JP6004396B2 - Catalyst for producing dimethyl ether, substrate-supported catalyst, and method for producing dimethyl ether - Google Patents

Description

  The present invention relates to a catalyst for producing dimethyl ether, a substrate-supported catalyst, and a method for producing dimethyl ether using them.

  Dimethyl ether (hereinafter referred to as DME) is expected to be a next-generation clean fuel that replaces liquefied petroleum gas and light oil because it does not generate particulate matter such as black smoke and sulfur oxides even when burned. .

  As a method for producing DME, for example, a catalyst for producing DME containing one or more metal elements consisting of zinc, manganese and iron, copper element and aluminum oxide is used, and in the presence thereof, carbon oxide (one A method of reacting carbon oxide or carbon dioxide) and hydrogen is known (Patent Document 1).

JP 2008-000699 A

  By the way, carbon dioxide is one of the causes of global warming. If DME can be synthesized directly from carbon dioxide, its utility value is high from the viewpoints of global warming countermeasures and energy problems. . However, when DME was directly synthesized from carbon dioxide and hydrogen using a conventional catalyst for producing DME, there was room for improvement in the selectivity of DME.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a catalyst having a high DME selectivity even when carbon dioxide and hydrogen are used.

  The present invention provides a catalyst for producing DME formed by a sol-gel method and containing copper element, gallium element and aluminum oxide. Note that the copper element and the gallium element may be included in an oxide state.

  The sol-gel method includes obtaining a hydrolyzable aluminum compound dispersion, hydrolyzing the hydrolyzable aluminum compound in the dispersion to obtain a sol dispersion, and the sol dispersion. Adding an aqueous solution containing copper ions and gallium ions to obtain a metal ion-containing dispersion, distilling off the solvent of the metal ion-containing dispersion, obtaining a gel, and firing the gel; It is preferable to have.

  The catalyst may further contain one or more metal elements selected from the group consisting of yttrium, zirconium, cerium, zinc, lanthanium, manganese, and iron. Note that these metal elements may be included in an oxide state.

  The catalyst may be supported on a substrate and used as a substrate-supported catalyst. Supporting the catalyst on the substrate can facilitate the handling of the catalyst.

  The base material is preferably a heat-conductive base material excellent in heat-transfer properties such as a metal material and an oxide material because heat generated by the reaction can be quickly dissipated.

  The present invention provides a method for producing DME, in which a carbon oxide and hydrogen are reacted in the presence of the catalyst or the substrate-supported catalyst.

  According to the present invention, a catalyst having high DME selectivity can be provided even when DME is directly synthesized from carbon dioxide and hydrogen.

It is a graph showing DME and carbon monoxide with respect to the reaction temperature when carbon dioxide and hydrogen are reacted in the presence of a catalyst A1, their respective selectivity and production rate (logarithmic notation). It is a graph showing DME and carbon monoxide with respect to the reaction temperature when carbon dioxide and hydrogen are reacted in the presence of catalyst B1, their respective selectivity and production rate (logarithmic notation).

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[Catalyst for DME production]
The catalyst for producing DME according to the present embodiment (hereinafter also simply referred to as “catalyst”) is formed by a sol-gel method, and contains copper element, gallium element, and aluminum oxide. Note that the copper element and the gallium element may be included in an oxide state.

The content of the copper element in the catalyst is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and still more preferably 20 to 50% by mass with respect to the entire catalyst. .
The content of the gallium element in the catalyst is preferably 0.5 to 70% by mass, more preferably 1 to 60% by mass, and 2 to 50% by mass with respect to the entire catalyst. Further preferred.
The content of the aluminum oxide in the catalyst is preferably 30 to 90% by mass, more preferably 35 to 85% by mass, and further preferably 40 to 80% by mass.
The content of each component in the catalyst can be measured by, for example, ICP mass spectrometry or atomic absorption spectrometry.

  Examples of the sol-gel method include a one-step method and a sequential method. In the one-stage method, a dispersion containing a hydrolyzable compound and metal ions is prepared, the hydrolyzable compound in the dispersion is hydrolyzed to form a sol dispersion, and the sol dispersion is gelled and fired. Is. In the sequential method, a hydrolyzable compound dispersion is prepared, the hydrolyzable compound is hydrolyzed to form a sol-like dispersion, and metal ions are added to the sol-like dispersion, and the sol-like dispersion is gelled and fired. Is to do.

  The catalyst comprises a step of obtaining a hydrolyzable aluminum compound dispersion (hereinafter referred to as (A) step), and a step of hydrolyzing the hydrolyzable aluminum compound to obtain a sol dispersion (hereinafter referred to as (B). ) Step), a step of adding an aqueous solution containing copper ions and gallium ions to the sol-like dispersion to obtain a metal ion-containing dispersion (hereinafter referred to as step (C)), and the metal ion-containing dispersion. The solvent is distilled off to form a gel (hereinafter referred to as (D) step) and a step of baking the gel (hereinafter referred to as (E) step). It is preferable.

  In the step (A), for example, a hydrolyzable aluminum compound is dispersed in an aqueous solvent at 60 to 80 ° C. to obtain a dispersion. As the aqueous solvent, water is usually used, and alcohols such as ethylene glycol, methanol, and ethanol and water-soluble organic solvents such as N, N-dimethylformamide may be included. Examples of the hydrolyzable aluminum compound include aluminum alkoxide, and specific examples include aluminum isopropoxide, aluminum ethoxide, and aluminum butoxide.

  In the step (B), for example, an acid or a base is added to the dispersion obtained in the step (A) to hydrolyze the hydrolyzable aluminum compound, and the sol-like dispersion in which the aluminum hydrolyzate is precipitated in an aqueous solvent. Obtain a liquid. In the case of using an acid, the hydrogen ion concentration of the dispersion is, for example, pH 3 or less, preferably pH 2 or less. Examples of the acid include inorganic acids such as nitric acid, hydrochloric acid, and sulfuric acid. Further, when a base is used, the hydrogen ion concentration of the dispersion is set to pH 9 or more, for example. As the base, for example, an inorganic base such as ammonia, sodium carbonate, or sodium hydroxide is used. Among these, a method in which an inorganic acid is added to adjust the hydrogen ion concentration of the dispersion to pH 3 or less is preferable.

  In step (C), an aqueous solution containing copper ions and gallium ions is added to the sol-like dispersion obtained in step (B) to obtain a metal ion-containing dispersion. An aqueous solution containing copper ions and gallium ions is usually prepared by adding a copper salt composed of copper ions and a counter anion and a gallium salt composed of gallium ions and a counter anion to water. Examples of the counter anion include nitrate ion, halide ion, acetate ion and the like.

  In the step (D), for example, a gel is obtained by distilling off the solvent of the metal ion-containing dispersion. By using a gel, the copper ions and gallium ions added to the aluminum hydrolyzate in step (C) can be uniformly dispersed. The resulting gel is usually dried.

In step (E), the gel obtained in step (D) is baked. By baking, the aluminum hydrolyzate becomes aluminum oxide (Al ₂ O ₃ ), and the catalyst for DME production according to the present embodiment containing copper element and gallium element can be obtained. Firing is usually performed in the air, the firing temperature is usually 250 to 700 ° C., and the firing time is 2 to 10 hours.

  According to the above process, a catalyst for producing DME is usually obtained in a powder form. The obtained catalyst may be used in the form of a powder, or may be used after being formed into a granular shape, a spherical shape, a cylindrical shape, a cylindrical shape, or the like.

  The catalyst for producing DME according to this embodiment may further contain one or more metal elements selected from the group consisting of yttrium, zirconium, cerium, zinc, lanthanium, manganese, and iron. Note that these metal elements may be included in an oxide state. In order to contain the metal element in the catalyst for producing DME, in the step (C), an aqueous solution containing the metal ion may be added to the sol dispersion obtained in the step (B).

  In addition, the content in case the said catalyst contains these metal elements can be 0.1-30 mass% with respect to the whole catalyst, for example.

The specific surface area of the catalyst is preferably 10 to 500 m ² / g. The specific surface area of the catalyst can be measured by, for example, the BET method or the Langmuir method.

The acidity of the catalyst can be confirmed, for example, by observing the catalyst adsorbed with pyridine by infrared absorption spectroscopy. In the infrared absorption spectrum, the absorption in the vicinity 1450 cm ^-1 is derived from the Lewis acid, the absorption in the vicinity 1540 cm ^-1 is derived from Bronsted acids. It is preferable that the absorption in the vicinity of 1450 cm ⁻¹ is observed even at 200 ° C. or higher when the temperature is continuously increased.

[Base material supported catalyst for DME production]
The catalyst for producing DME according to this embodiment may be supported on a substrate and used as a substrate-supported catalyst for producing DME.

  As the base material, it is preferable to be a heat conductive base material having excellent heat conductivity such as a metal material and an oxide material because heat generated by the reaction can be quickly dissipated. Iron, copper, aluminum, nickel, titanium Selected from the group consisting of metals such as iron carbide, aluminum carbide, nickel carbide, titanium carbide, etc., metal nitrides such as iron nitride, aluminum nitride, nickel nitride, titanium nitride, alumina, silica, zeolite, zirconia and titania More preferably, it is a molded body of at least one kind of material. Examples of the shape of the heat conductive substrate include a plate shape, a net shape, and a honeycomb shape.

  The substrate-supported catalyst for DME production according to this embodiment is obtained by immersing the substrate in the metal ion-containing dispersion obtained in the step (C) of the catalyst for DME production, and then the steps (D) and (E). It can be obtained through a process.

[DME manufacturing method]
The DME production catalyst and the DME production substrate-supported catalyst according to this embodiment are preferably subjected to a reduction treatment before the reaction for producing DME. The reduction treatment is performed, for example, by holding at 250 to 500 ° C. in a reducing atmosphere such as hydrogen gas for usually 1 hour or longer, preferably 3 hours or longer.

  In order to produce DME using a catalyst for producing DME or a substrate-supported catalyst for producing DME, for example, carbon oxide and hydrogen may be brought into contact with the catalyst. The reaction temperature is usually 150 to 350 ° C., and the reaction pressure is usually 0.1 to 10 MPa. The catalyst can be used alone to produce DME from carbon oxide and hydrogen without being used in combination with other catalysts.

  Examples of the carbon oxide include carbon monoxide and carbon dioxide.

  Carbon oxides and hydrogen as raw materials are usually supplied in a gaseous state. Carbon oxide and hydrogen may be diluted with an inert gas such as nitrogen, argon or helium.

  The reactor is not particularly limited, and usual reactors such as a fixed bed reactor, a fluidized bed reactor, a moving bed reactor, and a slurry reactor can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to an Example at all.

Example 1
[Catalyst for DME production]
To about 150 mL of pure water at 70 ° C., 14.761 g of aluminum isopropoxide powder (manufactured by Wako Pure Chemical Industries, Ltd., first grade, purity 95.0%) ground with a mortar and 10.2 mL of ethylene glycol were added at the same temperature. And stirred for 15 minutes or longer to disperse. Next, dilute nitric acid was added little by little to adjust the hydrogen ion concentration to pH 1 to 2 to obtain a sol dispersion. To this dispersion, 5.185 g of copper nitrate trihydrate (manufactured by Wako Pure Chemical Industries, Ltd., special grade, purity 99.0%) and gallium nitrate n hydrate (n = 6-7, Mitsuwa Chemicals Co., Ltd.) Manufactured by gallium purity 19.04%) Add copper ion and gallium ion aqueous solution in which 0.789 g is dissolved in about 50 mL of pure water, stir at the same temperature for 30 minutes or more, and then dry under reduced pressure with an evaporator to obtain a gel It was. After this gel was pulverized, it was calcined at 500 ° C. for 5 hours in the air, and the obtained calcined product was subjected to reduction treatment at 450 ° C. for 10 hours in a hydrogen atmosphere to obtain 5.0 g of Catalyst A1. The mass composition of the catalyst according to this preparation was 27 mass% for Cu, 3 mass% for Ga, and 70 mass% for Al ₂ O ₃ .

Comparative Example 1
Except for using 0.689 g of zinc nitrate hexahydrate (special grade, purity 99.0%, manufactured by Wako Pure Chemical Industries, Ltd.) instead of gallium nitrate n hydrate, 5.0 g of catalyst B1 was obtained. Mass composition of the catalyst according to this preparation, Cu 27 wt%, Zn is 3% by weight, _Al 2 _{O 3} was 70 mass%.

[DME production]
0.5 g of catalyst A1 (Example 1) was placed in the reaction tube of the fixed bed flow system reactor. Carbon dioxide, hydrogen, and argon (CO ₂ / H ₂ /Ar=15.0/5.0/2.0 mLmim ⁻¹ ) were introduced into the reaction tube and allowed to flow. The product gas after passing through the catalyst was analyzed by gas chromatography, and the production rate and selectivity of DME were measured. At this time, the reaction tube provided with the catalyst was heated by an electric furnace and controlled at 160 to 280 ° C.
A similar experiment was performed on the catalyst B1 (Comparative Example 1).

FIG. 1 is a graph showing DME and carbon monoxide, their selectivity and production rate (logarithmic notation) with respect to the reaction temperature when carbon dioxide and hydrogen are reacted in the presence of catalyst A1 (Example 1). FIG. 2 is a graph showing DME and carbon monoxide, selectivity and production rate (logarithmic notation) of each when catalyst B1 (Comparative Example 1) is used. When the catalyst A1 was used in the reaction at 160 to 280 ° C., it was found that the carbon monoxide selectivity was lower than that when the catalyst B1 was used, and the DME selectivity was increased.

Claims (6)

A catalyst for producing dimethyl ether by reacting carbon oxide and hydrogen,
A catalyst for producing dimethyl ether, which is formed by a sol-gel method and contains copper element, gallium element and aluminum oxide. The sol-gel method is
Obtaining a hydrolyzable aluminum compound dispersion;
Hydrolyzing the hydrolyzable aluminum compound in the dispersion to obtain a sol dispersion;
Adding an aqueous solution containing copper ions and gallium ions to the sol-like dispersion to obtain a metal ion-containing dispersion;
Distilling off the solvent of the metal ion-containing dispersion to obtain a gel;
Baking the gel;
The catalyst for producing dimethyl ether according to claim 1, comprising:   The catalyst for dimethyl ether production according to claim 1 or 2, further comprising one or more metal elements selected from the group consisting of yttrium, zirconium, cerium, zinc, lanthanium, manganese and iron.   A substrate-supported catalyst for producing dimethyl ether, wherein the catalyst for producing dimethyl ether according to any one of claims 1 to 3 is supported on a substrate. The substrate-supported catalyst for producing dimethyl ether according to claim 4, wherein the substrate is a substrate selected from a metal material and an oxide material .   Production of dimethyl ether in which carbon oxide and hydrogen are reacted in the presence of the catalyst for producing dimethyl ether according to any one of claims 1 to 3 or the substrate-supported catalyst for producing dimethyl ether according to claim 4 or 5. Method.

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