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US3249644A - Process for the production of 2, 6-dimethylnaphthalene - Google Patents

Process for the production of 2, 6-dimethylnaphthalene Download PDF

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US3249644A
US3249644A US283772A US28377263A US3249644A US 3249644 A US3249644 A US 3249644A US 283772 A US283772 A US 283772A US 28377263 A US28377263 A US 28377263A US 3249644 A US3249644 A US 3249644A
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dimethylnaphthalene
fraction
naphthalene
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US283772A
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Jr Alfred Hahn
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Sunoco Inc
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Sun Oil Co
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
    • C07C15/20—Polycyclic condensed hydrocarbons
    • C07C15/24—Polycyclic condensed hydrocarbons containing two rings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0059—General arrangements of crystallisation plant, e.g. flow sheets
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
    • C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
    • C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
    • C07C5/2729—Changing the branching point of an open chain or the point of substitution on a ring
    • C07C5/2732—Catalytic processes
    • C07C5/2735—Catalytic processes with metal oxides

Definitions

  • lRecycle fractions which are formed in the cracking of petroleum stocks and which include this boiling ran-ge often include major proportions or aromatic hydrocarbons that are mainly alkylnaphthalenes. Such fractions typically have aromatic contents varying within the range of 25 %-97%, but usually contain between 50% and 95%, depending upon the particular operation in which ⁇ the petroleum fractions are produced.
  • These hydrocarbon charge stocks are obtained in both catalytic and thermal cracking processes and in operations in which combinations of catalytic and thermal cracking steps are utilized. Additionally, these hydrocarbon charge stocks can ybe obtained as the reformate fraction from typical reforming processes, such as those using the well-known platinum catalyst.
  • Stocks having high alkylnaphthalene contents can also be obtained by extracting straight-run petroleum fractions of appropriate boiling ranges, such as kerosene, -or by extracting the abovementioned cracked fractions, such as catalytic ga-s oil, with suitable solvents, for example, furfural or sulfur dioxide, or 'by vselective adsorption using solid adsorbents, such as silica gel, activated carbon, molecular sieves, and the like.
  • suitable solvents for example, furfural or sulfur dioxide, or 'by vselective adsorption using solid adsorbents, such as silica gel, activated carbon, molecular sieves, and the like.
  • aromatic concentrates may be composed of 100% aromatic hydrocarbons.
  • the present invention is directed to the production of naphthalene and 2,6-dimethylnaphthalene from petroleum hydrocarbon charge stocks of the type referred to above.
  • the charge stock used in practicing this invention is a petroleum hydrocarbon fraction boiling substantially within the range of 400-900 F. and having an API gravity ranging from 5 40.
  • the char-ge stock will boil between 450 and 550 F. and ywill be composed by weight of 35 %-100% aromatic hydrocarbons including substituted condensed-ring aromatics, such as alkylnaphthalenes and from 65 %-0% non-aromatic type hydrocarbons.
  • alkyl and dialkyl are understood to be those radicals each having at least one and no more than 6 carbon atoms, branched or unbranched, joined or conjoined. Also the alkyl radicals or groups will usually appear at Ithe a and positions on the naphthalene nucleus. This type of charge material also contains substantial amounts of sulfur components that normally occur within this boiling range. Charge stocks most typically employed have an aromatic content within the range of 50%-95% by Weight and a sulfur content ranging from 1%-3%. In general, the substituted condensed-ring aromatic hydrocarbons constitute from 80% of the total aromatic type hydrocarbons present in the charge stock.
  • naphthalene by subjecting aromatic hydrocarbon stocks containing alkylnaphthalenes to high temperature dealkylation in ICC the presence of hydrogen.
  • the dealkylation conditions employed can effect only a par-tial dealkylation in one pass of the alkylnaphthalenes through the reactor.
  • the dimethyl portion of the recycled stream will contain 50%-70% by weight of a mixture comprisin-g 2,6- and 2,7-dimethylnaphthalenes. According to the present invention this material is utilized in a way to produce additional amounts of naphthalene and high purity 2,6-dimethylnaphthalene as an additional product.
  • the naphthalene is useful as the feed stock to processes which make Iphthalic anhydride or is useful alone as an insecticide.
  • the 2,6-dimethylnaphthalene is extremely usful a's an intermediate for the production of synthetic resins.
  • the charge material which enters the system through line 10 is a catalytic gas oil fraction boiling in the range of 440-525 F. and lcontaining alkylnaphthalenes.
  • the feed stock is a catalytic gas oil aromatic extract containing a major proportion of dicytclic aromatics together with a minor proportion of aromatics having only one aromatic ring 4and only a small amo-unt of saturated hydrocarbons.
  • a preferred charge stock may contain -dicyclic aromatics, 35% monocyclic aromatics and 5% saturates.
  • the heated charge material together with hydrogen from line 46 passes through line 10 -to a catalytic desulfurizer 11 which contain-s a desulfurization catalyst 12 such as cobalt molybdenum on alumina or molybdenum disulfide on alumina.
  • the conditions for conducting this catalytic desulfurization and conditioning step include a temperature within the range of 800-980 F.; pressure of l50-1000 p.s.i.g. with a range of 200-500 p.s.i.g. preferred; a hydrogen to hydrocarbon mole ratio of 3:1 to 25:1, preferably 5:1 -to 15:1 and a liquid hourly space velocity of 0.5-10 (volumes of charge per hour per bulk Volume of catalyst).
  • the hydrogen consumption under these condition-s should be between and 500 s.c.f. per barrel of liquid feed per percent sulfur in the feed, and preferably between 200 and 400 s.c.f. per barrel.
  • This conditioning step also effects cracking of most of the saturates and some of the'monocyclic aromatic hydrocarbons.
  • the sulfur of course, is converted mainly into hydrogen sulfide.
  • reaction product is sent through line 13 to fractionator 14 from which normally gaseous components are removed overhead through llne 15 and a C5 to 400 F. gasoline fraction is removed via line 16.
  • the 400 F. fraction which contains primarily alkylnaphthalenes is removed through line 17.
  • dealkylation reaction is effected thermally; that is, in the absence of any catalytic material.
  • the conditions for this thermal dealkylation include a pressure of 150-1000 p.s.i.g., preferably 200-500 p.s.i.g.; a
  • the dealkylation reaction which is effected in dealkylator 27 canbe carried out catalytically utilizing a desulfurizing catalyst, such as cobalt molybdate or molybdenum disulfide on alumina.
  • a desulfurizing catalyst such as cobalt molybdate or molybdenum disulfide on alumina.
  • the catalyst also effects the conversion of any remaining sulfur into hydrogen sulfide and hence permits the preparation of naphthalene and 2,6-dimethylnaphthalene having a negligible sulfur content.
  • the conditions for the catalytic dealkylation reaction include a pressure of 150-1000 psig-.with a range of 200-500 p.s.i.g. preferred; a hydrogen to hydrocarbon mole ratio of :1 to 25:1; a liquid hourly space velocity of 0.2-5.0; and a temperature above l000 F., usually between 1100 F. and l200 F., suiicient to dealkylate the alkylnaphthalene hydrocarbons and convert any remaining sulfur mainly into hydrogen sulfide.
  • reaction product from line 28 passes to fractionator 29 from which gases and a C5-500 F. aromatic gasoline fraction are removed, respectively, from lines 30 and 31.
  • Napthalene, as one desired product, is taken from line 32 as material boiling in the 400-450 F. boiling range.
  • this fraction is composed predominantly of I naphthalene and has a melting point of at least 78.6 Cl
  • the 450 F. -lmaterial withdrawn from fractionator 29 via line 33 is composed mainly of monomethyl and dimethylnaphthalenes with the alkyl groups in the position predominatin'g.
  • This stream also contains a small amount of material boiling above the dimethylnaphthalenes which desirably should be removed.
  • This material is passed through line 33 to fractionator 34 from which a monoalkylnaphthalene, such as monomethylnaphthalene, concentrate boiling in the range of 450-500 F. is obtained overhead through line 36 and passed as hereinafter shown into dealkylator 27,V a dialkylnaphthalene, such as dimethylnaphthalene, concentrate boiling from 500-520 F. is removed through line 37, and the higher boiling material is removed as bottoms via line 35.
  • a monoalkylnaphthalene such as monomethylnaphthalene
  • concentrate boiling in the range of 450-500 F. is obtained overhead through line 36 and passed as hereinafter shown into dealkyl
  • the 500-520 F. fraction removed from fractionator 34 via line 37 is admixed with the alkylnaphthalene containing material from line 17 and passed into a fractionation section indicated by columns 18 and 22.
  • column 18 material distilling below 500 F. and composed mainly of methylnaphthalenes and a small amount of ethylnaphthalenes is removed overhead and passes through line 19 with other materials hereafter specified to the dealkylator 27.
  • Material boiling above 520 F. is rejected from the bottom of tower 18 via line 21, and an intermediate fraction boiling from 500-520 F. and composed of dimethylnaphthalenes and generally a small amount of ethylnaphthalenes is taken through line 20 to tower 22.
  • the 500-510 F. cut from line 23 will contain, in addition to substantially all of the 2,6- and 2,7-isomers, minor amounts of the 1,3-, and1,6- and l,7-is omers, and generally a small amount of ethylnaphthalene. These other components all havel freezing points considerably Vlower than the 2,6- and 2,7-isomers hence; this cut is tional crystallization.
  • the 2,6- and 2,7-dimethylnaphthalene concentrate is removed from crystallizer 25 via line 38.4
  • the filtrate from crystall-izer 25 containing the other isomers, such as 1,3-, 1,6- and 1,7-dimethylnaphthalenes is passed through line 26 and line 49 in admixture with the material from lines 19, 24, and 36 through line 47 together with hydrogen from line 45 into dealkylator 27.
  • the concentrate of 2,6- and 2,7dimethylnaphthalene from line 38 is passed into a second crystallization zone containing crystallizer 39 wherein the 2,6-isomer is separated from the 2,.'7-isomer by fractional crystallization. Pure 2,6-dimethylnaphthalene is recovered in high yield through line 40.
  • the 2,7-dimethylnaphthalene isomer is removed from crystallizer 39 via line 41.
  • the crystallization which takes place in crystallizer 39 to separate the 2,6-isomer from the 2,7-isomer is performed, for example, by cooling a solution of the isomer 4concentrate from line 38 to a temperature in the range from 30 to 60 C. though higher temperatures can be used, e.g., up to I0 C.
  • a solution of the isomer 4concentrate from line 38 is cooled to a temperature in the range from 30 to 60 C. though higher temperatures can be used, e.g., up to I0 C.
  • the feed material from line 38 is dissolved in a solvent at room temperature, though higher temperatures can be employed, if desired, in order to reduce the amount of solvent needed.
  • the solvent ratio is critical but will usually be in the range from 0.5-2.5 parts by volume of solvent per part of hydrocarbon charge. Suitable solvents include the lower alcohols which are preferred.
  • Aliphatic hydrocarbons can be employed but relatively low temperatures should be used if aliphatic hydrocarbons are employed. Mixtures of aliphatic hydrocarbonsl in lower alcohols may also be employed. VAs a rule, a suitable solvent should be able to dissolve at least one gram of hydrocarbon per 10 millimeters of solvent at 25 C. and must remain liquid at the crystallization temperatures.
  • Suitable aliphatic hydrocarbons include propane, isobutane, n-pentane, nhexane, heptanes, etc. ⁇
  • Suitable alcohols include methanol, ethanol, isopropanol, n-butanol, amyl alcohols, etc.
  • ketones such as acetone
  • a bottom methyl isobutyl ketone, etc., and the like can be substituted for, or usedV in conjunction with the alcohols.
  • the solvents used can be the same in the earlier and hereinafter specified later crystallizations.
  • the solvents used for washing filter cakes can be the same as, or different from, the solvents used in the crystallization. Preferably, they are the same.
  • the concentrate of 2,6-dimethylnaphthalene which has crystallized from the cooled solution is filtered or otherwise separated from the solution containing dissolved constituents of the original hydrocarbon fraction.
  • the filter cake is washed with solvents to remove adhering mother liquor, though it'his lis not necessary.
  • the filter cake of 2,6-dimethylnaphthalene is next heated in orde'r to melt a portion thereof.
  • the heating is ⁇ to .a temperature from 5 50 C., more preferably ⁇ from 20-30 C.
  • the melted hydrocarbons are then removed from the unmelted portion of the filter cake, which portion constitutes a 2,6-dimethylnaphthalene in high concentration.
  • this concentrate has a melting point in the range from 50-75 C. However, it is still quite impure as may be seen from comparison with the melting point of pure 2,6-dimethylnaphthalene.
  • the heating step and the subsequent removal of melted material from the remaining solids are performed on the same filter, or in the same centrifuge, etc., that is used to separate crystals from mother liquor after the first crystallization.
  • these steps can be performed in separate heating and separation zones.
  • the amount of crystals which is melted is preferably in the range from 5%-50% by weight of the total crystals. Lesser amounts usually do not provide optimum purification 4of the 2,6-dime ⁇ t'hylnaphthalene, while greater amounts usually result in an undesirable extent of melting of 2,6-dimeth'yl-naphthalene. However, in general, any substantial extent of fractional melt-ing will result in a desirable purification of the unmelted 2,6-dimethylnaphthalene.
  • the 2,6-dimethylnaphthalene concentrate obtained by removing melted material from the heating step is next recrystallized at a temperature ranging from -30 C.l
  • the precipitated 2,6-dimethylnaphthalene is now removed byy filtration.
  • the filter cake can be washed using cooled solvent, but this is not essential.
  • the filtered crystals are usually permitted to warm to room temperature. There may be a small amount of material in the crystals which melts during thisy warming, and this material may be removed by suction through the filter, aided by washing with cooled solvent, such as methanol, if desired, but such removal is not essential.
  • the filter cake is Washed with, say, methanol, then recycled and dissolved in, say, n-pentane.
  • the 2,7-dimethylnaphthalene concentrate which is removed from crystallizer 39 is passed through line 41 into isomerizer 42.
  • isomerizer 42 a catalytic isomerization reaction effects a transfer of a substantial portion of the -alkyl groups to the a position.
  • 2,7-dimethylnaphthalene is converted into a mixture containing 2,6- and 2,7-dimethylnaphthalenes.
  • this isomerization reaction does not effect any shift of alkyl groups from one of the aryl rings to the other in the same molecule although some amount 'of disproportionation between separate molecules may occur.
  • the 2,7-dimethylnaphthalene is substantially converted to the 2,6-isomer, other a-methylnaphthalenes, such as 1,5-, 1,6-, 1,7- and 1,8- isomers may also be obtained.
  • One manner of effecting the isomerization in isomerizer 42 is to contact the 2,7-dimethylnaphthalene with any solid, acidic, cracking catalyst, such as silica-alumina, silica-magnesia, silica-zirconia and acid-activated clays.
  • the reaction temperature should be in the range of 300 500 C., and preferably 400450 C.
  • the liquid space velocity can vary between 0.1 and 2.0 volumes of hydrocarbon per volume of catalyst per hour and more preferably is maintained inthe range of 0.5-6. It is desirable to conduct the isomerization at a low pressure, generally in the range of 0.05-0.5 atmosphere, as otherwise coking tends to occur rapidly with resultant deactivation of the catalyst.
  • the low pressure can be maintained either by holding a vacuum on isomerizer 42 or by introducing an inert diluent along with the 2,7-dimethylnaphthalene, eg., nitrogen, hydrogen, methane, propane, butanes, and the like. Whenever the activity of the catalyst has dropped enough to require regeneration, this can be done in conventional manner merely by flowing air through the hot catalyt to burn ofiP the coke deposits. Thereafter the catalyst can be re-used for further isomerization.
  • an inert diluent along with the 2,7-dimethylnaphthalene, eg., nitrogen, hydrogen, methane, propane, butanes, and the like.
  • the isomerizate removed from isomerizer 42 via line 43 is recycled in either of two ways.
  • the isomerization conditions are chosen so that the isomerizate in line 43 contains, for all practical purposes, only an equilibrium mixture of 2,6- and 2,7dimethylnaphthalenes, the isomizate is recycled 4through lines 50 and 38 into crystallizer 39 in said second crystallization zone for separation of additional 2,6-di1nethylnaphthalene.
  • the isomerizate is passed via line 44 through line 23 into crystallizer 25 in said first crystallization zone wherein additional 2,6- and 2,7-dimethylnaphthalenes are obtained.
  • step (c) passing the filtrate from step (b), materials from step (a) boiling below 500 F. and above 510 F., and said fraction rich in monoalkylnaphthalene to said dealkylation reaction for conversion to naphthalene,
  • step (c) passing the filtrate from step (b), materials 8, from step (a) boiling below 500 F. and above 510 F., and said fraction rich in monoalkylnaphthalene to said dealkylation reaction for conversion to naphthalene, i
  • step (d) fractionally crystallizing in a second crystallization zone the 2,6- and 2,7-dimethylnaphtha- Iene product from step (b) to separate the 2,6- dimethylnaphthalene from the 2,7-dimethylnaphthalene,
  • step (f) isomerizing the 2,7-dimethylnaphthalene from step (d) to a mixture rich in 2,6-dimethylnaphthalene by contacting said 2,7-dimethylnaphthalenev with a solid, acidic, cracking catalyst, selected from the group consisting of silicaalumina, silica-magnesia, silica-zirconia and acid-activated .clays at a temperature in thev range of 300-500 C., a pressure in the range of 0.05-0.5 atmosphere, and a liquid hourly space velocity between 0.1 and 20 volumes of hydrocarbon per volume of catalyst per hour, and,

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  • Chemical & Material Sciences (AREA)
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Description

A. HAHN, JR
May 3, 1966 PROCESS FOR THE PRODUCTION OF 2.6-DIMETHYLNAPHTHALENE Filed May 28. 1965 ATTORNEY United States Patent O 3,249,644 PROCESS FOR THE PRODUCTION F 2,6-DIMETHYLNAPHTHALENE Alfred Hahn, Jr., Brookhaven, Pa., assigner to Sun @il Company, Philadelphia, Pa., a corporation of New Jersey Filed May 28, 1963, Ser. No. 283,772 4 Claims. (Cl. 26o- 668) naphthalenes, and in smaller quantity the ethylnaphthalenes. lRecycle fractions which are formed in the cracking of petroleum stocks and which include this boiling ran-ge often include major proportions or aromatic hydrocarbons that are mainly alkylnaphthalenes. Such fractions typically have aromatic contents varying within the range of 25 %-97%, but usually contain between 50% and 95%, depending upon the particular operation in which` the petroleum fractions are produced. These hydrocarbon charge stocks are obtained in both catalytic and thermal cracking processes and in operations in which combinations of catalytic and thermal cracking steps are utilized. Additionally, these hydrocarbon charge stocks can ybe obtained as the reformate fraction from typical reforming processes, such as those using the well-known platinum catalyst. Stocks having high alkylnaphthalene contents can also be obtained by extracting straight-run petroleum fractions of appropriate boiling ranges, such as kerosene, -or by extracting the abovementioned cracked fractions, such as catalytic ga-s oil, with suitable solvents, for example, furfural or sulfur dioxide, or 'by vselective adsorption using solid adsorbents, such as silica gel, activated carbon, molecular sieves, and the like. These aromatic concentrates may be composed of 100% aromatic hydrocarbons.
The present invention is directed to the production of naphthalene and 2,6-dimethylnaphthalene from petroleum hydrocarbon charge stocks of the type referred to above. Basically the charge stock used in practicing this invention is a petroleum hydrocarbon fraction boiling substantially within the range of 400-900 F. and having an API gravity ranging from 5 40. Preferably the char-ge stock will boil between 450 and 550 F. and ywill be composed by weight of 35 %-100% aromatic hydrocarbons including substituted condensed-ring aromatics, such as alkylnaphthalenes and from 65 %-0% non-aromatic type hydrocarbons. As used throughout this disclosure, alkyl and dialkyl are understood to be those radicals each having at least one and no more than 6 carbon atoms, branched or unbranched, joined or conjoined. Also the alkyl radicals or groups will usually appear at Ithe a and positions on the naphthalene nucleus. This type of charge material also contains substantial amounts of sulfur components that normally occur within this boiling range. Charge stocks most typically employed have an aromatic content within the range of 50%-95% by Weight and a sulfur content ranging from 1%-3%. In general, the substituted condensed-ring aromatic hydrocarbons constitute from 80% of the total aromatic type hydrocarbons present in the charge stock.
It has been proposed heretofore to prepare naphthalene by subjecting aromatic hydrocarbon stocks containing alkylnaphthalenes to high temperature dealkylation in ICC the presence of hydrogen. As a general rule, the dealkylation conditions employed can effect only a par-tial dealkylation in one pass of the alkylnaphthalenes through the reactor. In order to increase the yield of naphthalene, it is desirable to fractionate the reaction product to obtain the desired naphthalene product, to recover another fraction comprising unconverted and only partially converted alkylnaphthalenes which is commonly recycled to the dealkylator to effect further conversion into naphthalene.
In the high temperature `dealkylation processes of the kind referred to above, it is characteristic that alkyl groups in the ot position are removed from the naphthalene nucleus at about twice the rate as those alkyl groups in the position. Hence `the recycle fraction obtained from the reaction product contains considerably more -alkylnaphthalene than a-alkylnaphthalene. A typical composition of the recycle fraction is as follows:
Percentl -methylnaphthalene 70 -methylnaphth-alene .'P. 15 Dimethylnaphthalene 15 Based on the rates of demethylation of otand I-methylnaphthalenes, the dimethyl portion of the recycled stream will contain 50%-70% by weight of a mixture comprisin-g 2,6- and 2,7-dimethylnaphthalenes. According to the present invention this material is utilized in a way to produce additional amounts of naphthalene and high purity 2,6-dimethylnaphthalene as an additional product. The naphthalene is useful as the feed stock to processes which make Iphthalic anhydride or is useful alone as an insecticide. The 2,6-dimethylnaphthalene is extremely usful a's an intermediate for the production of synthetic resins.
The invention is described more specifically With reference to the accompanying drawing which is a schematic -flow sheet illustrating a combination but integrated process `for producing naphthalene and 2,6-dimethylnaphthalene from petroleum charge stocks containing alkylnaphthalenes.
VReferring now to the drawing, the charge material which enters the system through line 10 is a catalytic gas oil fraction boiling in the range of 440-525 F. and lcontaining alkylnaphthalenes. Preferably, the feed stock is a catalytic gas oil aromatic extract containing a major proportion of dicytclic aromatics together with a minor proportion of aromatics having only one aromatic ring 4and only a small amo-unt of saturated hydrocarbons. For example, a preferred charge stock may contain -dicyclic aromatics, 35% monocyclic aromatics and 5% saturates.
The heated charge material together with hydrogen from line 46 passes through line 10 -to a catalytic desulfurizer 11 which contain-s a desulfurization catalyst 12 such as cobalt molybdenum on alumina or molybdenum disulfide on alumina. The conditions for conducting this catalytic desulfurization and conditioning step include a temperature within the range of 800-980 F.; pressure of l50-1000 p.s.i.g. with a range of 200-500 p.s.i.g. preferred; a hydrogen to hydrocarbon mole ratio of 3:1 to 25:1, preferably 5:1 -to 15:1 and a liquid hourly space velocity of 0.5-10 (volumes of charge per hour per bulk Volume of catalyst). The hydrogen consumption under these condition-s should be between and 500 s.c.f. per barrel of liquid feed per percent sulfur in the feed, and preferably between 200 and 400 s.c.f. per barrel. This conditioning step also effects cracking of most of the saturates and some of the'monocyclic aromatic hydrocarbons. The sulfur, of course, is converted mainly into hydrogen sulfide.
From desulfurizer 11 the reaction product is sent through line 13 to fractionator 14 from which normally gaseous components are removed overhead through llne 15 and a C5 to 400 F. gasoline fraction is removed via line 16. The 400 F. fraction which contains primarily alkylnaphthalenes is removed through line 17.
Referring now to the high temperature dealkylation step, material obtained as hereafter specified and composed mainly of monomethyl and dirnethylnaphthalenes and a small amount of ethylnaphthalenes passes through line 47 together with hydrogen introduced via line 45 into dealkylator 27. In the preferred embodiment of the invention the dealkylation reaction is effected thermally; that is, in the absence of any catalytic material. The conditions for this thermal dealkylation include a pressure of 150-1000 p.s.i.g., preferably 200-500 p.s.i.g.; a
hydrogen to hydrocarbon mole ratio within the range of 3:1 to 25:1, preferably 5:1 to 15:1; a residence time of 2-300 seconds with a preferred residence time of 10-60 seconds; and a temperature above l000 F., preferably within the .range ofl l200-1400 F., sufficient to effect dealkylation of alkylnaphthalenes. In this reaction only a partial dealkylation occurs since the alkyl groups which are in the a position on the naphthalene nucleus are removed at about twice the rate as those in the position. Hence the reaction product which leaves dealkylator 27 through line 28 contains, in addition to the desired naphthalene, unreacted methylnaphthalenes and partially dealkylated naphthalenes. This mixture is enriched with respect to the -alkyl groups as compared to the charge.
material fed to dealkylator 27.
In another embodiment of the invention, the dealkylation reaction which is effected in dealkylator 27 canbe carried out catalytically utilizing a desulfurizing catalyst, such as cobalt molybdate or molybdenum disulfide on alumina. Frequently the presence of catalyst in this ste-p facilitates the dealkylation reaction, and in some cases permits it to be carried out at a lower temperature than that required for thermal dealkylation. The catalyst also effects the conversion of any remaining sulfur into hydrogen sulfide and hence permits the preparation of naphthalene and 2,6-dimethylnaphthalene having a negligible sulfur content. The conditions for the catalytic dealkylation reaction include a pressure of 150-1000 psig-.with a range of 200-500 p.s.i.g. preferred; a hydrogen to hydrocarbon mole ratio of :1 to 25:1; a liquid hourly space velocity of 0.2-5.0; and a temperature above l000 F., usually between 1100 F. and l200 F., suiicient to dealkylate the alkylnaphthalene hydrocarbons and convert any remaining sulfur mainly into hydrogen sulfide.
The reaction product from line 28 passes to fractionator 29 from which gases and a C5-500 F. aromatic gasoline fraction are removed, respectively, from lines 30 and 31. Napthalene, as one desired product, is taken from line 32 as material boiling in the 400-450 F. boiling range.
Typically, this fraction is composed predominantly of I naphthalene and has a melting point of at least 78.6 Cl
and a sulfur content that is less than parts per million. -i
The 450 F. -lmaterial withdrawn from fractionator 29 via line 33 is composed mainly of monomethyl and dimethylnaphthalenes with the alkyl groups in the position predominatin'g. This stream also contains a small amount of material boiling above the dimethylnaphthalenes which desirably should be removed. This material is passed through line 33 to fractionator 34 from which a monoalkylnaphthalene, such as monomethylnaphthalene, concentrate boiling in the range of 450-500 F. is obtained overhead through line 36 and passed as hereinafter shown into dealkylator 27,V a dialkylnaphthalene, such as dimethylnaphthalene, concentrate boiling from 500-520 F. is removed through line 37, and the higher boiling material is removed as bottoms via line 35.
The 500-520 F. fraction removed from fractionator 34 via line 37 is admixed with the alkylnaphthalene containing material from line 17 and passed into a fractionation section indicated by columns 18 and 22. In column 18 material distilling below 500 F. and composed mainly of methylnaphthalenes and a small amount of ethylnaphthalenes is removed overhead and passes through line 19 with other materials hereafter specified to the dealkylator 27. Material boiling above 520 F. is rejected from the bottom of tower 18 via line 21, and an intermediate fraction boiling from 500-520 F. and composed of dimethylnaphthalenes and generally a small amount of ethylnaphthalenes is taken through line 20 to tower 22.
In tower 22 the operating condition-s are adjusted to remove overhead in line 23 a 500-510 F. cut and removes'as a bottoms product a 5l0-520 F. boiling range fraction. It has beenfound that with sufficiently good fractionation substantially all of 26- and 2,7-dimethylnaphthalenes that were present in the charge fraction will appear in the 500-510 F. overhead cut. fraction which is composed of vother dimethylnaphthalenes (mainly the 1,3-, 1,6- and 2,3-isomers) passes through lines 24 and 48 in admixture with the 400-500 F. fraction in line 19 from tower 18 and other materials hereafter specified to dealkylator 27.
The 500-510 F. cut from line 23 will contain, in addition to substantially all of the 2,6- and 2,7-isomers, minor amounts of the 1,3-, and1,6- and l,7-is omers, and generally a small amount of ethylnaphthalene. These other components all havel freezing points considerably Vlower than the 2,6- and 2,7-isomers hence; this cut is tional crystallization. The 2,6- and 2,7-dimethylnaphthalene concentrate is removed from crystallizer 25 via line 38.4 The filtrate from crystall-izer 25 containing the other isomers, such as 1,3-, 1,6- and 1,7-dimethylnaphthalenes is passed through line 26 and line 49 in admixture with the material from lines 19, 24, and 36 through line 47 together with hydrogen from line 45 into dealkylator 27.
The concentrate of 2,6- and 2,7dimethylnaphthalene from line 38 is passed into a second crystallization zone containing crystallizer 39 wherein the 2,6-isomer is separated from the 2,.'7-isomer by fractional crystallization. Pure 2,6-dimethylnaphthalene is recovered in high yield through line 40. The 2,7-dimethylnaphthalene isomer is removed from crystallizer 39 via line 41.
The crystallization which takes place in crystallizer 39 to separate the 2,6-isomer from the 2,7-isomer is performed, for example, by cooling a solution of the isomer 4concentrate from line 38 to a temperature in the range from 30 to 60 C. though higher temperatures can be used, e.g., up to I0 C. Normally the feed material from line 38 is dissolved in a solvent at room temperature, though higher temperatures can be employed, if desired, in order to reduce the amount of solvent needed. The solvent ratio is critical but will usually be in the range from 0.5-2.5 parts by volume of solvent per part of hydrocarbon charge. Suitable solvents include the lower alcohols which are preferred. Aliphatic hydrocarbons can be employed but relatively low temperatures should be used if aliphatic hydrocarbons are employed. Mixtures of aliphatic hydrocarbonsl in lower alcohols may also be employed. VAs a rule, a suitable solvent should be able to dissolve at least one gram of hydrocarbon per 10 millimeters of solvent at 25 C. and must remain liquid at the crystallization temperatures. Suitable aliphatic hydrocarbons include propane, isobutane, n-pentane, nhexane, heptanes, etc.` Suitable alcohols include methanol, ethanol, isopropanol, n-butanol, amyl alcohols, etc. The
amount of alcohol in the solvent is preferably in the range It is also contemplated that ketones, such as acetone,
A bottom methyl isobutyl ketone, etc., and the like can be substituted for, or usedV in conjunction with the alcohols. The solvents used can be the same in the earlier and hereinafter specified later crystallizations. The solvents used for washing filter cakes can be the same as, or different from, the solvents used in the crystallization. Preferably, they are the same.
The concentrate of 2,6-dimethylnaphthalene which has crystallized from the cooled solution is filtered or otherwise separated from the solution containing dissolved constituents of the original hydrocarbon fraction. Desirably, the filter cake is washed with solvents to remove adhering mother liquor, though it'his lis not necessary.
The filter cake of 2,6-dimethylnaphthalene is next heated in orde'r to melt a portion thereof. The heating is` to .a temperature from 5 50 C., more preferably `from 20-30 C. The melted hydrocarbons are then removed from the unmelted portion of the filter cake, which portion constitutes a 2,6-dimethylnaphthalene in high concentration. Typically, this concentrate has a melting point in the range from 50-75 C. However, it is still quite impure as may be seen from comparison with the melting point of pure 2,6-dimethylnaphthalene. Advantageously the heating step and the subsequent removal of melted material from the remaining solids are performed on the same filter, or in the same centrifuge, etc., that is used to separate crystals from mother liquor after the first crystallization. However, if desired, these steps can be performed in separate heating and separation zones.
The amount of crystals which is melted is preferably in the range from 5%-50% by weight of the total crystals. Lesser amounts usually do not provide optimum purification 4of the 2,6-dime`t'hylnaphthalene, while greater amounts usually result in an undesirable extent of melting of 2,6-dimeth'yl-naphthalene. However, in general, any substantial extent of fractional melt-ing will result in a desirable purification of the unmelted 2,6-dimethylnaphthalene.
The 2,6-dimethylnaphthalene concentrate obtained by removing melted material from the heating step is next recrystallized at a temperature ranging from -30 C.l
to -60 C. in the presence of a solvent.
The precipitated 2,6-dimethylnaphthalene is now removed byy filtration. The filter cake can be washed using cooled solvent, but this is not essential. Following the filtration at reduced temperature, the filtered crystals are usually permitted to warm to room temperature. There may be a small amount of material in the crystals which melts during thisy warming, and this material may be removed by suction through the filter, aided by washing with cooled solvent, such as methanol, if desired, but such removal is not essential.
Therefore, the pure 2,6-dimethylnaphthalene which is in line 40 can be obtained by the following summary of processing steps:
1) The material in line 38 is dissolved, in say, npentane.
(2) The filter cake is heated to melt a portion thereof, and the melted portion is separated from the unmelted portion by filtration. u
(3) The solution is cooled and filtered.
(4) The filter cake is Washed with, say, methanol, then recycled and dissolved in, say, n-pentane.
(5) The solution is cooled.
(6) The purified 2,6-dimethylnaphthalene is filtered from the pentane solution. 5
(7) The 2,6-dimethylnaphthalene crystals are allowed to warm to room temperature, and if desired, any melted material is removed.
The 2,7-dimethylnaphthalene concentrate which is removed from crystallizer 39 is passed through line 41 into isomerizer 42. In isomerizer 42 a catalytic isomerization reaction effects a transfer of a substantial portion of the -alkyl groups to the a position. Thus, 2,7-dimethylnaphthalene is converted into a mixture containing 2,6- and 2,7-dimethylnaphthalenes. It should be noted, however, that this isomerization reaction does not effect any shift of alkyl groups from one of the aryl rings to the other in the same molecule although some amount 'of disproportionation between separate molecules may occur. Although the 2,7-dimethylnaphthalene is substantially converted to the 2,6-isomer, other a-methylnaphthalenes, such as 1,5-, 1,6-, 1,7- and 1,8- isomers may also be obtained.
One manner of effecting the isomerization in isomerizer 42 is to contact the 2,7-dimethylnaphthalene with any solid, acidic, cracking catalyst, such as silica-alumina, silica-magnesia, silica-zirconia and acid-activated clays. The reaction temperature should be in the range of 300 500 C., and preferably 400450 C. The liquid space velocity can vary between 0.1 and 2.0 volumes of hydrocarbon per volume of catalyst per hour and more preferably is maintained inthe range of 0.5-6. It is desirable to conduct the isomerization at a low pressure, generally in the range of 0.05-0.5 atmosphere, as otherwise coking tends to occur rapidly with resultant deactivation of the catalyst. The low pressure can be maintained either by holding a vacuum on isomerizer 42 or by introducing an inert diluent along with the 2,7-dimethylnaphthalene, eg., nitrogen, hydrogen, methane, propane, butanes, and the like. Whenever the activity of the catalyst has dropped enough to require regeneration, this can be done in conventional manner merely by flowing air through the hot catalyt to burn ofiP the coke deposits. Thereafter the catalyst can be re-used for further isomerization.
Depending upon the conditions chosen for operating the isomerization reaction, the isomerizate removed from isomerizer 42 via line 43 is recycled in either of two ways. In one embodiment, if the isomerization conditions are chosen so that the isomerizate in line 43 contains, for all practical purposes, only an equilibrium mixture of 2,6- and 2,7dimethylnaphthalenes, the isomizate is recycled 4through lines 50 and 38 into crystallizer 39 in said second crystallization zone for separation of additional 2,6-di1nethylnaphthalene. Alternately in another embodiment, if the isomerization conditions in isomerizer 42 are chosen so that substantial amounts of other dialkyl isomers are obtained, then the isomerizate is passed via line 44 through line 23 into crystallizer 25 in said first crystallization zone wherein additional 2,6- and 2,7-dimethylnaphthalenes are obtained.
I claim:
1. In a process involving,
( 1) hydrodesulfurizing a petroleum fraction boiling mainly in the range of 440-525 F. and containing mainly monocyclic and dicyclic aromatic hydrocarbons including dimethylnaphthalenes,
(2) separating from the desulfurization product material containing alkylnaphthalenes,
(3) subjecting such material to a dealkylation reaction at a temperature above l000 F. to produce naphthalene and,
(4) recovering from the dealkylation product naphthalene and a fraction rich in monoalkylnaphthalene, the steps for producing and recovering 2,6-dimethylnaphthalene which comprises:
(a) separating from the hydrodesulfurization product a fraction boiling essentially in the range of 500-510 F.,
(b) fractionally crystallizing in a first crystallization zone the 500-510 F. fraction to separate 2,6- and 2,7-dimethylnaphthalene from other dimethylnaphthalenes,
' (c) passing the filtrate from step (b), materials from step (a) boiling below 500 F. and above 510 F., and said fraction rich in monoalkylnaphthalene to said dealkylation reaction for conversion to naphthalene,
(d) fractionally crystallizing in a second crystallization zone the 2,6- and 2,7-dimethylnaphthalene product from step (b) to separate the 2,6- dimethylnaphthalene from the 2,7-dimethylnaphthalene, (e) recovering the 2,6.-dimethylnaphthalene, (f) visomerizing the 2,7-dimethylnaphthalene from step (d) to a mixture rich in 2,6 and 2,7- dimethylnaphthalene, and, (g) recovering 2,6-dimethylnaphthalene from said mixture. 2. Process according to claim V1 wherein said mixture from step (f) is recycled to said first crystallization zone. 3. Process according to claim -1 wherein said mixture from step (f) is recycled to said second crystallization zone.
4. In a process involving,
(1) hydrodesulfurizing a petroleum fraction boiling mainly in the range of 440-525 F. and containing mainly monocyclic and dicyclic aromatic hydrocarf bons including dimethylnaphthalenes,
(2) separating from the desulfurization product material containing alkylnaphthalenes,
(3) subjecting such material to a dealkylation reaction at a temperature above 1000 F..to produce naphthalene and,
(4) recovering from the dealkylation product naphthalene and a fraction rich in monoalkylnaphthalene, the steps for producing and recovering 2,6-dimethylnaphthalene which comprises:
. (a) separating -from the hydrodesulfurization product a fraction boiling essentially in the range of 5005l0 F.,
(b) fractionally crystallizing in a rst crystallization zone the 500510 F. fraction to separate 2,6- and 2,7-dimethylnaphthalene from other dimethylnaphthalenes,
(c) passing the filtrate from step (b), materials 8, from step (a) boiling below 500 F. and above 510 F., and said fraction rich in monoalkylnaphthalene to said dealkylation reaction for conversion to naphthalene, i
(d) fractionally crystallizing in a second crystallization zone the 2,6- and 2,7-dimethylnaphtha- Iene product from step (b) to separate the 2,6- dimethylnaphthalene from the 2,7-dimethylnaphthalene,
(e) recovering the 2,6-dimethylnaphthalene,
(f) isomerizing the 2,7-dimethylnaphthalene from step (d) to a mixture rich in 2,6-dimethylnaphthalene by contacting said 2,7-dimethylnaphthalenev with a solid, acidic, cracking catalyst, selected from the group consisting of silicaalumina, silica-magnesia, silica-zirconia and acid-activated .clays at a temperature in thev range of 300-500 C., a pressure in the range of 0.05-0.5 atmosphere, and a liquid hourly space velocity between 0.1 and 20 volumes of hydrocarbon per volume of catalyst per hour, and,
(g) recovering 2,6-dimethylnaphthalene.from said mixture.
References Cited by the Examiner UNITED STATES PATENTS DELBERT E. GANTZ, Primary Examiner.
ALPHONSO D. SULLIVAN, Examiner. C. R. DAVIS, Assistant Examiner.

Claims (1)

1. IN A PROCESS INVOLVING, (1) HYDRODESULFURIZING A PETROLEUM FRACTION BOILING MAINLY IN THE RANGE OF 440*-525*F. AND CONTAINING MAINLY MONOCYCLIC AND DICYCLIC AROMATIC HYDROCARBONS INCLUDING DIMETHYLNAPHTHALENES, (2) SEPARATING FROM THE DESULFURIZATION PRODUCT MATERIAL CONTAINING ALKYLNAPHTHALENES, (3) SUBJECTING SUCH MATERIAL TO A DEALKYLATION REACTION AT A TEMPERATURE ABOVE 1000*F. TO PRODUCE NAPHTHALENE AND, (4) RECOVERING FROM THE DEALKYLATION PRODUCT NAPHTHALENE AND A FRACTION RICH IN MONOALKYLNAPHTHALENE, THE STEPS FOR PRODUCING AND RECOVERING 2,6-DIMETHYLNAPHTHALENE WHICH COMPRISES: (A) SEPARATING FROM THE HYDRODESULFURIZATION PRODUCT A FRACTION BOILING ESSENTIALLY IN THE RANGE OF 500*-510*F., (B) FRACTIONALLY CRYSTALLIZING IN A FIRST CRYSTALLIZATION ZONE THE 500*-510*F. FRACTION TO SEPARATE 2,6- AND 2,7-DIMETHYLNAPHTHALENE FROM OTHER DIMETHYLNAPHTHALENES, (C) PASSING THE FILTRATE FROM STEP (B), MATERIALS FROM STEP (A) BOILING BELOW 500*F. AND ABOVE 510*F., AND SAID FRACTION RICH IN MONOALKYLNAPHTHALENE TO SAID DEALKYLATION REACTION FOR CONVERSION TO NAPHTHALENE, (D) FRACTIONALLY CRYSTALLIZING IN A SECOND CRYSTALLIZATION ZONE THE 2,6- AND 2,7-DIMETHYLNAPHTHALENE PRODUCT FROM STEP (B) TO SEPARATE THE 2,6DIMETHYLNAPHTHALENE FROM THE 2,7-DIMETHYLNAPHTHALENE, (E) RECOVERING THE 2,6-DIMETHYLNAPHTHALENE, (F) ISOMERIZING THE 2,7-DIMETHYLNAPHTHALENE FROM STEP (D) TO A MIXTURE RICH IN 2,6- AND 2,7DIMETHYLNAPHTHALENE, AND, (G) RECOVERING 2,6-DIMETHYLNAPHTHALENE FROM SAID MIXTURE.
US283772A 1963-05-28 1963-05-28 Process for the production of 2, 6-dimethylnaphthalene Expired - Lifetime US3249644A (en)

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Cited By (7)

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US3336411A (en) * 1964-10-09 1967-08-15 Marathon Oil Co Process for producing 2, 6-dimethylnaphthalene
US3485885A (en) * 1968-04-22 1969-12-23 Sun Oil Co Process for the purification of 2,6-dimethylnaphthalene
US3670040A (en) * 1970-03-01 1972-06-13 Sun Oil Co Fractionation of c{11 {11 {11 bicyclic aromatic hydrocarbons di or trianhydride complex formation
US3670039A (en) * 1970-05-01 1972-06-13 Sun Oil Co Fractionation of c{11 {11 {11 bicyclic aromatic hydrocarbons by tetrahalophthalic anhydride complex formation
EP0308962A3 (en) * 1987-09-24 1989-10-25 Nippon Mining Company Limited Process for production of dimethylnaphthalenes
US5186816A (en) * 1990-03-12 1993-02-16 Nippon Mining Co., Ltd. Method of producing high aromatic-content solvents
US6057487A (en) * 1997-12-30 2000-05-02 Chevron Chemical Company Method for producing 2,6-DMN from mixed dimethylnaphthalenes by crystallization, adsorption and isomerization

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US2700638A (en) * 1950-11-06 1955-01-25 Sinclair Refining Co Combination cracking process for producing aromatics from petroleum
US2750432A (en) * 1952-09-16 1956-06-12 Socony Mobil Oil Co Inc Production of naphthalene
US2795633A (en) * 1952-09-16 1957-06-11 Socony Mobil Oil Co Inc Demethylation process
US2858348A (en) * 1957-03-12 1958-10-28 Sinclair Refining Co Process for making naphthalene
US2958643A (en) * 1956-08-29 1960-11-01 Sinclair Refining Co Two-stage catalytic conversion process for producing naphthalene and an aromatic gasoline from cycle oils
US3109036A (en) * 1961-10-12 1963-10-29 Sun Oil Co Isomerization of dimethylnaphthalenes

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US2700638A (en) * 1950-11-06 1955-01-25 Sinclair Refining Co Combination cracking process for producing aromatics from petroleum
US2750432A (en) * 1952-09-16 1956-06-12 Socony Mobil Oil Co Inc Production of naphthalene
US2795633A (en) * 1952-09-16 1957-06-11 Socony Mobil Oil Co Inc Demethylation process
US2958643A (en) * 1956-08-29 1960-11-01 Sinclair Refining Co Two-stage catalytic conversion process for producing naphthalene and an aromatic gasoline from cycle oils
US2858348A (en) * 1957-03-12 1958-10-28 Sinclair Refining Co Process for making naphthalene
US3109036A (en) * 1961-10-12 1963-10-29 Sun Oil Co Isomerization of dimethylnaphthalenes

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3336411A (en) * 1964-10-09 1967-08-15 Marathon Oil Co Process for producing 2, 6-dimethylnaphthalene
US3485885A (en) * 1968-04-22 1969-12-23 Sun Oil Co Process for the purification of 2,6-dimethylnaphthalene
US3670040A (en) * 1970-03-01 1972-06-13 Sun Oil Co Fractionation of c{11 {11 {11 bicyclic aromatic hydrocarbons di or trianhydride complex formation
US3670039A (en) * 1970-05-01 1972-06-13 Sun Oil Co Fractionation of c{11 {11 {11 bicyclic aromatic hydrocarbons by tetrahalophthalic anhydride complex formation
EP0308962A3 (en) * 1987-09-24 1989-10-25 Nippon Mining Company Limited Process for production of dimethylnaphthalenes
US4963248A (en) * 1987-09-24 1990-10-16 Nippon Mining Co., Ltd. Process for production of dimethylnaphthalenes
US5186816A (en) * 1990-03-12 1993-02-16 Nippon Mining Co., Ltd. Method of producing high aromatic-content solvents
US6057487A (en) * 1997-12-30 2000-05-02 Chevron Chemical Company Method for producing 2,6-DMN from mixed dimethylnaphthalenes by crystallization, adsorption and isomerization

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