Nanostructured platinum in ordered mesoporous silica as novel efficient catalyst for propane total oxidation

Abstract

Mesoporous SBA-15 and KIT-6 supporting platinum catalysts were prepared and subsequently used in propane total oxidation. The properties of the prepared catalysts were investigated by low-angle X-ray diffraction, nitrogen physisorption, transmission electron microscopy, CO chemisorption, X-ray photoelectron spectroscopy and H₂-titration methods. Significant reaction rate enhancements have been achieved via mesopore introduction, with turnover frequencies (TOF) in the sequence: Pt/KIT-6 (60.30 × 10⁻³ s⁻¹) ≫ Pt/SBA-15 (19.27 × 10⁻³ s⁻¹) > Pt/Al₂O₃ (5.11 × 10⁻³ s⁻¹). The results indicate that the synthesized catalysts have ordered mesoporous structures and well-dispersed Pt species. They exhibit superior catalytic activities for propane total oxidation in comparison to the conventional Pt/Al₂O₃ catalyst. The 2-D hexagonal channels in SBA-15 and the 3-D cubic structure in KIT-6 can successfully control the particle sizes of platinum in the mesopores. By contrast, the platinum nanoparticles in KIT-6 are smaller than those in SBA-15, with homogeneous size distribution and exist in lower oxidation state, which are beneficial to the catalytic activity.