Role of V 2 O 5 –WO 3 /H 2 Ti 3 O 7 -nanotube-model catalysts in the enhancement of the catalytic activity for the SCR-NH 3 process R. Camposeco a,c , S. Castillo a,b,⇑ , V. Mugica c , Isidro Mejía-Centeno a , J. Marín a a Molecular Engineering Program, Mexican Institute of Petroleum, 07730 México, DF, Mexico b Department of Chemical Engineering, ESIQIE-IPN, 07738 México, DF, Mexico c Department of Chemistry UAM-A, 02200 México, DF, Mexico highlights  Titanium acid nanotubes TAN by sol– gel were obtained.  V 2 O 5 –WO 3 /TAN catalyze, the NOx reduction at high temperature.  Titanium acid nanotubes TAN showed thermal stability up to 420–450 °C.  Titanium acid nanotubes TAN showed good activity even with the presence H 2 O and SO 2 .  V 2 O 5 –WO 3 /TAN catalysts are truly a powerful tool for SCR-NH 3 . graphical abstract The V–W/TAN catalysts could be the main technology to remove NOx at high temperature even with the presence of H 2 O and SO 2 . 100 200 300 400 500 0 20 40 60 80 100 NOConversion (%) Temperature (°C) article info Article history: Received 14 August 2013 Received in revised form 17 December 2013 Accepted 2 January 2014 Available online 8 January 2014 Keywords: Titanium nanocrystals Titanic acid nanotubes SCR-NH 3 -process Titania acidity V 2 O 5 –WO 3 catalysts abstract In this work, a series of titanic acid nanotubes (TANs) were synthesized through the hydrothermal method. TiO 2 -nanocrystals as starting materials were used. V 2 O 5 –WO 3 was incorporated to the TANs by wet impregnation. The catalysts were characterized by XRD, BET, XPS, FTIR and STEM. The catalytic tests were focused on the Selective Catalytic Reduction of NO by NH 3 (SCR-NH 3 ). It was observed that the catalytic activity of the V 2 O 5 –WO 3 /TAN catalysts was strongly improved for the SCR-NH 3 process in a wide temperature interval in comparison with the V 2 O 5 –WO 3 /TiO 2 traditional catalysts. The strong tubular structure, titanic acid phase (H 2 Ti 3 O 7 ), good thermal stability (up to 460 °C) and high specific sur- face area (314 m 2 /g) help to promote the NO conversion between 300 and 440 °C. The highest catalytic activity can be correlated with the presence of acid sites. Brønsted acid sites increase significantly the light-off conversion at low temperatures. Lewis acid sites promote the NO reduction at high temperature. The V 2 O 5 –WO 3 /TAN catalyst showed very high activity (81%) at high temperatures (350–450 °C) even in the presence of water (10 vol.%) and SO 2 (50 ppm) in the feed stream. Besides, the sulfated and hydrated catalysts recovered their original catalytic activity. Ó 2014 Published by Elsevier B.V. 1. Introduction The Selective Catalytic Reduction (SCR) of NO by NH 3 in the presence of excess oxygen is probably the best world technology to remove NOx from stationary sources and one of the most prom- ising technologies for removing NOx from diesel engines [1,2]. The process uses V 2 O 5 –WO 3 /TiO 2 -based catalysts to facilitate the reac- 1385-8947/$ - see front matter Ó 2014 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.cej.2014.01.002 ⇑ Corresponding author at: Molecular Engineering Program, Mexican Institute of Petroleum, 07730 México, DF, Mexico. Tel.: +52 (55) 91758216; fax: +52 (55) 91756000. E-mail address: scastill@imp.mx (S. Castillo). Chemical Engineering Journal 242 (2014) 313–320 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej