US2882220A - Process for producing highly refined petroleum oils - Google Patents

Description

April 14, 1959 L. A. MIKESKA ET AL PROCESS FOR PRODUCING HIGHLY REFINED PETROLEUM OILS Filed Dec; 24, 1953 'FIGQI t t e t 2 ti l #1 SOLVE NT ZONE DISI'ILLATION 20m:

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KZ- E23 (0: Inventors Louis A. M ikeska Chester L Read Walter M. Bbsch By Attorney E XTRACTION United States Patent PROCESS FOR PRODUCING HIGHLY REFINED PETROLEUM OILS Louis A. Mikeska and Chester L. Read, Westfield, and

Walter M. Basch, Rumson, NJ., assignors to Esso Research and Engineering Company, a corporation of Delaware Application December 24, 1953, Serial No. 400,234

Claims. (Cl. 208-95) This invention is concerned with a process for producing a highly refined oil of the nature of white oil. The oil obtained by the process of this invention and used for preparing a white oil is particularly characterized by remarkably low content of aromatic constituents, qualifying the oil for specialty uses. The process by which such oils are obtained comprises a combination of treating steps in which a gas oil petroleum fraction is subjected to catalytic cracking. A cycle oil product from the catalytic cracking is then treated with a selective solvent to extract aromatic compounds and the raflinate of this treatment is treated with sulfuric acid or oleum and finally clay treated to provide the final oil product. This particular combination of treating steps has been found to provide a white oil type composition of desirable characteristics in advantageously high yields.

The term white oil is conventionally used to identify a highly refined lubricating oil employed for medicinal purposes, as a specialty lubricant, and as a component of pharmaceutical preparations. At the present time white oil is commonly made by treating a lubricating oil distillate with fuming sulfuric acid followed by a washing step and filtration through adsorbent clay. In some cases the lubricating oil distillate prior to the sulfuric acid treatment may be treated with a solvent such as phenol to remove a portion of the aromatic constituents present in the feed stock. In these conventional processes for making. white oil it is an inherent deficiency of the processes that the white oil product is obtained in relatively poor yields. This is in large part due to the excessive formation of acid sludges during the sulfuric acid treatment. In general, by'conventional processes, it is only possible to obtain a 50 to 70% yield of white oil based on the original lubricant feed stock. It is'one of the principal purposes of this invention to provide a novel process for producing an oil of the nature of white oil in appreciably higher yields than heretofore possible.

A secondary object of this invention concerns a search for an attractive manner of upgrading what is known as catalytic cycle stock. In the commercially used catalytic cracking process, the cracked products boiling in the range of about 600 to 1100 F. are known as cycle stock. At the present time cycle stock is primarily used as fuel and as such is of relatively low value. It is therefore one of the objects of this invention to provide a process for upgrading this cycle stock and in particular to convert cycle stock to a high quality white oil.

The present invention is based on the principle that a gas oil which is subjected to catalytic cracking, followed by the solvent extraction of resulting cycle stock, provides a'raflinate product containing only minor amounts ice of aromatic constituents. In particular it is possible to carry out these treating steps so as to obtain a cycle stock which contains only about 3 to 5% of aromatic compounds. Because of this low concentration of aromatic compounds, it is possible to treat this cycle stock with relatively small quantities of fuming sulfuric acid and to obtain high quality, high viscosity white oil in high yields.

The appended drawing illustrates the principles of this invention in a diagrammatic flow plan showing the process steps to be employed in obtaining a white oil from a catalytically cracked cycle stock.

Referring now to the drawing illustrating a specific example of the process to be employed, numeral 1 designates a crude petroleum distillation zone. A crude petroleum oil such as a mixed base crude oil is introduced into distillation zone 1 through line 2. The distillation operation is conducted to permit removal of volatile fractions overhead through line 3 and of heavier boiling products such as gasoline, kerosene and heating oils through side stream withdrawals as for example through lines 4, 5 and 6. The heavier boiling fractions having a boiling range of about 600 to 1100 F. and higher are withdrawn as a bottoms product through line 7. It is' particularly contemplated that in the practice of this invention, distillation zone 1 be of such a nature as to provide a higher boiling fraction boiling in the range of about 600 to 1100 F., preferably as obtained by vacuum distillation operations.

This fraction is then conducted to a catalytic cracking zone identified by the rectangle 8. The cracking operation to be conducted in zone 8 may be of any desired type employing a catalyst such as modified natural or synthetic clay or gel type catalysts. Examples of these are montmorillonite clays, silica-alumina, silicamagnesia composites and other conventional cracking catalysts. The operation may be of a continuous or bath nature employing fixed beds, moving beds, fluidized, or suspensoid systems. The heat required for cracking may be supplied as preheat of processed materials and/ or as the sensible heat of exothermically regenerated catalyst or in any other conventional manner. The cracking is carried out at temperatures of about 800 to 1000 F., and pressures of about atmospheric to 25 p.s.i.g. or higher.

The total cracked products are removed from cracking zone 8 and are conducted to a product fractionator 9. Fractionator 9 is. operated to remove lighter fractions of the cracked products through overhead 10, side streams 11, 12, 13, etc. A bottoms product is obtained from fractionator 9 which may be removed through line 14. In

the event the cracking operation conducted in-zone 8 was of a fluidized nature, the material withdrawn through line 14 will contain a small percentage of catalyst particles carried over from zone 8. In this case, it is necessary to pass the product stream of line 14 to a catalyst separationzone or settler 15, or otherwise to permit separation of the liquid hydrocarbon product from the catalyst. Thus, a clarified hydrocarbon stream is removed from zone 15 through line 16. This stream is conventionally he conduct at he arcccss, described here nictc is well known in the art, no further description of this phase of the process is considered necessary. The stream of line 16, derived as indicated, is then conducted to suitable dewaxing facilities identified by rectangle 17 in the drawing. The operation conducted in zone 17 may be chosen from any of the conventional dewaxing processes of a nature to reduce the wax content of the hydrocarbon fraction treated to any desired extent. In general, it is preferred that a solvent dewaxing operation be employed. For example, the hydrocarbon oil of line 16 may be diluted with about 2 to, 4 parts per volume of a solvent such as propane or methyl ethyl ketone. The mixture of hydrocarbon oil and solvent is then heated sufiiciently to secure the solution of all wax present. Thereafter, the mixture of oil and solvent is cooled to a temperature of about 25 to l P. so as to secure the crystallization of the wax present. The chilled mixture of oil, solvent and wax is then filtered to eliminate this wax, permitting removal from zone 17 through line 18 of a dewaxed hydrocarbon oil.

The dewaxed oil is then passed to a solvent extraction zone 19 wherein the oil is subjected to contact with a sol-. vent exerting a selective solvent action towards aromatic constituents. It should be noted that, as described, the oil is dewaxed prior to solvent extraction. However, if desired, the dewaxing operation may follow the solvent extraction operation so that, as will be seen, the raflinate of the solvent extraction operation may be subjected to dewaxing.

As is well known, a variety of solvents may be employed to secure the desired selective removal of aromatic constituents. Thus, for example, sulfur dioxide, phenol, furfural, nitrobenzene and other'solyentsmay be employed. While the contacting of the solvent and oil may be conducted in any desired contacting equipment of a batch or continuous nature, countercurrent treating technique is preferably employed. In such a system, the

oil feed of line 18 is introduced to a countercurrent con tacting tower 19 at a point near the bottom thereof. Tower 19 is provided with packing, perforated plates or equivalents to secure efiective liquid-liquid contacting. A solvent such as phenol is introduced at an upper-portion of the tower as through line 20. The oil passes upwardly through the tower while the solvent passes downwardly through the tower, permitting removal from the bottom of the tower of what is known as an extract phase through line 21. The extract phase will consist principally of the solvent, such as phenol, together with the constituents selectively extracted from the oil consisting principally of aromatic hydrocarbons. The material withdrawn from the top of tower 19 through line 22 is known as the raffinate phase and consists principally of the initial oil feed minus the aromatic constituents originally present in the feed, admixed with small proportions; of the solvent employed during the contacting. The raflinate is preferably passed'to a final distillation zone 23 wherein residual solvent is driven overhead through line 24 while the solvent-free raflinate stream is removed as a bottoms product through line 25.

This rafiinate stream is then subjected to the conventional treating steps applied in, white oil manufacture. Thus, in the first step of the finishing treatment, the raf finate stream of line 25 is passed to treating zone 26 for contact with fuming surfuric acid. For this purpose oleum having about 20% free S0 maybe introduced through line 27 for admixture with the raffinate inmixingzone 28. This mixture of fuming sulfuric acid and the rafiinate stream is then brought into. the continuous gravity settler identified by numeral 26. Sludge is removed: as a bot toms product fromzone 26' through line 29 and the treatedraflinate may be passed to successive treating zones for additional sulfuric acid treats. Thus, as: illustrated, raffinate removed from settler. 26 through; line 30 -is ;mixe.d with additional olcum introdu ed through line 31 and 4 is passed to a second gravity settler 42. Again, sludge is removed as a bottoms product from settler 42 through line 33 and the treated oil sream is withdrawn through line 34.

In general, in the process of this invention it is satisfactory to employ two fuming sulfuric acid treating stages. It is possible to employ either one or more than two stages if desired, but use of two stages is particularly preferred in most economically securing a high quality white oil product. In general, about 15 to 30 volume percent treat of fuming sulfuric acid is required. The acid treated oil may be washed with aqueous sodium carbonate to neutralize residual acidic materials.

The acid treated oil of line 34 may then be contacted with an alcohol to wash out or extract sulfonic acids. It is preferred to employ aqueous solutions of low. molecular weight alcohol such as C; to C aliphatic alcohols in this step of the process. About 20 to 75% of 30, to 70% alcohol is employed. For the alcohol contacting, alcohol such asisopropyl alcohol of about 50% strength may be introduced through line 35, for admixture with the acid treated oil in mixer 36. The alcohol oil mixture is then passed to a gravity settler 37 from which the alcoholic wash liquor is removed through line 38 and the washed oil is removed through line 39. Mahogany sulfonic acids maybe recovered from the alcoholic wash liquor of line 38 if desired. Residual water and alcohol may be re moved fromthe hydrocarbon oil by a steam stripping operation.

It is preferred to pass the alcohol washed oil product through a clay treating zone 40 to provide the finished product which is removed through line 41-. Clay treatment may be carried out as illustrated by conventional percolation through 30 to 60 mesh clay, using a clay such as Attapulgus clay, bauxite, or activated synthetic clay. The clay contacting iscarried out at temperatures below F., and at a treat of about 0.3 to 1.0 lb. per barrel of oil.

As described, the white oil product of this invention is derived by a combination treating process entailing catalytic cracking ofa petroleum distillate fraction boiling in the range of about 600 to 1100 F. A fraction boiling in substantially the same boiling range is separated' from the catalytically cracked products and is passed toa treating zone for the removal of aromatic hydrocarbons. As described, aromatic hydrocarbons are preferably removed in a solvent extraction operation, although it is to be understood that absorbent treating or the like may beemployed, if desired, in place of the solvent extraction. It has also been indicated that prior to or after removal of aromatic hydrocarbons, the oil is to be subjected to a dewaxing operation. This step of theprocess is optional and if used is employed to provide a finished oil product of a selected pour point. After removal of' the aromatic hydrocarbons, the oil" is then subjected to treatment with fuming sulfuric acid, alcohol, and clay toprovide the finished white oil.

As: a specific example of'thisinvention, a gasoil' boil;- ing in the range of 550 to 1050 F. was cracked ina fluid process using a silica-alumina catalyst to convert about 50% of the feedimaterial-to products boiling lower than the feed. A cycle stock was obtained from this operation representing about 30% of the original feed and boiling within. the same boiling range as the feed to the cracking operation. This cycle stockwas extracted. with phenol inacountercurrent tower; 204% of-phenol based on the oil, feed was. employed. The phenol solvent contained 4.8% water and anadditional 9.3% water wasadded near; the base, of the; tower. 49.8% was obtained,

Thi ra na e cwaxe nd dis ill d o o ta n a cut representing 27 to 98% on the; dewaxed; raflinate. is dis ill e. wa hen mpl y d: h fee stock f r the; white, oil: manufacturer. Inspections. of? the aforementioned products are given in Table I,

Table 1 White Oil Feed to Cycle Dewaxed Feed- Inspectlona Catalytic Stock Ratiinate Extract Raiiinate Distilled Cracking Reflinate .API Gravity 26.3 14. 8 33. 9 0. 2 32. 4 31.8 Refractive Index 75 C 1. 5445 1. 4503 1. 6302 1. 4548 1. 4558 Color Tag Robinson M 4% Flash, F 365 4 SUS Viscosity, 100 F... 152 192 BUS Viscosity, 210 F- 4.5. 4 42.9 43. 8 46. 6 Sulfur, Percent .04 .009 Aromatics, Wt. Percent. 52 86. 5 6.0

The manufacture of the white oil involved treating this feed stock with 18 vol. percent of 20% oleum in two applications. After acid treatment and separation of the sludge, the oil was neutralized with an aqueous sodium carbonate solution and was then washed with 50% isopropyl alcohol to remove soaps. The alcohol remaining in the white oil was removed by steam stripping. The white oil was finished by percolation through Attapulgus clay. The overall yield of white oil in this operation was 90.3%.

Inspections of this white oil are given in Table II in comparison with two commercially produced white oils. It will be seen that the white oil produced by the process of this invention was equal in every respect to the commercial products.

Table 11 White Oil From Commer- Commer- Whlte Oil Inspections Dewaxed cial White cial White Cycle Stock 011 #1 Oil #2 Refiinate Specific Gravity, 60/60 0.8660 0. 8676 0.8827 Color, Saybolt +30 +30 +30 Odor and Taste Pass Pass Pass Flash, P.M., F 416 346 416 Viscosity, Saybolt 100 195. 0 90 357 U.S.P. Acidity Pass Pass Pass U.S.P. Sulfur... Pass Pass Pass U.S.P. Cloud Pass Pass Pass The yield of 90.3% obtained in treating the extracted cycle stock is appreciably higher than may be obtained from other commercial stocks as will be noted from Table III where treatment of this product is compared with an extracted virgin distillate and a raw virgin distillate.

It will be noted that the extracted cycle stock gave appreciably higher finished oil yields, required less acid and produced less sludge than either of the other two stocks. The acid requirements in treating the cycle stock were only 2.66 pounds of oleum per gallon of white oil, while the requirements for the extracted virgin distillate and the raw virgin distillate were 6.7 and 12.8 pounds, respectively.

Processing of sludge from an operation of this type is very expensive if pollution of air and water are avoided. It costs appreciably more to process sludge and recover the acid from it under these conditions than to buy fresh acid and simply discard the sludge. Thus, a requirement of only half as much acid in processing the extracted cycle stock as compared to the most suitable stock now available or previously available provides a marked advantage economically. Furthermore, it is significant that the sludge produced by the process of this invention is of low viscosity, facilitating disposal. Thus, the sludge obtained in the example given had a viscosity ,1 that of a sludge derived from a solvent extracted virgin distillate. It has also been indicated that prior to or after removal of aromatic hydrocarbons, the oil is to be subjected to a dewaxing operation. This step of the process is optional and if used is employed to provide a finished oil product of a selected pour point. After removal of the aromatic hydrocarbons, the oil is then subjected to treatment with fuming sulfuric acid, alcohol, and clay to provide the finished white oil.

What is claimed is:

l. A process for producing a highly refined white oil which comprises the steps of catalytically cracking a virgin petroleum distillate boiling in the range of about 600 F. to about 1100 F., separating by distillation cracked products boiling in about the said range of from 600 F. to 1100 F., said cracked products having a higher content of aromatic hydrocarbons than said virgin distillate, refining said separated cracked products by selectively removing aromatic hydrocarbons therefrom, treating the resulting refined cracked products with from about 15 percent to about 30 percent by volume of fuming sulfuric acid, and recovering the said white oil.

2. Process as defined by claim 1 wherein said selective removal of aromatic hydrocarbons is eifected by solvent extraction.

3. The process defined by claim 1 in which said fuming sulfuric acid treatment is conducted in at least two successive stages.

4. The process defined by claim 1 including the step of dewaxing said cracked products prior to the step of removing aromatic hydrocarbons.

5. The process defined by claim 1 including the step of washing the white oil, after fuming sulfuric acid treatment, with from about 25 to about 75 percent by volume of a 30 to 70 percent aqueous solution of a low molecular weight aliphatic alcohol.

References Cited in the file of this patent UNITED STATES PATENTS 2,006,095 Bray et al. June 25, 1935 2,006,096 Bray et al. June 25, 1935 2,065,551 Beard Dec. 29, 1936 2,416,397 Lemmon Feb. 25, 1947 2,429,875 Good et al. Oct. 28, 1947 2,616,836 Schmidt et al. Nov. 4, 1952 2,660,552 Blanding Nov. 24, 1953 OTHER REFERENCES Chemical Refining of Petroleum, Kalichevsky et al., Chemical Catalogue Co., New York, 1933, page 58.

Sachanen: "Conversion of Petroleum," 1940, pp. 97, 98 and 99. 1

Claims (2)

1. A PROCESS FOR PRODUCING A HIGHLY REFINED WHITE OIL WHICH COMPRISES THE STEPS OF CATALYTICALLY CRACKING A VIRGIN PETROLEUM DISTILLATE BOILING IN THE RANGE OF ABOUT 600* F. TO ABOUT 1100* F., SEPARATING BY DISTILLATION CRACKED PRODUCTS BOILING IN ABOUT THE SAID RANGE OF FROM 600* F. TO 1100* F., SAID CRACKED PRODUCTS HAVING A HIGHER CONTENT OF AROMATIC HYDROCARBONS THAN SAID VIRGIN DISTILLATE, REFINING SAID SEPARATED CRACKED PRODUCTS

4. THE PROCESS DEFINED BY CLAIM 1 INCLUDING THE STEP OF DEWAXING SAID CRACKED PRODUCTS PRIOR TO THE STEP OF REMOVING AROMATIC HYDROCARBONS.

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