Alzchem Trostberg Gmbh

Bernd Schulz

Hans-Peter Krimmer

Eberhard Jacob

Benedikt Hammer

The invention relates to the use of aqueous guanidinium formiate solutions, optionally combined with urea and/or ammonia and/or ammonium salts, for the selective catalytic reduction of nitrogen oxides using ammonia in exhaust gases of vehicles. The inventive guanidinium formiate solutions enable a reduction of the nitrogen oxides by approximately 90%. Furthermore, said guanidinium formiate solutions can enable an increase in the ammonia forming potential from 0.2 kg, corresponding to prior art, up to 0.4 kg ammonia per liter of guanidinium formiate, along with freezing resistance (freezing point below &#x2212;25&#xb0; C.). The risk of corrosion of the inventive guanidinium formiate solutions is also significantly reduced compared to that of solutions containing ammonium formiate.

Use of aqueous guanidinium formate solutions for the selective catalytic reduction of nitrogen oxides in exhaust gases of vehicles

The invention relates to a method for the selective catalytic reduction of nitrogen oxides using ammonia in exhaust gases of vehicles, whereby solutions of guanidine salts with an ammonia forming potential of between 40 and 850 g/kg, optionally in combination with urea and/or ammonia and/or ammonium salts, are catalytically decomposed in the presence of catalytically active, non-oxidation-active coatings of oxides selected from the group containing titanium dioxide, aluminum oxide, silicon dioxide or the mixtures thereof, and hydrothermally stable zeolites which are fully or partially metal-exchanged. The guanidine salts according to the invention enable a reduction of the nitrogen oxides by approximately 90%. Furthermore, said guanidine salts can enable an increase in the ammonia forming potential from 0.2 kg, corresponding to prior art, up to 0.4 kg ammonia per litre of guanidine salt, along with freezing resistance (freezing point below &#x2212;25&#xb0; C.). The risk of corrosion of the guanidine salt solutions used according to the invention is also significantly reduced compared to that of solutions containing ammonium formiate.

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Waldkraiburg, Germany

Bernd Schulz