The influence of La incorporation on the performance of the CuxCeyLa1-(x+y)O2-δ catalysts for CO2 hydrogenation to methanol

Abstract

The effect of La incorporation on the catalytic performance of Cu–CeO2 for CO2 hydrogenation to methanol was investigated. The increase of the CeO2 lattice constant and shift in the F2g band from Raman spectroscopy confirmed La incorporation into the CeO2 lattice. The La atomic percent of ≤ 19 % was the upper limit for the amount of La incorporated fully into the CeO2 lattice without any phase segregation. XPS results of Cu0.25Ce0.56La0.19O2-δ assumed to have full La incorporation, showed a maximum concentration of oxygen vacancies that facilitated CO2 adsorption and conversion to methanol.The lattice fringes from HRTEM and lattice expansion confirmed that Cu was located on the catalyst surface for the synthesized catalysts. Cu0.25Ce0.56La0.19O2-δ showed an improvement in the methanol space-time yield when the temperature was increased from 260 °C to 280 °C, in contrast to the catalysts with excess La on the surface. The descriptors for the methanol production were the availability of oxygen vacancies and the metal-metal oxide interaction (Cu–CexLa1−xO2-δ and Cu–La2O2CO3). The smaller metallic Cu crystallite size for Cu0.25Ce0.19La0.56O2-δ suggested increased interactions between Cu0 and the CexLa1−xO2-δ support, which was conducive for methanol formation. The highest performance of Cu0.25Ce0.56La0.19O2-δ at a higher temperature of 280 °C and pressure of 50 bar with a methanol space-time yield of 55.2 gCH3OH.kgcatal.h−1 was attributed to the excellent thermal stability of the formed CexLa1−xO2-δ solid solution support interacting with Cu which prevented sintering.