Hybrid photocatalytic membranes embedding decatungstate for heterogeneous photooxygenation

Abstract

The incorporation of decatungstate in polymeric membranes provides new heterogeneous photocatalysts for the oxidation of organic substrates under oxygen atmosphere at 25°C. Photocatalytic membranes have been prepared yielding polymeric films with a high thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support. Catalyst screening has been performed under both homogeneous and heterogeneous photooxygenation conditions. The photocatalyst activity has been evaluated in terms of the substrate conversion, turnover numbers, and recycling experiments. A membrane induced selectivity behavior has been evidenced by comparison with homogeneous oxidations.

Membrane Reactors: Advanced Systems for Intensified Chemical Processes

“…The development of new efficient heterogeneous photocatalytic systems might guarantee a minimal environmental impact. An ideal photocatalyst should undergo photoexcitation employing sunlight at room temperature, promote fast and selective processes, activate dioxygen to form reactive oxygenated species, be stable and easily recyclable for multi-turnover processes [48].…”

“…Catalyst stability was positively influenced by the polymeric environment in which it was confined. Moreover, the selective separation function of the membrane results in an enhancement of the phenol mineralization in comparison with the homogeneous reaction [48].…”

Photocatalytic Processes in Membrane Reactors

“…In the immobilized system, the catalyst can be coated on the walls of the reactor, supported on a solid substrate or deposited around the case of the light source, using supported materials such as alumina, zeolite [113,146], AC [58,59], silica support [11,103,147], glass beads [55,56], and polymeric membranes [60,70,104,148]. In the immobilized system, the catalyst can be coated on the walls of the reactor, supported on a solid substrate or deposited around the case of the light source, using supported materials such as alumina, zeolite [113,146], AC [58,59], silica support [11,103,147], glass beads [55,56], and polymeric membranes [60,70,104,148].…”

Catalytic Membranes and Membrane Reactors

“…In this respect, the design of alternative heterogeneous photo-oxygenation systems able to employ visible light, oxygen, mild temperatures, and solvent with a low environmental impact (water or neat reaction) has been investigated by the immobilization of the decatungstate in polymer membranes [68,69]. The successful heterogenization has been guaranteed by a proper choice of both, the catalyst and the polymer material.…”