H型镁碱沸石负载对Cu-ZnO-Al2O3催化剂上CO加氢生成烃类的影响

采用三种不同方法制备了Cu-Zn-Al基甲醇催化剂,然后在水相悬浮液中与H型镁碱沸石混合分散,以制得负载型甲醇催化剂.运用X射线衍射、N2吸附-脱附、透射电镜、程序升温还原、NH3程序升温脱附、H2程序升温脱附和X射线光电子能谱对催化剂进行了表征.考察了催化剂催化CO加氢反应生成二甲醚和烃类的性能.该催化剂是在低和高过饱和度条件下采用共沉淀法和均匀沉淀法制得的.制备方法对前驱体的结构特性(如纯度、结晶度和催化剂颗粒粒径分布)有显著影响.低过饱和度的沉淀条件有利于Cu物种的高度分散,增加了催化剂中金属的比表面积,所得催化剂粒径分布均匀.这些效应进而会影响分子筛的性质,导致其微孔孔体积较小,分子筛酸性位被堵塞.通过Cu比表面积和CO转化速率之间的关联可考察甲醇催化剂的性能.     

H型镁碱沸石负载对Cu-ZnO-Al_2O_3催化剂上CO加氢生成烃类的影响（英文）

采用三种不同方法制备了Cu-Zn-Al基甲醇催化剂,然后在水相悬浮液中与H型镁碱沸石混合分散,以制得负载型甲醇催化剂.运用X射线衍射、N_2吸附-脱附、透射电镜、程序升温还原、NH_3程序升温脱附、H_2程序升温脱附和X射线光电子能谱对催化剂进行了表征.考察了催化剂催化CO加氢反应生成二甲醚和烃类的性能.该催化剂是在低和高过饱和度条件下采用共沉淀法和均匀沉淀法制得的.制备方法对前驱体的结构特性(如纯度、结晶度和催化剂颗粒粒径分布)有显著影响.低过饱和度的沉淀条件有利于Cu物种的高度分散,增加了催化剂中金属的比表面积,所得催化剂粒径分布均匀.这些效应进而会影响分子筛的性质,导致其微孔孔体积较小,分子筛酸性位被堵塞.通过Cu比表面积和CO转化速率之间的关联可考察甲醇催化剂的性能.     

前驱体CeOHCO3的结构对CeO2催化性能的影响（英文）

以尿素替代水为溶剂,采用改良的尿素水解法制备不同结构的CeOHCO3和CeO2,并运用N2吸附-脱附、X射线衍射、H2程序升温还原、O2程序升温脱附、X射线光电子能谱、扫描电镜及甲烷燃烧反应对CeO2催化剂进行表征和催化性能测试.结果表明,CeO2催化性能和前驱体CeOHCO3的晶相结构(六方相或八面体相)存在直接关系.与以八面体为前驱体制得的颗粒状CeO2相比,以六方相为前驱体制得的棒状CeO2具有比表面积大、氧化还原能力强、表面氧空缺浓度高以及催化甲烷燃烧活性高的特点.     

MgO催化剂上以H2O2为氧源的苯乙烯环氧化反应

采用直接焙烧Mg(NO3)2·6H2O制备了固体MgO催化剂,并以H2O2为氧源,乙腈为溶剂,考察了其对苯乙烯环氧化反应的催化性能.运用X射线衍射、N2吸附-脱附、热重和CO2程序升温脱附对催化剂进行了表征.结果表明,MgO表面碱的强度在苯乙烯环氧化反应中起主导作用,而其表面的碱量、比表面积及孔体积等的影响较小.经75...     

碳球为模板水热合成Mg-Co复合氧化物及其催化分解N_2O（英文）

用自制的碳球为模板剂,尿素为沉淀剂,120℃水热合成尖晶石型Mg-Co复合氧化物(MgCo_2O_4),在其表面浸渍K_2CO_3溶液制得K改性催化剂,用于催化分解N2O。用X射线衍射(XRD)、N2物理吸附-脱附、扫描电镜(SEM)、H2程序升温还原(H2-TPR)、O2程序升温脱附(O2-TPD)、X射线光电子能谱(XPS)等技术对催化剂进行结构表征,考察了钴镁离子/碳球的质量比、尿素/钴镁离子的物质的量比等制备参数对催化剂活性的影响。结果表明,钴镁离子/碳球的质量比为0.192、尿素/钴镁离子的物质的量比为2,制得的MgCo_2O_4催化剂活性较高。K改性MgCo_2O_4催化剂在400℃有氧无水、有氧有水条件下连续反应50 h,N2O转化率分别保持在91%和62%,稳定性较好。     

静电纺丝法制备MgO纳米纤维

以聚乙烯醇(PVA)作为络合剂与醋酸镁反应制得前驱体，采用静电纺丝法制得聚乙烯醇(PVA)／醋酸镁复合纤维，经焙烧后得到分布均匀、具有较高比表面积和多孔结构的。MgO纳米纤维．对所制得的纳米纤维的结晶度、纯度和表面形貌，分别采用X射线粉末衍射、差热一热重分析(TG-DTA)、红外光谱(IR)、扫描电镜(SEM)等分析测试手段进行了表征．结果表明，煅烧温度对纳米纤维的结晶度和形貌有很大影响．     

共沉淀法制备氧化铝负载Co-Mo双金属氮化物催化剂

采用硝酸铝和硝酸钴的乙醇溶液与钼酸铵的碳酸铵水溶液共沉淀制备了Al2O3负载Co-Mo双金属氧化物前驱体,结合氨程序升温还原法制得了氮化物催化剂Co-Mo-N/Al2O3.利用X射线衍射和N2物理吸附方法表征了制备的前驱体和钝化态Co-Mo-N/Al2O3催化剂的晶相和孔结构,用程序升温脱附、程序升温表面反应及扫描电子显微镜考察了共沉淀法和浸渍法制备的催化剂的晶格稳定性、活性中心和表面形貌,用氨分解反应表征了Co-Mo-N/Al2O3催化剂的活性.结果表明,焙烧温度对催化剂比表面积有较大影响,低温焙烧的样品中活性组分散性较好,673K焙烧制得催化剂的氨分解活性最高.与浸渍法制备的Co-Mo-N/Al2O3催化剂相比,共沉淀法制备的催化剂具有更高的晶格稳定性、更均匀的活性组分分布和更高的氨分解活性.     

低温固相法制备高比表面积的纳米MgO

 以草酸和乙酸镁为原料,采用低温固相化学反应合成出前体MgC2O4·2H2O, 再通过焙烧得到纳米MgO. 采用X射线衍射、 N2物理吸附、透射电镜和热重-差热技术对前体和MgO样品进行了表征,并考察了焙烧气氛的影响. 结果表明,在流动干燥的氮气中520 ℃焙烧4 h后制得了比表面积高达412 m2/g的纳米MgO; 此MgO为面心立方结构,晶粒尺寸为4～5 nm, 粒子堆积成在一定程度上长程有序的介孔结构,并具有十分优良的抗高温烧结性能, 600和800 ℃焙烧2 h后,其比表面积仍分别高达357和153 m2/g.     

载体对钯催化剂催化苯酚加氢制环己酮性能的影响

分别以MgO,-γAl2O3和镁铝水滑石(HT)为载体,PdCl2为活性金属前驱体,采用等体积浸渍法制得Pd质量分数为0.5%的Pd/MgO,Pd/Al2O3和Pd/HT催化剂,考察了它们对苯酚加氢制环己酮的催化活性和选择性.采用X射线衍射、N2吸附、H2程序升温脱附、CO2程序升温脱附和X射线光电子能谱等手段对这些催化剂进行了表征,并与催化活性和选择性关联.实验结果表明,载体的平均孔径越大,催化剂的表面Pd含量越高,催化剂表面的碱中心越多,则越有利于氢和苯酚在催化剂表面的吸附,从而提高苯酚的转化率和环己酮选择性.在反应温度为130℃,H2与苯酚摩尔比为4,LHSV为0.19 h-1的条件下,0.5%Pd/HT催化剂上苯酚的转化率可达90%,环己酮的选择性可达97%以上.     

新型介孔SO4^2-/TiO2固体酸的制备及其催化酯化性能

以无定形高比表面积水合钛酸(H2Ti2O5·xH2O)为载体,采用等体积浸渍法制备了新型晶须状介孔SO42-/TiO2固体酸催化剂,利用X射线衍射、N2吸附-脱附、扫描电镜、红外光谱、热重和氨程序升温脱附等技术考察了催化剂的结构特征和表面酸性及其对乙酸与正丁醇液相酯化反应的催化活性.结果表明,SO42-/TiO2同体酸催化剂不仅具有纳米级晶粒、晶须状形貌、高比表面积和介孔结构,还保持了完善的锐钛矿晶型、较强的酸性和较高的热稳定性;当焙烧温度高于500℃时,催化剂表面结合的SO42-逐渐流失,酸中心数逐渐减少.在m(催化剂)=0.2 g、n(正丁醇)/n(乙酸)=1.5和反应时间3 h条件下,500℃焙烧的催化剂活性最高,正丁醇转化率达94%,乙酸正丁酯选择性为100%,且催化性能和分离沉降性能均优于SO42-/P25催化剂.     

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%.     

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.     

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.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.