Method for producing porous silica alumina particles

Abstract

To provide porous silica-alumina particles having a high specific surface area and a high pore volume.SOLUTION: Amorphous porous silica-alumina particles having a small residual amount of alkali metal ions and mineral acid ions are provided by repeating a step of obtaining a mixture gel slurry through mixing of silica hydrogel with pseudo-boehmite alumina hydrate and washing and drying the mixture gel slurry.SELECTED DRAWING: None

Description

[Technical Field]

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

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

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

[0004] Furthermore, as an example of the pH swing method (immersion method), there is a preparation method, as described in Patent Documents 5 and 6, in which the pH of the reaction mixture is changed, thereby precipitating silica and alumina, and enabling the production of amorphous silica-alumina in a single container. [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 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, with conventional techniques, porous silica alumina obtained from the preparation methods described in Patent Documents 1 to 6 has a relatively small specific surface area, i.e., 400 m². 2 There was a problem in that it tended to be much smaller than / g.

[0007] Furthermore, there was a problem in that the pore volume tended to be smaller than 1.0 ml / g.

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

[0009] Against this technical backdrop, the inventors diligently studied to solve the above problems and, as a result, discovered that porous silica-alumina particles with a high specific surface area and high pore volume could be obtained, leading to the development of the present invention. The present invention, developed to solve the aforementioned problems and achieve the above objectives, is as follows. That is, the present invention is, firstly, a method for producing porous silica alumina particles, a. A step to obtain an aqueous solution of pseudoboehmite alumina hydrate, b. A step to obtain an aqueous silica hydrogel solution, c. A step of obtaining a silica-alumina mixture aqueous solution by mixing the above-mentioned pseudo-boehmite alumina hydrate aqueous solution and the above-mentioned silica hydrogel aqueous solution, adjusting the pH of the slurry to a range of 7.0 to 9.0, and promoting the reaction at a temperature of 40 to 60°C for 10 minutes to 2 hours, d. A first washing step in which the silica-alumina mixture aqueous solution is filtered to obtain a silica-alumina mixture cake 1, and then washed. e. Dispersing the silica-alumina mixture cake 1 in water, adjusting the pH to 8.0-12.0 at a temperature of 30-50°C, and then further heating to 80°C or higher to obtain a silica-alumina gel slurry. f. A first drying step in which the silica alumina gel slurry is dried to obtain silica alumina particles 1, g. After resuspending and stirring the obtained silica-alumina particles 1 by drying, filtration is performed and washing is carried out to obtain a silica-alumina particle cake 2, which is a second washing step; h. A method for producing porous silica-alumina particles is proposed, which includes a second drying step of drying the silica-alumina particle cake 2 to obtain silica-alumina particles 2.

[0010] Secondly, the present invention also provides amorphous porous silica-alumina particles, where the specific surface area SA measured by the BET method is in the range of 400 - 600 m 2 / g, the pore volume PV measured by the BJH method is in the range of 1.25 - 2.00 ml / g, the average pore diameter PD measured by the BJH method is in the range of 8 - 20 nm, and the mass ratio of silica to alumina is in the range of 2 / 98 - 70 / 30.

[0011] Regarding the above-mentioned porous silica-alumina particles according to the present invention, it is further considered that a more preferable solution is that they contain alkali metal ions (M + ) in an amount of 0.1% by mass or less in terms of M2O conversion, and the residual amount of inorganic acid ions is 1.0% by mass or less.

Advantages of the Invention

[0012] The present invention aims to provide porous silica-alumina particles having a high specific surface area and a high pore volume as the porous silica-alumina particles.

Modes for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail. [Porous Silica-Alumina Particles] The porous silica-alumina particles of the present invention (hereinafter also simply referred to as "silica-alumina particles") are porous particles composed 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, crystalline silica-alumina such as zeolites are not included in the silica-alumina of the present invention. Whether or not 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°, then the silica-alumina of the present invention can be determined to be amorphous.

[0015] The silica-alumina particles obtained in this invention have a silica-to-alumina ratio S / A in the range of 2 / 98 to 70 / 30, calculated as the mass ratio of SiO2 and Al2O3, respectively, preferably in the range of 5 / 95 to 65 / 35. If the alumina ratio is lower than S / A:70 / 30, the amount of solid acid tends to decrease, and if these particles are used as a decomposition catalyst, the required decomposition rate cannot be obtained. 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 resulting silica-alumina particles obtained by the BET method is 400-600 m². 2 The range is / g, preferably 420-550m 2 The range is / g. The reason for setting the lower limit is that when used as a decomposition catalyst, a moderately high specific surface area SA is advantageous in terms of contactability and reactivity with hydrocarbons. On the other hand, if the specific surface area SA is 600m 2 If the amount exceeds / g, the pore size PD becomes too small, smaller than the size of the hydrocarbon molecules of the reactants, preventing diffusion into the pores and potentially preventing an effective reaction.

[0017] Furthermore, the pore volume PV by the BJH method is in the range of 1.25 to 2.00 ml / g, preferably in the range of 1.30 to 1.90 ml / g. When the pore volume PV is less than 1.25 ml / g, the effective reaction sites with hydrocarbon molecules decrease. On the other hand, when the pore volume PV exceeds 2.00 ml / g, in use as a decomposition catalyst, the crushing strength or abrasion strength of the molded product becomes weak, and there is a risk of pulverization when filled in the reactor, making operation impossible.

[0018] The average pore diameter PD measured by the BJH method is in the range of 8 to 20 nm (80 to 100 Å), preferably in the range of 10 to 18 nm (100 to 180 Å). The reason for setting the lower limit is that when the average pore diameter PD is too small, there are many pores smaller than the hydrocarbon molecule size of the reactant, and diffusion into the pores becomes impossible, resulting in the possibility of no effective reaction. On the other hand, the reason for setting the upper limit is that the specific surface area decreases and the active sites of the decomposition reaction decrease.

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

[0020] [Method for Producing Porous Silica-Alumina Particles] <Step of Obtaining Aqueous Solution of Pseudo-Boehmite Alumina Hydrate> 《a-1. Preparation Step》 Methods for preparing pseudo-boehmite alumina particles are widely known, and among them, the method of neutralizing an aluminum salt and / or aluminate solution to form a precipitate of pseudo-boehmite alumina particles is preferred. Any aluminum salt can be used as the aluminum salt, such as aluminum sulfate, aluminum chloride, or aluminum nitrate. Any aluminate can be used as the aluminate, such as sodium aluminate or potassium aluminate. The neutralization reaction can be carried out by adding an alkaline aqueous solution such as sodium hydroxide, potassium hydroxide, or ammonia water to an aluminum salt aqueous solution, adding an acid aqueous solution such as sulfuric acid, hydrochloric acid, or nitric acid to an aluminate aqueous solution, or mixing the aluminum salt aqueous solution and the aluminate aqueous solution. However, from the standpoint of manufacturing cost, the method of mixing the aluminum salt aqueous solution and the aluminate aqueous solution to obtain a pseudo-boehmite alumina hydrate aqueous solution is preferred.

[0021] 《a-2. Aging process》 After mixing the two liquids to carry out the neutralization reaction, the pH of the solution is adjusted to a range of 7.0 to 10.0 and the temperature to 30 to 70°C to accelerate the reaction to obtain pseudoboehmite alumina hydrate (hereinafter also referred to as "maturation"). 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. Also, if the pH is lower than 7.0, the pore volume of the final pseudoboehmite alumina particles tends to decrease, which may make it difficult to produce pseudoboehmite alumina particles suitable for the catalyst.

[0022] The aging temperature preferably falls within the range of 30 to 70 °C. When the temperature is 30 °C or lower, the particles tend to strongly aggregate, and the pore volume of the powder obtained through the aging and drying process may become small. Also, when the temperature is 70 °C or higher, it is not preferable because vaterite is likely to precipitate. The aging time preferably ranges from 5 minutes to 120 minutes, more preferably from 10 to 100 minutes, and even more preferably from 10 to 90 minutes. If it is outside this range, the pore volume of the finally obtained pseudo-boehmite alumina particles may be 0.8 cc / 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, considering 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] <Step of obtaining silica hydrogel aqueous solution> Methods for preparing silica hydrogel are widely known. Among them, the pH during formulation can be adjusted by controlling 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 at a predetermined specified concentration calculated in advance. The reaction can be carried out by supplying the silicate aqueous solution and the acid while stirring in a reactor maintained at 10 to 100 °C, preferably 20 to 95 °C, to obtain a silica hydrogel solution.

[0024] 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.

[0025] 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 concentration of the silicate to be supplied is 30% by mass or less in terms of SiO2, preferably 10% by mass or less. The lower limit of the silicate concentration is not particularly provided. However, for example, if it is supplied at 5% by mass or more, it is preferable because a large-volume mixing container or a large amount of water is not required to adjust the required amount of SiO2. On the other hand, the reason for setting the upper limit is that due to the gelation caused by the neutralization with the inorganic acid, the stirrer becomes overloaded due to the influence of the strong gel-like substance and stops or sufficient stirring cannot be performed.

[0027] According to the above adjustment method, an aqueous solution of silica hydrogel with a specific surface area in the range of 190 - 600 m 2 / g can be easily obtained by the BET method.

[0028] <Step of obtaining an aqueous solution of silica-alumina mixture> (Mix the aqueous solution of pseudo-boehmite alumina hydrate and the aqueous solution of silica hydrogel to obtain an aqueous solution of silica-alumina particle mixture.) Mix an aqueous solution of pseudo-boehmite alumina hydrate adjusted to a solid content concentration of 1 - 5% by mass and an aqueous solution of silica hydrogel adjusted to a solid content concentration of 5 - 10% by mass, and further adjust it to a range of pH 7.0 - 10.0, more preferably a range of pH 8.0 - 9.0, and carry out aging at a temperature in the range of 40 - 60°C for 10 minutes to 2 hours to obtain an aqueous solution of silica-alumina mixture. When mixing these two solutions, the aqueous solution of silica hydrogel may be added to the aqueous solution of pseudo-boehmite alumina hydrate, or the aqueous solution of pseudo-boehmite alumina hydrate may be added to the aqueous solution of silica hydrogel.

[0029] <d. First washing step> After filtering the aqueous solution of silica-alumina mixture obtained in the above step c, a silica-alumina mixture cake 1 is obtained. Transfer this mixture cake 1 to a washing container and wash it with water at 50 - 70°C to remove unreacted raw materials, impurity ions, etc., and obtain a silica-alumina mixture cake 1.

[0030] The temperature of the washing water is preferably in the range of 50 to 70°C, which is higher than room temperature, in order to improve the removal efficiency of unreacted raw materials, impurity ions, etc. The amount of water at 50 to 70°C used here is preferably such that the washing is carried out using about 35 times the mass of the silica alumina particles theoretically obtained.

[0031] <Step of obtaining silica alumina gel slurry> After dispersing the silica alumina mixture cake 1 obtained in the above step d in water, the pH is adjusted to a range of 8.0 to 12.0, more preferably pH 8.5 to 11.5, at a temperature of 30 to 50°C, and then further heated to 80°C or higher and stirred for 1 to 20 hours, more preferably 1 to 15 hours, to promote the reaction from the silica alumina mixture to the silica alumina gel and obtain a silica alumina gel slurry. Here, in the heating at 80°C or higher, since it aims to promote and complete the aging of the silica alumina gel, it may be carried out at normal pressure or under pressurized conditions such as in an autoclave. By carrying out under pressurized conditions, there is an advantage that the treatment time can be shortened.

[0032] <f. First drying step> The silica alumina gel slurry obtained in the above step e is dried to obtain silica alumina particles 1.

[0033] To obtain silica alumina particles 1 by drying, spray drying or other commonly used drying devices can be used. The drying temperature is not particularly limited, but if the temperature is too high, it is not preferable because of the phase transition from pseudo-boehmite alumina to gamma-alumina. Therefore, the inlet temperature is preferably 500°C or lower, and the outlet temperature is preferably 200°C or lower, that is, it is preferable to dry in the range of an inlet temperature of 300 to 500°C and an outlet temperature of 130 to 200°C.

[0034] <g. Second washing step> The silica alumina particles 1 obtained in the above step f are suspended and stirred again, then filtered and washed to obtain a silica alumina particle cake 2.

[0035] In order to reduce the residual alkali metal ion concentration of the silica alumina particles 1 obtained in the step f, it is preferable to use a suspension having a temperature in the range of 40 to 70°C. Further, it is preferable to perform filtration separation on the suspension with an aqueous solution containing a water-soluble acidic substance. Examples of the water-soluble acidic substance used herein include ammonium sulfate, ammonium nitrate, ammonium chloride, and the like.

[0036] Furthermore, after the filtration separation, in order to remove residual salts and the like, washing and filtration separation are performed with warm water or the like containing a water-soluble basic substance to obtain silica alumina particle cake 2. The temperature of the washing water is preferably in the range of 50 to 70°C, which is higher than room temperature, in order to improve the removal efficiency of unreacted raw materials, impurity ions, and the like. Examples of the water-soluble basic substance used herein include aqueous ammonia, hydroxide salts, carbonates, and hydrogen carbonates (the salts mentioned here mean alkali metal salts and alkaline earth metal salts).

[0037] <h. Second drying step> The drying of the filtered silica alumina particle cake 2 obtained in the step g is performed by the drying method described in the step f to obtain the target silica alumina particles 2.

[0038] [[ID=第十四条]] Depending on the remaining amount of impurities such as impurity ions, after the step g, the steps f and / or g may be performed again as necessary.

Examples

[0039] 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.

[0040] <Measurement method or evaluation method> The measurement method or evaluation method in the examples and the like is as follows.

[0041] (Measurement method for the content of each element, compound, and metal component (Si, Al, Na, SO4 2- )) Three g of the sample was placed in a 30 ml lidded zirconia ball, which was then heat-treated (200°C, 20 minutes) and calcined (700°C, 5 minutes). After that, two g of Na2O2 and one g of NaOH were added and melted for 15 minutes. Further, two 5 ml of H2SO4 and two 200 ml of water were added and dissolved, and then the mixture was diluted with pure water to a volume of 500 ml to prepare the sample. The content of each component in the obtained sample was measured on an oxide-reduced mass basis using an inductively coupled plasma (ICP) emission spectrometer (Shimadzu Corporation, ICPS-8100, analysis software ICPS-8000).

[0042] (Method for measuring pore volume PV and average pore diameter PD) Pore ​​volume (PV) and average pore diameter (PD) were measured using BELSORP-mini Ver2.5.6 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 under vacuum evacuation, and the pore volume (PV) (ml / g) and average pore diameter (PD) (nm) were calculated using the desorption side isotherm of the relative pressure (P / P0 = 0.99) of the BJH method.

[0043] (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 (Type B-2), heated at 500°C for 2 hours, and then cooled to room temperature in a desiccator to obtain the sample for measurement. Next, 1 g of this sample was taken and measured using a fully automated surface area analyzer (Yuasa Ionics Co., Ltd., MultiSorb Type 12) to determine the specific surface area SA (m²) of the sample. 2 The concentration (per g) was measured using the BET method.

[0044] (Method for measuring average particle size) The particle size distribution of the catalysts 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 70-95%, and the measurement was performed under the conditions of circulation speed: 2.8 L / min, ultrasonic irradiation: 3 minutes, and number of repetitions: 30. From the obtained particle size distribution, the median diameter (D50) was adopted as the average particle size.

[0045] (Method for measuring ignition loss (also known as loss of ignition; hereinafter simply referred to as "ignition loss")) The catalyst sample used for measurement was calcined at 1000°C for 1 hour, and the mass loss due to calcination was used to calculate the result.

[0046] (X-ray diffraction measurement conditions) X-ray diffraction of silica-alumina particles was measured using a Rigaku MiniFlex scanner. The measurement conditions were as follows: operating axis 2θ / θ, CuKα as the radiation source, continuous measurement method, voltage 40kV, current 15mA, starting angle 2θ=5° to ending angle 2θ=50°, sampling width 0.020°, and scan speed 10.000° / min. The criterion for determining amorphous material was that it should not exhibit diffraction peaks with a full width at half maximum (FMAX) of less than 1.0° in the range of 5° ≤ 2θ ≤ 50°.

[0047] [Example 1] (Step a) Step to obtain an aqueous solution of pseudoboehmite alumina hydrate. A 200L stainless steel tank with a steam jacket was filled with 60kg of water. While stirring, 24g of a 25% sodium gluconate aqueous solution was added, followed by 885g of a sodium aluminate aqueous solution containing 22.6% Al2O3 and 17.3% Na2O. Then, 1408g of a 24% aluminum sulfate aqueous solution was added over 2 minutes to prepare a pseudo-boehmite alumina seed slurry with a pH of 7.2. To this seed slurry, a 22.6% Al2O3 and 17.3% Na2O aqueous solution was added dropwise at a flow rate of 275ml / min, and a 23.6% aluminum sulfate solution was added dropwise at a flow rate of 488ml / min, both over 20 minutes while maintaining a temperature of 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 sodium aluminate solution containing Al2O3:22.6% by mass and Na2O:17.3% by mass, and stirring was continued at 60°C for 2 hours to prepare an aqueous solution of pseudoboehmite alumina hydrate.

[0048] (Step b) Step to obtain an aqueous silica hydrogel solution. 4.72 kg of 25% by mass sulfuric acid and 2.0 kg of pure water were placed in a 40 L plastic tank and adjusted to 30°C. While stirring this sulfuric acid solution, a sodium silicate solution with an 8.5% by mass 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. Then, the flow rate was reduced to 0.1 kg / min and the sodium silicate solution was added dropwise for 30 minutes until the pH reached 4.0. After the dropwise addition was complete, stirring was continued for 165 minutes to obtain an aqueous silica hydrogel solution. 400 ml of 15% concentration ammonia water was added to this silica hydrogel to adjust the pH to 7.0 and allowed to mature for 1 hour.

[0049] (Step c) Step to obtain an aqueous silica alumina mixture After stirring and mixing 78,191 g of the pseudo-boehmite alumina hydrate aqueous solution and 893 g of the silica hydrogel aqueous solution, the pH was adjusted to 8.8 with 15% by mass of aqueous ammonia, and the mixture was aged at a temperature of 40-60°C for 10 minutes to obtain a silica alumina mixture aqueous solution.

[0050] (Step d) First washing process The silica-alumina mixture aqueous solution obtained in step c above was filtered, and the filtered silica-alumina mixture cake 1a was washed with 105 L of 60°C water to remove sulfate ions and sodium ions. (At this stage, the impurity content was 0.1% by mass in terms of Na2O concentration on a dry basis, SO4 2- The concentration was 2.1% by mass.

[0051] (Step e) Step to obtain silica alumina gel slurry. 23.0 kg of silica-alumina mixture cake 1a obtained in step d above was mixed with 7 kg of 60°C warm pure water to adjust the silica-alumina concentration to 10% by mass, and then stirred 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 it was transferred to a 50 L sealed tank with a steam jacket and aged at 95°C for 10 hours.

[0052] (Step f).First drying step The matured slurry obtained in 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 with an average particle size of 70 μm.

[0053] (Process g) Second washing process 300 g of the silica-alumina particles 1a obtained in step f above were suspended in 3000 g of ammonium sulfate at 60°C at a concentration of 10% by mass, stirred for 20 minutes, and then solid-liquid separation was performed using a vacuum filter. 3000 g of warm pure water at 60°C was poured over the remaining cake and resuspended. Subsequently, the pH was adjusted to 8.8 with 15% by mass aqueous ammonia, stirred for 20 minutes, and then solid-liquid separation was performed using a vacuum filter to obtain silica-alumina mixed cake 2a.

[0054] (Step h).Second drying step The silica-alumina particle cake 2a obtained from the filter was removed from the filter into a stainless steel tray and dried overnight at 130°C to obtain the target silica-alumina particles I. The chemical composition analysis and physical properties are shown in Table 1.

[0055] [Example 2] (Process a~c) Aqueous solutions of boehmite alumina hydrate and silica hydrogel were obtained in the same manner as in Example 1. After weighing 2400 g (based on Al2O3) and 600 g (based on SiO2) of slurry, the mixture was stirred and mixed, and the pH was adjusted to 8.8 with 15% by mass of aqueous ammonia, and the mixture was aged for 10 minutes. (Step d) This mixed slurry was filtered and washed in the same manner as in Example 1. (At this stage, the impurity content was Na2O: 0.9% by mass, SO4 based on dry weight) 2- (It was 1.7% by mass.) (Steps e~h) The subsequent processing was carried out in the same manner as in Example 1 to obtain the desired silica-alumina particles II.

[0056] [Example 3] (Process a~c) Similar to Example 1, aqueous solutions of pseudoboehmite alumina hydrate and silica hydrogel were obtained. After weighing 1800 g (based on Al2O3) and 1200 g (based on SiO2) of slurry, the mixture was stirred and mixed, and the pH was adjusted to 8.8 with 15% by mass of aqueous ammonia, and the mixture was aged for 10 minutes. (Step d) This mixed slurry was filtered and washed in the same manner as in Example 1. (At this stage, the impurity content was Na2O: 1.8% by mass, SO4 based on dry weight) 2- (It was 1.1% by mass.) (Steps e~h) The subsequent processing was carried out in the same manner as in Example 1 to obtain the desired silica-alumina particles III.

[0057] [Example 4] (Process a~c) Aqueous solutions of boehmite alumina hydrate and silica hydrogel were obtained in the same manner as in Example 1. After weighing 1200 g (based on Al2O3) and 1800 g (based on SiO2) of slurry, the mixture was stirred and mixed, and the pH was adjusted to 8.8 with 15% by mass of aqueous ammonia, and the mixture was aged for 10 minutes. (Step d) This mixed slurry was subjected to solid-liquid separation using a vacuum filter in the same manner as in Example 1, and then washed with warm pure water. (At this stage, the impurity content was Na2O: 2.7% by mass, SO4 based on dry matter.) 2- (It was 0.8% by mass.) (Steps e~h) The subsequent processing was carried out in the same manner as in Example 1 to obtain the desired silica-alumina particles IV.

[0058] [Example 5] (Process a~c) Aqueous solutions of boehmite alumina hydrate and silica hydrogel were obtained in the same manner as in Example 1. After weighing 1200 g (based on Al2O3) and 1800 g (based on SiO2) of slurry, the mixture was stirred and mixed, and the pH was adjusted to 8.8 with 15% by mass of aqueous ammonia, and the mixture was aged for 10 minutes. (Step d) This mixed slurry was filtered and washed in the same manner as in Example 1. (At this stage, the impurity content was Na2O: 0.6% by mass, SO4 based on dry weight) 2- (It was 3.2% by mass.) (Steps e~h) The subsequent processing was carried out in the same manner as in Example 1 to obtain the target silica-alumina particles V.

[0059] [Comparative Example 1] *Method that does not use pseudo-boehmite alumina (Process a'~c') 4.72 kg of 25% by mass sulfuric acid and 2.0 kg of pure water were placed in a 40 L resin tank and adjusted to 30°C. While stirring this sulfuric acid solution, a sodium silicate solution with an 8.5% by mass 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. Then, the flow rate was reduced to 0.1 kg / min and the sodium silicate solution was added dropwise for 30 minutes until the pH reached 4.0. After the dropwise addition was complete, stirring was continued for 165 minutes to obtain a silica hydrogel. 500 ml of 15% by mass aqueous ammonia was added to this silica hydrogel to adjust the pH to 7.0 and allowed to mature for 1 hour. The finished silica hydrogel weighed 35.54 kg. Half of this was transferred to a 50 L steam-jacketed tank, and 1 kg of pure water was added. Then, while maintaining the slurry temperature in the tank at 45°C, 8.45 kg of a 23.6 mass% aluminum sulfate solution was added over 5 minutes with stirring. The pH after addition was 2.96. Next, 5.31 kg of a sodium aluminate solution with concentrations of 22.6 mass% Al2O3 and 17.3 mass% Na2O was added over 3 minutes to adjust the pH to 7.0, and stirring was continued at 45°C for 2 hours. (Process d~h) Subsequently, the silica-alumina mixture slurry was treated in the same manner as in Example 1 to obtain silica-alumina particles VI.

[0060] [Comparative Example 2] (Process a'~c') 35.54 kg of silica hydrogel was prepared in the same manner as in Comparative Example 1. 31.1 kg of this silica hydrogel was weighed and transferred to a 50 L steam-jacketed tank, and 1 kg of pure water was added. Then, while maintaining the slurry temperature in the tank at 45°C, 4.22 kg of a 23.6 mass% aluminum sulfate solution was added over 5 minutes with stirring, and the pH after addition was 3.50. Next, 2.66 kg of a sodium aluminate solution (Al2O3: 22.6 mass%, Na2O: 17.3 mass%) was added over 3 minutes to adjust the pH to 6.9, and stirring was continued at 45°C for 2 hours. (Process d~h) This silica-alumina mixture slurry was treated in the same manner as in Example 1 to obtain silica-alumina particles VII.

[0061] Table 1 summarizes the component composition, loss on ignition (LOI), pore volume (PV), average pore diameter (PD), and specific surface area (SA) of samples No. I to VII prepared as described above. X-ray diffraction measurements of samples No. I to VII confirmed that they are amorphous silica-alumina particles. Samples No. I to V exhibit a sufficient balance of pore volume (PV) and specific surface area (SA), while samples No. VI and VII have a small average pore diameter (PD) and inferior pore volume (PV).

[0062] [Table 1] [Industrial applicability]

[0063] The porous silica-alumina particles according to the present invention are expected to have thermal insulation properties due to their high pore volume and high specific surface area. In addition to the above physical properties, since they are composed of silica-alumina, they possess solid acids and can therefore be used as catalysts or optical materials for petroleum refining, or as additives to cosmetics, resin fillers, and surface coating materials (for purposes such as optical scattering and refractive index adjustment).

Claims

[Claim 1] A method for producing porous silica alumina particles, a. A step to obtain an aqueous solution of pseudoboehmite alumina hydrate, b. A step to obtain an aqueous silica hydrogel solution, c. A step of obtaining a silica-alumina mixture aqueous solution by mixing the pseudo-boehmite alumina hydrate aqueous solution and the silica hydrogel aqueous solution, adjusting the pH of the slurry to a range of 7.0 to 9.0, and promoting the reaction at a temperature of 40 to 60°C for 10 minutes to 2 hours, d. A first washing step in which the silica-alumina mixture aqueous solution is filtered to obtain a silica-alumina mixture cake 1, and then washed. e. A step of dispersing the silica-alumina mixture cake 1 in water, adjusting the pH to 8.0 to 12.0 at a temperature of 30 to 50°C, and then further heating to 80°C or higher to obtain a silica-alumina gel slurry. f. A first drying step of drying the silica alumina gel slurry to obtain silica alumina particles 1, g. A second washing step in which the silica-alumina particles 1 obtained by drying are resuspended and stirred, then filtered and washed to obtain a silica-alumina particle cake 2, h. A method for producing porous silica-alumina particles, comprising a second drying step of drying the silica-alumina particle cake 2 to obtain silica-alumina particles 2.

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