CO2 hydrogenation to methanol on intermetallic PdGa and PdIn catalysts and the effect of Zn co-deposition

The behaviour of Pd deposited on Ga2O3 and In2O3 by CVI is compared for the hydrogenation of CO2 to methanol. Ga2O3 alone is inactive, but In2O3 has good conversion, and selectivity as high as 89 % to CH3OH. The addition of Pd to the catalysts had relatively little effect for In2O3, but in contrast, the addition of Pd to Ga2O3, has a very big effect, inducing high activity and selectivity to methanol. Both oxides form Pd intermetallics - Pd2In3 and Pd2Ga. However, for the In catalysts there is also a thick (∼3 nm) overlayer of the oxide, while for the Ga catalyst there was no such overlayer. Hence this is why addition of Pd to the Indium catalysts has relatively little effect on performance compared with Ga. Furthermore, the effect of Pd and Zn co-deposition on Ga₂O₃ and In₂O₃ was investigated, as well as the effect of the support morphology. Upon co-deposition of Pd and Zn, and after reduction, the Pd2In3 catalyst remains phase stable, whereas the Pd2Ga alloy is replaced by PdZn, and is improved in methanol yield