Phase transfer catalyzed reaction for synthesis of sulfides and disulfides using hydrogen sulfide

Abstract

This study focuses on utilization of hydrogen sulfide (H2S) in the synthesis of fine chemicals such as Dibenzyl Sulfide (DBS), Benzyl Mercaptant (BM) and Dibenzyl Disulfide (DBDS). This involves first absorption of H2S in either aqueous ethanolamine (MEA) or methyldiethanolamine (MDEA) and then reaction of this H2S richaqueous solution with organic reactants. Two reaction systems have been studied in the present work – first being the reaction of benzylchloride (BC) with H2S rich aqueous MDEA in the presence of Tetrabutyl Phosphonium bromide (TBPB) as a PT catalyst under liquid-liquid (L-L) phase transfer catalysis to synthesize DBS and BM and in second system, DBDS was synthesized by adding sulfur powder in H2S rich aqueous MEA using Amberlite IR-400 as a PT catalyst at liquid liquid-solid (L-L-S) PTC. The overall objective of this study is to maximize conversion of reactant, maximize selectivity of desired product, searching for mechanism and calculation of kinetic parameter. In all the systems under study, desirable products were obtained with 100% selectivity at some level of process parameters. Reaction time, temperature,catalyst loading, stirring speed, reactants concentration and solvent concentration were chosen as reaction parameters. Amberlite catalyst was recovered and reused 4 times with successive decrease in BC conversion in each run.