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.