WO2015069129A1 - Process and catalyst for obtaining fatty acid methyl esters - Google Patents

Abstract

The invention refers to a process and catalyst for obtaining fatty acid methyl esters, by the chemical processing of fats with content of free fatty acids, in order to be used as diesel biofuel, also referred to as biodiesel, intermediates for synthetic biofuels for aviation, or environmental-friendly solvents. The process according to the invention consists of treating the fats with methanol and with super-acid solid catalyst S0427Ti02-La203j at temperatures of 68±2°C, the water resulting din esterification reaction of the fatty acids is separated from methanol in a rectification column and is removed, and methanol is recirculated, until the acidity index of the reaction mass drops under 2 mg KOH/g, the super-acid solid catalyst is removed by filtration, and the filtrate is treated in the next step with a heterogeneous alkaline catalyst, at temperatures of 67±2°C, for 60-90 minute, the catalyst is removed by filtration or centrifugation, glycerine is separated from the methyl esters of fatty acids by decantation or centrifugation, and is then treated with the heterogeneous alkaline catalyst separated before, at temperatures of 67±2°C, for 60-90 minute, the catalyst is removed by filtration or centrifugation, and excess methanol is removed by distillation, first at atmospheric pressure and then under vacuum, glycerine is separated from the methyl esters of fatty acids by decantation or centrifugation, which is finally filtered through an inorganic filtering layer. The heterogeneous alkaline catalyst according to the invention has the molecular formula: CH2,464- 2.5350o,428-o,528No.o3i-o.o43Clo.o3 i-o.o43Cao. io5-o.i29Sio.o64-o.o73, and the process for obtaining it consists of treating the calcium oxide with methanol with a molar ratio of 1 :4, at a temperature of 65°C for 60 minutes, treating the mixture with glycerine with a molar ratio of 1 : 1 to the calcium oxide, at temperatures of 65-70°C for 60 minutes, methanol is removed by distillation from the reaction mass, which is treated with a solvent, with triethanolamine with a molar ratio of 1 :2 to the calcium oxide, and with trialkylchlorosilane with a molar ratio of 1 :2 to the calcium oxide, at ambient temperature, for 60-120 minutes, the resulting suspension is filtered, and the solvent is removed by drying.

Description

PROCESS AND CATALYST FOR OBTAINING FATTY ACID METHYL ESTERS

The invention refers to a process and catalyst for obtaining fatty acid methyl esters of by chemical processing of fats with content of free fatty acids, in order to be used as Diesel biofuel, also referred to as biodiesel, intermediates for synthetic biofuels for aviation, or environmental-friendly solvents.

Many processes are known for obtaining alkyl esters of fatty acids, by the esterification of free fatty acids and/or transesterification of triglycerides contained in fatty matters of vegetal or animal origin, with a lower alcohol, preferably methanol, in the presence of homogeneous catalytic system of acid, alkaline or heterogeneous type.

US Patent 6.642.399 describes a process in a single liquid phase for the esterification of a mixture of fatty acids and triglycerides, including: (a) obtaining a solution consisting of fatty acids, triglycerides, an alcohol, an acid catalyst such as sulphuric acid and a co-solvent, with a lower temperature than the boiling point of the solution, with the aforementioned alcohol being selected from methanol, ethanol, and mixtures thereof, and the molar ratio between the alcohol and the triglycerides, plus one third of the fatty acids is in the interval between 15:1 and 35: 1, with the co-solvent in sufficient quantity to form a unique liquid phase; (b) keeping the solution for a period required for the esterification of the fatty acids, catalysed by the acid; (c) neutralizing the acid catalyst and adding an alkaline catalyst such as sodium or potassium hydroxide, for the transesterification of triglycerides and (d), after a period, separating the esters from that solution.

The process has downsides related to the need to neutralise the acid catalyst, remove the co-solvent by distillation and use appreciable quantities of acid water to purify the raw alkyl esters.

US Patent 6.399.800 describes a method to obtain alkyl esters of tatty acids from fats, including: (a) the saponification of fats with an alkaline hydroxide such as sodium or potassium hydroxide, (b) eliminating water from saponified fat down to a content of 0-10% in water, (c) the esterification of the dehydrated saponified fat, w ith an alcohol and an inorganic acid catalyst such as sulphuric acid, to form alkyl esters of the fatty acids, with the molar ratio between fatty acids:alcohol:acid catalyst 1 :30:2.5, and (d) recovering the alkyl esters of the fatty acids.

The process has downsides related to the use of large quantities of an alkaline hydroxide for saponification and large quantities of inorganic acid, for neutralisation/esterification, which causes_, large quantities of inorganic salts, and implicitly wastewater, to be obtained as by-products. US Patent 8.440.847 described a method for the conversion of free fatty acids (FFA) from oils, into methyl esters, at atmospheric pressure, with the following steps: esterifi cation of the FFA using a weak acid catalyst, such as p-toluenesulphonic acid, an ionic resin or combinations thereof, dissolved in an alcohol; separating the excess alcohol, the acid catalyst, the water, the glycerine, soap and other non-lipidic soluble impurities from the intermediate obtained in step (a); neutralisation of the oil in step (b); drying the oil in step (c); and transesterification of the oil in step (d) using an alkaline catalyst such as sodium or potassium hydroxide and an alcohol.

The process has downsides related to laborious purification operation both after the FFA esterification step and after the transesterification step, due to the presence of alkaline soaps in the raw alkyl esters.

WO Patent 201 1033346 describes a process to convert fats with a high content of free fatty acids, (FFA=20-85%) to biodiesel, including: (a) obtaining fatty matter containing 20- 85% FFA, with no previous treatment or purification; (b) esterification of the fatty matter with low alcohols, in the presence of heterogeneous acid catalyst such as macroreticulated resin or gel (ex. Tulsion-42 or Indion-130); (c) heating the reagents from step (b), to temperatures of 55-65°C, with mechanical stirring over a period of 8-10 hours to obtain ester oil; (d) transesterification of the oil resulting in step (c) in the presence of methanol and a homogeneous alkaline catalyst such as sodium or potassium hydroxide, and of sodium or potassium methoxide, for 1 -2 hours at 55-70°C; (e) separating the product obtained in step (d) into biodiesel and glycerine, followed by the recovery of methanol; (f) washing the biodiesel with hot water and then drying it, in order to obtain biodiesel as the end product.

The process has downsides related to the purification of raw biodiesel by washing with hot water, due to the resulting wastewater and the impurification of the raw glycerine obtained as secondary product with alkaline soap.

US Patent 7.700.793 describes a method to produce an ester from fatty matter, including: mixing the fatty matter with an alcohol and a co-solvent such as tetrahydrofuran; contacting the mixture with a first insoluble solid catalyst, containing acid groups such as a cation-exchanging resin, at pressures of 50-5000 kPa, preferably 1000-5000 kPa, to produce an initial reaction mixture in which 90-99% of the free fatty acids have been converted to esters; contacting the initial reaction mixture, after removing water from the system, with a second insoluble solid catalyst containing basic groups, such as an anion-exchanging resin, at pressures of 50-5000 kPa, preferably 1000-5000 kPa, to produce a final reaction mixture, based on the alkyl esters of fatty acids. Similarly, methods are presented to obtain alkyl esters by the esterification of free fatty acids and by transesterification of triglycerides.

The process has downsides related to conducting the esterification and/or transesterification reactions under pressure, which involves substantial investments in machinery and using a co-solvent requiring energy consumption to be removed from the system by distillation.

US Patent 5.525.126 describes a process to produce alkyl esters from fatty matters containing at least 40% free fatty acids, using one type of heterogeneous catalyst, without producing soap, including: mixing the fatty matter with an alcohol and a catalyst consisting of a mixture of calcium acetate and barium acetate with a ratio of 3: 1, heating the reaction mixture to 200-220°C and pressure at least 400 psi.

The process has downsides related to conducting the reactions at high temperature and very high pressure, so the technology is uneconomical.

WO Patent 2013054306 describes a process to produce esters, especially biodiesel, a process that includes placing fats with content of triglycerides and free fatty acids in proportion of 0.1 -99%, preferably between 1 -30%, in contact with a low alcohol, in particular methanol and with a heterogeneous catalyst, of the group 4 silicate, preferably titanosilicate with less than 3 % (weight) Na, and 3% (weight) . The catalyst also contains a promoter selected from among cations, anions and/or organic compounds or combinations thereof. The process of transesterification takes place at temperatures of 40-400°C, preferably between 120-230°C.

The process has downsides related to conducting the reactions at high temperatures, requiring high consumption of energy.

Many methods are known for the preparation of heterogeneous catalysts for their use in the esterification processes of free fatty acids or in transesterification processes of triglycerides of fatty acids.

US patent 8,445,400 describes a new heterogeneous solid acid catalyst, based on glycerine, with the following properties: molecular formula CH053-0 87 So.o 15-0.03 Oo _.035-0.51 ; acid density in the interval 1 .6-4.6 mmol/g; specific area 2 - 12.6 m² / g; insoluble in water and organic solvents such as chloroform, hexane, pyridine and N,N-dimethyl-formamide, reusable. The process for obtaining this catalyst includes partial carbonisation simultaneously with the sulfonation of glycerine by reaction with concentrated or fuming sulphuric acid, at temperatures of 200-300°C, under a stream of nitrogen or dry air, for a period, until the reaction mixture becomes a black powder, cooling it to 20-30°C by washing with warm water at neutral pH, followed by drying the product at 1 10-130°C. A method for the esterification of free fatty acids from vegetal or animal fat containing 3-85% (FFA) uses the above-mentioned heterogeneous solid acid catalyst based on glycerine and an alcohol, with the molar ratio fatty acid - to alcohol in the interval between 1 : 1 and 1 :30, at temperatures of 35-90°C and periods of 1-12 hours. Conversion varies in the interval 45-99%.

The process has downsides related to conducting the reactions at temperatures of 200- 300°C, requiring high consumption of energy.

US patent 2010130769 describes a transesterification heterogeneous catalyst consisting of: calcium carbonate 70-95% (weight), calcium oxide 5-25% (weight), and calcium hydroxide 5-25% (weight), a method for the preparation of this catalyst, by calcination of limestone with content of at least 95% calcium carbonate, at 600°C, in air, for at most 2 hours, and a method to produce esters of fatty acids and glycerine, by placing triglycerides in contact with a low alcohol and the aforesaid heterogeneous catalyst, the process of transesterification resulting in a mixture of biodiesel, alcohol and glycerine. The transesterification takes place at temperatures of 50-150°C, with very good results obtained at 85°C and a gravimetric ratio triglycerides:methanol of 50:50.

The process has downsides related to the need to conduct the transesterification under pressure and a great excess of methanol, in order to obtain satisfactory conversion.

WO patent 20101 1301 1 describes a catalyst composition for obtaining biodiesel, based on calcium oxide, from calcinated natural waste, consisting of clamshells and eggshells, with ratios from 90: 10 to 10:90, with the catalyst having the specific area of 50 - 200 m²/ g. The process for obtaining the aforesaid catalyst composition includes: a) washing and drying the clamshells, followed by grinding and sieving; b) calcinating the clamshells; c) washing and drying the eggshells, followed by grinding and sieving; b) calcinating the eggshells; e) finely grinding and homogenising the composition of clamshells and eggshells; f) calcinating the material after mixing it with other ingredients (e.g. aluminium oxide) and transforming it into granules by extrusion in an oven at temperatures of 750-1000°C, tor 3-12 hours. The process for producing biodiesel by the reaction between triglycerides containing 0-5% free fatty acids and 10- 10000 ppm water together with an alcohol in the presence of the aforesaid catalyst is conducted at pressures between atmospheric pressure and 90 bar, preferably between 3 and 15 bar, with molar ratios alcohohoil in the interval 20: 1, preferably 5: 1 .

The process has downsides related to conducting the transesterification under pressure. The technical problem solved by this invention is the simplification of the process by producing and using heterogeneous catalysts, at atmospheric pressure, making it possible to use fatty matters with high content of free fatty acids, of low quality or recovered from waste.

The process according to the invention eliminates the downsides that were mentioned by that, in the first step, fats, chosen from among oils including microalgal, rapeseed, camelina, soy, sunflower, safflower, linseed, hemp, cotton, peanut, pumpkin, corn germ, coconut, palm kernel, ricin, olive oil, lard, fish oil, rendered fat, bovine, ovine fat, as they are or as mixtures, in natural state (raw), purified, recovered from waste, are treated with methanol in proportion of 0.308-0.566% in weight to the fat and with super-acid solid catalyst, fresh or recovered from previous batches, of the type Sd^/TiC^-La^_, having the ratio Ti:La =30: 1, in proportion of 0.04-0.055% in weight to the fat, at temperatures of 68±2°C, the water resulting from the esterification reaction of the fatty acids is separated from methanol in a rectification column and is removed, and methanol is recirculated, until the acidity index of the reaction mass drops under 2 mg KOH/g, and then the super-acid solid catalyst is removed by filtration, and can be reused, and the filtrate is treated in the next step with a heterogeneous alkaline catalyst, consisting of 27.3-29.9%) calcium methoxide glyceroxide, 42.1-46.7% silylated calcium methoxide glyceroxide, 23.1-25.1% triethylamine chlorohydrate, 2.3-3.6% other compounds, has the molecular formula: CH₂, 64-₂,5350o,4₂8- o,528No,o3i-o,o43Clo,o3i-o,043Cao,io5-o,i₂9Sio_;o64-o,o73, insoluble in water and organic solvents of the types hydrocarbons, dichloromethane, chloroform, carbon tetrachloride, N,N- dimethylforrnamide, dimethylsulfoxide and reusable, so the heterogeneous alkaline catalyst is obtained by a process in which calcium oxide is treated with methanol with a molar ratio of 1 :4, at a temperature of 65°C for 60 minutes, the mixture is treated with fresh glycerine or raw glycerine, a by-product resulting from the process, with a molar ratio of 1 : 1 to the calcium oxide, at temperatures of 65-70°C for 60 minutes, methanol is removed by distillation from the reaction mass, which is treated with a solvent, chosen from tetrahydrofuran, benzene, dichloromethane, fresh or recovered from previous batches, in proportion of 536-625% in weight fata de calcium oxide, with triethanolamine with a molar ratio of 1 :2 to the calcium oxide, and with trialkylchlorosilane, such as trimethylchlorosilane or t-butyl- dimethylchlorosilane, with a molar ratio of 1 :2 to the calcium oxide, at ambient temperature, for 60-120 minutes, the resulting suspension is filtered or centrifuged, washed on filter with solvent and the solvent is removed from the catalyst cake, by drying with solvent recovery, the heterogeneous alkaline catalyst being fresh or recovered from previous batches, in proportion of 0,05-0,06%) in weight to fat, at temperatures of 67±2°C, for 60-90 minute, the catalyst is removed by filtration or centrifugation, glycerine is separated from the methyl esters of fatty acids by decantation or centrifugation, and is then treated with the heterogeneous alkaline catalyst separated before, at temperatures of 67±2°C, for 60-90 minute, the catalyst is removed by filtration or centrifugation, and excess methanol is removed by distillation, first at atmospheric pressure and then under vacuum, glycerine is separated from the methyl esters of fatty acids by decantation or centrifugation, which is finally filtered through an inorganic filtering layer, selected from acid-treated bentonite, diatomite, activated coal and Kieselgel 60 GF254 silica gel, bentonite, activated coal and bentonite, with the mention that for fats with acidity index less than 2 mg KOH/g and water content less than 0.1%, the first stage, that of esterification of free fatty acids with super-acid solid catalyst, can be skipped.

The invention has the following advantages:

• it achieves a viable economic method, by using cheap fatty matters, with a high content of free fatty acids, of lower quality or recovered from waste;

• produces and uses heterogeneous catalysts for the process, which are easily removed by filtering, without requiring additional operations for the purification of methyl esters;

• achieves a partial utilization of raw glycerine, a by-product resulting from the process, in obtaining heterogeneous catalysts for the transesterification step;

• produces and uses in the transesterification step heterogeneous catalysts with amphiphilic character, which facilitate the contact of the hydrophobic reagent (triglycerides) with the hydrophilic one (methanol), while being at the same time easy to handle, due to resistance in the presence of moisture and carbon dioxide;

• ensures low consumptions of raw materials and the possibility to reuse the catalysts and by-products, thus contributing to reduced manufacturing costs;

• ensures low consumptions of energy, by conducting technological operations at relatively low temperatures;

• does not require costly investments, due to conducting the process at atmospheric pressure.

Here are 10 examples of implementation of the invention:

EXAMPLE 1

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, electrically heated oil bath, cooler condenser assembled with a collector flask for distillate, insert 257 g methanol 99.8% and 112 g calcium oxide 99.9%. Start the stirring and heating, maintaining the mixture at 65°C for 60 minutes. Insert 185 g glycerine 99.5% over the mixture in the vessel, maintaining the mixture at 65-70°C for 60 minutes. Methanol is removed by distillation from the reaction mass, over which 600 g benzene and 102 g triethylamine 99.5% are introduced under stirring. Then insert, under stirring and in small portions, 110 g trimethylchlorosilane 99%. The reaction is slightly exothermal. Keep the reaction mass under stirring for 60 minutes. Filter the suspension and wash on filter with 100 g benzene and recover the benzene from the product cake, by drying. The result is 528 g heterogeneous alkaline catalyst with the molecular formula: CH_2j5320o,52i o_;o43Clo,o43Cao,i28Sio,073, consisting of 29.9% calcium methoxide glyceroxide [H₃C-0-Ca-0-CH₂-CH(OH)-CH₂-OH], 42,7% silylated calcium methoxide glyceroxide, [H₃C-0-Ca-0-CH₂-CH(OH)-CH2-0-And(CH₃)3], 25, 1 % triethylamine chlorohydrate [(C₂H₅)₃N.HC1], and 2.3% other compounds.

EXAMPLE 2

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer and electrically heated oil bath, with the flask assembled with a rectification column with structured filling, supplied in the middle with water vapours-methanol, coupled at the upper part with a reflux distributor, thermometer, condenser and methanol collector flask, and at the lower part with an aqueous distillate collector flask, insert in the 4-neck flask 1000 g microalgal oil, with saponification index 196.52 mg KOH/g, acidity index 78.61 mg KOH/g, and 0.09% water, which is treated with 448 g methanol and 50 g super-acid solid catalyst of the type S0₄ ²7Ti0₂-La₂0_3i having the ratio Ti:La =30: 1 and the number of active centres = 0,91 meq/g. Start the stirring and heat the mixture in the flask to 68±2°C. The resulting methanol and water vapours supply the rectification column. The reflux ratio is adjusted so that the temperature of vapours at the top of the column remains at 65±0.2°C. The methanol collected in the flask is reintroduced in the 4-neck flask and the water separated in the lower collector flask is removed. Maintain stirring and heating for approx. 6 ore, until no water is separated, and the acidity index of the reaction mass decreases to 1.87 mg KOH/g. Remove the super-acid catalyst by filtration, to be used for subsequent batches, and transfer the filtrate to an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, condenser and electrically heated oil bath. Over the filtrate in the flask, introduce 50 g heterogeneous alkaline catalyst obtained according to example 1 and start the stirring and heating. Maintain the reaction mass under stirring at 67±2°C for 60 minutes, then remove the catalyst by filtration. Separate by decantation 218 g of glycerine 26.23%, from the methyl esters of fatty acids, which are reintroduced in the flask together with the catalyst that was previously separated by filtration. Maintain the reaction mass under stirring at 67±2°C for 60 minutes, then remove the catalyst by filtration. Remove excess methanol by distillation, first at atmospheric pressure, then under vacuum. Separate by decantation 8 g of raw glycerine 95.43%, from the methyl esters of fatty acids, which is filtered through a filtrating layer of acid-treated bentonite. Obtain 949 g of methyl esters of fatty acids with composition of fatty acids according to table 1 and properties according to table 2.

EXAMPLE 3

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, electrically heated oil bath, cooler condenser assembled with a collector flask for distillate, introduce 259 g of methanolic distillate recovered from batches according to example 1 and 1 12 g of calcium oxide 99.9%. Start the stirring and heating, maintaining the mixture at 65°C for 60 minutes. Over the mixture in the vessel, introduce 193 g of raw glycerine with concentration 95.43%), recovered from batches according to example 2, maintaining the mixture at 65-70°C for 60 minutes. Methanol is removed by distillation from the reaction mass, over which introduce, under stirring, 500 g tetrahydrofuran and 102 g triethylamine. Then introduce in small portions, under stirring, 1 10 g trimethylchlorosilane. The reaction is slightly exothermal. Keep the reaction mass under stirring for 60 minute. Centrifuge the suspension, wash the cake with 100 g tetrahydrofuran and recover the tetrahydrofuran from the product cake by drying. The result is 534 g of heterogeneous alkaline catalyst with the molecular formula: CH2,535 o,528No.o43Clo.o43Cao_>i29Sio.o72_J consisting of 29.5% calcium methoxide glyceroxide [H₃C-0-Ca-0-CH₂-CH(OH)-CH₂-OH] 42, 1% silylated calcium methoxide glyceroxide [H₃C-0-Ca-0-CH2-CH(OH)-CH₂-0-And(CH₃)3], 24,8%) triethylamine chlorohydrate [(C₂H₅)3N.HC1], and 3.6% other compounds.

EXAMPLE 4

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, electrically heated oil bath, cooler condenser assembled with a collector flask for distillate, introduce 257 g methanol and 1 12 g calcium oxide. Start the stirring and heating, maintaining the mixture at 65°C for 60 minutes. Over the mixture in the vessel, introduce 185 g glycerine, maintaining the mixture at 65-70°C for 60 minutes. Methanol is removed by distillation from the reaction mass, over which introduce, under stirring, 700 g dichloromethane, fresh or recovered from previous batches and 102 g triethylamine. Then introduce in small portions under stirring 155 g Λ-butyl-dimethylchlorosilane 97%. The reaction is slightly exothermal. Keep the reaction mass under stirring for 120 minute. Filter the suspension and wash on filter with 100 g dichloromethane and recover the se dichloromethane from the product cake by drying. The result is 571 g heterogeneous alkaline catalyst with the molecular formula: CH2,46 0o,428No.o3iClo.o3iCa_0>io5Sio.o64_! consisting of 27.3% calcium methoxide glyceroxide [H₃C-0-Ca-0-CH₂-CH(OH)-CH₂-OH], 46,7% silylated calcium methoxide glyceroxide [H₃C-0-Ca-0-CH₂-CH(OH)-CH₂-0- And(CH₃)2(C₄H9)], 23, 1% triethylamine chlorohydrate [(C₂H₅)₃N.HC1], and 2.9% other compounds.

EXAMPLE 5

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer and electrically heated oil bath, with the flask assembled with a rectification column with structured filling, supplied in the middle with water vapours-methanol, coupled at the upper part with a reflux distributor, thermometer, condenser and methanol collector flask, and at the lower part with an aqueous distillate collector flask, insert in the 4-neck flask 1000 g microalgal oil, with saponification index 198.65 mg KOH/g, acidity index 121,32 mg KOH/g, and 0.25% water, which is treated with 566 g methanol recovered from batches according to example 2 and 55 g super-acid solid catalyst of the type S0₄ ²7Ti02-La₂03_; recovered from batches according to example 2. Start the stirring and heat the mixture in the flask to 68±2°C. The resulting methanol and water vapours, supply the rectification column. The reflux ratio is adjusted so that the temperature of vapours at the top of the column remains at 65±0.2°C. The methanol collected in the flask is reintroduced in the 4-neck flask and the water separated in the lower collector flask is removed. Maintain stirring and heating for approx. 7 ore, until no water is separated, and the acidity index decreases to 1.28 mg KOH/g. Remove the super-acid catalyst by filtration, and transfer the filtrate to an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, condenser and electrically heated oil bath. Over the filtrate in the flask introduce 55 g of heterogeneous alkaline catalyst obtained according to example 3 and start the stirring and heating. Maintain the reaction mass under stirring at 67±2°C for 90 minute, then remove the catalyst by filtration. Separate with a liquid-liquid centrifuge 249 g of glycerine 15.23%, from the methyl esters of fatty acids, which is reintroduced in the flask together with the catalyst that was previously separated by filtration. Maintain the reaction mass under stirring at 67±2°C for 60 minutes, then remove the catalyst by filtration. Remove excess methanol by distillation, first at atmospheric pressure, then under vacuum. Separate with a liquid-liquid centrifuge 4 g of glycerine 96.22%, from the methyl esters of fatty acids, which is filtered through a diatomite filtering layer. Obtain 942 g methyl esters of fatty acids with composition of fatty acids according to table 1 and properties according to table 2. EXAMPLE 6

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer and electrically heated oil bath, with the flask assembled with a rectification column with structured filling, supplied in the middle with water vapours-methanol, coupled at the upper part with a reflux distributor, thermometer, condenser and methanol collector flask, and at the lower part with an aqueous distillate collector flask, insert in the 4-neck flask 1000 g residual oil collected from public food units, with saponification index 187.25 mg KOH/g, acidity index 15.67 mg KOH/g, and 0.17% water, which is treated with 374 g methanol and 40 g super-acid solid catalyst of the type S04² Ti0₂-La₂03_; of the type S0₄ ²7Ti0₂-La₂0_3j having the ratio Ti:La =30: 1 and the number of active centres = 0.91 meq/g. Start the stirring and heat the mixture in the flask to 68±2°C. The resulting methanol and water vapours, supply the rectification column. The reflux ratio is adjusted so that the temperature of vapours at the top of the column remains at 65±0.2°C. The methanol collected in the flask is reintroduced in the 4-neck flask and the water separated in the collector flask is removed. Maintain stirring and heating for approx. 7 ore, until no water is separated, and the acidity index decreases to 1,54 mg KOH/g. Remove the super-acid catalyst by filtration, and transfer the filtrate to an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, condenser and electrically heated oil bath. Over the filtrate in the flask introduce 50 g heterogeneous alkaline catalyst obtained according to example 4 and start the stirring and heating. Maintain the reaction mass under stirring at 67±2°C for 60 minutes, then remove the catalyst by centrifugation. Separate by decantation 220 g of glycerine 35.43%, from the methyl esters of fatty acids, which is reintroduced in the flask together with the catalyst that was previously separated by filtration. Maintain the reaction mass under stirring at 67±2°C for 60 minutes, then remove the catalyst by filtration. Remove excess methanol by distillation, first at atmospheric pressure, then under vacuum. Separate by decantation 14 g of glycerine 95.83%, from the methyl esters of fatty acids, which is filtered through a filtering layer of activated coal and Kieselgel 60 GF254 silica gel. Obtain 939 g methyl esters of fatty acids with composition of fatty acids according to table 1 and properties according to table 2.

EXAMPLE 7

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, electrically heated oil bath and condenser introduce 1000 g rapeseed oil, with saponification index 179,89 mg KOH/g, acidity index 0,33 mg KOH/g, and 0.04% water, together with 308 g methanol and 50 g heterogeneous alkaline catalyst obtained according to example 1. Start the stirring and heating. Maintain the reaction mass under stirring at 67±2°C for 90 minute, then remove the catalyst by filtration. Separate by decantation 188 g glycerine 42.53%, from the methyl esters of fatty acids, which is reintroduced in the flask together with the catalyst that was previously separated by filtration. Maintain the reaction mass under stirring at 67±2°C for 60 minutes, then remove the catalyst by filtration. Remove excess methanol by distillation, first at atmospheric pressure, then under vacuum. Separate by decantation 16 g glycerine 96.13%, from the methyl esters of fatty acids, which is filtered through a filtering layer of activated coal and bentonite. Obtain 953 g methyl esters of fatty acids with composition of fatty acids according to table 1 and properties according to table 2.

EXAMPLE 8

In an installation consisting of a 4-neck flask fitted with electrical stirring, thermometer, electrically heated oil bath and condenser introduce 1000 g camelina oil, with saponification index 188,45 mg KOH/g, acidity index 0,87 mg KOH/g, and 0.09% water, together with 430 g methanol and 60 g heterogeneous alkaline catalyst prepared according to example 4, recovered from previous batches. Start the stirring and heating. Maintain the reaction mass under stirring at 67±2°C for 60 minutes, then remove the catalyst by filtration- Separate by decantation 290 g of glycerine 28.56%, from the methyl esters of fatty acids, which is reintroduced in the flask together with the catalyst that was previously separated by filtration. Maintain the reaction mass under stirring at 67±2°C for 90 minute, then remove the catalyst by filtration. Remove excess methanol by distillation, first at atmospheric pressure, then under vacuum. Separate by decantation 18 g glycerine 95.99%), from the methyl esters of fatty acids, which is filtered through a filtering layer of bentonite. Obtain 959 g methyl esters of fatty acids with composition of fatty acids according to table 1 and properties according to table 2.

EXAMPLE 9

Follow the process described in the examples 2, 5 or 6, replacing microalgal oil or residual oil, with rapeseed, camelina, soy, sunflower, safflower, linseed, hemp, cotton, peanut, pumpkin, corn germ, coconut, palm kernel, ricin, olive oil, lard, fish oil, rendered fat, bovine, ovine fat, as they are or as mixtures, in natural state (raw), purified or recovered from waste, with acidity index greater than 2 mg KOH/g. The yields and properties of the products obtained are within the limits of the values presented in the above examples.

EXAMPLE 10

Follow the process described in the examples 7 or 8, replacing rapeseed or camelina oil with soy, sunflower, safflower, linseed, hemp, cotton, peanut, pumpkin, corn germs, coconut, palm kernel, ricin, olive, microalgal oil, cocoa butter, lard, fish oil, rendering fat, bovine, ovine fat, as they are or as mixtures, in natural state (raw), purified or recovered from waste, with acidity index under 2 mg KOH/g and water content less than 0.1 The yields and properties of the products obtained are within the limits of the values presented in the above examples.

Tablel. Composition in fatty acids of methyl esters of fatty acids

Table 2. Properties of the methyl esters of fatty acids

4. Water content, % (mg/kg) 125 1 12 154 117 142

5. Methanol content, % (wgt.) 0.10 0.12 0.1 1 0.14 0.19

6. Monoglyceride content, % (wgt.) 0.67 0.59 0.55 0.62 0.56

7. Diglyceride content, % (wgt.) 0.14 0.17 0.1 1 0.14 0.18

8. Triglyceride content, % (wgt.) 0.17 0.13 0.18 0.15 0.18

9. Free glycerine content, % (wgt.) 0.010 0.012 0.015 0.015 0.010

10. Metal (Ca+Mg) content, mg/kg 3.43 2.76 3.92 2.95 2.69

Claims

1. A process for obtaining fatty acid methyl esters, by the chemical processing of fats with content of free fatty acids, in several steps, characterised by the fact that in the first step, fats are treated with methanol in proportion of 0.308-0.566% in weight to the fat and with super-acid solid catalyst, fresh or recovered from previous batches, of the type S04² Ti0₂-La₂03, having the ratio Ti:La =30: 1, in proportion of 4-5,5% in weight to the fat, at temperatures of 68±2°C, the water resulting din esterification reaction of the fatty acids is separated from methanol in a rectification column and is removed, and methanol is recirculated, until the acidity index of the reaction mass drops under 2 mg KOH/g, and then the super-acid solid catalyst is removed by filtration, and can be reused, and the filtrate is treated in the next step with a heterogeneous alkaline catalyst, fresh or recovered from previous batches, in proportion of 5-6% in weight to the fat, at temperatures of 67±2°C, for 60-90 minute, the catalyst is removed by filtration or centrifugation, glycerine is separated from the methyl esters of fatty acids by decantation or centrifugation, and is then treated with the heterogeneous alkaline catalyst separated before, at temperatures of 67±2°C, for 60-90 minute, the catalyst is removed by filtration or centrifugation, and excess methanol is removed by distillation, first at atmospheric pressure and then under vacuum, glycerine is separated from the methyl esters of fatty acids by decantation or centrifugation, which is finally filtered through an inorganic filtering layer.

2. A heterogeneous alkaline catalyst for obtaining methyl esters of fatty acids by chemical processing of fats, characterised by the fact that it consists of 27.3-29.9% calcium methoxide glyceroxide, 42.1-46.7% silylated calcium methoxide glyceroxide, 23.1-25.1%) triethylamine chlorohydrate, 2.3-3.6% other compounds, has the molecular formula:

CH_2>464_-2.5350o,428-o_>528 o.o3i-o.o43Clo.o3i-o.o43Cao. io5-o.i29Sio.o64-o.o73, is insoluble in water and organic solvents of the types hydrocarbons, dichloromethane, chloroform, carbon tetrachloride, Ν,Ν-dimethylformamide, dimethylsulfoxide and is reusable.

3. A process for obtaining the aforesaid heterogeneous alkaline catalyst, characterised by the fact that calcium oxide is treated with methanol with a molar ratio of 1:4, at a temperature of 65°C for 60 minutes, the mixture is treated with fresh glycerine, or raw glycerine, a by-product resulting from the process, with a molar ratio of 1 : 1 to the calcium oxide, at temperatures of 65-70°C for 60 minutes, methanol is removed by distillation from the reaction mass, which is treated with a solvent in proportion of 536-625% in weight to the calcium oxide, with triethanolamine with a molar ratio of 1 :2 to the calcium oxide, and with trialkylchlorosilane with a molar ratio of 1 :2 to the calcium oxide, at ambient temperature, for 60-120 minutes, the resulting suspension is filtered or centrifuged, washed on filter with solvent and the solvent is removed from the catalyst cake, by drying with solvent recovery.

4. A process according to claim 1, characterised by the fact that fats are chosen from microalgal, rapeseed, camelina, soy, sunflower, safflower, linseed, hemp, cotton, peanut, pumpkin, corn germs, coconut, palm kernel, ricin, olive, microalgal oil, cacao butter, lard, fish oil, rendering fat, bovine, ovine fat, as they are or as mixtures, in natural state (raw), purified or recovered from waste, and the inorganic filtrating layer is selected from acid-treated bentonite, diatomite, activated coal and Kieselgel 60 GF254 silica gel, bentonite, activated coal and bentonite.

5. A process according to claim 1, characterised by the fact that in the case of fats with acidity index under 2 mg KOH/g and water content under 0.1%, it is possible to skip the first step, that of esterification of the free fatty acids with super-acid solid catalyst.

6. A process according to claim 3, characterised by the fact that the solvent is chosen from tetrahydrofuran, benzene, dichloromethane, fresh or recovered from previous batches, and trialkylchlorosilane is of the type trimethylchlorosilane or r-butyl- dimethylchlorosilane.