Operando Synchrotron X‐ray Powder Diffraction and Modulated‐Excitation Infrared Spectroscopy Elucidate the CO 2 Promotion on a Commercial Methanol Synthesis Catalyst

Optimal amounts of CO 2 are added to syngas to boost the methanol synthesis rate on Cu‐ZnO‐Al 2 O 3 in the industrial process. The reason for CO 2 promotion is not sufficiently understood at the particle level due to the catalyst complexity and the high demands of characterization under true reaction conditions. Herein, we applied operando synchrotron X‐ray powder diffraction and modulated‐excitation infrared spectroscopy on a commercial catalyst to gain insights into its morphology and surface chemistry. These studies unveiled that Cu and ZnO agglomerate and ZnO particles flatten under CO/H 2 and/or CO 2 /H 2 . Under the optimal CO/CO 2 /H 2 mixture, sintering is prevented and ZnO crystals adopt an elongated shape due to the minimal presence of the H 2 O byproduct, enhancing the water‐gas shift activity and thus the methanol production. Our results provide a rationale to the CO 2 promotion emphasizing the importance of advanced analytical methods to establish structure–performance relations in heterogeneous catalysis.