Role of WO3 in mixed V2O5-WO3/TiO2catalysts for selective catalytic reduction of nitric oxide with ammonia

✍ Scribed by J.P. Chen; R.T. Yang

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 789 KB
• Volume: 80
• Category: Article
• ISSN: 0926-860X
• DOI: 10.1016/0926-860x(92)85113-p

✦ Synopsis

A series of TiO,-supported V,O, and V,O,+ WOI catalysts were prepared to study the role of WO, in the commercial selective catalytic reduction (SCR) catalysts. The activities of these catalysts were measured under both dynamic and steady-state conditions. The catalysts were characterized by temperature-programmed reaction (TPR), ammonia chemisorption and proton magic angle spinning nuclear magnetic resonance (MAS NMR) measurements. The following effects of WO, on Vz0JTi02 in the commercial WO,-V,O,/TiO, (coimpregnated) SCR catalyst are observed: (1) It increases the activity and widens the temperature window for SCR. (2 ) It significantly increases the poison resistance to both alkali metal oxides and arsenious oxide. (3) It reduces ammonia oxidation (as well as SO, oxidation which is known from the published literature ). These results have been correlated directly with ammonia chemisorption and proton MAS NMR measurements. These results suggest that the Brcansted acid sites are the active sites for SCR. Addition of WO, in V205/Ti02 increases the Brensted acidity (both Brensted acid site density and strength of the acid, i.e., proton donicity), whereas the alkali poison decreases the Bnmsted acidity.