JPS6050721B2 - Method for producing porous inorganic oxide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a porous inorganic oxide, and more particularly to a method for producing an inorganic oxide with a controlled pore structure suitable as a catalyst carrier.

Alumina, silica, titania, silica-alumina,
Porous inorganic oxides such as boria are used as catalyst supports, desiccants, adsorbents, fillers, etc. by utilizing their porous structure.

By the way, when such a porous inorganic oxide is used as a catalyst carrier, it is required to have physical and chemical properties suitable for the purpose.

For example, physical properties include optimal pore structure, high physical strength, good formability and shape retention, good heat resistance, and appropriate thermal conductivity, specific heat, and specific gravity. On the other hand, the chemical properties include stable quality and no deterioration, chemical properties suitable for the reaction, good dispersibility of the catalytic metal, and no acidity or basicity. Appropriateness is required. Among the above-mentioned physical properties, those that are particularly important for catalyst supports are pore structure and physical strength. In this case, the pore structure is anti-
There are important factors that influence reaction activity and catalyst life, including specific surface area, pore diameter, pore shape, and pore volume. usually,
In a catalytic reaction, the larger the specific surface area, the greater the number of active sites involved in the reaction, giving higher activity. The pore size provides a path for molecules involved in the reaction to diffuse into the active sites within the catalyst pores, and the larger the pore size, the easier it is for the reaction molecules to diffuse into the catalyst pores. However, when the pore diameter becomes too large, the specific surface area decreases and the reaction activity of the catalyst decreases. Therefore, it is important to take these matters into account and adjust the pore diameter to an optimal range. In addition, regarding the shape of the pores, it is better to have a uniform and straight shape with a small degree of labyrinth, and in the shape of the passage through which the reaction molecules diffuse, the inlet should be narrow in the shape of an ink bottle, and the middle should be constricted. A gourd shape, a meandering shape, etc. are not preferred because they reduce the reaction activity of the catalyst. Pore volume! Although the product does not directly control the catalytic activity, if it is too large, the packing density of the catalyst in the reaction vessel will decrease, which will lower the overall activity, which is undesirable.
However, in the case of a reaction in which a substance that poisons the catalyst gradually accumulates in the catalyst pores as the reaction progresses, for example, in the case of hydroprocessing of heavy oil, Large pore volumes may be preferred to withstand the accumulation of toxic substances. Physical strength is related to its abrasion and destructive properties during catalyst filling and use4, so
From a practical standpoint, those with high strength are preferred. Of particular importance in connection with the chemical properties of the catalyst support are its acidic and basic properties.

Generally, it is well known that many inorganic oxides exhibit the properties of solid acids or solid bases, and even if inorganic oxides alone do not exhibit such acidic or basic acid properties,
It is also known that the effect can be expressed by mixing this inorganic oxide with another inorganic oxide. Furthermore, it is well known that even complex compounds having the same composition can have different properties depending on the method of preparing the complex compound. For example, in the case of silica-alumina, if the same raw material is used to produce it using different manufacturing methods such as the deposition method, gel mixing method, or coprecipitation method, the acidity of the obtained silica-alumina will change. The intensity distribution etc. will be different. These chemical properties of inorganic oxides are important factors that affect the performance and performance of catalysts, such as activity, selectivity, and lifespan, so it is necessary to control them appropriately in relation to the target reaction. For this purpose, it is usually effective to combine two or more compounds in that the chemical properties can be drastically changed. It is important to decide whether to adopt the standardization method. Conventionally, the method for producing porous inorganic oxides used as catalyst carriers is as follows:
After forming crystal grains that serve as seeds, which are precursors for producing porous inorganic oxides, growing these crystal grains and turning them into sol or gel-like substances, processes such as washing, dehydration molding, drying, and firing are carried out. Generally, the desired catalyst carrier is manufactured using the following methods.

In this manufacturing operation, the important steps for controlling the above-mentioned physical and chemical properties are the step of obtaining a sol or gel-like substance and the step of dehydration or drying. Conventionally,
A method for producing crystal particles that serve as seeds, which are precursors for producing porous inorganic oxides, and grow these crystal particles to produce crystal particles that serve as seeds in the gelation process to obtain a gel-like substance. , heterogeneous precipitation method, homogeneous precipitation method, and hydrolysis method.

In the heterogeneous precipitation method, inorganic compounds are neutralized with acid or alkali to produce crystal grains that serve as seeds, but the size of the crystal grains produced due to the uneven local concentration during neutralization It has the disadvantage that it becomes uneven. The homogeneous precipitation method is a method that overcomes the disadvantages of the heterogeneous precipitation method, but it uses urea or hexamethylenetetramine as a neutralizing agent and heats it to decompose these neutralizing agents and destroy the crystal particles. must be generated. In addition, the hydrolysis method generates crystal particles by hydrolyzing an inorganic compound without using a neutralizing agent, and from the viewpoint of obtaining crystal particles of uniform size, it is different from the heterogeneous precipitation method. They belong to the same category. When the porous inorganic oxide is composed of two or more components, methods for producing crystal particles that serve as seeds in the gelation process include the deposition method (Japanese Patent Publication No. 47-8045) and the coprecipitation method (Japanese Patent Publication No. 43-1989). -25343).

In the deposition method, prepared crystal particles are well dispersed, other compounds to be added are dissolved therein, a neutralizing agent is added under uniform coexistence conditions, and other crystal particles are newly added on top of the crystal particles. However, the disadvantage is that the product is surface-coated and non-uniform in quality. The coprecipitation method is a method in which two or more compounds constituting a porous inorganic oxide are dissolved in a coexisting state and simultaneously co-precipitated. Although qualitatively uniform crystal particles can be expected with this method, since the precipitation conditions (such as pH) differ depending on the substance, it does not result in truly uniform precipitates. The pore structure of a porous material is generally controlled by growing crystal particles generated by neutralization or hydrolysis of the above-mentioned inorganic compound.

A common method for growing crystal particles into a gel state is as follows:
These include aging, hydrothermal treatment, and addition of growth materials. The most common method among these is the aging method. This is because when crystal particles of different sizes coexist, the solubility is greater on the surface of small particles with higher surface energy than on the surface of large particles, so the ion concentration of the mother liquor becomes unsaturated on the surface of small particles, and vice versa. The surface of large particles becomes supersaturated, so the small particles eventually dissolve and only the large particles grow. In addition, it is necessary to strictly control the PHL temperature, time, etc., and to use strong stirring in order to grow uniform crystal grains under ripening conditions. The hydrothermal treatment method promotes grain growth by carrying out this aging at high temperature and high pressure, but it is not often used because it is difficult to control the uniform growth of crystal grains. In addition, the method of adding growth raw materials is a method in which the growth of crystal grains is promoted by adding compounds that are raw materials necessary for the growth of crystal grains. The disadvantage is that crystal grains are likely to be formed and non-uniform grains are likely to grow.
In addition, as a method often used to produce porous inorganic oxides consisting of two or more components, the generation and growth of crystal particles are performed by the various methods described above. There is a gel mixing method (Japanese Patent Publication No. 46-5817) in which gel-like substances are mixed. This method is characterized by the ability to easily produce multi-component porous inorganic oxides mixed in arbitrary proportions, but sufficient mixing is required to achieve homogeneity of the product, and It is difficult to control the pore structure. Above, we have described the generation and growth of crystal grains that serve as seeds in the conventional gelation process of porous inorganic oxides. When obtaining a catalyst, there is a drawback that the specific surface area inevitably decreases as the pore size increases, and it cannot be used as a method for producing catalyst carriers that require a large pore size.

Therefore, conventionally, various methods have been proposed for maintaining the specific surface area of porous inorganic oxides at a large value and adjusting the average pore diameter to a large value.

The principle of these methods is to control the growth of crystal particles constituting the porous inorganic oxide and to control the shrinkage of the gel structure of the gel-like material due to the surface tension of water during the drying process of the gel-like material produced. It's summery. However, it should be noted that in such a method, since the surface area of the resulting carrier is approximately constant, adjusting the average pore diameter is nothing but adjusting the pore volume. An example of such a method is the method of changing the drying rate of hydrogel (J. POlyrTlerSci).
ence. vOl. 34, Pl 29), and a method of applying shear force to concentrated hydrogels (Japanese Unexamined Patent Publication No. 49-31597), but these methods have the disadvantage that the range of pore volume that can be adjusted is extremely narrow. have.

In addition, in order to make the average pore diameter relatively large and to adjust the pore volume within a wide range, a method of adding a water-soluble polymer compound such as polyethylene glycol to the hydrogel (Japanese Unexamined Patent Publication No. 52-10449) 52-50637, JP-A-54-104493) and a method of replacing part or most of the water in the hydrogel with alcohol or the like (JP-A-50-12358 & JP-A-51-4093). The former method prevents the fine aggregation of hydrogel particles due to the surface tension of water acting during drying, and changes the pore volume depending on the amount added. In the latter method, the surface tension of water is changed by changing the amount of alcohol substitution, and the pore volume of the carrier is finally adjusted by changing the degree of aggregation of hydrogel particles. Both methods are economically unfavorable because the anti-agglomeration agent must be removed by firing, and it is also difficult to prevent the surface area from decreasing during firing.

The latter method not only requires an alcohol recovery device, but also has the disadvantage that the oxide produced by this method has poor water resistance and is easily damaged when it contains water. In addition, the water strongly bonded to the surface hydroxyl groups of the crystal particles is replaced with a solvent that is immiscible with water and forms an azeotrope with water, such as benzene, toluene, xylene, ethyl acetate, etc. Method for preventing shrinkage of gel structure during dehydration process (Japanese Patent Application Laid-Open No. 49-880
0), but it has the disadvantage that it requires a large amount of solvent that cannot be partially recovered and is expensive.

As a method to remove the influence of surface tension of water, there is a method of keeping the water in the pores in a frozen state and drying it under vacuum (Japanese Unexamined Patent Publication No. 49-1
0596) is also available.

This method has the disadvantage of requiring expensive equipment with significant low temperatures (below -160 DEG C.) and significant high vacuum. In addition, unlike these methods, there is a method in which powdered inorganic oxide is solidified as it is or as a xerogel with a special binder or adhesive and molded (JP-A-51-55791, JP-A-54-125192, JP-A-Sho 54-125192, JP-A-Sho. 54-1677 and JP-A-49-137517), these methods not only have the disadvantage of using special additives like the above-mentioned method, but also have the disadvantage of having small pores and large pores. It is said that oxides with a so-called double-peak pore distribution are easily obtained, and when used as a catalyst support, they often have lower activity than those with a single-peak pore distribution. have shortcomings. The conventional methods for producing porous inorganic oxides with controlled pore structures have been described above, but each of these methods has the drawbacks mentioned above and has not yet been satisfactory. . The inventors
In view of the above-mentioned unsatisfactory circumstances regarding the production technology of inorganic oxides with controlled pore structures suitable for catalyst supports, we have developed a method that does not use special additives such as anti-agglomerating agents found in conventional methods. In order to develop a method for easily manufacturing porous inorganic oxides without going through particularly complicated manufacturing processes, we continued our intensive research and finally completed the present invention.

That is, according to the present invention, in a method for producing a porous inorganic oxide using a hydrosol-forming substance as a raw material, (a). obtaining the seed hydrogel from a hydrogel-forming material; (b) varying the pH of the hydrogel alternately between a hydrogel dissolution region and a hydrogel precipitation region and to at least one of the hydrogel dissolution region and the hydrogel precipitation region; (c) Drying the hydrogel to form a xerogel, followed by baking to form an inorganic oxide. A method for producing a porous inorganic oxide is provided, the method comprising the step of converting the porous inorganic oxide.

When a porous inorganic oxide is produced by drying its precursor hydrogel to xerogel and converting it to an inorganic oxide by calcination, the pore structure formed inside the resulting inorganic oxide is , consists of the following three types of voids.

(1) Voids that form where crystallized water or bound water in crystal particles evaporates and desorbs.

(2) Voids between grown crystal grains.

(3) voids between aggregated particles where grown crystal particles aggregate;
In other words, voids are created when crystal particles with different agglomeration states agglomerate not only in the first order, but also in the second and third order.

Among these voids, the micropores formed by the voids in (1) are inappropriate as a means for freely adjusting the pore structure, and the voids in (2) and (3) are It serves as a means of adjusting the pore structure. In the present invention, in order to adjust these voids (2) and (3), during the hydrogel growth process, while supplying a hydrogel forming substance, the pH of the hydrogel slurry is adjusted between the hydrogel dissolution region and the hydrogel precipitation region. By alternating between
It controls the size, shape, and distribution of the hydrogel crystal particles and the aggregation state of the hydrogel (the number of contact points of the crystal particles, the strength of bonding at the contact points, etc.). Briefly speaking, the characteristics of the present invention are that porous inorganic oxides having a desired composition and controlled pore structure can be produced by simple operations and without using any special substances. The characteristics of the method of the present invention are as follows.

That is, according to the present invention, (1) Since hydrogel particles serving as seeds can have any desired shape, size, and composition, porous inorganic oxides having a desired pore structure and composition can be used. Easy to get.

In addition, in the case of the present invention, since the hydrogel slurry is forcibly held in the precipitation (growth) region and dissolution region of hydrogel particles, in the dissolution region (2
) The viscosity of the hydrogel slurry is reduced, and the added compound is easily and uniformly dispersed. (3) Furthermore, the rate of dissolution of the hydrogel fine particles, which normally occurs gradually in the growth region of the hydrogel particles, is greatly accelerated and stabilized. This has the advantage of producing uniform hydrogel particles with a certain size, while in the precipitation region (4)
The added compound and the hydrogel particles dissolved in the dissolution region are forcibly and quickly absorbed into the uniformly sized hydrogel particles, which significantly promotes the growth of crystal particles compared to other methods. be done.

This is an advantage.

In addition, since the operation of holding the particles alternately in the precipitation region and the dissolution region is repeated multiple times, (5) a precipitation operation close to the uniform precipitation method can be performed, and (6) the precipitation operation required for the growth of hydrogel particles can be performed multiple times. (7) Since compounds can be added, the pore structure can be easily adjusted by controlling the amount and pattern of addition. (8) Since the agglomeration state of the hydrogel particles can be adjusted, shrinkage during drying of the hydrogel can be easily controlled without using other compounds such as additives. (9)
) Since the agglomeration state of hydrogel particles can be adjusted, the physical strength can also be increased (10
) In the process of ripening, etc., the ripening time is shortened because the ripening is performed to eliminate only the non-uniform particles generated from the finally added compound. (11) Easy to use for various compounds Various porous inorganic oxides having desired compositions can be easily obtained by applying this production method to (1)
2) Many advantages can be obtained such as the overall operation is very simple and it is very economical since no special materials or equipment are used.

The features of the method for producing a porous inorganic oxide according to the present invention have been described above, and the method for producing a porous inorganic oxide according to the present invention will be described in more detail.

In the production of the porous inorganic oxide of the present invention, the starting materials used for hydrogel formation are
It is an element selected from the group elements or a compound thereof.

Particularly preferably used starting materials for producing the porous inorganic oxide of the present invention include: (1) Regarding the A group elements, magnesium,
■For group A elements, boron or aluminum, ■A
As for group elements, they are titanium or zirconium. Particularly preferably used starting materials for the production of the inorganic oxide of the present invention are: (1) magnesium for group A elements, (2) boron or aluminum for group A elements, and (2) titanium or zirconium for group A elements. It is.

Specific examples of hydrogel-forming substances preferably used in the production of the porous inorganic oxide of the present invention are as follows.

■For magnesium raw materials of group A elements, examples include magnesium hydroxide [Mg(0H)2], magnesium oxide (MgO), magnesium carbonate (MgCO3, MgC
O3-3H20), magnesium nitrate [Mg(NO3)
2.6FI20], magnesium chloride (MgCl.

・6H20), magnesium sulfate (MgSO4・7H2
0) etc. ■ Regarding boron raw materials of group A elements, for example, boric acid (H3BO3), ammonium borate (N
HiB5O3・4H20), Sodium borate (Na2B4
O7・10H20), sodium perborate (NaBO3
・4H20) etc. can be used.

Regarding aluminum, which is a group A element, for example, aluminum metal (A1), aluminum chloride (AICl
3, AlCl3・6FI20), aluminum nitrate [A
l(NO3)3・9H20], aluminum sulfate [Al
2(SO4)3, A12(SO4)・1 measurement. O], polyaluminum chloride [Al2(0H)NCl6-n)m(
1 x 5, m x 10)], ammonium alum [
NHL)2S04・. Al2(SO4)3・24H20
], Sodium aluminate (Na.AlO2), Potassium aluminate (KA]02), Aluminum isopropoxide (
A1 [0CH(CH3)2]3), aluminum ethoxide [A1(0C2H5)3], aluminum t-butoxide (A1[0C(CH3)3]3), aluminum hydroxide [A1(0H)3], etc. There is. Particular preference is given to aluminum salts, such as aluminum chloride (AlC
l3, AlCl3・6H20), aluminum nitrate Al
(NO3)3・9H20], aluminum sulfate [Al2
(SO4)3, A12(SO4)3・181(20),
Aluminates, such as sodium aluminate (NaAlO2
), and aluminum hydroxide [A1(0H)3]. ■ Regarding silicon raw materials of group A elements, ultrafine particles of silicon oxide or silicic anhydride are used as colloidal solutions such as colloidal silica (SlO2.
SiO2・YH2O (X=1-4)] Silicon tetrachloride (S
iCI4), silicate ester [Si(0CH3)4,S
i(0C2H5)4] etc.

Particularly preferably, colloidal silica (SiO2●XH2
O), Sodium silicate [Na2O-XSiO2・YH2O
(X=1-4)]. ■For titanium raw materials of group B elements, examples include orthotitanic acid (H4TiO4), metatitanic acid (H2TlO3), titanium oxide (TiO2)
, titanium chloride (TlCl3, TlCl4), titanium sulfate [Tl. (SO4)3, Ti(SO4)2, titanium oxide sulfate (TiOSO4), titanium bromide. (TiBr4),
Titanium fluoride (TiF3, TiF4), titanate ester (TiCO-CH(CH3)2]4), etc. can be used.
In addition, zirconium raw materials for Group B elements include, for example, zirconium chloride (ZrCl.O8H2O), zirconyl hydroxide [ZrO(0H)2], sulfuric acid/zirconyl [ZrO
(SO4)], sodium zirconyl sulfate [ZrO(S
O4)●Na2sO4], zirconyl carbonate [ZrO(C
O3)], zirconyl ammonium carbonate [NH4)! R
O(CO3)2], zirconyl nitrate [ZrO(NO,)
2], zirconyl acetate [ZrO(C2H3O2)2],
Zirconyl ammonium acetate [(NH4)2Zr0(C
2H3O2)3], zirconyl phosphate [ZrO(HPO
4)2], zirconium tetrachloride (ZrCl4), zirconium silicate (ZrSiO4), zirconium oxide (Z
rO2), etc. The hydrogel-forming material preferably used in the production of the porous inorganic oxide of the present invention is one that ultimately provides the following porous inorganic oxide support.

Alumina, silica, magnesia, titania, poria, zirconia, silica-alumina, silica-magnesia, silica-titania, silica-zirconia, alumina
Magnesia, alumina titania, alumina poria and alumina zirconia. Next, the production of the porous inorganic oxide of the present invention will be described in more detail.

(1) Production of seed hydrogel slurry In the present invention, the seed hydrogel slurry consists of: - an element selected from the elements of Groups ■, ■, and ■ of the periodic table mentioned above (hereinafter defined as a hydrogel-forming substance); It is formed using one or more types of

The particles contained in the hydrogel slurry (hydrogel particles) act as seeds when hydrogel particles are grown by adding a hydrogel-forming substance in the subsequent hydrogel growth process, and the hydrogel slurry usually contains hydroxide. It exists in the form of This seed hydrogel slurry is generally produced according to conventionally known methods.
That is, conventional methods such as a heterogeneous precipitation method, a homogeneous precipitation method, a coprecipitation method, an ion exchange method, a hydrolysis method, and a metal dissolution method can be employed. In this case, if large seed hydrogel particles are to be obtained, the seed hydrogel slurry obtained by these methods is aged or hydrothermally treated. The heterogeneous precipitation method is a method in which a hydrogel-forming substance is neutralized with a solution containing an acid salt or an alkaline salt.

For example, adding ammonia, sodium hydroxide, etc. as a neutralizing agent to a solution of nitrates or sulfates while stirring;
Alternatively, a solution of an alkali metal salt or an ammonium salt is neutralized by adding hydrochloric acid or sulfuric acid as a neutralizing agent to convert the acid salt or alkaline salt into a hydroxide. A specific example of this heterogeneous precipitation method includes, for example, adding ammonia or sodium hydroxide as a neutralizing agent to a solution containing aluminum nitrate, magnesium nitrate, and/or titanium sulfate with stirring, or a method of forming a titania hydrogel slurry. The homogeneous precipitation method is the same in principle as the heterogeneous precipitation method, but differs in that the concentration of the neutralizing agent during neutralization is kept uniform and precipitation is performed uniformly.

For example, when performing homogeneous precipitation from a solution containing a hydrogel-forming substance in the form of an acid salt, an aluminia-releasing substance such as urea or hexamethylenetetramine is used as a neutralizing agent. A specific example of this homogeneous precipitation method includes, for example, dissolving the required amount of urea in a solution containing aluminum nitrate, magnesium nitrate and/or titanium sulfate, gradually heating this mixed solution while stirring, and removing the neutralizing agent. is gradually decomposed to release ammonia, and the released ammonia gradually neutralizes the metal salts and converts them into alumina hydrogel. In the coprecipitation method, two or more hydrogel-forming substances exhibiting acidity or alkalinity are simultaneously neutralized in a coexisting state, or one or more hydrogel-forming substances exhibiting acidity and one or more hydrogel-forming substances exhibiting alkalinity are simultaneously neutralized. This is a method to obtain a hydrogel slurry by mixing and neutralizing.

Specific examples of this method include, for example, a method of adding sodium hydroxide as a neutralizing agent to a mixed solution in which aluminum nitrate and magnesium nitrate coexist with stirring to generate a coprecipitated hydrogel slurry of alumina hydrogel and magnesia hydrogel; and a method of neutralizing a sodium aluminate solution by adding a magnesium nitrate solution with stirring to produce a co-precipitated hydrogel slurry of alumina hydrogel and magnesia hydrogel. The ion exchange method is a method in which cations or anions coexisting in a solution of a hydrogel-forming substance are ion-exchanged using an ion exchange resin to produce a colloidal gel.

Specific examples of this method include, for example, passing a dilute solution of sodium silicate through a cation exchange resin to exchange cations;
In this method, by heating the generated solution, the silica particles contained therein are polymerized to generate colloidal silica gel. Commercially available colloidal silica or colloidal alumina are usually produced by these methods. The hydrolysis method is a method in which water is added to a hydrolyzable hydrogel-forming substance to cause a hydrolysis reaction to produce a hydrogel slurry.

Specific examples of this method include, for example, a method in which an alcoholic solution of titanium tetrachloride or aluminum isopropoxide is gradually added to water with stirring to cause a hydrolysis reaction to produce a hydrogel slurry of alumina or titania. It will be done. The metal dissolution method is a method in which an alkaline substance formed by dissolving a metal is used as a neutralizing agent for an acidic hydrogel-forming substance.

Specific examples of this method include, for example, a method of producing basic aluminum hydroxide by maintaining an aluminum nitrate solution in a boiling state and gradually adding and dissolving metallic aluminum powder into the solution. is included. As mentioned above, seed hydrogels can be made in a variety of ways, and methods for making such hydrogel slurries are well known to those skilled in the art.

In addition, the hydrogel slurry obtained in this way is
The properties of the hydrogel particles, the size or crystalline morphology of the hydrogel particles can be changed by applying a suitable modification treatment, such as an aging treatment or a hydrothermal treatment.
For example, alumina hydrogel gives larger particles by ripening, and also gives larger particles with advanced pseudo-boehmite formation by aging in a heated state. The pseudo-boehmite hydrogel particles were further heated to 100 to 300°C.
When hydrothermally treated at , it gives boehmite crystalline hydrogel particles. The particle size can be varied in the range of about 50 to 5,000 A by adjusting the degree of hydrothermal treatment, but adjustment is difficult in practice.
In the present invention, when performing this hydrothermal treatment, crystal growth of the hydrogel particles may be controlled by allowing chromate ions, tungstate ions, or molybdate ions to coexist with the hydrogel particles. When the hydrogel particles are composed of magnesia hydrogel, by aging for several hours in a heated state, a hydrogel that is several times more stable with respect to water than the hydrogel as produced can be obtained. When titania hydrogel particles are aged in a boiling state for one hour or more, the crystal form changes from α type to β type. In the method of the present invention, a preferred method for producing a seed hydrogel slurry is as follows.

An aqueous solution containing an aluminum salt is maintained at a temperature above room temperature, and an acidic or alkaline solution is added to the solution to adjust the pH to 6.
to 11 to produce a seed alumina hydrogel slurry, or the slurry is further heated to 0. A method of aging for ~24 hours.

Neutralize the aluminum salt-containing aqueous solution or aluminum salt, and heat the resulting aluminum hydroxide to approximately 1000C to 30C.
A method in which hydrothermal treatment is performed in a temperature range of 0°C for about 3 to 2 hours, or a method in which chromate ions, tungstate ions, or molybdate ions are further added during this hydrothermal treatment.

10% sodium silicate aqueous solution with a silica concentration of 1 to 8% by weight
A method of maintaining the temperature at ~70°C and adding an acid to adjust the pH to 6 to 10 to produce a silica hydrogel slurry, or further aging the slurry at a temperature range of 100°C to 100°C for 0.5 to 2 hours. .

Either keep an aqueous solution containing a titanium salt at a temperature of 0°C to 100°C and add an alkaline solution to adjust the pH to 4 to 11, or gradually add a titanium salt or an aqueous solution containing a titanium salt to water at room temperature. A titania hydrogel slurry is produced by hydrolyzing the salt, or the slurry is further treated at a temperature in the range of 50°C to 100°C. A method of aging for ~24TIF1. An aqueous solution containing a zirconium salt is heated at 100C to 100C. By maintaining the temperature and adding an alkaline solution to the aqueous solution to adjust the pH to 4 to 11, or gradually adding a zirconium salt or an aqueous solution containing a zirconium salt to water at room temperature to hydrolyze the zirconium salt, Generate zirconia hydrogel slurry. or further the slurry at a temperature of 50°C.
0 in the range of °C to 100 °C. A method of aging for ~24 hours.

An aqueous solution containing an acidic magnesium salt was heated at 10°C to 100'
C., and add an alkaline solution to the aqueous solution to adjust the pH to 6 to 11 to produce a magnesia hydrokel slurry, or further heat the slurry at a temperature of 50.degree. C. to 100.degree. A method of aging for ~24 hours.

As mentioned above, when producing a seed hydrogel slurry, there are various methods for its production and for the modification treatment of the generated hydrogel, but matters related to the production of these seed hydrogel slurries are well known to those skilled in the art. hand,
It should be noted that the method of the present invention is not limited by these matters.

The production of this seed hydrogel slurry may be carried out appropriately depending on the type of hydrogel-forming substance used as a starting material and the physical properties of the intended product. In some cases, commercially available hydrosols may also be used as they are. The concentration of this hydrogel slurry is not particularly limited, as long as it is within a range that allows the entire slurry to be stirred, and is usually 1% by weight or less, particularly about 0.1 to 5% by weight.・(2) Uniform growth of seed hydrogel The method of the present invention is characterized in that it includes a step of uniformly growing the seed hydrogel and a step of dissolving the uneven micro hydrogel particles. It enables industrial production of porous inorganic oxides with desired physical properties.

In this step, the pH of the seed hydrogel obtained above is
is alternately varied between a hydrogel dissolution region and a hydrogel precipitation region, and the hydrogel dissolution region and/or
Alternatively, when varying the hydrogel precipitation region, the above-mentioned hydrogel-forming substances or PH regulators were added alone or in the form of a mixture, so that the size of the hydrogel particles finally grew uniformly and formed loose aggregates. Obtain hydrogel precipitation. As used herein, the term "hydrogel precipitation region" refers to a PH range that can cause growth and aggregation of hydrogel particles, and the "hydrogel dissolution region" refers to a PH range that can solubilize microparticles of hydrogel. Therefore, in the hydrogel precipitation region, the fine hydrogel particles dissolved in the dissolution region are rapidly occluded by larger hydrogel particles and grow into crystals of larger particles, while in the hydrogel dissolution region, the fine hydrogel particles that are present The particles are dissolved so that only hydrogel particles that have grown to a certain size are present. In the present invention, by repeatedly changing the pH of the hydrogel slurry while supplying a hydrogel-forming substance to the hydrogel slurry, loose aggregates with uniform particle sizes are finally formed. to obtain a precipitate of hydrogel particles. In summary, alternating and repeatedly varying the pH of the hydrogel slurry between hydrogel precipitation and hydrogel dissolution regions causes the growth of seed hydrogels into uniformly sized aggregates, i.e., the alignment of hydrogel particles. This shows the grain effect. Changing the hydrogel PH to the hydrogel dissolution or precipitation region is accomplished using a PH modifier.

As the pH regulator it is advantageous to use the hydrogel-forming substance itself. That is, when the hydrogel-forming substance is acidic, the acidic hydrogel-forming substance is used as a pH regulator to lower the pH of the hydrogel slurry;
On the other hand, when the hydrogel-forming substance is alkaline, the alkaline hydrogel-forming substance is used as a pH regulator to increase the pH of the hydrogel slurry. and,
The pH of the hydrogel slurry is satisfactory when the hydrogel-forming substance is neutral or when the hydrogel-forming substance alone is used.
If adjustment is difficult to achieve, other suitable acidic or alkaline substances are used as pH regulators. As the acidic substance in this case, any of organic acids, inorganic acids, and acid salts can be applied, and specific examples thereof include nitric acid (
HNO3), hydrochloric acid (HCl), sulfuric acid (H2SO4), carbonic acid (H2CO3), formic acid (HCOOE), acetic acid (CH3
COOH), etc., and alkaline substances include:
Ammonia (NH3) as an alkali or alkaline salt
, sodium hydroxide (NaOH), potassium hydroxide (K
OH), sodium carbonate (Na2CO3, Na2CO3
・H2O, Na2CO3・7H20, Na2C03・1
0H20), potassium carbonate (K2CO3, K2CO3・
1.51 (20), sodium bicarbonate (NaHCO3
), potassium hydrogen carbonate (K2HCO3), sodium potassium hydrogen carbonate (KNaCO36H2O), sodium aluminate (NaAlO2), and the like. Therefore,
Combinations of pH regulators used for PU variation include combinations of acidic or alkaline hydrogel-forming substances, combinations of acidic hydrogel-forming substances and alkaline substances, and combinations of alkaline hydrogel-forming substances and acidic substances, etc. It may be selected appropriately depending on the gel. The hydrogel-forming substance may be added at the same time as the moderating agent or at the same time as the pH
This can be done before or after the addition of the modifier. In the present invention, in order to finally obtain a hydrogel crystal-grown from a seed hydrogel into a sparse aggregate of uniform size, the pH of the hydrogel slurry is changed from a precipitation region to a dissolution region, and then the pH of the hydrogel slurry is changed from a precipitation region to a dissolution region, and then the pH of the hydrogel slurry is changed from a precipitation region to a dissolution region. It is said that it will fluctuate.

This process involves repeatedly changing the pH of the hydrogel periodically, and the pore structure of the catalyst is controlled by the number of repetitions. The number of repetitions is one or more times, usually in the range of 2 to 50 times. The hydrogel-forming substance is added in portions according to the number of repetitions to vary the pH of the hydrogel slurry to the precipitation region and/or dissolution region. The amount of hydrogel-forming material added at each time is such that uniform agitation of the reactor contents is maintained and a uniform hydrogel particle concentration is obtained throughout the entire addition procedure. If the hydrogel particle concentration becomes too high, uniform stirring of the hydrogel slurry becomes difficult, a concentration distribution of the hydrogel particles occurs, and uniform growth of the hydrogel particles is inhibited, which is not preferable. Generally, the amount of hydrogel-forming substance added per time is 2 to 200 mol%, calculated as oxide, of the hydrogel calculated as oxide contained in the hydrogel slurry, and the total amount The amount added is such that the concentration of hydrogel particles in the final hydrogel slurry is approximately 1 to 1, calculated as oxide.
The amount is in the range of 0% by weight. It is desirable that the amount of the hydrogel-forming substance added each time the pH is changed is the same as possible, but it is not necessarily necessary to add the same amount each time the pH is changed, and usually 11 times the average amount added each time.
It can be varied within a range of 4 to 4 times. The hydrogel-forming substance is added in a form that can be easily dissolved in the hydrogel, for example, in the form of a fine powder or an acidic or alkaline solution. When added as an aqueous solution, the concentration of the hydrogel-forming substance is , calculated as oxide, from 0.05 to 5% by weight, preferably from 0.1 to 3% by weight.The growth reaction of the seed hydrogel particles is carried out under stirring conditions; A hydrogel particle concentration distribution as uniform as possible in the reaction vessel, so that uniform growth of the hydrogel particles is achieved and to prevent particulate hydrogels from remaining in the hydrogel slurry without being occluded by larger hydrogel particles. Do it so that you can get it.

For this purpose, stirring is carried out as quickly as possible. The time the hydrogel slurry is held in the dissolution region is sufficient to sufficiently dissolve the new fine hydrogel resulting from the added hydrogel-forming material and to produce a uniformly sized hydrogel. If the hydrogel slurry is kept in the dissolution region for an unnecessarily long period of time, the hydrogel particles will be dissolved more than necessary and the crystal growth of the hydrogel particles will be significantly inhibited. This retention time is closely related to the PH value of the dissolution region and the type of hydrogel, and it is necessary to take an appropriate time depending on the type of hydrogel particles and the PH of the dissolution region. This holding time is usually in the range of about 1 minute to 60 minutes after the pH change; if the pH in the dissolution region is acidic, the smaller the pH value, the higher the pH value if it is alkaline. The holding time needs to be short. for example,
In the case of alumina hydrogel, the pH is in the range of 5 to 2,
The holding time is between about 1 minute and 3 minutes. When porous inorganic oxides are produced using hydrogels with non-uniform particle sizes, the specific surface area decreases due to sintering of fine particles during the firing process, and a large number of fine pores are formed. This makes it unsuitable as a catalyst carrier. By holding this dissolution region and the hydrogel slurry, the hydrogel particles are uniformly sized. The time that the hydrogel slurry is held in the precipitation region after the pH change is such that the hydrogel-forming substance added in the dissolution region and the dissolved fine hydrogel particles become uniform in size in the precipitation region and are occluded by the hydrogel particles, and new This is the combination of sufficient time for crystal growth of hydrogel particles to occur and time for the grown crystal particles to settle into a stable form. Ru.

Typically, this time is longer than the time held in the dissolution zone, ranging from about 1 minute to 10 minutes. This retention time is
In the case of alumina, the pH range is about 1 minute to 101
It is between 1 temple, and in the case of silica-alumina, the pH is 6~
11 within a range of about 1 minute to 1 [phase]. be. As is clear from the above, the pH of the hydrogel slurry is a means for keeping the hydrogel slurry in the dissolution region or the precipitation region, and its size affects the rate of dissolution and precipitation of the hydrogel particles. It depends very much.

In addition, this pH is a very important factor because it may also affect the crystal morphology of the growing hydrogel particles in the precipitation region. This PH range depends on the type of raw material of the hydrogel-forming substance, the type of PH regulator and the combination thereof, the type of hydrogel particles in the hydrogel slurry, the crystal form,
Although it varies depending on the concentration, temperature, and type or presence or absence of coexisting salts, it can generally be said that the pH range of 7±5 is the precipitation region, and the other acidic or alkaline regions are the dissolution region. Typical pH values for various hydrogels are shown in the precipitation region and dissolution region. In the case of alumina hydrogel, pH 6 to 11 is the precipitation region;
The pH below 5 is the melting range. In the case of silica hydrogel, a pH of 9 or lower is a precipitation region, and a pH of 9 or higher is a dissolution region. In the case of titania hydrogel, the region below PHL is the dissolution region, and the region above PHL is the precipitation region. In the case of magnesia hydrogel, a pH range of moderate to high is a solubility region, and a pH of 9 or higher is a precipitation region. In addition, in the case of zirconia hydrogel,
Below PH2 is the dissolution region, and above the PH source is the precipitation region.
In addition, composite oxidation products such as silica-alumina, magnesia-alumina, silica-magnesia, and alumina-titania
Regarding hydrogels, the PH range that forms the hydrogel dissolution region and the hydrogel precipitation region will differ somewhat from that of its constituent components depending on its composition; It can be easily determined by simple preliminary experiments. Alternatively, only a variation in the dissolution and precipitation regions of one component may be caused. When forming a hydrogel of a complex oxide, a mixed hydrogel formed from a mixture of hydrogel-forming substances containing each element constituting the target complex oxide is used as the seed hydrogel, or one of these mixed hydrogels is used. The component hydrogels are used to form a mixed hydrogel by a suitable method. For example, when obtaining a silica-alumina hydrogel, a mixed hydrogel slurry containing silicon and aluminum is used as a seed hydrogel, and an acidic PH regulator containing a mixed hydrogel-forming material containing silicon and aluminum is added to the hydrogel slurry, and a suitable alkaline A mixed hydrogel can be obtained by alternately adding a PH regulator and an acidic PH regulator containing an alumina hydrogel-forming substance, using a hydrogel slurry containing aluminum as one component as a seed hydrogel. Mixed hydrogels can also be obtained by alternating the addition of alkaline pH modifiers containing silica hydrogel-forming materials. Additionally, a mixed hydrogel can be obtained in the same manner using a silica hydrogel slurry as a seed hydrogel by a reverse method. The desired hydrogel can be obtained using the same method for other composite oxides. The temperature of the hydrogel is
It is a factor that influences the rate of dissolution and formation of hydrogel particles.

In addition, in the precipitation region, like the pH, it also affects the crystal morphology of the growing hydrogel particles. Showing the relationship between this temperature and the crystalline form of the hydrogel particles, in the case of alumina hydrogel, amorphous aluminum hydroxide is obtained at room temperature, and pseudoboehmite is obtained at temperatures above 50°C. Silica
In the case of alumina hydrogel, it is amorphous at around room temperature. In the case of magnesia hydrogel, it becomes water-stable magnesium hydroxide at temperatures above 50'C. In the case of titania hydrogel, β-titanic acid is produced at temperatures above 80°C. The amount of the hydrogel-forming substance added and the number of times the periodic pH fluctuation is repeated are very important factors for accurately controlling the pore structure of the finally obtained porous inorganic monoxide. It is desirable that the amount of the hydrogel-forming substance added each time is sufficient to shift the pH of the hydrogel slurry to the dissolution region or the precipitation region, but if it is insufficient, the hydrogel-forming substance may be added as a PH regulator as necessary. Add no acidic or alkaline substances. The amount added directly affects the crystal growth of the hydrogel particles. If the amount added is large, the crystal growth of the hydrogel particles will be promoted, but there is a risk that new microcrystals will be generated that will not be occluded by the hydrogel particles that should be grown.
When the amount of Yanghe added is small, there is no fear of new microcrystal formation, but the crystal growth of the hydrogel particles becomes very slow.
Generally, in order to finely control the pore structure of the oxide, it is more effective to add a smaller amount. Therefore, the amount added per time is preferably within the above-mentioned range.
Since the type and amount of ions coexisting in the hydrogel slurry also affect the crystal growth of hydrogel particles, it is desirable to appropriately control them.

In particular, polyvalent anions tend to be a factor that inhibits crystal growth, so their coexisting amount is preferably below a certain amount, usually below (very much) % by weight, preferably below 15% by weight. The PH cyclic variation operation is completed and the hydrogel slurry is placed in the final precipitation zone. This hydrogel slurry is aged in the next aging step, if necessary. The method for obtaining a hydrogel that has grown into a sparse aggregate of uniform size from a seed hydrogel has been described in detail above, but each operating condition shown above depends on the type of hydrogel and the structure of the required inorganic oxide. will be set appropriately.

Setting of such operating conditions is within the range that a person skilled in the art can easily carry out based on the teachings provided above. In addition, the hydrogel referred to in the specification of this application is
The hydrogel-forming substance used as the raw material for the porous inorganic oxide, especially hydroxide particles of at least one element selected from the elements of Groups Ⅰ, ②, and Ⅲ of the periodic table, are uniformly dispersed using water as a dispersion medium. It refers to a dispersion in which water becomes a continuous phase and each particle can move freely.It is usually a colloidal milky white liquid called a hydrosol, and it is formed by precipitation of each hydrosol particle. It includes both a solid state, usually called a gel, in which the individual hydrosol particles are aggregated or in contact with each other and are no longer able to move freely. Seed hydrogels serve as seeds for forming hydrogels in the method of the present invention, and refer to various hydrogels that have not been subjected to pH variation treatment in the precipitation or dissolution region of hydrogel particles. That is, they may be in a sol or gel state, and the hydrogel particles constituting these may be small or large, and furthermore, the hydrogel particles may be present in an aggregated state. Hydrogel particles refer to fine crystals of oxides of hydrogels and seed hydrogels, grown crystals, particles formed by agglomeration of grown crystals, and particles formed by higher-order aggregation of aggregated particles, respectively. A particle when considered as a single particle. Slurry refers to anything in which water and hydrogel coexist during the manufacturing process. The hydrogel dissolution region refers to the PH region in which when a hydrogel-forming substance is added to a hydrogel slurry, the added hydrogel-forming substance exists in a stable dissolved form in an aqueous medium and can dissolve fine hydrogel particles. On the other hand, the hydrogel precipitation region refers to a PH region where hydrogel-forming substances and dissolved fine hydrogels that exist in a stable dissolved form in an aqueous medium in the dissolution region can no longer stably exist and form precipitates. (3) Hydrogel ripening This hydrogel ripening, which is adopted as necessary and can be considered as the final step of the seed hydrogel growth process, consists of keeping the hydrogel in the hydrogel precipitation area for a certain period of time; This aging treatment achieves homogenization and stabilization of the hydrogel particles.

This aging effect can be enhanced by stirring or heating, and aging under heating is particularly preferred since the hydrogel particle crystals tend to be changed into a stable form. The ripening temperature is generally room temperature to 100'C,
Aging at temperatures above 100°C is carried out under pressure. Aging time ranges from about 3 to 24 hours. This aging of the hydrogel can be omitted in some cases, in which case the hydrogel is transferred to the next step without any special aging treatment. (4) Washing of hydrogel Washing of hydrogel is employed as necessary to remove coexisting unnecessary ions or impurities, and filtration and washing of hydrogel are usually repeated one or more times.

In this case, water is usually used as the cleaning liquid. In this cleaning step, components that act as catalyst poisons and components that reduce the strength of the porous inorganic oxide, such as sodium, iron, and sulfate radicals, are removed to the extent that they do not cause any harmful effects. When cleaning this hydrogel, in order to enhance the cleaning effect, it is necessary to use PH regulators such as ammonium, nitric acid, etc. that can be decomposed and removed in the subsequent calcination or calcination step. It is also possible to add acid, ammonium nitrate, ammonium chloride, etc. to the cleaning solution to control its pH within an appropriate range, thereby increasing the solubility of the cleaning solution for the impurity components. Furthermore, in order to increase the solubility of the cleaning solution for impurity components, the temperature of the cleaning solution is increased. It can also be increased. Increasing the temperature of this cleaning fluid can lower the surface tension of the water and increase offshore overspeed, resulting in improved cleaning efficiency. It is preferable to wash the hydrogel until the content of impurity components is as small as possible. Generally, the content of impurity components is, for example, Na2
0.2% by weight or less as O, and 0.2% by weight or less as Fe for iron. For sulfuric acid radicals, it is best to wash and remove them until they become less than 4% by weight as SO4, and if silica is mixed in as an impurity, wash and remove it until it becomes less than 2% by weight as SiO2. is preferable. This washing is carried out using conventional washing means such as a normal pressure filtration machine, a vacuum filtration machine, a pressure filtration machine or a centrifugal separator. (5) Adjusting the solids content of the hydrogel The solids content of the hydrogel is adjusted to a range of about 10 to 8% by weight, preferably about 15 to 65% by weight so that it can be easily molded.

If the solids content in the hydrogel is lower than about 1% by weight, it becomes difficult to maintain the shape of the molded product, while if the solids content is higher than about 80% by weight, the molding pressure during molding may be excessively high. At the same time, the pore structure of the porous inorganic oxide obtained as a final product also deteriorates.
The solid content in the hydrogel can be adjusted by heat drying, spray drying, normal pressure filtration, vacuum filtration, pressurized filtration, centrifugation, etc. until the desired solid content is obtained. This is done by dehydration. (6) Molding of Hydrogel The hydrogel whose solid content is adjusted to 10 to 8% by weight, preferably 15 to 65% by weight, is molded into a shape suitable for the purpose of use.

In this case, the shape of the molded product may be a columnar shape, a hollow cylinder shape, or a non-circular cross section, for example, a multilobed shape such as an ellipse, trilobes, and quadral lobes. Moreover, it may be a granular molded product. In general, suitable methods for forming these shapes include extrusion using a piston-type extruder or screw-type extruder, and tabletting using a tablet press or press. In addition, when forming into granules, there are, for example, a prilling method, a dropping method in oil, and a wet granulation method. (7
) Drying and baking of hydrogel molded products Hydrogel molded products molded into the required shape and dimensions are
It is turned into a xerogel by drying and converted into an inorganic oxide by baking.

A stable porous inorganic oxide can be obtained through this drying and firing process. To obtain stable inorganic oxides,
It is best to carry out firing at as high a temperature as possible, but depending on the type of hydrogel, sintering or changes in crystal form may occur due to firing, so appropriate conditions should be selected. Generally, the firing is carried out at a temperature of 300 to 1000°C, preferably 400°C.
Performed at ~800°C. Furthermore, before this firing, the hydrogel molded product is dried, and this drying is performed at room temperature or above. In practice, drying and calcining of the hydrogel molded product are carried out by drying the hydrogel molded product with hot air and then putting it in a heating furnace and firing it, or by putting the hydrogel molded product in a heating furnace and adjusting the temperature from 100°C to a predetermined firing temperature. This is carried out by raising the temperature to a temperature of 3 to 10 minutes. The industrial production of porous inorganic oxides according to the present invention is advantageously carried out by the method described above, and in particular, since the method of the present invention employs the special hydrogel growth process described above, porous A major advantage is that the composition and pore structure of the inorganic oxide can be easily controlled.

In order to explain the present invention in more detail, specific examples will be given below.

This specific example specifically explains the present invention, and includes:
The present invention is limited by these specific examples. It's not something that should be done. In addition, in this specification, the 0 periodic system cited is 'Webster7s7thNewCOllegia'.
teDictiOnary″G&CMerrjamCO
mpany, Sprin〆Ield, Massachusetts
Setts, USA (1965), P. This is the periodic law described in 628. In addition, the pore distribution of porous inorganic oxides was measured using the so-called mercury intrusion method (for details, see E
．． W. WASFIBURN, PrOc. Natl. Ac
ad. Sci. ,l,p. ll5 (1921), H, L
．． RITTER, L. E. DRAKE, Ind. Eng
．． Chem. Anal. , Bo, P. 782, 7.787
(1945), L. C. DRAKE, Ind. Eng.
Chem. ,■,P. 78O (1949), and H. P
．． GRACE, J. Anler. InSt3Chem.
Engr'. , Su, P. 3O7 (1956), etc.). The surface tension of mercury is 2
The contact angle used was 474 dyne/Cm at 5°C and 14
00, and the absolute mercury pressure was varied from 1 to 2000 k9/d. Comparative Example 1 1000g of aluminum nitrate aqueous solution (8.0% by weight as A'203) was diluted with 7000g of water, placed in a 20' enamel container with a lid, heated with stirring, and heated to 95°C.
I made it.

Dissolve 320g of sodium hydroxide in water and add 1
000 cc of solution was added to adjust the pH to 11, and the mixture was aged with stirring to produce a seed alumina hydrogel slurry. Next, an aluminum nitrate aqueous solution was continuously injected into the slurry at a rate of 20.2 cc/min and a sodium hydroxide 290 g/min aqueous solution at a rate of 26.2 cc/min, respectively, using a metering pump. This operation
I continued to listen. On the way, a small amount of slurry was extracted at the 3rd and 6th stages. These slurries were passed through the mouth, thoroughly washed with water to remove Na, and then passed through the mouth under pressure to obtain a corresponding passed-through cake. Each cake was molded using an extrusion molding machine having a die with 1.0 Tm1nφ holes, dried in an air stream at 80°C, and then baked at 500°C for 3 hours. The pore distribution of the obtained oxide is shown in FIG. 1 by the broken line.
Curve 1″ shows the results for the oxide formed from the slurry after 3 times, curve 2″ after 6 times, and curve 3″ after 9 times. Example 1 Aluminum nitrate aqueous solution (8.0% by weight as Ae2O3) Dilute 1000g with 7000g of water, put it in a 20e enamel container with a lid, and heat it to 95℃ while stirring.
I made it.

Dissolve 320g of sodium hydroxide in water and add 1
000 cc of solution was added to adjust the pH to 11, and the mixture was aged for 60 minutes with stirring to produce a seed alumina hydrogel slurry. Next, add 95% to this slurry.
Aluminum nitrate aqueous solution (while keeping its temperature at °C)
Add 400g of 8.0% by weight as Al2O3 and adjust the pH.
After holding for 5 minutes at 4.5, sodium hydroxide 29
393 cc of 0 g/f aqueous solution was added to make PHll, and the mixture was maintained for one hour. The same pH varying operation was repeated 6 times, and the slurries after the repeated operation 2 and 4 times were extracted. In this case, the slurry after the 2nd, 4th, and 6th operations corresponds to the slurry after the 3CyF1-, 6-powder, and 9-powder operations in the comparative example in terms of aluminum addition amount and slurry retention time. These slurries were filtered, pressed, molded, dried, and fired in the same manner as in the comparative example, and the pore distribution of the obtained oxides was measured. The results are shown in solid lines in FIG. In this FIG. 1, curve 1 shows the results for oxides formed from slurries after two, curve 92 and four, and six, respectively, repeats. The continuous addition method of the comparative example is similar to the method of the present invention in that it supplies the raw materials necessary for the growth of seed hydrogel particles, but differs from the method of the present invention in that the hydrogel particles are not exposed to a dissolution atmosphere. There is.

From the results of pore distribution measured by mercury porosimetry shown in Figure 1, in Example 1, the pore volume increases as the raw material addition time and the number of raw material additions increase, and the hydrogel particles grow. Furthermore, it is clear that the pore distribution is sharp and consists of pores of uniform size. On the other hand, it can be seen that in the continuous addition method of the comparative example, the pore distribution is broad and the pores are structured with non-uniform sizes. That is, from these results, by changing the pH of the slurry in the hydrogel dissolution region and precipitation region, it is possible to dissolve fine hydrogel particles in the dissolution region and uniformize the size of the hydrogel particles to grow the hydrogel. It is possible to fully understand the feature of the present invention that it is possible to In Examples 2 to 7 below, production examples of titania, silica, silica-alumina, silica-magnesia, alumina-titania, and alumina-magnesia are shown as typical examples of porous inorganic oxides other than alumina, The pore distribution of the obtained oxide is shown.

It is clear from these results that various porous inorganic oxides with controlled pore structures can be produced. Comparative Example 2 Titanium tetrachloride was gradually dissolved in deionized water while cooling to prepare an aqueous solution having a concentration of 500 g/l as Tlce4.

Next, 10' of deionized water was placed in an enamel container, brought to a boil, and 1.5,' of the titanium tetrachloride aqueous solution was added thereto. Furthermore,
After confirming that the liquid temperature was 95°C, 14% by weight ammonia water 2e was added to obtain a seed titania hydrogel slurry. Next, add 150 cc/min of the above titanium tetrachloride aqueous solution to this slurry in a boiling state, and add about 2 ml of ammonia water.
00cc/Min speed! was added continuously for 60 minutes while maintaining the pH at 7. On the way, a small amount of slurry was extracted from the third mill. Each of these slurries was aged at boiling for 1 hour, and then these slurries were passed through a vacuum sieve and washed 4 times with deionized water until chloride ions were no longer detected in the silver nitrate aqueous solution. After thorough washing, a mouth cake was obtained. Each cake was molded into a cylindrical shape using an extruder with a die hole of 1.2 TrrIrLφ, dried at 120°C for 3 hours, and then heated at 450°C.
It was baked for 1 hour. The pore distribution of this material is shown by the broken line in FIG. Curves 1'' and 2'' show the results for oxides formed from slurries of 3rd and 6th particles, respectively. Example 2 Titanium tetrachloride was gradually dissolved in deionized water while cooling to give 500 g/e as Tlce4.
An aqueous solution of the concentration was prepared.

Next, deionized water 10e was placed in an enamel container, brought to a boil, and the above titanium tetrachloride aqueous solution 1.5)e was added. Further, the liquid temperature was maintained at 95° C., and 14% by weight ammonia water 2e was added to obtain a seed titania hydrogel slurry. Next, 1.5' of titanium tetrachloride aqueous solution was added in a boiling state to make PHL and held for 5 minutes, and aqueous ammonia was further added to make pH 7 and held for 5 minutes. This operation was repeated to obtain slurries after repeating it 3 times and 6 times. After completing these repeated operations, the slurry was aged for 1 hour while being boiled to obtain a titania hydrogel slurry. This slurry was passed through a vacuum filter, and further washed with deionized water until chlorine ions were no longer detected with an aqueous silver nitrate solution to obtain a filter cake. 1.2 TIU each cake
It was molded into a cylindrical shape using an extruder having a die hole of rLφ, dried at 120°C for 3 hours, and then fired at 450°C for 1 hour. The pore distribution of this material is shown by the solid line in FIG. Curve 1 and Curve 2 show the results for the oxide formed from the slurry after three and six repetitions, respectively. Example 3 Sodium silicate (JIS No. 3) 100g/'solution 5' was added to the enamel container of 20e, heated to 50°C with stirring, and then a 2% sulfuric acid solution was added to adjust the pH to 4, and the mixture was heated for 5 minutes. The seeds were retained to produce a silica hydrosol slurry.

Next, 250 g/400 cc of sodium silicate solution was added to this slurry and held as PHll for 10 minutes, and a 20% by weight sulfuric acid solution was added and held as 1 powder as PH4. This operation was repeated 5 times each. The slurry that was repeated 7 and 9 times was filtered, washed, and washed in the same manner as in the comparative example.
The oxide was pressed, molded, dried, and fired, and the pore distribution of the obtained oxide was measured. The results are shown in FIG. In FIG. 3, curve 1 shows the results for the oxide formed from the slurry after 5 repetitions, curve 2 after 7 repetitions, and curve 3 after 9 repetitions. Example 4 As SiO2 8. Colloidal silica containing % of nominal amount (
Prepared by diluting Snowtex 0 (manufactured by Nissan Chemical Industries, Ltd.) with water) and 2000 g of an aqueous solution of aluminum sulfate (Ae2O).
2000 g of the aqueous solution (8% by weight as 3) was mixed well to form a uniform suspension.

Separately, 3000 g of water and 1000 g of the above suspension were placed in a 10e enamel container with a lid, and heated to 95° C. while stirring. To this suspension, add 30% of 14% by weight ammonia water.
After adding 0 cc to adjust the pH to 8, one powder was maintained to obtain a seed silica/alumina hydrogel slurry. Next, 200 g of the above suspension was added to this slurry to adjust the pH to 4, and the slurry was maintained at 1 ml, and 65 cc of ammonia water was further added to adjust the pH to 8.

This operation was repeated 9 times, 11 times, 13 times, and 15 times, respectively, and the slurry was filtered, washed, pressed, molded, dried, and fired in the same manner as in the comparative example, and the obtained oxide was Pore distribution was measured. The results are shown in FIG. In FIG. 4, curve 1 shows the results for the oxide formed from the slurry after 9 repetitions, curve 2 after 11 repetitions, curve 3 after 13 repetitions, and curve 4 after 15 repetitions. Example 5 A 350 g/e aqueous solution was prepared by dissolving magnesium chloride (MgC'2 61 (20)) in deionized water, and a mixture containing 330 g of silicate sorter JIS No. 3 and 100 g of sodium hydroxide in 1e. An aqueous solution was prepared.

Next, the above magnesium chloride aqueous solution 2' was added to a heated and stirrable enamel container, and the above mixed aqueous solution 2f was further added to obtain a seed silica/magnesia hydrogel slurry. Furthermore, the above mixed aqueous solution 2f was added to make PHL2, and after 2 powders were added, magnesium chloride aqueous solution 2e was added to make pH7. This operation was repeated every 2 times, and the slurry after repeating 2 times and 5 times was aged for 5 hours while stirring at room temperature.
Thereafter, a cake for molding was obtained through washing. Each cake was molded into a cylindrical shape using an extruder having a die hole of 1.2T0nφ holes, air-dried at room temperature for 3 hours, and then heated at 120°C for 3 hours.
It was dried for an hour and then fired at 500'C for 3 hours. The pore distribution of the obtained oxide is shown in FIG. In FIG. 5, curve 1 shows the results for the oxide formed from the slurry after two repetitions and curve 2 after five repetitions. Example 6 Titanium sulfate aqueous solution (containing 25% by weight as TiO2) 4
00g and aluminum sulfate aqueous solution (8 as Ae2O3)
A mixed aqueous solution was prepared by thoroughly mixing 5000 g of (% by weight).

675 g of this mixed solution was diluted with 1800 g of water, placed in a 20e enamel container with a lid, and heated to 85° C. with stirring. Next, 950 cc of 14% by weight ammonia water was added to adjust the pH to 9, and the mixture was maintained for 30 minutes to obtain a seed alumina/titania hydrogel slurry. Next, 388 g of a solution obtained by adding 700 g of concentrated sulfuric acid to the mixed solution was added to make PHL, and the mixture was kept as a powder. 605 cc of ammonia water was added to this to adjust the pH to 9, and this was maintained for 30 minutes. This operation was repeated 3, 6, 9, and 12 times to obtain slurries, which were then treated in the same manner as in the comparative example and fired at 500° C. for 3 hours. The pore distribution of the obtained oxide is shown in FIG. In FIG. 6, curve 1 shows the results for the oxide formed from the slurry after 3 repetitions, curve 2 after 6 repetitions, curve 3 after 9 repetitions, and curve 4 after 12 repetitions. Example 7 A mixed solution of 1000 g of a magnesium sulfate ion aqueous solution containing 5% by weight in terms of Mg0 (5625 g of an aluminum sulfate aqueous solution containing 8% by weight in terms of 5Ae203) was prepared.

7000 g of deionized water was placed in a 200e enamel container, 3313 g of the above mixed solution was added, and the mixture was heated to 95° C. with stirring.

Next, an aqueous solution 1e of 540 g/' of sodium hydroxide was added and PHLO. As No. 5, an alumina-magnesia hydrogel slurry was produced as seeds by holding for 60 minutes. Furthermore, 662g of the above mixed solution was added to this slurry and the pH was adjusted to 4.
．． 5 and held for 10 minutes, and 200 cc of 490 g/' solution of sodium hydroxide was added thereto to make PHLO. 5, and 1 conflict was retained. Repeat this operation 2 times, 4 times, 6 times.
A slurry was obtained after repeating the slurry several times, and thereafter filtered, washed, pressed, molded, dried, and fired in the same manner as in the comparative example, and the pore distribution of the obtained acid heptaide was measured. The results are shown in FIG. In FIG. 7, curve 1 shows the results for the oxide formed from the slurry after 2 repetitions, curve 2 after 4 repetitions, and curve 3 after 6 repetitions.

[Brief explanation of the drawing]

9 Figures 1 to 7 are graphs showing pore distribution for oxides obtained according to the present invention.

Claims (1)

[Scope of Claims] 1. A method for producing a porous inorganic oxide using a hydrogel-forming substance as a raw material, comprising: (a) obtaining the hydrogel from the hydrogel-forming substance; (b) adjusting the pH of the hydrogel to dissolve the hydrogel; While alternating between the hydrogel precipitation region and the hydrogel precipitation region, a hydrogel-forming substance is added during the pH variation to at least one of the hydrogel dissolution region and the hydrogel precipitation region, and finally crystal growth occurs to form loose aggregates. (c) drying the hydrogel to form a xerogel, and then firing the hydrogel to convert it into an inorganic oxide. 2. Claim 1, wherein the hydrogel-forming substance in step (a) and/or step (b) is at least one element selected from Groups II, III, and IV of the Periodic Table or a compound thereof. the method of. 3 The hydrogel-forming substance is
3. The method according to claim 2, wherein the compound is at least one compound selected from magnesium compounds, boron compounds, aluminum compounds, silicon compounds, titanium compounds, and zirconium compounds. 4. In step (b), the amount of the hydrogel-forming substance added when changing the pH is calculated as oxide per addition, and is 2 to 2 to The method according to any one of claims 1 to 3, wherein the amount is 200 mol%. 5. Periodic hydrogel pH fluctuations in which the pH of the hydrogel is varied from the hydrogel precipitation region to the hydrogel dissolution region and then back to the hydrogel precipitation region is performed one or more times, preferably 2 to 50 times. Any method of Items 1 to 4.