Effect of Process Parameters on Conversion and Selectivity for the Synthesis of Dibenzyl Sulfide Using Hydrogen Sulfide and Solid Reusable Tri-Phase Transfer Catalyst.

Abstract

Hydrogen sulfide (H2S) is often found in the by-product gas-streams of many petroleum and natural gas processing industries. Conventionally it is being used for the production of elemental sulfur by Claus Process which is further utilized in the production of sulfuric acid or rubber industries. But Claus process is an energy-expensive process as it requires a high amount of energy and process control over oxygen and H2S ratio. H2S-laden gas can be utilized well by absorbing into aqueous alkanolamine and it is used as a sulfiding agent to produce organo-sulfur compounds like thioether, mercaptans, disulfides etc., which have higher usability and better market value. Since the alkanolamine and benzyl chloride (BC) are two different phases and to carry out this triphasic reaction, phase-transfer-catalyst (PTC) has been used and often the application of PTC gives enhancement in reaction rate, more conversion for reactants and better selectivity of desired products. This work was undertaken to study the synthesis of Dibenzyl Sulphide (DBS) and Benzyl Mercaptan (BM) using H2S-rich monoethanolamine (MEA) and BC under Liquid-Liquid-Solid PTCs with a tri-phase catalyst. Owing to its solid state, availability, cost and reusability, Amberlite IR 400 is selected as a PTC. A parametric study was carried out which emphasized upon the impact of catalyst loading as one of the process variables on the conversion of BC and selectivity of DBS and parametric study with these substances revealed more that 90% selectivity for desired product at ambient condition. The overall objective of this study is to maximize conversion of reactant BC, maximize selectivity of desired product DBS. Reaction time, temperature, catalyst loading, stirring speed, reactants concentration and solvent concentration were chosen as parameters. These techniques can be used as an alternative to Claus process and also can act as a green route for synthesizing value-added fine chemicals like DBS, BM etc.