Layered vacuum pressure-swing adsorption for biogas upgrading

Biogas is an important source of renewable raw methane that can be upgraded and applied as fuel for vehicles. One of the economic limitations of the upgrading relies in the bulk separation of CO2. In a previous communication (Grande, C. A.; Rodrigues, A. E. Ind. Eng. Chem. Res. 2006, 46, 4595), we have compared the performance of equilibrium- and kinetic-based adsorbents for application in vacuum pressure-swing adsorption (VPSA) processes for biogas upgrading. The main disadvantage of using carbon molecular sieves (CMSs) is that less than 40% of the total capacity to remove CO2 is employed to satisfy purity requirements of methane product (>98%) with direct impact in process productivity. In this work, we report a new adsorbent layering strategy to improve the total productivity of CO2 removal, resulting in a kinetic VPSA process with size reductions up to 60%. © 2007 American Chemical Society.