Applied Catalysis B: Environmental 31 (2001) 233–240 Cloth catalysts for water denitrification II. Removal of nitrates using Pd–Cu supported on glass fibers Yu. Matatov-Meytal a , V. Barelko b , I. Yuranov c , L. Kiwi-Minsker c , A. Renken c , M. Sheintuch a,∗ a Department of Chemical Engineering, Technion-Israel Institute of Technology, 32000 Haifa, Israel b Institute of Chemical Physics, RAS, Chernogolovka, Russia c Institute of Chemical Engineering, EPFL, Lausanne, Switzerland Received 8 April 2000; received in revised form 25 July 2000; accepted 17 November 2000 Abstract The use of glass fibers in the form of woven cloth (GFC), as a new type of catalytic support, was studied for the reduction of aqueous nitrate solutions using a Pd/Cu–GFC catalyst. The activity (per gram Pd) and selectivity to nitrogen were found to be comparable with those found for Pd–Cu catalysts supported on the other carriers. The maximal initial removal activity was found for a catalyst with a Pd/(Pd + Cu) ratio of 0.81. The corresponding activity was 0.7 mmol min -1 (g Pd ) -1 , and the selectivity was 97 mol% at 25 ◦ C and pH 6.5 for initial nitrate concentration of 100 mg l -1 . The selectivity to nitrogen declined at high conversions of nitrate and high pH. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Catalytic denitrification; Nitrate; Pd/Cu catalyst; Glass fiber support 1. Introduction The catalytic conversion of dissolved nitrates into gaseous nitrogen is currently attracting considerable interest (see [1] and references therein). This process, which should be conducted at room temperature, is a slow one. Controlling the selectivity in order to avoid accumulation of ammonium and nitrite ions, which are formed during the reaction, remains the key issue in catalytic reduction of nitrates [2–5]. Pore diffusion resistance is significant in pellet- shaped catalysts even under these conditions [6,7]. Moreover, as we show here, diffusion resistance sig- nificantly hurts the selectivity to nitrogen. The reaction ∗ Corresponding author. Tel.: +972-4-8292920; fax: +972-4-8230476. E-mail address: cermsll@techunix.technion.ac.il (M. Sheintuch). can be performed with powdered catalysts, as was the practice in most laboratory-scale studies, but that will cause problems of high pressure drop in industrial size reactors. Attempts to solve the contacting problem of the three phases and to reduce the diffusion resistance have included the use of novel catalyst supports [8,9]. We have proposed the use of clothes catalysts made of fibrous carriers, having the same diameter as pow- der [1]. These are geometrically flexible and can be shaped in endless forms, which may be packed in the reactor to fit the particular use. Initial reports on the use of glass fiber cloth (GFC) catalysts for liquid-phase hydrogenation of various compounds showed positive results [10–12]. In our first effort, we found that Pd supported on GFC was active for nitrite reduction, but relatively inactive for nitrate reduction [1]. Literature studies suggest that the performance of Pd/Cu cata- lysts in nitrate reduction is significantly better than 0926-3373/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0926-3373(00)00284-8