JPS6114860B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a catalyst used in the production of fuel gas containing a large amount of methane by low-temperature steam reforming of hydrocarbons. More specifically, a liquid or gaseous hydrocarbon containing at least 3 or more carbon atoms in one molecule, mainly paraffinic, and having a boiling point of 250°C or less, in a weight ratio of 1.5 to 2.5 to hydrocarbon. From water vapor, reaction temperature 300 to 550℃ and normal pressure
This invention relates to a method for producing a catalyst used to produce gas containing a large amount of methane through continuous reaction under conditions of up to 100 atmospheres. Gas whose main component is methane, used for fuel gas or city gas, is generated when it is combusted.
Since it contains less harmful substances such as NOx and SOx than other fuels, it has become increasingly important as a clean energy source in recent years. This gas, whose main component is methane, is well known as natural gas, but the technology for industrially producing this gas is to process light petroleum fractions, which mainly consist of paraffinic hydrocarbons, in the presence of a nickel-based catalyst. A low-temperature steam reforming method that involves reacting with steam is generally widely known. The nickel in these nickel-based catalysts is in the form of nickel oxide at the time of preparation, and is reduced to active nickel by a reducing gas such as hydrogen in a reactor before being used in the reaction. Conventionally, these nickel-based catalysts have been prepared by a precipitation method. However, the performance of catalysts prepared by the precipitation method, such as their activity and lifespan, is greatly affected by the operating conditions during precipitation preparation, such as the temperature during precipitation, stirring speed, alkali addition rate, aging temperature, and aging time. It is very difficult to completely match these operating conditions for each lot, and as a result, the performance of the catalyst is not stable, and in extreme cases, it is difficult to completely match these operating conditions for each lot. It may be necessary to take samples and test their performance. Furthermore, when preparing a nickel catalyst by the precipitation method, nickel nitrate is used as the nickel raw material, and the alkaline reagent used as the precipitant is an aqueous solution of alkali metal hydroxide or carbonate. The presence of large amounts of nitrate radicals and alkali metals in the mixed precipitate causes a decrease in catalytic activity, so it is necessary to completely remove these. In order to completely remove these nitrate radicals and alkali metals, it is usually necessary to carry out washing and dehydration steps five or more times. As mentioned above, the preparation method of catalyst by precipitation method is as follows:
It is very complex and the operating conditions must be checked very carefully. In order to produce a nickel-based catalyst with stable performance for use in hydrocarbon low-temperature steam reforming reactions, conditions for precipitation, water washing steps, etc. must be extremely strictly controlled. The present invention was made in view of the above-mentioned circumstances, and as a result of intensive research to provide a catalyst for low-temperature hydrocarbon reforming reactions with high activity and stable performance.
By using nickel sesquioxide (a hydrate of Ni ₂ O ₃ ) as a nickel raw material, we not only simplified the manufacturing process, but also created a catalyst with extremely stable performance with no variation in activity between rods. They discovered that it can be manufactured and completed the present invention. That is, the present invention combines at least one kind of alumina hydrate or alumina obtained by calcining an alumina hydrate at a temperature of 100°C or lower, and nickel sesquioxide as NiO in the final catalyst.
This is a method for producing a catalyst for steam reforming of hydrocarbons, which comprises the steps of mixing by a normal mixing method so that the content is 40 to 90% by weight, followed by molding and firing. To explain the present invention more specifically, the nickel raw material used in the present invention is nickel sesquioxide, and the final catalyst contains 40 to 90% NiO.
% by weight. This is because if the amount of nickel contained in the catalyst is less than 40% by weight as NiO, the activity of the final catalyst will not be sufficient, and if it is more than 90% by weight, nickel will sinter during the reaction. This is disadvantageous because the process progresses quickly, which shortens the life of the catalyst. Preferably it is 45 to 85% by weight. As the alumina raw material, various alumina hydrates or various alumina hydrates are used at a temperature of 1000℃ or less, preferably
It is at least one kind of alumina obtained by firing at a temperature of 300 to 900°C. It is best to use alumina raw materials that do not contain α-alumina or contain almost no α-alumina, and if calcined products are used as alumina raw materials, calcined at a temperature of 1000℃ or less, preferably 300 to 900℃. Preferably. Although the reason for this is not clear, it is thought that when an alumina raw material containing α-alumina is used, the specific surface area of the resulting catalyst decreases, resulting in insufficient catalyst activity. The above-mentioned raw materials prepared in a predetermined ratio are sufficiently mixed by a conventional mixing method, then molded by tabletting or extrusion molding, and fired at a temperature of 300 to 500°C. In addition, when compressing into tablets, graphite or the like may be added in an amount of 2 to 5% by weight as an anti-friction agent, and an organic binder such as CMC may be activated to improve workability. It may be added within a range that does not have any influence. As mentioned above, the method for producing a nickel-alumina catalyst of the present invention is a very simple production process compared to the precipitation method, and is an economical catalyst that can easily produce a catalyst with stable performance. This is the manufacturing method. Example 1 404 g of nickel sesquioxide (Ni ₂ O ₃ ), 677 g of aluminum hydroxide (Al(OH) ₃ ) and 1000 c.c. of ion-exchanged water were mixed with a paddle stirrer for 1 hour, and then heated to 110°C.
It was dried. The resulting mixture was pulverized to 150 meshes or less and molded into a cylindrical shape of 3.5 mmφ x 3.5 mmH using a rotary tablet press. This molded product was calcined at 400°C for 4 hours to obtain catalyst A. The composition of this catalyst A is NiO45% by weight Al ₂ O ₃ 55
It was in weight%. Example 2 A catalyst having the following composition was obtained in the same manner as in Example 1, except that the ratio of nickel sesquioxide and aluminum hydroxide used was changed.

[Table] Comparative Example 1 Catalyst X was obtained in the same manner as in Example 1, except that 440 g of nickel oxide (NiO) and 550 g of alumina hydroxide (Al(OH) ₃ ) were used. The composition of this catalyst X is
The contents were 55% by weight of NiO and 45% by weight of Al ₂ O ₃ . Comparative Example 2 Catalyst Y was obtained in the same manner as in Example 1, except that 550 g of nickel hydroxide (Ni(OH) ₂ ) and 554 g of aluminum hydroxide were used. The composition of this catalyst Y is
The contents were 55% by weight of NiO and 45% by weight of Al ₂ O ₃ . Comparative example 3 Nickel nitrate hexahydrate 1950 in ion exchange water 10
g and 1,650 g of aluminum nitrate nonahydrate, and while stirring this solution, keep the temperature constant at about 80°C, and add potassium carbonate to 1 part ion-exchanged water.
A solution dissolved in the proportion of 415 g was gradually added at a constant flow rate to bring the final pH of the solution to 8. Furthermore, the resulting aqueous solution of the coprecipitate of aluminum hydroxide and nickel hydroxide was kept at a constant temperature of 80° C. and kept stirring for 2 hours for aging. After the precipitation was completed, water was removed from the resulting aqueous precipitate solution using a small filter press, and the resulting precipitate was stirred again in ion-exchanged water, and then water was removed using a small filter press. Four additional washing and dehydration steps were required until nitrate radicals and potassium were no longer detected in the waste water from the filter press. The finally obtained coprecipitate was dried at 110°C, pulverized to 150 meshes or less, and molded into a cylindrical shape of 3.5 mmφ x 3.5 mmH using a rotary tablet press. This was calcined in the air at 400°C for 4 hours to obtain catalyst Z. The composition of this catalyst Z is
NiO was 55wt% and Al ₂ O ₃ was 45wt%. Catalysts A to E, X, Y, Z prepared as above
Table 1 shows the results of an activity test performed by filling 180 c.c. of each of these into a stainless steel reaction tube with an inner diameter of 30 mmφ and a length of 1000 mm. As the raw material hydrocarbon, n-hexane, a special grade reagent, was used, and the feed rate was 540 c.c./hour.
Steam was mixed well with n-hexane at a ratio of 2 parts by weight per 1 part by weight of supplied n-hexane, and after preheating to 400°C, the reaction pressure was introduced into the catalyst bed with an inlet temperature of 400°C, and the reaction pressure was normal pressure. The height of the catalyst layer was approximately 25 cm. Note that undecomposed n-hexane was detected in the generated gas for catalysts X and Y, and only for catalyst X that carbon deposition was observed on the catalyst after the reaction.

[Table] As is clear from Table 1, catalyst A according to the present invention
~E and catalyst Z of Comparative Example 3 reached chemical equilibrium values in both gas production amount and composition, but nickel oxide,
Catalysts X and Y using nickel hydroxide have a small amount of produced gas and a low methane content, indicating that they do not have sufficient activity. Moreover, it can be seen that the manufacturing method of catalyst Z is more complicated than the manufacturing method of the present invention. Example 3 493 g of nickel sesquioxide (Ni ₂ O ₃ ), 517 g of aluminum hydroxide (Al(OH) ₃ ), 240 g of alumina sol (containing 10 wt% as Al ₂ O ₃ ) and 200 c.c. of ion-exchanged water were mixed in a kneader. After mixing for 1 hour,
Extrusion molding was performed using a pelleter having holes of 3 mmφ. This molded product was dried at 110°C, sized to have a length of 3 to 5 mm, and then calcined at 400°C for 4 hours to obtain catalyst F. The composition of catalyst F is 55% by weight of NiO,
The content of Al ₂ O ₃ was 45% by weight. Example 4 240 g of alumina obtained by calcining 583 g of nickel sesquioxide (Ni ₂ O ₃ ) and aluminum hydroxide (Al(OH) ₃ ) at 400°C 400 g of alumina sol (containing 10% by weight as Al ₂ O ₃ ) Catalyst G was obtained in the same manner as in Example 3 except that . The composition of this catalyst is
The contents were 65% by weight of NiO and 35% by weight of Al ₂ O ₃ . Example 5 120 g of alumina obtained by calcining 672 g of nickel sesquioxide (Ni ₂ O ₃ ) and aluminum hydroxide (Al(OH) ₃ ) at 600°C, alumina sol (10 as Al ₂ O ₃ )
Example 3 except that 800g (including weight%) was used.
Catalyst H was obtained in the same manner as above. The composition of this catalyst is
The contents were 75% by weight of NiO and 25% by weight of Al ₂ O ₃ . Table 2 shows the results of the activity tests for catalysts F to H. The hydrocarbon raw materials used and other experimental conditions were exactly the same as those described above.

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Claims (1)

[Claims] 1 Alumina hydrate and alumina hydrate 1000
Low-temperature steam of hydrocarbon, characterized by mixing at least one kind of alumina obtained by firing at a temperature of ℃ or less and nickel sesquioxide so as to contain 40 to 90% by weight as NiO, molding, and firing. Method for producing a reforming catalyst.