Masashi Ookawa

Preparation of New Solid Bases Derived from Supported Metal Nitrates and Carbonates

A highly basic solid catalyst was obtained by dispersing nitrates or carbonates of alkali metals such as KNO3, CsCO3 over alumina and zirconia at the surface density of 10-15 × 1018 cations m-2 and heating them at 773-873 K in an inert atmosphere. The temperature is far below the decomposition temperatures of the nitrates and the carbonates. Based on the temperature-programmed decomposition (TPD) experiments, two types of decomposition process are suggested; a bulk decomposition and an anion decomposition. Generation of a strong basicity relates to the anion decomposition. The basic center may be composed of the oxygen anions liberated from the decomposition of the nitrate or carbonate anions that are dissociatively adsorbed on the support surface during the preparation. These catalysts effectively catalyzed the double bond isomerization of aliphatic hydrocarbons and bicyclic hydrocarbons at moderate temperature.

Oxidation of aromatic hydrocarbons with H2O2 catalyzed by a nano-scale tubular aluminosilicate, Fe-containing imogolite

Imogolite is a nano-scale tubular clay mineral with the typical chemical composition (OH)3Al2O3SiOH. The Fe-containing imogolite was synthesized from FeCl3, AlCl3 and Na4SiO4 aqueous solutions. The fibrous morphology observed by AFM in this sample is similar to that of synthetic imogolite. In the catalytic oxidation of aromatic hydrocarbon compounds such as benzene, phenol and chrolobenzene, the aromatic ring was oxidized. When the side-chain is a hydrocarbon group such as methyl, both benzene ring and the side-chain group were oxidized. It was found that the side-chain group was preferentially oxidized.

Pore wall structure modeling of MCM-41 type silica using molecular dynamics simulation

Abstract Modeling of MCM-41 type porous silica was performed using the molecular dynamics (MD) simulation. Some porous silica models were generated for the materials with ca. 3 nm diameter and more than 1000 m 2 g −1 surface area. The hexagon and circle type of pore appeared as the cross-section depending on different density. The enthalpy difference between these models and α-quartz was larger than that between silica glass and α-quartz. MD calculation revealed that the mean Si-O-Si bond angle in MCM-41 type silica is smaller than that in silica. This result supports our experimental results.

06-P-05 -X- ray diffraction analysis of ordered mesoporous silica

Publisher Summary This chapter presents the X-ray diffraction analysis of ordered mesoporous silica. The analysis of the wall structure of MCM-41 prepared under acidic or basic condition is attempted by X-ray diffraction (XRD) using Mo Kα. The profiles of XRD in the wide-angle region for MCM-41 are similar regardless preparation methods. The significant difference is shown in the profiles of XRD and the interference function of silica glass and MCM-41. Correlation function suggests that the pore wall of MCM-41 prepared under acidic condition have a structure of narrow Si-O-Si angle compared with MCM-41 prepared under basic condition or silica glass.

40 On the generation of basic properties of supported nitrates and carbonates of group 1 and group 2 elements

Abstract A highly basic solid catalyst was obtained by dispersing nitrate or carbonate of Group 1 elements such as KNO 3 , CsCO 3 and nitrate of Group 2 elements such as Ca(NO 3 ) 2 over alumina and zirconia at the surface density of 10–15 cations nm −2 and activating them at 773–873 K, that is far below the decomposition temperature of carbonates, in an inert atmosphere. The basic center may be composed of the oxygen anions liberated from the decomposition of nitrate or carbonate anions that was dissociatively adsorbed on the support surface during the preparation. The catalysts derived from the carbonate of Group 2 elements are also highly basic, though the process of the basicity generation is different from that of nitrate of Group 1 and 2 elements and carbonate of Group 1 elements.

On the behavior of the selective oxidation by LiNiO2: Oxidative coupling of methane

The mobility of lattice oxygen and the fine structure of LixNi2–xO2 (0 ≤ x ≤ 1.0) were investigated by thermogravimetric analysis and extended X-ray absorption fine structure, respectively. It was proven that the lattice oxygen of LiNiO2 was mobilizable under reductive and oxidative atmosphere at 1033 K. The Ni–O bond lengths in NiO6 slabs markedly changed at around x = 0.65. The results were in good agreement with the dependence of the selectivity for the OCM reaction on LixNi2–xO2 catalysts. It was suggested from these data that the formation of active lattice oxygen species in LiNiO2 should be induced by structural distortion in NiO6.

Solid acid catalyzed disporportionation and alkylation of alkylsilanes

Catalytic disproportionation of alkylsilanes such as diethylsilane (E2), triethylsilane (E3) and diethyldimethylsilane (E2M2) were examined at 373–623 K in a closed recirculation apparatus. Strongly acidic catalysts, SA, HY, MgY, CaY, SO 3 /ZrO 2 and alumina, exhibited high activities. Catalytic alkylation of alkylsilanes with olefinic and acetylenic compounds using solid catalysts was examined in a closed recirculation reactor at 373–473 K. Alkylation of diethylsilane (E2) with these compounds took place smoothly on silicaalumina (SA) and SO 3 /ZrO 2 catalysts but not on alumina, which means protonic solid acid catalyzed the reaction. n -Alkylated products were the main products and the iso -alkylated ones were the minor products regardless the type of olefins. The product distribution indicates the reaction takes place via a nucleophilic attack of olefins on a Si cation.