Iron pillared clays efficient catalysts

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ELSEVIER
Applied Catalysis A: General 149 (1997) 257-264
A P P L E IY D C A T A L S S I
A: GENERAL
Iron pillared clays efficient catalysts for Friedel-Crafts reactions
B.M. Choudary et al. / Applied Catalysis A: General 149 (1997) 257-264
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Proton nuclear magnetic resonance (1H NMR) spectra were taken on a Gemini Varians 200 MHz for product analysis.
Keywords: Friedel-Crafts alkylations; K10 montmorillonite; Kunipia clay; Iron pillared clays; Iron content; Pillaring effect
1. Introduction The Friedel-Crafts reactions are of great interest due to their importance and common use in synthetic and industrial chemistry. Among the Lewis acids, anhydrous aluminium chloride was the most widely employed reagent to trigger the Friedel-Crafts reaction in the liquid phase in laboratory as well as in industry [1]. The major disadvantages encountered in the use of anhydrous aluminium chloride include corrosion, unfriendliness to environment, heavy expense due to requirement of large excesses of reagent and waste by-products induced by isomerisation in the reaction. In view of these reasons, there was a long-felt need and demand to substitute these reagents by less corrosive and environment friendly materials in the Friedel-Crafts reactions. Intensive re* Corresponding author.
0926-860X/97/$17.00 Copyright © 1997 Elsevier Science B.V. All rights reserved. PII S 0 9 2 6 - 8 6 0 X ( 9 6 ) 0 0 3 1 0-9
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B.M. Choudary et al.// Applied Catalysis A: General 149 (1997) 257-264
Received 15 April 1996; revised 2 August 1996
Abstract Friedel-Crafls alkylations of aromatic hydrocarbons have been carried out in the presence of a series of clay catalysts originating from K10 montmorillonite and Kunipia. It was found that the iron pillared clays (FePILCs) were the most efficient catalysts producing quantitative conversions with greatly reduced amounts of catalysts in lesser reaction times. Their efficiency is attributed to the higher Fe 3÷ contents in the catalysts and the pillaring effect.
search in this direction revealed the materials in the form of solid acids developed from natural clay, zeolites [2], sulfated zirconia [3], etc. Solid acids derived from montmorillonite, a class of smectite clay naturally available, by the process of exchange with different metal ions [4-6] and impregnation with the salts of the metals were explored as catalysts in the alkylation of aromatic hydrocarbons. These studies found that zinc chloride impregnated on K10 montmorillonite, called 'Clayzic' is the most effective material that catalysed alkylation of aromatic hydrocarbons successfully [7] and subsequently the process was commercialised. The report of Cseri et al., who studied the metal ion-exchanged montmorillonites [6] in the alkylation of aromatic hydrocarbons, indicated that the catalysts containing reducible cations (Fe 3÷, Sn4+, Cu 2+) exhibited high activities in spite of their low number of Lewis acid sites when benzyl chloride was the alkylating agent. We report in this article the results of the Friedel-Crafts alkylations of aromatic hydrocarbons catalysed by various metal supported montmorillonite catalysts including both metal hydroxy-oxy oligomers intercalated in the interlayers of montmorillonite, simply known as pillared clay catalysts, and analogous metal ion-exchanged montmorillonites. The same hydrocarbon, subjected for alkylation is used as solvent in these reactions. A detailed study correlating the iron contents and activities of the supported montmorillonites in alkylation of toluene with benzyl chloride is presented.
2. Experimental
2.1. Preparation of catalysts
K10 montmorillonite purchased from Fluka Chemicals and Kunipia clay obtained from Japan were used as such. The Fe3+-exchanged K10 montmorillonite was prepared as reported earlier by Laszlo and Mathy [5]. The Fe3+-ex changed Kunipia clay was prepared in a similar fashion. Iron pillared clays sourced from K10 montmorillonite (K10FePILC) and Kunipia (Kunipia FePILC) were prepared in accordance with an earlier procedure reported by Rightor et al. [8]. Aluminium pillared clay (A1PILC), titanium pillared clay (TiPILC), zirconium pillared clay (ZrPILC), cerium pillared clay (CePILC) and Ce-exchanged montmorillonite were prepared according to earlier reports in the literature [9-13].