Performance and Mechanism of Catalytic Propane Dehydrogenation over PtK₂/θ-Al₂O₃ Catalysts

Propane dehydrogenation (PDH), which produces propylene and by-produces hydrogen, attracts considerable attention in the chemical industry. Alkali metals, budget friendly and commonly used as additives to optimize the performance of Pt-based alloy catalysts, are extensively utilized in the PDH industry. Herein, the structure and catalytic performance of the commercial catalyst (PtK₂/θ-Al₂O₃) and contrast samples (Pt_0.3K_0.8/θ-Al₂O₃-N and Pt_0.3/θ-Al₂O₃) are analyzed. According to the catalytic test, the PtK₂/θ-Al₂O₃ exhibits better catalytic performance, which achieves >95% propylene selectivity and maintaining a high propane yield (>36%) during stability testing. Observations reveal that the initial propylene selectivity of the Pt-based catalysts is inversely correlated with the total acidity and strong acid site content. The introducing of K element significantly reduces the acidity of the catalyst and enhances the propylene selectivity. Moreover, the presence of Cl^-, co-introduced with K, improves the catalytic stability, while the slight increase in the acidity of catalysts decreases the propylene selectivity. The enrichment of the electron density of PtK₂ nanoparticles contributes to the improvement of catalytic performance. Density functional theory calculations suggest that lower propylene adsorption energy and higher barrier for propylene deep dehydrogenation reaction on the PtK₂-(100) surface enhance the propylene selectivity of the PtK₂/θ-Al₂O₃ catalyst.