Selective methanation of CO in the reformate gas (CO/CO 2 /H 2 /H 2 O = 0.175/17.9/70.9/11.1) proceeded over Ru catalysts supported on metal oxides and zeolites. CO was selectively methanated at wide temperature ranges (200-275°C) over Ru/c-Al 2 O 3 , Ru/TiO 2 Ru/H-Y and Ru/ H-beta catalysts. Higher Ru contents in Ru/c-Al 2 O 3 improved the selective CO methanation rate.

Selective methanation of CO was performed over Ni/TiO2. CO in reformate gas was completely removed at 150–300 °C. The CH4 concentration in the outlet gas could be maintained below 1% in the entire temperature region because Ni/TiO2 suppressed the CO2 methanation reaction. It can be considered that the formation of CO by the reverse water-gas-shift reaction is blocked by the application of TiO2 to the support of Ni catalyst and that it results in the high CO/CO2 selectivity of Ni/TiO2.

Adsorptive removal of t-butanethiol (TBT), an odorant additive, from city gas was carried out using metal ionexchange Y type zeolites at ambient temperature and pressure. The adsorption capacity of TBT on Na _ Y under the wet gas condition was extremely low, although that under the dry gas condition was certainly higher. The adsorption capacity of TBT on silver ion-exchange Y type zeolites (Ag(Na) _ Y) increased with higher silver ionexchange ratio in Ag(Na) _ Y under wet gas condition. In contrast, the adsorption capacity of TBT on Ag(Na) _ Y under the dry gas condition decreased with higher silver ion-exchange ratio in Ag(Na) _ Y. Formation of silver sulfide clusters in Ag(Na) _ Y causes the decrease in sulfur adsorption capacity of it under the dry gas condition. The adsorption capacity of TBT on copper ion-exchange Y type zeolites (Cu(Na) _ Y) increased with higher copper ion-exchange ratio in Cu(Na) _ Y under the wet gas condition. In the case of Cu(Na) _ Y, the decrease of TBT adsorption capacity under the dry gas condition did not occur with higher copper ion-exchange ratio in Cu(Na) _ Y. The both spent samples of Ag(Na) _ Y and Cu(Na) _ Y were regenerated by heat treatment in air. The decrease in adsorption capacity of TBT on Cu(Na) _ Y was slightly lower than that on Ag(Na) _ Y.