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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