KR20020028120A - Process for Preparing Fatty Acid Ester Using Metal-oxide Catalyst - Google Patents

Abstract

PURPOSE: Provided is a preparation method of fatty acid esters by reacting fatty acids with alcohols by using metal oxides catalyst and by eliminating glycerin from the resultant reaction products. The yield is high when fats and low molecular alcohol are reacted and the catalyst, not being soluble in the reactants, is recovered and reused, thereby making the reaction environment-friendly. CONSTITUTION: The process comprises: reacting the vegetable oils and animal fats with 2-40 times(mole ratio) much of alcohol and 0.1-10wt.%(based on the fats) of metal oxides catalyst at 60-200deg.C for 0.5-18 hours to obtain fatty acid esters and glycerin; and separating the above reaction products to isolate the esters. The above vegetable oils are oils of soybean, rapeseed, sunflower seed, castor seed and palm, the animal oil being tallow. The above alcohols are methanol, ethanol, propanol, n-butanol and 2-ethylhexanol while the metal oxides catalysts are Al2O3,γ-Al2O3, MgO, MnO and ZnO.

Description

Process for Preparing Fatty Acid Ester Using Metal-oxide Catalyst

The present invention relates to a method for producing a fatty acid ester using a metal oxide catalyst. More specifically, the present invention relates to a method for producing fatty acid esters by reacting animal or vegetable fats and alcohols in the presence of a metal oxide catalyst to obtain a mixture of fatty acid esters and glycerin, and then separating them.

In general, fatty acid esters are produced by reacting lower alcohols and fats and oils under high pressure conditions using a strong base such as sodium hydroxide, sulfuric acid, or a strong acid homogeneous catalyst. For example, German Patent No. 1,909,434 discloses a transesterification reaction carried out at 95 to 105 ° C. using methyl acetate and butyl alcohol as a catalyst in concentrated sulfuric acid as a general method using a strong acid homogeneous catalyst. In addition, the reaction for transesterifying animal and vegetable oils with methyl alcohol is also known to occur relatively well in the presence of concentrated sulfuric acid. For example, vegetable oils present in sunflower seeds are transesterified with methyl alcohol with concentrated sulfuric acid as a catalyst. Harrington et al. Have reported how to cause them (Ind. Eng. Chem. Prod. Res. Dev., 1985. 24: 314-318). According to this method, sunflower seeds containing vegetable oils are mixed with methyl alcohol in a molar ratio of 100 times or more, and then reacted with a concentrated sulfuric acid catalyst for 3 to 4 hours to obtain methyl ester in a yield of 40.7%. This result is lower than the yield of 72% obtained by the direct reaction between vegetable oil and methyl alcohol under the same experimental conditions, but indicates that the reaction occurs under the influence of water present in the seeds.

On the other hand, transesterification reactions with strong base homogeneous catalysts are also widely known (see Kinet. Katal., 10, 1969, 1382), since the reaction rate is faster than that with acid catalysts, it is more basic than electro acidic catalysts in commercial processes. Catalysts are widely applied. For example, European Patent No. 301,634 discloses an ester production process using strong base catalysts such as KOH, K ₂ CO ₃ , NaOH, and strong base catalysts in various European companies such as Novance Co. (France). Succeeded in commercializing the production method using to produce a methyl ester. In the current process using strong base catalysts, oils diluted to lower alcohols in several to several tens of times are decomposed into fatty acid esters and glycerine over 1 to 10 hours under sodium hydroxide catalyst, and then the fatty acid esters and glycerine are separated in a separation column. Are separated. At this time, the basic catalyst present in the glycerin layer is neutralized with concentrated sulfuric acid, precipitated, removed through filtration, and the filtered solution is sent to a distillation separation column, where the light alcohol is removed by distillation. The fatty acid ester separated in the separation column is washed several times with water and recovered in the drying tower as a final product.

The process using a homogeneous hydroxide hydroxide has a number of problems, in particular, the metal hydroxide catalyst including water has a disadvantage in that the high hydrophilicity so low solubility in vegetable oil is low reactivity. In order to solve this problem, a process using a metal alkoxide such as sodium methoxide (CH ₃ ONa) in place of the hydroxide homogeneous catalyst was developed by Sidobre Sinova Co. (Germany), Na, Various methods have been developed, such as continuous processes using metals (see French Patent No. 1584584) and transesterification of vegetable oils using Na and K (see US Pat. No. 3,852,315). However, the above-mentioned processes are processes using a homogeneous catalyst and have environmental problems in the purification process of the product. Since the homogeneous catalyst is easily dissolved in the reactants, several purification processes using water are inevitable. Therefore, not only does it cause an environmental problem such as the second treatment of the water used, but most homogeneous catalysts must be removed through a neutralization reaction, and thus cannot be reused, which increases the cost of the product. There is a constant need to improve this and develop new fatty acid ester production methods.

Accordingly, the present inventors have made efforts to overcome the shortcomings of the fatty acid ester production method using an electrically strong acidic or strong basic homogeneous catalyst and to develop a more environmentally friendly and economical method. Not only can the fatty acid ester be produced in a high yield, but these metal catalysts are not dissolved in the reactants, thereby making it easy to recover and reusable, making it more economical and environmentally friendly, and thus completing the present invention.

After all, it is an object of the present invention to provide a method for producing a new fatty acid ester using a metal catalyst.

1 is a schematic diagram schematically showing a combination reactor used in the present invention.

<Name of main part of drawing>

1. Reactor 2. Metering pump

3 .. Separator

Fatty acid ester production method of the present invention is 2 to 40 times (molar ratio) alcohol of animal and vegetable fats and oils and fats for 60 to 200 hours at 60 to 200 ℃ in the presence of 0.1 to 10% by weight of the metal oxide catalyst of the fat or oil Reacting to obtain a mixture of fatty acid esters and glycerin; And, separating the fatty acid ester from the electrical mixture.

Hereinafter, the fatty acid ester production method of the present invention will be described in more detail by dividing each step.

Step 1 : obtain a mixture of fatty acid esters and glycerin

Animal and vegetable fats and alcohols are reacted in the presence of a metal oxide catalyst to obtain a mixture of fatty acid esters and glycerin:

At this time, the animal and vegetable fats and oils, soybean oil, rapeseed oil, sunflower seed oil, castor oil, corn oil, palm oil or tallow is used, these fats and oils such as oleic acid, stearic acid, linoleic acid, linolenic acid, palmitic acid, myrilic acid, arachidic acid C ₈ to C ₃₀ containing saturated or unsaturated fatty acids are combined with glycerin and present in the form of mono-, di- or triglycerides.

And as alcohol, it is preferable that lower alcohols, such as methanol, ethanol, propanol, butanol, and 2-ethylhexanol, are used 2 to 40 times (molar ratio) of electrical maintenance. Animal and vegetable fats and oils are composed of a hydrophilic backbone (griserine) and a lipophilic backbone (fatty acid) in the molecule, but since they exist in the form of linear micelles, the reactivity by polar catalysts is very low. This micelle structure prevents other reactants, such as light alcohol, from accessing and also does not allow access of reactive hydrophilic groups and hydrophilic catalysts in the molecule. Particularly, since solid catalysts such as metal oxides and ion exchange resins contain 5 to 20% of water on their surfaces, when the catalysts are mixed with fats and oils with strong lipophilic properties, condensation occurs between the catalysts. Do not. This problem can be easily overcome by using an electric lower alcohol, because the high solubility of the lower alcohol dissolves the micelle structure of the fat and oil so that the catalyst can easily access the reactor of the fat and the reaction because the boiling point is low. It can be easily removed after it is finished. On the other hand, the amount of the lower alcohol should be used in excess in order to increase the ester conversion rate of fats and oils, it is preferably used in 2 to 40 molar ratio compared to the amount of the fats and oils used. If the amount of fats and oils used does not reach 2 molar ratio, the ester conversion rate of fats and oils will be lowered. If it exceeds 40 molar ratios, there will be no difference in the ester conversion rate of fats and oils with the increase of the amount of alcohol. It is not desirable because it only increases energy consumption.

As the metal oxide catalyst, oxides such as aluminum oxide (Al ₂ O ₃ ), γ-aluminum oxide (γ-Al ₂ O ₃ ), magnesium oxide (MgO), manganese oxide (MnO), zinc oxide (ZnO), It is used at 0.1 to 10% by weight of the electrical maintenance. Metal oxides have strong electrostatic properties due to the positively charged localization of the metal component and the negatively charged localization of the oxygen component on the surface. As a result, the surface of the metal oxide absorbs water, ionizes on the solid surface, and the surface of the metal oxide exhibits Bronsted acid or basic properties depending on the degree of adsorption of hydrogen ions or hydroxide ions. It can be used as a catalyst of the transesterification reaction of the present invention.

On the other hand, the above reaction should be carried out for 0.5 to 18 hours in the temperature range of 60 to 200 ℃, preferably 60 to 120 ℃. At the high temperature of 100 ° C. or more, the surface of the metal oxide adsorbed with water gradually releases water on the surface and loses its properties as Bronsted acid or base. However, due to the formation of strong electrostatic attraction due to electron formation between oxygen and metal, the surface of the metal oxide is characterized by Lewis acid or base. This strong electrostatic attraction causes micro-condensation of lower alcohols, so that evaporation does not occur despite the low boiling temperature of lower alcohols even at high temperatures, thereby enhancing the reactivity. As a result, the metal oxide catalyst used in the present invention This allows transesterification of animal and vegetable fatty acids over a wide temperature range. However, when the temperature of the reaction is higher than necessary, a part of the carbon body of the fat and oil starts to carbonize, so it is not preferable that the reaction temperature exceeds 200 ° C or more.

Second Step : Separation of Fatty Acid Ester from Reaction Mixture

The reaction mixture is separated to prepare a fatty acid ester. At this time, there are no particular limitations on the method for removing glycerin and unreacted materials. Conventional separation methods performed in the art may be used, and include fatty acid esters and glycerin. Any method may be sufficient as long as it can effectively remove glycerin from the reaction mixture.

On the other hand, the removal of glycerin of the present process can be effectively carried out by using a reactor in combination with a reactor and a bed separator, schematically illustrating the combination reactor used in the present invention in FIG. In Fig. 1, the reaction mixture comprising the fats and oils, alcohol, fatty acid esters and glycerin in the reactor 1 is transferred to the layer separator 3 by a fixed amount through the metering pump 2 during the reaction so that the glycerin is separated and the glycerin is removed. The reaction mixture is fed back to the reactor 1 to participate again in the reaction. Through such a device, the esterification exchange reaction of the first step, which is basically a chemical equilibrium reaction, shifts the chemical equilibrium toward the product, thereby improving the yield of fatty acid esters.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples in accordance with the gist of the present invention. .

Example 1 Preparation of Fatty Acid Ester Using Metal Catalyst

First, 90 g of soybean oil and 5 g of a metal oxide were injected into a reactor (capacity: 500 mL) of the combined reactor of FIG. 1, and then the temperature of the reactor was raised to 110 ° C. under reduced pressure (pressure: 20 mbar) while stirring to a mixture of soybean oil and a catalyst. Small amounts of water present were completely removed. Next, 64 g of methyl alcohol (7 molar ratio to oil and fat) was added at atmospheric pressure, and the reaction was continued for 18 hours while maintaining the temperature of the reactor at 110 ° C and refluxing. In the middle of the reaction, a fixed amount pump was used to transfer a certain amount (15 mL / min.) To the bed separator to remove the produced glycerin, and then, the reaction product in which the glycerin was removed was added again to improve the yield of fatty acid ester. . Finally, after completion of the reaction, the metal oxide is removed by filtration, methanol is removed using a rotary distillation, and then, the unremoved glycerin is precipitated and the oil component in the upper portion is distilled off to remove pure fatty acid ester. Prepared.

Yield of Fatty Acid Ester According to Catalyst Example catalyst Yield of fatty acid ester One γ-Al ₂ O ₃ 55% 2 Al ₂ O ₃ 30% 3 MgO 47% 4 MnO 48% 5 ZnO 32%

Comparative Example 1 Preparation of Fatty Acid Ester Using Strong Base Catalyst

Fatty acid esters were prepared using NaOH catalysts which are widely used in conventional processes. First, 90 g of soybean oil and 1 g of NaOH (20 meq) were injected into a reactor equipped with a reflux condenser, and then the temperature of the reactor was raised to 110 ° C. while stirring, and the pressure was reduced to 20 mbar, and a small amount was present in the mixture of the soybean oil and the catalyst. Water was completely removed. Next, after adding 64 g of methyl alcohol (7 molar ratio to oil and fat) at normal pressure, the reaction was maintained for 8 hours while maintaining the temperature of the reactor at 110 ℃, reflux. After the reaction was completed, the methanol was removed using a rotary distillation unit, and the reaction mixture was washed three times to remove grease and catalyst. The remaining lipophilic reactant was passed through a glass tube containing magnesium sulfate. Residual water was removed. Finally, the recovered oil component was distilled to recover the fatty acid ester in a yield of 64%.

In Example 1 and Comparative Example 1 above, since the catalyst is not dissolved in the reactant when the metal oxide catalyst is used in the preparation of the fatty acid ester, the catalyst is more easily prepared by a simpler process than the conventional production method using the strong base catalyst. You can see that can be removed. In addition, since the recovered metal oxide catalyst can be reused without pretreatment, fatty acid esters can be produced in a more economical and environmentally friendly manner.

As described and demonstrated in detail above, the present invention provides a method of preparing fatty acid esters by reacting animal or vegetable fats and alcohols in the presence of a metal oxide catalyst to obtain a mixture of fatty acid esters and glycerin, and then separating them. . According to the present invention, fatty acid esters can be produced in a high yield when the fat and oil are reacted with a metal oxide as a catalyst. In addition, since these metal oxide catalysts are not dissolved in the reactants, the metal oxide catalysts may be easily recovered and reused, and thus may be widely used as a method for preparing environmentally friendly fatty acid esters.

Claims (5)

A mixture of fatty acid esters and glycerin by reacting 2 to 40 times the molar ratio of animal and vegetable fats and oils and fats at 60 to 200 ° C. in the presence of 0.1 to 10% by weight of a metal oxide catalyst of the fat or oil. To obtain; And a step of separating the electric mixture. The method of claim 1, Animal and vegetable fats and oils are characterized in that the soybean oil, rapeseed oil, sunflower seed oil, castor oil, corn oil, palm oil or tallow Method for producing fatty acid ester. The method of claim 1, Alcohol is characterized in that methanol, ethanol, propanol, n-butanol or 2-ethylhexanol Method for producing fatty acid ester. The method of claim 1, The metal oxide catalyst is characterized in that the aluminum oxide (Al ₂ O ₃ ), γ-aluminum oxide (γ-Al ₂ O ₃ ), magnesium oxide (MgO), manganese oxide (MnO) or zinc oxide (ZnO). Method for producing fatty acid ester. The method of claim 1, The reaction temperature is characterized in that 60 to 120 ℃ Method for producing fatty acid ester.