GB2055886A - Overbased magnesium phenates - Google Patents

Abstract

Highly basic magnesium phenates are prepared by a process in which a magnesium alkoxy-alkoxide mixed with alkoxy-alcohol and a non- volatile oil is hydrolysed in the presence of a hydrocarbyl-substituted phenol or metal phenate which may be sulphurised and the mixture then carbonated in which the quantity of water added for the hydrolysis is at least one mole for each gram atom of magnesium present in excess of that required to neutralize the phenol and the total amount of water in all the steps is from 2.5 to 4 moles for every gram atom of excess magnesium. Sulphonates also may be present. The product has an improved viscosity.

Description

SPECIFICATION Improvements in the production of overbased magnesium detergent additives This invention relates to a process for making detergent additives of high basicity suitable for use in lubricating oils.

There is an increasing need for detergent additives which have high basicity, and this invention is concerned with high basicity phenates commonly known as overbased phenates particularly overbased magnesium phenates. These compounds have been found to be particularly useful as additives in lubricating oils used in connection with high-sulphur fuels, such as marine diesel fuels, since the high basicity will neutralise the acids formed by the burning of the fuel.

The use of dispersed overbased alkaline earth metal compounds such as overbased alkaline earth metal phenates and sulphonates as additives in lubricating oils is known. It has been proposed to produce overbased alkaline earth metal carbonates by carbonating a mixture of a magnesium methanolate in the presence of a surfactant such as an alkyl phenol, that may be sulphurised, or an alkylaryl sulphonate. However, one problem associated with this process is that the magnesium methanolate is sparingly soluble in methanol. An alternative process using carbonated metal alkoxyethanol complexes as intermediates in the preparation of such overbased additives is known from United States patents 3,1 50,089,3,277,002,3,71 8,859, 3,746,698 and 3,775,160 where the dispersed alkaline earth metal is a carbonate.These patents all require the special formation of a carbonated complex of the general formula;

where M is an alkaline earth metal generally calcium or magnesium and x is between 0.5 and 1.5.

These earlier processes described above require the use of a volatile hydrocarbon solvent which, although not detrimental to product quality decreases the plant capacity and also requires removal and recovery and separation of the solvent at the end of the reaction.

A problem associated with the production of overbased metal compounds is that of the viscosity of both the reaction mixture and the final product itself. The overbased materials consist of an alkaline earth metal compound, generally a carbonate, dispersed in the alkaline earth metal salt of the dispersing agent; the amount of dispersed alkaline earth metal being known as the overbasing amount. Generally these overbased materials are used as detergents in lubricating oils to react with acid residues formed in the oil thus, the greater the basicity of the material the better since this allows smaller amounts of the materials to be used for a given effect in a certain lubricating oil. However, to increase basicity it is necessary to increase the dispersed alkaline earth metal content which tends to increase the viscosity of the reaction mixture leading to processing problems.This problem is particularly marked if the alkaline earth metal is introduced in the form of the carbonated complex previously described and in order to overcome this problem it may be necessary to increase the amount of solvent used thus reducing reactor capacity and requiring solvent recovery.

The present invention relates to an improvement in the process of Belgian Patent 842137 in which the viscosity of the magnesium phenate is reduced by careful control of the amount of water used during hydrolysis and that by doing so the time required for filtration may be reduced.

An additional benefit of this control is a reduction of the alkoxy-ethanol content of the product with a resulting increase in Flash Point.

In our Belgian Patent 8421 31 we described a process which overcomes the problems of the previous process and does not require the formation of the metal complex.

The present invention therefore provides a process for the preparation of a colloidal suspension in oil of magnesium carbonate comprising: (1) forming a reaction mixture comprising: (a) magnesium alkoxyalkoxide together with the alkoxyalcohol from which it is derived (b) one or more sulphurised phenols having one or more hydrocarbyl substituents, each substituent having not more than 60 carbon atoms or mixtures of such sulphurised phenols (c) a non volatile diluent oil (2) Adding at least one mole of water for every gram atom of magnesium present in excess of the amount of magnesium required to react with the sulphurised phenol and hydrolysing the magnesium alkoxyalkoxide.

(3) After hydrolysis introducing carbon dioxide into the reaction mixture whilst at a temperature not above 1000C.

Wherein the total amount of water added during stages 1, 2 and 3 is from 2.5 to 4 moles of water for every gram atom of magnesium in excess of the amount of magnesium required to react with the sulphurised phenol.

and (4) Removing volatiles from the reaction mixture.

Magnesium alkoxyalkoxide may be prepared in situ by reacting a metal oxide or hydroxide with an alkoxy-alcohol such as ethoxy-ethanol. Alternatively the alkoxyalkoxide itself may be used as the starting material in which case we prefer to use a solution of the alkoxyalkoxide in the ether alcohol which is preferably ethoxyethanol. The alkoxyalkoxide may conveniently be prepared by dissolving magnesium metal in the aikoxy-alcohol which is preferably ethoxyethanol since the magnesium ethoxyethoxide is readily soluble in ethoxyethanol.

The or each hydrocarbyl substituent in the hydrocarbyl-substituted phenol preferably has at least nine carbon atoms. Although the hydrocarbyl substituent can be an alkenyl, alkynyl, aryl, aralkyl or alkaryl group, it is preferred that it should be an alkyl group and especially one containing 9 to 15 carbon atoms since compounds in which the alkyl group contains less than 9 carbon atoms have limited solubility in oil. Examples of suitable compounds include nonyl, decyl, dodecyl or tetradecyl phenol.

Substituents which could be used include dodecenyl, tetradecenyl and aromatic substituents such as phenyl-ethyl and benzyl. Mixtures of alkyl-phenols include for example a mixture of nonyl-phenyl and dodecyl-phenol.

It is preferred that the phenol be substituted with just one hydrocarbyl group, usually in the para position, but if desired there may be.more than one hydrocarbyl substituent and mixtures of mon- and di- substituted phenols may be used. We prefer however to use phenols containing at least 90% by weight of monoalkyl-phenol.

The hydrocarbyl-substituted phenol may have othersubstituents e.g. halogens such as chlorine or bromine, nitro- or sulphonic acid groups.

We have also found that where the products are obtained from sulphurised alkylphenols the sulphur content of the starting material has a bearing on the viscosity of the product for a given TBN. For example, we prefer to use a 70% nonyl-phenol sulphide 30% oil mixture containing from 5.5% to 7.5% by weight of sulphur to obtain a lubricant additive of TBN in the range 230 to 260.

When the surfactant is a sulphurised bridged phenol it will generally be of the general formula:

where R and Rr may be the same or different and may represent one or more alkyl groups. Sulphurised alkyl-phenols may be obtained as mixtures of derivatives based on mono- and di-alkyl-phenols or predominantly mono-alkyl and the process of the present invention is equally applicable to both types of sulphurised alkyl-phenol although we find the improved products are generally obtained when using the predominantly mono-alkyl-phenol. These sulphurised phenols are obtained by reacting the substituted phenol with a sulphur chloride e.g. SCI2, such sulphurised phenols haivng one or more hydrocarbyl groups as substituents, each substituent having not more than 60 carbon atoms.The preferred sulphurised phenols are of the formula set out above and have one hydrocarbyl group containing for example 9 to 15 carbons, per benzene ring, preferably the hydrocarbyl group is in the para position with respect to the hydroxy group. There may be 1, 2, 3 or 4 sulphur atoms in the bridge linking the two phenyl groups, generally 1 to 2 generally sulphurised bridged phenols are mixtures and we prefer to use material containing an average from 1.5 to 1.7 sulphur atoms per pair of phenyl groups. We prefer that the sulphurised phenol contain from 7.5% to 11.0% by weight of sulphur.

Examples of sulphonates that may be used include the traditional detergents such as C18 to C30 especially benzene-sulphonic acids or sulphonates and other long chain alkyl-substituted benzenesulphonic acids, the so-called mahogany sulphonates obtained by extracting crude oil fractions with sulphuric acid may also be used.

The non-volatile diluent oil can be any diluent oil, such as paraffinic or naphthenic hydrocarbon oil, e.g. of mineral origin obtained by conventional refining. Alternatively synthetic lubricating oils, vegetable oils, animal oils or mixtures of such oils may be used. We find that oils which have viscosities of 1 5 to 30cS at 1 000F are very suitable. As a further alternative one could use a lubricating oil or the kind described later in the specification.

In practice it is desirable to decide the relative amounts of magnesium alkoxyalkoxide and surfactant according to the TBN (total base number) desired for the overbased additive. The amount of ether alcohol in which the alkoxyalkoxide is dissolved is determined to some extent by the nature of the alcohol, and the amount of oil is governed by the requirement for a workable reaction medium of suitable viscosity as well as its amount in the final product, the finished product typically being about 60 wt.% active matter.

In a typical reaction mixture for producing overbased phenates the amounts of reactants are as follows: Molar Proportion Hydrocarbyl-substituted sulphurised phenol 1 Magnesium alkoxyalkoxide 2-5 Oil - about 35-40 wt.% of total weight of finished product.

At least 1. mole of water for each metal atom of magnesium present in excess of the number of metal magnesium atoms required to react with the phenol to hydrolyse the magnesium alkoxyalkoxide.

According to this invention a total of from 2.5 to 5 moles of water are used, preferably 3 moles.

However it is not essential to add-all the water at the start and water may be added during carbonation which has the advantage of reducing the reaction time. The reaction mixture is preferably heated when sufficient water is present to ensure hydrolysis of the magnesium alkoxyalkoxide preferably it is at a temperature in the range 500C to 700C. We prefer to use a temperature of about 600C since if the temperature during hydrolysis is below about 500C the reaction mixture tends to become too viscous and can separate into two layers. If however the temperature rises above 700C the final product tends to be of high viscosity.The water may be added together with further alkoxy alcohol or alternatively the amount of free aikoxyalcohol present during hydrolysis may be according to our copending application which has been found to further minimise the viscosity of the final product.

Once hydrolysis is complete carbon dioxide is passed through the product during which the temperature of the reaction mixture increases to about 1 000C but we prefer to ensure that the temperature does not rise above 1 000C since this tends to produce a product of high viscosity.

If the required amount of water has not been added before carbonation a further amount of water may be added during carbonation.

After carbonation the volatiles consisting mainly of the ether-alcohol and a solvent if one is used are removed from the reaction mixture. This can be done by distillation and if necessary blowing with carbon dioxide or an inert gas such as nitrogen. It is preferable to keep the distillation temperature below 1 500C to avoid decomposition of the product which can result in unpleasant odours and if a relatively high boiling ether-alcohol has been used in the reaction whose removal is difficult without exceeding the decomposition temperature of the desired product, low pressure distillation may be used.

The preferred product is found to be a colloidal suspension in oil of basic magnesium compounds, mainly carbonate but including basic carbonate, oxide or hydroxide together with magnesium surfactants acting as dispersant and when the surfactant is phenol the average diameter of the colloidal particles generally is less than 60 A. Usually the finished product is 50~70% e.g. 60% active ingredients in oil. Its TBN can vary from 150 to 400, usually 200-300, e.g. 240-260. We find that the process of the present invention allows a higher TBN product (around 250) to be obtained consistently without viscosity problems and without the need for a second solvent, although the use of one is not excluded.

The major constituents of the preferred magnesium metal sulphurized phenates obtained by our process have the structure:

where M is magnesium, R is a hydrocarbyl group. The final product can be a mixture of such phenates where x and n vary for different molecules and minor amounts of compounds in which more than two aromatic rings are joined by sulphur links may be present however generally n is 1 and/or 2 and x is 1 or 2 and possibly 3 or 4 with an average value of 1.5 to 2.

A minor amount of a sulphonate or a sulphonic acid may be added to the reaction mixture and we find that in some instances the presence of the sulphonate gives the final product improved solubility in highly viscous oils and also reduces the tendency of the product to form a skin.

The overbased detergent additives prepared by the process of this invention are very suitable for use in lubricating oils where their detergent properties inhibit formation of undesirable sediments whilst the high TBN of the product neutralises acids which may originate from fuel combustion thus reducing engine corrosion. The lubricating oils can be any animal, vegetable or any of the traditional mineral oils for example petroleum oil to SAE 30, 40 or 50 lubricating oil grades, castor oil, fish oils or oxidised mineral oil.

Alternatively the lubricating oil can be a synthetic ester lubricating oil and these include diesters such as di-octyl adipate, di-octyi sebacate, didecyl azelate, tridecyl adipate, didecyl succinate, didecyl glutarate and mixtures thereof. Alternatively the synthetic ester can be a polyester such as that prepared by reacting polyhydric alcohols such as trimethylolpropane and pentaerythritol with monocarboxylic acids such as butyric acid to give the corresponding tri- and tetra-esters. Also complex esters may be used, such as those formed by esterification reactions between a di-carboxylic acid, a glycol and an alcohol or a dicarboxylic acid.

The overbased detergent is generally added to the lubricating oil as a concentrate and we find that between 0.01% and 30% by weight, preferably between 0.1% and 5% by weight of a concentrate consisting of 60 wt% magnesium carbonate plus magnesium suiphurised-phenate and 40 wt.% oil is particularly useful.

The final lubricating oil composition may if desired contain other additives e.g. a Viscosity Index Improver such as an ethylene-propylene copolymer, an overbased calcium sulphonate or a dispersant such as polyisobutylene succinimide.

The invention is illustrated by the following Examples.

EXAMPLE 1 The following mixtures were prepared.~ A Oll/Suffactants Sulphurised nonyl phenol 2620 grams Sulphonic Acid 180 grams Diluent Oil 1800 grams The sulphurised nonyl phenol had a hydroxyl number of 172 mg. KOH/g. and contained 7.7% sulfur and 25% diluent oil. It has 98% monononyl components. The sulphonic acid was a C-24 alkylbenzene sulphonic acid with an equivalent of 550. The alkyl side chains of both surfactants were derived from propylene. The paraffinic diluent oil had a 5cS viscosity at 2100F.

B Water-Ethoxyethanol mixture 500 g. water were diluted to 1 litre with ethoxyethanol. As the mixing is exothermic, the final volume adjustment was made when the initial mixture had cooled.

To a solution of 16.5 g. magnesium in 165 g. ethoxyethanol were added 230 g. of mixture A. The product was stirred at 600C and the required amount of water or mixture B was run in as detailed in Table I. One equivalent of water to 1 gram atom overbasing magnesium is represented by 8.1 g. water or 16.5 ml mixture B. The hydrolysed product was saturated with carbon dioxide while allowing the temperature to rise from 600 to 1 000C over two hours. When CO2 was no longer absorbed the product was stripped in vacuo up to 1 500C pot temperature, and its final weight was adjusted to 300 9. by adding diluent oil, before filtering using 1.5 g. filter aid. The total base numbers were 250 l 2 mg KOH/g, The results, in Table I, show that increasing hydrolysis water from 1-3 moles reduces product viscosity, pour point and ethoxyethanol content.

TABLE 1 Mols H20 Water Addition Relative Viscosity OF % Ethoxy** Per Atom of Time Filtration cS at Pour Ethanol Excess Mg (Mins) Time 2100F Point Content 1 15* 900 6271 125 5.2 1.25 20* 450 3427 95 4.2 1.5 25* 150 1069 90 3.4 1.75 30* 133 374 65 2.8 2.0 33* 100 299 55 2.3 2.5 40* 65 166 45 2.4 2.5 5 325 H 214 40 2.0 2.5 120 150 204 40 2.2 3.0 50* 50 138 35 2.0 3.0 10 125H 158 40 2.1 4.0 65* 60 H 127 40 1.7 4.0 60 230 H 189 45 1.2 * As 50/50 mixture with ethoxyethanol, undiluted water on others ** Determined by gas chromatography Products marked H, where either more than 3 mois of water were added, or water had been added rapidly, developed haze in a heavy paraffinic base oil, showing the limiting conditions of hydrolysis.

EXAMPLE 2 Using the process of Example 1 hydrolysis and carbonation were effected at 1 000C, with the following results:~ TABLE 2 Mols H20 Water Addition Viscosity Pour Per Atom of Time cS at Point Excess Mg (Mins) 2100F OF 2 33 428 60 3 50 104 25 The first of these products has a higher viscosity than the analogons run in Table 1 , which was 299. The second has a low viscosity, but produced a haze in paraffinic oils.

CLAIMS 1. A process comprising the following steps: (i) forming a reaction mixture comprising: (a) magnesium alkoxyalkoxide together with the alkoxyalcohol (b) a surfactant which is one or more hydrocarbyl-substituted phenols or metal phenates wherein the or each hydrocarbyl group contains no more than 60 carbon atoms or one or more sulphurised phenols having one or more hydrocarbyl group substituents each substituent containing no more than 60 carbon atoms or mixtures of said surfactants.

(c) a non-volatile diluent oil (ii) adding at least one mole of water for every gram atom of the magnesium present in excess of the amount of magnesium required to neutralise the surfactant and hydrolysing the magnesium alkoxyalkoxide.

Wherein the total amount of water added during stages (i) (ii) and (iii) is from 2.5 to 4 moles of water for every gram atom of magnesium in excess of the amount of magnesium required to react with the sulphurised phenol.

(iii) introducing carbon dioxide into the reaction mixture (iv) removing volatiles from the reaction mixture.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   amount of magnesium required to neutralise the surfactant and hydrolysing the magnesium alkoxyalkoxide.

   Wherein the total amount of water added during stages (i) (ii) and (iii) is from
2. 2.5 to 4 moles of water for every gram atom of magnesium in excess of the amount of magnesium required to react with the sulphurised phenol.

   (iii) introducing carbon dioxide into the reaction mixture (iv) removing volatiles from the reaction mixture.