JPH05208801A - Method for producing synthetic gas from methane-containing gas and carbon dioxide-containing gas - Google Patents

Abstract

PURPOSE:To produce a synthetic gas containing CO and H2 by bringing a CH4- containing gas into contact with a CO2-containing gas in the presence of a catalyst having higher activity, simple in the catalyst preparing process, reduced in a carrying amount of an expensive active component metal and capable of imparting to the production a characteristic effectively converting CO2 into a usable synthetic gas. CONSTITUTION:A CH4-containing gas at 300-1200 deg.C is brought into contact with CO2-containing gas under the presence of a catalyst consisting of a high- purity ultrafine single crystal magnesium oxide and an element of group VII metal to produce the objective synthetic gas.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a synthesis gas containing carbon monoxide and hydrogen by contacting a gas containing methane and a gas containing carbon dioxide in the presence of a catalyst. In this specification, methane,
Carbon dioxide, carbon monoxide and hydrogen are replaced by CH ₄ ,
Sometimes referred to as CO ₂ , CO and H ₂ .

[0002]

2. Description of the Related Art The effective use of natural gas is drawing attention because of depletion of petroleum resources, measures against oil shocks, and diversification of raw materials for chemical industry. The recoverable reserves of natural gas are still comparable to petroleum, and new deposits have been discovered one after another, and the ultimate recoverable reserves are 2
It is estimated to be 100 to 250 trillion m ³ . In addition, this natural gas is widely distributed worldwide due to uneven distribution of petroleum resources. Nevertheless, the utilization rate of this natural gas is still low worldwide. Only two examples of practical use thereof are as they are or as liquefied natural gas as a fuel or as a starting material when steam-reforming to produce synthetic gas.

Under these circumstances, attempts have recently been made to directly oxidize methane, which is the main component of natural gas, to convert it into ethylene or ethane, or to oxidize it directly into methanol or formaldehyde. However, it has not reached the stage of industrialization yet.

Therefore, the only process in which natural gas is used as a raw material for the chemical industry and put into practical use is the production of synthetic gas by steam reforming as described above, and the synthetic gas is ammonia synthesis, methanol synthesis, or Fische.
It is used as a raw material for hydrocarbons, aldehydes, etc. by the r-Tropsch process. For example, methane is steam reformed on a nickel-based catalyst at 700 to 800 ° C. according to the reaction formula of CH ₄ + H ₂ O → CO + 3H ₂ . This reaction is an important source of syngas consisting of CO and H ₂ , but it is a very large endothermic reaction,
Furthermore, shift reaction CO + H ₂ O → C by CO ₂ + H ₂
It is always accompanied by generation of O ₂ , that is, a decrease in selectivity. Also, to prevent carbon deposition, it is necessary to supply much more than the stoichiometric amount of steam to the raw material side, and energy loss is large.

On the other hand, CO ₂ is extremely widely distributed in large amounts on the earth in various forms such as the atmosphere, water and minerals, and the amount can be said to be inexhaustible. The concentration of CO ₂ in the atmosphere is currently about 330 ppm, but it has been increasing year by year since continuous observation was started, and there are concerns about the effects on the climate and biosphere such as the “greenhouse effect”.

Under such a situation, as a countermeasure, promotion of energy saving and development of alternative energy C
In addition to reducing O ₂ emissions, CO ₂ recovery and immobilization by various physical, chemical or biological methods are being studied. So far, CO ₂ has been used as a raw material for the chemical industry, and examples of industrialization are urea synthesis from ammonia, synthesis of aromatic carboxylic acid by reaction with Kolbeschmitt's alkali salt of carboxylic acid, and reverse shift reaction by hydrogenation. And so on. Therefore, since the issue of global warming has been highlighted, attention has been focused on the immobilization of CO ₂ by catalytic technology. (1) Immobilization of CO ₂ by synthesizing a copolymer of CO ₂ and a comonomer, (2)
CO ₂ fixation by photocatalyst, (3) Electrochemical CO ₂
, (4) Methanation by catalytic hydrogenation of CO ₂ or methanol synthesis are promising.

However, CH ₄ + CO related to the present invention
There are very few reports on the reaction system of ₂ → 2CO + 2H ₂ and only a few examples. Saito et al. (Proceedings of the 52nd Catalytic Discussion Meeting (A) p46 (1983)) are CH ₄ / C
O ₂ = 1 and Ni / SiO ₂ under the reaction temperature of 700 ° C.
CH ₄ conversion when using a catalyst 64%, conversion to CO 75%, CH ₄ when using a Rh / Al ₂ O ₃ catalyst
It was reported that the conversion rate was 56% and the CH ₄ conversion rate to CO was 84%. The Uchijima et al. (66th catalyst debate Preprint p314 (1990), 67th catalyst debate Preprint p99 (1991)) _{is, CH 4 + 1 / 2O 2} → C
CH ₄ + CO ₂ → 2C to clarify the reaction mechanism of O + 2H ₂
The reaction system of O + 2H ₂ was investigated using a SiO ₂ -based catalyst, and the order of activity in the range of 300 to 800 ° C. was Ni.
/ Sio ₂ > Ru / SiO ₂ > Rh / SiO ₂ >> Pt /
SiO ₂ > Pd / SiO ₂ > Co / SiO ₂ , and the order is O.S. Tokunaga et al. (Fuel.990
(1989)) and is consistent with that in a similar study. Furthermore, according to their data, CH ₄ /
The temperature at which the conversion of CH ₄ by the Ni / SiO ₂ catalyst reaches 100% under the condition of CO ₂ = 1 and GHSV = 10000 h ⁻¹ is about 770 ° C.

This reaction system is intended to develop a CH ₄ -containing gas such as natural gas into a raw material for chemical industry, and CO
It is thought that this will attract attention in the future from the viewpoint of effective use of the _two gases, but as mentioned above, there are still few reports, and there is considerable room for improvement.

The present invention is an improvement over the prior art, and uses a catalyst having characteristics and effects such as higher activity, simple catalyst preparation process, and low amount of expensive active ingredient metal supported. , CH ₄ containing gas and CO ₂ containing gas are provided.

[0010]

Means for Solving the Problems As a result of intensive studies, the inventors of the present invention obtained a remarkable effect by using a catalyst prepared by a specific supporting method using high-purity ultrafine single crystal magnesium oxide as a carrier. The present invention has been completed and the present invention has been completed.

The manufacturing method of the present invention will be described in detail below.

The carrier raw material for preparing the catalyst useful in the present invention is B
ET specific surface area 5 to 170 m ² / g (specific surface area diameter 0.01
.About.0.2 .mu.m) and a purity of 99.9% or more of high-purity ultrafine powder single crystal magnesium oxide.
Magnesium oxide synthesized by the method disclosed in Japanese Patent Publication No. 9-9, that is, a method of oxidizing magnesium vapor and an oxygen-containing gas in a turbulent diffusion state is suitable. BET specific surface area 1
It is possible to produce magnesium oxide in excess of 70 m ² / g, and it is useful in the present invention, but the production cost is extremely high, and it is difficult to handle ordinary powders. Low. On the other hand, if the specific surface area is less than 5 m ² / g, the catalytic activity will decrease, which is not preferable. Therefore, the preferred range of high-purity ultrafine single crystal magnesium oxide is 5 to 170 m ^{2 of} BET specific surface area.
/ G.

The Group 8 metal element for catalyst preparation is preferably nickel (Ni) or ruthenium (R).
u), rhodium (Rh), palladium (Pd), and platinum (Pt), and one or more metal elements selected from them. As a precursor material thereof, acetylacetonato salt, nitrate, alkoxide, acetate , A carbonyl salt, etc., and any group 8 metal material that melts at a relatively low temperature, for example, 300 ° C. or lower, and thermally decomposes at 400 ° C. or lower to form a metal oxide can be applied. For example, acetylacetonato nickel has a melting point of 228 ° C. and a thermal decomposition temperature of about 300 ° C., and becomes nickel oxide (NiO) after thermal decomposition.

A method for preparing a catalyst using the above-mentioned high-purity ultrafine single crystal magnesium oxide and a Group 8 metal active component material is based on Japanese Patent Application No. 2-275371, and the method is shown below.

First, the above two kinds of raw materials, that is, the ultrafine powder single crystal carrier material and the active ingredient metal material, are mixed sufficiently well. At this time, if the mixing is sufficiently uniform, the mixing method is not limited, and a normal dry mixing method may be used. Next, the obtained mixed powder is molded using a normal dry molding machine. Any molding machine may be used as long as it is a dry molding machine, and for example, a dry compression molding machine such as a tableting machine or a briquetting machine is used. At that time, the shape of the molded body (tablet) is sphere, cylinder, ring, small grain,
Either may be used, and the size is usually within 20 mm, but both of them are determined from the viewpoint of use.

The tablets thus obtained were replaced with He, A
In an atmosphere of an inert gas such as r, N ₂ or the like, the active ingredient is once heated and held at a temperature higher than and close to the melting point of the active ingredient material to uniformly melt and disperse the active ingredient on the surface of the carrier material. Further, heat treatment is carried out in the same inert gas atmosphere at a temperature higher than the temperature at which the active ingredient material is thermally decomposed until it is completely decomposed.

For example, in the case of the ultrafine powder single crystal magnesium oxide (specific surface area 140 m ² / g) and acetylacetonato nickel, they are sufficiently dry-mixed and then molded in an inert gas at 230 to 250 ° C. It is heated and held for at least 10 minutes and at least 10 at a temperature of 300 to 400 ° C. in the same atmosphere gas.
Heat treatment for minutes.

The catalyst tablets thus obtained are optionally subjected to activation treatment in advance before use or immediately before use. For example, when the active ingredient material is a nickel metal salt, it is usually performed at 300 ° C. or higher in an H ₂ gas atmosphere immediately before use.

The supported amount of the Group 8 metal element is preferably 0.1 to 30 mol% as the metal after activation. If it is less than the lower limit, the supporting effect is small and the improvement of the catalytic activity is small. If the upper limit is exceeded, sintering tends to occur due to the metal, which rather reduces the activity and is economically disadvantageous.

The catalyst thus prepared is filled in an ordinary flow-type reactor, and a methane-containing gas such as natural gas and a CO ₂ -containing gas such as a cement factory burning exhaust gas are introduced to partially oxidize methane to carry out the reaction. Let it run continuously. The reaction temperature at this time is 300 to 1200 ° C., preferably 50.
0 to 900 ° C, reaction pressure is atmospheric pressure to 20 kgf / cm
² G, preferably atmospheric pressure to 5 kgf / cm ² G.

[0021]

EXAMPLES Examples will be shown below.

[0022]

[Examples 1 to 3] Acetylacetonato nickel was added to high-purity ultrafine single crystal magnesium oxide (BET specific surface area 140 m ² / g) manufactured by a gas phase oxidation method and thoroughly mixed in a dry system, and this was mixed with an ordinary compression molding machine. It was used to form a cylinder of φ5 × 5 mm. At this time, the amount of nickel supported was adjusted to 5 mol% as Ni. Then, this molded product was heated at 230 ° C. in a He gas stream to melt acetylacetonato nickel, and then 300 ° C. in the same atmosphere gas.
To heat-decompose the nickel precursor.

The thus obtained 5 mol% Ni /
Filling the microreactor with 0.1 g of MgO catalyst, H ₂
The reduction treatment was performed at 800 ° C. for 3 hours in an air stream. Continuing,
CH ₄ : CO ₂ : He = 15: 15: 70 vol% of a mixed gas of 100 ml / min was introduced into the microreactor, while the reaction temperature was 600 ° C. (Example 1) and 700 ° C.
The reaction was carried out at (Example 2) and 750 ° C. (Example 3). 2 ml of exhaust gas was sampled and the gas composition in the steady state was determined by gas chromatography, and CH ₄ conversion,
The CH ₄ conversion and CH ₄ conversion of CO to H ₂ was calculated. The results are shown in Table 1. At this time,
GHSV = 60,000 h ⁻¹ , total pressure = 1 atm.

[0024]

[Table 1]

[0025]

Examples 4 to 8 5 mol% Ni used in Examples 1 to 3
/ MgO catalyst (Example 4), 1 mol% Rh / MgO catalyst (Example 5) prepared in the same manner, 1 mol
% Ru / MgO catalyst (Example 6), 1 mol% Pd / M
An activity test was conducted in the same manner as in Examples 1 to 3 using the gO catalyst (Example 7) and the 1 mol% Pt / MgO catalyst (Example 8). The reaction conditions at this time are: reaction temperature = 740 ° C., G
HSV = 60,000 h ⁻¹ , total pressure = 1 atm. The results are shown in Table 2.

[0026]

[Table 2]

[0027]

INDUSTRIAL APPLICABILITY The present invention relates to CH ₄ containing gas and CO ₂
The present invention relates to a method for producing a synthesis gas containing CO and H ₂ by bringing a contained gas into contact with each other in the presence of a catalyst, and by producing according to the method of the present invention, the following effects are remarkably observed. That is, the activity is much higher. The catalyst preparation process is simple. The amount of expensive active ingredient metal supported is small. CO ₂ can be effectively utilized and converted into useful synthesis gas.

Claims (4)

[Claims] 1. In the presence of a catalyst comprising high-purity ultrafine single crystal magnesium oxide and a Group 8 metal element, a temperature of 300 to
A method for producing a synthesis gas containing carbon monoxide and hydrogen, which comprises contacting a methane-containing gas and a carbon dioxide-containing gas at 1200 ° C. 2. The Group 8 metal element is nickel (Ni), ruthenium (Ru), rhodium (Rh), or palladium (P).
The method for producing synthesis gas according to claim 1, wherein the synthetic gas is one or more metal elements selected from d) and platinum (Pt). 3. A 0.1 to 30 mol% Group 8 metal element
The method for producing synthesis gas according to claim 1, wherein the catalyst contained is used. 4. The catalyst is used to prepare a compact from high-purity ultrafine single-crystal magnesium oxide and a compound of a Group 8 metal element, and the compact is heated in an inert gas atmosphere to a temperature higher than the melting point of the compound. , And keep it at a temperature near the melting point,
The method for producing synthesis gas according to claim 1, which is prepared by heating at a temperature higher than the thermal decomposition temperature of the compound.