Abstract
The porous lithium aluminates were developed as a catalyst support for vapor phase synthesis of dimethyl carbonate. The porous lithium aluminates were prepared by the impregnation of activated alumina with Li salt and the subsequent thermal treatment at 800°C. The crystal structures of the materials were identified as the inverse spinel structure in which Li+ and part of Al3+ ions located in the sites octahedrally coordinated with oxide ions and other Al3+ ions located in the sites tetrahedrally coordinated with oxide ions. The Pd-Cu-Cl catalysts supported on these porous lithium aluminates were employed for the vapor phase dimethyl carbonate synthesis from methyl nitrite and carbon monoxide. These catalysts showed higher activities and selectivities for dimethyl carbonate formation than that supported on activated alumina. According to the measurements of physical properties of the catalyst carriers, the lithium aluminates had micropores of scores to hundreds angstrom of diameter and comparatively weak surface acidic sites as well as basic sites. The high catalytic performances of lithium aluminates supported Pd-Cu-Cl catalysts result from not only the acid-base properties but also these moderate porosity of the the lithium aluminates carriers.
