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Llllllillllllllllillllllllllllllllllllllllllllilllllllllllll llllllIllllllllllIllllllllllllllllllllllllllllIlllllllllllllllllllllllllllSOO5223589A United States Patent -- [19] [11] Patent Number: 5,223,589 Kulprathipanja et al. [45] Date of Patent: Jun. 29, 1993 [54] PROCESS FOR SEPARATING DURENE 3.422.848 1/1969 Liebman et a]. ......... .. 137/625.l5 FROM SUBSTITUTED BENZENE 3.706.812 12/1972 De Rosset et a1. 260/674 SA v 3,864,416 2/1975 Campbell et al. .. 260/674 A HYDROCARBOI\S 4.642.397 2/1987 Zinnen et al. .. 568/934 [75] Inventors: Santi Kulprathipanja, Inverness; 4,743.708 5/1988 Rosenfeld et al. ................ .. 585/828 Kenneth K. Kuhnle, St. Charles; Marjorie s. Patton, Darien, all of 111. OTHER PUBLICATIONS , . Chartov et al. Chem. Abstract 92(7) 58328d [73] Asslgnee: UOP’ Des Flames’ 111‘ (l972)-—Abstract only, page unavailable. [21] APPL No-i 872,191 Primary Examiner-Helen M. S. Sneed [22] Filed. Apr. 22, 1992 Assistant Examiner-Nhat D. Phan Attorney, Agent, or Firm-Thomas K. McBride; John F. [51] Int. (31.5 ......................... .. C07C 7/12; C07C 7/00 Spears’ 1L; Jack H_ Hall - [52] US. Cl. .................................. .. 585/828; 585/825; 585/831; 585/853 [57] ABSTRACT [58] Field Of Search .... ........ .. 585/825. 828, 831, 853 The separation Ofdurene in purity from coal tar or . petroleum fractions by an adsorptive chromatographic [56] References cued process and liquid phase with lithium-exchanged X US- PATENT DOCUMENTS zeolite as the adsorbent and liquid aromatic desorbents. 2.985.589 5/1961 Broughton er al. ................ .. 210/34 3.040.777 6/1962 Carson et al. ................ .. l37/625.l5 4 Claims, No Drawings 5,223,589 1 2 scale (deRosset U.S. Pat. No. 3,706,812) to commercial PROCESS FOR SEPARATING DURENE FROM scale in flow rates from a few cc per hour to many . SUBSTITUTED BENZENE HYDROCARBONS thousands of gallons per hour. We have found a speci?c adsorbent lithium FIELD OF THE INVENTION exchanged X zeolite, which, in combination with cer The ?eld of art to which this invention belongs is the tain aromatic desorbent liquids, will selectively adsorb solid bed adsorptive separation of durene. More speci? durene from its isomers. ' cally, the invention relates to a process for separating durene from a coal tar distillate or an alkylate stream SUMMARY OF THE INVENTION containing substituted benzene hydrocarbons boiling in The present invention is a process for separating the same range. durene from a heavy gasoline fraction hydrocarbon mixture comprising durene, isodurene, prehnitene and BACKGROUND OF THE INVENTION other polyalkylated‘ monocyclic aromatic hydrocarbons Durene in puri?ed form is in substantial demand as an boiling in the range from 150° to 225° C., the steps intermediate for a variety of uses, for example, synthetic comprising contacting the hydrocarbon mixture, under polymers, e.g., coatings for semiconductors, ?bers, plas adsorption conditions, with an X zeolite adsorbent ex tomizers, organic synthesis, etc. Readily available changed with lithium atoms at the exchangeable sites. sources of durene are coal tar distillates or fractions Durene is selectively adsorbed to the substantial exclu resulting from catalytic processing of petroleum and alkylation of o-xylene. Normally, puri?cation is accom sion of the other components. The other components, plished by re-crystallization of a fraction having a nar l,2,3,S-tetramethylbenzene (isodurene), 1,2,3,4-tet row boiling point range and/or melting point, but a ramethylbenzene (prehnitene) and other polyalkylated large number of theoretical stages is required. Accord monocyclic hydrocarbons, are relatively non-adsorbed ing to Chartov et al, durene could not be separated from and are removed from contact with the adsorbent and its isomers by adsorption on zeolites (Chem. Abstract 92 durene-is desorbed with a liquid aromatic desorbent _ (7)158328d (1972)), since the difference in critical diame having a boiling point of at least 5'’ higher or lower than ters between the isomers is too small. the boiling point range of said'hydrocarbon mixture, for Campbell et al. U.S. Pat. No. 3,864,416, disclosed that example, 1,2,3-trimethylbenzene (hemimellitene, some 2,4,5-trimethylcumene can be separated from mixtures times l,2,3-TMB herein) 1,3,5-trimethylbenzene (mesit of tetra-alkyl~substituted benzenes with X or Y zeolites ylene), toluene, p-xylene, chlorobenzene, benzene and exchanged with Group I-A metals, particularly sodium, m-xylene. The preferred desorbent is 1,2,3-TMB. potassium and cesium. However, the 2.4,5-trimethylcu Other embodiments of our invention encompass de mene is rejected while the other isomers are selectively tails about feed mixtures, adsorbents, desorbent materi adsorbed. In the present invention, 1,2.4,5-tetramethyl als and operating conditions, all of which are hereinaf benzene (durene) is unexpectedly selectively adsorbed ter disclosed. by lithium-exchanged X zeolite, whereas zeolites ex changed with ions other than lithium reject durene as DETAILED DESCRIPTION OF THE might be expected from the teachings of Campbell et al. INVENTION U.S. Pat. No. 4,743,708 discloses a process for sepa Adsorbents to be used in the process of this invention rating a C10 aromatic isomer, particularly paradiethyl‘ 40 comprise speci?c crystalline aluminosilicates or molec benzene from a feed stream of C10 aromatic isomers by ular sieves, namely X zeolites, exchanged at exchange contacting the stream with the adsorbent, zeolite beta. able cationic sites with lithium ions. The zeolites have It is also stated that durene is preferentially adsorbed known cage structures in which the alumina and silica over prehnitene and isodurene. However, the patentees tetrahedra are intimately connected in an open three-di do not teach applicants‘ separation with a lithium mensional network to form cage-like structures with exchanged zeolite. Patentee preferred sodium as the ion window-like pores. The tetrahedra are cross-linked by exchange cation. However, sodium-exchanged X zeo the sharing of oxygen atoms with spaces between the lite, was unsatisfactory in applicants‘ separation, for the tetrahedra occupied by water molecules prior to partial reason that durene and isodurene were coextracted and, or total dehydration of this zeolite. The dehydration of hence, no separation was obtained. It is more advanta geous to be able to separate durene by extraction on an the zeolite results in crystals interlaced with cells hav X zeolite than on a zeolite beta because X zeolite is ing molecular dimensions and thus, the crystalline alu commercially available. minosilicates are often referred to as “molecular sieves” The functions and properties of adsorbents and desor when the separation which they effect is dependent bents in the chromatographic separation of liquid com essentially upon differences between the sizes of the ponents are well known, but for reference thereto, Zin feed molecules as, for instance, when smaller normal nen et al U.S. Pat. No. 4,642,397 is incorporated by paraffin molecules are separated from larger isoparaf?n reference herein. molecules by using a particular molecular sieve. In the The invention herein can be practiced in ?xed or process of this invention, however, theterm "molecular moving adsorbent bed systems, but the preferred system sieves“, although widely used, is not strictly suitable for this separation is a countercurrent simulated moving since the separation of naphthalenes from other aro bed system, such as described in Broughton U.S. Pat. matic hydrocarbons having similar boiling points is No. 2,985,589, incorporated herein by reference. Cyclic apparently dependent on differences in electrochemical advancement of the input and output streams can be attraction of the different isomers and the adsorbent accomplished by a manifolding system, which are also 65 rather than on pure physical size differences in the iso known, e.g., by rotary disc valves shown in U.S. Pat. rner molecules. Nos. 3,040,777 and 3,422,848. Equipment utilizing these In hydrated or partially form the preferred type X principles are familiar, in sizes ranging from pilot plant crystalline aluminosilicates encompass those zeolites 5,223,589. 3 4 represented. in terms of moles of metal oxides, by the ticle size range, from about 16 to about 40 mesh (Stan formula 1 below: dard U.S. Mesh) (l.9 mm to 250 u). Feed mixtures which can be used in the separation process of the invention include complex mixtures con taining durene derived from petroleum or coal tar in narrow boiling point fractions in the range between where “M" is a cation which balances the electrova 150° C. and 225° C. In Table 1 following is an analysis lence of the tetrahedra and is generally referred to as an of a typical coal tar distillate fraction with a boiling exchangeable cationic site, “n“ represents the valence point range of l50°~2lO° C. which may be separated by of the cation and is a value up to about 9 and repre the present invention. The particular sample contained sents the degree of hydration of the crystalline struc about 32% (wt.) durene, 40% (wt.) isodurene, 0.6% ture. (wt.) prehnitene. Several components were identi?ed Adsorbents comprising the type X zeolites are useful only as C11 or higher aromatics and are listed as un for the adsorptive process for extracting durene from knowns. The sample contained various alkyl substituted hydrocarbon mixtures herein described. These zeolites 5 monocyclic aromatics, in addition to durene and isodu are described and de?ned in US. Pat. No. 2,882,244. rene. The term “type X structured” zeolites as used herein shall include all zeolites which have general structures TABLE 1 as represented in the above cited patent. Component Wt. ‘72 Typically, the type X structured zeolites, as initially 20 l-Methyl-3-Ethylbenzene 0.2 prepared, are predominantly in the sodium form. The Unknown #1 0.9 term “exchanged cationic site" generally refers to the l.2-Diethylbenzene 0.3 l-Methyl-2-Propylbenzene 0.9 site in the zeolite occupied by the cation “M“.
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