Regeneration performance and mechanism of modified walnut shell biochar catalyst for low temperature catalytic hydrolysis of organic sulfur

Abstract In this study, four different regeneration methods (WR, NR, AR and WNAR), regeneration conditions and regeneration mechanism of a Fe-Cu-KOH supported on WSB as a precursor catalyst (Fe-Cu-KOH/WSB) for low temperature hydrolysis of CS 2 and COS were investigated. The results showed that the WNAR method (Water washing + Nitrogen sweeping + Alkali steeping regeneration) had the best regeneration performance. Under optimal regeneration conditions (500 °C nitrogen sweeping temperature and 13% KOH steeping content), the regenerated Fe-Cu-KOH/WSB catalyst could achieve to 42.64 mg S/g sulfur capacity, and it was close to fresh catalyst (48.58 mg S/g). A small amount of sulfate and a large number of OH groups were washed away in water washing process. XPS, TG/DTA and DRIFTS results indicated that a large number of Fe 2 (SO 4 ) 3 were decomposed into Fe 2 O 3 in nitrogen sweeping process, which could recover a large number of surface area and active component. CO 2 -TPD results indicated that the supplement of OH groups in KOH steeping process recovered the alkalinity site strength, which was conducive to desulfurization. After three times regeneration, the sulfur capacity of Fe-Cu-KOH/WSB could reach 33.94 mg S/g, and it indicated that the WNAR method had good stability for the recovery of catalytic activity. From BET, CO 2 -TPD XPS and TG/DTA results, it could be seen that the decrease of adsorptive and catalytic ability was attributed to the oxidation of WSB, the block effect of KOH and decrease of CuO contents. This study provided a suitable regeneration method for industrial application of Fe-Cu-KOH/WSB on catalytic hydrolysis of organic sulfur.