Enhanced photocatalytic carbon dioxide reforming of methane to fuels over nickel and montmorillonite supported TiO2 nanocomposite under UV-light using monolith photoreactor

Abstract

Conversion of carbon dioxide (CO 2 ) and methane (CH 4 ) to fuels using photo-technology is a cleaner pathway compared to thermal reforming, since its uses only light irradiations, while producing valuable chemicals. In this study, structured nickel (Ni) and montmorillonite (MMT) supported TiO 2 composite, synthesized by a sol-gel method, was tested for photocatalytic reduction of CO 2 using fixed-bed and monolith photoreactors. The performance of structured nanocatalyst was evaluated using CO 2 -H 2 system via photocatalytic reverse water gas shift (RWGS) reaction and CO 2 -CH 4 system via photocatalytic dry reforming of methane (DRM). Using photocatalytic RWGS, CO was detected as the main products, while the performance of Ni-MMT/TiO 2 composite was expressively higher than using MMT/TiO 2 and TiO 2 catalysts. This was obviously due to larger surface area by MMT dispersion and hindered charges recombination rate by Ni. Similarly, using DRM, H 2 and CO were the main products, while their selectivity was greatly dependent on the initial CH 4 /CO 2 molar feed ratios. At a lower CH 4 /CO 2 ratio, more CO was produced, while a higher feed ratio promoted H 2 production. This shows, composite catalyst was more favorable for CO 2 adsorption, while CH 4 was competitively adsorbed during photo-catalysis process. Comparatively, Ni-MMT/TiO 2 catalyst reveals higher photo-activity and selectivity in a monolith photoreactor than using fixed-bed reactor under the same operating conditions. This enhanced photoactivity was due to higher photonic flux with enlarged active surface area due to monolithic support and efficient sorption process. The stability of Ni/TiO 2 dispersed MMT for CO and H 2 production via DRM process sustained in cyclic runs using monolithic support. Hence, using Ni/MMT modified TiO 2 catalyst in a monolith photoreactor, CO 2 and CH 4 can efficiently be converted to renewable fuels under light irradiations and would be a great benefit to the environment.