Experimental studies on intracrystalline diffusion of NO and NH3 in Cu-CHA

• Published in: Catalysis today Vol. 411-412; p. 113823
• Main Authors: Nakasaka, Yuta, Kushima, Keigo, Yasumura, Shunsaku, Shimizu, Ken-ichi, Totani, Keigo, Shibata, Gen, Masuda, Takao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.03.2023
• Subjects: Cu-CHA; Intracrystalline diffusivity; NH3-SCR; NO; NH3-SCR; Cu-CHA; Intracrystalline diffusivity
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2022.06.038

Equilibrium adsorption and intracrystalline diffusion of NO and NH3 in Cu-CHA were experimentally studied using constant volumetric method. The saturated amount of adsorbed NO on Cu-CHA at 373 K linearly increases with Cu loading, which indicates that Cu sites are the adsorption site of NO on Cu-CHA. Temperature dependence of adsorption equilibrium constant of NO gives the adsorption enthalpy (− 24 kJ mol-1), regardless of the Cu loading. The activation energy for NO diffusivity in Cu-CHA was evaluated from its temperature dependence of intracrystalline diffusivity (7.0 kJ mol-1). The intracrystalline diffusivity of NO in Cu-CHA is lower than that in Cu-ZSM-5, which can be ascribed to the narrower pore size of CHA. Intracrystalline diffusivity and effective diffusivity of NO were lower than those of NH3 in Cu-CHA. The Weisz-Prater Parameter was calculated using the NH3-SCR reaction rate on Cu-CHA at 508 K and the effective diffusivity of NO. The calculated result indicates that intracrystalline diffusion of NO in Cu-CHA limits the NH3-SCR reaction under the present conditions. [Display omitted] •Intracrystalline and effective diffusivity of NO and NH3 in Cu-CHA was measured.•Intracrystalline diffusivity of NO depends on the Cu content.•Equation for estimation of NO diffusivity in Cu-CHA was suggested and validated.•Overall reaction rate of NH3-SCR was controlled by NO diffusion rate.