US2619450A - Hydrogenolysis process for the production of lower boiling hydrocarbons from heavy residual oils with reduced formation of coke - Google Patents

Description

Nov. 25, 1952 H W FLEMlNG 2,619,450

HYDROGENOLYSIS PROCESS FOR THE PRODUCTION OF LOWER BOILNG HYDROCARBONS FROM HEAVY RESIDUAL OILS WITH REDUCED FORMATION OF COKE Filed Jan; 4, 1950 Patented Nov. 25, 1952 HYDROGENOLYSIS PROCESS FOR THE PRO- DUCTION F LOWER BOILING 'HYDRO- CARBONS FROM HEAVY RESIDUA'L OILS WITH REDUCED `'FORMATION 0F COKE Harold W. Fleming, Bartlesville, Okla., .assignor to APhillips Petroleum Company, a corporation of Delaware Application January 4, 195i), .Seral No. 136,829

(Cl. '19E-53.)

i Claims.

This invention relates tothe -hydrogenolysis of hydrocarbonaceous materials. In `one of its more specic'aspects it relates to animproved method for hydrogenolizing hydrocarbonaceous materials. -A lpreferred embodiment lof vmy invention relates to a method for the .hydrogenolysis of heavy residual hydrocarbon stocks in which the formation :of coke is substantially reduced.

The destructive hydrogenat'ion or hydrogenolysis of Vheavy residual Yhydrocarbon stocks, fsu'ch as .reduced crude, vacuum .reduced crude, topped crude cracking residuum, .and .like stocks, .has been known .for some time, having` .been `first developediniGermany. The process is quite useful in converting these and other high molecular Weight hydrocarbons into .lower boiling hydrocarbons boilinggenerally Within fthe gasoil range for use as cracking feeds, diesel oils, burning oils, and the like. Usually .the v.gasoline boiling range materials are notof exceptional quality-and must be further rtreated such as by reforming to 'provide a .good grade gasoline.

In general hydrogenolysis, which is cracking with hydrogenation, .is carried out lat pressures rangingfrom 1500 to 10,000 p.s. i. and higher, and at temperatures, varying considerably, but generally in the range of 800 to 1000 F. The heavy oil to be treated and hydrogen are preheated and introduced -to a reaction chamber containing a suitable hydrogenolysis catalyst. One -of the vbig problems `confronting any hydrogenolysis process is the for-mation of carbon in the reaction chamber, particularly in the vicinity of the feed inlet.

.Anobject of this invention -is to lprovide an im*- prov'ed hydrogenolysis process for the treatment of hydrocarbonaceous materials.

Another object of this invention is to lengthen the intervals between regeneration periods 'for va hydrogenolysis catalyst.

Another object is to provide a method lfor the reduction in the formation of coke and Acarbon when hydrogenolizing a hydrocarbonaceous vmaterial.

Still another object of this invention is a novel method for introducing the feed to a hydrogenolysis process whereby coke formation is maintained at a minimum.

Still further objects and advantages of this invention will be apparent to one skilled in the art `from the accompanying discussion and disclosure.

`I have found that the `deposition of coke raround the feed inlet to a hydrogenolysis reactor may be substantially eliminated if the feed is substantially free of suspended carbon and carbonaceous materials and, if certainprecautions are taken in handling the feedto the reactor. Theimainsource of `carbon stems from vthe unsaturates which .are present either in the original oil, such fas cracking residuum orare formed when the Voil is l.passed through a preheater by 'crackinga portion thereof. .In .any-event it is highly desirable to reduce the formation 'of this carbon which rapidly deactivates the catalyst.

I .have -discovered Ithat coke is :formed in the feed preheater -when the lfeed is preheated along With the hydrogen. This is .the result of having to `use excessively high preheater skin temperatures 'or excessively ylong preheat time .due to the large volume of material handled. The thus formed .coke ,is carried into the catalyst chamber with the .feed and .is deposited 4on Ythe catalyst near the feed inlet. I have also discovered that, even `though coke is not formed/in .the .preheater, it may be deposited on the catalyst as a result of contacting unsaturated materials in the charge oil with a catalyst at too high -a temperature. Under such conditions the heat of the catalyst will cause the unsaturates to crack to some 'degree thereby depositing carbon. .I have been able to overcome the lcarbon deposition found on a hydrogenolysis catalyst in `the vicinity of the .feed inlet by preheating the hydrogenolysis feed with only va minor amount of hydrogen present to a temperature at which lcracking and the tformation of coke and coke forming bodies does not take place. I have been able to further -prevent this coke formation by rstcontacting the feed, .preheated to a temperature at which no coke or coke forming ybodies are produced, With -a hydrogenolysis catalyst at a temperature just .slightly higher than the preheat temperature and then gradually raising the temperature of the .feed :in the presence of the 'catalyst vand added hydrogen to the hydrogenolysis temperature thereby hydrogenating the unsaturates duri-ng .this `gratlual increase in temperature land making materials less susceptible to 'degradation t0 carbon or carbonaceous materials.

In the Vpractice of my invention a hydrocarbonaceous .material having an initial boiling point generally `in Vthe .neighborhood tof 850 F., lor .higher, which may-be a residui-1m obtained by the yacuum fractionation of toppedscrude reducedcrude, virgin asphalt as from .propane vdeaspihalting, topped crude cracking bottoms, gas oil cracking bottoms, .gasoil from Ypitch production, -or other heavy hydrocarbon material, is preheated to fa temperature up -to 700 F. Yand preferably in the range of 500 to l700" F., :the temperature selected from this range being such that comparatively little vaporiza-tion and no production of Vcoke and/or coke forming bodies takes place in the preheater. A small quantity of dissolved hydrogen may also desirably be present in the preheated oil, generally in a quantity of not more than 200 to 400 cubic feet per barrel of charge. The reason for desiring a small amount of dissolved hydrogen present in the feed is to have it quickly available to saturate the easily cracked components of the feed material. This mode of operation provides hydrogen faster than the introduction of same in a separate vapor stream.

The preheated hydrocarbon containing a quantity of dissolved hydrogen is introduced to a hydrogenolysis zone at a space velocity in the range of 0.5 to 4 and preferably 1 to 2 volumes per volume of catalyst per hour where it is contacted with additional hydrogen over a suitable catalyst at a temperature below that at which coke may be formed. Catalysts which may be used with utility are the oxides, and suldes of molybdenum, molybdena supported on alumina, tungsten-nickel sulfide, and other catalyst promoting hydrogenolysis in or near the temperature ranges given herein. In the practice of my invention the upper one-tenth to one-half and preferably one-eighth to three-eighths of the catalyst bed is maintained at a temperature below that at which the hydrogenolysis treatment is effected. The temperature gradient in this section of the catalyst bed is maintained low near the feed inlet, gradually increased until the hydrogenolysis temperature is attained. A suitable temperature for the catalyst near the feed inlet is about 50 to 100 F. above the temperature of the feed, or in the range of about 550 to 750 F.

Additional hydrogen with which the cracked materials are saturated is also preheated separately and introduced at the top of the catalyst bed. It is not necessary to maintain as low a preheat temperature for this hydrogen as for the feed; however care must be taken not to heat it to such a temperature that on introduction to the catalyst Zone it raises the catalyst temperature above that desired. Suitable preheat temperatures for the hydrogen are in the broad range Yof 500 to 1000 F. and in the preferred range of 800 to 900 F. The total hydrogen circulated is generally in the range of 2500 to 40,000 cubic feet per barrel of oil and preferably in the range of 15,000 to 30,000 cu. ft. per barrel.

VThe preheated feed and hydrogen introduced at the top of the catalyst bed have been found not t form the quantities of carbon or coke usually produced when they are introduced at hydrogenolysis temperatures if they are gradually heated to hydrogenolysis temperatures in the presence of the hydrogenolysis catalyst. The hydrocarbonaceous material to be treated is brought to a suitable reaction temperature generally within the range of 825 to 925 F. and preferably in the range of say 850 to 900n F. These temperature ranges apply particularly to the use of a catalyst comprising supported molybdena and may be varied somewhat outside the given ranges when other catalysts are used. They may also be varied somewhat depending on the character of the feed stock and its susceptibility to carbon formation, however, preferably not above about 925 F. Pressures particularly adapted for use in hydrogenolysis process of this type are in the range of 500 to 10,000 p. s. i. and in the preferred range of 1000 to 6000` p. s. i.

`There are many aspects to be considered in regard to temperature control of the above described hydrogenolysis process. The process itself is well known to be somewhat exothermic, however the degree of exothermicity may vary with the depth of cracking, the amount of hydrogenation, and the character of the feed. When sufficient heat is generated in the lower portion of the catalyst bed to cause the upper one-quarter or one-half to be heated to a temperature above that desired means must be provided to withdraw excess heat so that the temperature gradient in the upper portion of the bed is maintained in the desired range. Suitable means for accomplishing this may include a jacket around the upper portion of the catalyst chamber, when the chamber construction is such that a coolant circulated through the jacket will provide uniform cooling. If the catalyst chamber is of too great diameter for this means of cooling to be adequate, cooling tubes through which gas, water, or other heat-exchange ma.- terial is passed may be installed. Additional cooling along the length of the catalyst bed may be effected by the use of cooled recycle hydrogen introduced at various points along the length of the catalyst bed.

1f suilcient heat is not present in the upper portion of the catalyst bed because of the downflow of feed material carrying away the heat, insufficient heat input, or start-up conditions, additional heat may be added by the use of suitable electric heaters, or circulation of flue gases or other heating media through the above described cooling tubes. In short any suitable means for regulating the temperature of a xed catalyst bed within the specific range desired may be resorted to.

The eflluent materials containing the products of the destructive hydrogenation, hydrogen, and residue are separated in any suitable manner, one embodiment of which is described more fully in the attached drawing. In most cases it will be desirable to recycle the hydrogen as discussed hereinabove and to also recycle the residue for further treatment.

A more complete understanding of some of the many aspects of my invention may be had by referring to the attached drawing which is a schematic flow diagram of one embodiment of the invention. Various valves, pumps, compressors, and other conventional equipment necessary for the practice of this invention will be familiar to one skilled in the art, and have been omitted from the drawing for the sake of clarity. The description of the drawing provides one method of operating my process, however, it is understood that this is merely representative of the broad aspects of my invention. Various minor changes may be made in adapting the described process to the various conditions within the scope of the invention.

Refer now to the drawing. Heavy hydrocarbonaceous material such as residuum to be destructively hydrogenated, is passed via line I 0 through preheater II to hydrogenolysis reaction zone I2. Hydrogen to be reacted with the heavy feed is passed via line I3 through preheater I4 to reaction zone I2. When a quantity of hydrogen is heated with the hydrocarbonaceous feed it is passed from line I3 through line I6 to line I 0. The preheated feed and hydrogen contact a suitable hydrogenolysis catalyst in reaction zone I2 at reaction conditions previously discussed, the hydrocarbonaceous material being destructively hydrogenated. Reaction effluent is with-v drawn 'from zone l2 through line li and is passed to high pressure separation zone i8. .In this zone the unreacted hydrogen is separated Without deliberate cooling or pressure reduction. Thus separated hydrogen Which is of high purity, i. e, 70 to 95 per cent pure and sometimes higher, is recycled to the hydrogenolysis reaction zone through lines le and i3 or may be used for temperature control by passing a portion thereof through lines iS, 20, and 2 to manifold 2S. The remaining portion of the hydrogenolysis eiiiuent is passed from acne i3 to low pressure separation zone 2l through line 22. In this zone the pressure of the eiuent is reduced so that the remaining unreacted hydrogen along with some methane may be recovered along with small quantities of normally gaseous hydrocarbons. This hydrogen may be of a purity generally in the range of 30 to 70 per cent. In one modication of my invention the thus recovered materials may be passed directly back to the reaction zone, however in a preferred modification of my invention this fraction is passed to a 'scrubbing zone 24 by means of line 23 Where light hydrocarbons such as ethane and propane are removed. Any suitable material, such as mineral seal oil, may be used for the scrubbing and is introduced to the scrubbing sone through line 2t. The overhead fraction comprising mostly hydrogen is passed from zone 2d through line 27] to a manifold 28 on reaction zone IZ. From this manifold the hydrogen may be vintroduced. at a plurality of points along the reaction chamber positioned such that a cooling effect may be obtained by introducing said hydrogen at any or all of the points of introduction. Suitable cooling and heating of the upper portion of the reaction zone may be practiced by utilizing the piping arrangement indicated or other suitable equipment. In this particular embodiment the cooling or heating apparatus is particularly advantageous When the diameter or zone l2 is such that external cooling or heating is not adequate. I-Ieat exchange material is introduced via line 29 and withdrawn via line 3l.

The normally gaseous hydrocarbons recovered from the hydrogen in scrubbing zone 24 are passed along with the solvent therefor through line 32 to stripping zone 33. This zone is equipped With a suitable reboiler for applying heat to cause separation of the hydrocarbons from the solvent. These hydrocarbons are recovered overhead via line 34 and are used as desired, While the solvent is recycled to zone 2d through lines 36 and 25.

The remaining material in low pressure separation zone 2l comprising generally C3 and heavier hydrocarbons is passed therefrom through line 31 to fractionation zone 38. In this zone suitable fractions are separated and recovered such as C3-C4 hydrocarbons through line 39, gasoline through line 4|, and gas oil through line 42. A bottoms fraction or residue is withdrawn from zone 33 through line 43 for recycle. If desirable, part or all of this fraction may be vacuum flashed as in zone 44 or Withdrawn from the system. When the former treatment is utilized a heavy gas oil or similar fraction is withdrawn overhead as through line t6 Whlle the vacuum residue is Withdrawn through line 41 for recycle to the reaction Zone through line l0.

An alternative mode of operation in regard to the introduction of hydrogen to the hydrogenolysis reaction zone is to pass all of the recycle hydrogen to the reaction .zone through a manifold at reaction temperature. In 'this method of operation only the make up hydrogen and hydrogen dissolved in the feed is introduced to the top of the hydrogenolysis .reaction zone. When such introduction of recycle hydrogen is carried out the uppermost point of introduction of the hydrogen is not above a point in the catalyst bed which is below reaction temperature. The exothermic heat produced by hydrogenation of unsaturates in the feed in the upper 11bto 1/'2 of the reaction zone, when operating in accordance With this embodiment of my invention, is sufficient to maintain the desired temperature gradient in this portion of vthe bed.

Advantages of this invention are illustrated by the following examples. The reactants `and their proportions, and other specic ingredients are presented as being typical and should not be construed to limit the invention unduly.

Example VI A series of runs were made using topped crude cracking residuum with an initial boiling point of about 850 F., and substantially free of suspended carbonaceous matter. The residuum and hydrogen were brought to reaction temperature by passing same together through a single coil preheater and Were charged to a reaction charnber containing millilite'rs of catalyst composed 4of 9 weight per cent molybdena supported on alumina gel containing 5 Weight per cent silica. Reaction 'conditions were: temperature- 850 to 900 F., pressure-1506 to 5000 p. s. i., and space velocities of 1 to 4 vol./vol./hr. In 'each of these runs, a coke ring was found starting "at the feed inlet, of varying depths, depending on the length of the run.

Example II Further runs were made similar to those in Example I except that the topped crude cracking residuum feed and hydrogen were preheated separately to only 600 F. and separately fed to the top of the reactor. Operating in this manner no vapors were present in the preheater with the oil feed. Reaction conditions were the same as in Example I, except that a gradient Was maintained in the upper one-quarter of the bed between 650 F. and S50-900 F. No coke rings were present when the catalyst was inspected after these runs. Other runs were made similar to those of this example wherein the hydrogen was preheated to temperatures as high as 900 F. With no coke formation.

It was determined from these runs that when the oil feed free of suspended carbonaceous matter and containing only small quantities of dissolved hydrogen Was preheated to a temperature at which substantially no gaseous hydrogen phase or no coke or coke forming bodies were formed, carbon laydown on the inlet portion of the hydrogenolysis catalyst Was eliminated.

Although this process has been described and exemplified in terms of its preferred modifications, it is understood that various changes may be made Without departing from the spirit and scope of the disclosure and of the claims.

I claim:

l. A method for the hydrogenolysis of heavy hydrocarbon residuum which comprises preheating a heavy hydrocarbon residuum With an initial boiling point of about 850 F. containing dissolved hydrogen in an amount not exceeding 200 to 400 cubic feet of dissolved hydrogen per barrel to a temperature in the range of 500 to 700 F. such that no coke and coke forming bodies are produced, preheating additional hydrogen to a temperature in the range of 800 to 900 F., contacting said residuum and hydrogen with a hydrogenolysis catalyst at a pressure in the range of 1000 to 6000 p. s. i., a space velocity of hydrocarbonaceous material in a range oi 1 to 2 liquid volume per volume catalyst per hour and a hydrogen circulation rate in the range of 15,000 to 30,000 cubic feet per barrel of residuum, maintaining the temperature of the upper one-quarter of the catalyst in a gradient of from 550 to 750 F. at the top to 850 to 900o F. at the bottom, maintaining the remaining portion of the catalyst also at a temperature in the range of 850 to 900 F., withdrawing reaction eluent and separating same into 70 to 95 per cent purity hydrogen, C1 to C4 hydrocarbons, gasoline, gas oil, and residuum, preheating and recycling the hydrogen of higher purity to said contacting, and recycling the hydrogen of lower purity to said catalyst as a temperature control, and recycling said separated residuum for further treatment.

2. A method for the hydrogenolysis of heavy hydrocarbonaceous material which comprises preheating a heavy hydrocarbonaceous material containing dissolved hydrogen in an amount not exceeding 200 to 400 cubic feet of dissolved hydrogen per barrel to a temperature up to 700 F. at which no formation of coke and coke forming bodies occurs, preheating hydrogen to a temperature in the range of 500 to 1000 F., contacting said preheated heavy hydrocarbonaceous material and hydrogen in the presence of a hydrogenolysis catalyst, and thereby destructively hydrogenating same, maintaining the upper one-quarter to one-half of the catalyst in a temperature gradient ranging from 50-100 F. above the preheat temperature of the hydrocarbonaceous material at the top to a. hydro-y genolysis reaction temperature at the bottom, maintaining the remaining portion of said catalyst at a hydrogenolysis reaction temperature,

recovering products from said destructive hydrogenation, separating said products, and controlling the temperature of the zone of catalyst where destructive hydrogenation takes place by recycle of cool hydrogen thereto.

3. A method for the hydrogenolysis of heavy hydrocarbon residuum which comprises preheating a heavy hydrocarbon residuum containing dissolved hydrogen in an amount not exceeding 400 cubic feet of dissolved hydrogen per barrel of oil to a temperature in the range ot 500 to 700 F. at which no formation of coke and coke forming bodies occurs, preheating additional hydrogen to a temperature in the range of 800 to 900 F., contacting said residuum and hydrogen with a hydrogenolysis catalyst at a pressure in the range of 500 to 10,000 p. s. i.. a space velocity of residuum to catalyst of 0.5 to 4 liquid vol./ vol/hr. and a hydrogen circulation rate in the range of 2500 to 40,000 cubic feet per barrel of hydrocarbon, maintaining the temperature of the upper one-quarter to one-half of the catalyst in a gradient of from 550 to 800 F. at the top to 835 to 925 F. at the bottom, maintaining the remaining portion of the catalyst at a temperature in the range of 825 to 925 F., withdrawing reaction products and separating same, and recycling hydrogen and residuum to said reaction.

4. A method according to claim 1, said hydrogenolyss catalyst comprising molybdenum oxide supported on silica-alumina.

HAROLD W. FLEMING.

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

UNITED STATES PATENTS Number Name Date 1,940,649 Russel Dec. 19, 1933 2,031,961 Kiss Feb. 25, 1936 2,330,069 Marshall Sept. 21, 1943 2,414,889 Murphree Jan. 28, 1947 2,541,317 Wilson Feb. 13, 1951

Claims (1)

1. A METHOD FOR THE HYDROGENOLYSIS OF HEAVY HYDROCARBON RESIDUUM WHICH COMPRISES PREHEATING A HEAVY HYDROCARBON RESIDUUM WITH AN INITIAL BOILING POINT OF ABOUT 850* F. CONTAINING DISSOLVED HYDROGEN IN AN AMOUNT NOT EXCEEDING 200 TO 400 CUBIC FEET OF DISSOLVED HYDROGEN PER BARREL TO A TEMPERATURE IN THE RANGE OF 500 TO 700* F. SUCH THAT NO COKE AND COKE FORMING BODIES ARE PRODUCED, PREHEATING ADDITIONAL HYDROGEN TO A TEMPERATURE IN THE RANGE OF 800 TO 900* F., CONTACTING SAID RESIDUUM AND HYDROGEN WITH A HYDROGENOLYSIS CATALYST AT A PRESSURE IN THE RANGE OF 1000 TO 6000 P. S. I., A SPACE VELOCITY OF HYDROCARBONACEOUS MATERIAL IN A RANGE OF 1 TO 2 LIQUID VOLUME PER VOLUME CATALYST PER HOUR AND A HYDROGEN CIRCULATION RATE IN THE RANGE OF 15,000 TO 30,000 CUBIC FEET PER BARREL OF RESIDUUM, MAINTAINING THE TEMPERATURE OF THE UPPER ONE-QUARTER OF THE CATALYST IN A GRADIENT OF FROM 550 TO 750* F. AT THE TOP TO 850 TO 900* F. AT THE BOTTOM, MAINTAINING THE REMAINING PORTION OF THE CATALYST ALSO AT A TEMPERATURE IN THE RANGE OF 850 TO 900* F., WITHDRAWING REACTION EFFLUENT AND SEPARATING SAME INTO 70 AND 95 PER CENT PURITY HYDROGEN, C1 TO C4 HYDROCARBONS, GASOLINE, GAS OIL, AND RESIDUUM, PREHEATING AND RECYCLING THE HYDROGEN OF HIGHER PURITY TO SAID CONTACTING, AND RECYCLING THE HYDROGEN OF LOWER PURITY TO SAID CATALYST AS A TEMPERATURE CONTROL, AND RECYCLING SAID SEPARATED RESIDUUM FOR FURTHER TREATMENT.

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