US 3203892 A
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Aug. 31, 1965 C. N. KIMBERLIN, JR., ETAL Filed April 19, 1965 NAPHTHA DISTILLATION ZONE 5 2 0|s 4'|EE Z$Es CRUDE g OIL HEAVY GAS OIL 1 27 BOTTOMS 7 y FLASH TOWER v MIXING ZONE I 2| 23 24 SWJAAAEE? 2s ACID STORAGE +28 METAL CONTAMINANTS CHARLES NEWTON KIHBERLIN. JR. HENRY GEORGE ELLERT inventors CLARK EDWARD ADAMS GLEN PORTER HAMNER Patent Attorney United States Patent 3,203,892 DEMETALLIZA'I'IONA E] 1TH H Y DROFLUORIC I'D Charles Newton Kimberiin, Jr., Henry George Ellert, Clark Edward Adams, and Glen Porter Hamner, Baton Rouge, 1a., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Apr. 19, 1963, 'Ser. No. 274,236 18 Claims. (Cl. 2ll8252) This application is a continuation-in-part of application Serial No. 3,391 filed January 19, 1960, now abandoned.
The present invention relates to the upgrading of hydrocarbon oils and more particularly relates to an improved process for removing metallic contaminants from high boiling petroleum fractions.
The present invention relates to a process of removing metallic contaminants from high boiling hydrocarbon fractions by contacting the fractions with hydrofluoric acid and subsequently separating the HP from the reaction eflluent.
Specifically, the presesnt invention relates to a process of contacting the high boiling fraction with relatively concentrated HF wherein the entire reaction efliuent is treated to remove HF. More specifically, the present invention relates to a process wherein the entire reaction efiluent is treated to remove substantially all the HF before the removal of either solids or oil from the reaction eflluent.
More specifically, the present invention relates to a process of demetallizing high boiling hydrocarbon fractions by contacting the hydrocarbon fractions with concentrated hydrofluoric acid whereby the acid reacts with metallic contaminants to form finely divided solid particles wherein the entire reaction efiiluent is treated to remove HF by flashing or other suitable means, and the remaining oil and solid metallic contaminants are separated and a hydrocarbon yield of 99%+ based on feed is recovered.
The adverse effects of iron, nickel, vanadium and other metallic contaminants found in petroleum fractions boiling above about 950 F. upon catalysts employed in petroleum processing operations and upon combustion equipment in which such high boiling fractions are used as fuels have long been recognized. In catalytic cracking operations, for example, very small concentrations of such contaminants in the feed to the cracking unit lead to the rapid poisoning of the catalyst, causing a significant decrease in the yield of cracked liquid products, an increase in the production of coke and gases, and a marked shortening of the catalyst life. Metallic contaminants present in residual fuels have similarly deleterious effects in that they attack the refractories used to line boilers and combustion chambers; cause slagging and deposits on boiler tubes, combustion chamber walls and blades of gas turbines; and severely corrode high temperature metallic surfaces with which they come in contact.
Much research has been devoted to the problem of developing methods for removing metallic contaminants from high boiling petroleum fractions in order to overcome these difiiculties. leretofore, no wholly satisfactory method for accomplishing this had been found. The contaminants are largely unaffected by conventional desalting techniques, solvent extraction, chemical treatment, and other methods proposed in the past. It has, therefore, generally been necessary to limit the feed stocks to catalytic cracking units and other catalytic processes to those fractions which boil below the range in which metallic contaminants are found and to avoid as much as possible the use in residual fuels of high boiling residual fractions containing high contaminant concentrations.
The present invention provides a new and improved method for removing metallic contaminants from high 32%,892 Patented Aug. 31, 1965 boiling petroleum fractions which is highly effective, results in improved yields of decontaminated oil, and is economically attractive. In accordance with the invention, the contaminants in the oil are removed by treating the contaminated fraction with hydrofluoric acid under controlled conditions and thereafter removing the HF from the reaction mixture prior to removing the contami nants. The hydrofluoric acid acts apparently as a selective metal cleaning agent toward the contaminants. The acid in the present process may be used repeatedly and, since little or no oil is consumed in reaction with the acid, the product yields are 99%+ based on hydrocarbon feed. The process of the invention is applicable to the treatment of high boiling gas oils, deasphalted oil, residual fractions and crude oils.
The process of the invention is based upon studies made of the nature and properties of the metallic contaminants found in heavy gas oils and in residual fractions boiling in excess of 950 F. It has been found that such contaminants are innate constituents of the oil and are usually complex organic chelate compounds of the porphyrin type. Two forms of the contaminants have been observed, one volatile at temperatures between about 1050 and 1250 F. and the other substantially non-volatile at such temperatures. It is believed that the volatile contaminants are single, monomeric porphyrins and that the non-volatile compounds are formed by the polymerization of two or more such porphyrins.
v The non-volatile contaminants are of low solubility in the oil and are normally colloidally dispersed therein. The volatile contaminants, on the other hand, are in true solution. Because of entrainment during fractionation of the oil, both volatile and non-volatile contaminants may be present in distillate petroleum fractions boiling as low as 950 F. or in some instances even slightly lower. The mechanism by which the hydrofluoric acid removes metals from the porphyrins and complexes, regardless of whether these are in soluble or colloidal form, is probably one in volving selective cleavage of the porphyrin molecule. The metals are recovered as a solid comprising 5 to 20 wt. percent metal in a carbonaceous, coke-like material that is insoluble in both the oil and the aqueous-acid phases while the bulk of the porphyrin molecule remains in the oil. This is a substantially different phenomenon from that which takes place where these same metal contaminated stocks are treated with other concentrated acidic reagents, such as H or hydrogen chloride or other halogen acids. Here, the principal reaction is a coagulating step involving precipitation of the whole molecule, i.e., the porphyrin molecule itself is precipitated, along with asphaltenes and other high molecular weight hydrocarbons associated with the organic metallic complex. The coagulation step results in considerable loss of hydrocarbon material as acid hydrocarbon sludge. Furthermore, prior art acid treating processes do not affect significantly the volatile oil-soluble porphyrins. Though these soluble metals, and about one-third of the vanadium in Bachaquero crude is in this form, may be converted to the insoluble colloidal form by such techniques as heat soaking or solvent precipitation, this not only requires an extra processing step, but also is impractical for removing small concentrations of metals, for example, from gas oils. Prior art treatment of crudes containing volatile porphyrins with aqueous HCl (e.g., 37% HCl) was completely ineffective in removing these porphyrins. Thus, by op erating in accordance with the present invention, no pre liminary deasphalting, solvent precipitating, or thermal treating step is necessary.
The treatment of high boiling petroleum fractions with halogen acids is well known in the art. In general, the halogen acids form a molecular type of complex with the hydrogen deficient components of the oil (e.g., compounds containing polynuclear aromatic structures) and with sulfur and nitrogen containing compounds. These halogen acid complexes are insoluble in the remainder of the oil, i.e., the parafiinic and naphthenic portions, and they can separate into a heavy layer which is sludgelike. Some of these complexes may be soluble in excess halogen acid, particularly if the acid contains very little water. In the presence of a considerable proportion of water, however, a third aqueous acid layer or phase may form which contains very little oil or complex. The halogen acid forms a molecular complex with the oil components and can be separated from the remainder of the oil. Depending on the particular conditions of temperature, pressure, type and concentration of halogen acid, removal of the complex will remove a considerable proportion of the hydrogen deficient, sulfur and nitrogen compounds from the oil.
The oil soluble metal constituents of petroleum are of the ponphyrin type and other types which are nitrogen containing and hydrogen deficient which also form halogen acid complexes and separate with the other complexes. The amount of complex separated depends both on treating conditions and on the oil treated, but with high boiling petroleum fractions the complex portion will usually amount to greater than about 5% of the feed and may be as much as 50% or more of the feed. Applicants found that the halogen acid molecular complexes, i.e., with HCl, HI and HBr, may be decomposed by removing the halogen acid as by heating and/ or stripping and the original compounds recovered substantially unchanged.
The halogen acids are active catalysts under certain conditions for cracking, alkylation, rearrangements, etc. Under these conditions, such undesirable reactions will take place particularly with the complexed molecules and lead to coke, gas and sludge formation. Hydrogen iodine, for example, is a strong reducing agent in which reaction iodine is produced giving rise to vfurther complicated reactions.
In accordance with the present invention, it has unexpectedly been found, with hydrogen fluoride, under certain conditions of acid concentration that the soluble metal compounds in petroleum can be selectively decomposed to an insoluble metal inorganic compound without significant modification of the organic component of the complex compounds. It has not been found possible to obtain this highly selective metal compound cleavage reaction with the other halogen acids, i.e., HOl, HBr or HI.
Removal of the complexes formed with halogen acids from the treated oil will allow removal of metal compounds but this is always accomplished with considerable loss of oil yield. Removal of the halogen acid from the molecular complexes formed with HOl, HBr and HI liberates the metal compounds substantially unchanged, which metal compounds go back into solution in the oil. After treatment with HF under the conditions of the present invention and removal of the HF in accordance with this invention, the metals are cleaved from the organic portion of the compounds so the metals can be separated, e.g., by filtration, with the loss of only negligible amounts, less than 0.5% of oil.
The sludge formation that occurs when concentrated HCl is contacted with crude is caused by reaction of the crude with the acid whereby an acid sludge is formed which on settling usually settles to the bottom of the settler and is withdrawn before removal of the acid or oililayer.
Further, when concentrated hydrofluoric acid was contacted with a crude oil, allowed to separate into two or more liquid phases and either the acid layer or oil layer withdrawn, a substantial loss of oil product resulted.
Applicants unexpectedly found that if the reactor effluent obtained after contact of the oil with the hydrofluoric acid prior to any settling taking place were treated to remove substantially all of the HF in the reaction product that a substantial portion of the metallic contaminants could be removed by filtration with substantially no loss of oil. Yields as high as 99.5% based on cnude feed have been obtained while removing up to to 99% of all metal contaminants present from the fraction treated.
It is believed that the effective removal of metals, While losing practically no hydrocarbon product, is due to the removal of the HF prior to any separation of acid or oil layer. It is believed that as the HP is removed, the HF- oil complex is broken up and the organic portion of the complex redissolved in the oil :layer. Also, as the HP is removed there is no HF remaining to complex with any oil components which would thereby normally be lost with the removed acid layer or left behind when the oil layer was removed. The metal portion of the complex is cleaved from the organic portion and precipitated.
The HF can be removed in any conventional manner as by flashing, stripping with steam or an inert gas, low temperature distillation, etc. Since the hydrocarbons normally treated boil above about 950 F., the HF removal step can be carried out at effectively high temperature without loss of any hydrocarbons.
The reaction product can obviously be allowed to settle and then the HF can be removed by suitable stripping means. As long as a layer containing hydrocarbon material is not removed before removal of all the HF present substantially no oil is lost.
It is preferred to carry out the process continuously in which case no separate layers of acid or hydrocarbons would ever be allowed to form. In this case, the HF would continuously be removed overhead as vapor from the HF free oil containing the precipitated contaminant.
It is more likely that some phase separation may ocour in a batch technique more so than in a continuous process. Further, in some situations where relatively less concentrated HP is used in large amounts and an oil free HF-oil complex free aqueous acid layer forms, this layer can be separately withdrawn to lessen the load on the distillation or stripping equipment. However, it is preferred to operate under conditions of acid concentration and acid dosage wherein such a layer does not form.
The simplicity of the process and the elimination of the settling equipment and the time required for settling results in substantial savings in investment in equipment and increases throughput due to omitting the settling step.
All of these advantages are obtained in addition to high met-ails removal and substantially no loss in crude due to formation of an insoluble acid hydrocarbon metal contaminant sludge.
Further, the present process provides an efiicient economic method of recovering vanadium and nickel from high metal crudes.
The concentration of metallic contaminants and the ratio of volatile to non-volatile compounds in crude oils vary considerably. The metals content of any distillate fraction will therefore depend upon the type and concentration of contaminants in the crude oil from which the fraction was distilled, the boiling range of the fraction, and the amount of entrainment which took place during the distillation. Heavy gas oils distilled from typical crudes may contain from about 1 to about 20 pounds of metal contaminants per 1000 barrels. Residual fractions and gas oils derived from crudes which are particularly high in contaminants may contain as much as 200 pounds of metal per 1000 barrels. Examples of crudes treated are Venezuelan, Bachaquero, Kuwait and West Texas resids, and South Louisiana gas oil.
The treating temperature, the volume of acid employed, and the intensity with which the oil and the acid are mixed in carrying out the process of the invention may be varied considerably. It is preferred to treat at temperatures between about 200 and about 450 F., although in some cases temperatures as high as 550 F. may be employed. The temperature employed depends, of course, upon other operating conditions. Intensive agitation of the oil and acid to obtain good contact need not be avoided since formation of emulsions between the oil and acid is no problem because the HP is removed by flashing. The tendency toward emulsion formation is somewhat greater with the more highly concentrated acids. The volume of acid employed may range between about 0.05 and about 1.5 volumes, preferably 0.1 to 1.0 volume and more preferably about 0.3 to 0.5 or to less than 0.5 per volume of oil treated.
The exact nature and objects of the invention may be more fully understood from the following description and the attached drawing which illustrates a preferred embodiment of the invention.
Referring now to the drawing, reference numeral 1 designates a crude oil distillation zone which may constitute, for example, an atmospheric pipe still or a combination of atmospheric and vacuum distillation towers. Crude oil may be introduced into distillation zone 1 through line 2 and separated in a variety of fractions having difierent boiling ranges. Light hydrocarbon gases in the C to C range, such as methane, ethane, ethylene, propane and the like, may be taken off through an overhead line 3. Naphtha may be withdrawn from the distillation zone through an upper side stream withdrawal line such as line 4 and middle distillates such as kerosene and light gas oil may be withdrawn through other lines such as line 5. These middle distillate fractions may boil up to about 900 F. and will be substantially free of metallic contaminants. A heavy gas oil fraction boiling in the range between about 950 F. and about 1300 F. is withdrawn from the lower portion of the distillation zone through line 6.
The residual fraction boiling above the heavy gas oil is taken off as a bottoms product through line 7. Both the residual fraction and the heavy gas oil may contain substantial quantities of metallic contaminants, and may be passed directly to the demetallizing process. It is obviously desirable to treat each of these streams separately Whenever a specific feed stock is desired. Any one or more fractions may be mixed prior to metals removal as desired. Furthermore, if desired, this crude distillation may be simplified so that only a light fraction boiling below about 400 F. is taken overhead and the topped crude is submitted to the HF treatment.
High boiling oil withdrawn either through line 6 or 7 is now passed directly to mixing zone 10. The latter is provided with suitable means for agitation and heating coils; jacketing or other means are provided for maintaining the temperature within the mixing zone at the desired level. The reactor is fabricated from suitable materials resistant to HP attack at the temperature used. Only a moderate degree of agitation and mixing is necessary. The preferred temperature is in the range of about 250 to 400 F. and more preferably in the range of about 250 to 350 F. It is an important element of the present invention that excellent results are obtainable at these lower temperature levels, enabling operation without excessive corrosion or pressures. Above about 550 to 700 F., depending upon the concentration of the reagent of the present invention, less satisfactory results are obtained due to the cracking characteristics of hydrofluoric acid reagent on oil and the formation of an acid hydrocarbon sludge reaction product.
Aqueous hydrofluoric acid, in concentration of from 50 to 100%, preferably 70 to 99, and specifically 90 to 99%, is introduced into mixing zone 10 from acid storage zone 14 through line 15 and mixed with the oil. The ratio of acid to oil, i.e., the acid dosage, is determined by the acid concentration, the temperature and the contact time, and may be 0.1 to 1.0 ratio by weight, preferably 30 to 50%, of oil. Contact time within mixing zone 10 may vary from /2 to 240, preferably 2 to 120 minutes. Excellent demetallization can be obtained at between 10 and 60 minutes of contact. Pressures in the mixer are suflicient to maintain the reactants in the liquid phase at the temperatures used and, for example, may be 50 to 1200 p.s.i.g. Preferably, the pressures are about 200 to 400 p.s.i.g. and on flashing to atmospheric pressure at the same temperature of treatment substantially all of the HF present is removed.
After the oil and acid have been mixed, the entire reactor efliuent mixture is passed directly via line 16 and a suitable pressure release valve 19 to flash zone 20, where acid vapors are flashed overhead through line 21, condensed and sent to storage 14 for recycle to mixer 10.
The HF may be removed by other means than by flashing, for example, stripping with steam, normally gaseous hydrocarbon, or inert gases, and distillation or other suitable means. The amount of HP in the oil that remains after removal of the bulk of HP is less than 200 ppm. and preferably less than 50 ppm.
It is a peculiarity of the process of the present invention, and a measure of the specificity of the reagent, that the metal contaminants are recovered as solid precipitates rather than in the form of heavy sludges or as acidsoluble salts or compounds. Accordingly, the metal precipitates and oil are passed through line 23 through filter 24, centrifuge or other suitable solids liquid separation means and an oil or low metal content withdrawn and recovered through line 25 and the solids removed by line 28. A demetallized oil product of 99.5% plus yield is obtained. Oil yields of to 99.5% plus can easily be obtained. Preferably, and more commonly, yields of 98 to 99.5% plus are obtained. The lower yields, e.g., are occasioned by using excessive contact times at high temperatures and with high concentrations of acid.
The process described above may be subject to many variations and modifications. Thus, the separation of metals from the oil may be accomplished by centrifugation instead of filtration. The oil may be water-washed to remove the metals since a large percentage is water soluble even though insoluble in concentrated aqueous HF and oil. If desired, a small amount of solvent may be added to the oil feed not to deasphalt, but to increase the mobility of the oil, particularly if a highly viscous oil is being demetallized. Preferably, an aromatic or paraffinic type of solvent would then'be used. The solvent may be added after the contact with HF, but before removal of HF. In accordance with this process, 50 to 100% of the metallic contaminants may be removed, preferably greater than 75%, thus reducing the metals re maining in the oil to less than ppm. preferably less than 50 ppm.
The product produced by the demetallization technique may be used as fuel or as catalytic cracking feed stock. The treated oil may be solvent precipitated or extracted With light hydrocarbons, e.g., from C to C to remove the asphaltene fractions, and to more completely remove any small amount of metals that may remain in the oil. Thus, when using n-pentane, a yield as high as 90 volume percent of oil after deasphalting, based on feed to demetallization step containing less than 1 to 10 parts per .million of vanadium, may be achieved without production of gas, naphtha, or other undesirable fractions as obtained by more conventional processes.
The patentability of the present invention is not to de pend on any particular theory as to the mechanism of the reactions occurring but rather on the process as described and carried out.
The process of the present invention may be further illustrated by the following specific examples.
In order to show that the mechanism by which the HF demetallization takes place is completely different from that occurring with other hydrogen halide acids, a comparison was made of the effects of these reagents upon an undeasphalted topped crude which contains both soluble and colloidally dispersed metal containing porphyrins.
EXAMPLE 1 Comparison of aqueous mineral acids for dcmezallization [0.5 acid/oil wt. ratio, 400 F., 1 hr. contactleed 400 F. heavy lake mix The halogen acids used in these experiments were the standard laboratory reagents. Dilute sulfuric acid was used to avoid side reactions such as sulfonation, oxidation, coking, etc. At the above conditions, HF gave excellent demetallization with negligible yield loss. HCl and HBr gave relatively slight demetallization, and sulfuric acid was completely ineffective. Demetallization was obtained with 58% HI at these conditions, but about 9 wt. percent of sludge was formed. Demetallization, in this case, appears to proceed by a relatively non-selective sludging of the metal-containing asphaltenes, and may Well depend upon a redox process since considerable free iodine was found in the product. The mode of action of HI is obviously different from that of HF. As shown in subsequent example, aqueous HF is very effective at practical, low temperatures, whereas at comparable conditions, HI is completely ineffective.
In these runs the entire reactor effluent from the HF oil reactor was flashed to atmospheric pressure while maintaining the mixture at 400 F. After removal of the HF flashing, less than 50 p.p.m. HF remained in the oil. The oil contained the precipitated metallic contaminants which were removed by filtration.
The products from runs with HCl, HBr and HI were treated in a similar manner. Sulfuric acid was removed by washing the product with water. These data clearly show that the action of HF on metals removal is different from that of HCl, HBr, HI, and H 80 These data further show that HCl will not remove volatile porphyrins from the treated crude.
EXAMPLE 2 To illustrate further the superiority of HF over HI and HCl for demetallization, identical experiments were run on 400 F.+Heavy Lake Mixed Crude using 0.1 weight of 90% HF, HI and HCl. The desired amount and concentration of acid in each case was obtained by charging anhydrous acid to the reaction zone which contained the calculated amount of water and oil. Treat conditions were 250 F. for 60 minutes. In these runs no phase separation was made between the acid and oil and all of the acid was removed by flashing or solvent stripping. The remaining oil was filtered to remove any solids present and analyzed for metals and yield. Results obtained are reported below:
These results clearly show for minimum product degradation and maximum metals removal that HP is far superior to HI and HCl for demetallization. Furthermore, as shown by these data, excellent demetallization is obtained with HF without degradation of the product.
8 EXAMPLE 3 The maximum temperature suitable for the process depends upon acid concentration, allowable corrosion rates, product degradation and process pressure. In general, the aqueous HF becomes less corrosive as the concentration of HP is increased. Lower corrosion rates are also obtained at lower temperatures. Consequently, it is desirable to operate the process at low temperatures, 200 to 400 F., preferably 250 to 350 F., using acid of 90% or higher concentration. Higher temperatures can be used, but corrosion becomes severe and cracking or sludging of the oil may become extensive with substantial loss of product oil yield resulting. At temperatures above about 400 F. and with 95% HF, at high dosage rates, e.g., above 0.5, sludging of residual feed stocks results.
The effect of temperature and time on degree of metals removal from 400 F.+Heavy Lake Mixed Crude (420 p.p.m.) is shown by the following data obtained using 90% HF and a weight ratio of acid/oil of 0.1.
Acid strength, wt. percent HF 90 90 90 90 Wt. ratio acid/oil 0.1 0.1 0. 1 0. 1
Stirring time, minutes 15 15 60 60 Temperature, F--. 400 300 250 150 Vanadium, p.p.m., filtered product 82 124 134 172 Corrosion rate, inches/year Acid strength, Temp, wt. percent F. Carbon Type 316 HF steel stainless Monel Nickel steel The above data show that higher concentrations of HF are less corrosive than lower concentrations. It has been found that the corrosion rate of Monel with HF of about concentration or higher is tolerable at temperatures up to about 400 F.; however, at higher temperature above about 400 F. the corrosion rate increases rapidly even with the high concentrations of acid.
Hydrofluoric acid will also promote the cracking of hydrocarbons depending on acid strength and temperature. Acids of higher strength promote cracking at lower temperatures. For example, when a West Texas vacuum residuum (9.4 API gravity) was contacted with an equal weight of HP at 400 F. for one hour the formation of gas was observed indicating cracking conditions. Vanadium content, however, was markedly reduced from 47 p.p.m. V to 0.6 p.p.m. V. Insoluble solids make was 1.5 wt. percent.
Operation at higher temperatures is possible with HF acid of lower strength without cracking, or sludge formation; however, corrosion of the reactor is severe. This is illustrated by the following data obtained for contacting 400 F.+ Heavy Lake Mixed Crude (420 p.pm. V) with 1.3 weight acid to oil. An equal volume of benzene was added with the feed to the reactor in order to facilitate handling. The benzene and HF were removed by distillation and the solids filtered from the remaining oil before 5 analysis of the metal free oil product.
The effect of hydrofluoric acid concentration is shown below. Of particular interest are the data on 100% HF, i.e., anhydrous. In the liquid phase, significant demetallization took place, while in the vapor phase there was none. The HF was removed from the treated oil prior to removal of any precipitated solids and without removal of any separate phase.
Efiect of HF concentration [0.1 acid/oil wt. ratio] HF concentration 70 90 95 100 ,100 60 60 60 60 60 1 0.5 acid/oil wt. ratio. Vapor phase. Oil heated to temperature and HF vapor passed thbrtiugll. ec
EXAMPLE 5 The effect of ratio of acid to oil used in demetallization with aqueous HF is shown in the following series of tests. The feed used was 400 F.+ Heavy Lake Mixed Crude which contains 420 p.p.m. V.
Acid strength, wt. percent HF 50 50 50 50 Temperature, F 400 400 400 400 Stirring time, minutes. 60 60 15 15 Wt. ratio acid/oil 1. 0. 0. 1 0. 02 Vanadium, p.p.m. filtered product 115 220 279 320 Acid strength, wt. percent HF 70 70 70 70 70 Temperature, F 400 400 400 400 400 Stirring time, minutes 30 60 15 15 15 Wt. ratio acid/oil 1.0 0.5 0. 1 0.02 0. 002 Vanadium, p.p.m., filtered product- 70 97 159 356 395 Acid strength, wt. percent HF 90 90 90 Temperature, F 250 250 400 Stirring time, minutes" 60 60 15 Wt. ratio acid/oil 0.5 0. l 0.1 Vanadium, p.p.m., filtered product 73 134 82 It is noted that in all instances a higher ratio of acid to oil gives improved metals removal under otherwise similar conditions. Significant metals removal, however, is obtained with as little as 0.02 weight of acid per weight of feed.
EXAMPLE 6 In showing the effectiveness of HF on removing very low concentrations volatile metal contaminants a heavy vacuum gas oil feed from South Louisiana crude was treated with 0.5 weight of 90% I-UF or 90% HCl at 250 F.
Demelallizatz'on of South Louisiana gas oil At these conditions good metals removal with HF occurs with essentially no oil loss.
l 0 EXAMPLE 7 HF demetallizatl'on of West Texas deasphalted residuum Feed Filtered Product Oil yield, wt. percent" 100 99. 5+ Oil quality-N i,
p.p.m 3 0.0
At these conditions, HF treating gave good nickel removal Without oil degradation.
EXAMPLE 8 In order to further illustrate the present invention, the following runs were made. HF and HCl acid'solutions of concentration were contacted with portions of a 400 F.+ residual fraction for 60 minutes at 300 F. at a rate of 0.5 acid to oil. In one set of runs the acid was separated from the treated oil by flashing (steam stripping, distillation, etc.) and the remaining oil was filtered to remove any solids and the solids free oil analyzed for metals concentration. In the other set of runs after contacting the acid-oil mixture was allowed to settle into an oil phase and an acid phase, the oil phase was withdrawn, filtered and analyzed for metals and the oil yield was recorded. The results obtained are given below.
Feed-400 F.+ Heavy Lake Mixed Crude containing 420 p.p.m. V. Treating time was 60 minutes at 250 F. with 95% concentrated HP or HCl, at ratio of acid to oil of 0.5.
1 About one-third to one-half the metal porphyrins were present in the feed as volatile porphyrins.
Metals contaminants were removed primarily as solid inorganic precipitates.
3 Metal contaminants were removed as metal acid hydrocarbon sludge.
At concentrations of H01 of 37% or less, substantially no sludge forms, however, at the concentrations used the H01 attacks the hydrocarbons and precipitates an acid sludge.
The above data clearly illustrate the improvement in metals removal and yield obtained by passing the entire reactor eifiuent to a zone wherein the acid treating agent is removed prior to removing the precipitated contaminants from the treated oil. The data also clearly show that the action of HF in metals removal is completely different from that of HCl, and that the acid removal step prior to phase separation is critical.
EXAMPLE 9 In order to show the type of material and chemical composition of precipitated contaminants obtained in accordance with the present invention, a topped Bachaqucro crude having 400 p.p.m. V was contacted with anhydrous HF at 250 F. for ten minutes with a ratio of HF to crude of 0.4. Metallic contaminants precipitated which were insoluble in both the oil and the concentrated acid. The entire efliuent from the reactor was flashed to remove substantially all of the HF in the reaction effluent, i.e., less than 200 ppm. of HF remained in the oil. The oil containing the precipitated metallic contaminants was filtered to remove the contaminants. The oil was recovered with a 99+ percent yield and contained 110 p.p.m. V. The separated solids were analyzed and the results are given below.
The 27% of the sample unaccouted for is believed to be oxygen, and other trace metals. The low carbon content of the water soluble portion shows the main metals product is inorganic. It would appear that the metals are removed as a complex with oxygen and HP. The water insoluble portion represents a small amount of coke-like material formed in the reaction.
The vanadium can be recovered as a by-product by known means. For example, the vanadium can be recovered by water washing, either by washing the HF free oil containing the solids precipitate or by water washing the separated solids precipitate. On water washing the vanadium forms water soluble salts. The vanadium may be recovered from the aqueous solution by precipitation in a manner known in the art.
It is believed that the HF reacts with the porphyrin complex and cleaves the metal from the hydrocarbon portion of the complex leaving the hydrocarbon portion to go back into solution in the oil layer. This reaction distinguishes over the HF extraction processes wherein the HF selectively extracts the metal porphyrins resulting in a considerable loss in yield of product oil. The analysis of the metal contaminant recovered clearly shows that the metals are removed without removing the porphyrin complex.
The temperature and contact time and acid concentration and dosage are interrelated so that, for example, by increasing temperatures, contact time may be decreased for a given degree of metals removal. The eifect of temperature and contact time becomes more important for metals removal below 100 ppm. Under specific treating conditions somewhat better metals removal can be obtained but at the expense of oil product yield by going to higher temperatures and higher concentrations of acid.
The invention is not to be limited by any theory of mechanism of reaction. Obvious variations which occur to those skilled in the art are intended to be covered.
What is claimed is:
1. An improved process for the selective removal of metallic contaminants from a petroleum oil having constituents boiling above about 950 F. which comprises contacting said oil with concentrated HF, precipitating said metallic contaminants as an insoluble mass, and separating said HP from said precipitated metallic contaminants and said treated oil prior to withdrawing oil.
2. An improved process for the selective removal of metallic contaminants from a petroleum oil having constituents boiling above about 950 F. which comprises contacting said oil in a treating zone with concentrated HF acid at elevated temperatures and pressures precipitating said contaminants as an oil-insoluble precipitate, separating said HF from said treated oil, and said precipitated metallic contaminants, and recycling said HF to said treating zone.
3. The process of claim 2 wherein the entire reaction mixture from the contacting zone is treated to remove substantially all the HF present in the reaction mixture prior to withdrawing oil.
4. The process of claim 2 wherein the entire reaction mixture from the contacting zone is treated to remove substantially all the HF present in the reaction mixture and the remaining oil, containing solids precipitate, is separated from the solids and an oil yield of 98%-+ based on feed is recovered.
5. The process of claim 4 wherein the HF is removed by flashing to a lower pressure.
6. An improved process for the selective removal of metallic contaminants from a petroleum oil having constituents boiling above about 950 F. which comprises contacting said oil at temperatures no higher than 550 F. with about 0.05 to 1.5 volumes per volume of oil of concentrated HF precipitating said metallic contaminants as an oil insoluble material, thereafter removing substantially all of the HF from said reaction mixture by vaporization, and subsequently separating said precipitated solids from said oil to obtain a 98%+ hydrocarbon yield.
7. The process of claim 6 wherein said petroleum oil is contacted with aqueous HF acid having a concentration of from about 50% to about 99% by volume.
8. An improved process for demetallizing topped petroleum crude oil which comprises treating said oil with 0.1 to 1.0 volume, based on oil, of concentrated hydrofluoric acid at a temperature of from about 200 to about 400 F., precipitating metallic contaminants, separating said hydrofluoric acid from said oil, and pre cipitated metallic contaminants prior to any phase separation and recycling said hydrofluoric acid to said process, and recovering a high yield of demetallized oil product.
9. The process of claim 8 wherein said treated oil is deasphalted with a hydrocarbon having from 3 to 8 carbon atoms, and the demetallized and deasphalted oil is thereafter catalytically cracked.
10. An improved process for demetallizing a petroleum fraction having constituents boiling above about 950 F. which comprises passing said fraction to a mixing zone, passing 10 to 100% by weight of concentrated HF acid having a concentration of from about to 100% to said zone, contacting said mixture from 2 to 120 minutes in said zone, passing said mixture directly to a vaporization zone, vaporizing said HF from said oil and recycling said vaporized HF to said process, withdrawing a stream of oil and precipitated metallic impurities from said vaporization zone, passing said stream to a separation zone, to remove said precipitated metals, and recovering an oil product of substantially diminished metal content in high yield.
11. The process of claim 10 wherein the oil is recovered in 98%l+' yield and at least 50 to of the metallic contaminants are removed.
12. The process of claim 10 wherein the recovered oil has less than 200 ppm. of HF remaining.
13. The process of claim 10 wherein the hydrofluoric acid is removed by distillation.
14. The process of claim 10 wherein the precipitated metallic contaminants are removed from the substantially HF free oil by water washing.
15. An improved process for demetallizing a petroleum fraction having constituents boiling above about 950 F. which comprises passing said fraction to a mixing zone passing 30 to 50% by weight of HF acid having a concentration of to 99% to said zone, contacting said mixture for 15 to 60 minutes in said zone at a temperature of 250 to 400 F., passing the entire reactor effluent directly to a flash zone, flashing substantially all of said HF to a concentration of less than 200 ppm. of HF from said oil, recycling said vaporized HF to said process, withdrawing the remaining oil and precipitated metallic contaminants from said zone, passing said with 13 14 drawn stream to a solids separation zone to remove said 18. The process of claim 15 wherein the recovered oil solids, and recovering an oil product of substantially product has less than 50 p.p.m. of HF.
reduced metal content.
16. The process of claim 15 wherein the oil feed con- References Cited by the Examiner tains up to 450 p.p.m. of metallic contaminants and 75 5 UNITED STATES PATENTS 090% finemetalsareretqoved 2,971,905 2/61 Bieber et a1. 20s 252 17. The process of claim 15 wherein the 011 15 re 3,061,539 10/62 Moritz et aL 2O8 252 covered in 99% yield and contains less than 100 p.p.n1. of metal contaminants. ALPHONSO D. SULLIVAN, Primary Examiner.