This work presents a mathematical modeling framework for the simulation and optimization of pressure/vacuum swing adsorption (PNSA) processes for post-combustion CO2 capture. A single-stage P/VSA process for CO2 capture from dry flue gas is considered using new zeolite 13X-based adsorbents resulting from perturbation on the 13X zeolite isotherm. A two-bed six-step P/VSA cycle configuration with light product pressurization is employed in systematic simulation and optimization studies. First a zeolite 13X, the current benchmark commercial adsorbent for CO2 capture, is considered. Accordingly, the model is used to study and evaluate new zeolite 13X-based adsorbents for more efficient CO2 capture. The results from systematic comparative simulation studies demonstrate that a modified zeolite 13X-based adsorbent appears to have better process performance compared with the original zeolite 13X. Furthermore, process optimization studies employing the above potential adsorbents are performed to minimize energy consumption for specified minimum requirements in CO2 purity and recovery. The optimization results indicate that the minimum target of 95% in CO2 purity and 90% in CO2 recovery is easily met for the P/VSA process under consideration for both potential adsorbents under different operating conditions resulting in different energy requirements and CO2 productivity. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.