JPS6129778B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a novel catalyst in which an iron group metal-rare earth oxide-platinum group metal active component is supported as a substrate on a carrier having a binary pore structure, a method for producing the same, and a method for producing carbon dioxide and/or carbon dioxide using the catalyst. Or it relates to a method of methanating carbon monoxide. Currently, a methanation method using a nickel catalyst is used to increase the calorific value of gas fuel by methanating carbon monoxide in water gas with hydrogen, or to increase the purity of hydrogen for ammonia synthesis. However, the activity of the nickel catalyst is relatively low, and the reaction operation must be carried out at a relatively high temperature.Therefore, there is a high possibility that nickel catalysts will be half-melted, resulting in a shortened lifespan. Further, there are other drawbacks, such as the fact that carbonaceous deposits are generally noticeable on the surface of the catalyst during the reaction, which tends to cause catalyst deterioration, and the catalyst is susceptible to strong poisoning by trace amounts of sulfur compounds. Research has been conducted on ways to prevent carbon precipitation by adding carbonates of alkali metals, but no fundamental solution has yet been found. On the other hand, it has been known for a long time that the ruthenium catalyst exhibits the highest activity for the methanation reaction of carbon monoxide, but in this case, the by-product of hydrocarbons with 2 or more carbon atoms is large.
Methane production selectivity is generally poor. Furthermore, ruthenium catalysts are said to have the advantage of being considerably more resistant to poisoning by sulfur compounds than nickel catalysts, but ruthenium is extremely expensive, and its oxides are volatile, resulting in short catalyst life. Due to its short length and other shortcomings, it has not been used as an industrial catalyst for methanation. The purpose of the present invention is to fundamentally overcome the above-mentioned drawbacks of conventional carbon monoxide methanation catalysts, and also to reverse the performance of conventional methanation catalysts in converting carbon monoxide methanation into carbon monoxide. It is an object of the present invention to provide a catalyst capable of carrying out reaction at a much higher reaction efficiency than in the case of conventional methods, and a methanation method using the catalyst. The present inventors have developed a novel iron group metal for reduction in which a combination of an iron group metal as a catalyst substrate, an oxide of a rare earth element, and a platinum metal are supported on a shaped support having a micro-macro pore structure. It has been found that metal-rare earth oxide-platinum group metal based supported catalysts exhibit high methanation activity, high methane production selectivity, excellent stability and lifetime. The catalyst of the present invention not only improves the efficiency of the conventional method described above, but also produces large amounts of methane, a typical clean gas fuel, using water and carbon or carbon dioxide, which are inexhaustible on earth, as basic raw materials. Industrial establishment of the method for synthesis is expected. In addition, the catalyst of the present invention can eliminate large amounts of carbon monoxide contained in blast furnace gas generated in the steel manufacturing process, large amounts of carbon dioxide by-produced during hydrogen production through the conversion reaction of water and carbon monoxide, and hydrocarbon fuels. It becomes possible to open the way to effective chemical use or recycling of carbon dioxide as a combustion product. As the carrier for the catalyst of the present invention, one having a micro-macro binary pore structure is used. Its micropore size is 40~200Å, macropore size is 3000~
8000 Å is preferred, and shaped bodies of alumina or preferably silica with a dual pore structure of this type are used. The shape of the molded object is, for example, 3 to 4 in diameter.
mm spheres are preferred, but other shapes are also possible. Generally, commercially available products can be used as carriers for the catalyst of the present invention as long as they contain both micro and macro pores. Alternatively, a layer of fine particles forming micropores can be formed on the pore walls by using 6-7 nm spherical silica (manufactured by Du Pont) dispersed in the form of a sol in a macro-uniform pore carrier. It is also possible to create a binary pore system by making each. A particularly preferred carrier can be produced, for example, as follows. Homogeneous alkali-free silica gel powder is molded, fired at a high temperature such as 800℃, treated with aqua regia, and then washed with water.
Drying at 200° C. gives a shaped silica support with a micro-macro binary pore structure. The substrate of the catalyst component applied on the carrier is an iron group metal,
For example, nickel, cobalt or iron. This substrate metal contains rare earth element oxides, such as lanthanum,
Combining oxides of cerium, praseodymium or samarium and platinum group metals such as ruthenium, rhodium, platinum, palladium or iridium. The amount of iron group metal supported is preferably 3 to 12% by weight based on the total catalyst. The rare earth element oxide is used in an amount such that the atomic ratio of iron group metal to rare earth element is 2:1 to 10:1, and the platinum group metal is used in an amount such that the atomic ratio of iron group metal to platinum group metal is 10:1 to 30:1. Preferably, each is present in an amount of 1. The catalyst of the present invention is prepared by impregnating a molded support having a micro-macro binary pore structure with nitrates or chlorides of iron group metals, rare earth elements, and platinum group metals in the form of an aqueous solution, drying, and then ammonia treatment. It can be produced by sequentially performing thermal decomposition, hydrogen reduction, and heat treatment. Impregnation is generally carried out by spraying, sprinkling or dipping to any desired depth from the outer surface of the carrier. A series of operations of impregnation, drying, ammonia treatment, pyrolysis, hydrogen reduction, and heat treatment can be performed separately in any order for iron group metals, rare earth elements, and platinum group metals, or in combination of two or more thereof. . In order to produce the catalyst of the present invention, the following operation can be preferably carried out. First, the carrier is impregnated with an aqueous solution of platinum group metal chloride or nitrate in an amount just enough to fill the pores, and the carrier is air-dried at room temperature while being gently rolled. The concentration of the aqueous solution at that time is set such that a predetermined amount of support is included in the amount of impregnating liquid. Then, 60 to 150 g of ammonia gas was added to the atmosphere containing 80 mmHg of ammonia gas and 15 mmHg of water vapor (e.g., saturated steam of 10% ammonia water kept at 20°C).
After being exposed for a few seconds, the salt is heated to 350°C in air to decompose the salt into oxides. This is heated from room temperature to 400°C in a hydrogen stream to be reduced to a reduced metal state, and then heat treated for stabilization by keeping it at 400°C for 0.5 to 1 hour. While rolling the product thus obtained at room temperature, the pore volume
By spraying and impregnating a mixed aqueous solution of each nitrate of an iron group element and a rare earth element at a predetermined concentration in an amount that accounts for 1/3 to 1/5, and performing the same operation as described above, the ternary composition system of the present invention is supported. A catalyst is obtained. Since rare earth element oxides are stable, they remain as oxides under the hydrogen reduction conditions described above. The catalyst of the invention is used in particular for the methanation of carbon dioxide, carbon monoxide or mixtures thereof. To perform methanation using this catalyst, carbon dioxide and/or carbon monoxide and hydrogen are passed through the catalyst to cause a reaction. In this case, carbon dioxide and/or carbon monoxide are generally used together with hydrogen in an amount greater than the stoichiometric amount for methane formation, and the reaction can also be carried out by diluting the reaction components with an inert gas. When the catalyst of the present invention is used, the reduction in conversion is relatively small even when the reaction is carried out at a high rate, so that the reaction can preferably be carried out at a gas hourly space velocity of 10,000 gas hourly or more per catalyst. The method for methanating carbon dioxide and/or carbon monoxide according to the present invention can be carried out, for example, as follows. The catalyst is packed into the reactor so that the filling voids are approximately evenly spaced, preferably on the order of about 55-60% larger. When a small amount of catalyst is used, a reaction tube with an inner diameter slightly larger than the diameter of the catalyst particles is used, and the catalyst is packed in a single row, and when a large amount of catalyst is used, a spring-like Raschig ring, for example, is used. By mixing these, the porosity can be adjusted. By packing the catalyst in this way, there is less pressure loss due to ventilation resistance even when the flow rate is high, and unreacted gas is quickly distributed to the rear of the catalyst layer, making the reaction distribution inside the reactor more even. It is possible to carry it as a burden. The reaction gas is at a temperature of 220-400°C, preferably 260-360°C,
Conducts over the catalyst at a space velocity of 10,000 to 100,000/hour. The general characteristics of the performance of the catalyst of the present invention are as follows. Since the methanation activity of carbon dioxide is extremely high, not only can carbon monoxide be methanated alone, but even if carbon monoxide and carbon dioxide are mixed, if more than the stoichiometric amount of hydrogen coexists, both will be completely methanated. It can be converted to This is because when CO coexists, the methanation of CO ₂ is suppressed until the conversion of CO to methane is almost completed, and once the conversion of CO is completed, the methanation of CO ₂ occurs rapidly at higher temperatures. This is for the purpose of Due to the combined synergistic effect of the catalyst components, the selectivity for methane production is close to 100%, and there is no deterioration due to carbon deposition. Also, like the ruthenium catalyst, it has high resistance to poisoning by sulfur compounds. Due to the combined effect of the ruthenium component and lanthanum oxide, volatilization is suppressed and the catalyst activity is stable even when the catalyst is exposed to high temperatures in an oxidizing atmosphere. Because it uses a dual-pore carrier with a large effective diffusion coefficient despite being a multi-surface material, the catalyst has high activity, and there is relatively little reduction in conversion rate even at high flow rates, achieving highly efficient methanation. can. Even when operating at a high reaction rate at a high flow rate, the above-mentioned packing structure flattens the reaction distribution, so the catalyst bed temperature does not locally rise, preventing runaway reactions, half-melting of the catalyst, and side reactions. can be avoided. Example 1 Micropore average diameter 50 Å and macropore average diameter
A silica molded support with a binary pore structure of 6000 Å (diameter 3.0 mm, BET surface area 360 m ² /g) was coated with 8.7% Ni.
Using a catalyst supporting −4.9% La ₂ O ₃ −0.55% Ru, each raw material gas shown in Table 1 was heated at a space velocity of 10,000.
As a result of one pass at 300°C and 300°C, the conversion of carbon dioxide and carbon monoxide was 100% and the selectivity of methane produced was over 99%, as shown in the table. Space-time yields were obtained. The minor by-products were ethane and carbon monoxide in the case of carbon dioxide methanation, and ethane and propane in the case of carbon monoxide methanation.

[Table] Example 2 Using the same carrier as in Example 1, a gas consisting of 6.0% carbon dioxide, 18% hydrogen and 76% nitrogen was applied to a catalyst having the ternary composition shown in Table 2 at a space velocity of 10,000/hour and 227 As a result of one pass at ℃, the results shown in the table were obtained. Cases of unitary and binary compositions are listed for comparison. In the case of the ternary composition system according to the invention, a significant increase in activity due to the combined effect of the catalyst components is observed.

[Table] Example 3 A gas consisting of 6.0% carbon monoxide, 18% hydrogen and 76% nitrogen was added to a catalyst with the ternary composition shown in Table 3 using the same carrier as in Example 1 at a space velocity of 10000/.
The results shown in the table were obtained after one pass at 265°C and 265°C. In this case as well, the activity of the three-way catalyst is significantly higher than that of the one-way and two-way composition catalysts.

[Table] Example 4 Using the Ni-La ₂ O ₃ -Ru catalyst of Example 2, with the same gas composition and temperature as Example 2, the space velocity was 74200.
/・As a result of passing in hours, the carbon dioxide conversion rate
7.8%, methane space-time yield of 15.5 mol/h, and methane selectivity of 98.6%. Example 5 Using the Ni-La ₂ O ₃ -Ru catalyst of Example 2, a gas consisting of 12% carbon monoxide and 88% hydrogen was passed through at 290°C and a space velocity of 42500/hr, resulting in carbon monoxide conversion. rate 100%, methane space-time yield 228 mol/
・Results of 98% in time and methane selectivity were obtained. Example 6 Using the Ni-La ₂ O ₃ -Ru catalyst of Example 2, a gas consisting of 12% carbon dioxide and 88% hydrogen was passed through at 340°C and a space velocity of 43300/hour, resulting in a carbon dioxide conversion rate of 100. %, methane space-time yield 232 mol/・
A methane selectivity of 99% was obtained. Example 7 Micropore average diameter 200 Å and macropore average diameter
4.3% Ni was applied to an alumina molded support with a binary pore structure of 5000 Å (diameter 4.0 mm, BET surface area 210 m ² /g).
Using a catalyst supporting −2.5% La ₂ O ₃ −0.7% Ru,
As a result of passing a gas consisting of 6.0% carbon dioxide, 18% hydrogen and 76% nitrogen at a space velocity of 13300/hour, the results shown in Table 4 were obtained.

[Table] Example 8 Silica/alumina spherical molded support with a macro-uniform pore structure having an average macropore diameter of 7600 Å (diameter
3.5 mm, BET surface area 1.0 m ² /g) was impregnated with 6 to 7 nm spherical silica in an amount corresponding to 9 volume% of the pore volume, dried and fired at 400°C, and then impregnated with 2.0% Ni. -Produce a catalyst supporting 1.2% La ₂ O ₃ . This catalyst contains 6% carbon dioxide, 18% hydrogen and nitrogen.
Gas consisting of 76% at 290℃ and space velocity 16000/
- As a result of the methane space-time yield of 16.2 mol/hour (3.1 times that of the case without pore adjustment using 6-7 nm spherical silica). Example 9 Alumina spherical molded support with a microuniform pore structure having an average micropore diameter of 60 Å (diameter 3.5 mm, BET
A catalyst having a surface area of 210 m ² /g) is calcined at 1100° C. for 30 minutes in air to produce a catalyst in which 2.0% Ni-1.2% La ₂ O ₃ is supported on the carrier. This catalyst contains 6% carbon dioxide, 18% hydrogen and nitrogen.
Gas consisting of 76% at 283℃ and space velocity 90000/
・As a result of increasing the time, a space-time methane yield of 23.6 mol/hour (715 times that in the case of final calcination) was obtained. Example 10 The same amount of catalytic material as in Example 9 was applied to the same carrier as in Example 9 (calcined at 1100°C) by a spraying method while rolling the carrier, so that the support layer was formed from the outer surface of the carrier. A catalyst is produced that is uniformly supported to a thickness of 0.5 mm. Using this catalyst, carbon dioxide 12% and hydrogen 88%
At 350℃, a gas consisting of a space velocity of 51000/・
As a result, a space-time yield of methane of 317 mol/hour was obtained (2.2 times that when using a catalyst in which the catalytic material was supported on the entire support).

Claims (1)

[Scope of Claims] 1. A reduction catalyst in which a combination of an iron group metal as a catalyst substrate, an oxide of a rare earth element, and a platinum group metal is supported on a molded carrier having a micro-macro binary pore structure. . 2 A molded support having a micro-macro binary pore structure is impregnated with nitrates or chlorides of iron group metals, rare earth elements, and platinum group metals in the form of an aqueous solution, dried, and then subjected to ammonia treatment, thermal decomposition, and hydrogen reduction. A reduction method in which a combination of an iron group metal as a catalyst substrate, an oxide of a rare earth element, and a platinum group metal are supported on a molded support having a micro-macro binary pore structure, which is characterized by sequentially performing a heat treatment and a heat treatment. Production method of catalyst for use. 3. A series of operations of impregnation, drying, ammonia treatment, pyrolysis, hydrogen reduction, and heat treatment can be carried out separately in any order for iron group metals, rare earth elements, and platinum group metals, or in combination of two or more of them. A method according to claim 2, characterized in that: 4 Carbon dioxide and 1. A method for methanating carbon dioxide and carbon monoxide using a catalyst, which method comprises conducting a reaction between carbon monoxide and hydrogen. 5. Process according to claim 4, characterized in that the reaction components are diluted with an inert gas. 6. The method according to claim 4 or 5, characterized in that the reaction is carried out at a gas hourly space velocity of 10,000 gas hourly or more per catalyst.