Adsorption/desorption of dimethylsulfide on activated carbon modified with iron chloride

The adsorption capacity of activated carbon for the natural gas contaminant dimethylsulfide (DMS) was improved by impregnating it with FeCl3 introduced in solution to affect surface modification. A DMS adsorption mechanism and roles of impregnated FeCl3 on the capacity enhancement were proposed based on experimental tests results.Samples of activated carbon and activated carbon impregnated with FeCl3 were tested as DMS sorbents. Samples loaded with DMS were subsequently extracted with n-octane and the resulting solvents were analyzed for sulfur species using a gas chromatograph equipped with a sulfur chemiluminescence detector. No other sulfur compounds were detected in the liquid samples other than DMS. DMS, dimethyl disulfide, and carbonyl sulfide were recovered from identical DMS-adsorbed samples of activated carbon impregnated with FeCl3 subjected to temperature programmed desorption (TPD) in a nitrogen gas stream. Only DMS was recovered from the activated carbon samples. The TPD patterns indicate different kinetics of DMS desorption related to the carbon phase and the new active sites created by the FeCl3 impregnation. The new active sites improved DMS adsorption capacity and likely had stronger affinity with DMS molecule. As a reference, similar tests were investigated using methyl mercaptan (MM) as an adsorbate on the carbon sorbents. A different adsorption mechanism was found and discussed from these experimental results. Regeneration of the used carbon sorbents by thermal desorption was also explored.