A vacuum swing adsorption process using 13X zeolite pellets with jice steps was designed to split an equimolar mixture of propylene/propane: pressurization with feed; high-pressure feed; high-pressure puige with product; cocurrent blowdown; and countercurrent vacuum blowdown, where the enriched propylene product is withdrawn. In the process, the partial pressure of the C,-mixture is controlled with nitrogen, which is used as inert gas. With an equimolar feed of C, 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 lowered to 0.1 bar. After 15-20 cycles, the cyclic steady-state condition is achieved, 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 productivity of 0.785 mol/kg-h is obtained, The experimental work was complemented with numerical simulations, and the effect of different operating parameters on the pe@ormance of the VSA was considered.

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A vacuum swing adsorption process using 4A zeolite pellets with five steps was designed to split an equimolar mixture of propylene/propane. The equimolar feed of C3 is diluted to 50% with nitrogen at 5 bar and 423 K, and the product is obtained when the total pressure is lowered to 0.1 bar. After 15 cycles, cyclic steady-state conditions are reached, a propylene-enriched stream of 97 mol% relative to the propylene/propane mixture, with 4.4% of nitrogen, a recovery of 26% (molar basis), and a productivity of 1.03 mol/(kg h) are obtained. The experimental work is compared with numerical simulations, and the effects of different operating parameters on the VSA process are analyzed.

The use of vacuum pressure swing adsorption (VSA-PSA) with carbon molecular sieves (CMS) as selective sorbents is evaluated as an alternative technology for methane−nitrogen and propane−propylene separations. The larger molecules, methane and propane, are very low-diffusing species, resulting in processes where nitrogen and propylene are retained in the bed. For the methane−nitrogen separation, a Skarstrom cycle (pressurization, feed, blowdown, and purge) was used with the advantage of recovering methane in the feed step with a low-pressure drop. At ambient temperature, from a mixture with 20% of nitrogen balanced by methane, a purity >93% was obtained. For the propane−propylene mixture, a five-step cycle was usedpressurization, feed, rinse, intermediate depressurization, and countercurrent blowdownwhere purified propylene is obtained as a low-pressure product. Starting with an equimolar mixture at 373 K, the purity of propylene was 83% with a product recovery of 84%.