Transesterification of soybean oil by PAAc catalytic membrane: Sorption properties and reactive performance for biodiesel production

A catalytic performance study for biodiesel production by a novel catalytically active membrane from polyacrylic acid (PAAc) crosslinked with 4,4′-diamino-2,2′-biphenyl sulfonic acid (PAAc-BDSA) was performed. Evaluation of oil and methanol sorption capacity as well as heterogeneous acid catalyzed transesterification of soybean oil by PAAc-BDSA was compared to polyvinyl alcohol, PVA (88% and 99% hydrolysed) catalytically active membranes crosslinked with sulfosuccinic acid (PVA-88-SSA and PVA-99-SSA). PAAc-BDSA membranes with similar ion exchange capacity (IEC) presented at least twice the swelling degree (Q) for soybean oil and methanol than PVA-88-SSA and PVA-99-SSA membranes. Effective diffusion coefficients of PAAc-BDSA for methanol and a mixture of methanol-glycerol determined by sorption method show that in this membrane the diffusion was at least 4 to 6 times faster than in PVA-88-SSA and PVA-99-SSA. Soybean oil transesterification reaction rate fits pseudo-first order kinetics and methyl ester yield follows the order 90, 92 and 73% for PVA-88-SSA, PVA-99-SSA and PAAc-BDSA, respectively. Higher diffusion coefficients and sorption of methanol and glycerol by PAAc-BDSA membrane make it a candidate for application in membrane reactors for simultaneous biodiesel production and glycerol separation.