Liquid-phase synthesis of mercaptans and sulfides in the reaction of hydrogen sulfide with alkylene oxide: Estimating catalyst efficiency

Abstract

A method for the synthesis of β-hydroxypropyl mercaptans and β-hydroxyalkyl sulfides based on the reaction of liquefied hydrogen sulfide with alkylene oxides is proposed. Our technique allows (1) the use of the maximum possible concentration of hydrogen sulfide in the reaction mixture, (2) the process to be performed within a broad range of temperatures, (3) the use of various catalytic additives, and (4) requires no solvent. Kinetic dependencies of the reaction of hydrogen sulfide with alkylene oxides, particularly propylene oxide, are investigated under conditions that allow the reaction components to exist in the liquefied state. In the case of propylene oxide, an excess in the reaction mixture of two consecutive macroscopic stages is observed: the first macro stage includes the formation of 2-hydroxypropane-1-thiol followed by formation of 1,1′-di(2-hydroxypropane) sulfide at the second stage. Staging the accumulation of mercaptan and sulfide allows us to control the process, directing the reaction toward the quantitative production of either mercaptan or sulfide under certain conditions. For example, the use of an excessive amount of hydrogen sulfide results primarily in the formation of 2-hydroxypropane-1-thiol. In addition, the activity of 14 homogenous and heterogeneous catalysts, including activated carbon, ion-exchange resins, metal oxides, water, and triethylamine, is studied. A principle for evaluating the efficiency of catalytic additives based on our mathematical model of the process is proposed. Triethylamine is found to be the most efficient catalyst, raising the reaction rate by a factor of more than 100; i.e., the reaction time without the catalyst was ∼50 h, while in the presence of small amounts of triethylamine, the reaction ceased within a few minutes.