Direct Stepwise Oxidation of Methane to Methanol over Cu–SiO2

Cu supported on SiO2 can be used to directly convert methane to methanol in a stepwise process with no intrinsic need for a zeolite support. Effects of parameters such as the O2 activation temperature, activation time, CH4 reaction temperature, CH4 partial pressure (pCH4), and Cu wt % on methanol yield were investigated. Increasing the O2 activation temperature in the 200–800 °C range significantly improved the methanol yield, and when carried out at 800 °C, a methanol yield of 11.5 μmol/gcatalyst was obtained after reaction with methane at 200 °C for the sample with 2 wt % Cu. Yield per mole of Cu increased exponentially from 1.0 to 59.1 mmol with decreased Cu wt % from 30 to 1, respectively. The increase in the O2 activation time also strongly influenced the yield which corresponded to the increase in yield by a factor of >2 between 1 and 8 h. Increasing pCH4 from 0.05 to 1 atm resulted in a 5-fold increase in yield after activation at 450 °C; however, it resulted in at least 20% lower yields after acti...