The Selective Catalytic Reduction of NO by Hydrocarbons over Pt- and Ir-Based Catalysts

Platinum- and iridium-based catalysts are the most active ones among noble metals for the selective catalytic reduction of NO by hydrocarbons (HC-SCR). Yet, the level of our understanding of the behavior of these two metals varies greatly. From the early stages of the research efforts in the HC-SCR field Pt-based catalysts were identified as “promising” and have been studied extensively for this application. Subsequently, there is a substantial body of literature focusing on the catalytic performance of such systems, as well as on the fundamental chemistry taking place on their surface under HC-SCR conditions. A fairly good understanding of the behavior of such catalysts has been developed and different reaction mechanisms have been proposed and debated extensively. In contrast, limited information is available regarding the properties and HC-SCR behavior of Ir-based catalysts. Recent reports have demonstrated advantages in the HC-SCR performance of such catalysts and have documented substantial iridium particle size, support and promoter effects.     

贵金属催化剂制备条件对氧化性能的影响

采用浸渍法制备了贵金属负载型催化剂,考察了载体脱氧、负载方法、贵金属种类及还原途径等制备因素对双甘膦催化氧化合成草甘膦的影响.结果表明:活性炭载体表面用不同脱氧前处理剂处理,其催化效果相差很大;采用浸渍法对贵金属进行负载,干浸法与湿浸法相比,干浸法更佳.贵金属铂和钯均能有效提高催化性能,其中铂炭催化剂的催化活性更高;对3种还原方法进行了比较,采用液气串联还原途径时,催化剂效果最佳;最终得到在90℃、0.34 Mpa反应条件下,用Pt/AC催化剂,草甘膦产品纯度达97.6%,收率达75.4%.     

载体对Pt催化剂制备邻苯基苯酚催化性能的影响

分别以活性炭(AC)、γ-Al2O3、MgO、TiO2为载体,氯铂酸为活性金属前驱体,采用等体积浸渍法制得不同载体负载的Pt催化剂,考察了它们对环己烯基环己酮(dimer)脱氢制备邻苯基苯酚(OPP)的催化活性和选择性。并用X射线衍射(XRD)、X射线光电子能谱(XPS)、H2程序升温脱附(H2-TPD)、CO2程序升温脱附(CO2-TPD)等对催化剂进行表征。结果表明,载体对所制备的催化剂表面Pt含量、酸碱性和对氢吸附能力等微观性能有影响,以γ-Al2O3为载体制备的Pt-K/γ-Al2O3催化剂,由于催化剂表面Pt质量分数高达0.41%,碱性强和碱中心多,利于氢和中间产物在催化剂表面的吸附,从而提高环己烯基环己酮的转化率和OPP选择性。Pt/γ-Al2O3催化剂在LHSV 0.12 h-1、H2空速33 mL/(g.h)、反应温度380℃的条件下,在200 t/a的工业化装置运转8 000h后,环己酮二聚物转化率仍能达99%以上,OPP选择性达90%以上。     

助催化剂对甲苯歧化与烷基转移催化剂性能的影响

采用助催化剂对丝光沸石进行改性,通过红外光谱（FT—IR）方法表征了该改性分子筛制备的催化剂样品表面酸性的变化,并探讨了酸性变化对甲苯歧化与烷基转移反应催化活性的影响。结果表明,助催化剂WO3的加入能有效地调节催化剂表面酸性,经氢气还原后催化剂B酸量随助催化剂量增加而增加,且与助催化剂相对含量呈对数关系;而L酸量随助催化剂相对含量的增加先上升,随后趋于平稳;催化剂的反应活性随助催化剂含量的增加而增加,但副反应也随之加大。     

Structure and Catalytic Properties of Iron-Containing Bimetallic Catalysts

The world's largest industrial process, ammonia synthesis, uses promoted iron catalysts. Fifty years ago fused and promoted iron catalysts were first utilized in the Fischer-Tropsch synthesis. The importance of this latter process has increased during the last few years because of the current energy crisis. Iron sulfide catalysts were also used by Varga [1] for the high pressure hydrogenation of coal. This procese, however, has been substituted by other methods.     

纳米CeO_2载体对Au-Pd催化剂性能的影响

采用十六胺和不同铈前驱体(硝酸铈铵或硝酸亚铈)分别合成了纳米CeO2(H4和H3),考察了纳米CeO2载体的织构性质对Au-Pd催化剂甲醇部分氧化制氢(POM)性能的影响,用HRTEM、N2吸附、XRD和TPR等对样品进行了表征。结果表明,铈前驱体对载体的性能有较大的影响,以硝酸铈铵为前驱体所制H4载体具有较小的粒径(约5 nm)和平均孔径(5.3 nm)、较大的比表面积(243 m2/g),而硝酸亚铈所制H3载体具有较大的平均孔径(7.9 nm)。POM结果表明,纳米CeO2负载的Au-Pd催化剂具有较好的催化性能,300℃时,Au-Pd/H3的活性和H2选择性分别达100%和59.7%。低温时催化剂的活性和H2选择性为:Au-Pd/H3>Au-Pd/H4,而高温时顺序相反,这是由于低温时催化剂的孔径对反应物和产物的扩散影响较大,高温时催化剂的比表面积和活性组分分散度起主要作用。     

预处理条件对整体式催化剂载体的性能影响

工业堇青石打磨成适当大小的长方体,用草酸溶液沸煮预处理后作为整体式催化剂的载体,利用自动物理吸附仪和电子压力机分别考查了酸预处理条件对堇青石载体的比表面积、失重率以及机械强度的影响。实验结果表明用20%的草酸沸煮处理2 h时堇青石载体的失重率有所增加,可以在保证较强的机械强度前提下获得较为理想的比表面积。     

焙烧温度对双金属催化剂甲苯加氢重整反应催化性能的影响

以类层柱Ni-Co/Mg(Al)O水滑石为前驱体,经不同温度焙烧制备了系列焦炉煤气中焦油模型化合物甲苯加氢重整制合成气催化剂. 在常压、反应温度800℃、水/碳摩尔比0.7和体积空速12000 h-1的条件下,在35 h评价时间内850℃焙烧的催化剂可完全转化甲苯,CH4和CO的平均产率分别为34%和66%,而低于750和高于950℃焙烧的催化剂活性较差. 850℃焙烧时催化剂比表面积较大,形成了尖晶石和固溶体,活性金属与载体间的相互作用较强,还原后活性金属颗粒小且均匀分布. 催化剂上有少量须状碳生成,绝大部分积碳可被H2消除,积碳是可逆过程.     

碱性MgO载体对钴基催化剂催化性能的影响

以分步浸渍法制备了碱性MgO-钴墓催化剂.采用XRD、TPR、TPD和催化活性评价等技术,考察了负载型MgO-CoO催化剂的表面性质及其对CH4与CO2重整反应催化性能的影响.结果表明,共沉淀法制备的MgO载体有较高的比表面积(S(BET)(MgO)),CoO在MgO的表面呈高分散性.以此为载体负载的钴基催化剂具有优异...     

膨润土酯化反应固体酸催化剂的制备研究

对天然膨润土进行酸活化,制备负载ZnCl₂的膨润土固体酸催化剂,研究了膨润土固体酸催化剂在乙酸乙酯合成反应中的催化性能。研究结果表明,用10%（φ）的盐酸活化天然膨润土,在恒温磁力搅拌器中搅拌4 h,水浴温度80℃,ZnCl₂的最佳负载量为1.5 mol/L,550℃下焙烧活化3 h得到的膨润土固体酸催化剂效果最好;在催化剂使用量为7g/L,反应温度为80～90℃时,乙酸转化效率最高可达82.6%,催化剂可重复使用3次。     

卤素及取代效应对Cu系催化剂催化性能的影响

采用软硬酸碱理论,并结合离子半径和取代效应研究了铜系催化剂对甲醇氧化羰基化反应的影响。结果表明,交界碱Br-比软碱I-和硬碱Cl-更适宜与交界酸Cu2 和软酸Cu 配位,促进控制步骤CO对Cu-OCH3键插入的进行。在Cu(5-R-phen)Br2(R = 5-NH2、5-CH3、5-Cl、5-NO2;phen = 菲咯啉)中,弱给电子效应的甲基最有利于CO的活化和CO对Cu-OCH3键的插入反应,催化活性最高。同时在Cu(R?-phen)Br2 (R? = 2-CH3、4-CH3、5-CH3、2,9-dimethyl、4,7-dimethyl、5,6-dimethyl)中,含单甲基催化剂的活性比相应的含双甲基的高;邻近配位N原子的甲基空间位阻效应显著,且甲基越多,活性越低。以活性最高的Cu(5-CH3-phen)Br2为催化剂,在总压力4MPa,CO与氧气的分压比为19:1,反应时间4 h,反应温度130℃,催化剂浓度0.011mol/L的条件下的条件下,碳酸二甲酯的转化数和选择性分别为67.2和96.9%。     

合成甲醇催化剂组成和制法对催化性能的影响

讨论了合成甲醇催化剂的组成和制备方法对催化性能的影响，同时比较了国内外目前合成甲醇催化剂的各种制法和催化性能，对各种催化剂的组成也进行了探讨。     

Effect of Sublimation Treatment on the Catalytic Performance of MFI Catalysts in Pyridine and 3‐Picoline Synthesis

Mordenite framework inverted (MFI)‐structure catalysts with framework trivalent metal cations and extra‐framework metal cations were prepared by the sublimation method to synthesize pyridine and picolines. The results show that the sublimation treatment of volatile metal halides, i.e., GaCl₃ and FeCl₃, consumes the silanol groups of the parent sample. Most of the Ga cations are incorporated into the zeolite framework, which produces hydroxyl groups and dramatically enhances the proportion of Brönsted acid sites. At the same time, a large number of Fe cations exist in the extra‐framework, causing an increase in the proportion of Lewis acid sites. The increased acid amount and strength effectively improve the activity and stability of the catalyst. Moreover, the generated stronger acid sites increase the selectivity of pyridine. The Ga cations of the modified zeolite can promote the dehydrogenation step for pyridine synthesis, which markedly increases the pyridine selectivity.     

Effect of P Content on the Catalytic Performance of P-modified HZSM-5 Catalysts in Dehydration of Ethanol to Ethylene

A series of phosphorus (P) modified HZSM-5 catalysts were prepared and characterized with various techniques. These catalysts were used in dehydration of ethanol to ethylene at different temperatures. It was found that not all the P-modified catalysts favor this reaction at high temperatures. Over the catalyst with 3.4 wt% P, the main product is ethylene at 573–713 K, due to the presence of weak acid sites after P modification. When the P loading is below 3.4 wt%, ethylene and higher hydrocarbons are observed at high temperatures. As P content is above 3.4 wt%, higher reaction temperature is necessary for ethanol dehydration to ethylene.     

Innovative Process for the Synthesis of Nanostructured Ruthenium Catalysts and their Catalytic Performance

An efficient, reproducible process for the solvothermal synthesis of Ru/γ-Al₂O₃ nanocatalysts has been developed. This synthesis employs a low boiling point alcohol acting as solvent and reducing agent. The reaction is performed in autoclave under nitrogen overpressure, by heating the solution of metal precursor and stabilizing agent in the presence of the support. These systems show very promising performances, also with an application perspective, in the selective hydrogenation of phenol to cyclohexanone carried out at 160 °C under 5 MPa of hydrogen: a selectivity to cyclohexanone as high as 83% has been reached at a phenol conversion value of 88%. This paper is dedicated to the memory of Professor Carlo Carlini, with great sorrow.     

合成α-氯丙烯酸甲酯过程中的催化剂催化效应的研究

研究了催化剂V2O5-P2O5/SiO22的制备，并考察了制备工艺条件及反应条件对该催化剂的性能的影响，解释和分析了催化剂的制备、组成及反应条件等因素对合成α-氯丙烯酸甲酯的影响。实验结果给出常压下合成α-氯丙烯酸甲酯的最佳催化剂条件和反应条件：催化剂V2O5-P2O5/SiO2，V／P摩尔比为1：2．8，浸渍时间3h，活化温度为450℃；在空速1200h^-1，反应温度300℃，氯乙酸甲酯／甲缩醛摩尔比为2．4：1的条件下，所得甲缩醛转化率为76．2％，α-氯丙烯酸甲酯的选择性为58．5％，收率为44．58％。     

Influence of Ageing Conditions on the Performance and Structure of Commercial Three-Way Catalysts

The ageing behaviour of engine test bench and road aged commercial three-way catalysts (TWCs) is compared. Their catalytic performances are tested and the findings are correlated to structural investigations. The TWCs were tested on a chassis dynamometer using the New European Driving Cycle and the catalytic activities were determined by measurements of the oxygen storage capacity and the light-off (LO) temperature. Selected catalysts were characterised by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analysing system, nitrogen adsorption (BET) and X-ray fluorescence spectroscopy. A linear increase of the emissions with duration for the HC and CO components and of the LO temperature was observed. A surface area decrease and a growth of Pd particles after ageing could be detected. Also a crystalline BaAl₂Si₂O₈ phase was identified, which can be attributed to a reaction of NO _x storage component with cordierite support material.