title: Solar photothermochemical alkane reverse combustion.
abstract: A one-step, gas-phase photothermocatalytic process for the synthesis of hydrocarbons, including liquid alkanes, aromatics, and oxygenates, with carbon numbers (Cn) up to C13, from CO2 and water is demonstrated in a flow photoreactor operating at elevated temperatures (180-200 °C) and pressures (1-6 bar) using a 5% cobalt on TiO2 catalyst and under UV irradiation. A parametric study of temperature, pressure, and partial pressure ratio revealed that temperatures in excess of 160 °C are needed to obtain the higher Cn products in quantity and that the product distribution shifts toward higher Cn products with increasing pressure. In the best run so far, over 13% by mass of the products were C5+ hydrocarbons and some of these, i.e., octane, are drop-in replacements for existing liquid hydrocarbons fuels. Dioxygen was detected in yields ranging between 64% and 150%. In principle, this tandem photochemical-thermochemical process, fitted with a photocatalyst better matched to the solar spectrum, could provide a cheap and direct method to produce liquid hydrocarbons from CO2 and water via a solar process which uses concentrated sunlight for both photochemical excitation to generate high-energy intermediates and heat to drive important thermochemical carbon-chain-forming reactions.
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington TX 76019;
authors.forename: Wilaiwan
authors.initials: W
authors.lastname: Chanmanee
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington TX 76019;
authors.forename: Mohammad Fakrul
authors.initials: MF
authors.lastname: Islam
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Texas at Arlington, Arlington TX 76019 dennisb@uta.edu macdonn@uta.edu.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Dennis
authors.affiliation: Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington TX 76019; dennisb@uta.edu macdonn@uta.edu.
authors.forename: Frederick M
authors.initials: FM
authors.lastname: MacDonnell
keywords: CO2 reduction; Fischer–Tropsch; photochemistry; solar fuel; water splitting