Research on the low temperature catalytic hydrolysis of COS and CS2 over walnut shell biochar modified by Fe–Cu mixed metal oxides and basic functional groups

Abstract In the present study, a series of walnut shell biochar (WSB) catalysts modified by metal oxides and basic functional groups were examined for the simultaneous catalytic hydrolysis of carbonyl sulphide (COS) and carbon disulphide (CS2) at low temperatures. The effects of the type and amount of metal oxides, calcination temperature and type and content of alkali were investigated. Meanwhile, the hydrolysis reaction mechanism was investigated by dynamic analysis method. The corresponding results revealed that Fe2O3, CuO and –OH (KOH) were the primary active components for the catalytic hydrolysis of CS2 and COS. Moreover, the optimal precursor was nitrate, and the best calcination temperature was 400 °C. Depending on the preparation conditions, the activity of walnut shell biochars for catalytic hydrolysis could be significantly improved, yielding a 100% removal rate of CS2 and COS after 330 min and 240 min, respectively, and a sulphur capacity of 48.54 mgS/gbiochar. Additionally, the recyclability of the catalyst is good. The structure and surface properties of the catalysts were characterized by XRD, BET, TG–DTA, FTIR, DRTFIR and XPS. The generation of sulphate decreased the number of active components and was the primary mechanism of catalyst deactivation.