Investigation of carbon dioxide photoreduction process in a laboratory-scale photoreactor by computational fluid dynamic and reaction kinetic modeling

Abstract

The production of solar fuels via the photoreduction of carbon dioxide to methane by titanium oxide is a promising process to control greenhouse gas emissions and provide alternative renewable fuels. Although several reaction mechanisms have been proposed, the detailed steps are still ambiguous, and the limiting factors are not well defined. To improve our understanding of the mechanisms of carbon dioxide photoreduction, a multi-physics model was developed using COMSOL. The novelty of this work is the computational fluid dynamic model combined with the novel carbon dioxide photoreduction intrinsic reaction kinetic model, which was built based on three-steps, namely gas adsorption, surface reactions and desorption, while the ultraviolet light intensity distribution was simulated by the Gaussian distribution model and Beer-Lambert model. The carbon dioxide photoreduction process conducted in a laboratory-scale reactor under different carbon dioxide and water moisture partial pressures was then modeled based on the intrinsic kinetic model. It was found that the simulation results for methane, carbon monoxide and hydrogen yield match the experiments in the concentration range of 10−4 mol·m−3 at the low carbon dioxide and water moisture partial pressure. Finally, the factors of adsorption site concentration, adsorption equilibrium constant, ultraviolet light intensity and temperature were evaluated.

Investigation of CO2 Photoreduction in an Annular Fluidized Bed Photoreactor by MP-PIC Simulation

“…47,48 It has been analyzed in the publication. 45 From Thompson et al's experiments, 29 CO, H 2 , and CH 4 are the main final products and other publications have demonstrated it as well. 46 Therefore, in this work, we consider CO, H 2 , and CH 4 as the main final products by CO 2 photoreduction.…”

“…CO 2 photoreduction is a complex reaction system, and the reaction mechanism and kinetics have been investigated. − Generally, CO 2 photoreduction is a mass-transfer-controlled process and thus the kinetic equation is widely accepted to be based on the Langmuir adsorption equation, rather than the Arrhenius rate equation . For the reaction model, the Thompson model based on the Langmuir equation is applied .…”

“…H 2 is produced from water splitting. Other products, such as formaldehyde and methanol, are the intermediate products and possible final products. , It has been analyzed in the publication . From Thompson et al’s experiments, CO, H 2 , and CH 4 are the main final products and other publications have demonstrated it as well .…”

Design and Development of Photocatalytic Systems for Reduction of CO2 into Valuable Chemicals and Fuels

“…The adsorption sites and equilibrium constant, temperature, and UV lighting affect the surface concentration, and thus the CH 4 , CO, and H 2 yields. Gas adsorption on the photocatalyst surface is one of the crucial steps to improve the CH 4 yield in the CO 2 photoreduction process [99].…”

“…However, the potential for CO 2 photoreduction on an industrial scale is largely limited by the regional solar intensity that depends on geographic location. Recent technological advances in the field of photo-assisted CO 2 reduction include various strategies and approaches, the most studied of which are photocatalysis (PC), photoelectrocatalysis (PEC), and photovoltaic-integrated systems [94][95][96][97][98][99][100][101]. In the photocatalytic process, simultaneous activation, and reduction of CO 2 by photogenerated electrons in the conductive band and oxidation of H 2 O on photogenerated holes in the valence band should be carried out.…”