The heterogeneously catalysed reaction of hydrogen with carbon monoxide and carbon dioxide (syngas) to methanol is nearly 100 years old, and the standard methanol catalyst Cu/ ZnO/Al 2 O 3 has been applied for more than 50 years. Still, the nature of the Zn species on the metallic Cu 0 particles (interface sites) is heavily debated. Here, we show that these Zn species are not metallic, but have a positively charged nature under industrial methanol synthesis conditions. Our kinetic results are based on a self-built high-pressure pulse unit, which allows us to inject selective reversible poisons into the syngas feed passing through a fixed-bed reactor containing an industrial Cu/ZnO/Al 2 O 3 catalyst under high-pressure conditions. This method allows us to perform surface-sensitive operando investigations as a function of the reaction conditions, demonstrating that the rate of methanol formation is only decreased in CO 2-containing syngas mixtures when pulsing NH 3 or methylamines as basic probe molecules.

A series of ZnO/Cr 2 O 3 catalysts with different Zn:Cr ratios was prepared by coprecipitation at a constant pH of 7 and applied in methanol synthesis at 260−300 °C and 60 bar. The X-ray diffraction (XRD) results showed that the calcined catalysts with ratios from 65:35 to 55:45 consist of ZnCr 2 O 4 spinel with a low degree of crystallinity. For catalysts with Zn:Cr ratios smaller than 1, the formation of chromates was observed in agreement with temperature-programmed reduction results. Raman and XRD results did not provide evidence for the presence of segregated ZnO, indicating the existence of Zn-rich nonstoichiometric Zn−Cr spinel in the calcined catalyst. The catalyst with Zn:Cr = 65:35 exhibits the best performance in methanol synthesis. The Zn:Cr ratio of this catalyst corresponds to that of the Zn 4 Cr 2 (OH) 12 CO 3 precursor with hydrotalcitelike structure obtained by coprecipitation, which is converted during calcination into a nonstoichiometric Zn−Cr spinel with an optimum amount of oxygen vacancies resulting in high activity in methanol synthesis. Density functional theory calculations are used to examine the formation of oxygen vacancies and to measure the reducibility of the methanol synthesis catalysts. Doping Cr into bulk and the (10−10) surface of ZnO does not enhance the reducibility of ZnO, confirming that Cr:ZnO cannot be the active phase. The (100) surface of the ZnCr 2 O 4 spinel has a favorable oxygen vacancy formation energy of 1.58 eV. Doping this surface with excess Zn charge-balanced by oxygen vacancies to give a 60% Zn content yields a catalyst composed of an amorphous ZnO layer supported on the spinel with high reducibility, confirming this as the active phase for the methanol synthesis catalyst.

One of the major goals of current research on energy conversion is the mitigation of CO 2 emission. A beneficial scenario for CO 2 utilization is the catalytic conversion of industrial waste or process gases into valuable products. Within the crossindustry approach of Carbon2Chem the synthesis of methanol from steel mill exhaust gases is a promising way to close the carbon cycle based on additional sustainably produced H 2 . New catalyst requirements have to be met due to fluctuating feed gas composition and availability as well as gas separation and purification issues.

The suitability of a commercial and industrially applied Cu‐based catalyst for the synthesis of methanol by CO2 hydrogenation was investigated. Unexpectedly, this system showed high stability and well‐performance under conditions that may be relevant for chemical energy conversion using hydrogen and energy from renewable technologies. This Cu‐based catalyst demonstrated excellent suitability for dynamical process operation that may be essential for effective compensation of the volatility of renewable energy sources.

The influence of impurities in steel mill exhaust gases on ternary Cu/ZnO/Al2O3 catalysts was studied for conventional methanol synthesis, which is one of the central reactions within the cross‐industrial approach of Carbon2Chem®. A series of hydrocarbons was identified as inert spectators for methanol synthesis. Several catalyst poisons like N‐containing compounds or O2 show reversible characteristics at low pressure. However, by increasing the partial pressure of O2, poisoning becomes irreversible, indicating different poisoning mechanisms concerning the reversibility of deactivation.

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