Comparative study on CuO-La2O3/ZrO2 catalysts prepared by amino acid complexing-combustion in CO2 hydrogenation

For preparation of functional materials, the facile and efficient complexing-combustion method has many advantages such as the easily operating, no washing and filtration process, a slight loss of the products obtained, material saving, and so on. Here, CuO-La2O3/ZrO2 catalysts were prepared by using various amino acids as complexing-combustion agents for CO2 hydrogenation to methanol. Based on the results of characterization by N-2 physical adsorption, SEM, XRD, XPS, and chemisorption, along with the experimental data, it was found that the structure and catalytic activity of as-obtained catalysts depended on the group type and carbon chain length of amino acids. Among them, L-glutamic acid had two carboxyl hydrophilic groups and a moderately long carbon chain, which was conducive to the formation of a larger specific surface area along with abundant pores and a smaller grain size of CuO. Moreover, the prepared catalyst showed a higher Cu dispersion and the abundant surface acidic/basic sites. As a result, the larger Cu+/Cu-0 surface area contributed to the active adsorption of H-2 and CO2 molecules, which greatly improved the hydrogenation of CO2, while the methanol production increased with the increase of surface basicity/acidity. For example, the selectivity to methanol of 87.9%, which corresponded to a methanol yield of 120 mg/(h g(catalyst)), was obtained along with a stable online performance (life span more than 144 h) at 2.2 MPa, 220 degrees C, H-2/CO2 = 2, and GHSV = 3000 h(-1).

Automated summary

CuO-La2O3/ZrO2 catalysts were prepared using various amino acids as complexing-combustion agents for CO2 hydrogenation to methanol. The structure and catalytic activity of the catalysts depended on the group type and carbon chain length of amino acids. L-glutamic acid showed the best performance, with a selectivity to methanol of 87.9% and a stable online performance for over 144 hours.