JPH0371174B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a catalyst for steam reforming of methanol, and more particularly to an improved method for producing a catalyst for steam reforming of methanol containing a copper oxide, a zinc oxide, and an aluminum oxide. . Hydrogen gas is used in many fields, such as ammonia synthesis, hydrogenation of various organic compounds,
It is widely used in chemical industries such as petroleum refining and desulfurization, and demand is also increasing for metallurgical and semiconductor industries. Furthermore, due to recent advances in fuel cell technology, hydrogen gas is expected to be used as a new energy source, and the demand for hydrogen gas is on the rise. One of the conventionally widely used methods for producing hydrogen gas is hydrogen obtained by steam reforming from hydrocarbons such as liquefied petroleum gas (LPG), liquefied natural gas (LNG), and naphtha. There is a method in which hydrogen gas is produced by removing carbon monoxide and carbon dioxide from a reformed gas consisting of gas, carbon monoxide and carbon dioxide by a conventional method. This conventional method generally has (1) an unstable supply of hydrocarbons and an unstable price; (2) Desulfurization of the raw material is required, and (3) the reaction temperature is extremely high at 800 to 1000°C, making it particularly unsuitable for medium- to small-scale hydrogen gas production. On the other hand, a method is known in which methanol and steam are reacted to obtain reformed gas. Although this steam reforming reaction of methanol has been known for a long time, there have been few examples of producing hydrogen gas by this method. One of the reasons for this is that no practical catalyst suitable for industrialization of this method has been developed. Furthermore, in this methanol steam reforming reaction, in addition to the main reaction () described below, the reverse shift reaction () described below also occurs as a side reaction, and the hydrogen that has been produced is wasted and carbon monoxide gas is produced as a side reaction. live. CH ₃ OH + H ₂ O3H ₂ + CO ₂ () CO ₂ + H ₂ CO + H ₂ O () As a result, if the purpose is to produce hydrogen gas, the removal from the reformed gas is less than that of carbon dioxide. However, in order to suppress the concentration of carbon monoxide gas in the reformed gas as much as possible, and to prevent the waste of hydrogen gas, which is the target gas, the progress of the reaction () above is slowed down. It is advantageous to suppress it as much as possible. Based on thermodynamic equilibrium, in order to suppress the progression to the right side in the above reaction () and lower the concentration of carbon monoxide gas in the reformed gas, the reaction temperature must be lowered in the reaction (), and the It is known that the proportion of water can be increased. However, in this case, the steam reforming reaction of methanol is carried out in the presence of a large excess of water, and a large amount of heat is required to evaporate this large amount of water, making it uneconomical. The ratio (molar ratio) of water to methanol is kept as close to 1 as possible. Furthermore, if the temperature is lowered, the rate of the reforming reaction will decrease, which is disadvantageous. Therefore, as an industrial catalyst for the methanol steam reforming reaction, it is essential that it has sufficient activity even at low temperatures, and at the same time, it must have so-called durability, which means that the catalyst activity does not decrease even when used for a long time. In addition, it is preferable to have so-called heat resistance, which maintains the same high activity even at high temperatures as at low temperatures. Known catalysts include copper, chromium, and manganese oxide catalysts (Japanese Patent Publication No. 54-11274), copper, zinc, and aluminum-containing catalysts (Japanese Patent Publication No. 49-47281), copper, zinc, aluminum, and thorium oxide catalysts (USP4091086),
Copper, zinc, aluminum, chromium oxide catalyst and nickel, aluminum oxide catalyst
-56302), but none of these catalysts can satisfy all of the above three conditions. For example, Japanese Patent Application Laid-Open No. 57-56302 describes the following. That is, as example 1, CuO44
It is described that the reaction was carried out using a low-temperature conversion classical catalyst having a composition of 5% by weight of ZnO and 11% by weight of Al ₂ O ₃ and a molar ratio of water to methanol of 5. However, in this case, the reaction results deteriorated over time and stable results could not be obtained. Incidentally, the method for producing the catalyst used is not described at all here. Furthermore, Japanese Patent Application Laid-open No. 49-47281 describes as follows. That is, according to Example 1, a precipitate was obtained from a mixed aqueous solution of copper nitrate, zinc nitrate and aluminum nitrate using sodium carbonate as a precipitant,
This is heated and molded to produce Cu:Zn:Al in atomic ratio.
A catalyst with a ratio of 6:3:1 was prepared. Using this catalyst 6, 5 kg of methanol per hour under 30 atmospheres (absolute pressure)
A mixture of 30 kg of water was evaporated to 340°C and passed through the catalyst at this temperature, reducing the temperature to about 220°C. And ^14.1Nm3 of gas flows out every hour.
This gas contains CO ₂ and H ₂ in a ratio of 1:3,
Its CO content is said to have been less than 0.05% by volume. These examples all involve steam reforming of methanol using catalysts containing oxides of copper, zinc, and aluminum, but in the former case,
The disadvantage is that the catalyst activity deteriorates significantly over time.
In addition, in the latter case, the reaction is carried out under conditions where the molar ratio of water to methanol is 10, which is a large excess of water, which is thermoeconomically disadvantageous, and is therefore of little industrial significance. Furthermore, the durability of catalyst activity and heat resistance are unknown. As mentioned above, it is known that a catalyst containing oxides of copper, zinc, and aluminum is used in the steam reforming method of methanol, but the catalyst activity deteriorates over time or the molar ratio of water to methanol is high. The ratio is much larger than the stoichiometric amount, and it has drawbacks such as low industrial value and cannot be said to be satisfactory. The present inventors have developed an industrial catalyst that has sufficient activity even at low temperatures, has so-called durability that does not reduce catalytic activity even after long-term use, and has so-called heat resistance that maintains high activity even under high temperatures. The present invention was completed through intuitive research on catalysts containing oxides of copper, zinc, and aluminum that can be used as catalysts. That is, the present invention provides a method for producing a methanol steam reforming catalyst containing a copper oxide, a zinc oxide, and an aluminum oxide, in which basic copper carbonate, copper hydroxide, and copper oxide are used. At least one type of copper compound selected from the group consisting of; at least one type of zinc compound selected from the group consisting of basic zinc carbonate, zinc hydroxide, and zinc oxide; and alumina sol mixed. This is a method for producing a catalyst for steam reforming of methanol, which is characterized by drying, calcination, and molding. In the present invention, the catalyst is produced by mixing a specific copper compound, zinc compound, and alumina sol and calcining the mixture, and the respective copper and zinc compounds are basic carbonates, hydroxides, and oxides.
There are no particular restrictions on the quality of both the copper compound and the zinc compound, and reagents or industrial chemicals may be used. The copper compound, zinc compound, and alumina sol can be mixed by simply mixing the respective compounds, or by obtaining a mixture of the copper compound and zinc compound by, for example, a coprecipitation method, and then mixing the alumina sol with this mixture. good. In the former case, there is no particular restriction on the order in which the three components are mixed, and the three components may be mixed all at once;
Two of the three may be mixed in advance, and then the mixture of the two may be mixed with the other one. In the latter, the raw materials for copper and zinc are:
There are no particular restrictions on the compound as long as it is a water-soluble compound, but nitrates are preferred from a practical standpoint. Furthermore, water-insoluble raw materials such as metals such as copper and zinc are used after being dissolved by adding an acid such as nitric acid. Alkali is usually used as the precipitant when co-precipitating copper and zinc using these raw materials, but as an alkali,
Caustic alkali, alkali carbonate, alkali bicarbonate, etc. are used, and sodium carbonate is particularly preferably used. The coprecipitation operation is usually carried out at a temperature from room temperature to around 90°C. Mixing of component aqueous solution and precipitant aqueous solution to obtain coprecipitation is as follows:
It can be carried out by a method known per se such as a batch method, a semi-batch method, and a continuous method. Separately, the precipitate slurry thus obtained is
Washed. Preferably, the precipitated slurry is sufficiently washed so that substantially no alkali remains. Next, after adding the alumina sol to the mixture of the copper compound and the zinc compound, or adding the mixture of the copper compound and the zinc compound to the alumina sol, the mixture of the copper compound and the zinc compound and the alumina sol are mixed by a conventional method. , is summed and mixed. The alumina sol used in the present invention may be any commercially available alumina sol, and the alumina sol used is a fine particulate one having an average diameter of usually 1 micron or less, preferably 200 millimicrons or less. Ru. When such fine-particle alumina sol is used, it is possible to obtain an excellent catalyst because of its extremely good dispersibility. Furthermore, alumina sol stabilized on the acidic side with an organic acid is generally used. In addition, the catalyst used must not contain substances that have a poisonous effect on the copper catalyst. The atomic ratio of the copper compound, zinc compound, and alumina sol in the present invention is 0.2 to 2, preferably 0.3 to 1.5, and 0.01 to 0.5, preferably 0.04 to 0.4 for zinc to 1 copper, and 0.01 to 0.5, preferably 0.04 to 0.4. The thus obtained mixture of copper compound, zinc compound and alumina sol is dried and calcined. Drying is carried out in a conventional manner, for example, under normal pressure or reduced pressure, or in a stream of inert gas such as air or nitrogen at a temperature of about 100° C. or less. Firing can be performed by a method known per se. That is, for example, firing is performed in a firing furnace such as an electric furnace or a gas firing furnace in an atmosphere containing oxygen gas, and firing in air is preferable. Firing temperature is at least 250℃, preferably 300-500℃
The firing time is 0.5 to 5 hours, preferably 1 to 3 hours. After firing, the copper oxide, zinc oxide and aluminum oxide are usually shaped by conventional methods. That is, it is formed using a perforated plate and a tablet press, with or without the addition of a lubricant such as graphite. Then,
It is activated as a methanol steam reforming catalyst by reducing it by a conventional method. This reduction is
This can be done by preheating the catalyst at 150-400℃ in a reducing gas atmosphere such as hydrogen gas, carbon monoxide gas or a mixture thereof, or by adding methanol or a mixture of methanol and water to the heated catalyst. It is also possible to reduce the gas by contacting and decomposing the gas. The reaction conditions employed in the methanol steam reforming reaction using the catalyst produced according to the present invention are a reaction temperature of 150 to 400°C, preferably 180 to 350°C.
It is. Further, the ratio of water to methanol is 1 to 7 mol, preferably 1 to 5 mol, per 1 mol of methanol, but the ratio may be more than 7 mol and less than 30 mol. In addition, the space velocity of methanol vapor is 50 to 50000/hr ^-1 , preferably 100 to
15000hr ^-1 , reaction pressure is 50Kg/cm ² G or less,
Preferably it is 30 kg/cm ² G to normal pressure. Further, if necessary, the reaction can be carried out by adding hydrogen gas, carbon monoxide gas, carbon dioxide gas, nitrogen gas, etc. in advance in an amount of about 0.1 to 5 mol per mol of methanol. The amount of carbon monoxide in the reformed gas thus obtained is extremely small, and is usually of a level that hardly poses a practical problem, or at most, a level that is not difficult to remove. Further, hydrogen gas can be easily obtained by removing carbon dioxide gas in the reformed gas by a conventional method using, for example, an aqueous sodium carbonate solution, an aqueous potassium carbonate solution, an aqueous aminoethyl alcohol solution, or activated carbon. The catalyst obtained in the present invention has excellent low-temperature activity, durability, and heat resistance, and is suitable for use in methanol steam reforming reactions. The present invention will be explained in more detail by the following examples. Example 1 The atomic ratio of copper, zinc and aluminum is 1:
A catalyst was prepared consisting of 0.75:0.25 of the respective oxides of copper, zinc and aluminum. That is, an aqueous solution containing copper nitrate (1st class reagent) and zinc nitrate (1st class reagent) and an aqueous solution of sodium carbonate (1st class reagent) in a predetermined composition ratio are heated to 73°C and mixed with thorough stirring to form a base. A co-precipitate of basic copper carbonate and basic zinc carbonate was obtained. After over-separating and washing this coprecipitate, alumina sol (alumina content: 10 wt%) in a predetermined ratio was added and mixed. After drying the mixture of the predetermined composition thus obtained at 80°C, it was dried at 380°C in an air stream.
It was fired in After crushing the fired product, 3 wt% of graphite was added as a lubricant, and the mixture was compressed into tablets. 10 ml of this tablet-shaped catalyst was filled into a reactor with an inner diameter of 10 mmφ, heated in a hydrogen stream at 200° C. for 6 hours for reduction, and then reacted under predetermined reaction conditions. During this reaction period, 5 days per dose
A high-temperature reaction was carried out at 360°C, then the temperature was lowered to 280°C and the activity of the catalyst was examined. This was repeated several times. The reaction conditions and reaction results are shown in Table 1. Comparative Example 1 Aluminum nitrate (grade 1 reagent) was used instead of alumina sol as an aluminum source, and
The same procedure as in Example 1 was carried out, except that an aqueous solution of aluminum nitrate, copper nitrate (1st grade reagent), and zinc nitrate (1st grade reagent) dissolved in water and an aqueous solution of sodium carbonate (1st grade reagent) were mixed. Ta. The reaction conditions and reaction results are shown in Table 1. Comparative Example 2 The same procedure as in Example 1 was carried out except that aluminum hydroxide powder (reagent) was used instead of alumina sol. The reaction conditions and reaction results are shown in Table 1. Example 2 A catalyst with the same atomic ratios of copper, zinc and aluminum as in Example 1 was prepared. Copper hydroxide (reagent) and zinc hydroxide (reagent) in a specified composition ratio
and alumina sol (10wt% content) were mixed. This mixture was dried at 70°C and then calcined at 380°C in a stream of air. The steps after granulation were carried out in the same manner as in Example 1. The reaction conditions and reaction results are shown in Table 1.

【table】

[Table] *Top: Initial reformed gas composition
Lower row Reformed gas composition after the final heat resistance test
Example 3 The atomic ratio of copper, zinc and aluminum is 1:1 in Table 2 and below.
The same procedure as in Example 1 was conducted except that the ratio was 0.4:0.2 and a mixed gas of hydrogen and carbon monoxide (H ₂ 50%) was used as the reducing gas for the catalyst. The reaction conditions and reaction results are shown in Table 2. Comparative Example 3 A catalyst having the same composition as in Example 3 was prepared as follows. An aqueous solution containing copper nitrate (1st class reagent) and zinc nitrate (1st class reagent) in a predetermined composition ratio and a solution in which aluminum hydroxide fine powder (reagent) is suspended in an aqueous sodium carbonate solution are heated to 80°C, respectively. The mixture was mixed with thorough stirring to obtain a coprecipitation slurry. This coprecipitated slurry was filtered, separated, washed, dried at 70°C, and calcined at 380°C in a stream of air.
The operations following granulation were carried out in the same manner as in Example 1, except that a mixed gas of hydrogen and carbon monoxide (H ₂ 50%) was used as the reducing gas for the catalyst. The reaction conditions and reaction results are shown in Table 2.

【table】

[Table] Example 4 Atomic ratio of copper, zinc and aluminum is 1:
A catalyst was prepared consisting of the respective oxides of copper, zinc and aluminum in a ratio of 1.35:0.1. That is, an aqueous solution containing copper nitrate (industrial use) and zinc nitrate (industrial use) in a predetermined composition ratio is heated to 75° C., and this is designated as solution A. Separately, an aqueous solution containing a predetermined amount of sodium carbonate was heated to 75°C, and this was designated as solution B. On the other hand, put water in a reaction tank equipped with a stirrer,
The temperature was raised to 75° C. with thorough stirring, and solutions A and B were started to be supplied at the same time and each was supplied at a constant rate so as to end at the same time, and mixed to obtain a coprecipitate. After filtering, separating and washing this coprecipitate, an amount of alumina sol (alumina content
10wt%) was added and mixed. The thus obtained mixture having a predetermined composition was dried at 100°C and then fired at 400°C in a stream of air. After crushing the fired product, 3 wt% of graphite was added as a lubricant, and the mixture was compressed into tablets. 10 ml of this tablet-shaped catalyst was filled into a reactor with an inner diameter of 10 mmφ, heated to 200° C., and methanol vapor was introduced little by little into the reactor for reduction. Subsequently, a reaction was carried out in the same manner as in Example 1 under predetermined reaction conditions. Table 3 shows the reaction conditions and reaction results. Comparative example 4 γ-alumina (reagent) instead of alumina sol
The same procedure as in Example 4 was carried out except that the powder was crushed into fine particles (100 mesh or less). Table 3 shows the reaction conditions and reaction results.

【table】

[Table] Example 5 Atomic ratio of copper, zinc and aluminum is 1:
A catalyst was prepared consisting of the respective oxides of copper, zinc and aluminum in a ratio of 1:0.35. That is, an amount of copper nitrate (reagent 1
A copper slurry solution was prepared by adding an aqueous ammonium bicarbonate solution to an aqueous solution containing a copper-based compound. The above copper slurry liquid was added to a separately prepared zinc oxide (grade 1 reagent) slurry solution having a predetermined composition ratio, and carbon dioxide gas was blown into the solution while stirring to cause coprecipitation of basic copper carbonate and basic zinc carbonate. Obtained. The subsequent operations were carried out in the same manner as in Example 1. Table 4 shows the reaction conditions and reaction results. Comparative Example 5 A catalyst having the same composition as in Example 5 was prepared as follows. Copper nitrate (reagent 1) in an amount that gives a predetermined composition ratio
A copper-aluminum hydroxide slurry solution was prepared by adding an aqueous ammonium bicarbonate solution to a solution in which aluminum hydroxide fine powder (reagent) was suspended in an aqueous solution containing aluminum hydroxide. The copper-aluminum hydroxide slurry was added to a separately prepared slurry of zinc oxide (grade 1 reagent) having a predetermined composition ratio, and carbon dioxide gas was blown into the slurry with stirring to obtain a coprecipitated slurry. This coprecipitated slurry was filtered, separated, washed, dried at 80°C, and calcined at 380°C in a stream of air.
The subsequent operations were performed in the same manner as in Example 1. Table 4 shows the reaction conditions and reaction results. Example 6 A catalyst with the same atomic ratios of copper, zinc, and aluminum as in Example 5 was prepared. An aqueous solution containing copper nitrate (industrial use) and zinc nitrate (industrial use) in a predetermined composition ratio and an aqueous solution of sodium hydroxide (industrial use) are each heated to 70°C and mixed with thorough stirring to form copper oxide. A mixture of zinc oxide and zinc oxide was obtained. After over-separating and washing this, alumina sol (10 wt% content) in an amount to give a predetermined ratio was added and mixed. The subsequent operations were carried out in the same manner as in Example 1. Table 4 shows the reaction conditions and reaction results.

【table】

【table】

Claims (1)

[Claims] 1. In a method for producing a catalyst for steam reforming of methanol containing copper oxide, zinc oxide and aluminum oxide, a catalyst selected from the group consisting of basic copper carbonate, copper hydroxide and copper oxide is used. At least one type of copper compound, at least one type of zinc compound selected from the group consisting of basic zinc carbonate, zinc hydroxide, and zinc oxide, and alumina sol are mixed, dried, A method for producing a catalyst for steam reforming of methanol, which comprises firing and molding.