(21b) Benzene Reduction from Gasoline by Pervaporation Using Cation-Exchanged Membrane Containing Metal Ions

The EPA's new regulations under Mobile Sources Air Toxics Phase 2 (MSAT2) is forcing refiners to reduce the annual average benzene content in gasoline to 0.62 vol% effective Jan. 11, 2011. After July 1, 2012, a maximum benzene content in gasoline will be 1.3 vol%. The regulations allow refineries to trade credits to meet the 0.62 vol% specification. Typical sources of benzene contributions to gasoline include reformate, FCC naphtha, light straight run naphtha, and VGO hydrocracked naphtha, etc. Reduction of benzene by membrane pervaporation is more attractive than by hydrogenation. Differences on sorption, diffusion, and pervaporation properties between benzene and substituted benzene on cation-exchanged membranes are the driving force for benzene separation. Different types of composite membranes based on polyelectrolytes will be synthesized by interfacial reaction with oppositely charged ionic surfactants, or by cross-linking with metal ions. A series of cations, Cu(II), Ag(I), and Co(II) will be investigated.