Improved methanol synthesis from CO2 hydrogenation over CuZnAlZr catalysts with precursor pre-activation by formaldehyde

Formaldehyde (FA) was introduced into precursor slurries of CuZnAlZr catalysts (CZAZ) from co-precipitation in order to improve its catalytic performance in CO2 hydrogenation to methanol. The obtained CZAZ catalysts with and without FA pre-activation were characterized by X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, X-ray diffraction, N2O-H2 titration, N2 adsorption-desorption, scanning electron microscopy and transmission electron microscope, respectively. The results indicated that FA pre-activation led to Cu2+ reduction to Cu+ in CZAZ precursors. After calcination in N2 the copper components existed in state of Cu2O, which could provide highly-dispersed active Cu0 particles with a weak interaction between metal and supports. Meanwhile, FA pre-activation also gave rise to more crystallized semiconductor ZnO phase especially calcination in N2 at a high temperature. Therefore, the obtained CZAZ catalysts with FA pre-activation on precursor exhibited better catalytic performance in CO2 hydrogenation due to the synergistic effect of Cu0 particles and crystallized semiconductor ZnO phase.