US2501064A - Separation of aromatic and sulfur compounds - Google Patents

Description

March 21, 1950 A. P. LIEN ET AL SEPARATION OF' AROMATIC AND SULFURv COMPOUNDS Filed July 2, 1946 WNY y UT.

Patented Mar. 21, 1950 SEPARATION OF ROMATIC AND SULFUR COMPOUNDS Arthur P. Lien, Hammond, Ind., :and Bernard L. Evering, Chicago, Ill., assgnors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application July 2, 1946, vSerial No. 681,121

This invention relates to a process for separately vrecovering aromatic hydrocarbons and sulfur compounds from hydrocarbon oils. .More particularly, it relates to a process for treating solutions comprising aromatic hydrocarbon and sulfur compounds with liquid HF-BF3 mixtures and thereafter recovering separate fractions containing I-IF-BFa, aromatic hydrocarbons and sulfur compounds, respectively.

It is known A.that liquid HF-BFa mixtures are solvents for aromatic hydrocarbons and sulfur compounds contained in various hydrocarbon mixtures, for example, in various petroleum fractions Wherein they are found in admixture with paraiilnic and naphthenic hydrocarbons. The extraction of vthe aromatic hydrocarbons and s111- fur compounds by liquid HF-BFs may be accompanied by more or less catalytic cracking, isomerization of paraiiin hydrocarbons, alkylation or other reactions, depending on the operating conditions such as temperature, ratio of hydrocarbon charging stock to the HF-BFa, the concentration of BFS in the HF, etc. The primary purpose of the process of treating a hydrocarbon mixture containing aromatic hydrocarbons and sulfur compounds may, in fact, be to eifect a chemical conversion of the hydrocarbon charging stock under the catalytic influence of HF-BFs mixtures, 4and the extraction of aromatic hydrocarbons and sulfur compounds by liquid HF-BFs mixtures may be incidental Ato said conversion.

One object of our invention is to provide a process for the separate recovery of Varomatic hydrocarbons and sulfur compounds from ymaterials containing the same, for example, petroleum hydrocarbon mixtures such as crude oil, lubricating oil fractions, gas oil, gasoline, naphthas and vthe like, or from coal tar fractions. Another object of our invention is to provide a process for the preferential dissociation of co-ordination compounds vof aromatic hy'drocarbons-BFx-.HF in the rpresence -of .co-.ordination compounds of .sulfur compounds-HF-.BF3- An Aadditional*object of .our invention ris to provide a process lfor the separation of .boron fluoride from .co-ordination compounds thereof with aromatic hydrocarbons and sulfur compounds. .Further objects of our invention will become apparent :from the ensuing description fthereo'f, read :in conjunction with the accompanying schematic-flow diagram.

We have discovered a novel process for the liberation `of aromatic hydrocarbons ifi-'om solu tions thereof 'in 'liquid .hydrogen iiiuoride-:boron Afluoride mixtures which lalso .contain .sulfur com- 12 Claims. (Cl. 19E-13) pounds. We have alsordiscoveredfa process :for the 55 separate recovery of aromatic hydrocarbons and organic sulfur compounds from solutions thereof in `liquid hydrogen fluoride-boron fluoride mixtures, preferably mixtures containing a minor proportion of boron uoride betWeenabout 1 and about 40 Weight per cent, based on the weight ofhydrogen fluoride.

Solutions of `aromatic hydrocarbons in .liquid HF-BFs have heretofore 'been prepared and it has been proposed to liberate aromatic hydrocarbons therefrom by distilling HF .and BFs from said solutions at a .10W temperature, for example, about 19 C., as set forthin ILS. Patentf2,343,84'1 of R. E. Burk. However, .it has `not heretofore beenappreciated that aromatichydrocarbons and organic sulfur compounds .could be separately regenerated .from their joint solution in -liquid HF-BEs.

.In the interests of .simplifying the nomenclature .used herein, We refer to solutions of aromatic hydrocarbons .and organic sulfur compounds in liquid I-IF-BF3, although we appreciate the fact .that these are not simple solutions in the ordinary sense vof the term. Rather, it appears that BFs or BFa and HF .unite chemically in the so-called solutions with aromatichydrocarbons and organic sulfur compounds to produce co-ordination compounds i. e., more or less stable .chemical compounds sometimes known as complexes and theseco-ordination compounds are soluble vin 4the HF component of the solution, which is present in excess. Free HFis present in the solutions and preferably also some free BFS. K

We have discovered that co-ordination compounds of aromatic hydrocarbons with BF3 and HFcan generally be more readily dissociatedthan co-ordination compounds of organic sulfur com lpounds with BF3 and HF. When the aromatic hydrocarbon co-ordination compounds are heated to temperatures between about 100 F. and about 200 F., preferably .between about 120 F. and about 160 F. appreciable dissociation occurs, resulting in the liberation of free HF and 'BFS on the one hand, and aromatic hydrocarbons on the other. In a preferred form of our invention, dissociation of the aromatic hydrocarbon co-ordination compoundsis effected with simultaneous Vaporization-of HF and BFS and .their removal from the dissociationvzone at about the .rate at which they are formed, tending thus to increase .the degree of `completion of .the dissociation reaction. The dissociation of the aromatic hydrocarbon coordination compounds can be effected at superatmospheric pressures, le. g., .between about 5 and .about -100 p. s. i., but it is preferable to .con-

3 duct the dissociation and distillation of HF and BFa at atmospheric pressure or even at subatmospheric pressures between about 0.2 and about 10 p. s. i. absolute.

'Ihe removal of HF and BF3 accompanying dissociation of the aromatic hydrocarbon co-ordination compounds is also very important for the reason that, as these uorides are removed, free aromatic hydrocarbons separate from the solu tion and can be recovered, preferably in a zone separate from the dissociation zone by gravity separation methods, e. g., settling, decantation, or centrifuging. Simultaneously, a stratum of higher specific gravity than the aromatic hydrocarbons separates from the solution which has been substantially denuded of HF and BFs. The

relatively higher specific gravity stratum consists l of co-ordination compounds of organic sulfur compounds with BFa and HF and may contain a small proportion of free HF and BFS.

We have found that the co-ordination compounds of sulfur compounds referred to above are more resistant to dissociation than the co-ordination compounds of aromatic hydrocarbons and that a higher temperature is therefore necessary to liberate BFg and HF from said co-or dination compounds of organic sulfur compounds. Specifically we have found that temperatures in the general range of about 160 F. to about 500 F. are necessary to dissociate said co-ordination compounds of the organic sulfur compounds, and preferred temperatures are between about 200 F. and about 400 F. The dissociation of the coordination compounds of organic sulfur compounds can be effected under a super-atmospheric pressure, for example, between about 5 and about 100 p. s. i., but is preferably conducted at substantially atmospheric pressure or even at subatmospheric pressures, with removal of free HF and BFa from the dissociation zone at substantially the rate at which they are evolved. Inert gases may be passed through the zones wherein co-ordination compounds of aromatic hydrocarbons or sulfur compounds are being dissociated in order to facilitate stripping of HF and BFs from said zones. Suitable inert gases include carbon dioxide, nitrogen, methane, ethane, propane and the like.

Our process finds its preferred application to light gas oil and lower boiling hydrocarbon oils. In general, We have found that the lighter the feed stock, the greater the degree of selectivity of separation of sulfur compounds and aromatic hy* drocarbons.

In order to illustrate, but not to limit, our invention reference is made to the accompanying schematic flow diagram which depicts one embodiment of our process. The charging stock can be any liquid hydrocarbon mixture containing aromatic hydrocarbons and organic sulfur compounds. The charging stock may be, for example, a petroleum gas oil containing aromatic hydrocarbons and organic sulfur compounds, or a distillate or residual lubricating oil fraction. It should preferably be in a substantially anhydrous condition. Predrying of the charging stock can be effected by conventional processes for drying hydrocarbon oils, as by percolation through a bed of adsorptive alumina or silica gel, or may be effected by contacting the charging stock with an aqueous HF-BF3 mixture, e. g., aqueous HF-BFs produced in the process because of the gradual accumulation of water in the reaction system even when a pre-dried charging stock is employed.

It is desirable to reduce the viscosity of viscous charging stocks by dilution thereof with a suitable amount of a light parainic hydrocarbon, e. g., pentane, hexane or a paraflinic gasoline or naphtha fraction. The low boiling parafhnic diluents serve not only to reduce the viscosity of the charging stock, thereby facilitating contacting operations, but also aid in the recovery of HF from the treated charging stock, as will be explained hereinafter.

The charging stock is introduced from source I0 by pump il through. line 52, heater i3 and line lll to a low point in contacting vessel l5. Make-up HF and BFS are introduced into line Il! through line il although a portion may be introduced through line l E. Generally speaking we prefer to employ liquid HF-BF3 mixtures which are substantially anhydrous or which contain only a trace of water, i. e., an amount of the order of 0.01 to l weight per cent and in any case not more than about 3 weight per cent. 'v'v'e prefer to employ mixtures containing between about l and about l0 weight per cent of boron fluoride based on the weight of hydrogen fluoride, although we may employ solutions wherein the weight of boron fluoride is in excess of the weight of hydrogen fluoride. In contactor I5, which is preferably provided with suitable means of agitation (not shown) the hydrocarbon charging stock is treated under controlled conditions of time, pressure, temperature and ratio of charging stock to HF-BFs. The contacting operation may involve simply the extraction of aromatic hydrocarbons and sulfur compounds from the charging stock or it may involve chemical conversion of the charging stock as a principal or incidental proc ess, the operating conditions being suitably adjusted to effect the desired purpose.

For example, extraction of aromatic hydrocarbons and organic sulfur compounds from hydrocarbon fractions containing the same, for ex ample, petroleum or coal tar fractions may be effected at temperatures between about -30 F. and about 200 F., preferably at temperatures between about 65 F. and about 85 F. The pressure in contactor l5 is ordinarily adjusted to maintain the charging stock and a substantial proportion of the HF-BFx in the liquid phase. We prefer to employ BF3 in an amount sufficient to exert a positive partial pressure, e. g., 5 to 200 p. s. i. g. The existence of a positive partial pressure of B Fs in the contacting zone indicates that BFa is present in an amount in excess of that which is necessary to combine with aromatic and sulfur compounds in the charging stock. Between about 5 and about 300 volume per cent of the liquid HF-BFs mixture or even more may be used, based on the volume of hydrocarbon charging stock although, generally, amounts between about l0 and about 100 volume per cent are employed.

A portion of the sulfur compounds in the charging stock can be converted to HzS by charging hydrogen, also, to contactor l5. A hydrogen partial pressure between about 50 and 3,000 p. s. i. g., preferably about 200 to about 2,000 p. s. i., may be employed. Increased hydrogenation may be effected by employing a nickel liner in contactor I5. When hydrogen is employed, we prefer to use temperatures between about 150 F. and about 500 F., preferably about 250 F. to about 400 F.

If a hydrocarbon charging stock such as gas oil containing both aromatic hydrocarbons and organic sulfur compounds is to be cracked in contactor l5, temperatures between about F.

and about '400th may befemployed. l Usually a temperature-'of theorder of about 2122.1. is suitable, preferred temperatures ranging between about 180'* F'. and about 300 F. They pressurein the contacting zonewill be adjusted'to maintain substantially yliquid phase conversion conditions. At a. temperature of about 212 F. ythe pressure may be of theiorder of400 p. s. i. g. The charging stock 'is caused to -pass upwardly through aliquid column of catalyst in the contacting zone at a space velocity which may be about 1 volume of charging stock per hour per volume of catalyst in the reactor, although space velocities between about 0.2 and about-4 may be used. The cra-cking catalyst comprises liquid HF-BFa mixtureswhich may contain between about 1 and about 40 per cent by weight of BFa based on'the HF.

It should be understood that the ratio of catalyst to charging stock in the cracking process mayvary depending upon the Atype of charging stock YAand the operating conditions which it is desired `to employ in contacting zone l5. Generally speaking larger amounts of catalyst are required .with charging stocks of more refractory character, ire., stocks more decient in hydrogen and richer in aromatic hydrocarbons, and lesser amounts of catalystare required with relatively clean or more highly parainic charging stocks.

The weight ratio of hydrocarbon to catalyst introduced into the reactor may thus vary from about :1 to 1:2.

Contacting-maybe effected in any suitable type of contactor von a batchwise, multiple batch, semi-continuous or continuous basis but we prefer to employ a continuous process with a tower type contactor and to pass the charging stock upwardly through a column of the liquid I-IF-BFs mixture with or without mechanical agitation. We may use concurrent or countercurrent contacting. The contactor may be of the type described in Ups. Letters Patent'No. 2,238,802 and No.'2,349,821. It may be'about 5 to 50 feet high and should be designed to withstand a maximum operating pressure which, with high temperatures-may -be as much as 1000 p. s. i. g. or more. Beforecontacting is initiated the contactor may be filled about 1/2 to full of the liquid HFLBFS and its temperature may be adjusted as desired byconventional means. The bulk of the fluoride y solution separates from the eiuent product stream in the upper part of the contactor although some of the :fluoride solution is carried with the eluent product stream through line I9 and cooler` to separator 2 l. Fluoride material K whichsettles 'out' in this settler-or separator can berreturne'd by lines 23 "and 24 to contactor I5, a `pump 22 being lemployed Awhen separator 2| is loperated at a vpressure below the reactor pressure or if the settler is not elevated sufciently to insure gravity return.

Boron fluoride together with a small amount of 'fixed gases which may be produced can be vented from the top of separator 2| through line 25 and passed through line 26 which leads to the base of absorber 21. The remaining liquid product'stream'flows over'weir 28 and passes by line 29 to BFa stripper 30 which is provided with a suitable reheating means or reboiler 3| at its base. Line 29 may be providedwith a suitable pressure reducing valve or pump depending upon therelative pressuresfinseparator 2| and stripper 3Ilrespectively VThe stripper vmay operate at a rpressure 'of'about 200 -or 300 prs. i., for example insure the removal of substantiallyall of the BF; which passesby line 32compressor 33 (if neces-. sary), and line 2S to the base of absorber 21. Make-,up BFa can be supplied from source 34 and introduced into the contacting system by compressor 35 to line 26.

.After vremoval of BFs, the product stream passes `byline 36 to azeotropic distillation still 31 which is provided with a suitable reheating means or reboiler 31 at its base and which may be provided with reflux means at its top. In the azeotropic still the HF is distilled with a. light parain hydrocarbon such as propane, butane, pentane, etc. which may have been introduced with the charging stock to serve also as a Viscosity-reducing diluent, or may be introduced into the still from source 4| and valved line 42r through settler d3, line t6 and reilux pump 41. In the operation of the azeotropic still, a butane-HF azeotrope, -for example, passes overhead through line 38, condenser 39 and lines 4U and 42 to settler 43, which is operated at as low a temperature as can be obtained with available cooling water, preferably well below 100 F. The condensed azeotrope separatesv into a heavier HF stratum which is withdrawn by line 44 to HF storage tank 45. The upper butane stratum is returned by line 00 and pump 41 to still 31 and may eventually leave the still with the product stream through line 49. Light gases may be vented from settler 43 through valved line 48; such gases should contain no BFs, but if they do, they can be introduced through line 2B to absorber 21.

The product stream is .withdrawn from the base of the azeotropic still 31 through line 49. The product stream is usually substantially free from organic iiuorides and hence may require no special treatment for their removal. Conventional bauxite or equivalent treating system l is preferably employed at this point, however, to remove any traces of iluorides which may be present. The product stream leaves the fluoride removal zone by line 5| and may, if desired, be subjected to further nishing treatments as may, in the specic case, be required or desirable, such as fractional distillation, washing, contacting with active absorbent clay or the like.

It should be understood that we are not re stricted to azeotropic distillation for the purpose of removing HF from the products. Ordinary or flash distillation may be used for this purpose.

A solution of BFS, aromatic hydrocarbons and sulfur compounds in liquid-HE' is withdrawn from contacter l5 through line 512 or from settler 2| through lines 23 and 53 and passed through pressure reducing valve 5d to a recovery drum 55 which is preferably operated near atmospheric pressure, for example, at about 5 to about 50 lbs. gauge pressure and at a temperature between about and about 200 F., preferably between about and about 160 F. Under these conditions cri-ordination compounds of aromatic hydrocarbons and BFa are dissociated and free HF and BF3 are vaporized and passed overhead through line 50. This mixed eiiluent may pass directly through condenser 51 to receiver 58, where HF is collected as a liquid and from which BFS -may be flashed overhead through line di) to line i8. Liquid HF may be pumped from receiver 5S through line 50 and pump 0| to HF storage tank- 45, provided with a valved vent line 4'5". There is a tendency for moisture to Vaccumulate in the system even when substantially dry charging stocks are employed because of .the

extremely hygroscopic nature of HF and BFa; to remove moisture from these luorides it is desirable, from time to time, to introduce the effluent rom line 56 through valved line 62 into distillation column 63 provided with heating means 64. In distillation column 63, substantially anhydrous HF and BFa are vaporized and pass overhead through line 65 and condenser` 51 to receiver 58. A portion of the condensate in receiver 58 is returned through line 66 to serve as reflux in distillation column 63. Aqueous HF-BFg may be withdrawn from the base of column E3 through line 61 and treated by known methods for the recovery of the fluoride components. A portion of the aqueous HF-BFB may be used to pre-dry the charging stock to the process.

l Heating of the materials in drum 55 results in dissociation of the BF2-HF aromatic hydrocarbon co-ordination compounds or complexes and distillation of HF and BFS, whereby the aromatic hydrocarbons are thrown out of solution. The residue in drum 55, comprising aromatic hydrocarbons and sulfur compound co-ordination compounds, is withdrawn through line 63 to settler 69 wherein an upper stratum of aromatic hydrocarbons is formed and can be recovered from the lower stratum of sulfur-containing coordination compounds and is removed by line 'Ill for such further treatment as may be required or desirable, e. g., washing with water or alkaline solutions such as ammonia, contacting with adsorbent clays or bauxite and fractional distillation into fractions of desired boiling range. The

aromatic hydrocarbons recovered by the process of our invention may be used in the preparation of high solvency naphthas or valuable materials for organic synthesis.

The complex material which settles out in settler 69 is withdrawn through valved line 1| to recovery drum l2 which is provided with heating means 13. This drum is operated, preferably at about atmospheric pressure, although higher pressures of the order of about 5 to about 50 lbs.

per square inch may be used, and at temperatures between about 160 F. and 500 F., preferably between about 250 F. and about 350 F. Under these conditions co-ordination compounds of BFa-HF-sulfur compounds are dissociated and free HF and BFs are vaporized and passed overhead through line I8, compressor 'M and line I8 into absorber 21 or through line M into contactor l5. It is preferably to pass the effluents of line I8 to absorber 21, this arrangement offering the advantages of providing better control of the amount and composition of the HF-BFS mixture entering contactor I5 and the possible elimination of compressor 14.

A concentrate of organic sulfur compounds is withdrawn from drum 'l2 through line 'l5 and may be subjected to such finishing treatments as are required or desirable, e. g., washing with ammonia or aqueous allralies, fractional distillation and the like. The organic sulfur compounds can be adapted to various uses such as manufacture of extreme pressure agents for lubricating oils and greases, oxidation to sulionic acids or other organic syntheses.

Further purification and concentration of the aromatic hydrocarbons and sulfur compounds withdrawn respectively through lines 'lll and 15 can be effected by subjecting them, separately, to repeated extraction with liquid HF-BFs mixtures containing, preferably, between about 1 and about 40 weight per cent of BFs based on the HF.

These treating operations may be effected in contactors of the type of contacter I5; the apparatus used for re-treating may, in fact, essentially du plicate the contacting, settling and fractionation equipment described for use in the main treating operation. The re-treating operations may be carried to a suiiicient length to obtain essentially pure aromatic hydrocarbons free from organic sulfur compounds and organic sulfur compounds substantially free of aromatic hydrocarbons.

In our studies of the desulfurization of hydrocarbon oils containing aromatic hydrocarbons and organic sulfur compounds, we have observed that BFa or liquid HF-BFc mixtures extract appreciable quantities of sulfur compounds before the extraction of aromatic hydrocarbons is initiated. The extraction of aromatic hydrocarbons from the feed stock begins only after variable proportions of the organic sulfur compounds have been extracted, depending on the boiling range of the charging stock. For example, in the extraction of 750 cc. of furnace oil from Slaughter crude oil, containing 1.46 weight per cent of sulfur in the form of organic sulfur compounds in sequence with a solvent consisting of l() grams of liquid HF and with 34 grams of RFB-10 grams of HF for 1/2 hour at 70-74" F. under a pressure of 25 p. s. i. g., we have observed that "I2 weight per cent of the sulfur was removed but that this degree of sulfur removal was accompanied by only a slight change in refractive index (from nD2 of 1.4771 to 1.4680) and specic dispersion (from 129 to 124) indicating that substantially no aromatic hydrocarbons had been extracted from the feed stock. However', above this level of sulfur compound extraction, aro matic hydrocarbons were being extracted in rapidly increasing quantity as evidenced by a rapid drop in the specific dispersion of the refined oil.

We have also extracted a heavy naphtha containing 0.39 weight per cent of sulfur in the form of organic sulfur compounds with 50 cc. of HF and 10 grams of BFs per liter of naphtha for one hour at about F., followed by a gravity separation of a hydrogen fluoride solution (extract phase) and a lower specific gravity stratum refined naphtha or raflinate phase). It was observed in this experiment that although 94 weight per cent of the sulfur was extracted from the naphtha, the specific dispersion of the naphtha remained unchanged at a value of 116, indicating that no aromatic hydrocarbons were extracted from the naphtha. However,` under conditions leading to more thoroughgoing extraction of the organic sulfur compounds from the naphtha we have found that aromatic hydrocarbons are simultaneously extracted with the organic sulfur compounds.

It is thus possible, by careful control of the quantity of HF-BFs to extract substantially all the organic sulfur compounds from solutions with aromatic hydrocarbons, preferably by multiple batch extractions.

We have also observed that liquid, substantially anhydrous HF exhibits different solvent properties from BF3 solutions in .liquid HF. Whereas liquid HF-BF3 mixtures exhibit a pronounced capacity to dissolve and extract aromatic hydrocarbons of the most diverse types, e. g., monoor polynuclear aromatics and benzenoid- (e. g., phenanthrene) or quinonoid type (e. g., anthracene) aromatic hydrocarbons, liquid HF alone is much more selective in its action and extr cts little or no mononuclear aromatic hydrocarbons or benzenoid type polynuclear aromatic hydrocarbons while exhibiting a marked solvent power towards quinonoid-type' poly-- nuclear aromatic hydrocarbons such as anthracene. However, liquid. HF, like BFS solutions in liquid HF, is a good solvent for organic sulfur compounds.

We have noted that hydrocarbon charging stocks containing organic sulfur compoundscan be practically desulurized by treating with HF vapor. The sulfur compounds and some polynuclear aromatic hydrocarbons in the charging stock react with some of theHF forming a complex which is insoluble in the oil and the complex can be gravity separated as a liquid along with dissolved HF.

Thus, it is possible to treat mixtures of organic sulfur compounds and aromatic hydrocarbone of the type which are not markedly sol'- uble in liquid HTF with liquid HF in an amount sulicient to extract a substantial proportion of the sulfur compounds, preferably by multiple batch extraction, in order to obtain sulfur-free aromatic hydrocarbons on the one hand and organic sulfur compounds substantially free of aromatic hydrocarbons on the other.

Make-up HF can be added to the system from source 'iii to storage tank d5. Hydrogen iluoride is pumped from this storage tank by pump 'il .s

and passed by line lt to the upper part of absorber 2l which may be operated at a pressure between about 50 and about 400 p. s i. or higher, e. g., about 250 p. s. i. At such pressures and at a relatively low temperature of the order of about 100 F. the BFS is absorbed in the HF but hydrocarbon gases are not absorbed therein and may be vented from the top of the absorber through valved line l5. By this means losses of BFS are substantially prevented iwhile the system is being purged of methane or other light gases which may tend to accumulate in the system as the result of cracking or other reactions. It should be understood that make-up HF `can be introduced directly into the top of the absorber and that line Sil and/or 50 may likewise lead to the absorber rather than to an HF storage tank.

Our invention is not limited to the use oi HF as an absorbent for BFS since any other selective absorbent liquid may be employed. An intimate liquid mixture or solution of HF and an aromatic hydrocarbon (particularly an alkyl aromatic hydrocarbon containing I to il carbon atoms per molecule) is particularly advantageous because BFS reacts wi i such mixture to form a complex which is soluble in liquid HF. Thus, we may introduce such alkyl aromatics (for example a portion of the aromatic hydrocarbons from line 10) into the upper part of .the absorber through line 80' and we may obtain an intimate mixture of such aromatics and l-IF'either by the manner in which these liquids are introduced into the absorber tower or by the use of mechanical means. Any BFS which is not absorbed in the HF in the lower part of the absorber will thus be chemically combined with the HF-aromatic mixture at the top of the absorber so that practically no BFS will leave the top of the tower with extraneous gases even when the absorber is operated at pressures as low as atmospheric pressures. By this method of operation we may avoid the necessity of employing compressors 33 and it and like-- Wise avoid the necessity of operating drum l2 at the higher temperatures and pressures which would be required for the introduction of liberated HFaud BFS intov a high pressure absorber.v

When liquid HF alone is used to absorb the BFS, the resulting solution is passed into contactor t5 through valved line il and line I4. When appreciable quantities of aromatic hydrocarbons are employed in absorber 2i to aid in the absorption oi BFs, it is preferable to pass all or a substantial proportion of the resulting solution through line iland valved line 8 l ,thence through pressure reducing valve 54 into recovery drum 55 in order to separate aromatic hydrocarbons from the iiuoride components prior to the introduction of. the latter into contactor I5.

Although in referring to the accompanying schematic Aflow diagram we have described a process wherein HF and BFS are used together, it should be understood that our invention is not thus limited. Although aromatics whose nor.- mal boiling points are below 600 F. are not appreciably soluble at ambient` temperatures in liquid hydrogen uoridesome of the aromatics having boiling points above 600 F. are appreciably soluble at ambient temperatures in liquid hydrogen fluoride. Thus in the case of a charging stockV thaty contains HF-soluble high boiling aromatics, it is possible, if desired, to take advantage of the peculiar solvent powers of liquid, substantially anhydrous` HF. Using HF alone as the lsolvent it is not possible, however, to separately recover aromatic hydrocarbons and sulfur cornpounds from their solution in the hydrogen uoride. However, HF alone could be used in the operation of contactor i5 following which a hydrogen fluoride extract. phasel withdrawn throughk their different thermal stabilities, as pointed out above. Conversely the charging stock can rst be contacted with BFa alone in contactor I5, following which a BFS-containing phase is witndrawn through. line 52 and can be treated in a separate zone (not shown) with liquid HF to produce a solution which is passed into recovery drum 55 in order tor institute operations for the recovery of the components of the solution.

The following examples are adduced in order to illustrate, but not unduly to limit, the results obtainable by the process of our invention.

EXAMPLE I In order to demonstrate the effect of BFS-HF mixture as a desulfurizing agent, a sampley or" Mid-Continent virgin gas oil containing 0.12 per cent sulfur was treated in two steps (A and B) as shown in the following table:

Upon completion of step A, a 445 g. sample of raiinate was withdrawnv for analysis, following which 414 additional grams of charging stock were added to the remaining reactor contents together with 47 grams of BFs. Contacting in both steps was effected in a 1570 cc. carbon steel bomb fitted with a 1725 R, P. M. stirrer and a bleed-olf tube terminating at a point well above the liquid level of the liquid HF solution, allowing ready removal of supernatant raffinate. Upon completion of the second step, the rainate and HF phases were separated by settling and were treated as pointed out below.

It was noted that the amount of BFs required to give a positive pressure on the reactor in these runs was several times that required for ordinary parainic charging stocks. This observation, coupled with the fact that in the two runs a total of 85 grams of BFS remained bound in the catalyst phase, indicates the formation of BF?. complexes. The fact that only 2.5 grams of BF; would be consumed by reacting mol for mol with the sulfur present indicates the formation of a BFs-aromatic hydrocarbon complex; this is further borne out by the analysis shown below, as well as discussed more fully hereinafter.

The catalyst layer (HF phase) (611 g.) from the above runs was subjected to dissociative distillation at 190 F. to remove HFBF3. comparatively low temperature, 68 g. of BFs distilled and were collected, indicating that the BFS- aromatic complex, is a rather loosely-held addition compound. Most of the HF originally added to the reactor also distilled over at temperatures below 190 F., along with some organic material. Upon removal of a substantial proportion of the free HF and BFS by distillation, the catalyst layer separated upon standing into a supernatant aromatic hydrocarbon stratum and a lower stratum comprising principally co-ordination compounds of BFa-HF-organic sulfur compounds.

The following tabulation presents a comparison of the charging stock and the products produced in each step.

The hydrocarbon product (rainate) from the above runs was water-white as compared to the straw-colored feed. As shown in the above table the sulfur content was reduced to zero indicating that the HF-BFs medium is a very eiiicient agent for extraction of sulfur from hydrocarbons, either at or 120 F. The process appears to take place through the formation of an addition complex between sulfur compounds and BFa, followed by solution of this complex in the liquid HF phase.

Of considerable interest is the fact that substantial quantities of aromatics have been removed from the original gas oil and that the resultant product is highly parainic as shown by specific dispersions, refractive indices and specic gravities. Corresponding to disappearance of aromatics from the upper hydrocarbon phase is the fact that the catalyst phase increased substantially in volume and that the hydrocarbon obtained from the catalyst layer in the manner described below is very highly, if not completely, aromatic as shown by the physical properties listed in the above table.

The residue remaining after dissociation of At this 12 aromatic-co-ordination compounds and distillation of excess HF and BFs consisted of two distinct layers. The upper layer, light in color, proved to be highly aromatic as previously mentioned. The bottom layer was quite dark and viscous, apparently consisting of an organically bound BFa-sulfur compound complex. Heating this complex to 358 F. resulted in the liberation of 10 g. BFs, which, together with the 68 g. recovered on the original heating at F., gives a total recovery of 78 g. as compared to the 85 g. which disappeared into the catalyst during the two runs (the remainder of BFs was bled out with the gases leaving the reactor).

EXAMPLE II A transformer distillate from Winkler crude oil, which distillate contained 1.54 per cent sulfur, was treated in sequence at 50 F. with varying amounts of BFa as shown in the following table. The same reactor was used as in Example I.

Treatment of Winkler transformer distillate with H F-BFs Conditions C D In run C just enough BFs was added to provide one mol of BF: per mol of sulfur in the feed. The 21 g. of BF: thus added was completely absorbed, leaving no pressure on the reactor and liberating no BFa on bleeding out the product. As shown in the following table the raffinate (product) retained a substantial amount of sulfur as well as aromatics, the content of the latter being indicated by specific dispersion, refractive index and specific gravity. Upon completion of run C, a 426 g. sample of rainate was withdrawn for analysis and an additional 448 g. of distillate and 91 g. of BFs were added to the reactor to carry out run D.

In'run D, an excess of BFS was used, i. e., sufficient to give a positive pressure of 65 p. s. i. on the reactor contents when stirred at 50 F. Of the 91 g. of BFa added, only 25 g. were recovered on bleeding out the product. As shown in the table, the sulfur compound removal was good and most of the aromatics were extracted to give a substantially paramnic-naphtnenic rainate.

Approximately 300 g. of the 1088 g, of hydrocarbon treated in the two runs went into solution in the liquid HF layer. The sulfur content of this layer was 5.6 weight per cent. On heating this layer to 190 F. HF distilled o. After distillation of the material boiling up to 190 F., the residue separated by gravity into two layers. The upper layer was transparent and, as shown by the data in the table, consisted substantially of aromatic hydrocarbons. The bottom layer was a black complex which was hydrolyzed with aqueous am- -monia (on heating) to give a product with the properties listed in the last column of the following table:

1 Boiling Range, 637708 F.

It will be noted that, in both examples, the aro-, matic layer obtained contains about the same amount of sulfur as the charging stock but markedly less sulfur than that of the total extract or of the separated sulfur layer.

Having thus described our invention whatwe claim is:

1. Thev process of regenerating aromatic hydrocarbonsl from a solution of aromatic hydrocarbons and sulfur compounds in liquid HF-BFa, said solution comprising co-ordination compounds of BFs and I-IF .with aromatic hydrocarbons and organic sulfur compounds, which process comprises subjecting said solution to a dissociative distillation operation at a temperature between about 100 F. and about 200 F., separating a distillate comprising HF and BF3 from said distillation operation, separating a distillation residue comprising free aromatic hydrocarbons and HF-BFs co-ordination compounds of organic sulfur compounds, subjecting said residue to gravity separation, and separately recovering an aromatic hydrocarbon fraction and a fraction comprising co-ordination compounds of organic sulfur compounds.

2. A process of treating -a solution of aromatic hydrocarbons and sulfur compounds in liquid HF-BFa, which process comprises subjecting said solution to dissociative distillation at a temperature between about 100 F. and about 200 F., recovering a distillate comprising HF land BF3, separating a distillation residue comprising aromatic hydrocarbons and co-ordination compounds of BFs-HF-organic sulfur compounds, subjecting said residue to gravity separation and separately recovering an aromatic hydrocarbon fraction and a fraction comprising co-ordination compounds of organic sulfur compounds, and subjecting the last named fraction to dissociative distillation at a temperature between about 160 F. and about 500 F.

3. A hydrocarbon treating process which comprises contacting a hydrocarbon charging stool: containing aromatic hydrocarbons and organic sulfur compounds with liquid HF containing BFS under conditions adapted to form a solution of aromatic hydrocarbons and sulfur compounds in said liquid HF, subjecting said solution to dissociative distillation at a temperature between about 100 F. and about 200 F. and recovering as a distillate fraction a substantial proportion of I-IF and BFS therein contained, recovering a residue from said distillation and subjecting the same to gravity separation, separately recovering an aromatic hydrocarbon fr-action and a fraction of higher specific gravity comprising coordination compounds of BFa-HF-organic sulfur compounds from said gravity separation, and recycling at least a portion of said distillate fraction to said hydrocarbon treating process.

4. A hydrocarbon treating process which comprises contacting a hydrocarbon charging stock containing aromatic hydrocarbons and organic sulfur compounds with liquid HF containing BF3 under conditions adapted to form a solution of aromatic hydrocarbons and sulfur compounds in said liquid HF, subjecting said solution to disso- -ciative distillation at a temperature between about 100 F. and about 200 F. and recovering as a distillate fraction a substantial proportion of HF and BF3 therein contained, recovering a residue from said distillation and subjecting the same to gravity separation, separately recovering an aromatic hydrocarbon fraction and a fraction of higher specific gravity comprising co-ordination compounds of Blb-HF-organic sulfur compounds from said gravity separation, subjecting said fraction of higher specific gravity to dissociative distillation at a temperature between about 160 F. and about 500 F. and. separately recovering HF-BFg and organic sulfur compounds, and recycling at least a portion of the HF and BFS derived from said dissociative distillation operations to said hydrocarbon treating process.

5. A hydrocarbon treating process which comprises contacting a hydrocarbon charging stock containing components boiling above about 600 F. and containing organic sulfur compounds and aromatic hydrocarbons with liquid HF under conditions adapted to form a solution of aromatic hydrocarbons and organic sulfur compounds in said liquid HF, contacting said solution with BFs to produce a second solution, subjecting said second solution to a dissociative distillation operation at a temperature between about F. and about 200 F., separating a distillate comprising HF and BFz from said distillation operation, separating a distillation residue comprising free aromatic hydrocarbons and co-ordination compounds of organic sulfur compounds, subjecting said residue to gravity separation, and separately recovering an aromatic hydrocarbon fraction and a fraction comprising co-ordination compounds of organic sulfur compounds, subjecting the last named fraction to thermal dissociation at a temperature between about 160 F. and about 500 F. and separating a fraction comprising HF-BF3 and a fraction comprising organic sulfur compounds.

6. The process of claim 5 wherein the charging stock is a gas oil containing organic sulfur compounds and aromatic hydrocarbons.

7. The process of claim 5 wherein the charging stock is a lubricating oil containing organic sulfur compounds and aromatic hydrocarbons.

8. The process of claim 4 wherein hydrocarbon treating is effected under substantially noncracking conditions.

9. The process of claim 5 wherein the hydrocarbon treating is effected under substantially non-cracking conditions.

10. The process of claim 2 where the first named dissociative distillation is eiectedat a temperature between about F. and about F. and wherein the last named dissociative distillation step is carried out at a temperature between about 200 F. and about 400 F.

11. The process of claim 4 wherein the iirst named dissociative distillation step is carried out at a temperature between about 120 F. and about 160 F. and wherein the last named dissociative distillation step is carried out at a temperature between about 200 F. and about 400 F.

12. A hydrocarbon treating process which comprises contacting a hydrocarbon charging stock containing components boiling above about 600 F. and containing organic sulfur compounds and aromatic hydrocarbons with liquid HF under conditions adapted to form a solution of aromatic hydrocarbons and organic sulfur compounds in said liquid HF, contacting said solution with BFa to produce a second solution, subjecting said second solution to a dissociative distillation operation at a temperature between about 100 F. and about 200 F., separating a distillate comprising HF and BF3 from said distillation operation, separating a distillation residue comprising free aromatic hydrocarbons and co-ordination compounds of organic sulfur compounds, subjecting 75 said residue to gravity separation, and separately recovering an aromatic hydrocarbon fraction and a fraction comprising (zo-ordination compounds file of this patent:

UNITED STATES Pii'riaxizfrs of organic sulfur compounds. Number Name Date ARTHUR p, LIEN, 2,343,841 Burk Mar. 7, 1944 BERNARD L. EVERING. 5 2,375,675 MatuSZak May 8, 1945 2,378,762 Frey June 19, 1945 REFERENCES CITED 2,405,995 Burk Aug. 20, 1946 d 2,408,173 Matuszak Sept. 24, 1946 The iollowm,D refei ences aie of leoora 1n the 2,427,009 Lien et al Sept' g, 1947

Claims (1)

1. THE PROCESS OF REGENERATING AROMATIC HYDROCARBONS FROM A SOLUTION OF AROMATIC HYDROCARBONS AND SULFUR COMPOUNDS IN LIQUID HF-BF3, SAID SOLUTION COMPRISING CO-ORDINATION COMPOUNDS OF BF3 AND HF WITH AROMATIC HYDROCARBONS AND ORGANIC SULFUR COMPOUNDS WHICH PROCESS COMPRISES SUBJECTING SAID SOLUTION AT A DISSOCIATIVE DISTILLATION OPERATION AT A TEMPERATURE BETWEEN ABOUT 100*F. AND ABOUT 200*F., SEPARATING A DISTILLATE COMPRISING HF AND BF3 FROM SAID DISTILLATION OPERATION, SEPARATING A DISTILLATION RESIDUE COMPRISING FREE AROMATIC HYDROCARBONS

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