Tomohiro Yoshinari

Role of supported metals in the selective reduction of nitrogen monoxide with hydrocarbons over metal/alumina catalysts

Abstract The promoting effect of supported metals on alumina catalyst was investigated for the reduction of nitrogen monoxide in oxygen-rich atmospheres. For NO reduction with propene over impregnated CoO/A1 2 O 3 , the first reaction step was found to be the oxidation of NO to NO 2 probably catalyzed by dispersed cobalt species. The next reaction step, which is the reaction of NO 2 with propene to form N 2 , was considered to take place on the alumina surface. Although the activity of impregnated FeO/A1 2 O 3 was low because of the presence of large iron oxide particles catalyzing propene oxidation with dioxygen, FeO/A1 2 O 3 prepared with sol-gel method showed excellent deNO x activity.

Performance of solid acid type catalysts for the selective reduction of nitrogen oxides by hydrocarbons and alcohols

Abstract The performance and characteristics of solid acid type catalysts such as H-ZSM-5 and alumina for the title reaction were investigated. NO reduction on these catalysts was characterized by high efficiency of reducing agent consumed in the presence of oxygen. The catalytic activity was found to be correlated to the solid acidity of the catalysts. Among various reducing agents, methanol was the most efficient for NO reduction at low temperature. It was suggested that the oxidation of NO to NO2 is an important reaction step in the overall NO reduction. Although coexisting water vapor inhibited the reaction, methanol was still effective for alumina-catalyzed reduction at low temperature. Alumina showed excellent activity and durability for the de-NOx of diesel emissions.

Reduction of NOx in diesel exhaust with methanol over alumina catalyst

Abstract NO x reduction in diesel exhaust using selective catalytic reduction by methanol over alumina catalyst was investigated. Although a slight decrease in catalytic activity took place at the initial stage of the catalyst evaluation, more than 40% NO x conversion was obtained at 400°C and a space velocity of 10 000 h −1 by using a ball type alumina catalyst and methanol ( CH 3 OH/NO x mole ratio = 2) as a reducing agent. The experimental results using synthetic exhaust gases containing SO 2 indicated that the initial catalytic deactivation is ascribed to the formation of Al 2 (SO 4 ) 3 -like species on alumina surface through reaction with SO 2 . However, the formation stopped at a certain point in time. The stable activity following the initial deactivation did not depend on SO 2 concentration. A durability test of a honeycomb type alumina was also conducted, and more than 70% of NO x conversion maintained for more than 4000 h at a CH 3 OH/NO x mole ratio of 6. In this case a gradual decrease in the activity of alumina occurred due to catalyst sintering.

High efficiency of alumina and H-zeolite catalysts for selective reduction of nitrogen monoxide by methanol in the presence of oxygen and water vapor

Abstract Alumina, Co/alumina, and H-ZSM-5 zeolite showed excellent catalytic activity for nitrogen monoxide reduction by methanol and ethanol at 300–400°C in the presence of high concentrations of oxygen and water vapor. Due to the inhibiting effect of water, propane, propene and 2-propanol did not reduce nitrogen monoxide effectively at such low temperatures over the alumina catalyst. Cu-ZSM-5 zeolite did not catalyze nitrogen monoxide reduction by methanol at all, whereas it showed activity for nitrogen monoxide reduction by ethanol.

Promotive effect of Sn on the catalytic activity of Al2O3 for the selective reduction of NO by methanol

The effect of various metal additives on the catalytic performance of A12O3 was investigated for the selective reduction of NO by methanol in oxidizing atmosphere. The addition of Sn promoted the catalytic activity of alumina for the NO reduction at low temperatures. Moreover, it was found that Sn/Al2O3 catalyst maintained its high activity even in the presence of SO2.