FR2616441A1 - Process for the preparation of superbase additives and compositions containing the said additives - Google Patents

Abstract

Process for the preparation of very fluid and stable superbase additives of high basicity by bringing an alkali or alkaline-earth metal derivative and at least one surfactant into contact with carbon dioxide in a diluent oil and a hydrocarbon solvent, in the presence of an oxygenated promoter and of a nitrogenous promoter, characterised in that the temperature at the beginning of the carbonation is allowed to change up to a value of between 25 and 60 DEG C and the temperature is then maintained at this value during the optimum carbonisation period, determined by measuring the alkalinity value. The additives according to the invention are employed in lubricating oils and fuel oils.

Description

 The present invention relates to a process for the synthesis of overbased additives for lubricating oils, with high basicity, very fluid and stable.

 Overbased additives are alkali or alkaline earth metal salts of organic acids, overbased by carbonation with carbon dioxide. The term overbased is used to designate the excess of alkali or alkaline earth metal over the stoichiometric amount necessary to neutralize the organic acid used.

 These additives are in the form of a colloidal dispersion of alkali or alkaline earth metal carbonate in oil or in a hydrocarbon solvent. The colloidal dispersion is stabilized by the presence of salts of organic acids, with a surfactant effect.

The basicity of these overbased products is characterized by their alkaline value (VA) expressed in mg of
KOH per gram of product. It is determined by titration using a strong acid according to standard ASTM D-2896.

 Overbased additives have been used in lubricating oils for many years. Due to the presence of organic acid salts, these additives act as detergents and dispersants in the lubricant, which improves engine cleanliness in organs such as pistons and liners.

 Overbased additives also have the property of combating the acidity caused in engines by the combustion of organic sulfur derivatives contained in fuels as well as by oxidation of the components of oils during engine operation.

 The use of increasingly sulfur-containing fuels, in particular for fuel oil or heavy fuel oil engines associated with increasingly severe operating conditions makes it essential to use lubricating compositions capable of neutralizing large quantities of acids formed during the -combustion.

 Overbased additives also find applications as anti-corrosion agents in burner boilers using fuel oil because they preferentially complex the oxides and vanadium compounds present in the fuel. The compound that normally deposits on the walls of ovens during combustion is responsible for the oxidation and corrosion of ovens. Alkaline earth metals and especially magnesium form high melting eutectics with vanadium oxides which do not adhere to the walls of the furnace tubes.

 For reasons of economy, the overbased additives must have high alkaline values, preferably greater than 300 mg of KOH / g.

 Their viscosity must be low enough to facilitate their handling when formulating lubricants or additives for fuels.

 Finally, they must have a translucent appearance with no cloudiness or traces of deposit even during prolonged storage.

 There are many methods of preparing overbased additives.

 European patent application 5337 and American patent 4 617 135 describe methods which consist in carbonating a mixture of alkylarylsulfonate and magnesium oxide in a diluent oil and xylene, in the presence of methanol, water and ammonia.

 European patent applications 25,325 and 164,286, as well as American patents 2,074,723 and 4,137,184, describe the carbonation of a mixture of sulfonic acid and calcium oxide or hydroxide. In these patents the molar ratio of the alkali or alkaline earth metal derivative to the sulfonic acid varies from 0.75 and 18.

 British patents 2,055,885 and 2,114,993 and 2,037,310, European patent application 13,807, French patent 2,528,224 and American patents 2,026,567, 2,074,723 and 4,347,147 relate to the use of different oxygenated and nitrogenous promoters.

 US Patents 2,026,567 and 3,929,216 provide a method of carbonation of the alkaline earth metal derivative without the addition of water.

 US Patent 4,541,938 claims a process of continuously removing the water produced by carbonation, while in US Patent 3,878,116 the additive is stabilized after carbonation by treatment with water. In this same patent, the methanol is removed by distillation at a temperature above 1040C.

 In all these patents carbonation is carried out at temperatures between 300C and the reflux temperature of the mixture of solvents.

 During the use of these additives in dilution in a hydrocarbon base, alone or in mixture with antiwear, anticorrosion additives ... we often observe the appearance of a disorder followed over time by a gradual decantation. It is a phenomenon of flocculation or destabilization of the alkali or alkaline earth metal carbonate, which is detrimental to the performance of the additive.

 In French patent application 85 14 664 we have described a process which makes it possible to obtain additives with high basicity and low viscosity.

 We have now found an improved process which makes it possible to obtain additives with very high basicity and low viscosity and whose colloidal stability is impeccable.

 This process consists in bringing an alkali or alkaline earth metal derivative and at least one surfactant into contact with carbon dioxide in a diluent oil and a hydrocarbon solvent in the presence of an oxygenated promoter and a nitrogenous promoter, characterized in this is allowed to change the temperature at the start of carbonation to a value between 25 and 600C and preferably between 30 and 500C and then the temperature is maintained at this value for the optimal duration of carbonation.

 The alkaline value of the mixture maintained between 25 and 500C increases at the start of the reaction, reaches a plateau and then drops rapidly. The optimal duration of carbonation is before this fall. It is determined experimentally, by assaying the VA, as described above (French patent application 85 14 664).

 The improvement consists in replacing the natural stage of the exothermic reaction with the temperature range of between 25 and 600C and preferably 30 and 500C.

 The alkali or alkaline earth metal derivatives are generally oxides or hydroxides of sodium, potassium, barium, magnesium and calcium or mixtures thereof. The most commonly used oxides and hydroxides of calcium and magnesium.

 We call surfactant a molecule composed of a lipophilic hydrocarbon part and a hydrophilic part. The hydrophilic part can be a sulfonic acid, carboxylic acid, phenolic, phosphonic or thiophosphonic group. These compounds are used in the form of their metal salts. On the other hand, surfactants based on nitrogenous compounds, such as amines, amides, imines and imides do not require the presence of metal atoms.

 Among the surfactants most commonly used are sulfonic acids of petroleum or synthetic origin.

 Sulfonic acids of petroleum origin are obtained by sulfonation of petroleum distillates. The average molecular weight of petroleum sulfonic acids is generally greater than 320.

 Synthetic sulfonic acids are particularly appreciated in the context of the invention. These are acids obtained by sulfonation of olefins or also alkylaromatic compounds. Olefins are used whose number of carbon atoms is greater than or equal to 12.

The alkyl chains of the alkyl aromatics contain at least eight carbon atoms. The structure of the chains is linear or branched.

In general there are several alkyl chains on the aromatic nucleus. Benzene, toluene, xylene or naphthalene alkylated by cuts of C13-C14 or C 16-C18 alphaolefins, by chlorinated paraffins or by Cg or Cl2 propylene oligomers are commonly used. Most commonly used didodecylbenzene sulfonic acid which we will refer to as C24-benzene sulfonic acid.

 The role of the diluent oil is to allow easy handling at room temperature. Among these dilution oils, mention may be made of paraffinic oils of the 75, 100 or 150 Neutral type or else of naphthenic oils of the 100 Pale Solvent type.

 Hydrocarbon solvents either have a C6 to C8 aliphatic structure or an aromatic structure. The most commonly used solvents are heptane, isooctane, nonane, toluene, xylene and chlorinated aromatic compounds or their mixtures.

 the oxygenated promoters are mainly aliphatic alcohols, generally from C1 to C5, such as methanol, ethanol, glycol or their mixtures.

 The nitrogenous promoters are inter alia ammonia, ammonium chloride, ammonium carbonate or ethylenediamine.

 According to a preferred implementation of the invention, about 100 parts by weight of a mixture consisting of a diluent oil and a hydrocarbon solvent, about 5 to 45 parts by weight of a sulfonic acid, are introduced into a reactor. alkaline earth metal oxide or hydroxide and an alcohol.

 The molar ratio of the alkaline earth metal derivative to the sulfonic acid must be between 6 and 25 and preferably between 6.2 and 20.

 About 0.2 to 30 moles of oxygenated promoter are used per mole of sulfonic acid.

 After addition of the nitrogenous promoter, the mixture is brought into contact with carbon dioxide.

 If an alkaline earth metal hydroxide is used, the mixture contains only the water supplied by the amino promoter. When using an alkaline earth metal oxide, it is necessary to add to the mixture 0.5 to 1 mole of water per mole of oxide.

 As the carbonation reaction is exothermic, using large reactors it is unnecessary to heat at the start of the reaction. On the other hand, for small reactors, the effect of natural heat dissipation is such that it is preferable to rapidly bring the temperature of the reactor to the selected value by heating.

 In both cases, when the temperature has reached the value chosen between 25 and 600C and preferably between 30 and 500C it must be maintained at this level.

 The introduction of carbon dioxide is continued by monitoring the evolution of the alkaline value by taking samples at regular intervals from the reactor. The alkaline value of the mixture increases, reaches a plateau and then drops rapidly. The optimal duration of carbonation is on the landing before the fall.

 At the end of the carbonation reaction, the total amount of carbon dioxide introduced is such that its molar ratio (a) to the stoichiometric excess of alkaline earth metal oxide or hydroxide (b) on sulfonic acid (c) is understood between 0.5 and 1.2 and preferably 0.8 and 1.

mole C02
a =
mole b - 0.5 mole C
The methanol and the water produced by the carbonation reaction are then removed by heating the carbonate mixture under reduced pressure to 0.8 to 0.5 bars. The maximum temperature is of the order of 100 to 105 ° C. This temperature is maintained for at least ten minutes.

 The solid residues are then removed by centrifugation and / or filtration on diatomaceous earth.

 After removal of the solvent, a product with a clear appearance, brown in color, is recovered.

 For carrying out the reaction, a jacketed reactor is preferably used, provided with a vigorous stirring system, a temperature regulation, a condenser, a system allowing a partial vacuum to be produced. , a gas diffusion system and a solvent recovery device.

 The additives obtained are characterized by their alkaline value (VA) determined according to standard ASTM-D 2896 and expressed in mg ROH / g of product. Their viscosity is measured at 200C or 1000C and expressed in m / s. The calcium content is expressed as a weight percentage of the product.

To evaluate the colloidal stability of the additive, it is diluted with a mixture of oils of the type 600 Neutral / Bright
Stock Solvent in proportion 8o / 20 until a VA of 70 is obtained or by a mixture 175 Neutral / 600 Neutral in proportion 80/20 until a VA of 10 is obtained.

 The additive is considered to be stable if the dilution does not show haze or a settling zone after a stay of three months at room temperature and after 1 month at 600C.

 The overbased additives according to the invention are used in lubricating oils of natural or synthetic origin. They are used at a concentration of between 0.1 and 30% by weight and preferably between 0.5 and 15% by weight, depending on the applications.

 Magnesium additives are also used as fuel additives. The magnesium fuel content should be between 5 and 200 ppm.

 The following examples illustrate the invention without, however, limiting it.

EXAMPLE 1
150 ml of xylene, 35 g of slaked lime are successively introduced into a 250 ml double-jacketed reactor equipped with an agitator, a carbon dioxide inlet, a dropping funnel, a condenser and a thermometer. , 22.5g of diluent oil, 26.5g of C24-alkylbenzene-sulfonic acid with 70% active material, and 10.5g of methanol. An increase in temperature is then observed which corresponds to the formation of the neutral calcium sulfonate. The temperature of the reactor is then regulated at 48.90 C. One gram of 20% ammonia is added at the same time as the introduction of carbon dioxide begins at a flow rate of 405 ml / minutes. From this initial point Po, successive samples are taken over time after respectively 12, 21, 22.5, 25.5, 28 and 30.5 minutes of carbonation.

Each sample is subjected to heating at 0.5 bars up to 1000 ° C., the temperature of 100 ° C. being maintained for 10 minutes so as to remove the methanol as well as the water produced by carbonation. The samples are then centrifuged and freed of solvents.

 Table 1 shows the alkaline values obtained as a function of the carbonation time from point Po.

TABLE 1
Duration VA Aspect Stability
min
12 315 Clear brown Stable
21,461
22.5 470
25.5 468
28,420 "deposit after 1 day
30.5 365
Under these conditions the lime / sulfonic acid molar ratio is 13 and it is found that the optimal duration of carbonation, according to the maximum VA, is 22.5 minutes.

Beyond this, we can see a drop in VA associated with a loss of product stability.

The molar ratio of carbon dioxide introduced to the excess of the alkaline earth oxide or hydroxide (a) is equal to 0.89.

EXAMPLE 2
The procedure is as in Example 1 but introducing 40 g of slaked lime and 30.7 g of sulfonic acid. The CO2 flow is 391ml / min. The optimal duration of carbonation determined from the maximum VA is 24.5 minutes, and a = 0.87. We collect a clear brown additive, VA 508mg
KOH / g and stable when diluted in oil. Its lime / sulfonic acid molar ratio is 13, its screw # cosity is 297.10 6m2 / s at 1000C and its calcium level is 18.6%.

EXAMPLE 3
The procedure is as described in Example 1 with the difference that 40 g of slaked lime, 28.6 g of sulfonic acid, 15.5 g of methanol are introduced and that the CO 2 flow rate is 415 ml / min. The optimal duration of carbonation is 24.5 min. and a = 0.86. An additive of VA equal to 492 mg KOH / g and whose stability is good is collected. The lime / sulfonic acid molar ratio is initially equal to 14.

The viscosity is ll5.l0 # 3m2 / s at 200C.

EXAMPLE 4 (comparative)
The procedure is as in Example 1 except that the maximum temperature for removing methanol is 1300C, this temperature being maintained for 10 minutes. An additive is then collected whose VA is close to zero.

This result is accompanied by a very large amount of residue removed by centrifugation.

EXAMPLE 5
The procedure is as in Example 1, but 26.6 g of slaked lime, 42 g of sulfonic acid, 11.8 g of methanol and 2.1 g of ammonia at 20 8 are introduced into the reactor. The carbonation is carried out at 320C at a flow rate of 200ml / min.

The optimal duration of carbonation is 24 minutes.

Initially the lime / sulfonic acid molar ratio is 6.35 and a = 0.64. The additive obtained has an alkaline value of 299 mg KOH / g and it is stable in dilution. Its viscosity is 62.10 4m2 / s at 200C.

EXAMPLE 6 (comparative)
The procedure is as in Example 5 but the maximum temperature reached during the removal of methanol is only 800C. A product of VA 307 mg KOH / g is then collected and which exhibits slight instability after 1 month at 60 C.

Its viscosity is 11.625.10 # 3m2 / s at 200C.

Comparative examples 4 and 6 make it possible to measure the importance of the methanol elimination conditions for the alkaline value and the stability of the product obtained.

EXAMPLE 7 (comparative)
The procedure is as described in Example 3 with the difference that 9.8 g of methanol are added and that the carbonation is carried out at 56.50C at a flow rate of 482 ml / min, a = 0.87. The optimal duration of carbonation is then 21 minutes. A product is collected whose VA is 470 mg KOH / g and which is unstable in oil. This example shows the importance of the carbonation temperature for the final stability of the product. The viscosity is l6,650.10 # 3m2 at 200C.

EXAMPLE 8
The procedure is as in Example 1, but 26 g of slaked lime are introduced into the reactor, 30 g of sulfonic acid and 10.3 g of methanol. The carbonation is carried out at 420C at a flow rate of 252ml / min. The optimal duration of carbonation is then 26 minutes. The additive obtained has a clear brown appearance, a VA of 392 mg KOH / g and it is stable when diluted in oil.

 The initial lime / sulfonic acid molar ratio is 8.78. The viscosity is 22,850.10 # 3m2 / s at 200C.

EXAMPLE 9 (comparative)
The operation is carried out under the same conditions as in Example 8 with the difference that 18 g of slaked lime and 7.1 g of methanol are introduced. Carbonation is carried out at a flow rate of 176 ml / min, a = 0.84. The different molar ratios are identical to those of Example 8, except for the lime / sulfonic acid ratio which is here equal to 6.02.

 The additive collected after an optimal duration of carbonation of 26 minutes has a VA of 306 mg KOH / g but it is unstable in oil. Its viscosity is 6.10- m / s at 200C and its calcium level is 11.9% #.

EXAMPLE 10
The procedure described in Example 2 is repeated, but 59 g of sulfonic acid and 38.7 g of methanol are introduced. Carbonation is carried out at 390C at a flow rate of 308ml / min, and a = 0.8. The optimal duration of carbonation is 30 minutes. The additive obtained has a VA of 413 mg KOH / g and it is stable when diluted in oil. Initially the lime / sulfonated acid molar ratio is 6.9 and the viscosity is 236.10 -m / s at 200C.

EXAMPLE 11
The procedure described in Example 10 is identified, but by voluntarily extending the carbonation up to 36 minutes, a = 1. Under these conditions, the optimal duration of carbonation is exceeded. The additive collected has a
VA of 400mg KOH / g but it is unstable in dilution. Its viscosity is 7575.2.l0 # 3m2 at 200C.

EXAMPLE 12
The procedure described in Example 1 is repeated, but 16.2 g of C16 # 6 ~ 18-alkyl C16 # 18-alkylxylenesulfonic acid containing 96E of active material and 30 g of the diluent oil are introduced. The optimal duration of carbonation is 23 minutes and a = 0.89. A liquid brown additive of VA 412 mg KOH / g, of viscosity 1.05 × 10 3 m 2 / s at 800C and stable in dilution is collected.

EXAMPLE 13
The procedure of Example 1 is repeated, but 26.9 g of a mixture of alkylbenzenesulfonic acids containing 68% of active material and of which the alkyl chains are branched and linear are introduced. The optimal duration of carbonation is still around 23 minutes, and a = 89, but the VA of the additive obtained is 485 mg # KOH / g. Its viscosity is 25.8.10 # 3m2 / s at 200c and it is stable in dilution.

EXAMPLE 14
The procedure of Example 10 is repeated, but 30 g of calcium oxide and 7.8 g of water are introduced into the reactor. Carbon dioxide is introduced at a flow rate of 295ml / min. After an optimal carbonation time of 31 minutes, a = 0.82, a clear brown additive of
VA 425mg KOH / g and stable when diluted in oil. Its viscosity is 37.6.10 3m2 / s at 200C.

EXAMPLE 15
The procedure of Example 1 is repeated, but 20.5 g of C24-alkylbenzenesulfonic acid containing 70% active material, 13.73 g of light magnesium oxide (calcined at low temperature) 9.8 g are introduced into the reactor. methanol and 5g of water.

The carbon dioxide flow rate is 85 ml / min, a = 1.03. The optimal duration of carbonation is 1 hour 30 minutes.

An additive of VA 465 mg KOH / g is then collected which is stable in dilution. Initially the magnesium oxide / sulfonic acid molar ratio is 12.43. The viscosity is from 115.10 to 20 C.

Claims (14)

1 - Process for preparing overbased additives by  contact of an alkali or alkaline earth metal derivative  and at least one surfactant with anhydride  carbonic, in a diluting oil and a solvent  hydrocarbon in the presence of an oxygenated promoter and a  nitrogen promoter characterized in that it is allowed to evolve  the temperature at the start of carbonation up to a  value between 25 and 600C and we maintain  then the temperature at this value for the duration  optimal carbonation. 2 - Method according to claim 1 characterized in that  the temperature is maintained between 30 and 50 OC. 3 - Method according to claims 1 or 2 characterized in  what the optimal duration of carbonation is  determined experimentally by measuring the value  alkaline. 4 - Method according to one of claims 1 to 3  characterized in that the alkali metal derivative or  alkaline earth is a sodium oxide or hydroxide,  potassium, barium and preferably calcium or  magnesium. 5 - Method according to one of claims 1 to 4  characterized in that the surfactant is an acid  alkylsulfonic or an alkylarylsulfonic acid such as  didodecylbenzenesulfonic acid. 6 - Method according to one of claims 1 to 5  characterized in that the diluent oil is an oil  paraffinic type 75, 100 or 150 Neutral or a  naphthenic oil of type 100 Pale-Solvent. 7 - Method according to one of claims 1 to 6  characterized in that the hydrocarbon solvent a  C6 to Cg alphatic hydrocarbon or a hydrocarbon  aromatic. 8 - Method according to one of claims 1 to 7  characterized in that the oxygenated promoter is a  C1 to C5 aliphatic alcohol. 9 - Method according to one of claims 1 to 8  characterized in that the nitrogenous promoter is  ammonia, ammonium chloride, carbonate  ammonium or ethylene diamine. 10 - Method according to one of claims 1 to 9  characterized in that the molar ratio of the derivative of  alkaline earth metal with sulfonic acid is included  between 6 and 25 and preferably between 6.2 and 20. li - Method according to one of claims 1 to 10  characterized in that 0.2 to 30 moles of  oxygenated promoter per mole of sulfonic acid. 12 - Method according to one of claims 1 to 4  characterized in that the molar ratio (a) of the gas  carbon dioxide introduced in stoichiometric excess of  the alkaline earth oxide or hydroxide on the acid  sulfonic is between 0.5 and 1.2 and  preferably between 0.8 and 1.  13 - Method according to one of claims 1 to 12  characterized in that after carbonation methanol  and the water is removed by heating for at least  10 minutes at a temperature of 100 to 105 0C under a  pressure from 0.8 to 0.5 bar. 14 - Lubricating composition characterized in that it  contains a natural or synthetic lubricating oil  and 0.1 to 30% by weight and preferably 0.5 to 15% by weight  an overbased additive prepared according to claims 1  to 13. 15 - Fuel composition characterized in that it contains 5  200 ppm magnesium as an overbased additive  prepared according to claims 1 to 13.