Studies on the Low-Temp Oxidation of Coal Containing Organic Sulfur and the Corresponding Model Compounds

Abstract

This paper selects two typical compounds containing organic sulfur as model compounds. Then, by analyzing the chromatograms of gaseous low-temp oxidation products and GC/MS of the extractable matter of the oxidation residue, we summarizing the mechanism of low-temp sulfur model compound oxidation. The results show that between 30˝C to 80˝C, the interaction between diphenyl sulfide and oxygen is mainly one of physical adsorption. After 80˝C, chemical adsorption and chemical reactions begin. The main reaction mechanism in the low-temp oxidation of the model compound diphenyl sulfide is diphenyl sulfide generates diphenyl sulfoxide, and then this sulfoxide is further oxidized to diphenyl sulphone. A small amount of free radicals is generated in the process. The model compound cysteine behaves differently from diphenyl sulfide. The main reaction low-temp oxidation mechanism involves the thiol being oxidized into a disulphide and finally evolving to sulfonic acid, along with SO 2 being released at 130˝C and also a small amount of free radicals. We also conducted an experiment on coal from Xingcheng using X-ray photoelectron spectroscopy (XPS). The results show that the major forms of organic sulfur in the original coal sample are thiophene and sulfone. Therefore, it can be inferred that there is none or little mercaptan and thiophenol in the original coal. After low-temp oxidation, the form of organic sulfur changes. The sulfide sulfur is oxidized to the sulfoxide, and then the sulfoxide is further oxidized to a sulfone, and these steps can be easily carried out under experimental conditions. What's more, the results illustrate that oxidation promotes sulfur element enrichment on the surface of coal.

Effects of organic sulfur on oxidation spontaneous combustion characteristics of coking coal

“…Few scholars have reported on the impact of organic sulfur on the spontaneous combustion of coal (Borah et al, 2001;Gorbaty et al, 1990). Through their temperature-programmed oxidation experiment, Zhang et al (2015; found that the oxidative activity of organic sulfur functional groups was in the order of mercaptan> sulfide> thiophene. However, the reaction mechanism of spontaneous combustion caused by organic sulfur functional groups was not analyzed in depth, and the selection of organic sulfur model compounds was not comprehensive.…”

Reaction Mechanism of Aldehyde Groups during Coal Self-Heating

“…Zhang et al found that the distribution of organic sulfur in coal is related to the degree of metamorphism of coal and the interaction of sulfur-containing functional groups 18 and oxygen is mainly physisorption between 30 and 80 °C. 19 As one of the oxygen-containing functional groups, the aldehyde group has been studied by many scholars. Xu et al 20 inferred that the aldehyde group in the coal structure is one of the main factors for the redox reaction.…”

Prospective Approach to the Anaerobic Bioconversion of Benzo- and Dibenzothiophene Sulfones to Sulfide

“…In the composition of organic molecules, sulfur is most often found in the form of mercaptans, sulfide, disulfides, thioethers, sulfoxides, sulfones, thiophene, sulfoacids, etc. [3]. Biodesulfurization is a promising alternative to the traditional chemical method of controlling chemical transformations of S-containing molecules; it is based on the use of living aerobic (oxidative pathway: 4S and Kodama) or anaerobic (reductive pathway: C–S Cleavage) bacterial cells [1,2,4].…”

“…Toxic organic sulfones and sulfoxides, as is known, can be formed in the processes of conversion of petroleum feedstock, for example, during the leakage of petroleum products [7] and during the combustion of coal [3]. Thermal decomposition of the sulfone-containing compounds that is used to remove sulfur in the form of SO 2 could be a part of the final recovery step in an oxidative desulfurization process [8], but the thermal stability of sulfones depends upon the chemical environment of the sulfone group.…”