One of the ways to utilize CO2 is to obtain ethanol for the subsequent production of synthesis gas, a mixture of hydrogen and carbon monoxide that can be used to generate electricity and heat. The conversion of ethanol into synthesis gas usually involves nickel-based catalysts, which have a major drawback: when heated, their metal particles sinter (stick together), with carbon being deposited on their surface, which makes the catalyst less efficient.
To solve this problem, the RUDN scientists developed a bimetallic catalyst in which nickel and copper nanoparticles played the role of the active substance, while an alloy based on aluminum, zirconium and cerium oxides was used as a carrier. Thanks to this substrate, carbon particles were no longer deposited on the surface of the catalyst.
In order to compare the efficiency of the new compounds with that of monometallic (nickel or copper) catalysts, the authors conducted an experiment for obtaining ethanol from carbon dioxide. The chemical reaction took place at a temperature of 650°C in the course of seven hours, during which the scientists recorded the conversion products using special sensors.
They found that the addition of copper to the nickel catalyst helps obtain synthesis gas with an increased concentration of hydrogen. While the proportion of H2 and CO each in the synthesis gas was 50% after the use of a conventional nickel catalyst, the addition of copper (at a concentration of 1%) caused the proportion of hydrogen to rise to 55–68% (depending on the composition of the substrate) and the proportion of carbon monoxide fall to 32–45%. Over the entire reaction time, the activity of copper-nickel catalysts decreased by a mere 5–10% (depending on copper content).
“Our studies have shown that the addition of a small amount of copper to a nickel catalyst helps maintain its activity at high temperatures due to the fact that it prevents the nanoparticles from sticking together. The application of bimetallic nanoparticles to a substrate of metal oxides helps avoid another negative effect, i.e., the deposition of carbon on the catalyst surface. The proposed catalytic system will be useful for utilizing greenhouse gases and obtaining compounds for the chemical and power industries in a simple and environmentally friendly way,” Anna Zhukova, candidate of chemical sciences, is quoted as saying by the Russian Science Foundation.
