論文

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.

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.

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.

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.

Under fixed-bed flow conditions, silane, diethoxysilane, and tetraethoxysilane are formed by the disproportionation of triethoxysilane over a KF/Al2O3 or a heat-treated hydrotalcite catalyst. The reactions at 393 K give preponderantly either silane with 17-21% yields or diethoxysilane with 5-10% yields. The preponderance depends on the contact time and the amount of KF loaded on Al2O3. (C) 1998 Elsevier Science B.V.

The disproportionation of triethylsilane over CaY zeolite was examined using a fixed-bed flow reactor. The reactions at 673-723 K gave diethylsilane and tetraethylsilane, the conversion of triethylsilane being 50%. Practically no hydrocarbons were included in the product. The effects of the degree of Ca2+ exchange and the reaction variables on the catalytic performance were examined.

SBA-15 was hydrothermally synthesized at 80 A degrees C for 48 h, and then the surfactant template for mesopore formation was removed by extraction with ethanol, washing with nitric acid, and heating at 200 A degrees C. Addition of alkali metal chlorides to a synthesis gel of SBA-15 increased its mesopore diameter in the following order: no added salt < LiCl < KCl < CsCl. The micropore volume did not change with the addition of any alkali metal and was around 0.17 mL g(-1). These results suggest that alkali metal salt is inside the mesopore with a micelle template. When a small amount of potassium chloride was impregnated in SBA-15 after extraction and washing, micropore volume reduced almost to zero with heating at 400 A degrees C in dry air, and the mesopore diameter and pore wall thickness were reduced by a larger amount than for non-impregnated SBA-15. It is likely that the micropores in the mesopore wall vanish due to condensation of silanols and/or reconstruction of siloxane bonds on the micropore wall, which are catalyzed by alkali metal halides.

When the SiO2-overlayer of silicon surface was removed by treating silicon grains with aqueous HF solution, the reactivity of silicon towards methanol increased. Thus, trimethoxysilane was formed with almost complete conversion of silicon in three hours and > 98% of selectivity, when the mixture of the silicon grains and a catalyst (copper(1) chloride) was preheated at 513 K and brought in contact with methanol at 513 K. When the silicon with the SiO2-overlayer was used for the reaction after its mixture with copper(I) chloride was heated at 513 K, the reaction started after a long induction period and the rate of the silicon conversion was very low. However, when the preheating was done at 723 K, the reaction proceeded without induction period, irrespective of the presence of the SiO2-overlayer. The selectivity for trimethoxysilane was only about 60%. X-ray photoelectron spectroscopy was used to evaluate the thickness of the oxide layers of silicon surface. The morphology of the reacting silicon grains was also examined by SEM.

Hollow silica spheres containing ordered mesopores with radial orientation were synthesized from core-shell structured mesoporous silica spheres with pure silica core and propyl group-grafted silica shell. The silica core was selectively impregnated with sodium acetate owing to the hydrophilicity of the core. Sodium acetate acted as a catalyst for silica decomposition with dimethyl carbonate (DMC), and after impregnation, treatment with DMC was performed to remove the core by the reaction of silica with DMC. The obtained hollow spheres contain ordered mesopores with radial orientation and are mono-disperse. The final shell thickness could be controlled by changing the shell thickness of the initial core-shell spheres, as well as by modifying the degree of decomposition of the shell. 9-Phenylanthracene encapsulated in the hollow spheres was gradually released through the mesopores as vapor into an air stream by diffusion limitation. © 2012 Elsevier Inc. All rights reserved.

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.

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.

The reaction of silicon with methyl chloride was carried out in the presence of butadiene. The products consisted of 1,1-dichlorosilacyclopent-3-ene, 1-methyl-1-chlorosilacyciopent-3-ene and 1-chlorosilacyclopent-3-ene besides methylchlorosilanes. Silacyclopent-3-enes accounted for 25% of the whole products. The high selectivity for silacyclopent-3-enes indicates that surface silylene is the intermediate in the reaction of silicon with methyl chloride.

Pyridin-2-one reacts with methanol over gamma-alumina in the vapor phase to afford exclusively 1-methylpyridin-2-one. Thus, 1-methylpyridin-2-one was obtained in a 99% selectivity at a 100% conversion at 573 K.

MFI-type zeolite with a core-shell structure and minimal defects was synthesized by crystal overgrowth of aluminum-free MFI-type zeolite on aluminum-containing MFI-type zeolite crystals. The purpose of the zeolite shell is to passivate acid sites on the external surface of the zeolite core. When both the shell and the core are synthesized in the presence of fluoride ion, defects are minimal. In the case of synthesizing the shell in the absence of fluoride ion, core growth does not occur. When the core is synthesized in the absence of fluoride ion, significant defects develop and cause mesopores to form in the core-shell zeolite. As catalysts for methylation of toluene with methanol, only the core-shell zeolite with minimal defects shows high selectivity for p-xylene (96%). © 2011 Elsevier Inc. All rights reserved.

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.

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.

The synthesis of 1,3-butadiene via the dehydration of crotyl alcohol (2-buten-1-ol) over solid acids (six silica-alumina catalysts, two zeolite catalysts, and one γ-alumina catalyst) was assessed. Crotyl alcohol conversion and butadiene selectivity were both 95% or more over commercial silica-alumina catalysts. However, a sudden decrease in catalytic activity was observed during the reaction. Since the deactivated catalyst was regenerated by drying at 150°C -200°C, results showed that the main cause of the catalyst deactivation was the adsorption of water formed during the reaction and not the coke formation. An analysis of the deactivated catalyst indicated that, since the formation of Al-OH by the hydrolysis of the Al-O-Al bond increased the hydrophilicity of the catalyst surface, the adsorption of water on the catalyst surface was promoted, while that of crotyl alcohol was probably inhibited. Also, based on the catalyst characterization, the silica-alumina catalysts with few silanol groups, few alumina-rich zones, and a low Si/Al ratio were preferable.