論文

Transition metal catalysts in various liquid polymer media supported on silica gel were prepared and used for vapor-phase hydrosilylation. Tetraammineplatinum(II) chloride and potassium hexachloroplatinate(IV) in a polyethylene glycol (PEG) medium showed high and stable activity. Deactivation of the catalyst was not observed unless a high platinum concentration in PEG was used. When the amount of PEG was 40 vol% of the pore volume of silica gel, PEG was coated on the pore walls of the silica gel, and did not block the pore openings. Active species in the PEG were formed only during the reaction.

Pd(II) chloride and Cu(II) chloride in various liquid polymer media supported on silica gel were prepared and used in a catalyst system for vapor-phase synthesis of acetaldehyde by Wacker-type oxidation of ethylene. This catalyst system supported on silica gel prepared by impregnation was quickly deactivated, while use of polyethylene glycol (PEG) as a liquid polymer medium supported on silica gel showed stable catalytic activity. PEG inhibited the formation of Pd metal particles, which deactivate the catalyst system. Addition of alkali metal salts, especially LiCl, to the PdCl(2)-CuCl(2) catalyst system with PEG enhanced catalytic activity for 22 h, even when the I'd content was high, leading to high activity but poor stability. LiCl also inhibited the formation of metal particles. (C) 2008 Elsevier Inc. All rights reserved.

東京工業大学では,工学部応用化学系学科,理学部化学科,総合理工学研究科化学系研究室の3つのグループが2年ずつ持ち回りで一日体験化学教室を開催している。初回開催の1990年から14年間を経て,現在の体験教室の形となった。本稿では,2004年に行った工学部応用化学系学科主催の一日体験化学教室の内容を紹介する。また,体験教室の準備段階で明らかとなった問題点とその解決策,および開催後に新たに明らかとなった問題点を示し,2005年の体験教室に向けての対策を紹介する。

The authors studied Meerwein-Ponndorf-Verley (MPV) reduction of crotonaldehyde using batch and tubular flow reactors. Various ZrO2/SiO2 catalysts prepared from commercially available carriers and precursors were subjected to activity testing using autoclave batch reactors. To determine the degree of Zr dispersion in the ZrO2/SiO2 catalysts, X-ray photoelectron spectroscopy (XPS) measurements and the benzaldehyde-ammonia titration (BAT) method were carried out. The results suggested a positive correlation between Zr dispersion and crotonaldehyde conversion. Durability tests using tubular flow reactors were performed with the most suitable catalyst, which was selected through batch reactions and catalyst characterizations. Almost no degradation of the catalytic activity was observed over 2,200 h in a liquid-phase reaction, while catalyst durability was short in a gas-phase reaction. It was surmised that in the liquid-phase, 2-propanol (hydrogen donor) in the feed had dissolved the reaction byproducts to purge from the catalyst. In addition, a continuous process flow design that includes 2-propanol regeneration was proposed for industrial production.

A core-shell, carbon-filled zeolite@zeolite was created through the epitaxial growth of shell zeolite on a core zeolite filled with carbon. The catalytic dehydrations of alcohols on the core-shell structure were enhanced under microwave irradiation by comparison with conventional heating using an oil bath at the same solution temperatures; however, the dehydrations on the sole core zeolite were not enhanced under microwave irradiation, which indicated the presence of a higher temperature area in the shell near the border with the core. The core-shell structure exhibited thermal non-equilibrium with microwave irradiation because of the extremely different dielectric losses of the core and the shell; that is, the carbon in the core generated much heat from microwaves, but the shell did not. (C) 2014 Elsevier Inc. All rights reserved.

Cyclooligosiloxanes, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane were efficiently deoligomerized with dimethyl carbonate using an alumina-supported potassium fluoride catalyst under a continuous vapor-phase flow condition to form dimethoxydimethylsilane monomer. In the deoligomerization of larger cyclooligosiloxanes, the catalyst was deactivated. The addition of a small amount of methanol suppressed the deactivation. These results strongly suggest a new method for recycling silicone via monomers.

Hexamethyldisiloxane and hexamethylcyclotrisiloxane were almost completely deoligomerized with dimethyl carbonate over alumina-supported potassium fluoride catalyst to form methoxytrimethylsilane (85% yield) and dimethoxydimethylsilane (94% yield), respectively, and moreover the addition of a small amount of methanol to the hexamethyldisiloxane deoligomerization reaction enhanced the methoxytrimethylsilane yield to 98%.

The disproportionation of triethoxysilane was carried out in a fixed-bed flow reactor over the solids obtained by heat-treating calcium hydroxide at various temperatures. In the disproportionation, the reaction proceeding to completeness to afford silane and tetraethoxysilane occurs to far lesser extent: predominantly diethoxysilane is obtained together with tetraethoxysilane. Dimethoxysilane is obtained by the disproportionation of trimethoxysilane also over the heat-treated calcium hydroxide.

The reaction of metallic silicon with methanol in the presence of an allyl alkyl ether affords an organosilicon compound, the reaction giving a unique method of synthesizing organosilicon compounds without using organic halides.

Alkoxysilanes can be synthesized from silicon or silicon oxide. For example, trimethoxysilane is formed directly from silicon by reaction with methanol vapor using copper(I) chloride as a catalyst. Silica gel supporting catalytic component, such as potassium hydroxide, reacts with dimethyl carbonate vapor to form tetramethoxysilane. Rice hull ash can also be used as a silica source, the ash reacting with dimethyl carbonate vapor, even in the absence of a catalyst. These reactions are gas-solid reactions. The rate of alkoxysilanes formation was measured and the effect of the reaction variables on the rate was examined. Together with the kinetic measurements, the microscopic measurement of the solid and the surface analysis techniques were employed to know the activation process of the solid surface by the catalysts. © 1994, The Japan Petroleum Institute. All rights reserved.

In the reaction of silicon, methanol and ethylene, use of a high-pressure flow reactor operating at 240 degreesC at 0.86 MPa of ethylene and 0.18 MPa of methanol gave a 33% selectivity for ethyldimethoxysilane, which was much higher than that using an atmospheric-pressure flow reactor (8%) or using an autoclave (4%). The selectivity increased proportionally with the ethylene pressure below 0.5 MPa. This indicates that the addition of ethylene or methanol to a surface silylene intermediate determines the selectivity and that the ethylene addition is a first-order reaction. Above 0.5 MPa the slope of the selectivity change was smaller. By feeding propylene instead of ethylene, n- and iso-propyldimethoxysilanes were obtained as organosilanes with 15 and 2% of selectivity, respectively. The reaction of silicon, ethanol and ethylene resulted in 28% selectivity for ethyldiethoxysilane at 0.99 MPa of ethylene and 0.21 MPa of ethanol at 240 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.

The liquid-phase reactions of silicon, methanol and ethylene in an autoclave gave ethylmethoxysilanes (HSi(C2H5)(OCH3)(2) and Si(C2H5)(OCH3)(3)) besides HSi(OCH3)(3) and Si(OCH3)(4). The reaction conditions for obtaining a high selectivity for the ethylmethoxysilanes were examined. With the use of a high pressure of ethylene and a small amount of methanol in toluene as a solvent at 433 K, ethylmethoxysilanes were obtained in 26% selectivity at silicon conversion of 59%. The direct reaction of silicon with ethanol and ethylene gave HSi(C2H5)(OC2H5)(2) and Si(C2H5)(OC2H5)(3).

When the reaction of metallic silicon with methanol in the presence of a small amount of thiophene was carried out at 653 K, methyldimethoxysilane was formed together with trimethoxysilane and tetramethoxysilane, the selectivity for methyldimethoxysilane:being 22%. Further adding a small amount of trioxane, trimer of formaldehyde, to the reaction system improved the selectivity for methyldimethoxysilane. This indicates that formaldehyde formed by the dehydrogenation of methanol takes part in methyldimethoxysilane formation. The reaction of silicon with ethanol also gave a 14% selectivity of ethyldiethoxysilane with a 43% silicon conversion. (C) 2000 Elsevier Science B.V. All rights reserved.