Catalyst for removing nitrogen oxides from the exhaust gas of diesel engines

摘要

The invention relates to a catalyst for removal of nitrogen oxides from the exhaust gas of diesel engines, and to a process for reducing the level of nitrogen oxides in the exhaust gas of diesel engines. The catalyst consists of a support body of length L and of a catalytically active coating which in turn may be formed from one or more material zones. The material zones comprise selectively catalytically reductive (SCR-active) mixed oxide consisting of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide and optionally tungsten oxide. In addition, the material zones comprise at least one compound selected from the group consisting of barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide, strontium carbonate, praseodymium oxide, lanthanum oxide, magnesium oxide, mixed magnesium/aluminum oxide, alkali metal oxide, alkali metal hydroxide, alkali metal carbonate and mixtures thereof. Noble metal may optionally also be present in the catalyst.

主权项

1. A catalyst for removing nitrogen oxides from the exhaust gas of diesel engines, consisting of a support body of length L and a catalytically active coating composed of one or more material zones comprising:
a) a catalytically active mixed oxide consisting of cerium oxide, zirconium oxide, rare earth sesquioxide and niobium oxide; and b) at least one compound selected from the group consisting of barium oxide, barium hydroxide, barium carbonate, strontium oxide, strontium hydroxide, strontium carbonate, praseodymium oxide, lanthanum oxide, magnesium oxide, mixed magnesium/aluminum oxide, alkali metal oxide, alkali metal hydroxide, alkali metal carbonate and mixtures thereof, and wherein the catalytically active mixed oxide, based on the total amount thereof, has the following composition: CeO2: 15-50% by wt. Nb2O5: 3-25% by wt. RE2O3: 3-10% by wt. ZrO2: remainder.