US2966454A - Removal of nickel and vanadium from residual stocks - Google Patents

Description

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United States Patent REMOVAL OF NICKEL AND VANADIUM FROM RESIDUAL STOCKS Luke W. Corbett, Westfield, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Apr. 3, 1959, Ser. No. 803,931

10 Claims. (Cl. 208-251) The present invention relates to the removal of metallic contaminants from petroleum oil and more particularly relates to an improved process for the removal of nickel andvanadium components from high boiling petroleum gas oils and residua.

It has long been recognized that petroleum gas oils and residua that include constituents boiling in excess of about 950 F. normally contain iron, nickel, vanadium and other metallic contaminants which have an adverse eifect upon various catalysts employed in petroleum processing operations and upon combustion equipment wherein such petroleum fractions are burned as fuel oils. In operations such as catalytic cracking, hydrofining and the like, the presence of very small concentrations of these contaminants in the feed stream leads to rapid poisoning of the catalysts causing a significant decrease in the product yield, an increase in coke and gas production, and a marked shortening in the life of the catalyst. In residual type fuels, such contaminants attack the refractories used to line boilers and combustion chambers; cause slagging and build-up of deposits upon boiler tops, combustion chamber walls and the blades of gas turbines; and severely corrode high temperature metallic surfaces with which they come into contact.

The advent of high-speed gas turbines has required the removal of substantially all of the metals content from fuels. Even as little as 2 p.p.m. of vanadium is injurious to these turbines and requires the addition of an additive such as magnesium oxide. These additives, while they lessen the corrosion caused by the metals, create an undesirable ash which erodes the high-speed turbine blades.

Although there have been numerous methods proposed in the past for removing these contaminants from high boiling petroleum fractions, it has been found that such methods are largely ineffective in removing substantially all of the metals. As a result, it has generally been necessary to restrict high-speed gas turbine fuels to those fractions which do not contain the contaminants in high concentration.

It has been found in accordance with the instant invention that such metallic contaminants may be removed by subjecting the contaminated oil to oxidation, preferably by air-blowing, and thereafter deasphaltening the oxidized oil. The term deasphaltening has been coined for the purpose of this invention. It will be defined subsequently.

The drawing further illustrates the invention by means of a schematic diagram. Residual stock taken from tank 1 is passed through line 2 and preheated in furnace 3. This preheated oil passes through line 4 into oxidizing drum 5. Air, after it passes through knock-out drum 6, passes through line 7 into the oxidizing drum and is sprayed through air spray 8 into the residual oil. Since the process is exothermic, it is desirable to partially enclose the oxidizing drum 5 in a veritable insulating shield 9 which may be cooled by an external pump circuit.

This removal of heat from the system allows the use of higher air rates through the residual oil. Quench steam or a small amount of water introduced through line 10 further serves to control the temperature. Air-blowing is preferably carried out in the temperature range of 425-550 F. with typical air rates of 25-200 cu. ft. of air/min./ton of base being blown. The quantity of air which is used is another way of controlling the exothermic reactions of the process, since the heat of reaction is about 2 B.t.u./1b./asphalt/ F. softening point rise. The air-blowing reaction involves dehydrogenation and polymerization leading to the evolution of steam and small quantities of carbon dioxide. These gases are removed from the oxidizing drum 5 through line 11 and are disposed of after they are condensed in barometric condenset 12. The oxidized asphalt is removed through line 13 and passed to deasphaltening tower 14. This tower may range from a simple (l-stage) mixer settler to a complex (multi-stage) counter-current tower. A solvent, preferably pentane through octane, is introduced into the bottom of the deasphaltening tower 14 from solvent accumulator 15 through line 16. The asphaltenes leave the deasphaltening tower 14 through line 17, are heated in furnace 18 and passed through line 19 into stripper 20 wherein small amounts of solvent are removed through line 21 and recycled to the solvent accumulator 15. The asphaltenes are removed from the stripper 20 through line 22. The mixture of petrolenes and solvent leaves the top of the deasphaltening tower 14 through line 23 and is heated in heat exchanger 24 to flash off the solvent in stripper 25. The flashed solvent leaves the stripper 25 through line 26 and is recycled to the solvent accumulator 15. The product is removed from the bottom of the stripper 25 through line 27 and again heated, this time in furnace 28, and further stripped by passing through line 29 into stripper 30. Any remaining solvent is recycled through line 31 to the solvent accumulator 15. The final product is withdrawn from the bottom of the stripper 30 through line 32.

The majority of the metallic contaminants in residual oils are found in the asphaltenes. However, the petrolenes contain a sufficiently high concentration of metals to create many of the difliculties referred to in the introductory paragraphs. It has been found in accordance with the invention that these metallic contaminants are largely concentrated in a particular fraction of the petrolenes. It has further been discovered that oxidation, preferably by air blowing, converts these metal containing petrolene fractions into asphaltenes. The subsequent removal by the deasphaltening process shown herein of the original asphaltenes along with the petrolene fraction converted to asphaltenes effectively removes substantially all of the metal contaminants.

The distinction between deasphaltening and conventional deasphalting must be maintained. Firstly, petrolenes and asphaltenes should be defined. That portion of an asphalt that is soluble in a certain class of petroleum solvents is termed petrolenes, whereas those constituents remaining insoluble are referred to as asphaltenes. See Abraham, Asphalt and Allied Substances, D. Van Nostrand Co., New York (1945) pp. 71 and 1165. Deasphaltening is the process whereby petrolenes and as phaltenes are separated from a hydrocarbon mixture by means of these petroleum solvents. The petroleum solvents are composed entirely of open-chain hydrocarbons with a gravity of 86-88 Baum, and at least of the solvent distills between and F. Pure solvents such as n-pentane, n-hexane, n-heptane or isooctane accomplish essentially the same separation and have the advantage of uniformity of solvent composition. The data shown in Table II illustrate the physical and compositional difference between these two basic components of asphalt. The differences in the two processes can best be illustrated by comparing the yields and the characteristics of the products of the two processes when applied to a particular residual stock.

As an example, two samples of Lagunillas pipe still residual having a specific gravity of 1.011 were deasphalted and deasphaltened. In the deasphalter 7 to 1 parts of propane were used in an eight-stage extrac- In the deasphaltening operation, normal hexane in a 10 to 1 ratio was used in a one-stage extraction at 77 F. The following products were obtained:

TABLE II Petrolenes Asphaltenes Weight Percent 85 15 Specific Gravity 60 F. .973 1. 23 O/H Ratio by weight..... 7. 7 11.0 Softening Point, F. 400+ Penetration 77 F Compo ition:

Percent Parai'fins and Naphthenes. 17 0 Percent Aromatic Oils 83 0 Percent Asphaltenes 0 100 As can be readily seen from the character of the extracted oils, i.e. deasphaited oil in the first example, and the petrolenes in the second, the two processes are quite different. A comparison of the rejected material, i.e. precipitated asphalt and asphaltenes, further illustrates this diiference. Consider, for example, the specific gravity and the C/H ratio of the respective compounds. This distinction is emphasized by measured composition analysis of the product fractions in which it will be noted that there is considerable dissimilarity in the respective fractions.

The practice of air-blowing asphalt stocks, fluxes and residuals is well known in the art. The resulting oxidized asphalt is harder, has better temperature susceptibility and weathering properties than the untreated asphalt. The unox-idized asphalts have softening points in the range of from about 70 to about 175 F. Although conversion of metal containing fractions begins with the start of air-blowing, it is desirable to have at least a F. softening point rise in the material being treated. A rise in softening point 100 F. or more, however, is preferred, while a rise in softening point of 200 F. or more is considered impractical for this invention because of product handling problems. Furthermore, it has been found that essential conversion of metal containing compounds is accomplished before this amount of softening point rise is reached.

Many modifications of air blowing are recited in patent literature. An early patent to Salathe, US. Patent No. 564,341, discloses the use of air as an oxidizing agent. Davis, U.S. Patent No. 671,078, teaches the use of potassium chromate, and Mittash et a1. U.S. Patent No. 1,487,020 uses oxygen carrying gases for oxidation. In addition to these basic oxidizers many modifiers and catalysts have been discovered which alter the physical properties of the resulting product or speed up the conversion time. The use of such modifiers and catalysts in the air blowing reaction is, of course, within the scope of this invention. Some of the agents which may be used are more fully described in the following patents: Abson, US. Patent No. 1,782,186, chlorides of zinc, copper, iron; Hampton, US. Patent No. 2,115,306, aluminum chloride, sulfuric acid; Bradley, US. Patent No. 2,347,626, maleic anhydride; Hoiberg, US. Patent No. 2,450,756, phosphorus oxides, sulfides, chlorides; Van der Berge, US. Patent No. 2,465,960, nitrated phenols; Smith, US. Patent No. 2,506,283, calcium and magnesium oxides; Illman, U.S. Patent No. 2,640,803, fluorinated phosphoric acids, and Hardman, US. Patent No. 2,776,932, fiuobo'rate of metal above atomic No. 22. British Patent 518,655 shows the use of iron, copper, lead, manganese resinates; British Patent 534,798 uses naphthenates, of cobalt, manganese, iron, lead, vanadium, zirconium, copper, etc.', and German Patent 208,378 shows manganese.

The above list of catalysts and modifiers are merely representative of those known in the art and are not intended to include all those which may be used in the practice of the invention.

If additives or chemical modifiers are employed the preferred materials would be taken from the following: ferric chloride, phosphorous pentoxide, zinc chloride or maleic anhydride. The reason for this is that their use for other purposes has been reduced to practice, andthey can be handled in a practical and economical manner.

Solvents suitable for deasphaltening include n-pentane, n-hexane, n-heptane, iso-octane and 86-88" Baum petroleum naphtha or any mixtures of these. Other solvents of a similar type and boiling characteristics may be used. However, the above are readily available at a low cost and have more satisfactory handling qualities.

The solvent to feed ratio may be varied from 3 to 25 depending upon the selectivity desired. The higher ratios accomplished greater selectivity of separation. However, for this invention the preferred ratio would be of the order of 8 to 10.

The advantages of the present invention are more clearly shown in the following examples:

Example 1 Tia Juana Medium 550 vis. stock straight run flux with an initial softening point of 94 F. was air blown to a 220 softening point and then deasphaltened with n-hexane. The petrolene fraction obtained was analyzed for metals content and compared with the untreated flux. The following data were obtained:

TABLE III Wt. Vanadium Nickel Fraction Percent Fraction ppm. Percent ppm. Percent Untreated Tia Juana Medium 450 100 31 100 Deasnhaltened only 87 184 35 24 75 Airblo'vn to 220 8.1. de-

asphaltened petrolenes.. 65 39 5 7 10 A Bachaquero residium with an initial softening point of 100 F. was air-blown to a softening point of 215 F. and deasphaltened with n-hexane. These data were The above two examples clearly show the value of air-blowing in accordance with the invention. In the two examples treated, the metals content in the petrolenes was reduced to less than of the total metals content of the untreated flux. Failure to air-blow the stock results in unsatisfactory metals removal; that is, well over 100 p.p.m. of metals remain in the petrolenes. To attempt to treat the air-blown stock by conventional deasphalting would be highly undesirable. The air-blown stock is much more immobile than the oxidized material and has a softening point generally in excess of 200 F. In order to solvent precipitate this air-blown stock, unusually high solvent ratios and temperatures are required. At these high temperatures conventional deasphalting solvents, for example, propane, exert considerable pressures. In order to keep the solvents in the liquid phase pressure throughout the deasphalter must be in excess of 400 p.s.i. The extremely low yield, i.e. less than of deasphalted oil is another drawback of deasphalting air-blown stock. Further, the 85% plus precipitated asphalt would be unwieldy because of its excessively high softening point.

Many modifications of the above described examples can be made without departing from the scope and spirit of the invention.

What is claimed is:

1. An improved process for upgrading a metallic contaminated petroleum fraction including constituents boiling above 950 P. which comprises oxidizing said fraction and thereafter solvent deasphaltening said fraction.

2. The process of claim 1 wherein said oxidizing is accomplished by air-blowing.

3. The process of claim 1 wherein said solvent is a hydrocarbon containing from five to eight carbon atoms, inclusive.

4. The process of claim 3 wherein said solvent is hexane.

5. An improved process for demetalizing a contaminated petroleum fraction, including constituents boiling above 950 F. and having a softening point between and 115 R, which comprises air-blowing said fraction thereby increasing said softening point from about 10 F. to about 200 F.; thereafter contacting said fraction with a parafiinic hydrocarbon solvent containing from 5 to 8 carbon atoms and thereafter withdrawing a petrolene and an asphaltene fraction.

6. The process of claim 5 wherein from 3 to 25 parts of said hydrocarbon solvent are added to each part of the petroleum fraction.

7. The process of claim 5 wherein from 8 to 10 parts of said hydrocarbon solvent are added to each part of the petroleum fraction.

8. The process of claim 5 wherein the air-blowing is carried out at a temperature of from about 425 to about 550 F.

9. The process of claim 5 wherein the softening point rise is between 100 and 200 F.

10. A process for extracting substantially metal-free petrolenes from metal contaminated asphalts which comprises air-blowing said asphalt, extracting said petrolenes with a petroleum naphtha solvent having a gravity of from about 86 to 88 Baum, at least of said solvent boiling between and F., and thereafter flashing ofi said solvent and recovering petrolenes essentially free of metals.

Short Oct. 8, 1940 Read July 23. 1957

Claims (1)

1. 5. AN IMPROVED PROCESS FOR DEMETALIZING A CONTAMINATED PETROLEUM FRACTION, INCLUDING CONSTITUENTS BOILING ABOVE 950*F. AND HAVING A SOFTENING POINT BETWEEN 70 AND 115*F., WHICH COMPRISES AIR-BLOWING SAID FRACTION THEREBY INCREASING SAID SOFTENING POINT FROM ABOUT 10* F. TO ABOUT 200*F., THEREAFTER CONTACTING SAID FRACTION WITH A PARAFFINIC HYDROCARBON SOLVENT CONTAINING FROM 5 TO 8 CARBON ATOMS AND THEREAFTER WITHDRAWING A PETROLENE AND AN ASPHALTENE FRACTION.

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