Study on the adsorption of 1,5-, 1,6- and 2,6-dimethylnaphthalene on a series of alkaline and alkaline earth ion-exchang
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Study on the adsorption of 1,5-, 1,6- and 2,6-dimethylnaphthalene on a series of alkaline and alkaline earth ion-exchanged faujasite zeolites Natthakorn Kraikul · Pramoch Rangsunvigit · Santi Kulprathipanja
C Springer Science + Business Media, LLC 2006
Abstract Adsorption of the equilibrium mixture of 1,5-, 1,6- and 2,6-dimethylnaphthalene (DMN) was investigated on a series of alkaline and alkaline earth ion-exchanged faujasite zeolites using pulse test and breakthrough techniques. It was found that the adsorption of the DMNs would proceed through a complex mechanism governing by at least molecular diffusion, acid-base interaction, preferential interaction with cation and molecular displacement. All ion-exchanged faujasite zeolites only provided rejective systems for 2,6-DMN and some of them were potential adsorbents for the 2,6-DMN purification.
1 Introduction Large scale production of 2,6-Dimethylnaphthalene (2,6-DMN), a starting material for high performance engineering plastic and liquid crystal polymer, e.g. polyethylene naphthalene (PEN), currently encounters two major drawbacks that subsequently limit widespread utilization of the polymer. For instance, the largest commercialized process licensed by BP Amoco faces problems from the complexity of the synthesis and the thermodynamic limitation of the isomerization from 1,5-DMN to 2,6-DMN (ChemSystems, 2000) as shown in Eq. (1), which is called the 2,6-triad. CH3
CH3 K1,5-1,6
H3C CH3
Keywords Dimethylnaphthalene . Adsorption . Pulse test . Breakthrough . Faujasite . Zeolite N. Kraikul . P. Rangsunvigit () The Petroleum and Petrochemical College, Chulalongkorn University, Bangkok 10330, Thailand e-mail: [email protected] S. Kulprathipanja UOP LLC, 50 East Algonquin Road, Des Plaines, IL 60017-5016, USA
K1,6-2,6
CH3
H3C
(1) Besides the limitation of 2,6-DMN yield, thermodynamics also controls the composition of the isomerized product in a solvent-free system at 10%, 42%, and 48%wt of 1,5-, 1,6- and 2,6-DMN, respectively (ChemSystems, 2000; Kraikul et al., 2005), which entails another separation problem. Because DMN isomers have very close physical properties and molecular size, typical separation techniques cannot recover 2,6-DMN from the equilibrium mixture with high purity as industrial requirements (ChemSystems, 2000). In the process of BP Amoco, freeze crystallization was employed as a means for the
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2,6-DMN purification (Smith et al., 1999). However, energy intensive of the process entails the high production cost (ChemSystems, 2000) and draws many attentions to an adsorptive separation approach. Selective adsorption of 2,6-DMN has been conducted over a wide range of adsorbent. L-zeolite (Verduijn et al., 1992), activated carbon (Barger et al., 1991) and ion-exchanged faujasite zeolites (Barger et al., 1991; Inui and Pu, 1995; Maki et al., 1988; Nakao et al., 2004; Rota et al., 1996) have been utilized as adsorbents in literatures. Most processes encounter the problem of 2,6-DMN purity; thus, a crystallization process is usuall
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