US3844734A

US3844734A - Conversion of hydrocarbon oil to a synthetic natural gas

Info

Publication number: US3844734A
Application number: US00318701A
Authority: US
Inventors: M Johnson
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1972-12-27
Filing date: 1972-12-27
Publication date: 1974-10-29
Anticipated expiration: 1991-10-29

Abstract

A crude hydrocarbon oil or gas oil is cracked with a ''''used'''' cracking catalyst having a high metal content under conditions of severity to produce gasoline and lighter products to an optimum extent. Effluent is cooled to obtain a gasoline fraction with large amounts of H2 and light gases and a heavier product stream which is recycled to the cracking operation. Gasoline and higher components are dehydrosulfurized, using generated hydrogen for the purpose. Thus treated stream is cooled to obtain a liquid and a gas stream. A portion of the gas stream is used as a hydrogenrich gas for the catalytic hydrodesulfurization. Another portion is treated to remove H2S therefrom and thus treated gas and liquid obtained upon the cooling, after some preheat, are passed to a synthetic natural gas reactor, preferably after further treatment to produce a stream containing less than about one part per million of sulfur. The process is self-sustaining in hydrogen. Coke deposited on catalyst on regeneration yields sufficient heat to supply steam requirement for Synnat process.

Description

United States Patent 11 Johnson [451 Oct. 29, 1974 CONVERSION OF HYDROCARBON OIL TO A SYNTHETIC NATURAL GAS Marvin M. Johnson, Bartlesville, Okla.

Assignee: Phillips Petroleum Company, Bartlesville, Okla.

Filed: Dec. 27, 1972 Appl. No.: 318,701

[75] Inventor:

[5 6] References Cited UNITED STATES PATENTS 11/1970 Smith, Jr 208/89 5/1973 Carr et al 48/213 X Primary Examiner-R. E. Serwin [5 7] ABSTRACT A crude hydrocarbon oil or gas oil is cracked with a used cracking catalyst having a high metal content under conditions of severity to produce gasoline and lighter products to an optimum extent. Effluent is cooled to obtain a gasoline fraction with large amounts of H and light gases and a heavier product stream which is recycled to the cracking operation. Gasoline and higher components are dehydrosulfurized, using generated hydrogen for the purpose. Thus treated stream is cooled to obtain a liquid and a gas stream. A portion of the gas stream is used as a hydrogenrich gas for the catalytic hydrodesulfurization. Another portion is treated to remove H 8 therefrom and thus treated gas and liquid obtained upon the cooling, after some preheat, are passed to a synthetic natural gas reactor, preferably after further treatment to produce a stream containing less than about one part per million of sulfur. The process is self-sustaining in hydrogen. Coke deposited on catalyst on regeneration yields sufficient heat to supply steam requirement for Synnat process.

4 Claims, 1 Drawing Figure NZYCOZ CRACKED GAS a I COMPRESSOR 2, i' lz 7 AND LIGHT LIQUID AIR HYDROCARBONS CA c HYDRODESULFURIZATION AND HYDROGENATION OF OLEFINS CRACKER '-2s 32 H2 GAS-OIL I HEAVY RICH GAS HYDROCARBON COMPRESSOR 27 29 2- STEAM m as PREHEATER 5 34 GAS SEPARATOR SYNNAT REACTOR 5 l \UQUID r H2S\ 1 PHASE -37 35- '54 49 as as 5l- 53- 4| 55 LC 46 1 s2 ZnO 42 Bed 11 s REMOVAL umr 45 CONVERSION OF I-IYDROCARBON OIL TO A SYNTHETIC NATURAL GAS This invention relates to the production of a synthetic natural gas. In one of its aspects it relates to a conversion of a crude oil or gas oil to a synthetic natural gas or gaseous fuel. In a further aspect of the invention, it relates to a combination of steps converting a crude oil or other liquid hydrocarbons to a feed for a catalytic,

synthetic natural gas-producing operation.

cooled forming a liquid condensate and a hydrogen-' rich stream, a portion of the hydrogen-rich stream is cycled to the catalytic hydrodesulfurization while another portion is subjected to treatment to remove therefrom H 8 whereupon it with liquid obtained in the last mentioned cooling is passed to a synthetic natural gas-producing operation. In another of its concepts, the invention provides an operation as described wherein heavier reaction products obtained upon cooling the cracking effluent are recycled to the cracker to extinction. In a further concept of the invention, it provides a process as described wherein the synthetic natural gas reactor feed stream is subjected to a final desulfurization to yield a feed stream containing less than about one part per million of sulfur. Further, still another concept of the invention provides a process which in regenerating the catalyst used to crack the feed stock in the cracking operation is regenerated and only regeneration provides sufficient heat to yield steam for operation of the synthetic natural gas producing step. In a more specific concept of the invention, the feed to the synthetic natural gas producing reactor (SYNNAT a trademark) is a full range naphtha which permits obtaining high yields of fuel gas from the crude oil.

I have conceived a combination of steps for producing a synthetic natural gas or fuel involving steps as herein described which is self-sustaining in hydrogen requirement, i.e., there is no need to convert a portion of the crude to hydrogen in a separate operation. Further, in the combination of steps, as herein described, coke deposited on a cracking catalyst will yield on regeneration sufficient heat to provide the steam requirement for operation of the Synnat process. This includes waste heat recovery on all process steps described and suitably positioned heat exchange zones.

Calculations show that a crude with a I-I/C ratio of 1.786 will net approximately 6.66 M SCF/B of feed of 754 Btu/SCF, which corresponds to a thermal efficiency of 80 percent over-all. The reaction sequence can be generally depicted as follows:

1.08 C 1.08 4.07 N; l.O8 CO 4.07 N

2.65 cu +1.10 H2O 2. 10 cu, 0.55 co 0.5

The respective equations represent (I) the catalytic cracking reaction, (2) theregeneration of the catalyst, and (3) the conversion process that occurs in the Synnat unit. There is essentially no change in the HIC ratio in the desulfurization olefin saturation step.

The net gas yield and over-all thermal efficiency are dependent to an extent on the feed composition, employing of course conditions suitable to each, and lesser yields of product gas will be obtained from feeds higher in aromatic content. The approximate relationship between composition of the feed and efficiency is shown in Table I.

TABLE I O I in It is an object of this invention to produce synthetic natural gas or fuel. It is another object of the invention to provide a process for the production of a synthetic natural gas or fuel. It is a further object of this invention to provide a combination of steps in a unitary operation permitting the conversion of a crude oil or gas oil to a synthetic natural gas, the operation being selfsustaining in heat required to generate steam used in the process.

Other aspects, concepts, objects and the several advantages of the invention are apparent from a study of this disclosure, the drawing and the appended claims.

ciently to condense therefrom substantially C and higher boiling products, desulfurizing gases and vapors thus obtained including any C material not separated therefrom while simultaneously hydrogenating oletins contained therein, cooling to separate a hydrogen rich light gas from a liquid fraction, using a portion of said hydrogen rich light gas for the hydrogenation of said olefins, subjecting another portion of said hydrogenrich gas together with liquid obtained upon cooling the desulfurized stream to a synthetic natural gasproducing operation for conversion to a natural gas or fuel.

In one embodiment of the invention which is now preferred, the C and higher boiling materials obtained upon cooling of the catalytic cracking effluent are recycled to the catalytic cracking operation. Also in said embodiments the combined liquid and gas which has been treated to remove H S therefrom is passed to a further or final sulfur-removal step, for example, through a zinc oxide bed, to produce a feed for the Synnat reaction zone containing less than about one part per million of sulfur.

Also according to the invention and as a feature thereof, the conditions of operation including the cracking and regeneration of catalyst are so selected as to provide sufficient heat-from the regeneration of the cracking catalyst and from the Synnat reactor that the steam requirements in the Synnat reactor can be met.

Conventional cracking catalyst such as synthetic or natural zeolites, synthetic or natural clays, bauxite, brucite, silica-alumina and the like can be used in the practice of this invention. These catalysts are used under high severity conditions to produce a mixture of hydrogen-rich light gas and naphtha. Thus used or spent known cracking catalyst adapted to severely crack a heavier crude oil normally not suited to producing a gasoline and containing up to about 2 weight percent metals such as nickel, vanadium and iron, present as the oxide, in the catalyst, for example supported on a suitable carrier, e.g., silica-alumina, a zeolite, etc., can be employed.

The oil is advantageously catalytically cracked at a temperature of from about 800 to l,300 F and preferably the cracking will be conducted at a temperature in the range of from about 900 to l,l F. The regeneration of the used catalyst is conducted in a temperature range of from about l,l00 to about l,400 F or even somewhat higher.

The catalytic cracking operation can employ a fixedbed, moving bed or fluid or other process.

In the second stage of the operation, the noncondensed gases and naphtha range hydrocarbons are hydrotreated using a hydrotreating catalyst, e.g., a nickel molybdate or equivalent catalyst to effect at least a partial desulfurization and complete saturation of olefins. The catalyst used is any type of hydrogenation catalyst which functions in the presence of sulfur, for example, sulfides or oxides of tungsten, molybdenum, chromium, vanadium, etc. A now preferred type of catalyst is a mixture or chemical combination of an oxide or sulfide of an iron group metal with an oxide or sulfide of a metal of Group VlB, such as a mixture of an oxide or sulfide of nickel or cobalt with an oxide or sulfide of molybdenum or tungsten. Especially preferred, now, is a nickel molybdate or a cobalt molybdate catalyst. The catalyst is preferably on a porous support selected from activated alumina or a silicaalumina cracking catalyst. These catalysts are known in the art.

The temperature in the hydrotreating step will usually be in the range of from about 500 to about 750 F. a temperature in the approximate range of from about 550 to about 650 F being now preferred. A pressure of from about 100 to about 2,000 psig can be used. A pressure of from about 200 to 700 psig is now preferred. Hydrotreating of this kind is known in the art. in general.

A portion of the hydrogen-rich gas is recycled to remove the exothermic heat from the hydrodesulfurization reactor and to aid in the desulfurization. This gas also hydrogenates the olefins as earlier explained. The balance of the gas phase obtained from the hydrodesulfurization reactor is sent to a hydrogen sulfide removal step. e.g., a Girbotol unit to remove hydrogen sulfide from the gas. This operation is described in Petroleum Refiner, September, 1960, page 267 and is known as the Girbotol process.

Aqueous solutions of monoethanolamine and diethanolamine are generally employed in the Girbotol process for removal of hydrogen sulfide from the gases. The absorber normally operates at about F at the inlet and 108 F at the outlet at about 300 psi pressure. The stripper in the Girbotol unit usually is operated at about 200 F and from about 5 to about 10 psig pressure. One skilled in the art can select different condi tions depending on the results he wishes to reach.

The gas from the Girbotol unit is passed with the liquid stream obtained in the separation of gases resulting from the hydrodesulfurization effluent and the combined gas and liquid stream is further desulfurized as may be necessary. It is now preferred to contact the stream with a zinc oxide or equivalent bed to remove trace amounts of hydrogen sulfide. The thus obtained sulfide free gas, containing less than about one part per million of sulfur, is passed to the Synnat reactor. In this reactor, a synthetic natural gas stream is produced.

The Synnat process is described in the art. Patents related to this operation are U.S. Pat. No. 3,506,417 issued Apr. 14, 1970, Harold J. Hepp and E. O. Box, Jr.; U.S. Pat. No. 3,506,4l8 issued Apr. 14, 1970, William G. Billings and U.S. Pat. No. 3,522,024 issued July 28, 1970, William G. Billings and William T. Nelson. The disclosures of these patents are incorporated herein.

The conditions for the Synnat operation now preferred in this invention are a reforming temperature, which can vary appreciably, and which will be usually in the range of from about 700 to l,000 F preferably in the range of from about 750 to 875 F. The reaction pressure will be ordinarily in the range of from about 100 to about 2,000 psig, preferably 200-700 psig. The steam to hydrocarbon weight ratio will be ordinarily at least about 1.2 to 1, generally in the range of from about 1.211 to about 6:1.

Referring now to the drawing the feed hydrocarbon, for example, a West Texas atmospheric gas oil, as described herein, is passed by l, 2, heat exchanger 3, and 4 into cracker 5. The temperature in cracker 5 is' maintained at a level of the order-of about 900 F. A catalyst, as described herein, which has been used and which is one having a metal content is employed to maximize yields of C and lighter hydrocarbon. Other catalytic products including gases are formed.

Spent catalyst is passed by 6 together with air entering at 7 into a regenerator 8 at which a catalyst is regenerated under conventional conditions which include a temperature of the order of about l,l00 F. Gaseous regeneration products which include nitrogen and carbon dioxide are removed from the system at 9 by way of heat exchangers l0 and 11 and pass from the system at 12. Liquid water is passed by 13 and 14 through heat exchangers 11 and 10 resulting in steam which can be used in the process and which is obtained at 15.

From cracking reaction zone 5 a cracked effluent is passed by 20 through heat exchanger 3 and 21 into a gas separatorcooling zone 22 from the bottom of which a cycle oil containing essentially C and heavier hydrocarbons is returned by way of 2, heat exchanger 3 and 4 to cracker 5.

Non-condensed gases are removed from separator 22. These gases which contain hydrogen and C -C, hydrocarbons, both saturated and unsaturated are passed by 23 to the suction of cracked gas compressor 24 and by 25 to catalytic hydrodesulfurization in a nickel molybdate hydrodesulfurization catalyst containing vessel 26. Here the non-condensed gases and vapors are at least partially desulfurized and are passed by 27 cooler 28 and 29 to gas separator zone or vessel 30. A portion of non-condensed gas is taken from vessel 30 by 31 and compressor 32 and recycled as a hydrogen-rich gas to vessel 26 to aid in the desulfurization there taking place. The liquid phase from vessel 30 is passed by 34, 35,

preheater

36, 37 and 38 to a synthetic natural gas producing reactor 39 to which steam obtained at is passed by 16. Preferably, however,,the stream in 37 is preheated at 41 and passed by 47 into and through a 'zinc oxide bed 48 and thence by 49 as a sulfur free stream to reactor 39. The stream in 49 normally will contain less than about one part per million of sulfur.

Returning to gas separator 30 a portion of the hydrogen-rich gas is passed by 50 into an H 8 removal unit of the Girbotol type. This consists essentially of an absorber 51 to which is passed, into the top, a hydrogen sulfide removal solvent or absorbent such as an aqueous solution of monoethanolamine. The enriched solution is passed by 52 to stripper 53 wherein it is heated and stripped of 1-1 8 which is removed from the system at 54. The lean solvent, after suitable temperature adjustment not shown, is passed by 55 to the top of the absorber. The H S-free gas in 35 is passed together with the liquid from 34 to the synthetic natural gas reactor as earlier described. A synthetic gas product is removed at 57 passed through heat exchanger 41 and by 42, after cooling at 43 from the process as product gas obtained at 44. Steam is generated in cooling the synthetic natural gas stream by liquid water introduced at 45 into heat exchanger 43 and recovered therefrom as steam is passed by 46 to 16 and thence to the synthetic natural gas reactor as a portion of the steam requirement there.

Properties of Feed to Cat Cracker lJnit West Texas Atmospheric Gas Upon cracktng under conditions as noted below in the table the effluent presented analysis as also follows.

Average Temperature, F. 898

Pressure, psig 10 Process Cycles, per minute 14 Steam, Pounds/Barrel 19.7

Conversion. Volume Fresh Feed 52.34

Severity Factor 5.94

Weight of Moles/100 Lbs.

Yield Fresh Feed of Fresh Feed G soline (C -C Cycle Oil 48.20

Coke 13.91

Gasoline. ASTM (C,-,C,, hydrocarbons) Cycle Oil FD I04F 2% 492F 10 136 10 522 20 156 20 554 30 182 30 583 40 214 40 610 60 290 60 658 352 80 725 EP 432 826 Gravity, AP1 51.4 26.8

Bromine Number 78 Sulfur,-Wt. .86

Carbon Residue .16

K Factor 1 1.51

Moles Olefin/ Lbs. Fresh Feed 0.130

Typical'crude oils which can be used as feedstock in this invention include paraffinic-base, naphthenic-base, asphaltic-base or mixed base crude oils, or fractions of the crude oil. Gas oils and distillates boiling above about 400 F are now preferred as feedstock in this invention.

The foregoing information and data which have been given to illustrate the operation of the invention are inclusive of actual data obtained in runs which are characterized, knowledge in the field and engineering and related information. These have been incorporated together to more fully illustrate the invention.

Reasonable variation and modification are possible in the scope of the foregoing disclosure, the drawing and the appended claims to the invention the essence of which is that there has been provided a combination of steps for producing a synthetic natural gas or fuel from a hydrocarbon oil in a manner and under conditions such that the process is self-sustaining in hydrogen, heat requirements for producing steam, does not require hydrogen to be produced in a separate step, yielding said gas or fuel in a simplified operation which comprises essentially the cracking of the oil under conditions of severity to produce optimum amount of C and lighter products using a high metal content used cracking catalyst, hydrotreating C and lighter products thus obtained, using hydrogen produced in the process to hydrogenate the olefins contained in the gases and to hydrodesulfurize the same, passing gases thus treated to further treatment to remove hydrogen sulfide therefrom, passing thus pretreated gas and liquid, obtained from the hydrodesulfurization step upon cooling the hydrodesulfurization effluent, to a Synnat reaction operation and recovering from said operation a synthetic natural gas or fuel.

I claim: 1. The production of a synthetic natural gas or fuel which comprises in combination the steps as follows:

1. catalytically cracking a hydrocarbon oil in presence of a high metals content cracking catalyst under conditions to produce an optimum maximum of C and lighter products, 2. hydrodesulfurizing said products, 3. separating said products into a liquid fraction and a hydrogen-rich gas, 4. using a portion of the hydrodesulfurization, 5. removing hydrogen sulfide from the remainder of said hydrogen-rich gas, and 6. passing thus treated hydrogen-rich gas together hydrogen-rich gas for said 3. An operation according to claim 1 wherein the catalyst used in the cracking operation is regenerated and heat obtained from the regeneration is used to produce steam for the Synnat operation.

4. An operation according to claim I wherein the liq-' uid and gas prior to being passed to the Synnat operation are treated to produce a stream containing less than one part per million of sulfur and such a stream is passed to the Synnat operation.

Claims

1. THE PRODUCTION OF A SYNTHETIC NATURAL GAS OR FUEL WHICH COMPRISES IN COMBINATION THE STEPS OF FOLLOWS:

1. CATALYTICALLY CRACKING A HYDROCARBON OIL IN PRESENCE OF A HIGH METALS CONTENT CRACKING CATALYST UNDER CONDITIONS TO PRODUCE AN OPTIMUM MAXIMUM OF C12 AND LIGHTER PRODUCTS,

2. An operation according to claim 1 wherein C12 and higher boiling products obtained from the cracking are recycled to said cracking.

2. hydrodesulfurizing said products,

2. HYDRODESULFURIZING SAID PRODUCTS,

3. SEPARATING SAID PRODUCTS INTO A LIQUID FRACTION AND A HYDROGEN-RICH GAS,

3. An operation according to claim 1 wherein the catalyst used in the cracking operation is regenerated and heat obtained from the regeneration is used to produce steam for the Synnat operation.

3. separating said products into a liquid fraction and a hydrogen-rich gas,

4. An operation according to claim 1 wherein the liquid and gas prior to being passed to the Synnat operation are treated to produce a stream containing less than one part per million of sulfur and such a stream is passed to the Synnat operation.

4. using a portion of the hydrogen-rich gas for said hydrodesulfurization,

4. USING A PORTION OF THE HYDROGEN RICH GAS FOR SAID HYDRODESULFURIZATION,

5. REMOVING HYDROEN SULFIDE FROM THE REMAINDER OF SAID HYDROGEN-RICH GAS, AND

5. removing hydrogen sulfide from the remainder of said hydrogen-rich gas, and

6. passing thus treated hydrogen-rich gas together with liquid obtained from the hydrodesulfurization operation to a Synnat or synthetic natural gas producing operation.

6. PASSING THUS TREATED HYDROGEN-RICH GAS TOGETHER WITH LIQUID OBTAINED FROM THE HYDROESULFURIZATION OPERATION TO A SYNNAT OR SYNTHETIC NATURAL GAS PRODUCING OPERATION.