Alkylation of naphthalene with isopropanol over a novel catalyst UDCaT-4: Insight into selectivity to 2,6-diisopropylnaphthalene and its kinetics Ganapati D. Yadav * , Sanket S. Salgaonkar Department of Chemical Engineering, University Institute of Chemical Technology (UICT), University of Mumbai, Matunga, Mumbai 400 019, India Received 5 April 2005; received in revised form 16 August 2005; accepted 23 August 2005 Available online 2 November 2005 Abstract Numerous routes to 2,6-naphthalenedicarboxylic acid, a feedstock for high performance polyester polyethylene naphthalate, exist starting with the alkylation of an aromatic ring. However, the route beginning with naphthalenic compounds has an economic advantage because of reduction in the number of reaction steps to build the naphthalene ring. This has spurred a lot of interest in the shape selective dialkylation of naphthalene. Mono alkylation of naphthalene is simple, but its further shape selective dialkylation to 2,6-dialkylnaphthalene (2-DAN), is challenging. Avariety of solid acid catalysts especially zeolites have been reported in studies to investigate the effect of acidity, pore geometry and shape selectivity in this reaction. However, the activity of most catalysts is susceptible to coke formation within a few hours of time on stream. It is in this perspective that we report the novelties of UDCaT-4, a synergistic combination of persulfated alumina and zirconia with hexagonal mesoporous silica, which exhibits tremendous stability, activity and selectivity in the vapour-phase isopropylation of naphthalene with isopropanol to 2,6-diisopropyl- naphthalene (DIPN). It leads to better yields and selectivity in comparison with other catalysts reported in literature. A systematic investigation of the effects of various operating parameters was accomplished. Furthermore, a mathematical model was developed to describe the reaction pathway and the model validated with experimental results. # 2005 Elsevier B.V. All rights reserved. Keywords: Alkylation; Naphthalene; Monoisopropylnaphthalene; Isopropanol; Heterogeneous catalysis; 2,6-Diisopropylnaphthalene; UDCaT-4; Persulfated alumina; Zirconia; Hexagonal mesoporous silica; Selectivity 1. Introduction Alkylation of naphthalene with propylene or IPA has been successfully demonstrated by numerous research groups by using a variety of catalysts. H-mordenite, for instance, results in high selectivity but it suffers from severe deactivation and thus leads to low activity [1]. Proper dealumination of H-mordenite catalysts [1,2], increases the mesoporosity and also results in low acid density. Thus, selectivity of 2,6-DIPN is enhanced and its isomerisation and further polyalkylation are minimized. At 250 8C, H-mordenite resulted in 10% conversion and 6% DIPN selectivity, while its dealumination enhanced the conversion and selectivity to 27% and 11%, respectively [2]. Under similar conditions, 90% conversion and 40% DIPN selectivity were obtained with USY [2]. Moreau et al. [3] investigated the influence of pore structure on the selectivity patterns at 473 K and concluded that HY zeolites exhibit high 2,6- and 2,7-DIPN selectivity of 41% at 95% conversion, compared to H-mordenite and Hb which gave 6% and 3% selectivity at 19% and 28% conversion, respectively. Kamalakar et al. [4] concluded that lanthanum and potassium modified Y zeolite is a good catalyst with 81% conversion and 28% yield of 2,6-DIPN, since lanthanum promotes alkylation while potassium optimizes acidity and reduces coking. Anand et al. [5] adopted a multi- step temperature programmed steaming procedure to control the rate of dealumination of HY and they report an optimum acid site density and strength at 700 8C, wherein a conversion of 93% with 30% selectivity towards 2,6-DIPN was obtained. Maheshwari et al. [6] compared the isopropylation of naphthalene with the alkylation and selectivity behavior of HM, Hb, HY and HZSM-5 with MCM-41 and reported that the www.elsevier.com/locate/apcata Applied Catalysis A: General 296 (2005) 251–256 * Corresponding author. Tel.: +91 22 2410 2121; fax: +91 22 2414 5614. E-mail addresses: gdyadav@yahoo.com, gdyadav@udct.org (G.D. Yadav). 0926-860X/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2005.08.047