HK1146733B - Production of fatty acid and fatty acid ester - Google Patents

Description

Process for producing fatty acid and fatty acid ester

The present invention relates to a process for forming fatty acids, fatty acid esters, or mixtures thereof from starting materials including soap, and the use of the formed mixtures.

Background

Biodiesel is primarily a fatty acid methyl ester formed by transesterification of long chain fatty acids with alcohols (methanol). Fatty acid esters of natural fats are mainly composed of triglycerides, and thus water-soluble glycerin, which cannot be used as biodiesel, is released in transesterification. In addition, the alcohol (methanol) and the salt of the fatty acid (later soap) mixed into the glycerin aqueous solution are released in the process. This fraction (fraction) containing glycerol, alcohol and soap still has a high energy content, in particular in the case of the soap. Theoretically, 10 wt% glycerol is produced from triglycerides. Depending on the process conditions, the proportion of soap can vary greatly and increase from the original total amount of triglycerides to tens of percent. Because the soap compounds are dispersed and partially dissolved in the aqueous solution of glycerin formed, their separation from the aqueous solution is difficult. The soap interferes with the phase between the fat-soluble fatty acid ester and the water-soluble glycerin and tends to form emulsions to varying degrees, creating challenging problems with separation techniques in large-scale processes. Removal of alcohols such as methanol would also require a high input of vacuum distillation. It can therefore be concluded that the production of biodiesel using the above-described process in modern technology is an underutilization of the most energy-rich part of the raw material. The purification of the compounds produced in this process in order to increase their use value is already highly uneconomical only with regard to the purification steps required.

To a large extent due to the above reasons, non-cost effective solutions for the utilization of mixtures of aqueous glycerol, soap and alcohol (methanol) have been found.

There is no commercially economically desirable solution for converting multi-component mixtures containing glycerol as a component into commercially available products. The importance of this technical drawback is particularly emphasized by the significant growth in renewable resources for energy feedstocks other than fossil feedstocks.

Brief description of the invention

The present invention relates to a process for forming fatty acids, fatty acid esters, or mixtures thereof from starting materials including soap.

More specifically, the method according to the invention is characterized in that:

-adding a metal ion forming agent to the starting material to produce a mixture comprising an insoluble phase and a liquid phase,

-separating the insoluble phase from the liquid phase, and

adding an acid to the insoluble phase to form a fatty acid, or adding a monohydric alcohol and an acid catalyst to form a fatty acid ester, thereby forming two phases, an aqueous phase and an organic phase, or first adding an acid and then adding a monohydric alcohol and an acid catalyst to at least a portion of the formed fatty acid in order to esterify the fatty acid. .

The use according to the invention is further characterized by the use of the fatty acids or fatty acid esters or mixtures of fatty acids or fatty acid esters produced by the process according to the invention as a feedstock in esterification reactions of fatty acids or in processes in which lipids are hydrotreated, and the use of the alcohol mixtures produced in the production of biodiesel for the production of fatty acids or fatty acid esters or mixtures thereof according to the process of the invention.

The present invention provides a new solution to the problems associated with the process in which esters of fatty acids are produced from glyceride-containing fats (by treating them with alkali metal alkoxides) by using methanol or other short-chain alcohols according to established methods. Water soluble alkali metal salts of glycerol and other alcohols, as well as fatty acids, soaps, are formed in this process. The glycerol and soap of the mixture reduce the utilization of the total carbon contained in the original fat used in the process, thus reducing the economic efficiency of the process. The main disadvantage of the utilization of glycerol formed in the production of biodiesel, compared to pure glycerol, is that it contains water, soaps and toxic methanol or other short-chain alcohols as impurities.

It is well known that the presence of soap in water and in mixtures containing water-insoluble oils prevents the separation of the aqueous and oily phases from each other. In an aqueous solution of an impure polyol, this soap interferes with the phase between the water and the lipids formed from the fatty acid esters, so that it becomes complicated to separate said phase and even in the best case it contains water and other components which are better soluble in the aqueous phase.

The advantage of the present invention is the integrated unit operation mechanism by means of which the esters formed from fatty acids containing hydrocarbon chains and short chain alcohols can be reformed from impure glycerol substreams (minor flow) which are difficult to utilize energy economy, which are released from the transesterification of organic fats. The apparatus for the process is simple and the technology associated therewith is known in terms of production and use. The process according to the invention is not limited to production scale, but it is easily scalable.

The present invention allows, among other things, the recovery and recycling of energy rich soaps to fatty acids or alcohol esters of free fatty acids. The technical and economic advantages of the process according to the invention are that, for the production of fatty acid esters and fatty acids, with which the overall carbon utilization of the fractions consisting of compounds containing alcohol groups and impurities can be solved by a process which requires neither energy-demanding unit operations such as heating nor pressure-boosting unit operations and which requires only the use of such chemicals which can be introduced into the internal circulation of the process according to the invention for functioning.

In each respect the present invention achieves the principle of sustainable development more efficiently by enhancing the overall utilization of raw materials and thus reducing the need for using other raw materials compared to the prior art. The process according to the invention consists of a functional mechanism, which has the prerequisite to continuously improve the production costs of fatty acids and of their alcohol esters to a level acceptable to the consumer.

Brief description of the drawings

Fig. 1 depicts the main execution steps of the method according to the invention.

Detailed description of the invention

Since no beneficial solution has been found for the utilization of mixtures comprising soap and polyols and monohydric alcohols, these components should be separated from each other in some way in order to utilize these components separately.

We have found that soap can be easily precipitated from an oil-water-alcohol emulsion comprising glycerol, the naturally separated precipitate is recovered and subjected to a methylation procedure whereby the finished biodiesel, i.e. methyl esters of fatty acids, is formed from the soap. Other esters can also be produced by this method. In this regard, the soap component of the impure glycerol fraction has long been available as a feedstock for biodiesel. Thus, the soap can be separated from the other components almost quantitatively. The remaining glycerol solution can be used alone without soap.

Accordingly, the present invention relates to a process for forming fatty acids, fatty acid esters, or mixtures thereof from a starting material comprising soap (preferably alcohol and soap). The alcohol is preferably methanol, ethanol, 1-propanol or a polyol, most preferably glycerol.

The term "soap" refers to salts of fatty acids.

In particular, the present invention relates to a process comprising several steps wherein a metal ion forming agent is added to a starting material to produce a mixture comprising an insoluble phase and a liquid phase. The insoluble phase is separated from the liquid phase and an acid is added to the former. After separation of the insoluble phase, it is preferred to repeat the addition of the precipitating ion forming agent to the liquid phase and the treatment of the precipitate formed as described above. This step can be repeated until the formation of precipitates has been substantially reduced. Acid is added to the combined insoluble phases to form fatty acids. The fatty acid is recovered and used as is or with the addition of a monohydric alcohol and an acid catalyst to form a fatty acid ester. Thus, two phases, an aqueous phase and an organic phase, are formed. These phases are separated from each other and preferably are all collected. The organic phase thus contains the fatty acid ester. Optionally, the monohydric alcohol and the acid are added to the insoluble phase without separate recovery of the fatty acid, whereby an aqueous phase and an organic phase are also formed, wherein the organic phase contains the fatty acid ester.

Thus, the fatty acid can be used as such or by treating the fatty acid with a monohydroxy short chain alcohol to form therefrom a fatty acid ester suitable for biodiesel using the alcohol. The procedures required for the method can be carried out by the person skilled in the art and without complicated apparatus, likewise the additives (reagents) required are known, safe and they have a defined end use form.

In general, the present invention comprises a process based on the main natural step by which long chain fatty acids or fatty acid esters are produced from organic soaps or mixtures thereof. Herein, the term "long chain" refers to a hydrocarbon chain of at least C4, i.e., a hydrocarbon chain having at least 4 carbon atoms. Preferably, the hydrocarbon chain has C₁₀To C₂₀More preferably C₁₂To C₂₀Length of (d).

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

-converting the water-soluble or dispersed soap formed from the fatty acid into the form of a water-insoluble soap using a metal ion forming agent, and

esterification of the water-insoluble soap formed from the fatty acid with an alcohol to give an alcohol ester of the fatty acid or conversion thereof into free fatty acid by treatment with an acid.

According to a preferred embodiment of the invention, the method comprises the steps of:

optionally adding an acid, preferably an organic acid, more preferably acetic acid, formic acid or lactic acid, to the starting material to adjust the pH to a value of 3-8, preferably to a value of 6-8,

metal ion formers, such as inorganic salts of alkaline earth metals, preferably forming Ca²⁺Or Mg²⁺More preferably calcium chloride or magnesium chloride, most preferably calcium chloride, is added to the mixture as a solid or as an aqueous solution in an amount to precipitate at least 40% of the soap, preferably in an amount to form a stoichiometric amount of metal ions relative to the amount of soap, most preferably 5-10% by weight stoichiometric excess (stoichiometric process), whereby an insoluble phase and a liquid phase are formed, wherein the insoluble phase comprises soap and the liquid phase comprises a polyol, preferably glycerol, and a monohydric alcohol, preferably methanol, ethanol or 1-propanol, most preferably methanol, or a mixture thereof,

separating the insoluble phase, wherein the soap has been converted from the first liquid phase into insoluble soap, preferably by filtration or by decantation or by another step generally used for recovering the precipitate,

-adding an acid, preferably hydrochloric acid or sulfuric acid, to the insoluble phase, whereby a fatty acid or a mixture of fatty acids is formed,

optionally, an acid treatment by using a mixture of an acid catalyst and an alcohol, wherein the acid catalyst is preferably hydrochloric acid or sulfuric acid, whereby an organic phase (which comprises the fatty acid ester or a mixture of fatty acid esters) and an aqueous phase (which comprises water and inorganic salts) are formed, and

-collecting the organic phase.

According to another preferred embodiment of the invention, the mixture, which is the fraction formed by transesterification of the lipids, is used as starting material in the process. According to a particularly preferred embodiment, the molar amount of monohydric alcohol added to the fatty acid fraction relative to the molar amount of organic matter is at least 40%, preferably an equal amount.

Particularly preferably, the process according to the invention also comprises a step in which the optional solid matter component is separated from the starting material by filtration. After this, the acidity of the starting material is adjusted by using the necessary amount of an acid, preferably acetic acid, formic acid or lactic acid, most suitably acetic acid.

Soluble soaps present in the filtered starting material are prepared by reacting a metal ion former, preferably an inorganic salt of a divalent alkaline earth metal, more preferably Ca²⁺Inorganic salt of (1), most preferably CaCl₂And added to the mixture to convert to insoluble soap. Most suitably, the salt is added as a solid, whereby large amounts of water are avoided. The mixing time is controlled until the formation of a precipitate substantially ceases. When the solid has been separated from the liquid phase, for example by filtration, a wet "soap cake" remains, which is dried according to a particularly preferred embodiment, after which usually 5 wt.%, preferably 0.1-4 wt.%, most suitably 0.1-2.5 wt.% of water remains in the precipitate.

The insoluble fraction (precipitate) formed is separated from the liquid fraction by filtration or by decantation or by other methods commonly used for recovering precipitates. For the acid treatment of the insoluble fraction, it is preferred to use hydrochloric acid as an aqueous solution, most suitably at a concentration of 0.5-10%. The acid is added in an amount sufficient to release the fatty acid.

According to a particularly preferred embodiment of the invention, the acid treatment and esterification are carried out as acid-catalyzed esterification or by gradual esterification. Preferably, the soap precipitate is subjected to HCl-methanol treatment at a temperature above the boiling point of methanol, more preferably above 65 ℃, most preferably at 80 ℃. As a result of this treatment, a two-phase mixture is formed, wherein the second phase, the organic phase, is formed from the methyl esters of the fatty acids, which are both collected, preferably the phase containing the salts formed in the esterification is added to the starting material. Thus, the aqueous solution containing the inorganic salt released in the esterification reaction can be recycled to the inorganic salt treatment step of the soap.

Compounds added in different steps of the process, e.g. salts of divalent alkaline earth metals, e.g. CaCl₂Or the side fractions formed by these reactions (other than NaCl) do not leave the process completely, but they are preferably recycled internally in the process or they form separate economically valuable fractions and thus improve the overall economy of the process.

According to a particularly preferred embodiment of the present invention, the fatty acids produced are used for the manufacture of alcohol esters of fatty acids. More preferably, the fatty acid esters produced from these fatty acid esters and the present invention are further used in the manufacture of biofuels such as biodiesel. Most suitably, the product of the invention is suitable as a feedstock in the esterification of fatty acids, or in a process wherein lipids of vegetable or animal origin are subjected to hydrotreatment, in particular in a process for the manufacture of a so-called HVO ("hydrogenated vegetable oil").

According to a preferred embodiment, the esters of the invention are used for the manufacture of biodiesel or renewable diesel. Accordingly, the fatty acid can be used for other fuels like diesel.

Accordingly, it is preferred to obtain the starting material for use in the process of the present invention, e.g., from a glycerol fraction containing methanol produced in the manufacture of biodiesel, which typically contains at least about 2-10% soap. Since water causes soap formation during transesterification, its presence is not detrimental in the present invention, but the amounts of water and monohydric alcohol are minimized in the above-mentioned transesterification. Less than 20%, preferably 2-10% of the water is released into the glycerol fraction containing methanol. This water content is preferred in the starting materials used in the process of the present invention.

According to "EU-directive 2003/30/EY", "biodiesel" means "methyl esters produced from vegetable or animal oils, of diesel quality, usable as biofuels". Thus, biodiesel consists of fatty acid esters.

On the other hand, the term "renewable diesel" refers to fat that has been hydrotreated from animals, plants or microorganisms, whereby "microbial fat" refers to fat obtained from bacteria, yeasts, molds, algae or other microorganisms.

Both the fatty acids and fatty acid esters formed in the present invention can be used in the manufacture of biofuels. They can be used as such or they can be blended with other components, or the acid or ester structure can be degraded using methods known in the art and the double bonds can be saturated, thereby obtaining an n-paraffin product which on the other hand can be mixed into other components.

Examples

EXAMPLE 1 preparation of fatty acid ester

0.5 l of the minor fraction containing glycerol and soap obtained from the biodiesel production with rapeseed oil was weighed, and solid calcium chloride was added thereto under stirring until no more precipitate was formed (0.9 mol). The soap precipitate was separated from the liquid glycerol fraction by filtration and washing with water, after which the precipitate was dried. Thus, 171g of a substantially dry precipitate were obtained.

0.54g of the obtained precipitate was weighed out, and then 2ml of a mixture of methanol and hydrochloric acid, in which the portion of methanol was 45.8% and the portion of acid was 54.2%, was added thereto. The mixture was heated to 80 ℃ in a closed vessel for one and a half hours, and then the fatty acid methyl ester (1ml) was separated therefrom by a usual separation procedure.

Example 2 production of fatty acids and their esterification

The precipitate obtained above was treated with hydrochloric acid so that the pH of the aqueous layer was permanently acidic (pH 2). The mixture is heated to 62 ℃ and a fatty acid-containing skin layer is separated therefrom. The salts are removed from the layer by washing with water, after which the water remaining in the layer after washing and the water formed with the fatty acids is removed by drying using a dehydrating agent, whereby the fatty acids remain.

11.4g of the obtained fatty acid mixture was weighed, and then methanol (four times the molar amount) and HCl gas were added thereto as a catalyst. The resulting oil layer was washed with a methanol-water mixture and with water until the washing water became neutral, after which an oily ester layer (6ml) was separated from the resulting oil-solution mixture.

The fatty acid mixture obtained and the corresponding fatty acid ester mixture are very suitable for the manufacture of, for example, diesel fuel.

Claims (22)

1. A process for forming fatty acids, fatty acid esters or mixtures thereof from a starting material comprising an alcohol and a soap, wherein the alcohol is selected from methanol, ethanol, 1-propanol, glycerol or mixtures thereof, characterized in that:

-adding a metal ion forming agent to the starting material to produce a mixture comprising an insoluble phase and a liquid phase,

-separating the insoluble phase from the liquid phase, and

-adding an acid to the insoluble phase to form a fatty acid, or adding a monohydric alcohol and an acid catalyst to form a fatty acid ester, thereby forming two phases, an aqueous phase and an organic phase, or adding first an acid and then a monohydric alcohol and an acid catalyst to at least a portion of the formed fatty acid in order to esterify the fatty acid.

2. A process according to claim 1, characterized in that the monohydric alcohol is methanol, ethanol or 1-propanol.

3. A process according to claim 1, characterized in that the alcohol is glycerol.

4. A process according to claim 1, characterized in that the starting material is a fraction formed by transesterification of a lipid.

5. A process according to claim 1, characterized in that the metal ion forming agent is calcium chloride or magnesium chloride.

6. A process according to claim 5, characterized in that the metal ion forming agent is calcium chloride.

7. A method according to any of the preceding claims, characterized in that the metal ion forming agent is added as a solid or as a liquid.

8. A process according to claim 7, characterized in that the metal ion forming agent is added as a solid.

9. A process according to claim 1, characterized in that the metal ion forming agent is added in an amount such that at least 40 mol% of the soap of the starting material precipitates.

10. A method according to claim 9, characterized in that the amount of metal ion forming agent added is an amount which forms a stoichiometric amount of metal ions relative to the amount of soap.

11. The process according to claim 9, characterized in that the metal ion forming agent is added in a stoichiometric excess of 10 mol%.

12. A process according to claim 1, characterised in that the insoluble phase comprises the soap.

13. A process according to claim 1, characterized in that the liquid phase comprises the polyol or the monohydric alcohol or a mixture of several alcohols.

14. A process according to claim 1, characterized in that an acid is added to the insoluble phase, thereby forming a fatty acid or a mixture of fatty acids.

15. A process according to claim 14, characterized in that the acid is hydrochloric acid or sulfuric acid.

16. A process according to claim 1, characterized in that a monohydric alcohol and an acid catalyst are added to the insoluble phase to form the fatty acid ester.

17. The process according to claim 16, characterized in that the acid catalyst is hydrochloric acid or sulfuric acid.

18. A process according to claim 1, characterized in that first an acid is added to the insoluble phase to form a fatty acid, and then a monohydric alcohol and an acid catalyst are added to at least a portion of the formed fatty acid to esterify the fatty acid.

19. A process according to any one of claims 16 to 18, characterised in that the molar amount of monohydric alcohol is at least 40% relative to the molar amount of organic material.

20. A process according to claim 19, characterized in that the molar amount of monohydric alcohol is equivalent to the molar amount of organic substance.

21. A process according to claim 1, characterized in that the organic phase comprises a fatty acid ester or a mixture of fatty acid esters and the aqueous phase comprises water and an inorganic salt.

22. The process according to claim 1, characterized in that the organic and aqueous phases are separated from each other and collected.