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

The catalysts supported on LiAl 5 O 8 (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, N 2 adsorption-desorption isotherms, fourier transform infrared spectroscopy and temperature-programmed reduction of H 2 . Li/Al molar ratio and calcination temperature greatly influence the structure of crystalline phase of Li-Al-O oxides. Desirable LiAl 5 O 8 (spinel) was formed at 800°C, while LiAl 5 O 8 (primitive cube) formed at 900°C is undesirable for the reaction. A high Li/Al molar ratio, which was related with LiAlO 2 , 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 CuCl 2 -PdCl 2 /LiAl 5 O 8 (spinel) with better electron transfer ability and low Pd 2+ reduction temperature exhibited a better catalytic ability.