Unveiling the Catalytic Pathway of Rh(II)/Silicalite-2 in Propene Carbonylation to Methyl Butyrate: A DFT Study.

The hydroesterification of olefins provides a highly efficient way to produce high value-added ester products from simple and abundant olefin feedstocks. In this work, DFT calculation was performed to investigate the detailed reaction mechanism of propene hydroesterification over Rh(II)/Silicalite-2 catalysts. Three possible mechanistic pathways were systematically explored and compared in terms of their adsorption configurations, reaction energies, and transition-state barriers. Among them, the Carbonylation-First pathway exhibited the most favorable energy profile with the lowest overall kinetic barriers, indicating it to be the most likely way for ester formation. A comparison of methyl butyrate and methyl isobutyrate formation revealed that the linear product is energetically more favorable, particularly along the Carbonylation-First pathway. Moreover, the Rh(II) center demonstrates a different catalytic effect over conventional Rh(I) species by significantly lowering the energy barrier for CO insertion, a key step in both hydroformylation and hydroesterification. These findings provide fundamental insight into the role of Rh(II)/zeolite systems in carbonylation reactions and offer theoretical guidance for the design of catalysts.