Sulfur-Promoted Hydrocarboxylation of Olefins on Heterogeneous Single-Rh-Site Catalysts
Sulfur poisoning is a severe problem in industrial applications, attracting broad interest in fundamental research studies. Although a number of studies about sulfur resistance have been implemented in many reactions on nanoparticle catalysts, few investigations focus on carbonylation reactions using heterogeneous single-metal-site catalysts (HSMSCs). Herein, we present an unanticipated sulfur-promoted performance in olefin hydrocarboxylation reactions on a single-Rh-site catalyst supported on porous ionic polymers (Rh1/PIPs) with 1000 ppm H2S in CO feed. Ex situ EXAFS and in situ DRIFTS revealed a ternary cycle mechanism of olefin hydrocarboxylation reactions with Rh–H complexes as predominant active species in both pure and H2S-containing feedstock. Moreover, the transformation of the Rh mononuclear complex with the addition of H2S was also demonstrated. Density functional theory studies were performed to verify the feasibility of the proposed pathway and confirm that the energy barriers of transition states with the sulfur ligand were much lower than those in normal feed, for example, a decline of 3.4 kcal/mol for the rate-determining step of migration and insertion of CO. This work provides a distinctive example for the insight of sulfur effect on carbonylation, which could be potentially beneficial for further applications of HSMSCs.
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