US2880173A - Inorganic salt removal from oil-soluble sulfonates - Google Patents

Description

March 31, 1959 VOL. SEDIMENT J.. M. HONEYCUTT 2,880,173

INORGANIC SALT REMOVAL FROM OIL-SOLUBLE SULFONATES Filed April 10, 1957 SEDIMENT VS. ACETONE FOR VARIOUS SULFONATE 0.5 o-eam m I I% s m LEGEND SULFONATE' COAGULANT MIXTURE 50% 50% 30% 70% 75% |s% 82% lo% 90% -TWO PHASES BEYOND THESE P 2o so To ACETONE IN COAGULANT MIXTURE Jerald M. Honeycufl Inventor United States Patent O INORGANIC SALT REMOVAL FROM OIL-SOLUBLE SULFONATES Jerald M. Honeycutt, Bellaire, Tex., assignor to Esso Research and Engineering Company, a corporation of Delaware Application April 10, 1957, Serial No. 652,059

'8 Claims. (Cl. 252-33) This invention relates to the removal of inorganic salts from oil-soluble sulfonate detergents. More specifically, this invention pertains to the removal of inorganic salts such as sodium chloride from alkaline earth metal, especially oil-soluble calcium and barium soaps of sulfonic acids.

Oil-soluble alkaline earth metal sulfonates are today conventionally employed as detergent additives for lubricating oils and especially for motor oils. While there are many other uses for these sulfonates, such as emulsifiers and as thickeners in greases, this invention will find its greatest applicability in the treatment of motor oil detergent additives.

The sulfonates with which this invention is mainly concerned are the oil-soluble soaps of alkaryl sulfonic acids, such as mahogany acids produced during the treatment of lubricating oil distillates with concentrated to fuming sulfuric acid and synthetic sulfonates produced by the sulfonation of certain hydrocarbons. These sulfonic acids may be represented by the following structural formula:

where R is one or more alkyl, alkaryl or aralkyl groups and the nucleus may be a single or condensed aromatic ring or a partially hydrogenated ring. The alkyl radicals will generally contain a total of from 17 to 36 carbon atoms per sulfonic molecule.

While the sulfonic acids synthetically produced are generally mixtures of compounds having various molecular weights, typical of these acids are dinonyl naphthalene sulfonic acid, didodecyl benzene sulfonic acid, and mixtures of monoand di-tetrapropyl benzene sulfonic acids. The molecular weight of the sulfonic acids may vary between 350 to 600 and preferably will average about 400 to 560. Occasionally slightly lower molecular weight compounds are employed together with higher molecular weight sulfonic acids. Apparently the characteristics of the higher molecular weight acids are sufiicient to solubilize the lower molecular weight compounds which normally by themselves would not have the necessary degree of oil solubility. In the formation of these acids from petroleum fractions the lower molecular weight compounds which are water-soluble are usually extracted from the acid treated oil by the addition of water. The more desirable high molecular weight oil-soluble acids are normally recovered as sodium or alkali metal soaps by neutralization with sodium carbonate or other alkali metal base followed by extraction with aqueous alcohol. Sodium carbonate, sulfate, sulfite and the like are first removed and the remaining sodium sulfonate is then generally diluted with a light lubricating oil, e.g. a parafiinic or napthenic oil having a viscosity between 40 and 60 S.U.S., to yield generally about a 30 to 70 wt. percent sodium sulfonate concentrate. The alkyl aryl sulfonic ice acids prepared by sulfonation of the alkyl benzene or the like are converted to the alkali metal salt in a similar manner.

To prepare the alkaline earth metal salts these sodium sulfonates are reacted with calcium or other alkaline earth metal chloride to effect a double decomposition type reaction. While other methods for the preparation of the calcium sulfonate are known the above methods have been found to be most attractive from an economic standpoint.

One of the primary difliculties in the preparation of calcium sulfonates by the above described processes is that sodium chloride, sodium sulfate or other inorganic salt is held in the alkaline earth metal sulfonate solution apparently in the form of a relatively stable colloidal suspension. Water washing and other conventional techniques for the removal of water-soluble salts were tried but were found ineffective for removing substantial portions of the salt. The salt is undesirable because it forms hazy solutions when the sulfonate is blended with mineral oils and even causes precipitates to form when the oils contain other detergents and detergent inhibitors.

It has now been found that a calcium sulfonate con- I taining inorganic salt may be treated with a composition comprising a specific coagulant such as a low molecular weight ketone, e.g. acetone, and methyl ethyl ketone, or isopropyl alcohol or the like in an organic solubilizer comprising petroleum naphtha, petroleum ether, narrow cut naphthas, hexane, heptane, octane and the like, to effectively remove the inorganic salt contaminants therefrom. Of the above coagulants acetone has been found to give the best results. It has been further found that the particular treatment employed is so effective and reliable when controlled that it is suitable for use as an analytical or control test for product purity. In general the process of this invention comprises treatment of the inorganic salt contaminated calcium sulfonate with cer tain mixtures of coagulant in solubilizer. From the thus treated sulfonate the sediment may be removed by any conventional means, especially preferred being centrifugation, filtration, settling and decanting and the like. While the acetone to solubilizer ratio will vary with the amount of calcium sulfonate employed, to eflect relatively complete salt removal homogeneity in the system must be maintained since this desalting process fails if the system becomes two-phased. On the other hand, if too little coagulant is added a haze is formed and the sediment or precipitate which occurs is in a fluid rather than solid form, indicating that some of the concentrate mixture is entrained in the salt. Thus if the sediment flows as a fluid the amount of salt precipitated cannot be determined accurately. Further in precipitating the salt as a fluid some of the organic product is lost, thus making the process less economically attractive for commercial scale operations.

For ease of discussion the term sulfonate concentration as employed herein means the weight percent of alkaline earth sulfonate in the sulfonate concentrate. The term coagulant refers to acetone, methyl ethyl ketone, isopropyl alcohol and the like, and coagulant mixture means the coagulant plus the solubilizer.

The sulfonate concentration is not critical and may vary from 30 to 70%. The criticality relates to the ratio of sulfonate to the coagulant mixture and to the ratio of coagulant to solubilizer.

Several tests were carried out employing a 30 wt. percent concentrate calcium sulfonate in a solvent refined and clay contacted lubricating naphthenic oil having a viscosity of about 40 S.U.S. The sulfonate was prepared by sulfonating a polypropyl benzene fraction boiling in the range of about 650 to 800 F., forming the sodium soap of the sulfonic acids and then converting the sodium sulfonate to the calcium sulfonate by double decomposition with calcium chloride. The sulfonic acids had an average molecular weight of about 415. Acetone was employed as the coagulant and hexane as the solubilizer. The results are shown in the following table and depicted in graph form in the drawing.

Table 2. A method of removing entrapped inorganic alkali metal salt contaminants from an oil-soluble alkaline earth metal sulfonate concentrate, previously prepared from alkali metal sulfonate, which comprises admixing therewith a composition comprising a low molecular weight ketone and a hydrocarbon solubilizer in an amount sufii- Vol. Percent of Vol. Per- Sulfonate cent Coneen- Coagulant trate 1 Mixture coagulant Mixture Percent Dry Soap cent Acecent Solutone bilizer Vol. Per- VoLPercent Sedi- State of Sediment l 7.5 75 l i Flows.

Solid.

Flows.

0. Solid.

Flows.

D Solid.

Flows. Do. Do. Solid.

Flows. Do.

Solid.

Flows. D Do.

1 Containing wt. percent sulfonate. 3 Based on coagulant mixture 3 Initial sediment after centrifuging/sediment obtained after a 24-hour period.

In the above tests the defined quantities of coagulant mixture were admixed with the defined quantities of sulfonate concentrate at room temperature. The mixtures were then immediately centrifuged and recentrifuged after a 24 hour period.

Those tests wherein the sediment occurred in fluid form are inoperative for the purposes of this invention since the amount of salt obtained can not be determined from the volume of sediment. Also substantial loss of detergent product would be realized. Where two phases formed substantially no sedimentation occurred.

The above tests show that high volume ratios of coagulant mixture to the 30% sulfonate concentrate in the range of about 9/1 to 2/1 are necessary for the removal of substantial amounts of salt. Within these ranges, however, it is also necessary to maintain specific ratios of coagulant to solubilizer ranging from 1:1 for the larger volumes of sulfonate concentrate to about 3:1 for the smaller volumes of sulfonate concentrate, e.g. 10 vol. percent. More accurately these ratios can be expressed as based on dry soap, i.e. the volume percent of sulfonate in the sulfonate concentrate. Thus the ratio of coagulant mixture to dry soap would be from about 30/1 to 7/1, the ratio of coagulant to solubilizer being as noted above.

What is claimed is:

1. A method of removing entrapped inorganic alkali metal salt contaminants from an oil-soluble alkaline earth metal sulfonate, previously prepared from alkali metal sulfonate, which comprises admixing therewith a composition comprising a coagulant selected from a group consisting of alcohols and ketones and a hydrocarbon solubilizer in an amount sufiicient to form a relatively clear solution and insufficient to result in two liquid phases, precipitating in the form of a solid sediment said salt contaminants and removing said contaminants from said solution of the sulfonate.

cient to form a relatively clear solution and insuflicient to result in two liquid phases, precipitating in the form of a solidsediment said salt contaminants and removing said contaminants from said solution of the sulfonate concentrate.

3. A method of removing entrapped inorganic sodium salts from an oil-soluble calcium sulfonate, previously prepared from alkali metal sulfonate, contaminated therewith, which comprises adding to said contaminated calcium sulfonate acetone and a hydrocarbon solubilizer in an amount sufficient to form a relatively clear solution and insuificient to result in two liquid phases, contrifuging the total mixture to precipitate in the form of a solid sediment said salt contaminants and removing said contaminants from said solution of the calcium sulfonate.

4. A process for the removal of entrapped inorganic sodium salt contaminants from an oil-soluble calcium sulfonate concentrate, previously prepared from alkali metal sulfonate, which comprises admixing with said concentrate a coagulant hydrocarbon solubilizer mixture, wherein said coagulant is selected from a group consisting of alcohols and ketones in the volume ratio of 30/1 to 7/1 of said mixture to calcium sulfonate, said mixture having a solubilizer to coagulant volume ratio of about 1/1 to 3/1 precipitating in the form of a solid sediment said salt contaminants and removing said contaminants from said concentrate.

5. A method in accordance with claim 4 wherein said coagulant is acetone.

6. A method in accordance with claim 4 wherein said coagulant is methyl ethyl ketone.

7. A method in accordance with claim 4 wherein said coagulant is isopropyl alcohol.

8. A process for the removal of entrapped sodium chloride from calcium sulfonate in a lubricating oil, said sulfonate having been previously prepared from an alkali metal sulfonate, which comprises admixing therewith References Cited in the file of this patent acetone as a coagulant and hexane as a solubilizer in an amount suificient to form a relatively clear solution and UNITFD STATES PATENTS insufiicient to result in two liquid phases, precipitating in 2,373,793 Susle Apr. 17, 1945 the form of solid sediment the sodium chloride and re- 5 2,713,035 Clarke July 12, 1955 moving the sediment from said solution. 2,738,326 Alldfirson e a1 1955

Claims (1)

1. A METHOD OF REMOVING ENTRAPPED INORGANIC ALKALI METAL SALT CONTAMINANTS FROM AN OIL-SOLUBLE ALKALINE EARTH METAL SULFONATE, PREVIOUSLY PREPARED FROM ALKALI METAL SULFONATE, WHICH COMPRISES ADMIXING THEREWITH A COMPOSITION COMPRISING A COAGULANT SELECTED FROM A GROUP CONSITING OF ALCOHOLS AND KETONES AND HYDROCARBON SOLUBILIZER IN AN AMOUNT SUFFICIENT TO FORM A RELATIVELY CLEAR SOLUTION AND INSUFFICIENT TO RESULT IN TWO LIQUID PHASES, PRECIPITATING IN THE FORM OF A SOLID SEDIMENT SAID SALT CONTAMINANTS AND REMOVING SAID CONTAMINANTS FROM SAID SOLUTION OF THE SULFONATE.

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