US 3369994 A
Description (OCR text may contain errors)
Feb. 20, 1968 w, SLATER ET AL 3,369,994
HYDRocoNvERsIoN oF HYDRocARBoNs Filed Deo. 29, 1965 WKVAWY United States Patent O 3,369,994 HYDROCONVERSION F HYDROCARBONS William Lfslater, La Habra, and Warren G. Schlinger, Pasadena, Calif., assignors to Texaco Inc., New York,
N.Y., a corporation of Delaware Filed Dec. 29, 1965, Ser. No. 517,248 Claims. (Cl. 208-58) This invention -is directed to the conversion of petroleum hydrocarbons boiling above the middle distillate range into good yields of middle distillates and lighter hydrocarbons liquid fractions. More particularly, it is directed Ito the production of naphtha and middle distillates from heavy hydrocarbon fractions which for the most part boil above about 700 F. at atmospheric pressure.
In the refining of petroleum, the crude oil is ordinarily distilled at atmospheric pressure in an operation called topping to remove liquids such as naphtha, kerosine and gas oils. After about a 650-700" F. overhead temperature has been reached, because of the danger of cokin'g at higher temperature, the distillation is then carried out at reduced pressure. When as much overhead as possible has been removed in this manner the distillation is interrupted and there is left a bottoms fraction, termed vacuum residuum which is a heavy tar-like material and has little commercial value.
However, there are some crude oils which are extremely heavy as produced and do not contain sufficient light materials to justify distillation. Such a crude for example is San Ardo crude obtained from California which is characterized by its extreme heaviness. San Ardo crude generally contains only about 17 volume percent boiling below 650 at atmospheric pressure. v
IIt is towards the conversion of heavy stocks such as vacuum residuum or San Ardo crude or the like that the present invention is directed although it not necessarily limited to the treatment of such stock.
Various processes are already known in the ar-t for converting heavy stocks into lighter materials. For example it is known to pass an intimate mixture of a hydrocarbon oil and hydrogen under conditions of turbulent flow through a tubular reaction zone at elevated temperature and pressure, the eluent which comprises unreacted hydrogen, vaporous hydrocarbons and liquid hydrocarbons being passed to a separation zone where a liquid-vapor separation is made. The separated liquid is countercurrently contacted with hot hydrogen at substantially the temperature and pressure maintained in the tubular reaction zone and the unreacted hydrogen together with hydrocarbon vapors removed from the liquid or formed by cracking during the contacting is combined with .the vaporous portion of the effluent from the tubular reaction zone and the combined stream is ythen passed into contact with a hydrogenation catalyst. Such a process is disclosed in U.S. Patent 3,089,843, issued May 14, 1963, to Eastman and Schlinger.
However, although the described process gives good yields of middle distillates it circulates large volumes of hydrogen to prevent the formation and deposition of coke in the tubular reaction zone. This in itself does not present a problem commercially in many reiineries because, ldue to the presence of catalytic reformers there is an abundance of hydrogen. However, in refineries where there are no catalytic reformers or Where there is a shortage of hydrogen, the operation of the described process or any other hydrogen-consuming process may be limited.
It is an object of the present invention -to convert heavy petroleum fractions into good yields of middle distillates without the formation of excessive amounts of coke. It is another object of the present invention to convert heavy hydrocarbon liquids in the presence of hydrogen to good yields of middle distillate and lighter fractions using less circulating hydrogen than is required by the processes of the prior art. `It is another object of the present invention to increase the through-put of hydrocarbon charge stock without proportionately increasing the amount of hydrogen. These and other objects will be apparent to those skilled in the artfrom the following disclosure.
In the process ofthe present invention a hydrogen containing gas and a heavy hydrocarbon charge lst-ock having a Conradson carbon residue of at least 1% by weight is formed into an intimate mixture which is passed through a tubular reaction zone under conditions of turbulent flow at an elevated temperature and pressure for a period of ltime sufficient to convert a substantial amount of the charge stock into lighter boiling hydrocarbons. However, it is a feature of the present invention that the intimate mixture is passed through a tubular reaction zone under conditions of turbulent llow at a temperature below reaction temperature for at least 4 seconds. lIn a preferred embodiment of the present invention the hydrogen and hydrocarbon are formed into an intimate mixture at a temperature below the react-ion temperature, The resulting mixture is passed through a tubular reaction zone at a turbulence level of at least 25 and preferably at least 50 for a period of at least 4 seconds below reaction temperature and is then brought to a temperature of between about 800and 950 F. and held at that temperature under conditions 0f turbulent flow for a period of time between about 10 seconds and 1 hour.
The reaction pro-duct is then passed to a separation zone wherein a separation is made between the gas phase of the euent which comprises hydrogen and vaporous hydrocarbons and the liquid phase of the effluent which comprises liquid hydrocarbons having some hydrogen and lighter hydrocarbons dissolved therein. The liquid phase is then subjected to countercurrent con-tacting Iwith hy- Idrogen separately heated to a temperature between about 800 and 950 IF. During this contacting, dissolved vaporous hydrocarbons are removed from the liquid w-ith additional vaporous hydrocarbons which, in all probability, are formed by 'the cracking that takes place during the contacting. These latter vaporous hydrocarbons together with unreacted hydrogen from the contacting lare combined with the gas phase separated from the effluent from the tubular reaction zone and 'the combined stream of hydrogen and vaporous hydrocarbons is then in the preferred embodiment contacted with a hydrogenation catalyst at a temperature between 500 and 850 F. The product from the -catalytic treatment may then be separated into dierent fractions for end use 0r for additional treatment. Hydrogen separated from the reaction product may be recycled to the tubular reaction zone or to the contacting zone or apportioned therebetween.
The residue withdrawn from the bottom of the contacting or stripping zone is an extremely heavy, tar-like material which, depending on the charge stock and operatling conditions, may be solid at ordinary temperatures.
Suitable charge stocks for the process of the present invention include heavy hydrocarbons having a Conradson carbon residue of at least y1% by weight such as crude oils and heavy fractions of crude oils for example Santa Maria crude, ySan Ardo crude, Arabian crude, reduced or topped crude, vacuum residuum, shale oil, coal tar oil, tar sand oil and mixtures thereof and the like.
Hydrogen as used in a process of the present invention need not be pure hydrogen but may contain minor amounts of impurities such as H2S or NH3 and hydrocarbons such as methane and ethane, etc. As used herein, the term hydrogen includes gases containing as low at 40% hydrogen but preferably containing at least about 60L 70% hydrogen. Hydrogen is introduced into contact With the hydrocarbon charge stock in two places.
In one instance the hydrogen is brought into contact with the hydrocarbon charge stock to form an intimate mixture which is passed through a tubular reaction one under conditions of highly turbulent iiow. In this oase the hydrogen is introduced in an amount of at least 1,000 stan-dard cubic feet per barrel (s.c.f.b.) of charge' stock. It is known to pass a mixture of hydrogen and heavy hydrocarbon through a tubular reaction zone at elevated temperature and pressure using at least 5,000 s.c.f.b. hydrogen. However, in the process of the present invent-ion, it is possible to carry out this reaction with hydrogen rates as -low as 1,000 s.c.f.b.
In the other instance, hydrogen is brought into. Contact with the liquid portion of the eluent from the tubular reaction zone. Because of the lincreased conversion due to the novel feature of the present invention, the hydrogen used in the contacting of the liquid portion of the tubular reaction zone effluent may be as low as 3,000 s.c.f.'b. of charge to the tubular lreaction zone. In this way, it is possible to carry out -a preferred embodiment of the present invention with a total hydrogen circulation rate of about 4,000 s.c.f.b.
Hydrogen from any source which provides a -gas containing at least 40% hydrogen may be used. Syn-thesis gas, electrolytic hydrogen or catalytic reformer by-product hydrogen `are examples of hydrogen containing gases which may be used in the process of `the present invention.
It is a feature of the present invention that the oil charge stock and hydrogen are maintained under conditions of turbulent flow preferably at reaction pressure but at a temperature below reaction temperature for lat -least 4 seconds. By so doing, it has been found that the hydrogen is given a much greater opportunity to penetrate completely into the particles of oil which are formed during the high turbulence thereby permitting the conversion which occurs in the hot tubular reaction zone to take place in the presence of much less hydrogen than was known in the prior art and yet still `avoid the formation of large amounts of high polymers and coke which might plug up the apparatus, Under conditions of turbulent ilow specifically at a turbulence level of at least 25, the hydrocarbon and hydrogen form an intimate mixture in which it is believed the liquid hydrocarbon is in the form of a mist of iine droplets suspended in hydrogen. By permitting the reactants to be in the form of this turbulent intimate mixture for some time prior to bringing. the mixture to reaction temperature, it is possible to carry out lthe subsequent reaction at reduced hydrogen rates despite the fact that hydrogen is more soluble in the oil at higher temperatures than it is at lower temperatures. That is to say, at constant pressure, hydrogen is more soluble in oil at 800 F. than it is in the same oil at 200 F.
The reaction temperature is that temperature at which appreciable cracking begins. Although the reaction temperature may vary from -one charge stock to another, the variation does not extend over a Wide range and is generally considered to fall within the range of from 790'- 800'l F. Accordingly, reaction temperature for the purposes of the present invention is defined as the lowest temperature at which appreciable cracking commences and ordinarily will lie between 790 and 800 F.
The turbulence level-as used herein is represented by the ratio of the average apparent viscosity of the flowing stream to the kinematic `or molecular viscosity. After the preliminary holding period, the reactants are passed through the tubular reaction zone at reaction temperature and elevated pressure and maintained under these conditions for a period of time suicient to convert a substantial portion of the charge stock to lighter hydrocarbons. These reaction conditions include a temperature between about 800 and 950 F., preferably a temperature between 825 and 900 F. The pressure may range between about 500 and 5,000 p.s.i.g. and higher although pressures of between 1,000 and 4,000 p.s.i.g. are preferred. The residence time at reaction conditions may range between about 5 seconds and 2 hours. Suitably the residence time ranges from 20 seconds to 5 minutes. The eluent from the tubular reaction zone is separated into a gas phase comprising hydrogen and vaporous hydrocarbons and a liquid phase comprising unvaporized hydrocarbons.
The liquid phase is permitted yto descend through a stripping tower where it is countercurrently contacted with hot hydrogen at a temperature between about 775 and 900 F. During this contacting additional cracking takes place and the sweeping action of hydrogen serves to remove vaporous hydrocarbons dissolved in the liquid, said hydrocarbons either having been carried over from the tubular reaction zone or formed within the liquid during the contacting. Because of Athe improved conversion ob-V tained in the rtubular react-ion zone by the novel feature of the present invention, it is possible to obtain a greater conversion or correlatively a reduced tar yield using lower hydrogen rates during the contacting than was previously possible in this type of operation.
The stripping hydrogen together with vaporous hydrocarbons is removed from the stripping or contacting Zone and is combined with the gas phase separated from the tubular reaction zone eluent and in a preferred embodiment, the combined stream is passed into contact with a hydrogenation catalyst. Prefer-ably, this contacting takesA place at a temperature between about 400 and 850 F., suit-ably between 600 and 825 F. Catalysts which may vbe used in the hydrogenation zone include those catalysts having hydrogenating activity such as for example platinum, rhodium, palladium and nickel and the oxides-and/ or suldes of metals such as cobalt, molybdenum, nickel, tungsten, chromium, iron, magnesium, vanadium, and mixtures thereof. The catalytic materials may be used alone but preferably are deposited on or mixed with a support such as alumina, magnesia, silica, zinc oxide, natural or synthetic zeolites having uniform pore openings or mixtures thereof. Particularly suitable hydrogenating catalysts are nickel tungsten sulfide, cobalt molybdate, sometimes considered to be a mixture of cobalt oxide and nickel oxide, nickel molybdate also sometimes considered to be a mixture of nickel oxide and molybdenum oxide, nickel oxide, cobalt oxide, nickel sulde, cobalt sulfide, and molybdenum sulde.
The pressure in each of the reaction Zones is substantially the same, allowance for normal pressure drop to permit passage of the reactants through the various reaction zones 'being taken into consideration.
For a better understanding of the invention, reference is made here to the attached drawing which shows diagrammatically a flow scheme for the practice of a preferred embodiment of the present invention.
Charge oil is introduced into the system through line 11 and with hydrogen from line 12 is sent to holding unit 14 through which is passed at a temperature below the reaction temperature of the oil under conditions of highly turbulent flow. The mixture of oil and hydrogen then isftransferred through line 15 to oil-hydrogen heaterreactor 16 through which it passes under conditions of highly turbulent flow at a temperature between about 800 and 950 F. and a pressure of about 1500 p.s.i.g.
Effluent from oil-hydrogen heater-reactor 16 passes through line 17 into the upper section of tower 20 which acts as a separation zone to separate hydrogen and vaporous hydrocarbons from liquid hydrocarbons. The hydrogen and vaporous hydrocarbons are withdrawn from the upper section of tower through line 22 and by the addition of cooled hydrocarbon liquid from line 41 are quenched to a temperature between about 500 and 850 F. In separator a vapor liquid separation is made and the liquid is withdrawn through line 26 and may be re moved from the system through line 27 or may be recycled to the upper section of tower 20 through lines 28 and 17 or to oil-hydrogen heater-reactor 16 through lines 30 and 15 or to holding unit 14 through lines 31 and 11.
The cooled hydrogen and vaporous hydrocarbons pass through line 32 to catalyst unit 33 in which they are contacted with a hydrogenation catalyst. Ellluent from catalyst unit 33 is transferred through line 34 to high pressure separator 35 from which hydrogen is removed through line 36 and recycled, a portion being sent to holding unit 14 through lines 12 and 11 and a portion being sent to hydrogen heater 37 through line 38. From high pressure separator 35 liquid phase is removed through line 40, a portion being returned through line 41 to quench the material in line 22 and the balance being sent through line 42 to low pressure separator 44 where the product is separated into light hydrocarbons removed through line 45 and heavier hydrocarbons removed through line 46. If desired, additional fractionation may be made of the fractions removed by means of lines 45 and 46 to obtain the desired products.
The liquid portion of the eluent from oil hydrogen reactor 16 descends through tower 20 and is contacted therein with an upwardly owing stream of hot hydrogen heated in hydrogen heater 37 to a temperature of about 80G-900 F. and introduced into the lower section of tower 20 through line 49. During the contacting the hydrogen removes vaporous hydrocarbons from the liquid. These vaporous hydrocarbons may either be low molecular weight hydrocarbons formed by additional cracking which takes place during the contacting or may be dissolved lighter hydrocarbons formed by the cracking which occurs in oil-hydrogen heater-reactor 16. The upwardly flowing stream of hydrogen and vaporous hydrocarbons is combined in the upper section of tower 20 with the hydrogen and vaporous hydrocarbons removed from the efliuent from oil-hydrogen heater-reactor 16. Unconverted liquid descends through tower 20 from which it is removed by means of line 51. This material is tar-like in nature and ordinarily is diluted with a lighter oil and used as fuel. It may also be used either diluted or undiluted as the charge stock to a gas generator where it is subjected to partial combustion to produce synthesis gas. The product synthesis gas is useful per se or may be subjected to a water `gas shift reaction for production of hydrogen.
To prevent the build up of impurities in the hydrogen a purge is made by means of line 52 and make-up hydrogen is introduced into the system -through line 53.
For the sake of simplicity, various items of equipment such as valves, pumps, compressors, heat exchangers and the like have been omitted from the drawing. However, their presence will be obvious to those skilled in the art. Similarly, various units depicted as separate zones may be integrated within the walls of a single vessel or vice versa. For example, holding unit 14 and oil-hydrogen reactor 16 may be positioned within a single shell whereas although tower 20 is shown as a single vessel the upper separation zone of tower 20 may be separate from rather than integral with the contacting zone of tower 20.
The process of the present invention is particularly suitable for the conversion of dirtyl stocks, that is stocks containing at least 1.0% Conradson carbon into good yields of lighter materials which can be separated into useful fractions such as gasoline, kerosine, lubes and fuel oils and which in appropriate cases, may be subjected to additional treatment such as cracking, hydrocracking, re-
forming, hydrogenation and the like to produce products of improved qualities.
The following example is given for illustrative purposes only.
A B C Charge:
Gravity, API 16. 5 18. 3 17. 7
Carbon residue, wt. percent 7. 96 7.37 7. 37 Operating Conditions:
Holding Unit outlet, F 800 800 800 Oil-Hydrogen reactor outlet F 897 895 886 Hydrogen heater outlet, Fit 957 950 941 Tower overhead, F 876 879 863 Residence time, holding unit, secs. 19.0 19.5 3. 5
Residence time, oil-hydrogen reactor,
Secs 42. 3 44. 2 43. 2 Average system pressure, p. 1, 500 1, 500 1,500 urbullene level ...t i 75 70 70 ecye e y ro en un vo er- Gas rates:
Hydrogen to oil-hydrogen reactor,
s.c.f.b. chg 1,851 1, 631 2, 050 Hydrogen to hydrogen heater, s.c.f.b.
chg 8, 896 4, 216 3, 849
Product Oil, vol. percent chg 76. 4 83. 7 69.9 Product Tar, vol. percent chg 25. 5 17.4 31.4 Quality:
Gravity, API 29. 8 30.0 30. 1 Carbon residue, wt. percent 0. 40 0. 32 0. 2 Distillation, F.:
10 330 308 318 622 606 618 736 732 728 Product tar:
Gravity, API -0. l 5. 5 4. 5 Carbon residue, wt. percent 25.33 30. 96 19. 9
Obviously, many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.
1. In a process for the hydroconversion of a heavy hydrocarbon oil feed stock having a Conradson carbon residue of at least 1% by weight and selected from the group consisting of crude, reduced crude, residua, shale, tar sand and coal tar oils and mixtures thereof in which process an intimate mixture of hydrocarbon charge stock and hydrogen is passed through a tubular reaction zone under conditions of turbulent flow, the improved method ofconserving hydrogen which lcomprises forming an intimate mixture of hydrogen and said hydrocarbon oil feed stock at a pressure between about .500 and 5000 p.s.i.g and a temperature at Which said feed stock is liquid but not greater than 790 F. in an amount at least 1000 and less than 5,000 s.c.f.b. hydrogen per barrel of feed stock, passing said intimate mixture through a tubular reaction zone under conditions of turbulent flow at a temperature at which said feed stock is liquid but not greater than 790 F. for a period of time of at least 4 seconds, then maintaining said intimate mixture under conditions of turbulent tlow at reaction conditions of temperature and pressure for a period of time of between 5 seconds and 2 hours, said period of time at reaction conditions being accompanied by the consumption of hydrogen.
2. The process of claim 1 in which the turbulence level is at least 25.
3. The process of claim 2 in which the turbulence level is between 50 and 1000.
4. The process of claim 1 in which the effluent from the tubular reaction zone is separated into a liquid portion and la gaseous portion and the liquid portion is contacted with a stream of separately heated hydrogen, thereby forming a stream of hydrogen and vaporous hydrocarbons, said contacting taking place at substantially the same temperature and pressure as those in the tubular reaction zone.
5. The process of claim 4 in which the contacting hydrogen is supplied at a rate between 3,000 and 10,000 s.c.f.b. per barrel of hydrocarbon oil feed stock.
6. The processl of claim 4 in which unreacted contacting hydrogen and hydrocarbon vapors separated from said liquid portion during contacting are combined with said gaseous portion.
7. The process of claim' 6 in which the combined stream is contacted with a hydrogenation catalyst at a temperature between 4'00 and 850 F. and a pressure between about 500 and 5,000 psig.
8. The process of claim 7 in which the hydrogenation catalyst comprises a compound of molybdenum.
9. The process of claim 7 in which the :hydrogenation catalyst comprises a compound of nickel.
l 10. The process .of claim7 in which'rn'aterial,l liquid at prevailing conditions, is removed from the combined stream prior to bringing said combined stream into 'con-y 2,706,705 4/1955 Oettinger er al. 20s-59 ABRAHAM RIMENS, Primary Examiner.
DELBERT E. GANTZ, Examiner.
l2/l965 Schlinger et al. 20S- 58