Propylene/propane separation by vacuum swing adsorption using 13X zeolite

A vacuum swing adsorption process using 13X zeolite pellets with five steps was designed to split an equimolar mixture of propylene/propane: pressuriz ation with feed; high-pressure feed; high-pressure purge with product; cocu rrent blowdown; and counter-current vacuum blowdown, where the enriched pro pylene product is withdrawn. In the process, the partial pressure of the C- 3-mixture is controlled with nitrogen, which is used as inert gas. With an equimolar feed of C-3 diluted to 50% with nitrogen, the column is fed at 5 bar and 423 K, and the product is obtained when the total pressure is lower ed to 0.1 bar. After 15-20 cycles, the cyclic steady-state condition is ach ieved, a propylene-enriched stream of 98% mol relative to propylene/propane mixture with 3.2% of nitrogen, a recovery of 19% (molar basis), and a prod uctivity of 0.785 mol/kg.h is obtained. The experimental work was complemen ted with numerical simulations, and the effect of different operating param eters on the performance of the VSA was considered.