Conversion of CO₂over a Co-Based Fischer–Tropsch Catalyst

The conversion of CO 2 over a CoPt/Al 2 O 3 catalyst was investigated. Single-gas adsorption studies indicated that carbon was deposited on the catalyst by exposure to both CO 2 and CO in the absence of H 2 cofeed. When CO 2 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 CO 2 conversion and selectivity during reaction of syngas mixtures with different ratios of CO, CO 2, and H 2 . Absence of 14 C in unconverted CO and the unequal molar concentration of 14 C in the products from reaction at 220 °C and 2 MPa provided strong evidence that 14 CO 2 was not converted by the reverse water gas shift reaction. The antecedence of the carbon from CO 2 mattered, and the carbon did not become part of a common carbon pool for hydrocarbon synthesis. Conversion of CO 2 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.