KR100839363B1 - Method for Preparing Biodiesel Using Supercritical Alcohol and Solvent - Google Patents

Abstract

The present invention relates to a method for producing biodiesel from vegetable oils using a supercritical alcohol, and more particularly, to esterifying a vegetable oil in the presence of a supercritical alcohol and a supercritical solvent having a boiling point similar to that of the alcohol. It relates to a method for producing a fatty acid alkyl ester (biodiesel).

According to the present invention, the methanol content can be drastically lowered, high reaction yield can be obtained even under relatively low misleading pressure and pressure, and no separate equipment for recovering the solvent used in the supercritical reaction is required. It is possible to manufacture diesel.

Supercritical, Alcohol, Oil, Biodiesel, Solvent, Homogeneous, Fatty Acid Alkyl Ester

Description

Method for Preparing Biodiesel Using Supercritical Alcohol and Solvent

1 is a schematic diagram showing a biodiesel manufacturing method according to the present invention.

2 is a biodiesel manufacturing process according to the present invention.

Figure 3 is a graph showing the fatty acid composition of the biodiesel prepared by the manufacturing method according to the present invention.

Figure 4 is a graph showing the yield of fatty acid methyl ester of biodiesel before and after the cosolvent prepared by the production method according to the present invention.

<Explanation of symbols for the main parts of the drawings>

1: palm oil 2: pump

3: preheating tube furnace 4: reactor

5: reactor furnace 6: reverse pressure regulator

7: product tank 8: alcohol tank

9: cosolvent tank V1-V12: valve

PI: Pressure gauge PC: Pressure regulator

TI: Thermometers TIC: Thermometers and Regulators

Field of invention

The present invention relates to a method for producing biodiesel from a vegetable oil using a supercritical alcohol, and more particularly, to esterifying the vegetable oil in the presence of a supercritical alcohol and a supercritical solvent similar in boiling point to the alcohol. It relates to a process for producing fatty acid alkyl esters (biodiesel).

Background of the Invention

The rapid increase in population and industrial development of the twentieth century has led to the rapid increase in the use of fossil fuels, resulting in an energy shortage problem that is disrupting the balance of energy supply and demand. As coal and petroleum resources are gradually depleted in the world, interest in the development of alternative energy is increasing, and researches on recycling natural resources and waste oil obtained through cultivation and using them as energy sources have recently been made. It is attracting new attention.

Bio-diesel is an alternative that emerged as a result of these studies and is a generic term for pollution-free fuels made from vegetable oils such as soybean oil, rapeseed oil, waste vegetable oil and seaweed oil. Because of its properties similar to diesel, it is used as a fuel additive in diesel vehicles, which are mainly diesel, or as a vehicle fuel.

Generally, biodiesel is produced by esterification reaction between vegetable oil and alcohol in the presence of a catalyst (acid, alkali, lipase, etc.) (Scheme 1).

Although there are various methods of transesterification using methanol, a method of using alkali as a catalyst, a method of using lipase lipolytic enzyme or a supercritical fluid (for example, methanol), the alkali catalyst method is the most common. However, the method for producing fatty acid alkyl esters using the conventional alkali catalysts requires that the catalyst is combined with free fatty acids to produce fatty acid soaps as by-products, resulting in excessive alkali catalysts, resulting in lower yields. In addition, the fatty acid soap produced as a by-product makes it difficult to separate the fatty acid alkyl ester layer from the glycerin layer and requires an additional process for removing the catalyst and fatty acid soap.

In order to solve these problems, a supercritical process using a supercritical or subcritical alcohol without a catalyst has been developed. The production of biodiesel using alcohol and / or alcohol in a supercritical state of 25 MPa or less is used. Method (US 6,187,939), preparation of fatty acid alkyl esters by esterification of lower alcohols of C ₁ to C ₅ in supercritical state (US 6,288,251), of alcohols of C ₁ to C ₂₄ in supercritical or subcritical state The manufacturing method of the mono ester by a transesterification reaction or a dehydration reaction (JP 2000204392A2), etc. are mentioned, for example.

Supercritical fluids are fluids that exist above the critical temperature and pressure, and because they can continuously change their density from a lean state close to the ideal gas to a high density near the liquid density, the equilibrium properties of the fluid (solubility, entrainer effect), Not only transfer properties (viscosity, diffusion coefficient, thermal conductivity) but also solvation and molecular clustering can be controlled. When such physical property control is easily used in processes such as reaction and separation, solvent properties corresponding to various liquid solvents can be obtained with a single solvent. That is, the physical properties can be tuned to a desired state by changing the pressure and temperature.

In addition, supercritical fluids are substances with intermediate properties between liquids and gases. Supercritical fluids have both dissolving power in liquid phase and diffusivity in gas phase, making them ideal for solvents in extraction systems or mobile phases in chromatography, but also at higher temperatures and pressures, especially at higher pressures. Due to its pressure-dependent dissolving ability, it has been used for separation, purification, extraction, fractionation and recrystallization of various materials. Therefore, it is known that the supercritical process has the advantage of increasing the reaction rate by forming a uniform phase, eliminating the need for pretreatment of free fatty acids, and simplifying the aftertreatment process.

In particular, according to Saka Shiro (hereinafter referred to as the 'Saka process'), supercritical methanol and oil are reacted, and fatty acid alkyl is produced when the molar ratio of methanol to oil is 42: 1 under the conditions of temperature of 270 to 350 ° C and pressure of 17 to 43 MPa Highest yields of esters ( Fuel , 80: 693, 2001; Bioresource Tech . , 91: 289, 2004; WO 2004/108873).

On the other hand, in the production of biodiesel using a supercritical process, supercritical methanol and oil are known to form a single phase, but there is a problem that does not achieve a uniform phase under relatively low temperature and pressure. Therefore, in order to keep the supercritical methanol and oil in a homogeneous phase, the pressure and temperature must be increased and a large amount of methanol must be added. According to the Saka process, the molar ratio of methanol to oil is 42: 1, the amount of methanol used is too high, not only a lot of energy is consumed during the evaporation and recovery of methanol, but the overall process equipment becomes large, and the investment cost is too high. It has the disadvantage of being. In addition, in order to increase the yield of the esterification reaction, the pressure and the temperature must be kept high, which causes a lot of side reactions.

In order to improve the Saka process as described above, a method of using a supercritical co-solvent such as CO ₂ or propane has been proposed (Fuel, 84: 347, 2005; JP 2005-053871A2). According to this approach, the molar ratio of methanol to oil can be reduced to around 24: 1, which significantly reduces energy consumption. However, co-solvents such as CO ₂ and propane have to be recovered and reused because they cause various environmental problems in disposal, and the boiling point requires a separate compression and condensation facility in addition to the methanol recovery process.

Thus, the present inventors have made efforts to solve the problems of the prior art as a result, as a result of esterifying the vegetable oil in a supercritical state using a solvent similar to the lower alcohol and boiling point, it is possible to drastically reduce the lower alcohol consumption The present invention was completed by confirming that a high reaction yield can be obtained even at a relatively low temperature and pressure, and that biodiesel can be produced economically since a separate facility for the recovery of the solvent is not required.

After all, it is an object of the present invention to provide a method for producing a fatty acid alkyl ester (biodiesel), characterized in that the esterification of a vegetable oil in the presence of supercritical lower alcohol and a supercritical solvent similar in boiling point to the lower alcohol.

In order to achieve the above object, the present invention comprises the steps of (a) esterifying a vegetable oil in the presence of a supercritical lower alcohol and a supercritical solvent similar in boiling point to the lower alcohol; And (b) recovering a fatty acid alkyl ester (biodiesel) from the esterified reaction solution.

In the present invention, the supercritical solvent similar in boiling point to the lower alcohol may be selected from the group consisting of CFC series, HCFC series and HFC series.

In the present invention, the lower alcohol may be characterized in that methanol.

In the present invention, the vegetable oil is palm oil, soybean oil, rapeseed oil, canola oil, safflower oil, corn oil, rapeseed oil, linseed oil, sunflower oil, poppy oil, walnut oil, peanut oil, cottonseed oil, rice bran oil, camellia oil and castor oil and olive oil It may be characterized in that selected from the group consisting of.

In the present invention, step (a) may be performed in a reactor having a stirring means.

In the present invention, step (a) may be performed in a fluidized bed reactor.

In the present invention, the step (a) may be characterized by esterifying the vegetable oil and lower alcohol in a molar ratio of 1: 5 to 1:20.

In the present invention, after the step (b), it may be characterized in that it further comprises the step of recovering the lower alcohol and the solvent to recycle to the esterification process.

Hereinafter, the present invention will be described in detail.

In the present invention, while using a co-solvent to reduce the amount of alcohol used in the supercritical process, in order to avoid the need for a separate facility for recovering the used co-solvent, a co-solvent similar in boiling point to methanol was devised.

In the method for preparing biodiesel according to the present invention, as shown in FIG. 1, a vegetable oil is esterified in the presence of a supercritical low alcohol and a supercritical solvent having a boiling point similar to that of a lower alcohol, and a fatty acid alkyl ester is obtained from the esterified reaction solution. Recover.

Vegetable oils used in the present invention are palm oil, rapeseed oil, canola oil, safflower oil, soybean oil, corn oil, rapeseed oil, linseed oil, sunflower oil, poppy oil, walnut oil, peanut oil, cottonseed oil, rice bran oil, camellia oil, castor oil, olive oil Any one selected may be used, but is not limited thereto.

In addition, alcohol is used a C ₁ ~ C ₅ which may be a lower alcohol, preferably methanol, such as methanol, ethanol. Cosolvents similar in boiling point to methanol are CFC, HCFC or HFC-based materials, and include CCl ₃ F, CClF ₂ CCl ₂ F, CHClCF ₂ , CH ₃ CCl ₂ F, CF ₃ CF ₂ CHCl ₂ , CClF ₂ CF ₂ CHClF, Preference is given to using one or more selected from the group consisting of CHF ₂ CF ₃ , and CH ₂ CH ₂ OH, but is not limited thereto.

Meanwhile, the reactor used in the present invention may use a batch process and a continuous process using a batch reactor having a fluidized bed, a tubular reactor, a continuous stirred tank reactor, and the like, and the reactors have a stirring means, so that a high yield in a short time Can be obtained.

As shown in FIG. 2, the biodiesel manufacturing process according to the present invention opens vegetable valves, alcohols, and cosolvents in each of the tanks 1, 8, and 9 by opening the valves V2, V8, and V11. After the injection is completed, the valves V2, V8 and V11 are closed. Alcohol and co-solvent of the reactants injected into each tank are first injected into the reactor 4 using the feed pump 2. After the alcohol and the cosolvent have been injected into the reactor, the vegetable oil is also injected into the reactor 4 using the feed pump 2. At this time, the temperature of the vegetable oil is maintained at 50 ~ 70 ℃ in order to prevent the coagulation and viscosity of the vegetable oil. When the injection of the vegetable oil into the reactor 4 is completed, the pressure in the reactor 4 is increased with the back pressure regulator 6 while the temperature is increased by using the preheater tube furnace 3 and the reactor furnace 5. Increase. The temperature in reactor 4 is 300 degreeC-500 degreeC, Preferably it is 350 degreeC-400 degreeC. The reaction pressure is 20 to 60 MPa, most preferably 35 MPa. After reaching the predetermined temperature and pressure, if the temperature and pressure is stable, react for 20 to 50 minutes until the steady state of the reactants, and when the steady state is reached, the sample is taken from the product tank (7) and fractionated.

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

Example  One: Supercritical  Alcohol and Common solvent  Biodiesel Manufacturing

1-1 Preparation of Starting Material and Manufacturing Equipment

Commercial starting materials were palm olein oil (Film, Lohas F & B Co., Ltd.) and methanol (99.5% Daesung Industrial Co., Ltd.), and co-solvent used HCFC-141 (99.5%, Ulsan Chemical Co., Ltd.). On the other hand, the biodiesel manufacturing apparatus used the apparatus shown in FIG. The reaction tube of the apparatus used a tubular reactor made of 316L sus (Premet Technology Co., Ltd.) wound on a coil having an inner diameter of 4.35 mm and a length of 12 m.

1-2 Supercritical  Alcohol and Common solvent  Biodiesel Manufacturing

The palm olein oil (1.77 ml / min) of 1-1 was maintained at 60 ° C. in order to prevent coagulation and maintain viscosity, and was injected into a raw material tank, and the raw material tank in which palm olein oil was injected was heated to 250 ° C. Methanol (2.48 ml / min) and co-solvent HCFC-141 (0.12 ml / min) were also injected into the raw material tanks, respectively, and the raw material tanks into which methanol and HCFC-141 were injected were heated to 300 deg. C and 55 deg. The methanol and HCFC-141 (20: 1) were first injected into a reactor preheated to 220 ° C. at 5.25 ml / min in a feed tank using an HPLC pump and then palm olein oil at the same flow rate. When the palm olein oil was injected into the reactor, the temperature and pressure were adjusted to 350 ° C. and 35 MPa, and the reaction was performed for 40 minutes, and then the product was collected. The collected sample was heated to 70 ° C. and then vacuum distilled to separate excess methanol, glycerin and biodiesel.

Comparative example  One: Common solvent  Biodiesel Preparation without Addition

It was prepared in the same manner as the method for producing biodiesel using the cosolvent, but the cosolvent was not added.

Experimental Example  One: Supercritical  Characterization of Biodiesel Using Alcohol and Solvent

Biodiesel isolated in Example 1 was analyzed by gas chromatography (gas chromatograph, HP6890). As a result of the analysis, as shown in Table 1, 60% by weight of various fatty acid methyl esters, 20% by weight of monoacylglycerol, 15% by weight of diacylglycerol, 4% by weight of other aliphatic compounds, and triacyl Glycerol and glycerin were less than 1% by weight, respectively. As shown in Figure 3, the fatty acid composition of the fatty acid methyl ester of biodiesel is 0.1% by weight of heavy chain fatty acids (C12: 0), 0.8% by weight of myristic acid (C14: 0), 30.02 of palmitic acid (C16: 0) Wt%, stearic acid (C18: 0) 3.29 wt%, oleic acid (C18: 1) 34.04 wt%, linoleic acid (C18: 2) 15.14 wt%, linolenic acid (C18: 3) 0.13 wt% and icosanes (C20 : 1) 0.34 wt%.

Furtherance weight% Fatty acid methyl ester 60 Monoacylglycerol 20 Diacylglycerol 15 Other aliphatic compounds 4 Triacylglycerol & Glycerin 1 or less

In addition, cetane number was measured by JIS K2280 measuring method, and the pour point, kinematic viscosity, and flash point were measured by the method prescribed | regulated to JIS K2269, JIS K2283, and JIS K2265, respectively. As a result, the cetane number was 52, the flash point (PMCC) was 134 ° C, the kinematic viscosity was 15.50mm ² / sec, and the pour point was -6.5 ° C, which was similar to the general biodiesel fuel.

Experimental Example  2: Common solvent  With added biodiesel Common solvent  Yield measurement of no additive biodiesel

The biodiesel added with the co-solvent prepared in Example 1 and the biodiesel without the co-solvent prepared in Comparative Example 1 were compared and analyzed according to the composition of methanol / palm olein oil.

As a result, as shown in FIG. 4, when the molar ratio of methanol was greater than 10 for both the biodiesel added with the cosolvent and the biodiesel without the cosolvent, the yield of fatty acid methyl ester (FAME) was improved, and the molar ratio of methanol was increased. The yield remained constant even as it increased. In addition, the yield of fatty acid methyl ester (FAME) was improved in general when the co-solvent was added than when the co-solvent was not added. In particular, when the molar ratio of methanol / palm olein oil was 5, the yield was clearly observed. Therefore, it can be seen that addition of cosolvent in the production of biodiesel can not only improve the yield of fatty acid methyl ester (FAME) but also lower the molar ratio of methanol / palm olein oil.

As described above in detail specific parts of the present invention, it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

As described in detail above, the present invention has an effect of providing a method for producing biodiesel using a supercritical low alcohol and a supercritical solvent similar in boiling point to lower alcohol. According to the present invention, methanol content can be drastically lowered, high reaction yield can be obtained even at relatively low temperature and pressure, and there is no need for a separate equipment for recovering the solvent used in the supercritical reaction. It is possible to manufacture diesel.

Claims (8)

Method for preparing fatty acid alkyl ester (biodiesel) comprising the following steps: (a) esterifying the vegetable oil in the presence of a supercritical lower alcohol and a supercritical solvent similar in boiling point to the lower alcohol; And (b) recovering fatty acid alkyl esters (biodiesel) from the esterified reaction solution. The method of claim 1, wherein the supercritical solvent having a boiling point similar to that of the lower alcohol is selected from the group consisting of CFC series, HCFC series and HFC series. The method of claim 1, wherein the lower alcohol is methanol. According to claim 1, wherein the vegetable oil is palm oil, soybean oil, rapeseed oil, canola oil, safflower oil, corn oil, rapeseed oil, linseed oil, sunflower oil, poppy oil, walnut oil, peanut oil, cottonseed oil, rice bran oil, camellia oil and castor oil and Characterized in that it is selected from the group consisting of olive oil. The method of claim 1, wherein step (a) is performed in a reactor having a stirring means. The method of claim 1 wherein step (a) is performed in a fluidized bed reactor. The method of claim 1, wherein step (a) comprises esterifying the vegetable oil and the lower alcohol in a molar ratio of 1: 5 to 1:20. The method of claim 1, further comprising, after step (b), recovering the lower alcohol and the solvent and recycling them to an esterification process.

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