Continuous process for propylene/propane separation by use of silver nitrate carrier and zirconia porous membrane

Abstract

A continuous isothermal separation process was developed for components of olefin/paraffin mixtures. This process features a combination of two steps: absorption of olefin by silver ion in an aqueous solution at high pressure and isothermal regeneration of the absorbing solution using a ceramic membrane. The process takes advantage of: (1) the specific and reversible interaction between silver ions and olefin molecules; and (2) pressure drop across a ceramic membrane. Silver ions act as a carrier for olefin transport through the porous membrane. The zirconium oxide membrane serves as a depressurizing device for the olefin containing silver nitrate solution, allowing olefin to be released at the low pressure side of the membrane. Silver nitrate solution is recycled to the absorption chamber. Process performance was experimentally evaluated using propylene/propane mixtures in a bench-scale system. The experimental results are: propylene production rates as high as 3.4 cm 3(STP)/(cm 2 min) and a stable continuous separation process with silver utilization efficiency as high as 60% and propylene recovery ratio as high as 80%. This process has features that circumvent previous shortcomings of the pressure-swing adsorption/desorption process for olefin separation.