It is possible that this catalytic system could also be used for an engine running on natural gas. In addition to the
catalyst for selective reduction of nitrogen oxides the NH3-SCR system includes catalysts of urea hydrolysis and
final reduction of, e.g. ammonia. This technology has a number of thermal limitations, because hydrolysis of
urea at T>400-500oC may produce crystalline compounds poorly soluble in water, such as triurea and carbamyl
urea, which are incapable of hydrolysis. In addition, the number of active V4+ sites at these temperatures in V-Ti
composition decreases, V5+ and higher phases appear, which oxidize ammonia at the stage of NOx and nitrogen
reduction, significantly reducing the catalyst's efficiency.