JPH0679179A - Tungsten sulfide catalyst for reducing carbon dioxide gas - Google Patents

Abstract

PURPOSE:To prepare a catalyst for reducing carbon dioxide gas for reducing the carbon dioxide gas selectively and economically under the mild conditions of low temperature and normal pressure for the purpose of solidifying carbon dioxide gas as a prime factor of global greenhouse effect at high speed and in large production amount. CONSTITUTION:A tungsten sulfide catalyst for reducing carbon dioxide gas composed of tungsten sulfide to which nickel and cobalt are added or tungsten sulfide is carried on a carrier of alumina, silica, active carbon, zeolite, active china clay, iron oxide, zirconia, titania, fee, yttrirrite, thoria, lanthania, neodymia or the like. Tungsten sulfide is an inexpensive substance, and is strong against acid and of good durability. The carbon dioxide gas is reacted with hydrogen and reduced effectively into carbon monoxide at low temperature, and the reaction is the gas phase reaction which can be carried out at high speed to reduce the large amount of carbon dioxide gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon dioxide reducing catalyst for reducing carbon dioxide to convert it into carbon monoxide and using it as a raw material or fuel for chemical products.

[0002]

2. Description of the Related Art In recent years, environmental pollution on a global scale has been widely highlighted as a problem that threatens the survival of humankind. Among them, the most difficult problem to address is global warming due to carbon dioxide. Unlike nitrogen oxides and sulfur oxides, which have been problematic so far, carbon dioxide is not toxic in itself, but it emits a huge amount of about 20 billion tons per year worldwide, and it is released into the atmosphere. With the increase of carbon dioxide concentration in the environment, climate change due to greenhouse effect will occur, and it is threatened that tens of millions of environmental refugees will occur. In order to prevent this, the suppression of carbon dioxide emissions through energy substitution and energy saving is being promoted as a policy, but since carbon dioxide emissions are closely related to economic and social development, the Suppression is an extremely difficult situation. Therefore, in order to prevent the global warming caused by carbon dioxide, the development of carbon dioxide reduction / immobilization technology is indispensable.

The carbon dioxide reduction / immobilization method by catalytic hydrogenation reaction in which carbon dioxide gas is reacted with hydrogen for reduction is compared with photochemical reaction method, electrochemical reaction method, polymer synthesis method, organic synthesis method and the like. The ability to reduce and immobilize carbon dioxide per unit time and unit area is large, and a large amount of carbon dioxide can be processed. In addition, existing Fischer-Tropsch hydrocarbon synthesis technology can be applied, and since it is a gas phase reaction, it also has the advantage of easy separation of products. Until now, a method using a noble metal catalyst such as ruthenium or rhodium has been studied as a reduction / immobilization method of carbon dioxide gas by a catalytic hydrogenation reaction (for example, F. Solymosi
and A. Erdohelyi, J. Mol. Catal., Vol.8, 471 (198
0)).

However, in this method, 1) the catalyst used is expensive, and it is easily poisoned by sulfur compounds such as hydrogen sulfide and sulfurous acid gas, and the catalytic activity is drastically reduced.
2) Carbon dioxide gas is reduced to methane in this reaction, but since this reaction is an exothermic reaction in which the energy of the product is lower than that of the raw material, the energy yield is poor. 3) The reaction does not proceed well unless the pressure is high. 4) Generally, the reaction is carried out at a high temperature, and since fossil fuel is used for obtaining the temperature, there is a drawback that carbon dioxide emission is not substantially suppressed.

Although tungsten sulfide is used as a hydrodesulfurization catalyst or a hydrogenation catalyst for ethylene-based hydrocarbons in some cases, it is not poisoned by sulfur compounds such as hydrogen sulfide and sulfurous acid gas, is non-toxic and strong against acid. It has the feature of being durable. Moreover, there is no need to use expensive precious metals. Tungsten sulfide is black and absorbs sunlight well. However, almost no studies have been reported so far using a tungsten sulfide catalyst for carbon dioxide reduction.

[0006]

In view of the above points, the present invention addresses global warming caused by carbon dioxide, is not poisoned by sulfur compounds, is durable, economical, and has low temperature and atmospheric pressure. An object of the present invention is to provide a tungsten sulfide catalyst for carbon dioxide gas reduction, which can selectively reduce carbon dioxide gas to carbon monoxide under mild conditions.

[0007]

The catalyst for carbon dioxide gas reduction of the present invention is a tungsten sulfide catalyst characterized by adding nickel or cobalt to tungsten sulfide, or a sulfide characterized by supporting it on a carrier. It is a tungsten catalyst. The catalyst of the present invention reacts carbon dioxide gas with hydrogen gas to efficiently reduce carbon monoxide.

The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, although tungsten sulfide alone has a low activity for reducing carbon dioxide gas, addition of nickel or cobalt to tungsten sulfide has an activity for reducing carbon dioxide gas. It was found that the activity was significantly improved, and by further supporting it on a carrier, the activity was dramatically improved.

Tungsten sulfide used in the present invention is
Tungsten sulfide such as tungsten disulfide and tungsten trisulfide, 1) heating a predetermined amount of a mixture of tungsten and sulfur in a nitrogen stream at 800 to 900 ° C. for 24 hours, 2) heating tungsten trioxide with potassium carbonate, React with sulfur, hydrogen sulfide, carbon disulfide, etc.,
3) heating tungsten hexachloride in a hydrogen sulfide stream,
4) A method of melting and electrolyzing a mixture of tungsten trioxide, borax, sodium sulfate, sodium fluoride, etc. 5) Heating tungsten trioxide in a hydrogen sulfide stream or a mixed gas stream of hydrogen sulfide and hydrogen. Is prepared,
6) Obtained by dissolving tungstic acid obtained by adding strong acid to tungstates such as scheelite and iron manganese heavies in ammonium water to convert it to ammonium tungstate, and saturating it with hydrogen sulfide and ammonium sulfide. Ammonium tetrathiotungstate, hydrogen,
What was prepared by heating and decomposing at a temperature of 400 to 700 ° C in a stream of nitrogen or an inert gas such as argon or helium, or 7) tungsten trisulfide was further inert to hydrogen, nitrogen, or argon or helium. Those prepared by heating and decomposing in a gas stream have particularly high catalytic activity.

The carrier used in the present invention includes alumina, silica, activated carbon, zeolite, activated clay, iron oxide,
Examples thereof include zirconia, titania, ferrite, yttria, thoria, lanthania, neodymia and mixtures thereof. It is preferable that these carriers have a large surface area such as porous and fine particles. Further, the alumina is most preferably γ-alumina.

The tungsten sulfide catalyst for carbon dioxide reduction of the present invention is an aqueous solution of ammonium tetrathiotungstate obtained by saturating an aqueous solution of ammonium tungstate with hydrogen sulfide or ammonium sulfide, an aqueous ammonia solution, nitric acid, hydrochloric acid or sulfuric acid. Nickel salt or cobalt salt is added to the acidic solution, or a carrier in the state of porous particles, fine particles, sol, etc. is added with stirring and dried, and then hydrogen, nitrogen, or an inert gas such as argon or helium is added. It is prepared by heating and decomposing in an active gas stream. In addition, tungsten sulfide such as tungsten disulfide or tungsten trisulfide, or tungsten sulfide supported on a carrier is converted into hydrogen,
It is also prepared by heating in an inert gas stream such as nitrogen or argon or helium for decomposition, and then adding to a nickel salt solution or cobalt salt solution and drying. The heating temperature at that time is preferably 400 ° C to 700 ° C. Further, it is also prepared by adding nickel or cobalt to tungsten sulfide or tungsten sulfide supported on a carrier and heating. The heating temperature at that time is preferably 600 ° C to 900 ° C.

Tungsten sulphide supported on a carrier is obtained by adding porous or fine particles to an aqueous solution of ammonium tungstate,
A carrier in the form of a sol is added with stirring, saturated with hydrogen sulfide or ammonium sulfide, neutralized with an acid such as hydrochloric acid or sulfuric acid, filtered, and then in a nitrogen or inert gas atmosphere at 100 to 150 ° C. It is obtained by heating and drying overnight at. In addition, ammonium tungstate ammonium sulphate solution or ammonia solution in the porous or fine particles,
It can also be obtained by adding a carrier such as a sol with stirring to dry it, heating it in an oxygen stream, and then heating it at 350 to 600 ° C. in a stream of hydrogen sulfide or a mixed gas of hydrogen and hydrogen sulfide. To be

The content of nickel or cobalt in the carbon dioxide reduction catalyst of the present invention is Ni / Mo or Co.
The atomic weight ratio of / Mo is preferably 0.0001 to 2. By adding nickel or cobalt to tungsten sulfide, the active sites and surface area of the catalyst are increased, and the catalytic activity for carbon dioxide reduction is significantly improved. However, when the content of nickel and cobalt in the catalyst becomes higher than that. The surface area of the catalyst is reduced and the catalytic activity is reduced. The amount of the catalyst of the present invention supported on the carrier is preferably 0.001 to 35% by weight.

By passing a gas containing carbon dioxide and hydrogen through the catalyst of the present invention thus obtained, carbon dioxide reacts with hydrogen on the catalyst and is converted into carbon monoxide with a selectivity of almost 100%. It At this time, the reaction gas may contain an inert gas such as argon or helium, a nitrogen gas, or hydrogen sulfide. Even if an inert gas or nitrogen is contained, the reaction is hardly affected, and when hydrogen sulfide is contained, the catalytic activity is improved. Further, the molar ratio of carbon dioxide gas / hydrogen in the reaction gas is preferably close to 1. Carbon monoxide, which is a reaction product, can be used as a fuel as it is, and recently, using the existing methanol production process from synthesis gas (carbon monoxide and hydrogen) and C1 chemical technology, it has recently been used as a fuel for automobiles. It can also be used by converting it into the raw material for methanol and chemical products that are being bathed. Since the reaction for converting carbon dioxide gas into carbon monoxide is an endothermic reaction, the energy yield is good, and carbon monoxide as a product has stored heat from a heat source such as solar energy or waste heat.

[0015]

EXAMPLES Among the examples of the present invention, particularly representative ones are shown below.

Example 1 Nickel nitrate hexahydrate (80 mol% with respect to ammonium tetrathiotungstate) in an aqueous ammonia solution of ammonium tetrathiotungstate and fine powder of titania as a carrier (with respect to ammonium tetrathiotungstate) (500% by weight) was added with stirring, vacuum-dried at room temperature, and then heated in a hydrogen stream at 450 ° C. for 1 hour. 1 g of the obtained catalyst was filled in a quartz U-shaped reaction tube having a diameter of 1 cm, and 30 ml of a mixed gas of carbon dioxide gas and hydrogen 1: 1 was added.
The reaction product was analyzed by using a gas chromatograph. As a result, 200
2% at ℃, 9% at 300 ℃, 20% at 400 ℃, 500
At 30 ° C., 31% of carbon dioxide had been converted to carbon monoxide. No reaction products other than carbon monoxide were found.

COMPARATIVE EXAMPLE 1 1 g of commercially available tungsten disulfide (WS2) was used to have a diameter of 1 cm.
In a U-shaped reaction tube made of quartz, and a mixed gas of carbon dioxide gas and hydrogen at a ratio of 1: 1 was circulated at a flow rate of 30 ml / min for reaction in the same manner as in Example 1, and the obtained reaction product was subjected to gas chromatography. It was analyzed using a graph. As a result, the conversion rate of carbon dioxide gas to carbon monoxide was 0% at 200 ° C, 0.2% at 300 ° C, 2% at 400 ° C, and 9% at 500 ° C.

Example 2 Cobalt nitrate hexahydrate (50 mol% relative to ammonium tetrathiotungstate) was added to an aqueous ammonia solution of ammonium tetrathiotungstate, and γ was used as a carrier.
-Alumina fine powder (400 wt% with respect to ammonium tetrathiotungstate) was added with stirring, vacuum dried at room temperature, and then heated in a hydrogen stream at 500 ° C for 50 minutes. Using 1 g of the obtained catalyst, a mixed gas of carbon dioxide gas and hydrogen 1: 1 was added in an amount of 30 ml / m in the same manner as in Example 1.
The reaction product was analyzed by a gas chromatograph by circulating the reaction product at a flow rate of in. As a result, 1.2% at 200 ° C, 7.5% at 300 ° C, 18% at 400 ° C, 5%
At 00 ° C, 29% of carbon dioxide was converted to carbon monoxide. No reaction products other than carbon monoxide were found.

Example 3 Ammonium tetrathiotungstate was heated in a hydrogen stream at 450 ° C. for 1 hour, and 1 g of the ammonium tetrathiotungstate was added to 5 ml of a 10% nickel nitrate hexahydrate aqueous solution. After stirring overnight, it was vacuum dried. The obtained catalyst 5
In the same manner as in Example 1, using 00 mg, a mixed gas of carbon dioxide gas, hydrogen, and hydrogen sulfide 5: 5: 1 was added at 30 ml / min.
The reaction product was analyzed by using a gas chromatograph. As a result, at 200.degree.
Carbon dioxide gas of 8%, 5% at 300 ° C., 12% at 400 ° C., and 20% at 500 ° C. was converted to carbon monoxide.

Example 4 Tungsten trisulfide supported on 90% by weight of activated carbon was heated in an argon gas stream at 400 ° C. for 1 hour and 20 minutes. 1 g of 10% aqueous solution of cobalt nitrate hexahydrate,
It was added to 7 ml and dried in a nitrogen stream with stirring overnight. Using 500 mg of the obtained catalyst, a mixed gas of carbon dioxide gas, hydrogen and argon 3: 3: 1 was caused to flow at a flow rate of 30 ml / min for reaction in the same manner as in Example 1, and the reaction product was subjected to gas chromatography. Used for analysis. As a result, 1% at 200 ° C., 5.5% at 300 ° C., 13% at 400 ° C., and 22% at 500 ° C. were converted to carbon monoxide.

Example 5 Tungsten trisulfide supported on 85 mol% iron sesquioxide was heated at 550 ° C. for 30 minutes in a helium gas stream. 1 g of the 20% aqueous solution of nickel nitrate hexahydrate,
It was added to 4 ml and dried with stirring in a nitrogen stream overnight. Using 500 mg of the obtained catalyst, a mixed gas of carbon dioxide gas, hydrogen and argon 1: 1: 1 was circulated at a flow rate of 10 ml / min for reaction in the same manner as in Example 1, and the reaction product was subjected to gas chromatography. Used for analysis. As a result, 2.5% at 200 ° C., 8% at 300 ° C., 21% at 400 ° C., and 31% at 500 ° C. converted carbon dioxide into carbon monoxide.

Example 6 Nickel nitrate hexahydrate (110 mol% with respect to ammonium tetrathiotungstate) in a nitric acid aqueous solution of ammonium tetrathiotungstate and zeolite pellets as a carrier (800 with respect to ammonium tetrathiotungstate) (% By weight) was added with stirring, vacuum dried at room temperature, and then heated in a nitrogen stream at 500 ° C. for 1 hour. Using 1 g of the obtained catalyst, in the same manner as in Example 1, 30 ml of a mixed gas of carbon dioxide gas, hydrogen and nitrogen 1: 1: 1.
The reaction product was analyzed by using a gas chromatograph. As a result, 200
2% at ℃, 6% at 300 ℃, 19% at 400 ℃, 500
27% of carbon dioxide gas had been converted to carbon monoxide at 0 ° C.

Example 7 Cobalt nitrate hexahydrate (50 mol% based on ammonium tetrathiotungstate) in an aqueous solution of ammonium tetrathiotungstate, and yttria fine powder as a carrier (700 wt% based on ammonium tungstate). %) Was added with stirring, dried in vacuum at room temperature, and then heated at 500 ° C. for 1 hour in a nitrogen stream. Catalyst 1 obtained
g in the same manner as in Example 1, carbon dioxide and hydrogen 1:
The mixed gas of No. 1 was circulated at a flow rate of 30 ml / min to cause reaction, and the reaction product was analyzed using a gas chromatograph. As a result, 0.6% at 200 ° C and 4.
Carbon dioxide gas of 5%, 11% at 400 ° C., and 19% at 500 ° C. was converted to carbon monoxide.

Example 8 Nickel nitrate hexahydrate (100 mol% with respect to ammonium tetrathiotungstate) in an aqueous solution of ammonium tetrathiotungstate and fine ferrite powder (900 with respect to ammonium tetrathiotungstate as a carrier). (% By weight) was added with stirring, vacuum-dried at room temperature, and then heated at 550 ° C. for 45 minutes in a nitrogen stream. Using 1 g of the obtained catalyst, a mixed gas of carbon dioxide gas, hydrogen and argon 2: 2: 1 was added in an amount of 30 ml / in the same manner as in Example 1.
The reaction product was circulated at a flow rate of min for reaction, and the reaction product was analyzed using a gas chromatograph. As a result, 200 ℃
2.1%, 7.1% at 300 ° C, 19.5% at 400 ° C.
%, 28.5% of carbon dioxide gas was converted to carbon monoxide at 500 ° C.

Example 9 Nickel nitrate hexahydrate (60 mol% relative to ammonium tetrathiomolybdate) in an aqueous ammonia solution of ammonium tetrathiotungstate and fine silica powder (800 to ammonium tungstate as a carrier).
(% By weight) is added with stirring and vacuum-dried at room temperature,
It heated at 500 degreeC for 50 minutes in hydrogen stream. Using 1 g of the obtained catalyst, a mixed gas of carbon dioxide gas and hydrogen at a ratio of 1: 1 was circulated at a flow rate of 30 ml / min for reaction in the same manner as in Example 1, and the reaction product was analyzed using a gas chromatograph. . As a result, 2.5% at 200 ° C., 8% at 300 ° C., 17% at 400 ° C., and 26% at 500 ° C. were converted to carbon monoxide.

Example 10 Cobalt nitrate hexahydrate (100 mol% with respect to ammonium tetrathiomolybdate) in an aqueous ammonia solution of ammonium tetrathiotungstate and fine powder of zirconia as a carrier (with respect to ammonium tetrathiotungstate) (700 wt%) was added with stirring, and the mixture was vacuum dried at room temperature and then heated at 450 ° C. for 1 hour in a hydrogen stream. Using 1 g of the obtained catalyst, a 1: 1 mixed gas of carbon dioxide and hydrogen was circulated at a flow rate of 20 ml / min for reaction in the same manner as in Example 1, and the reaction product was analyzed using a gas chromatograph. . As a result, at 200 ℃ 1.5
%, 5.5% at 300 ° C., 14.5% at 400 ° C., 50
At 0 ° C., 24% of carbon dioxide was converted to carbon monoxide.

Example 11 Cobalt nitrate hexahydrate (50 mol% relative to ammonium tetrathiotungstate) in an aqueous solution of ammonium tetrathiotungstate and fine powder of neodymia as a carrier (850 relative to ammonium tetrathiotungstate) (% By weight) was added with stirring, dried, and then heated in a hydrogen-hydrogen sulfide stream at 500 ° C. for 40 minutes. Using 1 g of the obtained catalyst, a mixed gas of carbon dioxide gas and hydrogen at a ratio of 1: 1 was circulated at a flow rate of 30 ml / min for reaction in the same manner as in Example 1, and the reaction product was analyzed by gas chromatography. As a result, at 200 ℃ 1.2%, 300
Carbon dioxide of 5% at 40 ° C., 14% at 400 ° C. and 23% at 500 ° C. was converted to carbon monoxide.

Example 12 Tungsten trisulfide supported on 85% by weight of lanthanum was 550 in a mixed gas flow of hydrogen sulfide and hydrogen of 1: 1.
Heat at 45 ° C. for 45 minutes. 1g of nickel nitrate-6
Add to 4 ml of 20% aqueous solution of hydrate, and add 1 in a nitrogen stream.
Dry overnight with stirring. Using 500 mg of the obtained catalyst, a mixed gas of carbon dioxide gas, hydrogen and argon 7: 7: 1 was circulated at a flow rate of 20 ml / min for reaction in the same manner as in Example 1, and the reaction product was analyzed by gas chromatography. Used for analysis. As a result, at 200 ℃ 2.3%, 300
7.8% at ℃, 20.5% at 400 ℃, 3 at 500 ℃
0.5% of carbon dioxide had been converted to carbon monoxide.

Example 13 90% by weight of thoria-supported tungsten trisulfide was heated in a stream of hydrogen at 430 ° C. for 1 hour and 20 minutes. 1 g thereof was added to 8 ml of a 10% aqueous solution of nickel nitrate hexahydrate, and the mixture was dried with stirring in a nitrogen stream overnight. Using 500 mg of the obtained catalyst, a mixed gas of carbon dioxide gas, hydrogen and nitrogen 3: 3: 1 was added in an amount of 30 ml / in the same manner as in Example 1.
The reaction product was circulated at a flow rate of min for reaction, and the reaction product was analyzed using a gas chromatograph. As a result, 200 ℃
1.1%, 6.5% at 300 ° C, 17.5 at 400 ° C
%, 28% of carbon dioxide at 500 ° C. was converted to carbon monoxide.

Example 14 Cobalt nitrate hexahydrate (120 mol% based on ammonium tetrathiotungstate) in an aqueous ammonia solution of ammonium tetrathiotungstate and activated clay (900 wt% based on ammonium tetrathiotungstate) as a carrier. %) While stirring and vacuum drying at room temperature, and then at 50 ° C. at 470 ° C. in a mixed gas flow of hydrogen and argon.
Heated for minutes. Using 1 g of the obtained catalyst, a mixed gas of carbon dioxide gas, hydrogen and helium 4: 4: 1 was caused to flow at a flow rate of 30 ml / min for reaction in the same manner as in Example 1, and the reaction product was analyzed by gas chromatography. Analyzed. As a result, 0.5% at 200 ° C, 4.2% at 300 ° C, 40%
Carbon dioxide gas of 10.5% at 0 ° C. and 17.5% at 500 ° C. was converted to carbon monoxide.

Example 15 Tungsten trisulfide was heated in a hydrogen stream at 550 ° C. for 45 minutes. 20% of cobalt nitrate hexahydrate
The solution was added to 4 ml of the aqueous solution and dried with stirring in a nitrogen stream overnight. Using 500 mg of the obtained catalyst, while circulating a mixed gas of carbon dioxide gas and hydrogen at a ratio of 1: 1 at a flow rate of 1 ml / min, a sunlight collected by a Fresnel lens having a diameter of 1.5 m was irradiated and reacted. The obtained reaction product was analyzed using a gas chromatograph. as a result,
About 4% of carbon dioxide was converted to carbon monoxide.

Example 16 To a fine powder of tungsten disulfide, 18% by weight of nickel fine powder was added and mixed well, and the mixture was mixed in an argon stream at 80% by weight.
Heated at 0 ° C. for 45 minutes. Using 500 mg of the obtained catalyst, a mixed gas of carbon dioxide gas and hydrogen 1: 1 was added at 1 ml / mi.
While circulating at a flow rate of n, sunlight condensed by a Fresnel lens having a diameter of 1.5 m was irradiated to cause a reaction, and the obtained reaction product was analyzed using a gas chromatograph. As a result, about 5% of carbon dioxide was converted into carbon monoxide.

[0033]

INDUSTRIAL APPLICABILITY As described above, the present invention is a tungsten sulfide catalyst for carbon dioxide gas reduction, which is durable, economical, and capable of selectively reducing carbon dioxide gas to carbon monoxide under mild conditions of low temperature and atmospheric pressure. Is provided. Tungsten sulphide is a cheap, non-toxic substance that is not poisoned by sulfur compounds, and has the characteristics that it is strong and durable against acids. With the catalyst of the present invention, carbon dioxide gas undergoes a reverse water gas shift reaction and is selectively reduced to carbon monoxide, but since this reaction is a gas phase reaction, it is possible to treat a large amount of carbon dioxide gas and endothermic reaction. Therefore, the energy yield is good, and if solar heat or waste heat is used as a heat source, the product carbon monoxide will have stored those heats and can also be used as a heat pump. Further, carbon monoxide, which is a reaction product, can be used as a fuel as it is, or it can be used by converting it into a raw material for methanol or a chemical product, which is in the limelight as an automobile fuel, by using the existing C1 chemical technology. Therefore, it is very effective in terms of global environment conservation and energy measures.

Claims (3)

[Claims] 1. A tungsten sulfide catalyst for carbon dioxide gas reduction, wherein at least one of nickel and cobalt is added to tungsten sulfide. 2. Support on at least one carrier selected from alumina, silica, activated carbon, zeolite, activated clay, iron oxide, zirconia, titania, ferrite, yttria, thoria, lanthanum, neodymia. The tungsten sulfide catalyst for carbon dioxide reduction according to claim 1, which is characterized in that. 3. Ni / Mo or Co / Mo in the catalyst
The tungsten sulfide catalyst for carbon dioxide gas reduction according to claim 1 or 2, wherein the atomic weight ratio is 0.0001 to 2.