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

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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 (Pt0.3K0.8/θ-Al2O3-N and Pt0.3/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.