A series of anodic-alumina-supported silver catalysts (Ag/Al
2O
3) were synthesized to investigate the promotional effect of H
2 and electrical heating possibility on the selective catalytic reduction (SCR) of NO by C
3H
6.
It was observed that the SCR activity of Ag/Al
2O
3 catalyst was greatly improved at low temperatures in the presence of H
2. Moreover, this promotional effect became more significant with increasing H
2 concentration. According to the results of the reaction without C
3H
6, H
2 did not significantly improve the activity; this indicates that the H
2 acted as a promoter but did not directly participate in NO
x reduction. The results of NO
x-TPD (Temperature Programmed Desorption) and NO
x-H
2-TPR (Temperature Programmed Reduction) showed that the NO
x adsorbed on the catalyst surface was quickly desorbed in the presence of H
2, while NO
x desorption became faster by increasing the concentration of H
2 added to the flow as well as the Ag loadings. In the case of catalysts with low Ag loadings, nitrate poisoning was considered to be the main reason for low NO
x conversion at low temperatures. On the other hand, in the case of the high Ag loadings, the scarcity of Ag
nδ+ clusters was inferred to result in unfavorable SCR activity.
Additionally, electrical heating tests on the SCR by C
3H
6 in the presence of Ag/Al
2O
3 catalysts showed excellent denitration activity and rapid reaction rate. On the basis of the electrical heating pattern, a new strategy for controlling NOx emission from diesel engines was formulated.
抄録全体を表示