以TiO2/γ-Al2O3/堇青石为载体的金属氧化物催化剂的应用研究

以Ti O2/γ-Al2O3/堇青石为复合载体,制备了以K,V,Cs,Sn,Pt等为活性组分的催化剂,催化剂于空气中在马弗炉700℃老化3 h。采用差示扫描量热(DSC)/热重(TG)测试方法确定催化剂的活性。实验结果表明,添加Pt能降低颗粒物(PM)起燃温度,特别是对PM中石墨化固体组分(GSF)的消除有利。K和Cs对降低起燃温度及对PM中可溶性有机组分(SOF)的最大燃烧温度起作用,K对PM中GSF部分的去除比Cs要好。老化中催化活性降低是比表面积下降和活性组分挥发流失的共同结果。     

Ni/SiO2催化剂的制备条件对催化间二硝基苯加氢反应性能的影响

将Ni/SiO₂催化剂应用于间二硝基苯加氢反应中,考察了该催化剂制备过程中焙烧温度和还原温度对其催化性能的影响,并通过BET、XRD、TEM、TPR等方法对催化剂进行了表征.结果表明,在实验研究范围内,随着焙烧温度的提高,Ni/SiO₂催化剂比表面积降低,NiO与载体SiO₂之间的相互作用逐渐增强,催化剂的还原温度明显提高,活性组分Ni的晶粒度增大,焙烧温度为773 K时催化剂具有最佳的催化反应性能,此时活性组分Ni以高分散状态存在.催化剂的还原温度对Ni/SiO₂催化剂的结构和催化性能影响显著,当还原温度较低时,活性组分还原不完全,催化剂活性较低;而还原温度太高会使活性组分烧结,导致催化剂活性明显降低;还原温度为723 K时催化剂表现出最佳的活性和选择性.     

Nd2O3基复合氧化物上炭黑和NOx的同时催化去除特性

利用程序升温反应（TPR）技术，对同时催化去除柴油机炭黑和氮氧化物反应进行了研究.结果表明：稀土金属氧化物及其负载金属氧化物能在富氧条件下使炭黑（C）和氮氧化物（NO_x）互为氧化还原，主要生成CO₂和N₂，达到C-NO_x两者的同时催化去除.在Nd₂O₃等稀土氧化物上负载K和Mn等金属氧化物能降低炭黑的起燃温度，提高NO的还原转化率，其中K/Mn/Nd₂O₃ 上的催化反应同无催化反应相比，其炭黑起燃温度降低了170℃，最大NO→N₂转化率达到75.4％.K能显著降低起燃温度，并存在最佳负载量（2 mmol•g^-1）.K负载量过多，可能导致稀土金属氧化物上原有活性位的覆没.     

负载型湿式氧化催化剂RuO2/γ-Al2O3活性与稳定性

采用浸渍法制备了RuO₂/γ-Al₂O₃催化剂，以苯酚为目标有机物重点研究了进水pH值和温度对RuO₂/γ-Al₂O₃催化剂组分溶出和活性的影响.结果表明，催化剂在降解苯酚过程中存在着组分溶出现象，随着进水溶液pH值降低催化剂组分溶出量增加，且在进水为酸性时苯酚去除率高于碱性时的去除率.反应温度升高，催化剂组分溶出量降低，苯酚去除率增加.采用在负载型RuO₂/γ-Al₂O₃催化剂中掺杂Ce和Zr的方法对抑制催化剂组分溶出进行了初步研究，发现掺杂Ce和Zr后有效地降低了RuO₂/γ-Al₂O₃催化剂组分的溶出，且提高了催化剂的活性.     

制备条件对Cu/Al2O3 选择性催化还原NO的影响研究

考察了制备方法、活性组分负载量和焙烧温度对Cu/Al₂O₃ 选择性催化还原NO的影响。结果表明，采用溶胶-凝胶+浸渍法制备的Cu/Al₂O₃催化剂活性最好；负载Cu质量分数为15%时，催化剂的活性温域最宽，最大活性温度最低，催化活性最好；最佳焙烧温度为750 ℃。     

Ni、Pt对柴油车排气颗粒物去除催化剂的修饰作用

以改性整体式堇青石蜂窝陶瓷为载体,用Ni和Pt修饰Cu-K-V/TiO₂/γ-Al₂O₃ /cordierite催化剂,制备了用于消除柴油车排气颗粒物的催化剂;采用DSC/TG方法确定催化剂的活性及BET、TG-IR等方法对催化剂进行了表征,探讨了Ni和Pt对Cu-K-V/TiO₂/γ-Al₂O₃ /cordierite催化剂的修饰作用及老化对催化剂的影响.研究发现经Ni和Pt修饰后的催化剂能有效降低柴油车排气颗粒物的最大燃烧速率时的温度,特别是对颗粒物中最难燃烧的石墨化部分的去除;而且Ni和Pt的添加能提高颗粒物的去除效率.对含Pt催化剂,老化会降低催化剂的活性;而对含Ni的催化剂,老化使催化剂的活性增加,这可能是Ni向催化剂非孔道的外表面迁移的结果.     

负载型La-K-Cu-Mn-O催化剂同时去除颗粒物和NOx性能

通过在柴油机排放颗粒物过滤器上负载La_0.8K_0.2Cu_0.05Mn_0.95O₃复合金属氧化物催化剂并进行实际柴油机尾气挂烟,利用程序升温反应技术,对同时催化去除柴油机颗粒物和氮氧化物反应进行了实验研究。研究结果表明,空白载体上实际柴油机排放颗粒物燃烧生成的CO₂曲线呈双峰,分别对应于可溶性有机物和干碳烟的燃烧。负载型催化剂能有效降低可溶性有机物和干碳烟的燃烧温度,促进NO向N₂转化。与淤浆法相比,浸渍法负载的催化剂效果更好,浸渍法负载催化剂可以将起燃温度降至160 ℃,最高的NOx向N₂转化率达63.4%。     

脱除NOx复合催化剂的研究

研究了以莫来石质多孔陶瓷作载体、溶胶-凝胶法Al₂O₃ 和TiO₂涂层作为扩表剂和Cu作为活性组分的系列催化剂的制备及催化活性分析。试验以NH₃为还原剂催化还原NOx,在自制NOx催化还原装置上,系统地考察了制备方法、Cu活性组分负载量和焙烧条件等因素对催化剂活性的影响。利用光学显微照片和XRD等表征方法对催化剂的物相结构进行了研究。     

含CeO2催化剂用于柴油车尾气炭烟氧化的研究

采用共沉淀法合成含CeO₂催化剂M-Ce-O（M＝Fe、Cu、Zn、Co、Ni、Mn）和纯CeO₂,对催化剂进行TPO活性测试及BET、XRD、FT-IR和H2 -TPR表征。结果表明,在Ce中添加过渡金属,改变了CeO₂的晶相结构,比表面积增大,催化剂促进炭烟的燃烧,其促进炭烟氧化的活性顺序为：Ni-Ce-O＞Mn-Ce-O＞Cu-Ce-O＞Fe-Ce-O＞Ce-O＞Co-Ce-O＞Zn-Ce-O,其中,Ni-Ce-O表现出较高的活性,对应起燃温度降至340 ℃。TPR表明,催化活性与500 ℃以下的表面可还原氧量相关。     

活性炭负载AlCl3固体酸催化甲基氯硅烷再分配反应性能与结构研究

以活性炭为载体，采用浸渍蒸发煅烧法制备了负载型AlCl₃固体酸催化剂，并以甲基三氯硅烷(M₁)和三甲基氯硅烷(M₃)的再分配反应为模型反应，在φ20 mm×800 mm的固定床反应器中，310℃、n (M₁/M₃)=1.0、液时空速1.5 h^-1下考察了催化剂的制备条件对其反应活性的影响，并对催化剂的稳定性进行了初步考察.运用N2等温吸附-脱附法、XRD、TG-DSC和吡啶吸附Raman光谱等手段对催化剂的结构和酸性进行了表征.结果表明，较佳的催化剂制备条件为：活性炭经过2.0 mol·L^-1盐酸溶液处理6 h，AlCl₃负载量为1.87 mmol·g^-1，450～500℃焙烧活化;催化剂在100 h内表现出良好的催化稳定性.催化剂的XRD和TG-DSC表征结果表明，AlCl₃负载到活性炭载体上经活化后不再以AlCl₃晶相存在，催化剂在485～600℃时活性组分出现分解;吡啶吸附Raman光谱分析表明催化剂的活性组分为Lewis酸.     

载体γ-Al_2O_3的改性对担载型催化剂La_(0.8)K_(0.2)-Mn_(0.95)Cu_(0.05)O_3/γ-Al_2O_3碳烟催化燃烧性能的影响

采用混合法制备La0.8K0.2Mn0.95Cu0.05O3/γ-Al2O3担载型钙钛矿型催化剂,担载前载体于0.5 mol/L的H2SO4溶液中进行浸渍改性。运用程序升温氧化对各担载型催化剂进行活性评价,考察载体改性时间对催化剂活性的影响。采用XRD和FTIR对催化剂进行了表征,结果显示,改性后的担载型催化剂能够保持良好的钙钛矿结构;与6 h和24 h的相比较,发现载体γ-Al2O3经过12 h浸渍改性后,混合法制备的担载量为20%的担载型催化剂表现出较好的催化活性,将碳烟的起燃温度降至389℃,该温度在柴油车排气温度范围内。     

同时消除柴油机尾气排放炭颗粒和NOx催化剂的研究进展

介绍了简单氧化物、复合氧化物(尖晶石和钙钛矿)催化剂都具有同时消除柴油机尾气中的炭颗粒和NO的活性．但是炭颗粒的起燃温度较高,生成N2的选择性差。在消除炭颗粒和氮氧化物时,有N2O生成,造成二次污染,炭颗粒与催化剂的接触形式直接影响炭颗粒的燃烧温度。     

Innovative means for the catalytic regeneration of particulate traps for diesel exhaust cleaning

Catalytic traps for diesel particulate removal are multifunctional reactors coupling filtration and catalytic combustion of soot. This paper reviews the most recent developments carried out at Politecnico di Torino concerning two different trap types: zirconia-toughened-alumina foams catalysed with Cs–V catalysts, operating according to a deep filtration mechanism, and cordierite or SiC wall-flow filters catalysed with perovskite catalysts (e.g. LaCr_0.9O₃), enabling shallow-bed filtration. The preparation and characterisation of these two trap types are described and the performance of the traps (filtration efficiency, pressure drops, etc.) evaluated on a diesel engine bench under various operating conditions. A final critical assessment points out that most chances of practical application in mobile sources lie in wall-flow type traps for their superior filtration efficiency (>95%) and their compatibility with active trap regeneration means (e.g. fuel post-injection) that can occasionally rise on purpose the exhaust gas temperature to accelerate the catalytic combustion of trapped soot. Conversely, completely passive solutions based on deep filtration catalytic traps show only promise for stationary applications at temperatures higher than 350°C, due to insufficient catalyst activity at lower temperatures.     

自蔓延燃烧法制备锰氧化物催化剂及其催化燃烧炭烟颗粒

柴油机尾气中的炭烟颗粒是城市雾霾的主要来源之一,严重污染环境和危害人体的健康。因此,降低和消除柴油车尾气中的炭烟颗粒具有重要的意义。本文以高锰酸钾和一水柠檬酸为原料,通过自蔓延燃烧法成功制备了一系列锰氧化物催化剂。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、N₂吸附-脱附、H₂程序升温还原（H₂-TPR）、O₂程序升温氧化（O₂-TPD）和X射线光电子能谱（XPS）等手段对催化剂进行了表征,并考察了该系列催化剂催化炭烟颗粒燃烧的活性。结果表明,制备的锰氧化物催化剂均具有良好的催化燃烧炭烟活性。当高锰酸钾与一水柠檬酸的摩尔比为12∶1、煅烧温度为450℃时,制备的催化剂具有较低的还原峰温度,较大的比表面积和孔径以及化学吸附氧和Mn⁴⁺含量,从而表现出最佳催化燃烧炭烟颗粒的性能,其催化燃烧炭烟温度T₁₀、T₅₀和T₉₀分别为284℃、327℃和360℃。     

Bench Scale Experiments of Diesel Soot Oxidation Using Pr0.7Sr0.2K0.1MnO3 Perovskite Type Catalyst Coated on Ceramic Foam Filters

Potassium and strontium substituted praseodymium manganate type perovskite catalyst coated on ceramic foam filters have been studied for diesel particulate removal. The synthesized catalyst coated filter pieces have been characterized by using XRD, SEM and TG analysis, whereas their catalytic activity towards soot oxidation was tested using a bench scale facility with real diesel engine exhaust. The catalyst coated filters decrease the soot oxidation T_initial value by 150 °C and T_final by 100 °C as compared to bare soot oxidation reaction, which can be considered as high activity under the actual conditions of diesel engine. The catalytic materials show good thermal stability, while their low cost will also add to their potential for practical applications. Although perovskites have been studied for laboratory evaluations of catalytic soot oxidation, present results further substantiate the possibility of using low-cost, supported, non-noble metal based catalysts for diesel exhaust emission control applications, especially for the cost-effective retrofitment of in-use vehicles with old generation engines.     

低温等离子体改性LaCoO_3催化剂去除炭烟颗粒的催化性能

采用低温等离子体对LaCoO_3复合氧化物进行表面改性,利用XRD、FT-IR、H2-TPR和O_2-TPD等对催化剂表面物化性能进行表征,分析等离子体对催化剂表面物化性质的影响。采用程序升温氧化反应评价催化剂对模拟柴油机炭烟催化氧化的活性。结果表明,等离子体改性促进了催化剂表面晶格氧的活化,增加了活性氧物种数目,从而增强了催化剂对炭烟催化氧化活性,炭烟催化起燃温度Ti由278℃降到274℃,峰值温度Tm由354℃降至345℃,燃尽温度Tf由425℃降至386℃。     

尖晶石型Mn_(1-x)M_xCo_2O_4柴油车尾气处理催化剂的制备及其应用

尖晶石型复合氧化物因具有独特的结构特征而成为相对理想的柴油车尾气处理催化剂。采用溶胶-凝胶法制备尖晶石型Mn_(1-x)M_xCo_2O_4催化剂,通过X射线衍射(XRD)和程序升温氧化(TDO)等对Mn_(1-x)M_xCo_2O_4催化剂进行表征。结果表明,制备的样品Mn_(1-x)M_xCo_2O_4均为尖晶石型复合氧化物;掺杂Cu、Ce后,催化剂的氧化性能有不同程度的变化。在固定床微型反应器上对催化剂催化活性进行评价,结果表明,与纯MnCo_2O_4相比,Mn_(0.9)Ce_(0.1)Co_2O_4催化剂催化活性提高,Mn_(0.9)Cu_(0.1)Co_2O_4催化剂催化活性降低,但CO_2选择性增加。     

Development of catalysts based on pyrovanadates for diesel soot combustion

Pyrovanadates of potassium and cesium were prepared and tested as catalysts for low-temperature combustion of carbon. Their catalytic activity was investigated by both temperature-programmed oxidation and thermogravimetric analysis and compared with that displayed by the metavanadates of the same elements, previously proposed as promising catalysts for soot combustion in diesel emissions. Pyrovanadates show an intrinsic catalytic activity noticeably higher than that of the corresponding metavanadates. In particular, cesium pyrovanadate is capable of lowering the ignition temperature of carbon down to 255°C and to provide a high combustion rate already at about 300°C. Such quite interesting results were confirmed in a pilot plant study on the performance of -Al₂O₃ ceramic foam traps whose pore walls had been lined with catalysts based on either Cs meta- or pyro-vanadates, so as to enable trap self-regeneration by catalytic combustion of the filtered particulate.     

Application of glass soot catalysts on metal supports to achieve low soot oxidation temperature

K–Ca–Si–O glass was applied to metal supports for use as a catalyst for diesel soot combustion. Glasses were processed from the melt and by a sol–gel route. Catalyst activity for the oxidation of diesel exhaust soot and flame soot from an oil lamp was compared by thermogravimetric analysis (TGA). The results show that a K-based catalytic glass coating on metal substrates can reduce the temperature where half of the engine soot is oxidized (T₅₀) to as low as 360 °C under loose contact conditions, and offers catalytic stability for long term combustion cycling. Scanning electron microscopy observations show that sol–gel glass processing is effective for coating complex wire mesh shapes without pore clogging.