Interlayer Cations as Reaction Directors in the Transformation of Limonene on Montmorillonite

Abstract

Abstract--Clays may catalyze chemical reactions by acting as Br6nsted acids, Lewis acids, and/or Lewis bases. The changes occurring when limonene (p-menthadiene) is heated in the presence of montmoriUonite illustrate how Brrnsted and Lewis acidity may operate competitively, the nature of the interlayer cations determining which reaction dominates. The rate at which the starting material disappears increases with the acidity of the clay, which depends upon the interlayer cations (Na < Mg < A1 < H). The concentration of disproportionation and isomerization products reaches a maximum after reaction times which decrease with increasing surface acidity of the clay. p-cymene is produced by oxidation in concentrations inversely related to the surface acidity of the clay. The course of the chemical reaction can thus be steered in the preferred direction by an appropriate choice of interlayer cations.

Catalytic conversion of limonene over acid activated Serra de Dentro (SD) bentonite

“…The use of acid activated clays in the transformation of terpenes and the conversion of apinene to camphene and limonene is a well-documented test www.elsevier.com/locate/apcata Applied Catalysis A: General 318 (2007) 108-120 reaction [14][15][16] with which to evaluate the catalytic activity of the acid clays. Indeed, acid treated clays have been evaluated previously, in a non-systematic manner, for the production of pcymene [17,18].…”

Reactions of the Conjugated Dienes Butadiene and Isoprene Alone and with Methanol Over Ion-Exchanged Montmorillonites

“…Frenkel and Heller-Kallai (1983) showed that the products formed by the reaction of limonene over different ion-exchanged montmorillonites are functions of the interlayer cation.…”