US2943047A - Hydrorefining of heavy mineral oils - Google Patents

Description

June 28, 1960 c. P. REEG r-:TAL

HYDROREFINING oF HEAVY MINERAL ons Filed Jan. 27, 1958 HYDROREFINING F HEAVY MINERAL OILS j Cloyd P. Reeg, Long Beach, and Frank C. Price, Garden Grove, Calif., assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California l A Filed Jan. 27, 1958, Ser. No. 711,387

Claims. (Cl. 208-211) United I'States Patent O y c 2,943,047 v Patented June :28, :106,0

,Y Ce I nents, asphaltenes, carboids, and/,or rnitrogenous'ronft-Y pounds. f

It has been found that conventional pretreatment steps such as vacuum distillation, thermal coking, or liquid phase deasphalting using lower pa-rains, do `not. entirely solve the problem of removing such deposit-forming materials, -unless severe pretreating conditions are employed entailing sacrificial yields. VWhile the light fractions from thermal coking do not cause difiiculty the heavier coker distillates still tend to form deposits, as does the A rafnate from conventional deasphalting of the total crude oil, using for example n-pentane as `the deasphalting agent. As a corollary to the above, thermal coking and liquid phasedeasphalting are subject to the disadvantage that relatively low liquid yields are obtained if those ltreatments are made suiiiciently severe or exhaustive to give a nondeposit-forming distillate Yor rafinate. `It is hencehighly desirable to provide a more selective method for removing the deposit-forming constituents without removing all of the heavier components,

some of which do not tend tofform deposits.

In the case of lvacuum distillation, it has been found that only `about 40-50% by volume of nondeposit-form ing distillate can be economically produced without ernployingcracking temperatures. The residue, constitut- 1 ing the vacuum distillation bottoms, must then be subto extract from said residue an additional quantity of Y oil which is then subjected to hydrorefning along with the gaseous mixture `derived from the vaporization step.

The principal objective of the invention is to provide means for hydrorefiningcrude oils, or heavy fractions thereof, while avoiding to a maximum extent the normallyjoccurring deposition of coke and other deactivati ing -deposits upon the catalyst. Another objective is to provide methods for removing the precursors of such deactivating deposits from the feed oil, while maintaining maximum over-all liquid yields. Still another object is to achieve maximum vaporization of the feed'oil by pressure stripping with the hydroreiiner recycle gas in such manner asto minimize utility costs. Specifically, it is desired toA avoid the expensive -depressuring and repressuring of recycle gas. Other objects will be apparent from the more detailed descriptionvwhich follows.

The process of this invention is ladapted mainly for the treatment of total crude oils,or reduced crude oils.

It is especially adapted for the treatment of crude shale oils, i.e. the full-range oil produced directly from the retorting of shale rock. Crude shale oils present dificult'problems in refining in that they contain `a high proportion of asphaltenes and carboids and up to about 4%l of nitrogenin theform of organic nitrogen compounds.` i In addition, metals may be present in the form of porphyrin-metal complexes or other organometallic compounds. Crude shale oils also possessan unusually high pour point. For example, the crude oil from Coloradoshale isnormally a solid at room temperature, and its pourpoint maybe in excess of 100"Y F.

From the standpoint of refining flexibility, the most desirable initial vtreatment for such oils consists of catalytic hydrorefining to decompose nitrogenous compounds and sulfur compounds, to hydrogenate asphaltenes and carboids, tofdecompose organo-metallic compounds, and in general to improve the color and handleability of the oil for subsequent refining procedures such as cracking, reforming and the like. The rst major difficulty encountered in .attempting to hydroreine such oils consists in the tendency of the oil to deposit deactivating solids upon hot catalytic surfaces when the feedstockV is brought into contact therewith. The exact nature of the depositforming constituents is not known, but they mayV comprise any of the above-noted organo-metallic compojected to coking or deasphalting with attendant disad- Vantages above noted. By going to extremely high vacuum, higher distillate yields may be obtained, but such distillates then `will include some of the heavier, depositforming bodies. The process of this invention is de` signed to overcome the major disadvantages of each of the foregoing processes.

While `as above indicated, conventional -liquid phase deasphalting of the tot-al crude oil is ineffective for removing all deposit-forming components unless exhaustive deasphalting conditions are employed, resulting in low rainate yields, it has now been found that the asphaltic concentrateproducedin the vaporization step of this invention may be subjected to such deasphaltingto recover as much as 50-75% thereof as suitable feed to the hydrorening step. Since the hydrocarbons recovered in the deasphalting step are extremely high boiling, their recovery vin the vaporization step .is impractical, and moreover the wihdrawal of some liquid phase from the vaporization step is a mechanical convenience in that it functions as ya vehicle for the asphaltic materials which would normally'be solid or semisolid. It is hence preferred to remove from about 1 25 by volume of the, initial feedstock as bottoms from the vaporization step,l

and'to effect further recovery of nondepost-forming hydrocarbons .therefrom by liquid phase deasphalting.

Whileit has been indicated that crude oils, and especially Vshale oils', are the feeds of major concern herein,

Vit is not intended to preclude the use of heavier distillate fractions, some of which present similar problems in catalytic hydrorefining, though to -a decidedly lesser extent. In general, any crude oil, heavy distillate, or other heavy fraction having an end boiling point in Yexcess of about` 700 F. may be employed. It is also contemplated that mixtures of crude oils and distillate fractions may be employed, as Welllas' Amixtures of petroleum crudes and crude shaleoil.

I, The crude shale oil described herein may be produced for example by the retortngprocedures described in U.S. Patents 2,501,153, 2,640,015, and 2,640,019. In general, the retorting procedure consists in initiating combustion in a body of moving shale rock, and utilizing the hot combustion gases to educt the oil from uncombusted shale rock upstreamwardly.`

, The process of this invention will now be describedv in more detail in connection with the attached flow sheet;

which is' intended merely to illustrate the principal modications, but is not intended to be limiting in scope. The initial feedstock is brought in through line 1, wherein it is mingled with the major portion o f hydroreiiner recycle gas from line 2. This combined stream is then preheated to a temperature sufficient to achieve the desired vaporizaton of oil in preheater 3. This temperature may range anywhere between about 200 and 850 F. but is preferably within about 100 F. of the temperature to be employed in the subsequent hydrorefining step.

The mixed phase efiluent from preheater 3 is then transferred via line 4 to a centrifugal separator 5, which may be of -the Webre cyclone type. This unit consists of an outer cylindrical shell 6 enclosing an axially positioned open-ended vapor outlet conduit 7 which extends upwardly to near the top of shell 6, and terminates at its lower end in vapor outlet port 9', located below the center portion of shell 6. The feed inlet line 4 enters shell 6 tangentially thereto at a point approximately midway between the top of vapor outlet conduit 7 and the vapor outlet port 9. The liquid portion of entering feed spirals downwardly inside shell 6 by centrifugal force, and forms a liquid level indicated approximately at 11. The entering gas phase spirals upwardly around vapor outlet conduit 7 and enters the top thereof and thence flows downwardly and out through vapor outlet port 9. In this manner, the liquid and gas phases are rapidly and effectively separated, and maximum vaporization isobtained. An additional stream of recycle gas may if desired be diverted through line 12, preheated in heater 14` to a temperature 50 to 100 F. in excess of that prevailing in separator 5, and then admitted via line 16 into the lower extremity of separator 5. By this means, additional vaporization by stripping is obtained. Any fresh makeup hydrogen required in the hydrorening operation is preferably admitted via line 17 at this point in order to utilize to a maximum extent its stripping capacity.

The pressure in separator is preferably maintained at substantially that prevailing in the hydrorefiner 40, hereinafter described. Specifically, in order to obtain a maximum recovery of oil free from deposit-forming constituents, it is preferred that the pressure should be within about 300 p.s.i.g. above or below the hydrorener pressure. However, other pressures may be used to somewhat less over-all advantage.

The liquid phase accumulating in separator 5 is withdrawn via valve 18 and line 19 more or less continuously in response to liquid level controller 20. The proportion of feed which is vaporized in separator 5 may be controlled in response to any desired process variable such as temperature, or relative recycle gas volume admitted thereto. In the modification illustrated, feed temperature is the controlling variable; when the flow of liquid in line 19 becomes too great, indicating insulcient vaporization, flow-controller 22 opens valve 23 to admit additional heating agent to feed preheater 3. Too small a ow rate in line 19, indicating excessive vaporization, is corrected by a reduction in temperature.

Ordinarily, the liquid stream removed in line 19 will comprise only about l-25% by volume of the total liquid feed. It is an important feature of this invention that the 75-99% vapor phase fraction removed ,from separator 5 is produced under deasphalting conditions substantially identical to those prevailing in the` hydroreiner, hence totally excluding therefrom any deposit-forming constituents. To the best of our knowledge this objective cannot be achieved by other methods such as vacuum distillation, coking, or conventional liquid phase deasphalting. An overhead or rainate of analogous proportions from such conventional procedures still may contain deposit-forming constituents which would rapidly deactivate the catalyst in the hydrorefiner. This result is achieved moreover with a minimum of utility requirements in that the major heat input is utilized in the sub-n aflins may be employed, and mixtures of one or more of such components of the same or different boiling points may be used. The amount of solvent to be used may vary between about 0.5 and volumes'per volume of oil admitted to mixing valve 25. Normally when npentane is used for example, suitable proportions range between about 1 and 5 volumes per volume of oil. Atmospheric temperatures and pressures may be utilized, but preferably somewhat elevated temperatures are desirable in order to keep the heavy oil in liquid phase. Temperatures between about 50 and 300 F. may be employed. The preferred boiling range for the solvent lies within the limits of about 50 and +450 F.

The mixture of solvent and oil is then transferred via line 27 to liquid-liquid phase separator 28, wherein the solvent forms a supernatant phase. The lower phase, consisting of heavy asphaltic oil is withdrawn via line 29, and may be blended with fuel oil, or put to any conventional use.

The supernatant solvent phase in separator 28 is Withdrawn via line 30 and transferred to distillation column 32 wherein the solvent is removed overhead via line 33, and recycled to mixing valve 25 via storage tank 34 and line 26. The bottoms from column 32 is withdrawn via line 36, and is utilized in the hydrorening operation to be subsequently described.

Returning -to separator 5, .the gaseous portion of the feed is introduced therein at a considerable velocity, and .tends to spiral upwardly around outlet conduit 7, entering the top thereof and flowing downwardly and out through vapor outlet port 9, and thence into hydroreliner 40 via line 41 and preheater 42, along with the bottoms from column 32. In order to prevent entrainment of liquid in the gas phase from separator 5, a depending cylindrical drip ring 43 is provided in the top of separator 5.

In hydroreiiner 40 the pretreated mixed feed is contaeted with a suitable sulfactive hydroreiining catalyst under conditions of hydrorening. The catalyst may be disposed in a fixed stationary bed, or the various moving bed, or fluidized bed techniques may be employed. *Gen-1 erally, the fixed bed technique is most satisfactory. The catalyst may comprise any of the oxides and/or suliides of the transitional metals, and especially an oxide or sulfide of a group VIII metal (particularly iron, cobalt or nickel) mixed with an oxide or sulfide of a group VIB metal (preferably molybdenum or tungsten). Such catalysts may be employed in undiluted form, but preferably are distended and supported on an adsorbent carrier in proportions ranging between about 2% and 25% by weight. Suitable carriers include in .general .the diicultly reducible inorganic oxides, e.g. alumina, silica, zirconia, titania, clays such as bauxite, bentonite, etc. Preferably the carrier should `display little or no cracking activity, and hence highly acidic carriers are generally to be` avoided. The preferred carrier is activated alumina, and especially activated alumina containing about 3-15% by weight of coprecipitated silica gel.

The preferred hydroreining catalyst consists of cobalt oxide plus molybdenum oxide supported on silica-stabilized alumina. `Compositions containing between about` 2% and 8% of C00, 4% and 20% of M003, 3% and 15% of SiOa, and thel balance A1203, andwherein the Operative lPreferred Temperature, 60o-875 eso-soo Pressure, p.s.l.g 100-5, 000 400-2, 000 Liquid hourly space velocity 0. -15 1-10 Hydrogen ratio, s.c.f.[bbl -r 300-8, 000 500-5, 000

Within 'the above` operating conditions', the specific hydrorefining conditions selected should be such as'to meet required `product specifications.

The product from hydrorefiner 40 is withdrawn via l-ine l45, condensed in cooler 46 and transferred to highpressure separator 47. .Hydrogen-rich recyclegas, containing minor amounts of light hydrocarbon gases, is withdrawn via line 48, and sufficient thereof is diverted through lines 2 and 12 to separator 5 to achieve the ends above'descn'bed. Any remaining portion of recycle gas not utilized in separator 5 may be recycled directly via lines 50 and 41.

The liquid product accumulating in separator 47 may then .be flashed into low-pressure separator 5.2 via line 53. Low-pressure olf-gas is withdrawn -via line 54, and liquid product via line 55. This liquid product is then suitable for use in conventional refining units as for example distillation columns, catalytic cracking units, catalytic reforming units, catalytic hydrocracking, and the like.

'I'he following example is cited -to illustrate one practical application of the process to a typical Colorado crude shale oil, but manifestly it vis not intended .that this should be in scope.

Example Feed characteristics.-Gravity, API, 20.4; total nitrogen, 1.84 percent; sulfur, 0.72 wt. percent; Ramsbot-tom carbon residue, 3 wt. percent; pour point, 90 F.; initial boiling point, 346 F.; 60% boiling point, 700 F.

Hydrorefinng catalyst-3% CoO plus 9% M003 supported on 1A" pellets of silica-stabilized alumina (5% SiO2-95% A1203), prepared by impregnating pelleted carrier first with aqueous ammonium molybdate, then with aqueous cobalt nitrate, drying and calcining.

The total feed is blended with 3,000 s.c.f./bbl. of hydrogen-rich recycle gas, and introduced into cyclone separator 5 at a temperature of 825 F. and pressure 2,200 psig. An additional stream of fresh makeup hydrogen is introduced via line 16 at 850 F., and at the rate of 1,000 s.c.f./bbl. of initial feed. Liquid bottoms product is withdrawn at the rate of barrels per 100 barrels of fresh feed.

The bottoms product is subjected to pentane deasphalting at 75 F. using 2 volumes of pentane per volume of feed thereto. Upon distilling off pentane from the resul-ting extract phase, 85% by volume of Athe separator bottoms is recovered for hydrorefining. The asphalt phase amounts to about 2% of the fresh feed.

The vapor phase from separator 5 is then blended with the solvent-free extract from the deasphalting step. The blend is then preheated to about 700 F. and subjected to hydroreflning at an average bed temperatur-e of 800 F., pressure 2000 p.s.i.g., hydrogen ratio 5,000 s.c.f./bbl., and liquid hourly space velocity 1.0. Theproduct is recovered in 106% yield, contains about 0.11% nitrogen and 0.037% sulfur, and has a gravity of 37.3 API.

Operation under the above conditions can be continued for several weeks without shutdown for catalyst regeneration, and without substantial decline in product quality. When the raw crude oil is used directly in the hydrorelner, plugging of the reactor and catalyst deactivation require shutdown within a few hours, or days at the most. When thev feed to the hydrorener consists of a 98% fractionof the'crude oil, obtained byva'cuum distillation with pentanc deasphalting ofthe `bottoms,'the catalyst life is improved as compared to Vusing the crude oil, bn t not tothe extentobtained when using the' 98%feed fraction prepared as' described in the foregoing example.

The foregoing description of specific methods and ma'- terials for usev in this invention is not intended to be limitingin'scope-except where indicated. Many variations Will occur to those skilled in the art and all such variations which` yield essentially the same result are intendedtoI be included. The true scope-ofthe invention Y is intended to be embraced within the following claims.

`We c laim: I ,I j j l l. In a process Vfor the catalytic 'hydro'reninggof'a high-boiling mineral oilfeedstock,v wherein the conditions of hydrorening and the feedstock are such that said catalyst would normally be rapidly deactivated by the deposition of s olid materials on the catalytic surfaces, the improved method of pretreatment to avoid such deactivation which comprises subjecting said feedstock to partial vaporization in equilibrium with hydrogen-rich recycle gas from said hydrorefining, the conditions of temperature, pressure and hydrogen ratio in said partial vaporization step being adjusted so as to vaporize between about 75% and 99% of said feedstock, subjecting the liquid residue from said partial vaporization to liquid-liquid extraction with a parafinic solvent to produce a highly asphaltic raffinate and a nonasphaltic extract, separating said extract from said raffinate, recovering dissolved oil from said extract, blending said recovered oil with the vapor phase from said partial vaporization step and subjecting the resulting blend to said catalytic hydrorefning.

2. A process as dened in claim 1 wherein said feedstock is essentially a crude oil.

3. A 'process as defined in claim 1 wherein said feedstock is essentially a crude shale oil.

4. A process for hydrorefining a feedstock which is essentially a full-range crude oil, which comprises first subjecting said feedstock to partial vaporization in equilibrium with hydrogen-rich recycle gas derived from the hydrorefining step hereinafter defined, said partial vaporization being carried out at a temperature within about 100 F., and at a pressure within about 300 p.s.i.g. of the temperature and pressure prevailing in the hydrorefnng step hereinafter defined, thereby producing a gas phase comprising between about 75% and 99% of said feed oil and a liquid phase comprising about 1% to 25% thereof, separating said liquid phase and subjecting the same to liquid-liquid extraction with a lower paraflnic solvent to produce a highly asphaltic rafnate and a nonasphaltic extract, recovering dissolved oil from said extract, blending said recovered oil with said gas phase, and then subjecting the resulting blend to hydrorefining at a temperature between about 600 and 875 F., a pressure between about 100 and 5000 p.s.i.g. and a hydrogen ratio between about 300 and 8,000 standard cubic feet per barrel of liquid feed, and in the presence of a hydrorefning catalyst, cooling the product from said hydrorefning step and condensingl the major portion thereof at substantially the pressure prevailingl in said hydrorefining zone, thereby producing a supernatant hydrogen-rich recycle gas phase, and contacting at least a portion of said recycle gas phase with said initial feed to effect partial vaporization asfabove described.

5. A process as defined in claim 4 wherein said hydrorefning catalyst consists essentially of a minor proportion of cobalt oxide plus molybdenum oxide supported on a carrier which is predominantly activated alumina.

6. A process as defined in claim 4 wherein said solvent boils between about 50 and 450 F.

7. A process as defined in claim 4 wherein said feedstock is essentially a crude shale oil.

8. A process for Ahydrorelining a feedstock which is essentially a full-range crude oil, which comprises first 7 Y subjecting said feedstock to partial vaporization in equilibrium with (1) hydrogen-rich recycle gasV derived from the hydrorefning step hereinafter defined, and (2) fresh makeup hydrogen required for said hydrorelining step, said partial vaporization being carried out at a temperature within about 100"Y F., and at -a pressure within about 300 p.s.i.g. of-the temperature and pressure prevailing in the hydrorening step hereinafter defined, thereby producing a gas phase comprising between about 75 %v and 99% of said feed'oil and a liquid phase comprising about 1% to 25% thereof, separating said liquid phase and subjecting the same to liquid-liquid extraction with a lower `paraiinic solvent to` produce a highly asphalticV rainate and a nonasphaltic extract, recovering dissolved oil from said extract, blending said recovered oil with said gas phase, and then subjecting the resulting blend to hydrorefining at a temperature between about 600 and 875 F., a pressure between about 100 and 5000 p.s.i.g. and a hydrogen ratio between about 300 and 8000 standardcubic feet per barrel of liquid feed, and in the pres- 9. A process as defined in claim 8 wherein the feed` stock in said partial vaporization step is iirst equilibrated with said recycle gas and the resulting liquid phase is then stripped with said freshmakeup hydrogen.

l0. A process as dened in claim 9 wherein the rate of injection of fresh makeup'hydrogen in said stripping peration is the same as the rate of hydrogen consumption in said hydrorening step.

References Cited in the rile of this patent UNITED STATES PATENTS `2,606,141 Meyer Aug. 5, 1952

Claims (1)

1. 8. A PROCESS FOR HYDROREFINING A FEEDBACK WHICH IS ESSENTIALLY A FULL-RANGE CRUDE OIL, WHICH COMPRISES FIRST SUBJECTING SAID FEEDSTOCK TO PARTIAL VAPORIZATION IN EQUILIBRIUM WITH (1) HYDROGEN-RICH RECYCLE GAS DERIVED FROM THE HYDROREFINING STEP HEREINAFTER DEFINED, AND (2) FRESH MAKEUP HYDROGEN REQUIRED FOR SAID HYDROREFINING STEP, SAID PARTIAL VAPORIZATION BEING CARRIED OUT AT A TEMPERATURE WITHIN ABOUT 100*F., AND AT A PRESSURE WITHIN ABOUT 300 P.S.I.G. OF THE TEMPERATURE AND PRESSURE PREVAILING IN THE HYDROREFINING STEP HEREINAFTER DEFINED, THEREBY PRODUCING A GAS PHASE COMPRISING BETWEEN ABOUT 75% AND 99% OF SAID FEED OIL AND A LIQUID PHASE COMPRISING ABOUT 1% TO 25% THEREOF, SEPARATING SAID LIQUID PHASE AND SUBJECTING THE SAME TO LIQUID-LIQUID EXTRACTION WITH A LOWER PARAFFINIC SOLVENT TO PRODUCE A HIGHLY ASPHALTIC RAFFINATE AND A NONASPHALTIC EXTRACT, RECOVERING DISSOLVED OIL FROM SAID EXTRACT, BLENDING SAID RECOVERED OIL WITH SAID GAS PHASE, AND THEN SUBJECTING THE RESULTING BLEND TO HYDROREFINING AT A TEMPERATURE BETWEEN ABOUT 600* AND 875*F., A PRESSURE BETWEEN ABOUT 100 AND 5000 P.S.I.G. AND A HYDROGEN RATIO BETWEEN ABOUT 300 AND 8000 STANDARD CUBIC FEET PER BARREL OF LIQUID FEED, AND IN THE PRESENCE OF A HYDROREFINING CATALYST, COOLING THE PRODUCT FROM SAID HYDROREFINING STEP AND CONDENSING THE MAJOR PORTION THEREOF AT SUBSTANTIALLY THE PRESSURE PREVAILING IN SAID HYDROREFINING ZONE, THEREBY PRODUCING A SUPERNATANT HYDROGEN-RICH RECYCLE GAS PHASE, AND CONTACTING AT LEAST A PORTION OF SAID RECYCLE GAS PHASE WITH SAID INITIAL FEED TO EFFECT PARTIAL VAPORIZATION AS ABOVE DESCRIBED.

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