Impact of ageing on the distribution of platinum group elements and catalyst poisoning elements in automobile catalysts

The distribution of platinum group elements (PGEs) and catalyst poisoning elements (Pb, Zn, P and S) on the surface of gasoline and diesel automobile catalysts was investigated within this study. Laser ablation–inductively coupled plasma mass spectrometry (LA–ICPMS) provides both the sensitivity and the spatial resolution required for the surface analysis of sectioned automobile catalysts, and scanning along channels reveals the distribution of longitudinal changes in PGE and catalyst poisoning elements. Changes in catalyst surface features were studied for fresh catalysts and after ageing of the catalyst up to 80 000 km for both types of catalysts studied. The PGEs in the gasoline catalyst were found to decrease at the front of the catalyst after ageing, whereas the diesel catalyst presented a more constant loss along the catalyst. The fraction of poisoning elements (Pb, P and Zn for the gasoline catalyst and P and Zn for the diesel catalyst) retained by the catalyst is distributed non‐uniformly over the length of the catalyst. This could indicate different ageing mechanisms for gasoline and diesel catalysts. Copyright © 2003 John Wiley & Sons, Ltd.     

STUDY ON THE OXIDATIVE COUPLING OF METHANE III.CATALYTIC PERFORMANCE OF TiO2-BASED CATALYSTS STUDIED BY CO2-TPD AND TPR-TPO

The effects of surface acidity-basicity and surface oxidation reduction property of Li-La-Mn/TiO2 (I) and Li-La-Mn-W/TiO2 (II) catalysts on oxidative coupling of methane were studied by CO2-temperature programmed desorption (CO2-TPD) and temperature programmed reduction temperature programmed oxidation (TPR-TPO). The results show that there exist strong basic sites on catalysts I and II, but the quantity of these sites on catalyst II is more than that on catalyst I. Besides, the strength of basics site on catalyst II is stronger than that on catalyst I. The surface of catalyst II is easier to reduce and re-oxidize than that of catalyst I. The surface of catalyst II is easier to reduce and re-oxidize than of catalyst I, and the extent of reduction and reoxidation of catalyst II is more intensive than catalyst I, which results in a lowing of the reaction temperature and enhances the activity and C2 hydrocarbon yield as well as gas hourly space velocity(GHSV). Catalyst II is excellent for the oxidative coupling of methane (OCM).     

Mild hydrotreating over NiMo/sepiolite catalyst

Summary In order to introduce an alternative catalyst for hydrotreating (HDT) reaction a study of NiMo supported on natural sepiolite catalysts is presented. The sepiolite catalyst has been prepared in this laboratory and a NiMo/Al₂O₃ commercial catalyst is used as a reference. The textural properties of the materials and their catalytic activity in hydrotreating (HDT) and hydrodesulfuration (HDS) using a FCC feed at 400-475°C and 50 MPa total pressure, have been evaluated. The support of the commercial catalyst is alumina containing mesopores. The sepiolite support is a hydrated magnesium phylosilicate containing micropores but with an open structure that confers the possibility to use it as a catalyst. The hydrotreating conversion (wt.% HDT) is defined here as the net hydrotreating conversion into products boiling below 380°C. For the commercial catalyst the wt.% HDT was only 5% higher than for the catalyst supported on sepiolite and the product selectivity was very similar. HDS conversion was 20% lower for the sepiolite supported catalyst. Taking into account these results the sepiolite is a suitable support of HDS catalysts.     

cotpp-pt/c作直接甲醇燃料电池阴极催化剂

四苯基钴卟啉;pt催化剂;直接甲醇燃料电池;氧还原     

静电纺丝制备质子交换膜燃料电池催化剂层综述

质子交换膜燃料电池催化剂层在成本、耐久性以及性能上的局限是制约燃料电池汽车商业化的瓶颈. 已有文献证明静电纺丝技术制备的纳米纤维催化剂层能提高催化剂利用率、增加三相界面和三相通道以及提高耐久性. 作者结合所在课题组的工作综述了静电纺丝技术制备质子交换膜燃料电池催化剂层的研究进展. 首先,介绍了质子交换膜燃料电池催化剂层的发展历程,并从制备方式和结构两个方面对其进行分类和总结;接下来,从静电纺丝纳米纤维催化剂层的制备、物理特性表征、电化学性能分析及耐久性表征等方面进行了总结;最后,从三相界面、三相通道以及量产适用性的视点比较了三种结构的催化剂层,介绍了质子交换膜燃料电池催化剂层的发展趋势,并梳理了静电纺丝法制备质子交换膜燃料电池催化剂层领域待研的问题.     

MoO3催化碳酸二甲酯与乙酸苯酯合成碳酸二苯酯

采用焙烧法制备了MoO3催化剂并将其用于碳酸二甲酯(DMC)与乙酸苯酯(PA)合成碳酸二苯酯(DPC)反应,考察了焙烧温度对催化荆性能的影响,并用X射线衍射(XRD)对催化剂结构进行了表征.结果发现,在400或500℃焙烧的催化剂具有良好的催化性能,DMC转化率为73.9%,DPC和甲基苯基碳酸酯的选择性分别为39.5%和56.5%.XRD结果表明,该催化剂物相组成为正交晶系MoO3,且(021)或/和(110)晶面有利于酯交换反应.催化剂使用5次后DMC转化率从73.9%降至10.2%,多次重复使用后的催化剂在窄气气氛中于400或500℃焙烧即可再生,再生后催化剂的性能几乎和新鲜催化剂相当.     

催化剂对基团转移聚合的影响

本文研究了催化剂的种类和用量对硅烯醚型引发剂引发的基团转移聚合的影响。发现四丁基二苯甲酸氢铵(Bu_4NH(C_6H_5CO_2)_2,TBABB)和HsI_2的催化效果较好。只需引发剂的4％的HgI_2即可使MMA的基团转移聚合达到完全转化。认为有效的氧负离子催化剂应由较稳定的铵正离子和电负性较大的氧负离子所组成。过量的催化剂不利于基团转移聚合的进行。考察了TBABB催化剂对温度的依赖性及其浓度对聚合速率,分子量和分子量分布,转化率的影响。     

Surprisingly efficient catalytic Cr-mediated coupling reactions

[reaction: see text] With use of 1 mol % of Cr catalyst 5, surprisingly efficient Cr-mediated couplings of aldehydes with various types of nucleophiles have been realized. The catalyst set of Cr catalyst 5 and Ni catalyst 4 is used for alkenylation, alkynylation, and arylation, whereas the catalyst set of Cr catalyst 5 and CoPc (cobalt phthalocyanine) is used for 2-haloallylation, alkylation, and propargylation. Only the Cr catalyst 5 is required for allylation. The reaction rates in DME and THF have been found significantly faster than that in MeCN.     

乙二醇单乙醚醋酸酯合成用固体催化剂的筛选及催化作用分析

采用自建动态酯化反应实验装置，通过色谱分析测定了不同催化剂上乙二醇单乙醚醋酸酯合成反应的转化率－时间关系曲线。根据多种催化剂的活性及寿命，筛选出一种较为理想的锆基催化剂。该催化剂在实验条件下，反应２ｈ，转化率达９７％，对目标产生的选择性为１００％。     

Immobilized Catalysts for Iridium‐Catalyzed Allylic Amination: Rate Enhancement by Immobilization

The first immobilized catalyst for Ir‐catalyzed asymmetric allylic aminations is described. The catalyst is a cationic (π‐allyl)Ir complex bound by cation exchange to an anionic silica gel support. Preparation of the catalyst is facile, and the supported catalyst displayed considerably enhanced activity compared with the parent homogeneous catalyst. Up to 43 consecutive amination runs were possible in recycling experiments.     

TiSiW_(12)O_(40)/TiO_2催化合成磷酸三甲苯酯的研究

应用TiSiW_(12)O_(40)/TiO_2催化剂合成磷酸三甲苯酯研究结果表明，该催化 剂具有较高的催化活性。考察了催化剂用量、反应温度和反应时间对酯产率的影响 。在典型反应条件（催化剂用量为原料总量的1.0%，反应温度为100-120 ℃，反应 时间为8h）下所得磷酸三甲苯酯的产率为85.5%。该催化剂易于回收且可重复使用 ，具有良好的活性稳定性。     

生物油模型化合物催化裂化制备芳香烃的实验研究

通过HZSM-5分子筛催化剂对生物油典型模型化合物(乙酸、愈创木酚、正庚烷和环己烷等)在550℃进行了催化裂化反应,研究模型化合物催化裂化特性和反应机理以及催化剂性质。结果表明,正庚烷和环己烷裂化产物主要是芳香烃(53%和91%,均为积分面积分数),对于此类不含氧的模型化合物,催化裂化反应过程更容易进行;随着催化剂用量的增加,可以有效增加乙酸裂化产物中芳香烃含量(12%到90%,均为积分面积分数);愈创木酚结构比较复杂,HZSM-5催化剂主要脱除了甲氧基,催化剂用量的增加可以使芳香烃类稳定物质更容易形成。     

煤基固体酸催化合成席夫碱反应

以煤基活性炭(AC)和苯胺(ANI)为原料,通过原位-溶液聚合法制备了煤基固体酸催化剂AC@PANI-SO_3H(APS),利用扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)和热重分析(TG)等技术手段对催化剂进行了结构和性能的表征。研究了该催化剂在微波辐射下催化合成Schiff碱化合物的活性,并对其催化工艺条件进行了优化考察。结果表明,催化剂用量5%(以每摩尔邻苯二胺用量为基准),反应时间3~20 min,溶剂选用乙醇(Et OH),Schiff碱化合物产率可达80%~93%,说明该催化剂在微波催化合成席夫碱反应中变现出良好的催化活性,反应时间短,工艺简单操作,且催化剂能重复使用5次。通过红外发现,催化剂重复5次后活性下降的主要原因是固体酸表面键合的磺酸基官能团消失,从而导致活性降低。     

温控Noyori配体的合成及在苯乙酮不对称氢转移反应中的应用

设计并合成了一种新型的聚乙二醇单甲醚(MPEG)修饰的温控Noyori配体.将其与[RuCl2.(p-cymene)]2络合形成的催化剂用于水/环己烷两相体系中苯乙酮不对称氢转移反应.以甲酸钠为氢源,考察了反应温度、时间、甲酸钠用量、底物与催化剂摩尔比以及溶剂用量等因素对催化反应的影响.结果表明,反应体系中含催化剂的水相具有浊点,并且催化剂显示出良好的不对称催化性能,在甲酸钠/苯乙酮/催化剂的摩尔比为300:100:1、环己烷/水体积比1:1及30℃的反应条件下反应6h,苯乙酮的转化率为99.7%,产物α-苯乙醇的对映选择性(e.e.)为93.9%.催化剂相易与产物相分离并与直接循环使用,循环使用的催化剂活性明显下降,但产物对映选择性仍保持不变.     

Highly active Pd containing EMT zeolite catalyst for indirect oxidative carbonylation of methanol to dimethyl carbonate

Palladium containing EMT zeolite catalyst(Pd/EMT) was prepared and used for the indirect oxidative carbonylation of methanol to dimethyl carbonate(DMC).The EMT zeolite was employed as a new catalyst support and compared with the conventional Pd containing FAU zeolite catalyst(Pd/FAU).The Pd/EMT in contrast to the Pd/FAU catalyst exhibited high intrinsic activity with the turnover frequency of 0.25 s^-1 vs.0.11 s^-1.The Pd/EMT catalyst showed high CO conversion of 82% and DMC selectivity of 79%,that maintained for at least 130 h,while the activity of the Pd/FAU catalyst rapidly deteriorated within 12 h.The enhanced interactions between Pd and EMT zeolite inhibited the sintering of palladium clusters and maintained the Pd2+ active sites in the Pd/EMT catalyst.The stabilization of the mono-dispersed Pd clusters within the EMT zeolite is paramount to the excellent performance of the catalyst for the indirect oxidative carbonylation of methanol to DMC.     

直接热分解法制备的碳载Pt-Sn催化剂对乙醇氧化的电催化性能

以Pt( NO3)2和SnO为前驱体采用直接热分解法制备了碳载Pt-Sn (Pt-Sn/C)催化剂.用X射线衍射(XRD)、透射电镜(TEM)和X射线光电子能谱(XPS)等技术对催化剂进行了表征,用循环伏安法和CO溶出等方法研究了催化剂对乙醇氧化的电催化性能.结果表明,Pt-Sn/C催化剂中的Pt-Sn粒子具有Pt-S...     

Influences of the adsorption state of catalyst on the performance of DS-PEC for visible light driven water splitting

Adsorption state of catalyst on photoanode is an important factor on influencing the performance of dye-sensitized photoelectrochemical cells(DS-PECs) for water splitting. Photoanode TiO_2(1 + 2) was assembled with Ru(bpy)3phosphoric acid derivative(complex 1) as photosensitizer and complex 2 as water oxidation catalyst to compare with photoanode TiO_2(1 + 3). The photocurrent density of photoanode TiO 2(1 + 3) with catalyst 3 synthesized with only one end fixing on the surface of TiO_2 is about four-fold of the photoanode assembled with catalyst 2 fixing with two claws on the surface of TiO 2. The phenomenon should be caused by the littery arrangement and shorter distance of catalyst 2 from the active center of catalyst to TiO_2 on the surface of semiconductor which led to lowly efficient electron transfer.     

柴油深度脱芳烃Pd-Pt/USY催化剂的EXAFS研究

为满足日趋严格的环保要求和适应汽车工业的快速发展,柴油深度脱芳烃已成为国内外普遍关注的课题．近年来的研究表明,Pd－Pt/USY催化剂具有较高的芳烃加氢活性和较强的耐硫中毒能力[’－     

大孔碳载Ir催化剂对氧还原的电催化性能和抗甲酸能力

本文用X射线能量色散谱(EDS)、X射线衍射(XRD)谱、拉曼光谱和电化学等技术研究了直接甲酸燃料电池(DFAFC)中Vulcan XC-72炭黑载Ir(Ir/XC)和大孔炭载(Ir/MC)催化剂对氧还原的电催化性能和抗甲酸的能力。发现Ir/MC催化剂对氧还原的电催化性能要优于Ir/XC催化剂,氧起始还原电位比在Ir/XC催化剂上正移0.1V,极限电流密度比在Ir/XC催化剂上大30％左右。由于Ir/MC和Ir/XC催化剂的Ir粒子平均粒径和相对结晶度相似,因此,这只能归结于MC有大的孔径和孔率及高的石墨化程度。另外2种催化剂都有很好的抗甲酸能力。因此MC是一种比XC更好的催化剂的炭载体。     

超临界干燥方法对甲烷燃烧催化剂LaMnAl11O19结构及活性的影响

 摘要：用水热合成法制备了锰取代的六铝酸盐催化剂，并比较了超临界干燥法和普通烘箱干燥法对催化剂结构及甲烷燃烧反应活性的影响．DTA－MS结果表明，超临界干燥过程中，催化剂前驱物中的表面铝羟基部分被乙氧基取代．这种表面修饰作用可保持铝分散的均匀性，使催化剂前驱物中碳酸锰和碳酸镧的分解温度明显降低，且氢氧化铝的脱水温度维持在较适宜的范围内；焙烧后，易形成六铝酸盐相．甲烷燃烧反应结果表明，用超临界干燥方法制得的催化剂对甲烷燃烧反应的催化活性明显高于用普通烘箱干燥方法制得的催化剂．