Methanol, an important chemical, fuel additive, and precursor for clean fuels, is produced by hydrogenation of carbon oxides over Cu‐based catalysts. Despite the technological maturity of this process, the understanding of this apparently simple reaction is still incomplete with regard to the reaction mechanism and the active sites. Regarding the latter, recent progress has shown that stepped and ZnOx‐decorated Cu surfaces are crucial for the performance of industrial catalysts. Herein, we integrate this insight with additional experiments into a full microkinetic description of methanol synthesis. In particular, we show how the presence or absence of the Zn promoter dramatically changes not only the activity, but unexpectedly the reaction mechanism itself. The Janus‐faced character of Cu with two different sites for methanol synthesis, Zn‐promoted and unpromoted, resolves the long‐standing controversy regarding the Cu/Zn synergy and adds methanol synthesis to the few major industrial catalytic processes that are described on an atomic level.

The promoting effect of Al, Ga, and Mg on the support in Cu/ZnO catalysts for methanol synthesis has been investigated. Different unpromoted and promoted ZnO supports were synthesized and impregnated with Cu metal in a subsequent step. All materials, supports, and calcined and activated catalysts were characterized by various methods, including contactless (microwave) conductivity measurements under different gas atmospheres. Small amounts of promoters were found to exhibit a significant influence on the properties of the oxide support, concerning textural as well as electronic properties. We found correlations between the conductivity of the ZnO support and the activity of the catalyst in the reverse water-gas shift reaction (rWGS) as well as in methanol synthesis. In rWGS the activation energy and reaction order in H₂ are decreased upon promotion of the ZnO support with the trivalent promoters Al³⁺ and Ga³⁺, indicating an electronic promotion. In methanol synthesis, results point to a structural promotion by Al³⁺ and Ga³⁺. A detrimental effect of Mg²⁺ doping was observed in both reactions. This effect is discussed in the context of the reducibility of ZnO under reaction conditions, which can be tuned by the promoter in different ways. The reducibility is seen as a critical property for the dynamic metal support interaction of the Cu/ZnO system

Long-term stability of catalysts is an important factor in the chemical industry. This factor is often underestimated in academic testing methods, which may lead to a time gap in the field of catalytic research. The deactivation behavior of an industrially relevant Cu/ZnO/Al2 O3 catalyst for the synthesis of methanol is reported over a period of 148 days time-on-stream (TOS). The process was investigated by a combination of quasi in situ and ex situ analysis techniques. The results show that ZnO is the most dynamic species in the catalyst, whereas only slight changes can be observed in the Cu nanoparticles. Thus, the deactivation of this catalyst is driven by the changes in the ZnO moieties. Our findings indicate that methanol synthesis is an interfacially mediated process between Cu and ZnO.