Coal Desulfurization. The Protodesulfurization of Naphthalene Thiols and Sulfides

Abstract

Basic information concerning the chemistry of organosulfur compounds is needed for the design of new coal desulfurization reactions. A study of the nucleophilic replacement of sulfur by oxygen in aryl thiols and sulfides led to the discovery of an acid-catalyzed reductive desulfurization reaction that proceeds readily under surprisingly mild conditions. Specifically, the treatment of 1- and 2-naphthalenethiol, 1- and 2-naphthyl alkyl sulfides, and di-1- and di-2-naphthyl sulfide with triflic acid in methylene chloride at 40°C leads to the formation of naphthalene as the principal organic product. The scope and limitations of the reaction have been explored and the reaction mechanism has been investigated. Several lines of evidence indicate that the process is best described as an electrophilic protodesulfurization reaction that yields naphthalene and oxidized sulfur compounds.