Stable Facilitated Transport Membranes for C4 Separation

C4 olefins are important petroleum refinery and petrochemical plant products- They are used in a variety of downstream processes, such as the production of alkylate fuel for gasoline- About 65 million metric tons of alkylate fuel is produced globally from C4 olefins- Other downstream products are secondary butyl alcohol, maleic anhydride, and butylene oxide, butyl rubber, and methyl methacrylate, to name just a few- The C4 olefins are obtained from the C4 fraction produced by catalytic crackers and steam crackers at petrochemical plants and petroleum refineries- About 130 million metric tons of crude C4 fraction are produced globally- The C4 fraction is a mixture of mono-olefin isomers (1-butene, cis-2- butene, trans-2-butene, and isobutylene), di-olefin isomers (1,3-butadiene and 1,2 butadiene), and paraffin isomers (n-butane and isobutane)- The various components of the mixture have different downstream uses and must often be separated from the balance of the mixture and recovered at high purity to be useful- Unfortunately, the relative volatilities of the C4 fraction components are very close, making conventional distillation infeasible- Instead a complex and costly series of separation processes, including extractive distillation, must be used- A membrane that is highly selective for C4 olefins could become the basis for or a key component of a much more energy efficient, less complex, and less capital intensive separation process- In this program, Compact Membrane Systems (CMS) will develop an innovative facilitated transport membrane (FTM) for C4 olefin separations- CMS has recently demonstrated membranes that offer high flux and excellent ethylene/ethane and propylene/propane selectivity- CMS proposes to build on this earlier work and develop modified membranes for use in separation of C4 olefins from cracker C4 fractions- C4 hydrocarbons have lower volatility than C2 and C3 hydrocarbons- Therefore, modifications of the membrane polymer used in earlier work will include higher use temperature capability-