Unveiling H_(2)O_(2)-optimized NO_x adsorption-selective catalytic reduction(AdSCR)performance of WO_(3)/CeZrO_(2) catalyst

Recently,NO_x emissions in the cold-start period have been a great challenge in eliminating diesel vehicle exhaust.In this study,a type of NO_x adsorption-selective catalytic reduction(AdSCR)bifunctional catalyst was developed to remove NO_x in the cold-start period by constructing additional NO_x adsorption sites on the surface of the selective catalytic reduction of NO_x with NH_(3) catalyst.The AdSCR catalyst exhibited both NO_x adsorption-storage performance and NH_(3)-SCR activity.The amount of oxygen vacancies directly affected the adsorption performance of NO_x on the catalyst surface.In this study,H_(2)O_(2)with different pH values was employed to adjust the electronic structure of the CeZrO_(2) support and construct oxygen vacancies on the surface of CeZrO_(2),which contributed to improving NO_x adsorption and storage on the WO_(3)/CeZrO_(2)(W/CZ)catalyst below 200℃.The catalytic performance results show that CZ supports modified by alkaline H_(2)O_(2) rather than acidic and neutral H_(2)O_(2) significantly improve the NO_x adsorption capacity without decreasing the NH3-SCR activity.The characterization results show that the CZ support modified by alkaline H_(2)O_(2)possesses more surface oxygen vacancies and chemisorbed oxygen than CZ supports modified by acidic and neutral H_(2)O_(2).Oxygen vacancies are not only the active sites of NH_(3)-SCR,but also the active sites of NO_x adsorption.Therefore,the W/CZ catalyst modified by alkaline H_(2)O_(2)exhibited an excellent AdSCR performance.This study proposes a novel perspective to address the issue of NO_x emissions from diesel vehicles during the cold start period.

Determining hydrothermal deactivation mechanisms on Cu/SAPO-34 NH_(3)-SCR catalysts at low-and high-reaction regions:establishing roles of different reaction sites

Hydrothermal deactivation is a constant chal-lenge in commercial catalytic process aimed at NOx emission control,which may be observed in the low(150-400℃)or high(400-550℃)-reaction regions.To the best of our knowledge,there is a lack of systematic research regarding the correlation between the reaction sites and the mechanism of hydrothermal degradation at various reaction regions.For a targeted investigation of this,Cu/zeolite catalysts have been prepared using different amounts of polyvinyl alcohol for adjusting their redox and acid properties.These catalysts exhibit hydrothermal deactivation in different reaction regions.No change is observed in the reaction mechanism even with hydrother-mal deactivation,but various reaction sites determine the performance deterioration in the low-and high-reaction regions.The redox properties and weak acid sites affect the hydrothermal deactivation in the low-reaction region,whereas the moderate/strong acid sites related to the structure mainly influence the hydrothermal deactivation in the high-reaction region.This work provides several the-oretical insights for optimizing the hydrothermal stabilities of Cu/zeolite catalysts.