Dynamic adsorption of nitrogen dioxide on zeolites

The dynamic adsorption of nitrogen dioxide on Zeolon 900H, Zeolon 900K, Zeolon 900Na, Zeolon 200H, Zeolon 500H, H/ZSM-5, Na/ZSM-5, and CaA zeolites is studied. Breakthrough curves C/C₀ = σ(t) (C₀ is the initial concentration of NO₂ at the adsorption column inlet and C is the breakthrough concentration at the column outlet) is measured over a temperature range of 290–430 K. It has been shown that the time dependence of C/C₀ is described by the Wheeler–Jonas equation. The parameters of this equation, the adsorption constant rate k_v and dynamic adsorption capacity (DAC) are determined by fitting the theoretical curves to the experimental data for the aforementioned zeolites at 290–430 K. The Hertz–Knudsen equation is used to obtain theoretical temperature dependence of k_v. For this dependence, the curve fitting method is also used to determine the adsorption activation energy E_ad. It is found that the activation energy ranges within 300–500 cal/mol, which shows that the adsorption of NO₂ on these zeolites is a physical process, with the electronic structure of the molecules being perturbed only slightly during the adsorption process. A theoretical formula for calculating the time of protective action of the sorbent is derived. It is shown that the DAC and the corresponding protective action time for the studied sorbents depend on the temperature and increase in the series Zeolon 900Na < Na/ZSM-5 < Zeolon 900K < H/ZSM-5 < Zeolon 500H < Zeolon 200H < Zeolon 900H for gas mask filters at room temperature (293 K), and increase in the series CaA < H/ZSM-5 < Zeolon 900H < Zeolon 500H < Na/ZSM-5 < Zeolon 200H < Zeolon 900K < Zeolon 900Na for systems of purification of flue gases from thermal power plants at 350 K.