V2O5-MoO3-SiO2表面复合氧化物催化剂的制备与表征

采用表面改性法制备了V2O5-SiO2,MoO3-SiO2,V2O5-MoO3-SiO2复合氧化物催化剂,并用TPR和IR技术研究了催化剂的表面结构及V=O,M0=O的活性,同时用化学吸附IR技术研究了催化剂样品对异丁烷的化学吸附性能.实验结果表明:这些复合氧化物催化剂对异丁烷都有较高的化学吸附能力;SiO2能缓解表面Lewis碱位V=O和Mo=O的氧化能力,有利于选择氧化.     

溶胶-凝胶法制备MoO3-CeO2-SiO2氧化脱硫催化剂

采用溶胶.凝胶法制备了MoO3-CeO2-SiO2复合氧化物催化剂,通过X射线衍射、傅里叶变换红外光谱和X射线光电子能谱对催化剂进行了表征.在温和条件(40℃,常压)下,以过氧化羟基异丙苯(CHP)为氧化剂,甲苯为溶剂,二苯并噻吩(DBT)为模型硫化物,在固定床流动反应器上考察了该复合氧化物催化剂的氧化脱硫反应性能,并研究了催化剂中Mo/Si和Ce/Si摩尔比对反应活性的影响.结果表明,Mo物种主要以MoO3的形式存在,最佳Mo/Si和Ce/si摩尔比分别为0.1和0.02.适量CeO2的引入可以提高SiO2上MoO3的分散度.不含CeO2的催化剂中钼主要以高价态的钼离子(Mo6+)存在,添加CeO2后,可能有一定量的低价态的钼离子(MO3+)生成,MoO3-CeO2-SiO2催化剂高的氧化脱硫活性可能与Mo5+的存在有关.     

NiO-MoO3/SiO2光催化剂的结构与光吸收性能

采用表面改性法制备了负载型复合半导体NiO-MoO3/SiO2, 用程序升温还原、 X射线衍射、 拉曼光谱、 透射电镜、 比表面积测定和紫外-可见光漫反射光谱技术对固体材料的组成结构和光吸收性能进行了表征. 结果表明, NiO-MoO3/SiO2的平均粒径约为10 nm, 在载体表面存在xNiO·MoO3复合氧化物的微晶, NiO和MoO3在固体材料表面产生相互修饰作用. NiO的加入有助于提高MoO3在载体SiO2表面的分散程度, 抑制MoOx的聚合, 减小微晶尺寸, 而且可以增强固体材料的光吸收性能, 提高复合半导体对光能的利用率.     

光促甲烷和水合成甲醇和氢催化剂的研究

用表面改性法制备TiO2/SiO2，以等体积浸渍法制备负载型复合半导体催化剂(MoO3,ZnO)-TiO2/SiO2，通过XRD、BET、TPR、IR、UV-Vis DRS和TPD等技术对材料的表面形态结构、吸光特性、化学吸附性能及光催化甲烷和水的反应性能进行了表征和分析。结果表明，MoO3-TiO2/SiO2和ZnO-TiO2/SiO2的表面物种均具有显著的量子尺寸效应，在表面分别形成Mo—O—Ti和Zn—O—Ti复合结构；MoO3和TiO2在载体表面的复合可提高对光能的利用率并可增强对甲烷的化学吸附性能， 结果使得MoO3-TiO2/SiO2的光催化反应性能明显优于ZnO-TiO2/SiO2；在固定床环隙反应器中，150℃MoO3-TiO2/SiO2光催化气相甲烷和水合成了目的产物甲醇和氢，甲醇的选择性达到87.3％。     

Cu/NiO-MoO3/SiO2光催化CO2与CH3OH合成碳酸二甲酯的反应性能

 采用表面改性法制备了MoO3-SiO2复合氧化物,用等体积浸渍法制备了Cu/NiO-MoO3/SiO2光催化剂,并用XRD, Raman, IR, TPD-MS, UV-Vis DRS和光促表面反应研究了催化剂的结构、化学吸附性能、吸光性能和光促CO2与CH3OH合成碳酸二甲酯(DMC)的反应性能. 结果表明, Cu和NiO的引入提高了MoO3在SiO2表面的分散度,且Cu和NiO在MoO3-SiO2表面分散均匀; 在金属Cu位和Lewis酸位Mo6+(或Ni2+)的协同作用下, CO2在催化剂表面形成活性较高的的卧式吸附态, CH3OH在催化剂表面形成分子吸附态和解离吸附态; NiO与MoO3复合后部分形成了 Mo-O-Ni 键联,提高了对光的吸收强度; 金属Cu的负载扩展了材料在可见光范围的吸收; 与热表面催化相比,光催化反应在较低的温度下就能显著进行,并提高了CH3OH的转化率,在110 ℃常压和空速300 h-1的条件下,CH3OH转化率可达13.9%,DMC选择性可达90.1%.     

铋钼复合氧化物表面上激光促进异丁烷选择氧化制甲基丙烯酸

 用共沉淀法制备了Bi和Mo的复合氧化物固体材料．运用XRD,IR,TPD和激光促进表面反应（LSSR）技术研究了其晶体结构、表面构造、化学吸附特性和激光促进异丁烷选择氧化反应性能．结果表明：Bi－Mo－O复合氧化物含有α－Bi2Mo3O12和少量γ－Bi2MoO6晶相;其表面上存在着Lewis碱位（MoO和Mo—O—Bi键中的O）及Lewis酸位（Bi3＋）;异丁烷的两个甲基H分别吸附在两个相邻的Lewis碱位MoO上,形成双位分子吸附态;在常压和200℃条件下,用一定频率的激光激发MoO键1000次,异丁烷的转化率可达11．2％,其反应产物是异丁烯、甲基丙烯醛和甲基丙烯酸,其中甲基丙烯酸的选择性为90％．根据实验结果,探讨了激光促进异丁烷选择氧化为甲基丙烯酸的表面反应机理．     

Mo-P-O/SiO2催化剂上的异丁烷选择氧化反应

 采用溶胶－凝胶法制备了MoO3／SiO2和Mo－P－O／SiO2催化剂，用X射线衍射、红外光谱、程序升温还原、程序升温脱附和活性评价等手段研究了催化剂的表面结构、晶格氧活泼性、化学吸附性能以及异丁烷选择氧化反应性能．结果表明，活性组分在催化剂表面分散较好；异丁烷吸附在催化剂表面Lewis碱位的MoO端氧上形成分子吸附态；MoO3／SiO2和Mo－P－O／SiO2两种催化剂对异丁烷选择氧化都有较好的选择性，将PO3－4引入到MoO3／SiO2催化剂中可提高含氧化合物的选择性     

MoO3-TiO2/SiO2上光促表面催化甲烷和水合成甲醇和氢气

用分步等体积浸渍法制备了负载型复合半导体催化剂MoO3-TiO2/SiO2,通过XRD,BET,TPR,IR,UVDRS和TPD等手段对其进行了表征,结果表明,活性组分在载体表面高度分散,并具有量子尺寸效应,吸光阈值显著蓝移;TiO2在SiO2表面分散可增强MoO3与载体的相互作用,调变吸光性能,所形成的表面活性基元能够有效地吸附活化甲烷和水.在100℃下利用固定床环隙反应器借助紫外光的激发,通过“光-表面-热”协同作用,气相甲烷和水在MoO3-TiO2/SiO2表面生成了甲醇和氢,选择性达到85.6%.     

SiO2负载MoVNbO复合氧化物催化剂上乙烷低温氧化制乙酸

 采用有机金属络合物浸渍表面反应技术制备了SiO2为载体的复合氧化物催化剂Mo3V1Nb0.3Ox/SiO2,并用N2吸附,IR,UV-Vis,TPR和微反技术研究了催化剂的表面结构、晶格氧的活性和对乙烷选择氧化反应的性能. 实验结果表明,复合氧化物与SiO2表面以M-O-Si键连接,金属离子处在四面体和八面体配合物结构之中;含铌的表面复合氧化物中晶格氧的活性明显提高. 在252 ℃,0.5 MPa和空速 2000 h-1的反应条件下,乙烷与氧在Mo3V1Nb0.3Ox/SiO2催化剂上发生反应,生成乙酸和乙醛,乙烷的转化率达16.1%,产物乙酸和乙醛的总选择性为90.3%.     

不同Si/Al比对Mo/ZSM-5催化性能的影响

采用浸渍法在不同Si／Al比的HZSM-5上制备了3种MoO3含量相同的Mo／ZSM-5样品，并在相同的实验条件下对其进行了活性测试，同时运用XRD、XPS、NO—TPD等技术分别对催化剂的体相和表面结构进行了表征．实验结果表明，Si／Al比对Mo／ZSM-5上NO的选择性催化还原性能有明显的影响，Si／Al比为28的1#样品其转化率在530℃达到94％以上，而Si／Al比较大的2#和3#样品最高转化率只有48％和41％．对3种Mo／ZSM-5样品的XRD表征只发现有HZSM-5和MoO3两种物相存在，分子筛骨架差异不大；而XPS表征却发现1#样品的表面M03d5／2含量远大于2#和3#样品，并且有Mo^4 和(或)Mo＼ 5 存在，表明3种样品的表面性质存在很大差异．在3种样品中，1#样品具有最大的NO吸附能力，这与表面特性差异相吻合．     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.