JP2009034654A - Hydrogenation catalyst, method of manufacturing the same, and method for producing methane gas using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst to be used for the reaction of producing methane by reaction of hydrogen with carbon dioxide, carbon monoxide, or their gas mixture, wherein the catalyst has high activity, improved durability, and is free from a defect, that is, deterioration of capability due to wear even if it is used for a fluidized-bed reactor; and to provide a method for producing the catalyst. <P>SOLUTION: The catalyst is obtained by forming a coating of zirconium oxide, preferably an oxide mixture of zirconium oxide and an oxide of at least one metal of cerium, lanthanum, and barium, on the surface of at least one metal powder of iron-group transition elements (Ni, Fe, Co). The ratio of the zirconium oxide or the oxide mixture to the iron-group elements is adjusted to be 1 to 44% by mole to the total of both. When using the oxide mixture, the ratio of the oxide of metals other than the zirconium in the mixture is adjusted to be 15.5 to 50% by mole in the total of the oxide and zirconium oxide. The catalyst may be a granular catalyst by using a binder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a catalyst for producing methane gas from carbon monoxide gas, carbon dioxide gas or a mixed gas thereof and hydrogen gas, and a production method thereof. The invention also relates to a process for producing methane gas using the catalyst.

The treatment of carbon dioxide emitted with the combustion of fossil fuels is an urgent issue as a cause of global warming. On the other hand, attempts have been made to increase calorie by converting low-calorie gas mainly composed of carbon dioxide, carbon monoxide and hydrogen obtained by gasification of woody biomass and coal into methane gas. Is expected to be used for carbon dioxide treatment.

So far, Raney nickel catalysts or hydrogenation catalysts in which nickel is supported on a support such as alumina or silica have been used as catalysts for the reaction of hydrogenating a gas mixture of carbon dioxide and carbon monoxide and converting it to methane gas. It is known. Although these catalysts are inexpensive, since the reaction rate is low, it was necessary to carry out the reaction under a high pressure of 1 MPa or more.

As a catalyst for efficiently converting carbon dioxide into methane with hydrogen, an alloy in which a rare earth element, particularly Ce, is added to Ni as an active component has been proposed (Patent Document 1), but this catalyst also requires high pressure. . An alloy of Zr, Ti, Nb, Ta called “valve metal” such as an iron group metal such as Ni or Co is obtained in an amorphous state by a liquid quenching method as a typical means, and methanation of carbon dioxide. It has been disclosed that a practical reaction rate can be realized even at atmospheric pressure by using a catalyst (Patent Document 2). A catalyst formed by oxidation-reduction treatment using this amorphous alloy as a precursor has also been proposed (Patent Documents 3 and 4). This type of catalyst has a selectivity to methane close to 100% and makes it possible to obtain methane by a simple process that only removes the water produced by the reaction.

A catalyst combining nickel and tetragonal zirconia has also been proposed (Patent Document 5). Among them, yttrium (Y), lanthanide element (La, Ce, Pr, Nd, Sm, Gd, Td, Dy, Eu), or Mg or Ca is added in an amount of 15 mol% or less as a stabilizing element to tetragonal zirconia. A carrier having Ni and / or Co supported thereon gives a high reaction rate even at a reaction pressure of 1 atm.

Even if the catalyst is an oxidation-reduction treatment using the amorphous alloy as a precursor, or a catalyst composed of nickel and tetragonal zirconia, the active metal is deposited on the surface of the zirconia support and adheres. It is thought that it has taken the form. The problem with this type of catalyst is low durability due to the following reasons.

Since the generation of methane by the reaction of carbon dioxide and carbon monoxide with hydrogen is an exothermic reaction, the higher the reaction rate, the greater the amount of heat generated within a unit time and the higher the reaction space. When the temperature becomes high, the metal present on the surface of the carrier medium diffuses to cause aggregation. Thereby, the surface area of the active metal is reduced and the active sites are reduced. On the other hand, when the catalyst is used in a fluidized bed, the catalyst particles are vigorously brought into contact with each other inside the reactor, the surface is worn, and the active metal falls off. With this mechanism, known methanation catalysts have a short life.

As a form of a catalyst that prevents the active metal from diffusing and agglomerating and prevents the active metal from falling off due to wear, it has been proposed that the metal be in an oxide state and dispersed in the support (patent) Reference 6). That is, the catalyst is in a form in which nickel oxide and zirconium oxide are “dispersed and embedded uniformly in the form of fine particles” in an inorganic carrier such as silica.
JP-A-8-127544 JP 10-43594 A JP 10-263400 A JP 10-244158 A JP 2000-126596 A JP 2000-126596 A

An object of the present invention is to use an active component in a metal, that is, in a reduced state, in a catalyst used for a reaction for producing methane by reaction of carbon dioxide, carbon monoxide, or a mixed gas thereof with hydrogen, and durability of the catalyst. It is an object of the present invention to provide a catalyst and a method for producing the same which eliminate the problem of known catalysts having low properties and eliminate the disadvantage of deterioration in performance due to wear even when used in a fluidized bed reactor. It is also within the scope of the present invention to use this catalyst to provide a method for producing methane from biomass and other carbon dioxide, carbon monoxide or a mixed gas thereof and hydrogen.

The catalyst for catalytically reacting carbon monoxide gas, carbon dioxide gas or a mixed gas thereof and hydrogen gas of the present invention into methane gas has a basic form of an iron group transition element (Ni, Fe, Co) Hydrogenation in which the surface of at least one metal powder is provided with a coating of zirconium oxide, and the ratio of zirconium oxide to iron group elements is in the range of 1 to 35 mol% of the total amount of both. It is a catalyst.

In a preferred embodiment of the hydrogenation catalyst of the present invention, zirconium oxide and at least one metal of cerium, lanthanum, and barium are formed on the surface of at least one metal powder of an iron group transition element (Ni, Fe, Co). Oxidation of metals other than zirconium in the mixed oxide by providing a mixed oxide coating with the oxide, the ratio of the mixed oxide to the iron group transition element in the range of 1 to 35 mol% of the total amount of both This is a hydrogenation catalyst in which the ratio of the product is in the range of 15.5 to 50 mol% of the total amount with zirconium oxide.

The hydrogenation catalyst of the present invention has a structure in which an iron group transition metal as an active component is present in a reduced state and the periphery thereof is coated with zirconium oxide or a mixed oxide containing zirconium oxide. In addition to the high activity, the conventional catalyst having a structure in which an iron group transition metal is deposited around the support of zirconium oxide or a mixed oxide containing zirconium oxide is attached to the support due to the high temperature in use. The active metal is less likely to diffuse and aggregate, and the catalyst is unlikely to deteriorate. In particular, when used in a fluidized bed reactor, there is no problem if the active metal is removed due to wear of the catalyst powders, and there is no need to bother the decrease in activity caused by it. In a preferred embodiment provided with a mixed oxide coating of zirconium oxide and an oxide of at least one metal of cerium, lanthanum and barium, higher activity and stability of catalyst performance can be obtained.

The method for producing the basic form of the hydrogenation catalyst of the present invention comprises immersing a metal or compound particle of an iron group transition element in an aqueous solution of a salt of zirconium, heating the aqueous solution, and The compound of the zirconium oxide layer on the surface of the metal or compound particles is reduced to metal.

A method for producing a preferred embodiment of the hydrogenation catalyst of the present invention comprises mixing a metal or compound particle of an iron group transition element with a salt of zirconium and a salt of at least one metal of cerium, lanthanum and barium. After immersion in an aqueous solution and heating the aqueous solution to form a zirconium oxide layer on the surface of the metal or compound particles, the zirconium oxide layer is separated from the aqueous solution and heated in a reducing atmosphere to convert the iron group transition element compound. Consisting of reduction to metal. As described above, cerium, lanthanum, and barium serve to improve the oxygen storage capacity of zirconium oxide and increase the activity of the catalyst.

In manufacturing the catalyst, various modifications can be adopted. For example, as the iron group transition element, metal particles may be used as they are, compound particles such as oxides may be used, or a complex may be used. As the zirconium salt, in addition to a normal soluble salt, an organic metal form such as an alkoxide, a zirconium compound colloid, or the like can also be used.

Regardless of the basic aspect or the preferred aspect, the catalyst of the present invention is not limited to a powder form and can be formed in a granular form. The granular hydrogenation catalyst can be produced by mixing the hydrogenation catalyst powder produced by any of the above methods with a binder, granulating the powder into particles having an appropriate size and shape, and firing the particles. Usable binders such as silicate, titanate, aluminate and zirconate are suitable, and it is recommended to use one selected from these, but sugars and other organic substances, alumina sol Etc. can also be used. Needless to say, the particulate catalyst is suitable for use in a fixed bed reactor. The granulation can be carried out by any means such as spraying an aqueous solution or water suspension of the binder and granulating it with a granulator.

In the method for producing methane gas using the catalyst of the present invention and using a fluidized bed reactor, the above-mentioned powdered hydrogenation catalyst is heated to a raw material gas, that is, carbon monoxide gas, carbon dioxide. The raw material gas is brought into contact with a gas or a mixed gas of these gases and hydrogen gas in a fluidized bed state, methane gas is recovered from the reaction gas, and unreacted gas is recycled to the raw material gas.

In the method of producing methane gas using the catalyst of the present invention and using a fixed bed reactor, in the fixed bed reactor filled with the above-described particulate hydrogenation catalyst, heated raw material gas, that is, Carbon monoxide gas, carbon dioxide gas or a mixed gas thereof and hydrogen gas are contacted with a catalyst to perform methanation, methane gas is recovered from the reaction gas, and unreacted gas is circulated and used as a raw material gas.

Catalyst production example 1

10 g of nickel oxide NiO powder was added to an acidic (pH 3) aqueous solution of oxyzirconium salt (“Zircosol ZA” manufactured by Daiichi Rare Element Industries, containing 15 wt% as ZrO ₂ ), and ammonia water was added dropwise with stirring. Then, ZrO (OH) was deposited on the surface of the NiO powder to coat the surface. The NiO powder having this coating layer was filtered off, dried, heated in air, and then heated to 500 ° C. for 5 hours in a hydrogen stream of 1 atm to reduce Ni. The composition of the obtained powder catalyst at _{molar%, Ni: 74%, ZrO} 2: was 26%.

Catalyst production example 2

In the same manner as in Production Example 1, 10 g of nickel oxide NiO powder was charged into an acidic (pH 3) colloidal aqueous solution of zirconium (“Zirconia sol ZSL-10A” manufactured by Daiichi Rare Element Industries, containing 10 wt% as ZrO ₂ ). Aqueous ammonia was added dropwise with stirring to precipitate ZrO (OH) + Ce (OH) ₄ on the surface of the NiO powder to coat the surface. The NiO powder having this coating layer was filtered off, dried, heated in air, and then heated to 500 ° C. for 5 hours in a hydrogen stream of 1 atm to reduce Ni. The composition of this powder catalyst was mol%, Ni: 58%, and ZrO ₂ : 42%.

Catalyst production example 3

Prepare a solution obtained by adding 20 g of cerium nitrate to an acidic (pH 3) aqueous solution of the same oxyzirconium salt used in Catalyst Production Example 1, add 10 g of nickel oxide NiO powder, and stir in the same manner as in Production Example 1. Water was dropped to deposit ZrO (OH) + Ce (OH) ₄ on the surface of the NiO powder to coat the surface. The NiO powder having this coating layer was filtered off, dried, heated in air, and then heated to 500 ° C. for 5 hours in a hydrogen stream of 1 atm to reduce Ni. The composition of this powder catalyst was mol%, Ni: 69%, Zr—Ce mixed oxide: 31%, and CeO ₂ in the mixed oxide: 40%.

Catalyst production example 4

The powdered catalyst produced in Catalyst Production Example 1 is sprayed with an aqueous solution of sodium silicate as a binder, granulated by the tumbling granulation method, dried, and then calcined in the atmosphere at 500 ° C. for 4 hours, A hydrogenation catalyst was obtained. This granular catalyst was spherical with an average particle diameter of 5 mm.

Example reaction

A reaction tube having an inner diameter of 100 mm provided with a gas heating layer at the bottom was filled with 50 g of the granular hydrogenation catalyst produced in Catalyst Production Example 4. As a raw material gas, a composition simulating biogas, that is, a mixed gas composed of 20% by volume, carbon monoxide 20%, carbon dioxide 50%, and hydrogen 60% is introduced into the reaction tube from the lower part at a flow rate of 1 L / min. Supplied with. The source gas was heated to 275 ° C. and passed through the catalyst bed. The reaction gas exiting the reaction tube outlet was analyzed by gas chromatography to obtain the following result (volume%).
_{CO: 1%, CO 2:} 65%, H 2: 2%, CH 4: 32%.

The above methanation operation was carried out continuously, and the composition of the reaction gas was examined every predetermined time. At the beginning of the reaction, the conversion was 99%, and the catalytic activity remained unchanged after 168 hours.

Claims (7)

A catalyst for catalytically reacting carbon monoxide gas, carbon dioxide gas or a mixed gas thereof with hydrogen gas to form methane gas, which is at least one of iron group transition elements (Ni, Fe, Co) A hydrogenation catalyst in which a surface of a metal powder is provided with a coating of zirconium oxide, and the ratio of zirconium oxide to iron group elements is in the range of 1 to 35 mol% of the total amount of both. A catalyst for catalytically reacting carbon monoxide gas, carbon dioxide gas or a mixed gas thereof with hydrogen gas to form methane gas, which is at least one of iron group transition elements (Ni, Fe, Co) The surface of the metal particles is coated with a mixed oxide of zirconium oxide and an oxide of at least one metal of cerium, lanthanum and barium, and the ratio of the mixed oxide to the iron group transition element is The hydrogenation catalyst which made it the range of 1-444 mol% of total amount, and made the ratio of the oxide of metals other than zirconium in mixed oxide the range of 15.5-50 mol% of the total amount with a zirconium oxide. A method for producing a hydrogenation catalyst according to claim 1, wherein particles of iron group transition element metal or compound are immersed in an aqueous solution of a salt of zirconium, and the aqueous solution is heated to produce a metal of iron group transition element. Alternatively, a production method comprising forming a zirconium oxide layer on the surface of the compound particles, separating the solution from an aqueous solution, and heating in a reducing atmosphere to reduce the iron group transition element compound to a metal. 3. A method for producing a hydrogenation catalyst according to claim 2, wherein particles of iron group transition element metal or compound are mixed with a salt of zirconium and a salt of at least one metal of cerium, lanthanum and barium. Immerse in an aqueous solution and heat the aqueous solution to form a zirconium oxide layer on the surface of the iron group transition element metal or compound particles, then separate from the aqueous solution and heat in a reducing atmosphere to heat the iron group transition A process comprising reducing an elemental compound to a metal. A method for producing a granular hydrogenation catalyst, comprising adding a binder to the hydrogenation catalyst powder produced by the method of claim 3 or 4 and calcining the granulated product. A method for producing methane gas from carbon monoxide gas, carbon dioxide gas or a mixed gas thereof and hydrogen gas, wherein the powdered hydrogenation catalyst according to claim 1 or 2 is in a fluidized bed state by a heated raw material gas. A manufacturing method comprising bringing a raw material gas into contact with the product, recovering methane gas from the reaction gas, and circulating the unreacted gas into the raw material gas. A method for producing methane gas from carbon monoxide gas, carbon dioxide gas or a mixed gas thereof and hydrogen gas, wherein the raw material gas is packed with a granular hydrogenation catalyst produced by the method of claim 5. A production method comprising contacting a catalyst with a catalyst in a vessel, recovering methane gas from a reaction gas, and recycling unreacted gas as a raw material gas.