Intermolecular condensation of hfinsoluble linear fused-ring polycyclic aromatic hydrocarbons

Oct. 17, 1950 a. p. lien 2,525,809

INTERMOLECULAR CONDENSATION OF HF-INSOLUBLE LINEAR FUSED-RING POLYCYCLIC AROMATIC HYDROCARBONS

Filed July. 10. 1947

Sheets-Sheet 1

Sirippi ng Gas

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POLYCYCLIC

Oct. 17, 1950 a. p. lien

INTERMOLECULAR CONDENSATION OF HF-INSOLUBLE^ LINEAR FUSED-RING

Filed July 10, 1947

AROMATIC HYDROCARBONS

Sheets-Sheet 2

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Polycyclic Aromatic Hydro c arbans

<img file="US2525809A_D0003.tif" />

Attorney

Patented Oct. 17, 1950

2,525,809

UNITED STATES PATENT OFFICE

2,325,809

INTERMOLECULAR' CONDENSATION OF III - INSOLUBLE' LINEAR 1USED-RING POLYCYCLIC AROMATIC HYDROCARBONS

Arthur F. Lien, Hammond, Ind., assignor: to Standard Oil Company, Chicago, Ill., a corporation of Indiana

Application July 10, 1947, Serial No. 760,061

Claims. (Cl. 260·—670)

2

This invention relates to a process for effecting the intermolecular chemical condensation of certain polycyclic aromatic hydrocarbons. More particularly it relates to a process for the separation of substantially HF-insoluble polycyclic aromatic hydrocarbons such as naphthalene and alkyl naphthalenes from their mixtures with saturated hydrocarbons by a process which involves intermolecular chemical condensation of said aromatic hydrocarbons to produce HF-soluble ¹⁰polynuclear aromatic hydrocarbons which are extracted from said saturated hydrocarbons, both the chemical condensation and extraction steps: being performed in a medium consisting essentially of liquid anhydrous hydrogen fluoride ¹⁵which functions as a catalyst in the chemical reaction and a solvent in the extraction operation. This application is a continuation-in-part of my previous application for Letters Patent S. N. 681,122 filed on July 2, 1946, now U. S. Patent No. 2,426,624, patented September 2, 1947.

Although the literature has indicated that liquid hydrogen fluoride is a solvent in general for aromatic hydrocarbons, I have found that this is not true, strictly speaking. Thus, I have ob- ²⁵served that monocyclic aromatic hydrocarbons are substantially insoluble in liquid hydrogen fluoride. Moreover, I have found, as more fully set forth in U. S. Patent No. 2,426,624, that polynuclear aromatic hydrocarbons of quinonoid so structure exhibit substantial solubility in liquid hydrogen fluoride whereas under similar conditions polynuclear aromatic hydrocarbons of benzenoid structure are substantially insoluble in liquid hydrogen fluoride. Examples of benzenoid 35 type polynuclear aromatic hydrocarbons are naphthalene, alkyl naphthalenes and phenanthrene. Examples of quinonoid type polynuclear aromatic hydrocarbons are anthracene, pyrene and perylene. 40

There are numerous instances in which it is desirable to separate saturated hydrocarbons, viz. alkanes, cycloalkanes and alkylcycloalkanes, from associated polycyclic aromatic hydrocarbons of similar boiling range. Thus, it is desirable 45 to remove aromatic hydrocarbons including HFinsoluble polycyclic aromatic hydrocarbons from kerosenes or heater oils to depress their sootproducing capacity upon combustion. It is desirable to remove aromatics from gas oils, either 50 virgin or cracked, to improve their cracking characteristics. It is also desirable to remove aromatics from Diesel fuel fractions to improve cetane number. The removal of certain aromatics from lubricating oil fractions increases V. I. and reduces carbonization tendencies; Another application of this invention is in the separation of alkylnaphthalenes, particularly methylnaphthalenes, from hydroformer bottoms. The process of the present invention affords not only a method of separating certain aromatic hydrocarbons from saturated hydrocarbons but also leads to the production of valuable HF-soluble polynuclear aromatic hydrocarbons. The process of this invention may also be applied to effect the chemical condensation of naphthalene and alkylnaphthalenes in fractions derived from coal tar or by coal hydrogenation.

One object of my invention is to provide a process for effecting the intermolecular condensation of substantially HF-insoluble polynuclear aromatic hydrocarbons, preferably polynuclear aromatic hydrocarbons containing only one naphthalenic structure such as naphathalene and alkylnaphthalenes, employing a catalyst consisting essentially of liquid, substantially anhydrous hydrogen fluoride. Another object of my invention is to convert HF-insoluble polynuclear aromatic hydrocarbons by an intermolecular condensation reaction into HF-soluble polynuclear aromatic hydrocarbons which are separated from the reaction mixture as a solution in liquid hydrogen fluoride. An additional object of my invention is to effect- separation of saturated hydrocarbons, which are insoluble in liquid hydrogen fluoride, from HF-insoluble polycyclic aromatic hydrocarbons by the treatment of hydrocarbon mixtures: containing both with a catalyst consisting essentially of liquid' hydrogen fluoride under conditions adapted to effect intermolecular chemical condensation of said aromatic hydrocarbons to form HF-soluble polynuclear aromatic hydrocarbons while avoiding substantial cracking of said saturated hydrocarbons. These and other objects of my invention will become apparent from the ensuing description of my invention read in conjunction with the accompanying figures,

I have discovered that HF-insoluble polynuclear aromatic hydrocarbons such as naphtha¢,525,809 lene and alkylnaphthalenes in the presence of liquid substantially anhydrous hydrogen fluoride undergo intermolecular condensation reactions producing hydrogen and polynuclear aromatic hydrocarbons such as perylene and even higher molecular weight hydrocarbons and that the intermolecular condensation products exhibit preferential solubility in substantially liquid anhydrous hydrogen fluoride. For example, the following reaction may be effected:

<img file="US2525809A_D0004.tif" />

The products of the condensation reaction may be removed from the reaction zone as a solution in liquid hydrogen fluoride when the latter is employed in quantity sufficient to function not onlv as a catalyst but also as a solvent for the reaction, products. When the amount of hydrogen fluoride employed is insufficient to extract the desired amount of polynuclear aromatic hydrocarbon condensation product from the reaction mixture, at least a part of the reaction mixture may be extracted with additional hydrogen fluoride either in the reaction zone or in a separate zone under conditions particularly favorable for the extraction operation.

I have made the surprising observation that mixtures of saturated hydrocarbons and HF-insoluble polycyclic aromatic hydrocarbons such as naphthalene or alkylnaphthalenes may be treated with a catalyst consisting essentially of liquid, substantially anhydrous hydrogen fluoride under certain operating conditions to effect intermolecular chemical condensation of said aromatic hydrocarbons without simultaneously effecting substantial cracking of said saturated hydrocarbons, although treatment of saturated hydrocarbons with liquid hydrogen fluoride under the same operating conditions in the absence of said aromatic hydrocarbons would result in appreciable or substantial cracking of said saturated hydrocarbons· In other words, the intermolecular chemical condensation of HF-insoluble polynuclear aromatic hydrocarbons in a mixture thereof with saturated.hydrocarbons, such as paraffins, can be made to proceed preferentially in the presence of a liquid substantially anhydrous hydrogen fluoride catalyst under reaction conditions which would otherwise be suitable for effecting substantial cracking of saturated hydrocarbons. By liquid, substantially anhydrous hydrogen fluoride I mean hydrogen fluoride Which may contain up to about 10 weight per cent of water, but which preferably contains 5 weight per cent or less, e. g. 1 or 2 weight per cent, of water.

. When alkylnaphthalenes and the like containing relatively large alkyl groups, e. g. containing 5 or more carbon atoms, are subjected to the process of this invention, they tend to produce paraffin hydrocarbons having the same number of carbon atoms as the alkyl group, as well as intermolecular condensation products.

. I have further made the surprising observation that mononuclear aromatic hydrocarbons, particularly a low boiling mononuclear aromatic hydrocarbon such as benzene, may exert a sub4 stantial inhibiting effect on the intermolecular chemical condensation reaction when present in the reaction zone in sufficient quantity whereas saturated hydrocarbons appear to exert substantially no inhibitory effect.

The intermolecular chemical condensation reactions herein under consideration may be catalyzed not only by liquid hydrogen fluoride but also by mixtures thereof with minor proportions of BFa, viz. about 1 to about 40 weight per cent of BF3 based on the weight of hydrogen fluoride, preferably between about 1 and about 10 weight per cent BF3, although even less than 1 per cent of BF3 may be used. Mixtures of HF and BF3 appear to exert far greater catalytic activity than hydrogen fluoride alone in both intermolecular condensation and cracking, reactions. Moreover, mixtures of HF and BF3 exhibit remarkably different solvent powers from liquid hydrogen fluoride alone. Thus, mixtures of HF and BF3 exert far greater solvent capacity for all types of aromatic hydrocarbons than HF alone. Both monocyclic and polycyclic aromatic hydrocarbons are soluble to a substantial extent in mixtures of HF and BF3. Benzenoid-type dicyclic aromatic hydrocarbons are also soluble in HF-BF3 mixtures. It is desired for the purposes of this invention to effect only the intermolecular condensation reaction with mixtures of HF and BF3; thereafter it is desirable to remove substantially all the BF3 from the reaction mixture and to effect extraction of said mixture with liquid substantially anhydrous hydrogen fluoride, which selectively dissolves the hydrocarbon produced by the intermolecular chemical condensation reaction.

Suitable HF-insoluble polycyclic aromatic hydrocarbons which may be subjected to intermolecular chemical condensation in accordance with this invention include naphthalene_: and alkylnaphthalenes, such as methylnaphthalenes, ethylnaphthalenes, propylnaphthalenes, n-butylnaphthalenes, sec-butylnaphthalenes, tert-butylnaphthalenes and the like. Preferred charging stocks are naphthalene, methyl-, ethyl- and tertbutylnaphthalenes. I may employ the pure polycyclic aromatic hydrocarbons or mixtures thereof as charging stocks or I may employ commercially available fractions containing these and similar polycyclic aromatic hydrocarbons, e. g., as found in certain kerosenes, furnace oils, hydroformer bottoms fractions, gas oils derived from thermal or catalytic cracking operations, Diesel fuel fractions and the like.

In order to effect intermolecular condensation of said aromatic hydrocarbons it is important to avoid the presence of substantial amounts of mononuclear aromatic hydrocarbons, particularly a mononuclear aromatic hydrocarbon boiling below about 450° F. in the charging stock. Usually the presence of more than about 15 per cent by weight of a low boiling mononuclear aromatic hydrocarbon is undesirable since its presence in these or larger amounts may substantially retard or wholly prevent the propagation of the intermolecular condensation reaction of the polycyclic aromatic hydrocarbons. The low boiling mononuclear aromatic hydrocarbons are preferably removed from the charging stock to the present process; removal may be effected by conventional methods such as distillation or by other operations, the particular mode of removing mononuclear aromatic hydrocarbons being selected in consideration of the precise nature of the chargingstock.

2,525,806

When hydrogen fluoride is employed as the sole catalyst, suitable temperatures for effecting the intermolecular chemical condensation reaction fall between about 150° F. and about 450° F. However, the rate of the condensation reaction at temperatures below about 250° F. is too slow to be of practical significance and I have found it preferable to use temperatures of. at least about 250° F. Ordinarily I prefer to effect the intermolecular condensation reaction at temperatures between about 300° F. and about 450° F., for example at a temperature of about 330° F.

Sufficient pressure is employed in. effecting the intermolecular condensation reaction to maintain at least a substantial proportion of the reactants and catalyst in the liquid phase. When hydrogen fluoride is employed as a sole catalyst suitable pressures usually fall between about 50 and about 1500 p. s.i.

When hydrogen fluoride is employed as the sole catalyst for the intermolecular condensation reaction, it may be used in amounts between about 0.5 and about 25 or even a greater number of parts by weight (calculated as 100 per cent HF) per part by weight of chemically condensable polycyclic aromatic hydrocarbon in the charging stock. Ordinarily I prefer to employ between about 1 and about 15 parts by weight of liquid substantially anhydrous hydrogen fluoride per part of condensable aromatic hydrocarbon. The hydrogen fluoride employed for the purposes of the present invention should contain at least about 90 per cent by weight of hydrogen-fluoride. I prefer to employ commercial anhydrous hydrogen fluoride which usually contains at least about 98 per cent by weight of hydrogen fluoride.

The time of reaction will be correlated with the other reaction variables to secure the desired extent of intermolecular condensation. Ordinarily I may employ reaction periods varying between about 10 and about 200 minutes, for example about 60 minutes.

It is desirable to effect intimate contacting of the liquid hydrogen fluoride or other catalyst with the reactants. Conventional equipment can be used -to effect the necessary contacting in the course of the intermolecular condensation reaction, for example stirring -and pumping equipment such as -has been employed heretofore in effecting alkylation of isoparaffins with olefins in the presence of a liquid hydrogen fluoride catalyst. The condensation reaction may be carried out as a batch, semi-continuous or continuous process. Both chemical condensation and extraction may. be effected simultaneously by continuously .counterflowing a hydrocarbon charging stock and liquid hydrogen fluoride catalyst thr.ough .a vertical tower which may be packed, if desired, with HF-resistant materials to provide for intimate intermingling of the counterflowing streams. In another mode of operation the hydrocarbon charging stock may be caused to flow upwards through a pool of liquid hydrogen fluoride maintained in the reaction zone, when the temperature of operation is such that the hydrogen fluoride phase ds themore dense .phase.

Following the chemical condensation operation or in some -instances simultaneously therewith, steps are taken to effect the extraction of polynuclear aromatic hydrocarbons produced in the condensation reaction, the extraction being effected with liquid substantially anhydrous hydrogen fluoride. It may be preferred to effect the condensation reaction and the solvent extraction operation under different operating, conditions..

Thus while it is ordinarily desirable to effect ifitermolecular condensation of polycyclic aromatic hydrocarbons with liquid hydrogen fluoride as the catalyst at temperatures above about 250° F. it is usually desirable to effect extraction of the resultant HF-soluble polynuclear aromatic hydrocarbons from the reaction mixture at temperatures below about 150° F., for example temperatures between about —30° F. and 150° F., preferably between about 40° F. and about 100° F. A suitable extraction operation can usually be effected at about room temperature. Furthermore it may be desired to effect the solvent extraction operation with a higher HF:oil ratio than that employed in the chemical condensation step. Thus it may be desirable to effect the condensation reaction employing an HF:total oil weight ratio between about 0.1 and 1 whereas the ratio for the extraction operation can be higher, for example as high as 3 or even 5. In the condensation reaction which is effected at relatively high temperatures the possibility exists that the employment of a very high HF:oil ratio may result in the cracking of some of the saturated hydrocarbons, whereas at the relatively low temperature usually employed in the extraction operation, even very high HF:oil ratios will not induce substantial cracking of saturated hydrocarbons.

The extraction operation will be effected under pressure sufficient to maintain the liquid phase in the extraction zone. Usually I may employ pressures between about 5 and about 100 p. s. i. The extraction operation may be effected in conventional equipment such as is normally employed to effect selective solvent extraction of petroleum oils.

Referring to Figure 1, a suitable hydrocarbon charging stock comprising saturated hydrocarbons and HF-insoluble polycyclic aromatic hydrocarbons, which may be a kerosene fraction containing substantially no mononuclear aromatic hydrocarbon boiling below about 450° F., is passed from source 18 through line II into heater 12 wherein it is heated to a suitable temperature, for example between about 150° F. arid about 450° F. From the heater, .the hydrocarbon charging stock passes into reactor (3 which is provided with agitating means such as paddle stirrer 14 and a temperature control jacket 15. Liquid, substantially anhydrous hydrogen fluoride is passed from storage tank 16 through valved line 17 and heater 18 into reactor 13. Sufficient pressure is maintained in the reactor to hold the hydrocarbon reactants and the hydrogen fluoride catalyst for the most part in the liquid phase. The back pressure on the reactor is controlled by a pressure control valve 19 in vent line 20. The pressure tends to increase during the course of the intermolecular-condensation reaction since it proceeds with .the evolution of hydrogen.

Upon completion of the desired reaction the reaction mixture is withdrawn from reactor 13 through line 21 and line 22 into settler 23. If desired, the settler may be operated under substantially the same conditions of temperature and pressure as those maintained in the reactor. Usually, however, it is desirable to operate the settler at a lower temperature and a correspondingly lower pressure. To this end it is usually desirable to withdraw at least a portion of the reaction mixture through valved line 24 and cooler 25 to adjust the temperature of the reaction mixture to a suitable value, usually below about 150° F., for. example,, about room tempera-’

2,525,809

Ί ture, before passing the mixture into the settler. The pressure in the settler is controlled by pressure control valve 26 in vent line 27. In order to facilitate the settling and extraction which occur in settler 23 it may be desirable to add liquid hydrogen fluoride thereto through valved line 28 which is connected to valved line 17 leading from HF storage tank I G. In the settler a gas comprising a substantial portion of hydrogen is withdrawn through vent line 27.. An upper raffinate phase 29 comprising saturated hydrocarbons and unconverted HF-insoluble polycyclic aromatic hydrocarbons is formed; this phase⁷ is withdrawn through line 39, whence all or a portion thereof may be withdrawn through valve line 31 for recycle to line H and heater 12 to reactor ! 3. Part or all. of the reffinate. phase may be withdrawn through valve line 32.

A lower extract phase. 33 comprising hydrogen fluoride and extracted hydrocarbons such as quinonoid-type polynuclear aromatic hydrocarbons and HF-soluble polynuclear aromatic hydrocarbons produced by the condensation reaction is formed in settler 23. The extract phase is withdrawn through valved line 34, whence part or all thereof may be passed into line 31 for recycle to reactor !3. Usually it is undesirable to allow the hydrocarbon concentration of the hydrogen fluoride in the reactor to exceed about 40 weight per cent since an excessive amount of hydrocarbon in solution in the HF tends to reduce or impair its catalytic activity.

For this reason and for the further reason that it is usually desired to recover the polynucleai’ aromatic hydrocarbon formed in the intermolecular condensation reaction, at least a part of the extract phase in the reactor 23 is continuously or intermittently withdrawn through valved line 35 and heater 36 into tower 37 wherein HF is stripped from the extract phase. Temperatures between about 150 and about 500° F. and relatively low pressures such as 50 p. s. i. g. or even lower are maintained in tower 37. If desired, a stripping gas may be introduced by line 38 into the lower portion of the tower to aid in the vaporization of the hydrogen fluoride. Suitable stripping gases comprise light paraffin hydrocarbons such as methane, ethane, propane, nbutane, isobutane, pentanes and the like. Hydrogen fluoride-soluble aromatic hydrocarbons are withdrawn from tower 37 through valved line 39. A vapor stream comprising hydrogen fluoride is withdrawn from tower 37 through valved line 49 whence it may be passed through condenser 41 and line 42 into HF storage tank 16. When a stripping gas is employed in tower 37 to aid in the vaporization of hydrogen .fluoride it may be desirable to divert a portion of the . gas stream from line 40 into valved line 43 and condenser 44 to liquefy its hydrogen fluoride content; from condenser 44 the gas-liquid mixture is passed into an accumulator drum 45, whence stripping gas is diverted through valved vent line 46 and liquid hydrogen fluoride is passed through valved line 47 which leads into line 42 passing into the hydrogen fluoride storage tank 16. The hydrogen fluoride storage tank is provided with a valved vent line 48 through which volatile materials which tend to accumulate in the system may be removed from time to time. Part or all of the stripping gas may be recycled from line 46 to line 38 leading into tower 37.

Although it will be desirable to strip hydrogen fluoride from the extract phase by vaporization in large scale operations, in small or batch scale operations it may be more desirable' simply to dilute the extract phase with water or to dilute it with alkaline solutions whereupon the hydrocarbon materials contained in the extract phase will form a distinct phase which can be separated and utilized as desired. The disadvantage of this method of operation, of course, is that the hydrogen fluoride is of no further use in the condensation reaction.

• The oil fractions having relatively high concentrations of saturated hydrocarbons leaving the system through line 32 are adaptable to many uses depending upon their boiling ranges, viscosities and other properties. Thus, depending upon the charging stock passing to reactor 13, the oil fraction leaving through line 32 may be adapted for use as a burning oil, lubricating oil, high cetane number Diesel fuel or as a charging stock for cracking processes. Thus when the relatively saturated hydrocarbon oil leaving the system through line 32 boils above the gasoline boiling range, e. g., in the gas oil range, it may be subjected to cracking with liquid hydrogen fluoride as a catalyst or it may be cracked thermally or in the presence of solid cracking catalysts, for example alumina-silica or magnesia-silica type solid cracking catalysts under conventional conditions of temperature and pressure.

The hydrogen fluoride-soluble materials leaving the reaction system through line 39 comprise not only polynuclear aromatic hydrocarbons but also certain of the olefinic, sulfur, nitrogen and oxygen compounds that may have been present in the charging stock. The polynuclear aromatic materials withdrawn through line 39 may be of value as chemical raw materials for such processes as oxidation, halogenation, nitration, sulfonation, amination, etc.; they may also be of value as insecticidal, materials, plasticizers for natural or synthetic rubbers, vinyl resins, etc.

Figure 2 illustrates an embodiment of my invention wherein a minoi’ proportion of BF3 is employed as a promoter for hydrogen fluoride catalyst in the intermolecular condensation reaction but not in the subsequent extraction operation. A hydrocarbon charging stock comprising saturated hydrocarbons and HF-insoluble polycyclic aromatic hydrocarbons is passed from source 108 through valved line 101 and heater 102 into reactor 103 which is provided with a motor driven paddle stirrer or equivalent agitating means 104, a temperature control jacket (85 and a valved vent line 106 containing a pressure control valve 107. Hydrogen fluoride containing a minor proportion of BF3, for example, about 0.5 to about 10 per cent of BF3 based on the weight of the hydrogen fluoride is passed from source 108 through valved line 109 and heater HO into the reactor. The reactor may be operated upon a charging stock such as cracked gas oil employing a catalysttoil weight ratio between about 0.05 and about 1.0, e. g. about 0.5, at a temperature between about 80° F. and about 250° F., e. g. about 200° F., and a pressure between about 5 and about 300 p. s. i. g„ e. g. about 180 p. s. i. g.

After the intermolecular condensation of HFinsoluble polycyclic aromatic hydrocarbons has proceeded to the desired extent, for example after a reaction period of about 30 to about 60 minutes, at least a portion of the reaction mixture is withdrawn through valved lines 111 and ί 12 into a stripper II3. Operating conditions in the stripper are adjusted to effect the vaporization of substantially all of the BF3 contained in

2,525,809 the reaction mixture. A part or all of the HF may also be vaporized in the stripper. Suitable operating conditions for the stripper are a temperature between about —30° F. and about 150° F., and a pressure between about 0 and about 40 p. s. i. g. Control of the temperature in the stripper may be facilitated by passing all or part of the reaction mixture from line ί ί ί through valved line 11® into heater or cooler 115, whence it passes through line 115 into line: I ί 2 and thence into the stripper. To aid in the vaporization of BFs and, optionally, hydrogen fluoride in the stripper, a stripping gas may be introduced into the lower portion thereof through valved line 117. Suitable stripping gases include light paraffin hydrocarbons such as methane, ethane, propane, etc.

When stripping gases are not employed or are introduced into the stripper in relatively small quantity, the BF3, which may also contain some HF, passing overhead through valved line I i 8 may be passed through compressor 119 and cooler 120 into HF-BF3 charging line 109 and passed into the reactor. Usually it is preferred to divert the gas stream from line 118 through valved line 121, compressor 122 and cooler 123 into separating drum 12®. In drum 12® hydrogen produced in the intermolecular condensation reaction effected in reactor 103, BF3, and such stripping gases as . were introduced into stripper 113 are removed through valved vent line 125; this gas stream may be treated to effect the recovery of BF3 by conventional methods, for example by absorption in cold liquid hydrogen fluoride. Suitable operating conditions for drum' 12® are temperatures between about 40° F. and about 140° F. and pressures between about 50 and about 350 p. s. i. g. A liquid phase comprising principally hydrogen fluoride but which may also contain some relatively volatile hydrocarbons is formed in drum 124 and is withdrawn through valved line 126.

The reaction mixture which has been stripped, of BF3 is withdrawn from stripper 113 through valved line 127 whence it passes into extraction or settling tower 128, Usually it is desirable to pass at least a portion of the stripped reaction mixture through by-pass cooler I27A before introducing it into tower 128. ......

If hydrogen fluoride has been added to reactor 103 in amount'sufficient to serve not only as a catalyst but also as a solvent for the intermolecular condensation products, tower 128 may be utilized simply as a settling zone in which two- liquid phases are formed, viz, an upper hydrocarbon phase containing a reduced content of condensable hydrocarbons and relatively enriched in saturated hydrocarbons and a lower phase comprising a hydrogen fluoride solution of certain polynuclear aromatic hydrocarbons. Ordinarily it is desirable to employ tower 128 both for further extraction of the reaction mixture with liquid hydrogen fluoride and as a settling zone. To this end liquid hydrogen fluoride from source 129 may be passed through valved line 130 and line 131 into the upper portion of tower 128. A liquid phase comprising hydrogen fluoride may be passed from drum 124 through valved line 132 through a heater or cooler 133 to join the hydrogen fluoride stream passing through line 130.

A liquid stream relatively enriched in saturated hydrocarbons is withdrawn from the upper end of tower 128. through valved line. 134.

A liquid hydrogen .fluoride solution of HF*SQlUhle hydrocarbons and some of the sulfur, nitrogen and oxygen compounds which may have been present in the charging stock are withdrawn from the lower end of tower 128 through valved line 135 and heater 136 into tower 137 wherein removal of hydrogen fluoride by vaporization is effected,

When tower 128 is employed simply as a settler suitable operating conditions are temperatures between about 30° F. and about 150° F. and. pressures between about 0 and about 100 p. s. i. g-. Essentially the. same conditions of temperature and pressure may be maintained in the tower 128 when it is employed, for. extraction. . The HF:oil weight ratio employed in the extraction operation will naturally depend on the specific constitution of the hydrocarbons charged thereto but in general will fall between about 0.1 and about 2.0.

In tower 137 conditions are maintained suitable for. the vaporization of substantially all the hydrogen fluoride contained in the stream charged thereto. Suitable conditions are temperatures between about 150° F. and about 500° F. and pressures between about 0 and about 50¹p. s. i. g. Hydrogen fluoride vapors are removed overhead through valved line (38 whence part or all thereof may be diverted through valved line 139 and condenser 140 for recycle through line 141 to join the hydrogen fluoride stream passing through line (3( into tower (28. The HF-soluble materials are removed from tower 137 through valved line (42.

The specific examples presented in the following table will serve to illustrate the principles and some applications of the process of this invention, fout.it is. not intended that they should serve unduly to limit the invention. The hydrogen fluoride employed in catalyzing the condensation reactions and to effect the extraction was commercial liquid, substantially anhydrous hydrogen fluoride. The reactions'were effected by intimately agitating the liquid hydrogen fluoride with the charging stocks in a carbon steel pressure vessel having a capacity of 1575 cc., provided with a stirrer which was operated at about 1725 R. P;.M: during, .the reaction period. Following stirring of the reactants for a period of time indicated in the table as contact time, stirring was. discontinued and liquid phases were allowed to separate in the pressure vessel by gravity settling. When the reaction temperature was above room temperature, the high temperature contacting was followed by a settling period at room temperature.

. Run 1 indicates that, xylene, which may be taken as typical, of monocyclic aromatic hydrocarbons, is substantially insoluble in liquid hydrogen fluoride at moderate temperatures. It was also obvious that no cracking had. occurred in this run.

Run 2 indicates that even at the high temperature of 330° F. and the extended contacting period of 3 hours, liquid hydrogen fluoride dissolves substantially no toluene from its solution in n-heptane. Also notable is the fact that 20 volume per cent of toluene completely inhibited the cracking of n-heptane which would otherwise occur under these conditions. Run 2 also indicates very clearly that monocyclic aromatic hydrocarbons do not undergo intermolecular. condensation, to form HF-soluble polynuclear aromatic hydrocarbons even under relatively stringent, operating conditions.

Run 3 shows that a dicyclic benzenoid hydro2,526,809 carbon, specifically amylnaphthalene, remains substantially undissolved in liquid hydrogen fluoride at room temperature. This run also indicates that more stringent operating conditions are necessary to effect condensation reactions with a dicyclic hydrocarbon. No cracking was observed to occur in this run.

Run 5 differs from run 4 in that the n-heptane diluent of the latter was replaced by benzene. Run 5 demonstrates clearly that a relatively large amount of a low boiling aromatic hydro5 carbon not only inhibits cracking but also the intermolecular chemical condensation reaction which otherwise proceeds preferentially with reRun No..__________________________________

Feed:

Aromatic_______________________________

Diluent..--------------------------Volume per cent diluent in feed..______

HF, volume per cent on feed.______________

Reaction temp., °F________________________

Contract time, Hrs„-----------------------Refractive index (wd²⁰):.

Feed------------—----------------Raffinale__________________—_______—_

Feed solution..________________________

Raffinate solution--------------------—

Pure diluent___________________________

Weight per cent cracking products__________

Aromatic removal, weight per cent:

On ran²⁰-------------------------------On actual weight_______________________ xylene_____ toluene____

<td> n-heptane-</td><td> n-heptane-</td>

<td> 80.....</td><td> ro</td>

<td> 20' —</td><td> 90</td>

<td> 70-80-.....</td><td> 330 ¹ — _</td>

<td> 0.33.......</td><td></td>

1.4107.

1.4112.

1.4091:

1.4091.

1.3890.

0_____

1.3890.

amyl-naphthalene.

1.4280.

1.4282.

1.3890.

2-Methylnaphthalene n-heptane._______

80_________________

20_________________

70-80______________

0.33_______________

<td> n-heptaue. 80—</td><td> benzene, RO</td><td> cetane___ R4</td>

<td> 20- _ _</td><td> 20— —</td><td> 200</td>

<td> 330 1_____ 3________</td><td> 330 ϊ____ 3-_______</td><td> 330 i_____ 0.5-.....</td>

<td></td><td></td><td></td>

<td> 1.4332--. 1.4234-- 1.3890--. 0— —</td><td> 1.5226--. 1.5228--1.5011-.0</td><td> 1.4623., - 1.4496-.- 1.4349.. . 1 6</td>

<td> 22.2_____ 26.0-.. 2</td><td> 0________ 4.0-,. _</td><td> 46.4_____ 57.0.___</td>

<td></td><td></td><td></td>

cetane.

200.

329.1

0.5.

61.4.

none.

i Cooled to room temperature (70-75° F.) to separate phases.

<td> Run No_____ _________</td><td> 8</td><td> 9</td><td> 10</td><td> 11</td><td> 12</td><td> 13</td><td> 14</td><td> 15</td><td> 16</td>

<td></td><td></td><td colspan="3"> Hydroformer Bottoms Fractions</td><td></td><td colspan="2"> Furnace Oil</td><td colspan="2"> Lube Oil·</td>

<td> Feed: Aromatic___ —</td><td> total ____</td><td> 332M95⁰ F—_</td><td> 495°-600° F„,_</td><td> 495°-600° FA__</td><td></td><td></td><td></td><td></td><td></td>

<td rowspan="3"> Diluent _________ Volume per cent diluent in feed. HF, volume per cent on feed. Reaction temp., °F._ — Cnntant time, TTrs</td><td> n-heptane, 80.........</td><td> n-heptane³—&lt;_ 80____________</td><td> n-heptane³____ 80.____________</td><td> n-heptane³—— 80.............</td><td> n-heptane³RO</td><td> none..</td><td> none..</td><td> none,.</td><td> none.</td>

<td> 20_________</td><td> 20_____________</td><td> 20 _ _________</td><td> 20</td><td> 20</td><td> 20</td><td> 90</td><td> 52</td><td> 52.</td>

<td> 70-80...... 0.33.......</td><td> 70-80__________ 0.33.........</td><td> 70-80__________ 033</td><td> 212⁴......... 4R</td><td> 70-80.............. 0 33</td><td> 75_____ 1.0</td><td> 330 ⁴___ 1.1</td><td> 72_____ 1.25</td><td> 330.⁴ 3.0</td>

<td> Refractive index (πη²⁰) · Feed— __ _____ Raffinate___________ Feed solution_____</td><td> 1.5938_____ 1.5805_____ 1.4327.....</td><td> 1.5672_______ 1.5606........ 1.4350.......</td><td> 1.5980......... 1.5887_________ 1.4418... „</td><td> 1.5980_________ 1.5719--.______ 1.4418...</td><td> 1.7175 ⁸„ _______ 1.6303 ⁸........... 1.4619.........</td><td> 1.4767. 1.4712-</td><td> 1.4767. 1.4679-</td><td> 1.5082. 1.4973-</td><td> 1.5082. 1.4839.</td>

<td> Raffinate solution</td><td> 1.4282.....</td><td> 1.4340.....</td><td> 1.4400-........</td><td> 1.4280.........</td><td> 1.4288........</td><td></td><td></td><td></td><td></td>

<td> Pure dihipnt</td><td> 1.3890.....</td><td> 1.3980.........</td><td> 1.3980. —_</td><td> 1.3980........</td><td> 1 3QR0</td><td></td><td></td><td></td><td></td>

<td> Specific Dispersion: Reed</td><td> 2R4</td><td> 22«</td><td> 271</td><td> 271</td><td> 550 δ.</td><td> 129____</td><td> 129—</td><td> 129</td><td> 129.</td>

<td> Raffinate</td><td> 247</td><td> 230</td><td> 266</td><td> 234</td><td> 327</td><td rowspan="2"> 129-___</td><td> 122___</td><td> 124</td><td rowspan="2"> 108.</td>

<td rowspan="3"> Weight per cent cracking products. Aromatic removal, weight per cent: On hd²⁰_______- - On actual weight,,. Specific Gravity: Raffinate</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td> 11.2....... 11 5</td><td> 2.7,.......— 4.0</td><td> 4.1___________</td><td> 31.5-.,-________</td><td> 52.0............... 56 0</td><td></td><td></td><td></td><td></td>

<td></td><td></td><td></td><td></td><td></td><td> 0.855..</td><td> 0.855..</td><td> 0.912</td><td> 0.912.</td>

<td> Feed</td><td></td><td></td><td></td><td></td><td></td><td rowspan="2"> 0.848,,</td><td rowspan="2"> 0.828..</td><td> 0.898</td><td rowspan="2"> 0.876.</td>

<td></td><td></td><td></td><td></td><td></td><td></td><td></td>

S. A. E. 20 grade oil from Mid-Continent crude oil.

Reaction mixture derived from Tun 10.

Contains 10% benzene.

&lt; Cooled to room temp. (70-75° F.) to separate phases.

⁸ Calculated.

Runs 4, 5 and 6 were conducted upon j 2-methylnaphthalene as the charging stock. In run 4, where n-heptane was the diluent, considerable chemical condensation occurred, as will be evident from the data concerning aromatic removal presented in the table. In run 4, the 0 molecular weights of the aromatic hydrocarbons in the feed, raffinate and extract phases, respectively, were 142, 175 and 317. The molecular weight of the extracted aromatic hydrocarbon mixture indicates that it contains a considerable ^{5 6}proportion of a dimer derived from the methylnaphthalene charging stock and also some higher molecular weight condensation products.

A comparison Of run 4 with run 2, which was 7 carried out under identical operating conditions, shows that intermolecular chemical condensation is characteristic of dicyclic aromatic hydrocarbons and not of monocyclic aromatic hydrocarbons. 7 spect to the cracking of paraffin hydrocarbons.

Run 6 like run 4 shows that intermolecular chemical condensation of an HF-insoluble polycyclic aromatic hydrocarbon can be readily effected in the presence of a saturated hydrocarbon having a relatively long chain which, as run 7 demonstrates, would undergo extensive cracking in the absence of polycyclic aromatic hydrocarbon. A comparison of run 6 with run 4 shows that a shorter contact time can be balanced or even overbalanced by the use of a larger amount of HF to effect the intermolecular condensation. Shortening the time in rim 6 to Ve of that in run 4 but increasing the amount of hydrogen fluoride by 10-fold under otherwise similar operating conditions resulted in more extensive conversion and extraction in run 6 than were obtained in run 4.

The following is an analysis of the cracked products obtained from run 7.

Run 7

Product

Weight Per Cent on Charge methane_______ ethane._______ propane_______.

isobutane______ mbutane_______ isopentane_____ n-pentane____

Ce—400° F— HF.-soluble oil.

61.4

It will be noted that although in run 7 extensive cracking of the cetane occurred, substantially no cracking occurred in run 6.

The charging stock in run No. 8 was hydroformer bottoms containing hydrocarbons boiling from 332° F. to about 800° F. This run indicates that about 11 per cent of the total hydroformer bottoms was extracted by liquid hydrogen fluoride at about room temperature. Since the raffinate phase derived from run 8 has a considerably lower refractive index than the charging stock, this indicates that polycyclic aromatic hydrocarbons more highly condensed than naph-. thalene are being removed as a solution in the liquid hydrogen fluoride. In order to study this phenomenon further the hydroformer bottoms · was divided into two distillate fractions boiling, respectively, in the range 332 to 495° F. and 495 to 600° F. and a residual fraction boiling from 600° F. to the end boiling point of the hydroformer bottoms. The n-heptane diluent of runs 9-12, inclusive, contained about 10 volume per cent of benzene.

Runs 9 and 10 indicate that fractions of the hydroformer bottoms comprising predominantly dicyclic aromatic hydrocarbons, specifically naphthalene and alkylnaphthalenes, do not dissolve appreciably in liquid hydrogen fluoride at moderate temperatures. The amount of aromatics extracted in run 12 from the highest boiling fraction of the hydroformer bottoms is in sharp contrast to the amounts of extract obtained in runs 9 and 10. The high degree of extraction obtained in run 12 is explainable on the basis that the fraction of hydroformer bottoms employed as the charging stock in that run contained substantial quantities of tricyclic quinonoid-type aromatic hydrocarbons such as anthracene and alkyl anthracenes.

However, an HF-insoluble fraction containing naphthalenes can be subjected to high temperature intermolecular condensation in the presence of HF, as in run 11, thereby producing HFsoluble polynuclear aromatic hydrocarbons. A comparison of run 11 with run 4 indicates that it is desirable to employ higher temperatures than ¹212° F., since at higher temperatures the intermolecular condensation reaction proceeds at a far greater rate. Run 11 also shows that by the process of this invention it is possible to separate HF-insoluble polycyclic aromatic hydrocarbons from HF-insoluble monocyclic aromatic hydrocarbons, providing the latter are not present in quantity sufficient to prevent ’intermolecular chemical condensation of the former.

Run 13 shows that liquid hydrogen fluoride does not extract an appreciable proportion of hydrocarbons from a heavy oil. The identical specific on both feed and raffinate indicates that no extraction oil such as furnace dispersion obtained obtained in run 13 of aromatic hydro10 carbons has occurred. However, at elevated temperatures in the presence of HF, as in run 14, there is an indication that an intermolecular condensation reaction of the dicyclic aromatic hydrocarbons occurs with resultant increase in the amount of hydrocarbons passing into solutionin the liquid hydrogen fluoride. . The operation of run 14 is of a type which would be useful in producing a burner fuel of superior burning qualities or a Diesel fuel of improved cetane number.

Runs 15 and 16, relating to the treatment of a lubricating oil stock parallel runs 13 and 14, respectively. In run 15 the treatment of hydrogen fluoride at room temperature resulted in a limited degree of dearomatization, presumably by the extraction of quononoid-type polycyclic aromatic hydrocarbons. At the higher temperature employed in run 16 a markedly higher degree of aromatic hydrocarbon extraction was obtained because of the condensation of dicyclic aromatic hydrocarbons to HF-soluble polycyclic aromatic hydrocarbons.

The intermolecular chemical condensation of alkyl naphthalenes in the presence of a catalyst consisting essentially of liquid hydrogen fluoride is being claimed in my copending application Serial No. 135,166, filed December 27, 1949.