Hydrogenation of Carbon Dioxide over K‐Promoted FeCo Bimetallic Catalysts Prepared from Mixed Metal Oxalates

• Published in: ChemCatChem 2017-04, Vol.9 (7), p.1303-1312
• Main Authors: Gnanamani, Muthu Kumaran, Hamdeh, Hussein H., Jacobs, Gary, Shafer, Wilson D., Hopps, Shelley D., Thomas, Gerald A., Davis, Burtron H.
• Format: Article
• Language: English
• Subjects: bimetallic catalysts; carbon dioxide; cobalt; hydrogenation; iron; potassium
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201601337

The hydrogenation of carbon dioxide over K‐promoted FeCo bimetallic catalysts prepared by sequential oxalate decomposition and carburization of FeCo with CO was studied in a fixed‐bed reactor at 240 °C and 1.2 MPa. The initial CO2 conversion was found to be dependent on K loading, whereas both unpromoted and K‐promoted FeCo catalysts (except 90Fe10Co3.0K) exhibited similar levels of CO2 conversion after a few hours of time on stream. A decarburization study on freshly activated and used FeCo suggests that potassium increases the stability of iron carbides and graphitic carbon under a reducing atmosphere. Also, K addition tends to decrease the hydrogenation function of FeCo bimetallic catalysts and, thus, controls product selectivity. Under similar CO2 conversions, potassium enhanced acetic acid formation while suppressing ethanol production, which indicates that a common intermediate might be responsible for the changes observed with C2 oxygenates. Promoting effect of potassium: In the hydrogenation of CO2 over K‐promoted FeCo bimetallic catalysts, initial CO2 conversion was dependent on K loading, whereas most catalysts exhibited similar conversion levels after a few hours. Decarburization suggests that potassium stabilizes iron carbides and decreases the hydrogenation function of the catalysts; thus, it controls product selectivity. Potassium enhanced acetic acid formation and suppressed ethanol production.