A series of Ce-Ti mixed-oxide catalysts were prepared by the sol–gel method for selective catalytic reduction
(SCR) of NO with ammonia as reductant. These catalysts were characterized by XRD, BET, and XPS
techniques. The experimental results show that the best Ce-Ti mixed-oxide catalyst yielded 98.6% NO
conversion, and 100% N2 selectivity at typical SCR reaction temperatures (300–400 ◦C) and the high gas
hourly space velocity of 50,000 h−1. As the Ce loading (the mass ratio of CeO2/TiO2) was increased from
0 to 0.6, NO conversion increased markedly, but decreased at higher Ce loading. The most active catalyst
was obtained with a Ce loading of 0.6. The high activity might be attributed to high Ce loading, strong
interaction between Ce and Ti, high concentration of amorphous Ce on the catalyst surface, or the increase
of chemisorbed oxygen or/and weakly bonded oxygen species, resulting from the presence of Ce3+ after
Ce addition. The effect of the calcination temperature was also investigated, and the optimal calcination
temperature was 500 ◦C. The presence of oxygen played an essential role in NO reduction, and the activity
of the Ce(0.6)Ti catalyst was not depressed when oxygen concentration was higher than 1%. The effect of
SO2 and H2O on the activity of the Ce(0.6)Ti catalyst was bound up with the reaction temperature.