Molecular simulation of the effects of activated carbon structure on the adsorption performance for volatile organic compounds in fumes from gasoline

Improving the adsorption performance of activated carbon can effectively reduce the emission of volatile organic compounds (VOCs). In this paper, the influences of pore size, functional groups, and water molecular content on the adsorption for four gasoline evaporation VOCs (n-butane, n-hexane, p-xylene, and ethanol) were investigated in terms of equilibrium adsorption capacity and threshold pressure by molecular simulation. The simulation results show that capillary condensation can increase the equilibrium adsorption capacity of gas, while functional groups and water molecules will reduce the effective adsorption volume of activated carbon. On the other hand, the threshold pressure depends primarily on the interaction energy and the number of adsorption sites. The superposition effect of the adsorption force field makes the lowest threshold pressure of four VOCs. The threshold pressure of n-butane, n-hexane, and p-xylene is increased by the presence of functional groups and water molecules, while functional group modification and a certain amount of water molecules can improve the adsorption capacity of ethanol at low pressure. The results of the study can provide a reference for the selection of activated carbon in vehicle carbon canisters and the development of high-performance activated carbon.