US3256175A - Production of lubricating oils from aromatic extracts - Google Patents

Description

June 14, 1966 R. H. KozLowsKl ETAL 3,256,175

PRODUCTION OF LUBRICATING OILS FROM AROMATIC EXTRACTS Filed Oct. 23, 1964 z BY i?" Z657;

TORNEYS United States Patent PRODUCTION 0F LUBRICATING OILS FROM AROMATIC EXTRACTS Robert H. Kozlowski, Berkeley, and Robert L. Jacobson,

Pmole, Calif., assignors to Chevron Research Company, a corporation of Delaware Filed Oct. 23, 1964, Ser. No. 406,138 4 Claims. (Cl. 208-58) This application is a continuation-in-part of our copgriging application Serial No. 163,923, filed January 2,

This invention relates to the production of lubricating oils and lubricating oil base stocks by catalytic hydrogenati-on. In particular, the invention relates to the production of improved lubricating oils by a combination of solvent treating and catalytic hydrogenation.

In the conventional production of lubricating oils by petroleum rening, crude oil segregated on the basis of its high content of desirable lube constituents is distilled to obtain fractions boiling in the lubricating oil range, each of said fractions representing a source of lubricating oil of a separate viscosity range. The said fractions are then separately s-olvent treated, usually with solvents for aromatics such as SO2, phenol, furfural, and the like, to obtain lubricating oil raflinates often referred to as neutral distillates, and aromatic extracts. The severity of the solvent treating of each fraction in terms of solvent dosage or solvent t-o oil ratio is controlled to produce a raffinate having the viscosity `desired in the particular lubricating oil product and to sufficiently improve the color and stability such that salable lubricating oil can be recovered directly or produced by further simple treatment such as dewaxing, acid treating, and/ or clay contacting.

The aromatic extracts so produced contain a high percentage of the materials causing oils to have poor color, instability, and low viscosity index, and hence they are recognized as having no value insofar as lubricating oil production is concerned. Accordingly, the extracts are disposed of by blending into low grade fuel oil or into thermal cracker or cat cracker feed.

By means of the present invention an increased yield of high quality lubricating oil can be obtained from the crude oil by converting such aromatic extracts into recoverable lubricating oil by severe catalytic hydrogenation. In accordance with the invention a crude oil is distilled to obtained fractions boiling in the lubricating oil range, including a light fraction and a heavy fraction representing sources for lubricating oils of separate viscosity ranges, and the said fractions are separately solvent treated to obtain respectively a light lube rainate and a light aromatic extract and a heavy lube rainate and a heavy aromatic extract. At least a portion of the heavy aromatic extract is hydrogenated by contacting with a sulfactive hydrogenation catalyst and hydrogen at severe conditions of elevated temperature, high pressure, and low space velocity whereby a substantial portion thereof is converted to distillate fuels, From the products of the severe hydrogenating there are separated distillate fuels and a hydrogenated oil having a viscosity in the range of the light lube raffinate, and at least a portion of the hydrogenated oil is combined with the light raffinate. The combined light raffinate and hydrogenated oil, and the heavy rainate, can then be further separately treated if desired or necessary, to obtain improved quality lubricating oils in separate viscosity ranges.

3,256,175 Patented June 14, 1966 The attached drawing, to which more detailed reference will be made hereinafter, illustrates diagrammatically a flow scheme for carrying out the invention and certain alternates in the manner of combining the hydrogenated oil recovered from severe hydrogenation of the extract with the light railinate.

Reference herein to materials boiling in the lubricating oil range is intended to include the boiling range of all materials conventionally recovered as lubricating oil. It is recognized that lubricating oils are rarely specied on the basis of boiling range, other than to specify a flash point, the primary criterion being always viscosity to define different lubricating oil grades. Thus, depending on the properties of the initial crude oil, the boiling range of a particular viscosity range lube oil may vary within substantial limits. Generally, however, lubricating oils boil essentially entirely above about 550 F.

The term raffinate is used herein in its broadest sense as referring to a solvent relined oil recognized as containing the desirable lubricating oil constituents. Preferred lubricating oils are essentially naphthenic in basic structure, and have alkyl substituents of varying cornplexity. Essentially parainic or waxy hydrocarbons are not desired, nor are essentially aromatic hydrocarbons, because of their poor lubricating properties. Where the crude distillate is treated with a solvent selective for aromatics, the reference to the lubricating oil portion as a rafliuate is technically correct since the undesired aromatic hydrocarbons dissolve in the solvent as the extract phase. Nevertheless, it is conventional in the lube oil refining art to refer to the nonaromatic material obtained by solvent extraction as the raffinate even in those cases where a solvent is used which rejects the aromatic constituents and dissolves the desired lubricating oil material.

The manner of employing the severe catalytic hydrogenation of an aromatic extract for producing lubricating oil in the present invention is quite different from previous methods proposed for using catalytic hydrogenation in the refining of lubricating oils. While hydroiinishing has been employed heretofore as a substitute for acid treating or clay contacting of refined lube oils or raffinates, such processes use relatively mild conditions of low temperature, low pressure, and high space velocity so as to avoid lowering the viscosity of the raflinate. Destructive hydrogenation has also been proposed as a substitute for solvent extraction of crude lube oils, using severe conditions of high temperature and pressure. In such v processes, the proposal was to subject to destructive hyand, as a result, it is possible to achieve bettercontrol.

over the yield of lubricating oil in different viscosity ranges.

The catalysts heretofore employed or proposed for .usev

in the prior art lube oil hydrofining'processes were usually either hydroning catalysts, such as molybdenum oxide, cobalt molybdate, nickel-tunsten sulfide, etc., or hydrogenation catalysts such as nickel or platinum. Usually the catalyst metals, oxides, or suldes are supported on a carrier such as alumina, silica-alumina, or magnesia. The older supported hydroning catalysts have invariably a low metal content of less than 15% by weight. Recently, more active catalysts have been discovered. For example, there is disclosed in our U.S. Patent No. 3,114,701 certain highly active catalysts comprising nickel sulde and molybdenum sulde in combination with a support such as alumina, with unusually high molybdenum content of 15.5-30% and high nickel content of 4-10%. The term sulfactive hydrogenation catalyst is used herein with reference to all such catalysts as are recognized as useful for hydrogenation of nitrogen and sulfur compounds in oils and for the hydrogenation of oils containing nitrogen and sulfur compounds. The term thus excludes the noble metal hydrogenation catalysts such as platinum and nickel unpromoted with a Group VI metal, which are poisoned -by sulfur and nitrogen compounds. Further, it will be appreciated that markedly superior results are obtained by using'the catalysts having highest activity for the hydrogenation of oils containing nitrogen and sulfur compounds.

The hydrogenation of the aromatic extract suiciently to convert it to material suitable for lubricating oil is a difficult job to accomplish, and accordingly requires severe conditions. In particular, the pressure employed will be at least 2,000 p.s.i.a. hydrogen partial pressure and may range upwards of 10,000 p.s.i.a. Generally pressures of 200G-3000 p.s.i.a. are preferred. The temperature should be in the range G50-800 F., extremely high temperatures being avoided in order to favor hydrogenation, and the space velocity will be in the range 0.2-1 LHSV so as to provide suicient time for the conversion without using excessively high temperatures. The hydrogen-to-oil ratio is generally between 2,000 and 10,000 standard cubic feet per barrel (s.c.f./'b'bl.). Because of the diiculty of hydrogenating the highly aromatic and contaminated oil, there is preferably used a highly active catalyst such as the suiided high metal content nickelmolybdenum catalysts. As a guide in determining the suitability of a particular catalyst, it should be capable of removing at least 95% of the nitrogen compounds contained in the extract by hydrogenation to ammonia at conditions in the aforementioned ranges. The obtaining of greater than 95 nitrogen removal is used as a guide or criterion for determining that suiicient hydrogenation is being accomplished. At the conditions necessarily employed, at least a portion of the aromatic extract will be converted to distillate fuel comprising hydrocarbons boiling in the range of gasoline, kerosene, and middle distillates lower boiling than generally included in lubricating oil. Accordingly, such distillate fuels are separated from the products of the hydrogenating to recover a heavier portion comprising hydrogenated oil suitable for incorporating into lubricating oil.

The heavy hydrogenated oil can be incorporated into lubricating oil in several ways. The hydrogenated oil may simply ybe blended with the light rainate obtained from the solvent treating. In another, and frequently superior method, the hydrogenated oil is combined with the light fraction prior to the solvent treating step so that a major portion of the hydrogenated oil is ultimately recovered in combination with the light rainate produced in solvent treating. vThe aromatics content of the hydrogenated oil is sufficiently low, usually below by volume, such that very little of it is extracted by an aromatic solvent such as phenol, but the solvent treating advantageously improves the hydrogenated oil in other respects such as color and stability.

In other methods of operation, the combining of the hydrogenated oil with the ranate and the treatment of other oils in the process may be carried out as illustrated in the attached drawing. Referring to the drawing, a crude oil such as an atmospheric residuum or a vacuum distillate in line 10 is distilled in distillation zone 11 to obtain a light fraction in line 12 and a heavy fraction in line 13 representing sources for lubricating oils of Separate viscosity ranges. In addition, there may be obtained a lighter lubricating oil fraction or a lighter nonlubricating oi-l distillate -in line 14. In the case of the residual feed there may be obtained'an asphaltic residuum in line 15. The oils in lines 12 and 13 are rich in polycyclic hydrocarbons preferably, including both naphthenic and aromatic hydrocarbons, and contain nitrogen cornpounds i-n addition to other hetero organic contaminants such as sulfur and oxygen compounds.

The light lubricating oil fraction in line 12 is passed to solvent-treating zone 17 wherein it is contacted with a solvent for aromatics such as phenol, furfural, and the like, in a manner well known. After recovery of solvent from the resulting two phases, there is recovered in line 18 a light lubricating oil rainate and in line 19 a light aromatic extract. The heavy fraction in line 13 is similarly treated in solvent treating zone 20 to obtain, after recovery of the solvent, a heavy lube rafiinate in line 21 and a heavy aromatic extract in line 22. If the feed is a residual, all or part of the residue in line 15 may be passed via line 16 to zone 20, in which casea bright stock is obtained in line 21 and heavy resins in line 22.

In the embodiment illustrated, the light fraction in line 12 is solvent-treated in combination with a hydrogenated oil in line 28 obtained as set forth hereinafter, using a relatively mild solvent dosage to obtain a high yield of light ranate in line 18 of poor color and higher than desired viscosity and a low yield of aromatic light extract in line 19. The heavy fraction in line 13 is treated in zone 20 using a relatively severe solvent dosage to obtain a high yield of aromatic heavy extract in line 22 and a relatively lower yield of heavy raffinate in line 21, which is a heavy lubricating oil base stock of good color and desired viscosity. y

At least the heavy aromatic extract in line 22 is passed to severe hydrogenation Zone 23 wherein it is thoroughly hydrogenated by contacting with a sulfactive hydrogenation catalyst and hydrogen at severe conditions of high temperature and pressure and low space velocity whereby a substantial portion thereof is converted to distillate fuels. In carrying out the catalytic hydrogenation any suitable equipment arrangement may be used for contacting the oil with the catalyst in the presence of excess hydrogen. For example, the catalyst may be maintained as one or more fluidized lbeds, gravitating beds, or iixed beds of small particles, through which the oil and hydrogen are passed, upow or downfiow, concurrent or countercurrent. A slurry of catalyst in oil may also be used. Usually, the catalyst is in the form of small pellets or rod-like extrusions contained in a reactor as several fixed beds, and the oil and hydrogen are passed together downow through the bed at controlled temperature, pressure, and ow rate. The effluent is cooled to separate product oil from hydrogen-rich gas which is recycled. The oil thus obtained is passed via line 24 to distillation zone 25 wherein the products lof hydrogenation are separated into distillate fuels and lighter hydrocarbons in line 26 and in line 27, a hydrogenated oil having a viscosity in the range of the light fraction. As indicated, all or a portion of the hydrogenated oil in 'line 27 is returned vi-a line 28 to the solventtreating zone 17 for extraction in admixture with the light fraction of line 12. The light ranate in line 18 will thus contain a major portion of the hydrogenated oil so passed via line 28.

In the particular embodiment illustrated in the drawing, this rainate is passed to hydrogenation zone 29 wherein it is hydrogenated by contacting with a sulfactive hydrogenation catalyst and hydrogen at less severe conditions, including lower temperature and higher space velocity as compared-to the conditions used in zone 23 in hydrogenating the aromatic extract, whereby no substantial portion of the raffinate in line 18 is converted to light distillates. While conditions in zone 29 are substantially less severe than in zone 23, the conditions are more severe with respect at least to pressure than used in simple, mild hydroning of finished lubricating oils. Thus, hydrogenation in zone 29 is preferably carried out in the manner disclosed and claimed in our prior-led copending application Serial No. 163,923, namely by employing pressures in the range 150G-3000 p.s.i.a. hydrogen partial pressure, temperature of 650-750 F., and space velocity of 0.5-3 LHSV to accomplish a significant lowering of the viscosity with limited conversion of nitrogen compounds to ammonia in the range 30-60%, Whereby the color and oxidation stability of the hydrogenated oil are improved.

The hydrogenated oil obtained in line 30 is passed to distillation zone 31 wherein light hydrocarbons'and any small amount of distillate fuels produced.may be withdrawn through line 32 and the desired light lubricating oil base stock recovered in line 33. In one type of operation of the process of this invention, all or a portion of the severely hydrogenated oil in line 27 may be diverted through line 37 and passed via line 35 to distillation zone 31. The hydrogenated oil so passed can be recovered in the light lubricating oil product of line 33. In this case, however, it will frequently be found desirable to withdraw a small bottoms portion in line 34 to obtain more precise adjustment of the nal lubricating oil viscosity.

In another embodiment illustrated in the drawing, the light aromatic extract of line 19 is also passed to severe hydrogenation zone 23 with the heavy aromatic extract of line 22. It will then be found advantageous to separate the severely hydrogenated oil into a heavy portion dewaxing process.

The invention may 'be further explained and the advantageous results obtainable thereby be better demonstrated by means of the following examples. In the examples, where reference is made to a suliided nickelmolybdenum catalyst, the catalyst employed was prepared by impregnating a high purity alumina base with nickel nitrate, calcining, then impregnating with ammonium molybdate, being calcining, again impregnating with ammonium molybdate, and calcining. The oxide catalyst so produced, which contained about 6% nickel and about 20% molybdenum, was suliided by contacting With hydrogen containing dimethyl disulfide, equivalent on hydrogenation to 2% H28, at about 500 F. to convert the metal oxides substantially to the sulfdes prior to the use in the catalytic hydrogenation process.

EXAMPLE 1 uct, the properties of which are also given in Table I. l

Stock Gravity, APT Viscosity, SSU at 100 F Viscosity, SSU at 210 F Viscosity Index ASTM- Aniline Point Aromatics, percent Pour Point, F Natural Oxidation Stability, hours Nitrogen, p.p.m Boiling Range, F Percent Nitrogen Remova1 Color,

1 Black.

2 -l-Saybolt.

in line 27 and a somewhat lighter portion in line 36. The heavy portion in line 27 will contain most of any remaining aromatic constituent in the oil, and is accordingly returned via line 28 to solvent extraction zone 17. In many cases, however, the aromatics content will be low enough so that re-extraction is not needed, and the heavy portion can instead be passed via line 38 to hydrogenation zone 29 with the Ilight ratlinate. The lighter portion in line 36 may be passed via line 35 for direct recovery with the light lube fraction of line 33 in distillation zone 31.

Thus, in accordance with the illustrated embodiment of the invention, there are recovered in lines 33 and 21 light and heavy lubricating o ils or lube oil base stocks in separate viscosity ranges, of improved color and oxidation stability. In most cases, however, it will be desirable to give these fractions at least some further mild treatment as by clay contacting preceded by or following dewaxing to meet all specifications desired for` the ultimate salable lubricating oils. In addition, it will be understood that various inhibitors and additives will be added to the product fractions ultimately sold. Dewax- It will be noted that the lube oil produced by catalytic 5 lhydrogenation of the extract in accordance with the invention was quite similar to the raflinate. In most respects, such as aromatics content, pour point, and viscosity index, the hydrogenated extract was .superior to the lube oil raffinate. The viscosity, however, is substantially lower than that of the rainate. A higher yield of lube oil more closely resembling the aforementioned rainate in viscosity is obtained by catalytic hydrogenation of an extract obtained by solvent treating a heavier naphthenic lube distillate, as in the following example.

EXAMPLE 2 are also compared with'those of the raffinate produced in preparing the extract feed of Example 1.

ing said heavy fraction to obtain a heavy lube rainate and a heavy aromatic extract,

Table 'II Hydrogenated Extract Pro crt Extract p Y whole 16% 84% Stock Overhead Bottoms Ratlnate of Example 1 Gravity, API Viscosity, SSU at 100 F Viscosity, SSU at 210 F Viscosity Inder Color, ASTM Aniline Point Aromatics, Percent Pour Point, F

Natural Oxidation Stability,

Boiling Range, F 723-997 352-944 37H60 Nitrogen, p.p.m 8, 000 210 Percent Nitrogen Removal" 97 lBlack. 2 Clear yellow.

In the foregoing example it will be noted that a major portion of the severely hydrogenated oil produced by treating the heavier aromatic extract of the higher viscosity fraction had a viscosity substantially the same as that of the rainate produced by solvent extraction of the lower viscosity fraction of Example 1. The boiling ranges of these oils, however, are not the same as the hydrogenlated oil has a higher end point.

The rafiinates produced by solvent extraction in the above examples were of good quality, and would not require further hydrogenation but only mild clay treating to finish them as product lubricating oils. The obtaining of raiiinates of this quality, it will be recognized, depends on the severity of solvent treating in terms of the dosage or solvent to oil ratio in particular. By using in accordance with the invention a relatively severe or high solvent dosage in treating the heavier fraction, there is obtained a greater amount of aromatic extract for conversion to oil resembling the raffinate of the lighter fraction, thereby increasing the total production of lighter lubricating oil. This yield of lighter lubricating oil can be further increased by using la relatively mild solvent dosage in the solvent extraction of the relatively light fraction, and then hydrogenating at less severe conditions the light rainate so as to adjust its viscosity, color, and oxidation stability. Where instead, it is desired to obtain a higher yield of the heavy lube product, the conditions of solvent treating the relatively heavy raffinate can be milder, and the resulting heavy raffinate can be given a less severe hydrogenation.

lt will be recognized that the light and heavy distillate fractions and the light and heavy lubricating oils referred to herein are not necessarily in adjacent viscosity ranges, but may be separated by an oil of intermediate viscosity. Further, it will be understood that the solvent treating zones referred to are not necessarily separate units and that the entire process is not necessarily carried out continuously. Thus, there may be but one solvent treating unit which is used alternately to treat the light fraction and then at another time to treat the heavy fraction, the fractions derived from the distillation and the raiiinates and extracts being temporarily held in storage. Likewise, where there is employed both severe hydrogenation and a less severe hydrogenation the same processing equipment may in many cases be used for both treatments in blocked operation at different times,intermediate storage again being required.

We claim:

1. The process which comprises distilling crude oil to obtain fractions boiling in the lubricating oil range, including a light fraction and a heavy fraction representing sources for lubricating oils of separate viscosity ranges,

solvent treating said light fraction to obtain a light lube raffinate and a light aromatic extract, solvent treathydrogenating at least a portion of said heavy extract by contacting wit-h a sulfactive hydrogenation catalyst and hydrogen at severe conditions of high temperature and pressure and low space velocity Whereby a substantial portion thereof is converted to distillate fuels,

separating from the products of said hydrogenating distillate fuels and a hydrogenated oil having a viscosity in the range of said light ratinate,

and combining at least a portion of said hydrogenated oil with said light raffinate.

2. The process of claim 1 wherein a major portion of said hydrogenated oil is combined with said light raiiinate by combining said hydrogenated oil with said light fraction prior to solvent treating said light fraction.

3. The process which comprises distilling crude oil t0 obtain fractions boiling in the lubricating oil range, including a light fraction and a heavy fraction representing sources for lubricating oils of separate viscosity ranges,

solvent treating said light fraction to obtain a light lube raffinate and a light aromatic extract, solvent treating said heavy fraction to obtain a heavy lube ratinate and a heavy aromatic extract,

combining at least a portion of said light extract with at least a portion of said heavy extract and hydrogenating the combined extracts by contacting with 'a sulfactive hydrogenation catalyst and hydrogen at severe conditions of high temperature and pressure and low space velocity whereby a substantial portion thereof is converted to distillate fuels,

separating from the products of said hydrogenating distillate fuels and a hydrogenated oil having a viscosity in the range of said light raiiinate,

combining at least a portion of said hydrogenated oil with said light rainate and hydrogenating the combined light raflinate and hydrogenated oil by contacting with a sulfactive hydrogenation catalyst and hydrogen at less severe conditions including lower temperature and higher space velocity as compared to the conditions used in hydrogenating said extracts, whereby no substantial portion thereof is converted to light distillates.

4. The process which comprises distilling crude oil to obtain fractions boiling in the lubricating oil range,- including a light fraction and a heavy fraction representing sources forlubricating oils of separate desired viscosity ranges;

solvent treating said light fraction in combination with a hydrogenated oil obtained as set forth hereinbelow using a relatively mild solvent dosage to obtain a high yield of light raiiinate of poor color and higher than desired viscosity and a low yield of aromatic light extract;

solvent treating said heavy fraction using a relatively severe solvent dosage to obtain a high yield of by no substantial portion thereof is converted to aromatic heavy extract and a low yield of heavy light distillates;

raffinate which is a heavy lubricating oil base stock and recovering as the principal product of said less of good color and desired viscosity; severe hydrogenating a light lubricating oil base stock v combining at least a portion of said light extract with 5 of good color and desired viscosity.

at least a portion of said heavy extract and hydrogenating the combined extracts by contacting with References Cited by the EXalllllel a sulfactive hydrogenation catalyst and hydrogen at UNITED STATES PATENTS severe conditions of high temperature and pressure and low space velocity whereby a substantial portion 10 gamer et al 20S-264 thereof is converted to distillate fuels erge? 20S-"254 2 905 636 9/1959 Watkins et al. 208-254 separating from the products of said severe hydrogenat- 2944006 7/1960 Scott 208 89 ing distillate fuels and a hydrogenated oil having a 2983676 5/1961 Howlgl 208 254 viscosity in the range of said light rainate; 2988501 6/1961 Inwood 208 254 Combining Said hydl'ogenated the Said 15 Tucker fraction for solvent treating as aforesaid; 3014860 12/1961 Douwes et aL 208 254 hydrogenating Said light ra'nate by Contacting with 3,046,218 7 /1962 Henke et aL 208 144 a sulfactive hydrogenation catalyst and hydrogen at 3,094,480 5/1963 Richardson 20g 143 less severe conditions including lower temperature and higher space velocity as compared to the 20 DELBERT E. GANTZ,Prmary Examiner. conditions used in hydrogenating said extract, where- S. P. JONES, Assistant Examiner.

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