Journal of Molecular Catalysis A: Chemical 260 (2006) 35–42 Liquid phase mononitration of chlorobenzene over WO x /ZrO 2 : A study of catalyst and reaction parameters K.M. Parida ∗ , P.K. Pattnayak, P. Mohapatra Colloids and Materials Chemistry Cell, Regional Research Laboratory (CSIR), Bhubaneswar 751 013, Orissa, India Received 17 May 2006; received in revised form 25 June 2006; accepted 26 June 2006 Available online 9 August 2006 Abstract To study the effect of W concentration and activation temperature of the catalysts a series of WO x /ZrO 2 samples with varying concentration of W (10–25 wt.%) were prepared and activated at 650/750 ◦ C. XRD of sample shows 15 wt.% W stabilizes the tetragonal phase of zirconia up to 750 ◦ C. Above and less than 15 wt.% shows peaks corresponding to monoclinic WO 3 and monoclinic ZrO 2 , respectively. Further, the tungsten modification stabilizes the specific surface area of ZrO 2 . There is an increase in the surface area observed up to 15wt.% W, which declines on further increase in the concentration. The NH 3 TPD confirms the presence of acid sites with varying strength from the broad desorption profile. The 15 wt.% W and activated at 750 ◦ C shows maximum acidity. The results of the nitration reaction of chlorobezene imply the 15wt.% W and activation at 750 ◦ C shows maximum activity. Not only yield, a better para-selectivity is also achieved with WO x /ZrO 2 samples. Effect of activation temperature, W concentration and reaction parameters such as reaction temperature, reaction time, the presence of solvent and solvent free medium on activity and selectivity are studied in details. © 2006 Elsevier B.V. All rights reserved. Keywords: WO x /ZrO 2 ; Chlorobenzene; Acidity; Nitration; Selectivity; Solvent 1. Introduction Nitration of aromatic compounds is a ubiquitous reaction to realise organic intermediates required in large tonnages for the fine chemical industry. Mononitrohalobenzene, especially para-nitrochlorobenzene, are versatile intermediates for dyes, pharmaceuticals and perfumes [1]. The conventional nitration process [2,3], employing a nitrating mixture of nitric and sulfu- ric acid, for the last 150 years has remained unchallenged in the commercial arena owing to uneconomical alternative options. By classical method with a mixture of nitric and sulphuric acids, predominantly ortho- and para-products close to the ratio of 1:2 are resulted [2,3]. Due to the commercial importance of para- chloronitro benzene, a lot of studies were carried out to increase the para-selectivity. A mixture of acetic anhydride and nitric acid in the presence of sulphuric acid was used by Menke [4] and Paul [5] and afforded high para-selectivity at low temperature. ∗ Corresponding author. Tel.: +91 674 2581 636 305/425; fax: +91 674 2581 637. E-mail addresses: kmparida@yahoo.com, kmparida@rrlbhu.res.in (K.M. Parida). Although the conventional method of using concentrated H 2 SO 4 provides better yield and selectivity too, the main dis- advantage of this process is handling of the corrosive acid and also the waste acid disposal causes serious environment threats. In addition, the separation of products is another difficult step in this process. As in the recent time more emphasis has been given to develop clean process, it is essential to find a suitable alternate catalyst to meet the requirements. Use of solid acid catalyst seems to be the right solution. In this contest, it was reported that claycop can produce 98% yield having ortho to para ratio of 13:85 when fuming nitric acid is used as the nitrating agent [6]. Choudhary et al. [7] claimed to increase the ortho to para ratio to 8:92 using Fe 3+ exchanged montomorillonite-K10 catalyst in presence of nitric acid and acetic anhydride. Also, pillared clay was studied for this reac- tion as a solid acid catalyst [8]. Even beta-zeolite was used as catalyst for the same reaction [9] and reported to be efficient. Similarly several other reports are also available in the recent past in studying the nitration reaction of aromatics using solid acid catalysts [10–15]. The application of SO 4 2- /ZrO 2 catalyst in the nitration reac- tion of halobenzenes is reported first time by us [16]. It has 1381-1169/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2006.06.046