The Cu-ZnO synergy in methanol synthesis Part 3: Impact of the composition of a selective Cu@ZnOx core-shell catalyst on methanol rate explained by experimental studies and a concentric spheres model

- Selective Cu@ZnOx core-shell catalysts of various compositions were synthesized.
- The catalytic sites are of the type CuxZn(1−x)Oy.
- A predictive model for determining the core-shell catalysts activity was developed.
- A correlation between activity and Zn migrated for three catalyst designs is shown.

Highly selective catalysts for methanol synthesis from CO2 and H2 are required for increasing the process efficiency that actually produces large amounts of CO. The understanding of the Cu-ZnO synergy allowed the possibility to design core-shell catalysts of the type Cu@ZnOx with enhanced selectivity for methanol. This type of core-shell structure was synthesized with variable compositions and the catalytic efficiency as well as the physicochemical properties were scrutinized in order to build structure-reactivity relationships. Zn migration is responsible for the formation of the CuxZn(1−x)Oy active phase. The experimental results were compared with theoretical calculations based on a geometrical model taking into account the amount of Zn migrated. A direct correlation was found between theory and experiment. Finally, a linear correlation of catalyst activity versus Zn migrated is shown for three different catalyst designs, thus confirming that a high Zn migration is needed for obtaining an efficient methanol synthesis catalyst.

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