GB2031935A - Method of removing mechanical impurities from antisludge oil additives - Google Patents

Abstract

A method of removing mechanical impurities from antisludge oil additives, comprising incorporating into a solution of an antisludge oil additive 0.025- 10% by weight of a polar liquid having a dielectric constant of at least 17, followed by recovering mechanical impurities by separation of phases. The polar liquid may be a ketone, alcohol, ethylene glycol, glycerol, water or aq. solution of an alkali or alkaline-earth nitrate and may be absorbed on a solid carrier, e.g. Ca(OH)2 or CaCO3.

Description

SPECIFICATION Method of removing mechanical impurities from antisludge oil additives This invention relates to a method of removing mechanical impurities from antisludge oil additives.

The present invention provides a method of removing mechanical impurities from antisludge oil additives, comprising incorporating into a solution of an antisludge oil additive 0.025-10% by weight of a polar liquid having a dielectric constant of at least 17, followed by recovering mechanical impurities by separation of phases.

Owing to the present invention it has become possible to effect purification of antisludge additives after the synthesis thereof from the most difficultly removable fraction of mechanical impurities with a particle sizeof 0.5p. The method according to the present invention makes it possible to prepare antisludge additives with a degree of purity of below 500 mg/100 g of the additive.Furthermore, it has become possible to simplify the process equipment, i.e. to replace a multi-stage labour-consuming purification of additives by means of centrifugation with a separation factor of 1,000 and ultracentrifuges with a separation factor of 15,000 for automatic centrifuges or settling apparatus, since the sedimentation rate of mechanical impurities, after coagulation thereof, is increased by thousands of times as compared to the sedimentation rate of mechanical impurities in the starting additives.

In accordance with the present invention, it is preferable to introduce a polar liquid adsorbed on a solid carrier into a solution of the antisludge additive. The amount of the solid carrier employed may be suitably from 0.01 to 10% by weight of the antisludge additive. Furthermore, it is preferable that the particle size of the solid carrier is 5-10 times greater than the particle size of mechanical impurities of the fraction of 0.5-5y.

Owing to the present invention it has become possible to perform more rapidly and efficiently the heterocoagulation of mechanical impurities on the surface of a solid carrier wetted with a polar liquid having a dielectric constant of at least 17. Since the coagulation rate is proportional to the area of the interface surface, the use of a solid carrier with a great surface area makes it possible to substantially increase the rate of purification of antisludge additives.

In orderto avoid penetration of additional mechanical impurities into the solution of the antisludge additive during purification thereof, it is preferred to use, as the solid carrier, calcium hydroxide or calcium carbonate.

After incorporation of the polar liquid, the solution of the antisludge additive is preferably subjected to the effect of a non-uniform electrostatic field created by a pulse voltage of constant polarity for effecting separation of phases. The electrostatic field preferably has an intensity of from 0.1 to 5kV/cm and a non-uniformity coefficient of from 5 to 50.

The use of an electrostatic non-uniform oriented field makes it possible to substantially increase the rate of phase separation and thus rapidly and effectively purify antisludge additives from mechanical impurities. Furthermore, it is thus possible to effect coagulation and separation of mechanical impurities in a single apparatus.

The present invention permits purification of the following antisludge additives from mechanical impurities: barium or calcium salts of high-molecular sulphonic acids; calcium alkylsalicylates; barium salts of alkylphenol disulphides; the calcium salt of dietherodithiophosphoric acid; oily solutions of zinc dialkyldithiophosphates; and barium alkyipheno- lates.

As it is well known, mechanical impurities present in antisludge additives after the synthesis thereof comprise mainly calcium hydroxide and calcium carbonate; about 70% by weight of the impurities constitutes the fraction with a particle size of 0.5-5y, while 30% by weight constitutes the fraction with a particle size of not greater than 0.4jut.

Purification of antisludge lubricating oil additives is effected by way of separation of phases, e.g. by centrifugation; in accordance with the present invention the separation of phases is effected in the presence of a polar liquid with a dielectric constant of at least 17, whereby coagulation and sedimentation of mechanical impurities occur.

The polar liquid with a dielectric constant of at least 17 may be suitably an aqueous solution of one of the following compounds: ketones such as acetone and methylethylketone; alcohols such as methanol, ethanol, propanol, butanol, isopropanol and isobutanol; ethylene glycol; glycerol; water; and aqueous solutions of nitrates of alkali and alkaline-earth metals.

Coagulation of contaminating impurities with polar compounds is explained by the ability of the latter to be selectively adsorbed on hydrophilic particles of the solid phase of mechanical impurities. Thus, water wets mineral particles of contaminants in the additive much betterthan it wets the additive molecules. This is due to the fact that the heat of adsorption of water molecules on particles of the solid phase, i.e. mechanical impurities recovered from the solution of the non-purified antisludge additive, is 25-26 calls compared to 1.88 cal/g for the additive molecules (the latter value is given for a molecule of the calcium salt of the sulphonate additive). Therewith, the additive molecules are desorbed from particles of mechanical impurities; the latter lose their aggregative stability and are coagulated along the outline of the wetting region.

It has been found that a polar liquid with the above mentioned characteristic should be introduced into the antisludge additive solution being purified in an amount of from 0.025 to 10% by weight. This value has been determined on the basis of considerations that the introduced liquid be totally adsorbed on particles of mechanical impurities without forming an individual phase and be substantially completely withdrawn with the impurities upon subsequent separation of phases of the solution of the antisludge additive.

It should be noted that the residue formed upon coagulation of solid particles is deposited by cosettlement of particles where the separation of phases occurs with a clear interface. The resulting larger aggregates entrain smaller particles, which is accompanied by a clearly pronounced clarification of the liquid over the residue.

A solution of an antisludge additive without a coagulation agent, i.e. a polar liquid with a dielectric constant of at least 17, possesses a high sedimentation stability. Upon incorporation of a coagulation agent in an amount of below 0.025% by weight, particles of mechanical impurities are not coagulated, which might be explained by high solubilizing properties of the additive. With an increasing amount of the incorporated polar liquid to 1.0% by weight, the aggregative stability of the particles of mechanical impurities in the additive solution is broken and the process of coagulation of mechanical impurities starts to proceed at a noticeable speed which does not exceed 20 mm/hr.Upon increasing the amount of the incorporated polar liquid to 10.0% by weight, the speed of formation of a residue of mechanical impurities and speed of its sedimentation is increased and becomes as high as 200 mm and more without using any forced separation methods. Therefore, upon introduction of a polar liquid in an amount of from 5 to 10 by weight into a solution of an antisludge additive, the process of phase separation may be performed in a settling apparatus.

To obtain the coagulation effect, intermixing of the polar liquid and the additive solution should be performed in a high-speed mechanical stirrer with the speed of 5,000 r.p.m. Upon coagulation in industrial apparatus, the intermixing is effected in hydrodynamic mixers.

The same coagulation effect may be attained without, however, using a hydrodynamic mixer, provided that a polar liquid is introduced into the antisludge additive solution, which polar liquid is adsorbed on a solid carrier having a particle size of from 2.5 to 50R. The solid carrier may be suitably an inorganic salt such as sodium chloride, sodium carbonate, sodium nitrate or calcium nitrate, or a hydrophilic powder such as filtroperlite, kieselguhr or Hyfla-Super gel. It is, however, advisable to use as the solid carrier calcium hydroxide or calcium carbonate, since these compounds are basic components of mechanical impurities in antisludge additives; incorporation of such a carrier into the antisludge solution would not provide additional contamination.

As has been mentioned above, the particle size of the most difficult to remove fraction of mechanical impurities is 0.5-5# and the carrier particle size should preferably exceed by 5-10 times the particle size of this fraction, i.e. be equal to 2.5-501l. On the one hand, heterocoagulation occurs more rapidly and effectively at a greater difference between the particle sizes of the mechanical impurities and the carrier, and, on the other hand, with increasing particle size of the carrier its specific surface area is decreased and the efficiency of coagulation is descreased. The choice of this ratio between fractions of mechanical impurities and the carrier is optimal and results in the most efficient heterocoagulation.

It should be noted that upon incorporation of a polar liquid adsorbed on a solid carrier into a solution of the antisludge additive, the polar liquid should be adsorbed in the form of a thin film approaching the thickness of mono-layer, since this condition ensures a high coagulation effect of the polar liquid and, consequently, a high degree of purification of the additive. Taking into consideration the foregoing, as well as the above-mentioned optimal amount of the introduced polar liquid, it is possible to conclude that the amount of the incorporated carrier with a humidity of from 0.1 to 50% should be preferably from 0.01 to 10% by weight relative to the amount of the antisludge additive.

It has been found that upon incorporation of a polar liquid into a solution of an antisludge additive, the electrokinetic properties of the mechanical impurities are substantially changed. Thus, the electrophoretic mobility of coagulated particles of mechanical impurities in electrical fields is increased by 3-4 times, and the zeta-potential of mechanical impurities is increased by an order of magnitude which is associated with the increasing difference in the dielectric constants of the dispersed phase and the dispersing medium.

In the absence of a polar liquid, particles of mechanical impurities in the additive solution carry a weak positive charge, and for such particles in electrical fields the phenomenon of interelectrode circulation and double electroform is imminent, i.e.

their electrokinetic properties are of no practical importance.

Upon incorporation of a polar liquid in an amount of from 0.025 to 1% by weight into the additive solution there occurs a sharp increase in the zetapotential of the particles of mechanical impurities and a unidirectional electrophoresis is observed, i.e.

deposition of a solid phase on the electrodes. In the investigation of the electrokinetic properties of electrophoretic residues of mechanical impurities it has been found that they retain a positive charge on the surface of settling electrodes. This property of the residues makes it possible to easily purify the surface of the settling electrodes over a period of from 10 to 15 seconds by changing the polarity of the corona and settling electrodes.

Where the settling electrodes comprise rotating discs, the resulting substantially dry residue of mechanical impurities is continuously cleaned off by a blade.

Therefore, it has been found that it is possible to effectively and rapidly perform the purification of antisludge additives from mechanical impurities, when after incorporation of the polar liquid the additive solution is subjected, for separation of phases, to the effect of a non-uniform electrostatic field created by a pulse voltage of constant polarity.

This method of separation of phases makes it possible to remove mechanical impurities from an antisludge additive by way of coagulation and a separation of impurities in a single apparatus.

The intensity of the electrostatic field is preferably from 0.1 to 5kV/cm, and the coefficient of nonuniformity of the electrostatic field is preferably from 5 to 50 units. The electrostatic field is preferably created by a rectified voltage without smoothing the R-C circuit, i.e. by a pulse voltage of constant polarity with a frequency of half-waves of 100 Hz.

With increasing intensity of the electrical field, the electrophoretic speed of movement of the particles of mechanical impurities in the additive is increased, but the field intensity should not exceed a certain value above which there is observed a breakdown in the solution where polar liquids are present in an amount of from 0.025 to 1% by weight.

Most optimal conditions are created in the system for coagulation and separation of mechanical impurities at a field intensity of from 1 to 3kV/cm.

The non-uniformity coefficient of the field is varied depending on the content of the solid phase in the additive. The higher the content of the solid phase, the higher is the coefficient of non-uniformity of the field. Thus, alteration of the solid phase content from 7,840 mg/100 g to 770 mg/100 g results in alteration of the non-uniformity coefficient from 5 to 50.

The invention will be further described with reference to the following illustrative Examples.

Example 1 This Example illustrates the removal of mechanical impurities from an antisludge additive based on a calcium salt of petroleum sulphonic acid prepared bythefollowing known method: The starting stock for the preparation of the calcium salt of petroleum acid was produced by sulphonation of a petroleum oil with a viscosity of from 10 to 14 cSt at a temperature of 500C and a molecular weight of above 350 by oleum with the formation of a 40-60% oily solution of sulphonic acid with a viscosity of from 40 to 60cSt at a temperature of 500C.

To obtain a neutral calcium sulphonate with a pH of 7, containing at least 5% by weight of sulphonate ash, the oily solution of sulphonic acid was charged into a mixer, into which a mineral oil, i.e. a diluent, with a viscosity of from 10 to 14 cSt at 500C was initially added to decrease the total viscosity of the solution to 20-25 cSt at a temperature of 100 C, after which calcium hydroxide was added thereto.

Determination of the sulphonate ash-content comprised evaporation of a weighed portion of a solution of calcium sulphonate in the presence of sulphuric acid and calcination of the solid residue to a constant weight. Stirring of the resulting suspension was effected at a speed of 1,460 r.p.m Neutralization of a petroleum sulphonic acid with calcium hydroxide was effected at a temperature of from 80 to 950C.

After the formation of a neutral calcium sulphonate with a pH of 7 and a sulphonate ash-content of at least 5% by weight, a high-ash petroleum calcium sulphonate was prepared with a sulphonate ashcontent of at least 17% by weight and an alkalinity of 100-130 mg KOH/g of the additive. Such an ashcontent and alkalinity were necessary to impart the required properties to the antisludge additive. To this end, to the neutral calcium sulphonate present in the mixer was added a 20% phenol as a catalyst for completion of the process of preparation of calcium sulphonate with a high ash-content, and then calcium hydroxide was also charged into the mixer in an amount of 6-7% by weight. The tempera- ture of the mixture was elevated to 102 C and the reaction mass was kept at this temperature for one hour.Then the reaction mass temperature was gradually raised to 1 250C while distilling off water and the reaction mass was kept at this temperature for one hour, after which 5 vol.% of CO2 were passed through the reaction mass under a pressure of 0.7 atm.g. and at a temperature of 125 C. The process was conducted in this manner for 2 hours, after which the reaction mass temperature was lowered to 800C and the pressure was released to atmospheric.

The process was considered completed if the oily solution of calcium sulphonate contained 17% by weight of sulphonate ash.

In the case of a satisfactory analysis the product in the oily solution was pumped into vacuum columns, wherein the phenol catalyst was distilled off under a residual pressure of 30-40 mm Hg and a gradual elevation of temperature to 180-200 C. Distillation of phenol was ended when the content of the latter was reduced to at most 0.5% by weight.

In this manner a solution of a sulphonate additive was obtained with an initial degree of purity of 3,850 mg/100 g of the additive, Into the thus-prepared solution of the additive was added a hydrocarbon solvent having a density of 0.7-0.8 g/cm3 and a boiling range of from 80 to 1 200C in an amount of 50% by weight. Then water was added to this solution in an amount of 7.5% by weight at room temperature.

After centrifugation for 5 minutes in a centrifuge with a separation factor of 1,000, there was obtained a sulphonate additive with a degree of purity of 110 mg/100 g of the additive.

Example 2 100 g of an oily solution of an additive of a calcium alkylsalicylate prepared by a known method with a degree of purity of 7,950 mg/100 g of the additive was mixed at a temperature of 1250C with 2 g of a 20% suspension of a carrier, i.e. calcium hydroxide having a particle size of 2.5-50R. The suspension was prepared in an oil (diluent) with a viscosity of 10-14 cSt at a temperature of 50 C, into which water was added under vigorous stirring in an amount of 5% by weight of the carrier.

Coagulated residues were separated in a centrifugal field in centrifuges with separation factors of 1,000 and 15,000 respectively. After the first centrifugation with a separation factor of 1,000, the additive had a degree of purity of 540 mg/100 g of the additive (0.011% by weight of mechanical impurities). After the second centrifugation with a separation factor of 15,000, the additive had a degree of purity of 0.008% by weight of mechanical impurities (90 mg/100 g of the additive).

Example 3 100 g of an oily solution of a sulphonate additive with a degree of purity of 7,840 mg/100 g were mixed with 10 g of a 0.1% suspension of a carrier, i.e.

calcium carbonate having a particle size of 2.5-50 in glycerol, at a temperature of 125 C. The suspension was prepared in an oil (diluent) with a viscosity of 10-14 cSt at a temperature of 50 C, into which glycerol was added under vigorous stirring in an amount of 50% by weight of the carrier.

Coagulated residues were separated in centrifuges with separation factors of 1,000 and 15,000 respectively. After the first centrifugation with a separation factor of 1,000, the additive had a degree of purity of 650 mug/1 00 g (0.035% by weight of mechanical impurities). After the second centrifugation with a separation factor of 15,000, the additive contained 0.02% by weight of mechanical impurities, i.e. its degree of purity was 150 mg/100 g of the carrier.

Example 4 100g of an oily solution of an additive, i.e. the barium salt of an alkylphenol disulphide with an initial degree of purity of 2,100 mg/100 g of the additive, were dilluted with a hydrocarbon solvent having a density of 0.7-0.73 g/cm3 and a boiling range of from 80to 1300C in a volumetric ratio of 1 :1.5, 20 g of a 50% suspension of the carrier, i.e.

kieselguhr having a particle size of 2.5-50F, were added to the mixture under stirring and at a temperature of 60 C. The suspension was prepared in a hydrocarbon solvent, into which an aqueous solution of methylethylketone was added under vigorous stirring in an amount of 0.5% by weight of the carrier.

After centrifugation for 5 minutes with a separation factor of 1,000, the additive had a degree of purity of 100 mg/100 g of the additive (content of mechanical impurities of 0.009% by weight).

Example 5 Into 100 g of an oily solution of an additive, i.e.

barium sulphonate prepared as described in the foregoing Example 1 with a starting degree of purity of 6,400 mgf100 g of the additive, there was added a hydrocarbon solvent having a density of 0.7-0.73 g/cm3 and a boiling range of 80 to 1 30 C in a volumetric ratio of 1:1.5. Then, into the mixture there was added 10% by weight of a 0.1 M solution of isopropanol at a temperature of 600C under vigorous stirring.

After centrifugation for 5 minutes with a separation factor of 1,000, the additive had a degree of purity of 110 mug/1 00 g of the additive (0,020% by weight of mechanical impurities).

Example 6 Into 100 g of an oily solution of an additive, i.e.

barium sulphonate with an intial degree of purity of 6,400 mug/1 00 g of the additive, there was added a hydrocarbon solvent having a density of 0.7-0.73 g/cm3 and a boiling range of from 80 to 1300C in a ratio of 1 : 1.5% by volume. then to the mixture was added 0.75% by weight of a 0.1 M aqueous solution of calcium nitrate at a temperature of 60 C under vigorous stirring.

After centrifugation for 5 minutes with a separation factor of 1,000, the additive had a degree of purity of 80 mg/100g of the additive (0.02% by weight off mechanical impurities).

Example 7 Into 100 g of an oily solution of an additive, i.e. the calcium salt of dietherodithiophosphoric acid with an initial degree of purity of 3,850 mg/100 g of the additive, there was added a hydrocarbon solvent having a density of 0.7-0.73 g/cm3 and a boiling range of from 80 to 1300C in a volumetric ratio of 1:1.5. Then, into this mixture there was added 7.5% by weight of water at a temperature of 600C under vigorous stirring.

After centrifugation for 5 minutes with a separation factor of 1,000, the additive had a degree of purity of 110 mg/100 g of the additive (0.10% by weight of mechanical impurities).

Example 8 Into a solution of an additive, i.e. calcium sulphonate with an initial degree of purity of 7,840 mg/100 g of the additive (content of mechanical impurities of 3.9% by weight), there was added 1.0% by weight of water under stirring and at a temperature of 60 C.

Then this system was subjected to an electrostatic field with an intensity of 1.5kV/cm and a coefficient of non-uniformity of the field of 50. Coagulation of mechanical impurities and separation thereof from the additive solution were effected simultaneously in a single apparatus.

After applying this electrostatic field for 15 minutes and additive was obtained having a degree of purity of 380 mug/1 00 g of the additive (content of mechanical impurities of 0.018% by weight).

Example 9 Into a solution of an additive, i.e. barium salt of an alkylphenol disulphide with an initial degree of purity of 2,100 mg/100 g of the additive (content of mechanical impurities of 1.2% by weight, there was added 0.09% by weight of water under stirring and at a temperature of 60 C. The system was subjected to an electrostatic field having an intensity of 2.5kV/cm and a coefficient of non-uniformity of the field of 25.

Coagulation of mechanical impurities and the removal thereof from the additive solution were effected simultaneously in the same apparatus.

After applying this electrostatic field for 15 minutes an additive was obtained having a degree of purity of 40 mg/100 g of the additive (content of mechanical impurities of 0.010% by weight).

Example 10 Into a solution of an antisludge additive, i.e. a zinc dialkyldithiophosphate and a barium alkylphenolate, with an initial degree of purity of 770 mg/100g of the additive (content of mechanical impurities of 0.8% by weight), there was added water in an amount of 0.025% by weight under stirring and at a temperature of 60 C. Then the system was subjected to an electrostatic field having an intensity of 1.5kV/cm and a non-uniformity coefficient of 5. Coagulation of mechanical impurities and separation thereof from the solution were performed in the same apparatus.

After applying this electrostatic field for 15 mi nutes an additive was obtained having a degree of purity of 185 mg/100 g of the additive (content of mechanical impurities of 0.010% by weight).

Example 11 Into a solution of an additive, i.e. calcium sulphonate, with an initial degree of purity of 3,290 mg/100 g of the additive and a content of mechanical impurities of 4.7% by weight, water was added in an amount of 0.5% by weight under stirring and at a temperature of 60 C. The system was subjected to an electrostatic field having an intensity of 1kV/cm and a coefficient of non-uniformity of the field of 10.

Coagulation of mechanical impurities and the removal thereof from the solution were effected in the same apparatus.

After applying this electrostatic field for 30 minutes an additive was obtained having a degree of purity of 211 mg/100 g of the additive (content of mechanical impurities of 0.01% by weight) Example 12 Into a solution of an antisludge additive comprising a calcium salt of sulphonate acid (prepared by a procedure similar to that described in Example 1) with an initial degree of purity of 3,290 mg/100 g of the additive (content of mechanical impurities of 4.7% by weight), water was added in an amount of 0.5% by weight at a temperature of 60 C and under stirring. This mixture was subjected to a electrostatic field having an intensity of 3kV/cm and a coefficient of non-uniformity of the field of 10. Coagulation of mechanical impurities and the removal thereof from the solution were performed in the same apparatus.

After applying this electrostatic field for 30 minutes an additive was obtained having a degree of purity of 69 mg/100 g of the additive (content of mechanical impurities of 0.01% by weight).

Claims (8)

1. A method of removing mechanical impurities from antisludge oil additives, comprising incorporating into a solution of an antisludge oil additive 0.025-10% by weight of a polar liquid having a dielectric constant of at least 17, followed by recovering mechanical impurities by separation of phases.

2. A method as claimed in Claim 1, wherein a polar liquid adsorbed on a solid carrier is introduced into a solution of the antisludge additive.

3. A method as claimed in Claim 2, wherein the solid carrier is calcium hydroxide or calcium carbonate.

4. A method as claimed in Claim 2 or 3, wherein the amount of the solid carrier is from 0.01 to 10% by weight of the antisludge additive.

5. A method as claimed in any of Claims 2 to 4, wherein the particle size of the solid carrier is 5 to 10 times greater than the particle size of mechanical impurities of the fraction of0.5to5#

6. A method as claimed in any of Claims 1 to 5, wherein, after incorporation of the polar liquid, the additive solution is subjected to the effect of a non-uniform electrostatic field created by a pulse voltage of constant polarity for effecting separation of phases.

7. A method as claimed in Claim 6, wherein said electrostatic field has an intensity of from 0.1 to 5kV/cm and a non-uniformity coefficient of from 5 to

8. A method of removing mechanical impurities from antisludge oil additives, substantially as herein described in any of the foregoing Examples.