临氢水热处理对Ni/γ-Al_2O_3催化剂结构和性能的影响

采用浸渍法制备了Ni负载量为17%的Ni/γ-Al2O3催化剂.在氢气压力4 MPa,温度180℃条件下对Ni/γ-Al2O3催化剂进行了不同时间的水热处理.通过XRD、TG、H2-TPR和低温氮气物理吸附等手段对水热处理前后的催化剂进行表征,并考察其催化1,4-丁炔二醇加氢反应性能.结果表明,临氢水热处理导致载体γ-Al2O3水合相变为薄水铝石,随着水热处理时间的延长,薄水铝石的结晶度逐渐增大.γ-Al2O3的水合相变引起活性组分Ni晶粒的聚集及催化剂比表面积和孔容下降,从而导致催化剂活性降低.     

Cu-Ni/γ-Al_2O_3双功能催化剂上二甲醚水蒸气重整制氢

用沉积-沉淀法分别制备了Cu/γ-Al2O3、Ni/γ-Al2O3和Cu-Ni/γ-Al2O3催化剂,并研究了它们在二甲醚水蒸气重整(DMESR)制氢反应中的催化性能.采用比表面积测定(BET)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)、X射线光电子能谱(XPS)、NH3程序升温脱附(NH3-TPD)、程序升温氧化(TPO)和透射电子显微镜(TEM)等表征手段对催化剂的物相结构、微观形貌、还原性能、表面酸性和积炭特性等进行了研究.结果表明:Cu、Ni均为二甲醚水蒸气重整制氢的活性组分,Cu、Ni和γ-Al2O3之间存在着相互作用;镍的加入可以有效地提高铜组分在γ-Al2O3上的表面富集与分散,优化铜组分的分布状态,促进CuO颗粒的细小化,并可增强铜组分和载体之间的相互作用,有效地防止铜晶粒的团聚,从而提高催化剂的活性及稳定性;铜的加入可以改善催化剂中金属镍的分散性,减少镍颗粒的尺寸,降低催化剂对CH4的选择性,提高催化剂的H2产率,并在一定程度上抑制了积炭的形成与沉积.在350℃的温度下,反应进行100h后,Cu-Ni/γ-Al2O3催化剂仍保持95%的二甲醚转化率,说明该催化剂具有较好的活性和稳定性.     

CuO/ZnO/Y2O3/γ-Al2O3双功能催化剂上二甲醚水蒸气重整制氢

将沉积-沉淀法制备的CuO/ZnO/Y2O3催化剂同γ-Al2O3进行机械混合,制备了CuO/ZnO/Y2O3/γ-Al2O3双功能催化剂,用于二甲醚水蒸气重整制氢反应,实验结果表明其活性、稳定性等均优于常用的CuO/ZnO/Al2O3/γ-Al2O3催化剂.结合N2吸附.脱附(BET)、N2O化学吸附(N2O chemisorption)、NH3程序升温脱附(NH3-TPD)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)等表征手段研究了两种催化剂在表面酸性及微观结构上的差异,发现CuO/ZnO/Y2O3催化剂具有相对较高的铜分散度,铜品粒更加细小化,并且具有高温稳定性的Y2O3可能起到隔离铜的作用,在一定程度上防止了铜晶粒的团聚,从而改善了重整组分的性能,提高了双功能催化剂的重整制氢活性及稳定性.     

低温等离子体协助B2O3/γ-Al2O3 选择催化还原NO（英文）

研究了低温等离子体协助催化条件下甲烷选择性催化还原NO反应(SCR).反应气体经等离子体活化后,生成NO2,HCHO,CH3NO和CH3NO2等活性更高的中间产物.程序升温表面反应表明,这些中间产物可在等离子体后置催化装置上进一步反应,从而使NOx还原为N2.在考察的一系列催化剂(包括γ-Al2O3,Ag/γ-Al2O3,B2O3/γ-Al2O3,Ga2O3/γ-Al2O3,In2O3/γ-Al2O3等)中,B2O3/γ-Al2O3表现出最好的催化活性.当反应温度为300oC时,NOx转化率达到最高.与γ-Al2O3催化剂相比,在10wt%B2O3/γ-Al2O3催化剂上,300oC时,NOx转化为N2的转化率从33.4%提高至51.0%.催化剂的酸性对于经等离子体活化后的反应气体在催化剂上的SCR反应起到重要作用.同时,催化剂上吸附态NOx对于NOx的转化也起到一定作用.     

低温等离子体协助B_2O_3/γ-Al_2O_3 选择催化还原NO(英文)

研究了低温等离子体协助催化条件下甲烷选择性催化还原NO反应(SCR).反应气体经等离子体活化后,生成NO2,HCHO,CH3NO和CH3NO2等活性更高的中间产物.程序升温表面反应表明,这些中间产物可在等离子体后置催化装置上进一步反应,从而使NOx还原为N2.在考察的一系列催化剂(包括γ-Al2O3,Ag/γ-Al2O3,B2O3/γ-Al2O3,Ga2O3/γ-Al2O3,In2O3/γ-Al2O3等)中,B2O3/γ-Al2O3表现出最好的催化活性.当反应温度为300oC时,NOx转化率达到最高.与γ-Al2O3催化剂相比,在10wt%B2O3/γ-Al2O3催化剂上,300oC时,NOx转化为N2的转化率从33.4%提高至51.0%.催化剂的酸性对于经等离子体活化后的反应气体在催化剂上的SCR反应起到重要作用.同时,催化剂上吸附态NOx对于NOx的转化也起到一定作用.     

金属离子对Ru-Pt/γ-Al2O3催化剂上对氯硝基苯选择加氢反应的影响

 采用混合醇还原法制备了聚乙烯吡咯烷酮(PVP)稳定的Ru-Pt/γ-Al2O3双金属催化剂,考察了其催化对氯硝基苯(p-CNB)选择加氢反应的性能,探讨了反应温度、压力、第三金属离子的种类、添加量及添加方式对反应的影响. 结果表明,以Ru-Pt/γ-Al2O3为催化剂,在1.0 MPa和50 ℃的条件下反应1 h,p-CNB的转化率可达48.2%,生成对氯苯胺(p-CAN)的选择性为87.3%. 在反应体系中添加适量的Fe3+或Sn4+离子时,在相同的反应条件下,p-CNB的转化率和p-CAN的选择性分别提高到100%和99.0%. Fe3+或Sn4+的添加量及添加方式对p-CNB的转化率有较大的影响,加入Fe2+,Co2+和Ni2+离子也有利于提高催化剂的活性和选择性. Ru-Pt/γ-Al2O3催化剂体系对其它氯硝基苯的加氢反应也有明显的催化作用.     

Au/γ-Al2O3的制备与表征及其催化苯甲醛直接酯化

采用直接浸渍-还原法和赖氨酸保护浸渍-还原法制备了γ-Al2O3负载的纳米金催化剂(3%Au/γ-Al2O3),并考察了其在苯甲醛与醇直接酯化反应中的催化性能.在常压无碱条件下,以赖氨酸保护浸渍-还原法制备的Au/γ-Al2O3在苯甲醛与不同脂肪醇直接酯化的反应中表现出优良的催化性能,在该催化剂催化下,苯甲醛与乙醇反应中苯甲醛的转化率可达到94.0%,苯甲酸乙酯选择性为98.5%.通过催化剂的X射线粉末衍射(XRD)、透射电镜(TEM)及X射线光电子能谱(XPS)、N2物理吸附-脱附等表征结果分析了影响催化剂性能的因素.结果表明:赖氨酸浸渍还原法制备的Au/γ-Al2O3表面上纳米金粒径小、分散性好.高分散的纳米金颗粒是提高苯甲醛与醇直接酯化反应催化性能的关键因素.     

高性能汽车尾气净化催化剂的制备

 采用浸渍法制备了Pt/γ-Al2O3和Rh/CeO2-ZrO2-Y2O3,然后将两者按一定的比例混合制江涂覆在蜂窝载体上制得整体式催化剂,用汽车尾气模拟气对催化剂的性能进行了评价. 结果表明,Pt/γ-Al2O3催化剂中引入Rh/CeO2-ZrO2-Y2O3组分后极大地提高了催化剂的低温活性和热稳定性,催化剂的起燃温度仅为240 ℃; 在900 ℃水热老化后,催化剂的起燃温度仅升高约20%. 这说明Pt/γ-Al2O3与Rh/CeO2-ZrO2-Y2O3之间存在一定的协同效应.     

CeO2-La2O3/γ-Al2O3催化还原SO2反应机理的研究

 采用浸渍法制备了负载型CeO2/γ-Al2O3,La2O3/γ-Al2O3和CeO2-La2O3/γ-Al2O3催化剂,并用XRD和XPS对催化剂进行了表征,在n(SO2)/n(CO)=1/3,载流气体为N2,气体流量为1 L/min,催化剂用量为15 g的条件下,考察了催化剂催化CO还原SO2反应的性能,研究了催化剂的活化过程、催化活性和反应物配比对活性的影响. 结果表明,CeO2-La2O3/γ-Al2O3在催化还原SO2反应中的活化温度比单组分催化剂CeO2/γ-Al2O3或La2O3/γ-Al2O3下降了50~100 ℃,而且具有更高的活性. 这可以解释为由CeO2的redox反应与La2O3的COS中间物反应之间的协同作用所致. 还对SO2还原反应机理进行了探讨,发现CeO2的redox反应所生成的单质硫是整个过程中COS中间物反应的重要来源. 在此基础上,对CeO2-La2O3/γ-Al2O3催化CO还原SO2反应提出了redox-COS叠加反应机理.     

Ce和Mg改性的γ-Al2O3负载Pt催化剂催化乙二醇水相重整制氢

 采用浸渍法制备了Ce和Mg改性的 γ-Al2O3 负载Pt乙二醇水相重整制氢催化剂. 采用催化活性评价、N2物理吸附、CO化学吸附、X射线衍射(XRD)和程序升温还原(TPR)等手段系统研究了催化剂的活性、选择性及物化性质. 实验结果表明, Ce和Mg改性的 γ-Al2O3 负载Pt催化剂的活性明显高于Pt/γ-Al2O3 催化剂. 在498 K和2.58 MPa条件下,乙二醇的转化率由72.3%提高到100%, 氢的选择性接近100%. 在Pt/(Ce)γ-Al2O3 和Pt/(Mg)γ-Al2O3 催化剂的XRD谱中,除了 γ-Al2O3 特征峰外,还分别出现了CeO2和Mg-Al层状化合物及微弱的Mg-Al尖晶石结构化合物的特征峰. Ce的存在促进了Pt对乙二醇的吸附-裂解作用和CO水煤气变换反应; Mg的存在中和了 γ-Al2O3 表面的酸性,增加了载体的碱性中心,影响了PtCl2-6的分散,抑制了乙二醇的脱水反应.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.