显著提高。