Synthesis of dimethyl ether from methane mediated by HBr

Dimethyl ether (DME) was synthesized from methane through a two-step process,in which CH_3 Br was prepared from the oxidative bromination reaction of methane in the presence of HBr and oxygen over a Rh-SiO_2 catalyst and then,in the second step,CH_3Br was hydrolyzed to DME over a silica supported metal chloride catalyst. 12 mol%ZnCl_2/SiO_2 catalyst was found to be the most active,but it deactivated because of Cl- losing.