Applied Catalysis B: Environmental 24 (2000) 13–21 Selective catalytic reduction of NO with ammonia over V 2 O 5 doped TiO 2 pillared clay catalysts R.Q. Long, R.T. Yang ∗ Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109-2163, USA Received 27 April 1999; received in revised form 15 June 1999; accepted 30 June 1999 Abstract A series of vanadia doped TiO 2 -pillared clay (TiO 2 -PILC) catalysts with various amount of vanadia were studied for selective catalytic reduction (SCR) of NO by ammonia in the presence of excess oxygen. It was found that the V 2 O 5 /TiO 2 -PILC catalysts were highly active for the SCR reaction. The catalysts showed a broad temperature window, and the maximum NO conversion was higher than that on V 2 O 5 /TiO 2 catalyst and was the same as the commercial V 2 O 5 + WO 3 /TiO 2 catalyst. The V 2 O 5 /TiO 2 -PILC catalysts also had higher N 2 /N 2 O product selectivities as compared to V 2 O 5 doped TiO 2 catalysts. In addition, H 2 O + SO 2 slightly increased the activities at high temperatures (>350 ◦ C) for the V 2 O 5 /TiO 2 -PILC catalysts. Addition of WO 3 to V 2 O 5 further increased the activities of the PILC catalysts. These results indicate that TiO 2 -PILC is a good support for vanadia catalysts for the SCR reaction. In situ FT–IR experiment indicated that both Brønsted acid sites and Lewis acid sites exist on the catalyst surface, but with a large proportion being Brønsted acid sites at low temperatures (e.g., 100 ◦ C). The reaction path for NO reduction by NH 3 on the V 2 O 5 /TiO 2 -PILC is similar to that on V 2 O 5 /TiO 2 catalyst, i.e., N 2 originates from the reaction between gaseous NO and NH 3 adspecies. ©2000 Elsevier Science B.V. All rights reserved. Keywords: Selective catalytic reduction; SCR of NO by NH 3 ; TiO 2 -pillared clay; Vanadia doped TiO 2 -pillared clay 1. Introduction Much research effort has been devoted to the study of the selective catalytic reduction (SCR) of nitric ox- ide with ammonia because of its environmental im- portance. Supported V 2 O 5 , Fe 2 O 3 , Cr 2 O 3 , CuO and noble metals as well as ion-exchanged zeolite cata- lysts have been investigated [1]. V 2 O 5 /TiO 2 catalysts are presently used. The mechanism of the reaction on V 2 O 5 /TiO 2 is extensively studied and several differ- ent mechanisms have been proposed [1–10]. In com- ∗ Corresponding author. Tel.: +1-734-936-0771; fax: +1-734-763- 0459 E-mail address: yang@umich.edu (R.T. Yang) mercial use, WO 3 and/or MoO 3 are usually added to V 2 O 5 /TiO 2 as promoters. The addition of WO 3 to V 2 O 5 /TiO 2 catalysts can increase the activity for SCR and reduce ammonia oxidation and greatly increase the poison resistance of the catalysts to alkali and ar- senious oxides [2,11]. Besides TiO 2 , vanadia supported on other sup- ports, such as Al 2 O 3 , SiO 2 , TiO 2 /SiO 2 , etc., have also been studied [1,12,13], but V 2 O 5 /TiO 2 catalysts remain to be favored due to their high activity and resistance to poisoning by H 2 O and SO 2 . In our pre- vious work, pillared clays were studied as catalysts and supports in the SCR reaction [14–18]. Pillared clay, or pillared interlayer clay (PILC), is a unique two-dimensional zeolite-like material. Both Lewis 0926-3373/00/$ – see front matter ©2000 Elsevier Science B.V. All rights reserved. PII:S0926-3373(99)00092-2