JPH0692322B2 - Process for producing ethane and ethylene by partial oxidation of methane - Google Patents

Description

The present invention relates to ethane, by partially oxidizing methane or a natural gas containing methane with oxygen or an oxygen-containing gas.
It relates to a method for producing ethylene.

[Conventional technology]

Methane is an abundant resource that exists abundantly in the world as the main component of natural gas, but due to its low reactivity, most of it is consumed as fuel, and as a raw material for the production of useful substances. The usage of is limited.

However, in 1982, when Keller and Virgin partially oxidized methane in the presence of oxygen using various metal oxides as catalysts, ethane and ethylene were produced, which was published in the United States, Journal of Catalysis. , No. 73
Vol. 9, pp. 9-19, researchers in the world have paid attention to this reaction called oxidative coupling reaction of methane, and many catalysts have been reported so far.

For example, in the Chemical Society of Japan, 1987, Chemistry Letters, pages 483-484, lanthanide-based metal oxides, especially samarium oxide, are used in this reaction.
It has been reported that the catalyst has excellent ethylene selectivity. However, the C ₂ yield is about 12 to 13%, which is still insufficient for industrialization. Further, since the catalyst is mainly a rare earth element, there is a drawback that the raw material cost is high.

Further, according to JP-A-61-225141, alkali and alkaline earth elements, elements of Group IIIb of the periodic table, elements of atomic numbers 24 to 30, lanthanide elements, silver, cadmium, lead and bismuth are used as catalysts. The use of chlorides, bromides and iodides, either alone or in mixtures, of methane is described as converting methane to ethane ethylene. According to this method, when these metal halides are used alone, a reduction in conversion frequently occurs, and therefore it is advantageous to use them on a carrier such as pumice, and it is also effective conversion. It is stated that it is advantageous for the halide catalyst to be melted at working temperature in order to obtain the rate (see page 3, lower left column, line 10 to lower left column, line 16).

However, even under such advantageous conditions, the conversion rate of methane is as low as 20% or less, and therefore the C ₂ yield is about 12% at maximum, which is not sufficient for industrialization. Further, in order to increase the conversion rate, the reaction temperature is raised above the melting temperature of the halide, but therefore, halide and halogen are recognized in the outflow gas mixture, which is accompanied by deactivation of the catalyst. In order to prevent this, there is a drawback that a continuous regeneration operation of the catalyst is necessary. Further, although the specification describes that a catalyst to which an alkali metal halide is added is used, there is no description about a concrete means or the addition of these, and the yield is increased. No such fact is recognized.

Further, according to JP-A-61-282323, cobalt; at least one metal selected from the group consisting of zirconium, zinc, niobium, indium, lead and bismuth;
Phosphorus; at least one Group 1A metal; oxygen and optionally a catalyst selected from the group consisting of halogen and sulfur are described as being capable of converting methane to ethane-ethylene. Despite the complexity of the system, the results of the examples show that the C ₂ yield is as low as about 10%, which is not sufficient for industrialization. It is noted in this publication that the addition of halogen, preferably chlorine, to the catalyst substantially improves the conversion of methane and the selectivity towards higher hydrocarbons, especially ethylene and ethane (Patent Publication No. Page 3, lower left column, lines 3 to 6 and Page 4, upper left column, lines 5 to 8
However, since the comparative example is not described, it is not possible to know the degree of substantial improvement.

Furthermore, the Chemical Society of Japan, published in 1988, Chemistry
According to Letters, p. 237, two types of metal A, B are incorporated into the crystal lattice, which is one of the complex metal oxides represented by the general formula ABO ₃ , which is a perovskite type oxide. Some have been reported to have catalytic activity in oxidative coupling reactions. However, the maximum C ₂ yield described in this publication is 11.7% of SrZrO ₃ , which is still insufficient in terms of yield for industrialization of ethane / ethylene production. It is desired to improve the yield in the system.

[Problems to be Solved by the Invention]

The present inventor has noticed that the complex metal oxides called perovskite type and ilmenite type are prepared by firing oxides or metal salts of two kinds of metals at a high temperature of 1000 ° C. or higher. However, since these are considered to be promising as heat-resistant and long-life catalysts, in the partial oxidation reaction of methane for the production of ethane / ethylene, perovskite-type and ilmenite-type metal oxides are alkali halides. The present invention has been accomplished by obtaining the knowledge that the conversion rate of methane and the yield of ethane / ethylene can be improved by using a catalyst supporting a metal as a catalyst.

The purpose of the present invention is to use a specific catalyst,
It is to provide a method for efficiently producing ethane / ethylene.

[Means for Solving the Problems]

The present invention is characterized by producing ethane and ethylene by partially oxidizing methane using a catalyst in which an alkali metal halide is supported on a composite metal oxide composed of two kinds of metals.

Hereinafter, the present invention will be described in detail.

The catalyst used in the present invention is a perovskite type or ilmenite type composite metal oxide carrying an alkali metal halide, which can be obtained as follows.

In general, if there is a difference in ionic valence between the metal A and the metal B that compose the composite metal oxide, the smaller one is A, and if the valence is the same, the larger ionic radius is A, and an ideal perovskite structure is obtained. In the complex metal oxide of, the following equation holds.

Where Ra, Rb: Ion radius of metal A and B (Å), R
o: is the ionic radius (Å) of oxygen. However, there is a practically allowable limit, and the coefficient t is entered as shown in the following equation. Usually, when the coefficient t is in the range of 0.8 to 1.0, the perovskite structure is adopted, and when t is 0.8 or less, the ilmenite structure is adopted. It is said that.

In the method of the present invention, it is necessary to select a metal whose t falls within the range of 0.75 to 1.0. Further, the sum of the oxidation numbers of the metal A and the metal B maintains the electrical neutrality of the crystal as a whole,
Since it must be +6, it is necessary to use two kinds of metal such that the metal A ion and the metal B ion have a combination of monovalent and pentavalent, divalent and tetravalent, or trivalent and trivalent, respectively. Is.

Two kinds of metal oxides or salts that meet these conditions are mixed in a beaver so that the atomic ratio becomes 1: 1 respectively, and this is 1000 to 1500 in air or helium flow.
C., preferably 1100 to 1300.degree. C. for 1 to 30 hours, preferably 5 to 10 hours. The calcined product obtained by this operation is cooled to room temperature, then pulverized and confirmed by powder X-ray diffraction analysis to have a perovskite structure or an ilmenite structure, and then a catalyst is prepared by the following operation.

That is, the obtained perovskite type or ilmenite type mixed metal oxide is suspended in an aqueous solution of an alkali metal halide, and the suspension is stirred at 100 to 200 ° C.
When heated to evaporate to dryness, the catalyst of the present invention is obtained. At this time, the alkali metal halide is the metal A constituting the perovskite type or ilmenite type composite metal oxide.
On the other hand, the alkali metal is supported in an atomic ratio of 0.05 to 1.0, preferably 0.1 to 0.3. As the alkali metal halide, any combination of a halogen element such as fluorine, chlorine, bromine and iodine and an alkali metal element such as lithium, sodium, potassium and rubidium can be used, but sodium fluoride and chloride are preferable. Any one selected from lithium, sodium chloride, potassium chloride, lithium bromide, sodium bromide and potassium bromide is used.

The catalyst thus obtained can be crushed and used as a powder of 100 mesh or more, but if necessary, after being molded by a compression molding machine, further crushed, preferably 16 to 32 mesh granules Can also be used as Also, these catalysts can be used on a carrier.

When the oxidative coupling reaction of methane is carried out using the above catalyst, methane and oxygen are converted into CH ₄ / O ₂ (molar ratio) =
1 to 10, preferably 1.5 to 3 are used as a mixture. At this time, an inert gas such as helium, argon or nitrogen may coexist as a diluent. These mixed gas,
It is supplied to a reaction tube filled with a catalyst, and the gas phase reaction is usually carried out at 600 to 1000 ° C, preferably 700 to 850 ° C. The reaction is usually
Although it is carried out under atmospheric pressure, it may be carried out under pressure if necessary.

Methane separated from natural gas is usually used for the reaction, but methane produced from coal or other substances may be used. Furthermore, natural gas itself containing methane can also be used as a raw material. Oxygen that has been cryogenicly separated from air or that has been concentrated by a gas separation membrane can be used. Furthermore, it is possible to use oxygen in the air as it is.

In the present invention, the catalyst can be used in any of a fixed bed, a moving bed and a fluidized bed.

〔Example〕

Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.

Example 1 (1) Preparation of catalyst 0.80 g of sodium carbonate (special grade reagent) and 2.00 g of niobium pentoxide (special grade reagent) (metal ion ratio 1: 1) were mixed with a pestle,
It was baked in an electric furnace at 1100 ° C. for 10 hours in the air. Fired product is X
It was confirmed by line diffraction measurement that it was NaNbO ₃ having a perovskite structure. Next, add 0.094 g of sodium chloride to 10
It was dissolved in ml of distilled water, 1 g of NaNbO ₃ was added, and the mixture was evaporated to dryness in a steam bath.

(2) Reaction test 1 g of the above catalyst was filled in an alumina reaction tube, and a mixed gas of CH ₄ : O ₂ : He = 10: 5: 85 was flowed at a flow rate of 100 ml / min at 780 ° C. and atmospheric pressure. It was made to react.

The reaction product obtained by the above operation was introduced into a gas chromatograph for analysis using a sampling loop attached to the outlet of the reaction tube. The analysis results are shown in Table 1. In Table 1, the methane conversion rate and the oxygen conversion rate are the ratios of reacted methane and oxygen, the selectivity is the generation ratio of reaction products CO, CO ₂ , C ₂ H ₄ , and C ₂ H ₆ , and , C ₂ yield represents the total yield of the desired products C ₂ H ₄ and C ₂ H ₆ .

Comparative Example 1 NaNbO ₃ was synthesized by the method described in Example 1 (1), 1 g of NaNbO ₃ was used as it was without supporting an alkali metal halide such as sodium chloride, and the reaction temperature was 800 ° C. A reaction test was conducted under the same conditions as in Example 1 except for the above.
The results are shown in Table 1.

Example 2 (1) Preparation of catalyst 30 g of metallic lead (special grade reagent) and titanium oxide (special grade reagent) 11.
58 g of the mixture was mixed with a dairy drum and baked under the same conditions as in Example 1. It was confirmed by X-ray diffraction measurement that the fired product was PbTiO ₃ having a perovskite structure. Then sodium chloride
2.34 g was dissolved in 100 ml of distilled water, 30 g of PbTiO ₃ was added, and the mixture was evaporated to dryness in a steam bath.

(2) Reaction test Using 1 g of the above catalyst, a mixed gas of CH ₄ : O ₂ : He = 10: 5: 85 was used for 10 times.
The reaction was carried out by flowing at a flow rate of 0 ml / min. The results are shown in Table 1.

Comparative Example 2 Example 2 (1) was synthesized PbTiO ₃ 1 g in the description of the method, this without carrying alkali metal halides such as sodium chloride, and seeded for Sonoma a PbTiO ₃ 1 g, the reaction temperature of 800 A reaction test was conducted under the same conditions as in Example 2 except that the temperature was changed to ° C. The results are shown in Table 1.

Example 3 Using 30 g of the catalyst prepared in Example 2 (1), CH ₄ : O ₂ : He =
A mixed gas of 10: 5: 85 was caused to flow and reacted at a flow rate of 135 ml / min. The results are shown in Table 1.

Example 4 (1) Preparation of catalyst 1 g of barium carbonate (special grade reagent) and titanium oxide (special grade reagent)
0.405 g was mixed with a dairy drum and baked under the same conditions as in Example 1. It was confirmed by X-ray diffraction measurement that the fired product was BaTiO ₃ having a perovskite structure. Next, 0.05 g of sodium chloride was dissolved in 10 ml of distilled water, 1 g of BaTiO ₃ was added, and the mixture was evaporated to dryness in a steam bath.

(2) Reaction test The reaction was carried out under the same conditions as in Example 1 except that the reaction temperature was 800 ° C. The results are shown in Table 1.

Example 5 (1) Preparation of catalyst KNbO ₃ was synthesized in the same manner as in Example 1 using 5.2 g of potassium carbonate (special grade reagent) and 10 g of niobium pentoxide (special grade reagent). 0.325 g of sodium chloride was added to KN in the same manner as in Example 1.
Supported on 5 g of bO ₃ .

(2) Reaction test Using 5 g of the above catalyst, a reaction test was conducted under the same conditions as in Example 1. The results are shown in Table 1.

Example 6 (1) Preparation of catalyst PbTiO ₃ was synthesized by the method described in Example 2 (1). next,
Dissolve 0.42g of lithium chloride in 30ml of distilled water and add PbTiO
In addition to the ₃ 3g and evaporated to dryness in a steam bath.

(2) Reaction test A reaction test was conducted under the same conditions as in Example 1 except that 3 g of the above catalyst was used and the reaction temperature was 700 ° C. The results are shown in Table 1.

Example 7 (1) Preparation of catalyst 0.67 g of lithium carbonate (special grade reagent) and 4 g of tantalum oxide (special grade reagent) were mixed with a pestle, and the mixture was heated to 1100 ° C. in an electric furnace in the air.
It was baked for 10 hours. It was confirmed by X-ray diffraction measurement that the fired product was LiTaO ₃ having an ilmenite structure. next,
Dissolve 0.05 g of sodium chloride in 10 ml of distilled water, and add LiTaO ₃ 1
g was added and evaporated to dryness in a steam bath.

(2) Reaction test A reaction test was conducted under the same conditions as in Example 1 except that 1 g of the above catalyst was used and the reaction temperature was 750 ° C. The results are shown in Table 1.

Example 8 (1) Preparation of catalyst PbTiO ₃ was synthesized by the method described in Example 2 (1). next,
0.246 g of potassium chloride is dissolved in 30 ml of distilled water, and PbTi is added to this.
O ₃ 5 g was added and the mixture was evaporated to dryness in a steam bath.

(2) Reaction test A reaction test was conducted under the same conditions as in Example 1 except that 1 g of the above catalyst was used and the reaction temperature was 800 ° C. The results are shown in Table 1.

Example 9 (1) Preparation of catalyst PbTiO ₃ was synthesized by the method described in Example 2 (1). next,
Dissolve 0.139 g of sodium fluoride in 30 ml of distilled water.
5 g of PbTiO ₃ was added and evaporated to dryness in a steam bath.

(2) Reaction test Using 1 g of the above catalyst, a reaction test was conducted under the same conditions as in Example 8. The results are shown in Table 1.

〔The invention's effect〕

According to the method of the present invention, the yield of C ₂ compound is high in the oxidative coupling reaction of methane, and its industrial value is great.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C07C 2/84 11/04 // C07B 61/00 300

Claims (3)

[Claims] 1. In the presence of a metal oxide as a catalyst, 600
In a method for producing ethane and ethylene by partially oxidizing methane or a natural gas containing methane with oxygen or an oxygen-containing gas at ˜1000 ° C., from two kinds of metals carrying an alkali metal halide as a catalyst. Which is a perovskite-type and ilmenite-type composite oxide, wherein the two kinds of metals constituting the composite oxide are 1A group, 2A group, and 4B group metal ions 1 and 4A.
Group 1 or any one of 5A group metal ions, (Assuming that the two metals that make up the complex oxide are A and B, in the formula, Ra and Rb are the ionic radii (Å) of the metals A and B, R
A method for producing ethane and ethylene by partial oxidation of methane, characterized in that a complex oxide which allows o an ionic radius (Å) of oxygen, but t is 0.75 to 1.0 is used. 2. A composite metal oxide has a perovskite _{structure, PbTiO 3, BaTiO 3, SrTiO} 3, NaNbO 3, KNbO 3, NaTaO 3
The method for producing ethane and ethylene by partial oxidation of methane according to claim 1, which is 3. The method for producing ethane and ethylene by partial oxidation of methane according to claim 1, wherein the complex metal oxide is LiNbO ₃ or LiTaO ₃ having an ilmenite type structure.