Developing and understanding mixed metal oxide catalysts for the hydrogenation of CO2 to methanol

Anthropogenic CO2 emissions and the resulting effects of climate change remain as some of the most pressing issues today. Consequently, various carbon capture and storage (CCS) technologies have been proposed to drastically reduce the emission of CO2. The storage of CO2, however, still poses a crucial challenge. Furthermore, most bulk products in chemical industry are derived from fossil sources, which results in a considerable carbon footprint of a vast number of everyday consumables. In this regard, carbon capture and utilization (CCU) technologies offer a promising solution to resolve challenges concerning the permanent storage of CO2, by converting the greenhouse gas into value-added chemicals, which in turn, will also significantly contribute to the carbon neutrality of important chemical products. Among CCU technologies, the hydrogenation of CO2 to methanol has attracted increasing academic interest, due to the versatile applications of methanol, such as its utilization as a fuel additive or its facile conversion to further value-added bulk chemicals. CO2 + 3 H2 → CH3OH + H2O , ∆H_(R,298K)= -49.5 kJ/mol The main challenge of this reaction is the activation of CO2, which requires high energies and therefore high temperatures (e.g. T > 250 °C at 20 bar), at which the competing reverse water-gas shift (RWGS) reaction becomes thermodynamically favored, converting CO2 into the undesired by-product CO: CO2 + H2 → CO + H2O , ∆H_(R,298K)= +41.1 kJ/mol Recently, mixed metal oxide catalysts such as ZnZrOx have been reported to catalyze the hydrogenation of CO2 at very high methanol selectivity (> 90 %) and good CO2 conversion (10 %), while showing no sign of deactivation for over 500 hours of time on stream.

Anthropogenic CO2 emissions and the resulting effects of climate change remain as some of the most pressing issues today. Consequently, various carbon capture and storage (CCS) technologies have been proposed to drastically reduce the emission of CO2. The storage of CO2, however, still poses a crucial challenge. Furthermore, most bulk products in chemical industry are derived from fossil sources, which results in a considerable carbon footprint of a vast number of everyday consumables. In this regard, carbon capture and utilization (CCU) technologies offer a promising solution to resolve challenges concerning the permanent storage of CO2, by converting the greenhouse gas into value-added chemicals, which in turn, will also significantly contribute to the carbon neutrality of important chemical products.

Among CCU technologies, the hydrogenation of CO2 to methanol has attracted increasing academic interest, due to the versatile applications of methanol, such as its utilization as a fuel additive or its facile conversion to further value-added bulk chemicals.

CO2 + 3 H2 → CH3OH + H2O , ∆H_(R,298K)= -49.5 kJ/mol

The main challenge of this reaction is the activation of CO2, which requires high energies and therefore high temperatures (e.g. T > 250 °C at 20 bar), at which the competing reverse water-gas shift (RWGS) reaction becomes thermodynamically favored, converting CO2 into the undesired by-product CO:

CO2 + H2 → CO + H2O , ∆H_(R,298K)= +41.1 kJ/mol

Recently, mixed metal oxide catalysts such as ZnZrOx have been reported to catalyze the hydrogenation of CO2 at very high methanol selectivity (> 90 %) and good CO2 conversion (10 %), while showing no sign of deactivation for over 500 hours of time on stream.

Our group is interested in attaining a fundamental understanding of catalyzing the hydrogenation of CO2 to methanol over ZnZrOx catalysts to fill the gaps where current knowledge is still lacking. We are also looking into finding new mixed metal oxide formulations to further increase the methanol productivity of this type of catalyst. In doing so, we synthesize the catalysts via impregnation or co-precipitation routes and subsequently carry out an in-depth structural characterization. Ultimately, the mixed metal oxides are evaluated catalytically, and the results are correlated to structural findings to establish structure-performance relationships.

Our group is interested in attaining a fundamental understanding of catalyzing the hydrogenation of CO2 to methanol over ZnZrOx catalysts to fill the gaps where current knowledge is still lacking. We are also looking into finding new mixed metal oxide formulations to further increase the methanol productivity of this type of catalyst. In doing so, we synthesize the catalysts via impregnation or co-precipitation routes and subsequently carry out an in-depth structural characterization. Ultimately, the mixed metal oxides are evaluated catalytically, and the results are correlated to structural findings to establish structure-performance relationships.

Alexander Oing aoing01@student.ethz.ch

Alexander Oing
aoing01@student.ethz.ch