Modified alumina catalyst, preparation method thereof and acrolein hydration reaction

Abstract

The invention provides a modified aluminum oxide catalyst, a preparation method thereof and an acrolein hydration reaction. The modified aluminum oxide catalyst comprises a fluorine element, a boron element, a phosphorus element and an aluminum element, wherein the molar ratio of the fluorine element to the boron element to the phosphorus element to the aluminum element is (0.05-0.6): (0.01-0.5): (0.01-0.3): 1. The modified aluminum oxide catalyst provided by the invention is obtained by modifying aluminum oxide by adopting a fluorine element, a boron element and a phosphorus element, the electronegativity of fluorine is relatively high, the deprotonation capability of aluminum hydroxyl is favorably improved, phosphorus hydroxyl is introduced after the phosphorus element is doped, and thus # imgabs0 # acid is favorably generated; after boron is doped, the crystal form of the aluminum oxide can be changed, so that the Lewis acid content is reduced, and the total acid content of the modified aluminum oxide is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a modified alumina catalyst and a preparation method thereof, and an acrolein hydration reaction. Background Art

[0002] 1,3-propylene glycol (1,3-PDO) is a colorless, odorless, viscous liquid and a key monomer for the production of high-performance polytrimethylene terephthalate (PTT). PTT has excellent toughness and colorability, is recyclable, and is biodegradable. In recent years, PTT has received widespread attention. In addition, 1,3-propylene glycol is also widely used in the pharmaceutical industry, food and cosmetics industry as an important chemical raw material. At present, the demand for 1,3-propylene glycol is relatively strong, but domestic production capacity is insufficient and mainly relies on imports.

[0003] At present, there are three main methods for producing 1,3-propylene glycol in industry: acrolein hydration hydrogenation, ethylene oxide carbonylation, and biological fermentation. The above three processes for producing 1,3-propylene glycol all require 3-hydroxypropanal as a key intermediate. The ethylene oxide carbonylation reaction requires high pressure conditions, large equipment investment, and a complex catalytic system with high technical difficulty. The biological fermentation method has developed rapidly in recent years, but the corresponding strain technology in China is still immature and the cost is too high. The process conditions of acrolein hydration hydrogenation are relatively mild, the technical difficulty is not great, and the hydrogenation process is relatively mature. Therefore, the use of acrolein to prepare 1,3-propylene glycol still has certain advantages.

[0004] Acrolein is a very active α,β-unsaturated carbonyl compound that easily undergoes self-polymerization at room temperature. In the acrolein hydration hydrogenation method, acrolein hydration is the most critical step; the reason is that acrolein and 3-hydroxypropanal are both very active, and both will undergo side reactions such as self-polymerization and polycondensation in aqueous solution, and these side reactions will intensify with increasing temperature, which will not only lead to waste of raw materials, but also some by-products that are difficult to separate will affect the purity of the product; therefore, the development of an efficient and highly selective hydration catalyst is the key to the acrolein hydration hydrogenation method.

[0005] The hydration of acrolein to form 3-hydroxypropionaldehyde is an acid-catalyzed addition process. The strength and type of the acid have a great influence on the reaction. If the strength of the catalyst acid is not enough, the conversion rate of the reactants is very low. If the strength of the acid is too high, it will lead to an increase in side reactions.

[0006] The hydration reaction of acrolein in a heterogeneous system is the focus of current research, among which chelate resin catalysts are widely studied and have successful industrial application examples. The active groups of chelate resin catalysts are basically concentrated in aminophosphoric acid, aminocarboxylic acid, amide carboxylic acid, thiocarboxylic acid and other categories; in recent years, some chelate ion exchange resins for metal ion exchange have also been developed. However, there are still some problems with the above catalysts, such as the catalyst life is not long, and the selectivity and conversion rate will decrease in the long-term operation of 200h. This is because its active groups will fall off during the long-term operation process; in order to make up for the loss of conversion rate, it is generally necessary to increase the temperature, but the increase in temperature often leads to the intensification of side reactions such as polymerization, thereby affecting the conversion rate, so the process operation stability is poor. In addition, the applicable space velocity of chelate resin catalysts is generally low, and the time efficiency is poor.

[0007] At present, the conversion rate and selectivity of the hydration reaction catalyzed by resin catalysts and immobilized inorganic acid systems are not very ideal. In addition, the conversion rate and selectivity of the resin catalyst system will decrease during long-term operation. The US patent application with patent publication number US5276201A prepared H by impregnation method. 3 PO 4 / TiO 2 、NaH 2 PO 4 / TiO 2 , H 3 PO 4 / γ-Al 2 O 3 、NaH 2 PO 4 / γ-Al 2 O 3 Four catalysts were prepared and their catalytic effects on the hydration reaction of acrolein were studied. An 18.5% aqueous solution of acrolein was used as the raw material, and H 3 PO 4 / TiO 2 As a catalyst, after 1 h at 70 °C, the conversion rate of acrolein reached 42% and the selectivity was 81%. Further studies have shown that in a fixed bed reactor, the use of H 3 PO 4 / TiO 2 As a catalyst, when the reaction temperature is 50-70°C, after a long period of 900h, the reaction conversion rate can be maintained at 50%±2% and the selectivity is 81%±2%. The immobilized inorganic acid catalyst has a certain stability, but its conversion rate and selectivity are not very ideal. Therefore, it is still of great significance to develop a highly efficient and highly selective hydration catalyst. Summary of the invention

[0008] The main purpose of the present invention is to provide a modified alumina catalyst and a preparation method thereof, and an acrolein hydration reaction, so as to solve the problems of short service life and low selectivity of the catalyst used in the acrolein hydration reaction in the prior art.

[0009] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a modified alumina catalyst is provided, which comprises fluorine, boron, phosphorus and aluminum, and the molar ratio of fluorine, boron, phosphorus and aluminum is 0.05-0.6:0.01-0.5:0.01-0.3:1.

[0010] Furthermore, the molar ratio of the fluorine element, the boron element, the phosphorus element and the aluminum element is 0.1-0.4:0.05-0.3:0.05-0.2:1.

[0011] Furthermore, the molar concentration of total acid in the above-mentioned modified alumina catalyst is 2.07-2.50 mmol / g; and / or, the molar concentration of B acid in the modified alumina catalyst is 0.75-0.98 mmol / g; and / or, the molar concentration of L acid in the modified alumina catalyst is 1.10-1.68 mmol / g; and / or, the particle size of the modified alumina catalyst is 20-40 mesh.

[0012] According to another aspect of the present invention, a method for preparing the aforementioned modified alumina catalyst is provided, the preparation method comprising: sequentially mixing, drying and calcining raw materials including alumina, a fluorine source, a boron source, a phosphorus source and water to obtain a modified alumina catalyst.

[0013] Furthermore, the temperature of the mixing treatment is 20-50° C.; and / or the mixing treatment time is 1-6 hours; preferably, the mixing treatment temperature is 30-40° C.; and / or the mixing treatment time is 2-4 hours.

[0014] Furthermore, the temperature of the above-mentioned calcination treatment is 550-800°C; and / or the calcination treatment time is 4-8h; and / or the fluorine source is any one or more of ammonium fluoride, ammonium tetrafluoroborate and ammonium hexafluorophosphate; and / or the boron source is selected from any one or more of boric acid, ammonium borate and ammonium tetrafluoroborate; and / or the phosphorus source is selected from any one or more of diammonium phosphate, phosphoric acid and ammonium hexafluorophosphate.

[0015] Furthermore, the above-mentioned aluminum oxide is aluminum oxide that has been subjected to acidification treatment; and / or the mass ratio of the acidification treatment reagent to the aluminum oxide is 1 to 2:1; and / or the acidification treatment temperature is 20 to 30°C; and / or the acidification treatment time is 1 to 3 hours; preferably, the acidification treatment reagent is a nitric acid solution, and the mass concentration of the nitric acid solution is 3 to 18wt%, preferably 7 to 15wt%.

[0016] Furthermore, the preparation method further comprises: subjecting the calcined product to molding and crushing treatments in sequence to obtain a modified alumina catalyst; wherein the molding treatment pressure is 20 to 25 MPa; and / or the molding treatment time is 2 to 4 minutes.

[0017] Furthermore, the specific surface area of ​​the above-mentioned aluminum oxide is 120 to 250 m 2 / g, preferably 150 to 200 m 2 / g.

[0018] According to another aspect of the present invention, there is provided an acrolein hydration reaction, in which acrolein is hydrated under the action of a catalyst to prepare 3-hydroxypropionaldehyde, and the catalyst is the aforementioned modified alumina catalyst.

[0019] The modified alumina catalyst of the present invention is obtained by modifying alumina with fluorine, boron and phosphorus. Fluorine has a high electronegativity, which helps to improve the deprotonation ability of aluminum hydroxyl groups. After doping with phosphorus, phosphorus hydroxyl groups are introduced, thereby helping to generate Acid; after being doped with boron, the alumina crystal form will be changed, which helps to reduce the amount of Lewis acid, so that the total acid amount of the modified alumina is reduced. It is preferred to control the molar ratio of fluorine, boron, phosphorus and aluminum within the above range, which helps to control the B / L acid ratio of the modified alumina catalyst within a certain range, thereby helping to improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction and the service life of the catalyst, and further helps to improve the conversion rate and selectivity of the acrolein hydration reaction. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0021] As analyzed in the background technology of the present application, the catalysts used in the prior art for acrolein hydration reaction have the problems of short service life and low selectivity. In order to solve this problem, the present application provides a modified alumina catalyst and a preparation method thereof, and an acrolein hydration reaction.

[0022] It should be noted that B acid refers to a substance that can donate protons; L acid refers to a substance that can accept electron pairs; and the B / L acid ratio represents the ratio of the molar concentration of B acid to the molar concentration of L acid.

[0023] In a typical embodiment of the present application, a modified alumina catalyst is provided, which includes fluorine, boron, phosphorus and aluminum, and the molar ratio of fluorine, boron, phosphorus and aluminum is 0.05-0.6:0.01-0.5:0.01-0.3:1.

[0024] The modified alumina catalyst of the present application is obtained by modifying alumina with fluorine, boron and phosphorus. Fluorine has a high electronegativity, which helps to improve the deprotonation ability of aluminum hydroxyl groups. After doping with phosphorus, phosphorus hydroxyl groups are introduced, thereby helping to produce Acid; after being doped with boron, the alumina crystal form will be changed, which helps to reduce the amount of Lewis acid, so that the total acid amount of the modified alumina is reduced. It is preferred to control the molar ratio of fluorine, boron, phosphorus and aluminum within the above range, which helps to control the B / L acid ratio of the modified alumina catalyst within a certain range, thereby helping to improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction and the service life of the catalyst, and further helps to improve the conversion rate and selectivity of the acrolein hydration reaction.

[0025] In order to further control the B / L acid ratio of the modified alumina catalyst within an appropriate range, in one embodiment of the present application, the molar ratio of the above-mentioned fluorine element, boron element, phosphorus element and aluminum element is preferably 0.1-0.4:0.05-0.3:0.05-0.2:1.

[0026] In one embodiment of the present application, the molar concentration of total acid in the above-mentioned modified alumina catalyst is 2.07-2.50 mmol / g, and / or the molar concentration of B acid in the modified alumina catalyst is 0.75-0.98 mmol / g, and / or the molar concentration of L acid in the modified alumina catalyst is 1.10-1.68 mmol / g; and / or the particle size of the modified alumina catalyst is 20-40 mesh.

[0027] The acid amount of the modified alumina catalyst within the above range helps to improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction and the service life of the catalyst, thereby helping to improve the conversion rate and selectivity of the acrolein hydration reaction. It is preferred to control the particle size of the modified alumina catalyst within the above range, which helps to increase the active sites of the catalyst and the structural stability of the catalyst, thereby helping to improve the service life of the catalyst and the conversion rate and selectivity of the acrolein hydration reaction.

[0028] In another typical embodiment of the present application, a method for preparing the aforementioned modified alumina catalyst is provided, the preparation method comprising: sequentially mixing, drying and calcining raw materials including alumina, a fluorine source, a boron source, a phosphorus source and water to obtain a modified alumina catalyst.

[0029] By first mixing alumina, a fluorine source, a boron source, a phosphorus source and water, it is helpful to evenly distribute the fluorine source, the boron source and the phosphorus source on the surface of the alumina, and the precursor after the mixing treatment is calcined to help form Al-F bonds, Al-OP bonds and Al-OB bonds, while removing other impurity elements. The modified alumina catalyst prepared by the above preparation method has a B / L acid ratio in a suitable range, which helps to improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction and the service life of the catalyst, thereby helping to improve the conversion rate and selectivity of the acrolein hydration reaction.

[0030] In one embodiment of the present application, the temperature of the above-mentioned mixing treatment is 20-50°C; and / or, the mixing treatment time is 1-6h; preferably, the mixing treatment temperature is 30-40°C; and / or, the mixing treatment time is 2-4h; and / or, the calcination treatment temperature is 550-800°C; and / or, the calcination treatment time is 4-8h; and / or, the fluorine source is any one or more of ammonium fluoride, ammonium tetrafluoroborate and ammonium hexafluorophosphate; and / or, the boron source is selected from any one or more of boric acid, ammonium borate and ammonium tetrafluoroborate; and / or, the phosphorus source is selected from any one or more of diammonium phosphate, phosphoric acid and ammonium hexafluorophosphate.

[0031] It is preferred to control the temperature and time of the mixing treatment within the above range, which helps to further improve the uniformity of the dispersion of the fluorine source, boron source and phosphorus source on the surface of alumina and the interaction between the fluorine source, boron source and phosphorus source and the surface of alumina, thereby helping to further improve the catalytic activity of the modified alumina catalyst. It is preferred to control the temperature and time of the calcination treatment within the above range, which helps to further improve the catalytic activity of the modified alumina catalyst. It is preferred to control the types of the fluorine source, boron source and phosphorus source within the above range, which helps to improve the interaction between the fluorine source, boron source and phosphorus source and the surface of alumina, thereby helping to control the B / L acid ratio of the modified alumina catalyst within a certain range, thereby helping to improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction and the service life of the catalyst, thereby helping to improve the conversion rate and selectivity of the acrolein hydration reaction.

[0032] In one embodiment of the present application, the above-mentioned aluminum oxide is aluminum oxide that has been subjected to acidification treatment; and / or, the mass ratio of the acidification treatment reagent to the aluminum oxide is 1 to 2:1; and / or, the acidification treatment temperature is 20 to 30°C; and / or, the acidification treatment time is 1 to 3 hours; preferably, the acidification treatment reagent is a nitric acid solution, and the mass concentration of the nitric acid solution is 3 to 18wt%, preferably 7 to 15wt%.

[0033] Alumina after acidification has more active sites, which helps to improve the catalytic activity of the modified alumina catalyst on the one hand, and helps to improve the interaction between alumina and fluorine source, boron source and phosphorus source on the other hand, thereby helping to further improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction and the service life of the catalyst, thereby helping to improve the conversion rate and selectivity of the acrolein hydration reaction. Excessive acidification is not conducive to maintaining the stability of the alumina structure, and insufficient acidification is not conducive to making the alumina surface have sufficient active sites. It is preferred to control the mass ratio of the acidification reagent to the alumina, the temperature and time of the acidification treatment within the above range, which helps to make the surface of the alumina have abundant active sites while taking into account its stability, thereby helping to further improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction. It is preferred to control the acidification reagent to be a nitric acid solution, and control the mass concentration of the nitric acid solution within the above range, which helps to further improve the catalytic activity of the modified alumina catalyst.

[0034] In order to make the modified alumina catalyst suitable for fixed bed reactors and expose more active sites, in one embodiment of the present application, it is preferred that the above-mentioned preparation method also includes: subjecting the calcined product to molding and crushing to obtain a modified alumina catalyst; wherein the molding pressure is 20 to 25 MPa; and / or the molding time is 2 to 4 min.

[0035] In order to further improve the stability and catalytic activity of the modified alumina catalyst, in one embodiment of the present application, the specific surface area of ​​the alumina is preferably 120 to 250 m 2 / g, preferably 150 to 200 m 2 / g.

[0036] In another typical embodiment of the present application, an acrolein hydration reaction is provided, in which acrolein is hydrated to obtain 3-hydroxypropionaldehyde under the action of a catalyst, and the catalyst is the aforementioned modified alumina catalyst.

[0037] Since the catalyst in the above-mentioned acrolein hydration reaction is the modified alumina catalyst of the present application, the acrolein hydration reaction has a higher conversion rate and selectivity.

[0038] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0039] Example 1

[0040] 11.84 g of ammonium fluoride, 4.95 g of boric acid and 9.8 g of phosphoric acid were added to 200 mL of water and stirred until they were completely dissolved into a transparent clear solution. 40 g of alumina (with a specific surface area of ​​170 m 2 / g) is added to the above-mentioned mixed solution and stirred in a water bath at 40°C for 2h for mixing. The solution is then poured into a watch glass and dried in an oven at 110°C for 5h. After drying, the block alumina is ground into powder using a mortar, and the powder is calcined at 550°C for 4h. The catalyst powder is filled into a mold and maintained at a pressure of 20MPa for 2 minutes. The tablets are crushed and a modified alumina catalyst with a size of 20 to 40 mesh is sieved out using a sieve. Among them, the molar ratio of fluorine, boron, phosphorus and aluminum in the modified alumina catalyst is 0.4:0.1:0.1:1.

[0041] Example 2

[0042] The difference from Example 1 is that the mass of ammonium fluoride is 8.88 g, the mass of boric acid is 3.96 g, and the mass of phosphoric acid is 7.84 g, and the modified alumina catalyst is finally obtained. The molar ratio of fluorine element, boron element, phosphorus element and aluminum element in the modified alumina catalyst is 0.3:0.08:0.08:1.

[0043] Example 3

[0044] The difference from Example 1 is that the mass of ammonium fluoride is 11.84 g, the mass of boric acid is 4.95 g, and the mass of phosphoric acid is 7.84 g, and the modified alumina catalyst is finally obtained. The molar ratio of fluorine element, boron element, phosphorus element and aluminum element in the modified alumina catalyst is 0.4:0.1:0.08:1.

[0045] Example 4

[0046] The difference from Example 1 is that the mass of ammonium fluoride is 8.88 g, the mass of boric acid is 3.96 g, and the mass of phosphoric acid is 9.8 g, and the modified alumina catalyst is finally obtained. The molar ratio of fluorine element, boron element, phosphorus element and aluminum element in the modified alumina catalyst is 0.3:0.08:0.1:1.

[0047] Example 5

[0048] The difference from Example 1 is that ammonium tetrafluoroborate is used to replace ammonium fluoride and boric acid, the mass of ammonium tetrafluoroborate is 8.16 g and the mass of phosphoric acid is 9.8 g, and a modified alumina catalyst is finally obtained. The molar ratio of fluorine, boron, phosphorus and aluminum in the modified alumina catalyst is 0.4:0.1:0.1:1.

[0049] Example 6

[0050] The difference from Example 5 is that the specific surface area of ​​alumina is 120 m 2 / g, and finally obtained modified alumina catalyst.

[0051] Example 7

[0052] The difference from Example 5 is that the temperature of the mixing treatment is 30° C., and a modified alumina catalyst is finally obtained.

[0053] Example 8

[0054] The difference from Example 5 is that the mixing treatment time is 4 hours, and a modified alumina catalyst is finally obtained.

[0055] Example 9

[0056] The difference from Example 5 is that the temperature of the mixing treatment is 50° C., and a modified alumina catalyst is finally obtained.

[0057] Example 10

[0058] The difference from Example 5 is that the alumina is acid-treated alumina. Specifically, 40 g of alumina is added to 40 g of nitric acid solution. The mass concentration of the nitric acid solution is 15 wt %. The mixture is stirred at 25° C. for 1 hour. After the acidification treatment is completed, it is rinsed with ultrapure water. The washed sample is dried to remove moisture to obtain acid-treated alumina, and finally a modified alumina catalyst is obtained.

[0059] Embodiment 11

[0060] The difference from Example 5 is that the alumina is acid-treated alumina. Specifically, 40 g of alumina is added to 40 g of nitric acid solution. The mass concentration of the nitric acid solution is 5 wt%, and the mixture is stirred at 25°C for 1 hour. After the acidification treatment is completed, it is rinsed with ultrapure water, and the washed sample is dried to remove moisture to obtain acid-treated alumina, and finally a modified alumina catalyst is obtained.

[0061] Example 12

[0062] The difference from Example 5 is that the alumina is acid-treated alumina. Specifically, 40 g of alumina is added to 40 g of nitric acid solution. The mass concentration of the nitric acid solution is 20 wt %. The mixture is stirred at 25° C. for 1 hour. After the acidification treatment is completed, it is rinsed with ultrapure water. The washed sample is dried to remove moisture to obtain acid-treated alumina, and finally a modified alumina catalyst is obtained.

[0063] Comparative Example 1

[0064] The difference from Example 1 is that the aluminum oxide is not modified in any way.

[0065] Performance Testing

[0066] The catalysts prepared in the above examples and comparative examples were tested for B acid, L acid and total acid, and the catalysts were applied to acrolein hydration reaction. Specifically, 5 g of catalyst particles (20-40 mesh) were loaded into a fixed bed tubular reactor, and the reactor temperature was raised to 60°C. A metering pump was used for 2 h. -1 A 15% mass fraction of acrolein aqueous solution (containing 500 ppm of hydroquinone inhibitor) was pumped through the fixed bed at a constant rate. The reaction temperature was set to 60°C. After this state was maintained for 5 hours to establish steady-state conditions, the effluent was cooled and collected after 4 hours of reaction. The liquid composition was analyzed by gas chromatography, and the conversion rate of acrolein and the selectivity for generating 3-hydroxypropanal were calculated. The results of the B acid amount, L acid amount, total acid amount, the conversion rate of acrolein and the selectivity for generating 3-hydroxypropanal are shown in Table 1.

[0067] The catalysts prepared in Examples 5 and 10 were subjected to long-term evaluation. Specifically, 5 g of catalyst particles (20-40 mesh) were loaded into a fixed bed tubular reactor, and the reactor temperature was raised to 60°C. A metering pump was used to pump the catalyst particles at a rate of 2 h. -1 A 15% mass fraction of acrolein aqueous solution (containing 500 ppm of hydroquinone inhibitor) was pumped through the fixed bed at a constant rate. The reaction temperature was set to 60°C and maintained at this state for 5 hours to establish steady-state conditions. After reacting for 300 hours, the effluent was cooled and collected, and the liquid composition was analyzed by gas chromatography, and the conversion rate of acrolein and the selectivity of generating 3-hydroxypropanal were calculated. The results are shown in Table 2.

[0068] Table 1

[0069]

[0070]

[0071] Table 2

[0072] Example Conversion rate / (%) Selectivity / (%) Example 5 73.5 91.2 Example 10 73.8 91.6

[0073] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0074] The modified alumina catalyst of the present application is obtained by modifying alumina with fluorine, boron and phosphorus. Fluorine has a high electronegativity, which helps to improve the deprotonation ability of aluminum hydroxyl groups. After doping with phosphorus, phosphorus hydroxyl groups are introduced, thereby helping to produce Acid; after being doped with boron, the alumina crystal form will be changed, which helps to reduce the amount of Lewis acid, so that the total acid amount of the modified alumina is reduced. It is preferred to control the molar ratio of fluorine, boron, phosphorus and aluminum within the above range, which helps to control the B / L acid ratio of the modified alumina catalyst within a certain range, thereby helping to improve the catalytic activity of the modified alumina catalyst in the acrolein hydration reaction and the service life of the catalyst, and further helps to improve the conversion rate and selectivity of the acrolein hydration reaction.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A modified alumina catalyst, characterized in that: The modified alumina catalyst comprises fluorine, boron, phosphorus and aluminum, and the molar ratio of the fluorine, boron, phosphorus and aluminum is 0.05-0.6:0.01-0.5:0.01-0.3:

1.

2. The modified alumina catalyst according to claim 1, characterized in that The molar ratio of the fluorine element, the boron element, the phosphorus element and the aluminum element is 0.1-0.4:0.05-0.3:0.05-0.2:

1.

3. The modified alumina catalyst according to claim 1 or 2, characterized in that The molar concentration of total acid in the modified alumina catalyst is 2.07 to 2.50 mmol / g; and / or, the molar concentration of B acid in the modified alumina catalyst is 0.75 to 0.98 mmol / g; and / or, the molar concentration of L acid in the modified alumina catalyst is 1.10 to 1.68 mmol / g; And / or, the particle size of the modified alumina catalyst is 20 to 40 meshes.

4. A method for preparing a modified alumina catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises: The raw materials including alumina, a fluorine source, a boron source, a phosphorus source and water are sequentially mixed, dried and calcined to obtain a modified alumina catalyst.

5. The preparation method according to claim 4, characterized in that: The temperature of the mixing treatment is 20 to 50° C.; and / or the time of the mixing treatment is 1 to 6 hours; Preferably, the temperature of the mixing treatment is 30-40° C.; and / or the time of the mixing treatment is 2-4 hours.

6. The preparation method according to claim 4 or 5, characterized in that: The calcination temperature is 550-800°C; and / or the calcination time is 4-8h; And / or, the fluorine source is any one or more of ammonium fluoride, ammonium tetrafluoroborate and ammonium hexafluorophosphate; and / or, the boron source is selected from any one or more of boric acid, ammonium borate and ammonium tetrafluoroborate; and / or, the phosphorus source is selected from any one or more of diammonium phosphate, phosphoric acid and ammonium hexafluorophosphate.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The aluminum oxide is aluminum oxide that has been acidified; and / or, the mass ratio of the acidification reagent to the alumina is 1 to 2:1; and / or, the temperature of the acidification treatment is 20 to 30° C.; and / or, the time of the acidification treatment is 1 to 3 hours; Preferably, the reagent for the acidification treatment is a nitric acid solution, and the mass concentration of the nitric acid solution is 3 to 18 wt %, preferably 7 to 15 wt %.

8. The preparation method according to any one of claims 4 to 7, characterized in that The preparation method further comprises: The product after the calcination treatment is subjected to molding treatment and crushing treatment in sequence to obtain the modified alumina catalyst; wherein the pressure of the molding treatment is 20 to 25 MPa; and / or the time of the molding treatment is 2 to 4 minutes.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The specific surface area of ​​the alumina is 120 to 250 m 2 / g, preferably 150 to 200 m 2 / g.

10. An acrolein hydration reaction, wherein acrolein is hydrated under the action of a catalyst to prepare 3-hydroxypropionaldehyde, characterized in that: The catalyst is the modified alumina catalyst according to any one of claims 1 to 3.

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