|Número de publicación||US3051645 A|
|Tipo de publicación||Concesión|
|Fecha de publicación||28 Ago 1962|
|Fecha de presentación||23 May 1960|
|Fecha de prioridad||23 May 1960|
|También publicado como||DE1470628A1|
|Número de publicación||US 3051645 A, US 3051645A, US-A-3051645, US3051645 A, US3051645A|
|Inventores||Good George M, Wilson William B|
|Cesionario original||Shell Oil Co|
|Exportar cita||BiBTeX, EndNote, RefMan|
|Citas de patentes (6), Citada por (56), Clasificaciones (8)|
|Enlaces externos: USPTO, Cesión de USPTO, Espacenet|
Aug. 28, 1962 w. B. WILSON ETAL 3,
UPGRADING HEAVY HYDROCARBON OILS Filed May 23, 1960 3 Sheets-Sheet 1 n: V 3 LL. 5' m FIG. I 3 2.0 E gn u z gfi D A 3 a: LIJ I.O
G q o l I 0 2o 40 so 80 I00 PERCENT w STRAIGHT RUN RESIDUE I00 I WW' F 5 o m 80 3 FIG. 3
1 2 l u so 0 o [C 40 O E LIJ II O 0 1 I l l l I 0 w 0 2o so I00 SULFUR REMOVAL (PERCENT BY WEIGHT) INVENTORS WILLIAM B. WILSON GEORGE M. GOOD WAZEEM QM THEIR ATTORNEY Aug. 28, 1 w. B. WILSON ETAL 3,051,545
UPGRADING HEAVY HYDROCARBON OILS Filed May 23, 1960 5 Sheets-Sheet 2 PERCENT WEIGHT NITROGEN REMOVED 0 2O 4O 6O 80 I00 PERCENT WEIGHT SULFUR REMOVED INVENTORS WILLIAM B.WILSON GEORGE M. GOOD BY THEIR ATTORNEY 3,951,645 UPGRADING I-EAVY HYDRQCARBGN H5 William B. Wilson, Pleasant Hill, and George M. Good, Piedmont, Califi, assignors to Shell Gil Company, New York, N.Y., a corporation of Delaware Filed May 23, 1960, Ser. No. 30,878 6 Claims. (Cl. 208-239) This invention relates to a process for upgrading hydrocarbon oils containing metals and heteroatomic compounds. The invention relates particularly to the processing of heavy hydrocarbon oils containing relatively large amounts of such impurities.
Because of increased demand for petroleum products and because of the almost negligible supplies of paraflinbase crudes, the petroleum industry today processes largely naphthenic, aromatic, or mixed-base crude petroleum. In addition to being less parafinic in character, these latter crude oils also contain larger quantities of metals and heteroatomic compounds. It is well known that most of such impurities tend to be concentrated in the heavy oil portions of the crude and particularly in the residual fraction. The long residues which are produced from the usual distillation of crude oil are therefore normally processed further in one of two ways. They are vacuum distilled or extracted in order to separate at least part of the more volatile and normally more valuable portions, or else they are cracked. In either case, the byproduct of such processing is a residual fraction having still higher content of metals and heteroatomic compounds.
The disposal of such residuals in the past was facilitated by their extensive use as industrial and marine fuels. However, because of steadily increasing demand for further distillates and also because of restrictions imposed in many industrial areas on the use of such materials because of air pollution problems, there has been a steady impetus to devise methods by which such contaminantcontaining heavy oils could be economically upgraded to more valuable products. A solution to the problem of meeting increasing distillates demand is, of course, utilization of one or more of the basic refinery cracking processes, e.g. either thermal or catalytic cracking. Thermal cracking of such high contaminant residuals is of only marginal value since (1) the gasoline produced thereby is usually of inferior quality and (2) the cracked residue, which represents a still sizeable proportion of the yield, is still higher in the same contaminants and is heavier. Catalytic cracking, on the other hand, is virtually impossible from a practical viewpoint because of excessive eontamination of the catalyst by the metallic impurities contained in such heavy oils and because of the excessive formation of coke on the surface of the catalyst.
It is known that heteroatomic materials such as thiophenic compounds, pyrrolic compounds, and pyranylic materials can be removed by catalytic hydrogenation processes. Such processes, moreover, are also moderately effective in removing metallic contaminants from heavy feeds. Catalytic hydrogenation is currently gaining rapidly in its extent of utilization. It is used Widely in the treatment of gasoline, kerosene, light fuel oils (furnace oils), lubricating oils and transformer oils. However, catalytic hydrogenation is basically and inherently a costly process which involves costly catalyst and equipment, and its use is by necessity limited to those stocks which may be hydrogenated economically (l) by virtue of their low contaminants content or (2) by virtue of the fact 3,051,645 Patented Aug. 28, 1962 that they are extremely high value products which can thus bear expensive processing costs.
It is therefore an object of this invention to provide an improved process for the removal of heteroatomic compounds -from hydrocarbon oils. It is also an object of the invention to provide an improved process for the removal of metalliferous materials from heavy hydrocarbon oils, particularly residual oils. It is a further object of the invention to provide a process whereby heretofore unsuitable feed stocks are upgraded so that they may be used in conventional catalytic processing operations. It is a particular object of the invention to provide a process for treating residual hydrocarbon oils whereby greater quantities of such oils may be catalytically cracked economically and practically. -It is also an object of the invention to provide an improved process for the recovery of vanadium compounds from hydrocarbon oils. These and other objects will be apparent from the description of the invention and the drawing, which consists of four figures, and wherein:
FIGURE 1 is a graphical comparison of the sulfur distribution in various residues treated in difierent manners;
FIGURE 2 is a graphical correlation of the removal of nitrogen compounds from residues treated in accordance with the invention;
FIGURE 3 is a graphical correlation of the removal of vanadium compounds from residues treated in accordance with the invention; and
FIGURE 4 is a schematic flow diagram illustrating a preferred method for practicing the process in a continuous manner.
Briefly, the process of the invention involves reacting heavy hydrocarbon oils and residues under conditions of incipient cracking in the liquid phase with a magma mainly of an alkali metal hydroxide whereby at least two separable phases are formed, separating the thus formed phases and recovering a reaction product greatly improved with regard to content of metals and heteroatomic compounds, and improved with regard to other properties which are critical to the further employment and treating of the product by conventional refining processes, especially conversion processes.
The feed to the present process may be any higher boiling hydrocarbon oil at least about 50% by volume of which boils above about 450 F. Though even lighter hydrocarbons can in principle be processed, the present process is most advantageous for treatment of oils containing materials which cannot be distilled in commercial equipment without extensive cracking, e.g. residual materials and hydrocarbon oils containing asphaltenes, resins and the like. The process finds its greatest utility in the treatment of stocks containing appreciable amounts of hetero atoms and/ or metals. It is, therefore, particularly useful for the treatment of reduced crudes, vacuum residues, cracked gas oils, residues and the like which cannot otherwise be deeply flashed without excessive carryover of metal contaminants. In addition, certain crude petroleum oils which contain only small amounts of gaso line and kerosene boiling range hydrocarbons and which have been topped to remove lighter components may also be processed. Certain petroleum crude oils, oils from tar sands and oils from shale thus maybe processed Without being extensively reduced.
The active agent used in the process of the present in vention is the magma which appears to function (1) as a reagent, (2) as catalyst, and (3) as a solvent. Though the function of the magma is not fully understood, it appears also to act to inhibit certain undesirable side reactions, especially free radical chain reactions, while simultaneously promoting other desirable reactions with the hydrocarbon feed. The essential component of the magma is an alkali metal caustic which may be sodium hydroxide, potassium hydroxide or mixtures thereof. Both fused caustics, which contain essentially no water, may be used as well as aqueous caustic solutions. When aqueous solutions are used, however, the water content must not exceed about 50% by weight when using potassium or 25% by weight when using sodium. Because of excessive pressures produced by the presence of water at the reaction temperature of the process, it is preferred in any event to use a caustic magma containing no more than 30% by weight water, a water content of no more than being particularly preferred when sodium is used.
The temperature at which the operation is carried out is important. Qualitatively, the desired temperature is that of incipient cracking, i.e. Where thermal cracking would normally begin to take place, but below that temperature at which extensive thermal decomposition occurs. The temperature of incipient cracking varies with the nature of the particular oil being processed. But in all cases for satisfactory operation of the process of the invention, the final temperature will be within about 375 to about 475 C. For most heavy oils and residues the preferred temperature of reaction is from about 400 C. to about 430 C.
Because the reactions which take place are largely in the liquid phase, the pressure is generally not an important factor in the process of the invention. However, it is desirable usually to suppress vaporization of the reactants in order to minimize reactor size. Consequently, superatmospheric pressures are preferred. Any higher pressures can be used if desired, but it is preferred to employ operating pressures of at least 200 p.s.i.g. but below about 1,500 p.s.i.g. Above this pressure the eco nomic advantage of lower reactor volume is offset by the higher cost of such high pressure equipment.
Contacting of the two phases, i.e. the oil and the magma, may be carried out batchwise, as in an autoclave, or continuously. Continuous operation is preferred for commercial application of the process. Intimate contactingof the magma with the oil feed is very important in order to obtain the unique advantages which characterize this process. It is therefore necessary to impart a high shear rate and degree of turbulence to the materials as they are mixed. Moreover, it is also preferred to keep the mixed materials under a high degree of turbulence during the reaction period. When in-the-line mixing of the magma and feed is employed, it is preferred to use a mixing valve downstream of the injection point of the two components. When the reaction is carried out continuously the flow therethrough must be of sufficient velocity that the reactants are within the turbulent flow range. If a conventional pressure reaction vessel isused, both the initial mixing and sustained turbulance of the system may be obtained by the use of one or more turbine mixers.
The required contact time of the oil with the magma varies widely, depending upon (1) the particular stock being processed and (2) the desired degree of improvement of the limiting function for which the process is employed. At the lower temperatures contact times up to an hour or more may be used, but at the higher tem peratures contact times may be as short as about one minute. Generally, however, the contact time should be from about 2 to about minutes.
During the mixing and reaction of the magma with the feed, the magma, being essentially insoluble, remains as a separate phase immiscible with the liquid feed. However, the phase may be highly dispersed as in the form of an emulsion. The ratio of the two phases charged to'the reactor may vary widely, e.g. from as low as 0.025 to as high as 1.5 or even higher, basis weight ratio of caustic to feed. A weight ratio of caustic to feed (caustic ratio) of at least about 0.1 is preferred, and a weight ratio of at least 0.25 is preferred for feeds containing particularly high contents of sulfur and metals. Even higher ratios, up to about 1.1 to 1 are still further preferred since even betterresults are obtained therewith. However, though still greater caustic-to-feed ratios may be employed, no greater benefits have been observed above about 1.5 to 1. Thus the preferred range is from about 0.1 to 1.5 parts by weight caustic per part by weight of feed. In all events, the ratio of caustic to feed should not be less than about 0.025 for each percentage by weight of sulfur combined in the feed.
It will, of course, be recognized that the magma will ordinarily contain sizeable amounts of materials other 7 than the caustic, for example water, carbonates, sulfides,
particles of coke, metals, and soluble carbonaceous compounds such as alkyl phenols. In order to obtain more efficient utilization of the hydroxide in the magma, the magma is preferably reused at least in part. In a typical case, the once-used magma consists of 12.2% K S, 28.5% K CO 34.0% KOH, 22.9% H 0, and 2.4% coke, metals and soluble carbonaceous compounds. If the magma and oil are contacted countercurrently, the magma near the inlet may contain a sizeably greater concentration of the hydroxide with lesser amounts of the carbonate and sulfides, and that at the outlet may contain correspondingly greater concentrations of the carbonate and sulfides and less of the hydroxide. When part of the magma is recirculated, it is preferably fortified by the addition of the hydroxide so that the hydroxide content of the magma to be used constitutes at least 50% by weight of the magma. Such fortification may be accomplished by regeneration of the hydroxide from the corresponding carbonates and sulfides, and/ or by the addition of higher strength caustic.
REMOVAL or HETERO ATOMS Probably the most important aspect of the use of the process for the removal of hetero atoms from heavy oils and residues, is the removal of sulfur. It is appreciated that it has many times been suggested to remove compounds from various oils by treating them with aqueous caustic or solid caustic and that caustic treatment of oils is frequently applied in the refining of oils, particularly light oils, and materials previously treated with acid. The purpose of such treatment has been either to neutralize acidic materials formed or left from the acid treatment or to remove phenols, naphthenic acids, or other acidic substances in the oil, Most oils, and particularly the lighter oils, contain'small amounts of highly odoriferous'mercaptans, which are acidic in nature, and which are removed fairly extensively with aqueous alkali. Such treatments are, however, wholly unrelated to the present process. The heavy oils and residues with which the invnetion is concerned do not contain any appreciable amount of mercaptans or other acidic sulfur compounds and such treatments as were common heretofore are ineffective in bringing about any material reduction in their sulfur content. Thus, the sulfur compounds present in the oils treated by the process of the invention are refractory compounds, e.g. benzothiophenes, having no appreciable acidity. Accordingly, the sulfur therein is not removed as, for example, alkali metal mercaptide but as an alkali metal sulfide, which necessitates scission or cracking of the sulfur-containing molecules in the oil. Thus, chemically the desulfurization problem of heavy oils and residuals is the rapid removal of benzothiophenic and dibenzothiophenic sulfur, which comprise from 60 to of the sulfur compounds present. In fact, the major reason that hydrodesulfurization of residues is usually impractical is that the known hydrogenation catalysts have such low catalytic activity for such materials and that very low space rates are needed. Under such conditions, the deactivation of the catalyst by coke is excessive.
Example I A quantity of a Los Angeles Basin-Ventura/Four Corners crude straight run residue (reduced crude) was divided into several parts which were treated as follows:
(a) Thermally cracked for 45 minutes at 420 The figures in parentheses indicate the overall removal of sulfur on a Weight basis. A sample of the original residual feed and each of the above reaction products was fractionated and each of the fractions was examined with regard to sulfur content. The results are shown in FIGURE 1 of the drawing.
The indicated distribution of sulfur in the feed shows that the sulfur compounds tend to be concentrated in the heavy ends. Curve A shows that thermal treatment alone is not very effective to remove sulfur even from light ends and becomes even more ineffective on the 60% and heavier bottoms fractions. Curve D shows that though hydrodesulfurization is very effective on the front end of the residue, it is almost totally ineflective on the last 20% bottoms fraction. Curves B and C, however, show that treatment with caustic magma (magma cracking) in accordance with the invention is quite efiective to remove sulfur compounds essentially independently of their molecular weight or the molecular weight of the fraction in which they are contained.
A most advantageous feature of the magma cracking of heavy oils and residues in contrast to conventional thermal treatment is that thermal reactions involving cracking the hydrogen-rich alkyl fragments into gas, gasoline, and gas oils which normally occur at the conditions used are inhibited. This is illustrated by the following example.
Example II A straight-run residue prepared from a 89%/ 11% mixture of Los Angeles Basin-Venture and Four Corners crudes and which contained 1.91% by weight sulfur was treated separately by conventional thermal treatment and in accordance with the process of the invention. The operating conditions for both treatments were essentially identical and the amount of residue (bottoms) produced from the two treatments was also approximately the same. However, as can be seen from the following table, the results were significantly different.
TABLE I.COMPARISON OF THERMAL TREATMENT \VITH MAGMA CRACKING [Operating conditions: Temperature 420 C. time 45 The lower yields of gas, gasoline, and coke show the aforementioned inhibiting action of the caustic magma. Of particular interest, however, is a comparison of the residue properties. Even though the residue yield was essentially the same for both operations, the residue produced by magma cracking was considerably less viscous (87 versus 5950 seconds) notwithstanding the fact that the magma-cracked residue had an at least equal or even higher molecular weight. Though a small viscosity reduction would be expected from the better sulfur removal obtained with the process of the invention, this in no way accounts for the almost seventy-fold lower viscosity of the magma-cracked product. Though the reason for this startingly lower viscosity is not fully understood, it is significant that the hydrogen/carbon ratio of the magma-cracked residue is markedly higher, which indicates (1) that on a net basis, no additional asphaltenes and resins are formed in magma cracking as in thermal cracking and (2) that inhibited cracking and conversion of asphaltenes to less polar materials take place. This is also confirmed by the lower Ramsbottom carbon content of the magma-cracked residue.
The process of the invention is applicable to a wide range of oils, crudes, and residues. Though the degree of sulfur removal that can be obtained by magmacracking under practical operating conditions varies somewhat with different feeds, it is observed that the heavier the feed the more amenable it is to deep desulfurization. This may be seen from the following example.
Example III Three residues produced from the commercial processing of Los Angeles Basin-Ventura crude were treated in accordance with the invention. Different severity treatment with regard to temperature and caustic magma concentration were employed, the more severe conditions being used for the lighter (higher API gravity) stocks and less severe conditions being used for the heavier stocks. The results were as follows:
TABLE II.-DESULFURIZATION 0F HEAVY RESIDUES BY MAGMA CRACKING From the preceding table it may be seen that equivalent sulfur removal is obtained on heavier stocks at milder conditions than on lighter stocks. Moreover, this unexpected phenomenon also appears to be essentially independent of the amount of sulfur contained in the stock being treated. Such independence with regard to the effects of both sulfur and molecular weight has heretofore been unattainable with other sulfur removal processes.
In addition to the foregoing examples in which Los Angeles Basin-Ventura crude residues were employed, further tests were made which show that the process of the invention is applicable to a wide range of heavy oils and residues from various crude oils. This is shown by Examples IV through XI following, in which a wide variety of such materials were treated.
4 Examples IV Through XI Feed Stock Los Angeles Basin Vacuum Flasher Pitch Los Angeles Basin Thermal Cracked Residue. Lagomar straight run residue Kuwait straight run residue...
Bachaquero straight run residu Santa Maria straight run residue K OH Thermally and Catalytically cracked gas oil from LOH Alberta crude.
Air-blown (California) Heavy Valley residue NaOH The conditions and results obtained are shown in Table III following.
TABLE III.-DESULFURIZATION OF VARIOUS CRUDE RESIDUES BY MAGMA CRACKING Example IV V VI VII VIII IX X XI Temperature, O 400 400 424 438 400' 400 418 400 Pressure, p.s.i.g 625 240 1, 650 1,650 800 560 330 l, 650 Contact Time, min. 60 30 15 30 60 45 20 165 Water in Magma,
percent by wt 28 28 13 13 28 28 28 14 Magma/Oil Phase Ratio 0.4 0. 4 0.3 0.3 0. 4 0. 4 O. 4 0.6 Sulfur Content,
Feed, percent wt- 2. 5 2.0 2. 4 4. 1 3. 8 5. 7 1.1 1.2 Sulfur Content,
Product, percent Wt 1.1 1.2 1.2 1.5 2.0 3.0 0.4 0.7 Desuliurization,
percent Wt 56 40 50 63 47 47 64 42 The process of the invention is not, however, limited to the removal of sulfur hetero atoms. ther hetero atoms, such as nitrogen, are also removed, which is shown by the following example.
EXAIMPLE XII A number of tests were performed in which a Los Angeles Basin-Venture straight run residue was magma cracked in accordance with the invention. Several different operating severities' were employed, i.e. diflerent temperatures, caustic magma strength, etc. The product therefrom was then analyzed both with respect to sulfur and to nitrogen content. Since sulfur removal is correlatable with the operating severity, the nitrogen removal in each run was then correlated with sulfur removal, the results of which are shown in FIGURE 2 of the drawing. The figure shows that nitrogen removal is moderate at lower severities but as severity of the magma cracking is increased to the preferred minimum level of desulfurization (at least 60%), the extent of nitrogen removal per additional increment of operating severity becomes almost six times as great. Consequently, when processing heavy oils and residues for removal of nitrogen compounds, it is preferred to operate in such a manner that over 6 0% of the sulfur compounds are removed.
The removal of oxygen compounds from heavy hydrocarbon mixtures has generally not been a problem in commercial practice. However, it is noteworthy that the removal of oxygen-containing materials has been indicated to proceed even more rapidly than the removal of the sulfur and nitrogen compounds upon treatment in accordance with the process of the invention.
REMOVAL OF METALS Almost all crude oils contain significant amounts of metals in concentrations as high as several hundred parts per million. Practically speaking, an essentially metalfree crude oil is a rarity. Consequently, the metal content of crudes must be reckoned with in all oil refineries. The presence of metals in petroleum fractions is disadvantageous from at least three standpoints: (1) poisoning and deactivation of catalysts; (2) the formation of corrosive or fluxing salts upon combustion; (3) stability of prod ucts.
Of most concern in petroleum oils is vanadium, a large percentage of which is present in the form of porphyrin complexes which are concentrated in the residual fractions of petroleum. Heretofore, the catalytic processing of heavy metal-containing fractions has been largely impractical because of the lack of any economical process for effectively removing these materials. However, in addition to facilitating processing heavy residia and oils catalytically, the removal of metallic contaminants is likewise important from the standpoint of lighter fractions which are separated from crudes and residues containing them. That is, despite the fact that the metals are concentrated in the heavy oil and residual portions of the crude, they are easily entrained in various distillation and flashing operations into the lighter fractions and, moreover, they are decomposed and volatilized under the temperature conditions normally necessary for separating, for example, heavy gas oil fractions from crude. Thus, even the lighter gas oil fractions are likely to contain significant amounts of metals. The excellent degree of removal of vanadium from residuals by the process of the invention is shown by the following example.
Example XIII A number of tests were performed in which a Los Angeles Basin-Ventura straight run residue was magma cracked in accordance with the invention. Several different operating severities were again employed, and the product therefrom was analyzed with respect to vanadium content. As in the previous example, the degree of vanadium removal'was correlated with sulfur removal, the results of which are shown in FIGURE 3 of the drawing. This correlation shows clearly that over of the vanadium is removed at even low severity operation (40% sulfur removal), whereas over 96% of the vanadium is removed at the minimum preferred level of desulfurization (60%). Of particular importance, however, is that even above 99% removal of vanadium is obtained at the 80% desulfurization level of severity, which is readily attained in the process.
In addition to vanadium, other metallic contaminants contained in the heavy oils and residues are removed by the process of the invention. Chief among these are nickel and iron. At an operating severity corresponding to 60% sulfur removal, about 55% of the nickel and 88% of the iron were found to be removed from the same type of residue employed in Example XIII. At 80% sulfur removal, over 70% of the nickel and over of the iron are removed by the process of the invention. It will be understood that the operating severities to attain a given degree of metals removal varies considerably among differcnt residual fractions and among different crudes. The Los Angeles Basin-Venture crude straight run residue, which has been used throughout the examples, actually represents a diflicultly treated stock, i.e. one which requires a comparatively high severity treatment to effect a given level of hetero atom or metals removal. Consequently, many other feed stocks will be found to be even more easily treated. As an example, essentially all of the vanadium in a Venezuelan reduced crude may be removed at a severity corresponding to only 20-30% desulfurization.
Particular economic advantage is attained by the process of the invention in the processing of heavy oils and residues preparatory for catalytic cracking. As a practical matter, feeds to catalytic cracking units are severely limited to a maximum metals content. Thus, to take a typical situation, only 40% of a reduced crude may be recovered as catalytic cracking feed stock by vacuum flashing without exceeding this limit. However, the same residue, after treating according to' the invention, may allow 60 or 70% to be recovered as catalytic cracking feed stock by vacuum flashing. The degree of metals removal obtainable with this process is such that some reduced crudes may be amenable to catalytic cracking in their entirety, whereas in the past only the solvent deasphalted raftinates or vacuum gas oils therefrom could be completely catalytically cracked economically. Moreover, the cracked products obtained therefrom will be g superior due to the low sulfur content of the resultin products.
Though the process of this invention may be practiced in a batchwise or semi-batchwise manner, for example, with conventional mixer-settling equipment, because of the large volumes of residue and heavy oils which are processed in most petroleum refineries, the process is preferably and most economically performed in a continuous manner. A preferred way in which the process is performed continuously is illustrated by FIGURE 4 of the drawing, a detailed description of which follows.
Referring now to the drawing, 30,000 barrels per day of Los Angeles Basin-Ventu-ra straight run residue (reduced) containing 1.7% by weight sulfur and 93 ppm. vanadium metal is passed by means of line 1 to heat exchanger 201 wherein the residue is heated to a temperature of about 625 F. by exchanging heat With reactor efiiuent, which is described hereinafter. The heated residue feed material is passed via line 3 to furnace 203 wherein it is heated to 850 F. The exit feed from the furnace is mixed with magma from line 9, and the mixture of feed and magma are passed through line 7, which contains a mixing valve 205 to effect intimate mixing of the residue with the magma, to reaction zone 207. The magma from line 9 is comprised of 170,000 lbs. per hour of 71% potassium hydroxide and 5,000 lbs. per hour of recycled oil-magma rag produced as described hereinafter. Re-
' action zone 207 consists of one or more parallel reaction chambers appropriately lined to avoid corrosion from the caustic magma and so sized that the mixed magma and feed may have a residence time of about minutes therein.
Fresh or regenerated magma supplied to the process consists of 71% wt. potassium hydroxide aqueous solution. The magma is maintained at a temperature well above its solidification temperature. Thus, in the process illustrated by the drawing, magma is supplied at a temperature of about 300 F. through line 35, oil-magma rag is added from line 23, and the mixture is passed to heat exchanger 209 wherein it exchanges heat with the hot reactor efiiuent. By this means, the magma is heated further to about 630 F. after which it is passed by means of line 9 to line 7 wherein it is mixed with residue feed as described before. The temperature to which the residue is heated is adjusted so that the combined mixture of hot magma and residue are at the appropriate reaction temperature, in this case 800 F. For higher severity operation, the outlet temperature of the residue from furnace 203 is, of course, raised accordingly.
The reacted mixture of magma and magma-cracked residue is passed by means of line 11 to heat exchanger 209 wherein it exchanges heat with magma from line 35 and is cooled from approximately the reaction temperature (300 F.) to about 720 F. The partially cooled reaction mixture is passed further through line 11 to heat exchanger 201 wherein it exchanges heat with incoming feed and is cooled further to about 405 F. In any event, the mixture of magma and oil reaction product must not be cooled to the solidification temperature of the magma. Preferably it is cooled to a temperature at least 50 F. above the solidification temperature. The cooled mixture of reacted magma and cracked residue is mixed with 48,000 lb./hr. of recycled water from line 33 and the mixture if passed by means of line 19 into a first settling zone 211. In settling zone 211 the mixture of reacted magma, residue, and water is allowed to settle upon which two layers are formed with an intermediate interfacial emulsion or rag. The upper layer in settling zone 21]. consists of a layer of reacted oil and small amounts of entrained magma and other impurities. The lower layer consists of a layer of aqueous solution of unreacted magma containing impurities removed from the treated oil as well as sulfides and carbonates produced during the reaction step. The interfacial rag is an emulsion of largely unreacted magma, oil product, and some impurities.
This emulsion is withdrawn at a rate of about 5,000 lb./hr. through line 23 and mixed with fresh magma to the process in line 35 prior to heat exchange and passage to reaction zone 207. About 1,500 lb./hr. of gaseous products are formed during the reaction step and are collected in the upper part of settling zone 211 from which they are passed by means of line 21 to further treating recovery, or disposal. The lower layer of used contarninated magma is drawn off through line 25 for regeneration, in which case it may be recycled to the process with fresh magma in line 35, for other caustic treating processes, or for waste disposal. About 218,000 lb./hr. of used magma are produced, the composition of which is as follows: KOH-84,000 lbs.; K S-12,000 lbs.; K CO 30,000 lbs.; and H O92,000 lbs. The upper layer contained in settling zone 2.11 is Withdrawn through line 27 wherein it is mixed with 42,000 lb./ hr. of Water from line 29, and the mixture of oil from the upper layer and water are passed together to a second settling zone 213, wherein the mixture is settled into two distinct phases with little or no interfacial emulsion between. The water from settling zone 213 which has removed essentially the final trace amounts of magma from the reacted oil is Withdrawn through 33 and passed to line 19 wherein it is mixed with cooled reaction product and magma as described above. The magma treated oil product, which comprises the upper layer in zone 213, is passed at a rate of 412,500 lb./hr. by means of line 31 to further processing such as catalytic cracking, vacuum distillation, catalytic hydrogenation, and the like.
The magma-oil mixture may form an extensive emulsion, therefore various measures will be taken to overcome this. For example, demulsifying agents such as those which are well known in the art of crude desalting, may be added either to the water in line 29 or 33 or to the magma-oil mixture; or electrostatic precipitation means may be used in the settling zone; or combinations of these techniques may be used. It is recognized, of course, that other separation techniques may be used for separating the oil and magma layers and the emulsion, among which is the use of centrifugal action either with or without diluents added to increase the density difference between the phases.
In addition to the upgrading of hydrocarbon oils, the process of the invention is further advantageous in that valuable by-product vanadium metal or vanadium pentoxide may be recovered from the magma. The recovery of vanadium from this source is particularly advantageous since (1) the vanadium pentoxide may be recovered in higher purity than in conventional ore recovery processes and (2) the vanadium or vanadium compounds produced according to the invention are especially low in radioactivity as recovered without extensive and costly refining.
Vanadium pentoxide, which is the principal per-cursor for vanadium metal, is produced from various primary ores such as Patronite, Bravoite, Sulvanite, Davidite, Roscoelite, and Montroselite. The ore is usually roasted with common salt forming largely sodium vanadate which is leached in successive stages with water and dilute sulfuric acid, after which it is precipitated with concentrated sulfuric acid thus forming vanadium pentoxide. The V 0 produced in this manner without further excessive refining steps is normally about purity, the major impurities being calcium and sodium salts. However, it
g has been found that V 0 may be extracted simply and directly from the caustic magma produced in accordance with the invention in purities of nearly The extraction of vanadium pentoxide from the caustic magma is illustrated by the following example.
Example XIV The once-used potassium hydroxide magma which was employed in the treatment of Bachaquero straight run residue in Example VIII was treated as follows:
Upon separation of the magma from the treated oil in Example VIII, 290 grams of the magma were analyzed and found to contain 0.264 gram of vanadium. The magma was washed with carbon tetrachloride to facilitate handling at normal temperatures and diluted with water. The diluted magma was filtered to remove the iron and nickel compounds which are insoluble in the diluted magma. The filtrate was then weakly acidified (pH 5-6) by the addition of acetic acid which resulted in decomposition of the carbonates and sulfides contained in the diluted magma and the consequent evolution of carbon dioxide and hydrogen sulfide gases. The acidified dilute magma was again filtered upon which an initial portion of vanadium was removed as a potassium vanadate precipitate. The potassium vanadate thus removed by filtration contained 0.076 gram of vanadium. To the weakly acid filtrate was then added an aqueous solution of tannic acid which formed an insoluble complex phase. The complex phase was separated from the bulk of the filtrate and ignited to decompose the complex, care being taken that the temperature during ignition did not exceed about 600 C. The product from the ignition was found to be about 88% pure V containing 0.188 gram of vanadium.
The thus recovered vanadium oxide was then tested with regard to radioactivity and compared with several commercially available vanadium compounds. The results are shown in Table IV below.
TABLE IV.RADIOACTIVITY OF VANADIUM COMPOUNDS Radioactivity, Disintegrations/minute gram V 0 from magma cracking None detected ($3.5 std. dev.)
The foregoing data clearly indicated that the vanadium obtained from petroleum in accordance with the invention is much lower in radioactivity than that which is normally obtainable. Moreover, low radioactivity vanadium may be produced in this manner without extensive rerefining as is now required in the purification of orederived vanadium metal. Such low radioactivity is of particular advantage when the metal is used for sensitive instruments which require a low radioactivity background.
We claim as our invention:
1. Process for upgrading heavy hydrocarbon oils containing contaminants selected from the group consisting of metals and heteroatomic compounds of sulfur and nitrogen which comprises the steps (1) intimately contacting the oil in the liquid phase with a magma consisting essentially of the carbonate, sulfide and hydroxide of a metal selected from the group consisting of sodium, potassium, and mixtures thereof and no more than about 30% by weight water, basis the metal hydroxide content of the magma, the ,weight ratio of metal hydroxide in the magma to hydrocarbon oil being from 0.1 to 1.5, the magma comprising at least 50% by weight of said hydroxide, at a temperature between about 375 and 450 C., and a pressure of at least 200 p.s.i.g..f0r at least one 12 minute at the high end of the contacting temperature range to at least about 1 hour at the low end of said range thus forming a reaction mixture of magma and reacted oil product, (2) cooling the reaction mixture to.
a temperature above the solidification temperature of the magma, (3) adding water to the cooled reaction mixture, (4) separating in a first separation zone the cooled reaction mixture of reacted oil product and magma into at least three phases, (a) a vaporous phase comprising normally gaseous oil reaction product, (b) an upper liquid phase comprising normally liquid reaction product, and (c) a lower liquid phase comprising reacted magma and water, (5) withdrawing separately the normally gaseous reaction product from the first separation zone, (6) withdrawing separately the upper liquid phase from the first separation zone, (7) mixing the withdrawn liquid phase of oil reaction product with water, (8) separating in a second separation zone the mixture of liquid oil reaction product and water into two liquid phases, (d) an upper liquid phase substantially freed of magma and having substantially reduced content of contaminants, and (e) a lower liquid phase of water containing magma removed from the liquid oil reaction product. I
2. The process of claim 1 in which the lower liquid phase of water containing magma is added to the cooled reaction mixture in step (3) of the process.
3. The process of claim 1 in which a separate layer of emulsion of magma and oil reaction product is formed between the interfaces of the upper and lower liquid phases, which layer of emulsion is withdrawn separately and recycled to step (1) of the process.
4. The process of claim 1'in which vanadium compounds are recovered from at least part of the magma 7 from which the oil phase has been separated.
5. Process for upgreading heavy hydrocarbon oils containing contaminants selected from the group consisting of metals and heteroatomic compounds of sulfur and nitrogen which comprises contacting the heavy hydrocarbon oil in the liquid phase at a temperature between about 375 and 475 C., and a pressure of at least 200 p.s.i.g. and a contact time of from about one minute to about two hours, with a magma consisting essentially of sodium carbonate, sulfide and hydroxide and water, the weight ratio of water to sodium hydroxide in the magma being not more than 0.43 to 1 and the weight ratio of metal hydroxide to hydrocarbon oil being from 0.1 to 1.5, and separating from the contacted mixture an oil phase having substantially reduced content of contaminants.
6. The process of claim 5, in which the weight ratio of sodium hydroxide in the magma to hydrocarbon oil is from 0.25 to 1.5. I
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