Simulation of pressure-temperature swing adsorption (PTSA) process was performed in a commercial two-layer six-bed adsorption system during six sequential steps of cyclic operation to remove mercaptans from natural gas. The feed is a mixture of methane with water vapor, carbon dioxide, heavy hydrocarbons (C3+) and mercaptan impurities. The process is working in the cyclic operational mode to continuously reduce the mercaptan content from 134 to less than 10 ppmv which is determined as the standard level in the environmental regulations. The bed consists of two layers of activated alumina to specifically remove water vapor and 13X zeolite to remove mercaptan, respectively, from natural gas. The cycle steps i.e. adsorption at high pressure, depressurization to the lower pressure, two steps heating with purging hot purified natural gas, cooling the column and pressurization by feed were simulated sequentially. The dynamic model equations were constructed from four mole balances; model molecule of mercaptans, model molecule of heavy hydrocarbons, carbon dioxide and water vapor in natural gas, a total mass balance, a pressure drop equation and two energy balances of solid and gas phases in the adiabatic column. It was observed that the cyclic adsorption was approached to the steady conditions after seven cycles running the program. The predicted molar fractions out of the process were compared with the real results and good agreement was observed between the real data and simulated results. The influential parameters of the process were investigated through a parametric analysis of the process efficiency. Pressure of adsorption stage, purge to feed ratio at regeneration step and temperature of the 1st and 2nd heating steps were found to be the most influential parameters affecting the natural gas purification efficiency. For the sake of energy saving some suggestions were proposed for upgrading the design conditions with no significant effect on the purification performance. The results revealed that reduction of adsorption pressure from 6.8 to 6.1 Mpa, changing purge/feed ratio from 0.06 to 0.045, and combination two heating stages to one stage with 510 K and 12 h operation could be replaced in the operational conditions without significant changes in purification of the product. (C) 2014 Elsevier B.V. All rights reserved.