Pt–Fe Nanoparticles Dispersed on Mesoporous Silica as Selective Catalysts for Dehydrogenation of Isobutane.

A series of catalysts composed of Pt–Fe nanoparticles supported on mesoporous silica SBA-15 (ca. 7 nm pore diameter) have been prepared by ultrasound-assisted coimpregnation of the metal precursors and evaluated in the nonoxidative dehydrogenation of isobutane. Prereduced catalytic systems were characterized by STEM-HAADF + EDS mapping and XAS to determine the chemical environment of the highly dispersed platinum active sites on the iron host matrix. While the monometallic platinum (nanoparticles) supported on SBA-15 material presented a rapid catalyst deactivation under reaction conditions, coordinatively unsaturated Pt–Fe (Pt ≪ Fe) sites located in the mesopores of SBA-15 showed a high steady-state activity (43% conversion) and selectivity (96% to isobutylene) in the dehydrogenation of isobutane at 550 °C for several hours. Temperature-programmed reduction profiles determined not only the substantially higher reducibility of FeO_x species with doping amounts of platinum in the as-prepared (calcined) catalysts but also the detrimental structural changes undergone after consecutive reaction–regeneration cycles. Finally, reactivation under controlled conditions allows to minimize irreversible catalyst deactivation after successive cycles. [ABSTRACT FROM AUTHOR]