Removal of dimethyl sulfide and t-butylmercaptan from city gas by adsorption on zeolites

The removal of dimethyl sulfide (DMS) and t-butylmercaptan (TBM) from city gas by use of zeolites was studied. Na-Y, Na-X, and Ca-X showed high removal ratios of the sulfur compounds at 1 h after the start of the adsorption run in city gas flow, though DMS broke through rapidly for a few hours. On the other hand, H-beta and USY showed continuously high removal ratios for 9 h, and trace amounts of H2S were detected in the effluent gas. The adsorption mechanisms on Na-Y and H-beta were studied by adsorption in the absence of hydrocarbons, IR spectroscopy, and temperature programmed desorption (TPD). The desorbed peaks of DMS and TBM during TPD of binary components on Na-Y were located over the same temperature ranges as the peak during TPD of DMS and that of TBM, respectively, which findings suggested that the adsorption states at binary adsorption were similar to those at single component adsorption. The main adsorption site was presumably Na+. On H-beta, TBM reacted to H2S on Bronsted acidic sites. On the adsorption run in the absence of hydrocarbons, the removal ratio of TBM was enhanced on H-beta in the presence of DMS. During TPD of binary components on H-beta, a peak of m/e = 41 at 120 degreesC grew, which findings indicated that the polymerization of isobutene-like compounds produced from TBM was depressed by co-existent DMS. (C) 2001 Elsevier Science B.V. All rights reserved.