Standing harsh hydrothermal treatment (similar to 10% H2O, similar to 1050 K) is a prerequisite for deNO(x) catalysts of tomorrow in diesel exhaust gas treatment. New catalytic materials composed of Mn-, Fe- and Ce-ZrTiSiW mixed oxide were evaluated in the selective catalytic reduction NO by NH3 at high gas hourly space velocity (330,000 mL g(-1) h(-1)) and after high temperature hydrothermal treatment, 16 h at 1023 K in H2O/air (10/90). They were compared with a Fe-ZSM5 SCR catalyst treated in the same manner. CeZrTiSiW exhibits the best performance and keeps high NO conversion (>80%) from 630 to 800 K. It is stable and fully selective to N-2 up to 823 K. It is more active and selective than Fe-ZSM5. The presence of NO2 in the feed (NO2/NO = 0.85) boosts the NO conversion by shifting the light-off temperature (50% NO conversion) from 560 K to 460 K. (C) 2011 Elsevier B.V. All rights reserved.