During the landfill gas (LFG) upgrading process of carbon dioxide (CO2) separation by pressure swing adsorption (PSA), if the non-harmful volatile organic compounds (VOCs) are not removed completely, they would cause a rapid failure of the adsorbents due to irreversible adsorption. This point was not given enough concern previously, and no special procedures were generally adopted for VOC removing in practical LFG upgrading engineering. The aim of this study is to demonstrate the harmfulness of VOCs to the adsorbents in PSA process, thereby, five typical VOCs in LFG, including toluene, ethylbenzene, p-xylene, cyclohexane, and butanone were selected and their effect on CO2 adsorption performances of zeolite 13X, 5A and activated carbon were studied for the first time through different adsorption experiments, i.e. the measurement of CO2 equilibrium adsorption isotherm on the adsorbents with or without VOC-loaded, CO2 adsorption experiment simulating the practical PSA operation, and CO2 diffusion coefficient measurement in the dynamic adsorption process. Results of these adsorption experiments demonstrated that all the VOCs adsorbed on the adsorbents irreversibly and lead to CO2 adsorption performances deteriorating. Therefore, conclusion could be drawn that all the VOCs should be removed sufficiently to keep high efficient operation of PSA for LFG upgrading. (C) 2018 Elsevier Ltd. All rights reserved.