GB2114993A

GB2114993A - Production of "overbased" sulphonates in the presence of 1,3- dioxolane

Info

Publication number: GB2114993A
Application number: GB08135085A
Authority: GB
Inventors: Robert Laurent; Robert Tirtiaux; Marcel Prillieux
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1981-11-20
Filing date: 1981-11-20
Publication date: 1983-09-01

Abstract

1,3-Dioxolane is added as a reaction promoter in the production of basic alkaline earth metal sulphonates, wherein a mixture of an oil-soluble sulphonate or sulphonic acid, a hydrocarbon solvent, water and the 1,3-dioxolane is treated with a stoichiometric excess of an alkaline earth metal compound and the mixture is then carbonated.

Description

SPECIFICATION Preparation of basic alkaline earth metal sulphonates The present invention relates to the production of basic alkaline earth metal sulphonates especially basic calcium and magnesium sulphonates. The basic alkaline earth metal sulphonates produced by the present invention are particularly useful as additives for lubricating oils and the present invention also provides lubricating oils containing these basic alkaline earth metal sulphonates.

The term basic alkaline earth metal sulphonate is used to describe materials containing a stoichiometric excess of the metal compared to that required to neutralize the sulphonic acid.

Basic alkaline earth metal sulphonates are well known as is their use as additives for lubricants.

Barium, Calcium and Magnesium Sulphonates, have been used and many methods have been proposed for their production the preferred techniques being the carbonation of an oil solution of a reaction mixture containing a sulphonic acid or sulphonate, an excess of a compound of the alkaline earth metal generally the alkoxide, oxide or hydroxide, usually a hydrocarbon solvent in the presence of reaction promoter systems often comprising an alcohol and/or water sometimes together with a copromoter.

It is important that where the highly basic sulphonates are to be used as additives for lubricating oils they be not too viscous, are free of sediment, are soluble in the oil and do not cause the lubricating oil to be hazy. It is also preferred that they have as high a Total Base Number (TBN), being the number of milligrams of KOH equivalent to 1 gram of the product when titrated with strong acid,-since this results in the most economic use of the metal. It is also important that the compound perform well as an additive in an oil in use in an engine.

We have now discovered a new promoter system which is effective either as sole promoter or together with other promoters in the production of a highly basic sulphonates.

The present invention therefore provides a process for the production of basic alkaline earth metal sulphonates comprising forming a mixture of: (a) an oil soluble sulphonate or sulphonic acid (b) a hydrocarbon solvent (c) water (d) 1-3 dioxolane.

Adding a stoichiometric excess of an alkaline earth metal compound above that required to react with (a) where (a) is a sulphonic acid and then carbonating the mixture.

The sulphonate acid used in the process of this invention may be natural or synthetic, the synthetic alkylaryl sulphonates and sulphonic acids being preferred.

The basic alkaline earth metal sulphonates with which this invention is concerned consist of an oil solution of the alkaline earth metal sulphonate which itself acts as a surfactant to disperse the excess alkaline earth metal which is present as colloidal alkaline earth metal derivatives such as carbonate, oxide and hydroxide. Thus it is important that the sulphonate or sulphonic acid be oil soluble.

The excess of the alkaline earth metal compound provides the basicity of the compound and the amount of alkaline earth metal that should be used depends upon its quality and the desired TBN of the product. The excess may be achieved by starting with the sulphonic acid and adding an amount necessary to give the required excess after reaction with the acid or by starting with the alkaline earth metal sulphonate and then adding the required excess. We prefer to use from 1 to 45 more preferably 1 to 25 equivalents of alkaline earth metal for each equivalent of sulphonic acid present in the reaction mixture, this would include alkaline earth metal present if a sulphonate is used as the starting material in which case the equivalents of sulphonic acid from which the sulphonate is derived would be number of equivalents of acid.

The hydrocarbon solvent is used in an amount sufficient to keep the reaction mixture fluid during carbonation and may be aliphatic such as hexane or heptane or aromatic such as benzene, toluene or xylene, toluene being the preferred solvent. We find that 2 to 6 parts, preferably 3 to 5 parts by weight of hydrocarbon solvent per part of alkaline earth metal compound is particularly suitable, the quantity used depends upon the nature of the metal. We have found that the dioxalane and the water should be added before the excess of the alkaline earth metal compound since otherwise carbonation does not occur.

The amount of water that should be added will depend upon the nature of the alkaline earth metal compound and the amount of excess alkaline earth metal compound present. Where magnesium oxide is used we prefer to use from 0 to 2 more preferably 0.5 to 2 parts by weight of water based on the total amount of magnesium oxide. Where calcium oxide or hydroxide is used we prefer to use from 2-20 wt.% preferably 5 to 1 5 wt.% of water used on the weight of the calcium hydroxide or oxide.

We have also found that the presence of another oxygen containing organic compound in addition to the dioxalane in the reaction mixture improves both the product and the reaction enhancing the formation of the basic colloidal alkaline earth metal compound. Examples of suitable oxygen containing compounds include alcohols, mono-ketones and aldehydes and where water is added to the reaction mixture we find that where the oxygen containing organic compound is an alcohol it should contain less than 4 carbon atoms, preferably less than 3 carbon atoms the preferred compounds being alcohols such as ethanol and methanol, methanol being preferred. If it is a ketone we find it should contain from 3 to 6 carbon atoms acetone being preferred.

As with the other ingredients the amount of the oxygen containing organic compound that should be used depends upon the amounts of the other ingredients, especially the amount of the excess of the alkaline earth metal compound, we prefer to use from 0 to 4 more preferably 0 to 2 parts more preferably 0.5 to 2 by weight of the oxygen containing organic compound based on 10 the total weight of the alkaline earth metal compound.

The addition of an oil soluble alkyl phenol to the reaction mixture is also useful in that it can give rise to products of improved viscosity especially alkaline earth metal is magnesium. The alkyl phenols may be simple phenols, such as nonyl phenol, decyl and dedecyl phenol bridged phenols of the general formula:

Where R is an alkyl group containing at least 8 carbon atoms, X is sulphur or (CH2) and n is 1 or 2. The amount of the phenol that should be incorporated depends upon the nature of the other ingredients, but in our preferred process for the production of basic magnesium sulphonates from magnesium oxide, we prefer to use from 0 to 1 parts by weight based on the total weight of magnesium oxide present in the reaction mixture.

It should be appreciated that within the ranges of amounts specified above the preferred amounts of materials to be used will depend upon the relative proportions of all the various components in the reaction mixture.

The Carbonate content of the final product can be controlled by stopping carbonation of the reaction mixture at any particular moment alternatively carbonation may be continued until there is no further significant uptake of carbon dioxide. Where the alkaline earth metal is Calcium we prefer to carbonate at a temperature in the range 15 to 700C preferably 250C-500C because if higher temperatures are used the product is difficult to filter. Where magnesium is used we prefer to carry out the carbonation at the reflux temperature which depends upon the components of the reaction mixture and the pressure.Generally carbonation is effected at a temperature in the range 25 0--2000 C preferably 50-1 500 C. The use of dioxolane as reaction promoter is equally applicable to processes involving more than one carbonation stage and in which various components of the reaction mixture are added or removed between carbonation stages. We have found that staged addition of the alkaline earth metal compound and water can lead to further increase in the basicity of the product.

After carbonation the product is stripped to remove the volatile materials such as alcohol, water, dioxolane and solvent and the remaining solids in the reaction mixture are removed preferably by filtration or centrifugation. The product may be stripped first and then filtered or vice versa. Further carbon dioxide may be passed through the reaction mixture during stripping. The final product is thus obtained as an oil solution of the basic alkaline earth metal sulphonate.

The basic alkaline earth metal sulphonates obtained from the process of the present invention are useful additives for lubricants where there basicity neutralises acids formed by the operation of the engine and the surfactant part of the compound helps disperse unwanted residues in the oil to reduce the formation of harmful deposits. When the alkaline earth metal is magnesium the sulphonate also enhances the antirust properties of the lubricant. The amount of the sulphonate that should be included in the oil depends upon the type of oil concerned and its application. For crankcase oils, we prefer to use from 0.01% to 5 wt.% based on the weight of the oil.

The basic alkaline earth metal sulphonates of this invention may be used in a wide variety of lubricating oils. The oils may be natural or synthetic or mixtures thereof and the main uses are in crankcase lubricants, two cycle and aviation lubricants.

The sulphonates may be used in combination with other conventional additives for lubricating oils such as for example other highly basic metal additives particularly other alkaline earth metal sulphonates and alkaline earth metal phenates and sulphurised phenates. In addition the oils may contain ashless dispersants such as the products obtained by the reaction of polyamines or polyols with polyisobutylene succinic anhydride and anti-oxidants, antiwear agents and anti corrosion additives such as the well known zinc dialkyldithiophosphates. The oils may also contain viscosity index modifiers such as the well known olefine copolymers.

Sulphonic acid and toluene are charged to a 200 ml reactor fitted with a stirrer and a reflux condenser. The dioxolane is added and the mixture stirred, the calcium hydroxide added together with the water. The reaction mixture is cooled to 300C and carbonated at 300C until the stoichiometric amount of carbon dioxide has been introduced. The diluent oil is then added and the product stripped at 1 450C under reduced pressure. The product is then filtered using Clarcel DCB as a filter aid.

Example 1 In this Example the following ingredients were used; grams C24 Alkyl Benzene Sulphonic acid 150 Paraffinic Diluent oil 120 viscosity 150 SSU at 1000C (SB 150) 1~3 310 Dioxolane 140 Water 13 C(OH)2 1 st charge 93 2nd charge CO2 48 The mixture was carbonated for four hours at a temperature from 25 to 30 C.

The properties of the product were as follows Soap, mass % 28 TBN mg KOH/g 290 Hydroxyl Base No. mg KOH/g 11 Appearance Clear Viscosity at 1 000C (cSt) 60 Solubility 5 mass% in a Paraffinic lubricating oil base stock of viscosity 600 S.S.U. at 1000C (SB 600) Clear Example 2 The process of Example 1 was repeated except that the water was omitted. It was not possible to obtain a product.

Example 3 The process of Example 1 was repeated replacing the 1-3 Dioxolane with Dioxane and no reaction took place.

Example 4 In this Example the following ingredients were used Charges in grams grams C24 Alkyl Benzene Sulphuric Acid 290 Paraffinic Diluent oil Viscosity 150 at 1 000C (SB 150) 350 Toluene 600 1~3Dioxolane 275 Water 25 Ca(OH)2 1 sot charge 180 CO2 164 The mixture has carbonated for three hours first at 300C and then for a further four hours at 500 C.

The properties of the product were as follows TBN Soap, mass % 20 mg KOH/g 410 Hydroxyl Base No. mg KOH/g 5 Appearance Viscosity at 1 000C (cSt) Clear Solubility 5 mass% in paraffinic lubricating oil base stock of viscosity 600 95 SSU at 1000C (SB 600) Clear

Claims

1. A process for the production of basic alkaline earth metal sulphonates comprising forming a mixture of: (a) an oil soluble sulphonate of sulphuric acid (b) a hydrocarbon solvent (c) water (d) 1-3 dioxolane Adding a stoichiometric excess of an alkaline earth metal compound above that required to react with (a) where (a) is a sulphonic acid and then carbonating the mixture.

2. A basic alkaline earth metal sulphonate whenever prepared by the process of claim 1.