Boron-containing metal doped catalyst as well as preparation method and application thereof

Abstract

The invention discloses a boron-containing metal doped catalyst and a preparation method and application thereof.The catalyst comprises active metal components existing in the form of phosphate and a boron-containing compound, the active metal components comprise a first active metal component Li and further comprise at least one of second active metal components Be, Na, K, Mg, Zn, Fe and Ba, and the boron-containing compound is a boron-containing compound. The second active metal component at least accounts for 5.3 wt% of the catalyst, and the boron-containing compound accounts for 1.3 wt% of the catalyst. The catalyst provided by the invention improves the conversion rate and selectivity in catalyzing the isomerization reaction of epoxypropane, and especially improves the stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and in particular relates to a boron-containing metal-doped catalyst and a preparation method and application thereof. BACKGROUND

[0002] Allyl alcohol compounds are important chemical intermediates and fine chemical products. Due to the presence of both carbon-carbon double bonds and hydroxyl groups in the molecular structure, allyl alcohol can undergo various chemical reactions with ethers, esters, aldehydes and other compounds, and has wide application potential. Common industrial synthesis methods of allyl alcohol include isomerization of propylene oxide, hydrolysis of chloropropene, reduction of propenal and hydrolysis of propenyl acetate. At present, foreign countries mainly use the isomerization of propylene oxide to produce allyl alcohol. This method is widely used due to its simple process, high yield and no pollution. Patent US7847135B1 proposes a lithium phosphate catalyst containing boron for isomerization of propylene oxide, but the conversion rate is between 25.8-58.6%, which is not high. Patent CN118022786A proposes a phosphate catalyst doped with alkaline earth metals, which greatly improves the conversion rate to 70-96% in the application of isomerization of propylene oxide. Although these patents solve the problem of low conversion rate, the stability has not been significantly improved. The existing catalysts for isomerization of propylene oxide are prone to coking and carbon deposition, which further leads to the decline of the catalytic performance of the catalyst. Therefore, it is necessary to develop a catalyst with anti-coking and high stability to solve this problem. SUMMARY

[0003] Therefore, the present application aims to provide a boron-containing metal-doped catalyst to solve the technical problems of poor stability of existing catalysts, easy coking and carbon deposition, and further decline of the performance of the catalyst.

[0004] To achieve the above-mentioned purposes, the technical solution of the present application is as follows:

[0005] A boron-containing metal-doped catalyst, the catalyst comprising an active metal component in the form of a phosphate and a boron-containing compound,

[0006] The active metal component comprises a first active metal component Li, and further comprises at least one of a second active metal component Be, Na, K, Mg, Zn, Fe and Ba, and the second active metal component accounts for at least 5.3wt% of the catalyst, and the boron-containing compound accounts for 1.3wt% of the catalyst.

[0007] The optimization of the phosphate to the cation helps to improve the selectivity and promote the stability of the catalyst.

[0008] Further, the molar ratio of the second active metal component (in terms of phosphate in phosphate salt), the boron-containing compound and the first active metal component is (0.2-1):(0.15-1):(0.5-5); preferably (0.25-0.8):(0.18-0.8):(0.6-4); further preferably (0.3-0.6):(0.2-0.5):(0.8-2). By optimizing the amount of different elements, the catalytic activity of the prepared metal-doped catalyst can be improved.

[0009] Further, the boron-containing compound is at least one of boric acid, boric acid salt, and boron phosphate.

[0010] Further, the average particle size of the catalyst is 20-50 nm. The prepared nanoscale metal-doped catalyst can provide a larger specific surface area, which not only reduces the diffusion resistance of the catalyst particles in the catalytic reaction, but also exposes more active sites, thereby improving the activity of the catalyst and more effectively catalyzing the reaction.

[0011] The anion of the catalyst is mainly phosphate. In the isomerization reaction of propylene oxide, the Lewis acid metal cation can produce a synergistic effect with the phosphate to isomerize propylene oxide into the target product allyl alcohol. The catalyst has the advantages of easy control of reaction conditions, high catalytic activity, few side reactions, and good selectivity. The above technical solution can obtain a metal-doped catalyst by optimizing the active components and preparation process. The traditional lithium phosphate catalyst has the disadvantages of low reaction activity and poor stability. By doping with metal and boron, the catalyst exhibits better catalytic performance, especially in stability.

[0012] Specifically, the reaction formula of the metal-doped catalyst prepared by the above technical solution in the isomerization reaction of propylene oxide is shown in formula (1). Boronic acid compounds also participate in the reaction, but the specific mechanism is not clear, so it is not listed:

[0013]

[0014] The metal-doped catalyst prepared by using lithium hydroxide and boron reagent and one or more elements of Be, Na, K, Mg, Zn, Fe, and Ba phosphate as active components has the advantages of high catalyst activity, few by-products, and high stability in the isomerization reaction of propylene oxide. It is speculated that the boron element enhances the reaction activity in the preparation process of the catalyst in the above technical solution, and the addition of M element further enhances the stability of the catalyst. Further combining the ultrasonic treatment in step S2 can promote the precipitation process of catalyst preparation to be more uniform, improve the structural stability of the prepared catalyst, and make the particle size of the prepared metal-doped catalyst more uniform, which is beneficial to improving the catalytic activity of the catalyst.

[0015] The molar ratio of the second active metal component (calculated based on the phosphate in the phosphate salt), the boron-containing compound and lithium element in the mixed solution obtained in step S2 is (0.2-1):(0.15-1):(0.5-5); preferably (0.25-0.8):(0.18-0.8):(0.6-4); further preferably (0.3-0.6):(0.2-0.5):(0.8-2); and / or,

[0016] The concentration of lithium element, the second active metal component and the boron-containing compound in the mixed solution obtained in step S2 is 0.02-0.8 mol / mL, preferably 0.05-0.08 mol / mL. This is advantageous for improving the stability of the subsequent reaction system.

[0017] Further, the phosphate salt solution of the second active metal component in step S2 is added dropwise to the mixed solution in step S1; preferably, the dropwise adding speed is 10-200 mL / min, preferably 20-120 mL / min; and / or,

[0018] The step S2 adopts the dropwise adding mode to add the M-containing metal phosphate salt solution to the lithium hydroxide solution container containing boron element to carry out the reaction, which is advantageous for controlling the reaction progress and improving the operability. In addition, the specific operation device for the dropwise adding operation of the M-containing metal phosphate salt solution in step S2 is not limited, and a plunger pump, a microsyringe, a diaphragm pump and the like can be selected, and the person skilled in the art can select according to the actual working condition, and the protection scope of the present application is not limited thereby.

[0019] The ultrasonic power of the ultrasonic condition is 50-600 W, the ultrasonic time is greater than the dropwise adding time of the phosphate salt solution of the second active metal component to the mixed solution in step S1, and the ultrasonic temperature is 60-70℃, preferably 65℃. The ultrasonic operation can promote the generation of uniform and finer precipitated particles in step S2.

[0020] The ultrasonic time in step S2 is greater than the dropwise adding time, and after the dropwise adding is completed, the ultrasonic operation is continued for a certain time to improve the uniformity of the generated precipitate. The time for continuing the dropwise adding after the dropwise adding is completed is not limited in the present application, for example, the ultrasonic operation can be continued for about 10-20 min, and the person skilled in the art can set it in the actual process

[0021] Further, the washing operation in step S3 includes: adding the solid obtained by solid-liquid separation into water with the same weight as before separation, and washing the solid at 30-100℃ until the pH is 12-14, preferably washing the solid at 60-90℃ until the pH is 12.5-13.

[0022] The specific operation of solid-liquid separation of the post-reaction material after the metal precipitation reaction is not limited, and the purpose of the solid-liquid separation operation is to separate the solid phase of the post-reaction material from the liquid phase, and a person skilled in the art can select a suitable solid-liquid separation method according to the needs, such as filtration, suction filtration, centrifugal separation, decantation, gravity sedimentation and the like, and the protection scope of the present application is not limited thereby. Washing can remove the residual impurities on the surface of the solid, which is beneficial to improve the efficiency of the subsequent roasting and activation operation and to improve the catalytic performance and stability of the prepared metal-doped catalyst.

[0023] Further, the temperature of the roasting operation in step S3 is 300-700 DEG C, and the roasting time is 1-30 h; preferably, the temperature of the roasting operation in step S3 is 400-550 DEG C, and the roasting time is 15-20 h. By optimizing the roasting conditions, the catalytic activity and stability of the catalyst are improved, and the catalyst is prevented from caking and sintering.

[0024] The application of the above-mentioned catalyst or the catalyst prepared by the above-mentioned preparation method in the preparation of propylene alcohol by isomerization of propylene oxide. The catalyst is sieved to an approximate size after being pressed into a sheet, and is loaded on silica from top to bottom. The catalyst is placed in the center area of the reactor. In the reaction process, propylene oxide is introduced into the reactor by inert gas as the carrier gas. After the reaction is completed, the product is collected by condensation in a cold trap. Finally, the obtained product is separated by gas chromatography.

[0025] The reactor for the isomerization reaction of propylene oxide in the present application is a fixed bed reactor, and the specific structure and specifications are not limited. The volume of the reaction tube of the fixed bed reactor can be selected to be 10-1000 mL, and the pressure resistance is 8-10 MPa.

[0026] Compared with the prior art, the metal-doped catalyst containing boron and the preparation method and application thereof have the following advantages:

[0027] The preparation method of the catalyst in the present application uses a specific kind of element as an active component, and a metal-doped catalyst is prepared by combining ultrasonic operation. The catalyst exhibits better catalytic performance in the catalytic isomerization reaction of propylene oxide, especially in stability, so that the overall reaction conditions are mild and easy to control, and the product yield is high. The metal-doped catalyst method has important industrialization popularization and application value. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0029] The present application will be described in detail below with reference to the embodiments.

[0030] Embodiment 1

[0031] A boron-containing metal-doped catalyst, the preparation of which comprises the following steps:

[0032] (1) M is selected as Be, Be3(PO4)2, Na2B4O7, LiOH are weighed as 54.25g, 60.37g, 45.51g respectively according to n(P):n(B):n(Li) as 0.5:0.3:1.9, the boron reagent and lithium hydroxide are put into a container and then deionized water is added to dissolve to obtain solution A, the M-containing reagent is dissolved in another container with deionized water, stirring until no precipitate is obtained to obtain phosphate solution B; the two solutions are kept at 65℃ and the molar concentration of the substances in the two solutions is 0.05 mol / mL;

[0033] (2) phosphate solution B is added to solution A at a speed of 100 mL / min, and stirring is continued under the condition of ultrasonic 300W, until the solid is completely precipitated;

[0034] (3) after the co-precipitation is completed, solid-liquid separation is carried out, the solid is washed at 80℃, the pH is measured as 12.5, after drying, the catalyst is obtained by calcining at 500℃ for 18h.

[0035] Example 2

[0036] A boron-containing metal-doped catalyst, the process and raw material parameters of the preparation of which are the same as those of example 1, the difference is that: M is selected as Na, Na3PO4, Na2B4O7, LiOH are weighed as 81.97g, 40.24g, 35.93g respectively according to n(P):n(B):n(Li) as 0.5:0.2:1.5, the molar concentration of the substances in the two solutions is 0.07 mol / mL; the speed of adding phosphate solution B to solution A is 40 mL / min; the power of ultrasonic operation is 350W, the pH of the solid after suction filtration is 13 after washing with ionized water at 75℃; the calcination operation is carried out at 550℃ for 16h.

[0037] Example 3

[0038] A boron-containing metal-doped catalyst, the process and raw material parameters of the preparation of which are the same as those of example 1, the difference is that: M is selected as K, K3PO4, Na2B4O7, LiOH are weighed as 84.91g, 60.37g, 31.14g respectively according to n(P):n(B):n(Li) as 0.4:0.3:1.3, the molar concentration of the substances in the two solutions is 0.08 mol / mL; the speed of adding phosphate solution B to solution A is 80 mL / min; the power of ultrasonic operation is 200W, the pH of the solid after suction filtration is 12.8 after washing with ionized water at 80℃; the calcination operation is carried out at 450℃ for 18h.

[0039] Example 4

[0040] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 1, except that M is selected as Mg, and Mg3(PO4)2, Na2B4O7, and LiOH are weighed according to n(P):n(B):n(Li) as 0.3:0.2:1.1, 39.43 g, 40.24 g, and 26.35 g, respectively, and the molar concentration of the substances in the two solutions is 0.06 mol / mL; the speed of adding the phosphate solution B into solution A is 70 mL / min; the power of the ultrasonic operation is 550 W, the pH of the solid after suction filtration is 12.5 after washing with ionized water at 60°C; and the calcination operation is performed at 520°C for 19 h.

[0041] Example 5

[0042] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 1, except that M is selected as Zn, and Zn3(PO4)2, Na2B4O7, and LiOH are weighed according to n(P):n(B):n(Li) as 0.5:0.4:1.5, 96.53 g, 80.49 g, and 35.93 g, respectively, and the molar concentration of the substances in the two solutions is 0.06 mol / mL; the speed of adding the phosphate solution B into solution A is 60 mL / min; the power of the ultrasonic operation is 300 W, the pH of the solid after suction filtration is 12.7 after washing with ionized water at 90°C; and the calcination operation is performed at 470°C for 19 h.

[0043] Example 6

[0044] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 1, except that M is selected as Fe, and Fe3(PO4)2, Na2B4O7, and LiOH are weighed according to n(P):n(B):n(Li) as 0.5:0.3:1.5, 89.37 g, 60.37 g, and 35.93 g, respectively, and the molar concentration of the substances in the two solutions is 0.07 mol / mL; the speed of adding the phosphate solution B into solution A is 60 mL / min; the power of the ultrasonic operation is 300 W, the pH of the solid after suction filtration is 12.6 after washing with ionized water at 85°C; and the calcination operation is performed at 500°C for 18 h.

[0045] Example 7

[0046] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 1, except that M is selected to be Ba, and Ba3(PO4)2, Na2B4O7, and LiOH are weighed according to n(P):n(B):n(Li) of 0.5:0.2:1.5 as 120.37 g, 40.24 g, and 33.53 g, respectively, and the molar concentration of the substances in the two solutions is 0.09 mol / mL; the speed of adding the phosphate solution B into solution A is 50 mL / min; the power of the ultrasonic operation is 300 W, the pH of the solid after suction filtration is 12.6 after washing with ionized water at 65°C; and the calcination operation is performed at 500°C for 18 h.

[0047] Example 8

[0048] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 1, except that M is selected to be Na and Mg, and Na3PO4, Mg3(PO4)2, Na2B4O7, and LiOH are weighed according to n(P-Na):n(P-Mg):n(B):n(Li) of 0.2:0.2:0.3:1.5 as 32.79 g, 26.29 g, 60.37 g, and 35.93 g, respectively, and the molar concentration of the substances in the two solutions is 0.08 mol / mL; the speed of adding the phosphate solution B into solution A is 60 mL / min; the power of the ultrasonic operation is 400 W, the pH of the solid after suction filtration is 12.9 after washing with ionized water at 65°C; and the calcination operation is performed at 510°C for 17 h.

[0049] Example 9

[0050] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 1, except that M is selected to be Be and Zn, and Be3(PO4)2, Zn3(PO4)2, Na2B4O7, and LiOH are weighed according to n(P-Be):n(P-Zn):n(B):n(Li) of 0.2:0.2:0.3:1.5 as 21.70 g, 38.61 g, 60.37 g, and 35.93 g, respectively, and the molar concentration of the substances in the two solutions is 0.07 mol / mL; the speed of adding the phosphate solution B into solution A is 60 mL / min; the power of the ultrasonic operation is 300 W, the pH of the solid after suction filtration is 12.5 after washing with ionized water at 80°C; and the calcination operation is performed at 520°C for 18 h.

[0051] Example 10

[0052] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 1, except that M is selected to be K, Fe, Ba, and the mass of K3PO4, Fe3(PO4)2, Ba3(PO4)2, Na2B4O7, and LiOH is 21.23 g, 17.87 g, 30.01 g, 60.37 g, and 35.93 g, respectively, according to n(P-K):n(P-Fe):n(P-Ba):n(B):n(Li) = 0.1:0.1:0.1:0.3:1.5, and the molar concentration of the substances in the two solutions is 0.07 mol / mL; the speed of adding the phosphate solution B into solution A is 60 mL / min; the power of the ultrasonic operation is 300 W, the pH of the solid after the suction filtration and washing with ionized water at 85°C is 12.6; and the calcination operation is performed at 490°C for 20 h.

[0053] Example 11

[0054] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 6, except that the boron reagent is selected to be boron phosphate, and the mass of Fe3(PO4)2, BPO4, and LiOH is 89.37 g, 31.73 g, and 35.93 g, respectively, according to n(P):n(B):n(Li) = 0.5:0.3:1.5.

[0055] Example 12

[0056] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 6, except that the boron reagent is selected to be boric acid, and the mass of Fe3(PO4)2, H3BO3, and LiOH is 89.37 g, 18.55 g, and 35.93 g, respectively, according to n(P):n(B):n(Li) = 0.5:0.3:1.5.

[0057] Example 13

[0058] A boron-containing metal-doped catalyst, the process and raw material parameters for preparing the catalyst are the same as those in Example 6, except that M is selected to be Fe, and the mass of Fe3(PO4)2, Na2B4O7, and LiOH is 160.86 g, 30.18 g, and 119.75 g, respectively, according to n(P):n(B):n(Li) = 0.9:0.15:5.

[0059] Comparative Example 1

[0060] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that no boron reagent was added and Fe3(PO4)2, LiOH were weighed according to n(P):n(B):n(Li) of 0.5:0:1.5 as 89.37 g and 35.93 g, respectively.

[0061] Comparative Example 2

[0062] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that no M was added and H3PO4, Na2B4O7, LiOH were weighed according to n(P):n(B):n(Li) of 0.5:0.3:1.5 as 49.00 g, 60.37 g, and 35.93 g, respectively.

[0063] Comparative Example 3

[0064] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the solution concentration was 0.01 mol / mL.

[0065] Comparative Example 4

[0066] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the dropping speed was 5 mL / min.

[0067] Comparative Example 5

[0068] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the microwave power was 20 W.

[0069] Comparative Example 6

[0070] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the washing temperature was 25°C.

[0071] Comparative Example 7

[0072] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the pH was 10.

[0073] Comparative Example 8

[0074] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the calcination operation was performed at 750°C for 18 h.

[0075] Comparative Example 9

[0076] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the calcination operation was performed at 500°C for 48 h.

[0077] Comparative Example 10

[0078] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that Fe was selected as the metal dopant, the amount of Fe3(PO4)2added was 8.9 g, and the amount of Na2B4O7and LiOH was 60.37 g and 35.93 g, respectively, according to the ratio n(B):n(Li) of 0.3:1.5.

[0079] Comparative Example 11

[0080] A boron-containing metal-doped catalyst was prepared according to the same process and raw material parameters as in Example 6, except that the amount of Na2B4O7added was 1.6 g, Fe was selected as the metal dopant, and the amount of Fe3(PO4)2and LiOH was 89.37 g and 35.93 g, respectively, according to the ratio n(P):n(Li) of 0.5:1.5.

[0081] Test Examples and Comparative Test Examples

[0082] An isomerization method of propylene oxide was performed using the metal-doped catalysts of Examples 1-13 or the catalysts of Comparative Examples 1-11, in which the nitrile compound was selected, the propylene oxide sample rate was 0.6 mL / min, the reactor heating temperature was 295°C, the nitrogen carrier gas was 120 seem, the pressure was 0.1 MPa, and the product was collected and observed in a gas chromatograph.

[0083] As shown in Table 1, Test Examples 1-13 and Comparative Test Examples 1-11 show the propylene oxide conversion rate, allyl alcohol selectivity, and stability.

[0084] Table 1

[0085] Catalyst Propylene oxide conversion / % Allyl alcohol selectivity / % Stability / h Example 1 83 92 600-650 Example 2 81 93 550-600 Example 3 82 93 550-600 Example 4 88 89 600-700 Example 5 92 93 650-700 Example 6 96 98 800-850 Example 7 91 94 600-650 Example 8 86 92 600-650 Example 9 89 93 650-700 Example 10 95 96 700-750 Example 11 91 95 750-800 Example 12 94 96 700-750 Example 13 81 90 500-550 Comparative Example 1 55 92 750-800 Comparative Example 2 33 81 150-200 Comparative Example 3 68 81 250-350 Comparative Example 4 40 91 200-300 Comparative Example 5 65 92 450-500 Comparative Example 6 43 87 300-350 Comparative Example 7 21 56 150-200 Comparative Example 8 90 91 50-100 Comparative Example 9 89 91 100-150 Comparative Example 10 12 45 60-100 Comparative Example 11 50 82 100-150

[0086] The above description is merely preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the protection scope of the present application.

Claims

1. A boron-doped metal catalyst, characterized in that: The catalyst comprises an active metal component in the form of a phosphate and a boron-containing compound. The active metal component includes a first active metal component Li, and also includes at least one of a second active metal component Be, Na, K, Mg, Zn, Fe, and Ba, wherein the second active metal component accounts for at least 5.3 wt% of the catalyst, and the boron-containing compound accounts for 1.3 wt% of the catalyst.

2. The boron-doped metal catalyst according to claim 1, characterized in that: The molar ratio of the second active metal component (calculated as phosphate in phosphate), the boron-containing compound and the first active metal component is (0.2-1):(0.15-1):(0.5-5); preferably (0.25-0.8):(0.18-0.8):(0.6-4); more preferably (0.3-0.6):(0.2-0.5):(0.8-2).

3. The boron-doped metal catalyst according to claim 1, characterized in that: The boron-containing compound is at least one of boric acid, borate, and boron phosphate.

4. The boron-doped metal catalyst according to claim 1, characterized in that: The catalyst has an average particle size of 20-50 nm.

5. A method for preparing a boron-doped metal catalyst, characterized in that: Includes the following steps: S1: The boron-containing compound is added to a lithium hydroxide solution and stirred continuously; wherein, Li is the first active metal component; S2: Under continuous stirring and ultrasonic conditions, the phosphate solution of the second active metal component is added to the mixture in step S1; wherein, the second active metal component includes at least one of Be, Na, K, Mg, Zn, Fe, and Ba; S3: After the co-precipitation process in step S2 is completed, the catalyst is obtained by solid-liquid separation, washing, and calcination; The catalyst is any one of the boron-doped metal catalysts according to claims 1 to 4.

6. The method for preparing a boron-doped metal catalyst according to claim 5, characterized in that: In the mixture obtained in step S2, the molar ratio of the second active metal component (calculated as phosphate in phosphate), the boron-containing compound, and lithium is (0.2-1):(0.15-1):(0.5-5); preferably (0.25-0.8):(0.18-0.8):(0.6-4); more preferably (0.3-0.6):(0.2-0.5):(0.8-2); and / or, The concentrations of lithium, the second active metal component, and the boron-containing compound in the mixture obtained in step S2 are 0.02-0.8 mol / mL, preferably 0.05-0.08 mol / mL.

7. The method for preparing a boron-doped metal catalyst according to claim 5, characterized in that: In step S2, the phosphate solution of the second active metal component is added dropwise to the mixture from step S1; preferably, the dropping rate is 10-200 mL / min, more preferably 20-120 mL / min; and / or, The ultrasonic power of the ultrasonic conditions is 50-600W, the ultrasonic time is longer than the time for adding the phosphate solution of the second active metal component to the mixture in step S1, and the ultrasonic temperature is 60-70℃, preferably 65℃.

8. The method for preparing a boron-doped metal catalyst according to claim 5, characterized in that: The washing operation in step S3 includes: adding the solid obtained from solid-liquid separation to water of the same weight as before separation, and washing the solid at 30-100°C until the pH is 12-14, preferably at 60-90°C until the pH is 12.5-13.

9. The method for preparing a boron-doped metal catalyst according to claim 5, characterized in that: In step S3, the roasting temperature is 300-700℃ and the roasting time is 1-30h; preferably, the roasting temperature in step S3 is 400-550℃ and the roasting time is 15-20h.

10. The application of the catalyst according to any one of claims 1 to 4 or the catalyst prepared by any one of claims 5 to 9 in the isomerization of propylene oxide to prepare propenol.

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