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Journal of Rare Earths 2013年第5期31卷 477-484页

作者： Azhagapillai Prabhu Ahmed Al Shoaibi Chandrasekar Srinivasakannan Muthaiahpillai Palanichamy velayutham murugesan Department of Chemical Engineering The Petroleum InstituteAbu DhabiUAE Department of Chemistry Anna University

Cerium incorporated KIT-6 mesoporous materials were synthesized through direct hydrothermal method and characterized by using X-ray diffraction （XRD）, nitrogen sorption isotherm （BET）, Fourier transform infrared spectroscopy （FT-IR）, inductively coupled plasma - atomic emission spectroscopy （ICP-AES）, diffuse reflectance ultraviolet visible spectroscopy （DRS-UV-Vis）, ther- mogravimetric analysis （TGA）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM） methods. It ap- peared that stable cerium ions were inserted into the silica framework of KIT-6, thus generating acid properties in their host materials. The catalytic activity of Ce-KIT-6 materials was evaluated in the vapor phase dehydration of cyclohexanol to cyclohexene and dicy- clohexyl ether at different temperatures with various Si/Ce molar ratios. Ce-KIT-6 （25） showed higher activity with 54% cyclohexa- nol conversion and 64% selectivity to cyclohexene. The catalytic results indicated that Ce-KIT-6 mesoporous materials could be used as versatile and stable acid catalysts.

关键词： Ce-KIT-6 dehydration eyclohexanol cyclohexene dicyclohexyl ether rare earths

CeAlPO-5分子筛催化剂上二苯基甲烷选择性氧化生成二苯甲酮(英文)

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催化学报 2012年第7期33卷 1086-1094页

作者： Subbiah DEVIKA Muthiahpillai PALANICHAMY velayutham murugesan Department of Chemistry Anna University

Selective oxidation of diphenylmethane to benzophenone requires active and selective catalysts. The framework incorporation of cerium in AlPO-5 molecular sieves creates active cerium sites in isolation. These active sites are responsible for selective oxidation. Cerium incorporated AlPO-5 with different Al/Ce ratios were synthesized, and the vapor phase oxidation of diphenylmethane in air over these catalysts was studied at 250, 275, 300, 325, and 350 °C. The diphenylmethane conversion and selectivity for benzophenone were more than 90%. CeAlPO-5(25) was found to be more active than other catalysts. The stability of the catalyst was verified by the time on stream study which indicated steady diphenylmethane conversion and benzophenone selectivity. Hence framework incorporated CeAlPO-5 molecular sieves are stable and active catalysts for the selective oxidation of diphenylmethane.

关键词： CeAlPO-5 molecular sieve hydrothermal synthesis oxidation diphenylmethane benzophenone

Al-MCM-48分子筛对苯酚与乙酸异丙酯异丙基化反应的催化性能(英文)

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催化学报 2012年第3期33卷 478-486页

作者： Kandan VENKATACHALAM Pitchai VISUVAMITHIRAN Balachandran SUNDARAVEL Muthiapillai PALANICHAMY velayutham murugesan Department of Chemistry Anna University

Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethyl-ammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffraction patterns and transmission electron microscopy images. The catalytic performance of the materials was evaluated in the vapor phase isopropylation of phenol with isopropyl acetate. Phenol conversion decreased with the increase in the Si/Al ratio of the catalysts. The major reaction product was 4-isopropyl phenol with 78% selectivity. The delocalization of phenolic oxygen electron pair over the aromatic ring promoted para-selective alkylation. Such delocalization could be aided by the hydrophilic surface of the molecular sieves. Although an ester was used as the alkylating agent, phenyl isopropyl ether was not formed in the reaction.

关键词： MCM-48分子筛异丙基苯酚醋酸异丙酯催化性能十六烷基三甲基溴化铵透射电子显微镜反应产物水热法合成

ZSM-5沸石结晶度对乙苯叔丁基化对位选择性的影响(英文)

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催化学报 2013年第2期34卷 294-304页

作者： PUSHPARAJ Hemalatha MANI Ganesh MUTHIAHPILLAI Palanichamy velayutham murugesan PARK Yong-Ki CHOI Won Choon JANG Hyun Tae Department of Chemical Engineering Hanseo University Seosan-si 356 706 South Korea Department of Chemistry Anna University Chennai 600 025 India Green Chemistry Research Division Korea Research Institute of Chemical Technology Jang-dong 100. Daejeon 305 600 South Korea

Highly crystalline ZSM-5 zeolites are important for para-selective alkylation of alkyl aromatics, because they carry few external acid sites for isomerization of p-dialkyl products. Such zeolites (Si/Al = 25, 50, and 75) were synthesized in a fluoride medium between pH 4 and 6. Their crystallinities, crystal sizes, and surface areas were higher than those of a commercial ZSM-5 zeolite. Their para selectivities in alkylation were tested for vapor-phase tert-butylation of ethylbenzene between 200 and 400 °C. As expected, all the catalysts showed more than 90% para selectivity. At 300 °C, ethylbenzene conversion decreased in the order ZSM-5(25, commercial) > ZSM-5(25) > ZSM-5(50) > ZSM-5(75). The catalysts had weak, medium, and strong acid sites, but all the acid sites of ZSM-5(75) were weaker than those of ZSM-5(25) and ZSM-5(50). The high activity of commercial ZSM-5 was caused by its strong acid sites being stronger than those of the synthesized zeolites. Although the activity of the commercial catalyst was higher than those of the present catalysts, the selectivity for 4-t-butylethylbenzene (4-t-BEB) was low. The optimum feed ratio (ethylbenzene:t-butyl alcohol) was 2:1 and the feed rate was 1.65 h?1 for high ethylbenzene conversion and 4-t-BEB selectivity. Time-on-stream studies showed slow catalyst deactivation. Highly crystalline ZSM-5 zeolites are therefore better than a commercial zeolite for para-selective alkylation of alkyl aromatics. They do not require much post-modification for high para selectivity. A fluoride medium is therefore better than an alkaline medium for obtaining highly crystalline para-selective ZSM-5 zeolites.

关键词： ZSM-5 Fluoride medium P-selectivity Ethylbenzene Tert-butylation Zeolite