Microkinetic analysis of ring opening and decarboxylation of γ-valerolactone over silica alumina

- Thermochemical analysis of γ-valerolactone and pentenoic acid interconversion.
- Apparent kinetic trends in γ-valerolactone and pentenoic acid interconversion.
- Apparent kinetic trends in γ-valerolactone and pentenoic acid decarboxylation.
- Reconciliation of apparent kinetic trends with detailed microkinetic model.
- Study provides a framework for analysis of system chemistry over any solid acid.

This study considers the thermochemistry and kinetics of γ-valerolactone and pentenoic acid interconversion as well as the decarboxylation of both molecules over amorphous silica alumina. Through microkinetic analysis, macroscopically observed production rates and product distributions are reconciled with a mechanistic description of all chemistries. Ring opening of γ-valerolactone, cyclization of pentenoic acids, and decarboxylation of either molecule occur in parallel at surface Brønsted sites through a sequence of proton-mediated elementary steps. Conceptually, this is illustrated as proceeding through gas-phase oxonium and carbenium ions that are stabilized through interactions with deprotonated Brønsted sites and/or the solid oxide lattice. This interpretation provides a rigorous thermochemical foundation for detailed microkinetic analysis, which we employ to regress elementary interaction energies and kinetic parameters-moving the field toward a fundamental description of reactivity in acid-catalyzed upgrading of γ-valerolactone.

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