Regeneration of water-deactivated Cu/SAPO-34(MO) with acids

Artikel i vetenskaplig tidskrift, 2020

The Cu/SAPO-34 catalysts, used for NH3 selective catalytic reduction (SCR), are systemically studied with various characterization techniques before and after low temperature water deactivation and regeneration using techniques such as XRD, BET, ICP-SFMS, 27Al MAS NMR, 29Si MAS NMR, and H2-TPR. Analysis of results suggests that, during low-temperature water deactivation, hydrolysis of Si-O-Al occurs resulting in Si condensation and formation of Si clusters. It is proposed that these formed Si clusters are mainly responsible for the deactivation of Cu/SAPO-34 catalysts since they suppress the mobility of [Cu-(NH3)]+ and hinder the formation of the transient [CuI(NH3)2]+-O2-[CuI(NH3)2]+ intermediate, which is considered to be the rate-limiting step for NH3-SCR reaction. The regeneration of the deactivated Cu/SAPO-34 catalysts with acid can be explained by the ability of the acid to convert the Si clusters back to Si-O-H, which is able to revert to the SAPO-34 framework via reverse hydrolysis as the temperature increases.