BR102013033582B1 - production process of biolubricants derived from castor oil with homogeneous tin-based catalyst - Google Patents

Abstract

PROCESS OF PRODUCTION OF BIOLUBRICANTS DERIVED FROM CASTLE OIL WITH TOMB-BASED HOMOGENEOUS CATALYST The main object of the present invention is to provide a process for the production of castor oil biolubricant from the transesterification of methyl ricinoleate (castor oil biodiesel) with trimethylolpropane alcohol (TMP), using as a homogeneous catalyst, tin dibutyldilaurate (DBTDL). As advantages of the processes developed in the present invention using the homogeneous catalyst DBTDL in TMP in the transesterification reaction of methyl ricinoleate, it stands out the fact of generating a small amount of residue (methanol), using operational conditions of low severity; present high reaction yield, simplicity and low cost when compared to conventional routes in the production of biolubricants.

Description

PROCESS OF PRODUCTION OF BIOLUBRICANTS DERIVED FROM CASTLE OIL WITH TIN-BASED HOMOGENEOUS CATALYST FIELD OF THE INVENTION

The present invention relates to a process for producing castor oil biolubricant from the transesterification of methyl ricinoleate (castor oil biodiesel) with trimethylolpropane alcohol (TMP), using tin dibutyldylurate (DBTDL) as a homogeneous catalyst ).

BACKGROUND OF THE INVENTION

In the last decade, there has been a worldwide concern regarding the impact on the environment, resulting from the use of petroleum products. Although only about 1% of all oil consumed is used in the formulation of lubricants, most of these products are discarded in the environment without any treatment. Some of these hydrocarbons are carcinogenic and resistant to biodegradation, representing a serious threat to the environment.

In this scenario, there is a concern on the part of the oil and energy companies to develop biodegradable lubricants.

Lubricants, depending on the applicability, must have certain physicochemical properties within certain specifications, such as, for example, viscosity, acidity index, corrosivity and pour point. In the case of biolubricants, usually represented by organic esters, oxidative, thermal and hydrolytic stability are fundamental, the former being one of the most important properties in the development of a biodegradable lubricant.

However, as a molecule highly resistant to oxidation is synthesized, with the double bonds removed or protected by steric impediments, it must be taken into account that the action of the microorganisms responsible for biodegradation will be hampered. In this context, the great challenge in the formulation of biolubricants is to find a molecule that has high oxidative resistance and is biodegradable.

The polluting potential of mineral oil is extremely worrying. It is estimated that 1 liter of mineral oil is capable of rendering 1 million liters of fresh water unfit for consumption. In the case of two-stroke engines, the main current application of biolubricants, the lubrication mechanism results in the release of unburned oil together with the exhaust gas, creating the possibility of environmental pollution.

In particular, when nautical engines are used in rivers, lakes or oceans, the oil not burned in the exhaust gas is released into the water, which can cause pollution in the water. In addition, tractors, agricultural machinery, chainsaws and other forestry equipment can also pollute forests and rivers due to partially burned oil, which is released.

Therefore, measures to reduce the impact on the environment must be adopted. In general, preservation of the environment occurs due to the intervention of the following driving forces: environmental catastrophes, public awareness, governmental guidelines and regulations, globalization of markets and economic incentives.

When it comes to lubricants, it is possible to replace mineral oils with synthetic biodegradable lubricants.

A promising alternative for the replacement of mineral lubricants is the use of esters of some fatty acids, derived from vegetable oils, which are biodegradable and can present feasible characteristics when compared to mineral oils, such as: pour point, viscosity, viscosity index and oxidative stability.

When it comes to the use of vegetable oils, it is known that in Europe sunflower and canola oils predominate, which are esters of glycerin and long-chain fatty acids (triglycerides). In Brazil, the oilseeds that deserve to be highlighted are soybeans and castor beans. The fatty acids found in natural vegetable oils differ in chain size and in the number of double bonds. Natural triglycerides are readily biodegradable and quite efficient as lubricants, however, they present limitations regarding thermal, hydrolytic and oxidative stability.

In this context, pure vegetable oils are used only in applications with low thermal demand, such as demoulding and chainsaw oils.

The disadvantages in relation to the use of vegetable oils as biolubricants can be overcome with the use of additives, but biodegradability, toxicity and price are compromised. An alternative to improve the quality and expand the applicability of vegetable oil as a biolubricant is to perform molecular modifications, through organic synthesis, using both homogeneous and heterogeneous catalysis.

Castor (Ricinus communis) or castor is a shrub from whose fruit an oil of excellent properties is extracted, with wide industrial applicability. Castor oil has been known since ancient times for its medicinal properties and as lighting oil. In the twentieth century, however, pharmacopoeia has ceased to be of great use and, currently, the major consumers are the chemical and lubricant industries.

Castor oil or “Castor Oil”, as it is known internationally, has unique physico-chemical properties, such as density, viscosity, alcohol solubility and lubricity, superior to all vegetable oils. Castor oil can be used in synthetic routes for a wide variety of products. From this oil, it is possible to obtain biodiesel, which replaces diesel oil derived from petroleum. In addition, this oil has in its composition ricinoleic acid (90%), which has the peculiarity of having a hydroxyl on carbon 12, in addition to having a double bond strategically positioned on carbon 9 of its 18-carbon chain.

Ricinoleic acid is a hydroxy acid, 18 carbon atoms, containing an unsaturation, cis configuration, in carbons 9 and 10. The direct use of castor oil or its hydrolysis products as a biolubricant is not technically feasible due to the low oxidative stability, high acidity and low viscosity index. Lubricating products must have high oxidative stability and low pour point, characteristics that are not usually easily found in plant-based products.

In view of the above, castor oil stands out due to the fact that it is the most dense and viscous of the vegetable oils usually known, reaching a viscosity 10 times greater than that of sunflower oil, presenting a good applicability within the chemical industry, since it has a lubricity power 30% higher than the other oils investigated.

Products derived from castor oil have interesting physicochemical properties for lubricant formulation. However, some of the processes described in the prior art that use it have some disadvantages in relation to the present invention.

The US patent document, US8410033, published on 03/01/2012, discloses a method of preparing diester-based compositions for the formulation of biolubricants, which are prepared by reacting vicinal diol species with monoester of one or more fatty acids.

Monoesters are derived from triglycerides extracted from algae. According to the authors, ester-based lubricants, in general, have excellent lubrication properties, due to the polarity of the ester molecules of which they are made up. These biolubricants are less volatile than conventional lubricants and are excellent solvents and dispersants. However, depending on the route of preparation of these esters, the process may be more expensive and laborious in terms of experimental execution.

Another prior art representative of the state of the art is the US patent document US6018063, published on 01/25/2000, which describes the synthesis of an estolide ester from oleic acid with properties suitable for formulating lubricants. This document informs that the stolide formed by the use of the invention described therein can be used without additives, which are generally used to improve the quality of the lubricant, which, consequently, would make this invention advantageous in relation to other routes of production of biolubricants.

The previous article on Salimon, Jumat; Salih, Nadia and Yousef, Emad; “Synthesis and Characterization of esters Derived from Ricinoleic Acid and Evaluation of their Low Property”; Malaysian Sains 41 (10) (2012): 1239-1244; the study of the chemical modifications carried out from the epoxidation of ricinoleic acid from castor oil is presented. The authors showed that the increase in the size of the intermediate ester chain had a positive influence on the low temperature properties of the diesters, due to the creation of a steric barrier around the molecule, inhibiting crystallization and, therefore, resulting in a low freezing.

Another invention that describes the production of biolubricants, from the transesterification reaction using the enzymatic route, is the US patent US6117827, published on 12/09/2000. In this document, the final product is a mixture of mono- and di-unsaturated fatty acids of chains in the range of 15 to 16 carbon atoms.

The aforementioned documents do not mention or even suggest the use of a specific catalyst, such as the DBTDL of the present invention, in the presence of TMP, in the process of obtaining biolubricants from castor oil.

The use of tin (IV) complexes, such as DBTDL, as a catalyst in the reactions of transesterification of vegetable oils can be found in some scientific publications.

As an example, there is the study developed by Ferreira, DAC, et al entitled “Methanolysis of soybean oil in the presence of tin (IV) complexes”, in Applied Catalysis A: General 317, 58-61, 2007. In the referred study , it was observed that in the methanolysis of soybean oil, at different reaction times, temperatures and amounts of catalysts, the order of reactivity in terms of yield in fatty acid methyl esters was: DBTDL> DBTO> modified dibutyltin oxide> BTA.

The Master's dissertation by Daniel Ribeiro de Mendonça - Federal University of Alagoas - under the title 'Use of tin (IV) catalysts in transesterification reactions: obtaining biodiesel', published in February 2008, investigated the use of complexes organometallic tin (IV) as catalysts in the alcoholization of vegetable oils (soybean oil and castor oil). In particular, the catalytic activity of the following tin (IV) compounds was investigated: BTA, DBTO and DBTDL in said reaction.

Within the scope of this study, transesterification reactions were carried out with different reaction times, vegetable oils, types of reactors (glass reactor coupled to a reflux condenser (RVCR) and stainless steel reactor (RP)), and the effect of alcohols (methanol , ethanol, isopropanol, butanol and isobutanol).

For the production of biodiesel from castor oil it was found that the best option in operational terms for methanolysis of castor oil would be the use of catalysts: - DBTO followed by BTA acid, both reactions operating at 120 ° C and in times of 2 hours. It was also found that, compared to soybean oil, castor oil showed lower activities in transesterification, possibly due to the effect caused by the size of the castor oil fatty acid chain, the degree of oil unsaturation and the interference of the group hydroxyl in deactivating the catalyst.

In the Masters thesis of Tatiana Maciel Serra - Federal University of Alagoas, under the title: - "Development of catalysts based on tin (I), for the production of fatty acid methyl esters, via transesterification and esterification", published in March The objective of the study was to investigate the catalytic activity of four metal complexes exhibiting Lewis acid character in 2010. These studies were directed to: tin dibutyldiacetate, tin dibutyldilaurate, dibutyl tin oxide and butylstanoic acid in the transesterification reactions of oil soy and castor beans.

One of the conclusions of the study was that for the studied reaction conditions, the yield values (% FAMEs) in soybean methanolysis were higher than those of castor oil methanolysis, and that the catalytic system that employed PR was more efficient. Furthermore, the hydroxyl group, present in C12 of the ricinoleic acid chain, may have had a negative influence on the reaction yields in castor oil methanolysis (% FAMEs).

Thus, it is possible to infer that until now, a process for obtaining castor oil biolubricants from the transesterification of methyl ricinoleate (castor oil biodiesel) has not been described in the state of the art using the DBTDL as a homogeneous catalyst. presence of a specific alcohol such as TMP.

The present invention has, as main motivation, the valorization of biomass as raw material, since there is a worldwide trend to gradually replace compounds of fossil origin by those of vegetable origin, highly biodegradable, without harming the environment. Thus, for the lubricant market, biolubricants become a feasible alternative and have already been used in many countries in Europe, through the development of more economical and simple processes.

Clearly, the advantages of the processes developed using the homogeneous catalyst DBTDL in TMP in the transesterification reaction of castor oil biodiesel: generate a small amount of residue (methanol), use operating conditions with low severity; present high reaction yield and simplicity and low cost when compared to conventional routes in the production of biolubricants.

In addition, methyl ricinoleate, obtained from a transesterification reaction of castor oil with methanol, is the main constituent of biodiesel. Thus, the transesterification of this compound with higher alcohols, such as, for example, the one used in the present invention, TMP, made it possible to obtain polyol esters, which are important precursors of synthetic base oils.

SUMMARY OF THE INVENTION

The present invention relates to a process for the production of biolubricants, derived from castor oil, which uses DBTDL as a homogeneous catalyst in TMP medium.

The production route for castor oil biolubricants used in the present invention was the transesterification of methyl ricinoleate (castor oil biodiesel) with trimethylolpropane alcohol (TMP), using the homogeneous di-butyl tin diuryl laurate (DBTDL ). This route proved to be quite feasible and promising due to: generating a small amount of waste (methanol), using operating conditions with low severity; present high reaction yield; simplicity and low cost when compared to conventional routes in the production of biolubricants.

• 1) Desenvolvimento de rota mais econômica e simples para produção de biolubrificantes; biolubrificante de mamona isento de aditivos em sua formulação; o biodiesel utilizado não precisa ter rigidez em sua especificação;
• 2) Na rota de produção de biolubrificante de mamona foram utilizados reagentes de baixo custo. A produtividade foi de 70% de biolubrificante de mamona puro, isento de outros componentes;
• 3) Uso de matéria-prima de origem vegetal e de reagentes com baixa toxicidade durante a reação;
• 4) Os testes comprovaram que os resultados obtidos com o biolubrificante de mamona, em termos de conversão (70%), superam aqueles obtidos pelo estado da técnica (aproximadamente 55%).
• 5) Produção de produto biodegradável; os efluentes utilizados podem ser parcialmente retornados ao processo;

Through the processes developed in the present invention, from the use of the said homogeneous catalyst, DBTDL in TMP alcoholic medium, it was possible to obtain biolubricants derived from castor oil with excellent advantages, such as:

• 1) Development of a more economical and simpler route for the production of biolubricants; castor oil biolubricant free of additives in its formulation; the biodiesel used does not need to be rigid in its specification;
• 2) Low-cost reagents were used in the production route for castor oil biolubricant. Productivity was 70% of pure castor oil biolubricant, free from other components;
• 3) Use of raw material of plant origin and reagents with low toxicity during the reaction;
• 4) The tests proved that the results obtained with the castor oil biolubricant, in terms of conversion (70%), surpass those obtained by the state of the art (approximately 55%).
• 5) Production of biodegradable product; the effluents used can be partially returned to the process;

DETAILED DESCRIPTION OF THE INVENTION

The process of production of biolubricants object of the present invention applies to fillers comprising methyl ricinoleate, in particular to castor oil biodiesel.

Broadly speaking, the process involves transesterification of methyl ricinoleate with trimethylolpropane, using a homogeneous catalyst, in this case di-butyl tin diuride (DBTDL).

In an initial stage, the load, comprising methyl ricinoleate, is subjected to heating in a reactor at temperatures ranging from 55 to 70 ° C, preferably 60 ° C, under vacuum (absolute pressure between 50 and 150 mmHg), and for a period at least 1 hour. This initial heating step is necessary to remove residual moisture from the load, since the presence of water can lead to the hydrolysis of methyl ricinoleate.

After removing the residual moisture from the load, it is heated in the reactor to a temperature of 165-175 ° C (preferably 170 ° C), under the same pressure condition, and then the TMP and then the DBTDL catalyst are added. , under agitation varying between 800 and 1200 rpm.

The addition of TMP and catalyst is carried out so that the molar ratio between methyl ricinoleate and TMP in the transesterification reaction is 3.2: 1, and the mass ratio of the catalyst to the mass of methyl ricinoleate is in the range of, 025% to 0.5%.

The reaction time varies from 5 to 7 h, with the reactor being kept under vacuum, absolute pressure ranging from 50 to 150 mmHg, in order to ensure that all methanol generated in the reaction is removed from the reaction medium.

The amount of methanol formed in the reaction depends on its conversion. For a conversion of 70%, for example, there is, in general, a production of 6.3% of methanol in relation to the total mass added of methyl ricinoleate and TMP.

• - evaporação, para remoção do TMP e;
• - destilação molecular para separar o ricinoleato de metila do biolubrificante.

For the recovery of the product, biolubricant, of the unreacted load (methyl ricinoleate), and of the unconsumed TMP, two steps are still necessary:

• - evaporation, to remove TMP and;
• - molecular distillation to separate the methyl ricinoleate from the biolubricant.

In this case, both evaporation and molecular distillation occur with the use of high vacuum, with mild temperatures thus maintaining the integrity of the generated biolubricant, especially with regard to oxidative stability and acidity. In addition, it is possible to reuse unreacted methyl ricinoleate, returning it to the reactor, as part of its supply (load).

For the removal of TMP by evaporation, the stream comprising biolubricant, TMP and unreacted methyl ricinoleate, is sent to an evaporator and subjected to temperatures between 120 ° C to 180 ° C and absolute pressure in the range of 0.1 to 0, 4 mmHg.

The entire circuit for the recovery of the TMP must remain warm, generally at a temperature of 70 ° C, in order to avoid the solidification of alcohol in the pipes. After TMP removal, a stream comprising methyl ricinoleate and biolubricant is sent to a molecular distillation column, operating under the temperature range between 190 ° C to 240 ° C, absolute pressure between 0.001 to 0.04 mmHg, obtaining a chain containing methyl ricinoleate and a chain containing the biolubricant.

The biolubricant obtained according to the process of the present invention has a viscosity at 40 ° C of 290 to 300 cSt., And at 100 ° C of 24.10 cSt, a viscosity index (IV) of 100 to 105, fluidity -33 at -39 ° C and total acidity index (IAT) in (mgKOH / g) from 0.30 to 0.50.

EXAMPLES EXAMPLE 1 - Transesterification of ethyl ricinoleate on a bench scale.

The bench scale reaction was performed in a glass reactor with a capacity of 50 mL, operated in batch. The reagents used were ethyl ricinoleate, TMP and DBTDL, as a reaction catalyst. The reactor remained under constant agitation (800 rpm) throughout the reaction. The operational conditions established are shown in Table 1.

* IV: índice de Viscosidade
IAT: índice de Acidez TotalAs a way of ensuring that all the ethanol generated was removed from the reaction medium, the reactor operated under vacuum. The formed ethanol was collected with the aid of a dry ice trap. The reaction conversion was 75% (measured with the aid of HPLC) and the final characteristics of the castor oil biolubricant formed in this reaction are shown in Table 2.

* IV: Viscosity index
IAT: Total Acidity Index

EXAMPLE 2 - Transesterification of methyl ricinoleate on a semi-industrial scale.

The reaction on a semi-industrial scale was carried out in two stages, namely: drying of castor oil biodiesel and the reaction. In the drying step, the temperature used was 60 ° C for 1h. The reaction temperature was maintained at 170 ° C for 7 hours, under a vacuum of 100 mmHg (0.13 bar), in order to guarantee the total removal of methanol generated during the reaction. The stoichiometric ratio of methyl ricinoleate and TMP was the same used (in example 1). The mass ratio of catalyst to the mass of methyl ricinoleate used in the reaction is between 0.25% and 0.5%.

Table 3 presents the physicochemical characteristics of castor oil biodiesel and the reaction product formed.

As can be seen in Table 3, the physicochemical properties were strongly altered after the reaction step. The conversion of the reaction was 73.85%, which is in accordance with what was obtained in example 1. The divergences between the physicochemical characteristics found in examples 1 and 2 can be explained due to the increase in complexity with the expansion of the volume produced.

In reaction units, in which the volumes are smaller, the operational variables are easily monitored and controlled, in addition to the fluid dynamics problems caused, which are smaller than in larger volumes. However, comparing the results illustrated in Tables 2 and 3, it is evident that in both cases, the potential for application will be the same.

* Viscosidade - ASTM D445
IV: índice de Viscosidade - ASTM D2270
Fluidez: ASTM D97
IAT: índice de Acidez Total - ASTM D664The castor oil biolubricant generated in the reaction, without the purification step, could already be used in chainsaws and marine fluids. However, as a way to increase the added value of this compound, this component was purified in a molecular distillation unit.

* Viscosity - ASTM D445
IV: Viscosity index - ASTM D2270
Fluidity: ASTM D97
IAT: Total Acidity Index - ASTM D664

* Viscosidade - ASTM D445
IV: índice de Viscosidade - ASTM D2270
Fluidez: ASTM D97
IAT: índice de Acidez Total - ASTM D664The reaction product was the raw material for the molecular distillation unit. The evaporation step was necessary in order to guarantee the total removal of alcohol (TMP). After this separation, the biodiesel-biolubricant castor mixture was conducted to the molecular distillation column, for the separation of these products. The separation temperatures in the evaporator and the molecular distiller were 160 ° C and 240 ° C, respectively. The yield in the separation of the castor oil biolubricant was 70% and its physico-chemical properties are shown in Table 4.

* Viscosity - ASTM D445
IV: Viscosity index - ASTM D2270
Fluidity: ASTM D97
IAT: Total Acidity Index - ASTM D664

The data presented in Table 4 corroborate the fact that the molecular distillation unit significantly improves the physicochemical properties of castor oil biolubricant and, consequently, increases the potential for application of this product. It is noticed that after the purification stage the product was much better than those traditionally presented. In addition, the separation yield was high, which makes the process very promising.

Claims (18)

PROCESS OF PRODUCTION OF BIOLUBRICANTS DERIVED FROM MAMONA OIL WITH HOMOGENEOUS CATALYST, THE TIN BASE, characterized by comprising the following steps:
a) to provide a load, comprising ethyl ricinoleate, to a reactor and heat, under vacuum, in order to remove residual moisture from the load;
b) add to the reactor containing the cargo, trimethylolpropane alcohol (TMP) and a homogeneous tin-based catalyst, under stirring, vacuum and temperature between 168 ° C and 172 ° C, for the time necessary to promote the ricinoleate transesterification reaction methyl, in order to obtain two streams, a stream comprising TMP, unreacted and biolubricating methyl ricinoleate, and a stream containing methanol;
e) direct the effluent stream from the reactor, comprising methanol, unreacted methyl ricinoleate and biolubricant to an evaporator, operating under vacuum and temperatures between 120 and 180 ° C in order to remove the TMP, obtaining a stream containing unreacted methyl ricinoleate and biolubricant;
f) direct the effluent stream from the evaporator, containing unreacted and biolubricating methyl ricinoleate, to a molecular distillation column, obtaining a methyl ricinoleate stream and a biolubricant stream. Process according to claim 1, characterized in that the homogeneous catalyst is tin dibutyldilaurate (DBTDL). Process according to claim 1, characterized in that the residual moisture is removed from the load at a temperature between 50-70 ° C. Process according to claim 1, characterized in that the time for removing moisture from the load is at least 1 hour. Process according to claim 1, 3 or 4, characterized in that the vacuum applied in steps a) and b) of the process comprises an absolute pressure ranging from 50 to 150mmHg. Process according to claim 1, characterized in that the transesterification reaction of step (b) occurs, preferably at a temperature of 165 to 175 ° C. Process according to claim 1, characterized in that the transesterification reaction of step (b) has a duration time varying from 5 to 7 hours. Process according to claim 1, characterized in that in the esterification reaction of step (b), the molar ratio between methyl ricinoleate and TMP is 3.2: 1. Process according to claim 1, characterized in that, in the transesterification reaction of step (b), the mass ratio of the catalyst to the ethyl ricinoleate mass is in the range of 0.25% to 0.5%. Process according to claim 1, characterized in that the molecular distillation column (e), operates continuously. Process according to claim 1, characterized in that the evaporator operates at an absolute pressure in the range of 0.1 to 0.4 mmHg. Process according to claim 1, characterized in that the molecular distillation column operates in the temperature range of 190 ° C to 240 ° C. Process according to claim 1 or 22, characterized in that the molecular distillation column of the step operates in the pressure range from 0.001 to 0.04 mmHg. Biolubricant obtained according to the process described in claim 1, characterized in that it has a viscosity at 40 ° C of 290 to 300 cSt. Biolubricant according to claim 14, characterized in that it has a viscosity at 100 ° C of 24.10 cSt. Biolubricant, obtained according to the process described in claim 1, characterized by having IV from 100 to 105. Biolubricant, obtained according to the process described in claim 1, characterized in that it has a fluidity of -33 to -39 ° C. Biolubricant, obtained according to the process described in claim 1, characterized by having IAT (mgKOH / g) of 0.3 to 0.5.