A chemical looping technology for the synthesis of 2,2′-dibenzothiazole disulfide
A novel chemical looping technology for the synthesis of 2,2′-dibenzothiazole disulfide (MBTS) with zero emissions has been developed. Through chemical cycling between carbonate and bicarbonate in the reaction system, the insoluble 2-mercaptobenzothiazole (MBT) can become soluble in the aqueous phase of sodium carbonate and then be oxidized efficiently by hydrogen peroxide and the absorption of CO2 with high selectivity. The mother liquor can be totally recycled by the desorption of CO2 without any generation of salt-containing wastewater. With the new synthesis technology, the product has high purity and reaches the standard of a superior product that can be applied as a vulcanization accelerator. When 5.0 wt% hydrogen peroxide was added dropwise over 40 min at 50 °C, the conversion ratio of MBT was over 98%. The mother liquor was recycled 5 times and no side-products were found. The whole process is clean and pollution-free, which greatly reduces the burden of hazardous waste treatment and brings great environmental benefits.