Influence of crystalline phase of Li-Al-O oxides on the activity of Wacker-type catalysts in dimethyl carbonate synthesis

Abstract

The catalysts supported on LiAl5O8 (spinel) for vapor phase synthesis of dimethyl carbonate (DMC) from methyl nitrite (MN) have been studied. Their catalytic activities on supports prepared by different methods were evaluated in a continuous reactor. The samples were characterized by powder X-ray diffraction, N2 adsorption-desorption isotherms, fourier transform infrared spectroscopy and temperature-programmed reduction of H2. Li/Al molar ratio and calcination temperature greatly influence the structure of crystalline phase of Li-Al-O oxides. Desirable LiAl5O8 (spinel) was formed at 800°C, while LiAl5O8 (primitive cube) formed at 900°C is undesirable for the reaction. A high Li/Al molar ratio, which was related with LiAlO2, also slowed the reaction rate. The electron transfer ability and the interaction with active component are the important properties of the spinel-based supports. The CuCl2-PdCl2/LiAl5O8 (spinel) with better electron transfer ability and low Pd2+ reduction temperature exhibited a better catalytic ability.