Reduction of nitrogen oxides by hydrogen

Reduction of nitrogen oxides can also be achieved by hydrogen  

Hydrogen is generated in the exhaust gases from combustion of hydrocarbons either by the water-gas shift (see Chapter 10) or by steam reforming above 770 K  

For the reduction of both nitric and nitrous oxides, the activity of Au/Al203 was greatly improved by the addition of transition metal oxides and ceria.37 

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