US2519930A - Recovering sulfonates of oilsoluble sulfonic acids from acid-treated hydrocarbon oils - Google Patents

Description

Patented Aug. 22, 1950 RECOVERING SULFONATES OF OIL- SOLUBLE SULFONIC ACIDS FROM ACID-TREATED HYDROCARBON OILS George Riethof, Pittsburgh, Charles W. Montgomery, Oakmont, and George P. Brown, Jr., Pittsburgh, Pa., assignors to Gull. Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application September 8, 1948, Serial No. 48,328

7 Claims. (Cl. 19641) This invention relates to an improved method of recovering sulfonates of oil-soluble sulfonic acids from acid-treated hydrocarbon oils. More particularly, the invention pertains to an improved method of neutralizing a sulfonated oil by the use of an alkylolamine, and separating the resulting alkylolamine sulfonic acid salts from the neutralized oil.

In the sulfonation of viscous hydrocarbon oils, especially petroleum hydrocarbon oils of the lubricating oil range, an acid oil layer is produced which contains dissolved sulfonic acids. This acid oil layer is separated from the suliuric acid layer and is neutralized. In some cases it is neutralized with an alkylolamine such as ethanolamine. The neutralization is carried out by adding the amine to the oil in small increments amid vigorous agitation until the oil shows a slightly alkaline reaction. This produces a mix in which the sulfonates tend to be emulsitied in the oil. The sulfonates are recovered by permitting the neutralized, slightly alkaline oil to settle over an extended period of time, during which the bulk of the ethanolamine sulfonic acid salts separate out. To remove the rest, it has been found necessary to wash the sulfonates out of the oil with water or a solvent such as isopropyl alcohol, etc.

Among the difiiculties experienced in practicing the prior art method outlined above is the frequent formation of relatively stable emulsions or suspensions of amine sulfonic acid salts in the neutralized oil. Excessively long settling times are required before any appreciable part of the sulfonates settles out of the oil. The settled sulfonate layers are relatively much smaller in volume than the oil layers and sharp separations of the oil and sulfonate layers are extremely diflicult, or impossible to perform in conventional apparatus. Appreciable amounts of the sulfonates always remain suspended or mixed in with the oil layer, and it is necessary to recover them by the use of several water or alcohol washes employing large volumes of wash solvent. Additional troublesome emulsion problems are encountered in these subsequent washing operations and long settling times, settling tanks or expensive centrifuge equipment, are required to separate the solvent layer from the oil layer. Finall in actual practice the large volumes of wash solvents must be recovered from the sulfonates and the oil layer.

In view of the disadvantages of the prior art methods, it is an object of the invention to pro- 2 vide an improved method for separating sulfonic acids from acid oil.

It is a particular object of the invention to provide a rapid and convenient method for the simultaneous production of oil-soluble sulfonic acid salts and refined mineral oil.

Another object of the invention is to provide an economic method for refining acid oil and recovering the refined oil substantially free of impurities without the use of large volumes of wash solvents.

We have discovered, in accordance with the invention, that alkylolamine sulfonic acid salts can be quickly and efiiciently prepared and separated from the acid oil containing oil-soluble sulfonic acids by neutralizing the sulfonic acids with an alkylolamine incompletely miscible with the neutralized oil and having 19. higher density than this oil, and using an excess of the alkylolamine. We have found that the excess alkylolamine is effective to dissolve the alkylolamine sulfonates and to separate from the oil an alkylolamine liquid layer containing the salts after a very short settling time. The amount of excess alkylolamine, therefore, should be sumcient to dissolve the sulfonates, leaving at most a negligibly small quantity of the sulfonates in the oil and creating conditions producing a clean separation between the oil and alkylolamine layer. In the present process the alkylolamine layer is separated from the oil layer and is then treated for the recovery of the excess alkylolamine. We have found that the alkylolamine can be recovered efliciently by subjecting a mixture containing salts of the sulfonic acids to vacuum distillation whereby the alkylolamine is vaporized and recovered. The use of the excess of the alkylolamine, therefore, does not present an economic problem, since this excess is recovered and available for use in subsequent practice of the process. The sulfonates are recovered from the still bottoms.

In cases where the oil layer contains an im- I portant amount of dissolved alkylolamine, this compound may be recovered by any suitable method. We prefer to use an alkylolamine having a boiling point appreciably below the boiling range of the oil, preferably at least 20 C. below the initial boiling point of the oil, and in this case the oil layer may be subjected to vacuum distillation to vaporize and recover the alkylolamine. The refined oil, substantially free of sulfonic acids and the alkylolamine, is recovered from the still.

The process of the invention may be applied to sulfonated oils or acid oils obtained by the treatment of the original oils with a sulfonating agent adapted to accomplish sulfonation of the oils. The usual sulfonating agents are concentrated or fuming sulfuric acid and chlorosulionic acid. The process is especially applicable to sulfonated or acid oils obtained by sulfonation of lubricating oil stocks such as raw distillates and residuums: but acid oils resulting from treatment of solvent extracts of such lubricating oil fractions are preferred, since the refined oil obtained from the neutralized acid oil may be used to supplement the supply of lubricating oil obtained as the railinate in the solvent extraction. The extract oil may be produced by the use of such solvents as furfural, aniline,

nitro-benzene, sulfur dioxide-benzene mixtures;

dichlorodiethylether, phenol, etc.

In accordance with a preferred manner of practicing the invention for the treatment of an acid-treated lubricating oil, said lubricating Oil having an initial boiling point above 270 C., and using an alkylolamine boiling below the initial boiling point of the oil, preferably below 250' C.. neutralization of the acid oil is performed by adding the alkylolamine to the oil in small increments while the oil is kept in a state of vigorous agitation, to achieve rapid and complete neutralization. Heat of neutralization is produced, which raises the temperature of the agitated mixture, thus assisting the process of neutralization. The addition of alkylolamine is continued until the acid oil is neutralized, as is evidenced by a slight alkaline reaction of the mixture. If the addition of the alkylolamine is stopped at this stage, the resulting mixture has the appearance of an emulsion and is with difficulty only partially separable into layers by settling. In the present process, the addition of alkylolamine is continued until an excess of at least 5 per cent by volume based on the acid oil, of alkylolamine, hasbeen added to the mixture. In some cases it may be desirable to add considerably more than the amount mentioned above. The resulting mixture is heated with occasional stirring at least to a temperature at which the emulsion breaks rapidly-about 80 C. in the case of ethanolamine, and is then run into settling tanks and permitted to settle. The settling is preferably accomplished at the elevated temperature of the mixture, which may be about 80 to 120 C. at this stage. because more rapid stratification of the oil and alkylolamine layers is accomplished at elevated temperatures; although the settling may be accomplished while the mixture is cooling to atmospheric temperature. In either case, a lower layer of alkylolamine, containing the alkylolamine sulfonates in solution. settles out at the bottom of the settling tank in a relatively short period of time.

This lower layer is drawn off from the oil layer and the alkylolamine may be recovered from the dissolved alkylolamine salts by eva oration. preferably by vacuum distillation. If it is desired to separate the su fonic ac ds as metal salts, the alkylolamine salts are decomposed in conventional manner by reacting them with the appropriate compounds such as metal oxides, hydroxides or carbonates. The alkylolamine is then distilled oil, preferably under vacuum.

The upper layer obtained in the above treatment contains the neutralized oil in which is dissolved a small amount, which in many cases may be less than about 0.5 per cent, of alkyiolmine. The alkylolamine is recovered from this layer by subjecting it to conventional distillation methods at reduced pressure to vaporize the alkylolamine which is then condensed in the conventional manner. In case the settling was completed at elevated temperatures, an additiox advantage is gained in that the hot oil layer be stripped free of the alkylolamine by simply reducing the pressure above the oil layer in a suitable container. The alkylolamine is flash-vaporized. The alkylolamine recovered from both the salts and the oil is preferably reused in the process to reduce operation costs. The oil stripped of alkylolamine is practically completely free of salts and may be used directly as a lubricating oil, turbine oil, hydraulic oil, etc.

While it is usually preferred to recover the alkylolamine. dissolved in the oil, the amine may be left in the 011 if desired, depending upon the amount of amine present and the intended application of the oil.

As previously stated, the alkylolamines suitable for use in the present process are those incompletely miscible with the neutralized oil at the settling temperature. The extent of the solubility of the alkylolamine in the oil is a critical factor inasmuch as the completeness of separation of the sulfonic acid salts from the oil layer is a function of the relative amounts of alkylolamine remaining in the oil layer and in the alnlolamine layer below it. The lower the solubility of the alkylolamine in the neutralized oil, the more complete will be the separation of the alkylolamine salts. In cases where an alkylolamine that is relatively soluble in the neutralized oil is employed, effective separation requires the use of an amount of the alkylolamine considerably greater than the amount necessary when using a less-soluble alkylolamine. The aikylolamine should not be miscible in all proportions with the neutralized oil at the settling temperature since in this case no separation is possible. We prefer to employ an alkylolamine which is soluble in the neutralized oil in an amount less 5 than 5 per cent by volume of the solution, and especially satisfactory results are obtained when an alkylolamine which is soluble in an amount less than 2 per cent by volume is used. In general, the amino group or groups should be unsubstituted, as the presence of such groups confers desired low oil solubility to the alkylolamine.

In practice, the difference between the densities of the neutralized oil and alkylolamine should preferably be at least about 0.04 gram per cc., with differences of at least about 0.09 gram Ethanolamine l-aminopropanol-2 3-aminopropanol-l 2-aminobutanol-l 4-aminobutanol-l l-aminobutanol-2 3-aminobutanol-2 l-amino-2-methylpropanol-2 's 3-aminopentanol-2 2-aminopentanol-3 1-amino-2-methylbutanol-2 3-amino-2-methylbutanol-2 Z-aminohexanol-B 4-amino-2-methylpentanol-2 4-amino-2-methylpentanol-5 3-amino-2,3-dimethylbutanol-2 4-amino-2,4-dimethylpentanol-2 1-amino-2,5-dimethylhexanol-2 5-amino-2,5 -dimethylhexanol-3 1,3-diamino-2-propanol The following examples are given for the purpose of illustrating the invention:

Example 1 To 200 parts by weight of acid oil, obtained from sulfonation with 20 per cent by weight of concentrated sulfuricacid of an oil boiling in the lubricating oil range resulting from furfural extraction of a Texas lube oil distillate having a viscosity of about 400 S. U. S. at 100 F., and containing about per cent by weight of the solution of oil-soluble sulfonic acids, is added with stirring, in increments, about 5 per cent by weight of the acid oil, of technical monoethanolamine. This amount of monoethanolamine is several times that sumcient to neutralize the sulfonic acids. At this time the mixture gives an alkaline reaction and the mixture has changed from a dark reddish-brown solution to a yellowish emulsion. To this emulsion is added an additional 5 per cent by weight of the original acid oil, of monoethanolamine, thus making a total of 10 per cent monoethanolamine by weight based on the original weight of acid oil. During the addition of the ethanolamine the temperature of the oil rises from 22 C. to 40C. The final mixture is heated with occasional stirring to 100 C. At about 85 C. the emulsion is broken and stratification takes place rapidly. The mixture is then allowed to cool to atmospheric temperature in a setting vessel. The lower layer, consisting of monoethanolamine salts of the oil-soluble sulfonic acids dissolved in excess monoethanolamine, is drawn off from the bottom of the settling vessel.

The alkylolamine layer is subjected to vacuum distillation to separate ,the excess monoethanolamine and to recover valuable monoethanolamine salts of the sulfonic acids. The oil layer is substantially completely free of sulfonic acid salts and contains only a very small amount of monoethanolamine.

Example 2 In this example, an acid oil similar to that of Example 1 is treated substantially as described above. The removal of the oil-soluble sulfonic acids from the acid oil is substantially quantitative. This is apparent from sulfur analyses of the original, sulfonated and finished oils as follows:

Clay treatment of the finished oil to quantitatively adsorb and remove any remaining sulfonates from the oil gives a treated oil which has substantially the same sulfur content as the finished oil before clay treatment. This indicates that substantially all of the sulfonates are removed from the oil layer by the alkylolamine treatment, and that no additional washing or similar treatment is necessary to produce a finished oil.

Example 3 An acid oil containing 0.88 per cent sulfur by weight is treated substantially as described in Example 1, with the exception that the final mixture of oil and excess monoethanolamine, which is heated to C., is separated into 011 and ethanolamine layers by settling at 100 C. Upon cooling the separated oil layer to atmospheric temperature, a small amount of ethanolamine separates from the oil but the sulfur contentof the oil is substantially unchanged, showing that the oil is free of sulfonic acids.

When accomplishing the separation at elevated temperatures as described in Example 3, the alkylolamine may be recovered from the oil layer by vacuum distillation without the necessity of additional heating. Thus, the oil layer, at the temperature of separation, may be passed through a vacuum flash tower for removal of the alkylolamine. i

The alkylolamine used in the foregoing examples was monoethanolamine because this is an eiiective agent in the process and is readily available. Similar results are obtained by substituting for the monoethanolamine an amount of another alkylolamine of the class herein described, especially one of those specifically mentioned, stoichiometrically equivalent to the amount of monoethanolamine employed to neutralize the sulfonic acids and an excess amount equal to the excess amount of monoethanolamine by volume employed to effect rapid layer separation.

The process of the invention has been illustrated as a batch extraction procedure for the sake of simplicity. However, it is also readily performed in more complex cocurrent and countercurrent continuous extraction systems with the additional benefits of the inherent advantages of these systems.

Obviously many modifications and variationsof the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In the method wherein a hydrocarbon oil is sulfonated with a sulfonating agent, the acid oil layer is separated from the sulfonating agent layer, and the acid oil layer is neutralized with a base, the improvement which comprises neutralizing the acid oil layer with an alkylolamine incompletely miscible with the neutralized oil and having a density greater than the density of the neutralized oil, and employing a sumcient excess of alkylolamine to dissolve the resulting alkylolamine sulfonic acid salts and form a liquid alkylolamine layer, and separating the layers containing in solution substantially all of the alkylolamine sulfonic acid salts formed in the neutralization.

2. In the method wherein a hydrocarbon'oil is sulfonated with a sulfonating agent, the acid oil layer is separated from the sulfonating agent layer, and the acid oil layer is neutralized with a base, the improvement which comprises neutralizing the acid oil layer with an alkylolamine 7, incompletely miscible with the -neutraliaed oilandhavingadensitygreaterthanthedensityot the neutralized oil, and employing an amount equal to at least per cent oi excess 'alkylolarnine by volume, based on the acid oil, and suflicient to dissolve substantially all oi the resulting alkyl-- olamine sulionic acid salts .and form a liquid alkylolamine layerbelow the oil layer. and se arating the layers.

8. The method of claim 2, wherein the alkylolamine is soluble in the neutralized oil to the extent oi less than 2 per cent by volume.

- 4. The method of-claim 2, wherein the alkylolamine is monoethanolamine.

5. In the method wherein a hydrocarbon oil is suli'onated with a suli'onating agent, the acid oil layer is separated irom the sulionating agent layer, and the acid oil layer is neutralized with a base, the improvement which comprises neutralizing the acid oil layer with monoethanolamine, and employing a suiiicient excess of monoethanolamine to dissolve the resulting monoethanolamine sulfonic acid salts and form an oil layer and a monoethanolamine layer, and separating the layers containing in solution substantially all of the monoethanolamine suli'onic acid salts formed in the neutralization.

8. In the method wherein a hydrocarbon oil is sulfonated with a sulionating agent, the acid oil layer is separated from the sulionating agent guano 8". layer. and the acid 011 layer is neutrallaed with a base, the improvement which comprises neutralizing the acid oil layer with monoethanolamine, employing a suiiicient excess 0! monoethalonamine to dissolve the resulting monoethanolamine sulionic acid salts and form aliquid monoethanolamine layer containing in solution substantially all of the monoethanolamina sulionic acid salts formed in the neutralintm. maintaining the resulting mixture at an elevated temperature at which rapid stratification oi oil and monoethanolamine layers is accomplished. and separating the layers at said elevated temperature.

'I. The method of claim 6 wherein said elevated temperature is in the range of about 80 to C.

GEORGE RIE'IHOF.

CHAR-LES W. MONTGOMERY. GEORGE P. BROWN, Jl.

REFERENCES CITED The following references are of record in the tile 01' this patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,519,930 August 22, 1950 GEORGE RIETHOF ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 6, lines 67 to 69, inclusive, after the Word layers strike out containing in solution substantially all of the alkylolamine sulfonic acid salts formed in the neutralization and insert the same after layer and before the comma in line 66, same column; column 7, lines 25 to 27, inclusive, after layers strike out "containing in solution substantially all of the monoethanolamine sulfonic acid salts formed in the neutralization, and insert the same after layer and before the comma in line 24, same column;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case 1n the Patent Office.

Signed and sealed this 7th day of November, A. D. 1950.

THOMAS F. MURPHY,

Assistant Gammz'ssz'oner of Patents.

Claims (1)

1. IN THE METHOD WHEREIN A HYDROCARBON OIL IS SULFONATED WITH A SULFONATING AGENT, THE ACID OIL LAYER IS SEPARATED FROM THE SULFONATING AGENT LAYER, AND THE ACID OIL LAYER IS NEUTRALIZED WITH A BASE, THE IMPROVEMENT WHICH COMPRISES NEUTRALIZING THE ACID OIL LAYER WITH AN ALKYLOLAMINE INCOMPLETELY MISCIBLE WITH THE NEUTRALIZED OIL AND HAVING A DENSITY GREATER THAN THE DENSITY OF THE NEUTRALIZED OIL, AND EMPLOYING A SUFFICIENT EXCESS OF ALKYLOLAMINE TO DISSOLVE THE RESULTING ALKYLOLAMINE SULFONIC ACID SALTS AND FORM A LIQUID ALKYLOLAMINE LAYER, AND SEPARATING THE LAYERS CONTAINING IN SOLUTION SUBSTANTIALLY ALL OF THE ALKYLOLAMINE SULFONIC ACID SALTS FORMED IN THE NEUTRALIZATION.