Reversible Olefin Coordination to Silver Ions in Facilitated Olefin Transport Polymer Membranes

摘要

A highly selective dry complex membrane, AgBF_4-cellulose acetate (CA) was prepared and tested for the separation of ethylene/ethane and propylene/propane mixtures. The maximum selectivity for olefin over paraffin was found to be 280 for ethylene/ethane mixture and 200 for propylene/propane mixture. Solid state interactions of AgBF4 with cellulose acetate (CA) and/or olefins have been investigated using FT-IR, UV, and XPS. FT-IR and XPS studies clearly show that the silver ions are coordinated by carbonyl oxygen atoms among three different types of oxygen atoms present in CA ― two in acetate group and one in ether linkage. Upon incorporation of AgBF_4 into CA, the carbonyl stretching frequency of the free cellulose acetate at 1750 cm~(-1) shifts to a lower frequency by about 41 cm_(-1). The binding energy corresponding to carbonyl oxygen atom in O ls XPS spectrum shifts to a more positive B.E. by the incorporation of AgBF_4. Reversible olefm coordination to silver ions has been observed by FT-IR and UV studies. Treatment of the AgBF_4-CA membrane placed in a gas cell with propylene produces a propylene-coordinated membrane in which coordinated propylene is easily replaced by other olefm such as 1,3-butadiene.