Journal of Molecular Catalysis A: Chemical 215 (2004) 201–208 Acylation of toluene using rare earth cation exchanged zeolite  as solid acid catalyst V.N. Sheemol, Beena Tyagi, Raksh V. Jasra ∗ Silicates and Catalysis Discipline, Central Salt and Marine Chemicals Research Institute (CSMCRI), G.B. Marg, 364002 Bhavnagar, India Received 25 September 2003; received in revised form 16 January 2004; accepted 3 February 2004 Abstract The catalytic activity of rare earth cations exchanged zeolite  was studied for the acylation of toluene with acetic anhydride as an acylating agent and nitrobenzene, o-dichlorobenzene and dichloroethane as the solvent in liquid phase in the temperature range of 368–408 K. The rare earth cation exchanged zeolites were observed to have the catalytic activity in the following order: La- > H- = Ce- > Dy- > Eu- > Sm- > Gd- > Nd- > Pr- with more than 95% selectivity towards the p-isomer. Among the solvents studied, nitrobenzene is the most favored for toluene acylation reaction. The correlation of catalytic activities of the different catalysts with the cyclohexanol dehydration as well as DRIFT spectroscopy showed that the toluene acylation is a Brönsted acid catalyzed reaction. © 2004 Elsevier B.V. All rights reserved. Keywords: Acylation; Toluene; Rare earth cation; Zeolite ; Brönsted acidity 1. Introduction The acylated aromatic compounds are prominent interme- diates in many of the organic syntheses especially in pharma- ceutical and fine chemical industry. Presently, Friedel–Crafts acylation of aromatic compounds is commercially done [1] using Lewis acids such as AlCl 3 , BF 3 , ZnCl 2 , TiCl 4 , FeCl 3 as well as Brönsted acids like polyphosphoric acid and hy- drofluoric acid. However, these traditional catalysts have limitations such as environmental pollution hazards arising from the disposal of potential toxic wastes, reactor corrosion and difficulty in handling. Furthermore, the catalyst amount to be employed is more than the stoichiometric quantity re- quired as the catalyst has a tendency for complex formation either with the reactants or products [2]. Therefore, con- siderable research efforts are directed to develop alternative suitable catalysts to overcome these drawbacks. Zeolites, clays, and ionic resins are potential solid acid materials for developing catalysts to overcome above-mentioned limita- tions. Zeolites, particularly, exhibit good thermal stability, shape selectivity, and ease to modify their surface acidity by simpler processes like cation exchange. The present study ∗ Corresponding author. Tel.: +91-278-2471793; fax: +91-278-2567-562. E-mail address: rvjasra@csir.res.in (R.V. Jasra). reports the liquid phase acylation of toluene with rare earth exchanged zeolite  using acetic anhydride as an acylating agent. Methyl-p-tolylketone, p-isomer of acylated toluene is a colorless liquid with a penetrating floral fruity odor and finds applications in perfumery, flavors and fragrance in- dustry. There are some reports on the acylation of toluene with different acylating agents using solid acids. For exam- ple, Chiche et al. [3] has reported the acylation of toluene with C 2 to C 22 alkanoic acids with CeNa-Y (70% cation ex- change) and reported the maximum yield for C 12 and C 14 acids. Acetic acid was not observed to be effective for acy- lation. Gauthier et al. [4] from their study of acylation of toluene with octanoic acid and cation exchanged zeolite-Y concluded that acylation can also be catalyzed by Brönsted acid sites. Phosphotungstic acid (H 3 PW 12 O 40 ) supported on silica was shown [5] to be more active than zeolite-Y and  for acylation of toluene with crotonic acid. The acylation of lower aromatics with ion-exchanged montmorillonite clay has been discussed by Chiche et al. [6] and showed that Al 3+ exchanged clay was most active for acylation. It is re- ported that, the activity of La-exchanged zeolite-Y increases with an increase of La 3+ content in the zeolite for the acy- lation of toluene with acetyl chloride as an acylating agent [7]. It was observed from earlier studies on the acylation of aromatic compounds like anisole, veratrole and isobutyl- benzene [8,9] that rare earth cations exchanged zeolites and 1381-1169/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2004.02.002