Mass transfer characteristics of multi-pollutants in nano-pores of CeO2-TiO2 based SCR catalyst: A molecular dynamics study

Molecular dynamics (MD) simulation was carried out to investigate the diffusion behaviors of NH₃ and flue gases on CeO₂-TiO₂ (CT) catalyst for the selective catalytic reduction of NO with NH₃. The influence of temperature, gas mixtures, and slit width of catalyst on the diffusivity of the target molecules were studied. The results showed that both temperature and the competitive diffusion of the target molecules substantially impact gas diffusion within nano-slits. The NH₃ diffusion was demonstrated to have heightened sensitivity to temperature fluctuations. SO₂ showed the greatest hindering effect in all of five gases. The negative effect on NH₃ diffusion was greater when H₂O existed in the form of hydroxyl groups. Increasing the slit distance of catalyst significantly mitigated this effect, with a decrease in diffusion impedance from 32.51 % to 5.01 % as the distance expanded from 2.5 nm to 7.5 nm. As for NO, a similar suppressive effect was observed when mixed with SO₂, but the influence of hydroxyl groups was notably less pronounced compared to NH₃. Specifically, there was only a decrease of 15.14 % at a distance of 2.5 nm, followed by almost no decrease when the distance was increased to 7.5 nm.