Reduction of NO2 by hydrocarbons over H-form zeolites

The emission of NOx in the atmosphere causes a series of significant evironmental problems such as acid rains, photochemical smog, ozone depletion and green house effect. Roughly three quarters of the global production of NOx is due to anthropogenic activity of which combustion of fossil fuels account for more than half. Combustion of fossil fuels is in general used to free energy for the propulsion of cars, trucks, trains, boats, airplanes and to generate electricity in power plants or heat for industrial processes. During combustion NOx can be formed by oxidation of nitrogen containing organic compounds, oxidation of HCN or oxidation of N2 present in the air (Thermal NOx). Nitrogen can efficiently be removed from organic fuels by hydro-treating while HCN is only formed in fuel rich flames leaving the oxidation of N2 as the major source of NOx. To achieve reduction of NOx emissions governments world wide have installed restrictive legislations such as in 1971 the ‘clean air act’ in the USA and the Euro I-V norms in Europe which initiated the development of NOx reducing technologies. The development of the NH3-SCR process in the 70’s enables the efficient reduction of NOx from stationary sources. Thermal NOx can efficiently be reduced by CO and H2 (three-way catalyst) in car exhausts containing stoichiometric O2 levels. Exhausts of Diesel and Lean burn engines contain excess of O2 and thus is the development of new technologies required. The use of hydrocarbons for the reduction of NOx appears a promising technique and a wealth on research results on this topic has been reported in the last 20 years what until today did not result in a satisfactory solution.