JP2016155775A - Organic acid production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method that achieves a higher yield in a synthetic reaction of organic acids using hydrocarbons and carbon dioxide as raw materials.SOLUTION: An organic acid production method for producing organic acids having 2 or more and 10 or less carbon atoms using hydrocarbons having 1 or more and 6 or less carbon atoms and carbon dioxide as raw materials includes: a step X of introducing a gas x containing hydrocarbons having 1 or more and 6 or less carbon atoms into a reaction system in which a catalyst is present; and a step Y of introducing a gas y containing carbon dioxide and steam into the reaction system. In the gas x, the mole fraction of the hydrocarbons is 0.1 or more and 1 or less, and the mole fraction of steam is 0.1 or less. In the gas y, the mole fraction of the carbon dioxide is 0.1 or more and 0.995 or less, and the mole fraction of the steam is 0.005 or more and 0.36 or less. The mole fraction of the carbon dioxide in the gas y is higher than the mole fraction of the carbon dioxide in the gas x.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an organic acid.

Currently, there is a concern that the price of oil, which is mainly used as a raw material for chemical products, will rise and be exhausted. Therefore, intensive research has been conducted on methods for producing chemical products using carbon compounds instead of petroleum as raw materials. Carbon dioxide, which is inexpensive and can be obtained relatively easily, has attracted attention as a raw material for chemicals that substitute for petroleum. In order to satisfy the current demand for chemical products using carbon dioxide as a raw material, it is important to develop a method for synthesizing a carbon compound having 2 or more carbon atoms.
As a method for synthesizing a carbon compound having 2 or more carbon atoms using carbon dioxide directly as a raw material, a method for synthesizing acetic acid using carbon dioxide and methane as raw materials using a catalyst is known (for example, non-patent) Reference 1). In this document, the synthesis reaction of acetic acid exceeding the limitation of the equilibrium reaction is reported by the operation of supplying the raw material to the catalyst layer in two steps. The operation of supplying the raw material to the catalyst layer in two stages is as follows. As a first stage, methane is introduced into a reactor having a catalyst layer, and activation with dehydrogenation is performed on the catalyst. And hydrogen are introduced and reacted with methane active species on the catalyst to produce acetic acid.

In Non-Patent Document 1, various reaction conditions are studied in order to increase the yield of carboxylic acid. Regarding the reaction conditions for introducing water vapor into the reactor, the mole fraction of water vapor in the introduced gas has been studied in the range of 0.71 to 0.92. In order to obtain a carboxylic acid in a high yield, water vapor with a molar fraction of 0.84 is optimal in the first stage methane introduction step, and a molar fraction of 0.71 is obtained in the second stage CO ₂ introduction step. It is said to be optimal.
However, the present situation is that a method capable of obtaining carboxylic acid with higher yield from hydrocarbon and carbon dioxide is desired.

W. Huang et al., AIChE 2010, 56, 1279-1284.

  Under the circumstances of the above-described prior art, the object of the present invention is to provide an effective production method for improving the yield of organic acid in the synthesis reaction of organic acid using hydrocarbon and carbon dioxide as raw materials. It is.

  As a result of intensive studies and experiments to solve the above-mentioned problems, the present inventors have determined that the amount of water vapor introduced in each step is a specific condition in the synthesis reaction of organic acids using hydrocarbons and carbon dioxide as raw materials. Thus, the inventors have found that the method is effective for improving the yield, and based on this, the present invention has been completed.

That is, the present invention is as follows.
[1]
A method for producing an organic acid having 2 to 10 carbon atoms using a hydrocarbon having 1 to 6 carbon atoms and carbon dioxide as raw materials,
Introducing a gas x containing at least the hydrocarbon into a reaction system in which a catalyst is present; and
Introducing the gas y containing at least the carbon dioxide and water vapor into the reaction system; and
In the gas x, the mole fraction of the hydrocarbon is 0.1 or more and 1 or less, and the mole fraction of water vapor is 0.1 or less,
In the gas y, the molar fraction of the carbon dioxide is 0.1 or more and 0.995 or less, and the molar fraction of the water vapor is 0.005 or more and 0.36 or less,
The method for producing an organic acid, wherein a mole fraction of the carbon dioxide in the gas y is higher than a mole fraction of the carbon dioxide in the gas x.
[2]
The method for producing an organic acid according to [1], wherein a molar ratio between the water vapor and the carbon dioxide contained in the gas y is 0.005 or more and 2.5 or less.
[3]
The method for producing an organic acid according to [1] or [2], wherein the temperature in the reaction system is 160 ° C or higher and 340 ° C or lower.
[4]
The method for producing an organic acid according to any one of [1] to [3], wherein the hydrocarbon has 1 or 2 carbon atoms.
[5]
The method for producing an organic acid according to [4], wherein the hydrocarbon is methane.
[6]
The method for producing an organic acid according to [4], wherein the hydrocarbon is ethylene.
[7]
The method for producing an organic acid according to any one of [1] to [6], wherein the catalyst is a heterogeneous catalyst.
[8]
The method for producing an organic acid according to any one of [1] to [7], wherein the pressure in the reaction system is 3.1 MPa or more and 5.0 MPa or less.
[9]
The method for producing an organic acid according to any one of [1] to [8], wherein the introduction time of the gas x and / or the gas y is 3 seconds or longer and 150 seconds or shorter.
[10]
The method for producing an organic acid according to any one of [1] to [9], wherein a molar fraction of hydrogen contained in the gas y is 0.1 or less.

  According to the method for producing an organic acid according to the present invention, in the method for producing an organic acid using hydrocarbons and carbon dioxide as raw materials, the organic acid produced by setting the amount of water vapor introduced in each step to a specific condition. High acid yield can be achieved.

Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, In the range of the summary, various deformation | transformation can be implemented.
This embodiment
A method for producing an organic acid having 2 to 10 carbon atoms using a hydrocarbon having 1 to 6 carbon atoms and carbon dioxide as raw materials,
Introducing the gas x containing at least the hydrocarbon having 1 to 6 carbon atoms into the reaction system in which the catalyst is present; and
Introducing the gas y containing at least the carbon dioxide and water vapor into the reaction system; and
In the gas x, the mole fraction of the hydrocarbon is 0.1 or more and 1 or less, and the mole fraction of water vapor is 0.1 or less,
In the gas y, the molar fraction of the carbon dioxide is 0.1 or more and 0.995 or less, and the molar fraction of the water vapor is 0.005 or more and 0.36 or less,
The organic acid production method is characterized in that a molar fraction of the carbon dioxide in the gas y is higher than a molar fraction of the carbon dioxide in the gas x.

In the production of an organic acid using hydrocarbons and carbon dioxide as raw materials, the inventors of the present invention have a high yield of production of an organic acid by setting the amount of water vapor introduced in the process X and the process Y to predetermined conditions. I found out that it can be streamlined.
By making the mole fraction of the introduced water vapor in the process X 0.1 or less, the active species derived from hydrocarbons produced on the catalyst in the process X are inactivated by water vapor or water at the catalyst active point. It is presumed that poisoning, oxidation of the metal catalyst, and desorption due to water vapor of the catalyst component are suppressed. As a result, the carboxylic acid yield is estimated to be improved.
On the other hand, when the molar fraction of the introduced water vapor in Step Y is 0.005 or more and 0.36 or less, the elimination of the generated carboxylic acid strongly adsorbed on the catalyst is promoted and / or CO _2. It is presumed that the reverse reaction of the reaction that generates CO and H ₂ O (for example, Formula 1) is promoted by the reaction between hydrogen and dissociated hydrogen. It is presumed that the yield of carboxylic acid is improved as a result of improving the efficiency of the production of COOH groups from CO ₂ (Formula 2) by promoting this reverse reaction. Further, in the present embodiment, the water vapor can reduce the partial pressure decrease of CO ₂ by not excessively introduced, it is possible to increase the reaction amount of CO ₂ as a raw material, and is presumed.
CO ₂ + 2H ^* → CO + H ₂ O (Formula 1)
CO ₂ + H ^* → COOH ^* (Formula 2)
Here, the reaction system indicates only a space for reacting the catalyst and the raw material, and does not include a space for circulating, storing or separating and purifying the raw material and the product until the catalyst and the raw material are reacted. Specific examples of the reaction system include a reactor as a fixed bed filled with a catalyst, a slurry bed, a fluidized bed, a moving bed, or a simulated moving bed.

<Catalyst>
The catalyst used in the present invention refers to a homogeneous catalyst, a heterogeneous catalyst, a catalyst in which a homogeneous catalyst is fixed to a support or a heterogeneous catalyst, etc., because the separation of the raw material and the catalyst is relatively easy. Preferably, it is a heterogeneous catalyst. Specifically, the heterogeneous catalyst is a metal catalyst, a metal compound catalyst such as a metal oxide, a zeolite, a catalyst in which a metal or a metal compound is supported or ion-exchanged on a support, a metal complex, activated carbon, etc., preferably A catalyst having a metal compound supported on a carrier is preferred. A catalyst in which a metal compound is supported on a carrier is a single metal oxide or a single metal oxide such as titanium oxide, silicon oxide, aluminum oxide, zirconium oxide, lanthanum oxide, cerium oxide, or magnesium oxide. , A composite metal oxide composed of two or more metal elements such as spinel type and perovskite type, zeolite, activated carbon and the like can be used.

The elements constituting the catalyst include at least one of elements from Group 3 to Group 14 of the new IUPAC notation. From the viewpoint of utilizing d-electrons, elements from Group 6 to Group 12, more preferably Group 7 to Group 11, more preferably Group 8 to Group 10, are preferred. For example, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os, Mn, Re, Cr, Mo, W, Cu, Ag, Au can be mentioned, and Ni, Pd, Pt, Co, Rh, Ir Fe, Ru, Mo, W, Cu, and Ag are preferable, and Ni, Pd, Pt, Co, Rh, Fe, and Ru are more preferable.
The chemical state of the metal species is not limited to a metal, but may be a compound, a complex, or the like, but the higher the charge density that contributes to electron donation to the adsorption substrate, the more advantageous it is for high activation. It is preferable that

  A phosphorus-containing compound, boron-containing compound, alkali metal compound, alkaline earth metal compound, or the like can be added to the catalyst as an auxiliary agent. As an element constituting the catalyst, it can be composed of one or a plurality of elements. From the viewpoint of catalytic activity during the reaction, transition metals, groups 13 and 14 are usually preferred, and groups 6 to 14 are more preferred. Group elements, more preferably Group 8 to Group 10 elements.

  Catalyst preparation methods include impregnation method, solid phase reaction, flux method, hydrothermal synthesis method, changing the pH of the solution containing the catalyst raw material, or adding ions forming a compound, etc. Examples thereof include a coprecipitation method, a uniform precipitation method, a chemical vapor deposition method, and a physical vapor deposition method in which a catalyst or a precursor thereof is deposited.

The catalyst is present in the reactor. Specifically, the catalyst can be charged to the reactor as a fixed bed, fluidized bed, moving bed, or simulated moving bed. The reactor may be filled with one type of catalyst, or a catalyst mixture in which a plurality of types of catalysts having different activities or inactive inorganic substances are mixed may be used as the catalyst. Catalysts and catalyst mixtures with different activities may be installed in stages from the reactor inlet to the outlet.
The amount of catalyst shown in the present invention is the sum of the weight of the catalyst metal species and the catalyst carrier charged in the reaction system. When the catalyst is fixed to the reaction system, the weight of the fixed reaction system is not included.
When using a fluidized bed, moving bed, or simulated moving bed, the introduction time of the raw material gas corresponds to the residence time of each gas composition of the catalyst.

The organic acid produced by the method of the present invention is an organic acid having 2 to 10 carbon atoms constituting the molecule, preferably 2 to 8 carbon atoms, more preferably 2 or more carbon atoms, It is 5 or less, more preferably 2 or more and 4 or less, and most preferably 2 or more and 3 or less. Examples of the carbon constituting the organic acid include linear or branched carboxylic acids, saturated and / or unsaturated carboxylic acids, and the like. In particular, from the viewpoint that desorption from a catalyst is advantageous, a carboxylic acid in which a bond between carbons consists only of a saturated bond is desirable.
Specific examples of the organic acid include carboxylic acids having one or more carboxyl groups and having 2 to 10 carbon atoms. Specific examples include monocarboxylic acids and dicarboxylic acids. Specific examples of monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, pelargonic acid, capric acid, lactic acid, pyruvic acid, malic acid, acrylic acid, benzoic acid, salicylic acid, and isomers thereof. More specifically, examples include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, lactic acid, acrylic acid, and more specifically acetic acid and propionic acid. Specific examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, phthalic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, and more specifically, oxalic acid, malonic acid, succinic acid, Specific examples include succinic acid.

<Process X>
In step X of the present invention, a gas x containing at least a hydrocarbon having 1 to 6 carbon atoms is introduced into the reaction system. In the gas x, the mole fraction of hydrocarbon is 0.1 or more and 1 or less, and the mole fraction of water vapor is 0.1 or less.

(Gas x)
The gas x introduced into the reaction system in the process X is composed of hydrocarbons, water vapor, and gases other than hydrocarbons. Here, the “gas other than hydrocarbon” does not include water vapor.
The carbon number of the hydrocarbon is 1 or more and 6 or less. As described above, since hydrocarbons are activated on the catalyst, the smaller the number of carbon atoms, the smaller the steric hindrance for hydrocarbon adsorption on the catalyst. Therefore, the carbon number of the hydrocarbon is preferably 1 to 4, more preferably 1 to 3, further preferably 1 to 2, and most preferably 1. The hydrocarbon is preferably a saturated hydrocarbon or an unsaturated hydrocarbon. Saturated hydrocarbons are preferred from the viewpoint of having a large boiling point difference from the organic acid that is the product and advantageous for separation of the product and the unreacted raw material.
Specific examples of the hydrocarbon used in the present embodiment include methane, ethane, propane, butane, pentane, hexane, ethylene, propylene, butene, pentene, hexene, acetylene, and isomers thereof. From the above viewpoint, the hydrocarbon is preferably methane, ethane, propane, butane, ethylene, propylene, butene, acetylene, and isomers thereof, and more preferably methane, ethane, propane, ethylene, acetylene. And most preferred are methane and ethylene.
The hydrocarbon which is the raw material of the present invention is preferably introduced as a gas from the viewpoint of the simplicity of the reactor.

  In the gas x, the molar fraction of hydrocarbon is 0.1 or more and 1 or less. The molar fraction is preferably 0.4 or more, more preferably 0.6 or more, and still more preferably 0.8 or more, from the viewpoint that the higher the partial pressure of the hydrocarbon, the more advantageous the adsorption to the catalyst. In addition, the molar fraction is preferably 0.999 or less, more preferably 0.990 or less, and further preferably 0.950 or less, from the viewpoint of hydrocarbon purification cost.

  Examples of gases other than hydrocarbons include carbon dioxide, hydrogen, oxygen, inert gases such as nitrogen and argon, and the like. Among these, an inert gas is preferable from the viewpoint of preventing deterioration of the catalyst. When the gas contains oxygen, the concentration is preferably less than the explosion limit. Further, from the viewpoint of simplicity of the process, the molar fraction of the gas other than hydrocarbon in the gas x is preferably 0.5 or less, more preferably 0.2 or less, and further 0.05 or less. preferable.

  The molar fraction of hydrogen to be introduced is preferably 0.2 or less, more preferably 0.1 or less, and more preferably 0.05 or less from the viewpoint of suppressing the reverse reaction of the production of active hydrocarbon species by dehydrogenation on the catalyst. Is more preferable, and 0.01 or less is most preferable.

  In the gas x, the molar fraction of water vapor is 0.1 or less. When the amount of water vapor introduced into the reaction system is reduced, it is preferable to reduce the amount of water vapor introduced from the viewpoint of reducing the latent heat required to convert the liquid water into water vapor. In addition, when the amount of water vapor to be introduced is 0.1 or less, the deactivation of active species derived from hydrocarbons produced on the catalyst, poisoning by water at the catalytic active point, oxidation of the metal catalyst, and water vapor of the catalyst component It is presumed that desorption due to can be suppressed. From such a viewpoint, the molar fraction of water vapor in the gas x is more preferably 0.05 or less, further preferably 0.02 or less, and most preferably 0.01 or less.

  From the viewpoint of the purification cost of the gas x, the molar fraction ratio of water vapor to hydrocarbon (water vapor / hydrocarbon) is preferably 0.0001 or more, more preferably 0.001 or more, and further preferably 0.005 or more. From the viewpoint of increasing the hydrocarbon partial pressure, which is more advantageous for activating the hydrocarbon, the molar fraction ratio is preferably 0.2 or less, more preferably 0.1 or less, and most preferably 0.01 or less.

  In the gas x, the molar ratio of hydrocarbon to carbon dioxide (hydrocarbon / carbon dioxide) is preferably greater than 0.5, and from the viewpoint of efficiently activating the hydrocarbon with a catalyst, one or more is More preferably, 5 or more is more preferable, and 10 or more is most preferable.

  Gas x is not limited in its production process, production process, and introduction process to the reactor. Shale gas can also be used.

  In the process X, the introduction time of the gas x is preferably 3 seconds or more and 10 minutes or less. From the viewpoint of improving the coverage of the hydrocarbon-derived active species on the catalyst, it is preferably 5 seconds or longer, more preferably 10 seconds or longer, more preferably 20 seconds or longer, and even more preferably 30 seconds or longer. Further, if the hydrocarbon is sufficiently adsorbed on the catalyst and then introduced for an excessive period of time, the hydrocarbon flows unreacted, and from the viewpoint of reducing the yield, 5 minutes or less is preferable, 150 seconds or less is preferable, and 110 Seconds or less are preferable, and 90 seconds or less are preferable.

  In the step X, the total volume flow rate of the gas x to be introduced is preferably 0.0001 to 10000000 L / h, more preferably 0.001 to 1000000 L / h, more preferably 0, per 1 g of the catalyst charged in the reaction system. 0.01 to 100,000 L / h.

  In step X, the temperature in the reaction system is preferably 50 ° C. or higher and 1000 ° C. or lower, preferably 80 ° C. or higher, more preferably 110 ° C. or higher, and further preferably 160 ° C. or higher from the viewpoint of the reaction rate. Moreover, from a viewpoint of preventing the yield fall by sintering etc. of a catalyst, 790 degrees C or less is preferable, 490 degrees C or less is more preferable, and 340 degrees C or less is further more preferable.

The pressure in the reaction system in the process X is not less than atmospheric pressure and not more than 20 MPa. The higher the pressure, the higher the coverage of the hydrocarbon on the catalyst, so 0.7 MPa or more is preferable, more preferably 1.6 MPa or more, still more preferably 2.6 MPa or more, and most preferably 3.1 MPa or more. . The critical pressure of carbon dioxide is 7.4 MPa, and it is desirable that the raw material be introduced in the form of a gas. From the viewpoint of preventing carbon dioxide from liquefying when switching from process Y to process X, the reaction system according to the present invention is used. The pressure is preferably 7.4 MPa or less. From the viewpoint of reducing the energy required for pressurization as the pressure is lower, 6.5 MPa or less is more preferable, and 5 MPa or less is more preferable.
Furthermore, when the vapor pressure of the raw material hydrocarbon is lower than the above pressure, it is preferably introduced at a vapor pressure lower than that of the hydrocarbon.
In addition, the pressure described in this specification has shown the relative pressure (gauge pressure) with atmospheric pressure.

<Process Y>
In process Y, gas y containing at least carbon dioxide and water vapor is introduced into the reaction system.
In the gas y, the molar fraction of carbon dioxide is 0.1 or more and 0.995 or less, and the molar fraction of water vapor is 0.005 or more and 0.36 or less. Further, the molar fraction of carbon dioxide is higher than the molar fraction of carbon dioxide in the gas x.

(Gas y)
The gas y introduced into the reaction system in the process Y includes carbon dioxide, water vapor, and a gas other than carbon dioxide. Here, the “gas other than carbon dioxide” does not include water vapor.
In the gas y, the molar fraction of carbon dioxide is 0.1 or more and 1 or less. The molar fraction of carbon dioxide is preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more from the viewpoint of increasing the partial pressure, which is advantageous for adsorption onto the catalyst. Further, from the viewpoint of purification cost, 0.9 or less is preferable, 0.8 or less is more preferable, and 0.7 or less is more preferable.
Further, from the viewpoint of promoting the adsorption / desorption of the substrate to the catalyst due to the unsteady operation of the raw material introduction, the molar fraction of carbon dioxide in the gas y is higher than the molar fraction of carbon dioxide in the gas x.
Examples of the gas other than carbon dioxide include hydrocarbons such as methane, hydrogen, oxygen, inert gases such as nitrogen and argon, and the like.
In the gas y, the molar fraction of water vapor is 0.005 or more and 0.36 or less. If the amount of water vapor introduced into the reaction system decreases, it is preferable to reduce the amount of water vapor introduced from the viewpoint of reducing the latent heat required to convert the liquid water into water vapor. From the viewpoint of promoting the elimination of the produced carboxylic acid strongly adsorbed on the catalyst, by promoting the reverse reaction of the production reaction of CO and water (formula 1) by the reaction of CO ₂ and dissociated hydrogen, COOH from CO ₂ From the viewpoint of improving the production efficiency of the groups, and from the viewpoint of reducing CO ₂ partial pressure drop by not introducing excessive water vapor and efficiently using the raw material CO ₂ for the reaction, the molar fraction of water vapor is 0. .05 or less is preferable, 0.02 or less is preferable, and 0.01 or less is most preferable.

  From the viewpoint of simplicity of the process, it is preferable not to introduce other gases other than carbon dioxide and water vapor in the process Y. Further, from the viewpoint of the purification cost of carbon dioxide as a raw material, the other gas contained in carbon dioxide is 0.001 or more, preferably 0.01 or more, preferably 0.05 or more with respect to the molar fraction of carbon dioxide. Is most preferred.

  When the other gas other than carbon dioxide and water vapor is hydrogen as described above, the introduced hydrocarbon is an active species dehydrogenated on the catalyst. Inactivation may occur due to the reaction between the activated hydrocarbon species and the introduced hydrogen. For this reason, when the molar fraction of carbon dioxide is 1, the molar fraction of hydrogen is preferably 0.2 or less, more preferably 0.1 or less, and most preferably 0.05 or less.

The deactivation of the dehydrogenated hydrocarbon active species by reacting with the introduced hydrogen may cause more significant deactivation when the hydrocarbon active species is produced at a high coverage on the catalyst. Conceivable. Therefore, in this process Y, the amount of hydrogen to be introduced together with carbon dioxide is small, so that the active hydrocarbon species generated on the catalyst at a high coverage under the high pressure conditions in process X are efficiently used for the production of organic acids. It is speculated that it will contribute.
The smaller the amount of hydrogen introduced, the easier it is to condense with dehydrogenation of the active species and the generated organic acid on the catalyst, which is advantageous for the generation of an organic acid having a higher carbon number or having a plurality of carboxyl groups. Become. Specific examples of the organic acid having a higher carbon number or a plurality of carboxyl groups include acetic acid, propionic acid, oxalic acid, and succinic acid.

  In the gas y, the molar ratio of water vapor to hydrocarbon (water vapor / carbon dioxide) is preferably 0.005 or more, more preferably 0.1 or more, from the viewpoint of increasing the effect of introducing water vapor. 3 or more is more preferable, and 0.5 or more is most preferable. From the viewpoint of increasing the hydrocarbon partial pressure, the molar fraction ratio is preferably 2.5 or less, more preferably 2.1 or less, and even more preferably 1.6 or less, from the viewpoint of being advantageous for hydrocarbon activation. 1.0 or less is most preferable.

  In the gas y, the ratio of the molar fraction of hydrocarbon to carbon dioxide (carbon dioxide / hydrocarbon) is preferably greater than 0.5, and is 1 or more from the viewpoint of efficiently activating the hydrocarbon with a catalyst. Is more preferable, 5 or more is more preferable, and 10 or more is most preferable. In the process Y, it is also possible to carry out under the condition that no hydrocarbon exists.

  The gas y is not limited in its production process, production process, and introduction process to the reactor, but gas produced by refining petroleum, natural gas, exhaust gas from a factory, gas recovered from the atmosphere or formation, for example, Shale gas can also be used.

  In the process Y, the introduction time of the gas y is preferably 3 seconds or longer and 10 minutes or shorter. From the viewpoint of increasing the amount of reaction with the hydrocarbon-derived active species on the catalyst, it is preferably 5 seconds or more, more preferably 10 seconds or more, further preferably 25 seconds or more, and most preferably 45 seconds or more. In addition, with the passage of time in Step Y, the hydrocarbon-derived active species on the catalyst decrease by reacting with carbon dioxide, and the yield decreases as the amount of unreacted carbon dioxide circulates increases. From the viewpoint, the introduction time is preferably 5 minutes or less, more preferably 150 seconds or less, further preferably 110 seconds or less, and most preferably 90 seconds or less.

  In the step Y, the total volume flow rate of the gas y to be introduced is preferably 0.0001 to 10000000 L / h, more preferably 0.001 to 1000000 L / h, more preferably 0, per 1 g of the catalyst charged in the reaction system. 0.01 to 100,000 L / h.

  In step Y, the temperature in the reaction system is preferably 50 ° C. or higher and 1000 ° C. or lower, and is preferably 80 ° C. or higher, more preferably 110 ° C. or higher, and further preferably 160 ° C. or higher from the viewpoint of the reaction rate. Moreover, from a viewpoint of preventing the yield fall by sintering etc. of a catalyst, 790 degrees C or less is preferable, 490 degrees C or less is more preferable, and 340 degrees C or less is further more preferable.

The pressure in the reaction system in the step Y is preferably not less than atmospheric pressure and not more than 20 MPa. From the viewpoint of increasing the reaction probability of carbon dioxide to the active hydrocarbon species as the pressure increases, 0.7 MPa or more is preferable, more preferably 1.6 MPa, still more preferably 2.6 MPa or more, and most preferably 3.1 MPa. That's it. Moreover, the critical pressure of carbon dioxide is 7.4 MPa, and the pressure of the reaction system in the present invention is preferably 7.4 MPa or less from the viewpoint that introduction of the raw material in a gas is desirable. From the viewpoint of reducing the energy required for pressurization as the pressure is lower, the pressure of the reaction system is more preferably 6.5 MPa or less, and more preferably 5 MPa or less.
According to Le Chatelier's law, the higher the reaction pressure, the more advantageous is the reaction in which the number of product molecules is reduced. Therefore, the organic acid product having a large number of carbon atoms increases. This organic acid having a large number of carbon atoms is an organic acid having 2 or more carbon atoms, and examples thereof include acetic acid, propionic acid, oxalic acid, and succinic acid.

Either step X or step Y in the present embodiment may be performed first, and each step may be repeated two or more times in the manufacturing method. From the viewpoint of increasing the effect of switching between the process X and the process Y, the number of repetitions of the process X and the process Y is preferably 2 or more, more preferably 5 or more, and most preferably 10 or more. In the present embodiment, since it is preferable to react carbon dioxide with the hydrocarbon-derived active species generated on the catalyst, it is preferable to perform step X first and then perform step Y.
Furthermore, in this embodiment, in addition to the step X and the step Y, one or a plurality of steps can be added to the organic acid production step, and the order thereof is not limited. Process X, process Y, and other processes can be repeated in the organic acid production process periodically or not periodically. Examples of the process other than the process X and the process Y include an oxidation or reduction treatment performed for catalyst regeneration.

  Switching between the process X and the process Y can be performed by switching the gas introduced into the reactor from the upstream side of the reactor, or by moving the catalyst in the reactor having the concentration distribution of the raw material gas. Specifically, switching of the introduced gas to a fixed bed or moving bed reactor, or a fluidized bed or moving bed in a reactor having a concentration distribution of raw material gas.

  In the reaction mode in which the catalyst moves in the reaction system, such as a fluidized bed, a moving bed, and a simulated moving bed, the switching operation between the process X, the process Y, and the other processes is performed constantly in the reaction system by the gas x, Each of the above steps can be performed by a region having a component composition of each gas such as the gas y and the catalyst staying in the region for a predetermined time. In this case, the time required for each step means the average residence time of the catalyst in that region in the reaction step.

Moreover, in the process X and the process Y, the temperature, pressure, and gas introduction time in the reaction system do not have to be the same, and can be set to different conditions within a predetermined range described in this specification.
The difference in temperature and / or pressure between the process X, the process Y, and other processes means that the reaction system in a reaction mode in which the catalyst moves in the reaction system, such as a fluidized bed, a moving bed, or a simulated moving bed. There are regions where the composition of each gas, such as gas x and gas y, steadily changes and the temperature and / or pressure is different, and the catalyst stays in that region for a predetermined time. Can be implemented.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
The synthesis was performed under the following conditions, and the amount of organic acid produced was evaluated.
In addition, the molar fraction, production | generation rate, and production | generation activity of each component were measured as follows.

(Liquid chromatography)
[apparatus]
System controller: CBM-20A (manufactured by Shimadzu Corporation)
Liquid feed pump: LC-20AD (manufactured by Shimadzu Corporation)
Electrical conductivity detector: CDD-10Avp (manufactured by Shimadzu Corporation)
[column]
Shim-pack SCR-102H (manufactured by Shimadzu Corporation)
[Mobile phase]
5 mmol / L p-toluenesulfonic acid [reaction solution] 5 mmol / L p-toluenesulfonic acid + 100 μmol / L EDTA + 20 mmol / L Bis-Tris
[Measurement condition]
Column temperature 40 ° C, liquid feed rate 0.8mL / min

(Molar fraction)
The mole fractions of hydrogen, carbon dioxide, hydrocarbons, and other components described in this specification are shown by the following formula.
[Mole fraction of gas] = [Mole fraction of hydrocarbon] + [Mole fraction of carbon dioxide] + [Mole fraction of water vapor] + [Mole fraction of other components] = 1
In addition, when evaluating the molar fraction by gas chromatography, for the water vapor / carbon dioxide ratio, argon or helium is used as a carrier gas and a thermal conductivity detector is used. For hydrocarbons, heat is conducted using helium as a carrier gas. Use gas chromatography with degree detector or flame ionization detector. As for the water vapor / carbon dioxide ratio, a column that does not absorb water too strongly (for example, CP-Sil5, manufactured by GL Sciences Inc.) is used, and the hydrocarbon is a nonpolar type packed only with dimethylsiloxane, Alternatively, a polar type such as a mixed composition of dimethylsiloxane and diphenylsiloxane, which can appropriately separate the target hydrocarbon, is used.

(Production amount)
In this example and comparative example, the amount of each organic acid produced was determined by evaluating the water trap solution installed downstream of the reactor and the washing solution obtained by washing the reaction tube downstream with distilled water using the liquid chromatography. The sum of the organic acid in the trap liquid and the organic acid in the cleaning liquid was defined as the amount of production.

In Examples 1 to 7, saturated hydrocarbons and carbon dioxide were reacted in the presence of a catalyst to produce an organic acid, and the amount of organic acid produced was evaluated.
<Example 1>
Palladium chloride was dissolved in an aqueous solution containing 5 molar equivalents of hydrochloric acid, and a titanium oxide (rutile type) powder was impregnated with Pd species and supported at 500 ° C. in the atmosphere. Baked. The powder thus obtained was impregnated and supported with Co seeds using an aqueous solution having a concentration of 50 g / L in which cobalt nitrate was dissolved, and then the powder prepared by firing in the atmosphere at 500 ° C. was used as a catalyst. The amount of the supported metal species was Pd: 3 wt% and Co: 6 wt% when converted based on the chemical state of each metal species as metal. The powder catalyst was pelletized by applying a pressure of 20 MPa, and this was pulverized and reacted using a granular catalyst classified into 0.25 to 0.50 mm.

A central portion of one SUS tube (outer diameter: 3/8 inch, wall thickness: 1.0 mm, length: 56 cm) was filled by sandwiching 0.5 g of catalyst into quartz wool. An organic acid was produced using a flow reactor equipped with this SUS tube.
Prior to the start of the reaction, the catalyst was pretreated by heating at 400 ° C. for 1 hour in a H ₂ stream. During the catalytic reaction, the gas introduced into the reaction tube was controlled by a mass flow controller, and CH ₄ (gas x) was allowed to flow for 1 minute (step X). Thereafter, water was introduced into CO ₂ with a plunger pump, and a mixed gas (gas y) of CO ₂ and water vapor generated by heating was introduced for 1 minute (step Y). The operations of Step X and subsequent Step Y were repeated, and the reaction was performed for a total time of 1 hour. The gas flow rates were CH ₄ : 200 mL / min, CO ₂ : 200 mL / min, water vapor: 25 mL / min, and the reaction was carried out under pressure conditions of 200 ° C. and 4.0 MPa.

  Table 1 shows the evaluation results of the recovered liquid after the reaction for 1 hour. The pipe cleaning liquid was collected until no organic acid was detected, and after confirming that there was no residual organic acid in the pipe, the process moved to the next reaction step. As a result, the amount of each organic acid having 2 or more carbon atoms was acetic acid: 174 nmol and propionic acid: 127 nmol.

<Example 2>
The reaction was performed in the same manner as in Example 1 except that the reaction temperature in Step X and Step Y was 300 ° C. The results are shown in Table 1.

<Example 3>
In step Y, the reaction was carried out in the same manner as in Example 2 except that the amount of water vapor contained in the introduced gas y was 74 mL / min. The results are shown in Table 1.

<Example 4>
In Step X, the reaction was performed in the same manner as in Example 1 except that ethylene was used as the hydrocarbon of the gas x to be introduced. The results are shown in Table 1.

<Comparative Example 1>
In Step Y, the reaction was performed in the same manner as in Example 1 except that the gas y to be introduced was only carbon dioxide. The results are shown in Table 1.

<Comparative example 2>
In Step Y, the reaction was performed in the same manner as in Example 1 except that the amount of water vapor contained in the introduced gas y was 123 mL / min. The results are shown in Table 1.

<Comparative Example 3>
In Step X, the reaction was performed in the same manner as in Example 1 except that the gas x to be introduced was a mixed gas of CH ₄ : 200 mL / min and water vapor: 25 mL / min. The results are shown in Table 1.

As can be seen from Table 1, in the presence of a catalyst, CH ₄ (gas x) is introduced into the reactor, and then a mixed gas of CO ₂ + H ₂ O (gas y) is introduced as an organic acid. It was confirmed that acetic acid and propionic acid were produced. By changing the amount of water vapor introduced in Step X and Step Y, a difference was observed in the amount of organic acid produced.
Compared to Comparative Example 1 in which water vapor was not introduced into both gas x and gas y and Comparative Example 2 in which water vapor having a molar fraction of 0.38 was introduced only into gas y, the molar fraction of gas y was 0.005 or more, 0 In Examples 1 to 4 into which water vapor of .36 or less was introduced, the production amount of acetic acid and propionic acid was increased by about 2 to 20 times. From this result, it was found that introducing water vapor into the gas y is effective in producing an organic acid, but introducing excess water vapor reduces the amount of organic acid produced.

Comparing Comparative Example 3 in which the gas x contains water vapor having a molar fraction of 0.11 and Examples 1 to 4 in which the water vapor amount of the gas x is 0.10 or less, the gas x has a molar fraction of 0.1 or more. It is considered that the production amount of the organic acid decreased due to the inactivation of the active species derived from hydrocarbons on the catalyst.
Further, from Example 4, it was shown that the effects of the present invention can be obtained by using not only methane but also other hydrocarbons such as ethylene.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention.

  The organic acid production method using hydrocarbons and carbon dioxide as raw materials according to the present invention can achieve high yields of organic acids by using suitable reaction conditions as shown in this specification. And can be suitably used in industrially producing organic acids.

Claims (10)

A method for producing an organic acid having 2 to 10 carbon atoms using a hydrocarbon having 1 to 6 carbon atoms and carbon dioxide as raw materials,
Introducing a gas x containing at least the hydrocarbon into a reaction system in which a catalyst is present; and
Introducing the gas y containing at least the carbon dioxide and water vapor into the reaction system; and
In the gas x, the mole fraction of the hydrocarbon is 0.1 or more and 1 or less, and the mole fraction of water vapor is 0.1 or less,
In the gas y, the molar fraction of the carbon dioxide is 0.1 or more and 0.995 or less, and the molar fraction of the water vapor is 0.005 or more and 0.36 or less,
A method for producing an organic acid, wherein a mole fraction of carbon dioxide in the gas y is higher than a mole fraction of carbon dioxide in the gas x.   The manufacturing method of the organic acid of Claim 1 whose molar ratio of the said water vapor | steam and the said carbon dioxide contained in the said gas y is 0.005 or more and 2.5 or less.   The manufacturing method of the organic acid of Claim 1 or Claim 2 whose temperature in the said reaction system is 160 degreeC or more and 340 degrees C or less.   The method for producing an organic acid according to any one of claims 1 to 3, wherein the hydrocarbon has 1 or 2 carbon atoms.   The method for producing an organic acid according to claim 4, wherein the hydrocarbon is methane.   The method for producing an organic acid according to claim 4, wherein the hydrocarbon is ethylene.   The method for producing an organic acid according to any one of claims 1 to 6, wherein the catalyst is a heterogeneous catalyst.   The method for producing an organic acid according to any one of claims 1 to 7, wherein a pressure in the reaction system is 3.1 MPa or more and 5.0 MPa or less.   The method for producing an organic acid according to claim 1, wherein the introduction time of the gas x and / or the gas y is 3 seconds or longer and 150 seconds or shorter.   The method for producing an organic acid according to any one of claims 1 to 9, wherein a molar fraction of hydrogen contained in the gas y is 0.1 or less.