Oligomeric membranes for simultaneous chemical reaction and separation

Abstract

Thin films of oligomers were synthesized on PTFE substrates and they were studied for separation of product from liquid chemical reaction mixture. Three different types of membranes were fabricated using a technique called ‘covalent molecular assembly’. Covalent molecular assembly is a synthesis technique in which a substrate is sequentially immersed in chemical solutions to grow molecular moieties with covalent bonding to the underlying layer of molecules on the substrate. The first membrane was oligoimide PMDA-ODA. The second membrane was crosslinked oligoamide TC-TAB. The third membrane was Nickel terminated oligoimide Ni-PMDA-ODA. The first two membranes were studied for Friedel-Crafts’ alkylation reaction between benzene and methyl chloride in presence of ferric chloride catalyst. With 30psia chloromethane pressure, the reaction proceeded to 100% conversion and the first two membranes provided a permeate of 99% pure toluene product. The third membrane was catalytically active to convert p-nitrophenol to p-aminophenol in presence of sodium borohydride in ethanol. The purity of the permeate stream reached 98% in 40 min and was stable for 2 h. Thus, novel membranes were synthesized for enhanced separations.