Polysulfides for presulfiding of hydrogenation catalysts: synthesis, mechanism and applications

Abstract

Presulfiding agents are widely used in oil refining and chemical industry, how to produce safe and efficient presulfiding agent by more environmentally friendly synthesis process are still problems to be solved. In this study, the organic polysulfide FSA-55 was synthesized by a practical one-pot process using isobutene and sulfur as raw materials and organic amine as a catalysts. The product components were analyzed and the possible catalytic reaction pathways in the thermal conversion of sulfides were elucidated. The amine catalysts showed a catalytic activities in inducing the ring opening of the cyclic molecular structure of sulfur at high temperature, thereby releasing the reactive sulfur radicals, which react with unsaturated double bonds through addition reactions. Different molecular structures of polysulfide were generated through molecular rearrangement and cyclization reactions. The suitability of the product as a presulfiding agent was investigated by analyzing the thermal properties and studying the presulfiding effect on hydrogenation catalysts. The polysulfide has a wide decomposition temperature range (100–260 °C), which can effectively avoid the occurrence of concentrated exothermic phenomena during presulfiding of hydrogenation catalysts. The presulfiding degree of the catalysts can reach 58.32%, which shows the great potential of oil processing as a presulfiding agent.