US2525811A - Hf conversion of hydrocarbons - Google Patents

Description

Oct. 17, 1950 A. P. LIEN HAL up couvmsxon oF HYnRocARBoNs Filed' July 1o, 1947 Patented Oct. 17, 1950 nr ooNveasioN or mnocAanoNs Arthur P. Lien, Hammond, Ind., and Bernard L. f Evcring, Chicago, Ill., assignors to Standard Oil Company, Chicago, Ill., a corporation oi' Indiana Applicatie July 1o, 1941, sensi No. ramona s claim. (ci. 19e- 52) l This invention relates to the conversion of hyand it pertains more particularly to the conversion of high boiling hydrocarbons for the production of hydrocarbons in the gasoline and/or Diesel fuel boiling range and one or more valuable tars. In its more specific aspects the invention relates to a combination process wherein cnc step involves the separation of substantially HF- insoluble polycyclic aromatic hydrocarbons such as alkyl naphthalenes from saturated hydrocarbons by a process which involves intermolecular chemical condensation of said aromatic hydrocarbons to produce HF-soluble polynuclear aromatic hydrocarbons which are extracted from said saturated hydrocarbons. The chemical condensation and the `extraction steps are performed in a medium consisting essentially of liquid anhydrous hydrogen uoride which functions as a catalyst in the chemical reaction and as a solvent in the extraction operation. Also, the invention may eliminate sulfur at the higher temperatures by splitting out HrS from the organic sulfur compounds to form unsaturated hydrocarbons, although some of the organic sulfur compounds may be simply extracted by the hydrogen fluoride. The chemical condensation per se is claimed in copending application Ser. No 135,166, filed December 27, 1949, as a continuation in part of copending application Ser. No. 760,061, which was filed on even date hereof and in which condensation by combined use of HF and BF: is claimed.

An object of the invention is to provide a method and means for improving the cracking suscep^ drocarbons by use of a hydrogen fluoride catalyst In practicing our invention we employ a multistage operation wherein the incoming charging stock is first contacted under mild operating conditions for thepurpose of condensing and/or removing chemically condensable aromatics (and sulfur compounds) as an aromatic tar in high specific gravity while effecting only a slight amount of cracking so that a gas oil is produced which is substantially free from sulfur and condensable aromatics and which contains only a small amount, preferably less than 5%, of hydrocarbons of the gasoline boiling range. The gas oil from this first stage, either before or after removal of gasoline boiling range components, is then contacted with hydrogen iiuoride under cracking conditions in a second stage to produce gas, gasoline ,(and/or Diesel fuel) and an entirely different type of tar than is produced in the first stage. A portion `of the tar from the second reaction stage may be recycled thereto for increasing gasolineyields and rate of conversion while another portion of the tar from the `second stage is separated from catalyst to yield a valuable by-product having unique drying propquired. A further object is to obtain good yields erties. These and other features of the invention will bemore clearly apparent from the following detailed description of a specific example thereof read in conjunction with the accompanying drawing which is a schematic ow diagram of a system for converting an East Texas gas oil into gas, gasoline, a valuable oleiinic tar and a tarcomprising principally condensed ring polynuclear aromatic hydrocarbons.

While any aromatic and sulfur-containing charging stock may be employed, such charging stock should preferably be higher boiling than -gasoline and the preferred charge is a gas oil or reduced crude containing chemically condensable aromatic hydrocarbons. The invention will be described as applied to the conversion of a 37 API gravity East Texas gas oil which is introduced. into thesystem from source II) by pump I I and charge line I2 to first reactor I3. Hydrogen fluoride is introduced from storage tank I4 by pump I5 and lines I6 and I2 to said iirst reactor in such amounts that the total charge entering the first reactor will contain about l0 to 200%,

`preferably 15 to 50% hydrogen fluoride by volume based on gas oil charged. Reactor I3 is maintained at a conversion or condensing temperature in the range of 200 to 375 F., preferably about 250 to 330 F. by preheating the gas oil charge or` supplying heat to the reactor in any other known manner. First reactor I3 is operated under a pressure suiiicient to maintain liquid 3 phase conversion conditions. i. e. within a range of about 250 to 1000 p.'s. i., or preferably about 500 to 800 p. s. i. The time of contact in the reactor should be relatively long, usually'within the range of about 20 to 200 minutes (the lower temperatures requiring longer Contact times); with eflicient contacting means for `securing intimate contact, the time lat 330 F. maybeabout an hour. Aromatic condensation without excessive cracking When the HF concentration is high the contact time and temperature used will be relatively, low. Conversely higher temperatures and longer contact times will be used at lower HF concentra-ftins. The conditions should 'be such as to eifect condensation of condensable aromatics and removal of sulfur so that the hydrogen-fluoride insoluble material will be chiefly a parafnic gas oil, substantially free from condensable aromatics and sulfur and containing only a small amount, preferably less than of gasoline-boilingrange hydrocarbons, including benzene and methylbenzenes. l

vThe reactor itself may be a stirred autoclave, .a packed or unpacked towerwith or without mixving orices, a circulating system of the type commonly employed for effecting sulfuric acid alkylation, or any other effective contacting means. Since no invention is claimed in the contacting means per se. it will not be described in further detail.

vThe efliuent from the first reactor is withdrawn by line II through a cooler I8 (although such cooler may not be necessary) and introduced into settler I9 which may operate at substantially conversion pressure but at a temperature sufficiently low to insure the separation of the hydrogen fluoride phase as a lower layer, e. g. a temperature in the range of about 100 to 250 F. It should be understood that more than one settler may be employed and that separation may rst be effected at substantially reaction temperature and the hydrogen fluoride phase from this high temperature separation may be subsequently separated at a lower temperature. The separated hydrogen fluoride layer is withdrawn from the settler by line 20 and a portion of it may be recycled by line 2i andpump 22 to reactor inlet line I2 in order to decrease the amount of hydrogen fluoride that must be supplied from storage tank I4 and to maintain in reactor I3 about 25 to 50% or more, preferably at least about 30% by weight. of tar (hydrogen fluoride soluble hydrocarbons) based on the hydrogen fluoride in the reactor. At the beginning of the operation all of the hydrogen uoride-tar material withdrawn through line may thus be recycled to the reactor for the dual purpose of improving the catalyst effectiveness in the reactor and for degrading said tar and obtaining maximum yields of hydrogen fluoride-insoluble hydrocarbons such as gas oil therefrom. When desired equilibrium conditions are reached and there is for example about 40% by weight of tar in reactor I3 based on hydrogen uoridetherein, a sufilcient amount of the liquid withdrawn through line 20 is introduced through pressure reducing valve 23 into tar stripper 24 to maintain the substantially constant amount of tar in the reactor and to remove any excess tar.

The excess tar may be simply stripped of hydrogen fluoride by heating means 25 in the base of a conventional stripping tower so that a iirst tar is removed by line 26 which tar may be characterized by a specific gravity of about .98 and an is dependent on several variables.-

1 series of coils to provide the necessary holding time) and then ashed into tar or coke stripper 24 for hydrogen fluoride removal. If such a coking operation is employed, butane or other gas may be introduced at the base of tower 2l for stripping and removing hydrogen fluoride from coke particles and for providing a supporting and fluidizing medium so that the' solids may be removed in fluidized condition through line 26. In either vcase the hydrogen fluoride and any light hydrocarbons which may be associated therewith are withdrawn overhead from the tar stripper through line 23 to product stripper 30.

The hydrocarbon phase in settler I9 ows over baiile'I and is withdrawn through line 32. The

. material thus withdrawn consists chiefly of substantially aromatic-free gas oil and perhaps a small amount of gasoline-boiling-range 'components containing dissolved hydrogen iluoride. The withdrawn stream of these materials may be introducedv by lines 33 and 29 to product stripper 30 or may be introduced by- lines 34 and 35 to second reactor 36. If it is introduced into the product stripper 30 via lines 33 and 29 the dissolved hydrogen fluoride is removed therefrom by heater 31 and/or stripping gas introduced through line 38 and the hydrogen fluoride-free products are withdrawn by line 39 to fractionating d system diagrammatically illlustrated by tower 40, wherein a normally gaseous stream containing butanes is` withdrawn through line 4I, a light naphtha stream .through line 42, a heavy naphtha stream through line 43 and a gas oil stream through line 44. v'Thegas oil stream or at least a substantial portion thereof may then be returned by pump 45 and lines 46 and 35 to second reactorv 36. Thus in either type of operation a substantially aromatic-free gasoil produced in first reactor I3 is subsequently charged to second reactor 36. The substantially aromaticfree gas oil produced in our process or a fraction thereof is useful per se as a superiorDiesel fuel; Also such gas oil is particularly suitable as a charging stock for catalytic cracking with solid catalysts of the silica alumina or silica magnesia type in the systems and under the conditions generally known to the art in fixed bed (Houdry) moving bed (Thermofor Catalytic Cracking) or powdered catalyst (Fluid) processes; this particular gas oil is not only remarkably amenable to such cracking processes but it can be processed with less carbon deposition than would other-l wise be' obtained. This subject matter is claimed in our copending application Ser. No. 168,112, filed July 14, 1950, as a continuation-impart of the present application and also as-a continua? tion-in-part of our copending application Ser. No. 718,038, filed December 23, 1946.

We control the amount of gasoline boiling range non-condensable aromatics introduced into the second reactor by passing through line 33 controlled amounts of the stream from line 32' to stripper 30 and thence by line 39 to fractionator 40 where any mononuclear aromatics of'gasoline boiling range, formed by scission of side chains from aromatic nuclei in the first reactor, are removed as a part of the naphtha stream. The remainder of the stream in line 32 is sent directly by lines 34 and 35 to the second reactor. This proportioning of the stream in line 32 keeps the amount of aromatics, which tend to inhibit cracking in the second reactor. at a desirably low figure, that is, about 0.05 to 5% or less.

Hydrogen fluoride is withdrawn from storage tank I4 and introduced by pump 41 and line 48 to line 35 and second reactor 36, the amount of hydrogen fluoride thus introduced being such that the total stream entering the second reactor contains about to 400%. preferably about 50% to 200% by volume based on total gas oil (or gas oil plus gasoline) charged thereto. The second reactor may be of the same type as the first reactor, although it may be somewhat smaller in size. Conversion conditions in the second reactor 36 may be more severe than those in the first reactor I3, particularly if aromatics such as benzene of the gasoline boiling range are included in the charge. The temperature in reactor 36 should be in the range of 250 to 500 F., preferably 300 to 400 or about 350 F. The time of contact should be relatively short. i. e. Within the range of about 2 to 60 minutes, preferably 2 to 20 minutes, for example about 5 to l5 minutes. The weight space velocity may be about .5 to 5 or preferably about 1 to 2 parts by weight of oil charged per hour per part of hydrogen fluoride in the conversion zone. The reaction is primarily cracking and hydrogen transfer for production of isobutane, gasoline, and/or Diesel fuel and a valuable tar.

The product stream leaves the second reactor through line 49 and passes through cooler 50 to settler 5I wherein a hydrogen fluoride-tar phase separates out as a lower layer and is withdrawn through line 52. At the beginning of the operation, all of the liquid withdrawn through line 52 may be recycled by line 53 and pump 54 to line 35 and reactor 36 until the total amount of tar in the second reactor is within the range of about to 40%, or preferably about 25%, by weight based on the hydrogen fluoride contained in the second reactor. Thereafter, the amount of material recycled through line 53 is just suilicient to maintain the tar ratio in the reactor substantially constant, and the excess tar is introduced by line 55 to tar stripper 56 which is provided with a suitable heater 51 for removing the hydrogen fluoride. This tar stripper 56 like tar stripper 2l may be operated at a temperature in the range of 350 to 550?. and at a relatively low pressure of the order of about 5 to 50 pounds per square inch gage. An alternative method of operation, designed to increase the yield and improve the drying oil properties of the tar, is to operate the second reactor on a once-through basis with respect to tar.

The substantially hydrogen iluoride-free second tar withdrawn through line 58 is quite different in character from the iirst tar withdrawn through line 26. The second tar may have a specific gravity of approximately .90 to .94 and an iodine number of about 250 to 350 or more. It does not contain appreciable amounts of condensed aromatics or sulfur, but is a highly unsaturated polyene material having drying properties and is useful in the preparation of paints, coating materials, and the manufacture of synthetic plastics and resins.

The overhead from tar stripper 56 is passed 6 by line 69 to product stripper 30. The upper hydrocarbon layerwfrom settler 6I passes over baiile 60 and is withdrawn through line 6I to line 58 and product stripper-30. The product stripper 30 is operated under such conditions that substantially all of the HF is removed overhead as a butane azeotrope. the overhead stream passing through line 62 and cooler 63 to separator 64 which may operate at condenser water temperature, preferably below 100 F. The relatively pure hydrogen fluoride which separates out as a lower layer is introduced by line 65 into storage tank I4, any required makeup hydrogen iiuoride being introduced through line 66.

Butane (chiey isobutane) flows over baille 61 and is withdrawn by pump 58. A part of this butane may be introduced at a low point in stripper 30 by line 38 as hereinabove described. The rest of the withdrawn butane stream may pass by line 69, line 10, and line I2 tofirst reactor I3 in order to facilitate tar degradation. At least a portion of the butane may be passed by lines 69, 1I, and 35 into second reactor 36 wherein it` may serve to prevent excessive gas production. Should it be required to vent any gases lighter than butane from the system, such gases may be removed from the top of settler 64 through line 12; if and when such venting is necessary the vented gases may be scrubbed Awith tar, e. g. from line 26, in order to remove the last traces of hydrogen fluoride from the vented gases and the hydrogen uoride-containing tar may then be returned to first reactor I3.

In the example hereinabove described. it will be noted that hydrocarbons from both tar strippers and from at least one of the product settlers are all introducedinto one and the same stripper 30 and the butanes may be returned if desired from settler 64 to first reactor I3. An alternative procedure is to operate settler I9 at a soiliciently low temperature and pressure so that at least a portion of the overhead from tower 30 may be introduced into settler I9. Similarly by operating settler 5I at sufiiciently low temperature and pressure, at least a portion of the overhead from product stripper 30 may be introduced thereto. An advantage of the system illustrated in the drawing is that settlers I9 and 5I may be operated at substantially conversion pressure, thus minimizing, if not entirely eliminating, the pumping required for recycle through lines 20 and 52 respectively.` The system illustrated in the drawing also provides for the removal of net butane production from the base of product stripper 30 since the azeotropicdistillation of hydrogen fluoride from products in stripper 30 will permit the removal of the net butane production with the bottoms stream while substantially Aall the hydrogen uoride is taken overhead as a butane azeotrope.

While we have described a specific example of the invention in considerable detail, it should be understood that the invention is not limited to the specific system or conditions therein. described since many alternative arrangements and operating conditions will be readily` apparent from the above description to those skilled in the art. Promoters such as boron triiluoride may be employed to enhance the activity of the catalyst and such promoters are particularly desirable when it is desired to eiect the cracking of naphthenes. Engineering details such as valves, pumps, heat exchangers, etc. have been largely omitted from the schematic drawings and conventional reiining methods are to be employed for fractionation and stripping where such operations are schematically illustrated in the drawings.

We claim:

1. The method of obtaining valuable products from a hydrocarbon charging stock which is higher boilingythan gasoline and which contains substantial amounts of polycycllc aromatics which are insoluble in hydrogen fluoride but which are condensable in the presence of hydrogen fluoride into higher molecular weight hydrogen iluoride soluble hydrocarbons with liberation of hydrogen, which method comprises treating said charging stock with a catalyst consisting essentially of hydrogen fluoride in a first conversion zone under conditions for effecting intermolecular chemical condensation of said polycyclic aromatic hydrocarbons into hydrogen fluoride-soluble condensed aromatics of higher molecular weight with simultaneous liberation of hydrogen, separating the condensed polycyclic aromatlcs and the hydrogen fluoride in which they are dissolved from hydrogen fluoride-insoluble hydrocarbons consisting essentially of a gas oil which is relatively free from condensable aromatics, subsequently contacting said gas oil with a catalyst consisting essentiallyof hydrogen iluoride under conditions for converting said gas oil into hydrocarbons of the gasoline boiling range and a. high boiling, highly oleflnic, hydrogenfluoride soluble product, substantially free from condensed aromatics, separating the olenic product and the hydrogen fluoride in which it is dissolved from hydrocarbon products insoluble in hydrogen fluoride and separately removing hydrogen fluoride associated, respectively, with the condensed polycyclic aromatic material, the highly olefinic product and the hydrocarbon products insoluble in hydrogen iluoride.

2. The method of claim l wherein a small amount, but less than of hydrocarbons of the gasoline boiling range is produced as well as gas oil in the first conversion zone, 'which includes the further step or separating said gasoline boiling range hydrocarbons from said gas oil before said gas oil is introduced into said second conversion zone.

3. The method of claim l which includes the step of introducing directly into the second conversion zone substantially all of the hydrogen fluoride insoluble products from the first conversion zone.

4. The method of treating a hydrocarbon charging stock which is higher boiling than gasoline and which contains substantial amounts of polycyclic aromatics which are insoluble in hydrogen fluoride but which are condensable in the presence of hydrogen fluoride into higher molecular weight hydrogen fluoride soluble hydrocarbons with liberation of hydrogen, which method comprises reacting said charging stock in a first conversion zone under aromatic condensation conditions at'a temperature in the range of 200 to 375 F. at a pressure sufficient to maintain liquid phase conversion conditions and in the range of 250 to 1000 pounds per square inch and for a time of contact within the range of 20 to 200 minutes while introducing about to 300% by volume of hydrogen fluoride per volume of hydrocarbon introduced into said first conversion zone; separating hydrogen fluoride and tar from products including a gas oil portion leaving the first conversion zone; subsequently contacting at least the gas oil portion of said products with a catalyst consisting essentially of hydrogen fluoride in a second conversion zone under cracking conditions including a temperature in the range of 250 to 500 F.. a pressure sufficient to maintain liquid phase conversion conditions, a catalyst-to-oll weight ratio in the range of .5:1 to 5:1 and a contact time in the range of 2 to 60 minutes; separating a, second tar from hydrogen fluoride insoluble products produced in the second conversion zone; separately stripping the two removed tars. and stripping at least thehydrogen fluoride insoluble products from the second conversion zone-in order to remove hydrogen fluoride therefrom; and recovering hydrocarbons of the gasoline boiling range from stripped products.

5. The methodof converting n, high boiling hydrocarboncharging stock containing chemically condensable polycyclic aromatics chiefly into three main products, namely, a high specific gravity tar, a lower specific gravity high boiling highly olenic product substantially free from` condensed aromatics, and gasoline boiling rangel hydrocarbons, which method comprises treating said charging stock with a catalyst consisting essentially of hydrogen fluoride under conditions for effecting condensation of condensable aromatics into higher` molecular weightJ hydrocarbons with liberation of hydrogen, separating from the reaction products a hydrogen fluoride layer containing said condensed aromatics from a hydrogen fluoride insoluble fraction, stripping hydrogen fluoride from said condensed aromatics and returning said hydrogen fluoride to the system, mixing additional catalyst consisting essentially of hydrogen lfluoride with the hydrogen fluoride insoluble layer and contacting said mixture at a temperature of at least about 300 F., at a pressure sumcient to maintain liquid phase conversion conditions with a hydrogen fluorideto-oil weight ratio of about .5:1 to 5:1 for a period of about 2 to 2O minutes to effect a conversion into low boiling parainic hydrocarbons and high boiling olenic hydrocarbons, the latter being associated with the hydrogen fluoride, separating the parafhnic hydrocarbons from the hydrogen fluoride-olelnic hydrocarbon mixture, removing hydrogen fluoride from the latter to produce a high boiling highly olefinic product substantially free from hydrogen fluoride and stripping hydrogen fluoride from the parafiinic hydrocarbons.

6. The method of obtaining valuable products from a hydrocarbon charging stock which is higher boiling than gasoline and which contains substantial amounts of polycyclic aromatics.

Iwhich are insoluble in hydrogen fluoride but which are condensable in the presence of hydrogen fluoride into higher molecular weight hydrocarbons with liberation of hydrogen, which method comprises treating said charging stock with a, catalyst consisting essentially of hydrogen fluoride in a first conversion zone under conditions for effecting intermolecular chemical condensatlon of said polycyclic aromatic hydrocarbons into hydrogen fluoride-soluble condensed aromatic compounds of higher molecular weight with simultaneous liberation of hydrogen, separating the condensed aromatic compounds, together with the hydrogen fluoride in which they are dissolved, from hydrogen fluoride-insoluble hydrocarbons consisting essentially of a gas oil which is relatively free from condensable aromatics, subsequently contacting said gas oil with a cracking catalyst which consists essentially of hydrogen fluoride under conditions for effecting as the `predominant reaction a conversion of said gas oil into hydrocarbons of the gasoline boiling 9 range and separating said last named hydrocarbons from higher boiling and lower boiling components.

7. The method of claim 6 wherein the first conversion zone is maintained at a temperature in the range of about 200 F. to 375 F., under a pressure in the range of about 250 to 1000 pounds per square inch and for a time of contact in the range of about 20 to 200 minutes with an amount of hydrogen uoride in the range of about 10 to 300 volume per cent based on stock charged.

8. The method of claim 6 wherein the gas oil contains about .05 to 5 per cent ofaromatics.

ARTHUR P. LIEN. BERNARD L. EVERING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,872,446 Halloran et ai Aug. 16, 1932 1,881,901 Osmer 1 Oct. 11, 1932 2,258,394 Tinker et al. Oct. 7, 1941 2,304,289 Tongberg Dec. 8, 1942 2,343,841 Burk Mar. 7, 1944 2,378,762 Frey June 19, 1945 2,405,995 Burk Aug. 20, 1946 2,454,615 Ridgway et al Nov. 23, 1948 l5 809 and 810. Published by Heath 8: Co., Boston,

Claims (1)

1. THE METHOD OF OBTAINING VALUABLE PRODUCTS FROM A HYDROCARBON CHARGING STOCK WHICH IS HIGHER BOILING THAN GASOLINE AND WHICH CONTAINS SUBSTANTIAL AMOUNTS OF POLYCYCLIC AROMATICS WHICH ARE INSOLUBLE IN HYDROGEN FLUORIDE BUT WHICH ARE CONDENSABLE IN THE PRESENCE OF HYDROGEN FLUORIDE INTO HIGHER MOLECULAR WEIGHT HYDROGEN FLUORIDE SOLUBLE HYDROCARBONS WITH LIBERATION OF HYDROGEN, WHICH METHOD COMPRISES TREATING SAID CHARGING STOCK WITH A CATALYST CONSISTING ESSENTIALLY OF HYDROGEN FLUORIDE IN A FIRST CON-P VERSION ZONE UNDER CONDITIONS FOR EFFECTING INTERMOLECULAR CHEMICAL CONDENSATION OF SAID POLYCYCLIC AROMATIC HYDROCARBONS INTO HYDROGEN FLUORIDE-SOLUBLE CONDENSED AROMATICS OF HIGHER MOLECULAR WEIGHT WITH SIMULTANEOUS LIBERATION OF HYDROGEN, SEPARATING THE CONDENSED POLYCYCLIC AROMATICS AND THE HYDROGEN FLUORIDE IN WHICH THEY ARE DISSOLVED FROM HYDROGEN FLUORIDE-INSOLUBLE HYDROCARBONS CONSISTING ESSENTIALLY OF A GAS OIL WHICH IS RELATIVELY FREE FROM CONDENSABLE AROMATICS, SUBSEQUENTLY CONTACTING SAID GAS OIL WITH A CATALYST CONSISTING ESSENTIALLY OF HYDROGEN FLUORIDE UNDER CONDITIONS FOR CONVERTING SAID GAS OIL INTO HYDROCARBONS OF THE GASOLINE BOILING RANGE AND A HIGH BOILING, HIGHLY OLEFINIC, HYDROGENFLUORIDE SOLUBLE PRODUCT, SUBSTANTIALLY FREE FROM CONDENSED AROMATICS, SEPARATING THE OLEFINIC PRODUCT AND THE HYDROGEN FLUORIDE IN WHICH IT IS DISSOLVED FROM HYDROCARBON PRODUCTS INSOLUBLE IN HYDROGEN FLUORIDE AND SEPARATELY REMOVING HYDROGEN FLUORIDE ASSOCIATED, RESPECTIVELY, WITH THE CONDENSED POLYCYCLIC AROMATIC MATERIAL, THE HIGHLY OLEFINIC PRODUCT AND THE HYDROCARBON PRODUCTS INSOLUBLE IN HYDROGEN FLUORIDE.

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