Kinetics of reaction of benzyl chloride with H2S‐rich aqueous monoethanolamine: selective synthesis of dibenzyl sulfide under liquid–liquid phase‐transfer catalysis

Abstract

AbstractThe development of viable alternative processes for the conversion of hydrogen sulfide (H2S) to produce commercially important chemicals is important in process industries, particularly in refineries handling large quantity of sour crude. This work was undertaken to synthesize value‐added chemicals such as dibenzyl sulfide (DBS) and benzyl mercaptan (BM) utilizing H2S from various by‐product gas streams. This process is a viable alternative to the expensive Claus process, which produces only the less valuable elemental sulfur product from H2S. The reaction between benzyl chloride (BC) and H2S‐rich aqueous monoethanolamine (MEA) was carried out in an organic solvent, toluene, using tetra‐n‐butylammonium bromide as phase‐transfer catalyst. Two products, DBS and BM, were identified in the reaction mixture and both chemicals have many industrial uses. The conversion of BC and the selectivity of DBS, were maximized by considering the effect of various parameters such as stirring speed, catalyst loading, concentration of BC, concentration of MEA, concentration of sulfide, and temperature. The highest selectivity of DBS obtained was about 99% after 480 min of reaction with excess BC at 60 °C. The apparent activation energy for the kinetically controlled reaction was found to be 51.3 kJ/mol. The MEA/H2S mole ratio was found to have a significant effect on the selectivity of DBS and BM. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.