Pervaporation separation of n-heptane/sulfur species mixtures with polydimethylsiloxane membranes

With the mixtures of n-heptane and different sulfur species making up the model gasoline, polydimethylsiloxane (PDMS)/polyetherimide (PEI) composite membranes were prepared and used for sulfur removal from gasoline. Effects of sulfur species, feed sulfur content and feed temperature on the desulfurization efficiency were investigated for a series of binary n-heptane/sulfur species mixtures by pervaporation. Experimental results indicated that the change of feed sulfur content produced insignificant effect on sulfur enrichment factor for every sulfur species, while the partial fluxes of sulfur species were proportional to feed sulfur content. With the feed temperature increase, total flux increased for every binary mixture. Sulfur enrichment factor decreased in the following order at the same temperature: thiophene > 2-methylthiophene > 2,5-dimethylthiophene > n-butyl mercaptan > n-butyl sulfide. Correspondingly activation energy of permeation was also obtained. In order to simulate the desulfurization process of real gasoline, effect of more sulfur species coupling exist on separation efficiency was also investigated. With the increase of sulfur species number according to the decrease order of sulfur enrichment factor, total sulfur enrichment factor decreased while total flux was almost invariable.