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

Abstract

AbstractFor 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 N2 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+/Cu0 surface area contributed to the active adsorption of H2 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 gcatalyst), was obtained along with a stable online performance (life span more than 144 h) at 2.2 MPa, 220°C, H2/CO2 = 2, and GHSV = 3000 h−1.