Fuel oil manufacturing method

Abstract

A method for producing fuel oil having excellent fluidity and containing saturated hydrocarbons as the main component, under relatively mild conditions, using vegetable oil as a raw material, is provided. [Solution] This is a method for producing fuel oil from vegetable oils and fats, comprising the steps of: (a) a decarboxylation step in which carbon dioxide is removed from ester groups of vegetable oils and fats using a decarboxylation catalyst to produce hydrocarbons; (b) an isomerization step in which the resulting hydrocarbons are isomerized using an isomerization catalyst; and (c) a hydrogenation step in which the resulting isomerized hydrocarbons are hydrogenated using a hydrogenation catalyst to produce fuel oil composed of saturated hydrocarbons, wherein the decarboxylation step, isomerization step, and hydrogenation step are carried out in this order, and the decarboxylation step, isomerization step, and hydrogenation step are carried out under a pressure of 1.0 MPa or less.

Description

[Technical Field]

[0001] The present invention relates to a method for producing fuel oil using vegetable oil as a raw material. [Background technology]

[0002] Fuels such as aviation fuels have strict requirements for volatility, fluidity, flammability, thermal stability, and trace elements, and meeting these requirements requires the appropriate adjustment of specific hydrocarbon components. Traditionally, petroleum-derived fuels have been the norm, but environmental concerns have led to the development of alternative fuels using renewable vegetable oils. This is particularly an urgent issue for aviation fuels due to international agreements.

[0003] Vegetable oils, which are primarily composed of triglycerides (also known as triacylglycerols) of long-chain fatty acids, have been considered potential renewable raw materials for the production of fuel oil. However, vegetable oils do not have the properties required for fuel oil in their original form, so their volatility, fluidity, etc. need to be efficiently improved.

[0004] While there are already commercially available methods for producing fuel oil from waste cooking oil, they involve complex processes aimed at improving the fluidity and stability of the fuel, and there is still room for improvement in efficiency, catalyst design, and fluidity. Therefore, new and improved methods for converting vegetable oils into fuel oil are highly desirable.

[0005] Regarding methods for producing fuel oil consisting of saturated hydrocarbons from vegetable oils, a method for producing biojet fuel with fewer steps has been disclosed. Patent Document 1 discloses a method for producing biojet fuel, characterized by comprising reaction steps in which a crude oil obtained by decarboxylating a feedstock oil containing triglycerides and / or free fatty acids using a decarboxylation cracking catalyst is hydrogenated, isomerized, and cracked under a hydrogen atmosphere using a hydrogenation catalyst and an isomerization catalyst. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6635362 Summary of the Invention [Problem to be solved by the invention]

[0007] The method of Patent Document 1 is characterized by the simultaneous hydrogenation and isomerization in one step using a composite catalyst. However, the catalyst responsible for hydrogenation and the catalyst responsible for isomerization differ in suitable active species and polarity, and the interaction between the two catalysts has the problem that fuel oil cannot always be produced with the expected efficiency. An object of the present invention is to provide a method for producing a fuel oil having excellent fluidity and consisting mainly of saturated hydrocarbons under relatively mild conditions using vegetable oil as a raw material. [Means for solving the problem]

[0008] In view of the above circumstances, the present inventors have investigated the possibility of separately carrying out the decarboxylation, isomerization, and hydrogenation steps and setting milder reaction conditions for each step. As a result, they have found that by carrying out the decarboxylation, isomerization, and hydrogenation steps in this order and optimizing the catalyst, each step can be carried out under a pressure of 1.0 MPa or less, thereby arriving at the present invention.

[0009] The present invention has the following configuration. (1) A method for producing fuel oil from vegetable oil, comprising: (a) a decarboxylation step in which carbon dioxide is removed from ester groups of vegetable oil using a decarboxylation catalyst to produce hydrocarbons; (b) an isomerization step in which the resulting hydrocarbons are isomerized using an isomerization catalyst; and (c) a hydrogenation step in which the resulting isomerized hydrocarbons are hydrogenated using a hydrogenation catalyst to produce fuel oil consisting of saturated hydrocarbons, wherein the decarboxylation step, isomerization step, and hydrogenation step are carried out in this order, and the decarboxylation step, isomerization step, and hydrogenation step are carried out under a pressure of 1.0 MPa or less. (2) The method for producing fuel oil according to (1) above, wherein the decarboxylation catalyst has magnesium oxide, magnesium hydroxide, or calcium oxide supported on the surface of a porous catalyst carrier and has basic surface activity. (3) The method for producing fuel oil according to (1) above, wherein the isomerization catalyst is a solid acid catalyst selected from silica, alumina, activated clay, and zeolite, and has acidic surface activity. (4) the hydrogen addition The method for producing fuel oil according to (1) above, wherein the catalyst is a catalyst in which cobalt, nickel, molybdenum, palladium, platinum, iron, or a combination thereof is supported on the surface of a porous catalyst support. (5) The method for producing fuel oil according to (1) above, characterized in that after the hydrogenation step, a cracking step is carried out using a cracking catalyst. (6) The method for producing fuel oil according to (1) above, wherein the fuel oil is aviation fuel. [Effects of the Invention]

[0010] According to the method for producing fuel oil of the present invention, fuel oil having excellent fluidity and consisting mainly of saturated hydrocarbons can be produced under relatively mild conditions using vegetable oil as a raw material. 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 fuel oil, such as aviation fuel, from vegetable oil. More specifically, the present invention relates to a method for producing fuel oil, which exhibits excellent fluidity and is composed of saturated hydrocarbons and is suitable for use as aviation fuel, by using vegetable oil as a starting material and sequentially carrying out a decarboxylation step, an isomerization step, and a hydrogenation step.

[0013] In the present invention, the starting vegetable oil is primarily composed of triglycerides. Triglycerides have a glycerol backbone esterified with 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.

[0014] The production process of the present invention involves multiple steps, so it is acceptable for the vegetable oils used as raw materials to contain a few percent of impurities. Specifically, the impurities include free long-chain fatty acids and glycerin produced by partial hydrolysis of the vegetable oils. It is also acceptable for the vegetable oils to contain small amounts of animal fats and oils.

[0015] The production method of the present invention is a method in which the decarboxylation step, isomerization step, and 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, isomerization step, and hydrogenation step are carried out under a pressure of 1.0 MPa or less.

[0016] In the present invention, the fuel oil production process is divided into three steps: decarbonation, isomerization, and hydrogenation. This makes it possible to optimize the reaction conditions and catalysts for each step. As a result, it is possible to improve the overall reaction efficiency and yield. In addition, because each step can be controlled independently, it is easy to identify the cause of any problems. Furthermore, when it is desired to produce fuel oil with superior performance, it is possible to narrow down the reaction conditions to the optimal step depending on the desired performance.

[0017] The reactor vessels for each step are filled with granular catalysts. In the first decarboxylation step, the raw material vegetable oil is injected as a liquid into the reactor vessel, and then the reaction proceeds as the gas to be reacted comes into contact with the catalyst in the reactor 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 reactor vessel from adhering to each other and to ensure that the reaction proceeds uniformly within the reactor vessel, it is preferable to stir the reactor vessel with a rotor or rotate the reactor 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 the vegetable oil to produce hydrocarbons. That is, in the decarboxylation step using a decarboxylation catalyst, the triglycerides that make up the vegetable oil are converted into hydrocarbons by removing carbon dioxide from the ester groups of the triglycerides and 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] The decarboxylation catalyst specifically includes magnesium oxide, magnesium hydroxide, or A porous catalyst supporting calcium oxide is used. The surface of the decarboxylation catalyst is activated by coating the porous catalyst support with magnesium oxide or the like, which provides the catalyst with basic surface activity and enhances its ability to remove carbonate from triglycerides. The magnesium oxide or the like 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 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, resulting in the production of 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 by hydrolysis, carbon dioxide removal is possible, and in either case, the vegetable oil can be converted to hydrocarbons.

[0022] The decarboxylation step is usually carried out at a temperature in the range of 300 to 500°C, preferably 400 to 470°C, depending on the catalytic activity and reaction conditions. The pressure during the reaction is in the range of 0.1 to 1.0 MPa, preferably 0.2 to 1.0 MPa. When the reaction temperature is high, decomposition of the product by the decarboxylation catalyst proceeds, and the molecular weight of the fuel oil tends to decrease. Therefore, in order to increase the fluidity of the fuel oil, it is preferable to set the reaction temperature higher.

[0023] (isomerization process) In the isomerization step, the obtained hydrocarbons are isomerized using an isomerization catalyst. The hydrocarbons obtained in the decarboxylation step are then isomerized using an isomerization catalyst, which converts linear molecules into branched molecules and improves cold flow properties.

[0024] The isomerization catalyst is characterized by having acidic surface activity. As the isomerization catalyst, a solid acid catalyst selected from silica, alumina, activated clay, zeolite, etc. is preferably used, and a solid acid catalyst containing zeolite is more preferred.

[0025] The reaction temperature in the isomerization step is in the range of 150 to 400° C., and preferably 200 to 350° C. The pressure during the reaction is in the range of 0.1 to 1.0 MPa, and preferably 0.2 to 1.0 MPa.

[0026] (Hydrogenation process) In the hydrogenation step, the isomerized hydrocarbons are hydrogenated in a hydrogen atmosphere using a hydrogenation catalyst to produce a fuel oil consisting of saturated hydrocarbons. The hydrocarbons obtained after the isomerization step may be derived from unsaturated fatty acids in vegetable oils or may contain double bonds due to the isomerization reaction. Therefore, the isomerized hydrocarbons are subjected to a hydrogenation reaction using a hydrogenation catalyst under a hydrogen atmosphere. This step saturates the double bonds in the isomerized hydrocarbons, resulting in saturated hydrocarbons that are chemically stable and easy to handle.

[0027] The hydrogenation catalyst used is a catalyst in which a metal such as cobalt, nickel, molybdenum, palladium, platinum, 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 may be a porous catalyst carrier such as alumina, silica, titania, magnesia, zeolite, or carbon. ZSM-based zeolites are preferred as zeolites. The surface area of ​​the porous catalyst carrier is 200 to 400 m. 2The preferred range is 1 / g. The 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 the hydrocarbons after isomerization to be efficiently hydrogenated, thereby obtaining saturated hydrocarbons.

[0028] The reaction temperature in the hydrogenation step is 150 to 450° C., preferably 250 to 400° C. The pressure during the reaction is in the range of 0.1 to 1.0 MPa, preferably 0.2 to 1.0 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.

[0029] In the method of the present invention, the reactions in any of the decarboxylation step, isomerization step, and hydrogenation step can be carried out under a pressure of 1.0 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 2.0 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.

[0030] In the method of the present invention, the isomerization step is carried out under a low pressure of 1.0 MPa or less. As a result, the production of aromatic compounds in the isomerization step can be almost completely suppressed. As a result, in the hydrogenation step, the chemical structure of the isomerized fuel oil that is the subject of the hydrogenation reaction becomes almost entirely aliphatic. Therefore, even when the hydrogenation reaction is carried out under a low pressure of 1.0 MPa or less, it is possible to almost completely hydrogenate the double bonds in the fuel oil.

[0031] The fuel oil obtained by the production method of the present invention contains, as its main component, saturated hydrocarbons with a carbon number roughly corresponding to the number of carbon atoms in the long-chain fatty acid groups originally contained in the vegetable oil used as the raw material ((the number of carbon atoms in the long-chain fatty acid groups)-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. The fuel oil preferably contains 70% by mass or more, and more preferably 80% by mass or more, of hydrocarbon compounds having 9 to 15 carbon atoms.

[0032] (Aircraft fuel) The production method of the present invention produces a fuel oil mainly composed of saturated hydrocarbons, but because it contains many branched structures produced in the isomerization step, it can be a fuel oil with excellent fluidity. In particular, it can produce a fuel oil composed of saturated hydrocarbons with a pour point of -40°C or lower. In other words, the fuel oil produced by the production method of the present invention is primarily composed of saturated hydrocarbons and has excellent fluidity and thermal stability, making it suitable as an aviation fuel.

[0033] However, the fuel oil produced by the production method of the present invention may not satisfy the performance standards for aviation fuel, and therefore, it may be necessary to further carry out appropriate modification or refining steps as necessary. In order to further improve the fluidity, it is preferable to carry out a cracking step after the hydrogenation step so that the carbon number of the main hydrocarbon becomes 10 to 12.

[0034] (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.

[0035] 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, preferably 0.5 to 1.0 MPa. As a result, it is possible to carry out all steps, including not only the decarboxylation step, isomerization step, and hydrogenation step, but also the cracking step, under a pressure of 1.0 MPa or less.

[0036] The present invention makes it possible to efficiently convert vegetable oils into fuel oils with excellent fluidity, which can be used as aviation fuel, etc. This is expected to promote the use of vegetable oils as fuels derived from renewable raw materials as an alternative to conventional petroleum-derived fuels, and to contribute to reducing the environmental load. [Example]

[0037] The present invention will be described in more detail below with reference to examples. [Example] Palm 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 silica as a porous catalyst support, the surface of which is coated with magnesium oxide. Reaction conditions: reaction temperature 450°C, reaction pressure 1.0 MPa. [Isomerization process] Isomerization catalyst: Zeolite-based solid acid catalyst. Reaction conditions: reaction temperature 280°C, reaction pressure 1.0 MPa. [Hydrogenation process] Hydrogenation catalyst: A catalyst that uses alumina as a porous catalyst support, with cobalt and molybdenum supported on its surface. Reaction conditions: Reaction temperature 400°C, reaction pressure 1.0 MPa. The resulting fuel oil had a pour point of -14°C and possessed the basic properties required for a fuel that could replace diesel fuel. [Example]

[0038] Soybean 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 silica as a porous catalyst support, the surface of which is coated with magnesium oxide. Reaction conditions: reaction temperature 450°C, reaction pressure 1.0 MPa. [Isomerization process] Isomerization catalyst: Zeolite-based solid acid catalyst. Reaction conditions: reaction temperature 280°C, reaction pressure 1.0 MPa. [Hydrogenation process] Hydrogenation catalyst: A catalyst that uses alumina as a porous catalyst support, with cobalt and molybdenum supported on its surface. Reaction conditions: reaction temperature 400°C, reaction pressure 1.0 MPa. [Cracking process] Cracking catalyst: ZSM type zeolite was used. Reaction conditions: reaction temperature 580°C, reaction pressure 1.0 MPa. The resulting fuel oil had a pour point of -42°C and possessed the basic properties required for aviation fuel.

Claims

1. A method for producing fuel oil from vegetable oil, comprising: (a) a decarboxylation step in which carbon dioxide is removed from ester groups of vegetable oils and fats using a decarboxylation catalyst to produce hydrocarbons; (b) an isomerization step in which the obtained hydrocarbons are isomerized using an isomerization catalyst; (c) a hydrogenation step in which the obtained isomerized hydrocarbons are hydrogenated using a hydrogenation catalyst to produce saturated hydrocarbons; (d) a cracking step in which cracking is carried out using a cracking catalyst after the hydrogenation step. The steps are as follows: the decarboxylation step, the isomerization step, the hydrogenation step, and the cracking step are carried out in this order; each of the decarboxylation step, the isomerization step, the hydrogenation step, and the cracking step is carried out under a pressure of 1.0 MPa or less; A method for producing fuel oil, wherein the cracking catalyst is a zeolite.

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

3. 2. The method for producing fuel oil according to claim 1, wherein the isomerization catalyst is a solid acid catalyst selected from the group consisting of silica, alumina, activated clay and zeolite, and has acidic surface activity.

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

5. 2. The method for producing fuel oil according to claim 1, wherein the fuel oil is an aviation fuel.