Study of silica-immobilized sulfur model compounds as calibrants for the AP-TPR study of oxidized coal samples

Abstract

Desulfurization of coal prior to combustion has developed the need for an accurate technique to determine which sulfur groups are present before and after chemical treatment. Atmospheric pressure-temperature programmed reduction (AP-TPR) is a technique that can determine the sulfur distribution by using model compounds as calibrants. This study deals with a series of model compounds for oxidized sulfur functionalities. It is proven by AP-TPR and AP-TPR-MS that the sulfur groups of these model compounds are decomposed and that decomposition products (SO/SO2) are only partially reduced. Diaryl sulfoxides and sulfones are found to be more stable than their aryl alkyl-substituted counterparts, and sulfones are more stable than the structurally related sulfoxides. Sulfates are generally found to be the most stable oxidized forms of sulfur.