Researchers at the US Department of Energy (DOE) Argonne National Laboratory, with colleagues at Universität Freiburg in Germany, have developed an effective low-pressure catalyst for the reduction of CO2 to methanol (CH3OH). In a paper in the Journal of the American Chemical Society, they report their investigation into the use of size-selected Cu4 clusters supported on Al2O3 thin films for CO2 reduction in the presence of hydrogen.
The industrial process of methanol (CH3OH) synthesis from syngas (CO, CO2 and H2 ) is carried out at high pressures (10 to 100 bar) using a Cu/ZnO/Al2O3 catalyst. Due to increasing emission of CO2 from fossil fuel combustion and other anthropogenic activities, this catalytic system has also become the focus of interest for obtaining sustainable CH3OH by hydrogenation of captured CO2 (CO2 + 3H2 → CH3OH + H2O). Efforts have been made to modify and improve the industrial Cu/ZnO/Al2O3 catalyst. Nevertheless, the high pressure required for achieving a quality yield of CH3OH using these catalysts brings a great challenge for reducing the energy input and cost for this process. Also, effective catalysts are in need for alternative feed streams with lower CO2 concentrations. Thus, developing an effective low-pressure catalyst for CO2 reduction to CH3OH is highly attractive.
Here, we report on Al2O3 supported Cu4 clusters as an effective catalyst for the reduction of CO2 to CH3OH at a low CO2 partial pressure (0.013 atm), with a higher activity than those of recently developed low-pressure catalysts.—Liu et al.
The team measured catalytic activity under near-atmospheric reaction conditions with a low CO2 partial pressure; they investigated the oxidation state of the clusters by in situ grazing incidence X-ray absorption spectroscopy.
Results indicate that size-selected Cu4 clusters are the most active low-pressure catalyst for catalytic CO2 conversion to CH3OH. Density functional theory calculations reveal that Cu4 clusters have a low activation barrier for conversion of CO2 to CH3OH.
…to our best knowledge the Al2O3 supported size-selected Cu4 clusters exhibit the highest reported activity to date for CO2 reduction to CH3OH at a low CO2 partial pressure. The unique coordination environment of Cu atoms in size-selected sub-nanometer clusters results in the active sites that are superior to those of larger Cu particles. These results for size-selected Cu clusters demonstrate their great potential for the development of novel low-pressure catalysts for CH3OH synthesis from catalytic conversion of CO2 using alternative feed streams with low CO2 concentration.—Liu et al.
Cong Liu, Bing Yang, Eric Tyo, Soenke Seifert, Janae DeBartolo, Bernd von Issendorff, Peter Zapol, Stefan Vajda, Larry A. Curtiss (2015) “Carbon Dioxide Conversion to Methanol over Size-Selected Cu4 Clusters at Low Pressures” J. Am. Chem. Soc. doi: 10.1021/jacs.5b03668