Process modeling and optimization of simultaneous direct conversion of CO2 and CH4 greenhouse gas mixture over TiO2/webnet photocatalyst

In this study, simultaneous direct conversion of CO2 and CH4 greenhouse gas mixture over the TiO2/webnet photocatalyst was studied. SEM, XRD and UV-visible spectra analyses were carried out for characterization of prepared catalysts. The experiments were done under UV irradiation in an appropriate gas-phase batch reactor. Effects of mesh size of webnet, TiO2/webnet dosage, calcination temperature, reactor's initial pressure, feed composition and UV light intensity were investigated and conversion of CO2 and CH4 were determined as process responses. Preliminary results showed that the most significant variables on the CO2 and CH4 conversion are TiO2/webnet dosage, calcination temperature and reactor's initial pressure. Thus, further experiments and optimization were performed with these three variables to evaluate process conditions using response surface methodology based on three-level central composite design. Maximum reduction of CO2 (26.32%) and CH4 (31.63%) were achieved at the optimum conditions: mesh size of 120, TiO2/webnet dosage of 1.15 g/cm2, calcination temperature of 400 °C, reactor's initial pressure of 60 psig, feed composition of 45% CO2:45% CH4:10% He and UV light intensity of 125 W.