The Reduction of Nitric Oxide in Automobile Emissions

Catalysts containing ruthenium are used to reduce nitric oxide in automobile exhaust emissions but volatile oxides formed under transient oxidising conditions during operation can severely affect them. However, basic oxides such as alkaline earths or rare earths can stabilise the ruthenium by forming ruthenates, which have little tendency to volatilise. The ruthenates are synthesised either before the catalyst is made or in position on the catalyst support, which may be monolithic or pelleted.