Tian JX, Hu JY, Wang K, Deng J and Luo GS* Green Chemistry, 2020, 22: 2778

Abstract: 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.