Multiphase Reactions (Utilization of Hydrogen Sulfide For the Production of Value-Added Chemicals)

During the course of many processes in the petroleum, coal, and natural gas processing industries, one or more gaseous byproducts containing hydrogen sulfide $(H_2S)$ are quite commonly produced. The $H_2S$ contents of these gas streams are to be brought down to a specified level before being used in further applications to meet the stringent environmental regulations. Conventionally, the H2S present in the gas streams is removed by ammonia- or alkanolamine-based (amine treating unit) processes. The concentrated $H_2S$-rich gas stream obtained from these units is further processed in the Claus unit (or LO-CAT process), where it is oxidized by air to produce elemental sulfur. Several disadvantages of air oxidation of $H_2S$ have led us to develop an alternative process to produce some value-added chemicals such as dibenzyl sulfide (DBS) and benzyl mercaptan (BM) from benzyl chloride, and aryl amines from nitroarenes, utilizing H2S present in various gas streams. In the present work, a methodology has been developed to produce value-added products utilizing the H2S present in the gas streams in two steps: (1) removal of H2S from gas stream by conventional methods (ammonia- and alkanolamine-based process) followed by (2) production of value-added chemicals utilizing H2S-rich solution obtained from the first step of the process. The present work is only devoted to the systematic study on the production of value-added chemicals utilizing H2S-rich aqueous ammonia or alkanolamines. Experiments were carried out in batch mode in a fully baffled mechanically agitated glass reactor under liquid-liquid (and Liquid-liquid-solid in case of anion exchange resin (AER) as the catalyst) mode. These reactions were carried out in an organic solvent (toluene), using a phase transfer catalyst (PTC), tetrabutylammonium bromide (TBAB), and un-impregnated inorganic solid catalyst - AER. All samples from the organic phase were analyzed by gas liquid chromatography. Initial sulfide concentrations were estimated by the standard iodometric titration method. The detailed kinetic studies were made for the effect of stirring speed, temperature, catalyst loading, concentration of reactants, $NH_3$ or alkanolamines concentration, and elemental sulfur loading on the reaction rate, conversion, and selectivity