A silica-boehmite composition, its preparation method and application
By adding silica sol solution to an acidic aluminum source solution and then neutralizing and aging it, a silica-boehmite composition with large pore volume and high Brønsted acid content was prepared, which solved the problems of high cost and insufficient performance in the prior art and realized the application of a highly efficient catalyst.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2022-04-27
- Publication Date
- 2026-07-17
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Figure BDA0003617767590000171 
Figure BDA0003617767590000172
Abstract
Description
Technical Field
[0001] This invention belongs to the field of catalyst materials, specifically relating to a silica-boehmite composition and a silica-alumina composition, as well as their respective preparation methods and applications. Background Technology
[0002] Hydrocracking and catalytic cracking are two crucial processes in petroleum refining. These processes convert larger heavy oil molecules in feedstocks into smaller molecules, yielding light petroleum products such as gasoline, aviation fuel, and diesel, as well as chemical products. Traditional microporous zeolite catalysts used in these processes suffer from diffusion limitations due to their small pore size, hindering the catalytic reaction of large molecules. To achieve efficient conversion of heavy oil molecules, mesoporous acidic catalysts are gaining increasing attention. Since the first report of the synthesis of ordered mesoporous silica-alumina materials in 1992, their ordered pore structure and large pore size have facilitated the diffusion of reactant and product molecules. However, due to their weak acidity, poor stability, and the need for template agents in their preparation, large-scale application in catalytic cracking and hydrocracking catalysts has been limited. To overcome the shortcomings of ordered mesoporous silica-alumina materials, the research and development of low-cost, stable, and non-ordered mesoporous acidic silica-alumina materials has proven to be more practical and has thus been a long-standing goal in the field of petroleum refining catalysis.
[0003] USP5045519 discloses a process for preparing a catalyst support based on aluminum silicate. This process prepares a high-purity, thermally stable silica-alumina catalyst support containing 0.5-50% silica. The catalyst is obtained by mixing an aluminum-containing compound with silicic acid in an aqueous medium, followed by drying and calcination. The aluminum-containing compound is obtained by hydrolyzing C2-C20+ alkoxyaluminum with water purified by ion exchange, simultaneously or subsequently adding orthosilicic acid purified by ion exchange to the aluminum-containing compound. Because organic materials such as alkoxyaluminum and orthosilicic acid are used as raw materials, the resulting product has a Na2O content of less than 50 ppm. This mesoporous aluminosilicate support has a certain degree of acidity, but the process method uses organic alkoxyaluminum as the aluminum source and ion-exchanged orthosilicic acid as the silicon source, strictly controlling the Na2O content to less than 50 ppm, resulting in high preparation costs.
[0004] CN 106582597B discloses a silicon-modified alumina, its preparation method, and its application. Modifying alumina with silica sol includes: (1) acidifying and dissolving a pseudoboehmite slurry with an inorganic acid to obtain a pseudoboehmite sol; (2) adding silica sol to the pseudoboehmite sol to obtain a first mixture; (3) adjusting the pH of the first mixture within the range of pH = 1-11 according to different requirements for the surface Brønsted acid content and pore volume improvement of alumina, and then reacting the silica-modified alumina with a surface rich in Brønsted acid (when the pH of the first mixture is adjusted to pH = 1-2) or the silica-modified alumina with a large pore volume (when the pH of the first mixture is adjusted to pH = 10-11) under heating conditions for a period of time to obtain a second mixture; (4) crystallizing the second mixture at 100-120℃ for 12-24h to obtain a third mixture; (5) filtering, washing, drying and calcining the third mixture to obtain silica-modified alumina. By adjusting the pH of the first mixture, a flexible switch can be achieved between focusing on improving pore volume and focusing on improving Brønsted acid content. The Brønsted acid-rich silica-modified alumina has a Brønsted acid (B / L) ratio of 0.40-0.95, and the macroporous silica-modified alumina has a pore volume of 0.8-1.2 cm³. 3 / g. This invention cannot simultaneously meet the requirements for preparing mesoporous silica-alumina materials with large pore volume and high Brønsted acid content. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a silica-boehmite composition and its preparation method that simultaneously satisfies the requirements of large pore volume and high Brønsted acid content. The preparation method provided by this invention eliminates the need for organoaluminum and organosilicon sources, offering the advantage of low cost. The silica-boehmite composition provided by this invention can be used as a catalyst in cracking processes involving macromolecules.
[0006] During their research, the inventors of this invention discovered that, in the preparation of the silica-boehmite composition, adding a silica sol solution to an acidic aluminum source solution can form a uniform and stable acidic silica-containing aluminum source solution. Using this acidic silica-containing aluminum source solution, a neutralization and gelation reaction is carried out with an aluminum-containing or aluminum-free alkaline solution. By controlling the conditions of the neutralization reaction and subsequent aging, washing, and drying, the resulting silica-boehmite composition exhibits large pore volume and high Brønsted acid content. Existing technologies cannot produce silica-boehmite compositions with the pore characteristics of this invention. To achieve the above objectives, this invention provides the following technical solution.
[0007] First, a silica-boehmite composition, comprising 20-50 wt% silica, 50-80 wt% alumina, and 0.01-0.12 wt% Na₂O, is characterized by XRD as a mixed phase structure of boehmite and amorphous silica. The product of the composition after calcination at 600°C for 3 hours is characterized as follows: pore volume of 1.1-2.2 mL / g and specific surface area of 240-420 m². 2 / g, with pore diameters of 12-30nm, and pyridine infrared spectroscopy analysis after desorption at 200℃ showed a Brønsted acid / (Brønsted acid + Lewis acid) ratio of 0.16~0.45.
[0008] Secondly, this invention provides an amorphous silica-alumina composition, which, as characterized by XRD, exhibits a mixture of amorphous silica and γ-alumina phases, with a pore volume of 1.1-2.2 mL / g and a specific surface area of 240-420 m². 2 / g, with pore diameters of 12-30nm, and pyridine infrared spectroscopy analysis after desorption at 200℃ showed a Brønsted acid / (Brønsted acid + Lewis acid) ratio of 0.16~0.45.
[0009] Furthermore, the present invention provides a method for preparing a silica-boehmite composition, comprising the following steps:
[0010] (1) Prepare an aluminum source solution containing silica sol, and then mix it with an alkaline solution to obtain a neutralized slurry;
[0011] (2) Adjust the pH of the neutralized slurry to 7-10, preferably 7.5-9.5, and carry out normal pressure aging, filtration, and washing to obtain filter cake; add water to the filter cake and slurry to obtain filter cake slurry;
[0012] (3) Adjust the filter cake slurry to pH 8-12, perform high-pressure aging, and then filter, wash and dry the slurry after high-pressure aging to obtain the silica-boehmite composition.
[0013] The conditions for the neutralization reaction in step (1) include: temperature 40-70℃, pH 6-10, preferably 7.5-9.5, and time 5-30 min; the conditions for atmospheric pressure aging in step (2) include: temperature 60-99℃ and time 1-24 h; the conditions for high pressure aging in step (3) are carried out in a closed container, including: temperature 121-200℃, pressure of autogenous vapor pressure, and aging time 1-48 h.
[0014] The concentrations and amounts of the aluminum source solution and alkaline solution containing the silica sol are such that the final prepared silica-boehmite composition contains 20-50% by weight of silica and 50-80% by weight of alumina, based on oxides.
[0015] The washing in step (3) results in a final composition with a Na2O content of 0.01-0.12%.
[0016] On the other hand, the present invention also provides a method for preparing amorphous silica-alumina, comprising calcining the silica-boehmite composition described in any one of the above-mentioned methods, wherein the calcination conditions include: a temperature of 450-800℃, preferably 500-700℃, and a time of 1-10h, preferably 2-5h.
[0017] Finally, the present invention also provides the application of any one of the amorphous silica-alumina compositions of the present invention in the cracking reaction of substituted aromatic hydrocarbons.
[0018] Compared with the prior art, the method for preparing the silica-boehmite composition provided by the present invention further promotes the growth of boehmite grains, increases pore volume, and promotes the interaction between silica sol and boehmite, increases the interaction between Si-O-Al, and increases the Brønsted acid content by forming a uniform silica-sol aluminum source solution, especially an acidic aluminum source solution, in a silica sol solution in an aluminum compound solution. The silica-alumina material after neutralization in the acidic solution undergoes two-step aging: atmospheric pressure aging and high pressure aging. This results in the final silica-boehmite composition having the characteristics of a mixture of boehmite and amorphous silica, large pore volume, and high Brønsted acid content. Unlike the silica-alumina support obtained by the prior art, the silica-boehmite composition and silica-alumina of the present invention have high isopropylbenzene cracking activity. Detailed Implementation
[0019] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0020] The silica-boehmite composition and amorphous silica-alumina phases described in this invention were characterized by X-ray diffraction (XRD) using a Philips XPERT series D5005 X-ray powder diffractometer. The test conditions were: Cu Kα rays (λ = 0.154 nm), Ni filter, voltage 40 kV, tube current 30 mA, step size 0.02°, and 2θ scan range of 5° to 70°.
[0021] Pore volume was determined using an ASAP 2420 nitrogen adsorption analyzer from Micromeritics, USA. Before measurement, the samples were pretreated under vacuum at 300℃ for 10 h. Pore volume was determined using the single-point adsorption method, and the specific surface area of the samples was calculated using the BET equation.
[0022] Pyridine was characterized by Fourier transform infrared (FT-IR) using a Nicolet 6700 Fourier transform infrared spectrometer with a DTGS detector, 32 scans, and a resolution of 4 cm⁻¹. -1 The sample was compressed to 10 mg / cm³. -2 The self-supporting sheet was tested at 450℃ (heating rate 50℃·min). -1 ), calcined in situ for 1 hour. Afterwards, the IR cell was evacuated at this temperature until P < 10. -3 Pa, maintained for 3 hours, the sample was cooled to 25°C, and the first spectrum was acquired. Pyridine vapor was introduced into the infrared cell and maintained for 15 minutes to reach adsorption equilibrium. Vacuum desorption was performed at 200°C for 20 minutes (10 -3 Pa) pyridine, then the sample was cooled to 25°C and the spectrum was collected. The peak areas of the two peaks were used to calculate... The amount of Lewis acid center, 1545cm -1 The peak at that location corresponds to the adsorption on Vibration of the pyridine ion at the acid center, 1450 cm⁻¹ -1 The peak at that point corresponds to the vibration of the pyridine molecule coordinated to the Lewis acid center.
[0023] XRF characterization was performed using a Rigaku Electric Industries, Ltd. (RIGE) 3271 X-ray fluorescence spectrometer. Elemental spectral line intensities were detected using a scintillation counter and a proportional counter, and elemental content was quantitatively analyzed using the external standard method. Powder samples were compressed into tablets, with a rhodium target, laser voltage of 50 kV, and laser current of 50 mA.
[0024] Cracking performance characterization: Amorphous silica-alumina sheets were compressed and ground into 40-60 mesh particles. Cumene cracking was carried out in a micro-fixed-bed reactor. The reactor was loaded with 16 g of 40-60 mesh quartz sand, and the isothermal section was loaded with 1.0 g of 40-60 mesh silica-alumina particles. The system pressure was 0.5 MPa, the H2 flow rate was 200 mL / min, and the heating rate was 2 °C / min. -1The reaction temperature was raised to 300℃. After stabilization, the reactants (a mixed solution of cumene and cyclohexane with a mass content of 10% cumene) were pumped into the apparatus using a plunger pump at a flow rate of 0.1 mL / min. An automated gas chromatography sampling program was set up to analyze the composition of the reaction products online, sampling and analyzing every 20 minutes. The reaction was terminated after 4 hours by stopping the feed. Only propylene and benzene were detected as products. The cumene cracking conversion rate was calculated based on the peak area from the chromatographic analysis, and the average of three conversion rates over the last hour was taken as the final conversion rate.
[0025] The silica-boehmite composition provided by the present invention preferably has a silica content of 30-45 wt%, an alumina content of 55-70 wt%, and a Na2O content of 0.02-0.10% based on oxides; the composition has a grain size of 3-5 nm and a relative crystallinity of 35%-60%.
[0026] The product characterization of the composition after calcination at 600℃ for 3 hours preferably shows a pore volume of 1.2-2.1 mL / g and a specific surface area of 260-400 m². 2 / g, with a pore diameter of 14-28nm, the pyridine infrared spectroscopy test after desorption at 200℃ shows that the Brønsted acid / (Brønsted acid + L acid) ratio is preferably 0.18-0.42.
[0027] Under the condition of satisfying the above-mentioned Brønsted acid / (Brønsted acid + L-acid) ratio, more preferably, the Brønsted acid is 25-65 μmol / g, more preferably 30-60 μmol / g, and the L-acid is 85-200 μmol / g, more preferably 90-185 μmol / g.
[0028] According to the present invention, an amorphous silica-alumina composition preferably has a pore volume of 1.2-2.1 mL / g and a specific surface area of 260-400 m². 2 The pore diameter is 14-28 nm. After desorption at 200℃, the Brønsted acid / (Brønsted acid + Lewis acid) ratio, as measured by pyridine infrared spectroscopy, is preferably 0.18-0.42. More preferably, after desorption at 200℃, the Brønsted acid concentration is 25-65 μmol / g, more preferably 30-60 μmol / g, and the Lewis acid concentration is 85-200 μmol / g, more preferably 90-185 μmol / g.
[0029] This invention provides a method for preparing a silica-boehmite composition. The method involves uniformly mixing silica sol with aluminum source materials in a neutralization synthesis process to form a silica sol-containing aluminum source solution. This solution is then neutralized with an alkaline solution. The resulting neutralized slurry is subsequently subjected to aging, washing, and drying steps to prepare the silica-boehmite composition. The neutralization process is carried out continuously in a stirred reactor. The resulting slurry is adjusted to a suitable pH, aged under normal pressure, filtered, and washed. The filter cake is then mixed with deionized water, the pH is adjusted, and the mixture is subjected to high-pressure aging in a sealed container. The resulting aged slurry is then filtered, washed, and dried to obtain the silica-boehmite composition.
[0030] Preferably, the concentration and amount of the aluminum source solution and alkaline solution containing the silica sol are such that the silica-boehmite composition obtained in the final preparation has a silica content of 30-45 wt% and an alumina content of 55-70 wt% as oxides; the washing in step (3) results in a Na2O content of 0.02-0.10% in the final composition.
[0031] There are no special requirements for the type of aluminum source and the concentration of the aluminum source solution in step (1). The aluminum source is preferably an acidic aluminum source, such as aluminum sulfate, aluminum chloride and / or aluminum nitrate, and the concentration based on alumina is preferably 10-100 g Al2O3 / L. The alkaline solution may or may not contain aluminum. The mass concentration of silicon oxide in the silica sol is preferably 10-40 wt%.
[0032] In step (3), an alkaline solution free of metal ions is preferably used to adjust the pH value. This solution can be an organic or inorganic base. Both steps (2) and (3) involve washing, preferably using deionized water, with a washing temperature of 50-95℃. Specific washing methods are conventional in the field, such as vacuum filtration washing, belt filter washing, plate and frame filter washing, and plate and frame filter-filter cake re-pulping-plate and frame filter washing.
[0033] The present invention does not have any special requirements for the drying in step (3), as long as the physical water in the product can be removed. Generally, oven drying, flash drying or spray drying can be used, and the drying temperature is preferably 80-120℃.
[0034] After obtaining the silica-boehmite composition by any of the above preparation methods, an amorphous silica-alumina can be obtained by calcination. The preferred calcination conditions are: temperature of 500-700℃ and time of 2-5h.
[0035] The silica-boehmite composition provided by this invention can be used as a catalyst support and catalyst matrix for various applications, and is particularly suitable as a catalyst or catalyst support for macromolecular reactions requiring improved diffusion performance and acidity. This silica-boehmite composition is suitable for macromolecular cracking reactions, exhibiting high cracking conversion of isopropylbenzene.
[0036] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents used in the examples are chemically pure reagents.
[0037] Examples 1-8 illustrate the silica-boehmite composition, silica-alumina composition, and preparation method of the composition provided by the present invention. Comparative Examples 1-4 illustrate the silica-boehmite composition, silica-alumina composition, and preparation method obtained by prior art.
[0038] Example 1
[0039] An industrial aluminum sulfate solution (Shandong Anbai Chemical Co., Ltd., with a concentration of 104 g / L based on alumina, 3 g H2SO4 / L free acid concentration, and Fe2O3 concentration ≤150 mg / L), industrial silica sol JN-30 (Qingdao Chengyu Chemical Co., Ltd., with 30 wt% silica) and deionized water were prepared to form a 5.0 L aluminum sulfate solution containing silica sol, with a concentration of 41.6 g / L based on alumina and 42 g / L based on silica.
[0040] A 6.5 L sodium aluminate solution was prepared by heating and dissolving NaOH (produced by Sinopharm Group), aluminum hydroxide (Guangxi Branch of Aluminum Corporation of China Limited, with an aluminum oxide content of 64.0 wt%) and deionized water. The concentration of Al2O3 was 220 g / L and the concentration of Na2O was 227 g / L, calculated as oxides.
[0041] Prepare a 1L solution of Na2CO3 (from Sinopharm Group) with a concentration of 200g / L.
[0042] Neutralization reaction: 5L of aluminum sulfate solution containing silica sol and 1.2L of sodium aluminate solution were added concurrently to a 2.0L neutralization reactor for neutralization reaction at 60℃, pH 7.5 and residence time of 15min.
[0043] Atmospheric pressure aging: After neutralization reaction, 720 mL of Na2CO3 solution was added to the slurry to adjust the pH to 9.0. The temperature was raised to 85℃ and kept constant for 5 hours. The aged slurry was filtered with a vacuum filter and washed with 60 L of 85℃ deionized water to obtain filter cake.
[0044] High-pressure aging: Take 1000g of filter cake and add deionized water under stirring to make 1.6L of slurry. Continue stirring and add 10mL of concentrated ammonia water to the above slurry until the pH is 10.8. Transfer the above slurry 1.6L to a 2L high-pressure reactor. Heat to 150℃ under stirring and keep at a constant temperature for 9 hours. After the constant temperature is completed, let it cool to room temperature naturally. Filter the slurry under vacuum. Wash the filter cake with 20L of deionized water at 90℃. Dry the filter cake at 120℃ for 24 hours to obtain the silica-boehmite composition PS1. Calcine PS1 at 600℃ for 3 hours to obtain the silica-alumina composition AS1.
[0045] XRD characterization revealed that PS1 possessed a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. AS1 possessed a mixture of amorphous silica and γ-alumina. XRF characterization of the chemical composition of AS1 is shown in Table 1. The pore volume, specific surface area, and dilatancy diameter of AS1 were measured using N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) were determined using pyridine infrared spectroscopy, and are shown in Table 2. The cumene cracking activity of AS1, tested in an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0046] Example 2
[0047] Take 1000g of the filter cake after filtration and washing of the slurry after normal pressure aging in Example 1, add deionized water under stirring to make 1.6L slurry, and continue stirring to add 20mL of concentrated ammonia water to the above slurry until the pH is 11.5. Transfer the above 1.6L slurry to a 2L high-pressure reactor, heat to 121℃ under stirring, and maintain the temperature for 45 hours. After the temperature is maintained, let it cool to room temperature naturally. Filter the slurry under vacuum, wash the filter cake with 20L of deionized water at 90℃, and dry the filter cake at 120℃ for 24 hours to obtain the silica-boehmite composition PS2. Calcine the PS2 at 600℃ for 3 hours to obtain the silica-alumina composition AS2.
[0048] XRD characterization revealed that PS2 possesses a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. AS2 possesses a mixture of amorphous silica and γ-alumina. XRF characterization of the chemical composition of AS2 is shown in Table 1. The pore volume, specific surface area, and piracene pore diameter of AS2 were measured using N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) were determined using pyridine infrared spectroscopy, and are shown in Table 2. The cumene cracking activity of AS2, tested in an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0049] Comparative Example 1
[0050] In Example 1, the filter cake from the atmospheric pressure aged slurry after filtration and washing was not subjected to further high-pressure aging. Instead, the filter cake from the atmospheric pressure aged slurry was directly dried at 120°C for 24 hours to obtain a silica-boehmite composition CPS1. CPS1 was then calcined at 600°C for 3 hours to obtain a silica-alumina composition CAS1. XRD characterization showed that CPS1 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. CAS1 had a mixture of amorphous silica and γ-alumina. The chemical composition of CAS1 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and pore diameter of CAS1 were measured by N2 adsorption, and the results are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) were measured by pyridine infrared spectroscopy, and the results are shown in Table 2. The cumene cracking activity of AS1, tested on an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0051] Example 3
[0052] A 5.0 L aluminum sulfate solution containing silica sol was prepared according to the method of Example 1, wherein the concentration was 41.6 g / L based on alumina and 42 g / L based on silica; a sodium aluminate solution was prepared according to the method of Example 1, wherein the concentration of Al2O3 was 220 g / L based on oxides and the concentration of Na2O was 227 g / L; and a Na2CO3 solution with a concentration of 200 g / L was prepared according to the method of Example 1.
[0053] 5 L of aluminum sulfate solution containing silica sol and 1.2 L of sodium aluminate solution were added concurrently via a peristaltic pump and a flow meter to a 2.0 L neutralization reactor equipped with stirring and temperature control. The neutralization temperature was controlled at 45 °C, the pH at 7.5, and the residence time at 10 min for the neutralization reaction. After neutralization, 300 mL of Na₂CO₃ solution was added to the slurry to adjust the pH to 8.5. The slurry was then heated to 70 °C and held at that temperature for 10 h. The aged slurry was filtered using a vacuum filter and washed with 60 L of 90 °C deionized water to obtain a filter cake. 1000g of filter cake was mixed with deionized water under stirring to form a 1.6L slurry. 10mL of tetraethylammonium hydroxide was added to the slurry under continued stirring until the pH reached 9.5. The 1.6L slurry was transferred to a 2L high-pressure reactor. The temperature was raised to 180℃ under stirring and maintained for 6 hours. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature. The slurry was then vacuum filtered, and the filter cake was washed with 20L of deionized water at 90℃. The filter cake was dried at 120℃ for 24 hours to obtain a silica-boehmite composition PS3. PS3 was calcined at 600℃ for 3 hours to obtain a silica-alumina composition AS3. XRD characterization showed that PS3 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. AS3 is a mixture of amorphous silica and γ-alumina. The chemical composition of AS3 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and pore diameter of AS3 were measured by N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) were determined by pyridine infrared spectroscopy, and are also shown in Table 2. The cumene cracking activity of AS3, tested in an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0054] Example 4
[0055] 1000g of filter cake from the slurry after atmospheric pressure aging in Example 3, after filtration and washing, was mixed with deionized water to form 1.6L of slurry under stirring. 22mL of tetraethylammonium hydroxide was added to the slurry under continued stirring until the pH reached 10.5. The 1.6L slurry was transferred to a 2L high-pressure reactor, heated to 130℃ under stirring, and maintained at this temperature for 36 hours. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature. The slurry was then vacuum filtered, and the filter cake was washed with 20L of deionized water at 90℃. The filter cake was dried at 120℃ for 24 hours to obtain a silica-boehmite composition PS4. PS4 was calcined at 600℃ for 3 hours to obtain a silica-alumina composition AS4. XRD characterization showed that PS4 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. AS4 is a mixture of amorphous silica and γ-alumina. The chemical composition of AS4 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and pore diameter of AS4 were measured by N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) were determined by pyridine infrared spectroscopy, and are also shown in Table 2. The cumene cracking activity of AS4, tested in an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0056] Comparative Example 2
[0057] In Example 3, the filter cake after atmospheric pressure aging and filtration and washing of the slurry was not subjected to further high-pressure aging. Instead, the filter cake after atmospheric pressure aging and filtration and washing was directly dried at 120°C for 24 hours to obtain a silica-boehmite composition CPS2. CPS2 was then calcined at 600°C for 3 hours to obtain a silica-alumina composition CAS2. XRD characterization showed that CPS2 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. CAS2 had a mixture of amorphous silica and γ-alumina. The chemical composition of CAS2 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and pore diameter of CAS2 were measured by N2 adsorption, and the results are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) in CAS2 were measured by pyridine infrared spectroscopy, and the results are shown in Table 2. The cumene cracking activity of CAS2, tested on an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0058] Example 5
[0059] 772g of aluminum nitrate nonahydrate produced by Sinopharm Group was dissolved in deionized water under stirring and the volume was adjusted to 3.0L to obtain an aluminum nitrate solution. 700g of industrial silica sol JN-30 (30% silicon oxide) from Qingdao Chengyu Chemical Co., Ltd. was added to the aluminum nitrate solution under stirring, and then deionized water was added to 5.0L to obtain an aluminum sulfate solution containing silica sol, wherein the concentration based on aluminum oxide was 21.0g / L and the concentration based on silicon oxide was 42g / L. Sodium aluminate solution was prepared according to the method of Example 1, with an Al2O3 concentration of 220g / L and a Na2O concentration of 227g / L based on oxides. 20g of concentrated nitric acid produced by Sinopharm Group was added to 100mL of deionized water under stirring, and then deionized water was added to adjust the volume to 200mL to obtain a dilute nitric acid solution. 5 L of aluminum sulfate solution containing silica sol and 1.2 L of sodium aluminate solution were added concurrently via a peristaltic pump and a flow meter to a 2.0 L neutralization reactor equipped with stirring and temperature control. The neutralization reaction was carried out at a controlled temperature of 55 °C, pH of 9.5, and a residence time of 25 min. After neutralization, 6 mL of dilute nitric acid solution was added to the slurry to adjust the pH to 9.2. The slurry was then heated to 60 °C and aged for 22 h. The aged slurry was filtered using a vacuum filter and washed with 60 L of 90 °C deionized water to obtain a filter cake. 1000g of filter cake was stirred with deionized water to form a 1.6L slurry. 10mL of ammonia was added to the slurry while stirring until the pH reached 9.5. The 1.6L slurry was transferred to a 2L high-pressure reactor. The reactor was heated to 170℃ while stirring and maintained at this temperature for 30 hours. After the temperature was maintained, the mixture was allowed to cool naturally to room temperature. The slurry was then vacuum filtered, and the filter cake was washed with 20L of deionized water at 90℃. The filter cake was dried at 120℃ for 24 hours to obtain a silica-boehmite composition PS5. PS5 was calcined at 600℃ for 3 hours to obtain a silica-alumina composition AS5. XRD characterization showed that PS5 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. AS5 is a mixture of amorphous silica and γ-alumina. The chemical composition of AS5 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and pore diameter of AS5 were measured by N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) in AS5 were determined by pyridine infrared spectroscopy, and are shown in Table 2. The cumene cracking activity of AS5 was tested in an atmospheric pressure fixed-bed microreactor and is listed in Table 2.
[0060] Example 6
[0061] 1000g of filter cake from the slurry after aging under normal pressure in Example 5 was washed and mixed with deionized water to form 1.6L of slurry. 18mL of ammonia was added to the slurry while stirring until the pH reached 10.0. The 1.6L slurry was transferred to a 2L high-pressure reactor and heated to 160℃ while stirring. The temperature was maintained for 24 hours. After the temperature maintenance, the mixture was allowed to cool naturally to room temperature. The slurry was then vacuum filtered, and the filter cake was washed with 20L of deionized water at 90℃. The filter cake was dried at 120℃ for 24 hours to obtain a silica-boehmite composition PS6. PS6 was calcined at 600℃ for 3 hours to obtain a silica-alumina composition AS6. XRD characterization showed that PS6 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. AS6 is a mixture of amorphous silica and γ-alumina. The chemical composition of AS6 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and dilatancy diameter of AS6 were measured by N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) were determined by pyridine infrared spectroscopy, and are also shown in Table 2. The cumene cracking activity of AS6, tested in an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0062] Example 7
[0063] 274g of aluminum chloride produced by Sinopharm Group was dissolved in deionized water under stirring and the volume was adjusted to 3.0L to obtain an aluminum chloride solution. 700g of industrial silica sol JN-30 (30% silicon oxide) from Qingdao Chengyu Chemical Co., Ltd. was added to the aluminum chloride solution under stirring, and then deionized water was added to 5.0L to obtain an aluminum chloride solution containing silica sol, wherein the concentration based on aluminum oxide was 21.0g / L and the concentration based on silicon oxide was 42g / L. Sodium aluminate solution was prepared according to the method in Example 1, with an Al2O3 concentration of 220g / L and a Na2O concentration of 227g / L based on oxides. A 200g / L Na2CO3 solution was prepared according to the method in Example 1. 5 L of aluminum chloride solution containing silica sol and 1.2 L of sodium aluminate solution were added concurrently via a peristaltic pump and a flow meter to a 2.0 L neutralization reactor equipped with stirring and temperature control. The neutralization reaction was carried out at a controlled temperature of 65 °C, pH of 6.2, and a residence time of 8 min. After neutralization, 350 mL of Na₂CO₃ solution was added to the slurry to adjust the pH to 7.5. The slurry was then heated to 95 °C and held at that temperature for 15 h. The aged slurry was filtered using a vacuum filter and washed with 60 L of 90 °C deionized water to obtain a filter cake. 1000g of filter cake was mixed with deionized water under stirring to form a 1.6L slurry. 40mL of tetrapropylammonium hydroxide was added to the slurry under continued stirring until the pH reached 10.8. The slurry was then transferred to a 2L high-pressure reactor and heated to 180℃ under stirring. This temperature was maintained for 20 hours, after which the mixture was allowed to cool naturally to room temperature. The slurry was then vacuum filtered, and the filter cake was washed with 20L of deionized water at 90℃. The filter cake was dried at 120℃ for 24 hours to obtain a silica-boehmite composition PS7. PS7 was calcined at 600℃ for 3 hours to obtain a silica-alumina composition AS7. XRD characterization showed that PS7 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. AS7 is a mixture of amorphous silica and γ-alumina. The chemical composition of AS7 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and pore diameter of AS7 were measured by N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) in AS7 were determined by pyridine infrared spectroscopy, and are shown in Table 2. The cumene cracking activity of AS7 was tested in an atmospheric pressure fixed-bed microreactor and is listed in Table 2.
[0064] Comparative Example 3
[0065] In Example 7, the slurry after constant pressure aging was filtered and washed to obtain a filter cake. 1000g of the filter cake was mixed with deionized water under stirring to form 1.6L of slurry. The pH was measured to be 7.3. The slurry was transferred to a 2L high-pressure reactor and heated to 180℃ under stirring. This temperature was maintained for 20 hours, and after the temperature was maintained, the mixture was allowed to cool naturally to room temperature. The slurry was then vacuum filtered, and the filter cake was washed with 20L of deionized water at 90℃. The filter cake was dried at 120℃ for 24 hours to obtain a silica-boehmite composition CPS3. CPS3 was calcined at 600℃ for 3 hours to obtain a silica-alumina composition CAS3. XRD characterization showed that CPS3 had a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. CAS3 is a mixture of amorphous silica and γ-alumina. The chemical composition of CAS3 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and pore diameter of CAS3 were measured by N2 adsorption, and are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) in CAS3 were determined by pyridine infrared spectroscopy, and are shown in Table 2. The cumene cracking activity of AS1 was tested in an atmospheric pressure fixed-bed microreactor and is listed in Table 2.
[0066] Example 8
[0067] The silica-boehmite composition PS1 from Example 1 was calcined at 700°C for 5 hours to obtain the silica-alumina composition AS8.
[0068] XRD characterization revealed that AS8 possesses a mixture of amorphous silica and γ-alumina phases. XRF characterization of the chemical composition of AS8 is shown in Table 1. The pore volume, specific surface area, and pore diameter of AS8 were measured using N2 adsorption, as shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) ratios, as determined by pyridine infrared spectroscopy, are also shown in Table 2. The cumene cracking activity of AS8, tested in an atmospheric pressure fixed-bed microreactor, is listed in Table 2.
[0069] Comparative Example 4
[0070] Siral 40, purchased from Sasol, was characterized by XRD. CPS4 exhibits a mixture of amorphous silica and boehmite. The relative crystallinity and grain size of the boehmite were calculated based on the boehmite phase diagram 2θ = 38°, and the results are shown in Table 1. CAS4 exhibits a mixture of amorphous silica and γ-alumina. The chemical composition of CAS4 was characterized by XRF, and the results are listed in Table 1. The pore volume, specific surface area, and dilatant pore diameter of CAS4 were measured by N2 adsorption, and the results are shown in Table 2. The Brønsted acid (B acid) and Lewis acid (L acid) and the ratio of B acid to (Brønsted acid + L acid) in CAS4 were determined by pyridine infrared spectroscopy, and the results are shown in Table 2. The cumene cracking activity of CAS4 was tested in an atmospheric pressure fixed-bed microreactor and is listed in Table 2.
[0071] Table 1
[0072]
[0073] Table 2
[0074]
Claims
1. A method for preparing a silica-boehmite composition, comprising the following steps: (1) Prepare an aluminum source solution containing silica sol, and then mix it with an alkaline solution to obtain a neutralized slurry; (2) Adjust the pH of the neutralized slurry to 7-10, carry out normal pressure aging, filtration, and washing to obtain filter cake; add water to the filter cake and slurry to obtain filter cake slurry; (3) Adjust the filter cake slurry to pH 8-12, perform high-pressure aging, and then filter, wash and dry the slurry after high-pressure aging to obtain the silica-boehmite composition. in, The conditions for the neutralization reaction in step (1) include: temperature 40-70℃, pH 6-10, and time 5-30 min; the conditions for atmospheric pressure aging in step (2) include: temperature 60-99℃ and time 1-24 h; the conditions for high pressure aging in step (3) are carried out in a closed container, including: temperature 121-200℃, pressure of autogenous vapor pressure, and aging time 1-48 h. The concentrations and amounts of the aluminum source solution and alkaline solution in the silica sol are such that the final prepared silica-boehmite composition contains 20-50 wt% silica and 50-80 wt% alumina (based on oxides). The washing in step (3) results in a final composition with a Na2O content of 0.01-0.12 wt%.
2. The method according to claim 1, wherein, In step (2), the pH of the neutralized slurry is adjusted to 7.5-9.5; the conditions for the neutralization reaction in step (1) include: pH 7.5-9.
5.
3. The method according to claim 1, wherein, The concentration and amount of the aluminum source solution and alkaline solution containing the silica sol are such that the silica-boehmite composition obtained in the final preparation has a silica content of 30-45 wt% and an alumina content of 55-70 wt% as oxides; the washing in step (3) results in a Na2O content of 0.02-0.10 wt% in the final composition.
4. The method according to claim 1, wherein, The aluminum source in step (1) is aluminum sulfate, aluminum chloride and / or aluminum nitrate, with a concentration of 10-100g Al2O3 / L based on aluminum oxide; the alkaline solution is an aluminum-containing alkaline solution or an aluminum-free alkaline solution; the silica sol has a silica mass concentration of 10-40 g.
5. The method according to claim 1, wherein, In step (3), an inorganic alkaline solution or an organic alkaline solution that does not contain metal ions is used to adjust the pH value.
6. The method according to claim 1, wherein, The washing in step (2) and / or (3) is a deionized water wash at a temperature of 50-95°C.
7. The method according to claim 1, wherein, The drying process described in step (3) is oven drying, flash drying, or spray drying, with a drying temperature of 80-120℃.
8. A method for preparing amorphous silica-alumina, comprising calcining a silica-boehmite composition prepared by any one of claims 1-7, wherein the calcination conditions include: The temperature is 500-700℃, and the time is 2-5 hours.