The Mechanism of CO and CO₂ Hydrogenation to Methanol over Cu‐Based Catalysts

Abstract

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.

Methanol Synthesis from Industrial CO2 Sources: A Contribution to Chemical Energy Conversion

“…However, later on, Chinchen et al [13] showed by isotopic labelling of CO 2 in syngas that CO 2 is the primary methanol source when methanol synthesis is performed over the commercial catalyst. The results obtained by Schlögl and co-workers [14], who also used 13 CO 2 -labeling for the determination of the carbon source, confirm this statement. It is worth to note that carbon monoxide acts as a scavenger of oxygen atoms coming from the water production [11].…”

Highly Active Au/δ-MoC and Cu/δ-MoC Catalysts for the Conversion of CO2: The Metal/C Ratio as a Key Factor Defining Activity, Selectivity, and Stability

“…This is not unexpected since formate is typically observed on CO 2 hydrogenation using Cu as catalysts. [60][61][62] Nevertheless, formate decomposition to the HCO intermediate is very unlikely since it is endothermic by 1.4 eV and HCOO hydrogenation towards formic acid or dioxymethylene (H 2 COO) ⎯as previous step of H 2 CO formation 26,56 ⎯ presents large energy barriers; 1.40 eV to H 2 COO formation. Clearly, reaction pathways via formate can be discarded and this species will at most behave as an spectator perhaps poisoning the surface.…”

IR-Spectroscopic Study on the Interface of Cu-Based Methanol Synthesis Catalysts: Evidence for the Formation of a ZnO Overlayer

“…Recently, a Cu/ZnO:Al (Al as dopant in the ZnO; ZnO:Al, lower Al-content of <3 wt%) catalyst has been compared with a Cu/MgO catalyst in methanol synthesis [20][21][22]. The Cu nano-structure in Cu/ZnO:Al and Cu/MgO is almost identical due to the common malachite-based precursor structure [20].…”