Applied Catalysis A: General 198 (2000) 197–206 Kinetics of -pinene enantiomeric isomerization over clinoptilolite Ayaz I. Allahverdiev a,1 , Said Irandoust a,1 , Bengt Andersson a,1 , Dmitry Yu. Murzin b,∗ a Department of Chemical Reaction Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden b Karpov Institute of Physical Chemistry, Moscow, Russia Received 27 June 1999; received in revised form 10 November 1999; accepted 11 November 1999 Abstract Kinetics of the liquid-phase isomerization of enantioisomers of -pinene using natural clinoptilolite was investigated. The experimental ranges of temperature and pressure (N 2 ) were T = 120–160 ◦ C and P = 1–10 bars, respectively. Initially, mainly camphene and limonene were produced; the ratio of enantiomers corresponded to the ratio of +/− isomers in -pinene. At relatively high conversions other monocyclic (terpinene and terpinolene) and tricyclic products (tricyclene) were formed. A kinetic model is developed which described the experimental data well. ©2000 Elsevier Science B.V. All rights reserved. Keywords: Natural clinoptilolite; -Pinene; Camphene; Selectivity; Activity; Zeolite catalyst; Isomerization; Tricyclic products; Monocyclic products 1. Introduction Selectivity (e.g. chemo-, regio- and enantioselectiv- ity) in complex heterogeneous catalytic reactions is one of the most important requirements in fine chem- icals applications (e.g. synthesis of pharmaceuticals, agrochemicals, flavors and fragrances [1]). Enantioselective reactions in heterogeneous cataly- sis are of growing interest, as enantiomers can possess different physiological properties. Terpenes are particularly known for the dependence of their physiological properties on spatial arrange- ment. Among such terpenes and their derivatives one should mention monocyclic substances, like men- ∗ Corresponding author. Present address: BASF Rus GmbH, B. Gnezdnikovskij per. 7, Moscow, 103009, Russia. Tel.: +7-095-956-91-70; fax: +7-095-956-91-74. E-mail address: dmitry.murzin@basf-rus.ru (D.Yu. Murzin) 1 Tel.: +46-31-772-3030; fax: +46-31-772-3035. thol, citral, limonene, and tricyclic ones (camphene, pinene). -Pinene, one of the most widely used bicyclic monoterpenes, is a chiral compound obtained from turpentine oil [2]. By isomerization of -pinene over different heterogeneous catalysts a series of valuable terpene products can be formed. These products are used in the pharmaceutical and perfume industries, and also in the syntheses of some organic compounds [2,3]. Industrially, the isomerization of (±)--pinene to camphene is mainly performed using powdered acid-hydrated TiO 2 [4]. The mixture of terpene prod- ucts (75–80%) consists mainly of tricyclic products ((±)--pinene; tricyclene; (±)-camphene; fenchenes, bornylene, etc.) (see Fig. 1). Camphene and tricyc- lene are important industrial chemicals from which many commercial products are made, among them camphor. (Note, that camphor which is found in the nature is an optically active (+) isomer.) The rest 0926-860X/00/$ – see front matter ©2000 Elsevier Science B.V. All rights reserved. PII:S0926-860X(99)00511-6