Conversion of CO2 over a Co-Based Fischer-Tropsch Catalyst

The conversion of CO2 over a CoPt/Al2O3 catalyst was investigated. Single-gas adsorption studies indicated that carbon was deposited on the catalyst by exposure to both CO2 and CO in the absence of H-2 cofeed. When CO2 was preadsorbed followed by H-2 flow, methane was produced, as well as traces of C-3-C-4 hydrocarbons, but no evidence of the reverse water gas shift reaction was found. Use was made of carbon-14-labeled carbon dioxide to track CO2 conversion and selectivity during reaction of syngas mixtures with different ratios of CO, CO2, and H-2. Absence of C-14 in unconverted CO and the unequal molar concentration of C-14 in the products from reaction at 220 degrees C and 2 MPa provided strong evidence that (CO2)-C-14 was not converted by the reverse water gas shift reaction. The antecedence of the carbon from CO2 mattered, and the carbon did not become part of a common carbon pool for hydrocarbon synthesis. Conversion of CO2 proceeded by a pathway separate from CO. Conclusions drawn from this experimental study were employed to determine implications for the industrial application of Co-catalyzed Fischer-Tropsch synthesis.