Pt supported on cross-linked poly(vinylsiloxanes) and SiCO ceramics — new materials for catalytic applications

Highlights: • Si–H groups present in cross-linked regular poly(vinylsiloxanes) reduce Pt⁴⁺ ions to Pt⁰. • Sizes of Pt crystallites formed are controlled by polymers' cross-link densities. • Pyrolysis of the systems leads to SiCO ceramics with dispersed Pt. • Unpyrolyzed and pyrolyzed systems can be applied as heterogeneous catalysts. In the work, the new approach to the preparation of metallic Pt dispersed in polysiloxane networks for catalytic applications is presented. Metal particles have been introduced into the preformed poly(vinylsiloxane) networks obtained by cross-linking of linear vinylsiloxane (D₂V and V₃) polymers with hydrosiloxanes of various contents of Si–H groups in the molecules and differing in molecular structures. The studies demonstrate unambiguously that Si–H groups remaining in the systems after cross-linking are capable of reducing Pt⁴⁺ ions from PtCl₄ solution to Pt⁰. Sizes of metal crystallites formed are controlled by cross-link densities in the systems. Pyrolysis of poly(vinylsiloxane) networks with incorporated Pt, performed at 1000 °C in Ar atmosphere leads, in turn, to metallic Pt particles dispersed in SiCO ceramics. All the prepared Pt-containing systems show activity in catalytic isopropyl alcohol conversion. Acetone is the major product of this process conducted in the presence of the unpyrolyzed materials. D₂V polymer-based systems are more active than the V₃-derived ones due to their lower cross-link densities which cause better accessibility of the catalytic sites for the reacting alcohol molecules. In the presence of the pyrolyzed systems, isopropyl alcohol transforms mainly to propene; these materials exhibit stable catalytic performance up to high temperatures.