ITFI20090187A1 - BIODIESEL PRODUCTION PROCESS FOR TRIGLYCYERID TRANSESTERIFICATION. - Google Patents

Description

PATENT APPLICATION FOR INDUSTRIAL INVENTION WITH THE TITLE:

BioDiesel production process for transesterification of triglycerides

FIELD OF INVENTION

The present invention refers to the field of trans esterification reactions, in particular it refers to the trans esterification of triglycerides for the production of alkyl esters of fatty acids to be used as biodiesel.

STATE OF THE ART

Chemically biodiesel is a fuel composed of a mixture of alkyl esters of long-chain fatty acids.

The production of BioDiesel (BD) from vegetable oils is a widely studied process now used on a large scale at the level of large, medium and small producers. Interest in BioDiesel has grown due to the possibility of using the product without particular variations in current combustion systems. However, in the processes used up to now there are numerous limitations and various problems.

Although presenting itself as an interesting system for the production of fuels, alternative to those based on products derived from petroleum, one of the problems that has slowed down its intensive industrial development is the use of a product of food importance as a raw material. Of particular interest is therefore the production of BioDiesel from used vegetable oils. In fact, the use of new vegetable oils, although widely studied and used, involves considerable ethical problems linked to the use of a food product as fuel. The recovery of used oils, food waste, and their disposal, is also an ecological problem of considerable magnitude. There are numerous studies all over the world on the risk of water contamination and on the possibility of entering directly or indirectly into the human food cycle.

BD is currently produced by transesterification reactions of lipids and in particular of triglycerides, such as animal fats and / or vegetable oils, with low molecular weight alcohols such as methanol. The most common production process uses methanol to produce methyl esters; however, ethanol can also be used, thus obtaining a biodiesel composed of ethyl esters. As a by-product, glycerol is obtained from the transesterification process. The reaction requires a catalyst and mainly alkaline catalysts such as sodium or potassium methoxides and hydroxides have been used. Despite the widespread industrial use of basic catalysts, there are many problems that the catalytic system entails. In fact, the total content of free fatty acids must not exceed 0.5% by weight. Furthermore, the formation of soaps (salts of fatty acids) and therefore of emulsions causes problems in the separation of pure biodiesel and the presence of wastewater to be purified. Glycerin, formed as a co-product, also needs purification before further processing or use. The production system with basic catalysts therefore involves a high cost as it requires purification systems and the use of highly refined and anhydrous vegetable oils as raw material.

Acid catalytic systems have been studied as an alternative to basic catalysis but have not obtained an important industrial development mainly due to the lower conversion speed while showing the advantage of being able to be used directly on raw materials rich in free fatty acids. The acid catalysts studied are sulfuric acid, hydrochloric acid, phosphoric acid, boron trifluoride, organic sulphonic acids (Liu, K: S. -J Am. Chem. Soc. 1994,, 7; f., 1179: - 1187). However, the homogeneous acid catalysts studied up to now involve separation and purification problems which increase the cost of the product.

To overcome the problem of catalyst separation, heterogeneous acid catalysts have been studied to be used supported in continuous flow beds but the results obtained have not been encouraging up to now (Ind. Eng. Chem. Res.

2005, 44, 5353-5363).

The purpose of the present invention is to identify an alternative process for the conversion of triglycerides into biodiesel with the use of an efficient reagent that can be used in the homogeneous phase and easily separable from the products. The purpose of the invention is also to provide a process that is efficient even on non-anhydrous triglycerides as well as on exhausted vegetable oils and that said process is simple and allows the easy separation of biodiesel from the other by-products of the trans-esterification reaction. .

DEFINITIONS AND ABBREVIATIONS BD = biodiesel

TMSCI = trimethyl chlorosilane or trimethylsilyl chloride

TMS2O = hexamethyldisiloxane

SUMMARY OF THE INVENTION

The present invention provides a process for the production of alkyl esters of fatty acids, or biodiesel, by trans-esterification of triglycerides, said process is carried out in the homogeneous phase in the presence of a lower alcohol containing up to 4 carbon atoms and is catalysed by trimethylchlorosilane. The aforementioned reaction can be carried out both starting from virgin vegetable oils, and starting from used edible oils (currently mostly unused, contributing to environmental pollution due to their incorrect disposal), and starting from animal fats of waste.

The process leads to the complete conversion of the triglycerides into the esters (preferably methyl or ethyl) of the corresponding fatty acids without therefore producing free fatty acids.

The process, given the absence of free fatty acids and soaps, therefore leads to the formation of two phases (an ester phase and a glycerine phase) clearly distinct and easily separable, making this operation simple and therefore having good conditions for reproducibility even on a scale. industrial.

TMSCI transforms, during the process, into an inert product, TMS2O, which is easily separable from the BD and subsequently can be re-transformed into TMSCI or used in other production processes.

Other advantages of the present invention are described below.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention is schematized below in a particularly preferred embodiment in terms of reaction conditions and alcohol used:

-

-

-

In which R, Râ € ™ and Râ € are aliphatic chains, containing from 5 to 28 carbon atoms, preferably from 16 to 22 carbon atoms, linear or branched saturated or partially unsaturated whose exact structure depends on the plant or animal species of the starting triglyceride.

The starting triglycerides can be of vegetable or animal origin.

Among the triglycerides of vegetable origin, edible oils (for example sunflower, olive, soybean oil, etc.), non-edible oils (for example rapeseed, palm, jatropha, algae oil, etc.) can be used. ).

Among the fats of animal origin, for example, lard, butter, etc. can be used. The process is not sensitive to the humidity of the starting triglyceride as the only drawback will be the hydrolysis of the TMSCI which can possibly be used in suitably increased quantities.

Therefore, in the process of the present invention also exhausted or waste triglycerides can be used as starting triglycerides, or recovered after use, for example for culinary purposes (e.g. frying), preservation oils, or waste animal fats.

Preferably, the process of the invention provides for the use of at least 1 equivalent, more preferably 1.3-2.0 equivalents, of alcohol with respect to the starting moles of trigicerides. Preferably the TMSCI is used in quantities not lower than 40% by moles with respect to the alcohol or in quantities not lower than 20% by weight, more preferably higher than 25% by weight, with respect to the starting triglyceride. Even more preferably 1.4-1.6 equivalents of alcohol are used, with respect to the starting triglycerides and 50-60% by moles of TMSCI with respect to the moles of alcohol (otherwise expressed as 27-35% by weight with respect to the starting triglyceride).

If waste triglycerides are used, to facilitate the completion of the reaction, it may be necessary to use the reagents in larger quantities than those indicated above; the man of art will be able to decide on a case-by-case basis how much and how to increase this quantity.

Preferably said alcohol containing up to 4 carbon atoms is selected from MeOH and EtOH.

Preferably the reaction is carried out at 50-120 ° C for 6-16 hours under vigorous stirring. In the case of vegetable oils the reaction is more preferably carried out at SO-70 ° C. In the case of animal fats, the reaction is more preferably carried out at 90-110 ° C.

Upon completion of the reaction, by letting the mixture settle, preferably at room temperature, two clearly distinct phases are observed which can therefore be easily separated in a manner known to man of the art. The two phases are separated thus obtaining:

- an upper phase containing biodiesel and volatile by-products; and

- a lower phase, or glycerine phase, containing a mixture of glycerin and 1-chloro-2,3-propanediol.

Biodiesel can be obtained pure free from volatile by-products simply by removing the latter from the upper phase by distillation under reduced pressure, about 2 mmHg. Said distillation is preferably carried out at 55-75 ° C, more preferably 65 ° C, at a pressure of about 2 mmHg. If MeOH is used, the volatile by-products essentially consist of a mixture of hexamethyldisiloxane (TMS2O), MeOH, and methyltrimethylsilylether (TMSOMe) in traces. All said volatile products can be separated from each other by fractional distillation, especially effective for the recovery of TMS2O which is a compound of commercial interest, or it can be retransformed into TMSCI according to what is known in the state of the art (Zhang, B.- h .; Shi, l.-x. Hebei Gongye Keji 2007, 24, 63-65; Cheng, X .; Zhang, Q. Huaxue Shijie 1988, 29, 65-67). The mixture of MeOH and TMSOMe, which have similar boiling points, can be recycled for subsequent synthesis.

The glycerine phase comprises a mixture of glycerin and 1-chloro-2,3-propanediol (amonochlorhydrin) in various proportions depending on the reaction temperatures used, and is remarkably acidic, due to the presence of hydrochloric acid.

The lower phase can be brought to neutral pH by treatment with a base preferably of inorganic origin (carbonates, preferably calcium carbonate).

Before the basic treatment, the glycerine mixture can be diluted with an organic solvent selected from the MeOH and EtOH group, and as a rule, for convenience, with the alcohol used in the BD formation reaction.

After removal of the basic agent, for example by filtration, glycerin and amonochlorhydrin can be separated by fractional distillation as reported in the literature (Org. Synth., Coll. Vol. 1, p.294 (1941); Vol. 2, p. .33 (1922)).

The process of the present invention for the production of BioDiesel has the following advantages:

- responds to the â € œGreen Chemistryâ € principle, that is, processes with a low environmental impact;

- guarantees the complete conversion of vegetable oil with a perfect separation into two distinct phases that can be easily separated (phase 1: Biodiesel, phase 2: glycerin and its derivative), which allows a complete recovery of the products without additional costs;

- BioDiesel is obtained with high purity, reducing the costs of purification, and ensuring excellent marketability;

- the process takes place efficiently at low temperatures (about 60 ° C for oils, about 100 ° C for animal fats);

- TMSCI is a low cost and low environmental impact reagent;

- TMS20, a transformation product of TMSCI, has a market, and a commercial value, at least equivalent to the initial reagent, otherwise it can be retransformed into TMSCI.

The by-products of processing can be recycled or have a low environmental impact.

- during the process the glycerin is partially transformed into Î ± -monoclorohydrin. The two products can be separated with distillation procedures to obtain

The process does not produce any waste fluid, unlike the currently used basic catalysis processes which instead produce large volumes of wastewater.

- The process can be used, with similar efficiency, with exhausted vegetable oil, or with waste animal fats, without the need for chemical pre-treatment and washing.

The present invention can be better understood in the light of the following embodiment examples.

EXPERIMENTAL PART

Materials

The oil used in this work is a sunflower oil produced by the company Oleificio Salvadoriâ € - Badia a Settimo (FI) characterized via <1> H-NMR consisting of linoleate 53.0%, oleate 34.0%, saturated fats 13.0% ). Calcium carbonate (Carlo Erba product, 99.5%), deuterated chloroform (Aldrich product, 99.8%), methanol (VWR product, 99.8%), deuterated methanol (d <4>) (Merck product, 99.8%), trimethylisilyl chloride (product Aldrich, 98%) were used without further purification.

Instrumentation and analytical methodologies

The <1> H-NMR and <13> C-NMR spectra were recorded with a Varian VXR 200 spectrometer, operating at the frequency of 199.985 MHz. All spectra are reported in ppm and referred to the TMS as an internal standard. Spectra processing was carried out using iNMR 3.0.1 software.

EXAMPLE 1 - Synthesis from edible oil

Numerous syntheses were carried out, varying the reaction times, the reaction temperature, and the amount of TMSCI used in the process.

The syntheses were carried out inside Sovirel <®> tubes fitted with screw caps. Inside the test tube, in a nitrogen atmosphere, sunflower oil is added (5 mL, 4.6 g, 5.24 mmol [Calculated PM = 878g / mole]). MeOH (0.95 mL, 0.75 g, 1.5 equiv, 23.58 mmol) and TMSCI are added. The mixture is vigorously stirred to form an emulsion, then it is brought to a temperature of 28-60 ° C by means of an oil bath and left to react under magnetic stirring for 8h.

Table 1 shows the conversions (%) as the percentage of TMSCI used varies (mol% with respect to methanol), while Table 2 shows the conversions (%) as the temperature varies.

Table 1. Conversions depending on the amount of TMSCI used (8h, 60 ° C) * TMSCI (mo!% Vs CH3OH) CONVERSION

2 35%

5 57%

10 76%

20 85%

30 88%

40 95%

50 100%

* Conversions evaluated by <1> H-NMR, calculating the value of the integral relative to the CH2-COO- signal and comparing it with that of the CH3 of the methyl esters formed in the transesterification process (Gelbard, G .; Brà ̈s, O. ; Vargas, R. M .; Vielfaure, F .; Schuchardt, U.F. J. Am. Oil C / »e / n. Soc. 1995, 72, 1239-1341).

Table 2. Conversions as temperature changes (TMSCI / CH3OH 1: 2, 8h) **

CONVERSION TEMPERATURE

rt (28-30 ° C) 77%

40 ° C 90%

60 ° C 100%

â € œ ratio in moles. Conversions evaluated as above.

Reactions carried out at higher temperatures, up to 120 ° C, gave the same conversion without decomposition of the products.

The synthesis that gave the best results therefore provides for the use of 1.5 MeOH equivalents compared to the commercial starting oil taken as a reference, TMSCI (1.5 mL, 1, 28 g, 11.79 mmol), 50% by moles with respect to at MeOH, and at 27.8% by weight with respect to the starting oil, and a temperature of 60 ° C for a reaction time of 8 hours. At the end of the reaction it is left to cool to room temperature, then the mixture is transferred to a separatory funnel and left to decant: two clearly distinct clear phases are observed. The supernatant phase contains the methyl esters of fatty acids (bio-diesel) together with the volatile by-products of the reaction. The lower phase contains glycerin and derivatives. The two phases are separated.

The upper phase is heated at 65 ° C for 2 hours under vacuum (2 mmHg) to eliminate all volatile by-products. The residue obtained is a bright yellow liquid (4.48 g, yield by weight with respect to the starting oil 97%). At the end the obtained phase has no residual acidity, and analyzed by <1> H-NMR and GC-MS it results constituted by a mixture of methyl esters with the following composition: methyl linoleate: 53.5%; methyl oleate: 35.2%; methyl palmitate methyl stearate: 11.3%. There is no evidence of the presence of impurities.

The volatile products that separate from the bio-diesel phase by distillation consist of a mixture of hexamethyldisiloxane (TMS20), MeOH, and methyltrimethylsilylether (TMSOMe) in traces.

The lower phase, or glycerine phase, recovered at the end of the process is considerably acidic, due to hydrochloric acid, and comprises a mixture of glycerin and 1-chloro-2,3-propanediol (Î ± -monoclorohydrin) in various proportions depending on the temperatures of reaction choices.

Table 3 shows the quantities of Î ± -monoclorohydrin measured by 13C-NMR analysis (integrating the homogeneous signals of CH2OH at Î ́ 64.04 and 64.30 ppm for the amonochlorhydrin and glycerin, respectively).

Table 3. Amount (%) of Î ± -monoclorohydrin present in the glycerine mixture as the reaction temperature varies under standard conditions (reagents and times)

A-monochlorhydrin TEMPERATURE

40 ° C 22%

60 ° C 26%

100 ° C 30%

120 ° C 32%

The lower phase is dissolved in MeOH (2 mL) and treated with calcium carbonate (0.5 g) until the pH is neutralized. The mixture is filtered and the solution obtained is concentrated, by distillation at reduced pressure, to give a colorless viscous liquid with a quantitative yield and containing 74% of glycerin and 26% of Î ± -monoclorohydrin in the case of the best synthesis.

EXAMPLESQ-2 â € ”Synthesis from waste oil

The best synthesis of example 1 was carried out using exhausted oil (5 mL, 4.6 g) obtained by heating the same sunflower oil, used in example 1, artificially aged in air at a temperature of 120 ° C for 72 h under stirring. In this case the oil takes on a slight brown color when the reagents are added which increases with heating and remains persistent in the separated BD at the end of the process. Under the same reaction conditions 1.5 equivalent of MeOH with respect to the starting oil, TMSCI, 50% by moles with respect to MeOH, and at 27.8% by weight with respect to the starting oil, 60 ° C for 8h, and subsequently carrying out the same type of work-up as the previous synthesis, biodiesel is obtained with a conversion of 95%. To achieve 100% of. conversion It is necessary to increase the reaction time (up to 14 hours) and / or the concentration of TMSCI (10% more than the best synthesis of example 1) obtaining after the work-up a dark brown liquid (4.35 g, yield by weight with respect to the starting oil 95%).

EXAMPLE 3 Synthesis with EtOH

The best synthesis of example 1 was carried out using sunflower oil (5 mL, 4.6 g), EtOH as alcohol (1.50 ml, 1.18 g, 1.63 equivalent with respect to oil) and TMSCI (1.5 mL, 1.28 g, 11.79 mmol), 50% by moles with respect to EtOH, and 27.8% by weight with respect to the starting oil. By conducting the reaction at 60 ° C for 14h, and subsequently carrying out the same type of work-up as the synthesis reported in example 1, biodiesel is obtained as a bright yellow liquid with a complete conversion (4.75 g, corresponding to 98% in moles compared to the starting oil).

EXAMPLE 4 Synthesis from animal fat

A synthesis similar to example 1 was carried out using minced animal fat (pork lard) (5 g), methanol (1.5 ml, 1.18 g, 37.03 mmol) and TMSCI (1.5 mL, 1.27 g, 11.73 mmol) in excess compared to the quantities used for virgin oil, and a temperature of 100 ° C for a reaction time of 16 hours. At the end of the reaction, two clearly distinct clear phases are observed: the yellow supernatant phase contains the methyl esters of fatty acids (bio-diesel) together with the volatile by-products of the reaction, the lower dark phase contains glycerin and derivatives. It is left to cool to room temperature, then the mixture is transferred to a separatory funnel and left to decant. The two phases are separated, and by subsequently carrying out the same type of work-up as the synthesis reported in example 1, the biodiesel is obtained as a bright yellow liquid (4.71 g, yield by weight with respect to the starting lard 94%).

Claims (10)

CLAIMS 1. Process for the production of alkyl esters of fatty acids, or biodiesel, by transesterification of triglycerides, said process is carried out in a homogeneous phase in the presence of a lower alcohol containing up to 4 carbon atoms, and is catalyzed by TMSCI . 2. Process according to claim 1 in which at least 1 equivalent of alcohol is used, with respect to the starting triglycerides moles, and a quantity of TMSCI not lower than 20% by weight with respect to the starting triglycerides. 3. Process according to claim 2 in which 1.3-2.0 equivalents of alcohol are used and TMSCI is used in quantities greater than 25% by weight with respect to the starting triglycerides. 4. Process according to any one of claims 1-3 wherein said lower alcohol is selected from MeOH and EtOH. 5. Process according to any one of claims 1-4 wherein the starting triglycerides are of vegetable or animal origin. 6. Process according to claim 5 wherein the starting triglycerides are virgin or exhausted vegetable oils. 7. Process according to any one of claims 1-5 wherein the reaction is carried out at 50-120 ° C for 6-16 hours under vigorous stirring. 8. Process according to any one of claims 1-6 in which upon completion of the reaction the mixture is left to decant to obtain two clearly distinct phases which are then separated to obtain: - an upper phase containing biodiesel and volatile by-products; - a lower phase comprising a mixture of glycerin and 1-chloro-2,3-propanediol (Î ± -monoclorohydrin). 9. Process according to claim 7 wherein the upper phase is then subjected to reduced pressure distillation of the volatile by-products to obtain pure biodiesel. 10. Process according to claim 8 wherein said volatile by-products are further subjected to fractional distillation to obtain TMS2O and a mixture of alcohol and alkyltrimethylsilylether.