US3238117A - Crude oil conversion process with coking in the first stage and the subsequent hydrocracking and reforming of the products - Google Patents

Description

3,238,117 RST STAGE W. F. AREY, JR.. ETAL ION PROCESS WITH COKING IN THE F1 AND THE SUBSEQUENT HYDROCRACKING AND REFORMING OF THE PRODUCTS Filed July 3, 1965 558mm .8 on N Jon m. mu mm mm; m N N MMWE F 0M1 Q m: N? O m i v. 21 5x8 E w 0 nm3 6 March 1, 1966 CRUDE OIL CONVERS William Floyd Arey,J Charles Newton Kimberlin, Jr, 'nven'mrs PutenfAflorney United States Patent CRUDE 01L CONVERSION PROCESS WHTH COK- ING IN THE FIRST STAGE AND THE SUBSE- QUENT HYDROCRACKING AND REFORMTNG OF THE PRODUCTS William Floyd Arey, Jr., and Charles Newton Kimberlin, Jr., Baton Rouge, La., assiguors to Esso Research and Engineering Company, a corporation of Delaware Filed July 3, 1963, Ser. No. 292,703 6 Claims. (Cl. 208-53) The present invention relates to a process for converting crude petroleum oil to desired products by a combination of steps including coking, hydrocracking, and reforming. More particularly, the invention concerns such a combination process wherein crude oil feed is subjected to a coking operation, the total liquid product thereby obtained is subjected to a hydrocracking operation, and the heavy naphtha portion of the hydrocracked product is subjected to a reforming operation.

In the conversion of petroleum crude oilsto commercial product it is desirable to obtain a maximum yield of products of high economic value such as gasoline and heating oil and a minimum of products of low economic value such as heavy residua. Combination processes which increase the production of high octane motor fuels are particularly valuable.

In accordance with the present invention, an improved combination process is employed wherein crude petroleum oil is supplied to a coking zone. For the purposes of this invention, the term crude oil is intended to embrace not only whole crude petroleum oil but also long residuum or topped crude, i.e. crude oil from which the lower boiling materials such as naturally-occurring gasoline or heavy naphtha fractions have been removed. Coke and gas are separated from the coker product and the entire liquid portion of the product is then subjected to a hydrocracking operation. After recycle hydrogen gas has been separated from the hydrocracking effluent, the latter is then fed to a distillation zone and separated by distillation into a number of cuts including a heavy naphtha fraction having 0; hydrocarbons and higher, one or more fractions including C hydrocarbons and lower, and a bottoms fraction boiling above about 430 F. If a heating oil product is desired, a side stream boiling in the range of 350 to 700 F. may also be taken off from the distillation zone. Also, it is usually preferred to have one cut of C to C hydrocarbons which can be blended into motor fuel. The heavy naphtha fraction obtained in the distillation is sent to a reforming zone where it is reformed to give a high octane product under conditions furnishing an excess of hydrogen. The latter is used in the hydrocracking step. With a large number of crude oils the reforming operation will furnish suflicient hydrogen for the hydrocracking step. However, if additional hydrogen is required it can be manufactured from the light gas, i.e. propane and lower.

The operation of the various steps in the combination process of the present invention will be better understood when reference is made to the drawing in which the single figure represents a flow diagram of the process. Referring now to the drawing in detail, the reference character 10 designates a line for feeding a whole petroleum crude oil, a long residuum or a topped crude into a coking zone 11. The crude oils which may be used include domestic crudes such as South Louisiana, West Texas, Midcontinent, and the like, or Middle East crudes such as Arabian or Kuwait.

Coking zone 11 may comprise any of the conventional coking units. Since the standard coking processes are well known in the art, it is not considered necessary to show the coking process in detail. The units presently 3,238,117 Patented Mar. 1, 1966 available for this purpose are of either the delayed coking or fluid coking variety. In a delayed coker, the feed is heated to about 750 F. to 950 F. and then sent into one of two or more coking zones which are connected by valves so that they may be put on stream for filling and then taken off stream for coke removal as the amount of coke formed therein builds up to the maximum capacity. The temperature in the coking zone is ordinarily in the range of about 775 F. to 850 F. and under a pressure of from about 40 to 60 p.s.i.g. In the present invention it is preferred to use a fluid type of coking unit wherein the feed is sprayed into a chamber for contact with hot particulate solids maintained in a fluidized condition by means of an upflowing stream of fluidizing gas such as steam or a light hydrocarbon gas. When the feed contacts the fluidized bed of solids, the oil undergoes pyrolysis, evolving lighter hydrocarbons and depositing carbonaceous residue on the solid particles, causing them to grow in size. The necessary heat for the pyrolysis is supplied by circulating a stream of the fluidized solids through an external heating or combustion zone and then passing the resulting hot coke particles back to the fluidized coking zone for contact with incoming feed. The

vaporous products formed in the fluidized coking chamber are separated from entrained particulate solids through a suitable cyclone type of separation unit.

In the present invention, when using a fluid coker operation the coking step is carried out at a temperature between about 800 F. and 1200 F. and a pressure between about atmospheric and 15 p.s.i.g. The coke particles are of an average size of between about and 1000 microns. The superficial velocity of the upflowing gas and vapor in the coking zone is between about 0.2 and 5 ft./second, thus maintaining a fluidized bed of coke particles. The circulation rate of coke solids in relation to oil feed is between about 5 and 10. The burner vessel of the coking unit is maintained at a temperature between about 1050" F. and 1600 F.

Coke produced in the process is removed from the coking zone through line 12. The remaining products of the coking operation, after separation from entrained coke particles, are sent through line 13 to separation zone 14 wherein gas is removed overhead through line 15 and the total liquid product from the coker is fed by means of line 16 into hydrocracking zone 17. The coker effluent entering zone 14 is cooled to about P. so that the separation in zone 14 gives a liquid product which is predominantly C and higher. Thus, most of the C and some C go overhead with the gas (through line 15) and may subsequently be recovered by known or conventional means. Zone 14 is preferably an integral part of the coking unit so that the cooling of the coker efliuent may be accomplished by heat exchange with the crude feed prior to introducing the feed to the coker through line 10. The liquid product leaving zone 14 through line 16 has an initial boiling point of about 150 F. and a final boiling point in excess of about 950 F. or higher.

The hydrocracking zone 17 maybe a fixed bed catalyst hydrocracking zone or it may be a fluid catalyst hydrocracking zone. In either case, with the present invention it is not necessary to pretreat the feed going to the hydrocracking zone 17, and hydrocarbon oil feeds containing more than 50 parts per mill-ion of nitrogen can be tolerated. With very high-nitrogen-containing feeds (above about 500 ppm. nitrogen) a mixed hydrocracking catalyst system is advantageously utilized in a fixed bed hydrocracker. If a fluid hydrocracking zone is used, the catalyst is preferably one comp-rising between 1 and 15 wt. percent of nickel on a silica-alumina crack-ing catalyst, although other catalysts such as cobalt on silicaalumina or 0.1 to 2 wt. percent of platinum or palladium on silica-alumina may be used. Particularly preferred is a catalyst comprising from about to 6 wt. percent of nickel on a silica-alumina cracking catalyst containing 70 to 90% silica and to 30% alumina. However, cracking catalysts having higher percentages of alumina may be used if desired. The .temperature in hydrocracking zone 17 when using a fluid operation is between about 580 F. and 900 F., preferably about 600 F. to 700 F. A reaction pressure of between about 400 and 1800 p.s.i.g., preferably 500 to 1500 p.s.i.g., is used. Hydrogen gas recycle rates of between about 3,000 and 15,000 cubic feet per barrel of feed, and preferably about 8,000 to 15,000 cubic feet per barrel of feed, are used. The hydrocarbon feed rate to the hydrocracking zone 17 is between about 0.5 and 5 w./hr./w., preferably between about 1 and 2 w./hr./w., and the catalyst holding time is in the range of from about 30 minutes and hours, preferably 1 to 3 hours.

If the hydrocracking operation is conducted with a fixed catalyst bed, it is preferred that at least a part of the catalyst base be a molecular sieve, that is, a crystalline zeolite alumino-silicate molecular sieve having uniform pore openings in the range of from about 6 to 15 A. Particularly desirable catalysts of this type are those having a platinum group metal or platinum group metal compound deposited on, composited with, or incorporated within a molecular sieve zeolite of 6 to 15 A. pore size which has been cationically exchanged to remove a major proportion, if not all, of its sodium content. Preferably, the sodium content is reduced below 10 wt. percent, based on zeolite. The preferred catalyst is palladium on such a molecular sieve base. Platinum group metals include platinum, palladium, rhodium, osmium, iridium, and the like.

Zeolites that have molecular sieve properties are now well known in the art. They include natural zeolites such as faujasite and the synthetic zeolites such as the 13X or 13Y sieves which have effective pore sizes of about 13 A. They also include mordenite which has an effective pore diameter of about 9 A.

In general, the anhydrous form of the crystalline molecular sieve zeolites that can be composited with platinum group metals and employed in the present invention have chemical formulas that may be expressed in terms of moles by the following:

0.0 :l: 0.2Me0 ZAl203.XSiOz In the above formula, Me is selected from the group consisting of metal cations and hydrogen, n is the valence of Me, and X is a number in the range of from about 2.2 to about 14. Most useful are those zeolites in which X is in the range from about 3 to about 6.5. Preferred molecular sieve zeolites for use as hydrocracking catalyst bases are those in which the zeolite has been base exchange so that sodium represents a minor molar proportion of the metal represented as Me.

One way of making the hydrogen form of the sieve is to base exchange it with an ammonium cation solution and thereafter calcine. The step in which the hydrogen form or the NI-l form of the sieve is composited with the noble metal may be in the nature of a wet impregnation or a base exchange reaction. Thus a platinum or palladium salt or an ammonium complex of these elements, for instance, Pt(NI-I Cl ammonium chloroplatinate and many others may be used. The palladium salts such as PdCl may also be used, either for impregnation or base exchange. The amount of catalytic metal in the finished catalyst is ordinarily between 0.01 and about 5.0 weight percent.

A BY molecular sieve may be prepared by mixing 646 grams of water, 157 grams of alumina hydrate (65% A1 0 244 grams of sodium hydroxide (97% NaO-H) and 2002 grams of a silica hydrosol and then heat soaking the mixture at 210 F. for 4 days. A crystalline product is formed which can be separated from the mother liquor by filtering and then washed with water. The product obtained is the sodium form of a 13Y molecular sieve. The sodium form can be converted to the ammonium form by ion exchange with a solution of ammonium chloride. To prepare a catalyst for a fixed bed hydrocracking operation, the ammonium form of the sieve may be impregnated with palladium by treating it with a solution of palladium chloride and converting the impregnated molecular sieve to the active catalyst by heating to a temperature in the range of 600 F. to 1000" F. to volatilize ammonia and to convert the base to the hydrogen or decationized form. The amount of palladium in the catalyst may be in the range of 0.01 to 5 wt. percent.

With certain feeds that have high nitrogen contents (above about 500 p.p.m.), a mixed catalyst or staged catalyst system may advantageously be employed. In such a case, the hydrocracker reactor contains two catalysts in series. For instance, the inlet portion of the fixed bed may be made up of a hydrogenation-type catalyst such as cobalt oxide-molybdenum oxide, or nickel oxide-molybdenum oxide, on a base of either alumina or silica-alumina. The downstream or outlet portion of the bed may consist of a crystalline zeolite catalyst such as palladium on a hydrogen form of 13Y molecular sieve.

In a fixed bed hydrocracking operation, a temperature of 300 to 900 F., preferably 500 to 800 tF., is employed and a pressure of 500 to 3000 p.s.i.g., preferably 1000 to 2500 p.s.i.g., is used. The hydrogen recycle rate may range from about 2000 to 30,000, and preferably about 3000 to 20,000 cubic feet of hydrogen per barrel of hydro cracking feed.

The product of the hydrocracking treatment is passed by means of line 19 into hydrogen separation zone 20 wherein hydrogen is separated from the product and recycled to the hydrocracking zone through lines 21 and 18. Associated with zone 20 there may be provided means (not shown) to treat the separated hydrogen by conventional methods to remove hydrogen sulfide and ammonia prior to recycle. After the recycle gas has been separated from the hydrocracker effluent the latter is fed by means of line 23 into a distillation zone 24 wherein conditions are maintained to separate the material into a number of cuts including a gaseous fraction comprising propane and lighter gases which are removed through line 25, a C to C fraction which is removed through line 26, a heavy naphtha fraction ranging from C hydrocarbons up to an end point of 350 to 430 P. which is removed through line 27, and a bottoms fraction having a boiling point of 350 to 430 F. and higher which is removed through line 30 and recycled to the hydrocracking zone 17 through line 16. If desired, a heating oil fraction may be taken as a side stream from the distillation zone through line 28.

The heavy naphtha fraction in line 27 is sent into a catalytic hydroforming zone 31 wherein reforming conditions are maintained that result in a net production of hydrogen. Preferably, the catalyst for the hydroforming comprises a fixed bed of a platinum catalyst supported on an alumina support wherein the alumina contains from 0 to 5 wt. percent of silica. The platinum content may range between about 0.01 and 5 wt. percent and preferably the catalyst contains combined halogen in an amount between about 0.3 and 2 wt. percent of fluorine or chlorine or both.

The temperature maintained in the hydroforming zone is preferably in the range of about 850 F. to 1000" F., the pressure is preferably between and 1000 p.s.i.g., and the reaction space velocity is in the range of 0.1 to 10 v./hr./v. The amount of hydrogen introduced into zone 31 is usually in the range of about 1000 to 10,000 cubic feet per barrel of naphtha feed.

The hydroformed products are passed through line 32 to a liquid-gas separator 33 for separating hydrogencontaining gas from liquid hydrocarbons. The separating means preferably includes a conventional absorption step or the like to remove impurities such as sulfur and nitrogen from the gas. The gas is passed overhead through line 34 and a portion of it is recycled to the hydroforming zone 01 via line 36. The hydrogen gas produced over and above the quantity recycled to the hydroforming zone is sent by means of line 35 and line 18 to the hydrocracking zone 17. Liquid hydrocarbons separated from the recycle gas in separating zone 33 are withdrawn from the bottom of the separator by means of line 37 and may be blended into finished gasoline.

While the hydroforming operation has been described as one involving a fixed catalyst bed, the hydroforming unit of zone 31 may comprise a fluid catalyst reforming zone in which the catalyst employed may comprise molybdenum trioxide on alumina. Reaction conditions in this case include pressures of 50 to 300 p.s.i.g., temperatures of 850 to 1000 F., and a feed rate of 0.5 to 2 w./hr./W. with a hydrogen recirculation rate of 1000 to 5000 standard cubic feet per barrel of feed.

The following is a specific example of the operation of the process of this invention. About 10,000 barrels per stream day of whole crude petroleum oil are introduced by means of line into coking zone 11. The crude oil of South Louisiana origin has an API gravity of 38.4 and a Conradson carbon content of about 0.8 wt. percent. About 11 tons of coke and about 9,700 barrels of liquid products having an API gravity of about 43 are produced per stream day in coking zone 11. All of this coke is burned in the regenerator of zone 11 to produce heat for the coking operation. With some feeds having a higher Conradson carbon content, a net coke make may result. The temperature in the coking zone is about 970 F. and the pressure is about 15 p.s.i.g. The liquid product from the coking zone has an initial boiling point of about 150 F. and a final boiling point of about 1000 F.

The fixed bed hydrocracking zone 17 is maintained at a temperature of about 680 F. and a pressure of 1500 p.s.i.g. The recycle stream in line 18 supplies 10,000 cubic feet of hydrogen per barrel of feed in the hydrocracking step. The catalyst comprises 0.5 wt. percent of palladium on a hydrogen form of a molecular sieve of about 13 A. The total feed to the hydrocracker amounts to about 12,700 b./d. being composed of about 9,700 b./d. of liquid products from the coker through line 16 and about 3,000 b./d. of recycle from the hydrocracker through line 30. The efiiuent from the hydrocracker 17 passes through line 19 into the high pressure separator 20.

The high pressure separator 20 is maintained at a pressure of about 1500 p.s.i.g. and a temperature of about 80 F. The excess hydrogen passes overhead through line 21 to be recycled to the hydrocracker via line 18. This recycle hydrogen may contain varying amounts of hydrocarbon gases, such as methane. To minimize the build-up of such gases, a small amount of the recycle hydrogen stream is purged via line 22 prior to the introduction of make-up hydrogen from line 35. About 13,600 barrels per stream day of hydrocarbon liquid product is withdrawn through line 23 (and a pressure reducing devicenot shown) into a distillation zone 24 which is at about 15 p.s.i.g. pressure. The total product is separated to give about:

17,000 s.c.f./d. of C gas through line 25 3,300 b./d. of C C hydrocarbon through line 26 7,300 b./d. of 180/400 F. naphtha 3,000 b./d. of hydrocarbons boiling above 400 F.

which are recycled through line 30 to line 16.

In this particular case, no heating oil product is withdrawn as such, although if such a product were desired it could be withdrawn as a separate side stream through line 28.

About 7300 barrels per stream day of heavy naphtha having a boiling range between about 180 F. and 400 F. are withdrawn through line 27 of the distillation vessel 24 and passed into the hydroforming zone 31 which contains a fixed bed of catalyst comprising about 0.5 wt. percent of platinum and 0.2 wt. percent of chlorine on alumina. The hydroforming zone 31 is maintained at a pressure of about 425 p.s.i.g. and a temperature of about 930 F. A liquid space velocity of 1 to 2 v./hr./v. is used. The hydroformed liquid products obtained in line 37 amounts to about 6000 barrels per stream day when reforming to a product having Research octane number (with 3 cc. of tetraethyl lead).

There are a number of advantages gained by employing the process of the present invention. The following are particularly noteworthy:

(1) The coking operation removes ash and the metalcontaining compounds that occur in crudes and residua. Removal of these components prior to contacting the oil with a catalyst is highly desirable as these materials tend to deactivate the catalyst. Feeding the total crude to the coker utilizes the coker as a distillation zone, with the undesirable coke product being burned to furnish heat for the process.

(2) Feeding the total liquid product from the coker to the hydrocracking zone results in stabilizing and desulfurizing the thermal naphtha and heating oil made in the coking operation. Thus, the need for a separate processing unit for this purpose is avoided. In addition, the inclusion of the low-boiling material in the feed to hydrocracking improves the operation of the hydrocracker because the light material increases the degree of vaporization of the heavy oil. Increased vaporization in a hydrocracker reactor gives improved results, i.e. better catalyst activity and activity maintenance. Also, the low-boiling coker product contains less nitrogen compounds than does the higher-boiling oil. Inclusion of the light components in the feed to hydrocracking means that the nitrogen content of the hydrocracker feed is lower than if the light components were not included. This is desirable, because the activity of a hydrocracking catalyst is greater with low nitrogen content feeds than it is with higher nitrogen content feeds.

(3) In addition to the above, this system of sending the thermal naphtha through the hydrocracker results in improved volatility of the final gasoline product.

It will be understood that it is not intended that the scope of this invention be limited by the foregoing description of specific embodiments and examples. The true scope of the invention is defined by the appended claims.

What is claimed is:

1. In a process wherein a feedstock from the class consisting of whole petroleum crude oils and topped spetroleum crude oils is converted to desired end products by a combination of coking, hydrocracking and reforming steps, the improvement which comprises the steps of subjecting the entire feedstock to a coking step to form a liquid product boiling in the range between F. and 1000 F. and thereafter subjecting the entire said liquid product of the coking step to a hydrocracking step.

2. A process for converting a feedstock from the class consisting of whole petroleum crude oils and topped crude oils to desired end products which comprises the steps of subjecting the entire feedstock to a coking step, to form a liquid product boiling in the range between 150 F. and 1000 F., subjecting the entire said liquid product of the coking step to hydrocracking and subjecting the heavy naphtha fraction of the hydrocracked product to a reforming step under conditions resulting in a net production of hydrogen.

3. Process as defined by claim 2 wherein the hydrogen produced in said reforming step is employed in said hydrocracking step.

4. Process as defined by claim 1 wherein said hydro cracking step is conducted in the presence of a catalyst comprising a molecular sieve zeolite impregnated with a platinum group metal.

5. Process as defined by claim 1 wherein said hydrocracking step is conducted in two stages, a hydrogenation catalyst being employed in one stage, and a hydrocracking catalyst being employed in the other stage.

6. In a process for converting a feedstock from the class consisting of whole petroleum crude oils and topped petroleum crude oils to desired end products by a combination of processing steps including coking, hydrocracking and reforming, the improvement which comprises: supplying the entire feedstock to a coking zone, subjecting said feedstock to coking conditions in said zone, including a temperature in the range of 8001200 F., separating from the products of said coking zone the entire liquid portion thereof, said entire liquid :portion boiling in the range between 150 F. and 1000 F., subjecting said entire liquid portion to hydrocracking, thereafter separating hydrogen from the hydrocracked products and then distilling the remaining hydrocracked products in a distillation zone into'a number of fractions, including a bottoms fraction boiling above about 300 to 430 F., a heavy naphtha fraction having 0; hydrocarbons and higher, and a fraction including C hydrocarbons and lower, recycling said bottoms fraction to the hydrocracking zone, subjecting said heavy naphtha fraction to' a reforming step under conditions resulting in a net production of hydrogen and employing the hydrogen thus produced in said hydrocracking step.

References Cited by the Examiner UNITED STATES PATENTS 3,008,895 11/1961 Hansford et al 2O8-112 3,072,560 1/1963 Paterson et al. 208- 3.119,763 1/1964 Haas et al. 20811O 3,132,090 5/1964 Helfren et al. 208

DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, PAUL E. COUGHLAN,

. Examiners.

Claims (1)

1. 2. A PROCESS FOR CONVERTING A FEEDSTOCK FROM THE CLASS CONSISTING OF WHOLE PETROLEUM CRUDE OILS AND TOPPED CRUDE OILS TO DESIRED END PRODUCTS WHICH COMPRISES THE STEPS OF SUBJECTING THE ENTIRE FEEDSTOCK TO A COKING STEP, TO FORM A LIQUID PRODUCT BOILING IN THE RANGE BETWEEN 150* F. AND 1000*F., SUBJECTING THE ENTIRE SAID LIQUID PRODUCT OF THE COKING STEP TO HYDROCRACKING AND SUBJECTING THE HEAVY NAPHTHA FRACTION OF THE HYDOCRACKED PRODUCT TO A REFORMING STEP UNDER CONDITIONS RESULTING IN A NET PRODUCTION OF HYDROGEN.

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