Process for the production of lubricants having biological origin

Abstract

A process for producing biolubricants is disclosed, wherein the viscosity of the obtained biolubricants is adjusted by choosing the molecular weight of the products.

Description

[0001] PROCESS FOR THE PRODUCTION OF LUBRICANTS HAVING BIOLOGICAL ORIGIN

[0002] DESCRIPTION

[0003] The present invention relates to a process for producing lubricants of natural origin, or "biolubricants" , which provides for adjusting a priori some of their properties .

[0004] Machines typically comprise parts moving relative to each other . This movement , which often takes place at very high speeds , involves the parts rubbing against each other, with the presence of friction, which, on the one hand, tends to oppose the movement and slow it down, and, on the other hand, increases the temperature of the parts more or less indefinitely . These two factors tend to damage the components , with particles detaching from them and the parts themselves possibly melting or sintering, until in the worst case the machine ends up locking up . To overcome this , since the earliest times , lubricants have been used : oily and / or fatty substances that reduce friction, facilitating sliding against one another, minimising particle shedding and making the temperature increase less rapid, although their cooling remains essential .

[0005] Most lubricants are liquids , in the form of oils ; among oils , mineral oils are used most of all .

[0006] One of the fundamental characteristics of oils is their kinematic viscosity : good viscosity enables the machine to perform at its best , minimising risks of breakdowns and lockups . It is essential that the viscosity of a lubricant is the best chosen specifically for each individual part to be lubricated, considering that having a lubricant with a viscosity that is too high means increased friction and resulting heat development , poor machine ef ficiency and loss of power that can lead to either excessively reduced productivity or a beyond-reasonable increase in energy costs . Conversely, a lubricant with a viscosity that is too low increases the risk of wear of parts , results in excessive heat generation, has a short life ( often too short ) and means the machine undergoes maintenance too frequently . Therefore, it is very important to be able to modulate the viscosity of lubricants appropriately and extensively, in order to achieve the desired viscosity in every dif ferent scenario , so that machines can operate under the best possible conditions .

[0007] Most lubricants suitable for machines ( including motor vehicles ) are produced as mineral oils , from petroleum . A merit of these oils is their low production costs , but there are some quite considerable problems . In particular, their disposal after use is a serious problem, since they are substances which, when put into soil or into water courses , tend to persist and pollute them .

[0008] To overcome this problem, processes have been studied for the regeneration of waste oils , such that not only is a large part of the waste oils prevented from ending up in soil or in water courses , but the waste returns to a new life, reducing the share of petroleum to be dedicated to them, and also achieving a certain economic advantage . Being a main by-product , bitumen is useful for asphalting roads and as a base for inks or similar . The Applicant , in particular, has filed numerous patents relating to this regeneration and is very active in this field .

[0009] Although that which has just been described may give the impression that the cycle is thus closed and the pollution by waste oils has been overcome , the reality is , unfortunately, very dif ferent : the essential step in starting regeneration is the collection of waste oil , for example by the appropriate mandatory consortia, and this collection manages to reach and intercept about 30% of the overall used oil . Therefore , a still maj ority proportion of waste oil is disposed of improperly and ends up in groundwater or in soil, causing ma jor environmental damage and a loss of material of some value .

[0010] Relatively recently, the use of lubricating oils of plant origin had begun in the field of mechanics , the oils being suitably treated and adapted for the particular use . The use of these lubricants exhibits many advantages per se . First of all, petroleum consumption can be reduced, thus extending the life of this important raw material , which is not renewable per se and is very useful for a great many uses , especially in the chemistry fields . Secondly, waste food oils can be recovered . Used food oils are commonly perceived not to be problematic substances , as they are not toxic, and the average person is convinced that , as they are food substances , their disposal is not problematic and, therefore , many of these oils end up in sinks , and onward into the sewer . In reality, although they are certainly not toxic substances , they are however rather resistant to decomposition and, in urban water treatment , they are completely and correctly eliminated with difficulty, partly because of their viscous nature, which hinders their rapid flow into the drains . Furthermore, their presence in sewers and their mixing with other substances therein often leads to the phenomenon of " fatbergs", which are formations of fat that rarely dissolve and which eventually clog the sewers , causing in the worst cases the sewage to escape from the sewers into the streets .

[0011] To address this , these oils also should be disposed of correctly . In particular, disposal should lead to their regeneration or to their use with the highest possible commercial value , so as to make it worthwhile to collect these materials as well , in order to make a profit from them . In this regard, one of the most established uses is for the production of biodiesel . Lately, however, as just stated, alongside this use is that of biolubricants .

[0012] Another advantage of biolubricants is that they do not contain synthetic substances and therefore have a low toxicity . Furthermore , when produced from food waste, the biolubricant also does not involve the problem of reducing foodstuffs in order to produce industrial and comparable products .

[0013] In order for biolubricants to be used optimally and therefore be able to establish themselves , it would be desirable , given that which has been said previously, to obtain them with viscosities suitable for the uses for which they are produced . At present , however, it has not yet been possible to program the viscosities of biolubricants and, therefore , they are destined for the uses for which they are suitable, irrespective of actual needs , rather than being produced in the desired quantities according to specific uses for which they are intended .

[0014] EP 1 529 828 discloses a method for producing oils as bases for lubricants , in particular fatty monoesters and fatty polyol esters , by esterifying the fatty acids of palm oil with an alcohol with only one hydroxyl group, in the presence of an acidic catalyst , at high temperature and using an azeotroping agent , such as toluene , to facilitate the removal of water that forms .

[0015] Raof Nurliyana Abdul et al . , Journal of the American Oil Chemists Society, 96 ( 5 ) , 2019, studies the effect of the molecular structure of liquid polyol esters on their physical , chemical and electrical properties , finding that properties such as viscosity are greatly influenced by molecular weight .

[0016] Neeraj J Tiwari et al . , European Journal of Lipid Science Technology, 107 ( 1 ) , 2005 , page 30 , studies the esterification of behenic acid and its derivatives .

[0017] The problem underlying the invention is to propose a process for producing biolubricants , which overcomes the drawbacks mentioned and which provides for obtaining the necessary viscosities for the usage purposes . This aim is achieved through a process for producing biolubricants , wherein the viscosity of the obtained biolubricants is adjusted by choosing the molecular weight of the produced oils , characterised in that the fatty acids to be esterified are produced from used food oils . The dependent claims describe preferred characteristics of the invention .

[0018] Appropriately, the molecular weight of the biolubricants produced is chosen by choosing the acid and alcohol that are reacted to obtain the ester . Thus , the adjustment of the viscosity is within the capabilities of the technician skilled in the art .

[0019] Both synthetic alcohols and acids can be chosen .

[0020] In a preferred embodiment , acids are produced by hydrolysis of used fats and oils , so as to re-enter the "circular economy" . RUCOs , in particular, are not always easy to dispose of / reuse, while , by virtue of the present invention, they have a valid use . In an alternative embodiment , to fatty acids derived from the hydrolysis of used fats and oils synthetic fatty acids are added to form a mixture of fatty acids , which is then subj ected to esterification . Among the synthetic acids which can be added, a preferred one is pelargonic acid . This addition provides for facilitating the fine-tuning of the viscosity of the lubricant which is produced .

[0021] Preferably, the fatty acids resulting from the hydrolysis of used fats and oils are esterified by appropriately choosing the alcohol leading to final esters with the desired molecular weight to obtain the desired viscosity . This viscosity is calculated according to the formula :

[0022] KV4Q = m . MW + q ( 1 )

[0023] Consequently, the desired molecular weight is calculated based on the relationship :

[0024] MW = Kv4o / m -q / m ( 2 )

[0025] Advantageously, the used fats and oils are hydrolysed in the presence of ZnO as catalyst , which is effective and widely available relatively inexpensively . The hydrolysis is carried out at a temperature of 180-250 ° C . The hydrolysis is carried out at a pressure of 10-20 bar .

[0026] Advantageously, the hydrolysis product undergoes fractional distillation, so that the acids can be separated and the molecular weight can be calibrated also based on them . The fractional distillation preferably takes place at a temperature of 240-260 ° C . Said fractional distillation preferably takes place at a pressure of 1-10 Torr .

[0027] In a preferred embodiment , the esterification takes place in the presence of ZnO as catalyst . The present invention relates to a process for producing biolubricants , suitable for obtaining biolubricants of desired viscosity . This takes place in particular by calibrating the obtained ester, by appropriately choosing the alcohol to be used in the esterification of the employed fatty acids .

[0028] The present invention has arisen from the discovery that there is a linear mathematical relationship between the molecular weight of a fatty acid ester and its kinematic viscosity . Said correlation is independent of the temperature and the chemical species involved : two biolubricants (bioesters ) obtained from dif ferent alcohols and / or acids , but having the same molecular weight , have the same kinematic viscosity . Thus , viscosity adjustment is rapid, selective and very simple . In particular, it has been verified that , with KV4Q indicating the kinematic viscosity of an ester (biolubricant ) , expressed in centistokes ( cSt ) , MW the molecular weight of the same ester molecule (biolubricant ) expressed in g / mol, and m and q two numerical constants derived experimentally, the following relationship is obtained :

[0029] KV4Q = m . MW + q ( 1 )

[0030] By virtue of relationship ( 1 ) and knowing how to obtain a fatty acid ester of a certain molecular weight , it is possible to program the kinematic viscosity of the same ester . In practice, one starts from the desired viscosity value and the target molecular weight is derived according to the relationship :

[0031] MW = Kv4o / m -q / m ( 2 )

[0032] Generally, the molecular weights are selected by calibrating the obtained ester, by appropriately choosing the alcohol to be used in the esterification of the employed fatty acids .

[0033] Once m and q are derived, formula ( 2 ) enables the desired biolubricants to be worked out .

[0034] In practice, the present invention can be applied in various ways . One can start from the direct synthesis of fatty acids , then onto the determination of the desired molecular weight by relationship ( 2 ) and, lastly, the choice of alcohols with which the fatty acids are reacted . Thus , biolubricants of desired viscosity can be obtained completely synthetically and from fresh raw materials , extending the scope of use of these lubricants .

[0035] Advantageously, it is preferable to work with processes for regenerating used food oils . Thus , lubricants can be obtained without consuming petroleum, with non-toxic waste and without channelling to industrial production substances that could be used for food, given that waste substances are concerned which are no longer usable in the food sector . Moreover, this food waste is prevented from entering the environment , said food waste in any case involving a lengthy disposal and one which could lead to phenomena of fouling or clogging of sewage systems , through the "fatberg" mechanism . Naturally, it is also possible to use as raw materials mixtures of used oils to be regenerated and synthetic fatty acids .

[0036] In particular, one can start from waste products such as UCOs and RUCOs , hydrolysing and esterifying them in the presence of zinc oxide as catalyst , as already described in some previous patents of the Applicant . The choice of the particular alcohols is what determines the molecular weight that is chosen in order to obtain the desired viscosity .

[0037] Using the process according to the present invention, in addition to lubricants , raw materials can also be obtained for paints and inks and additives for biofuels .

[0038] EXAMPLES

[0039] The present invention is now illustrated in more detail, based on some practical example embodiments .

[0040] For the targeted production of biolubricants , the process was carried out as follows: It started with UCOs and RUCOs. The raw materials were subjected in advance to a washing and centrifugation operation, so as to reduce the level of pollutants and to be able to minimise the formation of by- products of little or no interest. The UCOs and RUCOs thus purified were then hydrolysed in the presence of ZnO at a pressure of 10-20 bar and a temperature of 180-250°C. The hydrolysate was distilled (1-10 torr, 240-260°C) to obtain the pure fatty acids. Lastly, the fatty acids were esterified in the presence of zinc oxide, to obtain the end product.

[0041] The desired final viscosity was calculated, based on formulae (1) and (2) , and the alcohols to be used were chosen, according to the desired viscosity. In particular, the experiments carried out resulted in a value of m of 6.63 10“2and q of 16.9.

[0042] For comparison, the final viscosity of the product obtained was measured experimentally, to check the reliability of formulae (1) and (2) .

[0043] The results are summarised in the table below.

[0044]

[0045] The table above shows how different types of biolubricants can be obtained, according to operational requirements , with dif ferent kinematic viscosities . It is noted that the kinematic viscosity can be calibrated and targeted with high precision and that the formulae ( 1 ) and ( 2 ) are reliable , with extremely low errors , especially for higher kinematic viscosities .

[0046] The present invention gives the various processes already known for the regeneration of used food fats and oils , many of which are devised and patented by the Applicant itself , additional advantages , in terms of the possibility of modulating the products by the regeneration of used food oils , increasing the versatility of the recovery processes and giving the same processes greater added value, while also reducing the load on city sewerage systems . It is understood that the invention must not be considered to be limited to the particular arrangement illustrated above, which forms only one examplary embodiment thereof , but that various variants are possible , all within the capabilities of a technician skilled in the art , without thereby departing from the scope of protection of the same invention, which scope is defined in the claims that follow .

Claims

CLAIMS1) Process for producing biolubricants, wherein the viscosity of the obtained biolubricants is adjusted by choosing the molecular weight of the produced oils, characterised in that the fatty acids to be esterified are produced from used food oils .2) Process according to Claim 1, characterised in that the molecular weights are selected by calibrating the obtained ester, by appropriately choosing the alcohol to be used in the esterification of the employed fatty acids.3) Process according to either Claim 1 or Claim 2, characterised in that the biolubricant molecular weight to be obtained in order to have the desired kinematic viscosity is determined with the formula:MW = Kv4o / m -q / m (2) where MW is the biolubricant molecular weight, expressed in g / mol, KV4Q is the biolubricant kinematic viscosity at 40°C, expressed in centistokes, and m and q are two constants.4) Process according to Claim 3, characterised in that m is 6.63 ICT2.5) Process according to either Claim 3 or Claim 4, characterised in that q is 16.9.6) Process according to any one of the preceding claims, characterised in that said used food oils are UCOs and / or RUCOs .

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