JP5258618B2 - Method for producing copper catalyst - Google Patents

Description

  The present invention provides a copper catalyst having good catalytic activity and remarkably excellent durability in a reaction in which a copper catalyst is used such as methanol synthesis reaction or its reverse reaction, methanol reforming reaction, shift reaction or its reverse reaction. It relates to a manufacturing method.

Conventionally, a methanol synthesis process using synthesis gas (a mixed gas of CO and H ₂ ) as a main raw material (including a small amount of CO ₂ ) is a very important basic process in the chemical industry, and its energy saving and There is a constant demand for higher efficiency from the viewpoint of economy and the like. One of the most important technologies in the methanol synthesis process is to provide a high performance catalyst, and conventional catalysts include Cu / ZnO / Al ₂ O ₃ catalysts (current industrial catalysts such as “catalysts”). "Lecture, Vol. 7, edited by the Catalysis Society of Japan, Kodansha Co., Ltd., published July 20, 1989" (Non-Patent Document 1), pages 21-39), Cu / ZnO / SiO ₂ catalyst (Japanese Examined Patent Publication 63- No. 39287 (Patent Document 1) and the like are known.

On the other hand, methanol synthesis using CO ₂ and H ₂ as main raw materials has recently attracted particular attention from the viewpoint of recycling and recycling of carbon resources and global environmental problems. In methanol synthesis from raw material gas with high CO ₂ content, thermodynamic equilibrium of reaction and reaction inhibition effect of water generated with methanol (Applied Catalysis A: General, 38 (1996), p.311-318 For Patent Document 2)), a catalyst having higher activity than that employed in methanol synthesis from the above synthesis gas is required. In addition, in the synthesis of methanol from a raw material gas having a high CO ₂ content, the decrease in catalytic activity, which is thought to be caused by water generated together with methanol, is much greater than that in the synthesis of methanol from synthesis gas. Therefore, there is a need for a catalyst that is much more durable than the catalyst employed in methanol synthesis from synthesis gas. This is because the catalyst performance of the three-component catalyst employed in the above methanol synthesis is insufficient.

From this point of view, copper-based multi-component catalysts such as copper / zinc oxide / aluminum oxide / zirconium oxide and copper / zinc oxide / aluminum oxide / zirconium oxide / gallium oxide have been developed (for example, (See JP-A-7-39755 (Patent Document 2), JP-A-6-312138 (Patent Document 3), Applied Catalysis A: General, 38 (1996) p.311-318 (Non-Patent Document 2)) . Furthermore, a highly active catalyst in which 0.3 to 0.9 wt% of colloidal silica or water-dissolved silica is added as silica and calcined at 480 to 690 ° C. has been developed (Japanese Patent Laid-Open No. 10-309466 (Patent Document 4). )). Although these catalysts are highly active, their activity may not always be sufficiently reproduced even if they are produced with the same formulation. In general, in order to obtain a highly active catalyst with good reproducibility, it is known that stable pH during precipitation and sufficient washing of the precipitating agent are necessary (for example, JP-A-52-76288 ( Patent Document 5), Japanese Patent Laid-Open No. 7-8799 (Patent Document 6), Japanese Patent Laid-Open No. 2007-83197 (Patent Document 7)). Many improvements have been made for this purpose, but the reproducibility is not always good, and further improvements are desired.
Japanese Patent Publication No.63-39287 JP-A-7-39755 Japanese Patent Laid-Open No. 6-312138 JP-A-10-309466 JP-A 52-76288 Japanese Patent Application Laid-Open No. 7-8799 JP 2007-83197 A Catalyst Course, Volume 7, Catalytic Society, published by Kodansha Co., Ltd., issued July 20, 1989 Applied Catalysis A: General, 38 (1996) p.311-318

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a reproducible copper-based catalyst having good catalytic activity and remarkably excellent durability.

  As a result of intensive investigations to solve the above problems, the present inventors have found that the above problems can be solved by bringing the slurry in the middle of catalyst production into contact with clean water under specific conditions. It was. That is, the present invention relates to a method for producing a distillation catalyst comprising copper oxide, zinc oxide, and aluminum oxide as essential components and zirconium oxide, gallium oxide, and silicon oxide as optional components. The aqueous solution of the salt and the aqueous solution of the precipitant are mixed in water to form a precipitate of the catalyst precursor, and then the precipitate is sufficiently dispersed in water to reach the dissolution equilibrium of the precipitant; and The catalyst production method is characterized in that the slurry is always kept in contact with clean water.

  In the above production method, (1) the aqueous solution of each acidic metal salt and the aqueous solution of the precipitating agent are mixed in water to form a catalyst precursor precipitate, and then the catalyst precursor concentration in the slurry solution is kept constant. As it is, the slurry liquid phase part is continuously extracted and the water is supplied, and the step of removing the precipitant and (2) by extracting the slurry liquid phase part outside the system without adding water, It is preferable to include a step of increasing the content of the catalyst precursor in the slurry to obtain a cake-like precipitate, and (3) a step of drying and baking the cake-like precipitate to obtain a metal oxide.

  In the above production method, the precipitating agent is an alkali metal compound, and it is desirable to remove the precipitating material until the alkali metal contained in the catalyst after the precipitating agent is 0.1 wt% or less.

  Moreover, it is desirable that the temperature of the slurry liquid phase part and the cake-like precipitate before drying from which water is extracted are 10 to 40 ° C.

  In the present invention, the precipitation is preferably in the range of pH 5 to 9, and the precipitation concentration of the catalyst precursor in the slurry solution is preferably in the range of 0.5 to 12% by weight.

  The production method according to the present invention has high reproducibility, and the obtained catalyst has high activity, and the high activity is maintained over a long period of time and has excellent durability. The activity maintaining effect of the catalyst at this time is remarkable, and excellent activity and durability that cannot be expected with the copper-based multicomponent catalyst for methanol synthesis currently used or proposed are obtained. In particular, the present invention is extremely useful industrially.

<catalyst>
The copper-based catalyst of the present invention is a catalyst composed of a metal oxide containing copper oxide, zinc oxide and aluminum oxide as essential components and further containing zirconium oxide, gallium oxide and silicon oxide as optional components. Further, other oxides may be included as long as the gist of the present invention is not impaired.

  The ratio of each component is 20 to 60% by weight (preferably 30 to 50% by weight) of copper oxide and 10 to 50% by weight (preferably 20 to 40% by weight) of zinc oxide, when the total catalyst is 100% by weight. ), Aluminum oxide 2-10 wt% (preferably 4-8 wt%), zirconium oxide 0-40 wt% (preferably 10-20 wt%), gallium oxide 0-10 wt% (preferably 0.1 ˜5 wt%) and silicon oxide is 0˜2 wt% (preferably 0.3˜0.9 wt%). In such a quantitative range, the catalyst performance suitable for the reaction can be obtained by determining an appropriate catalyst production formulation and an appropriate composition according to the target reaction.

  In the copper-based catalyst of the present invention, the silicon oxide may be derived from colloidal silica or silica dissolved in water. Colloidal silica and water-dissolved silica may be used in combination.

  When using silica dissolved in water, natural fresh water, tap water, well water, industrial water, or the like can be used. These waters contain about 20 ppm to about 100 ppm of dissolved silica. The dissolved silica is silica (commonly referred to as colorimetric silica) measured by a spectrophotometric method using a molybdenum yellow method or a molybdenum blue method.

<Manufacture of catalyst>
The method for producing the catalyst is important for maximizing the performance of the catalyst having an appropriate composition. In general, the catalyst is prepared by mixing a liquid A composed of an aqueous solution containing a water-soluble salt of a metal component and a liquid B composed of an aqueous solution of a precipitating agent containing a basic substance to form a precipitate that becomes a catalyst precursor. It is formed by aging, appropriately aging, and then washing to remove the precipitant, and drying the washed precipitate, followed by baking at 280-690 ° C. to obtain a baked product.

  Here, when the liquid A and the liquid B are mixed to form a precipitate, the liquid A and the liquid B are mixed together to precipitate components in the liquid A, and the liquid A is increased to 2 or more. First, the liquid A comprising an aqueous solution containing one or more of the metal compounds and the liquid B comprising an aqueous solution containing a basic substance are mixed to precipitate the components in the liquid A, and then A precipitation method is also employed in which the solution A comprising an aqueous solution containing the remaining components of the metal compound is added to the solution containing the precipitate, and the solution is precipitated in the same manner. Various other variations are possible for the mixing method.

As the water-soluble salt of the metal component, nitrates and nitrites having good water solubility are preferably used. As the basic substance, for example, alkali metal salts such as sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide are preferably used. Further, sodium hydroxide, in the case of using potassium hydroxide is also used in combination blowing CO ₂ gas.

  After the formation of the precipitate, in order to obtain a highly active catalyst precursor, aging is appropriately performed, followed by washing. Although the washing here is performed to remove the alkali metal salt that is a precipitant, if this washing is insufficient and a large amount of alkali metal remains, the activity of the catalyst during the subsequent methanol production may be significantly reduced. Are known. Therefore, this washing is usually performed until the alkali metal is removed to a level that does not affect the methanol synthesis reaction. As a general washing method, the precipitate in the solution is squeezed to remove the water together with the precipitating agent dissolved by filter filtration, and then the clean water is added to the precipitate and the precipitate is added. Re-disperse in water. The slurry in which the precipitate is dispersed in water is filtered again. A method is adopted in which this series of operations is repeated until the precipitant in the precipitate becomes a target concentration or less. Alternatively, after the slurry is filtered through a filter plate to form a cake-like precipitate, a washing process is performed in which washing water is poured from above the filter plate to replace the filtrate present in the cake-like precipitate and drive it out. . Here, since the precipitating agent usually uses a compound having high water solubility, most of it is present in water. Therefore, the precipitant is efficiently removed by the washing water by the above operation.

  However, according to the study by the present inventors, although the precipitant in the filtrate is sufficiently low in the above method, the precipitant in the precipitate is often much higher than the concentration in the filtrate. It was confirmed that it remained at a high concentration. That is, the precipitant, particularly alkali metal, does not easily elute into the filtrate. Therefore, even if the concentration of the precipitant in the filtrate is simply decreased, the precipitant in the precipitate is not necessarily removed. According to a further study by the present inventors, in the method of washing with clean water after forming the above cake, in order for the precipitant concentration in the filtrate to be the same as the precipitant concentration in the precipitate, It was found that it was necessary to leave the slurry solution as it was with stirring for at least 2 hours after addition of clean water. This is because the precipitant is ionically bound to the precipitate and gradually dissolves in water in equilibrium, or is filtered to make the precipitate cake, and then water is added. Even if it is attempted to disperse the precipitate, it is presumed that it is difficult to diffuse and the precipitant remaining in the precipitate is difficult to escape. Therefore, when repeating filtration and water dispersion, it is necessary to repeat at least many times. It is desirable to remove the alkali metal content in the precipitate to 0.1% by weight or less with respect to the precipitate. However, such washing by repeated filtration and diffusion into water requires a very long time. .

In the prior art, since there is no description of the cleaning method, in particular, the reproduction of the catalytic activity has not always obtained satisfactory results, particularly in the case of scale-up. (For example, JP-A-7-8799, JP-A-7-39755, JP-A-10-272361, etc.)
As a result of repeated examination in view of the above situation, the present inventors have sufficiently reached the dissolution equilibrium of the precipitant in a state where the precipitate is highly dispersed in water, and always keeps the slurry state and is clean. It is a gist of the present invention that contact with water is necessary to efficiently remove the precipitant.

  Here, the purpose of always contacting with clean water is to supply water that does not contain a precipitating agent and replace it with water in which the precipitating agent has dissolved, and to achieve sufficient dissolution equilibrium of the precipitating agent. The state refers to a state when the conductivity change in the slurry solution becomes an error within 5% of the original conductivity in one hour after the precipitate is dispersed in water at a concentration of 2% by weight.

  The lower the content of the precipitant, the better. However, since it takes a very long time for the treatment to bring the content as close to zero as possible, in the present invention, the content of the alkali metal in the precipitate is 0. It is sufficient to remove to less than 1% by weight.

  That is, in the precipitate of the present invention, the produced precipitate is not filtered to form a cake, but is kept in a slurry state, preferably with continuous addition of clean water while extracting the slurry liquid phase portion, and then extracted. It is characterized by removing the precipitant in both the liquid phase part. There is no restriction | limiting in particular as a slurry density | concentration, What is necessary is just to be able to maintain a highly dispersed state of a precipitate, and there is no restriction | limiting in particular. In consideration of operability, the slurry concentration is practically 10% by weight or less, but if it falls below 1% by weight, the apparatus becomes large and the economy is lowered. With this method, since the treatment is always performed in a state where the precipitate and the water are in contact with each other, the contact time can be increased, and the washing time can be greatly reduced as compared with the operations of filtration and redispersion with water. In general, it is more efficient to repeat the operations of pressing the precipitate as much as possible, squeezing the water, adding new washing water, and squeezing the water. In the removal of the precipitant from the catalyst composed of a metal oxide containing aluminum oxide as an essential component and further containing zirconium oxide, gallium oxide, and silicon oxide as an optional component, for the reason described above, it remains in a slurry state. It is more efficient to replace the washing water. The slurry concentration is preferably maintained at the same concentration during washing.

  As an apparatus for performing such an operation to sufficiently reach the dissolution equilibrium of the precipitating agent in a highly dispersed state in water and always contact with clean water, a part for extracting water from the slurry and A device composed of a part for newly adding clean water, a part for newly added water, and a part for mixing the slurry after extracting the water, each part being connected so that the slurry can be circulated. I just need it.

  For example, when removing water, a so-called cakeless filtration (dynamic filter) having a scavenging mechanism that prevents the filter cake from becoming thicker as much as possible can be employed. A rotary cylindrical cakeless filter, a Shriver filter thickener, a multi-chamber cylindrical vacuum filter (Oliver filter) machine, a centrifugal slurry filter, or the like can be used.

  The slurry washed in this manner can be generally concentrated as it is and spray-dried, but generally, the slurry is filtered under pressure to form a cake-like precipitate. In this case, a vacuum filter, a filter press filter, a centrifugal dehydration filter, or the like can be used.

  The obtained cake-like precipitate is dried and fired to become a metal oxide. An apparatus for performing drying and baking at this time is not particularly limited, and a general dryer is used.

  The dried catalyst precursor is calcined at 280 to 690 ° C. (preferably 350 to 680 ° C., particularly preferably 480 to 670 ° C.) to obtain a calcined product. Firing is performed in an oxygen atmosphere (usually in air), whereby the metal component described above is in the form of an oxide.

  The catalyst thus obtained is used as it is or after being granulated or tableted by an appropriate method. The particle diameter and shape of the catalyst can be arbitrarily selected depending on the reaction system and the shape of the reactor.

<reaction>
The above catalyst is useful as a catalyst for the reaction of synthesizing methanol from hydrogen and carbon oxide or the reverse reaction thereof.

When the above catalyst is used for the reaction, this catalyst can be used as it is, but it is usually reduced with a reducing gas such as H ₂ gas or H ₂ —N ₂ mixed gas before use.

In the case of methanol synthesis, methanol is synthesized by reacting a raw material gas consisting of hydrogen and carbon oxide (CO ₂ alone or a mixed gas of CO ₂ and CO) on a catalyst. The reaction at this time is typically performed at a reaction temperature of 150 to 300 ° C. and a reaction pressure of 1 to 10 MPa. In the reverse reaction, methanol can be decomposed into hydrogen and carbon oxides. The reaction at this time is typically performed at a reaction temperature of 200 to 400 ° C. and a reaction pressure of atmospheric pressure to 1 MPa. These reactions can be carried out either in the gas phase or in the liquid phase. As a solvent for the reaction in the liquid phase, a water-insoluble or hardly water-soluble solvent is used, including a hydrocarbon solvent.

<Action>
In the copper-based catalyst of the present invention, the essential components copper oxide, zinc oxide and aluminum oxide (and optional components zirconium oxide, gallium oxide, palladium oxide and silicon oxide) are the skeleton and active. Since the alkali metal salt that inhibits the catalyst is sufficiently removed, the catalyst becomes highly active by being subjected to a calcination treatment in the temperature range of 480 to 690 ° C., and its activity is maintained for a long period of time and has excellent durability. It becomes.

  According to the study by the present inventors, when an alkali metal is present in the catalyst, crystallization of the metal oxide component in the catalyst is promoted, and the specific surface area of the active component is reduced. For example, even if only 0.4% by weight of an alkali metal is present in a catalyst mainly composed of copper oxide, zinc oxide, and aluminum oxide, Cu (reduced state), oxidation can be obtained by performing X-ray diffraction measurement of the catalyst. It became clear that crystals of zinc and zirconium oxide were growing considerably. On the other hand, for the catalyst mainly composed of copper oxide, zinc oxide, and aluminum oxide from which alkali metal has been removed to 0.1% by weight or less, after performing similar firing, X-ray diffraction measurement of the catalyst is performed. It was revealed that crystals of Cu (reduced state), zinc oxide, and zirconium oxide were hardly grown. That is, by sufficiently removing the alkali metal, crystal growth of each component in the catalyst is suppressed, and high dispersibility can be maintained for a long time.

As described above, the catalyst produced according to the present invention can stably reproduce its performance, and can cope with an industrial production method.

EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

<Manufacture of catalyst>
Example 1
Copper nitrate trihydrate (5.6 kg), zinc nitrate hexahydrate (4.1 kg), aluminum nitrate nonahydrate (1.4 kg), zirconium nitrite dihydrate (2.0 kg) and colloidal silica -O "0.1 kg of silicic acid anhydride (SiO2 content: 20 to 21% by weight) was dissolved in distilled water to prepare a 38 L aqueous solution. Separately, 15.7 kg of sodium carbonate decahydrate was dissolved in distilled water to prepare a 38 L aqueous solution, which was designated as solution B. Liquid A and liquid B were simultaneously dropped into 125 L of distilled water vigorously stirred (this method is referred to as a coprecipitation method). After allowing this to stand for a whole day and night, the obtained precipitate is continuously supplied with 2.4 m ³ of distilled water through a rotating cylindrical cakeless filter having a filtration area of 1 m ² , and the slurry liquid phase part is extracted at the same speed. Then, the cake was recovered with a pressure filter. The total treatment time of the precipitate at this time was 9 hr, and the filtrate conductivity was 60 mS / m. A portion of this cake was sampled and redispersed with water to give a 2% by weight slurry, and the filtrate conductivity was measured to be 30 mS / m at first. The degree was 31 mS / m.

The cake was dried at 110 ° C. and then calcined at 600 ° C. in air for 2 hours. Sodium in the obtained catalyst was 0.03 wt%, and the specific surface area of the catalyst after calcination was 85 m ² / g.

(Comparative Example 1)
The precipitate obtained in the same manner as in Example 1 was filtered with a filter press having a filtration area of 1.2 m ² , and 2.5 m ³ of distilled water was directly passed through the filter chamber for washing. It was collected. The total treatment time of the precipitate at this time was 7 hr, and the filtrate conductivity was 14 mS / m. A portion of this cake was sampled, redispersed with water to give a 2% by weight slurry, and the filtrate conductivity was measured to be 20 mS / m at first, but after 1 hour, the filtrate conductivity was Was 280 mS / m and did not reach equilibrium.

  The cake was dried at 110 ° C. and then calcined at 600 ° C. in air for 2 hours. Sodium in the obtained catalyst was 1.4% by weight, and the specific surface area of the catalyst after calcination was 32 m 2 / g.

(Comparative Example 2)
The precipitate obtained in the same manner as in Example 1 was filtered with a filter press having a filtration area of 1.2 m 2, and the obtained cake was redispersed in 200 L of distilled water in 30 minutes and immediately filtered again with a filter press. did. This operation was repeated three times. The total treatment time of the precipitate at this time was 10 hr, and the filtrate conductivity was 30 mS / m. A portion of this cake was sampled, redispersed with water to give a 2% by weight slurry, and the filtrate conductivity was measured. The initial value was 25 mS / m, but after 1 hour it became 240 mS / m. , Did not reach equilibrium.

  The cake was dried at 110 ° C. and then calcined at 600 ° C. in air for 2 hours. Sodium in the obtained catalyst was 1.3% by weight, and the specific surface area of the catalyst after calcination was 40 m 2 / g.

(Comparative Example 3)
The precipitate obtained in the same manner as in Example 1 was filtered with a filter press having a filtration area of 1.2 m2, the obtained cake was redispersed in 200 L of distilled water in 30 minutes, and stirring was continued for 2 hours. It filtered again with the filter press. This operation was repeated three times. The total treatment time of the precipitate at this time was 15 hr, and the filtrate conductivity was 11 mS / m. A portion of this cake was sampled, redispersed with water to give a 2% by weight slurry, and the filtrate conductivity was measured to be 9 mS / m at first, but 95 mS / m after 1 hour. , Did not reach equilibrium.

  The cake was dried at 110 ° C. and then calcined at 600 ° C. in air for 2 hours. Sodium in the obtained catalyst was 0.54% by weight, and the specific surface area of the catalyst after calcination was 51 m 2 / g.

(Activity evaluation)
The reaction tube was filled with 2 ml of the catalyst obtained above, and reduced at 300 ° C. by passing a reducing gas consisting of 10 vol% H 2 and 90 vol% N 2 at a temperature of 300 ° C. for 2 hours, followed by 25 vol% CO ₂ , H _{2 A} 75 vol% mixed gas was passed through the catalyst layer at a rate of 20 liters / hr, and the reaction was carried out under conditions of pressure 5 MPa and temperature 250 ° C. The reaction product gas was analyzed with a gas chromatograph, and the relationship between the reaction time and the amount of methanol produced was determined. Table 1 shows the amount of methanol produced (g-MeOH / L-Cat / hr) in 5 hours after the start of the reaction.

Claims (5)

A method for producing a catalyst comprising a metal oxide comprising copper oxide, zinc oxide, and aluminum oxide as essential components, and zirconium oxide, gallium oxide, and silicon oxide as optional components, each comprising an aqueous solution and a precipitate of each acidic metal salt The aqueous solution of the agent is mixed in water to form a catalyst precursor precipitate, and then the precipitate is sufficiently dispersed in water to reach the precipitant dissolution equilibrium, and the slurry state is always maintained. A method for producing a catalyst for synthesizing methanol from hydrogen and carbon oxides, characterized by being held and brought into contact with clean water. (1) The aqueous solution of each acidic metal salt and the aqueous solution of the precipitant are mixed in water to form a precipitate of the catalyst precursor, and then the slurry liquid phase is maintained while keeping the concentration of the catalyst precursor in the slurry solution constant. A step of removing the precipitant by continuously extracting the water and supplying water, and (2) extracting the slurry liquid phase outside the system without adding water, thereby providing a catalyst precursor in the slurry. 2. The hydrogen and carbon according to claim 1, comprising: a step of increasing the content concentration of a cake to form a cake-like precipitate; and (3) a step of drying and baking the cake-like precipitate to form a metal oxide. A method for producing a catalyst for synthesizing methanol from an oxide. The hydrogen and carbon oxide according to claim 2, wherein the precipitant is a solution of an alkali metal compound, and the precipitant is removed until the alkali metal contained in the catalyst is 0.1 wt% or less. Of a catalyst for synthesizing methanol from methanol. The production of a catalyst for synthesizing methanol from hydrogen and carbon oxide according to claim 2, characterized in that the temperature of the slurry liquid phase part and the cake-like precipitate before drying from which water is extracted is 10 to 40 ° C. Method. 2. The hydrogen according to claim 1, wherein the pH for forming the precipitate is in the range of 5 to 9, and the concentration of the catalyst precursor in the slurry solution is in the range of 0.5 to 12 wt%. Of a catalyst for synthesizing methanol from carbon oxides.