(374d) The Synthesis of Thermally Rearranged Polyimide Membranes for Natural Gas Separation Using Four Different Dianhydride Precursors

Natural gas purification via membrane separation is a promising method that could potentially result in a considerably cost-effective and sustainable purification process. A number of polymers have been studied; however, the two polymers that stand out are polyimide and polybenzoxazole. Among the two polymers, polybenzoxazole has better separation properties mainly because of the size and distribution of its free volume elements. Polybenzoxazole is made through the thermal rearrangement of a polyimide which is formed via the condensation reaction of diamine and dianhydride precursors. The properties of the thermally rearranged membranes are largely affected by the type of precursors used to make them. In an attempt to investigate those effects, four different dianhydride precursors were synthesized, cast into membranes and tested for permselectivity. The four dianhydride precursors used are 4,4’-oxydiphthalic anhydride (ODPA), 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (BTDA), 3,3’,4,4’-biphenyl tetracarboxylic dianhydride (BPDA), and benzene-1,2,4,5-tetracarboxylic dianhydride, which is also known as pyromellitic dianhydride (PMDA).