An efficient Li-modified heterogeneous Pd–Cu/Al2O3 Wacker catalyst for selective oxidation of 1-butene to 2-butanone

Abstract

2-Butanone, a critical industrial solvent and chemical intermediate, is traditionally produced via an energy-intensive two-step process involving acid-catalyzed hydration of 1-butene to secondary butyl alcohol, followed by dehydrogenation. Direct Wacker oxidation of 1-butene offers a simpler, more efficient alternative but is hindered by low selectivity and rapid catalyst deactivation in heterogeneous systems, primarily due to the reduction of Pd²⁺—the active species—to Pd^δ+ or Pd⁰, which aggregates into larger nanoparticles. Here, we report a strategy to enhance the performance of Pd–Cu/γ-Al₂O₃ catalysts through Li modification, leveraging alkali-mediated Pd–support interactions to stabilize small PdO clusters and electron-deficient Pd²⁺ states. The optimized Pd1Cu3/Li_0.15-Al-O catalyst achieves a 2-butanone selectivity of 92%, compared to 70% for unmodified Pd1Cu3/γ-Al₂O₃, with exceptional stability during prolonged evaluation. Structural characterizations reveal that Li-boosted oxygen linkages enhance metal–support interactions, maintaining the active Pd²⁺ state and preventing nanoparticle aggregation. This approach offers a rational design framework for electron-deficient noble metal catalysts, with potential applications in selective oxidation and beyond.