Stabilization of Cu/ZnO Based Catalysts by Nickel Additive in Methanol Decomposition

A series of Cu/Zn based catalysts with and without Ni, prepared by the co-precipitation method, has been studied for methanol decomposition. CO and H2 are the major products. The Cu/Zn catalysts show a low initial activity and a poor stability. The formation of the CuZn alloys was observed in the deactivated Cu/Zn catalysts which were used for methanol decomposition at 250 . When small amounts of Ni were added in the catalyst, the Cu/Zn/Ni(molar ratio 5/4/ x) catalysts showed a high activity at a low temperature. The activity and the stability of the catalyst depend on the nickel content. The activity of the Cu/Zn/Ni catalysts was maintained at a. relatively stable value of 78% conversion of methanol with 95% selectivity of H2, 93% selectivity of CO, and a more than 70% yield of hydrogen was obtained at 250 C when x >1. The stability of the Cu/Zn/Ni (molar ratio 5/4/x) catalysts showed the maximum (ca 88%) when x=1. The stabilization effect of nickel on the Cu/Zn based catalysts may lead to the increasin     

A Thermodynamic Model for Square-well Chain Fluid: Theory and Monte Carlo Simulation

A thermodynamic model for the freely jointed square-well chain fluids was developed based on the thermodynamic perturbation theory of Barker-Henderson, Zhang and Wertheim. In this derivation Zhang's expressions for square-well monomers improved from Barker-Henderson compressibility approximation were adopted as the reference fluid, and Wertheim's polymerization method was used to obtain the free energy term due to the bond connectivity. An analytic expression for the Helmholtz free energy of the square-well chain fluids was obtained. The expression without adjustable parameters leads to the thermodynamic consistent predictions of the compressibility factors, residual internal energy and constant-volume heat capacity for dimer, 4-mer, 8-mer and 16-mer square-well fluids. The results are in good agreement with the Monte Carlo simulation. To obtain the MC data of residual internal energy and the constant-volume heat capacity needed, NVT MC simulations were performed for these square-well chain fluids.     

Propylene Polymerization Catalyzed by Bis(R_3-indenyl) Zirconium Dichloride/Aluminoxane──Synthesis of Metallocenes and Influence ofSolvent Polarity on Polymerization

Three unbridged metallocenes, bis(2,4,7-Me3-indenyl)zirconium dichloride(1) , bis(2-Me-4, 7-Et2-indenyl)zirconium dichloride (2) and bis (2, 4, 6-Me3-indenyl) zirconium dichloride (3) were synthesized. The effect of solvent polarity on propylene polymerization catalyzed by the metallocenes in the presence of methylaluminoxane(MAO) and triisobutylaluminum(TIBA) was investigated in the toluene/CH2Cl2 mixed solvent. Changing the solvent polarity was found to influence the catalytic activity, polymer molecular weight and stereospecificity of the catalysts. The changes in the position of the substituents on the ligand caused the different responses of the catalyst to the changes in solvent polarity. The isotactic stereosequence of polypropylene was found to increase with the increase in the polarity of the reaction medium.     

Studies on the Basic Conformation of Lysozyme by Electrospray Ionization-Mass Spectrometry (ESI- MS)

In the present work, 2-mercaptoethanol and dithiothreitol were used to hydrogenise the internal disulfide bond in lysozyme. The experimental results indicate that the charge distribution of the proteins are different in the reaction process. From the calculated molecular weight, the reduction process of the disulfide bond in the molecules can be described, and the number of the disulfide bonds in the molecule can also be determined.     

Asymmetric Synthesis of (3R, 5R)-3-((tert-Butyldimethylsily)oxy)-5-((Z)-2-Bromovinyl)-Tetrahydro-Furan-2-one, an Intermediate for the Synthesis of Fostriecin

Fostriecin(CI-920) 11 a potential anticancer agent presently in phase I clinical trials at NCI is a novel phosphate ester produced by Streptomyces pulveraceus. Scheme 1 1 2 3 5 4 Synthesis of C10 epimer of compound 1 had been reported by Just G2. during the determination of its structure. On the basis of Just’s synthesis, a revised retro-asymmetric synthetic route of Fostriecin (scheme 1) was designed here of which compound 3 was synthesized from 5 with C3 in R configuration correspondi…     

Synthesis of Bis 〔bis (tert-butylcyclopentadienyl) neodymium chloride〕 and Structural trend of Bis〔bis(tertbutylcyclopentadienyl) lanthanide chloride〕

１　ＩＮＴＲＯＤＵＣＴＩＯＮＢｉｓｃｙｃｌｏｐｅｎｔａｄｉｅｎｙｌｌａｎｔｈａｎｉｄｅｃｈｌｏｒｉｄｅｓｆｏｒａｌｌｔｈｅｌａｎｔｈａｎｉｄｅｅｌｅｍｅｎｔｓｈａｖｅｂｅｅｎｓｙｎｔｈｅｓｉｚｅｄａｎｄｓｔｒｕｃｔｕｒａｌｌｙｃｈａｒａｃｔｅｒｉｚｅｄ〔１〕．Ｔｅｒｔ－ｂｕｔｙｌｃｙｃｌｏｐｅｎｔａｄｉｅｎｙｌｉｓａｓｕｉｔａｂｌｅｌｉｇａｎｄｆｏｒｐｒｅｐａｒａｔｉｏｎｏｆｌａｎｔｈａｎｏｃｅｎｅｃｈｌｏｒｉｄｅｓ．Ｔｈｅｓｙｎｔｈｅｓｅｓａｎｄｍｏｌｅｃｕ－ｌａｒｓｔｒｕｃｔｕｒｅｓｏｆ〔（…     

Crystal Structure of 1-Methyl-5-phenylhydantoin

1　INTRODUCTIONInourinvestigationofhemithioacetals,wediscoveredthatα-benzoylhemithioac-etalisquitestableandhastwoelectrophilicsitesthatcanreactwithalkylureastoformahydantoinring[1].Althoughthehydantoinringitselfdoesnotpresentanymedicinalactivity,somedisubstitutedhydantoinshavebeenwidelyusedasmedicineforitsregulareffectonthebioelectricactivityofthenervoussystem.Inordertoim-proveandexpandtheactivityaswellastopreventsideeffects,variouskindsofhy-dantoinderivativeshavebeenpreparedandtested[2].…     

3,4-二硒方酸芳香性和气相酸性的理论研究

在ＲＨＦ／６－３１１Ｇ水平优化得到３,４－二硒方酸（３,４－二氢硒基－３－环丁烯－１,２－二酮）３ 种平面构象异构体的平衡几何构型。进一步用ＭＰ２（ｆｕｌｌ）／６－３１１Ｇ／／ＲＨＦ／／６－３１１Ｇ方法计算单点能量,发现ＺＺ型异构体是能量最低构象,且ＺＺ和ＺＥ型能量非常接近。用优化的最稳定构象ＺＺ型异构体在ＲＨＦ／６－３１１Ｇ／／ＲＨＦ／６－３１１Ｇ、ＲＨＦ／６－３１１＋ Ｇ／／ＲＨＦ／６－３１１＋ Ｇ、ＭＰ２（ｆｕｌｌ）／６－３１１＋ Ｇ／／ＲＨＦ／６－３１１＋ Ｇ 和Ｂ３ＬＹＰ／６－３１１＋ Ｇ／／Ｂ３ＬＹＰ／６－３１１＋ Ｇ水平计算其气相酸性（ΔＧ°）和同键反应芳香性稳定化能（ＨＡＳＥ）。用基团加和法（ｇｒｏｕｐ ｉｎｃｒｅｍ ｅｎｔ ａｐ－ｐｒｏａｃｈ ） 在 ＲＨＦ／６－３１１ ＋ Ｇ／／ＲＨＦ／６－３１１ ＋ Ｇ 和 Ｂ３ＬＹＰ／６－３１１ ＋ Ｇ／／Ｂ３ＬＹＰ／６－３１１＋ Ｇ水平计算其磁化率增量（Λ）。计算结果指出标题化合物的同键反应芳香性稳定化能和磁化率增量均为负值,表明它具有芳香性,实现了标题化合物芳香性的几何、能量和磁性的判定。     

Synthesis and Structural Investigation of ｛CpEu〔CH(COOC_2H_5)_2〕〔μ-CH(COOC_2H_5)_2〕｝_2

１ＩＮＴＲＯＤＵＣＴＩＯＮＯｒｇａｎｏｌａｎｔｈａｎｉｄｅｃｏｍｐｌｅｘｅｓｉｎｖｏｌｖｉｎｇｂｏｔｈｃｙｃｌｏｐｅｎｔａｄｉｅｎｙｌａｎｄβ ｄｉｋｅｔｏｎａｔｏｃｈｅｌａｔｅｌｉｇａｎｄｓｈａｖｅｂｅｅｎｓｙｎｔｈｅｓｉｚｅｄ〔１ ４〕,ａｎｄｏ...     

Crystal Structure of Copper(Ⅱ) Complex with 3-Hydroxyl-1,5-diazacycloheptane-N,N'-diacetate

１ＩＮＴＲＯＤＵＣＴＩＯＮＡｌｏｔｏｆｓｔｕｄｉｅｓｈａｖｅｒｅｖｅａｌｅｄｔｈａｔｍｅｓｏｃｙｃｌｉｃｄｉａｍｉｎｅｓａｎｄｔｈｅｉｒｄｅｒｉｖａｔｉｖｅｓａｒｅｖｅｒｓａ ｔｉｌｅｃｈｅｌａｔｉｎｇａｇｅｎｔｓａｎｄｔｈｅｙｓｈｏｗｅｄｕｎｕｓｕ...