Photocatalytic CO2 reduction with H2O vapors using montmorillonite/TiO2 supported microchannel monolith photoreactor

•MMT/TiO2 catalyst coated over monolith was tested for CO2 photoreduction with H2O.•Microchannel monolith showed high CO2 conversion to fuels compared to cell reactor.•Highest yield rates obtained were 139 and 52 μmole g catal.−1 h−1 for CH4 and CO.•L–H model showed competitive adsorption with efficient CO2 adsorption on MMT/TiO2.•Kinetic model revealed photo-oxidation–reduction process over MMT/TiO2 catalyst.

In this study, the performance of a montmorillonite (MMT)/TiO2 coated monolith photoreactor was tested for the photocatalytic CO2 reduction. CH4 and CO were the main products having yield rates of 139 and 52 μmole g catal.−1 h−1, respectively. The other adequately significant products were C2H4, C2H6, C3H6 and C3H8. The catalytic reactor performance for CH4 production was in the order of MMT–TiO2–monolith (139 μmole g catal.−1 h−1) > TiO2–monolith (82 μmole g catal.−1 h−1) > MMT–TiO2–cell (43 μmole g catal.−1 h−1) > TiO2–cell (7.7 μmole g catal.−1 h−1). The higher yield rates in monolith photoreactor were due to the higher illuminated surface area and efficient light utilization. In addition, the profound hydrocarbon yield rates over MMT/TiO2 nanocatalyst supported microchannels were due to the efficient production and utilization of charges. The reaction rate and the adsorption–desorption phenomenon was postulated according to the Langmuir–Hinshelwood (L–H) model. A simple kinetic equation, derived to model the coupled effect of adsorptive photocatalytic reduction and oxidation, fitted-well with the experimental data.

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