The inhibition mechanism of H2O at hydrothermal aging over Pt/SiO2-Al2O3 for NO oxidation

Pt/SiO2-Al2O3 (Pt/SA) is commonly used as diesel oxidation catalysts (DOC) in industry, but it could be seriously deactivated caused by H2O at long-term high temperature. In this paper, the inhibition mechanism of water on Pt/SA for NO oxidation was studied. The fresh Pt/SA (Pt/SA-F) was treated in an air flow with/without 10% H2O at 700 °C for 10 h to obtain the hydrothermally/thermally aged catalysts named as Pt/SA-HA and -A, respectively. NO oxidation tests showed that Pt/SA-HA had lower activity than Pt/SA-A. A series of characterizations proved H2O didn’t affected Pt states and support structure as they were similar over two aged catalyst. 1H NMR and In-situ DRIFTS testified that water deactivation was a result of the acidity loss of catalysts, which inhibited the decomposition and desorption of reaction intermediate, finally resulting in bad NO oxidation activity. [Display omitted] •H2O inhibition mechanism at hydrothermal aging on Pt/SiO2-Al2O3 for NO oxidation was investigated.•H2O leaded to the loss of Brönsted acid sites (like-bridge Al-OH-Si).•The loss of acid sites induced by H2O suppressed decomposition of nitrate species resulting in low NO activity.