Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-II-6THE USE OF IONIC LIQUIDS AS EFFICIENT EXTRACTIONMEDIUM IN THE REACTIVE SEPARATION OF CYCLOOLEFINESFROM CYCLOHEXANEDaniel Gorri, Alicia Ruiz, Alfredo Ortiz, Inmaculada Ortiz*Departamento de Ingeniería Química y Química Inorgánica. Universidad de CantabriaAvenida de los Castros s/n. 39005 Santander. SPAINTel.: +34942201585; Fax: +34942201591; e-mail: ortizi@unican.esCyclohexane (CH) is the commonly used solvent in the manufacture of styrene-basedsynthetic rubber by anionic polymerization; n-butyl lithium is used as initiator. The presenceof certain impurities (e.g. water, cyclopentadiene, etc.) in the raw materials or in the solventused in polymerization may have a poisonous effect on the catalyst. In the manufacture ofhydrogenated synthetic rubber, during the hydrogenation process (after the anionicpolymerization) small quantities of cyclopentadiene (CP) are formed by degradation of thetitanocene compounds, which are used as hydrogenation homogeneous catalyst [1].Additionally, cyclopentadiene easily dimerizes at room temperature to formdicyclopentadiene (DCP) that must be also removed. In order to recycle and reusecyclohexane to the reaction process, the cyclopentadiene and dicyclopentadiene contents mustbe reduced to less than several parts per million. Because the low concentrations of the formercompounds in the cyclohexane stream, separation based on conventional distillation isdifficult and energy intensive [2].The separation of condensed olefins from the mixtures with the corresponding paraffinshas been investigated widely in literature [3]; the most promising alternative appears to beπ-complexation with silver ions. Separation by π-complexation is a subgroup of reactiveseparations where the mixture is contacted with a second phase, containing the complexingagent (Ag + ).Reliable data on the solubility of the olefins in a compatible solvent are required for theproper design of extraction systems. In this work, the ionic liquid BMImBF 4 has been selectedfor experiments because it is essentially immiscible with cyclohexane and it is able to dissolvea suitable silver salt (AgBF 4 ), allowing to absorb both CP and DCP due to reversiblecomplexation of silver ions with unsaturated olefinic double bonds. Experimental results wereobtained working at different concentrations (100-1000 ppm) of both dienes in the organicphase. The influence of temperature and silver concentration on the solubility of the dienes inthe BMImBF 4 -Ag + solution was assessed and the enthalpy (ΔHº) for the complex formationreaction was estimated.85