Process for recovering a biological fraction from the regeneration of waste oils

Abstract

A process for recovering a biological fraction from the regeneration of waste oils is disclosed, including basification, recover of the aqueous fraction and acidification thereof Such steps are performed on the flows coming from the fractional distillation step in packed column of the regenerated waste oils. Preferably, the process is performed batchwise, wherein each fraction coming from the fractional distillation of regenerated waste lubricants undergoes the process separately from the other fractions.

Description

[0001] PROCESS FOR RECOVERING A BIOLOGICAL FRACTION FROM THE REGENERATION OF WASTE OILS

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] This invention refers to a process for getting biolubricants , particularly to a process for recovering a biological fraction from the regeneration of waste oils from which biolubricants can be easily and readily produced .

[0004] BACKGROUND OF THE INVENTION

[0005] Lubricants are widely used in many fields of the art , especially in mechanics and electrical engineering . Most moving parts are commonly lubricated, in order to avoid gripping problems . Moreover, lubricants reduce the friction coef ficients of the materials , avoids the detachment of metal or hard parts , avoids material sintering, etc .

[0006] Lubricants used in industry are mostly mineral oils , produced by fractional distillation of oil and possibly through other petrochemical processes . This leads to products which allow high performances and have relatively low costs . Mineral oils have historically been preferred to plant or animal oils , because of the lower cost and of the fact that plant and animal oils , like olive oil and butter, for instance , are normally used for feeding people .

[0007] As a heavy drawback, mineral oils are difficult to dispose of and their careless disposal can pollute waters , soils and food . From this drawback, the need of reclaiming waste mineral oils has arisen since several years . The Applicant has filed many patents about such reclamation, resulting in a reduction of oil spread in the environment and of the related pollution, in a decrease in oil consumption due to the reuse of waste oils , in the production of enhanced, valuable byproducts , in an increase of the recycled fraction collected by the mandatory consortia and in other beneficial ef fects , even with good economical re- suits . The ef fort of the Applicant in optimising such reclamation processes and in inserting lubricant production in the so- called circular economy are continuing and the forecast is in their further increase .

[0008] Turning to lubricants of plant and animal origin, although they can be considered in principle edible, when wasted also they are pollutants , especially because of their long-lasting decomposition and of their trend to remain in the environment . Therefore , also the disposal of used plant and animal oils , like oils coming from deep frying and food preservation, involves some environmental problems , arising even if they are not harmful substances . Also in this case, the disposal of such oils , which can be called with a new word biolubricants , has got importance in the years , also because of phenomena like the so- called f atbergs .

[0009] Some processes use waste food grade oils for producing the so-called biodiesel, which can be put into diesel engines , instead of fuel produced by crude oil distillation . Sometimes , such waste food grade oils have been treated so as to produce biolubricants , in order to avoid their spread in the environment .

[0010] Biolubricants are getting more and more interest , becoming products which can be used in a reliable way, like mineral oils and very often they are produced from waste oils , so that they are no longer subtracted from the purpose of feeding persons .

[0011] The Applicant , with its application IT102023000020376, has developed a method for adjusting the viscosity of biolubricants , so that they can be produced suitably and tailored for any intended application .

[0012] The collection of oils and fats follows basically two routes : waste food oils are collected by a mandatory consortium and waste oils coming from motors and engines are collected by another consortium . This is due to the fact that , normally, the two kinds of lubricants need to be regenerated differently . This leads to the fact that waste oils , collected from engines , machines and motors partly contain waste biolubricants ; it is very important , especially to tailor their properties , that biolubricants are separated from mineral lubricants and treated differently, also taking into account their different chemistry : mineral oils are indeed normally hydrocarbons , while biolubricants are mostly organic and fatty acids or their esters .

[0013] The pending application EP 23425054 . 6 of the same Applicant discloses a process for producing biolubricants from exhausted biolubricants , used cooking oil (UCO) , regenerated used cooking oil (RUCO ) and the biological fraction of waste mineral oils is processed before any regeneration step of the waste mineral oil is performed . Such a process , however, does not allow to tailor the biolubricants produced according to the needs .

[0014] PROBLEM AND SOLUTION

[0015] The present invention faces the problem of proposing a new process , which overcomes the above problems , and which allows a perfect separation of the biological fraction of waste oils in a process for regeneration of waste oils . This aim is achieved through a process for recovering a biological fraction from the regeneration of waste oils , characterised in that it comprises an extraction step of organic and fatty acids from the oils to be regenerated and in that it is carried out starting from the fractions coming from a fractional distillation step in a process of regeneration of waste mineral oils . Subclaims disclose preferential embodiments of the invention .

[0016] According to a preferred embodiment , the extraction step takes place through basification of the starting fraction, recover of the aqueous layer and acidification of the latter .

[0017] According to an embodiment , the basification of the regenerated oils leads to a mixture which is separated into two layers , one, lighter, containing the mineral lubricants to be dehydrated and one, heavier, containing the biological fraction .

[0018] According to an embodiment , the layer containing the biological fraction is added with strong acids , lowering pH to 3 to 5 . According to an embodiment , the acidified liquid is mixed with organic solvents , so as to separate two layers , one , heavier, containing wastewater and one , lighter, containing the biological fraction recovered, to be distilled in order to remove the solvent .

[0019] According to an embodiment , the solvent is an organic solvent able to dissolve fatty acids with an affinity with the acids that is higher than the one exhibited by water . Preferably, the solvent is chosen among : hexane, heptane, octane, nonane , decane .

[0020] According to an alternative embodiment , the extraction step is performed by adding a polar solvent having a low boiling point to the fraction to be processed .

[0021] According to an embodiment , the said polar solvent is chosen among methanol , ethanol, isomers of propanol, isomers of butanol , isomers of hexanol , acetone, methyl-ethylketone .

[0022] According to an embodiment , the biological fraction is recovered by fractional distillation of the bottom (heavy ) layer of the mixture obtained from the fraction to be processed and the polar solvent .

[0023] According to an embodiment , the process is performed batch- wise .

[0024] According to an embodiment , each fraction coming from the fractional distillation of regenerated waste lubricants undergoes the process separately from the other fractions .

[0025] According to an embodiment , bases for lubricants which can make up the feed for the process according to the invention are : vacuum gasoil (VGO ) , spindle lubricant fraction ( SLF ) , light (LLF) and heavy oils (HLF ) , all of them being semi-finished product in the regeneration of waste oils .

[0026] According to an embodiment , basification is carried out in the presence of a strong base . Preferably, basification is performed with an inorganic strong base . Among such bases , the following can be reported : NaOH, KOH, Na2COs, K2CO3.

[0027] According to an embodiment , the mineral oils separated in the process are dehydrated . According to an embodiment, the mineral oils undergo further treatments. Preferably, the mineral oils are hydrofinished.

[0028] According to an embodiment, acidification takes place in the presence of strong acids.

[0029] According to an embodiment, acidification is performed with solid acids, directly added to the solution to be acidified.

[0030] According to an embodiment, the biological fraction is extracted from the aqueous solution with a solvent which is not miscible with water.

[0031] According to an embodiment, the organic fraction, containing the biological fraction, undergoes a fractional distillation. Preferably, the solvent removed in the said fractional distillation step is recycled to acidic solution. According to a preferred embodiment, fresh solvent is made up, in order to keep constant the amount of solvent performing the extraction.

[0032] According to an embodiment, the lubricant base coming from the regeneration of waste oils is mixed with a polar solvent, chosen among: methanol, ethanol, isomers of propanol, isomers of butanol, isomers of hexanol, acetone, methyl-ethylketone .

[0033] According to an embodiment, the ratio between the lubricant base and the polar solvent ranges from 0.8:1 to 1.3:1 by mass; preferably, such a ratio is 1:1.

[0034] According to an embodiment, the mixture of lubricant base and polar solvent settles into two layers.

[0035] According to an embodiment, the heavier layer (bottom layer) undergoes a fractional distillation step, to remove the polar solvent .

[0036] According to an embodiment, the polar solvent removed during the distillation step is recycled to the beginning of the process .

[0037] According to an embodiment, a make-up of polar solvent is provided, in order to keep the ratio between polar solvent and the lubricant base constant.

[0038] According to an embodiment, the biological fraction recovered through the process undergoes a process for producing biolubricants . BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further features and advantages of this invention will anyway be apparent from the following detailed description of embodiments thereof , given only as an example and with no purpose of limitation, the same being illustrated in the annexed drawings , wherein : fig . 1 represents a flow chart of the process according to a preferred embodiment of the invention; and fig . 2 represents a flow chart of the process according to an alternative embodiment of this invention .

[0040] BEST MODE TO CARRY OUT THE INVENTION

[0041] The present invention relates , as seen above , to a process for getting the biological fraction contained in waste oils to be regenerated . This process is now disclosed in further detail .

[0042] In the following, the steps of the process according to a preferred embodiment of this invention are illustrated on the basis of the flow chart of fig . 1 . In this process , the extraction step takes place through basification of the starting fraction, recover of the aqueous layer and acidification of the latter . The basification allows to extract the biological fraction, mainly made up by organic and fatty acids or their esters .

[0043] A mixer 1 , equipped with a stirrer 2 , is fed by two pipes , respectively 3 and 4 . The mixed liquid, after the stirring, exits through a pipe 5 and is fed to a settler 6 , allowing the extraction to be completed .

[0044] Two layers separate in the settler 6 . The top layer, containing a hydrocarbon liquid, leaves the extractor through a pipe 7 , feeding a dehydrating column 8 , where the remaining water is removed through a pipe 9 and the oily fraction is recovered from a pipe 10 . The dehydration column 8 can be a column for flash distillation or a packed column .

[0045] The bottom layer in the settler 6 , which contains an aqueous liquid, leaves the settler through a pipe 11 . The pipe 11 feeds a mixer 12 , having a stirrer 13 . The mixer 12 is fed also by a second pipe 14 .

[0046] The mixed liquid is fed by a pipe 15 to another mixer 16 , possessing a stirrer 17 . The mixer 16 is fed also by another pipe 18 .

[0047] The liquid mixed in the mixer 16 feeds , through a pipe 19, a settler 20 . The liquid within the settler 20 separates into two layers . The bottom layer, which is basically wastewater, is discharged through an outlet 21 . The top layer, which contains a solution in an organic solvent , leaves the settler through a pipe 22 and feeds a plate distillation column 23 , from which the product is collected from an outlet 24 . The distillation head leaves the column through the pipe 18 and is recycled to the mixer 16 . A feed 25 acts as a make up to the pipe 18 .

[0048] Now, the steps of the process according to the embodiment shown in fig . 2 are described, taking into account that elements which are identical to the ones shown and discussed in fig . 1 bear the same reference . In this process , the extraction step is performed by adding to the fraction to be processed a polar solvent having a low boiling point . This solvent preferentially dissolves organic and fatty acids than hydrocarbons .

[0049] The mixer 1 has a stirrer 2 and two feeds , 3 and 4 . The liquid in the mixer 1 leaves it from the pipe 5 .

[0050] The pipe 5 feeds a settler 6, wherein two layers separate . The top layer is removed through the pipe 7 and is fed to a dehydrating packed column 8 . This column 8 can also be a flash distillation column . The column 8 has two exits , consisting in a pipe 9 and a pipe 10 .

[0051] The bottom layer leaves the settler 6 through a pipe 26, which feeds a plate distillation column 23 , from which a product exits from the pipe 24 and other materials exit through a pipe 27 .

[0052] The process is now disclosed in detail , according to the annexed flow chart and with reference to the steps described above , according to the two embodiments shown above .

[0053] The process is performed downstream a process for the re- generation of waste oils ; at the end of such a process , the oil under regeneration undergoes a fractional distillation step, from which different bases for lubricants split into several fractions . Each fraction exhibits its well-defined boiling point . Therefore, the process according to this invention is carried out once per fraction of bases for lubricants obtained in the regeneration process , so as to be able to get tailored organic and fatty acids . Among such bases , the following can be mentioned : vacuum gasoil (VGO) , spindle lubricant fraction ( SLF ) , light (LLF ) and heavy oils (HLF ) , all of them being semifinished product in the regeneration of waste oils .

[0054] According to the embodiment in fig . 1 , the basis to be processed is fed through the pipe 4 , while an alkaline solution is fed from pipe 3 . As alkaline solutions , aqueous solutions of NaOH, KOH, Na2COs, K2CO3, readily available and cheap, can be suitable, although any strong base can be used advantageously . Normally, the alkaline solution is fed in an amount being 0 . 5 to 2 times by mass the mass of the bases to be treated .

[0055] The stirrer 2 is operated within the mixer 1 for a residence time of 0 . 5 to 2 hours at a temperature below water boiling point , preferably ranging from 60 to 90 ° C, so as to avoid boiling conditions which would excessively alter the composition ( concentrations ) of the solution, while keeping a high extraction rate .

[0056] The mixture oil plus water leaves the mixer 1 through the pipe 5 , which drives the mixture into the settler 6 , where the mixture separates into two layers , according to their weight : a top layer, lighter, containing the oily (mineral lubricants ) , water insoluble liquid to be dehydrated and a bottom layer, heavier, containing a water solution wherein the biological fraction of the regenerated waste oils is contained in the form of salts of organic and fatty acids .

[0057] The oily fraction is drawn through the pipe 7 and sent to a dehydrating step within the column 8 ; such a dehydration step is carried out at a temperature over 100 ° C, in order to have a fast removal of water because of the boiling process , preferably ranging from 120 to 160 °C, at a pressure not higher than the room pressure, preferably ranging from 0 . 400 to 1 , 01 bar, what avoids the related energy consumption and allows a much simpler equipment . After this dehydration, wastewater is removed by the pipe 9 and is sent to the water treatment facility, while dehydrated oils are recovered through the pipe 10 and sent either to further treatment steps ( like hydrofinishing) or directly to the market . These oils have lost 95-99 wt . % of the acids originally contained, which are now in the heavy layer . Therefore, their value becomes higher .

[0058] The aqueous fraction leaves the settler 6 through the pipe 11 and is fed to the mixer 12 . The mixer is further fed through the pipe 14 with an acidic solution . As acids , organic acids having a high boiling point , organic acids having a low boiling point or mineral acids can be employed . As organic acids exhibiting a high boiling point , citric acid and adipic acid can be used . As organic acids having a low boiling point , formic or acetic acids can be used . As mineral acids , HC1 , H2SO4 , H3PO4 can be used . Acids which are solid under normal conditions can be added directly as solid matters . In any case, pH of the solution within the mixer 12 , after admixture with the acid and stirring by the stirrer 13 should decrease from 9-11 to 3-5 , namely from a definitely basic condition to a definitely acid condition . This is achieved during a residence time of 0 . 5 to 2 hours under stirring under room conditions .

[0059] After mixing, the pipe 15 leads the acidic solution, containing free organic and fatty acids , to the mixer 16 . The acids in the aqueous phase do not separate from water and remain admixed thereto . Therefore , an extraction step is needed to remove acids from water, so as to gain the intended products . An organic solvent is fed to the mixer 16 through the pipe 18 . Part of this solvent is recycled from the further steps and a part is added as a make up from the feed 25 . The added solvent performs an extraction of organic and fatty acids from water . Therefore, the features of the solvent are the lack of miscibility with water and ability to dissolve the acids , having an af finity with the acids that is higher than the one exhibited by water . The organic solvent is to be chosen according to the particular fraction drawn from the regeneration process . Examples of such solvents are any isomers of hexane, heptane , octane , nonane, decane . The solvent is added in an amount of 0 . 10 to 10 times by mass the acid solution . The mixer 16 works at room pressure and temperature , with a residence time of 0 . 5 to 2 hours , so as to allow a complete extraction of the acids , without losing solvent by evaporation .

[0060] After mixing, the content of the mixer 16 is sent through the pipe 19 to the settler 20 . The liquid splits into two layers within the settler 20 , according to their weight : a bottom layer, containing wastewater (heavy ) and being discharged through the outlet 21 , from where it is sent to the water treatment facilities . And a top layer ( light ) , containing the organic solvent wherein acids are dissolved; the top layer is drawn and brought , through the pipe 22 , to the plate distillation column 23 . Namely, the acidified liquid is mixed with organic solvents , so as to separate two layers , one , heavier, containing wastewater and one, lighter, containing the biological fraction recovered, to be distilled in order to remove the solvent .

[0061] The column 23 operates at room pressure . The temperature ranges between 70 and 200 °C at the head and from 200 to 250 ° C at the bottom, allowing a verry good separation of highly boiling acids .

[0062] The fat acids , making up the biological content of the waste oils (waste biolubricants ) are recovered through the outlet 24 , which leads to the suitable stocking reservoirs . The head fraction, made up by almost all of the organic solvent fed, leaves the column from the pipe 18 and is recycled to the mixer 16, as already explained . The acids recovered from the outlet 24 can also be processed as biological fraction in a process according to EP 23425054 . 6 of the same Applicant .

[0063] The process according to this invention allows to recover up to 99 wt . % of the biolubricants , already separated according to their molecular weight and, therefore , to their own viscosi- ty, so that they can easily be employed in the suitable technical field . This means that averagely 0 . 5 to 5 wt . % of the waste oils to be regenerated can be recovered as acids for producing biolubricants .

[0064] The process according to the embodiment shown in fig . 2 is described in the following .

[0065] The base for lubricants to be processed is fed through the feed 4 . Feed 3 feeds a polar solvent having low boiling point . Among such solvent , methanol , ethanol , isomers of propanol , isomers of butanol, isomers of hexanol , acetone, methylethylketone . Preferably, the solvent and the basis are fed in a 1 : 1 mass relationship . The stirrer 2 mixes the two liquids under room temperature and pressure, for a residence time of 0 . 5 to 2 hours .

[0066] The mixture is brought by the pipe 5 to the settler 6, wherein two layers separate . The top layer ( light ) contains especially hydrocarbons , making up the mineral oils which have been regenerated and leaves the settler 6 through the pipe 7 . The pipe 7 feeds the dehydrating column 8 , where the hydrocarbons are separated from water at a temperature over 100 ° C, taking advantage of the boiling conditions , preferably ranging from 120 to 160 ° C, at a pressure not higher than the room pressure, so saving plant and energy costs , preferably ranging from 0 . 400 to 1 , 01 bar . After this dehydration, wastewater is removed by the pipe 9 and is sent to the water treatment facility, while dehydrated oils are recovered through the pipe 10 and sent either to further treatment steps ( like hydrofinishing) or to the sale .

[0067] The bottom layer (heavy) exits through th pipe 26 and is fed to the plate distillation column 23 . the biological fraction is recovered by fractional distillation of the bottom (heavy ) layer of the mixture obtained from the fraction to be processed and the polar solvent .

[0068] The column 23 operates at room pressure . The temperature ranges between 70 and 200 °C at the head and from 200 to 250 ° C at the bottom . The fatty acids , making up the biological content of the waste oils (waste biolubricants ) are recovered through the outlet 24 , which leads to the suitable stocking reservoirs . The head fraction, made up by almost all of the polar solvents fed, leaves the column from the pipe 27 . Preferably, it is recycled to the mixer 1 , through the inlet 3 .

[0069] The organic and fatty acids recovered from the outlet 24 can also be processed as biological fraction in a process according to EP 23425054 . 6 .

[0070] The inventive process allows to remove almost all of the organic and fatty acids contained in the semi-finished regenerated lubricant base, so enhancing the lubricant base itself , and to use the removed acids , which become valuable products , instead of being an impurity of the mineral lubricant bases .

[0071] It is anyway understood that the invention should not be considered limited to the particular arrangement described above , which is only an exemplary embodiment thereof , but that many modifications are possible, all at reach of the skilled person, without leaving the scope of the invention itself , as defined by the appended claims .

[0072] In particular, the systems formed by a mixer ( 1 , 16 ) and a settler ( 6, 20 ) could be replaced by series of mixers and settlers in countercurrent , spraying columns , plate or packed column extractors .

[0073] LIST OF REFERENCES

[0074] 1 Mixer

[0075] Stirrer

[0076] 3 Pipe

[0077] 4 Pipe

[0078] 5 Pipe

[0079] 6 Settler

[0080] 7 Pipe

[0081] 8 Dehydrating column

[0082] 9 Pipe 10 Pipe

[0083] 11 Pipe

[0084] 12 Mixer

[0085] 13 Stirrer 14 Pipe

[0086] 15 Pipe

[0087] 16 Mixer

[0088] 17 Stirrer

[0089] 18 P ipe 19 Pipe

[0090] 20 Settler

[0091] 21 Outlet

[0092] 22 Pipe

[0093] 23 Plate distillation column 24 Outlet

[0094] 25 Make up feed

[0095] 26 Pipe

[0096] 27 Pipe

Claims

CLAIMS1. Process for recovering a biological fraction from the regeneration of waste oils, characterised in that it comprises an extraction step of organic and fatty acids from the oils to be regenerated and in that it is carried out starting from the fractions coming from a fractional distillation step in a process of regeneration of waste mineral oils.

2. Process for recovering a biological fraction from the regeneration of waste oils according to claim 1) , characterised in that the extraction step takes place through basification of the starting fraction, recover of the aqueous layer and acidification of the latter.

3. Process as in claim 2) , characterised in that the basification of the regenerated oils leads to a mixture which is separated into two layers, one, lighter, containing the mineral lubricants to be dehydrated and one, heavier, containing the biological fraction.

4. Process as in claim 3) , characterised in that the layer containing the biological fraction is added with strong acids, lowering pH to 3 to 5.

5. Process as in claim 4) , characterised in that the acidified liquid is mixed with organic solvents, so as to separate two layers, one, heavier, containing wastewater and one, lighter, containing the biological fraction recovered, to be distilled in order to remove the solvent.

6. Process as in claim 5) , characterised in that the solvent is an organic solvent able to dissolve fatty acids with an affinity with the acids that is higher than the one exhibited by water.

7. Process as in claim 6) , characterised in that the solvent is chosen among: hexane, heptane, octane, nonane, decane .

8. Process according to claim 1) , characterised in that the extraction step is performed by adding to the fraction to be processed a polar solvent having a low boiling point.

9. Process according to claim 8) , characterised in thatthe said polar solvent is chosen among methanol, ethanol, isomers of propanol, isomers of butanol, isomers of hexanol, acetone, methyl-ethylketone .10 . Process as in claims 8 ) or 9 ) , characterised in that the biological fraction is recovered by fractional distillation of the bottom (heavy ) layer of the mixture obtained from the fraction to be processed and the polar solvent .11 . Process as in any previous claim, characterised in that it is performed batchwise . 12 . Process as ni any previous claim, characterised in that each fraction coming from the fractional distillation of regenerated waste lubricants undergoes the process separately from the other fractions .

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