US 3565795 A
Description (OCR text may contain errors)
United States Patent Office 3,565,795 Patented Feb. 23, 1971 3,565,795 LUBE EXTRACTION WITH HYDROXY KETONES Lorne W. Sproule, John M. MacDonald, and Charles C.
Hong, Sarnia, Ontario, Canada, assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Nov. 14, 1968, Ser. No. 776,314 Int. Cl. Cg 21/16 US. Cl. 208332 8 Claims ABSTRACT OF THE DISCLOSURE Polar materials, such as high molecular weight aroanatics, are separated from petroleum distillate fractions by contacting a petroleum distillate fraction with a selective extraction solvent. The solvents employed, in accordance with this disclosure are hydroxyl substituted aliphatic ketones such as 3-hydroxy-3-methyl-2-butanone. The results obtained with these solvents are compared with the results obtained with the use of phenol.
BACKGROUND This invention relates to a method of separating polar components from petroleum distillate fractions. More particularly, this invention relates to a method of selectively extracting the polar constituents from petroleum distillate fractions. Still more particularly, this invention relates to a liquid/liquid extraction process wherein certain selected solvents are used to extract polar components from petroleum distillate fractions. Yet more particularly, this invention relates to a process wherein certain hydroxy-substituted aliphatic ketones such as 3-hydroxy-3-methyl-2-butanone are used to selectively extract polar constituents from petroleum distillate fractions.
It is well known in the art to contact petroleum distillate fractions with solvents having a preferential selectivity for the more polar components to thereby remove these components from the petroleum distillate fraction. For example, it is known in the art to use such solvents as phenol, furfural, sulfur dioxide, nitrobenzene, etc., for this purpose. Moreover, it is known in the art that several factors will influence the degree of separation which can be achieved with these solvents. By far the most significant of these factors is the relative selectivity of the solvent toward the more polar components and the ease with which the selective solvent may be separated from both the polar components and the petroleum distillate fraction. In addition to these, other factors are known to influence the relative success of a selective extraction process; e.g., the relative solubility of the oil in the solvent, the relative solubility of the polar constituents in the solvent, the number of theoretical plates needed to achieve a given degree of separation, and the temperature at which the petroleum distillate fraction and the solvent are contacted. When considered in light of all of these facts, phenol is well known to yield the best overall results. Notwithstanding, the search has continued for even better selective solvents. For example, considerable effort continues to be devoted to the discovery of a selective solvent which is more selective than phenol.
BRIEF SUMMARY It has now been discovered that certain selective solvents, when used in accordance with this invention, are effective in removing the more polar constituents from petroleum distillate fractions, thereby improving the viscosity index, color, and oxidation stability of the petroleum distillate fraction. Accordingly, it is an object of this invention to provide a selective extraction process for the separation of the more polar constituents from a petroleum distillate fraction. Another object of this invention is to provide a selective extraction process for the separation of polar constituents wherein the loss of high viscosity index constituents is reduced. Still another object of this invention is to provide a selective extraction process for removing polar constituents from petroleum distillate fractions wherein the yield of useful petroleum product is increased. Other objects will be apparent from the following description.
According to this invention, the foregoing and other objects are accomplished by contacting a petroleum distillate fraction with certain selective solvents at conditions under which the more polar constituents of the petroleum distillate fraction are selectively extracted by the selective solvents. Moreover, the petroleum distillate fraction and the selective solvent will be contacted in such a manner as to insure good IniXing, and, hence, good contacting between the selective solvent and the polar constituents to be removed. The temperature at which the selective solvents and the petroleum distillate fraction are contacted should be such that the solvent (extract) phase and the petroleum distillate fraction (raffinate) phase are maintained in the liquid state and both are immiscible. It will be appreciated that the operable range of temperatures can be extended, somewhat, by the use of pressure to maintain both phases in the liquid state.
PREFERRED EMBODIMENT Essentially any petroleum distillate fraction containing polar materials may be upgraded by the method of the present invention. In general, these petroleum distillate fractions will boil between the range of 500 F. and 1400 F. This includes the lubricating and specialty oil fractions which are commonly improved by selective extraction of the polar constituents. The lubricating oil fractions boiling between 550 and 1100 F. are preferred feedstocks. The petroleum distillate fractions which may be treated by the method of this invention will have API gravities at 60 F. ranging between 15 and 35, pour points between 70 and +175 F. and viscosities at F. between 20 and 20,000 SUS. These petroleum distillate fractions may be cut from crude oils obtained from essentially any source; e.g., crudes obtained from ARAMCO, Kuwait, the Pan Handle, North Louisiana, Tia Juana, Western Canada, etc.
The solvents which may be used in the extraction process of the present invention are polar materials with high density. More specifically, the solvents used in this invention are the hydroxy ketones having between 2 and 3 carbon atoms between the oxygen of the hydroxyl group and the oxygen of the ketone group. The molecular weight is preferably below 200. A particularly preferred solvent which may be purchased from the Aldrich Chemical Company, 10 Ridgedale Avenue, Knolls, N.J., is 3- hydroxy-3-methyl-2-butanone, which may be represented structurally as:
r HsC-O-C-CHa Other hydroxy ketones may also be purchased. In particular other alkyl substituted hydroxy butanones (eg 4 hydroxy-3-n1ethyl-2-butanone) may be purchased from the Aldrich Chemical Company.
The petroleum distillate fraction and the selective solvent may be contacted in any suitable contacting apparatus, such as those which are well known in the prior art. It will be appreciated that good contacting is essential if the separation is to approach equilibrium. Accordingly, the apparatus employed should be designed such that the separation attained is comparable to that which would be obtained in a vessel having between 1 and '20 theoretical stages. Such separation can be attained in both batch and continuous equipment. For practical reasons, continuous operation will be preferred. In this type of operation, the selective solvent is generally introduced at or near the top of the contacting vessel and flows downwardly while contacting the petroleum distillate fraction. The solvent phase, enriched in polar constituents, is recovered as bottoms and separated by conventional means such as distillation. The petroleum distillate fraction, on the other hand, is fed to the contacting apparatus at or near the bottom and flows upwardly. The thus treated petroleum distillate fraction, reduced in polar constituent content, is recovered from the top and dissolved solvent is separated therefrom by convcntional means such as distillation.
The liquid/liquid extraction process of the present invention is operable over a wide range of temperatures. It will be appreciated, however, that the range of operable temperatures will vary with the particular solvent employed. For example, as has already been pointed out, the solvent phase and the petroleum distillate fraction phase must be immiscible at the temperature employed. Moreover, it is essential that both phases be maintained in the liquid state during the contacting step. In general, the solvents of the present invention may be employed at temperatures between the range of about 70 and 300 F.; however, best results will be obtained at temperatures between the range of about 100 and 200 F. This range is preferred.
The polar constituents which may be removed by the process of this invention are principally condensed aromatic components. In general, these materials will contain between about 20 and 100 carbon atoms per molecule. It will be appreciated, however, that other polar materials may be separated by the process of this invention. These include both nitrogen and sulfur compounds which might be present in the petroleum distillate fraction. In general, the process of this invention can be used to remove polar component concentrations ranging as high as 70 wt. percent of the petroleum distillate fraction. Best results, however, will be obtained when the concentration of polar components does not exceed 50 wt. percent.
The petroleum distillate fractions which are treated by the method of this invention will be substantially reduced in polar components, and hence, will exhibit improved viscosity indices, color and oxidation stability. Moreover, the petroleum distillate fractions treated by the method of this invention can be used as lubricating oils, diesel fuels, transformer oils, etc.
PREFERRED EMBODIMENT The invention is further illustrated by the following examples:
Example 1 30 milliliters of a 30-grade Western Canadian lube distillate having the following inspections:
API gravity at 60 F.: 23.0
Pour point: 120 F.
Viscosity at 210 F.: 75 SUS Refractive index at 140 R: 1.4943 Dewaxed viscosity index (+25 F. pour): 56
were solvent extracted by contacting with 30 milliliters of 3-hydroxy-3-methyl-2-butanone in a batch extractor at 160 F. under atmospheric pressure. The mixture was well stirred and allowed to settle. After settling, the extract (solvent-rich) and the raflinate (oil-rich) phases were separated, the solvent in each removed by distillation and the oil in each phase analyzed.
The raffinate phase contained 21.5 Wt. percent solvent while the extract phase contained 87.5 wt. percent solvent. The oil in the raffinate phase had a refractive index of 1.4872 at 140 F. and a dewaxed viscosity index of 63.6. The oil recovered from the extract phase was very aromatic and had a refractive index of 1.5310 at 140 F.
In the same manner batch extractions were carried out at F. on the distillate to which certain amounts of saturated and aromatic fractions had been added. These saturated and aromatic fractions were obtained by fractionation of the distillate itself and were used to vary the refractive index and viscosity index of the feed distillate. The raflinate and extract phases were analyzed as above. The data are summarized in the following tabulation.
Railinate phase Extract phase Refractive Dewaxed Refractive index of oil viscosity Wt. percent index of 011 Wt. percent at 140 F. index of oil solvent at 140 F. solvent To further illustrate the improved yield obtained with the solvent of this invention, the extraction of the 30-grade lube distillate with phenol at F. was investigated in the same experimental manner as in Example 1. The data for the ternary diagram are summarized in the following tabulation.
Rcflinate phase Extract phase Refractive Dewaxed Refractive index of 011 viscosity Wt. percent index of oil Wt. percent at 140 F. index of oil solvent at 140 F. solvent At a temperature of 180 F., phenol gave only 47 wt. percent yield of 90 viscosity index product oil at a solvent to oil ratio of 1.5 by weight in 3.3 ideal stages.
Having thus described and illustrated the invention, what is claimed is:
1. A process for extracting aromatic compounds from a petroleum distillate fraction which comprises contacting said distillate fraction with a selective extraction solvent selected from the group consisting of the alkyl substituted hydroxy butanones at conditions such that both the distillate fraction and the solvent phases are in the liquid state and partially immiscible, recovering an extract phase. enriched in aromatic compounds and a raflinate phase containing the petroleum distillate fraction With a reduced aromatic compound concentration. I
2. A process for the removal of aromatic compounds from a petroleum distillate fraction comprising contacting a petroleum distillate fraction with a sol-vent selected from the .group consisting of alkyl substituted hydroxy butanones at a temperature between 70 and 300 F. and recovering an extract phase enriched in aromatic compounds and a ratfinate phase containing said petroleum distillate fraction with a reduced aromatic compound concentration.
3. The process of claim 2 wherein said petroleum distillate fraction has a boiling range between about 500 and 1400 F.
4. The process of claim 3 wherein said solvent is 3- hydroxy-3-methyl-2-butanone.
5. A process according to claim 1 wherein the extraction solvent is a methyl substituted hydroxy butanone.
6. A process for extracting aromatic compounds from a petroleum distillate fraction which comprises contacting said distillate fraction with 3-hydroxy 3-methyl-2- butanone at conditions such that both the distillate fraction and the solvent phases are in the liquid state and 5 partially immiscible, recovering an extract phase enriched in aromatic compounds and a rafiinate phase containing the petroleum distillate fraction with a reduced aromatic compound concentration.
7. A process according to claim 6 in which the petroleum distillate fraction has a boiling range between 500 and 1400 F.
8. A process according to claim 7 whereby the petroleum distillate fraction having a boiling range between 500 and 1400 F. is contacted with 3-hydroxy-3-methyl- Z-butanone at a temperature between 70 and 300 F.
References Cited UNITED STATES PATENTS 2,026,812 1/1936 Birkheimer 208-332 2,191,767 2/1940 McCluer et a1. 208-332 2,246,257 6/1941 Kohn 208332 2,900,333 8/1959 Collins et a1. 208-333 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 260-674