Diffusion-Driven Selectivity in Oxidation of CO in the Presence of Propylene Using Zeolite Nano Shell as Membrane

The selective oxidation of CO over C₃H₆ is achieved in yolk-shell Pt@Silicalite-1 catalysts in which Pt nanoparticles are encapsulated in hollow silicalite-1 single crystals. The thin shell operates as a permselective membrane which limits Pt surface poisoning by C₃H₆. From adsorption measurements, we conclude that the catalytic selectivity arises from the fastest diffusion of CO over C₃H₆ through the silicalite-1 membrane

One-Pot Preparation and CO₂ Adsorption Modeling of Porous Carbon, Metal Oxide, and Hybrid Beads

Hierarchically porous carbon (C), metal oxide (ZrTi), or carbon–metal oxide (CZrTi) hybrid beads are synthesized in one pot through the in situ self-assembly of Pluronic F127, titanium and zirconium propoxides, and polyacrylonitrile (PAN). Upon contact with water, a precipitation of PAN from the liquid phase occurs concurrently with polymerization and phase separation of the inorganic precursors. The C, ZrTi, and CZrTi materials have similar morphologies but different surface chemistries. The adsorption of carbon dioxide by each material has been studied and modeled using the Langmuir–Freundlich equation, generating parameters that are used to calculate the surface affinity distributions. The Langmuir, Freundlich, Tóth, and Temkin models were also applied but gave inferior fits, indicating that the adsorption occurred on an inhomogeneous surface reaching a maximum capacity as available surface sites became saturated. The carbon beads have higher surface affinity for CO₂ than the hybrid and metal oxide materials