Mechanism of CO2 Reduction to Hydocarbons Over Ti-SBA-15

Wednesday, October 19, 2011: 4:35 PM
200 C (Minneapolis Convention Center)
Chieh-Chao Yang and Guido Mul, Faculty of Science and Technology (TNW), University of Twente, Enschede, Netherlands

Different gas mixtures containing CO, CO2, H2O or H2 were exposed to illumination in the presence of to this date the most effective catalyst for CO2 reduction, Ti-SBA-15, in order to clarify the route to hydrocarbons in photocatalytic CO2 reduction over this photocatalyst. A mixture of CO and H2O led to the highest quantities of CH4, C2H4, and C2H6 after 7 hours of reaction, whereas a mixture of CO2 and H2 lead to the lowest production rate of these products. H2O is thus more efficient in activation of CO and CO2 than H2. CH3OH was not detected as significant product, and when fed to the catalyst, did not yield extensive product formation. Formaldehyde was found very reactive over the catalytic system, yielding a product distribution (C1-C2) of similar nature as obtained by CO and CO2 activation. Finally, the backward reaction, hydrocarbon oxidation into CO or CO2, was found significant over this catalyst system. Based on i) results indicated above, and ii) available literature, a mechanism for photocatalytic CO2 reduction is proposed involving formation of CO in the initial stages, followed by consecutive formation of formaldehyde, which converts to CH4, C2H4, and C2H6, presumably by reaction with photo-activated H2O (OH radicals). Implications of this study to further improve on the activity of this class of photocatalysts are discussed. 

Extended Abstract: File Not Uploaded
See more of this Session: Catalysis for CO2 Conversion II
See more of this Group/Topical: Catalysis and Reaction Engineering Division