EA020085B1 - Production of fatty acid and fatty acid ester - Google Patents

Abstract

The present invention concerns a process for forming a fatty acid, a fatty acid ester or a mixture thereof from a soap-comprising starting material, in which process a metal-ion forming agent is added to the starting material, whereby a mixture is formed, which contains an insoluble phase and a liquid phase, the insoluble phase is separated from the liquid phase, and an acid is added into the insoluble phase to form a fatty acid, or a monohydric alcohol and an acid catalyst are added to form a fatty acid ester, whereby two phases are formed, an aqueous phase and an organic phase, or, first, an acid is added and then a monohydric alcohol and an acid catalyst are added into at least a portion of the formed fatty acid to esterify the fatty acid.

Description

The invention relates to a method for producing a fatty acid, fatty acid ester, or a mixture thereof from starting materials containing soaps, as well as to the use of the mixture obtained.

The level of technology

Basically, biodiesel is a fatty acid methyl ester, which is obtained by the transesterification reaction of long-chain fatty acids with alcohol (methanol). The fatty acid esters of natural fats consist mainly of triglycerides, resulting in the transesterification process, water-soluble glycerin is obtained, which is not applicable as biodiesel fuel. Then the alcohol (methanol) is mixed with an aqueous solution of glycerin, resulting in salts of fatty acids (hereinafter, soap). This fraction, containing glycerin, alcohol and soap, still contains, mainly due to soap, a large amount of energy. Theoretically, from a triglyceride, 10% by weight of glycerol is obtained. By changing the conditions of the process, it is possible to significantly influence the content of soap and increase its content to tens of percent of the initial amount of triglyceride. Since the soaps are dispersed and partially dissolved in an aqueous solution of the formed glycerin, their isolation from the aqueous solution is difficult. Soaps interfere with the phase boundary between fat-soluble fatty acid esters and water-soluble glycerol and contribute to the formation of various emulsions that create difficult problems in large-scale processes regarding separation methods. The removal of alcohol, in particular methanol, also requires expensive vacuum distillation. Thus, we can conclude that the industrial production of biodiesel fuel by the method described above, which is currently adopted, is characterized by insufficiently efficient use of the most energy-efficient raw material components. Cleaning the resulting substances to increase the efficiency of their use is very uneconomical, already only because of the need for purification steps.

Due to the reasons given above, no economically viable solution was found to the problem of using a mixture of aqueous glycerin, soap, and alcohol (methanol).

Thus, there are no economically viable solutions that would allow the transformation of multicomponent mixtures, including glycerin as a component, into commercial products. The value of this technological gap is particularly relevant due to the growing interest in raw materials related to renewable energy sources, in addition to fossil raw materials.

Brief description of the invention

The invention describes a method for producing fatty acids, fatty acid esters, or mixtures thereof from starting materials containing soaps.

In more detail, the method according to the present invention is characterized by the features indicated in the characterizing part of claim 1 of the claims 1.

The use according to the invention, on the other hand, is characterized by the features indicated in clauses 15 and 16 of the claims.

The invention proposes a new solution to the problem concerning the process of obtaining fatty acid esters in the traditional way from glycerol lipid-containing fats using methanol or other short-chain alcohols when they are treated with alkali metal alkoxides. During this process, glycerin and other alcohols are formed, as well as water-soluble alkali metal salts of fatty acids, and soaps. Glycerine and soap in the mixture reduce the degree of utilization of the total carbon contained in the original fat used in the process, and, consequently, the economic efficiency of the method is reduced. The main disadvantage of using glycerin produced in the production of biodiesel fuel, compared with the use of pure glycerin, is that it contains water, soap, and toxic methanol, or other short-chain alcohol as impurities.

It is known that the presence of soap in water and in a mixture containing a water-insoluble oil interferes with the separation of the water and oil phases. In a water solution of a polluted polyhydric alcohol, soap breaks the phase boundary between water and lipid derived from fatty acid esters, so phase separation becomes more complicated, and even in the best case, the solution contains water and other components that dissolve better in the aqueous phase.

An advantage of the invention is a set of work operations whereby an ester derived from a fatty acid containing hydrocarbon chains and short chain alcohols can be isolated from a process stream with a low content of contaminated glycerol, which is obtained by transesterification of organic fats and which is energy-inefficient. The equipment used in the process is distinguished by simple execution, the technology used in the method is known and used in production. The method according to the invention is not used on an industrial scale, but it easily allows for a change in the scale of production.

The invention allows, in particular, to restore energy-rich soaps and re-convert them into esters of alcohols and fatty acids or free fatty acids. The technical and economic advantage of the method according to the invention is that the problem of full utilization

- 1 020085 of carbon from the fraction consisting of compounds that contain alcohol groups and impurities in the production of fatty acids and their esters can be solved using a method that does not require, neither energy-consuming working operations, such as heating, nor working operations under pressure and which for implementation requires only the use of such chemical compounds that can be introduced into the internal cycle of the method according to the invention.

Compared to the prior art, every aspect of the invention more effectively corresponds to the principles of sustainable development by improving the integrated use of raw materials and, consequently, reducing the need to use other raw materials. The method according to the invention includes a functional system that has the prerequisites for reducing the cost of producing fatty acid esters and alcohols to a level acceptable to customers.

Brief description of the figures

FIG. 1 shows the main stages of the process according to the invention.

Detailed Description of the Invention

Due to the fact that no effective solutions have been found to the problem of using a mixture consisting of soap, polyatomic alcohols and monohydric alcohols, these components must be separated from each other in some way to use these components separately. The authors found that soap can be easily separated from an oil-water-alcohol emulsion containing glycerin, and the naturally separated precipitate can be separated and methylated to produce biodiesel fuel, i.e., fatty acid methyl ester. Through this process, other esters can also be obtained. In this regard, the components of the soap from the contaminated fraction of glycerin are suitable raw materials for biodiesel. Thus, soap can be separated from other components essentially quantitatively. The remaining solution of glycerin, not containing soap, can be used separately.

Thus, the present invention describes a method for producing a fatty acid, a fatty acid ester, or a mixture thereof from a starting material containing soap, preferably alcohol and soap. The alcohol is preferably methanol, ethanol, 1-propanol or a polyhydric alcohol, most preferably glycerol.

The term soap means a salt of a fatty acid.

In particular, the present invention describes a method comprising the steps in which an agent forming a metal ion is added to said starting material to form a mixture consisting of an insoluble phase and a liquid phase. The insoluble phase is separated from the liquid phase, an acid is added to the insoluble phase. After separation of the insoluble phase, it is desirable to repeat the addition to the liquid phase of the precipitating agent, forming metal ions, and process the resulting precipitate in the same way as described above. This stage can be repeated until the precipitate formation substantially stops. To obtain a fatty acid, an acid is added to the combined insoluble phase. Fatty acids are separated and used directly or monohydric alcohol and an acid catalyst are added to them to form a fatty acid ester. Thus two phases are formed, the aqueous phase and the organic phase. These phases are separated and preferably both are collected.

The organic phase thus contains the fatty acid ester. If desired, a monohydric alcohol and an acid are added to the insoluble phase without separating the fatty acid, resulting in the formation of the aqueous and organic phases, with the ester of the fatty acid in the organic phase.

Thus, the fatty acid can be used as such or from it can be obtained fatty acid ester, suitable as biodiesel fuel, which can be obtained using a monohydric short-chain alcohol by reacting the fatty acid with the specified alcohol. The operations required for the implementation of the described method can be carried out by a person skilled in the art without the use of sophisticated equipment, in addition, the necessary additives (reagents) are known, safe and presented in a suitable form for use.

In general, the invention relates to a method based mainly on natural processes by which long-chain fatty acid or fatty acid ester can be obtained from organic soap or mixtures thereof. In this context, the term “long chain” means a hydrocarbon chain of at least C ₄ , i.e. hydrocarbon chain consisting of at least four carbon atoms. Preferably, the hydrocarbon chain has a length of from C ₁₀ to C ₂ o, most preferably from C ₁₂ to C ₂₀ .

Thus, the method according to the invention comprises the steps of:

the conversion of a water-soluble or dispersed soap derived from fatty acids into a water-insoluble soap with an agent that forms metal ions; and esterifying a water-insoluble soap obtained from fatty acids with an alcohol to produce an ester of an alcohol and a fatty acid, or converting this water-insoluble soap to a fatty acid when interacting with an acid.

The method according to a preferred embodiment of the invention comprises the steps of:

- 2 020085 it is possible to add acid, preferably organic, most preferably acetic acid, formic acid or lactic acid, to the starting materials in order to bring the pH to a value from 3 to 8, preferably from 6 to 8;

adding a metal ion forming agent, for example, alkaline earth metal mineral salts, preferably a Ca ²⁺ or Md ²⁴ forming agent, most preferably calcium chloride or magnesium chloride, most preferably calcium chloride, as a solid or aqueous solution to the mixture in an amount to precipitate at least 40% of the soap, preferably in an amount that achieves a stoichiometric amount of metal ion in relation to the amount of soap, most preferably in stoichiometric from 5 to 10 wt.%, with the formation of insoluble and liquid phases, the insoluble phase contains soap, and the aqueous phase contains a polyhydric alcohol, preferably glycerol, and a monohydric alcohol, preferably methanol, ethanol or 1-propanol, most preferably methanol or their mixture;

separating the insoluble phase, in which the soap is in insoluble form, from the first liquid phase, preferably by filtration or decanting or using another operation commonly used to isolate the precipitate;

adding an acid, preferably hydrochloric or sulfuric acid, to the insoluble phase to produce a fatty acid or a mixture of fatty acids;

it is possible that the acid treatment can be carried out using a mixture of an acid catalyst and an alcohol, the acid catalyst being preferably hydrochloric or sulfuric acid, thus forming an organic phase containing an ester of fatty acid or a mixture of esters of fatty acids, and the aqueous phase containing water and mineral salts;

collecting the organic phase.

In accordance with another preferred embodiment of the present invention, the mixture, which is the fraction obtained by transesterification of the lipid, is used as a starting material for the process according to the invention. In accordance with the most preferred embodiment of the invention, the molar amount of monohydric alcohol added to the fatty acid fraction is at least 40% of the molar amount of organic matter, preferably an equivalent amount.

Most preferably, the invention includes the steps in which possible solid components are removed from the starting materials by filtration. Thereafter, the acidity of the starting materials is controlled using the necessary quantities of acid, preferably acetic acid, formic acid or lactic acid, acetic acid is most preferred.

Soluble soap present in the filtered starting materials is converted into an insoluble soap by adding to the mixture an agent that forms metal ions, preferably a mineral salt of a divalent alkaline earth metal, most preferably Ca ²⁺ mineral salt, most preferably CaCl ₂ . Most preferably, the salt is added as a solid to avoid the use of large quantities of water. The duration of mixing is monitored until the precipitate is almost completely precipitated. After separation of the solid from the liquid phase, for example, by filtration, a wet precipitate of soap remains, which, in accordance with the preferred embodiment of the invention, is dried, after which 5% by weight usually remains in the sediment. water, preferably from 0.1 to 4 wt.%, most preferably from 0.1 to 2.5 wt.%.

The resulting insoluble fraction (precipitate) is separated from the liquid fraction by filtration or decantation or other methods commonly used to separate the precipitate. The insoluble fraction is treated with an acid, preferably hydrochloric acid in the form of an aqueous solution, most preferably in the form of a solution with a concentration of from 0.5 to 10%. The acid is added in an amount sufficient to release the fatty acids.

In accordance with the most preferred embodiment of the invention, acid treatment and esterification are carried out by acid catalyzed esterification or step esterification. Preferably, the treatment of the precipitate of soap with hydrochloric acid / methanol is carried out at a temperature above the boiling point of methanol, most preferably above 65 ° C, preferably at 80 ° C. As a result of this treatment, a two-phase mixture is obtained, in which the second phase, i.e. the organic phase consisting of fatty acid methyl esters is collected. It is preferable to add the phase containing the salt formed during the esterification process to the starting materials. Thus, an aqueous solution containing mineral salts obtained by transesterification can be reused at the stage of processing the soap with a mineral salt.

Compounds added at different stages of the process, such as salts of divalent alkaline earth metals, for example, CaCl ₂ or the resulting fractions, other than NaCl, are not completely removed from the process, but are reused in the process or form separate economically advantageous fractions, which improves the overall economic efficiency of the process.

In accordance with the most preferred embodiment of the present invention, the resulting fatty acid is used to prepare fatty acid esters and alcohols. Nai

- 3 020085 more preferably, these fatty acid esters and fatty acid esters obtained according to the invention are further used for the production of biofuels, such as biodiesel. Most expediently, the product of the present invention is suitable as a raw material for the esterification of fatty acids or for processes in which vegetable or animal lipids undergo hydrotreatment, in particular as a raw material for processes where so-called LEO (hydrogenated vegetable oil) is obtained.

In accordance with a preferred embodiment, the esters according to the invention are used to produce biodiesel fuel or renewable diesel fuel. Accordingly, fatty acids can be used for other types of fuels similar to diesel.

Accordingly, the starting material used in the process of the present invention is preferably obtained, for example, from a methanol-containing glycerol fraction obtained from the production of biodiesel fuel, which usually contains at least about 2 to 10% soap. Since water causes the formation of soap in the transesterification reaction, its presence in the present invention is not unfavorable, but in the above-described transesterification reaction, the amount of water and monohydric alcohol is reduced to a minimum. Less than 20%, preferably from 2 to 10%, of water is contained in said methanol-containing glycerol fraction. Such a water content is preferred for the starting materials used in the process according to the present invention.

Biodiesel fuel means, in accordance with EC Directive 2003/30 / ΕΥ, methyl ester derived from vegetable or animal fats, which has the quality characteristics of diesel fuel, for use as a biofuel. Thus, biodiesel consists of esters of fatty acids.

On the other hand, the term renewable diesel fuel means hydrogenated animal, vegetable or microbial fat, and microbial fat means fat derived from bacteria, yeast, mold fungi, algae or other microorganisms.

Both fatty acids and the fatty acid esters obtained in this invention can be used to produce biofuels. They can be used in pure form or in mixture with other components, or such acidic or ester structures can be decomposed using methods known from the prior art, with saturation of double bonds, thus obtaining n-alkanes, which can also be mixed with other components.

Examples

Example 1. Obtaining esters of fatty acids.

0.5 l of a side fraction containing glycerin and soap obtained from the production of biodiesel fuel from rapeseed oil was collected, solid calcium chloride was added with stirring, and stirring was continued until the precipitate was separated (0.9 mol). The soap precipitate was separated from the liquid glycerol fraction by filtration, followed by washing with water, after which the precipitate was dried. In this way, 171 g of a substantially dry precipitate was obtained.

0.54 g of the obtained precipitate was weighed, 2 ml of a mixture of methanol and hydrochloric acid were added to it, in which the methanol content was 45.8%, the content of hydrochloric acid was 54.2%. The mixture was heated in a closed vessel to 80 ° C for half an hour, and fatty acid methyl esters (1 ml) were separated out from the mixture by means of suitable separating procedures.

Example 2. Obtaining fatty acids and their esterification.

The precipitate obtained above was treated with hydrochloric acid to obtain an acidic medium (pH 2) of the aqueous layer. The mixture was heated to 62 ° C, the surface layer containing fatty acids was separated. Salts were removed from the layer by washing with water, after which the water remaining in the layer after washing, as well as the water formed together with the fatty acids, was removed by drying using a dehydrating agent, after which only the fatty acids remained.

11.4 g of the resulting fatty acid mixture was weighed, methanol (fourfold molar excess) and HCl gas as a catalyst were added to it. The resulting oil layer was washed with methanol / water, then with water until neutral wash water, and then the oily layer of ether (6 ml) was separated from the resulting oil / solution mixture.

Both the resulting mixture of fatty acids and the mixture of the corresponding fatty acid esters are well suited for the production of diesel fuel.

Claims (17)

CLAIM 1. A method of producing a fatty acid from a soap-containing feedstock containing a polyhydric alcohol and a monohydric alcohol selected from the group consisting of methanol, ethanol, 1 propanol and a mixture thereof, the method is characterized by the following stages: adding acid to the feedstock to adjust the pH to 3 to 8; adding a metal ion forming agent that causes the formation of a soap precipitate to form a mixture containing an insoluble phase and a liquid phase; separation of the insoluble phase from the liquid and - 4 020085 adding acid to the insoluble phase to obtain a fatty acid. 2. A method of obtaining a fatty acid ester from a soap-containing feedstock containing a polyhydric alcohol and a monohydric alcohol selected from the group consisting of methanol, ethanol, 1 propanol and a mixture thereof, the method is characterized by the following stages: adding acid to the feedstock to adjust the pH to 3 to 8; adding a metal ion forming agent that causes the formation of a soap precipitate to form a mixture containing insoluble and liquid phases; separation of the insoluble phase from the liquid and the addition of a monohydric alcohol and an acid catalyst to obtain a fatty acid ester with the formation of two phases, aqueous and organic. 3. A method of obtaining a mixture of fatty acid and a fatty acid ester from a soap-containing feedstock containing a polyhydric alcohol and a monohydric alcohol selected from the group consisting of methanol, ethanol, 1-propanol and a mixture thereof, the method is characterized by the following stages: adding acid to the feedstock to adjust the pH to 3 to 8; adding a metal ion forming agent that causes the formation of a soap precipitate to form a mixture containing insoluble and liquid phases; separating the insoluble phase from the liquid phase and first adding an acid, and then adding at least a portion of the obtained fatty acid monohydric alcohol and an acid catalyst with the implementation of the esterification of the fatty acid. 4. The method according to any one of claims 1 to 3, characterized in that the feedstock is a fraction obtained by transesterification of a lipid. 5. The method according to any one of claims 1 to 3, characterized in that the agent forming the metal ions is calcium chloride or magnesium chloride, preferably calcium chloride. 6. The method according to any one of claims 1 to 5, characterized in that the added metal ion forming agent is a solid or liquid, preferably a solid. 7. The method according to any one of claims 1 to 6, characterized in that the metal ion forming agent is added in an amount that precipitates at least 40 mol% of soap from the feedstock, preferably the agent is added in an amount in which a stoichiometric amount of metal ions relative to the amount of soap, most preferably with a stoichiometric excess of 10 mol%. 8. The method according to any one of claims 1 to 7, characterized in that the insoluble phase contains soap. 9. The method according to any one of claims 1 to 8, characterized in that the liquid phase contains a polyhydric alcohol, or a monohydric alcohol, or a mixture of several alcohols. 10. The method according to any one of claims 1 to 9, characterized in that an acid, preferably hydrochloric or sulfuric acid, is added to the insoluble phase to obtain a fatty acid or mixture of fatty acids. 11. The method according to any one of claims 1 to 10, characterized in that a monohydric alcohol and an acid catalyst, preferably hydrochloric acid or sulfuric acid, are added to the insoluble phase to obtain a fatty acid ester. 12. The method according to any one of paragraphs. 1-10, characterized in that the acid is first added to the insoluble phase to produce a fatty acid, and then at least a portion of the obtained fatty acid is added monohydric alcohol and an acid catalyst to carry out the esterification of the fatty acid. 13. The method according to claim 11 or 12, characterized in that the molar amount of monohydric alcohol with respect to the molar amount of organic matter is at least 40%, preferably an equivalent amount. 14. The method according to any of the preceding paragraphs, characterized in that the organic phase contains a fatty acid ester or a mixture of fatty acid esters, and the aqueous phase consists of water and mineral salts. 15. The method according to any one of the preceding paragraphs, characterized in that the organic and aqueous phases are separated and collected. 16. The use of a fatty acid, or an ester of a fatty acid, or a mixture of fatty acids, or esters of fatty acids obtained according to the method according to any one of claims 1 to 15, as a raw material for the esterification of fatty acids or in lipid hydrotreatment processes. 17. The use of a mixture of alcohols obtained in the production of biodiesel for the production of fatty acids or fatty acid esters, or mixtures thereof according to the method according to any one of paragraphs 115.