KR20080062636A - Production method of biodiesel using supercritical alcohol - Google Patents

Abstract

A manufacturing method of bio-diesel using supercritical alcohol is provided to maximize the effects of mixing the supercritical alcohol and oil and fat to increase the yield of the bio-diesel. A manufacturing method of fatty alkyl ester uses a continuous reactor in a method of manufacturing fatty alkyl ester and glycerol by reacting supercritical alcohol and oil and fat without using a catalyst. The continuous reactor is filled with packing that is able to form turbulent flow inside. The packings are knit meshes, beads, rings or berl saddles. The oil and fat and the alcohol are reacted in a molar ratio of 1:10 to 1:35. The reaction is performed at 250-350deg.C and at a pressure of 30-50MPa for 1-60 minutes. The alcohol is one or more selected from a group consisting of methanol, ethanol, propanol, butanol and pentaploid.

Description

Production method of biodiesel using supercritical alcohol

1 is a structural diagram showing an example of a manufacturing apparatus used in the manufacturing method of the present invention.

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

1: Oil storage tank

2: alcohol storage tank

3: high pressure pump

4: Preheaters

5: Reactor

6: Main heater

7: Cooler

8: Back pressure regulator

9: Effluent collecting vessel

PG: Pressure gauge

Figure 2 is a graph showing the content of fatty acid methyl ester prepared according to one embodiment and comparative example of the present invention.

3 is a graph showing the effect of the volume of the reactor in the production of biodiesel using a supercritical alcohol.

Figure 4 is a graph showing the effect of increasing the pump flow rate in the production of biodiesel using supercritical alcohol.

The present invention relates to a method for producing fatty acid alkyl esters, that is, biodiesel by transesterifying triglycerides and supercritical alcohols without using a catalyst, and more particularly, transesterification reactions by maximizing the mixing of triglycerides and alcohols. The present invention relates to a method for producing a fatty acid alkyl ester which can increase the yield of biodiesel while reducing the amount of alcohol used.

Biodiesel is a material produced by reacting animal or vegetable fats with alcohol and has almost the same characteristics as diesel oil obtained from petroleum. Therefore, the amount of biodiesel is increasing as an alternative fuel for diesel engines. Biodiesel is called vegetable diesel, which is distinguished from diesel from petroleum, and it is known to have an effect of significantly reducing air pollution generation compared to conventional petroleum diesel.

Biodiesel currently produced worldwide is a fatty acid methyl ester produced using methanol as a raw material, such as U.S. Patent No. 5,514,820 or Korean Patent No. 10-0566106. The process of mixing the catalyst and reacting for several hours is used.

In the case of the alkaline catalyst process, if the oil used as a raw material contains water or free fatty acid, the viscosity of the biodiesel is due to the saponification substance generated by the saponification of the alkali compound used as the catalyst. Is not only increased and the separation of glycerol becomes difficult, but also the catalyst itself is consumed. To this end, a pretreatment process is used to convert free fatty acids to fatty acid methyl esters by adding an excess of alkali or using a strong acid as a catalyst. However, the process of removing the generated soap or wastewater is also required. There is this big problem. In order to solve this problem, an acid catalyst process has been developed, but has a problem that the amount of alcohol is used and the reaction time is several times longer than that of the alkali catalyst process.

Meanwhile, in the case of Republic of Korea Patent Publication No. 10-2006-0108327, various processes are studied, including a method of producing biodiesel biologically from fats and oils using a lipase produced using a protein fusion factor protein as a catalyst. It is becoming.

In addition, Japanese Patent Application Laid-Open No. 2000-109883 discloses a continuous process for producing fatty acid alkyl esters by reacting an alcohol without using either a metal alkali catalyst or an acid catalyst under conditions in which the alcohol is in a supercritical state. The food process is started. However, the above patent uses a supercritical alcohol, but the disadvantage of lowering the conversion rate of triglyceride or the yield of fatty acid methyl ester using a relatively low pressure of 3-15 MPa in the transesterification reaction. have.

In this regard, Japanese Patent Laid-Open No. 2000-204392 discloses a method for preparing biodiesel by transesterification or dehydration and ester reaction using an alcohol in a supercritical or subcritical state as a solvent. A method for producing biodiesel using up to 2% alkali catalyst is disclosed. However, in the case of using an alkali catalyst, the amount of methanol can be reduced. However, as in the conventional process, the problem of having to separate the alkali catalyst from the product after completion of the reaction occurs, which is economical in the case of the supercritical process, which is a high temperature and high pressure process. This has the disadvantage of being lowered. According to Saka and Kusadina's findings ( Fuel , 80 , pp.225-231, 2001 ) related to the patent content, rapeseed oil triglycerides and methanol at high temperature and high pressure conditions of 350 ° C, 45 MPa or more, using a batch reactor The molar ratio of was 1:42 to prepare biodiesel without using a catalyst. However, as the molar ratio of methanol is increased to increase the yield of biodiesel, there is a problem in that it is difficult to secure economic feasibility due to an increase in energy consumption cost input to the evaporation process of unreacted methanol.

On the other hand, U.S. Patent Application Publication No. 2006/0025620 discloses a method for converting triglycerides of fats and oils into fatty acids and glycerol through a hydrolysis reaction with water as a means to reduce the amount of methanol, which is a problem of the supercritical process. It describes the two-step process of the first reaction and the esterification reaction of reacting the obtained fatty acid with methanol, or the process of using water as an acid catalyst in the transesterification reaction of triglycerides. In the two-step process, the esterification reaction of fatty acids produced in the first reaction is faster than the transesterification reaction of triglyceride, so the reaction proceeds even at relatively low temperature and pressure conditions. There is a problem in that there is no consideration of an increase in the device and energy costs, such as the reaction time required for the reaction or the separation of glycerol produced before the two-stage reaction. Also, the related authors (Kusadina and Saka: Biores . Technol . , 91 , pp.289-295, 2004 ) on the effect of water addition showed that the FAME content decreased with the water content, acting as an acidic catalyst. The results that are inconsistent with the contents of the patent, and the result that can reduce the amount of methanol used has a problem that is not found from the examples of the patent and related documents.

In addition, Japanese Patent Application Laid-Open Nos. 2001-226694, 2001-302584, and 2003-055299, filed by Sumitomo Chemical Co., Ltd., disclose a method for producing biodiesel by reacting fats with alcohol in a supercritical state. The present invention discloses a method for producing biodiesel using a nickel-containing solid catalyst, a solid base catalyst, and manganese oxide and molybdenum oxide as catalysts, respectively, without using sodium hydroxide as a catalyst. The patents by Sumitomo Chemical all characterize the use of solid catalysts and present experimental results using a batch reactor. As mentioned above, when a catalyst is used, a process of adding a catalyst as well as a process of separating the catalyst from a product is required, which makes it difficult to secure economical efficiency compared to a process using an alkali catalyst. .

On the other hand, U.S. Pat. Since the pump capacity must be increased at the same time, it means an increase in the device cost and operating cost, and thus has the disadvantage of increasing the biodiesel production cost.

Therefore, the technical problem to be achieved by the present invention is to provide a method for producing an economical fatty acid alkyl ester which can increase the biodiesel yield by reducing the amount of alcohol while maximizing the mixing effect of supercritical alcohol and fats and oils.

In order to achieve the above technical problem, the present invention in the method for producing fatty acid alkyl ester and glycerol by reacting supercritical alcohol and fats and oils without using a catalyst, a filler capable of forming a turbulent flow therein Process for preparing fatty acid alkyl esters, characterized in that using a continuous reactor packed with a packing, preferably a knit mesh, beads, rings or a sadl saddle To provide.

More preferably, the present invention provides a method for producing a fatty acid alkyl ester, wherein the fat and oil and the alcohol are reacted in a molar ratio of 1:10 to 1:35.

More preferably, the present invention provides a method for producing a fatty acid alkyl ester, characterized in that the reaction for 1-60 minutes under the conditions of temperature 250-350 ℃, pressure 30-50 MPa.

Hereinafter, a method for preparing a fatty acid alkyl ester using the supercritical alcohol according to the present invention will be described in more detail.

In the present invention, in the production of biodiesel by transesterification without using a catalyst at a temperature and pressure conditions in which the fat and alcohol are reactants and the alcohol reaches a supercritical state, a turbulent state inside the continuous flow reactor By filling the flow-inducing filler to increase the mixing effect between the fats and oils and promoting the transesterification reaction, biodiesel can be produced in high yield with low alcohol usage.

When fats and oils react in a supercritical state or in the presence of a catalyst, biodiesel and glycerol, which are fatty acid alkyl esters, are produced as shown in the following scheme.

In the above scheme, R ₁ , R ₂ and R ₃ is an alkyl group having C ₁₂ -C ₂₄ carbon atoms, and R 'is preferably an alkyl group having a lower alcohol having about C ₁ -C ₅ carbon atoms.

As shown in the above scheme, the transesterification reaction between fats and oils is a reversible reaction, so in order to increase the yield of the product, the concentration of the reactants must be increased. It is desirable to increase the concentration to promote the production of fatty acid alkyl esters. However, this method inevitably increases the amount of alcohol used as a raw material, which increases the manufacturing cost.

Unlike the conventional alcohol, the supercritical alcohol used in the present invention has a dielectric constant that is reduced to have the characteristics of a nonpolar solvent, so that it is easy to mix with one of the reactants, fats and oils, and an ion product is obtained. As it increases, ionic reactions such as alcohololysis or transesterification occur well, and it is thought that biodiesel can be produced without a catalyst.

The supercritical state of alcohol refers to a state in which the temperature and pressure in the reactor reach or exceed the critical temperature and the critical pressure of the alcohol, respectively. For example, when methanol having 1 carbon atoms is used as a raw material for the biodiesel manufacturing process, methanol has a critical point of 239.4 ° C. and 8.09 MPa, which means that the temperature in the reactor is 240 ° C. and the pressure is 8.1 MPa or more.

Therefore, in the production method of the present invention, in order to produce a supercritical alcohol, it is preferable to appropriately control the temperature and pressure in the range of 240-600 ° C and 8.1-100 MPa. However, in case of 350 ℃ or higher, the biodegradation yield of triglyceride and fatty acid alkyl ester, which are the main components of fats and oils, occurs competitively with the transesterification reaction, and the biodiesel yield is decreased. There is a disadvantage that the economic efficiency is lowered. In addition, as the pressure increases, the yield increases, but when the pressure increases to 50 MPa or more, the increase in yield or reaction rate tends to be markedly reduced, thereby reducing economic efficiency. Therefore, more preferable reaction conditions are the range of temperature 250-350 degreeC and pressure 30-50 MPa. The reaction time may be selected from the range of 1 second to 2 hours depending on the temperature conditions, but in consideration of economical efficiency, the reaction time is in the range of 1-60 minutes.

In the biodiesel preparation of the present invention, a batch process and a continuous process may be used, and a continuous process having excellent productivity and easy maintenance of reaction conditions is preferable. As a reactor of a continuous process, a tubular reactor and a continuous stirred tank reactor can be used, and a tubular reactor is more preferable for producing high purity biodiesel with high reaction yield.

In the preparation of the biodiesel of the present invention, it is preferable to maintain the flow of the reactant in the tubular reactor in the turbulent region in order to increase the mixing effect between the fat and the alcohol which are the reactants. However, in order to manufacture a reactor having the size necessary for completing the reaction while maintaining the turbulent flow, the diameter of the tubular reactor must be reduced and the length must be increased, thereby increasing the apparatus cost and lowering the economic efficiency.

On the other hand, in the production of biodiesel of the present invention, the use of supercritical alcohol facilitates the mixing between the reactant fat and alcohol, but it is difficult to install a separate mixing equipment such as an agitator. Increasing the volume or mass ratio of alcohol may improve the mixing between reactants. However, due to the large molecular weight difference between fats and oils, a higher molar ratio of alcohol than the 1: 3 (triglyceride: alcohol) molar ratio required for the reaction should be used. For example, when palm oil and methanol are used as raw materials, if the mass ratio between the reactants is 1: 1, the molar ratio of triglyceride and methanol is 1: 26.5. Therefore, it is necessary to increase the molar ratio in order to increase the reaction yield according to the above reaction formula or to smoothly mix the reactants, but it is also preferable to minimize the amount of alcohol used since the energy consumption cost required for the recovery of unreacted materials is also increased.

The present invention uses the supercritical alcohol to prepare biodiesel in a reactor without using a catalyst. In the case of using a reactor filled with a packing having a suitable form to make the flow in the reactor turbulent, It is based on the surprising result that the mixing between the alcohol and the fat in the supercritical state is increased, so that the reaction yield can be increased even though the amount of alcohol used is reduced. Therefore, it is not necessary to reduce the reactor diameter in order to form a turbulent flow, and the reactor length can also be relatively reduced. As a result, since the amount of alcohol required for mixing can be reduced, it is possible to greatly improve the economics of the biodiesel process using supercritical alcohol, and it is very economical because it can reduce the cost required to recover the remaining alcohol without reacting. This effect of the present invention is very surprising to those skilled in the art to which the present invention belongs.

Fillers for turbulent flow in the reactor include knit mesh, beads, rings, and burl saddles. If you can, no form is limited.

In addition, as a material for preparing the filling filling in the reactor, supercritical high temperature such as metal and ceramic materials such as Hastelloy, Inconel, stainless steel alloy, etc. Any material that can withstand it may be used.

In the present invention, unlike the alkali or acid catalyst process, it is not necessary to use a filler having a micropore structure or a catalyst-carrying structure that provides a large contact area, and a form and a filler of a filler which can improve the flow in the reactor. The nature of the voids in the liver is a major factor in maximizing the improvement effect of the present invention.

As the main ingredient in the production of biodiesel of the present invention, conventional vegetable oil, animal oil or regenerated oil may be used. Vegetable oils include oils of plant origin such as palm oil, soybean oil, rapeseed oil, corn oil, rapeseed oil, sunflower oil, safflower oil, cottonseed oil, sesame oil, rice bran oil, palm kernel oil, camellia oil, castor oil, olibu oil, palm oil, and fried oils. Used waste cooking oil and the like are included. Animal fats include terrestrial oils and aquatic animal oils, as well as tallow, pork, sunny, fish oil, whale oil, tuna oil, and waste cooking oil using them for fried oil.

Alcohol, which is a substance reacting with fat and oil in the present invention, may be used as a single component or mixed with a lower alcohol having 1 to 5 carbon atoms, such as methanol, ethanol, propanol, butanol, pentanol and the like. In particular, methanol is most suitable for use in biodiesel production because of its low boiling point, which is easy to recover from the product and inexpensive.

In preparing the biodiesel of the present invention, triglyceride and alcohol in a fat or oil which is a reactant are mixed in a molar ratio of 1: 3-1: 60 and fed to the reactor. More preferred is in the range of molar ratio 1: 10-1: 35.

In the present invention, when the transesterification of fats and oils is completed, the unreacted alcohol is recovered by using an evaporator. At this time, in order to lower the evaporation temperature and increase the evaporation rate, it is preferable to lower the pressure in the evaporator to below atmospheric pressure. After alcohol recovery, the glycerol and fatty acid alkylester compounds produced by the transesterification reaction form two layers after standing for a certain time. In the upper part, a low-density fatty acid alkyl ester compound is collected, and in the lower part, a high-density glycerol layer is formed. At this time, glycerol and fatty acid alkyl ester, that is, biodiesel is separated. The separated biodiesel may be subjected to additional separation processes such as distillation to increase the purity.

Hereinafter, examples and the like will be described in detail to help understand the present invention. However, embodiments according to the present invention can be modified in many different forms, the scope of the invention should not be construed as limited to the following examples. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

The purity of the biodiesel finally obtained in the following examples was measured using Agilent GC 6890 and the column or method used for the analysis was based on European standards for the analysis of fatty acid methyl ester (FAME) (pr EN14103, 2003 ). On the other hand, FAME yield was defined by the following equation 1 from the mass of palm oil used in the reaction and the mass of recovered biodiesel.

Preparation of Example 1-4

The apparatus used in this embodiment is a continuous biodiesel production apparatus as shown in Figure 1 and the reactor was used by self-producing a tubular reactor having a diameter of 1.5 cm and a volume of 116 mL made of stainless steel. The inside of the tubular reactor was filled with a knit mesh made of hastelloy C-276 alloy having a volume of about 10 mL to increase the mixing effect of palm oil and methanol used as a raw material.

Purified palm oil (refined, bleached and deodorized palm oil) was put in the holding tank (1) and the flow rate of the high pressure pump (3) was adjusted according to the experimental conditions such as reaction time and molar ratio. In the case of Examples 1 and 2 was set to the reaction temperature 325 ℃, 350 and 350 ℃ in the case of Examples 3 and 4, Example 1 and 3 is about 20: 1 molar ratio of methanol and palm oil, 4 was set to about 30: 1 and the flow rate was adjusted so that the reaction time was about 15 minutes.

The refined palm oil and methanol were preheated to a reaction temperature (325 ° C. or 350 ° C.) through a preheater 4 using a high pressure pump and introduced into the reactor 5. In order to keep the temperature of the reactor 5 constant during the reaction, a heater 6 was installed around the reactor 5 to control the desired reaction temperature. After completion of the reaction, the temperature was rapidly lowered to room temperature through the cooler (7) to complete all the reactions in the reactor (5). The pressure of the entire biodiesel manufacturing apparatus was set to a back pressure regulator (8: back pressure regulator) installed after the heat exchanger. It was adjusted to 35 MPa through.

After a certain time since the biodiesel manufacturing apparatus shown in FIG. 1 was operated in a steady state according to each embodiment, the effluent collected in the effluent collection container 9 was collected to collect unreacted methanol remaining in the effluent. ) Was removed. After methanol was removed, the remaining product was allowed to stand for 30 minutes in a separatory funnel, and the lower glycerol layer was separated to recover biodiesel. The content of fatty acid methyl ester (FAME) in the recovered biodiesel was analyzed using Agilent GC 6890 according to European standard (pr EN14103) as described above.

The reaction conditions and analysis results according to each example are summarized in Table 1 below.

Reactor Inner Diameter (cm) Reaction temperature (℃) Reaction pressure (MPa) Methanol: Palm oil molar ratio Response time (min) FAME content (%) FAME yield (%) Example 1 1.5 325 35 20.4: 1 14.87 70.57 70.48 Example 2 1.5 325 35 30.1: 1 14.94 84.02 82.08 Example 3 1.5 350 35 21.3: 1 15.08 90.36 89.98 Example 4 1.5 350 35 29.3: 1 14.94 94.99 93.19

<Manufacture of Comparative Example 1-4>

The apparatus used in this comparative example used the same apparatus as in the example, and the reactor used a stainless steel tube having an internal diameter of 1/8 inch and 1/4 inch in addition to the tubular reactor having an inner diameter of 1.5 cm and a volume of 115 mL used in the examples. A reactor prepared by winding in the form of a coil of m and 6 m length was used. In the case of the comparative example, unlike the example, the reaction was carried out without any filling in the tubular reactor.

In the case of the comparative example, the reaction temperature was all set to 350 ° C., the molar ratio between methanol and palm oil was about 40: 1, and the flow rate was adjusted so that the reaction time was about 15 minutes.

The reaction conditions and analysis results according to the comparative examples are summarized in Table 2.

Reactor Inner Diameter (cm) Reaction temperature (℃) Reaction pressure (MPa) Methanol: Palm oil molar ratio Response time (min) FAME content (%) FAME yield (%) Comparative Example 1 0.1756 350 35 38.8: 1 12.37 93.93 86.07 Comparative Example 2 0.3048 350 35 43.8: 1 15.62 91.52 90.72 Comparative Example 3 1.5 350 35 44.7: 1 15.12 61.73 64.83 Comparative Example 4 1.5 325 35 39.5: 1 15.01 42.91 42.93

2 shows a comparison of FAME contents according to Comparative Examples 1-3 and Examples 1-4. As shown in Tables 1 and 2 and FIG. 2, the mixing effect of palm oil and methanol was improved when the knitted network was packed into the reactor despite the fact that the inner diameter of the tubular reactor was increased to decrease the flow rate of the reactants. Content and FAME yield were obtained. In particular, while maintaining or increasing the FAME content and FAME yield at the same level, the amount of unreacted methanol in the product is reduced after completion of the reaction by reducing the amount of methanol to palm oil consumption from 40: 1 to 30: 1 based on the molar ratio. I could make it.

<Manufacture of Comparative Example 5-7>

The continuous reactor used in this comparative example was constructed to have sizes of 23 mL, 45 mL, and 71.3 mL, respectively, with 1/4 inch tubes. In order to examine the effects of methanol and palm oil on the residence time in the reactor, the temperature was fixed at 350 ° C, the pressure was 35 MPa, and the molar ratio was 40: 1, and the reactors were alternately installed while maintaining the constant flow rate of each pump. Biodiesel was prepared. As shown in FIG. 3, as the volume of the reactor increased, the retention time was increased to 4.8 minutes, 9.7 minutes, and 15.6 minutes, respectively, and the FAME content was continuously increased.

<Manufacture of Comparative Example 8-11>

In this comparative example, a 71.3 mL reactor used in Comparative Example 5-7 was used, and biodiesel was prepared by increasing the flow rate of each pump under the conditions of temperature, pressure, and molar ratio used in Comparative Example 5-7. 4 shows the FAME content according to the increase in the pump flow rate, and in contrast to the results of Comparative Example 5-7, the retention time was reduced to 28.5 minutes, 20.7 minutes, 14.8 minutes, and 10.5 minutes, but the FAME content was rather increased. Indicated.

Comparative Examples 5-7 and 8-11 show the importance of the Reynolds number shown in FIGS. 3 and 4 as a result showing the importance of mixing the reactant palm oil and methanol. In other words, unlike a batch reactor, in a continuous reactor, if two reactants are in a laminar flow zone, stirring cannot be performed separately. Therefore, mixing between the two reactants is expected to be dependent on diffusion. It is known that the mass transfer resistance is greatly reduced, but as a result as shown in FIG. 4, it may be necessary to install a filling or the like to make the flow in the continuous reactor turbulent or improve mixing. On the other hand, the results of Comparative Example 5-7 is considered to increase the FAME content by the reaction proceeds further with the residence time under the same fluid behavior.

As described above, the production method of the present invention reduces the inner diameter of the reactor by using a supercharged alcohol and using a reactor filled with a filler capable of generating turbulent flow in the production method of biodiesel without a catalyst. By improving the mixing of fats and oils without increasing the length, biodiesel with a high fatty acid alkyl ester content can be produced, and the molar ratio of high fats to alcohol, which is a problem of the non-catalytic preparation using the conventional supercritical alcohol While dramatically reducing the yield of biodiesel, the productivity and yield can be improved. Therefore, the present invention can be expected to enhance the economics of the supercritical alcohol-using biodiesel manufacturing technology suitable for recycling waste cooking oil.

Claims (6)

In the method for producing fatty acid alkyl esters and glycerol by reacting supercritical alcohol and fats and oils without using a catalyst, A method for producing a fatty acid alkyl ester, characterized by using a continuous reactor packed with a packing capable of forming a turbulent flow therein. The method of claim 1, wherein the filler is a knit mesh, a bead, a ring, or a saddle. The method of claim 1, wherein the fats and oils are produced in a fatty acid alkyl ester, characterized in that the reaction in a molar ratio of 1:10 to 1:35. According to claim 1, wherein the production method is a method for producing a fatty acid alkyl ester, characterized in that the reaction for 1-60 minutes under the conditions of temperature 250-350 ℃, pressure 30-50 MPa. According to claim 1, wherein the oil is palm oil, soybean oil, rapeseed oil, corn oil, rapeseed oil, sunflower oil, safflower oil, cottonseed oil, sesame oil, rice bran oil, palm kernel oil, camellia oil, castor oil, olibu oil, palm oil, tallow, lard, sunny , Fish oil, whale oil, tuna oil and a method for producing a fatty acid alkyl ester, characterized in that any one selected from the group consisting of these waste oils. The method of claim 1, wherein the alcohol is any one or more selected from the group consisting of methanol, ethanol, propanol, butanol and pentanol.

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