US2138772A - Solvent refining of hydrocarbon oils - Google Patents

Description

Patented Nov. 2.), 1938 UNITED STATES 2,138,772 SOLVENT nnrmmg gr nrnaoonnnon Erich Saegebarth, Long Island City, N. Y., is-

signor to Edeleanu Gesellschaft, m. b. H., a corporation of Germany No Drawing. Application October 9, 1933, Serial No. 692,906

8' Claims.

extraction of undesirable constituents with selective solvents.

The invention has particular reference to the production of improved lubricating oils from heavy petroleum distillates, cylinder stocks, and residues, which contain substantial amounts of undesirable asphaltic, resinous, and color-bearing compounds, such as those from Mid-Continent fields. Imention these diflicultly refinable oils because of the striking improvement which can be effected by refining them according to my invention, but it will be understood that my invention finds advantageous application to the refining of hydrocarbon oils generally.

The aimof modern processes for refining mineral oil is to remove the undesirable constituents from crude oils or fractions thereof by extraction with selectiy'e solvents which do not react with the oil. The solvents employed separate the desirable constituents from the undesirable constituents to a greater or less degree, depending upon the nature of the solvent used and the conditions of use. Such solvents are relatively immiscible in the desirable hydrocarbons, so that an excess can be employed which will separate out, after mixing and standing, into a separate layer or phase which will contain the undesirable constituents extracted by the solvent.

This latter layer or phase, comprised of the bulk of the solvent and containing the extracted materials, is commonly known as the extract layer, extract solution or extract phase. The layer or phase comprised of the refined oil, together with that portion of the solvent dissolved therein, is commonly known as the raflinate layer, rafiinatesolution or rafiinate phase. The non-solvent portions of these layers, which are obtained by separately drawing ofi the two layers and removing the solvent contained therein, are known as the extract and rafiinate, the latter constituting the refined product.

I have discovered that para-chlorophenol has very good selective solvent properties rendering it highly advantageous for use in refining mineral oils. Para-chlorophenol dissolves to a great extent the asphaltic and color-bearing compounds which may be present and hence permits of an improved refining of heavy stocks containing such materials, as compared with the results obtained from using such solvents as liquid-S02 which have a low solvent power for asphaltic and colorbearing compounds. In addition, this solvent readily dissolves unsaturated hydrocarbons generally and also has a good solvent power for oxidizable and sludge-forming materials, all of which areundesirable in lubricating oils for use in internal combustion engines.

Particularly striking results are obtained in the refining of Mid-Continent and naphthenic base residual oils for lubricating purposes, as these oils cannot be successfully refined with-such solvents as liquid-S02 and are considered very difiicult to refine. The refined oils obtained by the practice of my invention have a very light color and are greatly improved in their physical and chemical properties, including gravity, viscosity index, viscosity-gravity constant, carbon residue, and stability against sludging and oxidation.

As para-chlorophenol readily dissolves unsaturated and aromatic hydrocarbons it may be employed to advantage for refining all types and fractions of mineral oils from which it is desired to remove such compounds, and it has general application in the field of solvent refining of hydrocarbon oils.

Extraction'can be accomplished in the same manner as with selective solvents heretofore employed. The oil may be extracted one or more times with the solvent in batches; or may be extracted by being passed counter-currently to the solvent through a vertical tower or through a series of mixing devices and settling tanks. Owing to the density of the solvent which I employ the extract layer will in each case be the lower layer.

The portions of solvent contained in the raffinate. and extract solutions can be removed and recovered therefrom by distillation, preferably under vacuum. The necessary heating will not decompose the solvent which I employ and this permits of repeated use with little make-up required. This is of importance from the economic and operating standpoint.

The following examples illustrate modes of carrying out my invention and demonstrate the remarkable results which can be obtained.

Example 1 In the first example an untreated Mid-Continent residual stock was extracted by the multiple-batch method. The stock was first extracted with 200% by volume of para-chlorophenol, at a temperature of 113 F., and the resulting raffinate layer was divided out and extracted with 100% by volume (relative to the original volume of untreated stock) of fresh solvent at the same temperature. The resulting second rafiinate solution was freed of solvent to secure the final rafflnate.

The action of the solvent which I employ may be greatly improved by carrying out the extraction of the oil therewith in the presence of propane or other low-boiling saturated hydrocarbon. As additional examples, I mention the low-boiling paramns: ethane, butane, pentane, etc. Mixtures of these may likewise be used. A low-boiling fraction of saturatednaphtha may also be S02 extraction of naphtha. 'Ihe presence of these saturated hydrocarbons increases the selectivity of the extraction and otherwise improves the extraction, thus permitting of greater raffinate yields and/or higher quality ramnates. Since they are low-boiling they may be easily removed from the ramnate by distillation.

Example 2 In this example the same untreated Mid-=Continent residual stock that was used in the pre= ceding example was employed. The stock was dissolved in 300% by volume of propane and the resulting solution was extracted successively with two batches of 100% by volume of para-chlorophenol, at a. temperature of 86 F.

The following'table gives the characteristics of the raifmates obtained in these two examples as compared with the characteristics of the original stock. In the table the gravity is given in degrees A. P. 1., the viscosity in seconds according to the Saybolt Universal method or measurement, "V. I. stands for the viscosity index, "V. G. C. stands for the viscosity-gravity constant, and carbon stands for the carbon residue deter- Dissolved in 800 Egitfiacted vol. percegt pro- W1 parapane an exggii chlorophenol traoted with 200+100 para-chlorost 113 F. phenol 2 l00% at 86 F.

20. 0 26. O 26. 4 997 502 361 147 104 83 79 103 96 0. 859 0. 819 0. 820 5. 6 2. l 0. Color Black Green Green Raflinate yield, per

cent by weight 48 Examples 3 and 4 For the purpose of illustrating the relative solvent power and selectivity of para-chlorphenol and ortho-chlorophenol for refining lubricating stocks heretofore considered very diflicult to treat successfully, a heavy distillate from a Mid-Continent crude oil, which had been dewaxed but otherwise untreated before solvent extraction, was subjected to extraction by the'multiple batch method using these solvents in quantities of 150% to 200% by volume relative to the original volume of the untreated stock, and at temperatures from 35 to 1200 F.

The results of these tests are given in the following table:

sect rar g fia or- 0 ortho-chloro phenol at phenol 120 F. 35 F 23. 2 29.1 27. 4 1287 643 761 92 73. 2 77. 4 78 103. 5 97. 5 0 2O 16 Garb. res.-- 1.9 0 28 0. 60 NPA color (diluted) Darker than 8 3% 4% Yield volume percent. 60. 4 51. 7

From the foregoing results it appears that the yield depends upon the nature and amount of solvent used as well as upon the temperature. It was found necessary to use a comparatively low temperature for treating with ortho-chlorocassava phenol because the solubility of the oil increases so much that at. about 45 F. no separation could be efiected.

Examples 5, 6 and 7 The relative effectiveness of para-chlorophenol and phenol is evident from the following results of treating the same Mid-Continent dewaxed distillate that was used in Examples 3 and 4, with 125% and 100% by volume of para-chlorophenol at F. as compared with 200% by volume of phenol at F.

These results indicate that para-chlorophenol is about twice as efiective as phenol as a solvent for extracting undesirable constituents of lubricating oil produced from Mid-Continent stock, 100% of the former applied in two treatments producing substantially the same yield and quality of rafinate as 200% of the latter applied in three treatments at a slightly higher temperature. I have also found, as shown by the results of Example 3 compared with those of Example 7, that para-chlorophenol is much more selective than phenol when used in the same amount under the same treating conditions, the ramnate produced being of a much superior quality.

I claim the following as my invention:

1. In the refining of heavy residual lubricating oil, such as derived from mixed-base crude petroleum with monochlorphenol in the absence of an auxiliary selective solvent, the method comprising extracting the residuum containing darkcolored material, residual carbon-forming constituents, as well as constituents of low and high viscosity index, with chlorphenol consisting essentially of the para. form of the compound substantially free from the ortho compound, forming an extract phase comprising low viscosity index constituents, residual carbon-forming constituents and dark-colored material dissolved in the solvent, and a rafiinate phase comprising high viscosity index oil having a relatively low residual carbon content and substantially free from dark-colored material.

2. The method of claim 1 in which the extraction is performed in the presence of a low boiling diluent of the class of the low boiling pararlins and saturated naphthas.

3. The method of claim 1 in which a low boiling diluent of the character and action of propane is added to the oil prior to separation of the extract and ramnate phases.

4. A process of refining mineral oil containing both high viscosity index hydrocarbons and low viscosity index hydrocarbons, comprising extracting the oil with a solvent consisting essentially of para-monochlorophe'nol to form a raifinate layer containing the high viscosity index hydrocarbons, and an extract layer containing the low viscosity index hydrocarbons of said mineral oil dissolved in the solvent, separating said layers from each other, and recovering the solvent therefrom.

5. The method of claim 4 in which the extraction is performed in the presence of a low boiling diluent of the class of the low boiling parafilns and saturated naphthas.

6. The method of claim 4 in which a low boiling diluent of the character and action of propane is added tothe oil prior to separation of the extract and raffinate phases.

7. In the refining of heavy residual lubricating oil, such as derived from mixed-base crude petroleum with monochlorophenol in the absence of an auxiliary selective solvent, the-method comprising extracting the residuum containing darkcolored material, residual carbon-forming constituents, as well as constituents of low and high viscosity index, with chlorophenol consisting essentially of the para form of the compound substantially free from the ortho compound, forming an extract phase comprising the low viscosity index constituents, residual carbon-forming constituents and dark-colored material dissolved in. the solvent, and a railinate phase of high viscosity index oil comprising around 50% of the residuum having a Conradson carbon content of the order of 1.8% and substantially free from dark-colored material.

8. In the refining of heavy residual lubricating oil, such as derived from mixed-base crude petroleum with monochlorophenol in the absence of an auxiliary selective solvent, the method comprising diluting the residuum containing darkcolored material, residual carbon-forming constituents, as well as constituents of low and high viscosity index by addition thereto of a low-boiling petroleum hydrocarbon, extracting the dilute mixture with chlorophenol consisting essentially of the para form of the compound substantially free from the ortho compound, forming an extract phase comprising low viscosity index constituents, residual carbon-forming constituents and dark-colored material dissolved in thesolvent, and a rafllnate phase comprising high viscosity index oil having a relatively low residual carbon content and substantially free from darkcolored material.

ERICH SAEGEBARTH.

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