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

Abstract

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-β and USY showed continuously high removal ratios for 9 h, and trace amounts of H 2S were detected in the effluent gas. The adsorption mechanisms on Na-Y and H-β 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-β, TBM reacted to H 2S on Brönsted acidic sites. On the adsorption run in the absence of hydrocarbons, the removal ratio of TBM was enhanced on H-β in the presence of DMS. During TPD of binary components on H-β, a peak of m/ e=41 at 120°C grew, which findings indicated that the polymerization of isobutene-like compounds produced from TBM was depressed by co-existent DMS.