US3159566A - Integrated petroleum refining process - Google Patents

Description

Dec. 1, 1964 J. w. SPRAGUE INTEGRATED PETROLEUM REFINING PROCESS Filed Dec. 4, 1962 M H m w m T mW A M J I! w J M m 2/ 5 m J m T Q N k m @N w 9 $5580? J g on m 4 k i QOEEQQQI I J 3 J Q mNK r w NI W J m f g m A| T H m $595 y m 6 R55 1. w 8 mk i fl AL N United States Patent 3,159,566 INTEGRATED PETRGLEUM REFINING PRUCESS .iames W. Sprague, Streetshoro,@hio, assignor to The fitandard Gil Company, Cleveland, fihio, a corporation of Ohio Filed Dec. 4, 1962, Ser. No. 242,179 2 Claims. (Cl. 203-79) The present invention relates to an integrated petroleum refining process involving a particular combination of a number of petroleum refining processes. The cornination which forms the subject matter of this invention results in a process whereby crude oil is converted to substantially completely gasoline and lighter products with a minimum simultaneous production of products heavier than gasoline such as furnace oils and the like.

A substantial research effort is devoted by the petroleum refining industryto the development of ways and means for maximizing the amount of gasoline which may be obtained from a given quantity of crude oil. Efiorts toward achieving this objective have been stimulated by the fact that, in general, gasoline is a more economically desirable product than heavier products such as furnace oil, diesel fuel, bunker fuel, and the like. The maximum amount of gasoline obtainable from a given quantity of crude oil has been limited by the available technology and further improvements in this area have awaited the development of new processing techniques. It is, therefore, one object of this invention to provide an integrated refining process by means of which it is possible to obtain a greater quantity of gasoline froma given quantity of crude oil than has been heretofore possible.

In brief, the invention relates to a process for the treatment of crude oil involving a combination of fractionation, catalytic reforming, fiuorotreating, hydrocracking, and hydrogenation. The manner in which these processes are combined in accordance with the present invention can best be explained by reference to the attached patent drawing. In this drawing, the process is represented by a schematic flow diagram. Pumps, heat exchangers, valves and other conventional equipment are not shown on the drawing since they would add nothing to an understanding of the invention. A written description of the flow diagram now follows.

Referring now to the attached patent drawing, crude oil is introduced through line 10 into a crude still 11 where it is divided into four fractions, viz.;

(1) An overhead fraction which includes the VC; hydrocarbons.

(2 A light naphtha fraction including 0 and c hydrocarbons.

(3) A heavy naphtha fraction, suitable for reforming,

having an end-point of 380 F.-

(4) A bottomsfraction having an initial boiling point of 380 F., and comprising the remainder of the crude oil. l

The overhead fraction consisting of the lighter components is processed in a gas plant which is unrelated to the process of this invention and it leaves the process] via line 12. The light naphthafraction is recovered'as 3,35%,556 Patented Dec. 1, 1964 tionator 22 via line 21 to the gasoline blending plant which is not a part of this invention.

The bottoms fraction obtained from the crude still 11 is transferred through line 13 to a fluorotreater unit 17. Hydrogen fluoride is added to the fluorotreater unit 17 through line 16. Treated product is transferred from the fiuorotreater unit 17 through line 18 to a catalytic hydrocracking unit 19. Efiiuent from the hydrocracking unit 19 is transferred through line 28 to a fractionator 29. In the fractionator 29 the efiluent from the hydrocracking unit 19 is divided into three fractions including a light ends fraction, a distillate fraction having an end point of 380 F. and a bottoms fraction having an initial boiling point of 380 F. The light ends fraction leaves the process via line 31 for further treatment in the gas plant which is not related to the present invention. The intermediate distillate fraction is transferred through line 30 to line 14 where it is mixed with the incoming feed to the catalytic reforming unit 15.

The bottoms fraction from fractionator 29 is transferred through line 27 to a catalytic hydrogenation unit 25 via line 23. Returning now to the bottoms fraction from fractionator 22, this fraction is also transferred by means of line 23 to the hydrogenation unit 25. Hydro gen is added to the hydrogenation unit 25 through line 24. Effluent from hydrogenation unit 25 is returned to the hydrocracking unit through lines 26 and 18. A detailed description of the various processing steps now follows.

In the first step in the process, crude oil is fractionated into four separate fractions. The first fraction comprises the lighter components of the crude oilup to and including the C fraction. The second or light naphtha fraction comprises the C and C hydrocarbons. The third, or heavy naphtha fraction is suitable for reforming and has an end point of 380 F. The bottom fraction comprises thoseheavier components of the crude oil boiling initially at 380 F. A conventional fractionating tower comprising a plurality of bubble-cap trays may be used for a crude oil distillation of the type here contemplated.

The initial fraction of the crude oil comprising those hydrocarbons boiling up to and including the C hydrocarbons is transferred to a gas plant for further treatment which forms no part of this invention. The second, or light naphtha fraction may be transferred to a fuel blending storage and is not further concerned. with the integrated process of this invention. The third fraction of the crude oil, namely that portion having an end point of 380 F., is transferred to a conventional catalytic remeans are conventional and the pretreatment is usually a side stream of line12a and canbe transferred directly w to fuel blending storage facilities. and thereafter is not concerned with the integrated process of this invention. The heavy naphtha fraction is transferred through line .14 to a catalytic reforming unit 15. Effluent from the latter unit is transferred through conduitZtB to a fracfluent boiling below 380 F. is transferred from the fracaccomplished by passing the feed over a bed of cobalt 'rnolybdatecatalyst in the presence of added hydrogen ditions depending upon the desired octane level of the product. Liquid hourly space velocities of one to six vol- 3- umes of hydrocarbon per volume of catalyst per hour are employed. A hydrogen-rich gas is separated from the reaction efilucnt and recycled to the reactors with the feed at a rate of 1000 to 10,000 s.c.f. of hydrogen per barrel of charge.

Effluent from the catalytic reforming unit is transferred to a conventional fractionator wherein a bottom fraction boiling above 380 F. is obtained and sepm'atcd for further treatment in accordance with the process of this invention. The fraction boiling below 380 F. is transferred to a gasoline blending plant for further treatment which is not a part of this invention.

The bottom fraction of the crude oil, namely, that fraction boiling above 380 F. is transferred to a fluorotreater. In this treater the bottoms fraction is contacted with 0.5 to 1.0% of gaseous hydrogen iluoride based on the weight of the oil at a temperature in the range of 75 to 200 F. This treatment is designed to remove a part of the nickel and essentially all of the other metal contaminants normally contained in this fraction as well as any nitrogenous compounds which may be present since all of these materials are known to have a deleterious effect upon hydrocracking catalysts. Very small concentrations of these contaminants in the feed streams will lead to rapid poisoning of the catalyst in the subsequent hydrocracking process, whereas hydrogen fluoride Wlil coagulate these contaminants and permit their ready removal without the formation of an acid sludge due to chemical reactions involving other constituents of the oil. The fluorotreating process is thus a selective one in which the yield of decontaminated oil is quite high, usually on the order of about 95%. Since the hydrogen fluoride is not consumed in the sludging reactions with the oil, it may be recovered and reused repeatedly. The material which is coagulated by the action of the hydrogen fluoride may be removed from the oil by any number of well-known separation methods, such as settling, filtration, or centrifugation. The eliluent from the fiuorotreating unit which is substantially free of deleterious metal and nitrogen compounds is next transferred to a hydrocracking process.

Hydrocracking processes are usually operated at pressures on the order of 500 to 5000 psi, preferably in the range of 800 to 1000 psi. and at temperatures in the range of 550 to 625 F. it is necessary to add hydrogen to the feed to a hydrocracker at a rate generally in the range of 1000 to 100,000 s.c.f. of hydrogen per barrel of feed, 5000 to 10,000 s.c.f. of hydrogen per barrel of feed ordinarily being sufficient. Space velocities on the order of 0.5 to 5 volumes of hydrocarbon per volume of catalyst per hour are employed.

Hydrocracking catalysts are of the so-called dual functional type. Such catalysts contain an acidic ingredient which serves as the cracking element in the catalyst and materials such as silica-alumina, silica-magnesia, silicaalumina-zirconia, beryllium oxide, indium oxide, fluorinated alumina or various acid-treated clays may be employed as the acidic constituent. The other element of the catalyst is the hydrogenation ingredient and it may be selected from the metals of Groups V to VIII of the Periodic Table and/or their oxides or sulphides. Illustrative of such materials are the oxides and/ or sulphides of molybdenum, tungsten, vanadium, and chromium. Other materials such as the oxides of iron, nickel and cobalt may also be employed. In general the hydrogenating ingredient will comprise 0.1 to 20% by weight f the hydrocracking catalyst.

The etlluent from the hydrocracking process is fractionated in conventional equipment into three fractions. The lightest fraction is transferred to a gas plant for further treatment which forms no part of the present invention. An intermediate fraction which includes the C hydrocarbons and has an end point of 380 F. iscombined with the pretreated virgin feed to the catalytic reformer. It has been observed that a hydrocraclzed distillate makes a better quality feed to the catalytic reforming process than a virgin material of the same boiling range and the process of this invention makes use of this fact.

The bottom fraction of the cfiluent from the hydrocracking unit which has an initial boiling point of 380 F. is combined with a bottom fraction having the same initial boiling point which is obtained by fractionation of the effluent from the catalytic reforming unit as described above. This combined stream is transferred to a catalytic hydrogenation unit and this step forms one of the key steps in the process. Neither of the materials making up this stream would make a satisfactory feed to a hydrocracking process because of the fact that they are largely condensed aromatic and consequently they are very difficult to crack. However, under severe hydrogenation conditions the relatively refractory aromatic compounds can be converted into naphthcnic compounds which may be cracked with considera ly greater facility. Hence, the hydrogenation step malzes it possible to continue recycling the heaviest fractions from the hydrocracker and the reformer to virtual extinction so that only products boiling within the gasoline range or lighter are produced ultimately by this process.

Catalytic hydrogenation units are customarily operated at fairly high pressures on the order of 1,000 to 5,000 p.s.i. and preferably about 3,000 psi. Temperatures on the order of 450 to 750 F. and preferably in the range of 500 to 600 F. are usually employed. Substantial quantities of hydrogen are required in the process and the ratio of hydrogen to hydrocarbon charge should be on the order of 2000 s.c.f. of hydrogen per barrel to 100,- 000 s.c.f. of hydrogen per barrel. The space velocity may vary from 0.5 to one volume of hydrocarbon per volume of catalyst per hour. A strong hydrogenation catalyst such as nickel or nickel supported on kicselguhr must be employed in this step of the process. The eflluent from the hydrogenation unit is returned as feed to the hydrocracking unit where it is treated along with the virgin feed. Hence, the production of products heavier than gasoline is substantially eliminated.

A specific example of the process of this invention is as follows:

A desalted Illinois Basin crude oil having the properties listed in Table I was used.

TABLE I Properties of Desalled Illinois Basin Crude Gravity, API 35.9 Specific gravity 0.8453

Pour point, F. 35 Total sulfur, wt. percent 0.25 Asphaltenes, wt. percent 0.3 Viscosity, SSU, at 72 F 53.1 Viscosity, SSU, at 100 F. 47.2 Viscosity gravity constant 0.821 Reid vapor pressure, p.s.i. 5.20 Nitrogen, wt. percent 0.149 Mercaptan sulfur, pounds per 1000 barrels 13.8 H 8 sulfur, pounds per 1000 barrels 22.6 Ramsbottom carbon (calc. wt. percent) 2.66 Neutralization number 0.0634- Vanadium, parts per million 2 Nickel, parts per million 5.5 Iron, parts per million 2.9

The crude is introduced, at a rate of one thousand barrels per day, through line 10 into crude still 11 where it is divided into four fractions. The overhead stream, leaving the crude still by means of line 12, contains mixed butanes, produced at a rate of 21 barrels a day, and a dry gas portion produced at a rate 4560 standard cubic feet per day and having the composition indicated in Table II. Line 12 conveys this overhead stream to a gas plantfor further processing not further concerned with the integrated proccss of this invention.

Component:

TABLE 11 a Dry Gas Composition Component:

, Percent Non-condensables 8.3 Methane 0.5 Ethane 0.2 Propane 91.0

The light naphtha side-stream, leaving the crude still by means of line 12a consists of mixed pentanes and hexanes, produced at a rate of 84 barrels per day and having the properties shown in Table III. This light side stream is transported to fuel blending storage and is not further concerned with the integrated process of this invention.

TABLE III Properties of Pentane-Hexane Side Stream Specific gravity 0.6883 A.P.I. gravity degrees 74.1 Percent sulfur 0.015 Mercaptan sulfur, pounds per 1000 barrels 3.3 H 8 sulfur, pounds per 1000 barrels 0.1

The heavy naphtha fraction, produced at a rate of 196 barrels per day, and having the properties shown in Table IV, is transferred through line 14 to the catalytic reforming unit 15 (cornbinedwith 334 barrels per day'of the intermediate fraction from fractionator 29 to give a total reformer feed of 530 barrels per day).

TABLE iv Properties of Heavy Naphflm API gravity Q degrees 54.7 Specific gravity 0.7600 Percent sulphur 0.031 Mercaptan sulfur, pounds per 1000 barrels 8.6 Basic nitrogen, parts per million 0.6 Percent paraiiins 40 Percent aromatics 7 Percent naphthenes 53 Initial boiling point, F. g 207 point, F. 218 30% point, F. 251 50% point, F. 279 70% point, F. 313 90% point, F. 350 Endpoint, F. 376

Thecatalytic reforming unit .15 is charged with 4425 pounds of a platinum-germanium on chlorided alumina catalyst (containing 0.35percent platinum and 0.13 percent germanium) and is operated under conditions of a temperature of 925 degrees F., a pressure of 500 p.s.i.g., a weight hourly space velocity of 1.33 and 6000 standard cubic feet of recycle gas per barrel of liquid feed. The efiiuent from the catalytic reforming unit is transferred through line 20 to a fractionator 22 where a fraction boiling below 380 F. is removed from the fractionator via line 21. This reformer'product stream, when fractionated by equipment not otherwise directly 'concerned with the integrated process of this invention, produces 124,000 standard cubic feet of gas per day having the composition shown in Table V, 29 barrels per day of mixed butanes and 422 barrels per day of liquid reformate, having the properties shown in Table VI, which is transferred to the gasoline blending plant (not otherwisea part of this invention).

. TABLE V Reformer Gas Product COmpOitiOib This reformer gas is suitable as process gas for the hydrocracking operation and may be conveniently cycled to to hydrocracker 19 for this purpose.

TABLE VI Reformaze Properties Gravity, API 42.6 Specific gravity 0.8112

The bottoms fraction obtained from the crude still 11, having the properties shown in Table VII, is transferred at a rate of 695 barrels per day through line 13 to the fluorotreater unit 17. Hydrogen fluoride is added to the fluorotreater unit 17 through line 16 at a rate, of 2050 pounds per day to produce 8,222 pounds per day of sludge containing 18 percent hydrogen fluoride. The supernatant fiuorotreater stock is heated in a stream of inert gas at about 375 F. to remove dissolved hydrogen fluoride to produce 676 barrels per day of a treated stock having the properties shown in Table VIII. The sludge is heated to recover 98.6 percent of the total hydrogen fluoride which is then recycled to the fiuorotreater.

TABLE VII Properties of 380 F. Crude Fraction Gravity, API 26.6 Specific gravity 0.8951

Sulfur, percent 0.24 Nitrogen, percent 0.197 Vanadium, parts per million 2.9 Nickel, parts per million 7.9 Iron, parts per million 4.2 R arnsbottom carbon 3.53 Initial boiling point, F. 402 10% point, F 438 30% point, F. Q. 567 50% point, F. 1 713 point, F. a 911 The fluorotreater effluent is transferred through line 18 (at a rate of 676 barrels per day) to the catalytic hydro cracking unit 19 (combined with 107 barrels per day of hydrogenerator effluent to give a total hydrocracker'feed of 783 barrels per day) which is charged with 6760 v pounds of a tungsten disulfide on silica -alumina (30 percent alumina) catalyst prepared by impregnation of silica alumina with silico tungstic acid followed by reduction in a stream of hydrogen sulfide at 500 to 700 degrees P. so as to contain 4.2 percent of tungsten disulfide in the finished cat'alyst. The hydrocracking unit 19 is-operatecl under conditions of a temperature of 650 degrees F, a pressure of 2000 p.s.i.g., a' liquid hourly space velocity of 1.5, and a hydrogen feed of 2700 standard cubic feet per barrel of liquid feed.

7 TABLE VIII Properties of Fluorotreater Effluent Gravity; API

Specific gravity 0.8914

Sulfur, percent a 0.22

2.01 V Vanadium, parts perjmillion 4 TABLE VllL-Continued Nickel, parts per million 3.3 Iron, parts per million 0.0

The eflluent from the hydrocracking unit 19 is transferred through line 28 to a fractionator 29 where it is divided into three fractions. The light ends fraction is sent by line 31 to further fractionation (not directly concerned with the integrated process of this invention) to produce 355 barrels per day of a light naphtha having the properties listed in Table IX, 185 barrels per day of mixed butanes with an iso to normal ratio of 5.37, and 69,800 standard cubic feet per day of dry gas having the composition shown in Table X.

TABLE IX Properties of Hydrocracker Light Naphtha Gravity, API 80.5 Specific gravity 0.6676

The intermediate distillate fraction from the fractionator 29, having the properties shown in Table XI, is produced at a rate of 334 barrels per day and transferred by means of line 30 to line 14 where it is mixed with the incoming feed to the catalytic reforming unit 15.

TABLE XI Properties of Hydrocracker Intermediate Distillate Gravity, APl 50.9 Specific gravity 0.7760

Paraffins, percent 49.0 Aromatics, percent 15.0 Naphthenes, percent 36.0 Sulfur, percent 0.00 Nitrogen, parts per million 0.3 Initial boiling point, F. 218 point, F. 240 30% point, F. 268 50% point, P. 300 70% point, F. 335 90% point, P. 363 End point, F. 379

The bottoms fraction from fractionator 29, which is a highly aromatic material containing many bicyclic compounds and having the properties shown in Table XII, is produced at a rate of 80 barrels per day and is transferred through line 27 to the catalytic hydrogena-. tion unit via line 23.

TABLE XII Properties of Hydrocracker Bottoms Fraction Gravity, API 11.6 Specific gravity 0.9891

Sulfur, percent 0.01 Nitrogen, percent 0.008 Initial boiling point, F. 396 10% point, F. 44-3 point, F. 483 50% point, F. 528 70% point, F. V 592 90% point, F. 735 End point, F. 863

The bottoms fraction from fractionator 22, a highly aromatic material produced at a rate of 9 barrels per cases 8 day and having the properties shown in TABLE XIII, is also transferred by means of line 23 to the hydrogenation unit 25 to provide a combined feed to this unit of 89 barrels per day. The hydrogenation unit 25 is charged with 512 pounds of fifty percent nickel on kicselguhr catalyst and operated under conditions of a tem- Jerature of 550 degrees, F., a pressure of 2000 p.s.i.g., a weight hourly space velocity of 0.4 and 10,000 standard cubic feet of gas recycle per barrel of liquid feed.

TABL XIII Properties of Reformer Bottoms Fraction Gravity, API 4.8. Specific gravity 1.038. Boiling range a Above 380 F.

The effluent from the hydrogenation unit 25, having the properties shown in Table XIV, is produced at a rate of 107 barrels per day and is transferred by means of lines 26 and 18 to the hydrocracking unit 19 where it is recessed as described above.

TABLE XIV Properties of Hydrogenation Unit Product Gravity, APT 32.6 Specific gravity 0.8622 Initial boiling point, F. 391 10% point, F. 409 30% point, F. 441 50% point, "P. 492 point, F. 568 point, F. 729 End point, F. 870

It will be apparent from the foregoing description that the process of the present invention will offer important economic advantages to those petroleum refiners who desire to minimize their production of products heavier than gasoline. Many modifications of the process will undoubtedly occur to those skilled in the art and this application for Letters Patent is intended to covor all such modifications as would reasonably fall witi in the scope of the appended claims.

I claim:

1. An integrated petroleum refining process comprising the steps of (a) fractionating a crude oil into an overhead frac tion, a light naphtha fraction, a heavy naphtha fraction, and a bottoms fraction,

(1)) subjecting said heavy naphtha fraction obtained in step (a) to a catalytic reforming operation,

(c) fractionating the catalytic reformate obtained in step (b) into at least two fractions,

(d) treating the bottoms fraction obtained in step (a) with hydrofluoric acid whereby nitrogeneous and metallic compounds are removed therefrom,

(e) subjecting said treated bottoms fraction obtained in step (d) to a catalytic hydrocracking operation,

(1) fractionating the hydrocracked eflluent from step (e) into alight fraction, an intermediate distillate fraction and a bottoms fraction,

(g) combining the intermediate fraction obtainedin step (f) with the feed to step (b) and subjecting same to a catalytic reforming operation,

(/1) combining the bottoms fraction obtained in step (c) with the bottoms fraction obtained in step (i) and subjecting this stream to a catalytic hydrogenation operation,

(i) combining the hydrogenated effluent from step (/1) with the feed to step (e) and catalytically hydrocracking same.

2. An integrated petroleum refining process compris ing the steps of .(a) fractionating'a crude oil into an overhead fraction, a light naphtha fraction including C and C hydrocarbons, a heavy naphtha fraction having an 9 end-point of about 380 F. and a bottoms fraction having an initial boiling point of about 380 F.

(b) subjecting said heavy naphtha fraction obtained in step (a) to a catalytic reforming operation,

(0) fractionating the catalytic reformate obtained in step ([2) into a light fraction, and into a heavy fraction having an initial boiling point of 380 F.

(d) treating the bottoms fraction obtained in step (a) with gaseous hydrofluoric acid whereby nitrogeneous and metallic compounds are removed therefrom,

(e) subjecting said treated bottoms fraction obtained in step (d) to a catalytic hydrocracking operation,

(1) fractionating the hydrocracked effluent from step (e) into a light fraction, an intermediate distillate fraction boiling within the gasoline boiling range and a bottoms fraction having an initial boiling point of about 380 F.

(g) combining the intermediate fraction obtained in step (1) with the feed to step (b) and subjecting same to a catalytic reforming operation,

(h) combining the bottoms fraction obtained in step (c) with the bottoms fraction obtained in step (1) and subjecting this stream to a catalytic hydrogenation operation,

(i) combining the hydrogenated efiluent from step (h) with the feed to step (e) and catalytically hydrocracking same.

References Cited in the file of this patent UNITED STATES PATENTS 15 2,859,169 Herman Nov. 4, 1958 2,971,905 Bieber et a1. Feb. 14, 1961 2,973,313 Pevere et a1. Feb. 28, 1961

Claims (1)

1. AN INTEGRATED PETROLEUM REFINING PROCESS COMPRISING THE STEPS OF (A) FRACTIONATING A CRUDE OIL INTO AN OVERHEAD FRACTION, A LIGHT NAPHTHA FRACTION, A HEAVY NAPHTHA FRACTION, AND A BOTTOMS FRACTION, (B) SUBJECTING SAID HEAVY NAPHTHA FRACTION OBTAINED IN STEP (A) TO A CATALYTIC REFORMING OPERATION, (C) FRACTIONATING THE CATALYTIC REFORMATE OBTAINED IN STEP (B) INTO AT LEAST TWO FRACTIONS, (D) TREATING THE BOTTOMS FRACTION OBTAINED IN STEP (A) WITH HYDROFLUORIC ACID WHEREBY NITROGENEOUS AND METALLIC COMPOUNDS ARE REMOVED THEREFROM, (E) SUBJECTING SAID TREATED BOTTOMS FRACTION OBTAINED IN STEP (D) TO A CATALYTIC HYDROCRACKING OPERATION, (F) FRACTIONATING THE HYDROCRACKED EFFLUENT FROM STEP (E) INTO A LIGHT FRACTION, AN INTERMEDIATE DISTILLATE FRACTION AND A BOTTOMS FRACTION, (G) COMBINING THE INTERMEDIATE FRACTION OBTAINED IN STEP (F) WITH THE FEED TO STEP (B) AND SUBJECTING SAME TO A CATALYTIC REFORMING OPERATION, (H) COMBINING THE BOTTOMS FRACTION OBTAINED IN STEP (C) WITH THE BOTTOMS FRACTION OBTAINED IN STEP (F) AND SUBJECTING THIS STREAM TO A CATALYTIC HYDROGENATION OPERATION, (I) COMBINING THE HYDROGENATED EFFLUENT FROM STEP (H) WITH THE FEED TO STEP (E) AND CATALYTICALLY HYDROCRACKING SAME.

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