检索结果-南通市图书馆

Oxidative Methylation of Toluene with Methane over Basic Zeolite Catalysts Promoted with Alkali Metal Bromides and Alkali Metal Oxides

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2000年第9期11卷 827-830页

作者： Ling Ping ZHOU Wei LI Ke Yi TAO Xuan Wen LI He Xuan LI college of chemistry and molecular engineering, peking university, {2. Department of chemistry, Nankai university, Tianjin 300071 peking Univ Coll Chem & Mol Engn Beijing 100871 Peoples R China Nankai Univ Dept Chem Tianjin 300071 Peoples R China

The catalytic effects for the oxidative methylation of toluene with methane over the basic zeolite catalysts prepared by promoting KY, KX, KM, KZSM-5 or KP with alkali-metal bromides and alkali-metal oxides have been investigated comparatively. The alkali-metal bromides promoted substrates are more effective than the alkali-metal oxides promoted systems. Moreover, the NaBr promoted systems are more active than KBr promoted systems. The most effective catalytic system (8wt%NaBr)/KZSM-5 gave a toluene conversion as high as 76.3% and a total C-8 selectivity of 76.4% (styrene/ethylbenzene=9.76) resulting in a total C-8 yield of 58.3%.

关键词： styrene methane oxidative methylation alkali-metal oxides alkali-metal bromides

SYNTHESIS OF MESOPOROUS POLY(STYRENE-co-MALEIC ANHYDRIDE)/SILICA HYBRID MATERIALS VIA A NONSURFACTANT-TEMPLATED SOL-GEL PROCESS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2000年第5期18卷 469-472页

作者： Jie-bin Pang Kun-yuan Qiu Yen Wei Department of Polymer Science and engineering, {2., peking university, beijing 100871, china. Department of chemistry, Drexel university, Philadelphia, Pennsylvania 19104, USA. peking Univ Coll Chem & Mol Engn Dept Polymer Sci & Engn Beijing 100871 Peoples R China Drexel Univ Dept Chem Philadelphia PA 19104 USA

Mesoporous poly(styrene-co-maleic anhydride)/silica hybrid materials have been prepared. The synthesis was achieved by the HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and styrene-maleic anhydride copolymer in the presence of 3-aminopropyl triethoxysilane (APTES) as a coupling agent and citric acid as a nonsurfactant template or pore-forming agent, followed by ethanol extraction. Characterization results from nitrogen sorption isotherms and powder X-ray diffraction indicate that polymer-modified mesoporous materials with large specific surface areas (e.g. 900 m(2./g) and pore volumes (e.g. 0.6 cm(3)/g) could be prepared. As the citric acid concentration is increased, the specific surface areas, pore volumes and pore diameters of the hybrid materials increase.

关键词： mesoporous hybrid material poly(styrene-co-maleic anhydride)/silica citric acid nonsurfactant template sol-gel process

SYNTHESIS AND CHARACTERIZATION OF STRUCTURALLY WELL-DEFINED POLYMER-INORGANIC HYBRID NANOPARTICLES VIA ATRP

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2002年第3期20卷 261-267页

作者： Jie Bai Jie-bin Pang Kun-yuan Qiu Yen Wei Department of Polymer Science & engineering {2. of chemistry & molecular engineering peking university beijing 100871, china Department of chemistry Drexel university Philadelphia, PA 19104 USA peking Univ Coll Chem & Mol Engn Dept Polymer Sci & Engn Beijing 100871 Peoples R China Drexel Univ Dept Chem Philadelphia PA 19104 USA

Atom transfer radical polymerization (ATRP) using cuprous chloride/2.2.-bipyridine (bipy) was applied to graft polymerization of styrene on the surface of silica nanoparticles to synthesize polymer-inorganic hybrid nanoparticles, 2.(4Chloromethylphenyl) ethyltriethoxysilane (CTES) was immobilized on the surface of silica nanoparticles through condensation reaction of the silanol groups on silica with triethoxysilane group of CTES. Then ATRP of St was initiated by this surface-modified silica nanoparticles bearing benzyl chloride groups, and formed PSt graft chains on the surface of silica nanoparticles. The thickness of the graft chains increased with reaction time. End group analysis confirmed the occurrence of ATRP. Thermal analysis indicated that thermal stabilization of these resulting hybrid nanoparticles also increases with polymerization conversion. The results above show that this 'grafting from' reaction could be used for the preparation of polymer-inorganic hybrid nanoparticles with controlled structure of the polymer's end groups.

关键词： atom transfer radical polymerization polymer-inorganic hybrid nanoparticles 2.(4-chloromethylphenyl)ethyltriethoxysilane surface-modification

SYNTHESIS OF HYBRID MESOPOROUS POLYSTYRENE-SILICA MATERIALS WITH NON-SURFACTANT CITRIC ACID AS TEMPLATE VIA SOL-GEL PROCESS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2002年第6期20卷 565-572页

作者： Jie Bai Jin-yu Zheng Kun-yuan Qiu Yen Wei Department of Polymer Science & engineering {2. of chemistry & molecular engineering, peking university beijing 100871, china Department of chemistry, Drexel university, Philadelphia, PA 19104, USA peking Univ Coll Chem & Mol Engn Dept Polymer Sci & Engn Beijing 100871 Peoples R China Drexel Univ Dept Chem Philadelphia PA 19104 USA

Hybrid mesoporous polystyrene-silica materials were successfully prepared through HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and triethoxysilyl-functionalized polystyrene obtained via atom transfer radical polymerization (ATRP) of styrene, in the presence of citric acid (CA) as non-surfactant template or pore-forming agent and followed by ethanol extraction to remove template molecules. The materials were characterized by infrared spectroscopy OR), N-2.adsorption-desorption measurements, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). The results indicate that the materials prepared with 50 wt%-60 wt% template contents have average pore sizes of 2.3 nm and large surface areas (ca. 886 m(2./g) as well as high pore volumes (ca. 0.53 cm(3)/g). The mesoporosity arises from interconnected channels and pores with disordered arrangements. The pore diameters and pore volumes increase as the template content is increased. The pore diameters show a little change upon heating at 2.0degreesC overnight. However, the materials do not have good hydrothermal stability.

关键词： atom transfer radical polymerization hybrid material mesoporous polystyrene silica

Adsorption and corrosion inhibition behavior of imidazole on cobalt electrodes studied by SERS and electrochemical methods

在线全文

学校读者我要写书评

暂无评论

Science china chemistry 2005年第6期48卷 497-503页

作者： GU Wei1, LIU Guokun2. REN Bin2. WU Deyin2. GU Renao1 & TIAN Zhongqun2.1. Department of chemistry, {2. of chemistry and Chemical engineering, Suzhou university, Suzhou 2.5006, china 2. State Key Laboratory for Physical chemistry of Solid Surfaces and Department of chemistry, {2. of chemistry and Chemical engineering, Xiamen university, Xiamen 361005, china 1. Department of chemistry College of Chemistry and Chemical Engineering Suzhou University 215006 Suzhou China 2. State Key Laboratory for Physical chemistry of Solid Surfaces and Department of chemistry College of Chemistry and Chemical Engineering Xiamen University 361005 Xiamen China

The interaction of imidazole with Co electrodes in an electrochemical system was studied by surface-enhanced Raman scattering (SERS) and electrochemical methods. The SER spectra of Co in an imidazole solution as a function of the applied potential were analyzed and the assignment of the Raman bands was made. It was found that there were three kinds of sur-face species on the Co surface in different potential regions and they were interchangeable de-pending on the potential. In a relatively negative potential region (?1.2.to ?0.9 V), imidazole was adsorbed on the surface and its orientation might change from a vertical configuration via the N-end of the pyridine ring to a tilted configuration via the C2.N3 double bond. In a more positive potential region (?0.8 to ?0.7 V), the SERS signal from the adsorbed imidazole weakened and finally disappeared, meanwhile the signal from the Co and imidazole complex strengthened gradually. At the open circuit potential (?0.6 V), we detected very strong bands from the Co ox-ides. By comparing the Tafel curves of the Co electrode in the solution without and with imidazole, we found that imidazole has a marked effect on the corrosion inhibition of the Co electrode. This result demonstrates that we may be able to reveal the complicated interaction of surface species with metal surface at the molecular level by combining the SERS and electrochemical methods.

关键词： cobalt, imidazole, inhibition, surface-enhanced Raman spectroscopy, Tafel plot.

SYNTHESIS AND PROPERTIES OF LIQUID CRYSTAL POLYSILOXANES WITH MESOGENIC STILBENE SIDE GROUPS

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2000年第2期18卷 95-99页

作者： Dong Zhang Yan-tao Zhu Da-hui Zhao Xin-hua Wan Qi-feng Zhou Department of Polymer Science & engineering, {2. of chemistry, peking university, beijing 100871, china peking Univ Coll Chem Dept Polymer Sci & Engn Beijing 100871 Peoples R China

A variety of mesomorphic side-chain polysiloxanes were synthesized by using hydrosilylation reaction with dicyclopentadienylplatinum(II) (DPPC) as the catalyst. The mesogenic groups are derivatives of stilbene with cyano or nitro tail groups. The products were characterized by DSC, X-ray diffraction and polarizing optical microscopy (POM). All the polymers were found to have relatively low T-g and can form a smectic liquid crystal phase.

关键词： liquid crystal polymer polysiloxane

Crystal Structure of Ethyl 4-benzoyl-1a,2.3,4-tetrahydro-3-methyl-1a-（4-methylphenyl）-1H-azirino〔1,2.a〕〔1,5〕 benzodiazepine-1-carboxylate(C2.H2.N2.3)

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Structural chemistry 1999年第4期 27-30页

作者： WANG HongZhongXU JiaXiMI BaoYuJIN Sheng* (college of chemistry and molecular engineering, peking university, {2.)

１ＩＮＴＲＯＤＵＣＴＩＯＮＢｅｎｚｏｄｉａｚｅｐｉｎｅｃｏｍｐｏｕｎｄｓａｒｅｉｍｐｏｒｔａｎｔｐｈａｒｍａｃｅｕｔｉｃａｌａｇｅｎｔｓ〔１，２〕．Ｒｅｃｅｎｔｌｙｉｔｈａｓｂｅｅｎｆｏｕｎｄｔｈａｔｂｅｎｚｏｄｉａ... 详细信息

１ＩＮＴＲＯＤＵＣＴＩＯＮＢｅｎｚｏｄｉａｚｅｐｉｎｅｃｏｍｐｏｕｎｄｓａｒｅｉｍｐｏｒｔａｎｔｐｈａｒｍａｃｅｕｔｉｃａｌａｇｅｎｔｓ〔１，２〕．Ｒｅｃｅｎｔｌｙｉｔｈａｓｂｅｅｎｆｏｕｎｄｔｈａｔｂｅｎｚｏｄｉａｚｅｐｉｎｅｔｒｉｃｙｃｌｉｃｄｅ...

关键词： crystal structure azirino1 2.1 5benzodiazepine 1

Lead (Ⅱ) Binding to Thionein

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 1999年第1期10卷 87-90页

作者： Wei Guo HE De Ying CHU Jing Yue YANG Dan Feng YAO Mei Cheng SHAO(college of chemistry and molecular engineering peking university. {2.) Coll. of Chem. and Molec. Eng. Peking University Beijing 100871 China

Lead (Ⅱ)-binding properties of rabbit liver thionein 2.(apo-MT2. have been *** kinds of complexes. Pb7-MT and Ph7-MT', are observed upon the binding of Ph2. to apo-MTat different PH. From their characteristic peaks in UV and CD spectra. it is deduced that Ph2. inPh7-MT is coordinated by four sulfhydryl groups in Td microsymmetry, while multiplecoordination types including two-coordination maybe present in Ph7-MT'

关键词： Thionein lead (Ⅱ) UV spectra circular dichroism multiple coordination

Microwave-assisted reaction of peptide formation by amino acid with phosphate:Exploration of the most possible channels for the origin of life

在线全文

学校读者我要写书评

暂无评论

Science china chemistry 2006年第4期49卷 351-356页

作者： HU Rong1, TIAN Jinping2.& YIN Yingwu2.3 1. college of chemistry & Environment Protection {2., Southwest university for Nationalities, Chengdu 610041, china 2. TH-UNIS Insight Co., Ltd., beijing 100085, china 3. Key Laboratory of Bioorganic Phosphorus chemistry & Chemical biology, Ministry of Education, Department of chemistry, Tsinghua university, beijing 100084, china 1. college of chemistry & Environment Protection {2. Southwest University for Nationalities Chengdu 610041 China 2. TH-UNIS Insight Co. Ltd. Beijing 100085 China 3. Key Laboratory of Bioorganic Phosphorus chemistry & Chemical biology Ministry of Education Department of Chemistry Tsinghua University Beijing 100084 China

Microwave-assisted reaction of peptide formation by amino acids with phosphate was studied. The results showed that the products were a mixture of peptides containing dipeptide, oc- tapeptides and cyclic peptides, which could be obtained in a short time. Polyphosphate was also produced synchronously by the intermolecular condensation of phosphate. The polymerization de- gree reached 99% (pyrophosphate 64%, trimetaphosphate 35%) after 2.h at 2.0℃ under microwave irradiation. The intermediates of the mixed anhydrides formed by the intermolecular condensation of phosphates and glycin were determined by ESI-MS. Peptides were also produced by the reaction of amino acids with trimetaphosphate in aqueous solution. The conversion degree of valine reached 46.5% even at room temperature. The cyclic process of peptide formation and phosphate polymeri- zation, regeneration and utilization in amino acids-phosphate system under microwave irradiation was detected and proved. Peptides could be continually formed only by inputting energy into this system. The above recycle may be the most possible process for primitive peptide formation in the origin of life.

关键词： microwave, phosphate, amino acid, peptide, origin of life.