Hidenobu Wakita

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 H2S 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 H2S on Bronsted 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.

Catalytic combustion of odors in domestic spaces on ion-exchanged zeolites

Abstract Performance of ZSM-5 zeolites, ion-exchanged with different kinds of metals (Me/H-ZSM-5; Me=Cu, Zn, Mn, Fe, Co, and Ni) and H-ZSM-5 itself, was investigated for the catalytic combustion of trimethylamine (TMA), which is one of the typical odors in domestic spaces. The highest activity was achieved on both Cu/H-ZSM-5 and Fe/H-ZSM-5. The activity of Cu/H-ZSM-5 for the combustion increased with an increase in the amount of ion-exchanged Cu. TPD and FT–IR for the catalysts were measured to investigate the role of ion-exchanged metals in the catalytic combustion of TMA, and it was found that the metals weakened the strong acid sites of H-ZSM-5, and strongly interacted with TMA adsorbed.

Relationship between oxidation states of copper supported on alumina and activities for catalytic combustion of NH3

The relationship between the oxidation state of Cu supported on an alumina catalyst (Cu/Al2O3) and the activity for combustion of NH3 was investigated. Combustion of NH3 on the catalyst treated in hydrogen at 800°C occurred at lower temperature than on the catalyst treated in air. It was also much better than Pt and Rh catalysts for the conversion of NH3 to N2. Characteristics of the catalyst were investigated by XRD, XPS, and the N2O pulse injection method to understand the reason of its high catalytic activity. The reason of the high activity of the catalyst treated in hydrogen at the high temperature was attributed to the lower oxidation state of Cu in the catalyst.