JP4920583B2 - Fatty acid lower alkyl ester and light oil alternative fuel - Google Patents

Description

The present invention relates to fatty acid lower alkyl ester le suitable for use in the alternative to diesel fuel.
This application claims priority based on Japanese Patent Application No. 2005-164269 for which it applied on June 3, 2005, and uses the content here.

In recent years, biomass fuel using organic matter derived from animals and plants as an energy source has attracted attention as an alternative to light oil. Diesel oil is a kind of petroleum product and refers to the portion that is distilled between dredged oil and heavy oil during the distillation of crude oil, and has a boiling range of about 250-400 ° C ("Chemical Dictionary" Kyoritsu Publishing Co., Ltd., (The 26th edition was issued on October 15, 1981).
As one of the biomass fuels, there is a fatty acid lower alkyl ester obtained by transesterifying natural fats and oils with a lower alkyl alcohol such as methanol. For example, Patent Documents 1 and 2 disclose a method for producing a fatty acid lower alkyl ester. It is disclosed.
Most of these fatty acid lower alkyl esters used as light oil substitute fuels are made from refined rapeseed oil and soybean oil as raw materials, but refined rapeseed oil and soybean oil are expensive, Then, it is beginning to consider using cheap crude palm oil as a raw material. Crude palm oil is an unpurified oil mainly composed of fatty acids (glycerides) of fatty acids having 16 to 18 carbon atoms.
Japanese Patent No. 2590538 Japanese Patent No. 3046999

  However, crude palm oil contains about several mass% free fatty acids. Free fatty acid consumes the alkali catalyst added in the transesterification reaction, and as a result, by-products such as alkali soaps are generated. If such a by-product is included in the final fatty acid lower alkyl ester, it is assumed that this may cause clogging of the fuel supply line and fuel injection nozzle when used as a light oil alternative fuel. Before the transesterification reaction, a pretreatment for removing free fatty acids from the crude palm oil is considered essential. However, when free fatty acids are removed in this way, there is a problem that the production yield of the raw material base is reduced accordingly. It is also possible to increase the production yield by converting the removed free fatty acid to methyl ester and returning it to light oil alternative fuel, but such a method requires an additional step of methyl esterification of free fatty acid, which is not efficient. Absent.

  The crude palm oil contains, in addition to free fatty acids, gums such as carotene, phospholipids, proteins, resinous substances, and oils and fats of fatty acids having 20 carbon atoms. The components originally contained in such crude palm oil, the alkali metal derived from the catalyst added in the transesterification reaction, the unreacted triglyceride, and the glycerides such as monoglyceride and diglyceride which are intermediates of transesterification are similarly described above. It is thought to cause clogging. Furthermore, among these, carotene also causes the resulting fatty acid lower alkyl ester to be colored brown. Therefore, it is also an important issue to reduce the amount of substances that can cause such clogging and coloring.

  The present invention has been made in view of the above circumstances, has no coloring, clogging of the fuel supply line and the fuel injection nozzle when used as a light oil alternative fuel, and is inexpensive and highly pure fatty acid lower alkyl ester. It is an object to provide efficiently with a manufacturing yield.

Fatty acid lower alkyl ester le of the present invention, and to remove gum from the crude palm oil, degummed to obtain a degummed material (A), using a cation exchange resin, the free fatty acids of the degumming thereof in Esterification step (B) for esterification with a lower alkyl alcohol to obtain an ester mixture, transesterification step (C) for transesterification of fats and oils in the ester mixture with lower alkyl alcohol, and transesterification step (C) The fatty acid lower alkyl ester has a purity of 99% by mass or more and has 20 carbon atoms. The lower alkyl ester content of the fatty acid is 0.3% by mass or less .
The production method preferably further includes a recycling step (E) in which the soap produced in the transesterification step (C) is decomposed with an acid to form a fatty acid, and the fatty acid is returned to the degumming step (A). .
The fatty acid lower alkyl ester of the present invention preferably further has a glyceride content of 0.1% by mass or less.
The light oil substitute fuel of the present invention contains the fatty acid lower alkyl ester of the present invention.
The light oil substitute fuel of the present invention preferably further contains an antioxidant.

  According to the present invention, there is no coloring, clogging of a fuel supply line and a fuel injection nozzle when used as a light oil alternative fuel is suppressed, and an inexpensive, high-purity fatty acid lower alkyl ester is efficiently provided with a high production yield. it can.

It is a schematic process drawing of the manufacturing method of this invention. It is a schematic process figure about a recycling process (E) among the manufacturing methods of the present invention.

Hereinafter, the present invention will be described in detail.
The crude palm oil used as a raw material in the production method of the present invention is an unrefined mixture obtained by squeezing the pulp of oil palm and mainly composed of oils and fats of fatty acids having 16 to 18 carbon atoms. In addition, the crude palm oil includes gums such as carotene, phospholipids, proteins, and resinous substances, free fatty acids, and oils and fats of fatty acids having 20 carbon atoms. In the present invention, any crude palm oil can be suitably used, but a crude palm oil having a free fatty acid content of 5% by mass or less and a peroxide value of 5 m equivalent / kg or less is particularly preferable.

  FIG. 1 is a schematic process diagram showing an example of the production method of the present invention. After performing a degumming step (A) and a free fatty acid esterification step (B), a transesterification step (C) and A distillation step (D). Here, the degumming step (A) and the esterification step (B) are positioned as pretreatments in the method for producing a fatty acid lower alkyl ester from crude palm oil. FIG. 2 is a schematic process diagram showing an example of a recycling process (E) in which soap generated in the transesterification reaction process (C) is decomposed with an acid to form a fatty acid, and this fatty acid is returned to the raw material degumming process (A). It is.

[Degumming step (A)]
Although there is no restriction | limiting in particular as a specific method of the degumming process (A) of crude palm oil, As shown in the figure, it adds a phosphoric acid to crude palm oil, and contains gum quality by filtering after that. A method of removing insoluble matters is preferable.
That is, the crude palm oil is preferably heated to 50 to 70 ° C., more preferably 60 to 70 ° C., phosphoric acid is added thereto, and the mixture is stirred for about 1 to 60 minutes. At this time, if necessary, a filtering agent and other additives may be added. After mixing and stirring, the mixture is filtered with a filter equipped with a filter such as a cloth filter to remove insoluble matter containing gum and a degummed product is obtained as a filtrate.

  Here, the amount of phosphoric acid added to the crude palm oil is preferably 0.01 to 0.1 parts by mass with respect to 100 parts by mass of the crude palm oil. In such a range, degumming effectively proceeds. The phosphoric acid is preferably added in the form of an aqueous solution. In that case, the phosphoric acid concentration of the aqueous phosphoric acid solution is preferably 70% by mass or more, more preferably 75 to 89% by mass. With such a concentration, water as a solvent is preferable since there is no possibility of adversely affecting the subsequent step rather than the degumming step (A).

  As the filter agent added to the crude palm oil as necessary, for example, diatomaceous earth, pearlite, alkali activated clay and the like can be used. Among these, diatomaceous earth, pearlite and the like are preferable, and pearlite is particularly preferable. The addition amount of a filter agent is 0.03-0.15 mass part with respect to 100 mass parts of crude palm oil, Preferably it is 0.03-0.1 mass part, Most preferably, it is 0.03. It is -0.05 mass part.

In the degumming step (A), crude palm oil containing a large amount of filter agent may be circulated and supplied to the filter to form a precoat phase on the surface of the filter so that the filtration can be performed more smoothly. The addition amount of the filter agent in that case is 0.2-1.0 mass part normally with respect to 100 mass parts of crude palm oil, Preferably it is 0.2-0.7 mass part, More preferably, it is 0.2-0. .4 parts by mass.
Moreover, it is preferable to remove water and impurities from the crude palm oil before and after the degumming step (A) and during the degumming step (A). Contaminants may be removed by the same method and the same apparatus as the gum removal, or may be removed by stationary separation or filtration in a crude palm oil storage tank, centrifugation, or the like. Contaminants include soil, gravel, and garbage, and in some cases, metal may be included.

[Esterification step (B)]
After the degumming step (A), a cation exchange resin is used to esterify the free fatty acid in the degummed product with a lower alkyl alcohol to obtain an esterification step (B) to obtain an ester mixture.
The free fatty acid is originally contained in the crude palm oil, and after the esterification of the free fatty acid in this esterification step (B), the transesterification step (C) described later is finally performed. This is very important when the resulting fatty acid lower alkyl ester is used as a light oil alternative fuel.

That is, when transesterification is performed in a state where free fatty acids are mixed, an alkali catalyst is consumed by the free fatty acids, and not only the transesterification does not proceed, but also a large amount of soap is generated. Nevertheless, if transesterification is to proceed, a large amount of alkali catalyst is required, saponification of fats and oils proceeds, and the amount of soap produced increases further. Moreover, it is thought that the by-products such as the generated alkali soap cause clogging of the fuel supply line and the fuel injection nozzle.
Therefore, by esterifying the free fatty acid in the esterification step (B) in advance, a fatty acid lower alkyl ester in which clogging when used as a light oil alternative fuel is suppressed is obtained. Moreover, since the consumption of the alkali catalyst by the free fatty acid in the transesterification step (C) can be suppressed by performing such an esterification step (B), the transesterification step (C) proceeds smoothly.
Furthermore, since such an esterification step (B) does not remove the free fatty acid out of the system but converts it to a fatty acid lower alkyl ester, the raw material-based production yield can be kept high. Moreover, such an esterification step (B) is incorporated between the degumming step (A) and the transesterification step (C) and is performed continuously with these steps. Efficient. A method of maintaining the production yield by esterifying the free fatty acid removed outside the system in another line and then mixing it with the finally obtained fatty acid lower alkyl ester can be considered. Is not efficient.

  Moreover, in this esterification process (B), since it esterifies using a cation exchange resin, it is continuous by the simple method of making the degumming thing obtained at the degumming process (A) contact a cation exchange resin. In addition, the esterification can be advanced, and a higher esterification reaction rate can be achieved as compared with other esterification methods such as a method using a solid catalyst and a method of adding sulfuric acid.

Furthermore, examples of the cation exchange resin include an acid type solid cation exchange resin and an acid gel type cation exchange resin. Particularly, the use of an acid gel type cation exchange resin is preferable because the esterification reaction rate is further increased. The reason for this is not clear, but can be inferred as follows. In other words, the catalytic activity of acid-type solid cation exchange resins decreases due to adhesion or adsorption of water generated by the esterification reaction, but water can be taken up as hydrated water in acidic gel cation exchange resins. This is considered to be due to the fact that the catalytic ability is not lowered by moisture.
The degree of crosslinking of the acidic gel type cation exchange resin is preferably in the range of 3 to 10%. If it is 3% or more, it is preferable at the point of resin strength, and if it is 10% or less, it is preferable from the point of the removal efficiency of a free fatty acid. The degree of crosslinking is more preferably 3 to 9%, more preferably 4 to 8%. Among them, those having a crosslinking degree of 4% are particularly preferable because the esterification reaction rate of free fatty acids is the highest and the mechanical strength of the resin is sufficient.

  Examples of the acid gel cation exchange resin that can be suitably used include a sulfonated product of styrene-divinylbenzene copolymer, for example, Diaion SK104 (trade name, degree of cross-linking 4%) manufactured by Mitsubishi Chemical Corporation, SK106 (Trade name, crosslinking degree 6%), SK 1B (trade name, crosslinking degree 6%) and SK110 (trade name, crosslinking degree 10%) and Dowex (trade name, crosslinking degree 4%) ), Amberlite (trade name, degree of crosslinking: 4%) manufactured by Rohm and Haas.

As a specific method of the esterification step (B), a column filled with a cation exchange resin is prepared, and a mixture of the lower alkyl alcohol and the degummed product obtained in the degumming step (A) is supplied to the column. And a method of passing it through.
The conditions for passing through the column are, from the viewpoint of esterification efficiency, the column temperature is preferably 40 to 70 ° C, more preferably 50 to 65 ° C, still more preferably 60 to 65 ° C, and the column residence time is preferably 60. -480 minutes, More preferably, it is 90-360 minutes, More preferably, it is 90-240 minutes.
Before supplying the mixture of the lower alkyl alcohol and the degummed product to the column, it is preferable to wash the cation exchange resin with alcohol as a pretreatment. As the alcohol for washing, it is preferable to use the same lower alkyl alcohol as that used for the esterification reaction. Such washing is preferably performed until the moisture in the alcohol before and after passing through the column does not change. By washing in this way, the water in the cation exchange resin is replaced with alcohol, and the esterification efficiency of free fatty acids can be further increased. Specifically, it is preferable to wash with 2 to 5 times the volume of cation exchange resin alcohol.

As the lower alkyl alcohol, an alcohol having 4 or less carbon atoms can be used, and specific examples include methanol, ethanol, propanol, butanol and the like. These may be used alone or in combination of two or more, but preferably methanol is used as shown.
Moreover, although the addition amount of a lower alkyl alcohol is suitably determined by the fatty acid distribution etc. in the crude palm used as a raw material, it is 5-30 mass parts normally with respect to 100 mass parts of degummed products, Preferably It is 10-28 mass parts, More preferably, it is 15-26 mass parts.
Further, the lower the amount of water in the lower alkyl alcohol, the better. For example, it is 1500 ppm or less, preferably 1000 ppm or less, more preferably 600 ppm or less.

[Transesterification step (C)]
After the esterification step (B), the oil and fat in the obtained ester mixture is transesterified with a lower alkyl alcohol in the presence of an alkali catalyst to carry out a transesterification step (C) to obtain an ester mixture. The fats and oils to be subjected to transesterification are contained in the crude palm oil as a main component, and are mainly fatty acids and fats having 16 to 18 carbon atoms.

As the lower alkyl alcohol used in the transesterification reaction step (C), those exemplified in the esterification step (B) can be used in the same manner, and methanol is preferably used as shown in the figure. The amount of the lower alkyl alcohol added is, for example, 5 to 50 parts by mass, preferably 5 to 45 parts by mass with respect to 100 parts by mass of the ester mixture.
The temperature of the transesterification step (C) is, for example, 30 to 120 ° C, preferably 50 to 100 ° C, and particularly preferably 60 to 80 ° C. Moreover, the processing time of a transesterification reaction process (C) can be set suitably, and about 30 to 90 minutes are suitable.
Further, a catalyst is usually used in the transesterification step (C), and examples thereof include alkali catalysts such as sodium hydroxide, potassium hydroxide, sodium methylate, and among these, sodium hydroxide and potassium hydroxide are preferable. . The addition amount of the catalyst is, for example, 0.1 to 0.4 part by weight, preferably 0.2 to 0.4 part by weight, and particularly preferably 0.2 to 0 part by weight with respect to 100 parts by weight of the ester mixture. 3 parts by mass.

By performing the transesterification step (C) in this way, an oil phase mainly composed of fatty acid lower alkyl ester and a phase mainly composed of glycerin (hereinafter referred to as glycerin phase) are produced. The oil phase is sent to the distillation step (D), and the glycerin phase is sent to the recycling step (E). Separation of the oil phase and the glycerin phase may be performed by stationary separation, centrifugation, or the like. In the case of stationary separation, the separation may be performed at 30 to 70 ° C. for about 30 to 90 minutes.
Further, before separating the oil phase and the glycerin phase, it is preferable to add water for washing the alkali catalyst.

  The transesterification step (C) may be carried out in one stage or two or more stages, but since this transesterification reaction is a reversible reaction, a fatty acid lower alkyl ester can be obtained in a higher yield. Two or more stages are preferable. More preferably, the first stage is advanced to a yield of about 95 to 96%, and the second stage is advanced to a yield of about 99%. Further, after the first stage, the oil phase mainly composed of fatty acid lower alkyl ester and the glycerin phase are separated, and only the oil phase is supplied to the second stage.

  Thus, when performing transesterification process (C) in two steps, according to the yield of fatty acid lower alkyl ester in the first step, the amount of lower alkyl alcohol added in the second step, treatment temperature and treatment time, Conditions such as the amount of catalyst added may be set more gently than in the first stage. Preferably, in the first stage, the amount of lower alkyl alcohol added is 10 to 50 parts by mass with respect to 100 parts by mass of the ester mixture. The addition amount is 0.2 to 0.4 parts by mass, the treatment temperature is 60 to 80 ° C., the treatment time is 30 to 90 minutes, and the second stage is based on 100 parts by mass of the oil phase supplied to the second stage. The lower alkyl alcohol addition amount is 1 to 10 parts by mass, the catalyst addition amount is 0.01 to 0.1 parts by mass, the treatment temperature is 50 to 70 ° C., and the treatment time is 1 to 15 minutes.

[Distillation step (D)]
The distillation step (D) is a step of distilling the oil phase obtained in the transesterification step (C). By including this step at least under reduced pressure, monoglyceride, diglyceride and triglyceride contained in the oil phase are included. Such as unreacted glycerides, lower alkyl esters of fatty acids having 20 carbon atoms, components derived from alkali metals such as alkali soaps, and carotene degradation products as residue, and the target fatty acid. A lower alkyl ester can be obtained as a distillate with high purity.
Since each component contained in the residue is thought to cause clogging of the fuel supply line and the fuel injection nozzle, after such a distillation step (D), the possibility of clogging is suppressed to a low level. Fatty acid lower alkyl esters that are suitably used in alternative fuels are obtained.

In particular, a lower alkyl ester of a fatty acid having 20 carbon atoms has a high melting point (for example, 55 ° C. for methyl arachidate), and if it exists as an impurity, it tends to cause clogging problems. The reason for this is not clear, but crude palm oil, unlike highly unsaturated oils such as rapeseed oil and soybean oil, contains a lot of saturated fatty acids with a high melting point, so when there is a lower alkyl ester of a fatty acid having 20 carbon atoms, This is considered to be due to the fact that this becomes a crystal nucleus to promote the formation of solid crystals and induce clogging.
The fatty acid lower alkyl ester obtained after such a distillation step (D) has a fatty acid lower alkyl ester purity of 99% by mass or more and a lower alkyl ester content of a fatty acid having 20 carbon atoms of 0.3% by mass or less, More preferably, it is 0.1% by mass or less, and the total content of glycerides such as monoglyceride, diglyceride, and triglyceride, which is considered to cause clogging, is 0.1% by mass or less. Suitable for use in.

  Such a distillation step (D) is effective because the crude palm oil is not a highly unsaturated oil but contains a lot of saturated fatty acids. That is, if the highly unsaturated oil is distilled under reduced pressure, the polymerization of unsaturated substances abundantly contained in the highly unsaturated oil proceeds, and the quality of the resulting fatty acid lower alkyl ester may not be ignored. With palm oil there is almost no such risk.

  Furthermore, according to such a distillation step (D), the carotene originally contained in the crude palm oil can be decomposed and left as a decomposition product in the residue at the bottom of the tower, so that the step of removing carotene is not performed separately. However, a colorless and transparent fatty acid lower alkyl ester having no brown color derived from carotene can be obtained.

As the method of the distillation step (D), a method in which atmospheric distillation and vacuum distillation are combined is suitable, and in particular, atmospheric pressure for removing lower alkyl alcohol (methanol in the illustrated example) and water as a distillate. A flash distillation step, a first reduced-pressure distillation step for removing glycerin as a distillate, and a fatty acid lower alkyl ester as a target product are obtained as a distillate, and carotene is decomposed, and the decomposition product, glyceride, carbon Examples include a method in which a lower alkyl ester of several 20 fatty acids, a component derived from an alkali metal such as alkali soap, and the like are sequentially subjected to a second vacuum distillation that leaves a residue at the bottom.
The flash distillation step is usually performed at 120 to 170 ° C., and the first vacuum distillation step is usually performed at 150 to 190 ° C. and 0.5 to 3 KPa, preferably 160 to 180 ° C. and 0.5 to 2 KPa. In the first vacuum distillation step, the lower alkyl ester derived from a fatty acid having 12 or 14 carbon atoms may be distilled off along with glycerin, but this may be converted into the target fatty acid lower alkyl ester. By returning, the raw material-based manufacturing yield can be maintained high.
Moreover, since the decomposition temperature of carotene is about 200 ° C., the second vacuum distillation step is usually performed at 180 to 250 ° C. and 0.1 to 3 KPa, preferably 190 to 230 ° C. and 0.6 to 2 KPa.

[Recycling process (E)]
In the recycling step (E), the soap in the glycerin phase produced in the transesterification step (C) is decomposed with an acid to form a fatty acid, and this fatty acid is degummed, preferably in the raw crude palm oil storage tank. It is a process of returning. Such a recycling step (E) can further increase the production yield. In the glycerin phase, in addition to glycerin and soap, usually a lower alkyl alcohol (methanol in the illustrated example), an alkali catalyst, water and the like are present.

The method of the recycling step (E) is not limited as long as the soap produced as a by-product in the transesterification step (C) can be decomposed with an acid to form a fatty acid and returned to the degumming step (A). Specifically, the following method is preferable.
First, without separating and removing the lower alkyl alcohol from the glycerin phase produced in the transesterification step (C), an acid such as sulfuric acid is added to the glycerin phase as it is, and then this is added for a short time, specifically 60 minutes. Stir and mix to produce a mixture containing fatty acids and sodium sulfate. Subsequently, sodium sulfate is removed from this mixture, and water is added to a mixture (including fatty acid and lower alkyl alcohol) obtained by removing some lower alkyl alcohol, glycerin and water, and the fatty acid is mainly used. Separated into a component phase and a phase containing water, lower alkyl alcohol and glycerin. And the phase which has a fatty acid as a main component is returned to the degumming process (A), Preferably, the crude palm oil storage tank of a raw material. On the other hand, for the phase containing water, lower alkyl alcohol and glycerin, water and lower alkyl alcohol are distilled by flash distillation to obtain crude glycerin as a residue. The water and lower alkyl alcohol distilled by flash distillation are then introduced into a lower alkyl alcohol rectification column, and the lower alkyl alcohol is recovered as a distillate and waste water is removed as a residue.
In addition, when transesterification process (C) is performed in two or more stages, it is preferable to separate and recover the glycerin phase at the end of each stage, and to provide all of these to this recycling process (E).

As an acid added to the glycerin phase, in addition to sulfuric acid, other acids such as hydrochloric acid and phosphoric acid may be used. Moreover, the temperature condition in that case becomes like this. Preferably it is 70 degrees C or less, More preferably, it is 10-70 degreeC, More preferably, you may be 40-60 degreeC. The addition amount of the acid may be adjusted to an amount that makes the solution after the addition acidic, but is preferably adjusted so that the pH is 2 to 6, more preferably 3 to 5.
Furthermore, the flash distillation step is usually 120 to 200 ° C, and the step of rectifying the lower alcohol is usually 60 to 120 ° C.
Thus, according to the method of adding an acid without separating and removing the lower alkyl alcohol from the glycerin phase, the acid decomposition can be carried out at a low temperature in a short time.

[Fatty acid lower alkyl ester and light oil alternative fuel]
As described above, according to the production method having the degumming step (A), the esterification step (B), the transesterification step (C), and the distillation step (D), it is an unpurified and inexpensive. Since crude palm oil is used as a raw material, it is low-cost, and when used as a light oil alternative fuel, it can continuously and efficiently eliminate substances that cause clogging and substances that cause coloring. In addition, fatty acid lower alkyl esters can be produced with a high production yield.
Specifically, the fatty acid lower alkyl ester produced in spite of the raw material of crude palm oil is 99% by mass or more and the lower alkyl of a fatty acid having 20 carbon atoms. The ester content is 0.3% by mass or less, and the total glyceride content is 0.1% by mass or less, which sufficiently meets the EU standard for light oil alternative fuels.

Thus, the fatty acid lower alkyl ester obtained from crude palm oil as a raw material can be used as it is as an alternative fuel for light oil for all uses such as automobiles, ships, agricultural machinery, construction machinery, power generation and heating. Since it does not contain carotene, which also acts as an inhibitor, it is oxidized to prevent oxidation due to oxygen in the air, causing changes in physical properties such as viscosity and density, and layer separation due to polymerization. It is preferable to add an appropriate amount of an inhibitor and use it as an alternative fuel for light oil.
As the antioxidant, tocopherol, gallic acid, propyl gallate, butylhydroxyanisole (BHA), t-butylhydroquinone (TBHQ) and the like can be suitably used, and these are usually 1 to 500 ppm, preferably 10 to 100 ppm. Add as follows.
Moreover, you may mix with the fatty-acid lower alkyl ester manufactured from crude palm oil, the fatty-acid alkyl ester obtained from another raw material, etc. and light oil as needed, and it is used as a light oil alternative fuel.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
The fatty acid methyl ester was manufactured from crude palm oil by the following steps.
(1) Degumming step (A)
To 100 parts by mass of crude palm oil heated to 65 ° C., 0.04 part by mass of a 75% by mass phosphoric acid aqueous solution and 0.03 part by mass of pearlite as a filter medium were added and mixed and stirred for 10 minutes.
Next, this was filtered (KST-142-JA-S (with jacket) pressure filter, filtration area 113 cm ² , pressure 1 kg / cm ² , temperature 45 ° C., pressure filtration with Advantec NO-5C filter paper). The insoluble matter containing gum was removed, and a degummed product was obtained as a filtrate.
Moreover, the raw crude palm oil is 0.3% by mass of the component having 12 carbon atoms, 1.1% by mass of the component having 14 carbon atoms, 43.9% by mass of the component having 16 carbon atoms, and the number of carbon atoms. The component which is 18 and does not have a double bond is 4.3% by mass, the component which has 18 carbon atoms and 1 double bond is 39.5% by mass, the component which has 18 carbon atoms and 2 double bonds is 10 It contained 0.8 to 1% by mass of a component having 0.1% by mass and 20 carbon atoms, and 3.3% by mass of free fatty acid. Moreover, POV (peroxide value) was 3.6 and AV (acid value) was 7.2. In addition, carbon number said here is what does not contain carbon derived from alcohol in ester.

(2) Esterification step (B)
Methanol was passed through a column packed with Diaion SK104 (trade name, degree of crosslinking: 4%) manufactured by Mitsubishi Chemical Corporation, which is an acidic gel cation exchange resin, and washed. Next, a mixture obtained by adding 20 parts by mass of methanol to 100 parts by mass of the degummed product obtained in (1) above was supplied to the column and allowed to pass through to obtain an ester mixture. At that time, the column temperature was 65 ° C., the column residence time was 120 minutes, and methanol having a water content of 600 ppm was used.

(3) Transesterification step (C)
The transesterification step (C) was performed in two steps on the ester mixture obtained in (2) above as follows.
First, 15 parts by mass of methanol and 120 parts by mass of sodium hydroxide as a catalyst are added to 120 parts by mass of the ester mixture, and the mixture is treated at a treatment temperature of 70 ° C. for 60 minutes (reaction in an autoclave with a paddle stirrer). An oil phase mainly composed of fatty acid methyl ester and a glycerin phase were produced, and a first-stage transesterification reaction was performed.
Next, this was allowed to stand at 40 ° C. for 60 minutes, and then separated into an oil phase and a glycerin phase, and 5 parts by mass of methanol and 0.05 part by mass of sodium hydroxide as a catalyst were added to 100 parts by mass of the oil phase. By performing the treatment at a treatment temperature of 60 ° C. for 5 minutes, an oil phase mainly composed of fatty acid methyl ester and a glycerin phase were made into a uniform layer, and a second-stage transesterification reaction was performed.
Next, 14 parts by mass of water for washing sodium hydroxide was added thereto, and then this was allowed to stand at 40 ° C. for 60 minutes, and then separated into an oil phase and a glycerin phase.

(4) Distillation step (D)
The oil phase obtained in the above (3) was first flash distilled at a normal pressure of 150 ° C. to remove methanol and water as a distillate.
Next, the first distillation under reduced pressure was performed on the residue of flash distillation under the conditions of 180 ° C. and 1.3 KPa to remove the distillate containing glycerin as a main component.
Furthermore, the second vacuum distillation was performed on the first vacuum distillation residue under the conditions of 220 ° C. and 1.3 KPa to obtain a fatty acid methyl ester as a distillate.
Table 1 summarizes the properties of the obtained fatty acid methyl ester and the evaluation results of the oxidation stability evaluated by the method described below.

(5) Recycling process (E)
To the mixture of the glycerin phases obtained in the first and second transesterification reactions of (3) above, sulfuric acid was added to pH 4.0, and the mixture was stirred and mixed at 60 ° C. for 60 minutes. Next, after removing sodium sulfate produced from this mixture, it is separated into a phase containing fatty acid as a main component and a phase containing water, methanol and glycerin, and the phase containing fatty acid as a main component is used as raw crude oil Returned to. On the other hand, about the phase containing water, methanol, and glycerin, water and methanol were removed by flash distillation at 150 ° C. to obtain crude glycerin. The water and methanol mixture distilled by flash distillation was then introduced into a methanol rectification column and distilled at 70 ° C. to recover methanol as a distillate, while the waste water was removed as a residue.

(Evaluation of oxidation stability)
The fatty acid methyl ester obtained in Example 1 was evaluated for oxidation stability by a method based on the CDM test (Conductometric Determination Method) of the European Biodiesel Standard Test Method (EN-14112: 2003). However, the measurement temperature was 110 ° C.
Specifically, first, clean air is sent in while heating the sample to 110 ° C. in a reaction vessel, and volatile decomposition products generated by oxidation are collected in water. By collecting the volatile decomposition product, the conductivity of water changes, and the time until the point at which such a change suddenly occurred (the bending point when plotted on a graph) was measured. It can be said that the longer this time, the higher the oxidation stability.

[Examples 2 and 3]
To the fatty acid methyl ester obtained in Example 1, propyl gallate was added as an antioxidant so that the concentration was 10 ppm in Example 2 and 100 ppm in Example 3. For these, the oxidation stability was evaluated in the same manner as in Example 1.

[Comparative Example 1]
The same crude palm oil as that used in Example 1 was used as a raw material, and the transesterification (C) was performed without performing the degumming step (A) and the esterification step (B). Subsequently, as the distillation step (D ′), only flash distillation at a normal pressure of 150 ° C. was performed to obtain a fatty acid methyl ester as a residue. The properties of the fatty acid methyl ester thus obtained are also summarized in Table 1.

[Example 4]
Oxidation stability was evaluated in the same manner as in Example 1 except that 190 ° C., 1.3 KPa, and 50 ppm of propyl gallate were added to the first vacuum distillation, and the results are shown in Table 2.

[Example 5]
Oxidation stability was evaluated in the same manner as in Example 1 except that 185 ° C., 1.3 KPa, and 50 ppm of propyl gallate were added to the first vacuum distillation, and the results are shown in Table 2.

[Example 6]
Oxidation stability was evaluated in the same manner as in Example 1 except that 183 ° C., 1.3 KPa, and 50 ppm of propyl gallate were added to the first vacuum distillation, and the results are shown in Table 2.

  In the table, “%” is based on mass.

  According to the present invention, there is no coloring, clogging of a fuel supply line and a fuel injection nozzle when used as a light oil alternative fuel is suppressed, and an inexpensive, high-purity fatty acid lower alkyl ester is efficiently provided with a high production yield. it can.

Claims (5)

Degumming step (A) to remove gum from crude palm oil and obtain a degummed product,
Esterification step (B) in which a free fatty acid in the degummed product is esterified with a lower alkyl alcohol using a cation exchange resin to obtain an ester mixture;
A transesterification step (C) in which the fats and oils in the ester mixture are transesterified with a lower alkyl alcohol;
Produced by a method for producing a fatty acid lower alkyl ester having a distillation step (D) at least a distillation under reduced pressure of the oil phase obtained in the transesterification step (C) ,
A fatty acid lower alkyl ester having a purity of fatty acid lower alkyl ester of 99% by mass or more and a lower alkyl ester content of a fatty acid having 20 carbon atoms of 0.3% by mass or less. The production method includes a recycling step (E) in which soap generated in the transesterification step (C) is decomposed with an acid to form a fatty acid, and the fatty acid is returned to the degumming step (A). The fatty acid lower alkyl ester according to claim 1. The fatty acid lower alkyl ester according to claim 1 or 2, wherein the glyceride content is 0.1 mass% or less. A light oil alternative fuel comprising the fatty acid lower alkyl ester according to any one of claims 1 to 3 . Furthermore, antioxidant is included, The light oil substitute fuel of Claim 4 characterized by the above-mentioned.

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