Study on the Desulfurization Performance of a Flexible Polyionic Liquid Membrane Derived from Polyacrylonitrile

A flexible polyionic liquid (PIL) nanofiber membrane-supported phosphomolybdic acid catalyst (PM-PIL) was fabricated via stepwise chemical transformation of polyacrylonitrile (PAN) nanofiber membranes. The nitrile groups of PAN were converted into pyridine units, followed by quaternization and anion exchange with phosphomolybdic acid (PMo), resulting in a polyionic liquid membrane with uniformly immobilized PMo species. Benefiting from its nanofibrous architecture and ionic liquid characteristics, the PM-PIL membrane simultaneously acts as a heterogeneous catalyst and a Pickering emulsion stabilizer, enabling efficient interfacial catalytic oxidation desulfurization. The PM-PIL membrane exhibited excellent catalytic performance toward dibenzothiophene (DBT) oxidation in an H2O2-based model oil system. Under optimized conditions (60 °C, O/S = 150:1), more than 90% DBT removal was achieved within 90 min, and complete desulfurization was obtained within 2 h. Compared with phosphomolybdic acid and poly(pyridine), the PM-PIL membrane showed markedly enhanced activity and stability, maintaining over 90% efficiency after six cycles. Product analysis confirmed selective oxidation of DBT to dibenzothiophene sulfone. This work provides a robust and recyclable membrane-based catalytic platform for efficient oxidative desulfurization.