Method for producing porous silica-alumina particles

Abstract

To provide a method for producing porous silica-alumina particles having a high specific surface area, a high pore volume, and enhanced particle strength.SOLUTION: A process for producing porous silica-alumina particles, comprising a step of obtaining an aqueous solution containing pseudo-boehmite alumina hydrate; a step of obtaining an aqueous solution containing silica powder; a step of obtaining an aqueous solution containing a silica-alumina mixture in which the aqueous solution containing pseudo-boehmite alumina hydrate is mixed with the aqueous solution containing silica powder, and the mixed slurry is maintained at a pH of 7.0-9.0, at a temperature of 40 to 95°C for 10 minutes to 10 hours to accelerate the reaction to pseudo-boehmite alumina hydrate; and a step of obtaining porous silica-alumina particles by drying the aqueous solution containing the silica-alumina mixture. The porous silica-alumina particles have a specific surface area (SA) of 400-600 m2 / g measured by the BET method, a pore volume (PV) of 1.0-2.0 mL / g measured by the BJH method, an average pore diameter (PD) of 6-30 nm measured by the BJH method, and a silica-to-alumina mass ratio of 2 / 98-70 / 30.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing amorphous porous silica-alumina particles having a high specific surface area and a high pore volume. [Background technology]

[0002] Methods for preparing silica-alumina compositions are well known in the art, and representative methods include the neutralization reaction method and the pH swing method.

[0003] Examples of the neutralization reaction (coprecipitation method, cogelation method) method include preparation methods such as those described in Patent Documents 1 to 4, in which silica hydrogel and a solution of a metal salt are mixed to produce amorphous silica-alumina that uniformly contains the metal salt inside.

[0004] The pH swing method (immersion method) includes preparation methods such as those described in Patent Documents 5 and 6, which change the pH of a reaction mixture, thereby precipitating silica and alumina, thereby enabling the production of amorphous silica-alumina in a single vessel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 27-3989 [Patent Document 2] Special Publication No. 31-1862 [Patent Document 3] Special Publication No. 30-5963 [Patent Document 4] Special Publication No. 32-413 [Patent Document 5] Special Publication No. 2010-537808 [Patent Document 6] Special Publication No. 2016-502971 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the prior art, the porous silica-alumina obtained by the preparation methods described in Patent Documents 1 to 6 has a relatively small specific surface area, i.e., 400 m 2 / g, which can result in low particle strength.

[0007] Furthermore, there is a problem that the pore volume tends to be smaller than 1.0 mL / g.

[0008] An object of the present invention is to provide a method for producing porous silica-alumina particles having a high specific surface area, a large pore volume, and improved particle strength. [Means for solving the problem]

[0009] Under such technical background, the inventors have conducted extensive research to solve the above problems, and as a result, have discovered a manufacturing method that can obtain porous silica-alumina particles having a large specific surface area, a large pore volume, and increased particle strength, and have developed the present invention. The present invention, which has been developed to solve the above problems and achieve the above objects, is as follows. That is, the present invention is a method for producing porous silica-alumina particles, comprising: a. Obtaining an aqueous solution containing pseudoboehmite alumina hydrate; b. Obtaining an aqueous solution containing silica powder; c. A step of promoting the reaction of a slurry obtained by mixing the aqueous solution containing the pseudoboehmite alumina hydrate and the aqueous solution containing the silica powder at a pH of 7.0 to 9.0 and at a temperature of 40 to 95°C for 10 minutes to 10 hours to obtain an aqueous solution containing a silica-alumina mixture; d. drying the aqueous solution containing the silica-alumina mixture to obtain porous silica-alumina particles; The present invention proposes a method for producing porous silica-alumina particles, comprising: However, porous silica alumina particles are The specific surface area SA measured by the BET method is 400 to 600 m 2 / g range, The pore volume PV measured by the BJH method is in the range of 1.0 to 2.0 mL / g. The average pore diameter PD measured by the BJH method is in the range of 6 to 30 nm. The mass ratio of silica to alumina is in the range of 2 / 98 to 70 / 30.

[0010] In the method for producing porous silica-alumina particles of the present invention, it is considered to be a preferred embodiment that the silica powder used in step b has a Na2O content of 0.4 mass% or less and a sulfate ion content of 0.5 mass% or less.

[0011] It is believed that the method for producing porous silica-alumina particles of the present invention preferably comprises a step of filtering out the solid content in the step d, and then washing and drying the solid content to obtain silica-alumina particles. [Effects of the Invention]

[0012] The present invention provides amorphous porous silica-alumina particles having a high specific surface area, a large pore volume, and enhanced particle strength. These porous silica-alumina particles have high heat insulating properties and a solid acid content, making them suitable for use as catalysts for petroleum refining, optical materials, or additives for cosmetics, resin fillers, and surface coating materials (for the purposes of optical scattering, refractive index adjustment, etc.). DETAILED DESCRIPTION OF THE INVENTION

[0013] Preferred embodiments of the present invention will now be described in detail. [Porous silica alumina particles] The porous silica-alumina particles of the present invention (hereinafter also referred to simply as "silica-alumina particles") are porous particles made of silica (SiO2) and alumina (Al2O3), and are configured as oxides having a high specific surface area and a high pore volume.

[0014] The porous silica-alumina particles of the present invention are amorphous. Therefore, zeolites and the like, which are crystalline silica-alumina, are not included in the silica-alumina of the present invention. Whether the silica-alumina of the present invention is amorphous can be determined from the X-ray diffraction pattern. Specifically, if the X-ray diffraction pattern obtained by X-ray diffraction measurement of the silica-alumina of the present invention does not show a diffraction peak with a full width at half maximum of less than 1.0° in the range of 5°≦2θ≦50°, the silica-alumina of the present invention can be determined to be amorphous.

[0015] The silica-alumina particles obtained by the present invention have a silica to alumina ratio (S / A) calculated as a mass ratio of SiO2 and Al2O3 in the range of 2 / 98 to 70 / 30, preferably 5 / 95 to 65 / 35. If the alumina ratio is lower than S / A:70 / 30, the solid acidity tends to decrease, and when the particles are used as a cracking catalyst, the required cracking rate cannot be achieved. On the other hand, if the silica ratio is lower than S / A:2 / 98, the specific surface area (SA) tends to decrease.

[0016] The specific surface area SA of the obtained silica alumina particles by the BET method is 400 to 600 m 2 / g, preferably 420 to 550m 2 / g. The reason for setting the lower limit is that when used as a cracking catalyst, a moderately high specific surface area SA is advantageous in terms of contact and reactivity with hydrocarbons. On the other hand, if the specific surface area SA exceeds the upper limit, the pore diameter PD becomes too small, becoming smaller than the molecular size of the hydrocarbon reactant, and there is a risk that the reactant will not be able to diffuse within the pores and an effective reaction will not occur.

[0017] Furthermore, the pore volume PV measured by the BJH method is in the range of 1.0 to 2.0 mL / g, preferably in the range of 1.10 to 1.90 mL / g. If the pore volume PV is smaller than the lower limit, there will be fewer effective reaction sites with hydrocarbon molecules. On the other hand, if the pore volume PV exceeds the upper limit, the crushing strength or abrasion resistance of the molded product will be reduced when used as a cracking catalyst, and powdering may occur when packed into a reactor, making operation impossible.

[0018] The average pore diameter PD measured by the BJH method is in the range of 6 to 30 nm (60 to 300 Å), preferably in the range of 7 to 18 nm (70 to 180 Å). The reason for setting the lower limit is that when the average pore diameter PD is too small, there will be many pores smaller than the hydrocarbon molecule size of the reactant, and it may not be able to diffuse into the pores, resulting in no effective reaction. On the other hand, the reason for setting the upper limit is that in addition to the decrease in specific surface area and the decrease in the active sites of the decomposition reaction, there may be a decrease in the crushing strength.

[0019] The silica-alumina particles of the present application are also characterized by having a small remaining amount of cationic and anionic impurity ion components. Examples of the remaining cations include alkali metal ions such as remaining sodium ions and potassium ions. The amount of these alkali metal ions (M + ) is 0.1% by mass or less in terms of M2O conversion, preferably 0.05% by mass or less. Furthermore, the remaining amount of inorganic acid ions such as sulfate ions and nitrate ions is 1.0% by mass or less, preferably 0.5% by mass or less. By reducing the impurity ion components, the poisoning of the solid acid sites and the active metal is suppressed.

[0020] [Method for producing porous silica-alumina particles] <Step of obtaining an aqueous solution containing pseudo-boehmite alumina hydrate> 《Step a-1. Preparation step》 Methods for preparing pseudoboehmite alumina particles are widely known, and a preferred method involves neutralizing an aluminum salt and / or aluminate solution to precipitate pseudoboehmite alumina particles. The aluminum salt may be any aluminum salt, such as aluminum sulfate, aluminum chloride, or aluminum nitrate. The aluminate may be any aluminate, such as sodium aluminate or potassium aluminate. The neutralization reaction may be carried out by adding an alkaline aqueous solution, such as sodium hydroxide, potassium hydroxide, or aqueous ammonia, to an aluminum salt aqueous solution; adding an acidic aqueous solution, such as sulfuric acid, hydrochloric acid, or nitric acid, to an aluminate aqueous solution; or mixing an aluminum salt aqueous solution with an aluminate aqueous solution. However, from the standpoint of production costs, the method of mixing an aluminum salt aqueous solution with an aluminate aqueous solution to obtain an aqueous solution containing pseudoboehmite alumina hydrate is preferred.

[0021] 《a-2. Aging process》 After mixing the two liquids to carry out the neutralization reaction, the reaction to form pseudo-boehmite alumina hydrate can be accelerated by adjusting the pH of the solution to a range of 7.0 to 10.0 and the temperature to a range of 30 to 70°C (hereinafter also referred to as "aging"). This accelerates the reaction and allows the production of pseudo-boehmite alumina hydrate. If the pH exceeds 10.0, a bayerite phase with a small specific surface area is formed, which may reduce the activity of the final catalyst. Furthermore, if the pH is lower than 7.0, the pore volume of the final pseudo-boehmite alumina particles tends to be reduced, making it difficult to produce pseudo-boehmite alumina particles suitable for use as a catalyst.

[0022] The aging temperature is preferably within the range of 30 to 70 °C. If the temperature is less than 30 °C, the particles tend to strongly aggregate, and the pore volume of the powder obtained through the aging and drying process may become small. Also, if it exceeds 70 °C, it is not preferable because vaterite tends to precipitate. The aging time is desirably in the range of 5 minutes to 120 minutes, preferably 10 to 100 minutes, and more preferably 10 to 90 minutes. If outside this range, the pore volume of the finally obtained pseudo-boehmite alumina particles may be 0.8 mL / g or less, and they may not be usable as pseudo-boehmite alumina particles for catalysts. Although there is no particular limitation regarding the aging time, from the perspective of production efficiency, within 120 minutes is preferable. If the aging time is too long, the specific surface area of the finally obtained pseudo-boehmite alumina particles tends to become small.

[0023] 《a-3. Washing step》 After filtering the pseudo-boehmite alumina hydrate obtained in the above step a-2, a pseudo-boehmite alumina cake is obtained. Transfer the boehmite alumina cake to a washing container and wash it with water at 50 to 70 °C to remove unreacted raw materials, impurity ions, etc., and obtain a pseudo-boehmite alumina cake. Add pure water to the boehmite alumina cake and stir to obtain an aqueous solution containing the pseudo-boehmite alumina hydrate.

[0024] <b. Step of obtaining an aqueous solution containing silica powder> Methods for preparing silica powder are widely known. Among them, the pH during formulation can be adjusted by adjusting the supply rates of the silicate aqueous solution and the acid, and the SiO2 concentration can be controlled by using a silicic acid aqueous solution and an acid with a pre-calculated specified concentration. The reaction can be carried out by supplying a silicate aqueous solution and an acid while stirring in a reactor maintained at 10 to 100 °C, preferably 20 to 95 °C, to obtain an aqueous solution containing silica powder.

[0025] Those that can be used as the silicate may be any of sodium silicate No. 1, No. 2, No. 3, potassium silicate, other soluble silicates, and diatomaceous earth. The acid may be an inorganic acid such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid or an organic acid such as formic acid, but an inorganic acid is preferred.

[0026] The silica powder used here preferably has a lower residual amount of impurities such as impurity ions, and the content of Na2O is in the range of 0.4% by mass or less, and the content of sulfate ions is preferably in the range of 0.5% by mass or less. More preferably, the content of Na2O is in the range of 0.10% by mass or less, and the content of sulfate ions is preferably in the range of 1.0% by mass or less.

[0027] According to the above adjustment method, an aqueous solution containing silica powder with a specific surface area in the range of 190 - 800 m 2 / g can be easily obtained.

[0028] <Step of obtaining an aqueous solution containing a silica-alumina mixture> (Mix an aqueous solution containing pseudo-boehmite alumina hydrate and an aqueous solution containing silica powder to obtain an aqueous solution containing a silica-alumina particle mixture.) Mix an aqueous solution containing the pseudo-boehmite alumina hydrate adjusted to a solid content concentration of 5 - 15% by mass and an aqueous solution containing the silica powder adjusted to a solid content concentration of 10 - 30% by mass, and further adjust it to a range of pH 7.0 - 9.0, more preferably a range of pH 7.5 - 9.0, and carry out aging at a temperature in the range of 40 - 95°C for 10 minutes to 10 hours to obtain an aqueous solution containing a silica-alumina mixture. When mixing these two solutions, the aqueous solution containing silica powder may be added to the aqueous solution containing pseudo-boehmite alumina hydrate, or the aqueous solution containing pseudo-boehmite alumina hydrate may be added to the aqueous solution containing silica powder.

[0029] <d. Drying step> Dry the aqueous solution containing the silica-alumina mixture obtained in the above step c to obtain silica-alumina particles.

[0030] To obtain dried silica-alumina particles, spray drying or other commonly used drying apparatuses can be used. The drying temperature is not particularly limited, but if the temperature is too high, it is not preferable because a phase transition from pseudo-boehmite alumina to gamma-alumina occurs. Therefore, an inlet temperature of 500°C or lower and an outlet temperature of 200°C or lower are preferable, that is, it is preferable to dry within the range of an inlet temperature of 300 - 500°C and an outlet temperature of 130 - 200°C.

[0031] <e. Washing step 2> The silica-alumina particles obtained in the step d are suspended in water and stirred as necessary, then filtered off and washed to obtain a silica-alumina particle cake.

[0032] In order to reduce the residual alkali metal ion concentration of the silica-alumina particles obtained in the step d, it is preferable to use a suspension having a temperature in the range of 40 - 70°C, and it is also preferable to perform filtration on the suspension with an aqueous solution containing a water-soluble acidic substance. Examples of the water-soluble acidic substance used here include ammonium sulfate, ammonium nitrate, ammonium chloride, etc.

[0033] Furthermore, after filtration, in order to remove residual salts and the like, washing and filtration are performed with warm water containing a water-soluble basic substance or the like to obtain a silica-alumina particle cake. The temperature of the washing water is preferably in the range of 50 - 70°C, which is higher than room temperature, in order to improve the removal efficiency of unreacted raw materials, impurity ions, etc. Examples of the water-soluble basic substance used here include aqueous ammonia, hydroxide salts, carbonates, hydrogen carbonates (the salts referred to here mean alkali metal salts and alkaline earth metal salts). Also, depending on the remaining amount of impurities such as impurity ions, the step d may be repeated thereafter, and if necessary, the step e may be performed again.

Examples

[0034] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples in any way.

[0035] <Measurement method or evaluation method> The measurement and evaluation methods used in the examples are as follows.

[0036] (Each element, compound and metal component (Si, Al, Na, SO4 2- ) content measurement method) A 3g sample was placed in a 30mL zirconia bowl with a lid, heated at 200°C for 20 minutes, and then calcined at 700°C for 5 minutes. After that, 2g of Na2O and 1g of NaOH were added and melted for 15 minutes. 25mL of H2SO4 and 200mL of water were added to dissolve the mixture, and the solution was diluted to 500mL with pure water to prepare the sample. The content of each component was measured on an oxide-equivalent mass basis using an inductively coupled plasma (ICP) optical emission spectrometer (Shimadzu Corporation, ICPS-8100, analysis software ICPS-8000).

[0037] (Method for measuring pore volume PV and average pore diameter PD) The pore volume PV and average pore diameter PD were measured using a BELSORP-mini Ver. 2.5.6 manufactured by Microtrac-Bell Co., Ltd. Specifically, nitrogen gas was adsorbed onto a sample that had been heat-treated at 500°C for 2 hours while evacuated, and the pore volume PV (mL / g) and average pore diameter PD (nm) were calculated using the desorption isotherm of the BJH method at relative pressure (P / P0 = 0.99).

[0038] (Method for measuring specific surface area SA) To measure the specific surface area SA, approximately 30 mL of the sample was placed in a porcelain crucible (B-2 type), heated at 500°C for 2 hours, and then cooled to room temperature in a desiccator to obtain a sample for measurement. Next, 1 g of this sample was taken and measured using a fully automatic surface area measuring device (Yuasa Ionics, Multisorb 12 type) to determine the specific surface area SA (m 2 / g) was measured by the BET method.

[0039] (Method for measuring average particle size) The particle size distribution of the particles in the examples was measured using a laser diffraction / scattering particle size distribution analyzer (LA-300) manufactured by Horiba, Ltd. Specifically, the sample was placed in a solvent (water) so that the light transmittance was in the range of 70 to 95%, and measurements were performed under the following conditions: circulation rate: 2.8 L / min, ultrasonic irradiation: 3 minutes, repetition number: 30 times. From the obtained particle size distribution, the median diameter (D50) was adopted as the average particle diameter.

[0040] (Method for measuring loss on ignition (LOI: ignition loss, loss of ignition; hereinafter simply referred to as "LOI")) The particles used as measurement samples were fired at 1000°C for 1 hour, and the mass loss due to firing was calculated as a percentage.

[0041] (Wear resistance (attrition) test conditions) Attrition The wear resistance was measured using the apparatus described in Catalyst and Chemical Formation Techniques, Vol. 13, No. 1, p. 65, 1996, by flowing microspherical particles through the catalyst tube constituting the apparatus at an air linear velocity of 30 m / s, measuring the amount of wear for one hour after the start, and expressing it as the wear ratio (CAI). A CAI of less than 10 is preferred.

[0042] (X-ray diffraction measurement conditions) X-ray diffraction of silica alumina particles was measured using a MiniFlex manufactured by Rigaku Corporation. The measurement conditions were as follows: the operating axis was 2θ / θ, a CuKα source was used, and the measurement was performed continuously at a voltage of 40 kV and a current of 15 mA, from a starting angle of 2θ = 5° to an ending angle of 2θ = 50°, with a sampling width of 0.020° and a scan rate of 10,000° / min. The criterion for determining whether a material is amorphous is that it does not exhibit a diffraction peak with a full width at half maximum of less than 1.0° in the range of 5°≦2θ≦50°.

[0043] [Example 1] (Step a-1) Step of obtaining an aqueous solution containing pseudoboehmite alumina hydrate A 200 L steam-jacketed stainless steel tank was charged with 60 kg of water, and 24 g of a 25% by weight sodium gluconate solution was added with stirring. Then, 885 g of a 22.6% by weight AlO and 17.3% by weight sodium aluminate solution was added. Subsequently, 1408 g of a 24% by weight aluminum sulfate solution was added over 2 minutes to prepare a pseudoboehmite alumina seed slurry with a pH of 7.2. To this seed slurry, a 22.6% by weight AlO and 17.3% by weight sodium aluminate solution was added dropwise at a flow rate of 275 mL / min, and a 23.6% by weight aluminum sulfate solution was added dropwise at a flow rate of 488 mL / min, each for 20 minutes while maintaining the temperature at 60 °C. The pH of the finished slurry was 7.2. After stirring for 5 minutes, the pH was adjusted to 8.8 with 642 g of an aqueous solution of sodium aluminate containing 22.6 mass % AlO and 17.3 mass % NaO, and stirring was continued at 60°C for 2 hours. Since the pH of the slurry had dropped to 7.05, the pH was again adjusted to 8.8 with 15% aqueous ammonia to obtain a pseudoboehmite alumina slurry.

[0044] (Process a-2) Cleaning process The pseudo-boehmite alumina slurry of step a-1 was filtered, and the resulting pseudo-boehmite alumina cake was washed with 105 L of water at 60° C. to remove sulfate ions and sodium ions. The weight of the washed pseudoboehmite alumina cake was 38.4 kg, and the solid content was 8.6%. (The impurity content at this stage was 0.1% by mass in terms of Na2O and 0.5% by mass in terms of SO4 2- The concentration was 1.0% by mass. 14.3 kg of pure water was added to 38.4 kg of pseudoboehmite alumina cake and stirred to obtain an aqueous solution containing pseudoboehmite alumina hydrate.

[0045] (Step c-1) Step of obtaining an aqueous solution containing a silica-alumina mixture The aqueous solution containing the pseudoboehmite alumina hydrate is mixed with silica powder A (Sylysia 780, manufactured by Fuji Silysia Corporation) in Table 1 to obtain an aqueous solution containing a silica-alumina particle mixture. To the aqueous solution containing the pseudoboehmite alumina hydrate, 2.21 kg of silica powder A in Table 1 was added on a dry basis, and then the pH was adjusted to 8.2 with 260 mL of 15% aqueous ammonia.

[0046] (Process c-2) Aging process The aqueous solution containing the silica-alumina particle mixture from step c-1 was transferred to a stainless steel steam-jacketed tank and stirred and aged at 50°C for 2 hours.

[0047] (Step d) Drying process The aqueous solution containing the silica-alumina particle mixture from step c-2 was treated with an emulsifier and then spray-dried to obtain silica-alumina particles 1. The yield was calculated from the weight and moisture content of the dried product, and the properties are shown in Table 2.

[0048] [Example 2] Under the conditions described in Example 1, silica powder B (Sylysia 250, manufactured by Fuji Silysia Ltd.) shown in Table 1 was used in place of silica powder A to obtain silica alumina particles 2 (other conditions were the same as in Example 1).

[0049] [Example 3] Under the conditions described in Example 1, 200 mL of 15% ammonia water was used in the step of obtaining an aqueous solution containing a silica-alumina mixture (step c-1), and the pH was adjusted to 7.8. The mixture was then aged and dried under the same conditions as in Example 1 to obtain silica-alumina particles 3.

[0050] [Example 4] Under the conditions described in Example 1, 340 mL of 15% ammonia water was used in the step of obtaining an aqueous solution containing a silica-alumina mixture (step c-1), and the pH was adjusted to 8.5. The mixture was then aged and dried under the same conditions as in Example 1 to obtain silica-alumina particles 4.

[0051] [Example 5] Under the conditions described in Example 1, 1400 mL of 15% ammonia water was used in (step c-1) the step of obtaining an aqueous solution containing a silica-alumina mixture, and the pH was adjusted to 9.5, followed by aging and drying under the same conditions as in Example 1 to obtain silica-alumina particles 5.

[0052] [Example 6] Under the conditions described in Example 1, 1.35 kg of silica powder A was added in (step c-1) on a dry basis, and then 260 mL of 15% ammonia water was used to adjust the pH to 8.2, followed by aging and drying under the same conditions as in Example 1 to obtain silica alumina particles 6.

[0053] [Example 7] Under the conditions described in Example 1, 3.15 kg of silica powder A was added in (step c-1) on a dry basis, and then the pH was adjusted to 8.2 using 300 mL of 15% ammonia water. The mixture was aged and dried under the same conditions as in Example 1 to obtain silica alumina particles 7.

[0054] [Example 8] Under the conditions described in Example 1, 3.15 kg of silica powder A was added in (step c-1) on a dry basis, and then 160 mL of 15% ammonia water was used to adjust the pH to 7.2, followed by aging and drying under the same conditions as in Example 1 to obtain silica alumina particles 8.

[0055] [Comparative Example 1] Under the conditions described in Example 1, the silica powder used in (step c-1) was replaced with silica hydrogel prepared by the following method, and (step c) and subsequent steps were changed to (step c') to prepare silica alumina powder.

[0056] <Method for preparing silica hydrogel> A 40-liter plastic tank was charged with 4.72 kg of 25% by weight sulfuric acid and 2.0 kg of pure water and adjusted to 30°C. While stirring this sulfuric acid solution, a sodium silicate solution with an 8.5% by weight SiO2 concentration and an SiO2 / Na2O molar ratio of 3.2, adjusted to 45°C, was added dropwise at a flow rate of 0.56 kg / min over 45 minutes. The flow rate was then reduced to 0.1 kg / min, and the sodium silicate solution was added dropwise over 30 minutes until the pH reached 4.0. After the addition was complete, stirring was continued for 165 minutes to obtain an aqueous silica hydrogel solution. 400 mL of 15% aqueous ammonia was added to this silica hydrogel, adjusted to pH 7.0, and aged for 1 hour to obtain a silica hydrogel.

[0057] (Step c') 78,191 g of the aqueous solution containing the pseudoboehmite alumina hydrate and 893 g of the aqueous silica hydrogel solution were mixed by stirring, and then the pH was adjusted to 8.8 with 15% by mass of ammonia water, and the mixture was aged at a temperature of 40 to 60°C for 10 minutes to obtain an aqueous solution containing a silica-alumina mixture.

[0058] (Step d') First cleaning step The aqueous solution containing the silica-alumina mixture obtained in step c' was filtered, and the filtered silica-alumina mixture cake 1a was washed with 105 L of water at 60°C to remove sulfate ions and sodium ions. (The impurity content at this stage was 0.1 mass% Na2O equivalent concentration on a dry basis, 0.1 mass% SO4 2- The concentration was 2.1% by mass.

[0059] (Step e') Step of obtaining silica-alumina gel slurry 7 kg of 60°C hot pure water was added to 23.0 kg of the silica-alumina mixture cake 1a obtained in the step d', and the silica-alumina concentration was adjusted to 10% by mass, followed by stirring to form a slurry. The temperature of this slurry was 45°C and the pH was 8.7. 1.8 L of 15% by mass ammonia water was added to this slurry to adjust the pH to 10.8, and then the slurry was transferred to a 50 L sealed tank equipped with a steam jacket and aged at 95°C for 10 hours.

[0060] (Step f').First drying step The aged slurry obtained in the step e' was homogenized in an emulsifier and then dried in a spray dryer at an inlet temperature of 300°C and an outlet temperature of 150°C to obtain silica alumina particles 1a having an average particle size of 70 µm.

[0061] (Step g') Second cleaning step 300 g of the silica-alumina particles 1a obtained in the step f' was suspended in 3000 g of ammonium sulfate at 60 ° C. with a concentration of 10 mass %, stirred for 20 minutes, and then subjected to solid-liquid separation using a vacuum filter. The remaining cake was resuspended by pouring 3000 g of warm pure water at 60 ° C. Subsequently, the pH was adjusted to 8.8 with 15 mass % ammonia water, and the mixture was stirred for 20 minutes. Then, the mixture was subjected to solid-liquid separation using a vacuum filter to obtain a silica-alumina mixed cake 2a.

[0062] (Step h').Second drying step The silica-alumina particle cake 2a obtained from the filter was taken out into a stainless steel tray and dried overnight at 130°C to obtain the desired silica-alumina particles 9.

[0063] [Table 1]

[0064] [Table 2]

[0065] As is clear from Table 2, the invention examples have higher yields and CAI of less than 10, which means that the particle strength is excellent compared to the comparative examples. [Industrial Applicability]

[0066] The porous silica-alumina particles according to the present invention have a large pore volume and a large specific surface area, and are therefore expected to have heat insulating properties. In addition to the above properties, since they are composed of silica-alumina and have solid acidity, they can be used as catalysts for petroleum refining, optical materials, or as additives for cosmetics, resin fillers, and surface coating materials (for the purposes of optical scattering, refractive index adjustment, etc.).

Claims

1. A method for producing porous silica-alumina particles, comprising: a. Obtaining an aqueous solution containing pseudoboehmite alumina hydrate; b. Obtaining an aqueous solution containing silica powder; c) mixing the aqueous solution containing the pseudoboehmite alumina hydrate with the aqueous solution containing the silica powder, and promoting the reaction of the resulting slurry at a pH of 7.0 to 9.0 and at a temperature of 40 to 95°C for 10 minutes to 10 hours to obtain an aqueous solution containing a silica-alumina mixture; d. A step of drying the aqueous solution containing the silica-alumina mixture to obtain porous silica-alumina particles; A method for producing porous silica-alumina particles, comprising: However, porous silica alumina particles are The specific surface area SA measured by the BET method is 400 to 600 m ２ / g, The pore volume PV measured by the BJH method is in the range of 1.0 to 2.0 mL / g, The average pore diameter PD measured by the BJH method is in the range of 6 to 30 nm, The mass ratio of silica to alumina is in the range of 2 / 98 to 70 / 30.

2. The method for producing porous silica-alumina particles according to claim 1, wherein the specific surface area is in the range of 420 to 550 m 2 / g.

3. A method for producing porous silica alumina particles as described in claim 2, wherein the average pore diameter PD is in the range of 7 to 18 nm.

4. The silica powder used in the step b is Na ２ 4. The method for producing porous silica-alumina particles according to claim 1, wherein the content of O is 0.4% by mass or less and the content of sulfate ions is 0.5% by mass or less.

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