Alumina-silica-titania composite oxide

Abstract

To provide an alumina-silica-titania composite oxide having a high pore volume and a large Bronsted acid amount.SOLUTION: An alumina-silica-titania composite oxide has the following configurations (1) to (5): (1) a content of Al is in a range of 10 mass% or more and 75 mass% or less in terms of Al2O3; (2) a content of Si is in a range of 5 mass% or more and 70 mass% or less in terms of SiO2; (3) a content of Ti is in a range of 1 mass% or more and 30 mass% or less in terms of TiO2; (4) a pore volume calculated based on a pore distribution measured by a nitrogen adsorption method is in a range of 0.8 mL / g or more and 2.0 mL / g or less; and (5) a Bronsted acid amount measured at 150°C by infrared spectroscopy using pyridine as a probe molecule is 5 μmol / g or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an alumina-silica-titania composite oxide. [Background technology]

[0002] Inorganic oxides such as alumina, silica, and titania are materials used in a variety of applications. For example, alumina is another name for aluminum oxide, and is a material widely used in applications such as ceramic materials, catalyst supports, and resin fillers. Silica is another name for silicon dioxide, and is also widely used in applications such as desiccants, catalyst supports, abrasives, and cosmetics. Titania is another name for titanium oxide, and is also widely used in applications such as pigments, catalyst supports, photocatalysts, and UV protection materials. The properties required for these inorganic oxides vary depending on the application, and a wide variety of materials have been developed.

[0003] Inorganic oxides such as alumina, silica, or titania can also form composite oxides. For example, some of these composite oxides are amorphous, while others are crystalline, such as zeolites. The properties of these materials change depending on the combination of inorganic oxides. Many of these composite oxides are known to exhibit acidity, with a greater acid content and stronger acid strength than the individual oxides (Non-Patent Document 1).

[0004] Such acidic properties are exhibited by the bonding of individual oxides via covalent bonds. For example, silica-alumina, a composite oxide of silica and alumina, is known to exhibit acidic properties due to the formation of Si-O-Al bonds. It is also known that silica-titania, a composite oxide of silica and titania, exhibits acidic properties due to the formation of Si-O-Ti bonds.

[0005] In addition to the composite oxides composed of two types of inorganic oxides described above, composite oxides composed of three types of inorganic oxides are also known. For example, Patent Document 1 discloses a porous titania support in which titania is supported on the surface of a silica-alumina composite oxide. However, no porous alumina-silica-titania composite oxides with solid acidity, particularly a high Bronsted acidity, have been known. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-33819 [Non-patent literature]

[0007] [Non-Patent Document 1] Kozo Tabe, Tetsuro Kiyoyama, Kazuo Fueki (eds.), "Metal Oxides and Complex Oxides," Kodansha, 1978 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to obtain a new alumina-silica-titania composite oxide having a large pore volume and a large Bronsted acid content. [Means for solving the problem]

[0009] According to the present invention, an alumina-silica-titania composite oxide having a large pore volume and a large Bronsted acid amount can be obtained.

[0010] Specifically, an alumina-silica-titania composite oxide having the following components (1) to (5) can be obtained. (1) The Al content is in the range of 10% by mass to 75% by mass in terms of Al2O3. (2) The Si content is in the range of 5% by mass to 70% by mass in terms of SiO2. (3) The Ti content is in the range of 1% by mass to 30% by mass in terms of TiO2. (4) The pore volume calculated based on the pore distribution measured by the nitrogen adsorption method is in the range of 0.8 mL / g or more and 2.0 mL / g or less. (5) The Bronsted acidity measured at 150°C by infrared spectroscopy using pyridine as a probe molecule is 5 μmol / g or more. [Effects of the Invention]

[0011] According to the present invention, an alumina-silica-titania composite oxide having a large pore volume and a large Bronsted acid amount can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention includes an invention relating to an alumina-silica-titania composite oxide having a large pore volume and a high Bronsted acid content (hereinafter also referred to as the "composite oxide of the present invention"). The composite oxide of the present invention will be described in detail below. In the present invention, when a numerical range is indicated by "to", the numerical range includes both the upper and lower limits. For example, when "1 to 2" is stated, it means "1 or more and 2 or less."

[0013] [Composite oxide of the present invention] The composite oxide of the present invention is a composite oxide composed of three inorganic oxides: alumina, silica, and titania. These inorganic oxides may exist as crystalline inorganic oxides or amorphous inorganic oxides in the composite oxide of the present invention. When the composite oxide of the present invention is used for applications utilizing the surface thereof, such as adsorbents and catalysts, it is preferable that the composite oxide be amorphous. Whether these inorganic oxides exist in the crystalline or amorphous state in the composite oxide of the present invention can be determined from the X-ray diffraction pattern of the composite oxide of the present invention. In the present invention, if there is a spectrum identified as crystalline titania such as anatase type and crystalline alumina such as gamma alumina, it can be determined that the composite oxide exists in a state containing crystalline inorganic oxides; otherwise, it can be determined that the composite oxide exists in an amorphous state. Note that aluminum hydroxide such as pseudoboehmite, which is an alumina compound, is not included in the crystalline alumina of the present invention.

[0014] The composite oxide of the present invention contains Al derived from alumina. In the composite oxide of the present invention, Al forms Si-O-Al bonds, and these bonds, which have an imbalance in charge, interact with surrounding OH groups, thereby increasing the Bronsted acidity. The Al content in the composite oxide of the present invention, calculated as Al2O3, must be in the range of 10% by mass to 75% by mass, preferably 15% by mass to 70% by mass, and more preferably 20% by mass to 70% by mass, based on the total mass of the composite oxide. The composite oxide of the present invention having an Al content in the above-mentioned range is likely to have an increased Bronsted acidity.

[0015] The composite oxide of the present invention contains Si derived from silica. In the composite oxide of the present invention, Si forms Si-O-Al bonds or Si-O-Ti bonds, and these bonds, which have an imbalance in charge, interact with surrounding OH groups, thereby increasing the Bronsted acidity. In addition, in the composite oxide of the present invention, Si also increases the specific surface area and pore volume. The Si content in the composite oxide of the present invention, calculated as SiO2, must be in the range of 5% to 70% by mass, preferably 10% to 65% by mass, and more preferably 10% to 60% by mass, based on the total mass of the composite oxide. The composite oxide of the present invention having a Si content within the above-mentioned range is likely to have an increased Bronsted acidity. Furthermore, the specific surface area and pore volume are likely to be high.

[0016] The composite oxide of the present invention contains Ti derived from titania. In the composite oxide of the present invention, Ti forms Si-O-Ti bonds, and these charge-biased bonds interact with surrounding OH groups to increase the Bronsted acidity. Furthermore, when an active component such as molybdenum is supported, Ti acts as a site for adsorbing the active component. The Ti content in the composite oxide of the present invention, calculated as TiO2, must be in the range of 1% by mass to 30% by mass, preferably 3% by mass to 25% by mass, and more preferably 5% by mass to 20% by mass, based on the total mass of the composite oxide. The composite oxide of the present invention having a Ti content within the aforementioned range is likely to have an increased Bronsted acidity. Furthermore, the specific surface area and pore volume are likely to be large.

[0017] The composite oxide of the present invention must have a pore volume calculated based on the pore size distribution measured by the nitrogen adsorption method in the range of 0.8 mL / g to 2.0 mL / g. Because pores function as adsorption sites, composite oxides of the present invention with a high pore volume are suitable for use in applications that utilize adsorption, such as materials for adsorption and catalysts. The composite oxide of the present invention preferably has a pore volume in the range of 0.9 mL / g to 2.0 mL / g, and more preferably in the range of 1.0 mL / g to 2.0 mL / g. The composite oxide of the present invention with a pore volume in the aforementioned range is more suitable for use in applications that involve adsorption.

[0018] The composite oxide of the present invention must have a Brønsted acidity of 5 μmol / g or more, as measured at 150°C by infrared spectroscopy using pyridine as a probe molecule. Such an alumina-silica-titania composite oxide has not previously been available that has both a large Brønsted acidity and a large pore volume. The composite oxide of the present invention, possessing these characteristics, is suitable for use in applications that utilize adsorption. It is particularly suitable for use as a catalyst material for adsorption of basic substances or catalytic reactions using a Brønsted acid. There is no particular upper limit to the Brønsted acidity, but it may be 100 μmol / g or less, 75 μmol / g or less, or 50 μmol / g or less.

[0019] The composite oxide of the present invention preferably has a Lewis acid content measured by infrared spectroscopy using pyridine as a probe molecule in the range of 50 μmol / g to 400 μmol / g, more preferably 75 μmol / g to 375 μmol / g, and particularly preferably 100 μmol / g to 375 μmol / g. Furthermore, the ratio of the Brønsted acid content to the total amount of the Brønsted acid content and Lewis acid content is preferably in the range of 1% to 30%, more preferably 1% to 20%, and particularly preferably 1% to 10%. The composite oxide of the present invention having a Brønsted acid content in the above-mentioned range has excellent properties as a solid acid catalyst for various oxidation reactions.

[0020] The composite oxide of the present invention preferably has high Ti dispersibility in the alumina-silica-titania composite oxide. Poor Ti dispersibility leads to Ti aggregation and enlargement, resulting in a reduced surface area of ​​the alumina-silica-titania composite oxide. The Ti dispersibility can be determined by ultraviolet absorption spectroscopy. Ti has semiconductor properties and absorbs wavelengths corresponding to its bandgap. It is known that the quantum size effect widens the bandgap and shifts the absorption wavelength to shorter wavelengths. A wavelength at the absorption edge in the ultraviolet absorption spectrum (hereinafter also referred to as the "UV absorption edge wavelength") of 350 nm or less can be considered to be high Ti dispersibility. Thus, no alumina-silica-titania composite oxide has been found to have a high Brønsted acid content, a large pore volume, and high Ti dispersibility. Because such alumina-silica-titania composite oxides have high Ti dispersibility, when used as catalyst supports for hydrocracking, for example, they provide many sites for supporting or adsorbing active metals such as molybdenum, thereby contributing to improved active metal dispersibility.

[0021] The composite oxide of the present invention preferably has a peak pore diameter calculated based on a pore size distribution measured by a nitrogen adsorption method in the range of 2 nm to 50 nm, more preferably in the range of 5 nm to 45 nm, and particularly preferably in the range of 5 nm to 20 nm. In the present invention, the peak pore diameter is defined as the pore diameter at which the cumulative pore volume is highest in the log differential pore volume distribution (dV / d(logD)). The composite oxide of the present invention having a peak pore diameter in the above-mentioned range is less likely to lose its pore structure when kneaded and molded into pellets, and has excellent performance as an adsorbent or catalyst in the form of a porous molded body.

[0022] In the composite oxide of the present invention, the volume of pores within ±2 nm of the peak pore diameter is preferably in the range of 0.01 mL / g to 1.00 mL / g, more preferably in the range of 0.05 mL / g to 0.90 mL / g, and particularly preferably in the range of 0.30 mL / g to 0.80 mL / g. The composite oxide of the present invention having a peak pore diameter within the above-mentioned range is less likely to lose its pore structure when kneaded and molded into pellets, and exhibits excellent performance as an adsorbent or catalyst in the form of a porous molded body. Furthermore, the ratio of the volume of pores within ±2 nm of the peak pore diameter to the pore volume is preferably in the range of 1% to 60%, more preferably in the range of 5% to 60%, and particularly preferably in the range of 20% to 60%. The composite oxide of the present invention having this ratio within the above-mentioned range is less likely to lose its pore structure when molded into pellets, and exhibits excellent performance as an adsorbent or catalyst in the form of a porous molded body.

[0023] The composite oxide of the present invention has a specific surface area of ​​150 m2 calculated by the BET single-point method based on the pore distribution measured by the nitrogen adsorption method. 2 / g~600m 2 / g, and preferably in the range of 175m 2 / g~550m 2 / g, and more preferably in the range of 200m 2 / g~500m 2 The composite oxide of the present invention having a specific surface area in the above range can be suitably used as a material for, for example, an adsorbent or a catalyst.

[0024] The composite oxide of the present invention may be in the form of a powder or a molded body. The shape can be freely adjusted depending on the application. For example, when the composite oxide of the present invention is used for applications such as an adsorbent or a catalyst, it is preferably a molded body with a minor axis of 1 mm or more. Furthermore, when the composite oxide of the present invention is used as a material constituting an adsorbent or a catalyst, it is preferably a powder. For example, the composite oxide may be a powder having a median diameter in the range of 10 μm to 200 μm, a powder having a median diameter in the range of 30 μm to 175 μm, or a powder having a median diameter in the range of 50 μm to 150 μm. By making the powder have a median diameter in the above range, handling during processing is improved. Furthermore, the powder may have a bulk density of 0.10 g / mL to 1.00 mL / g, a powder having a bulk density of 0.15 g / mL to 0.75 mL / g, or a powder having a bulk density of 0.20 g / mL to 0.50 mL / g.

[0025] The composite oxide of the present invention can be prepared, for example, by a production method comprising the following steps (I) to (III). However, the production method for the composite oxide of the present invention is not limited to the following production method. (I) A first step of preparing a first aqueous solution in which a silica precursor is mixed in water, a second aqueous solution containing a basic aluminum salt, and a third aqueous solution containing a titanium mineral salt in an acidic salt solution and an aluminum salt of the same mineral acid as the titanium mineral salt, mixing the second aqueous solution with the first aqueous solution, and then mixing the third aqueous solution with the mixed solution to obtain a mixed solution with a pH of 6.5 to 9.5, thereby obtaining a composite oxide gel precipitated in the mixed solution. (II) A second step of washing the composite oxide gel and then aging it at a pH of 10.0 to 11.0 and a temperature of 90°C to 98°C. (III) A third step of spray-drying the aqueous slurry containing the composite oxide gel obtained after the second step. Each step will be described in detail below.

[0026] [1st step] In this process, a first aqueous solution is prepared by mixing a silica precursor in water. Here, the silica precursor refers to a mixture of water and a soluble silicate compound, such as sodium silicate, or a solid silicate, such as silica hydrogel. More specifically, the first aqueous solution is prepared by mixing water with a silicate compound. The Si content of this first aqueous solution is preferably in the range of 1% to 10% by mass, calculated as SiO2. Adjusting the Si content within the aforementioned range is effective in obtaining a first aqueous solution with a viscosity that allows easy stirring and mixing without impairing industrial economic viability. Furthermore, the pH of this first aqueous solution is preferably in the range of 6.0 to 13.0. Adjusting the pH within the aforementioned range is effective in suppressing the precipitation of alumina when the second aqueous solution is mixed.

[0027] In this step, a second aqueous solution containing a basic aluminum salt is next prepared. Examples of the basic aluminum salt include compounds such as sodium aluminate and potassium aluminate. More specifically, the second aqueous solution is prepared by dissolving an aluminum compound in an alkaline aqueous solution. The Al content of this second aqueous solution is preferably in the range of 10% to 30% by mass, calculated as Al2O3. Adjusting the Al content within the aforementioned range is effective in obtaining a second aqueous solution having a target pH range without impairing industrial economic viability. Furthermore, the pH of this second aqueous solution is preferably in the range of 11.0 to 14.0. Adjusting the pH within the aforementioned range is effective in obtaining a coprecipitate of complex oxides by neutralization when the third aqueous solution is mixed with the second aqueous solution.

[0028] In this step, a third aqueous solution is prepared by adding a titanium mineral acid salt and an aluminum salt of the same mineral acid as the titanium mineral acid salt to the acidic salt solution. Here, titanium mineral acid salt refers to compounds such as titanyl sulfate, titanium tetrachloride, or titanium tetranitrate. Furthermore, mineral acid refers to compounds such as sulfuric acid, hydrochloric acid, or nitric acid. Additionally, aluminum salt of the same mineral acid as the titanium mineral acid salt refers to compounds such as aluminum sulfate, aluminum chloride, and aluminum nitrate. Specifically, these are mixed to prepare the third aqueous solution. The Ti content of this third aqueous solution is preferably in the range of 3% to 10% by mass, calculated as TiO2. Adjusting the Ti content within the aforementioned range is effective in dissolving the titanium mineral acid salt in water within a range that does not impair industrial economic viability. Furthermore, the pH of this third aqueous solution is preferably in the range of 1.0 to 2.0. Adjusting the pH within the aforementioned range is effective in neutralizing and coprecipitating a composite oxide when mixed with the first and second aqueous solutions. Furthermore, this third aqueous solution can also contain Al. In this case, the Al content is preferably in the range of 0.1% by mass to 10% by mass in terms of Al2O3 mass. By adjusting the Al content within the above range, it is possible to obtain a composite oxide of the target composition as a result of coprecipitation.

[0029] In this process, the first aqueous solution is mixed with the second aqueous solution, and then the third aqueous solution is added to obtain a mixed solution with a pH of 6.5 to 9.5. At this time, a composite oxide gel is formed in the mixed solution. By preparing the composite oxide gel through these processes, the pore volume of the finally obtained alumina-silica-titania composite oxide increases, and the Bronsted acidity also increases.

[0030] [Second process] In this step, the composite oxide gel obtained in the first step is washed and then aged at a pH of 10.0-11.0 and a temperature of 90-98°C. Here, aging refers to the process of dissolving minute sol particles and reprecipitating larger particles over time, resulting in uniform particle size and growth. More specifically, the washed gel is first reslurried with pure water, the pH is adjusted with aqueous ammonia, and the gel is stirred and mixed in a weak alkaline solution. The temperature is then raised to the aforementioned temperature and stirred and mixed for aging. Adjusting the pH within the aforementioned range during aging effectively improves the aging rate within a pH range in which the silica and alumina components in the gel can be dissolved and reprecipitated. Adjusting the temperature within the aforementioned range during aging also effectively improves the aging rate within a temperature range in which the gel does not boil. Using the composite oxide gel obtained in this step increases the pore volume and Brønsted acidity of the final alumina-silica-titania composite oxide.

[0031] [3rd step] In this step, the aqueous slurry containing the composite oxide gel obtained in the second step is spray-dried. Here, the aqueous slurry is prepared by diluting the composite oxide gel obtained in the second step with water. This aqueous slurry is then spray-dried to obtain alumina-silica-titania. The spray-drying condition is preferably an outlet temperature of 120°C or higher. Spray-drying under these conditions not only ensures sufficient drying, but also has the effect of evaporating and removing volatile components such as ammonia contained in the aqueous slurry. [Example]

[0032] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0033] The measurement and evaluation methods used in the examples are as follows [1] to [8].

[0034] [1] Composition measurement method A 3g sample was placed in a 30mL zirconia bowl with a lid, heated at 200°C for 20 minutes, and calcined at 700°C for 5 minutes. Then, 2g of Na2O2 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 purified water. The resulting sample was analyzed using an inductively coupled plasma (ICP) optical emission spectrometer (Shimadzu Corporation, ICPS-8100, analysis software ICPS-8000) to measure the content of each component on an oxide-equivalent mass basis. The silica content was calculated in terms of SiO2, the alumina content was calculated in terms of Al2O3, and the titania content was calculated in terms of TiO2.

[0035] [2] Solid acid amount measurement 50 mg of sample powder was molded into a 20 mm diameter disk, placed in an IR cell connected to a vacuum line, and evacuated at 500 °C for one hour. After evacuation, the temperature was lowered to 150 °C, and the IR (infrared absorption) spectrum of the sample disk was measured using a JASCO FT / IR-4600. Pyridine was then introduced, and the sample disk was evacuated at 150 °C for 10 minutes. The IR spectrum of the sample disk with pyridine adsorbed at 150 °C was then measured in the same manner as described above. The IR spectrum of the sample disk was then subtracted from the IR spectrum of the sample disk with pyridine adsorbed, and a graph was obtained. The areas of the absorption peaks assigned to the Brønsted acid site (B) and Lewis acid site (L) were calculated from this graph. Based on the calculated absorption peak areas, the Brønsted acid content and Lewis acid content were calculated using the method described in CA Emeis, J. Catal., 141, 347-354 (1993).

[0036] [3] X-ray diffraction measurement X-ray diffraction was measured using a MiniFlex manufactured by Rigaku Corporation. The measurement conditions were a 2θ / θ scan axis, a CuKα source, a continuous measurement method, a voltage of 40 kV, a current of 15 mA, a starting angle of 2θ = 25° to an ending angle of 2θ = 80°, a sampling width of 0.020°, and a scan rate of 10,000° / min.

[0037] [4] Pore volume measurement and calculation of peak pore diameter The pore size distribution of the sample was measured using a Microtrac-Bell Corporation BELSORP-mini Ver. 2.5.6. Specifically, the sample was heat-treated at 500°C for 2 hours while evacuated, and nitrogen gas was adsorbed onto the sample. The log differential pore volume distribution (dV / d(logD)) was calculated from the desorption isotherm at relative pressure (P / P0 = 0.99) using the BJH method. From this pore size distribution, the total pore volume in the pore size range of 2.4 nm to 192.4 nm was defined as the pore volume of the sample. The pore size with the highest cumulative pore volume in this pore size distribution was defined as the peak pore size. The volume of pores within ±2 nm of the peak pore size was calculated by integrating the cumulative pore volume within the range of ±2 nm of the peak pore size.

[0038] [5] Measurement of UV-visible diffuse reflectance spectrum and calculation of absorption edge UV-visible diffuse reflectance spectra were measured using a JASCO V-660 UV-visible spectrophotometer equipped with an ISV-772 integrating sphere unit for diffuse reflectance measurements. Specifically, 200 mg of the complex oxide powder sample was loaded into a diffuse reflectance cell holder, and the absorbance was measured at room temperature. Specifically, in measurement mode, the bandwidth was 5.0 nm, the measurement range was 500 nm to 200 nm, the data acquisition interval was 0.1 nm, the scan speed was 100 nm / min, and the light source switching wavelength was 340 nm. Background correction was performed over the wavenumber range of 500 nm to 200 nm. Background measurements were performed under the above conditions using a white reference plate. The absorption edge was calculated from the diffuse reflectance spectrum obtained above by performing a KM transformation using the Kubenk-Munk function (KM function). The maximum wavelength at which the spectral intensity value was 0.3 or greater was calculated as the UV absorption edge wavelength.

[0039] [6] Specific surface area measurement To measure the specific surface area, approximately 30 mL of the sample was placed in a porcelain crucible (B-2 type), heated at 600°C for 2 hours, and then cooled to room temperature in a desiccator to obtain a measurement sample. Next, 1 g of this sample was taken and the specific surface area of ​​the sample was measured using a fully automatic surface area measuring device (Macsorb HM-1220, manufactured by Mountec Co., Ltd.) using the BET single-point method.

[0040] [7] Particle size distribution and median size measurement The particle size distribution was measured using an image particle analyzer (CAMSIZER X2, manufactured by Microtrac). Specifically, the particle size was measured after 2 g of composite oxide powder was filled into the chute section. The particle size range for the basic camera was set to 0 mm to 20 mm, the particle size range for the zoom camera to 0 mm to 2 mm, and the particle shape was set to spherical particles. The particle size was defined as the value determined from the narrowest particle width of all the measured particle widths. The measurement mode was set to X-JET mode for air pressure dispersion. The particle size that is the median value of the particle number from the measured particle size distribution was taken as the median diameter.

[0041] [8] Bulk density 100.0 g of the sample was taken and transferred to a 250 mL measuring cylinder. The measuring cylinder was then capped and gently turned upside down repeatedly, after which the volume was read. This procedure was repeated five times and the average value was calculated. The bulk density (g / mL) was calculated from the weight (g) of the sample divided by the average volume (mL).

[0042] [Example 1] 5.9 kg of 25% sulfuric acid was placed in a 70 L steam-jacketed tank and adjusted to 30°C. Subsequently, 29.65 kg of a sodium silicate aqueous solution (AGC Si-Tech Co., Ltd., SiO concentration 24% by mass) diluted to 8.5% by mass in terms of SiO was added using a rotary pump. The pH after the addition was 1.8. Next, 3.3 kg of the above sodium silicate aqueous solution was added using a rotary pump. The pH after the addition was 2.7. Next, the above sodium silicate aqueous solution was added until the pH reached 4.0, and the mixture was stirred and mixed at pH 4.0 for 165 minutes. Then, 4.94 kg of ion-exchanged water was added. Then, 15% by mass ammonia aqueous solution was added until the pH reached 6.2, and the mixture was stirred and mixed at pH 6.2 for 60 minutes to prepare silica hydrogel A. 42.05 kg of ion-exchanged water was placed in a 100 L tank equipped with a steam jacket, and 25.8 kg of silica hydrogel A was added to prepare a first aqueous solution (Si content 2.4 mass %, pH 6.8). Then, 0.060 kg of 25 mass% sodium gluconate was added to 3.4 kg of a 22 mass% sodium aluminate aqueous solution (calculated as Al2O3) (manufactured by JGC Catalysts and Chemicals Co., Ltd.) to prepare a second aqueous solution containing a basic aluminum salt (Al content 22 mass%, pH 13.2). The first aqueous solution was heated to 60°C, and the second aqueous solution was added thereto and mixed with stirring. 1.82 kg of titanyl sulfate (manufactured by Teika Corporation) with a TiO2 content of 33 mass % was dissolved in 10.18 kg of ion-exchanged water to prepare a third aqueous solution containing titanium sulfate (Ti content 5 mass %, pH 1.5). Next, the third aqueous solution was added to the tank containing the first aqueous solution and the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed liquid (slurry) in which a composite oxide gel was precipitated. The resulting mixture was stirred at 60°C for 1 hour, then dehydrated using a flat filter and washed with 150 L of 0.5% by mass ammonium bicarbonate aqueous solution. The washed cake-like composite oxide gel was diluted with ion-exchanged water to 10% by mass, and the pH was adjusted to 10.5 with 15% by mass ammonia water. The resulting diluted water was transferred to an aging tank equipped with a reflux condenser and aged at 95°C for 10 hours while stirring. After the aging, the mixture was pulverized with a homogenizer and then spray-dried with a spray dryer to obtain an alumina-silica-titania composite oxide powder. The obtained alumina-silica-titania composite oxide powder was subjected to the above-mentioned measurements and analyses, and the results are shown in Table 1. The results of the following examples and comparative examples are also shown in Table 1.

[0043] [Example 2] A 100 L tank equipped with a steam jacket was charged with 42.17 kg of ion-exchanged water, and 18.8 kg of silica hydrogel A prepared by the method described in Example 1 was added to prepare a first aqueous solution. Thereafter, 0.096 kg of 25 mass % sodium gluconate was added to 4.83 kg of an aqueous solution of sodium aluminate having a concentration of 22 mass % in terms of Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. The first aqueous solution was heated to 60°C, and the second aqueous solution was added thereto and mixed with stirring. Solution A was prepared by dissolving 1.82 kg of titanyl sulfate (equivalent to 33 mass % TiO2) in 10.18 kg of ion-exchanged water, and this solution was mixed with 5.49 kg of an aluminum sulfate aqueous solution (solution B) diluted to 2.5 mass % to prepare a third aqueous solution containing titanium sulfate and aluminum sulfate. Next, the third aqueous solution was added to the tank containing the first aqueous solution and the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed liquid (slurry) in which a composite oxide gel was precipitated. An alumina-silica-titania composite oxide powder was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0044] [Example 3] A 100 L tank equipped with a steam jacket was charged with 42.28 kg of ion-exchanged water, and 11.72 kg of silica hydrogel A prepared by the method described in Example 1 was added to prepare a first aqueous solution. Thereafter, 0.132 kg of 25 mass % sodium gluconate was added to 6.26 kg of an aqueous solution of sodium aluminate having a concentration of 22 mass % in terms of Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. The first aqueous solution was heated to 60°C, and the second aqueous solution was added thereto and mixed with stirring. Solution A was prepared by dissolving 1.82 kg of titanyl sulfate (equivalent to 33 mass % TiO2) in 10.18 kg of ion-exchanged water, and this solution was mixed with 10.94 kg of an aluminum sulfate aqueous solution (solution B) diluted to 2.5 mass % to prepare a third aqueous solution containing titanium sulfate and aluminum sulfate. Next, the third aqueous solution was added to the tank containing the first aqueous solution and the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed liquid (slurry) in which a composite oxide gel was precipitated. An alumina-silica-titania composite oxide powder was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0045] [Example 4] A 100 L tank equipped with a steam jacket was charged with 42.35 kg of ion-exchanged water, and 7.03 kg of silica hydrogel A prepared by the method described in Example 1 was added to prepare a first aqueous solution. Thereafter, 0.156 kg of 25 mass % sodium gluconate was added to 7.21 kg of an aqueous solution of sodium aluminate having a concentration of 22 mass % in terms of Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. The first aqueous solution was heated to 60°C, and the second aqueous solution was added thereto and mixed with stirring. Solution A was prepared by dissolving 1.82 kg of titanyl sulfate (equivalent to 33 mass % TiO2) in 10.18 kg of ion-exchanged water, and this solution was mixed with 14.58 kg of an aluminum sulfate aqueous solution (solution B) diluted to 2.5 mass % to prepare a third aqueous solution containing titanium sulfate and aluminum sulfate. Next, the third aqueous solution was added to the tank containing the first aqueous solution and the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed liquid (slurry) in which a composite oxide gel was precipitated. An alumina-silica-titania composite oxide powder was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0046] [Example 5] 39.54 kg of ion-exchanged water was placed in a 100 L tank equipped with a steam jacket, and 18.75 kg of silica hydrogel A prepared by the method described in Example 1 was added to prepare a first aqueous solution. Thereafter, 0.120 kg of 25 mass % sodium gluconate was added to 5.27 kg of an aqueous solution of sodium aluminate having a concentration of 22 mass % in terms of Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. The first aqueous solution was heated to 60°C, and the second aqueous solution was added thereto and mixed with stirring. Solution A was prepared by dissolving 0.91 kg of titanyl sulfate (equivalent to 33% by mass of TiO2) in 5.09 kg of ion-exchanged water, and this solution was mixed with 13.65 kg of an aqueous aluminum sulfate solution diluted to 2.5% by mass to prepare a third aqueous solution containing titanium sulfate and aluminum sulfate. Next, the third aqueous solution was added to the tank containing the first aqueous solution and the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed liquid (slurry) in which a composite oxide gel was precipitated. An alumina-silica-titania composite oxide powder was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0047] [Example 6] 36.92 kg of ion-exchanged water was placed in a 100 L tank equipped with a steam jacket, and 0.096 kg of 25 mass % sodium gluconate was added to 4.83 kg of a 22 mass % sodium aluminate aqueous solution calculated as Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. 24.0 kg of a sodium silicate aqueous solution (SiO2 concentration: 24% by mass) diluted to 5% in terms of SiO2 was used as the first aqueous solution. The second aqueous solution was heated to 60°C, and the first aqueous solution was added thereto and mixed with stirring. Solution A was prepared by dissolving 1.82 kg of titanyl sulfate (equivalent to 33 mass % TiO2) in 10.18 kg of ion-exchanged water, and this solution was mixed with 5.49 kg of an aluminum sulfate aqueous solution (solution B) diluted to 2.5 mass % to prepare a third aqueous solution containing titanium sulfate and aluminum sulfate. Next, the third aqueous solution was added to the tank containing the first aqueous solution and the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed liquid (slurry) in which a composite oxide gel was precipitated. An alumina-silica-titania composite oxide powder was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0048] [Comparative Example 1] 36.92 kg of ion-exchanged water was placed in a 100 L tank equipped with a steam jacket, and 18.75 kg of silica hydrogel A prepared by the method described in Example 1 was added to prepare a first aqueous solution. Thereafter, 0.120 kg of 25 mass % sodium gluconate was added to 5.27 kg of an aqueous solution of sodium aluminate having a concentration of 22 mass % in terms of Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. The first aqueous solution was heated to 60°C, and the second aqueous solution was added thereto and mixed with stirring. Subsequently, a third aqueous solution containing 21.82 kg of an aqueous aluminum sulfate solution diluted to 2.5% by mass was added to the tank containing the first aqueous solution and the second aqueous solution using a roller pump at a constant rate over 10 minutes until the pH reached 7.2, thereby obtaining a mixed solution (slurry) in which a composite oxide gel was precipitated. An alumina-silica composite oxide was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0049] Comparative Example 2 42.06 kg of ion-exchanged water was placed in a 100 L tank equipped with a steam jacket, and 0.185 kg of 25 mass % sodium gluconate was added to 8.35 kg of a 22 mass % sodium aluminate aqueous solution calculated as Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. 1.8 kg of a sodium silicate aqueous solution (SiO2 concentration 24 mass%) diluted to 5% in terms of SiO2 was used as the first aqueous solution. The second aqueous solution was heated to 60°C, and the first aqueous solution was added thereto and mixed with stirring. Solution A was prepared by dissolving 1.82 kg of titanyl sulfate (equivalent to 33 mass % TiO2) in 10.18 kg of ion-exchanged water, and this solution was mixed with 18.94 kg of an aluminum sulfate aqueous solution (solution B) diluted to 2.5 mass % to prepare a third aqueous solution containing titanium sulfate and aluminum sulfate. Next, the third aqueous solution was added to the tank containing the first aqueous solution and the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed liquid (slurry) in which a composite oxide gel was precipitated. An alumina-silica-titania composite oxide was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0050] Comparative Example 3 43.27 kg of ion-exchanged water was placed in a 100 L tank equipped with a steam jacket, and 0.185 kg of 25 mass % sodium gluconate was added to 8.50 kg of a 22 mass % sodium aluminate aqueous solution calculated as Al2O3 to prepare a second aqueous solution containing a basic aluminum salt. Solution A was prepared by dissolving 1.82 kg of titanyl sulfate (equivalent to 33 mass % TiO2) in 10.18 kg of ion-exchanged water, and this solution was mixed with 17.58 kg of an aluminum sulfate aqueous solution (solution B) diluted to 2.5 mass % to prepare a third aqueous solution containing titanium sulfate and aluminum sulfate. Subsequently, the third aqueous solution was added to the tank containing the second aqueous solution at a constant rate over 10 minutes using a roller pump until the pH reached 7.2, thereby obtaining a mixed solution (slurry) in which a composite oxide gel was precipitated. An alumina-silica-titania composite oxide was prepared in the same manner as in Example 1, except for the method for preparing the mixed liquid.

[0051] Comparative Example 4 Solution A was prepared by dissolving 1.28 kg of titanyl sulfate (33% by weight, calculated as TiO2) in 15.60 kg of ion-exchanged water. 16.5 kg of Solution A was placed in a 70 L steam-jacketed tank and adjusted to 30°C. Subsequently, 23.64 kg of a sodium silicate aqueous solution (SiO2 concentration: 24% by weight) diluted to 8.5% by weight, calculated as SiO2, was added using a rotary pump. The pH after addition was 3.8. The sodium silicate aqueous solution was then added until the pH reached 4.0, and the mixture was stirred and mixed at pH 4.0 for 165 minutes. Then, 16.07 kg of ion-exchanged water was added. A 15% by weight ammonia aqueous solution was added until the pH reached 6.2, and the mixture was stirred and mixed at pH 6.2 for 60 minutes to prepare silica-titania hydrogel A. Silica-titania hydrogel A was pulverized using a homogenizer and then spray-dried using a spray dryer to obtain silica-titania composite oxide powder, which was then washed with acid and alkali, dehydrated, and dried.

[0052] [Table 1]

Claims

1. An alumina-silica-titania composite oxide having the following structures (1) to (5). (1) The content of Al is Al ２ O ３ In terms of the total mass, the content is in the range of 10% by mass to 75% by mass. (2) The content of Si is SiO ２ In terms of the total mass, the content is in the range of 5% by mass to 70% by mass. (3) The content of Ti is TiO ２ In terms of the total mass, the content is in the range of 1% by mass to 30% by mass. (4) The pore volume calculated based on the pore distribution measured by the nitrogen adsorption method is in the range of 0.8 mL / g or more and 2.0 mL / g or less. (5) The Bronsted acidity measured at 150° C. by infrared spectroscopy using pyridine as a probe molecule is 5 μmol / g or more.

2. 2. The alumina-silica-titania composite oxide according to claim 1, wherein the absorption edge wavelength of the absorption peak derived from Ti is 350 nm or less in a spectrum measured by ultraviolet spectroscopic analysis.

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