Alumina-titanium oxide composite oxides, their preparation methods and applications

Abstract

This invention relates to the field of hydrogenation reactions, and discloses an alumina-titanium oxide composite oxide, its preparation method, and its application. A method for preparing an alumina-titanium oxide composite oxide includes the following steps: (1) reacting an acidic solution containing aluminum and titanium with an alkaline solution containing aluminum to form a gel, obtaining a solid gel product; (2) subjecting the solid gel product obtained in step (1) to an aging reaction in the presence of a precipitant, obtaining an aging reaction product; (3) subjecting the aging reaction product obtained in step (2) to hydrothermal treatment, followed by drying and calcination, to obtain the alumina-titanium oxide composite oxide; wherein the temperature of the hydrothermal treatment is higher than the temperature of the aging reaction. This method enables the preparation of alumina-titanium oxide composite oxides with low titanium oxide content and specific crystal forms without the need for organic titanium-containing reagents, making it more environmentally friendly and easier for industrial production.

Description

Technical Field

[0001] This invention relates to the technical field of hydrogenation reactions, specifically to an alumina-titanium oxide composite oxide, its preparation method, and its applications. Background Technology

[0002] The pore structure of the support for hydrogenation catalysts and its interaction with the active metal have a significant impact on catalytic performance. This is due to the hydrogen spillover effect of the titanium dioxide support and the presence of Ti... 4+ Due to its high-temperature reducibility, titanium dioxide-based hydrodesulfurization catalysts exhibit high reactivity and good anti-coking properties. However, the small specific surface area and pore volume of titanium dioxide, along with its poor thermal stability, limit its application as a catalyst support. Combining titanium dioxide with alumina can effectively improve thermal stability and significantly improve the pore structure, resulting in higher reactivity in the hydrodesulfurization reaction. The anatase crystal form plays a major role in improving the hydrodesulfurization reactivity. In existing titanium-aluminum composite oxides synthesized via co-precipitation, when the titanium dioxide content is low, the titanium dioxide is dispersed in the alumina, failing to form the anatase phase, which is more conducive to the hydrodesulfurization reaction.

[0003] Patent application EP0339640A1 discloses a method for synthesizing an alumina-titanium dioxide composite material through co-precipitation of water-soluble aluminum and titanium salts. An aqueous solution of sodium aluminate is used as the alumina source, and solutions of TiOCl2 and / or TiCl3 and / or TiOSO4 are used as the titanium dioxide source. These are added to a reactor in parallel flow. During the reaction, the appropriate amounts of HCl or H2SO4 are added to control the pH value. The reactor temperature is maintained at approximately 50-57°C throughout the reaction. After vigorous mixing, the mixture is filtered, dried, and calcined to obtain the alumina-titanium dioxide material. Compared to the traditional impregnation method, the titanium dioxide in the composite oxide material prepared by the co-precipitation method is distributed within the alumina, without exhibiting anatase peaks.

[0004] Patent application CN1344586A discloses a supported nano-TiO2 composite carrier and its preparation method. This method involves preparing a titanium sol by mixing tetrabutyl titanate with ethanol, water, and nitric acid. The titanium sol is then added to a slurry prepared by mixing boehmite with water or anhydrous ethanol. The sample is then air-dried for 24 hours, dried at 60°C for 12 hours, dried at 120°C for 4 hours, and subsequently calcined at 200, 300, 400, and 500°C for 2 hours each. This method enables the loading of nano-TiO2 onto macroporous alumina. XRD results indicate that the nano-TiO2 has anatase crystal structure.

[0005] Patent application CN111050904A discloses a series of methods for synthesizing titanium-aluminum composite oxide supports, including co-extrusion, co-precipitation, continuous stepwise precipitation, and impregnation. The co-precipitation method involves simultaneously adding aluminum sulfate and titanium oxysulfate mixed in a fluid, along with sodium aluminate, to water at 60°C and pH 8.5. The flow rates of sodium aluminate and aluminum sulfate / titanium oxysulfate are kept constant, and the pH is maintained constant using NaOH or H₂SO₄. After the addition is complete, the pH is raised to 10, and the material is aged, then filtered, washed, dried, and calcined to obtain the titanium-aluminum composite oxide material. The titanium-aluminum support prepared by this method has a relatively high TiO₂ content (mass ratios of 20.9% and 48.0%, respectively), and exhibits characteristic peaks of anatase in the XRD results.

[0006] When the titanium dioxide content is relatively low, the co-precipitation method described above cannot obtain anatase-type titanium-aluminum composite oxide materials. When nano-titanium dioxide is loaded onto an alumina support via the sol-gel method, the synthesis process is complex and cannot be achieved using inexpensive and readily available raw materials and simple methods. Summary of the Invention

[0007] The purpose of this invention is to overcome the problems existing in the prior art and provide an alumina-titanium oxide composite oxide, its preparation method, and its application. This method can achieve the preparation of alumina-titanium oxide composite oxides with low titanium oxide content and specific crystal forms without using organic titanium-containing reagents, making it more environmentally friendly and easier for industrial production.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing an alumina-titanium oxide composite oxide, wherein the method includes the following steps:

[0009] (1) A gelling reaction is carried out between an acidic solution containing aluminum and titanium and an alkaline solution containing aluminum to obtain a solid gelling product;

[0010] (2) In the presence of a precipitant, the solid gelling product obtained in step (1) is subjected to an aging reaction to obtain an aging reaction product.

[0011] (3) The aging reaction product obtained in step (2) is subjected to hydrothermal treatment, and then dried and calcined to obtain alumina-titanium oxide composite oxide;

[0012] The temperature of hydrothermal treatment is higher than that of the aging reaction.

[0013] The second aspect of the present invention provides an alumina-titanium oxide composite oxide prepared by the method described in the first aspect.

[0014] The third aspect of this invention provides the application of the alumina-titanium oxide composite oxide described in the second aspect in a hydrodesulfurization reaction.

[0015] Compared with the prior art, the method provided by this invention uses a combination of co-precipitation and hydrothermal methods to prepare alumina-titanium oxide composite oxides. It can achieve the preparation of alumina-titanium oxide composite oxides without the use of organic titanium-containing reagents. Preferably, the method provided by this invention is more suitable for the preparation of alumina-titanium oxide composite oxides with low titanium oxide content and anatase crystal form. Furthermore, the method provided by this invention has a simple process, inexpensive and readily available raw materials, easily controllable operating conditions, and adjustable product properties.

[0016] The alumina-titanium oxide composite oxide provided by this invention has a low titanium oxide content, and the titanium oxide is in the anatase crystal form. It has a high pore concentration and a suitable range of most probable pore sizes, which is beneficial to the hydrogenation reaction. Attached Figure Description

[0017] Figure 1 These are the XRD patterns of the alumina-titanium oxide composite oxides prepared in Example 1 and Comparative Example 1;

[0018] Figure 2 The image shows the infrared skeleton of the alumina-titanium oxide composite oxides prepared in Example 1 and Comparative Example 2. 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 first aspect of this invention provides a method for preparing an alumina-titanium oxide composite oxide, wherein the method includes the following steps:

[0021] (1) A gelling reaction is carried out between an acidic solution containing aluminum and titanium and an alkaline solution containing aluminum to obtain a solid gelling product;

[0022] (2) In the presence of a precipitant, the solid gelling product obtained in step (1) is subjected to an aging reaction to obtain an aging reaction product.

[0023] (3) The aging reaction product obtained in step (2) is subjected to hydrothermal treatment, and then dried and calcined to obtain alumina-titanium oxide composite oxide;

[0024] The temperature of hydrothermal treatment is higher than that of the aging reaction.

[0025] The method provided by this invention, compared with the prior art, can prepare alumina-titanium oxide composite oxides without using organic titanium-containing reagents, by combining co-precipitation and hydrothermal methods and controlling the reaction conditions. By controlling the aging reaction and hydrothermal treatment conditions, this invention allows for aging at a lower temperature followed by hydrothermal treatment. The alumina-titanium oxide composite oxides obtained by this invention have a low titanium oxide content, exhibit anatase crystal form, high pore concentration, and a suitable range of most probable pore sizes, making them particularly suitable as supports for hydrogenation catalysts.

[0026] In this invention, there are no particular limitations on the preparation method of the acidic solution containing aluminum and titanium, as long as the titanium-containing compound can be dissolved in an aluminum solution to obtain the acidic solution. Preferably, in step (1), the acidic solution containing aluminum and titanium is prepared by dissolving the titanium-containing compound in an acidic aluminum solution.

[0027] In this invention, there is no particular limitation on the type of titanium-containing compound, as long as it meets the requirements of the gelation reaction. Preferably, the titanium-containing compound is titanium oxysulfate and / or titanium sulfate. By selecting titanium-containing compounds within the above range to prepare an acidic solution containing titanium and aluminum for the gelation reaction, the use of organic titanium reagents is avoided, ensuring that the entire preparation process is simple and environmentally friendly.

[0028] In this invention, there is no particular limitation on the type of acidic aluminum solution. Preferably, the acidic aluminum solution is selected from at least one of aluminum sulfate solution, aluminum nitrate solution, and aluminum chloride solution.

[0029] In this invention, there is no particular limitation on the type of aluminum-containing alkaline solution, as long as the gelation reaction is achieved. Preferably, in step (1), the aluminum-containing alkaline solution is a sodium aluminate solution and / or a potassium aluminate solution.

[0030] In this invention, the ratio of titanium to aluminum is controlled by adjusting the concentration of the acidic solution containing aluminum and titanium, thereby controlling the titanium content and preparing alumina-titanium oxide composite oxides in different ranges to meet different application scenarios. Preferably, in step (1), the concentration of the acidic solution containing aluminum and titanium, calculated as alumina, is 35-120 g / L, for example, it can be 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, 100 g / L, 110 g / L, 115 g / L, 120 g / L, or any value between any two groups. Preferably, in step (1), the concentration of the acidic solution containing aluminum and titanium, calculated as titanium oxide, is 5-80 g / L, for example, it can be 5 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, or any value between any two groups.

[0031] In this invention, there is no particular limitation on the concentration of the aluminum-containing alkaline solution, as long as it meets the requirements of the gelation reaction. Preferably, the concentration of the aluminum-containing alkaline solution, calculated as alumina, is 20-300 g / L, for example, it can be 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, 300 g / L, or any value between any two groups.

[0032] In this invention, preferably, the amounts of the acidic solution containing aluminum and titanium and the alkaline solution containing aluminum are such that, based on the total amount of the alumina-titanium oxide composite oxide, the content of aluminum oxide is 70-99% by weight, preferably 75-96% by weight, and the content of titanium oxide is 1-30% by weight, preferably 5-25% by weight. It should be noted that a small amount of impurities may be present in the alumina-titanium oxide composite oxide; therefore, when impurities are present, the sum of the contents of aluminum oxide, titanium oxide, and impurities must equal 100%. In this invention, the type of impurities is not specifically limited; for example, it can be SO3, Na2O, etc.

[0033] In this invention, the method of gelation reaction is not particularly limited and can be any method conventionally defined in the art. Preferably, in step (1), the gelation reaction is carried out continuously or intermittently, preferably continuously. On the one hand, carrying out the gelation reaction continuously is more conducive to controlling the pH of the gelation reaction process, effectively improving the quality of the alumina-titanium oxide composite oxide. On the other hand, continuous operation can increase the throughput per unit time and improve production efficiency.

[0034] The present invention does not particularly limit the equipment used for the gelation reaction, and any conventional choice in the art can be used. Specifically, for example, it can be carried out in a gelation tank.

[0035] According to a preferred embodiment of the present invention, the continuous gelation reaction process of the present invention includes: adding a certain amount of deionized water to the gelation tank in advance, and introducing an acidic solution containing aluminum and titanium and an alkaline solution containing aluminum from the top of the gelation tank, so that the acidic solution containing aluminum and titanium and the alkaline solution containing aluminum are mixed and contacted to carry out the gelation reaction, and the slurry generated by the gelation reaction flows out of the gelation tank continuously, while controlling the liquid level in the gelation tank to remain constant.

[0036] In this invention, the conditions for the gelation reaction are relatively flexible. Preferably, in step (1), the conditions for the gelation reaction include: a temperature of 50-70°C and a pH value of 4-7. Under this preferred method, it is more beneficial to improve the quality of the alumina-titanium oxide composite oxide. In this invention, the pH value should not be too high during the gelation reaction, as an excessively high pH will result in low pore volume and specific surface area of ​​the titanium-aluminum composite oxide product; the pH value should also not be too low, because a lower pH value will easily lead to a large difference in the formation rate of hydrated oxides of aluminum and titanium, which is not conducive to the uniform dispersion of titanium in alumina. In this invention, there is no particular limitation on the method of pH control. For example, the flow rates of the acidic solution containing aluminum and titanium and the precipitant can be adjusted. In this invention, there is no particular limitation on the flow rates of the acidic solution containing aluminum and titanium and the precipitant, as long as the pH value of the gelation reaction is met.

[0037] In this invention, the pH value of the reaction system is adjusted by adding a precipitant, so that the slurry obtained from the solid gelling product in step (1) undergoes an aging reaction. This invention allows for a wide range of precipitant types. Preferably, in step (2), the precipitant is selected from alkali metal compounds, and more preferably from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. In this invention, there is no particular limitation on the amount of precipitant used; the limitation is that it meets the pH value required for the aging reaction. Those skilled in the art can select the appropriate precipitant based on actual needs.

[0038] In this invention, the selection range for the aging reaction conditions is relatively wide. Preferably, in step (2), the aging reaction conditions include: a temperature of 60-98℃, a time of 4-9h, and a pH value of 7-11; more preferably, in step (2), the aging reaction conditions include: a temperature of 70-95℃, a time of 5-8h, and a pH value of 7.5-10. By controlling the aging reaction conditions, the pore structure of the alumina-titanium oxide composite oxide is regulated, thereby improving the quality of the alumina-titanium oxide composite oxide.

[0039] In this invention, preferably, after the aging treatment, step (2) further includes solid-liquid separation of the aging product to obtain a solid aging product. In this invention, the solid-liquid separation is a conventional operation in the art, specifically, for example, it can be at least one of sedimentation, filtration and centrifugation, which can be selected by those skilled in the art according to actual needs.

[0040] In this invention, preferably, the hydrothermal treatment temperature is 10-100°C higher than the aging reaction temperature, more preferably 10-80°C higher, and even more preferably 20-70°C higher. For example, it can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or any value between any two groups. By controlling the temperatures of the aging reaction and the hydrothermal treatment, the pore concentration of the alumina-titanium oxide composite oxide can be increased, while obtaining the anatase crystal form. When the temperature difference between the two is not within the above-mentioned preferred range, the alumina-titanium oxide composite oxide grain size is larger, affecting the specific surface area and most probable pore size of the composite oxide material.

[0041] In this invention, preferably, step (3) further includes washing the solid aging product before hydrothermal treatment. In this invention, the washing operation is a conventional operation in the art, requiring only a reduction in the content of impurity ions (e.g., residual sodium and sulfate) in the solid aging product, for example, such that the sodium oxide content in the obtained alumina-titanium oxide composite oxide is less than 0.1% by weight, preferably less than 0.06% by weight, and more preferably 0.01-0.05% by weight.

[0042] In this invention, preferably, step (3) includes: adding water (preferably deionized water) to the solid aging product after aging treatment, pulping it, and then performing hydrothermal treatment. In this invention, the amount of water used is such that the concentration of the slurry obtained after pulping, based on the weight of oxides (total amount of aluminum oxide and titanium oxide), is 50-180 g / L, preferably 70-150 g / L.

[0043] Provided that the temperature of the hydrothermal treatment is higher than that of the aging reaction, the selection range of the hydrothermal treatment conditions is relatively wide, in order to further optimize the pore structure characteristics of the alumina-titanium oxide composite oxide. Preferably, in step (3), the hydrothermal treatment conditions include: temperature 100-180℃, time 2-9h. In this invention, the hydrothermal treatment can change the state of titanium dioxide on alumina. The co-precipitation method combined with the hydrothermal method not only improves the pore concentration of the alumina-titanium oxide composite oxide, making the most probable pore size fall within a suitable range, but also allows the titanium dioxide dispersed in the alumina framework to aggregate into anatase, which is more conducive to improving the hydrogenation reaction activity, thus obtaining anatase-γ-Al2O3 support with a low titanium dioxide content.

[0044] In this invention, the range of drying conditions is relatively wide. Preferably, the drying conditions include a temperature of 60-200℃, and more preferably 100-160℃.

[0045] In this invention, the range of roasting conditions is relatively wide. Preferably, in step (3), the roasting conditions include: a temperature of 500-700℃ and a time of 2-6 hours, more preferably 550-650℃ and a time of 3-5 hours.

[0046] Preferably, in this invention, the method does not require the use of organic titanium-containing reagents. This invention prepares alumina-titanium oxide composite oxide materials via co-precipitation and hydrothermal treatment. The reaction process is simple, easy to operate, uses inexpensive and readily available raw materials, requires no organic reagents, and the production process is environmentally friendly.

[0047] The second aspect of the present invention provides an alumina-titanium oxide composite oxide prepared by the method described in the first aspect.

[0048] In this invention, preferably, based on the total amount of the alumina-titanium oxide composite oxide, the content of alumina is 70-99% by weight, and the content of titanium oxide is 1-30% by weight; more preferably, based on the total amount of the alumina-titanium oxide composite oxide, the content of alumina is 75-96% by weight, and the content of titanium oxide is 4-25% by weight. It should be noted that a small amount of impurities may be present in the alumina-titanium oxide composite oxide. Therefore, when impurities are present, the sum of the contents of alumina, titanium oxide, and the impurities must equal 100%. In this invention, the type of impurities is not specifically limited; for example, it can be SO3, Na2O, etc.

[0049] In this invention, the composition of the alumina-titanium oxide composite oxide was determined by measuring the characteristic spectral lines of each element using a Rigaku Electric Co., Ltd. 3271 X-ray fluorescence spectrometer, and the elemental content of the alumina-titanium oxide composite oxide was semi-quantitatively analyzed using the external standard method.

[0050] In this invention, preferably, the titanium oxide is anatase and the alumina is γ-crystalline. Using the method of this invention, a low-titanium-content anatase-type alumina-titanium oxide composite oxide carrier is prepared without the need for organic titanium reagents.

[0051] In this invention, the XRD diffraction pattern shows that titanium oxide exhibits typical anatase diffraction peaks at 25.3°, 48.1°, 54°, and 55.1°, indicating that titanium oxide has anatase crystal form.

[0052] In this invention, the crystal structure of the alumina-titanium oxide composite oxide was determined using a Philips XPERT series X-ray powder diffractometer.

[0053] The alumina-titanium oxide composite oxide prepared by the method provided by the present invention has a low titanium oxide content and the titanium oxide is anatase type, thus realizing the preparation of anatase type composite oxide with low titanium oxide content, which is more conducive to the preparation of hydrogenation support.

[0054] The alumina-titanium oxide composite oxide provided by this invention has a high pore concentration, which is beneficial for the hydrogenation reaction. Preferably, the pore volume of the alumina-titanium oxide composite oxide is 0.4-1.3 mL / g, and the specific surface area is 200-400 m². 2 / g, with a most probable pore size of 5-12nm; more preferably, the alumina-titanium oxide composite oxide has a pore volume of 0.5-0.9mL / g and a specific surface area of ​​220-300m². 2 / g, with a most probable pore size of 7-11nm.

[0055] In this invention, the pore structure characteristics of the alumina-titanium oxide composite oxide were determined by N2 adsorption-desorption characterization using a Micromeritics ASAP2420 adsorption instrument.

[0056] A third aspect of this invention provides the application of the alumina-titanium oxide composite oxide described in the second aspect in a hydrodesulfurization reaction. Preferably, the alumina-titanium oxide composite oxide is used as a catalyst support in the hydrogenation reaction.

[0057] The present invention will be described in detail below through embodiments. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0058] The composition of the alumina-titanium oxide composite oxide was determined by measuring the characteristic spectral lines of each element using a Rigaku Electric Co., Ltd. 3271 X-ray fluorescence spectrometer. The elemental content of the titanium-aluminum composite oxide was semi-quantitatively analyzed using the external standard method, yielding the composition of Al2O3, TiO2, SO3, Na2O, etc. in the sample.

[0059] The N2 adsorption-desorption characterization method is as follows: N2 adsorption-desorption characterization is performed on a Micromeritics ASAP 2420 adsorption instrument. Before the test, about 0.3g of alumina-titanium oxide composite oxide powder is taken and pretreated at 350℃ under vacuum for 10 hours.

[0060] The crystal form characterization method for alumina-titanium oxide composite oxides was as follows: A certain amount of alumina-titanium oxide composite oxide powder was pressed into sheets, and the crystal form of the samples was determined using a Philips XPERT series X-ray powder diffractometer. The test conditions were: Cu Kα rays (Kα = 0.154 nm), operating current 30 mA, operating voltage 40 kV, Ni filter, and scanning range 2θ = 5°-70°.

[0061] The infrared skeleton characterization method for alumina-titanium oxide composite oxides was as follows: A certain amount of alumina-titanium oxide composite oxide powder was added to KBr and pressed into sheets. The characterization was performed using a Nicolet 6700 infrared spectrometer manufactured by Thermo Fisher Scientific with a resolution of 4 cm⁻¹. -1 Scanning range 4000-400cm -1 The infrared spectrum of the alumina-titanium oxide composite oxide was obtained by scanning 32 times and using the single-point attenuation total reflection method.

[0062] Example 1

[0063] (1) Add 3L of deionized water to the gelling tank in advance, add titanium oxysulfate to aluminum sulfate solution to prepare an acidic solution containing aluminum and titanium, and pass the acidic solution containing aluminum and titanium and sodium aluminate solution from the top of the gelling tank to mix the acidic solution containing aluminum and titanium and sodium aluminate solution in the gelling tank to carry out the gelling reaction. The slurry after the gelling reaction flows out from the overflow pipe of the gelling tank. The liquid level in the gelling tank remains unchanged. When the pre-added deionized water is replaced by the slurry after the gelling reaction, the slurry collection begins, and then the filter cake (solid gelling product) is obtained by filtration.

[0064] The concentration of sodium aluminate solution (calculated as alumina) was 200 g / L, and the flow rate was 42 g / min. The concentration of titanium oxide in the acidic solution containing aluminum and titanium was 12.89 g / L, and the concentration of alumina was 58 g / L. By adjusting the flow rate of the acidic solution containing aluminum and titanium to 115-125 g / min, the pH value of the gelation reaction was approximately 6.3, and the temperature of the gelation reaction was 60℃.

[0065] (2) The gelation reaction product was aged by adding sodium carbonate solution to adjust the pH of the aging treatment. The aging conditions were pH 9.0, temperature 90℃, and time 6h.

[0066] (3) The aged mixture was filtered and washed sequentially to remove residual sodium and sulfate. The resulting filter cake (solid aged product) was then added to deionized water and slurried. The concentration of the resulting slurry was 130 g / L based on the weight of the titanium dioxide-alumina composite oxide. The resulting slurry was subjected to hydrothermal treatment at 150°C for 4 hours. After hydrothermal treatment, it was spray-dried and then calcined at 600°C for 3 hours to obtain alumina-titanium dioxide composite oxide A1. The composition of alumina-titanium dioxide composite oxide A1 was 10% by weight of titanium dioxide and 88.7% by weight of alumina, with the remainder being trace impurities from the synthesis and analysis processes. The specific physicochemical properties are listed in Table 1. Figure 1 The XRD patterns of Example 1 and Comparative Example 1 are shown below. Figure 1 It can be seen that in Example 1, titanium oxide exhibits anatase crystal form (titanium oxide shows diffraction peaks at 25.3°, 48.1°, 54°, and 55.1°, indicating that titanium oxide exhibits anatase crystal form), while aluminum oxide exhibits γ-Al2O3 crystal form (aluminum oxide shows diffraction peaks at 36°, 45°, and 67°, indicating that aluminum oxide exhibits γ-Al2O3 crystal form). Figure 2 The results are from infrared skeleton analysis, including 1100cm. -1 The peak at this location represents a characteristic peak of the Al-O bond. From... Figure 2 It can be seen that the characteristic vibration peak of the Al-O bond in Example 1 disappeared, indicating that the Ti part in Example 1 replaced the Al in the alumina structure, affecting the chemical environment around the Al atoms, and thus affecting the reaction activity of the catalyst prepared with alumina-titanium oxide composite oxide as a support.

[0067] Comparative Example 1

[0068] Following the method of Example 1, except that after aging in step (2), hydrothermal treatment was not performed, the aged mixture was filtered, washed, spray-dried, and then calcined at 600°C for 3 hours to obtain alumina-titanium oxide composite oxide S1. The final composition of alumina-titanium oxide composite oxide S1 was 10 wt% titanium oxide and 88.7 wt% alumina, with the remainder being trace impurities from the synthesis and analysis processes. Specific physicochemical properties are listed in Table 1. Figure 1 As can be seen, no anatase crystal form was detected. The alumina in Comparative Example 1 exhibits the γ-Al₂O₃ crystal form.

[0069] Comparative Example 2

[0070] This comparative example uses the preparation method described in the existing technical document (“Effects of the addition of titania onthethermal characterization of alumina-supported palladium”, Journal of Molecular Catalysis A, 2002, 180, 285-291) to prepare titanium dioxide-alumina composite oxide. 20 g of γ-Al₂O₃ (Sinopec Changling Catalyst Co., Ltd.) and 7.74 g of isopropyl titanate were dissolved in propanol, and the solution was measured to 15 mL and stirred thoroughly. Subsequently, γ-Al₂O₃ was dispersed in the above isopropyl titanate solution in isopropanol, dried overnight at 110 °C, and then calcined at 550 °C for 3 hours to obtain alumina-titanium dioxide composite oxide S2. The composition of alumina-titanium dioxide composite oxide S2 is 10.8 wt% titanium dioxide and 87.0 wt% alumina, with the remainder being trace impurities from the synthesis and analytical processes. Specific physicochemical properties are listed in Table 1. Compared to Example 1, the composite oxide prepared by this method has the crystal form of anatase-γ-Al2O3. Figure 2 Infrared skeleton analysis results show that, compared with pure alumina support, 1100 cm -1 The characteristic peaks of the Al-O bonds did not change, indicating that the method of impregnation with organic matter does not affect the framework structure of alumina.

[0071] Example 2

[0072] The method of Example 1 was followed, except that in step (1), the concentration of titanium oxide in the acidic solution containing aluminum and titanium was 20.67 g / L, the concentration of aluminum oxide was 46.64 g / L, and the flow rate was 110-120 g / min. The remaining conditions were the same as in Example 1. The resulting slurry was hydrothermally treated at 150°C for 4 hours, filtered, dried at 120°C for 6 hours, and calcined at 600°C for 3 hours to obtain alumina-titanium oxide composite oxide A2. The composition of alumina-titanium oxide composite oxide A2 was 19.3 wt% titanium oxide and 79.5 wt% aluminum oxide, with the remainder being trace impurities from the synthesis and analysis processes. Specific physicochemical properties are listed in Table 1. In Example 2, the aluminum oxide was in the same γ-Al2O3 crystal form as in Example 1.

[0073] Example 3

[0074] The method of Example 2 was followed, except that the temperature in step (3) of the hydrothermal treatment was 130°C and the hydrothermal time was 4 hours. The composition of the alumina-titanium oxide composite oxide A3 was 19.3% by weight of titanium oxide and 79.5% by weight of alumina, with the remainder being trace impurities from the synthesis and analysis processes. The specific physicochemical properties are listed in Table 1. In Example 3, the alumina was in the same γ-Al2O3 crystal form as in Example 1.

[0075] Example 4

[0076] The method of Example 2 was followed, except that the temperature in step (3) of the hydrothermal treatment was 110°C and the hydrothermal time was 4 hours. The composition of the alumina-titanium oxide composite oxide A4 was 19.3% by weight of titanium oxide and 79.5% by weight of alumina, with the remainder being trace impurities from the synthesis and analysis processes. The specific physicochemical properties are listed in Table 1. In Example 4, the alumina was in the same γ-Al2O3 crystal form as in Example 1.

[0077] Example 5

[0078] The method of Example 2 was followed, except that the aging treatment temperature in step (2) was 60°C. The composition of the alumina-titanium oxide composite oxide A5 was 19.3% by weight of titanium oxide and 79.5% by weight of alumina, with the remainder being trace impurities from the synthesis and analysis processes. The specific physicochemical properties are listed in Table 1. In Example 5, the alumina was in the same γ-Al2O3 crystal form as in Example 1.

[0079] Example 6

[0080] The method of Example 1 was followed, except that in step (1), the concentration of titanium oxide in the acidic solution containing aluminum and titanium was 31.75 g / L and the concentration of aluminum oxide was 46.64 g / L. The remaining conditions were the same as in Example 1. The resulting slurry was hydrothermally treated at 120°C for 4 hours, filtered, dried at 120°C for 6 hours, and calcined at 600°C for 3 hours to obtain alumina-titanium oxide composite oxide A6. The composition of alumina-titanium oxide composite oxide A6 was 29.3 wt% titanium oxide and 70.5 wt% aluminum oxide, with the remainder being trace impurities from the synthesis and analysis processes. Specific physicochemical properties are listed in Table 1. In Example 6, the aluminum oxide was in the same γ-Al₂O₃ crystal form as in Example 1.

[0081] Example 7

[0082] (1) The method of Example 1 is different except that in step (1), an acidic solution containing aluminum and titanium with different titanium oxide contents is used. Specifically, the titanium oxide concentration is 6.11 g / L, the aluminum oxide concentration is 58 g / L, and the flow rate is 120-130 g / min.

[0083] (2) The gelation reaction product is subjected to aging treatment. The aging treatment conditions are pH 8.0, temperature 70℃, and time 8h. The concentration of the aging mixture is 70g / L based on titanium dioxide-alumina.

[0084] (3) The aged mixture was filtered and washed sequentially to remove residual sodium and sulfate. The resulting filter cake (solid aged product) was then added to deionized water and slurried. The concentration of the resulting slurry was 130 g / L based on titanium dioxide-alumina. The resulting slurry was subjected to hydrothermal treatment at 170°C for 4 hours. After hydrothermal treatment, the mixture was spray-dried and then calcined at 600°C for 3 hours to obtain alumina-titanium dioxide composite oxide A7. The composition of alumina-titanium dioxide composite oxide A7 was 5.3 wt% titanium dioxide and 94.2 wt% alumina, with the remainder being trace impurities from the synthesis and analysis processes. The specific physicochemical properties are listed in Table 1. In Example 7, the alumina was in the same γ-Al2O3 crystal form as in Example 1.

[0085] Comparative Example 3

[0086] Following the method of Example 2, except that step (3) hydrothermal treatment was not performed, and after aging, the filter cake was obtained by filtration and washing, dried at 120°C for 6 hours, and calcined at 600°C for 3 hours to obtain alumina-titanium oxide composite oxide S3. The composition of alumina-titanium oxide composite oxide S3 is 19.3 wt% titanium oxide and 79.5 wt% alumina, with the remainder being trace impurities from the synthesis and analysis processes. The specific physicochemical properties are listed in Table 1. In Comparative Example 3, the alumina is the same as in Example 1, exhibiting the γ-Al2O3 crystal form.

[0087] Comparative Example 4

[0088] This embodiment uses the titration precipitation method described in patent application CN111050904A to prepare titanium oxide-alumina composite oxide. Sodium aluminate was diluted in water, and aluminum sulfate and titanium oxysulfate were added under vigorous stirring and heating at 60°C, resulting in a final pH of 6.5. The pH was adjusted to 7.2 using NaOH, and the mixture was aged at 60°C for 1 hour with stirring. The filter cake was re-slurryed with water, adjusted to pH 10 with ammonia, and aged at 95°C for 1 hour with stirring. Then, the slurry was filtered and washed with water to remove excess ammonia, dried, extruded, and calcined at 650°C or below for 1 hour with a gas flow rate of 10 mL / min and 25% (volume ratio) steam to obtain alumina-titanium oxide S4. The composition of alumina-titanium oxide S4 is 10.4 wt% titanium oxide and 88.9 wt% alumina, with the remainder being trace impurities from the synthesis and analysis processes. The specific physicochemical properties are listed in Table 1. In Comparative Example 4, the alumina is the same as in Example 1, exhibiting the γ-Al₂O₃ crystal form.

[0089] Table 1

[0090]

[0091]

[0092] As shown in Table 1, Examples 1-7 prepared using the method described in this invention all exhibit the anatase-γ-Al₂O₃ crystal form. When the preparation conditions are within the preferred range described in this invention, the most probable pore size of the alumina-titanium oxide composite oxide material is moderate, and it possesses a superior specific surface area. Compared to the comparative examples, the method described in this invention provides inexpensive and readily available raw materials for preparing the alumina-titanium oxide composite oxide material, and the preparation process is simple and short, allowing for the acquisition of the anatase-γ-Al₂O₃ crystal form composite oxide material.

[0093] Test case

[0094] The alumina-titanium oxide composite oxides of Examples 1-7 and Comparative Examples 1-4 were saturated with a mixed solution of ammonium molybdate heptahydrate, ammonia, and cobalt nitrate to make them contain 12.0% by weight of molybdenum oxide and 2.5% by weight of cobalt oxide, respectively. After drying, they were calcined at 450°C for 3 hours to prepare hydrodesulfurization catalysts.

[0095] In a fixed-bed continuous flow microreactor, a n-decane solution containing 1.0 wt% DBT (dibenzothiophene) and 1.0 wt% decahydronaphthalene was used as feedstock. The catalyst was loaded into the isothermal zone of the micro-fixed-bed reactor. Before the reaction, the catalyst underwent pre-sulfurization. The pre-sulfurization oil was a cyclohexane solution containing 5% CS2 (mass fraction). The pre-sulfurization temperature was 360℃, the hydrogen flow rate was 365 mL / min, the pre-sulfurization oil flow rate was 0.4 mL / min, and the pre-sulfurization pressure was 4 MPa. After pre-sulfurization, the catalyst was switched to the reaction oil. The hydrogenation reaction conditions were: reaction temperature 240℃, reaction pressure 4 MPa, hydrogen flow rate 100 mL / min, reaction oil flow rate 0.2 mL / min, and volumetric hourly space velocity (VHSV) 40 h⁻¹. -1 After the system stabilized, the product condensate was collected, and the product composition was analyzed by GC-MS.

[0096] Calculate the conversion rate x of DBT using the following formula:

[0097]

[0098] Where a represents the mass fraction of DBT in the product, and b represents the mass fraction of DBT in the raw material. The conversion rate data are shown in Table 2.

[0099] Table 2

[0100] DBT conversion rate (%) Example 1 79.22 Comparative Example 1 75.34 Comparative Example 2 74.17 Example 2 81.35 Example 3 84.46 Example 4 86.21 Example 5 77.02 Example 6 75.65 Example 7 76.12 Comparative Example 3 75.86 Comparative Example 4 65.17

[0101] As can be seen from Table 2, when the alumina-titanium oxide composite oxide material prepared by the method provided in this invention is used to prepare catalysts, the catalysts have better reactivity under the same conditions and can improve the conversion rate of the reaction raw materials.

[0102] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing an alumina-titanium oxide composite oxide, characterized in that, The method includes the following steps: (1) A gelling reaction is carried out between an acidic solution containing aluminum and titanium and an alkaline solution containing aluminum to obtain a solid gelling product; (2) In the presence of a precipitant, the solid gelling product obtained in step (1) is subjected to an aging reaction to obtain an aging reaction product; (3) The aging reaction product obtained in step (2) is subjected to hydrothermal treatment, and then dried and calcined to obtain alumina-titanium oxide composite oxide; In the aforementioned alumina-titanium oxide composite oxide, the titanium oxide is anatase and the alumina is γ-crystalline. Among them, the temperature of hydrothermal treatment is higher than that of aging reaction; The amounts of the acidic solution containing aluminum and titanium and the alkaline solution containing aluminum are such that, based on the total amount of the alumina-titanium oxide composite oxide, the content of aluminum oxide is 75-96% by weight and the content of titanium oxide is 4-25% by weight. The conditions for the aging reaction include: a temperature of 70-95℃, a time of 5-8 hours, and a pH value of 7.5-10. The temperature of the hydrothermal treatment is 10-100°C higher than the temperature of the aging reaction. In step (3), the conditions for hydrothermal treatment include: temperature 100-150℃ and time 2-9h.

2. The method according to claim 1, wherein, In step (1), the acidic solution containing aluminum and titanium is prepared by dissolving a titanium-containing compound in an acidic aluminum solution.

3. The method according to claim 2, wherein, The titanium-containing compound is titanium oxysulfate and / or titanium sulfate.

4. The method according to claim 2, wherein, In step (1), the acidic aluminum solution is selected from at least one of aluminum sulfate solution, aluminum nitrate solution and aluminum chloride solution.

5. The method according to claim 1, wherein, In step (1), the aluminum-containing alkaline solution is a sodium aluminate solution and / or a potassium aluminate solution.

6. The method according to claim 1, wherein, In step (1), the concentration of the acidic solution containing aluminum and titanium, calculated as aluminum oxide, is 35-120 g / L.

7. The method according to claim 6, wherein, In step (1), the concentration of the acidic solution containing aluminum and titanium, calculated as titanium oxide, is 5-80 g / L.

8. The method according to claim 1, wherein, In step (1), the concentration of the aluminum-containing alkaline solution, calculated as alumina, is 20-300 g / L.

9. The method according to claim 1 or 2, wherein, In step (1), the gelation reaction is carried out continuously or intermittently.

10. The method according to claim 9, wherein, In step (1), the gelation reaction is carried out continuously.

11. The method according to claim 1, wherein, In step (1), the conditions for the gelation reaction include: a temperature of 50-70℃ and a pH value of 4-7.

12. The method according to claim 1, wherein, In step (2), the precipitant is selected from compounds containing alkali metals.

13. The method according to claim 12, wherein, The alkali metal-containing compound is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

14. The method according to claim 1, wherein, The temperature of the hydrothermal treatment is 10-80°C higher than the temperature of the aging reaction.

15. The method according to claim 14, wherein, The temperature of the hydrothermal treatment is 20-70°C higher than the temperature of the aging reaction.

16. The method according to claim 1, wherein, In step (3), the roasting conditions include: a temperature of 500-700℃ and a time of 2-6h.

17. The method according to claim 1, wherein, This method does not use organic titanium-containing reagents.

18. The alumina-titanium oxide composite oxide prepared by the method according to any one of claims 1-17.

19. The alumina-titanium oxide composite oxide according to claim 18, wherein, Based on the total amount of alumina-titanium oxide composite oxide, the alumina content is 75-96% by weight and the titanium oxide content is 4-25% by weight.

20. The alumina-titanium oxide composite oxide according to claim 18, wherein, The alumina-titanium oxide composite oxide has a pore volume of 0.4-1.3 mL / g and a specific surface area of ​​200-400 m². 2 / g, with a most probable pore size of 5-12nm.

21. The alumina-titanium oxide composite oxide according to claim 20, wherein, The alumina-titanium oxide composite oxide has a pore volume of 0.5-0.9 mL / g and a specific surface area of ​​220-300 m² / g. 2 / g, with a most probable pore size of 7-11nm.

22. The application of the alumina-titanium oxide composite oxide according to any one of claims 18-21 in the hydrodesulfurization reaction.

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