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

Abstract

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.

Advances in the Design of Heterogeneous Catalysts and Thermocatalytic Processes for CO2 Utilization

“…Recently, bimetallic catalysts with Fe as active metal were studied to promote CO2 conversion. [227][228][229][230][231] Especially, addition of Co was found to increase the carbide formation, which was beneficial for the chain propagation reaction. It was also observed that the product selectivity could be tuned by changing the Fe/Co ratio.…”

Catalysts design for higher alcohols synthesis by CO2 hydrogenation: Trends and future perspectives

“…Moreover, K has been used to promote C 2+ oxygenates formation over FeCo-based catalysts [187]. H 2 conversion decreased with increasing K/(Fe + Co) ratio indicating that the hydrogenation activity is reduced at higher ratios (Fig.…”

Synergistic Effect of Alkali Na and K Promoter on Fe-Co-Cu-Al Catalysts for CO2 Hydrogenation to Light Hydrocarbons

“…The simultaneous introduction of K-Na exhibits the biggest shift to a low binding energy value. This is possibly because the introduced alkali metal ions exist in the form of oxides, which can provide more electrons for Fe@Cu or Fe-Co@Cu alloy phase [18,20]. Meanwhile, K ions have a bigger ionic radius than Na, and the corresponding oxides have a stronger capacity to provide electrons [30].…”

“…Meanwhile, a Fe or Co monometallic catalyst gives a poor C 2 + hydrocarbon selectivity, and produces more undesired CO and CH 4 [16,17]. Therefore, Fe-Co or Fe-Cu bimetallic catalysts are adopted, and corresponding promoters are also introduced to increase catalytic activity and C 2 + selectivity [18][19][20]. This is because the bimetallic catalysts can produce metallic alloy active sites after reduction, favoring H 2 activation for RWGS.…”