JPS6260940B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a catalyst for synthesizing methane by hydrogenating carbon oxide and a method for producing the same, and more particularly to a catalyst for synthesizing methane from highly concentrated CO gas containing alumina, nickel, and barium oxide in specific proportions, and a method for producing the same. Highly concentrated CO obtained by gasifying heavy oil and coal
The method of converting gas into methane to obtain alternative natural gas is a very promising process considering the current energy situation. In recent years, many reports have been published on methane synthesis from coal gasification gas. Particularly in the United States, full-scale research is being conducted.
In Japan and the United States, projects aimed at producing high-calorie gas are being set up as part of the Sunshine Plan. As a catalyst for methanation from CO, for example, Ni-Mo-MgO, Ni-Mo-ZrO ₂ , Ni-Fe-
Catalysts such as MgAl ₂ O ₄ have been proposed. This methane synthesis reaction is a reaction accompanied by the generation of a large amount of reaction heat, and it is very important from the economical point of view of the methane synthesis process to effectively utilize the reaction heat as an energy source. In order to make effective use of this reaction heat, it is most preferable to carry out the reaction at a high temperature, but if the catalyst normally used for methane synthesis reaction is used with such a high concentration of CO gas, sintering due to heat and steam in the atmosphere may occur. It is known that the catalyst deteriorates significantly due to the formation of carbonaceous matter and other causes. Furthermore, carbonaceous matter produced by bonding of carbon atoms on the catalyst sometimes causes clogging of the reaction tube, making it physically impossible to continue the reaction. For example, when a normal nickel-based methanation catalyst is used in such a process, the initial activity is too high, causing problems such as deterioration of catalyst activity and heat removal from the equipment due to extremely high heat generation. Therefore, operations such as diluting the catalyst and filling it or reducing the amount of raw material gas supplied are required. These methods are technically and economically problematic. Also, from several percent to several tens of percent
Although it is possible to reduce the initial activity by reducing the amount of nickel contained in the catalyst, reducing the nickel content below a certain amount will result in a significant decrease in the initial activity, resulting in a decrease in catalyst performance. In order to solve these problems, many conventional methods have been proposed to constantly remove reaction heat and maintain temperature control of the catalyst layer in order to avoid high-temperature reactions. However, in this method, the advantage of recovering and effectively utilizing the reaction heat is lost. An object of the present invention is to provide a highly practical catalyst for methane synthesis that suppresses local heat generation in the catalyst layer, prevents catalyst deterioration, and has a satisfactory level of catalyst performance, and a method for producing the same. . As a result of intensive research in line with this objective, the present inventors have developed a catalyst consisting of alumina, nickel, and barium oxide, in which the content of nickel is in the range of 3 to 30% by weight based on the total amount of alumina and nickel. It was discovered that the catalyst had excellent catalytic performance as a catalyst for methane synthesis, and patent application No. 173085 was filed. However, as mentioned above, the methanation reaction of high concentrations of CO is accompanied by extremely high heat generation, so the catalysts used in such reactions are stable while maintaining a certain level of activity, and it is possible to suppress the high heat generation to some extent. is required. As a result of further research, the present inventors found that a lower nickel content is practically preferable because it is easier to suppress heat generation, less deterioration of the catalyst, and the catalyst performance is at a satisfactory level. As a result, the present invention was achieved. That is, the catalyst of the present invention is composed of alumina, nickel, and barium oxide, and the content of nickel is in the range of 0.05% by weight or more and less than 3.0% by weight based on the total amount of alumina and nickel, and the content of barium oxide is This is a catalyst for producing methane by hydrogenation of carbon oxide, characterized in that the content of the catalyst is in the range of 0.3% by weight or more and 9.0% by weight or less based on alumina. The catalyst of the present invention is composed of alumina, nickel, and barium oxide, and the content of nickel must be in the range of 0.05% by weight or more and less than 3.0% by weight based on the total amount of alumina and nickel to satisfy the catalyst performance. This is necessary from the practical point of view that it is easy to suppress heat generation while maintaining the same level as possible, and prevents deterioration of the catalyst. Nickel content is 3.0% by weight
Although the above catalyst performance is at a high level, it generates a high amount of heat, which poses some practical problems. Further, if the nickel content is less than 0.05% by weight, the nickel content has no effect and the catalyst performance is poor. Further, the content of barium oxide varies depending on the properties of the carrier, but is usually in the range of 0.3% by weight or more and 9.0% by weight or less based on alumina. If it is less than 0.3% by weight, there is no effect of barium oxide inclusion, resulting in poor catalytic activity, and if it is contained in excess of 9.0% by weight, the solubility of barium nitrate and barium hydroxide is low, so it cannot be supported by normal impregnation methods. Moreover, it may cause clogging of the pores of the carrier or a reduction in the number of active sites due to coating with nickel atoms. For this reason, it is not preferable to contain excessive barium oxide, and there is little merit in containing barium oxide in excess of 9.0% by weight. The reason why carbon precipitation is suppressed and catalyst performance is improved by containing barium oxide in the present invention is not necessarily clear, but one consideration is that the surface state of alumina changes due to the inclusion of barium oxide. It is surmised that alumina is stabilized, thereby suppressing nickel from having a strong interaction with the carrier, and that a highly active catalyst can be obtained even with a low nickel content. In the present invention, the catalyst for methane production is obtained by supporting a barium salt solution such as barium nitrate or barium hydroxide and a nickel salt solution such as nickel nitrate on an alumina carrier by a conventionally known method such as an impregnation method, a kneading method, or a precipitation method. can be obtained. In this case, (1) a method in which barium oxide is supported on alumina and then nickel is supported, (2) a method in which nickel and barium oxide are simultaneously supported on alumina, (3)
There are three methods of supporting barium oxide after supporting nickel on alumina. In the present invention, barium oxide is first supported on alumina so that the content of barium oxide is in the range of 0.3% by weight or more to 9.0% by weight based on the alumina, and then nickel is supported on alumina so that the content of barium oxide is in the range of 0.3% by weight or more and 9.0% by weight or less based on the alumina. From 0.05% by weight or more based on the total amount of
Loaded in a range of less than 3.0% by weight (1)
The method described above is desirable from the viewpoint of catalyst performance, etc. Furthermore, the alumina used in the present invention is γ-
Alumina is most preferably used. The present invention will be specifically described below based on Examples, Comparative Examples, and Experimental Examples. Comparative example 1 100g of molded alumina carrier (water absorption rate 0.75)
The carrier was placed in a 500 c.c. beaker, and 75 c.c. of a 0.68 mol/nickel nitrate solution was added dropwise at room temperature while shaking the carrier to impregnate it. To ensure uniform loading,
Leave it as it is at room temperature for 12 hours, then dry it in a dryer using the usual method, and heat it in the air at 500℃ in an electric furnace for 3 hours.
Catalyst A with a nickel content of 2.9% by weight after being fired for a period of time
I got it. Comparative Examples 2 to 4 Same alumina carrier 100 as used in Comparative Example 1
Catalyst B with a nickel content of 5.0% by weight and catalyst C with a nickel content of 2.0% by weight were prepared in the same manner as in Comparative Example 1 except that the concentration of the nickel nitrate solution was changed. A catalyst D having a nickel content of 0.5% by weight was obtained. Example 1 100g of alumina carrier used in Comparative Example 1 was added to 500c.c.
0.26mol/
The carrier was impregnated dropwise with 75 c.c. of barium nitrate solution at room temperature. In order to uniformly support the product, it was allowed to stand at room temperature for 12 hours, dried in a dryer using a conventional method, and then fired in a Matsufuru furnace at 800°C for 3 hours to support 3.0% by weight of barium oxide on alumina. On the alumina carrier supporting this barium oxide,
As in Comparative Example 1, 75 c.c. of a 0.68 mol/nickel nitrate solution was added dropwise to impregnate. After allowing it to stand for 12 hours, dry it using a conventional method and heat it in the air at 500℃ in an electric furnace.
℃, nickel content 2.9% by weight after firing for 3 hours.
Catalyst E having a barium oxide content of 3.0% by weight was obtained. Comparative Example 5, Examples 2 to 4, and Comparative Example 6 After preliminarily supporting 3.0% by weight of barium oxide on an alumina support in the same manner as in Example 1, the same method as in Example 1 was carried out by changing the concentration of the nickel nitrate solution. Catalyst F with a nickel content of 5.0% by weight, 2.0% by weight, 0.5% by weight, 0.05% by weight and 0.03% by weight,
G, H, I and J were obtained respectively. Example 5 Catalyst A with a nickel content of 2.9% by weight prepared in Comparative Example 1 was placed in a 500 c.c. beaker, and 0.26 mol/
of barium nitrate solution was impregnated dropwise at room temperature. After standing at room temperature for 12 hours, it was dried by a conventional method and calcined in air at 500° C. for 3 hours in an electric furnace to obtain catalyst K in which 3.0% by weight of barium oxide was supported on alumina. The nickel content (amount relative to the total amount of nickel and alumina) and barium oxide content (amount relative to alumina) of the catalysts A to K thus obtained are shown in Table 1. Experimental Example 1 The initial methanation activities (r ₀ ) of catalysts A to K obtained in Comparative Examples 1 to 6 and Examples 1 to 5 were measured under the following reaction conditions using a normal atmospheric pressure fixed bed flow reactor. It was measured. The catalyst was crushed into 10 to 16 meshes and then used in an amount of 0.1 to 10 g depending on the catalyst activity. A Pyrex glass tube with an inner diameter of 20 mm was used for the reaction tube, and the catalyst was diluted with an alumina carrier before being filled.
The reaction conditions were normal pressure, temperature 290℃, H ₂ 9/hr, CO
3/hr, H ₂ /CO at a molar ratio of 3, the reduction treatment was carried out at 500°C in a H ₂ stream for 1 hour, and the results of the initial methanation activity of each catalyst at 290°C were determined. Note that a 3 mm thermowell is included in the catalyst layer so that the temperature of the catalyst layer can be measured. In this measurement, the CO conversion rate during the measurement was all below 10%, and almost no heat generation was observed in the catalyst layer. The results of the initial methanation reaction rate (r ₀ ) are shown in Table 1 and FIG. As shown in Table 1 and FIG. 1, the initial methanation activity is increased by adding barium oxide, and even with a small nickel content of 0.5% by weight, relatively favorable activity is shown. On the other hand, when barium oxide is not added, there is almost no activity at a nickel content of 0.5% by weight. Thus, it can be seen that the addition of barium oxide is effective for the initial methanation activity. In addition, catalyst K of Example 5, in which barium oxide was added after barium oxide was added, has an inferior initial methanation activity compared to catalyst E of Example 1, which was added barium oxide and then nickel. . Experimental Example 2 Catalysts A to K obtained in Comparative Examples 1 to 6 and Examples 1 to 5 were examined for changes in methanation activity due to high temperature treatment in a steam atmosphere using a conventional high pressure flow type fixed bed reactor. I processed it. The treatment method involved filling each catalyst into a stainless steel reaction tube with an inner diameter of 16 mm, and applying a pressure of 10 kg/cm ² G.
H ₂ 50/hr, H ₂ O 80c.c./hr, H ₂ / at temperature 600℃
A gas having a molar ratio of H ₂ O=2 was introduced and the treatment was carried out for 24 hours. The methanation reaction rate (r) after this 24 hour treatment is shown in Table 1. In addition, in order to examine changes in activity, the ratio (r/r ₀ ) to the methanation reaction rate (r ₀ ) obtained in Experimental Example 1 is shown in Table 1 and FIG.

[Table] As is clear from Table 1 and FIG. 2, the methanation reaction rate of catalysts A to D not containing barium oxide after high-temperature treatment in a steam atmosphere is significantly reduced. This is particularly noticeable in catalysts C and D, which have a low nickel content. On the contrary,
In catalysts E to I containing barium oxide,
It can be seen that the methanation reaction rate remains at a high level even after treatment, indicating that the stability of methanation activity is excellent. The r/r ₀ of these catalysts E to I shows a higher value as the nickel content increases, but the catalysts G to I containing a small amount of nickel also show the desired methanation activity, and the catalyst C which does not contain barium oxide shows the desired methanation activity. ~D does not show a significant decrease in catalyst activity. Catalyst F containing 5% by weight of nickel shows high initial activity and post-treatment activity, but because the initial activity is quite high, there is a problem in terms of heat generation.
Slightly lacking in practicality. Catalyst K is also inferior to catalyst E in activity after treatment. As explained above, the process of methanating highly concentrated CO gas obtained by gasifying heavy oil or coal is very promising, but there is still no suitable catalyst that can be used under the harsh reaction conditions in such a process. has not been obtained. The catalyst of the present invention, which contains alumina, nickel, and barium oxide in a specific range, can easily suppress heat generation in the reaction, and also has satisfactory methanation activity when converting CO gas to methanation. Therefore, it is suitably used as a catalyst for methane synthesis.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the initial methanation reaction rate (r ₀ ) and the nickel content (wt%) of catalysts A to I in Experimental Example 1, and Figure 2 shows the initial methanation reaction rate of catalysts A to I. FIG. 2 is a diagram showing the relationship between the ratio (r/r ₀ ) of (r ₀ ) and post-treatment methanation reaction rate (r) and the nickel content (wt%).

Claims (1)

[Claims] 1. Consisting of alumina, nickel, and barium oxide, the content of nickel is in the range of 0.05% by weight or more to less than 3.0% by weight based on the total amount of alumina and nickel, and the content of barium oxide is A catalyst for methane synthesis by hydrogenation of carbon oxide, characterized in that the content of alumina is from 0.3% by weight to 9.0% by weight. 2. First, add barium oxide to alumina so that the barium oxide content is 0.3% by weight or more based on the alumina.
It is characterized by supporting nickel in a range of 9.0% by weight or less, and then supporting nickel in such a way that the nickel content is in a range of 0.05% by weight or more to less than 3.0% by weight based on the total amount of alumina and nickel. A method for producing a catalyst for methane synthesis by hydrogenating carbon oxide.