Papers - Okamoto, Masaki

Vapor-phase hydrosilylation using a transition metal complex catalyst in a liquid polymer medium supported on silica gel

Masaki Okamoto, Hironari Kiya, Akihiko Matsumura, Eiichi Suzuki

CATALYSIS LETTERS (SPRINGER)  123 ( 1-2 ) 72 - 79 2008.06

ISSN  1011-372X

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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.

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東京工業大学における安全管理と環境安全教育

日野出洋文, 岡本昌樹

安全工学 47 ( 6 ) 339 - 346 2008

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Oxidative dehydrogenation of ethane over Cr/ZSM-5 catalysts using CO2 as an oxidant

Naoki Mimura, Masaki Okamoto, Hiromi Yamashita, S. Ted Oyama, Kazuhisa Murata

JOURNAL OF PHYSICAL CHEMISTRY B (AMER CHEMICAL SOC)  110 ( 43 ) 21764 - 21770 2006.11

ISSN  1520-6106

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Highly active catalysts for oxidative dehydrogenation of ethane with CO2 were characterized by temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), Fourier transform infrared (FTIR) spectroscopy, and X-ray absorption fine-structure (XAFS) analysis. In the active catalysts, Cr/H-ZSM-5 (SiO2/Al2O3 > 190), Cr6+ = O, or possibly Cr5+ = O was the catalytic species on the zeolite support. In contrast, little Cr6+ (or Cr5+) was detected in the less-active catalysts. The Cr6+ (or Cr5+) species was reduced to an octahedral Cr3+ species by treatment with ethane at 773 K, and the reduced Cr species was reoxidized to the Cr6+ (or Cr5+) species by treatment with CO2 at 673-773 K. The Cr redox cycle played an important role in the catalyst's high activity.

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Intermediacy of silylene and germylene in direct synthesis of organosilanes and organogermanes

M Okamoto

RESEARCH ON CHEMICAL INTERMEDIATES (VSP BV)  32 ( 3-4 ) 317 - 330 2006

ISSN  0922-6168

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In the direct synthesis of silicon compounds by reactions of elemental silicon with methyl chloride, methanol and hydrogen chloride, silylene formed on surface of silicon grains during the reaction is an intermediate. The reaction of surface silylene with a variety of unsaturated hydrocarbons provides new direct synthesis of organosilanes. In the direct synthesis of methylchlorogermanes from elemental germanium, surface germylene is not an intermediate, while tetrachlorogermane is synthesized by the direct reaction of germanium with hydrogen chloride via dichlorogermylene intermediate. Various unsaturated hydrocarbons or organic chlorides added to the system of tetrachlorogermane synthesis give new methods for the synthesis of organogermanes.

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東京工業大学における一日体験化学教室の内容と問題点

岡本昌樹

化学と教育 (公益社団法人 日本化学会)  53 ( 5 ) 268 - 271 2005

ISSN  0386-2151

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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。

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炭酸ジメチル処理によるSBA-15の細孔の三次元化

岡本昌樹, 福喜多祐子, 三村直樹

触媒 47 ( 6 ) 461 - 463 2005

Polysiloxane depolymerization with dimethyl carbonate using alkali metal halide catalysts

M Okamoto, S Suzuki, E Suzuki

APPLIED CATALYSIS A-GENERAL (ELSEVIER SCIENCE BV)  261 ( 2 ) 239 - 245 2004.04

ISSN  0926-860X

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Polydimethylsiloxane terminated by a methyl group was almost completely depolymerized in the mixture of dimethyl carbonate (DMC) and methanol using alkali metal halide catalysts to form dimethoxydimethylsilane (DMDMS) and methoxytrimethylsilane (MTMS) monomers. The various alkali metal halides tested as catalysts gave the same monomer yield. The depolymerization rate depended on the kind of alcohol but not on dialkyl carbonate. The results indicate that the siloxane bond is cleaved by methanol attack to form the corresponding monomers together with water and that dimethyl carbonate reacts with water formed as a byproduct to give methanol, whose amount is the same as that of the methanol consumed for cleavage of siloxane bonds. Therefore, dimethyl carbonate, not methanol, acts as the depolymerization reagent in the apparent reaction.
Depolymerization of poly(methylphenylsiloxane-ran-dimethylsiloxane) and poly(methylvinylsiloxane-ran-dimethylsiloxane) with dimethyl carbonate in methanol using potassium fluoride catalyst also proceeded to obtain dimethoxymethylphenylsilane and dimethoxymethylvinylsilane, respectively, together with dimethoxydimethylsilane and methoxytrimethylsilane from polydimethylsiloxane parts. Silicone rubber containing silica as an additive was also depolymerized to form dimethoxydimethylsilane together with a small amount of tetramethoxysilane formed from silica additive. Therefore, the depolymerization with DMC using alkali metal salt catalyst can be counted on for recycling silicone waste. (C) 2003 Elsevier B.V. All rights reserved.

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Direct synthesis of organotrichlorogermanes by the reaction of elemental germanium, hydrogen chloride, and alkene

Masaki Okamoto, Takehiko Chikamori, Takuya Asano, Eiichi Suzuki

Organometallics 23 ( 3 ) 595 - 599 2004.02

ISSN  0276-7333

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The reaction of elemental germanium, hydrogen chloride, and ethylene with copper(I) chloride catalyst gave ethyltrichlorogermane with a 66% selectivity, tetrachlorogermane also being formed. The addition of tetrachlorogermane to the reaction system increased the formation rate of ethyltrichlorogermane. The reaction of germanium, tetrachlorogermane, and butadiene resulted in the formation of 1,1-dichlorogermacyclopent-3-ene. These results indicate the intermediacy of dichlorogermylene, which is formed by the reaction of elemental germanium with tetrachlorogermane. In place of ethylene, allyl chloride was fed with hydrogen chloride. Allyltrichlorogermane was obtained with a 92% selectivity together with a small amount of tetrachlorogermane. It is highly plausible that the formation of allyltrichlorogermane is caused by the insertion of dichlorogermylene intermediate to the carbon - chlorine bond of allyl chloride.

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Organotrichlorogermane synthesis by the reaction of elemental germanium, tetrachlorogermane and organic chloride via dichlorogermylene intermediate

M Okamoto, T Asano, E Suzuki

DALTON TRANSACTIONS (ROYAL SOC CHEMISTRY)   ( 15 ) 2372 - 2376 2004

ISSN  1477-9226

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Organotrichlorogermanes were synthesized by the reaction of elemental germanium, tetrachlorogermane and organic chlorides, methyl, propyl, isopropyl and allyl chlorides. Dichlorogermylene formed by the reaction of elemental germanium with tetrachlorogermane was the reaction intermediate, which was inserted into the carbon-chlorine bond of the organic chloride to give organotrichlorogermane. When isopropyl or allyl chloride was used as an organic chloride, organotrichlorogermane was formed also in the absence of tetrachlorogermane. These chlorides were converted to hydrogen chloride, which subsequently reacted with elemental germanium to give the dichlorogermylene intermediate. The reaction of elemental germanium, tetrachlorogermane and organic chlorides provides a simple and easy method for synthesizing organotrichlorogermanes, and all the raw materials are easily available.

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Deoligomerization of cyclooligosiloxanes with dimethyl carbonate over solid-base catalysts

M Okamoto, K Miyazaki, A Kado, S Suzuki, E Suzuki

CATALYSIS LETTERS (KLUWER ACADEMIC/PLENUM PUBL)  88 ( 3-4 ) 115 - 118 2003.06

ISSN  1011-372X

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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.

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High-performance Cr/H-ZSM-5 catalysts for oxidative dehydrogenation of ethane to ethylene with CO2 as an oxidant

N Mimura, Takahara, I, M Inaba, M Okamoto, K Murata

CATALYSIS COMMUNICATIONS (ELSEVIER SCIENCE BV)  3 ( 6 ) 257 - 262 2002.06

ISSN  1566-7367

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Cr/H-ZSM-5 (SiO2/Al(2)O(3)greater than or equal to190) catalyst effectively dehydrogenated ethane to ethylene in the presence of CO2 oxidant. The maximum rate of formation of ethylene at 923 K was 0.516 mmol g-catalyst(-1) min(-1) and selectivity was over 90%. Carbon dioxide maintained the activity of the catalyst by removing coke from the surface of the catalyst. TPR profiles of the Cr/H-ZSM-5 catalysts suggest that there are high oxidation states Cr species such as Cr(VI) on the catalyst, which is considered key of higher activity. (C) 2002 Elsevier Science B.V. All rights reserved.

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Direct synthesis of phenylchlorogermanes from metallic germanium and chlorobenzene using metal chloride catalysts

Masaki Okamoto, Takuya Asano, Eiichi Suzuki

Catalysis Letters 78 ( 1-4 ) 33 - 36 2002.03

ISSN  1011-372X

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In the direct synthesis of phenylchlorogermanes, copper(I) chloride was the best catalyst among the metal chlorides tested, the products being diphenyldichlorogermane and phenyltrichlorogermane. The reaction mainly gave diphenyldichlorogermane
however at the beginning of the reaction, phenyltrichlorogermane was afforded by the reaction of chlorobenzene and dichlorogermylene formed from metallic germanium and chloride ion in the catalyst.

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A novel catalyst containing a platinum complex in polyethylene glycol medium supported on silica gel for vapor-phase hydrosilylation of acetylene with trichlorosilane or trimethoxysilane

M Okamoto, H Kiya, H Yamashita, E Suzuki

CHEMICAL COMMUNICATIONS (ROYAL SOC CHEMISTRY)   ( 15 ) 1634 - 1635 2002

ISSN  1359-7345

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Hydrosilylation of acetylene with trichlorosilane or trimethoxysilane was carried out using a vapor-phase flow reactor with use of tetraammineplatinum(II) chloride in polyethylene glycol medium supported on silica gel as a catalyst, which is an active and thermally stable supported liquid-phase catalyst prepared readily from easily available materials, tetraammineplatinum(II) chloride, polyethylene glycol and silica gel.

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Phenyltrichlorogermane synthesis by the reaction of chlorobenzene and the dichlorogermylene intermediate formed from elemental germanium and tetrachlorogermane

M Okamoto, T Asano, E Suzuki

ORGANOMETALLICS (AMER CHEMICAL SOC)  20 ( 26 ) 5583 - 5585 2001.12

ISSN  0276-7333

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Phenyltrichlorogermane was synthesized with high, selectivity, 96%, from elemental germanium, tetrachlorogermane, and chlorobenzene using no catalyst, almost all germanium and tetrachlorogermane being converted. Dichlorogermylene was formed as a reaction intermediate by the reaction of germanium with tetrachlorogermane and inserted into the C-Cl bond of chlorobenzene to yield phenyltrichlorogermane.

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Deoligomerization of siloxanes with dimethyl carbonate over solid-base catalysts

M Okamoto, K Miyazaki, A Kado, E Suzuki

CHEMICAL COMMUNICATIONS (ROYAL SOC CHEMISTRY)   ( 18 ) 1838 - 1839 2001.09

ISSN  1359-7345

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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%.

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Direct synthesis of alkyldialkoxysilanes by the reaction of silicon, alcohol and alkene using a high-pressure flow reactor

M Okamoto, J Komai, M Uematsu, E Suzuki, Y Ono

JOURNAL OF ORGANOMETALLIC CHEMISTRY (ELSEVIER SCIENCE SA)  619 ( 1-2 ) 235 - 240 2001.01

ISSN  0022-328X

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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.

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Direct synthesis of organodichlorosilanes by the reaction of metallic silicon, hydrogen chloride and alkene/alkyne and by the reaction of metallic silicon and alkyl chloride

Masaki Okamoto, Satoshi Onodera, Yuji Yamamoto, Eiichi Suzuki, Yoshio Ono

Journal of the Chemical Society, Dalton Transactions  ( 1 ) 71 - 78 2001

Accepted,  ISSN  1470-479X

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Dichloroethylsilane was synthesized by the reaction of metallic silicon, hydrogen chloride and ethylene using copper(I) chloride as the catalyst, the silicon conversion and the selectivity for dichloroethylsilane being 36 and 47%, respectively. At a lower reaction temperature or at a higher ratio of ethylene: hydrogen chloride a higher selectivity was obtained, however the silicon conversion was lower. The silicon-carbon bond formation is caused by the reaction of a surface silylene intermediate with ethylene. The reaction with propylene in place of ethylene gave dichloroisopropylsilane (22% selectivity) and dichloro-n-propyl-silane (8% selectivity) together with chlorosilanes. A part of the dichloroisopropylsilane is formed by the reaction of silicon, hydrogen chloride and isopropyl chloride formed by hydrochlorination of propylene. Use of acetylene instead of alkenes resulted in dichlorovinylsilane formation with a 34% selectivity. Alkyldichlorosilanes were also produced directly from silicon with alkyl chlorides, propyl and butyl chlorides. During the reaction the alkyl chloride is dehydrochlorinated over the surface of copper originating from the catalyst to afford hydrogen chloride and alkene. The hydrogen chloride formed participates in the formation of the silicon-hydrogen bond in alkyldichlorosilane, and the reaction of silicon, hydrogen chloride and alkene also causes alkyldichlorosilane formation. The reaction with isopropyl chloride gave a very high selectivity (85%) for dichloroisopropylsilane, the silicon conversion being 86%. © The Royal Society of Chemistry 2001.

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Direct synthesis of methyldimethoxysilane from metallic silicon and methanol using copper(I) chloride catalyst

M Okamoto, H Abe, Y Kusama, E Suzuki, Y Ono

JOURNAL OF ORGANOMETALLIC CHEMISTRY (ELSEVIER SCIENCE SA)  616 ( 1-2 ) 74 - 79 2000.12

ISSN  0022-328X

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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.

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Oxydehydrogenation of propane over vanadyl ion-containing VAPO-5 and CoAPO-5

M Okamoto, L Luo, JA Labinger, ME Davis

JOURNAL OF CATALYSIS (ACADEMIC PRESS INC)  192 ( 1 ) 128 - 136 2000.05

ISSN  0021-9517

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Vanadyl ion-containing VAPO-5 and CoAPO-5 are prepared by contact with a vanadyl sulfate solution or by impregnation with aqueous vanadyl oxalate and characterized by powder X-ray diffraction, electron spin resonance spectroscopy, and temperature-programmed reduction (TPR). Treatment of VAPO-5 with vanadyl ion results in incorporation of up to 1.0 wt% total vanadium into the AFI framework by filling lattice vacancies. At vanadium contents above ca. 1 wt%, extraframework vanadium is also obtained. TPR results show that framework vanadium can be reduced by hydrogen at a lower temperature than extraframework vanadium and vanadium in bulk V2O5. Oxydehydrogenation of propane over VAPO-5 samples reveals that framework vanadium is the most active and selective species for propylene formation (at 400 degrees C and 5% conversion, the selectivity is 72%); extraframework vanadium species are less active and selective. (C) 2000 Academic Press.

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Direct synthesis of organochlorosilanes by the reaction of metallic silicon with hydrogen chloride and alkene/alkyne

M Okamoto, S Onodera, Y Yamamoto, E Suzuki, Y Ono

CHEMICAL COMMUNICATIONS (ROYAL SOC CHEMISTRY)   ( 12 ) 1275 - 1276 1998.06

ISSN  1359-7345

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Organosilicon compounds were directly synthesized from metallic silicon, alkene/alkyne and HCl, EtHSiCl2 being obtained with 47% selectivity from Si, C2H4 and HCl ae 513 K, and CH2=CHSiHCl2 and EtHSiCl2 with 39 smd 23% selectivity, respectively, when C2H2 was used in place of C2H4.

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