US2780659A - Ethylbenzene from c8 aromatic hydrocarbons - Google Patents

Description

Feb. 5, 1957 D, A MCCAULAY ET AL 2,780,659

ETHYLBENZENE FROM C8 AROMATIC HYDROCARBONS Filed March 2l, 1955 United States Patent ETHYLBENZENE FROM Cs AROMATIC HYDROCARBONS David A. McCaulay, Chicago, Ill., and Arthur P. Lien, Highland, Ind., assignors to Standard Oii Company, Chicago, Ill., a corporation of Indiana v Application March 21, 1955, Serial No. 495,438

4 Claims. (Cl. 260-668) This invention relates to the separation of mixed Cs aromatic hydrocarbons into a xylene fraction that is substantially free of ethylbenzene and an ethylbenzene or diethylbenzene fraction. More particularly, it relates to a combination process for the separation of o-xylene free mixed C8 aromatic hydrocarbons into a substantially ethylbenzene-free mand p-xylene fraction and a substantially pure ethylbenzene fraction with no loss to production of ethylxylene.

As the source material for the production of styrene, ethylbenzene is a very important commercial material. Owing to a simultaneous large demand for benzene, which is the primary source of commercial ethylbenzene, ethylbenzene is in short supply and is forced to continue in short supply. Ethylbenzene occurs in nature in most petroleum oils. Also, it occursin the light oil derived as a by-product of the carbonization of coal. In recent years, a tremendous quantity of ethylbenzene has been made available, potentially, in the product from-petroleum naphtha conversion process, particularly the well known hydroforming process and platforming process. However, the ethylbenzene from all these sources is associated with dimethylbenzenes, i. e., xylenes. This mixture of Ca aromatic hydrocarbons can be resolved by superfract'ional distillation into an ortho-xylene concentrate and a mixture of ethylbenzene, para-xylene, and meta-xylene. This mixture is not a desirable feedto-a styrene production process. The best known method for resolving the mixture of Cs aromatic hydrocarbons into high purity fractions, i. e., fractions containing 95% or more of the desired compound, is by the fractional crystallization technique. This method is quite involved and quite expensive when high purity products are desired.

Other methods involve the separation of ethylbenzene by chemical reaction techniques. stantially pure ethylbenzene vis rapidly and substantially completely disproportionated to diethylbenzene and benzene by theaction of a liquid HF-BFs treating agent. It is also known lthat the treatment of a mixture of Ca aromatic hydrocarbons and non-aromatic hydrocarbons with liquid HF-BFs treating agent results in a product containing diethylbenzene, ethylxylene, some ethylbenzene and xylenes. The C10 aromatic fraction consisting of diethylbenzene and ethylxylene is very close'boiling and cannot be resolved by superfractional distillation; furthermore, the production of ethylxylene results in a decreased yield of xylene. so-called close-boiling xylene cut of a hydroformate or platformate results in a large loss of ethylbenzene to the non-aromatic product of liquid HF-BFa treatment. The greater the amount of non-aromatic hydrocarbons in the feed to the liquid HF-BFa treatment, the larger the loss of ethylbenzene. (This ethylbenzene can be recovered from admixture with the non-aromatic hydrocarbons by an extractive distillation process such as the aromatic separation process using phenol as the separating agent.)

Itis known that sub- It is an object of this invention to treat a mixture of at least one xylene isomer other than o-xylene and ethylbenzene to produce a xylene fraction that is substantially free of ethylbenzene without loss of xylene. Another object is the treatment of an essentially o-xylene-free mixed C8 aromatic hydrocarbon feed to produce a xylene fraction substantially free of ethylbenzene and a diethylbenzene fraction that is free of ethylxylene. Still another object is a process for the treatment of essentially o-xylene-free mixed Ca aromatic hydrocarbons to produce a maximum yield of essentially pure diethylbenzene and a maximum yield of a xylene fraction that is substantially free of ethylbenzene. Yet another object of the invention is to convert diethylbenzene into ethylbenzene. A particular object of the invention is the treatment of, a close-boiling feed consisting essentially of a mixture of m-xylene, p-xylene and ethylbenzene to produce a product that is substantially free of ethylbenzene and a substantially pure ethylbenzene product.

Another particular object is the treatment of a closeboiling feed comprising essentially a mixture of Ca aromatic hydrocarbons which has been fractionated to remove essentially all the o-xylene to produce a xylene product substantially free 0f ethylbenzene and a substantially pure meta-diethylbenzene product. Y

It has been found that a mixture of ethylbenzene and at least one xylene isomer other than o-xylene canbe treated with liquid HF and BFs to produce a xylene fraction substantially free of ethylbenzene and a diethylbenzene fraction that contains no detectable amount of ethylxylene. This ethylbenzene conversion process involves careful control of operating conditions, particularly the relationship of contacting temperature and contacting time. (Under the conditions of this process, oxylene interacts with ethylbenzene to form 1,2-dimethyl- 4-ethylbenzene.)

Secondly, it has been found that maximum conversion of ethylbenzene to diethylbenzene can be attained only by the treatment of said ethylbenzene-xylene feed in the absence of benzene and/or toluene; and also by carrying out the ethylbenzene conversion reaction in a single Also, the treatment of the present therein.

substantially homogeneous liquid phase system. This Single substantially homogeneous liquid phase can be attained only by the use of a feed which contains not more than about 2 3 volume percent of non-aromatic hydrocarbons, preferably less than about 1% of non-aromatic hydrocarbons.

It has been found that in addition to the effect of contacting temperature and/or contacting time, the amount of BFs present in the contacting zone determines the degree of conversion of ethylbenzene to diethylbenzene and/or ethylxylene. In order to produce a diethylbenzene aromatic hydrocarbon product by the treatment of a mixture of ethylbenzene and meta and/ or para-xylene, it is necessary to use at least 1 mole of BFa per mole of xylene present in the contacting zone. That is, allthe xylene must be held in the form of an HF-BFa-xylene complex. By complexing all the xylene', the possible reactions are reduced to the disproportionation of ethylbenzene to diethylbenzene.` In the presence of uncomplexed xylene, the predominating reaction is the interactionvof ethylbenzene and xylene to form ethylxylene. In order to disproportionate ethylbenzene into diethylbenzene, additional BFS must be present in the contacting zone over the at least l mole per mole of xylene Although appreciable conversion to diethylbenzene is obtained with only trace amounts of additional BFs present, the conversion of ethylbenzene is'maximzed by the use of at least 0.5 mole of addi! tional BFS per mole of ethylbenzene present in the feed.

toY theethylbenzene conversion process.

Better control of the product distribution is attained by the use of more than the minimum amounts "of BFa. ln general, about 1 mole of BFs per mole of Cs aromatic hydrocarbon in the feedis used. However, more than this amount may be used, e. g., 5 moles. lt ispreferred to operate with between about 1.5 and 3 moles of BEa per mole of C8 aromatic hydrocarbon present ,in the feed to the ethylbenzene conversion process.

The process of this invention must 'be carried .out under substantially anhydrous conditions. The'liquid HF used in the process should be substantially anhydrous, i. e., the liquidi-LF should contain less than 2 yor 3% of water.

The @liquid HF not only participates in the formation o f the polyallgylbenzene-BFa-HF complex, but "it also acts as a solvent for said complex. 'Therefore, it is necessary --to use at least enough liquid HF to participate in the formation ofthe complexes and also to dissolve the complexes. In general, at least about 2 moles of liquid HF per Amole of yCs aromatic hydrocarbon 'in the feed should -be used. YMore than vthis minimum amount may be used, e. g., as much as (50, moles. It is preferred to use :inthe ethylbenzene conversion processbetween about 6 -and 15 moles of liquid HF per mole of Cs aromatic hydrocarbon inthe feed.

A lliquid solution of meta and/or para-xylene- BFs-HFy complex and diethylbenzene-BFs-HF complex, at ambient temperatures, slowly changes to a liquid HF solution ofY xylene-BFa-'HF complex, diethylbenzene- BFa-HFcomplex and ethylxylene-BFa-HF complex. lf the liquid solution is permitted to 4stand` for Va sufcientV time, the solution will contain only meta-xylene- BFa-HF complex and 1,3,-5-ethylxylene-BFa-HF complex.

At temperatures below about 125 F. it is possible to treat a feed ymixture of meta-xylene, para-xylene and ethylbenzene under the above described conditions of liquidv HF and BF2I usage, to produce a liquid HF solution containing only a xy-lene complex, a diethylbenzene complex 'and some dissolved ethylbenzene and benzene. Apparently under the conditions of liquid I-lF-BFs usage described above, the only reaction in the liquid HF phase is the .-disproportionation of ethylbenzene to diethylbenzene, .chiefly meta-diethylbenzene and, under some conditions of temperature and time, only the meta-diethylbenzene. VIt is believed that the diethylbenzene reacts with the xylene to produce ethylxylene and ethylbenzene, which .ethylbenzene disproportionates to forni more` diethylbenzenes; and this process continues until an ,equilibrium condition is arrived at; by a proper ad justment of vtemperature and time, it is possible to convert the diethylbenzene virtually completely to ethylxylene. so'that .a substantially pure ethylxylene product is attained. However, at temperatures below :about 125 F. a nite period of time passes before detectable amounts of ethylxylene are produced. Thus by-taking advallvtege 0fl this "-induction period it is possible to treat d mixture of metaY and/ or para-xylene and ethylbenzen'e With liquid HF and BFS to produce a xylene fraction that is substantially free of ethylbenzene and a diethylbenzene fraction that is, free of detectable amounts of ethylstylene.

lat-temperatures above 125 F., the induction periodl S- SQ Short .that .appreciable amounts of ethylxylene are formedeven though the liquid HFsolution of aromatic hydrocarbon complexes is quenched. At a temperature of ,125. F. the maximum contacting time for the pro-- duction of essentially pure diethylbenzene is on the order of 2 or 3 minutes. Slightly higher temperatures may be tolerated by reducing the contacting time and by quenching the liquid HF solution of complexes, e. g., `by the addition of liquid propane. lt is only necessary to reduce the temperature of the liquid HF corn- Plex solution to below 100 F. in order to increase the induction period Ato a workable time. At a contact ing temperature of; about 100 F., the maximum coi1-r lil tacting time is about l0 minutes; at about 70 F., the maximum contacting time is about 30 minutes.

The temperature of contacting may be as low as 0 F. because the ethylbenzene conversion to diethylbenzene reaction reaches equilibrium within a few minutes even at this low temperature. The induction period at this low temperature is several days. When it is desired toproduce meta-.diethylbenzene as `the product and particularly when meta-xylene `is also a desired product, it is preferred to carry out the ethylbenzene conversion process at a ,temperature'between about'70 and 100 F. and to operate for times Vapproaching the maximum, i. e., between about 10 minutes and 30 minutes wherein the longer times correspond to the lower temperatures.

Even at higher temperatures and longer contacting times some ethylbenzene will remain unconverted. At the preferred conditions of liquid AHF and BFs usage and the preferred.temperature-time relationship, between aboutf and 95% of the ethylb'enzenefin ,a feed consist'ing essentially of ethylbenzene and mf -and/ or p-xylene will be converted to meta-diethylben-Zenc. The unconverted ethylrben'zene will be recovered along with the xylene. However, in all cases the amount of ethylbenzene `present in said xylene fraction will Vbe low enough lthat the xylene fraction is substantially et-hylbenzene-free, i. e., the xylene fraction will contain about 5% lor less of -ethylbenzene The higher the temperature of operation and the closer the rapproach to the maximum contacting time, the lower the content of ethylbenzene inthe product xylene fraction.

Substantially-liquid HF-inso'luble hydrocarbons such as 'parains and naphthenes readily wash ethylbenzene outof the acid phase. A lclose-boiling mixture of 'Cs aromatic hydrocarbons and non-aromatic hydrocarbons such as *is obtained 4by distillation of a hydroformate will normally contain about 50 volume percent of no naromatjc hydrocarbons such as parafiins, naphthenes and oletins in addition to small amounts of organic sulfur compounds. By superfractionation, .it is possible, to obtain a 'Ca aromatic hydrocarbon concentrate which contains on the order of v90% .of aromatic hydrocarbons consisting of ethylbenzene, xy'lene isomers and minor amounts of C9 aromatic hydrocarbons. When a Cs aromatic hydrocarbon feedA such as is described in this paragraph is contacted with a suflicient amount' of liquid; and at least about `1 mole of 'B123v per mole of aromatic hydrocarbon jin the feed, a rafnate phase and an extract phase are formed. The raffinate phase contains essentially 1all lthe 'non-aromatic hydrocarbons; I-t'has -been found that regardless ofthe amount of contacting carried out between the rainate phase andthe extract-phase, considerable amounts ofethylbenzene are present in the raffinate phase.

When treating a feed containing` as little 'as 10 volume pf'zrcent-iofV lnon-aromatic hydrocarbons, between about 20 and `30% o f vthe ethylbenzene-present 'in the feed will `be `found in the raffinate phase and will be lost y'to the-diethylbenzene product. Apparently the presence of non-aromatichydrocarbons-as -a separate rafiinate phase very adversely affects the ability of the liquid HlF-BFs treating agent -fto convert and maintain ethylbcnzene .in theext'raetphase in the yform .of diethylbenzene. (Ethylbenzene recovery ,byA extractive distillation processes orf-other extractive processesv from `the rafiinate phase is not considered asf-recoverableA ethylbenzene within the meaning yof ,this invention.) 1

.The presence of benzene. and toluene markedly reducesxthe. degree of conversion to diethylbenzene.

rThe `presence of dissolved non-.aromatic hydrocarbons and dissolved and/or complexed organic sulfur compounds in they :acid phaseY does not appear to adversely affect the. .disproportionation reaction .of ethyl'benzene to diethylbenzene. The4 solubility of non-aromatic vhydrocarbons in liquid HF is increased somewhat by Vthepr-'esencel of an aromatic complex in the liquid HF. However, under the conditions of liquid HF and BF: usage described above, not more than on the order of 2-3 volume percent of non-aromatic hydrocarbons can be tolerated in the feed if operation without a rainate phase in the contacting zone is desired. The maximum content of non-aromatic hydrocarbon will be dependent on the amount of liquid HF used and somewhat on the amount of BF3 used. It is preferred to operate with a minimum of non-aromatic hydrocarbon in order to improve the purity of the xylene product fraction. The preferred feed stock to the ethylbenzene conversion process comprises essentially a mixture of at least one xylene isomer other than o-xylene and ethylbenzene, i. e., the feed stock contains less than about 2 volume percent of non-aromatic hydrocarbons and the naturally occurring amounts of organic sulfur compounds, in addition to meta and/ or para-xylene and ethylbenzene.

The feed stocks obtained from hydroformates or platformates contain some small amounts of oleiins. These olefins readily alkylate some of the aromatic hydrocarbons and form alkyl aromatics which have a boiling point higher than the diethylbenzene product and may be readily separated therefrom by distillation'. The organic sulfur compounds present in feeds from hydroformates and platformates are readily removed from the product hydrocarbons by treatment with sulfuric acid or by treatment with substantially anhydrous liquid HF in the absence of BFs. y

The non-aromatic hydrocarbons, other than olefins, present in a mixed feed boil in about the same range as the Xylene isomers. As a consequence these non-aromatic hydrocarbons are concentrated in the product xylene fraction. Even when operating with a maximum of about 2-3 volume percent of non-aromatics in the feed, the product xylene fraction will contain 5% or less of non-aromatic hydrocarbons. This is usable in most operations requiring high purity xylene. The non-aromatie content cannot be decreased by washing of the complex containing liquid H F solution with a diluent such as butano, pentane, or hexane, owing to the fact that the diluent promotes undesired side reactions. These side reactions involve the disproportionation of di- In addition to this, the presence of vdiluent ..orthoand paradiethylbenzene isomers.

` Although it is preferred to operate the ethylbenzene :conversion process using a feed stock and amounts vof liquid HF and BFS such that substantially only oneV liquid phase is present in the contacting zone, it is to be understood that some gaseous BFa will he present under all operating conditions. In the contacting zone, the term single substantially homogeneous liquid phase is to be understood as including (a) conditions such that only a liquid HFsolution is present, or (b) such that a barely detectable amount of raffinate phase is present along with the liquid HF solution.

Diethylbenzene and triethylbenzene can be reacted with benzene in the presence of liquid HF and BFa treating agent to produce a' mixture consisting essentially of diethylbenzene, triethylbenzene, benzene and ethylbenzene. The ethylbenzene may be recovered as essentially pure ethylbenzene by distillation from the product mixture. Hereinafter the reaction of diethyland triethylbenzene with benzene to form ethylbenzene is spoken of as the diethylbenzene conversion process.

The feed stock to the diethylbenzene process should be essentially pure diethylbenzene and/or triethylbenzene or mixtures of these with other polyethylbenzenes. In order to maximize the yield of ethylbenzene, it is necessary that other aromatic hydrocarbons such as xylene and toluene be absent from the contacting zone. *E 4The amount of benzene present in the feed mixture of diethylbenzene (hereinafter'it is to be understood that diethylbenzene may include triethylbenzene, etc.) must be at least 1 mole for each ethyl group that is transferable; a transferable ethyl group is one that will result in the reduction of the number of ethyl groups on the polyethylbenzene and result in the formation of a molecule of ethylbenzene, e. g., triethylbenzene contains two transferable ethyl groups; thus theoretically 1 mole of triethylbenzene could react with 2 moles of benzene to form 3 moles of ethylbenzene. In the case of diethylbenzene itself, at least 1 mole of benzene must be present per mole of diethylbenzene present. However, the yield of ethylbenzene is improved by the use of more than the theoretical amount of benzene; as much as 20 moles per mole of transferable ethyl groups may be used. The preferred usage of benzene is between about 4 and 7 moles per mole of transferable ethyl group; 0r, in the case of a diethylbenzene feed, between about 4 and 7 moles per mole of diethylbenzene.

Substantially no reaction takes place between diethylbenzene and benzene when more than 1 mole of BFa is present per mole of diethylbenzene. Apparently the reaction does not proceed at an appreciable rate unless some uncomplexed diethylbenzene is present in the complex-containing HF solution. While some reaction will occur at very low BF3 usages such as 0.1 mole per mole of diethylbenzene, the degree of conversion is low and the reaction rate is very slow. It is preferred to operate the diethylbenzene conversion process with between about 0.3 and 0.5 mole of BFs per mole of diethylbenzene. f

Just as in the ethylbenzene conversion process, sucient liquid HF must be present to participate in the formation of the diethylbenzene complex and also to dissolve said complex. Thus the amount of liquid HF used should be from at least about 2 moles to as much or more than 50 moles per mole of diethylbenzene in the feed to the contacting zone. However, it is preferred to operate with a liquid HF usage between about 10 and 25 moles per mole of diethylbenzene in the contacting zone.

Somewhat elevated temperatures of contacting are desirable in order to speed up the reaction rate. The maximum temperature of contacting should be below about 200 F.; side reactions involving hydrogen transfer occur at temperatures in excess of about 200 F. It is preferred to operate at between about and 150 F.. Lower temperatures may be used if either degree of conversion is sacrificed or extremely long contacting times are tolerable.

By operating for a suiicient time at a particular contacting temperature, it is possible to attain a constant product distribution condition; the amount of ethylbenzene produced is dependent not only on temperature and contacting time, but also on the amount of benzene present in the contacting zone. Examples of suitable contacting times at particular temperatures are: 60 F.,

' about 16 hours; 100 F., about 2 hours; 150 F., l5-

30 minutes.

The annexed dra-wing which is a part of this specification shows an illustrative embodiment of a combination process for the treatment of a feed comprising essentially ethylbenzene, paraand meta-xylene Vto produce a substantially pure ethylbenzene product and a xylene fraction that is substantially free of ethylbenzene. It is to be understood that many features of process equipment, such as pumps and valves, have been omitted from this schematic flow drawing, as these details may be readily added thereto by one skilled in the art.

In this illustration, the feed consists of: 2 volume percent of non-aromatic hydrocarbons; this includes a very slight amount of organic sulfur compounds and olenic hydrocarbons. The total sulfur content of the feed is about 0.01 weight percent. The remainder of the'feed consists of Cs aromatic hydrocarbons in the following molar percentages on aromatic hydrocarbon: ethylbenzene, V115;, orthofxylene, trace; metarxylenc, 6lv and,` ara; xylene, 24. 'ihiszfeedwasobtained byiextractively'ths ll' ing, with phenol; asthe. separating: agent, a hydroformat' cut boiling between about.` 270Y and 390l F., which cut had contained about 12%. of non-aromatichydrocarbons, and. then. distilling. in a superfractionatorthe Cs cut to eliminate. all: the. o-xylene and C aromati'cs; some mandp-xylenewas lost inl this distillation.

TheV feed isA passed from source' 11 byl wayof lineI 1.2i into mixer 13. Substantially. anhydrous. liquid HF from source-llzvis passed by Wayk of valved line 16. and line 'i7 into mixer 13'. lin. Ithis: illustration, 9 moles of liquid HF per-mole of aromatic hydrocarbon in the feed arepresent in mixer 13. BFS- -from source 118. is.V passed through valved line I9. andA line 21 into mixer 13. In this illus:- tration, 1.51 moles VoBFg permoleofV aromatic hydrocarbon in the feedl are present in mixer: 13.

Mixer 13 is provided with heat exchanger 23. The complex formation is exothermic and heat exchanger 23 may be used either to Withdraw heat of complexing or to raise the temperature of the materials to the desired reaction temperature. Mixer d'3- maybe any -form of mixing chamber or maybe provided with a motor-driven agitator. In mixer 1-3, the` feed is dissolved into the liquid HF- partly in the form of a complex, and partly in free solution to form a single homogeneous liquid phase.

The liquid phase and undissolved gaseous BFa are passed from mixer 13 by Way of line 24 into reactor 26. Reactor 26 is provided with heat exchangers 27 andi 28, which heat exchangers maintain the desired contacting temperature in reactor 26. In this illustration, thecontacting temperature is 90 F. and the contacting time is about l minutes. No agitation is needed in reactor 26 as the single homogeneous liquid' phase provides more than adequate intimacy of contacting.

At the completion of the reaction time, the liquid HF solution is withdrawn from reactor 26l by way of line 29 and is passed into decomposer 35.'. Decomposer 31 is a vertical vessel providedl with an internal heat 'exchanger 32 and with a few fractionating trays not shown. In decomposer 31, the HF and the EP3 are removed from the single homogeneous liquid phase and pass out of decomposer E11-by way of line 35. Decomposer 31 should be operated in such a way that the BFS and HF are removed at such a rate that substantially no further reaction takes place. Decomposer 31 may be operated at temperatures below the boiling point of liquid HF by the use of a vacuum or mcy be operated at elevated temperatures, e. g., 150 F. In this illustration, decomposer 31 is operated at about 70 F. under a slight vacuum provided by vacunm pump 34.

HF and BF's are passed overhead through line 33, vacuum pump 34 and line 36 into heat exchanger 37. In heat exchanger 37, the HF vapors are condensed. The liquid HF containing some dissolved Bids and the gaseous BFS is passed by Way of liuc 38 into gas separator 39. A liquid HF stream saturated with BFS is Withdrawn from separator 39 and recycled to mixer 13 by way of line. 17.

Gaseous BF3 is withdrawn from separator 39 and is recycled to mixer 13 by way of line 21. Gradually a build-up in the B53 of hydrogen sulfide will occur from 'decomposition of organic sulfur compounds in decomposcr 31. Periodically, EP3 from separator 39 should be Withdrawn and passed through a purification zone, not shown, to remove undesired gases suchV as H23.

Preferablyv only a portion of the BFS and the HF are removed in decomposer 31. The remaining BFS and HF are removed from the decomposer along with the hydrocarbons.

From the bottom of decomposer 31 hydrocarbons and remaining HF and EP3 are Withdrawn and passed by way ofv line il into fractionator s2. Fractionator 42 is provided with an internal heat exchanger' 53. In fractionator 42, benzene formed in the ethylbenzene conversion is passed overhead along with HF and BF2, through valved 8 line. l44. A bottoms stream is withdrawn from. frac,- tionator '4.2 and isjnassedby way-ot line- 46 intotiraMiglia-v tor 47 which is provided; with .internal heat exchanger There is: taken overhead; from fractionator 47 by way of line 4,9 aproduct xylene fraction WhCh consists. of .meta andpara-rxylenes, wherein` the m-.isomer is present in an amount greater than in `the feed, the non-aromatic hydrocarbons present inthe feed, about 3 mole percent of ethylbenzenel and a small amount of organic sulfur compounds. From the bottom of tractionator 47 a substantially pure diethylbenzene fractionis withdrawn by way of. line 5l. This diethylbenzene fraction., from operation on this, type of feed, contains higher boiling alkylbenzenes. trace amounts of ethylxylenes and some organic sulfurcom- Pounds..

The product diethylbenzene from fraetionator 47 .may be treated to remove sulfur compounds and increased in purityby distilling away the, higher boiling alkyloenzene.

However, in this illustrative embodiment, the product diethylbenzene is passed by way of lines 51 and 52 into mixer 53. The benzenevv and HB2-EP3 fraction from fractionator 42Y is passed by way ofv Valved line v4.4i. and lines 54 and 56 into mixer 53. Make-up benzene from source` 5,7- is passedl by way of lines 58 and 56 into mixer 53.. In this illustration, 6 moles of benzene are `present in mixer 53 for each mole of transferable ethyl group present in :mixer 53.

Substantially anhydrous liquid HF from source 14 is passed by way or" valvedline. 59y and line 61 into mixer 53. In this illustration, 12 moles Vof liquid HF are `used per mole of polyethylbenzene. present in mixer v53. BFa from rsource 18' is passed by way of valved line -62 .and linef63finto mixer v53. In this illustration, 0.4 mole of BEs are used per mole of polyethylbenzene ypresent in mixer 53.

Mixer 53. vis provided with heat exchanger 64. Mixer 53 may be. similar in construction to mixer 13. The temperature ofthe materials in mixer 53 is adjusted to 140 F. The. materials are passed .from mixer 53 by way Lof line 6.6 into reactor 67. Reactor 67 is a vessel provided with Aheat exchangers 68 and 69. These heat exchangers serve -to maintain the temperature of contacting at about F. for a total contacting time of about 45 minutes.

- Reactor 67 is also provided with a turbomixer 71 which is driven by motor 72. In order to improve the degree of conversion of diethylbenzene, the contents of reactor 67 are thoroughly agitated by means of turbomixer 71. Two Vliquid phases are present in lreactor 67, namely, a benzene-.ethylbenzene phase and a liquid HF solution phase. A t the-completion of the contacting step, the contents of reactor 67 are passed by way of line 73 into decomposer 74.

Deeomposer 74 is provided with an internal heater 76. Decomposer 74 is similar in construction to decomposer 31 and maybe operated vin a similar fashion. In this illustration, decomposer 74 is operated at a bottoms temperatu-re'of'a'bout 70 F. under a slight vacuum. The HF vapors and BFa pass overhead through line 77, vacuum pump 78 and line 79 into heat exchanger 81. The HF is :condensed in heat exchanger S1 and the mixture of liquid HF and gaseous BFa is passed by way of line 82 into separator 83.

Separator- S3 is similar in construction to separator 59. 'fhe gaseous BFS from separator S3 is cycled by way of line 63 to mixerY 53. The liquid HF, saturated with BFS, from separator S3 is cycled by way of line 61 to mixer 53.

The hydrocarbon bottoms from decomposer 74 is passed through line VS( into fractionator 37 which is provided with internal heat exchanger 33. From fractionator 87, a benzene fraction is taken overhead through valved line 39. This benzene fraction is cycled by way of valv'ed line 89 and lines 54 and 56 to mixer 53.

The benzene-freehydrocarbons are removed from the bottom of fractionator 87 and are passed through line 91 into fractionator 92, which is provided with internal heat exchanger 93. From fractionator 92, a substantially pure product ethylbenzene is taken overhead by way of line 94 and isksent to storage not shown.

The bottoms fraction in fractionator 92 consists of diethylbenzene, triethylbenzene and some higher boiling alkylbenzenes. This bottoms fraction is withdrawn from fractionator 92 through valved line 96 and'is cycled by way of line 52 to mixer 53. In order to reduce the amount of higher vboiling alkylbenzenes in the recycle stream, periodically the bottoms from fractionator 92 are withdrawn and a narrow cut dicthylbenzene fraction and a -narrow cut triethylbenzene fraction obtained by fractional distillation; these narrow cut fractions are then charged to mixer 53.

In order to show some of the results obtainable by the ethylbenzene conversion process and the diethylbenzene conversion process, the following experimental runs are. described. Y

These runs were carried out using a carbon steel reactor provided With a 1725 R. P. M. stirrer. In all runs, the order of addition was: (l) feed, (2) liquid HF and (3) BFa. The contents of the reactor Were brought to the desired temperature and were agitated for the desired contacting time. At the completion of the contacting time, the stirring was stopped and the contents permitted to settle for about l minutes. The contents of the reactor were withdrawn in such a manner that two liquid phases (if any existed therein) were Withdrawn into separate receivers. The liquid phase(s) was withdrawn into a copper vessel filled with crushed ice. Decomposition of the complexes by the water resulted in the formation of a lower aqueous layer and an upper hydrocarbon layer. The hydrocarbon layer was Washed with dilute aqueous caustic to remove HF and BFS remaining therein and was then water Washed to remove traces of the aqueous caustic.

The product hydrocarbons were fractionated in a laboratory column providing about 30 theoretical plates. The narrow cuts were analyzed by a combination of specic gravity, boiling point, refractive index, ultraviolet and infrared techniques.

Runs A through D, shown in Table I, were made to note the effect of varying BFs usage, contacting time, temperature and the presence of a rainate phase, while holding other conditions constant.

TABLE I containing both'diethylbenzene and ethylxyle'n.v (Withinv the limit of experimental error, the product diethylbene'- zene consisted of the metaisomer and the product ethylxylene consisted of 4the 1,3-dimethyl-S-ethylbenzene.) Furthermore, Run B shows that by the use of about l mole of BFs per mole of aromatic hydrocarbon in thefeed that the degree of conversion of the ethylbenzene is substantially triple that of Run A.

Run D shows the effect of operating at a temperature above about 125 F. Run D had a contacting time of 30 minutes in order to maximize the ethylxylene production. However, at this high temperature any practicable contacting time, i. e., more than a few seconds, would result in a Cio aromatic hydrocarbon product containing both diethylbenzene and ethylxylene.

Run C shows the etectof a separate phase of non` aromatic hydrocarbons on (l) the degree of conversion' of the ethylbenzene, (2) the overall yield of Cs aromatic hydrocarbons and (3) the presence of side reactions leading to high boiling aromatic hydrocarbon production. Thus under conditions involving a feed containing volume percent of n-heptane and 50% of Cs aromatic hydrocarbons andan excess of BFs over that theoretically needed to complex the aromatic hydrocarbons, fully one-third of the aromatic hydrocarbons passed into thev ranate phase. Thus in a commercial operation'involvingl a close boiling mixture of Ca aromatic hydrocarbons and non-aromatic hydrocarbons, these aromatic hydrocarbons could be recovered only by special treatment of the non-aromatic hydrocarbon-rich ranate. Further, Run C shows that about one-half of the ethylbenzene in the feed passed into the rainate phase andA was not converted to the desired diethylbenzene. Also, it is of interest that about one-half of the benzene produced in the disproportionation reactionl was found in the ranate phase.v Although the overall ethylbenzene conversion was 50%, it is noteworthy that the C10 aromatic hydrocarbons in the extract phase correspond to an 85% conversion of the ethylbenzene'remaining in the- Run No A B C D Temperature, "F 75 70 75 145 ContactingTime, Minutes 30 30 30 30 Reactor Charge, Moles:

m-xylene 1. 1. 60 0.82 2. 41 pxylene 1. 60 1. 60 0. 81 Ethylbenzene 1. 60 l. 60 0. 81 0` 83 n-heptane (Vol. percent on feed). None N one (50%) None H 30. 0 60. 0 30. 0 22. 5 2.0 5.1 2. 7 3. 34

FIF/Aromatic. 6. 2 12. 5 l2. 3 7. 0 BFs/Xylcnes 0. 68 1. 59 1. 66 1. 39 BFH/Aromatics 0. 42 1. 06 1 11 l. 03

(Moles) (Percent) Total Ratt Ext Product Distribution, Mole Percent 0.02 Ethylbenzene Conversion, percent 30 88 (85) Run A shows that the use of lessV than l mole of BFa per mole of xylene in the feed at otherwise constant con- Runs E andF In these runs, an agitated pressure vessel was used asl ditions results in a Cio aromatic hydrocarbonv product the interaction zone. The feed was introduced into the vessel allowsd vlui-.the liquid and theBEs- Sommerdal, grads anhydrous hydroduorc acidwasv usadas the liqlldldl and commercial. Agrade b orou `trifiuoride was the source of the BFs. The reactor and its, contents were cooled to the desired temperature'and the-agitation continued for the desired .length of time. In the `runs'herein, only one liquid phase was 4present in the reactor. At the end of the contacting time, the contents of the reactor were withdrawn into a vessel containing cold water in order to decompose the complex. The water temperature in the quenching vessel was maintained at below about 80 F. The oil layer was decanted from the aqueous layer and was immediately washed with aqueous caustic solution, water Washed to remove caustic and dried to remove water. The yield of oil ineach of the runs was about 85 volume percent of the feed charged to the reactor. The oil loss isV believed to consist mainly of product benzene with some loss of the Cs aromatic hydrocarbon also.

The vmixture of hydrocarbons recovered from the reactor was carefully distilled in a superffractionation column and the composition of the total product determined by inspection of the distillation curves.

ln run No. E, the feed consisted of 3 parts by volume of C. P. orthoxylene and parts by volume of C. P. ethylbenzene. In Run- F, the feed was a concentrate of Ca aromatic hydrocarbons, derived by extract-ive distillation with phenol from the hydroformate produced in catalytic reforming over molybdena in the presence of hydrogen, of a virgin petroleum naphtha. This fraction contained about 3 volume percent non-aromatic hydrocarbons and had a sulfur content of about 0.01 weight percent. In addition to the Cs aromatic hydrocarbons, a slight amount of C9 aromatic hydrocarbons Were present. The distribution of C- aromatic hydrocarbons in mole percent was: Ethylbenzene, 12; ortho-xylene,` 2l; meta-Xylene, 48; and para-xylene, 19.

The operating conditions and product distribution are set out in Table II following:

TABLE. Il

Run No E F Feed Ethyl C; Nlix-l benzene tureV o-xylene HF, moles/mole of feed 11.2 11.2 BFZ, moles/mole of feed 1.9 1.0 Temperature, F 66 66 Time, Miuutes 10 5 Recovered Product D tribu on Benzene 9 p Ethylbonzene. 2 7 Xylenes 59 G3 C@ Aromatics 8 Diethylbenzone 1 5 2 1,2dimethyl4ethy1benzene 2 21 11 Heavier 4 4 1 Pure meta-isomer by infra-red.

2 185-190 C. fraction (9S-i% 13A-isomer by infra-red).

No attempt was made to adjust the product distribution obtained by distillation from the recovered liquid; product for the loss of benzene and Cs aromatic hydrocarbons in the water decomplexing operation. Therefore, the product distributions are of value as showing the purity of the diethylbenzene and ethylxylene produced. In View of the results of the earlier runs and the limitations of the infrared procedure, it is believed that the 185 if 190 C. product fraction produced in Runs El and F consists only of 1,2-dimethyl-4-ethylbenzene.

Runs E and F show that ortho-xylene does notl behave like meta-xylcne and para-xylene. In these runs, at'6u6r" F. and times of only 5 and 10 minutes, ortho-xylene and ethylbenzene interacted, Whereas in Run B, whiclrwas atV 70 and a time of 30 minuteg e... six times as long as Run-F., no interactiouof.metafxylene or para-Xmas and cfhylbenzeue toolsplace.

12 Run G I n this run, ml. (1.22 moles) of mesitylene and 25 ml. of n-heptane were contacted With 25 moles of liquid HF and 1.03 moles of BPB for 45 minutes at 709 F. The contents of the reactor were settled for 60 minutes and then withdrawn. Two phases were present in the reactor.

The hydrocarbons recovered from the rainate phase consisted o f 21.3 rnl. of n-heptane and 13.5 Inl. of mesitylene. The hydrocarbons from the extract phase consisted of 3.7 Vml. of n-heptane and 156.5 ml. of mesitylene (1.13 moles). Thus the extract hydrocarbons contained 2.4 volume percent of non-aromatic hydrocarbon. It is of interest that there was present in the extract phase 0.1 mole of mesitylene more than the theoretical amount of 1.03 moles. (It has been found that 1 mole of mesitylene and 1 mole of BFa are present in a mesitylene-BFa-HF complex.)

Run H This run was carried out to see if a feed correspondingA to the extract hydrocarbons of Run E could be treated to form a single liquid phase. Thus 171 ml. (1.23 moles) of mesitylene and 3.7 ml. of n -heptane were contacted with 25 moles of liquid HF and 1.03 moles of BFa under the same conditions as described in Run G. When the contents of the reactor were withdrawn only a single phase was found to be present therein. Thus ity was possible to form a single liquid phase by treating'a feed consisting of 2 .1 volume percent of non-aromatic hydrocarbon and the remainder polyalkyl aromatic hydrocarbon by the use of only 0.85 mole of BF3 por mole of aromatic hydrocarbon in the feed. The solubility of mesitylene in liquid HF alone is about 3 volume percent. Thus about 15 ml. of mesitylene could be dissolved in addition to thc amount complexed. Thus about 16' ml. of mesitylcne were brought into solution through the solubilizing action of the complex. Heptane is substantially insoluble in liquid HF alone so that virtually the entire amount dissolvedv in the complex ccmtainingr liquid HF is d ue to the solubilizing action of the complex.

Run I This run illustrates the results obtainable with the diethylbenzene conversion process. Benzene, 1,3-diethylbenzene, liquid HF and B133v were contacted for 16 hours at a temperature of 61 F. The pertinent information on this run is given below:

The productfrorn this run contained no detectable amounts of compounds other than those listed; Within experimental error, the triethylbenzene consisted of the" 1,335-isomer.

This; isl a eontinuationin-.part of our copending application Serial-No. 312,278, tiled September 30, 19542-, new abandoned.

a time between that which is sufficient to substantially attain an equilibrium condition in the disproportionation of said ethylbenzene to diethylbenzene and benzene-and not more than between about 2 minutes and v50 hours, the longer maximum times corresponding to the lower temperature, removing HF and BFs from said liquid HF- phase to recover hydrocarbons therefrom and separating a xylene fraction that is substantially free of ethylbenzene and a diethylbenzene fraction from said hydrocarbons.

2. The process of claim l wherein said BFs is present in an amount of about 1.5 moles per mole of said aromatic hydrocarbon, said liquid HF is present in an amount between about 6 and 15 moles per mole of said aromatic hydrocarbon and the contacting is maintained at a temperature between about 70 and 100 F. for a time between that necessary to substantially attain said equilibrium condition and not more than between about l minutes and 30 minutes, the longer maximum times corresponding to the lower temperature.

3. A process for the production, without appreciable loss ot xylene, of a xylene fraction that is substantially 'ree of ethylbenzene, which process comprises contacting a close boiling feed consisting essentially of a mixture of Cs aromatic hydrocarbons and not more than about 3% of non-aromatic hydrocarbons, which has'been fractionated to remove essentially all the o-xylene, with between about 6 and 15 moles of liquid HF per Vmoie of aromatic hydrocarbon in said feed and between about 1.5 and 3 moles of BFa per mole of aromatic hydrocarbon in said feed, at a temperature between about 0 and 125 F. for

a time between about 2 minutes and 50 hours, the longerV time corresponding to the lower temperature, separating a ranate phase comprising essentially non-aromaticl hydrocarbons and ethylbenzene from an extract phase, recovering an extract by removing HF and BFS from said feed, at a tempeature between about 0 and 125 F. for Y extract phase, and separating by fractional distillation a xylene fraction, that is substantially free of ethylbenzene, from said extract.

4. A process for the preparation of xylenc that is sub stantially free of ethylbenzene and of substantially pure ethylbenzene from a mixed feed consisting essentially of at least one xylene isomer other than o-xylene and of ethylbenzene, which process comprises the steps of (l) contacting said feed with between about 1.5 and 3 moles of BFz per mole of aromatic hydrocarbon in said feed and between about and l5 moles of liquid HF per mole of aromatic hydrocarbon in said feed, at a temperature -between about 70 and 100 s. for a time suicient to attain susbtantially the equilibrium condition in the formation of diethylbenzene, (2) separating hydrocarbons from HF and B123, (3') separating by distillation said hydrocarbons into (a) a benzene fraction, (b) a xylene fraction that is substantially free of ethylbenzene and (c) a diethylbenzene fraction, (4) passing the diethylbenzene and the benzene of step (3) to a second contacting zone, (5) introducing to said second zone additional benzene, (6) intimately contacting the hydrocarbons present in said second zone with between about l0 and 25 moles of liquid HF per mole of polyethylbenzene .in said second zone and between 0.3 and 0.5 mole of BFs per mole of polyethylbenzene in said second zone, at a temperature between about and 150 F. for a time between about 30 minutes and 2 hours, the longer times corresponding to the lower temperatures, and wherein the benzene frorn step (3) and the additional benzene of step (5) amount to between about 4 and 7 moles per mole of transferable ethyl group present in said second zone, (6) separating mixed hydrocarbons from HF and BFS, (7) separating by distillation said mixed hydrocarbons into (a) a benzene fraction, (b) a substantially pure ethylbenzene fraction and a polyethylbenzene fraction,

and (8) cycling the benzene and polyethylbenzene frac- 1 tions of step (7) to said second contacting zone.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A PROCESS FOR THE TREATMENT OF A MIXED FEED CONSISTING ESSENTIALLY OF AT LEAST ONE XYLENE SELECTED FROM THE CLASS CONSISTING OF META-XYLENE AND PARA-XYLENE AND ETHYLBENZENE FOR THE PRODUCTION OF DIETHYLBENZENE AND A XYLENE PRODUCT THAT IS SUBSTANTIALLY FREE OF ETHYLBENZENE, WHICH PROCESS COMPRISES CONTACTING SAID FEED WITH AT LEAST ABOUT 1 MOLE OF BF3 PER MOLE OF AROMATIC HYDROCARBONS IN SAID FEED AND WITH BETWEEN ABOUT 2 AND 50 MOLES OF LIQUID HF PER MOLE OF AROMATIC HYDROCARBON IN SAID FEED, AT A TEMPERATURE BETWEEN ABOUT 0* AND 125*F. FOR A TIME BETWEEN THAT WHICH IS SUFFICIENT TO SUBSTANTIALLY ATTAIN AN EQUILIBRIUM CONDITION IN THE DISPROPORTIONATION

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