Massive emission of multi-pollutants from the utilization of fossil fuels has caused severe environmental problems in past decades. The transport process of multi-pollutant molecules in nano-porous materials is involved, and considered to be one of the most significant processes, in the removal of these pollutants no matter by adsorption or catalysis. However, the mechanism of nano-scale transport is not fully understood due to the complexity in pore structures and diversity in pollutants. This work probes into the application of non-equilibrium molecular dynamics (NEMD) simulations to study the mass transfer of multi-pollutants at nano-scale. A dual control-volume (DCV) model of titanium-based nanopore is proposed and molecules of NO, NH3 and SO2, which are typical gaseous species in selective catalytic reduction (SCR) process for nitrogen oxides removal, are investigated. Simulations are performed to investigate the influences of temperature, pore width and hydroxyl site on diffusivity of objective molecules. The results show (1) the differential transport of NO, NH3 and SO2 in various temperature and pore conditions, (2) the impact of OH-groups on diffusion in different pore widths, (3) the influence of competitive diffusion of NH3 and SO2. These fundamental researches have provided guidance on the rational design of SCR catalysts for high deNOx activity and low SO2 oxidation.
Keywords Molecular dynamics, Gaseous molecules, Multi-pollutant, Nanopore transport, Diffusivity