Influence of Nanoscale Intimacy in Bi-Functional Catalysts for CO 2 -Assisted Dehydrogenation of C 5 -Paraffins.

In this study, Pt₁Sn₁ intermetallic nanoparticles (NPs) on SiO₂/CeO₂@SiO₂ composites were located either on SiO₂ or on CeO₂@SiO₂, thereby varying the average distance (intimacy) between metal sites and CeO_x sites from "closest" to "nanoscale". The catalytic performance of these catalysts was compared to dual-bed mixtures of Pt₁Sn₁@SiO₂ and CeO₂@SiO₂ powders, which provided a "milliscale" distance between sites. Several beneficial effects on the catalytic performance of CO₂-assisted oxidative dehydrogenation of C₅-paraffins were observed when Pt₁Sn₁ nanoparticles were located on SiO₂ in nanoscale proximity to the CeO₂ sites, as opposed to Pt and Sn species located on CeO₂@SiO₂ with the closest proximity and milliscale intimacy between Pt₁Sn₁ and CeO₂. The former catalysts exhibited the highest C₅-paraffin conversion of 32.8%, with a C₅ total olefin selectivity of 68.7%, while the closest-proximity sample had a lower conversion of 17.4%, with a C₅ total olefin selectivity of 20.9%. The FT-IR (Fourier transform infrared spectroscopy) spectroscopic study of the CO adsorption and X-ray photoelectron spectroscopy results revealed that the closest proximity between Pt and Ce inhibited PtSn alloy formation due to their strong interaction. However, for the nanoscale-proximity sample, neighboring CeO₂@SiO₂ did not disturb Pt₁Sn₁ intermetallic formation. This strategy can be applied to other CO₂ activation catalysts, instead of CeO₂@SiO₂. This paper aims to provide insights into the influence of metal–CeO_x intimacy in bi-functional catalysts. [ABSTRACT FROM AUTHOR]