(560dc) Synthesis and Characterization of Pt-Zn Intermetallic Nanocatalysts for Light Alkanes Oxidative Dehydrogenation
Supported Pt nanoparticle has been commercialized in dehydrogenation of alkane for more than 50 years, for its superior affinity to paraffinic C-H bond over C-C bond. One of the challenges for Pt catalyst in alkane dehydrogenation is large Pt size favor side reactions such as hydrogenolysis and coke formation. It is challenging for traditional synthesis method such as wet impregnation and colloidal chemistry to prepare Pt nanoparticle that is smaller than 2 nm. Recent development in the field pointed out a new direction that effectively reduced Pt particle size by alloying Pt with other metals (e.g., Sn, Cu, In). Pt-based intermetallic alloy can suppress side reactions, due to their advantage in ordered structure with isolated active Pt sites over solid solutions in which atoms are randomly arranged.
In this work silica supported Pt-Zn intermetallic nanoparticles with different Pt-Zn alloy phases were synthesized. Specifically, we use in situ XAS to characterize the transition of the pre-catalyst Pt/ZnO/SiO2 to the intermetallic nanocatalyst Pt1Zn1/SiO2 in H2 with a multi-stage temperature ramping. Pt-Zn intermetallic phases are identified as active sites for light alkanes oxidative dehydrogenation (ODH). It was found that at temperature above 600 oC, ZnO was fully reduced, and Pt1Zn1 was formed. The oxidation state and structural change of the catalysts under ODH condition was monitored by in situ XAS. A relationship between the stability of the Pt-Zn intermetallic phases in the nanocatalysts and the catalytic performance is established, and their deactivation mechanism in ODH reaction is discussed.
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