Green methanol from renewable feeds : Towards scalable catalyst synthesis and improved stability

Methanol is an important platform chemical in many applications.[1] The widely used Cu/ZnO-based catalysts for methanol synthesis have been studied in detail.[2]
CO2-rich feeds (e.g. from carbon capture and storage; CCS) can contribute to the reduction of the climate footprint of methanol production. Cu/ZnO/ZrO2 (CZZ) systems have been developed for the conversion of syngas with high CO2 content, combining good productivity with appropriate stability over long time on stream (ToS).[3,4] To obtain the CZZ material in sufficient amounts with the desired properties (e.g. high activity and stability), continuous co-precipitation has been implemented as a promising formation method.[5] Future methanol production is expected to use H2 from solar-based electrolysis which, due to occurring impurities, could affect catalyst stability. In this work, recent results on understanding the fundamentals of catalyst precursor synthesis, especially with regard to the effect of ZrO2 on precursor formation are presented (Figure 1a). An optimization of the synthesis procedure in terms of ageing time and productivity by seeding will be discussed (Figure 1b).
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Effects of long-term catalyst use in methanol synthesis with particular regard to deactivation phenomena will also be presented. For this, a baseline is established by deactivating catalysts under pure feed gases and analyzing them afterwards. It is found that sintering of metallic copper and also zinc oxide are the main causes of catalyst deactivation as it is known from literature.[6] Interestingly, sintering is even beginning during initial reduction (activation) of the material and is not reversible by re-reduction. In addition, it was observed that the amount of zinc oxide on the surface of the catalysts is increasing by reducing it. This is caused by the formation of a ZnOx overlayer, as literature found for CZA systems. [7] Potential impurities may be dosed additionally in future work.