Catalytic Slurry Process For Black Oil Conversion With Hydrogen And Ammonia

Abstract

A catalytic slurry process for effecting the conversion of a hydrocarbonaceous charge stock containing asphaltenes and metallic contaminants. The slurry constitutes charge stock, hydrogen, from about 1.0 to about 25.0 percent by weight of finely divided catalyst particles and, in a preferred embodiment, a portion of the previously produced product effluent. Preferred catalysts are the unsupported sulfides of the metals from Groups V-B, VI-B and VIII. Prior to an initial separation, hydrogen sulfide is commingled with the product effluent in order to convert the metals contained therein to the sulfides thereof.

Description

The process described herein is applicable to the conversion of petroleum crude oil residuals having a high metals content and comprising a hydrocarbon-insoluble asphaltene fraction. More specifically, our invention is directed toward a method for effecting a catalytic slurry process, in the presence of hydrogen, in order to convert atmospheric tower bottoms, vacuum column bottoms, crude oil residuals, topped and/or reduced crude oils, coal oil extracts, crude oils extracted from tar sands, etc., all of which are commonly referred to in the art as "black oil."

Petroleum crude oils, and particularly the heavy residuals derived therefrom, contain sulfurous compounds in exceedingly large quantities, nitrogenous compounds, high molecular weight organometallic complexes principally comprising nickel and vanadium as the metallic component and hydrocarbon-insoluble asphaltenic material. The latter is generally found to be complexed with sulfur, and, to a certain extent, with the metallic contaminants. A black oil is generally characterized in petroleum technology as a heavy hydrocarbonaceous material of which more than about 10.0 percent (by volume) boils above a temperature of about 1,050.degree. F. (referred to as nondistillables) and which further has a gravity generally less than 20.0.degree. API. Sulfur concentrations are exceedingly high, most often in the range of about 2.0 to about 6.0 percent by weight. Conradson carbon residual factors exceed 1.0 percent by weight and the concentration of metals can range from as low as about 20 p.p.m. to as high as about 750 p.p.m. by weight.

The process encompassed by the present invention is particularly directed toward the conversion of those black oils contaminated by large quantities of insoluble asphaltenes and having a high metals content--i.e. containing more than about 150 p.p.m. by weight. Specific examples of the charge stocks to which our invention is adaptable include a vacuum tower bottoms product having a gravity of 7.1.degree. API and containing 4.1 percent by weight of sulfur and 23.7 percent by weight of heptane-insoluble materials; a "topped" Middle-East crude oil having a gravity of 11.0.degree. API and containing about 10.1 percent by weight of asphaltenes and 5.2 percent by weight of sulfur; and, a vacuum residuum having a gravity of 8.8.degree. API, containing 3.0 percent by weight of sulfur and 4,300 p.p.m. by weight of nitrogen.

The utilization of our invention affords the conversion of such material into distillable hydrocarbons, heretofore having been considered virtually impossible to achieve on a continuous basis with an acceptable catalyst life. The principal difficulty, encountered in a fixed-bed catalytic system, resides in the lack of sufficient catalyst stability in the presence of relatively large quantities of metals--i.e. from about 150 p.p.m. to as high as 750 p.p.m., computed as the elements--and, additionally from the presence of large quantities of asphaltenic material and other nondistillables. The asphaltic material comprises high molecular weight coke precursors, insoluble in light hydrocarbons such as propane, pentane and/or heptane. The asphaltic material is generally found to be dispersed within the black oil, and, when subjected to elevated temperature, has the tendency to flocculate and polymerize whereby conversion to more valuable oil-soluble products becomes extremely difficult.

Candor compels recognition of the fact that many slurry-type processes have been proposed. Regardless of the various operating and processing techniques, the principal difficulty resides in the separation of the effluent to provide substantially catalyst-free distillable product, internal catalyst recirculation and "spent" catalyst withdrawal. Success has been achieved primarily through the use of intricate equipment at prohibitively high costs. An obvious alternative is to utilize the black oil as the charge to a coking unit for the production of coke and distillable hydrocarbons. In view of the steadily increasing demand for distillable hydrocarbons, particularly motor fuels, jet fuels and stocks for conversion into liquefied petroleum gas, coking is no longer suitable due to its relatively low yield of distillable hydrocarbons. Our invention affords a more economical and less difficult process from the standpoint of the desired product recovery, internal catalyst recirculation and catalyst withdrawal.

Therefore, in one embodiment, our invention provides a process for converting an asphaltene-containing hydrocarbonaceous charge stock which comprises the steps of: (a) forming a reactive slurry of said charge stock, hydrogen, ammonia and finely divided catalyst containing at least one metal component from the metals of Groups V-B, V-B and VIII; (b) reacting said slurry in a reaction zone, or coil, at cracking conditions including a pressure above about 500 p.s.i.g. and a temperature above about 800.degree. F.; (c) separating the resulting cracked product effluent, in a first separation zone, at substantially the same pressure and a temperature below about 900.degree. F., to provide a first vaporous phase and a first catalyst-containing liquid phase; (d) separating said first vaporous phase in a second separation zone, at substantially the same pressure and a temperature in the range about 60.degree. to about 140.degree. F., to provide a second liquid phase and a second vaporous phase, recycling at least a portion of the latter to combine with said charge stock and hydrogen; (e) separating said first catalyst-containing liquid phase and said second liquid phase in a third separation zone, at a reduced pressure from atmospheric to about 100 p.s.i.g., to provide a first distillable product stream and a third catalyst-containing liquid phase; and, (f) separating said third catalyst-containing liquid phase in a fourth separation zone, at a temperature above about 700.degree. F. and at subatmospheric pressure to provide a second distillable product stream and an asphaltene/catalyst sludge.

Other embodiments of our invention are directed toward particular operating techniques and preferred ranges of operating variables and conditions. Thus, the process is further characterized, in another embodiment, in that at least a portion of said first catalyst-containing liquid stream is recycled to combine with the charge stock. The catalyst concentration, within the slurry being introduced into the reaction chamber, is in the range of from about 1.0 to about 25.0 percent by weight, based upon fresh feed charge stock, and preferably from about 2.0 percent to about 15.0 percent. In a preferred embodiment, the process is further characterized in that said reactive slurry contains from 0.5 to about 10.0 percent by weight of ammonia. Since it is preferred to conduct the conversion in the substantial absence of hydrogen sulfide in the reaction zone, ammonia is injected, preferably in the recycled gaseous phase, in sufficient quantity to neutralize the hydrogen sulfide liberated during the course of the reaction. Hydrogen sulfide is then commingled with the reaction zone effluent in order to convert the catalytic metals to the sulfides.

SUMMARY OF INVENTION

The particular finely divided, solid catalyst utilized in the present slurry process, is not considered to be essential. However, it must be recognized that the catalytically active metallic component of the catalyst necessarily possesses both cracking and hydrogenation activity. In most applications of our invention, the catalytically active metallic component or components will be selected from the metals of Groups V-B, VI-B and VIII of The Periodic Table. Thus, in accordance, with The Periodic Table of The Elements, E. H. Sargent and Company, 1964, the preferred metallic components are vanadium, chromium, iron, cobalt, nickel, niobium, molybdenum, tantalum and/or tungsten. The noble metals of Group VIII, namely ruthenium, rhodium, palladium, osmium, iridium, and platinum, are not generally considered for use in a slurry-type process in view of the economic considerations involved with these relatively expensive metals. The foregoing metallic components may be combined with a refractory inorganic oxide carrier material, including alumina, silica, zirconia, magnesia, titania mixtures of two or more, etc., the final composite being reduced to a finely divided state. In such a composite, the active metallic components may exist in some combined form such as the oxide, sulfide, sulfate, carbonate, etc. Recent investigations and developments in catalytic slurry processing of heavy hydrocarbon charge stocks have indicated that the sulfides of the foregoing metals, and particularly those of Group V-B, offer more advantageous results. Furthermore, the process appears to be facilitated when the sulfide of the metal is unsupported, as contrasted to being combined with a refractory inorganic oxide carrier material. For this reason, the preferred unsupported catalyst for use in the process of the present invention, comprises tantalum, niobium or vanadium with a vanadium sulfide being particularly preferred. In the interest of brevity, the following discussion will be limited to the use of vanadium sulfides, in an amount of about 1.0 to about 25.0 percent by weight, as the catalyst in the present slurry process.

Regardless, of the character of the catalyst, it may be prepared in any suitable, convenient manner, the precise method not being essential to the present invention. For example, vanadium sulfides may be prepared by reducing vanadium pentoxide with sulfur dioxide, sulfuric acid and water to yield a solid hydrate of vanadyl sulfate. The latter is treated with hydrogen sulfide at a temperature of about 300.degree. C. to form vanadium tetrasulfide. Reducing the vanadium tetrasulfide in hydrogen, at a temperature of above about 300.degree. C., produces the vanadium sulfide which is slurried into the system. As hereinbefore set forth, the concentration of vanadium sulfide is preferably within the range of about 2.0 to about 15.0 percent by weight, calculated as the elemental metal. Excessive concentrations do not appear to enhance the results, even with extremely contaminated charge stocks having exceedingly high asphaltene contents.

DESCRIPTION OF DRAWING

In the accompanying drawing, illustrating one embodiment of our invention, a simplified flow diagram is presented. Details such as pumps, instrumentation and controls, heat-exchange and heat-recovery circuits, valving, startup lines and similar hardware have been omitted; these are considered to be nonessential to an understanding of the techniques involved. The utilization of such miscellaneous appurtenances, to modify the illustrated process flow, are well within the purview of those skilled in the art. Similarly, it is understood that the charge stock, operating conditions, catalysts, design of fractionators, separators and the like are exemplary only, and may be varied widely without departure from the spirit of our invention, the scope of which is defined by the appended claims.

With reference now to the drawing, the fresh feed charge stock, for example a reduced crude oil, enters the process by way of line 1. The charge stock is commingled with a hydrogen-rich recycle stream from line 3 and a vanadium sulfide catalyst-containing hot recycle stream from line 2. The mixture continues through line 1 into reaction coil 6 at a pressure above about 500 p.s.i.g. and a temperature above about 800.degree. F.; preferred conditions are a pressure from 1,000 to about 3,000 p.s.i.g. and a temperature in the range of from 825.degree. to about 1,000.degree. F. The hydrogen concentration, within the reactive slurry entering reaction coil 6, including makeup hydrogen introduced by way of line 4 is from 1,000 to about 50,000 s.c.f./bbl., and preferably from about 3,000 to about 20,000 s.c.f./bbl. In a preferred embodiment, the reactive slurry also contains from 0.5 to about 10.0 percent by weight of ammonia introduced into the hydrogen-rich recycle stream through line 5.

The product effluent from reaction coil 6 is admixed with from 1.0 to about 25.0 percent by weight of hydrogen sulfide from line 8, and the mixture continues through line 7 into hot separator 9, at substantially the same pressure as it emanates from reaction coil 6. Prior to being introduced into hot separator 9, the hydrogen sulfide-containing reaction coil effluent is utilized as a heat-exchange medium to lower its temperature to a level in the range of from about 700.degree. to about 900.degree. F. Hot separator 9 serves the principal function of providing a principally vaporous phase, line 10, and a catalyst-containing liquid phase, line 16, the latter containing primarily those hydrocarbons boiling above a temperature of about 650.degree. F. The vaporous phase in line 10 is cooled and condensed to a temperature in the range of about 60.degree. to about 140.degree. F., and introduced into receiver 11. The liquid phase in line 16 may be recycled, at least in part, by way of line 2 to combine with the fresh feed charge stock in line 1. Since hydrogen sulfide has been commingled with the reaction zone effluent, prior to separation in hot separator 9, the catalyst being recycled by way of line 2, with the hot separator liquid phase, is in the form of a sulfide. The quantity so recycled is such that the combined liquid feed ratio to reaction coil 6 is within the range of about 1.1 to about 6.0. High-pressure receiver 11 provides hydrogen-rich vaporous phase, being withdrawn by way of line 12, which vaporous phase is introduced into hydrogen sulfide removal system 13. The enriched hydrogen stream is recycled through line 3 by way of compressive means not illustrated in the drawing, and is admixed with makeup hydrogen in line 4 and ammonia from line 5. Hydrogen sulfide is withdrawn from the removal system by way of line 14, at least a portion of which is diverted through line 8 to combine with the reaction product effluent in line 7.

That portion of the catalyst-containing liquid phase from hot separator 9 not being recycled by way of line 2, continues through line 16 into flash fractionator 17. Similarly, the liquid phase from high-pressure receiver 11 is withdrawn by way of line 15 and introduced into flash fractionator 17, preferably at a locus above that through which the hot separator liquid is introduced. The separation in flash fractionator 17 is effected at a reduced pressure of from atmospheric to about 100 p.s.i.g. and a reboiler, or bottom temperature in the range of 600.degree. to about 800.degree. F. In the drawing, flash fractionator 17 is shown as separating the product into three individual streams. For the purposes of this illustration, a naphtha fraction, having an end boiling point of about 400.degree. F., and containing normally gaseous hydrocarbons, is withdrawn through line 18. A gas oil fraction, boiling up to a temperature of about 650.degree. F., is withdrawn through line 19, while a heavier fraction, containing catalyst particles and unreacted asphaltenes is withdrawn through line 20. The latter is introduced into vacuum column 21 wherein separation is effected to provide a light vacuum gas oil in line 22, a heavy vacuum gas oil in line 23 and, an asphaltene/catalyst sludge in line 24. In one embodiment, not illustrated in the drawing, vacuum column 21 is operated in a manner which provides a slop-wax cut which is recycled to the reaction coil in admixture with a portion of the asphaltene/catalyst sludge. When this embodiment is practiced, a recycle stream from hot separator 9 is generally not effected. The asphaltene/catalyst sludge may be subjected to a series of filtration and washing techniques, utilizing a suitable solvent to remove residual, soluble hydrocarbons therefrom. The remainder of the sludge is generally burned in air, resulting in vanadium pentoxide which is subsequently reduced with sulfur dioxide, sulfuric acid and water to produce vanadyl sulfate. The procedure then follows the previously described scheme for the preparation of fresh vanadium sulfide.

DESCRIPTION OF A PREFERRED EMBODIMENT

This illustration of a preferred embodiment will be presented in connection with a commercially scaled unit designed to process 25,000 bbl./day of a Laguna reduced crude having a gravity of about 9.8.degree. API. Other characteristics of the charge stock include an initial boiling point of 560.degree. F., a 10.0 percent volumetric distillation temperature of 700.degree. F. and a 50.0 percent volumetric distillation temperature of 1,000.degree. F.; the crude contains about 5,190 p.p.m. by weight of nitrogen, 9.6 percent by weight of heptane-insoluble asphaltenes, 2.8 percent by weight of sulfur, about 438 p.p.m. of vanadium and 74 p.p.m. of nickel, has a carbon/hydrogen atomic ratio of about 7.95 and an average molecular weight of about 598.

The reduced crude, in an amount of about 696 mols./hr., is admixed with 208 mols/hr. of ammonia, 13,865 mols/hr. of a hydrogen-rich recycled gaseous phase (12,336 mols/hr. of hydrogen) and a hot liquid recycle in an amount to result in a combined liquid feed ratio of 2.0. The total charge, containing about 5.5 percent by weight of a vanadium sulfide, is introduced into a reaction coil at a pressure of about 2,000 p.s.i.g. and a temperature of about 850.degree. F. About 14 mols/hr. of hydrogen sulfide are added to the reaction coil effluent prior to the introduction thereof into a hot separator at a temperature of about 750.degree. F. The separation effected in the hot separator is illustrated in table I, with reference being made to line numbers in the accompanying drawing. For convenience, the values are expressed in mols/hr. Not included are 208 mols/hr. of neutralized hydrogen sulfide. ---------------------------------------------------------------------------

TABLE I: HOT SEPARATOR STREAM ANALYSES

Component Line 10 Line 16 __________________________________________________________________________ Ammonia 25 2 Hydrogen 8,747 476 Methane 1,532 126 Ethane 95 82 Propane 86 53 Butanes 55 20 Pentane-400.degree. F. 237 54 400.degree. -650.degree. F. 296 187 650.degree.- 1,050.degree. F. 60 430 Residuum -- 30 __________________________________________________________________________

The vaporous phase from the hot separator is cooled and condensed, and passed into a high-pressure (about 1,900 p.s.i.g.) receiver at a temperature of about 100.degree. F. A hydrogen-rich vaporous phase is recycled therefrom to the reaction coil. The normally liquid stream from the receiver is introduced into a flash fractionator functioning at a temperature of 750.degree. F. and a pressure of 75 p.s.i.g. The hot separator liquid stream is also introduced into the flash fractionator, but through a locus below that through which the receiver stream is introduced. The separation effected in the cold receiver is presented in the following table II: ---------------------------------------------------------------------------

table ii: cold receiver stream analyses

component Line 12 Line 15 __________________________________________________________________________ Hydrogen 8,611 136 Methane 1,406 126 Ethane 71 24 Propane 43 43 Butanes 13 42 Pentane-400.degree. F. -- 235 400.degree.- 650.degree. F. -- 296 650.degree.- 1,050.degree. F. -- 60 Residuum -- -- __________________________________________________________________________

In this illustration, the flash fractionator provides an overhead stream containing hexanes and lower-boiling components, a side-cut naphtha stream of heptanes and other hydrocarbons boiling up to 400.degree. F., a light gas oil cut and a bottoms, catalyst-containing stream comprising 650.degree. F.-plus hydrocarbons. The latter is introduced into a vacuum column (55 mm. of Hg.) at a temperature of 800.degree. F. A heavy vacuum gas oil is recovered and an asphaltene/catalyst sludge is removed to a catalyst recovery system.

The overall yields and product distribution are presented in the following table III: ---------------------------------------------------------------------------

table iii: product distribution and yields

component Mols/Hr. __________________________________________________________________________ Hydrogen 612 Methane 252 Ethane 106 Propane 96 Butanes 62 Pentanes 32 Hexanes 44 Heptane-400.degree. F. 213 400.degree.- 650.degree. F. 483 650.degree.- 1,050.degree. F. 490 Residuum 30 __________________________________________________________________________

The foregoing specification indicates the method by which the process encompassed by our invention is effected, and illustrates the benefits afforded through the utilization thereof.

Claims

We claim as our invention:

1. A process for converting an asphaltene-containing hydrocarbonaceous charge stock which comprises the steps of:

a. forming a reactive slurry of said charge stock, hydrogen, ammonia and a finely divided catalyst containing at least one metal component from the metals of Groups V-B, VI-B and VIII;

b. reacting said slurry in a reaction zone, or coil, at cracking conditions including a pressure above about 500 p.s.i.g. and a temperature above about 800.degree. F.;

c. separating the resulting cracked product effluent, in a first separation zone, at substantially the same pressure and a temperature below about 900.degree. F., to provide a first vaporous phase and a first catalyst-containing liquid phase;

d. separating said first vaporous phase in a second separation zone, at substantially the same pressure and a temperature in the range of about 60.degree. to about 140.degree. F., to provide a second liquid phase and a second vaporous phase, recycling at least a portion of the latter to combine with said charge stock and hydrogen;

e. separating at least a portion of said first catalyst-containing liquid phase and said second liquid phase in a third separation zone, at a reduced pressure of from atmospheric to about 100 p.s.i.g., to provide a first distillable product stream and a third catalyst-containing liquid phase; and,

f. separating said third catalyst-containing liquid phase in a fourth separation zone, at a temperature above about 700.degree. F. and at subatmospheric pressure, to provide a second distillable product stream and an asphaltene/catalyst sludge.

2. The process of claim 1 further characterized in that said catalyst is an unsupported sulfide of at least one of the metals from Groups V-B, VI-B and VIII.

3. The process of claim 1 further characterized in that said catalyst constitutes from 1.0 to about 25.0 percent by weight of said charge stock, as the elemental metal.

4. The process of claim 2 further characterized in that said catalyst is an unsupported vanadium sulfide.

5. The process of claim 1 further characterized in that hydrogen sulfide is commingled with said cracked product effluent in an amount of from 1.0 to about 25.0 percent by weight, as elemental sulfur.

6. The process of claim 1 further characterized in that said reactive slurry contains from 0.5 to about 10.0 percent by weight of ammonia.

7. The process of claim 1 further characterized in that said slurry is reacted at a pressure from 1,000 to about 3,000 p.s.i.g. and a temperature in the range of from 825.degree. to about 1,000.degree. F.