Propane and Propylene Separation with Carbon Dioxide at Mild Temperatures by Gas-Phase Simulated Moving Bed in Binderfree Zeolite 13X

This work studied the separation of propane and propylene using carbon dioxide as a desorbent and binderfree zeolite 13X as adsorbent. The process occurred at a mild temperature (323 K) using the gas-simulated moving bed (SMB) technology. Adsorption equilibrium isotherms of propylene, propane, and carbon dioxide were measured gravimetrically in a temperature range from 323 to 423 K and a pressure up to 5 bar. Breakthrough experiments were performed at 323 K and 3 bar. Binary adsorption equilibrium data were obtained from the dynamic experiments. Non-ideal adsorption behavior was observed for the adsorbate–adsorbent pairs; therefore, the multicomponent adsorption equilibrium was predicted with the RAST-aNRTL model. An SMB experiment was performed in the gas-SMB unit. For the 0.5/0.5 propane/propylene (molar-based) feed composition, a propylene purity of 98.8% was obtained, with a recovery above 98% and a productivity of 40.8 kgC3H6 h–1 mads –3. This work experimentally demonstrated that it is possible to produce high-purity propylene with a high recovery using binderfree zeolite 13X as adsorbent and carbon dioxide as a desorbent at mild temperature (323 K).