Converting carbon dioxide (CO2) to methanol is widely recognized as a promising method to recycle carbon resources. But scientists have long faced difficult challenges when trying to improve processes.
At low temperatures, it is thermodynamically advantageous to convert CO2 to methanol. Under these conditions, CO2 becomes difficult to activate, resulting in a decrease in catalyst performance. Increasing the temperature speeds up the reaction, but also promotes a competing process known as the reverse water-gas shift reaction, which produces undesirable byproducts and reduces methanol selectivity. This persistent trade-off between catalyst activity and selectivity has limited progress in increasing methanol yield.
New catalyst design overcomes long-standing trade-offs
In a study published in chemistryResearchers led by Professor Jian Sun and Professor Jiafeng Yu from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) have developed a new catalyst design aimed at addressing this challenge.
Their approach uses an overlayer structure driven by strong metal-support interactions (SMSI) to spatially separate active sites within the catalyst. This design allows different reaction steps to be performed at different locations, increasing the efficiency of methanol production from CO2.
The research team achieved a space-time yield of 1.2 g·gcat-1·h-1 at 300°C and 3 MPa by restructuring the catalyst surface and changing the way reactants adsorb, dissociate, and move through the reaction pathway. Its performance is approximately three times that of conventional commercially available Cu/Zn/Al catalysts.
Direct CO2 to methanol
The researchers found that this catalyst promotes CO2 adsorption and is primarily active at zirconia (ZrO2) sites. This directs the reaction to methanol production via the formate pathway.
In traditional Cu-based catalysts, activation typically begins by breaking the C=O bond before hydrogenation occurs. The new strategy follows a different order. Hydrogenation occurs first at the ZrO2 site, followed by C=O bond cleavage.
According to the researchers, this change in reaction mechanism significantly reduces the production of carbon monoxide (CO) byproducts while preserving the Cu sites’ strong ability to efficiently dissociate H2.
“Our study may provide a new route to address the long-standing trade-off between activity and selectivity in methanol synthesis from CO2,” said Professor Sun.
