Fuel oil manufacturing method

Abstract

This invention provides a method for producing a highly fluid fuel oil, primarily composed of saturated hydrocarbons, using vegetable oils and fats as raw materials, under relatively mild conditions. [Solution] A method for producing fuel oil from vegetable oils, comprising the steps of (a) a decarboxylation step in which carbon dioxide is removed from the ester groups of vegetable oils using a decarboxylation catalyst to produce hydrocarbons, (b) an isomerization step in which the obtained hydrocarbons are isomerized using an isomerization catalyst, and (c) a hydrogenation step in which hydrogen is added to the obtained isomerized hydrocarbons using a hydrogenation catalyst to produce fuel oil consisting of saturated hydrocarbons, wherein the decarboxylation step, the isomerization step and the hydrogenation step are performed in this order, and the decarboxylation step, the isomerization step and the hydrogenation step are performed under a pressure of 1.0 MPa or less.

Description

Technical Field

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

Background Art

[0002] Fuels such as aircraft fuel have strict requirements for volatility, fluidity, flammability, thermal stability, trace components, etc. In order to meet these requirements, it is necessary to appropriately adjust specific hydrocarbon components. Conventionally, fuels derived from petroleum have been mainly used, but due to environmental considerations, the development of alternative fuels using renewable vegetable oils has been underway. Particularly regarding aircraft fuel, it has become an urgent issue due to international agreements.

[0003] Vegetable oils mainly consist of triglycerides of long-chain fatty acids (also called triacylglycerols) and have been considered potential renewable raw materials for the production of fuel oil. However, since vegetable oils do not have the performance required for fuel oil as they are, it is necessary to efficiently improve their volatility, fluidity, etc.

[0004] A method for producing fuel oil using waste cooking oil as a raw material has already been put into practical use, but it involves complicated processes aimed at improving the fluidity and stability of the fuel, and there is still room for improvement in terms of efficiency, catalyst design, and improvement of fluidity. Therefore, a new and improved method for converting vegetable oil into fuel oil is strongly desired.

[0005] Regarding the method for producing fuel oil composed of saturated hydrocarbons from vegetable oil, a method for producing biojet fuel with fewer steps has been disclosed. In Patent Document 1, a crude oil obtained by decarboxylation treatment of a raw material oil containing triglyceride and / or free fatty acid using a decarboxylation catalyst is hydrogenated, isomerized, and decomposed in a hydrogen atmosphere using a hydrogenation catalyst and an isomerization catalyst, and a method for producing biojet fuel characterized by having a reaction step is disclosed.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Patent No. 6635362 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The method described in Patent Document 1 is characterized by performing hydrogenation and isomerization simultaneously in a single step using a composite catalyst. However, the catalyst responsible for hydrogenation and the catalyst responsible for isomerization have different suitable active species and polarities, and the interaction between the two catalysts has resulted in the problem that fuel oil cannot always be produced with the expected efficiency. The present invention aims to provide a method for producing a fuel oil with excellent fluidity, mainly composed of saturated hydrocarbons, using vegetable oils and fats as raw materials, under relatively mild conditions. [Means for solving the problem]

[0008] In view of the above circumstances, the inventors have been investigating how to separate the decarboxylation, isomerization, and hydrogenation processes and make the reaction conditions for each process milder. As a result, they have found that by performing the decarboxylation, isomerization, and hydrogenation processes in this order and optimizing the catalyst, it is possible to carry out each process under a pressure of 1.0 MPa or less, leading to the present invention.

[0009] The present invention has the following configuration. (1) A method for producing fuel oil from vegetable oils, comprising the steps of (a) a decarboxylation step of removing carbon dioxide from ester groups of vegetable oils using a decarboxylation catalyst to produce hydrocarbons, (b) an isomerization step of isomerizing the obtained hydrocarbons using an isomerization catalyst, and (c) a hydrogenation step of hydrogenating the obtained isomerized hydrocarbons using a hydrogenation catalyst to produce fuel oil consisting of saturated hydrocarbons, wherein the decarboxylation step, the isomerization step and the hydrogenation step are carried out in this order, and the decarboxylation step, the isomerization step and the hydrogenation step are carried out under a pressure of 1.0 MPa or less. (2) The method for producing fuel oil according to (1), characterized in that 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) The method for producing fuel oil according to (1), characterized in that the isomerization catalyst is a solid acid catalyst selected from silica, alumina, activated clay, and zeolite, and has acidic surface activity. (4) The method for producing fuel oil according to (1), characterized in that the hydrogenation catalyst is a catalyst on 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), characterized in that a cracking step is performed using a cracking catalyst after the hydrogenation step. (6) The method for producing fuel oil according to (1), characterized in that the fuel oil is aircraft fuel. [Effects of the Invention]

[0010] According to the present invention's method for producing fuel oil, a fuel oil with excellent fluidity, mainly composed of saturated hydrocarbons, can be produced using vegetable oils and fats as raw materials under relatively mild conditions. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described in detail below, 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 aircraft fuel, from vegetable oils and fats. More specifically, the present invention is a method for producing fuel oil consisting of saturated hydrocarbons that exhibit excellent fluidity and are suitable for use as aircraft fuel, by sequentially performing a decarboxylation step, an isomerization step, and a hydrogenation step using vegetable oils and fats as starting materials.

[0013] In the present invention, the vegetable oil used as a starting material is mainly composed of triglycerides. Triglycerides have a glycerol skeleton with three fatty acid chains ester-bonded. 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 manufacturing process of the present invention involves multiple steps, making it acceptable even if the raw material vegetable oil contains impurities of a few percent. Specifically, these impurities include free long-chain fatty acids and glycerin produced by the partial hydrolysis of vegetable oil. Furthermore, it is also acceptable if a small amount of animal fat is present.

[0015] The manufacturing method of the present invention involves sequentially performing the decarboxylation step, the isomerization step, and the hydrogenation step in that order. Furthermore, the manufacturing method of the present invention involves performing the decarboxylation step, the isomerization step, and the hydrogenation step under a pressure of 1.0 MPa or less.

[0016] In this invention, the fuel oil manufacturing process is divided into three stages: a decarboxylation stage, an isomerization stage, and a hydrogenation stage. This allows for the optimization of reaction conditions and catalysts for each stage. As a result, it becomes possible to improve the overall reaction efficiency and yield. Furthermore, since each stage can be controlled independently, troubleshooting becomes easier. Moreover, when it is desired to produce fuel oil with superior performance, it is possible to focus on the optimal stage and improve the reaction conditions according to the required performance.

[0017] Each reaction vessel in each step is filled with granular catalyst. In the first decarboxylation step, the raw material, vegetable oil, is injected into the reaction vessel as a liquid, but thereafter, the reaction proceeds when the gas to be reacted comes into contact with the catalyst in the reaction vessel. Each reaction step can be carried out in a batch or continuous manner, but it is preferable to proceed with the reaction by sequentially moving through each step while being transported by an inert gas or water vapor flow gas. To prevent the granular catalyst 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 inside of the reaction vessel with a rotor or the like, or to rotate the reaction vessel itself, during the reaction.

[0018] The following describes each step of the manufacturing method of the present invention. (Decarboxylation process) In the decarboxylation process, a decarboxylation catalyst is used to remove carbon dioxide from the ester groups of vegetable oils and fats, thereby producing hydrocarbons. In other words, in the decarboxylation process using a decarboxylation catalyst, the triglycerides that make up vegetable oils and fats have carbon dioxide removed from their ester groups, and glycerol is also removed, converting them into hydrocarbons.

[0019] Decarboxylation catalysts are characterized by having an alkali metal compound or alkaline earth metal compound coated on the activated surface of a porous catalyst support, resulting in basic surface activity. Using such a catalyst, it is possible to efficiently decarboxylate from the ester groups of triglycerides and produce hydrocarbons.

[0020] As the decarboxylation catalyst, specifically, a porous catalyst supporting magnesium oxide, magnesium hydroxide, or calcium oxide is used. The surface of the decarboxylation catalyst is activated by coating the porous catalyst carrier with the magnesium oxide or the like, which gives the catalyst basic surface activity and enhances the ability to remove carbonic acid from triglycerides. Further, oxides of each metal such as aluminum, calcium, iron, and zirconium may be mixed in the magnesium oxide or the like. As the porous catalyst carrier, a porous catalyst carrier composed of alumina, silica, titania, magnesia, zeolite, carbon, or the like is used.

[0021] In the decarboxylation process of the present invention, the reaction can proceed even under conditions where water is present. That is, the raw material vegetable oil can be introduced into the decarboxylation process without installing a pretreatment process for removing water in advance. Due to the presence of water, the ester portion of the triglyceride may be hydrolyzed to generate free aliphatic carboxylic acid. However, the decarboxylation catalyst of the present invention not only functions effectively for removing carbonic acid from the ester group but also for removing carbonic acid from the carboxylic acid. Therefore, even if carboxylic acid is generated by partial hydrolysis in the vegetable oil, carbonic acid can be removed, and in any case, it can be converted into hydrocarbon.

[0022] The decarboxylation process is usually carried out in a temperature range of 300 to 500 °C, preferably 400 to 470 °C, according to the catalyst activity and reaction conditions. Also, the pressure during the reaction is in the range of 0.1 to 1.0 MPa, preferably in the range of 0.2 to 1.0 MPa. If the reaction temperature is high, the decomposition of the product by the decarboxylation catalyst progresses, 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 process, the obtained hydrocarbon is isomerized using an isomerization catalyst. The hydrocarbons obtained in the decarboxylation process are then isomerized using an isomerization catalyst. This isomerization converts linear molecules into branched molecules, improving low-temperature fluidity.

[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 preferable.

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

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

[0027] As the hydrogenation catalyst, a catalyst is used in which a metal such as cobalt, nickel, molybdenum, palladium, platinum, iron, or a combination thereof is supported on a catalyst support. The metal may also contain tungsten, ruthenium, copper, or a combination thereof. As the catalyst support, a porous catalyst support such as alumina, silica, titania, magnesia, zeolite, or carbon is used. ZSM-type zeolite is preferred. The surface area of ​​the porous catalyst support is 200-400 m². 2A range of / g is preferred. The above metal is supported on the surface of a porous catalyst support, and promotes the hydrogenation reaction by facilitating the absorption and dissociation of hydrogen molecules. With this configuration, double bonds present in the isomerized hydrocarbon can be efficiently hydrogenated, and saturated hydrocarbons can be obtained.

[0028] The reaction temperature in the hydrogenation step is 150 to 450°C, preferably 250 to 400°C. The reaction pressure 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 other inert gases such as nitrogen may also be present.

[0029] In the method of the present invention, the reactions in each of the decarboxylation, isomerization, and hydrogenation steps can be carried out under a pressure of 1.0 MPa or less. Furthermore, by optimizing each catalyst, it is possible to carry out the reaction 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 higher, and it is possible to reduce the investment amount in equipment installation. In addition, since the energy required to achieve high pressure can be reduced, it is possible to reduce manufacturing 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 generation of aromatic compounds in the isomerization step can be almost completely suppressed. Consequently, in the hydrogenation step, the chemical structure of the isomerized fuel oil targeted for hydrogenation is 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 complete the hydrogenation of double bonds in the fuel oil.

[0031] The fuel oil obtained by the manufacturing method of the present invention mainly contains saturated hydrocarbons with a number of carbon atoms ((number of carbon atoms of the long-chain fatty acid group) - 1) that is approximately equivalent to the long-chain fatty acid group originally present in the raw material vegetable oil. For example, palm oil contains hydrocarbons with 15 carbon atoms derived from palmitic acid, hydrocarbons with 17 carbon atoms derived from oleic acid, linoleic acid, and stearic acid, and hydrocarbons with 13 carbon atoms derived from myristic acid. The fuel oil preferably contains 70% by mass or more of hydrocarbon compounds having 9 to 15 carbon atoms, and more preferably 80% by mass or more.

[0032] (Aircraft fuel) In the manufacturing method of the present invention, a fuel oil mainly composed of saturated hydrocarbons is produced, and because it has numerous branched structures generated in the isomerization process, it can be made into a fuel oil with excellent fluidity. In particular, it is possible to produce a fuel oil consisting of saturated hydrocarbons with a pour point of -40°C or lower. In other words, the fuel oil produced by the manufacturing method of the present invention has saturated hydrocarbons as its main component and exhibits excellent fluidity and thermal stability, making it suitable as an aircraft fuel.

[0033] However, fuel oil produced by the manufacturing method of the present invention may not satisfy the performance standards for aircraft fuel, so it may be necessary to perform appropriate modification or refining processes as needed. To further improve fluidity, it is preferable to perform a cracking step after the hydrogenation step so that the number of carbon atoms in the main hydrocarbon becomes 10 to 12.

[0034] (Cracking process) In the cracking process, cracking is carried out using a cracking catalyst by contact cracking. As the cracking catalyst, acid-treated alumina, silica, silica-alumina, and zeolite can be used, but zeolite is preferred. Among zeolites, ZSM-type zeolites are preferred.

[0035] The reaction temperature for the cracking process 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 processes, including the cracking process as well as the decarboxylation, isomerization, and hydrogenation processes, under a pressure of 1.0 MPa or less.

[0036] This invention makes it possible to efficiently convert vegetable oils into fuel oils with excellent fluidity, making them suitable for use in aircraft fuel and other applications. This is expected to promote the use of fuels derived from renewable raw materials as an alternative to conventional petroleum-derived fuels, thereby contributing to a reduction in environmental impact. [Examples]

[0037] The present invention will be described in more detail below with reference to examples. [Examples] Palm oil was used as the vegetable oil used as a raw material. The reaction conditions for each step are as follows: [Decarboxylation process] Decarboxylation catalyst: A catalyst that uses silica as a porous catalyst support, with its surface 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] Hydrogenated 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 characteristics of a fuel that could replace diesel fuel. [Examples]

[0038] Soybean oil was used as the vegetable oil ingredient. The reaction conditions for each step are as follows: [Decarboxylation process] Decarboxylation catalyst: A catalyst that uses silica as a porous catalyst support, with its surface 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] Hydrogenated 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-based 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 characteristics of an aircraft fuel.

Claims

1. A method for producing fuel oil from vegetable oils, (a) A decarboxylation step in which carbon dioxide is removed from the ester group of a vegetable oil using a decarboxylation catalyst to produce a hydrocarbon, (b) An isomerization step in which the obtained hydrocarbon isomerized using an isomerization catalyst. (c) A hydrogenation step in which the obtained isomerized hydrocarbon is hydrogenated using a hydrogenation catalyst to produce fuel oil consisting of saturated hydrocarbons. It has each of the following processes: The decarboxylation step, the isomerization step, and the hydrogenation step are carried out in this order. A method for producing fuel oil, characterized in that each of the steps of the decarbonation step, the isomerization step, and the hydrogenation step is carried out under a pressure of 1.0 MPa or less.

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

4. The method for producing fuel oil according to claim 1, characterized in that the hydrogenation catalyst is a catalyst on 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 claim 1, characterized in that a cracking step is performed using a cracking catalyst after the hydrogenation step.

6. The method for producing fuel oil according to claim 1, characterized in that the fuel oil is aircraft fuel.