Synthesis and pervaporation performance to gasoline deorganicsulfide of soluble polyimide

A kind of soluble polyimide (PI) was synthesized based on 4, 4′-oxydiphthalic dianhydride (ODPA) and 4, 4′-diamino-3, 3′-dimethyldiphenylmethane (DMMDA) via low temperature solution polycondensation and chemical imidization. The structure and properties of the obtained PI were characterized by measurements of FT-IR, ¹H-NMR, DSC and TGA etc. The results showed that the PI was readily soluble in polar solvents such as DMF, DMAc and NMP etc. Its glass transition temperature was 264°C and 10% thermal decomposition temperature under N₂ was 521°C. The tensile strength was 137 MPa, and the elongation at break was 18%. The asymmetry membrane was prepared by phase inversion method of ODPA-DMMDA and was observed by SEM. In the sulfur reduction experiments, the membranes display good selectivity and high pervaporation performance for thiophene in the gasoline.The enrichment factor was 3.68 and the flux was 0.92 kg/m²h when tested with a n-heptane/thiophene feed at 350 K.