Influence of gas impurities on the hydrogenation of CO2 to methanol using indium-based catalysts

Abstract

In this study, the performance of an In₂O₃/ZrO₂ catalyst for hydrogenation of CO₂ to methanol is reported in the presence of typical impurities of industrial CO₂ feed gas streams. Experiments were performed with defined amounts of SO₂, H₂S, NO₂, NH₃ and hydrocarbons purposely added to the reaction mixture under industrially relevant conditions (225–275 °C, 50 bar total pressure, H₂ : CO₂ = 3 : 1). Comparative studies – with and without added impurities – further relate the observed effects to the behaviour of the commercial Cu/ZnO/Al₂O₃ methanol catalyst under identical treatments. Elemental analysis was used to determine the amount of sulphur, nitrogen and carbon residing on the catalyst after poisoning and after methanol synthesis. Moreover, temperature programmed desorption (TPD), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) allowed identifying potential catalyst poisons formed on the catalyst surface. This work discloses that H₂S and SO₂ impurities led to drastic deactivation of the In₂O₃/ZrO₂ catalyst (due to indium sulfide and -sulphate formation), while NH₃, NO₂ and hydrocarbon impurities have no major effect on the methanol production.