Active and stable Au/ZrO₂ catalysts for isomerization of allylic esters: A practical application of heterogeneous gold catalysis

The isomerization of allylic esters using zirconia-supported Au nanoparticle (NP) catalysts is an attractive solution for the efficient utilization and transformation of C4 derivatives in current industrial processes. The catalytic isomerization of allylic esters using zirconia-supported Au NPs was demonstrated to be both economical and environmentally friendly. This study introduces a novel application of gold catalysis for the transformation of but-3-ene-1,2-diyl diacetate (3,4-DABE) and but-2-ene-1,4-diyl diacetate (1,4-DABE), which are valuable intermediates for butanediol or tetrahydrofuran production. The reaction proceeded efficiently under solvent-free conditions, and the optimal catalysts exhibited high activity and stability. The Koros-Nowak criterion test and reaction condition modulation were conducted to optimize the catalytic efficiency. Catalysts with high gold loadings proved to be more efficient on a per-gold-atom basis. The partial pressure of oxygen was revealed to be a critical factor influencing the performance of supported Au NP catalysts in both batch and flow reactions. In particular, the oxygen atmosphere provided a modifying function to the surface of the supported Au NPs, facilitating the formation and maintenance of the Au^δ+ component, which is the active species with soft Lewis acidic properties. Theoretical calculations revealed that adsorption of oxygen molecules facilitated this reaction. Crucially, the catalytic system maintained its performance during a 50-day continuous-flow reaction scaled up to the kilogram level, confirming its suitability for industrial applications. This study highlights the economic and environmental benefits of the isomerization process and its potential as a practical solution for the industrial transformation of C4 derivatives.