JPH06279004A - Production of synthetic gas - Google Patents

Abstract

PURPOSE:To provide a process for converting carbon dioxide which is a main causal substance for global warming into industrially useful carbon monoxide and hydrogen by using methane as a reducing agent. CONSTITUTION:Carbon monoxide and hydrogen are produced by contacting a gas containing carbon dioxide and methane with a catalyst. The catalyst to be used in the above process is produced by supporting at least one kind of oxide selected from calcium oxide and lanthanum oxide on a heat-resistant oxide and supporting a ruthenium compound on the obtained carrier.

Description

Detailed Description of the Invention

[0001]

The present invention relates to industrially useful carbon monoxide and hydrogen (hereinafter abbreviated as syngas) for carbon dioxide, which is a major causative substance of global warming using methane as a reducing agent. On how to convert to.

[0002]

2. Description of the Related Art As carbon dioxide is a major causative agent of global warming, it is urgently required to reduce and effectively use carbon dioxide. In recent years, carbon dioxide chemical conversion methods have been widely used (electric reduction method, photosynthesis method). Method, catalytic hydrogen reduction method, etc.).

[0003] Among them, there are few reports of converting carbon dioxide into a synthesis gas useful as a raw material when synthesizing various organic compounds by using methane as a reducing agent, and alumina and silica-supported noble metals or Group VIII transition metal catalysts are used. The contact method used (React. Kinet. Catal., 24
(3-4), 253 (1984), 68th Catalytic Discussion Group (A) Proceedings, 3H327 (1991) and 70th Group Catalysis Discussion Group (A) Proceedings, 3F420 (1992)). .

In particular, it is described that a nickel catalyst belonging to a Group VIII transition metal supported on alumina and a noble metal rhodium or ruthenium catalyst are highly active in the initial stage of the reaction.

However, in the reaction for a longer time, the nickel catalyst supported on alumina has a large amount of carbon exudation on the surface of the catalyst, and the activity decreases in a short time.

On the other hand, the rhodium and ruthenium catalysts supported on alumina are superior in terms of catalyst life as a result of less carbon deposition as compared with nickel catalysts. However, comparing rhodium catalysts and ruthenium catalysts supported on alumina, , Ruthenium catalyst has the same activity as rhodium catalyst, but is inferior in catalyst life (Ap
plied Catalysis, 61 (199
0)).

[0007]

However, since the rhodium catalyst is expensive and economically disadvantageous, a less expensive ruthenium catalyst is used and a catalyst having activity and catalyst life equivalent to that of the rhodium catalyst is developed. Is desired.

[0008]

Means for Solving the Problems As a result of earnest studies on a ruthenium catalyst, the present inventors have found that a support having at least one oxide of calcium oxide and lanthanum oxide as a heat-resistant oxide is used. The present invention was completed by discovering that the stable activity was exhibited by.

That is, according to the present invention, when a gas containing carbon dioxide and methane is brought into contact with a catalyst to produce carbon monoxide and hydrogen, as a catalyst, at least one of calcium oxide and lanthanum oxide is used as a heat-resistant oxide. A method for producing a synthesis gas is characterized in that a catalyst prepared by further supporting ruthenium on the carrier supporting the above oxide is used. Hereinafter, the present invention will be described in detail.

One of the features of the present invention is to use a carrier in which at least one oxide of calcium oxide and lanthanum oxide is supported on a heat-resistant oxide.

The heat-resistant oxide is aluminum oxide having α-, δ-, θ-, and γ-type and a mixed crystal phase thereof, and in particular, γ-type aluminum oxide is air-calcined at 700 to 1100 ° C. and 30 to 150 m ² / Those having a surface area of g are preferable from the viewpoint of improving the activity and life of the catalyst. A carrier in which heat-resistant oxides carry calcium oxide and lanthanum oxide are
It can be obtained by drying and firing after preparation by an impregnation method in which each aqueous solution of metal salt is immersed. When impregnating in the impregnation method,
Each metal salt may be dipped at the same time, or the calcium metal salt may be dipped and fired first, and then the lanthanum metal salt may be dipped or the lanthanum metal salt may be dipped and fired first, and then the calcium metal salt may be dipped. I don't care.

The calcium metal salts include calcium carbonate, calcium acetate, calcium chloride, calcium nitrate, calcium oxalate, calcium sulfate, monobasic calcium phosphate, dibasic calcium phosphate and calcium formate, and the lanthanum metal salts include lanthanum acetate. , Lanthanum carbonate, lanthanum chloride, lanthanum nitrate, lanthanum oxalate and the like. More preferably, nitrates, acetates, and oxalates that are easily decomposed by heating are preferably used.

In the above method, the firing temperature is usually 300 to 1100 ° C. and air firing is performed. More preferably, firing is performed at 700 to 1000 ° C.

The total concentration of calcium oxide and lanthanum oxide in the carrier in the catalyst used in the present invention is 1 to 60% by weight, more preferably 5 to 40% by weight. The mixing ratio of calcium oxide and lanthanum oxide is not particularly limited.

The carrier may carry alkali metal oxides such as sodium oxide and potassium oxide and alkaline earth metal oxides such as magnesium oxide and strontium oxide.

The ruthenium compound supported on the carrier in the catalyst used in the present invention is 0.
It is from 01 to 10% by weight, more preferably from 0.1 to 5% by weight. If the ruthenium content is less than 0.01% by weight, a sufficient carbon dioxide conversion rate may not be obtained.
Even if it exceeds 0% by weight, the expected improvement in conversion is not recognized.

The catalyst for supporting ruthenium is prepared by, for example, an ordinary impregnation method using a ruthenium salt, followed by activation treatment, and more preferably alcohols such as methanol and ethanol. Also, it is preferable to adjust by immersing in an organic solvent such as acetone.

The ruthenium salt used in the preparation of this catalyst is
Although there is no particular limitation, it is preferable to use a metal salt that is soluble in alcohol such as ruthenium acetylacetonato, ruthenium carbonyl, and ruthenium chloride in consideration of the activity and life of the catalyst.

The catalyst activation treatment means calcination with air or the like and reduction with hydrogen, hydrogen sulfide or the like. 300-1000 ° C to obtain sufficient carbon dioxide conversion
It is preferable to carry out the reduction treatment.

The catalyst may be molded or used as it is, and may be molded into a desired size according to the reaction method.

The amount of methane in the present invention can be defined as the molar ratio of methane to carbon dioxide.
Specifically, the ratio of methane to carbon dioxide is 0.05 to 25
And 0.1 to 20 is preferable. If the ratio of methane to carbon dioxide is less than 0.05, the amount of carbon dioxide to be recycled increases, while if the ratio of methane to carbon dioxide exceeds 25, a sufficient carbon monoxide generation rate cannot be obtained, which is uneconomical. Also, carbon deposition is likely to occur on the catalyst, resulting in a decrease in activity.

In the present invention, it is preferable to add nitrogen, air or steam as a diluent gas to the system from the viewpoint of catalyst life.

The reaction temperature in the present invention is 300 to 100.
0 ° C is sufficient. More preferably, it is 400-950 degreeC.
If the reaction temperature is lower than 300 ° C., a sufficient conversion rate of carbon dioxide cannot be obtained, and if it exceeds 1000 ° C., the activity may decrease due to the sintering of the catalyst.

The reaction pressure is not particularly limited, and the reaction may be carried out at atmospheric pressure to 20 atm, preferably atmospheric pressure to 10 atm.

The raw material supply rate to the catalyst can be defined by the raw material supply rate (SV) per unit catalyst volume. In the method of the present invention, the SV is 500 to 10,000.
It is 0 / h. If the SV is less than 500 / h, the carbon monoxide generation rate is low, and if the SV is more than 100,000 / h, the conversion rate of the raw material is lowered, which may be uneconomical.

The reaction method is not particularly limited as long as the catalyst and the raw materials can be efficiently contacted, and the reaction can be carried out in a fixed bed, a fluidized bed or a moving bed, for example.

[0027]

EXAMPLES The present invention will be described below with reference to examples.
The invention is not limited by these examples.

Example 1 Spherical γ-type alumina having a diameter of 3 mm (KHA-2, Sumitomo Chemical Co., Ltd.)
4, specific surface area 172m ^{2 /} g) 10.2g at 1000 ℃
And heat treated for 6 hours. 20.0 g of the aluminum oxide (specific surface area 61 m ² / g) was added to a solution of 4.65 g of lanthanum nitrate hexahydrate dissolved in 20 cc of ion-exchanged water and immersed for 3 hours. Then, after evaporating to dryness in a hot water bath at 60 ° C., air calcination was performed at 800 ° C. for 2 hours to obtain a carrier containing 8% by weight of lanthanum oxide. The carrier 7.0 g 0.2
It was dipped in 8 g of an ethanol solution containing a wt% ruthenium chloride for 3 hours and dried under reduced pressure at 250 mmHg / 50 ° C. After that, reduction was carried out at 700 ° C. for 2 hours in a 10% hydrogen flow, and then, to 0.
A 1 wt% ruthenium catalyst was used.

1.5 g of this catalyst was added to SUS having an inner diameter of 16 mm.
Fill the 310s reaction tube, keep the reaction temperature at 700 ℃,
Where the carbon dioxide: methane: nitrogen molar ratio is 1: 1: 3.
The mixed gas to be supplied was supplied at 400 cc / min (SV
= 12000h- ¹ ). The outlet gas was fractionated by gas chromatography, and the yield of carbon monoxide and the degree of conversion reduction were calculated by the following formulas. The results are shown in Table 1.

CO yield (%) = mol number of outlet CO / (mol number of fed CO ₂ + mol number of fed CH ₄ ) × 100 conversion degree reduction rate (%) = conversion rate after 20 hours-initial stage of reaction Conversion Example 2 Aluminum oxide heat-treated in Example 1 (specific surface area 6
1 m ^{2 /} g) 23.1 g of calcium nitrate tetrahydrate 8.
47 g was added to a solution prepared by dissolving 23 cc of ion-exchanged water and immersed for 3 hours. After that, it was evaporated to dryness in a hot water bath at 60 ° C. and then air-baked at 800 ° C. for 2 hours to obtain a carrier containing 8% by weight of calcium oxide. The same operation as in Example 1 was carried out to obtain a 0.1 wt% ruthenium catalyst, and then the reaction was carried out under the same reaction conditions as in Example 1. The results are shown in Table 1.

Example 3 Aluminum oxide heat-treated in Example 1 (specific surface area 6
1 m ^{2 /} g) 20.0 g of calcium nitrate tetrahydrate 1
6.0 g was added to a solution prepared by dissolving 23 cc of ion-exchanged water and immersed for 3 hours. After that, it was evaporated to dryness in a hot water bath at 60 ° C. and then air-baked at 800 ° C. for 2 hours to obtain a carrier containing 16% by weight of calcium oxide. A 0.1 wt% ruthenium catalyst was obtained by the same procedure as in Example 1, and then reacted under the same reaction conditions as in Example 1. The results are shown in Table 1.

Example 4 Aluminum oxide heat treated in Example 1 (specific surface area 6
1 m ^{2 /} g) 20.0 g of lanthanum nitrate hexahydrate 2.9
g was added to a solution prepared by dissolving 23 cc of ion-exchanged water and immersed for 3 hours. Then, after evaporating to dryness in a hot water bath at 60 ° C., air calcination was performed at 800 ° C. for 2 hours to obtain a carrier containing 5% by weight of lanthanum oxide. By the same operation as in Example 1, 0.
A 1 wt% ruthenium catalyst was obtained and then reacted under the same reaction conditions as in Example 1. The results are shown in Table 1.

Example 5 The aluminum oxide heat-treated in Example 1 (specific surface area 6
1 m ^{2 /} g) 20.0 g of lanthanum nitrate hexahydrate 3.3
g, calcium nitrate tetrahydrate 8.9 g, ion-exchanged water 2
It was added to a solution dissolved in 3 cc and immersed for 3 hours. Then, after evaporating to dryness in a hot water bath at 60 ° C., it was air-baked at 800 ° C. for 2 hours to obtain a carrier containing 4.9 wt% lanthanum oxide and 8.3 wt% calcium oxide. The same operation as in Example 1 was carried out to obtain a 0.1% by weight ruthenium catalyst, and then the reaction was carried out under the same reaction conditions as in Example 1. The results are shown in Table 1.
Shown in.

Example 6 Aluminum oxide heat treated in Example 1 (specific surface area 6
1 m ^{2 /} g) 20.0 g of lanthanum nitrate hexahydrate 8.0
g, calcium nitrate tetrahydrate 4.2 g, ion-exchanged water 2
It was added to a solution dissolved in 3 cc and immersed for 3 hours. Then, after evaporating to dryness in a water bath at 60 ° C., the mixture was air-baked at 800 ° C. for 2 hours to obtain a carrier containing 12.5 wt% lanthanum oxide and 4.2 wt% calcium oxide. A 0.1 wt% ruthenium catalyst was obtained by the same drying process as in Example 1, and then reacted under the same reaction conditions as in Example 1. The results are shown in Table 1.

Comparative Example 1 To a solution of 16.1 mg of rhodium chloride dissolved in 6 cc of absolute ethanol was added spherical alumina having a diameter of 3 mm (Sumitomo Chemical Co., surface area 172 m ^{2 /} g) 6.0, and the mixture was immersed for 3 hours. After drying under reduced pressure, hydrogen was reduced at 700 ° C. for 2 hours to prepare a 0.1 wt% rhodium catalyst.

1.5 g of this catalyst was reacted under the same reaction conditions as in Example 1. The results are shown in Table 1.

Comparative Example ² 5.07 g of spherical alumina having a diameter of 3 mm (Sumitomo Chemical, surface area 172 m ^{2 /} g) was added to a solution prepared by dissolving 12 mg of ruthenium chloride in 5 cc of absolute ethanol, and immersed for 3 hours.
The same activation treatment as in Comparative Example 1 was performed to prepare a 0.1% by weight ruthenium catalyst, and then the reaction was performed by the same reaction operation as in Example 1. The results are shown in Table 1.

Comparative Example 3 Spherical alumina having a diameter of 3 mm (Sumitomo Chemical, surface area 172 m ²
/ G) 10.0 g, rhodium chloride 25.6 mg in water 1
After being immersed in a solution of 0 cc for 3 hours, the mixture was evaporated to dryness in a water bath at 60 ° C., and subsequently hydrogen reduced at 700 ° C. for 2 hours to obtain a catalyst containing 0.1% rhodium by weight. . Using 1.5 g of this catalyst, the same reaction operation as in Example 1 was performed. The results are shown in Table 1.

[0039]

[Table 1]

Example 7 10 g of the carrier obtained in Example 1 was replaced with 123 g of ruthenium chloride.
Was added to a solution prepared by dissolving 10 cc of ethanol and immersed for 3 hours. After drying under reduced pressure, hydrogen reduction was performed at 700 ° C. for 2 hours to prepare a 0.5 wt% ruthenium catalyst.

1.5 g of this catalyst was reacted under the same reaction conditions as in Example 1. After reacting for 100 hours, the degree of conversion reduction was as shown in Table 2. In addition, FIG. 1 shows the change with time up to 200 hours after the start of the reaction.

Example 8 10 g of the carrier obtained in Example 2 was added to 123 m of ruthenium chloride.
g was added to a solution prepared by dissolving 10 cc of ethanol and immersed for 3 hours. After drying under reduced pressure, hydrogen reduction was performed at 700 ° C. for 2 hours to prepare a 0.5 wt% ruthenium catalyst.

1.5 g of this catalyst was reacted under the same reaction conditions as in Example 1.

After reacting for 100 hours, the degree of conversion reduction is shown in Table 2.

Comparative Example 4 Using 128 mg of rhodium chloride, a 0.5 wt% rhodium catalyst was obtained by the same catalyst preparation as in Comparative Example 3, and then reacted under the same reaction conditions as in Example 1. Table 2 shows the degree of conversion reduction.

[0046]

[Table 2]

[0047]

EFFECTS OF THE INVENTION By using methane as a reducing agent for carbon dioxide as in the present invention and using a specific catalyst, a synthesis gas can be stably produced without catalyst deterioration.

[Brief description of drawings]

FIG. 1 CO ₂ , C in the reaction in Example 7 of the present invention
H ₄ conversion is a diagram illustrating CO, H ₂ yield, the reaction tube inlet, the time course of the carbon balance and CO selectivity outlet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sotaro Nakamura 6-chome, 18th, Asahi-cho, Suzuka City, Mie Prefecture 19-18 (72) Inori Inori Hisada Okada, 6-8-20, Yokkaichi-shi, Mie Prefecture

Claims (2)

[Claims] 1. In producing carbon monoxide and hydrogen by bringing a gas containing carbon dioxide and methane into contact with a catalyst,
A method for producing a synthesis gas, which comprises using as a catalyst a catalyst in which a ruthenium compound is further supported on a carrier in which at least one oxide of calcium oxide and lanthanum oxide is supported on a heat-resistant oxide. 2. The method for producing synthesis gas according to claim 1, wherein the refractory oxide is γ-type aluminum oxide.