MXPA05007587A - Process for regenerating lubricant oils using supercritical solvents. - Google Patents

Abstract

The present invention is related to an integral process for the regeneration of lubricant oils using solvents at supercritical temperature and pressure conditions. High-quality lubricant oils are obtained by the present process, which may be used as base or basic lubricant oils or directly in specific lubricating systems. The process includes filtering the lubricant oil and then bringing it into contact with the supercritical solvent so as to carry out a selective extraction of hydrocarbons, separating the mixture from the solvent and the extracted hydrocarbons by an expansion process, reusing the solvent for re-initiating the process. The inventive process is highly environmentally friendly since neither aggressive nor toxic substances are used.

Description

PROCESS FOR THE REGENERATION OF LUBRICATING OILS USED THROUGH THE USE OF SOLVENTS SUPERCRITICS DESCRIPTION TECHNICAL FIELD OF THE INVENTION The present invention relates to a process for effecting the regeneration or recovery of lubricating oils used by using solvents that are at temperature and pressure conditions above the values corresponding to their critical point of the vapor / liquid transition, by what are known as supercritical solvents. The regenerated lubricating oils obtained by means of the extraction with the process of this invention can be used as base or basic lubricating oils for the reformulation of new lubricating oils or they can be used directly as lubricants in different specific applications. Renewed lubricating oils do not contain the contaminants found in used lubricating oils, such as water, fuels, solid matter, metal compounds or mixtures of chemical substances generically called additives.

BACKGROUND OF THE INVENTION A lubricating oil is a viscous liquid, a product derived from petroleum or its primary refining, whose primary function is the separation of two solid surfaces in contact, by means of the formation of a film that reduces friction, wear and tear. materials and energy consumption. Other functions of a lubricating oil in various mechanical systems include: heat dissipation to maintain an appropriate working temperature, entrainment of polluting materials, protection of solid surfaces against oxidation and elimination of noise in work environments.

The regeneration of used lubricating oils is of transcendental importance for the economy of any country, since it allows to prolong the life of non-renewable resources, such as hydrocarbons derived from petroleum, as well as to reduce the payment of foreign currencies for the import of oils base or basic lubricants. The regeneration of used lubricating oils allows to obtain as final product regenerated lubricating oils that can be used again in the reformulation of lubricating oils by adding a balanced mixture of additives, for example anticorrosives, antioxidants, extreme pressure agents and suds suppressors, that are required for lubricants to fulfill their new functions. The regeneration of used automotive lubricating oils also has great relevance in the ecology of the countries as it clearly allows environmental pollution to be transcendentally abated, since this is a current issue that should be of interest to all. Due to the above and additionally, due to the dramatic and almost constant increase in oil prices, worldwide, greater interest has been fostered in the development of new environmentally friendly processes for the more efficient regeneration of used lubricating oils.

For the reasons stated above, in many countries the regeneration of different used lubricating oils is carried out. For example, in the United States of America, by means of different techniques, 4% of the total volume of automotive lubricating oils used is regenerated, in Japan 5%, in France and Italy it is regenerated around 20-30% and in Great Britain processes 10% of the total volume of used automotive lubricating oils.

As a result of the intense research and technological development that takes place in several countries on the regeneration of used lubricating oils, different regeneration techniques are reported in the specialized literature, such as: use of emulsifiers, clarification with propane, purification with acid-clay, etc. It is relevant to establish that currently available techniques are applicable for the removal of one or two types of pollutants from used lubricating oils, but not all possible contaminants, so it is generally necessary to apply several techniques in series to obtain lubricant oils recovered of adequate quality for later use, which makes these treatments result with low efficiency and little economic viability. Notwithstanding the availability of a significant number of specialized techniques, in general, with the use of these techniques for recovering used lubricating oils, the metals present are not eliminated.; additionally, in some of these recovery processes substances that are highly aggressive for the environment are used and the regenerated lubricating oil obtained has low viscosity values, which does not allow its immediate use in the preparation of basic oils for the reformulation of new lubricating oils or in other direct applications different to their original use.

In the patent 4,502,948 of the United States of America a method of regeneration of used lubricating oils, known as acid-clay, is presented, where it is required that the oil be treated with substances harmful to the environment, as are the solutions of sulfuric acid. The patented method consists of several steps of contact and separation of the used oil with different materials, including the use of an adsorbent material and high temperature conditions, between 121.1 and 232.2 ° C (250 to 450 ° F), which implies a high energy consumption. Although some pollutants are removed by this method (most of the water present and light hydrocarbons from oil contamination with fuel), the metals found in the oil used as a result of wear of the engine parts are not greatly reduced. In addition, steps must be included to eliminate contaminants introduced by the adsorption of the recovered oil. This method, together with others, is classified as a chemical treatment.

In Patent 6,712,954 of the United States of America a technique was developed for the processing of oils considered waste from which base oils are produced by means of the sequential use of the distillation between 1 0 and 150 ° C, in the presence of solutions concentrated potassium hydroxide, under atmospheric pressure; the distillation with high vacuum between 170 and 385 ° C and the extraction of the fraction of lubricating compounds between 50 and 90 ° C with a polar solvent, which is classified as irritant. This solvent has to be recovered later. It is widely known that all the operations included in this Patent require a high energy consumption, so that environmentally they are not very friendly and economically have a high cost since the efficiency of the recovery of base lubricating oils is low. By this method the water content is removed, metals are not.

It will be shown that the best regeneration process known to the applicant for lubricating oils used as the subject of this invention provides high quality base or basic lubricating oils.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows the different stages that make up the process for the regeneration of used lubricating oils through the use of supercritical solvents. The equipment identified with No. 1 corresponds to the container for storage of the used lubricating oil, this is filtered in the equipment No. 2 and later sent to the No. 3 equipment where the selective extraction with the supercritical solvent is carried out. Separation of the extracted lubricant and the supercritical solvent is done in the equipment No. 4, so the solvent is stored in the equipment No. 5 to be sent to the compressor, No. 6, and thus recover its supercritical conditions to contain it in the No. 7 vessel for recirculation in the process of this invention.

SPECIFICATION OF THE INVENTION In this invention a process is provided for the regeneration of used lubricating oils by the use of supercritical solvents, that is to say, that they are at temperature and pressure conditions above the values corresponding to their critical point of the vapor / liquid transition, so they are known as supercritical solvents. The process mentioned includes the steps of: a) filtering the used lubricating oil; b) the filtered oil of step (a) is contacted with a solvent that is under pressure and temperature conditions above its gas / liquid critical point; c) flowing the mixture formed by the solvent and the extract obtained in step (d); e) separating the extract or purified lubricants that are solubilized in the solvent and f) recycling the solvent after its compression or increase in pressure.

Another objective of this invention is to show that the regeneration process of used lubricating oils provides lubricating oils regenerated without solid contaminants.

Another objective of this invention is to show that the regeneration process of used lubricating oils provides lubricating oils regenerated without contamination of the different chemical additives that are added during the reformulation of new lubricating oils.

Another objective of this invention is to show that the regeneration process of used lubricating oils provides lubricating oils regenerated without metals.

A further object of this invention is to show that the process of regeneration of used lubricating oils provides lubricating oils regenerated without contaminants coming from fuels.

A further objective of this invention is to show that the lubricant oil regeneration process used for the purpose of this invention employs solvents that are at temperature and pressure conditions higher than those corresponding to their gas-liquid critical point.

Yet another objective of this invention is to show that the process of regeneration of lubricating oils used for the purpose of this invention employs solvents that are not harmful to the environment.

A further objective of this invention is to show that the process of regeneration of lubricating oils used for the purpose of this invention employs solvents that are not thermally regenerated, which makes this process highly attractive from the standpoint of energy, protection of the environment and economic.

It should be apparent to any expert in the subject of this patent application, that the process of regeneration of used lubricating oils presented in this invention does not employ substances harmful to the environment, which is another clear advantage over the techniques available in previous patents for the treatment of lubricating oils.

DETAILED DESCRIPTION OF THE INVENTION In this invention, a regeneration process of used lubricating oils is provided by using solvents that are under temperature and pressure conditions above the values corresponding to their critical point of the vapor / liquid transition, so they are so-called supercritical, for the production of base lubricants or basic high quality oils or oils for specific applications from the regeneration carried out to used lubricating oils containing contaminants such as fuels, solid materials, water, metal compounds and mixtures of chemical additives generally added to new lubricating oils during formulation or preparation. The steps included in the process of the present invention are: a) mechanically filtering the used lubricating oil to remove organic or inorganic solid matter of different dimensions; b) carry out the selective extraction of lubricating oils, from the used lubricating oils that have been filtered according to subsection (a), by means of a solvent that is at supercritical pressure and temperature conditions, ie , above the known values for its gas / liquid transition critical point; c) flowing the mixture formed by the solvent already containing lubricants solubilized selectively towards an area that is under conditions of pressure and temperature different from that of part (d); e) separating the extract or purified lubricants that are solubilized in the solvent by means of temperature and pressure conditions that are below the known values for the gas / liquid transition point of the solvent and f) taking advantage of the solvent again recycling it for its reuse in stage (b) of this process after its pressure increase, without its thermal or chemical regeneration being necessary.

The regeneration process of used lubricating oils included in this invention produces lubricating oils regenerated with high quality, since they lack contamination by light or combustible hydrocarbons, of solid contaminants, of metal compounds and also of chemical substances used as additives in the preparation of new lubricating oils, so that the regenerated lubricating oils can be used as base or basic oils for the preparation or formulation of new lubricating oils or as lubricants for specific industrial applications in accordance with their physicochemical characteristics.

The used lubricating oil that is to be regenerated is fed to the filtering system to eliminate the solid matter of different dimensions that has not been decanted, the oil that has been filtered enters an extraction vessel with adequate internal systems to efficiently perform the selective transfer of hydrocarbons between the used lubricating oil and the solvent that is at pressure and temperature conditions higher than the values corresponding to the critical point of the gas / liquid transition. The solvent, which is at supercritical temperature and pressure, flows from its storage container to the extraction vessel to be in intimate contact within the lubricating oil used by means of a bubbler and internal parts that cause an efficient transfer of oil. material, in order to selectively extract hydrocarbons or high quality lubricating oils, which are free of metal compounds, solids, fuels and chemical additives.

The substances in supercritical state that are used in this invention possess properties that provide them exceptional characteristics as solvents, since they have values of the coefficient of diffusion or diffusivity equal to those of a gas and simultaneously have density values similar to those of liquid solvents. These characteristics allow supercritical solvents to exhibit high capacity and selectivity to extract low volatility substances from complex mixtures. Also, the temperature and pressure values of the gas / liquid critical point of some substances that can be used in this invention as supercritical solvents are highly accessible, for example, for carbon dioxide are 304.1 K (30.95 ° C) and 7.38 MPa (approximately 73.8 atmospheres pressure), for ethane 305.4 K (32.25 ° C) and 4.88 MPa (approximately 48.8 atmospheres), propane presents 369.8 K (96.65 ° C) and 4.25 MPa (approximately 42.5 atmospheres), ethylene presents values of 282.4 K (9.25 ° C) and 5.04 MPa (approximately 50.4 atmospheres), propylene has 364.9 K (91.75 ° C) and 4.60 MPa (approximately 46.0 atmospheres) and trifluoromethane presents 299.3 K (26.15 ° C) and 4.86 MPa (approximately 48.6 atmospheres), respectively.

The mixture formed by the solvent and the high molecular weight hydrocarbons or high quality lubricating oils flow naturally by difference in the pressure to the expansion system that is at suitable temperature and pressure conditions and always below the values which correspond to the temperature and pressure of the critical point of the gas / liquid transition of the solvent, this to adequately modify the physicochemical characteristics, such as density, of the solvent. In the expansion system, the high-quality regenerated lubricating oils that are now in the liquid state or phase and the solvent that is now in the gaseous state or phase are efficiently separated by condensation or precipitation due to gravity. it can be reused or recycled after a compression stage without there being a need for it to be recovered by thermal or chemical means.

To establish the application that can be given to hydrocarbons of high molecular mass or regenerated lubricating oils that have been obtained with the process of this invention, a step of great importance is the realization of the evaluation or measurement of several of its physicochemical properties, having as reference analytical methods cited in the specialized literature. Depending on the high quality of the lubricating oils regenerated in the process of this invention, they can then be used as base or basic lubricants for the reformulation of new lubricating oils for gasoline engines, diesel engines, for speed boxes, also known as transmissions of movement or gears, or for hydraulic systems; likewise, they can be used without the need to reformulate them with the addition of mixtures of chemical additives, and in accordance with their physicochemical properties, in specific systems such as the lubrication of gear systems for manual transmissions of movement, which work in non-extreme conditions .

The lubricating oils used that can be treated with the regeneration process of this invention are mainly lubricating oils that were used in gasoline and diesel engines, in mechanical systems of motion transmission, in hydraulic systems or in heat exchange systems.

It should be evident to any reader, layman or expert in the subject of this patent, that the process of regeneration of used lubricating oils presented in this invention does not employ substances harmful to the environment, which is another clear advantage over the techniques available in previous patents for the treatment of used lubricating oils.

EXAMPLE 1 In this example the great advantages of the process developed in the present invention are shown. To this end, the evaluation of the hydrocarbon composition of the new automotive lubricating oil commercially known as Super SAE 15W / 40 monograde -where SAE stands for the Society of Automotive Engineers of the United States of America- was carried out. to carry out a study of the capacity to solubilize a hydrocarbon of high molecular mass representative of that oil by means of the use of ethane as solvent in the supercritical state.

The determination of the hydrocarbon composition of the commercial oil Ultra SAE15W / 40 monograde was carried out by means of a gas chromatograph coupled to a high resolution mass spectrometer. This equipment has an accuracy of ± 0.05 ng (I nanogram = 1 x 10 '9 g).

The results of the analysis of the composition of the hydrocarbons of the new Super SAE 15W / 40 automotive oil monograde are presented in Table 1.

Table 1.- Composition in% mass of the hydrocarbons of the new automotive lubricating oil, commercially known as Super SAE 15W / 40 monograde.

N C I II III IV V VI VII TOTAL /% mass 21 0.9 1.0 0.7 0.4 0.7 0.3 0.2 4.1 22 1.1 1.2 0.8 0.5 0.9 0.4 0.2 5.1 23 1.3 1.4 0.9 0.6 1.0 0.6 0.2 6.1 24 1.2 1.3 1.0 0.8 1.2 0.7 0.3 6.5 25 1.1 1.4 1.1 0.7 1.2 0.8 0.4 6.7 26 1.3 1.5 1.0 0.7 1.2 0.8 0.5 6.9 27 0.9 1.4 1.0 0.9 1.6 0.9 0.5 7.2 28 1.0 1.2 1.0 0.8 1.5 0.9 0.7 7.2 29 0.9 1.3 0.9 1.0 1.4 1.1 0.5 7.0 30 0.7 0.9 0.8 0.6 1.3 1.1 0.6 5.8 31 0.6 0.6 0.7 0.5 0.9 0.9 0.6 4.8 32 0.5 0.5 0.6 0.5 0.7 0.7 0.5 4.1 33 0.4 0.7 0.6 0.4 0.8 0.6 0.4 3.8 34 0.3 0.5 0.5 0.4 0.6 0.3 0.3 | 3.0 35 0.2 0.6 0.5 0.5 0.5 0.5 0.3 3.0 Where NC is the number of carbon atoms for the automotive lubricating oil; I is the concentration of hydrocarbons called linear paraffins; II is the concentration of monocyclic paraffins; III is the concentration of bicyclic paraffins; IV is the concentration of tricyclic paraffins; V is the concentration of tetracyclic paraffins; VI is the concentration of pentacyclic paraffins; VII is the concentration of hexacyclic paraffins.

From the experimental results shown in Table 1 it is observed that the new Super SAE 15W / 40 monograde oil has a higher concentration of hydrocarbons with 27 and 28 carbon atoms, since each group of hydrocarbons has a concentration of 7.2% mass .

Considering the results of the composition by type of hydrocarbons and The concentration of the different types of hydrocarbons in the oil studied, Table 1, has been selected to linear octacosane or n-octacosane (with formula condensed chemistry n-C ^ ss) as a representative hydrocarbon of oils automotive in order to show in this example the ability to solubilize it through the use of ethane as solvent in supercritical state, at different temperature and pressure conditions. It should be noted that n-octacosane is a hydrocarbon of linear molecular structure that belongs to the family of paraffins, with a high boiling point (about 551.15 K at a pressure of 15 mm of mercury), that is, with low pressure Steam or low volatility.

It is important to note that the hydrocarbon studied, called n-octacosane, is considered representative of the different hydrocarbons that make up the automotive lubricating oil new Super SAE 15W / 40 monograde.

Using the process described in this invention with the device shown in Figure 1, in this example experimental results were obtained of the solubility of n-octacosane in supercritical ethane under isothermal conditions of 308.15 K in the extraction equipment, at six different values of pressure in the range of 10 to 20 MPa. Table 2 contains the experimental results of the solubility in mole fraction (y) of n-octacosane in supercritical ethane.

Table 2.- Results of the solubility, expressed in mole fraction (y), of n-octacosane (n-C28H58) in supercritical ethane (C2H6), at 308.15 K, at six different pressure values (P) in the range of 10 to 20 MPa.

P / MPa Yn-octacosan 10 0.0034 12 0.0053 14 0.0072 16 0.0097 18 0.0122 20 0.0145 The experimental results in Table 2 indicate that the use of ethane under conditions of temperature and pressure higher than its gas / liquid critical point (305.4 K = 32.25 ° C and 4.88 MPa, approximately equal to 48.8 atmospheres), allows to solubilize the hydrocarbon not volatile n-octacosane, increasing the amount of n-octacosane solubilized by supercritical ethane as the pressure rises from 10 to 20 MPa. Thus, it is observed from the values of Table 2 that at 12 MPa an increase in solubility of 55.88% was obtained with respect to the value at 10 MPa, at 14 MPa an increase in solubility of 35.85% was obtained with respect to the result at 12 MPa, at 16 MPa an increase in solubility of 34.72% is obtained with respect to the value at 14 MPa, the increase in solubility at 18 MPa is 25.77% with reference to the value at 16 MPa and at the pressure of 20 MPa was obtained an increase in the solubility of 18.85% with respect to the result at 18 MPa. It is observed that the solubility of n-octacosane in supercritical ethane at 20 MPa pressure is 426.5% higher than the solubility value at 10 MPa.

This comparison shows that, under isothermal conditions, the pressure is a very important process parameter to achieve the maximum solubility of a hydrocarbon of linear structure, belonging to the family of paraffins, with low volatility, in a supercritical solvent.

EXAMPLE 2 Using the process described in this invention with the device shown in Figure 1, in this example experimental results of the solubility were obtained of n-octacosan in supercritical ethane under isothermal conditions of 323.15 K, at six different pressure values in the range of 10 to 20 MPa. Table 3 contains the experimental results of the solubility in molar fraction (y) of octacosan in supercritical ethane.

Table 3.- Results of the solubility, expressed in mole fraction (y), of octacosan (n-028? 58) in supercritical ethane (C2H6), at 323.15 K, at six different pressure values (P) in the range of 0 to 20 MPa.

It is observed from the experimental results included in Table 3 that when increasing the temperature from 308.15 K, see the results of Table 2 in Example 1, at 323.15 K the solubility of n-octacosane in supercritical ethane increases, considering the same pressure value in the range of 10 to 20 MPa.

To quantitatively establish the effect of the increase in temperature on the solubility of octacosan in supercritical ethane, the results of Tables 2 and 3 are compared. By means of this comparison, it is obtained that at 323.15 K and 10 MPa the solubility is greater in 8.82% that the corresponding one to 308.15 K and the same pressure, to 323.15 K and 12 MPa the solubility is greater in 24.53% than that corresponding to 308.15 K and the same pressure, at the constant pressure of 14 MPa the solubility at 323.15 K is greater in 33.33% than that corresponding to 308.15 K, at 323.15 K and 16 MPa the solubility is higher in 29.90% than that corresponding to 308.15 K and the same pressure, at 323.15 K and 18 MPa the solubility is greater in 35.25% than that corresponding to 308.15 K and the same pressure and at the constant pressure of 20 MPa the solubility is higher in 34.48% at 323.15 K than that corresponding to 308.15 K.

The comparison shows convincingly that temperature is also a very important process parameter to be considered in order to obtain the maximum solubility of a non-volatile hydrocarbon in a supercritical solvent.

EXAMPLE 3 In this example, the great advantages of the process developed in the present invention will be shown again, for this purpose the determination of the hydrocarbon composition of the new automotive lubricating oil commercially known as Ultra SAE 15W / 40 multigrade was carried out in order to carry out a study of the capacity to solubilize a hydrocarbon representative of that oil by means of the use of ethane as solvent in the supercritical state. The determination of the hydrocarbon composition of the multigrade Ultra SAE15W / 40 commercial oil was carried out by means of a gas chromatograph coupled to a high resolution mass spectrometer. This equipment has an accuracy of ± 0.05 ng (Inanogram = 1 x 10"9 g).

The results of the analysis of the composition of the hydrocarbons of the new automotive lubricating oil Ultra SAE 15W / 40 multigrade are presented in Table 4.

Table 4 - Composition in% mass of the hydrocarbons present in the commercial oil new Ultra SAE 15W / 40 multigrade.

N C I II III IV V VI Vil TOTAL / I% masaj 23 0.6 0.7 0.5 0.4 0.5 0.3 0.1 3.0 24 0.6 0.7 0.6 0.3 0.5 0.3 0.2 3.2 25 0.6 0.8 0.6 0.4 0.6 0.4 0.2 3.7 26 0.7 0.7 0.6 0.6 0.7 0.3 0.2 3.8 27 0.7 0.8 0.7 0.4 0.8 0.5 0.3 4.3 28 0.6 0.8 0.7 0.5 0.9 0.6 0.3 4.4 29 0.6 0.9 0.7 0.5 1.0 0.6 0.3 4.7 30 0.5 0.7 0.8 0.5 0.9 0.7 0.4 4.5 31 0.5 0.8 0.6 0.4 0.7 0.7 0.3 4.0 32 0.5 0.7 0.6 0.3 0.7 0.7 0.5 4.0 33 0.3 0.7 0.6 0.4 0.8 0.7 0.4 3.9 34 0.5 0.5 0.5 0.4 0.7 0.6 0.4 3.6 35 0.4 0.5 0.5 0.4 0.7 0.5 0.4 3.4 36 0.4 0.6 0.5 0.4 0.7 0.6 0.4 3.6 37 0.4 0.5 0.5 0.4 0.7 0.5 0.4 3.5 38 0.4 0.7 0.6 0.4 0.7 0.6 0.4 3.8 39 0.4 0.6 0.5 0.4 0.6 0.5 0.5 3.5 40 0.4 0.5 0.5 0.3 0.6 0.5 0.4 3.1 Where NC is the number of carbon atoms; I is the concentration of hydrocarbons called paraffins; II is the concentration of monocyclic paraffins; III is the concentration of bicyclic paraffins; IV is the concentration of tricyclic paraffins; V is the concentration of tetracyclic paraffins; VI is the concentration of pentacyclic paraffins; VII is the concentration of hexacyclic paraffins.

Of the results on the composition of hydrocarbons of the commercial oil Ultra 15W / 40 it can be observed that the concentration of hydrocarbons that have 29 and 30 carbon atoms, since each group of hydrocarbons presents a total concentration of 4.7 and 4.5% mass, respectively.

Considering the results of the composition by type of hydrocarbons and the concentration of the different types of hydrocarbons in the oil studied, Table 4, the hydrocarbon with the condensed chemical formula C30H62, called 2,6,10,15,19, has been selected. 23-hexamethyltetracosane, also colloquially known as squalane, as representative of the new automotive oil Ultra SAE 5W / 40 multigrade in order to show in this example the ability to solubilize it by using ethane as solvent in supercritical state, under different conditions of pressure under the constant temperature of 308.15 K. It should be noted that squalane is a hydrocarbon called branched paraffin with high boiling point (449.15 K at a pressure of 0.05 mm of mercury), that is, low vapor pressure or low volatility .

Employing the process described in this invention with the device shown in Figure 1 in this example, experimental results of squalane solubility in supercritical ethane were obtained under isothermal conditions of 308.15 K, at six different pressure values in the range of 10 to 20. MPa. Table 5 contains the results of the solubility in mole fraction (y) of squalane in supercritical ethane.

Table 5.- Results of the solubility, expressed in mole fraction (y), of squalane (C3oH62) in supercritical ethane (C2H6), at 308.15 K, at six different pressure values (P) in the range of 10 to 20 MPa .

The experimental results in Table 5 show that the use of ethane under conditions of temperature and pressure above its gas / liquid critical point allows solubilizing the non-volatile branched hydrocarbon called squalane, increasing the amount of squalane solubilized by supercritical ethane as the pressure rises from 10 to 20 MPa. Thus it is observed from the values of Table 5 that at 12 MPa an increase in the solubility of 35.04% is obtained with respect to the value at 10 MPa, at 14 MPa an increase in the solubility of 23.24% was obtained with respect to the result at 12 MPa, at 16 MPa, an increase in solubility of 6.36% is obtained with respect to the value at 14 MPa, the increase in solubility at 18 MPa is 3.50% with reference to the value at 16 MPa and at the pressure of 20 MPa a increase in solubility of 2.59% with respect to the result at 18 MPa. Overall it is observed that the solubility of squalane in supercritical ethane at 20 MPa pressure is 87.96% higher than the solubility value obtained at 10 MPa.

This comparison shows that the pressure is a very important process parameter to obtain the maximum solubility of a paraffinic hydrocarbon with a branched structure with low volatility in a supercritical solvent. It is important to note that the hydrocarbon studied, called 2,6,10,15,19,23-hexamethyltetracosane or squalane, is considered representative of the different hydrocarbons that make up the automotive lubricating oil new Ultra SAE 15W / 40 multigrade.

EXAMPLE 4 Employing the process described in this invention with the device shown in Figure 1 in this example, experimental results of the solubility of the hydrocarbon named 2,6,10,15,19,23-hexamethyltetracosane or squalane in supercritical ethane were obtained under isothermal conditions of 323.15 K, at six different pressure values, in the range of 10 to 20 MPa. Table 6 contains the experimental results of the solubility in molar fraction (y) of squalane in supercritical ethane.

Table 6.- Results of the solubility, expressed in mole fraction (y), of squalane (C3oH62) in supercritical ethane (C2H6), at 323.15 K, at six different pressure values in the range of 10 to 20 MPa.

It is observed from the experimental results included in Table 6 that upon increasing the temperature from 308.15 K, see the results of Table 5 in Example 3, at 323.15 K the solubility of squalane in supercritical ethane increases, considering the same pressure value in the range of 10 to 20 MPa.

To quantitatively establish the effect of the increase in temperature on the solubility of squalane in supercritical ethane, the results of Tables 5 and 6 are intercompared. By means of this comparison, it is obtained that at 323.15 K and 10 MPa the solubility is greater in 166.42% that the corresponding one to 308.15 K and the same pressure, to 323.15 K and 12 MPa the solubility is greater in 98.65% that the corresponding one to 308.15 K and the same pressure, to the constant pressure of 14 MPa the solubility to 323.15 K is greater in 65.57% than that corresponding to 308.15 K, at 323.15 K and 16 MPa the solubility is higher at 61.03% than that corresponding to 308.15 K and the same pressure, at 18 MPa the solubility is higher at 62.95% at 323.15 K than that corresponding to 308.15 K, and at the constant pressure of 20 MPa the solubility is higher in 61.75% at 323.15 K than that corresponding to 308.15 K.

The intercomparison shows very well. It is clear that temperature is a very important parameter to be considered in order to obtain the maximum solubility in a supercritical solvent of a hydrocarbon of non-volatile branched structure representative of the different hydrocarbons that make up the automotive lubricating oil new Ultra SAE 15W / 40 multigrade.

EXAMPLE 5 Employing the process described in this invention with the device shown in Figure 1 in this example, experimental results of the solubility of the hydrocarbon named 2,6,10,15,19,23-hexamethyltetracosane or squalane in supercritical ethane were obtained under isothermal conditions of 348.15 K, at four different pressure values, in the range of 14 to 20 MPa. Table 7 contains the experimental results of the solubility in mole fraction (y) of squalane in supercritical ethane.

Table 7.- Results of the solubility in mole fraction (y) of squalane (C3oH62) in supercritical ethane (C2H6), at 348.15 K, at four different pressure values in the range of 14 to 20 MPa.

It is possible to observe clearly from the experimental results included in Table 7 that upon increasing the temperature to 348.15 K from 308.15 K, see the results of Table 5 in Example 3, the solubility of squalane in supercritical ethane increases, considering the same pressure value in the range of 14 to 20 MPa. The same can be observed when establishing a comparison between the squalene solubility results at 348.15 K of this example and those obtained at 323.15 K and shown in Table 6 in Example 4.

The intercomparison shows very clearly that the temperature is a very important process parameter to be considered in order to obtain the maximum solubility in a supercritical solvent of a non-volatile branched hydrocarbon representatof the different hydrocarbons that make up the new automotlubricating oil Ultra SAE 15W / 40 multigrade.

Example 6 In this example, the great advantages of the regeneration process of used lubricating oils of this invention will be shown. Regeneration with ethane was carried out as a solvent under supercritical conditions of a sample of used automotlubricating oil, commercially known as Super SAE 15W / 40 monograde. The sample used was obtained from a motor vehicle that had a total length of 63,770 km, while the used oil was used in the vehicle's motor for 10,000 km of travel.

The regeneration of the lubricating oil used was carried out with the process of this invention and the device of Figure 1. The temperature of the vessel in which the selectextraction with the solvent is carried out at supercritical conditions of pressure and temperature was kept constant at 308.15 K and the pressure was 16 Pa, that is, conditions higher than those corresponding to the gas / liquid critical point of ethane.

As a result of the regeneration of the used automotlubricating oil Super 15W / 40 with supercritical ethane at 6 MPa and 308.15 K, the pollutants possessed by the used oil such as gasoline, insoluble solid materials and metals from natural wear of different engine components were eliminated. of the decomposition of the chemical addit used in the formulation of the lubricating oil. It should be noted that one of the results of great relevance that shows the great advantages of the process of this invention is the decrease in the content of iron and chromium in the oil regenerated with the process of this invention with respect to that observed in the lubricating oil used in 81.13. and 99.55%, respecty, as will be shown quantitaty below.

The inducty coupled plasma spectroscopy method was used to know exactly the type and concentration of the metals that have the samples of new, used and regenerated automotlubricating oils type Super SAE15W / 40 monograde.

The comparison of the concentration obtained for six different metals in each of the three samples of lubricating oil is shown in Table 8.

Table 8.- Results of the concentration of metals in three different samples of automotlubricating oil Super SAE 15W / 40 (new oil, used and regenerated with the process of this invention) Concentration / mg kg "'i New oil Used oil Oil Metals regenerated with supercritical solvent Calcium 2310 2020 0.158 Magnesium 70 36.3 10.8 Zinc 983 935 48.6 Chromium 0.015 28 0.126 Iron 12.5 160 30.2 Tin < 0.050 < 0.050 < 0.050 A decrease in the concentration of metals such as calcium, magnesium and zinc in the used lubricating oil is observed with respect to the corresponding concentration in the new lubricating oil. This can be explained as a consequence of the deterioration of the chemical addit that were originally used in the preparation of the new lubricating oil. However, when the comparison of the content of these metals in the oil used in relation to the contained in the oil regenerated with the process of this invention, it is evidently observed that there is a very low concentration thereof. This is due to the fact that during the regeneration of the oil used through the use of the supercritical solvent, these metals remain concentrated in the waste, since the solvent is highly selective towards the hydrocarbons of the used lubricating oil.

On the other hand, tin dnot vary its content; this is observed by comparing the value of the sample of the regenerated oil with the process of this invention with the concentration in the other two samples of lubricating oil. This is because the parts of the engine that are made of this metal have a negligible wear.

It can be seen from the results in Table 8 that the original chromium content of the new oil was increased to 28 mg / kg in the oil used. This is usually due to the wear and tear that occurs on the set segments-shirt, engine parts that are made of that metal. Likewise, from table 8 it is notable that the content of chromium in the oil regenerated with the process of this invention is very low, since it only contains 0.45% of that found in the used automotive lubricating oil sample. This clearly indicates that in the process of this invention the use of a solvent that is at supercritical conditions allows selectively extracting the hydrocarbons from the used oil and not the metals; which is undoubtedly highly favorable to define the new applications of the regenerated oils with this invention.

Regarding the iron content Table 8 shows that the used oil contains an order of magnitude more than the new oil. This could. due to abrasive and / or corrosive wear of crankshaft bearings, camshaft, liners, crankshaft and engine thrust bearings. But what is really surprising is that the oil regenerated with the process of this invention contains only 18.87% of the iron that the oil sample used; which clearly indicates that the regeneration process developed in this invention is not selective towards metals, so that regenerated oils can be reused without additional treatment, as usually happens in other previously developed processes.

As a final consideration related to the evaluation of the metal content of the Super SAE 15W / 40 monograde oil, it should be noted that other metals were studied such as: barium, sodium, lead, silicon, molybdenum, nickel, copper and aluminum, which are not reported due to which they are in a very small concentration in the studied samples of new and used oils, so they are not useful to establish the great advantages of the process of regeneration of used lubricating oils presented in this invention.

The results shown in this example that the process developed in this invention is highly selective in extracting the hydrocarbons from the used lubricating oil is in full congruence with the results included in Examples 1 to 5.

Example 7 In this example, the great advantages presented by the regeneration process of used lubricating oils of this invention will also be shown. The regeneration of a sample of used automotive lubricating oil, commercially known as Super SAE 15W / 40 monograde, was carried out with ethane as a solvent under supercritical conditions. The sample used was obtained from a motor vehicle that had a total route of 63,770 km, while the used oil was used in the vehicle's motor during 0,000 km of route.

The regeneration of the used lubricating oil was carried out with the process of this invention and the device of Figure 1. The temperature of the extractor in which the regeneration takes place was kept constant at 323.15 K and the pressure was 16 Pa, that is, conditions higher than those corresponding to the gas / liquid critical point of ethane.

As a result of the regeneration of the used automotive lubricating oil Super SAE 15W / 40 monograde with supercritical ethane at 16 MPa and 323.15 K, the pollutants that the used oil used as gasoline, insoluble solid materials and metals were eliminated.

To carry out the evaluation of the quality of Super Racing Premium 15W / 40 regenerated oil with the process of this invention, a comparison between several physicochemical properties of said oil with those of new oil and used oil is made in this example.

For the experimental determination of the physicochemical properties of the three different samples of lubricant oil studied there are different techniques established by the standards of the American Society for Testing and Materials (known in the technical media as ASTM for its acronym in English).

The different physicochemical properties determined in this example are included in Table 9.

Table 9.- Comparison of physicochemical properties of three different samples of automotive lubricating oil Super SAE 15W / 40 monograde (new oil, used and regenerated with the process of this invention) Viscosity is one of the physicochemical properties of greatest interest for know the quality and possible application of any lubricating oil. The results of the viscosity shown in Table 9 indicate that the viscosity, at 313 K, of the oil regenerated with the process of this invention decreased by 13.33 and 36.37% with respect to the viscosity values of the used and new oil samples, respectively. Likewise, at the temperature of 373 K, it can be seen that the viscosity of the oil regenerated with the process of this invention has a viscosity value that is 9.99 and 22.91% lower than the viscosity value of the used and new lubricating oil samples. , respectively. This is the \ It \ him Obvious result that the process of this invention produces oils. regenerated lubricants that can be considered as high quality base oils so that they can be added with a balanced mixture of suitable chemical additives to increase their viscosity (for example, anticorrosive additives, antioxidant additives, foam suppressant additives, dispersants, etc.) and have specific commercial or industrial applications.

The viscosity index is the value that indicates the variation of the viscosity of a lubricating oil with temperature. To determine the viscosity index, the variation of the viscosity value of the oil is compared to the temperatures of 313 and 373 K. In this method, the hydrocarbon oils rich in paraffinic hydrocarbons (ie of linear and branched structure) are characterized in that their viscosity decreases very little with temperature, so they have been assigned a viscosity index of 100, while the lubricating oils rich in naphthenic hydrocarbons (ie saturated cyclic structure), whose viscosity varies greatly with temperature gave them the index 0. According to this classification and with the results shown in Table 9 the new lubricant oil studied in this example is paraffinic origin, so the process of this invention has allowed selectively extracting in the oil named here as regenerated hydrocarbons of paraffinic nature, both linear and branched. Thus, the regenerated oil with a high viscosity index (= 138) can be classified as a high quality base lubricating oil that can be reformulated with a suitable mixture of chemical additives to have new automotive lubricating oils with high thermal stability again or to generate lubricating oils for other specific commercial or industrial applications that involve wide changes in working temperatures.

Regarding the density values, included in Table 9, of the different samples of lubricating oils studied it is observed that the oil regenerated with the processes developed in this invention has a lower density than that corresponding to the samples of used oil and new oil . This clearly indicates that selective extraction, with the supercritical solvent, of the paraffinic hydrocarbons found in the used oil does not include the separation of high density materials, such as gums, lacquers and muds formed in the engine, metallic compounds (see example 6) and additives chemicals of polymeric type. This shows very clearly that the process of this invention produces regenerated lubricating oils rich in paraffinic hydrocarbons that are considered of high quality, either to be reformulated again or to establish specific applications according to the characteristics shown in Table 9.

With regard to color, the regenerated oil did not vary with respect to the value determined for the oil used, which indicates the presence of similar components in both samples, such as paraffinic hydrocarbons. The difference in color observed in the new lubricating oil sample is due to the additives contained in its formulation.

The runoff temperature is that which indicates the minimum temperature at which the oil flows through the lubrication circuits. Then, when observing the corresponding values in Table 9, it can be established that the regenerated oil no longer contains the different additives contained in the new oil, which provide the latter with a higher runoff temperature.

The result of Table 9 corresponding to the concentration of gasoline evidently also shows that the process of this invention produces regenerated lubricating oil without the gasoline which contaminated the used lubricating oil.

On the other hand, comparing the content of insoluble compounds in pentane of the different samples studied, it is observed in Table 9 that both the new oil and the used oil have greater insolubles than the oil regenerated with the process of this invention. This indicates that the metals that were part of the original additives of the new oil are not present in the regenerated oil. Likewise, the regenerated oil does not contain the pollutants of the oil used as coal and metals from wear of the parts and mechanisms of the engine. The oil regenerated with the process of this invention contains only 15.38% of the insoluble materials in pentane that contains the used lubricating oil, which shows with clear evidence that the process of this invention is highly selective to extract paraffinic hydrocarbons that are the base of lubricating oils with high quality.

The insolubles in toluene represent the products from external contamination, corrosion and wear of the lubricated mechanisms and the coal formed by the incomplete combustion of the fuel and a possible partial coking of the oil. Thus, the results of Table 9 indicate that the oil regenerated with the process described in this invention contains very few insoluble materials in toluene (only one third of the materials contained in the lubricating oil used), because the use of solvents Supercritical makes the extraction selective towards paraffinic hydrocarbons, which are the basis of lubricating oils with high quality.

From all of the foregoing it should be evident that the present invention presents a highly efficient process for regenerating used lubricating oils. The process of this invention does not employ substances that are toxic or aggressive to the environment. The different examples serve to show that different pressure and temperature conditions of the solvent to be used can be applied within the process shown.

Claims (6)

NOVELTY OF THE INVENTION Having described this invention, it is considered as a novelty and therefore the content of the following clauses is claimed as property:

1. A process for the regeneration of used lubricating oils that are contaminated by solid particles, chemical additives, fuels and metal compounds; to obtain as a product high molecular weight hydrocarbons or high quality base lubricating oils, which comprises the following steps: a) Filter the used lubricating oil to remove the solid particles, b) Transfer the filtered lubricating oil to the extractor, c) Contact, at constant temperature and pressure conditions, which are selected in the temperature ranges from 278.15 to 373.15 K (5) at 100 ° C) and pressure from 4 to 24 MPa (approximately equivalent to 40 and 240 atmospheres of pressure, respectively), the lubricating oil filtered with the selected solvent flow that is already under defined conditions of temperature and pressure above its critical point gas / liquid, to carry out the selective extraction of hydrocarbons of high molecular mass, d) Allow the contact between used lubricating oil and solvent is intimate by means of the dispersion by bubbling of the solvent into the oil and that ? Transfer of matter from the lubricating oil to the solvent is very efficient by means of internal devices of the contactor for such purpose, e) Expand the mixture formed by the solvent and the high molecular weight hydrocarbons or extracted high quality lubricating oils that come out the upper part of the extractor in an expansion system, which is at suitable temperature and pressure conditions and always below the values corresponding to the temperature and pressure of the critical point of the gas / liquid transition of the solvent used; so these conditions are selected from the following temperature and pressure ranges: 293.15 to 353.15 K (20 to 80 ° C) and pressure of 0.1 to 15 MPa (approximately equivalent to 1 and 150 atmospheres of pressure, respectively), f) Efficiently separate in the expansion system high molecular weight hydrocarbons or high quality lubricant oils extracted that are now in phase or liquid state and the solvent that is now in phase or gaseous state, g) Recirculate the solvent used to be reused in the process after a compression stage, ie pressurization, without the need for it to be recovered by thermal means or chemical treatments, and h) Store in the corresponding container the solvent at supercritical conditions of temperature and pressure, for reuse in the process of this invention; so these conditions are selected in the temperature ranges of 278.15 to 373.15 K (5 to 100 ° C) and pressure of 4 to 24 MPa (approximately equivalent to 40 and 240 atmospheres of pressure, respectively),

A process for the regeneration of used lubricating oils according to clause 1, wherein the solvent is selected from the group consisting of carbon dioxide, methane, ethane, ethylene, propane, butane and pentane. Preferably carbon dioxide, ethane or propane,

A process for the regeneration of used lubricating oils according to clauses 1 and 2, where the used lubricating oils that can be treated are mainly the oils that were used in gasoline and diesel engines, in mechanical systems of transmission of movement, in hydraulic systems or in heat exchange systems.

A process for the regeneration of lubricating oils used in accordance with clauses 1 to 3, where the regenerated lubricating oil is of high quality since it is free of fuels such as gasoline and diesel.

A process for the regeneration of lubricating oils used in accordance with clauses 1 to 3, where the regenerated lubricating oil is of high quality and is free of chemical additive additives such as anti-corrosives, anti-oxidants, extreme pressure agents and suppressants of foam.

6. A process for the regeneration of used lubricating oils according to clauses 1 to 3, where the regenerated lubricating oil is of high quality and low concentration of metallic compounds: The concentration for calcium compounds is in the range of 0 to 0.16 mg / kg, magnesium compounds in the range of 0 to 1 mg / kg, zinc compounds in the range of 0 to 50 mg / kg, chromium compounds in the range of 0 to 0.13 mg / kg, for iron compounds in the range from 0 to 35 mg / kg and for tin compounds in the range from 0 to 0.05 mg / kg. The concentration of metallic compounds of barium, sodium, lead, silicon, molybdenum, nickel, copper and aluminum is, within the experimental uncertainty, 0 mg / kg.