Boosting COS catalytic hydrolysis performance over Zn-Al oxide derived from ZnAl hydrotalcite-like compound modified via the dopant of rare earth metals and the replacement of precipitation base

In this work, a series of Zn-Al oxides calcined from ZnAl hydrotalcite-like catalysts were prepared using the co-precipitation method and then applied to remove COS. The effects of the content of Sm and the species of rare earth metal on the catalytic activities of COS hydrolysis are investigated. Experimental results show that the prepared catalyst doped with 20 wt% Sm performs better catalytically. Based on the optimization of Sm dopant, the effect of the precipitation base in the ZnAl hydrotalcite-like compounds on the catalytic activities of the catalysts is further investigated. The results show that the prepared catalyst using KOH and K2CO3 as the precipitation base exhibits the best catalytic performance. The characterization results show that the doping of rare earth metals can weaken the crystallinity and the introduction of an appropriate amount of Sm ions can significantly enhance the proportion of adsorbed oxygen species. Moreover, the results show that the synergistic effect of the doping of Sm and the replacement of precipitating alkali contribute to the enhancement of the number of basic sites, especially weak and medium basic sites. Furthermore, combined with in-situ DRIFTS, the catalytic mechanism of COS hydrolysis on ZnAl-20Sm-Na MMO is proposed.