Selective separation of benzene from hydrocarbon mixtures via liquid–liquid extraction method using aqueous solutions of substituted cyclodextrins

The selective separation of benzene from hydrocarbon mixtures was investigated by way of liquid–liquid extraction using aqueous solutions of unsubstituted α-cyclodextrin (αCD), βCD and seven kinds of substituted CDs. Separation factor for benzene to cyclohexane was evaluated from the extraction of an equimolar mixture of benzene and cyclohexane. Hydroxypropyl-αCD showed the highest selectivity followed by 2,6-di-O-methyl-αCD, hydroxyethyl-βCD, hydroxypropyl-βCD and 2,6-di-O-methyl-βCD. Then, separation selectivity for benzene was compared among the nine kinds of CDs carrying out the extraction from an equimolar mixture of 3-methylpentane, n-hexane, benzene and cyclohexane. Finally, the extraction method was applied to reformate using the aqueous solutions of hydroxypropyl-αCD and hydroxypropyl-βCD. The results suggest that this method is effective for reducing the benzene content in reformate.