JP3199757B2 - Catalyst for producing methane-containing gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Background of the Invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for producing a methane-containing gas from methanol as a raw material.

[0002]

2. Description of the Related Art In recent years, LNG (liquefied natural gas) has been introduced as a raw material for city gas mainly in metropolitan areas. In the case of LNG, transportation at an extremely low temperature of -162 ° C.
Due to the need to store and technical and economical restrictions on handling, there are many problems with adoption in small and medium cities.
Therefore, there is an urgent need to complete the industrial technology for economically producing city gas containing methane obtained by converting the city gas raw material from LNG to methanol which is easy to handle and converting it.

[0003] The biggest problem in methanating methanol is that it is difficult to control the high heat of reaction generated by the methanation reaction. In particular, when methanation is performed using a multitubular reactor, a portion of the catalyst layer inlet side is always exposed to a high temperature of about 630 ° C. due to the high reaction heat (FIG. 1). This figure was measured under the conditions shown in Table 3.

[0004] The heat usually causes a decrease in the activity of the catalyst, and the exothermic peak is sequentially shifted to the exit side of the catalyst layer. Further, when a molded nickel / alumina-based catalyst effective for the methanation reaction is used, the heat load due to this heat generation and the progress of reduction of the catalyst significantly reduce the strength of the catalyst, and a part of the catalyst is powdered. . Eventually, the pressure loss of the reactor increases and operation becomes impossible. Therefore, the molded nickel / alumina-based catalyst used needs to have thermal durability in terms of both activity and catalyst strength.

[0005] Improvement of the catalyst activity leads to lowering of the temperature of the heat medium, and it is possible to lower the maximum temperature in the catalyst layer.
Therefore, it goes without saying that this works to extend the life of the catalyst. Furthermore, if the catalyst can maintain a high activity stably and can reduce the temperature of the heating medium to 350 ° C. or less, a hot oil can be used instead of the nitrate bath, which is problematic in industrial handling. Therefore, it is advantageous in terms of the process and has a great economic merit. Therefore, the conditions to be provided for the molded nickel / alumina-based catalyst having good thermal durability used for the methanation reaction of methanol are to maintain the low-temperature activity even after passing through the reaction history under a reducing atmosphere at a high temperature. While maintaining the methane yield,
It is a catalyst performance that maintains the catalyst strength required for an industrial catalyst for a long period of time and does not powder. This is also essential for long-term stable operation of an economical gasification plant.

The following catalysts have been proposed as catalysts for converting into a methane-containing gas by a gas phase catalytic reaction of methanol. (1) Nickel catalyst using activated aluminum and / or diatomaceous earth as carrier (JP-A-51-122102) (2) 25 to 50% by weight of nickel, at least 5% by weight of alumina molten cement, zirconium dioxide or Catalyst containing at least 5% by weight of titanium dioxide (JP-A-53-35702 and JP-A-54-111503) (3) On a support containing an oxide of an alkaline earth metal element or an oxide of a rare earth metal element For producing methane-containing gas using methanol or a mixture of methanol and water as a raw material, characterized in that nickel or a nickel oxide is supported on the catalyst (JP-A-60-209253, JP-A-60-209)
254).

However, as far as the present inventors know, as far as the present inventors know, the catalyst after a long-term high-temperature reaction has poor low-temperature activity and insufficient catalyst strength. Leaves a lot of trouble.

[Summary of the Invention] <Summary> As a result of many years of research, the present inventors have surprisingly found that a catalyst for producing methane-containing gas using methanol or methanol and water as raw materials has high activity and high activity. It has been found that a nickel / alumina-based catalyst having high thermal durability and maintaining both methane yield and catalyst strength stably for a long period of time can be obtained by taking a specific production mode.

That is, the molded nickel / alumina catalyst for producing a methane-containing gas by the gas-phase catalytic reaction of methanol according to the present invention comprises fine alumina hydrate and / or γ-alumina suspended in an alkaline solution. A composition comprising a solid product (a) and a calcium aluminate cement (b) by a mixing reaction of the solution obtained by the treatment and the nickel nitrate aqueous solution is subjected to a water-hardening condition of the calcium aluminate cement. It is obtained and molded.

DETAILED DESCRIPTION OF THE INVENTION <Preparation of Catalyst> Alumina hydrate and / or γ-alumina form the support of the catalyst according to the present invention. Therefore, its content is 10% of the total amount of the catalyst.
９０90% by weight, preferably 30-70% by weight.
Further, the particle size is 200 μm or less, preferably 50 μm, from the viewpoint of obtaining an effective contact effect with an alkaline solution.
Hereinafter, a fine powder having a center particle diameter of 10 to 30 μm is particularly preferable. The term "particle size" as used herein means the diameter of primary particles of alumina hydrate and / or γ-alumina. The “center particle size” is 3% of the total amount.
It means the particle size range occupying 0 wt% or more. Such a carrier can be prepared from a suitable alumina source compound by a suitable method, for example, a method described in “Handbook of Catalysts by Element”, pp. 33-39.

In the present invention, such a carrier is subjected to suspension treatment in an alkaline solution, for example, in a solution of a general base such as alkali carbonate or alkali bicarbonate which acts on the alumina surface. The suspension treatment time is at least 2 hours, usually 3 to 3 hours.
6 hours.

Next, the suspension composed of the alkali solution and the fine alumina is mixed with an aqueous solution of nickel nitrate to precipitate a basic salt containing a nickel component and an alumina component. After removing the alkaline component, it is dried and baked at 300 to 800 ° C. Calcium aluminate cement is added to the obtained oxide containing nickel oxide and alumina, followed by molding. The molded article can be hardened by subjecting the calcium aluminate cement to water hardening conditions in a conventional manner. For example, the catalyst according to the present invention can be obtained by accelerating the hydration reaction of calcium aluminate cement by water or steam treatment, followed by curing treatment, and then drying and firing to cure the molded product.

As the calcium aluminate cement, a commercially available calcium aluminate cement can be used. Such a calcium aluminate cement is, for example, 26.0% by weight of CaO as a chemical component, Al ₂ O
₃ 73.0 wt%, _SiO 2 0.3 wt%, _Fe 2 O
₃ 0.3 wt% and traces of Mg, Na, K, Cu, C
Those containing r, Mn, Ni, and Pb are typical.

The amount of the calcium aluminate cement is 3 to 20% by weight, preferably 5 to 10% by weight. If the amount is less than 3% by weight, no effect of improving the strength is observed, while if it exceeds 20% by weight, the initial activity is low and the rate of activity decrease due to a high degree of reaction increases. In the catalyst according to the present invention, a metal component other than nickel may be present for the purpose of a promoter or the like as long as the gist of the invention is not impaired. Furthermore, the "catalyst" according to the present invention is "molded". It goes without saying that the shape of the molded catalyst may be columnar, tablet, honeycomb, plate, or the like.

<Methanol Gas-Phase Contact Reaction> The catalyst obtained as described above is different from a reaction for obtaining a methane-containing gas using methanol or a mixture of methanol and water as a raw material, in a continuous high-temperature reaction even in a continuous high-temperature reaction. It has excellent performance for maintaining high methane yield and catalyst strength. In the case of producing methane from methanol-water, the following reaction formula shows that the theoretical molar yield of methane is, for example, 75 mol%.
It is. 4CH ₃ OH + H ₂ O → 3CH ₄ + CO ₂ + 3H ₂ O

EXPERIMENTAL EXAMPLE <Example 1> 1) Preparation of Catalyst Boehmite gel as alumina hydrate (central particle diameter: 20 to 20%) in an aqueous solution containing 1806 g of anhydrous Na ₂ CO ₃ (twice mole of nickel nitrate) 50 μ, water content: 23%) 434
g, and the suspension obtained by maintaining the suspension state for 3 hours by stirring is mixed and reacted with an aqueous solution containing 2277 g of Ni (NO ₃ ) ₂ .6H ₂ O to form a precipitate at 30 ° C. . The precipitate is removed, and the remaining alkali content is sufficiently removed by washing with pure water (the amount of alkali metal remaining in the catalyst is 0.1%).
Wt.% Or less), and dried at 120 ° C. for 15 hours.
For 3 hours. 30 g of calcium aluminate cement and a small amount of pure water are added to the calcined material, and the mixture is kneaded into a clay.
After drying at 20 ° C. for 10 hours to obtain granules of 10 to 15 mesh, tablet molding (1/4 inch in diameter × 1 / h in height)
8 inch column).

Next, the molded article is subjected to a humidification treatment (15 hours) by flowing steam (pressure: 1 kg / cm ² G or less, temperature: 60 ° C.) in a closed container (15 hours). 24
After standing for 3 hours, baking at 600 ° C. for 3 hours (heating rate:
600 ° C./15 hours) to complete the curing treatment, and a catalyst containing 3% by weight of calcium aluminate cement
1 was obtained. Similarly, catalysts having calcium aluminate cement contents of 5% by weight, 10% by weight and 20% by weight were prepared to obtain catalysts-2, 3, and 4. Each of these catalysts has a nickel loading of 50% by weight.

2) Activity evaluation These catalysts 1 to 4 were placed in a reactor (inner diameter: 11/2 inch /
(Length: 450 mm), reduced in a stream of hydrogen at 400 ° C. for 2 hours, and performed a continuous high-temperature reaction for 2,000 hours under the conditions shown in Table 1 except that the temperature of the heating medium in the reactor was 700 ° C. After that, an activity evaluation test was performed under the conditions shown in Table 1, and the results in Table 2 were obtained.

3) Evaluation of catalyst strength 6 liters of each of catalysts 1 to 4 were placed in a reactor (inner diameter: 11 / l).
(2 inches × length: 6 m), and reduced in a stream of hydrogen at 400 ° C. for 4 hours. Then, after the reaction was continuously performed for 200 hours under the conditions shown in Table 3, the catalyst surface layer was subjected to a stabilization treatment under a low partial pressure oxygen / nitrogen stream to extract the catalyst, and the exothermic peak temperature of 630 ° C. (FIG. 1) ) Of the catalyst was measured. The results are shown in Table 4 together with the measured values of the new catalyst.

The crushing strength is measured by applying pressure to the side surface (radial direction) of the cylindrical catalyst using a Kiya type hardness meter (model number 1600-D) and measuring the pressure at the time when the catalyst is crushed. went. The measurement was performed on 50 catalysts, and the average value was used as the measured value.

<Example-2> As a carrier, bayerite (central particle size: 80 to 130 µ, water content: 44%) 596
g γ-alumina (center particle size: 30 to 70μ, water content:
12%) except that 379 g was used.
Catalysts were prepared in the same manner as in Example 2 to obtain Catalysts 5 and 6. These catalysts were evaluated for activity and catalyst strength by the method of Example-1. The results are shown in Tables 2 and 4.

<Comparative Example> In the method of Example 1, boehmite gel was added to a precipitate after mixing, mixing, and washing of an aqueous solution of anhydrous Na ₂ CO _{3 and an} aqueous solution of nickel nitrate (after the addition). Except for the catalyst, catalysts were prepared by the method of Example 1 to obtain catalysts 7 and 8 having a cement content of 3% by weight and 10% by weight. Further, in the method of Example-2,
The addition of γ-alumina was performed on the precipitate after mixing, mixing, washing and firing of anhydrous Na ₂ CO ₃ aqueous solution and nickel nitrate aqueous solution (after addition, kneading with calcium aluminate cement), Catalysts were prepared by the method of Example 2 to obtain Catalysts 9 and 10 having a cement content of 5% by weight and 20% by weight. Example of Catalyst 7, 8, 9, 10
Activity evaluation and catalyst strength evaluation were performed by the method of 1. The results are shown in Tables 2 and 4.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

The catalyst according to the present invention, as described above,
It has high thermal durability when converting methanol to a methane-containing gas by a gas phase catalytic reaction, and stably maintains the activity and strength of the catalyst even when used for a long time under high temperature conditions.

The catalyst according to the present invention is obtained by previously reacting a solution obtained by suspending alumina hydrate and / or γ-alumina in an alkaline solution with an aqueous nickel nitrate solution.
The first feature is that a basic salt containing a nickel component and an alumina component, which is a precursor of the catalyst, is generated. This method makes it possible to maintain low temperature, high activity and high methane yield under high temperature conditions for a long period of time.

A second feature of the catalyst according to the present invention is that a nickel / alumina composition obtained from a basic salt containing a nickel component and an alumina component produced by the above-described production method can be specifically prepared by adding calcium aluminate cement. That is, the catalyst strength is improved. Even when the catalyst is used for a long time in a reducing atmosphere at a high temperature, the catalyst strength is industrially sufficient, and the ΔP of the reactor does not increase. In this way, a molded nickel / alumina catalyst for producing methane by a gas phase catalytic reaction of methanol, which has both high activity and high catalytic durability, has been found.

Although the reason for the effect of the present invention is not necessarily clear, the fine alumina hydrate and / or γ-alumina as a carrier are treated with an alkaline solution, so that the surface of the particles becomes compatible with the subsequent nickel nitrate. It is thought that they will be actively involved in the reaction. That is, it can be said that a part of the carrier can hold the nickel component in a tighter state. Having such a structure, the catalyst of the present invention not only has high temperature heat resistance from the active surface, but also has the effect of maximizing the material hardening characteristics of calcium aluminate cement. Presumed.

[Brief description of the drawings]

FIG. 1 shows the distribution of the temperature inside a catalyst layer of a multitubular reactor.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshihisa Watanabe 3-1, Chuo, Ami-cho, Inashiki-gun, Ibaraki Pref. 5-25-11, Notama, Minami-ku, City (56) References JP-A-53-35702 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01J 21/00-37/36 C07C 9/04

Claims (1)

(57) [Claims] A solid product (a) obtained by mixing and reacting a solution obtained by suspending fine alumina hydrate and / or γ-alumina in an alkaline solution and an aqueous nickel nitrate solution and calcium Production of a methane-containing gas by gas-phase catalytic reaction of methanol, obtained by subjecting a composition comprising aluminate cement (b) to the conditions of water hardening of calcium aluminate cement and being molded Nickel / alumina catalyst for