Biodiesel fuel production method

Abstract

The present invention provides a method for producing biodiesel fuel containing saturated hydrocarbons as a main component under relatively mild conditions using vegetable oils or animal fats as a raw material. [Solution] This is a method for producing biodiesel fuel from vegetable oils or animal fats, comprising a decarboxylation step in which carbon dioxide is removed from ester groups in the vegetable oils or animal fats using a decarboxylation catalyst to produce hydrocarbons, and a hydrogenation step in which the resulting hydrocarbons are hydrogenated using a hydrogenation catalyst to produce diesel fuel consisting of saturated hydrocarbons, wherein the decarboxylation step and the hydrogenation step are carried out in the stated order, and each of the decarboxylation step and the hydrogenation step is carried out under a pressure of 0.2 MPa or less.

Description

[Technical Field]

[0001] The present invention relates to a method for producing biodiesel fuel using vegetable oils or animal fats as a raw material. [Background technology]

[0002] As environmental concerns grow, biodiesel fuels produced from vegetable oils and animal fats are gaining attention as an alternative to fossil-fuel-derived diesel fuels. There are several types of biodiesel fuels. Biodiesel fuels made from waste cooking oil, converted from oils and fats into fatty acid methyl esters (FAME), are already being produced and used in Japan and other countries. However, producing FAMEs requires the raw material methyl alcohol, which requires facilities to process the alkaline compounds used as catalysts and the by-product glycerin. Therefore, a technology for producing biodiesel fuels using a simpler method was needed.

[0003] Patent Documents 1 and 2 disclose methods for producing biodiesel fuels mainly composed of hydrocarbons from vegetable oils and animal fats with fewer steps. Patent Document 1 discloses a method for producing biodiesel fuel in which fats and oils are brought into contact with an oil and oil decarboxylation cracking catalyst in a reaction vessel at 350°C to 475°C, causing a decarboxylation cracking reaction by the oil and oil decarboxylation cracking catalyst to produce mainly hydrocarbons with C8 to C24. Patent Document 2 also discloses a method for catalytic cracking of fats and oils in which a decarboxylation / hydrogenation catalytic cracking catalyst, in which MgO and a hydrogenation catalyst are supported on a carbon carrier, is brought into contact with fats and oils in a reaction vessel heated to 350°C to 475°C and placed in a hydrogen atmosphere at 1 to 10 atmospheres, to produce mainly hydrocarbons with 10 to 20 carbon atoms from the fats and oils. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5353893 [Patent Document 2] Patent No. 5896510 Summary of the Invention [Problem to be solved by the invention]

[0005] The biodiesel fuel production method described in Patent Document 1 produces hydrocarbons that can be used as biodiesel fuel solely through a catalytic cracking process in which fats and oils are brought into contact with a fat and oil decarboxylation cracking catalyst. Therefore, when fats and oils containing unsaturated fatty acid groups are used as raw materials, double bonds remain in the resulting hydrocarbons, which can cause the production of by-products such as coke (carbonized products) and aromatic compounds.

[0006] Furthermore, the catalytic cracking method for fats and oils described in Patent Document 2 simultaneously performs the decarboxylation and hydrogenation reactions of fats and oils in a single process. The decarboxylation / hydrogenation catalytic cracking catalyst used has an active substance involved in the decarboxylation reaction and an active substance involved in the hydrogenation reaction coexisting on a carbon support. Therefore, there is a concern that an interaction may occur between the two active substances, inhibiting the progress of each reaction.

[0007] An object of the present invention is to provide a method for producing a biodiesel fuel containing saturated hydrocarbons as a main component under relatively mild conditions using vegetable oils or animal fats as a raw material. [Means for solving the problem]

[0008] In view of the above circumstances, the present inventors have investigated the possibility of carrying out the decarboxylation reaction and the hydrogenation reaction in separate steps and setting milder reaction conditions for each step. As a result, they have found that by carrying out the decarboxylation step and the hydrogenation step in this order and optimizing the catalyst, each step can be carried out under a pressure of 0.2 MPa or less, thereby arriving at the present invention.

[0009] The present invention has the following configuration. (1) A method for producing biodiesel fuel from vegetable oils or animal fats, comprising: a decarboxylation step in which carbon dioxide is removed from ester groups of the vegetable oils or animal fats using a decarboxylation catalyst to produce hydrocarbons; and a hydrogenation step in which the resulting hydrocarbons are hydrogenated using a hydrogenation catalyst to produce diesel fuel consisting of saturated hydrocarbons, wherein the decarboxylation step and the hydrogenation step are carried out in this order, and the decarboxylation step and the hydrogenation step are carried out under a pressure of 0.2 MPa or less. (2) The method for producing biodiesel fuel according to (1) above, wherein the decarboxylation catalyst has magnesium oxide or calcium oxide supported on the surface of a porous catalyst support, and has basic surface activity. (3) the hydrogen Add to The method for producing biodiesel fuel according to (1) above, wherein the catalyst is a catalyst in which nickel, molybdenum, palladium, iron, or a combination thereof is supported on the surface of a porous catalyst support. (4) The method for producing biodiesel fuel according to (1) above, wherein a cracking step is carried out using a cracking catalyst after the hydrogenation step. (5) The method for producing biodiesel fuel according to (4) above, wherein the cracking catalyst is zeolite and the cracking is carried out under a pressure of 0.2 MPa or less. [Effects of the Invention]

[0010] According to the method for producing biodiesel fuel of the present invention, it is possible to produce biodiesel fuel containing saturated hydrocarbons as a main component under relatively mild conditions using vegetable oils or animal fats as raw materials. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the embodiments of the present invention are not limited to the specific embodiments described below.

[0012] The present invention relates to a method for producing biodiesel fuel from vegetable oils or animal fats. More specifically, the present invention relates to a method for producing biodiesel fuel consisting of saturated hydrocarbons by using vegetable oils or animal fats as a starting raw material, bringing the raw material into contact with a catalyst for reaction, and then carrying out a decarboxylation step and a hydrogenation step.

[0013] In the present invention, the starting vegetable oils or animal fats are primarily composed of triglycerides. Triglycerides have a glycerol backbone ester-linked to three fatty acid chains. Vegetable oils include, but are not limited to, soybean oil, palm oil, palm kernel oil, rapeseed oil, corn oil, olive oil, sesame oil, canola oil, rice bran oil, sunflower oil, coconut oil, jatropha oil, cottonseed oil, peanut oil, and castor oil. Animal fats include, but are not limited to, beef tallow, lard, mutton tallow, chicken fat, tallow, milk fat, butter, fish oil, and whale oil.

[0014] In the production method of the present invention, no particular distinction is made between vegetable oils and animal fats. There is no particular problem even if both are mixed. Waste cooking oil containing vegetable oils and animal fats as the main components can also be used as a starting material in the present invention.

[0015] The production method of the present invention is a method in which the decarboxylation step and the hydrogenation step are carried out sequentially in this order, and the production method of the present invention is a method in which the decarboxylation step and the hydrogenation step are carried out under a relatively low pressure of 0.2 MPa or less.

[0016] In the present invention, the biodiesel fuel production process is divided into two steps: a decarboxylation step and a hydrogenation step. This allows the reaction conditions and catalysts to be optimized for each step. As a result, it is possible to improve the overall reaction efficiency and yield. Furthermore, because each step can be controlled independently, it is easier to identify the cause of any problems. Furthermore, when it is desired to produce biodiesel fuel with superior performance, it is possible to improve the reaction conditions by focusing on the appropriate step depending on the desired performance.

[0017] The reaction vessels for each step are filled with granular catalysts. In the first decarboxylation step, the raw material, vegetable oil or animal fat, is injected as a liquid into the reaction vessel, and then the reaction proceeds as the gas to be reacted comes into contact with the catalyst in the reaction vessel. Each reaction step can be carried out batchwise or continuously, but a preferred method is to carry out the reaction by sequentially moving through each step while being transported by a flow gas such as an inert gas or water vapor. To prevent the granular catalysts in the reaction vessel from adhering to each other and to ensure that the reaction proceeds uniformly within the reaction vessel, it is preferable to stir the reaction vessel with a rotor or rotate the reaction vessel itself during the reaction.

[0018] Each step of the production method of the present invention will be described below. (Decarboxylation process) In the decarboxylation step, a decarboxylation catalyst is used to remove carbon dioxide from the ester groups of vegetable oils or animal fats to produce hydrocarbons. That is, in the decarboxylation step using a decarboxylation catalyst, the triglycerides that make up vegetable oils or animal fats are converted into hydrocarbons by removing carbon dioxide from the ester groups of the triglycerides and also removing glycerol.

[0019] The decarboxylation catalyst is characterized by having basic surface activity, with the activated surface of a porous catalyst support coated with an alkali metal compound or alkaline earth metal compound. The use of such a catalyst enables efficient decarboxylation of the ester groups of triglycerides to produce hydrocarbons.

[0020] Specifically, a porous catalyst carrying magnesium oxide or calcium oxide is used as the decarboxylation catalyst. The surface of the decarboxylation catalyst is activated by coating the porous catalyst support with magnesium oxide or calcium oxide, which imparts basic surface activity to the catalyst and enhances its ability to remove carbonate from triglycerides. The magnesium oxide or calcium oxide may further be mixed with oxides of aluminum, calcium, iron, or zirconium. As the porous catalyst carrier, a porous catalyst carrier made of alumina, silica, titania, magnesia, zeolite, carbon, or the like is used.

[0021] The decarboxylation step of the present invention allows the reaction to proceed even in the presence of moisture. That is, the vegetable oil or animal fat used as the raw material can be introduced into the decarboxylation step without a pretreatment step for removing moisture. The presence of moisture can cause the ester moiety of triglycerides to hydrolyze, producing free aliphatic carboxylic acids. However, the decarboxylation catalyst of the present invention effectively removes carbon dioxide not only from ester groups but also from carboxylic acids. Therefore, even if carboxylic acids are partially produced in the vegetable oil or animal fat by hydrolysis, carbon dioxide removal is possible, and in either case, the vegetable oil or animal fat can be converted to hydrocarbons.

[0022] The decarboxylation step is usually carried out at a temperature in the range of 360 to 550°C, preferably 430 to 520°C, depending on the catalytic activity and reaction conditions. The pressure during the reaction is in the range of 0.1 to 0.2 MPa, preferably 0.15 to 0.2 MPa. If the reaction temperature is high, decomposition of the product by the decarboxylation catalyst will proceed, and the average molecular weight of the biodiesel fuel will tend to decrease. Therefore, in order to increase the fluidity of the biodiesel fuel, it is preferable to set the reaction temperature higher.

[0023] (Hydrogenation process) In the hydrogenation step, the hydrocarbons are hydrogenated using a hydrogenation catalyst under a hydrogen atmosphere to produce a biodiesel fuel consisting of saturated hydrocarbons. The hydrocarbons obtained after the decarboxylation step may contain double bonds derived from unsaturated fatty acids in vegetable oils or animal fats. Therefore, the hydrocarbons are subjected to a hydrogenation reaction using a hydrogenation catalyst under a hydrogen atmosphere. This step saturates the double bonds in the hydrocarbons, resulting in saturated hydrocarbons that are chemically stable and easy to handle.

[0024] The hydrogenation catalyst used is a catalyst in which a metal such as nickel, molybdenum, palladium, iron, or a combination thereof is supported on a catalyst carrier. The metal may further contain tungsten, ruthenium, copper, or a combination thereof. The catalyst carrier used is a porous catalyst carrier such as alumina, silica, titania, magnesia, zeolite, or carbon. ZSM-based zeolite is preferred as the zeolite. The surface area of ​​the porous catalyst carrier is 200 to 400 m. 2 The preferred range is 1 / g. The above metal is supported on the surface of the porous catalyst support, and promotes the absorption and dissociation of hydrogen molecules, thereby accelerating the hydrogenation reaction. This configuration allows the double bonds present in hydrocarbons to be efficiently hydrogenated, resulting in saturated hydrocarbons.

[0025] The reaction temperature in the hydrogenation step is 200 to 500° C., preferably 300 to 450° C. The pressure during the reaction is in the range of 0.1 to 0.2 MPa, preferably 0.15 to 0.2 MPa. The atmospheric gas during the reaction is mainly hydrogen, but an inert gas such as nitrogen may also be present in addition to hydrogen.

[0026] In the method of the present invention, the reactions in both the decarboxylation step and the hydrogenation step can be carried out under a pressure of 0.2 MPa or less. Furthermore, by optimizing each catalyst, the reactions can be carried out under atmospheric pressure of 0.1 MPa. Therefore, production is possible even if the equipment itself does not have the durability to withstand high pressures of 0.5 MPa or more, and it is possible to reduce the investment required for installing the equipment. Furthermore, since the energy required to achieve high pressure can be reduced, it is possible to reduce production costs.

[0027] In the method of the present invention, almost no aromatic compounds are generated during the decarboxylation step. As a result, in the hydrogenation step, the chemical structures of the hydrocarbons subjected to the hydrogenation reaction are almost entirely aliphatic. Therefore, even when the hydrogenation reaction is carried out under a low pressure of 0.2 MPa or less, it is possible to almost completely hydrogenate the double bonds in the biodiesel fuel.

[0028] The biodiesel fuel obtained by the production method of the present invention contains, as its main component, saturated hydrocarbons with a carbon number roughly corresponding to the carbon number of the long-chain fatty acid group originally contained in the vegetable oil or animal fat used as the raw material ((the number of carbon atoms in the long-chain fatty acid group)-1). For example, palm oil contains a 15-carbon hydrocarbon derived from palmitic acid in palm oil, a 17-carbon hydrocarbon derived from oleic acid, linoleic acid, and stearic acid, and a 13-carbon hydrocarbon derived from myristic acid. Biodiesel fuel preferably contains 70% by mass or more, and more preferably 80% by mass or more, of hydrocarbon compounds with 9 to 15 carbon atoms.

[0029] The hydrocarbons obtained by the production method of the present invention may not satisfy the performance standards for various applications, and therefore, if necessary, it may be necessary to carry out appropriate modification or purification processes. For example, in order to further improve the flowability, it is preferable to carry out a cracking process after the hydrogenation process so that the carbon number of the main hydrocarbons is 10 to 12.

[0030] (Cracking process) In the cracking step, cracking is carried out by catalytic cracking using a cracking catalyst. Examples of cracking catalysts that can be used include acid-treated alumina, silica, silica-alumina, and zeolites, with zeolites being preferred. ZSM-based zeolites are preferred.

[0031] The reaction temperature in the cracking step is 300 to 650° C., preferably 450 to 600° C. The pressure during the reaction is in the range of 0.1 to 1.0 MPa, and the reaction can be carried out under a pressure of 0.2 MPa or less. As a result, it is possible to carry out all of the steps, including the decarboxylation step, hydrogenation step, and cracking step, under a pressure of 0.2 MPa or less.

[0032] The present invention makes it possible to efficiently produce biodiesel fuel from vegetable oils or animal fats, which can be used in a variety of applications such as aircraft, ships, turbines, etc. This is expected to promote the use of biodiesel fuel as a fuel derived from renewable raw materials as an alternative to conventional petroleum-derived fuels, and contribute to reducing the environmental burden. [Example]

[0033] The present invention will be described in more detail below with reference to examples. [Example] Rapeseed oil was used as the raw vegetable oil. The reaction conditions for each step are as follows. [Decarboxylation process] Decarboxylation catalyst: A catalyst that uses activated carbon as a porous catalyst support, the surface of which is coated with magnesium oxide. Reaction conditions: reaction temperature 480°C, reaction pressure 0.2 MPa. [Hydrogenation process] Hydrogenation catalyst: A catalyst that uses silica as a porous catalyst support, with nickel and molybdenum supported on its surface. Reaction conditions: Reaction temperature 430°C, pressure during reaction 0.2 MPa. The resulting biodiesel fuel had excellent low-temperature fluidity and oxidation stability. [Example]

[0034] Waste cooking oil was used as the raw material for vegetable oils and animal fats. The reaction conditions for each step are as follows. [Decarboxylation process] Decarboxylation catalyst: A catalyst that uses activated carbon as a porous catalyst support, the surface of which is coated with magnesium oxide. Reaction conditions: reaction temperature 480°C, reaction pressure 0.2 MPa. [Hydrogenation process] Hydrogenation catalyst: A catalyst that uses silica as a porous catalyst support, with nickel and molybdenum supported on its surface. Reaction conditions: reaction temperature 430°C, reaction pressure 0.2 MPa. [Cracking process] Cracking catalyst: ZSM type zeolite was used. Reaction conditions: Reaction temperature 600°C, reaction pressure 0.2 MPa. The resulting biodiesel fuel had excellent low-temperature fluidity, oxidation stability, and volatility.

Claims

1. A method for producing biodiesel fuel from vegetable oils or animal fats, comprising: a decarboxylation step of removing carbon dioxide from ester groups of the vegetable oil or animal fat using a decarboxylation catalyst to produce hydrocarbons; a hydrogenation step of hydrogenating the obtained hydrocarbons using a hydrogenation catalyst to produce saturated hydrocarbons; a cracking step of performing cracking using a cracking catalyst after the hydrogenation step, The decarboxylation step, the hydrogenation step, and the cracking step are carried out in this order, Each of the decarboxylation step, the hydrogenation step, and the cracking step is carried out under a pressure of 0.2 MPa or less, A method for producing biodiesel fuel, wherein the cracking catalyst is zeolite.

2. 2. The method for producing biodiesel fuel according to claim 1, wherein the decarboxylation catalyst has magnesium oxide or calcium oxide supported on the surface of a porous catalyst support, and has basic surface activity.

3. 2. The method for producing biodiesel fuel according to claim 1, wherein the hydrogenation catalyst is a catalyst in which nickel, molybdenum, palladium, iron, or a combination thereof is supported on the surface of a porous catalyst support.