Formation of Dimethyl Polysulfides via Reaction of Methanol and Elemental Sulfur

Abstract

Dimethyl polysulfides have been reported in the supercritical methanol extracts of coal and in the pyrolysis products of a high-sulfur Spanish coal that was first extracted with a mixture of dichloromethane and methanol. Dimethyl polysulfides and other products are shown to be formed by the reaction of methanol with elemental sulfur at elevated temperature and pressure. This reaction is a possible source of some of the dimethyl polysulfides observed by others in high-temperature methanol extracts.

Identification of Organic Sulfur Compounds in Supercritical Extracts from Polish Lignite

“…Diisopropyl sulfide, diisopropyl disulfide, and diisopropyl trisulfide were found in the reaction products of elemental sulfur with an iP and iP-T mixture at 360 °C under supercritical conditions, whereas none of these compounds was formed in the reaction of elemental sulfur with toluene. This is consistent with the findings of White et al, although in our case the reaction conditions were different. They studied the reaction of methanol with elemental sulfur at 240 °C in a sealed tube at a solvent vapor pressure.…”

“…Mild conditions of the SFE process involve slight changes in the structure of the extractable material. , Thus the SFE is quite often used as a coal structure investigation procedure, in our case to gain knowledge of the structure of organosulfur compounds. It has been reported that methyl polysulfides are present in the supercritical methanol extract of coals. , However, the methyl polysulfides can be also formed via the reaction of methanol with elemental sulfur as has been found by White et al Therefore, in our work attention has been focused on the consequences resulting from the presence of elemental sulfur in the initial coal. Every coal sample, being not well protected against air, contains a small amount of elemental sulfur due to the atmospheric oxidation of pyrite …”

“…Moreover, according to the model of the macromolecular constitution of coal , low-molecular-weight aliphatic OSC should be preferentially extracted from the micropore structure, whereas macromolecular network is untouched. Damste et al identified dimethyl tetra-, tri-, and disulfide in a Spanish brown coal by flash pyrolysis−gas chromatography−mass spectrometry, but these results were weakened by White et al…”

“…To compare the reactivity of methanol and 2-propanol in the reaction with elemental sulfur we performed an experiment in conditions comparable to those used by White et al A GC-MS analysis of the reaction product is shown in Table . No isopropyl sulfide and polysulfides were detected between 200 and 275 °C, whereas methyl mono-, di-, tri-, and tetrasulfides were detected in the reaction mixture of elemental sulfur and methanol at 240 °C . However, at a higher temperature under the SFE conditions isopropyl mono-, di-, and trisulfides were formed, Table .…”