Nanostructured PVDF-HFP membranes loaded with catalyst obtained by supercritical CO 2 assisted techniques

Abstract

Polymeric catalytic membrane reactors offer a larger flexibility over conventional reactors. The most-used method to generate polymer-based catalytic membranes is the phase inversion that, however, presents some limitations; in particular, the difficulty in generating a uniform distribution of the loaded materials. In this work, we use two new processes for the formation of membranes loaded with catalyst for potential applications in catalysis: supercritical assisted phase inversion and supercritical assisted gel drying, applied to formation of poly(vinylidene fluoride-co-hexafluoropropylene) membranes loaded with palladium nanoparticles. We analyzed the effect of process parameters (polymer concentration, catalyst concentration, pressure, temperature) on the membranes morphology. The supercritical phase inversion process produced cellular asymmetric structures with cell size ranging between 3 and 6 μm and nanoporous homogeneous networks, depending on the process conditions. Palladium nanoparticles homogeneous distributions were obtained only operating at selected process conditions, i.e., pressures larger than 150 bar and temperatures lower than 45 °C. Supercritical gel drying allowed homogeneous nanoporous membranes formation at all the tested process conditions: they were characterized by very high porosity (higher than 90%) and a very uniform catalyst distribution.