Membrane separation of propane and propylene is a big challenge to save separation energy to produce propylene. In this communication, we report Ag+-exchanged X-type zeolite (Ag-X) membrane for propane/propylene (C3s) separation. X-type zeolite membrane synthesized on porous α-alumina tube (10 mm i.d. and 3 cm long) was treated in AgNO3aq to obtain Ag-X membrane. Figure 1 compares the permeation results for the unary and binary systems for C3s. Ag-X membrane showed a remarkably high separation factor compared with membranes previously reported, and the separation factor of propylele exceeded 50 at 353 K. Although the propylene permeances in the both systems were almost the same, the permeation of propane was substantially hindered in the binary system. In order to understand the reason of the appearance of high propylene selectivity in the binary system, we measured the adsorption isotherms of C3s on Ag-X membrane. Figure 2 shows the adsorption isotherms of C3s at 313 K on Ag-X powder and membrane. We found that the adsorption of propylene on Ag-X is much superior to the propane adsorption over the whole p/ps range, suggesting that propylene strongly adsorbed on Ag-X inhibited the adsorption of propane. We concluded that high selectivity to propylene with Ag-X membrane appeared owing to the preferential adsorption of propylene against propane. Such a separation factor exceeding 50 ensure to produce polymer-grade propylene by membrane separation without distillation.

Strong adsorption of propylene helps propane/propylene separation through Ag+-exchanged X-type zeolite membrane

255th National Meeting (2018)

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