The Regeneration of the Spent Catalyst Resulted from 3,4,5,6-Tetrachloropyridine-2-Carbonitrile Synthesis

Abstract

In order to optimize the process conditions for regeneration of activated carbon form spent catalyst resulted from 3,4,5,6-tetrachloropyridine-2-carbonitrile synthesis. A two-step process involving the thermal desorption of spent activated carbon and the activation of activated carbon treated by thermal desorption with steam was designed. The influence of desorption temperature, time and the flow rate of nitrogen on the yield of chlorides, the iodine adsorption capacity and the yield of activated carbon were investigated, respectively . The optimal desorption conditions were: temperature of 650°C, time of 90min and the flow rate of nitrogen of 30ml/min. The yield of the chlorides obtained under the optimal conditions was 14.85%. The regeneration of activated carbon treated by thermal desorption with steam; the optimized conditions analyzed by RSM were regeneration temperature of 696°C, time of 84 min and flow rate of steam of 0.58g/min. The experimental results on the optimized conditions were iodine adsorption value of 1003.59mg / g, These methods can not only recover chloride in the spent activated carbon, but also the regeneration activated carbon could partially replace the fresh activated carbon, which would bring an obvious economical benefit and social benefit.