A promising low pressure methanol synthesis route from CO2 hydrogenation over Pd@Zn core–shell catalysts

Abstract

At present, there is no low pressure methanol synthesis from CO₂/H₂ with high yield despite the presence of an upstream process of aqueous phase reforming (APR) of biomass derivatives on an industrial scale for CO₂/H₂ production at ca. 2 MPa. This is due to the intrinsic thermodynamics of the system which leads to particularly high CO levels at low pressure through reversed water gas shift reaction (RWGS) for most studied catalysts. Here we report a new Pd@Zn core–shell catalyst that offers a significantly higher kinetic barrier to CO/H₂O formation in CO₂ hydrogenation to reduce the CO levels but facilitates CH₃OH formation at or below 2 MPa with CH₃OH selectivity maintained at ca. 70% compared to ca. 10% over industrial Cu catalysts. The corresponding methanol yield at 2 MPa reaches 6.1 g_methanol g_{active metal}⁻¹ h⁻¹, which is comparable to the best reported value among a wide variety of catalysts under 5 MPa. It is thus believed that this active Pd based catalyst opens up a promising possibility for low pressure and temperature methanol production using a renewable biomass resource for fossil-fuel-starved countries.