Impact of topology framework of microporous solids on methanol carbonylation: An operando DRIFTS-MS study

Methanol carbonylation was evaluated over heterogeneous catalysts based on Cu-exchanged zeolitic materials with different topology: Cu@MOR, Cu@FER, and Cu@ZSM-5. Despite the similar Si/Al ratios, it is crucial to acknowledge that the acid strength is influenced by the framework topology, as supported by the NH3-TPD results. This, along with other characterization techniques allowed us to estimate the impact of pore size and pore distribution in these microporous materials on catalytic performance. The channel structure influenced catalytic parameters such as conversion and selectivity. The higher methanol conversion achieved on Cu@FER shows the importance of Bronsted acid sites and redox centres location regarding the topology of the material. Concerning the selectivity, the production of acetic acid was endorsed by the 12-MR (MOR) channels, methyl acetate's production by the 10-MR (FER) channels. Finally, the presence of 6-MR (ZSM-5) channels led to a complete selectivity towards DME production. The reaction mechanism was elucidated via operando DRIFTS-MS and results revealed a bifunctional mechanism in which methanol adsorbs and dehydrates on acidic Bronsted sites and CO is activated over Cu+ species.

Automated summary

Methanol carbonylation was studied over Cu-exchanged zeolitic materials with different topologies: Cu@MOR, Cu@FER, and Cu@ZSM-5. Acid strength was found to be influenced by the framework topology as supported by NH3-TPD results. Pore size and distribution were found to affect catalytic performance, with Cu@FER showing higher methanol conversion due to the presence of Bronsted acid sites and redox centres. Selectivity for acetic acid, methyl acetate, and DME production was determined by the specific channel structure in each material. The reaction mechanism was elucidated using operando DRIFTS-MS and involved methanol adsorption and dehydration on acidic Bronsted sites, with CO activation occurring over Cu+ species.