A propane dehydrogenation catalyst and a method for preparing propylene by propane dehydrogenation

Abstract

The application belongs to the technical field of dehydrogenation catalysts, and discloses a propane dehydrogenation catalyst and a method for preparing propylene by propane dehydrogenation, wherein the catalyst is obtained by calcining a catalyst precursor, and the catalyst precursor is composed of spherical alumina and hydrotalcite in-situ grown on the spherical alumina; the spherical alumina is gamma-alumina, and the hydrotalcite is ternary hydrotalcite containing Ga 3+ or In 3+ in the layer plate. The catalyst of the application can achieve excellent propylene selectivity and high activity in the propane dehydrogenation reaction process, and can realize complete recovery of activity after regeneration and has strong regeneration stability. The catalyst of the application has a multistage structure and is convenient for industrial application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of dehydrogenation catalysts, and particularly relates to a propane dehydrogenation catalyst and a method for preparing propylene by propane dehydrogenation using the propane dehydrogenation catalyst. BACKGROUND

[0002] Propylene is an important basic chemical raw material, which can be used to produce polypropylene, acrylonitrile, propylene oxide, isopropyl alcohol and acrylic acid, etc. With the rapid development of domestic economy, the demand for these propylene downstream products is growing rapidly, and is under the huge demand of the domestic and international markets.

[0003] At present, the main methods for producing propylene include petroleum steam cracking, catalytic cracking, coal-based methanol to olefins and propane dehydrogenation. Among them, the propane direct dehydrogenation process has the advantages of easy availability of raw materials, environmental friendliness, high selectivity of propylene and by-product H2, etc., and is an important chemical process for producing propylene at present. The main catalysts used in industry are Pt-based catalysts and Cr-based catalysts. Because the Pt-based catalyst is extremely expensive, and the precursor Cr of the Cr-based catalyst pollutes the environment, it is necessary to develop a cheap and environmentally friendly propane dehydrogenation catalyst. VI

[0004] The bond energies of the methyl and methylene C-H bonds in the propane molecule are 422.2 kJ / mol and 410.5 kJ / mol, respectively. Therefore, in the process of propane dehydrogenation reaction, how to reduce the activation energy barrier and realize efficient breaking of the C-H bond is a great challenge. At present, a large amount of research has been done on the effective catalysis of metal oxides for propane dehydrogenation, mainly including the following ways: (1) adjusting the particle size of the metal oxide to obtain unsaturated metal sites, increasing the number of acid sites to promote C-H bond activation; (2) adjusting the dispersion degree of the metal oxide on the carrier; (3) modifying by doping metals to change the electronic structure of the active site. SUMMARY

[0005] Based on the above situation, the purpose of the present application is to provide a propane dehydrogenation catalyst and a method for preparing propylene by propane dehydrogenation, which has a high dispersion of active centers, exhibits high activity and excellent propylene selectivity in the propane dehydrogenation reaction, and can realize complete recovery of activity after regeneration and has strong regeneration stability.

[0006] The first aspect of the present application provides a propane dehydrogenation catalyst, which is obtained by calcining a catalyst precursor composed of spherical alumina and hydrotalcite grown in situ on the spherical alumina.

[0007] The spherical alumina is γ-alumina, and the hydrotalcite is a ternary hydrotalcite containing Ga 3+ or In 3+ . ​

[0008] The second aspect of the present application provides a method for preparing propylene by dehydrogenation of propane, which comprises: dehydrogenating propane in the presence of the above-mentioned propane dehydrogenation catalyst.

[0009] The catalyst precursor of the present application is a multi-level structure constructed by spherical alumina and layered double hydroxide (LDH), and the LDH is in-situ grown on the surface and internal pores of the spherical alumina, which can improve the dispersity of the LDH, and the catalyst formed from the catalyst precursor is also a multi-level structure, which is convenient for industrial application. By using the confinement effect of the layer plate on the trivalent metal in the topological transformation process of the LDH precursor, the Ga-O and In-O active sites uniformly dispersed in the layer plate are constructed, and the dispersity of the unit point active center of the catalyst is improved, and at the same time, the spherical alumina is used, which has high catalytic activity in the dehydrogenation of propane, high selectivity of propylene, and high regeneration stability that can completely restore the initial evaluation performance.

[0010] Other features and advantages of the present application will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0011] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0012] According to the first aspect of the present application, the present application provides a propane dehydrogenation catalyst, which is obtained by calcining a catalyst precursor, and the catalyst precursor is composed of spherical alumina and hydrotalcite in-situ grown thereon;

[0013] The spherical alumina is γ-alumina, and the hydrotalcite is a ternary hydrotalcite containing Ga 3+ or In 3+ in the layer plate.

[0014] In the present application, the particle size of the spherical alumina is 0.2-2mm, and the specific surface area is 100-200m 2 / g. The combination of the spherical alumina and the hydrotalcite can improve the activity and selectivity of propane dehydrogenation, and is also beneficial to the industrial application of the catalyst.

[0015] According to the present application, M 2+ composing the layer plate of the hydrotalcite can be Mg 2+ , Zn 2+ , Co 2+ , Mn 2+ or Ca 2+ , preferably Mg 2+ or Zn 2+ , and M 3+ is Ga 3+ and Al 3+or In 3+ and Al 3+ .

[0016] The catalyst precursor of the present application can be prepared by hydrothermal method, as long as the hydrotalcite in-situ grown on the spherical alumina can be obtained.

[0017] Preferably, the preparation method of the catalyst precursor comprises the following steps:

[0018] 1) dissolving M 2+ , M 3+ and urea, which constitute the hydrotalcite layer, in water to form a mixed solution, M 3+ is Ga 3+ or In 3+ , the molar ratio of M 2+ : M 3+ = 3-8:1, the molar ratio of (M 2+ + M 3+ ): urea = 1:4-4.5, and the total molar concentration of M 2+ and M 3+ in the mixed solution is 0.8-1.2 mol / L;

[0019] 2) mixing the mixed solution with the spherical alumina at a ratio of 0.7-1.5 mL:1 g and oscillating for 2 h, and then crystallizing at 100-130℃ for 12 h;

[0020] 3) extracting the reaction product, washing with deionized water until neutral, washing with acetone, and drying to obtain the catalyst precursor.

[0021] In the present application, the raw materials of M 2+ and M 3+ may be their nitrate salts, the mixing of the mixed solution with the spherical alumina can be directly carried out in a polytetrafluoroethylene liner, and the oscillation is carried out by placing the polytetrafluoroethylene liner on a shaker.

[0022] According to the present application, the calcination conditions include: the calcination temperature is 500-600℃, the heating rate is 2-10℃ / min, the time of calcination after constant temperature is 2-6h, the calcination atmosphere is 10% O2 / N2, Ar or air, and the flow rate of the atmosphere is 20-80 mL / min.

[0023] Preferably, the calcination conditions include: the calcination temperature is 500-550℃, the heating rate is 2-5℃ / min, the time of calcination after constant temperature is 2-6h, the calcination atmosphere is air, and the flow rate of the atmosphere is 20-80 mL / min.

[0024] In the present application, the content of Ga or In in the catalyst is 0.5-2.0 wt%. The catalyst with this content can show better catalytic performance.

[0025] According to a second aspect of the present application, the present application provides a method for preparing propylene by dehydrogenation of propane, which comprises: dehydrogenating propane in the presence of the above-mentioned catalyst for dehydrogenation of propane.

[0026] In the present application, the conditions for the dehydrogenation reaction include: the reaction temperature is 500-650℃; the reaction pressure is 0.1 MPa; the reaction feed composition is C3H8, Ar and optional H2, in terms of molar ratio, C3H8:Ar=5-20:80-95, C3H8:H2=1:1 (when H2 is contained); the mass space velocity of propane is 1-4 h -1 -1; and the catalyst usage is 0.10-2.0 g.

[0027] The substances and parameters not defined in the present application can be selected according to the prior art, which are the conventional technical means in the art.

[0028] The present application will be further described below in conjunction with examples, but is not limited by these examples.

[0029] Example 1

[0030] Step A: Mg(NO3)2·6H2O, Ga(NO3)2·xH2O and urea are dissolved in 3 mL of deionized water, wherein the molar ratio of Mg 2 :Ga + is 3:1, the molar ratio of (Mg 3+ +Ga 2+ ) / urea is 1:4, and the total molar concentration of Mg 3+ and Ga 2+ in the mixed solution is 1.2 mol / L. 3+ The above-mentioned mixed solution is added into a polytetrafluoroethylene liner containing 2 g of spherical alumina (particle size is 0.5 mm, specific surface area is 150 m 2 / g), the polytetrafluoroethylene liner is shaken in a shaking table for 2 h, and then crystallized at 120℃ for 12 h, and then filtered and washed with deionized water until neutral, and finally washed with acetone and dried to obtain a catalyst precursor.

[0031] Step B: the MgGaAl-LDHs@Al2O3 precursor prepared in Step A is calcined at 550℃, the temperature rising rate is 5℃ / min, the calcination time after constant temperature is 4 h, the calcination atmosphere is air, and the flow rate of the atmosphere is 40 mL / min.

[0032] That is, the MgGaAl-LDO@Al2O3 catalyst is prepared, and the actual content of Ga in the catalyst is 1.2 wt%.

[0033] Example 2

[0034] Step A: Mg(NO3)2*6H2O, In(NO3)2*xH2O, urea were dissolved in 3 mL deionized water, wherein the molar ratio of Mg 2 + :In 3+ = 3:1, the molar ratio of (Mg 2+ + In 3+ ) / urea = 1:4, the total molar concentration of Mg 2+ and In 3+ in the mixed solution was 1.2 mol / L, the above mixed solution was added to a polytetrafluoroethylene liner containing 2 g of spherical alumina (particle size 0.5 mm, specific surface area 150 m 2 / g), the polytetrafluoroethylene liner was placed in a shaking table and shaken for 2 h, crystallized at 120℃ for 12 h, washed by suction filtration, washed with deionized water until neutral, finally washed with acetone, and dried to obtain a catalyst precursor.

[0035] Step B: The MgInAl-LDHs@Al2O3 precursor prepared in step A was calcined at 550℃, the heating rate was 5℃ / min; the calcination time after constant temperature was 4 h; the calcination atmosphere was air; the flow rate of the atmosphere was 40 mL / min.

[0036] That is, the MgInAl-LDO@Al2O3 catalyst was prepared, and the actual content of In in the catalyst was 1.2 wt%.

[0037] Example 3

[0038] Step A: Zn(NO3)2*6H2O, Ga(NO3)2*xH2O, urea were dissolved in 3 mL deionized water, wherein the molar ratio of Zn 2 + :Ga 3+ = 3:1, the molar ratio of (Zn 2+ + Ga 3+ ) / urea = 1:3, the total molar concentration of Zn 2+ and Ga 3+ in the mixed solution was 1.2 mol / L, the above mixed solution was added to a polytetrafluoroethylene liner containing 2 g of spherical alumina (particle size 0.5 mm, specific surface area 150 m 2 / g), the polytetrafluoroethylene liner was placed in a shaking table and shaken for 2 h, crystallized at 110℃ for 12 h, washed by suction filtration, washed with deionized water until neutral, finally washed with acetone, and dried to obtain a catalyst precursor.

[0039] Step B: The ZnGaAl-LDHs@Al2O3 precursor prepared in step A was calcined at 550℃, the heating rate was 5℃ / min; the calcination time after constant temperature was 4 h; the calcination atmosphere was air; the flow rate of the atmosphere was 40 mL / min.

[0040] ZnGaAl-LDO@Al2O3catalyst was prepared, and the actual content of Ga in the catalyst was 1.2wt%.

[0041] Example 4

[0042] Step A: Zn(NO3)2·6H2O, In(NO3)2·xH2O, urea were dissolved in 3 mL of deionized water, wherein the molar ratio of Zn 2 + :In 3+ was 3:1, the molar ratio of (Zn 2+ +In 3+ ) / urea was 1:3, and the total molar concentration of Zn 2+ and In 3+ in the mixed solution was 1.2 mol / L; the above mixed solution was added to a polytetrafluoroethylene liner containing 2 g of spherical alumina (particle size 0.5 mm, specific surface area 150 m 2 / g); the polytetrafluoroethylene liner was placed in a shaking table and shaken for 2 h; the crystallization was carried out at 110°C for 12 h; the product was washed by suction filtration and washed with deionized water until neutral, and finally washed with acetone; and the product was dried to obtain a catalyst precursor.

[0043] Step B: the ZnInAl-LDHs@Al2O3 precursor prepared in step A was calcined at 550°C, the temperature rising rate was 5°C / min; the calcination time after constant temperature was 4 h; the calcination atmosphere was air; and the flow rate of the atmosphere was 40 mL / min.

[0044] ZnInAl-LDO@Al2O3catalyst was prepared, and the actual content of In in the catalyst was 1.2wt%.

[0045] Comparative Example 1

[0046] Step A: Mg(NO3)2·6H2O, urea were dissolved in 3 mL of deionized water, wherein the molar ratio of Mg 2+ :urea was 1:4, and the molar concentration of Mg 2+ in the mixed solution was 0.9 mol / L; the above mixed solution was added to a polytetrafluoroethylene liner containing 2 g of spherical alumina (particle size 0.5 mm, specific surface area 150 m 2 / g); the polytetrafluoroethylene liner was placed in a shaking table and shaken for 2 h; the crystallization was carried out at 120°C for 12 h; the product was washed by suction filtration and washed with deionized water until neutral, and finally washed with acetone; and the product was dried.

[0047] Step B: The container with 2.4 g MgAl-LDH@Al2O3 synthesized in step A was vacuumized, and Ga(NO3)2xH2O solution (0.15 g Ga(NO3)2xH2O was dissolved in 2 mL deionized water) was injected. After shaking at room temperature for 1 h, it was left to stand and dried in a vacuum drying oven at 60 °C for 12 h.

[0048] Step C: The Ga(NO3)2xH2O / MgAl-LDH@Al2O3 precursor prepared in step B was calcined at 550 °C, with a heating rate of 5 °C / min; the holding time after constant temperature was 4 h; the calcination atmosphere was air; and the flow rate of the atmosphere was 40 mL / min.

[0049] That is, Ga2O3 / MgAl-LDO@Al2O3 catalyst was prepared, and the actual content of Ga in the catalyst was 1.2 wt.%.

[0050] Comparative Example 2

[0051] Step A: Mg(NO3)2x6H2O and urea were dissolved in 3 mL deionized water, wherein the molar ratio of Mg(NO3)2x6H2O to urea was 1:4, and the molar concentration of Mg(NO3)2x6H2O in the mixed solution was 0.9 mol / L; the above mixed solution was added to a polytetrafluoroethylene liner containing 2 g spherical alumina (particle size was 0.5 mm, and specific surface area was 150 m2 / g), the polytetrafluoroethylene liner was placed in a shaking table and shaken for 2 h, and then crystallized at 120 °C for 12 h; after washing with deionized water until neutral, the product was finally washed with acetone and dried. 2+ : The molar ratio of urea was 1:4, and the molar concentration of Mg 2+ in the mixed solution was 0.9 mol / L; the above mixed solution was added to a polytetrafluoroethylene liner containing 2 g spherical alumina (particle size was 0.5 mm, and specific surface area was 150 m 2 / g) was added to a polytetrafluoroethylene liner containing 2 g spherical alumina (particle size was 0.5 mm, and specific surface area was 150 m

[0052] Step B: The container with 2.4 g MgAl-LDH@Al2O3 synthesized in step A was vacuumized, and In(NO3)2xH2O solution (0.1 g In(NO3)2xH2O was dissolved in 2 mL deionized water) was injected. After shaking at room temperature for 1 h, it was left to stand and dried in a vacuum drying oven at 60 °C for 12 h.

[0053] Step C: The In(NO3)2xH2O / MgAl-LDH@Al2O3 precursor prepared in step B was calcined at 550 °C, with a heating rate of 5 °C / min; the holding time after constant temperature was 4 h; the calcination atmosphere was air; and the flow rate of the atmosphere was 40 mL / min.

[0054] That is, In2O3 / MgAl-LDO@Al2O3 catalyst was prepared, and the actual content of In in the catalyst was 1.2 wt.%.

[0055] Comparative Example 3

[0056] Step A: Dissolve Zn(NO3)2·6H2O and urea together in 3 mL of deionized water, wherein Zn 2+ The molar ratio of urea to urea is 1:3, and the Zn content in the mixed solution is... 2+ The molar concentration was 0.9 mol / L; the above mixed solution was added to a container containing 2 g of spherical alumina (particle size 0.5 mm, specific surface area 150 m²). 2 The polytetrafluoroethylene (PTFE) liner ( / g) was placed in a shaker and shaken for 2 hours, then crystallized at 110°C for 12 hours.

[0057] Filter and wash, wash with deionized water until neutral, and finally wash with acetone and dry.

[0058] Step B: Vacuum the container containing 2.4g of ZnAl-LDHs@Al2O3 synthesized in step A, inject Ga(NO3)2·xH2O solution (0.15g Ga(NO3)2·xH2O dissolved in 2mL deionized water), shake at room temperature for 1h, let stand, and dry in a vacuum drying oven at 60℃ for 12h.

[0059] Step C: The Ga(NO3)2·xH2O / ZnAl-LDHs@Al2O3 precursor prepared in step B was calcined at 550℃ with a heating rate of 5℃ / min; the calcination time after isothermal treatment was 4h; the calcination atmosphere was air; and the flow rate of the atmosphere was 40mL / min.

[0060] The Ga2O3 / ZnAl-LDO@Al2O3 catalyst was prepared, and the actual Ga content in the catalyst was 1.2 wt%.

[0061] Comparative Example 4

[0062] Step A: Dissolve Zn(NO3)2·6H2O and urea together in 3 mL of deionized water, wherein Zn 2+ The molar ratio of urea to urea is 1:3, and the Zn content in the mixed solution is... 2+ The molar concentration was 0.9 mol / L; the above mixed solution was added to a container containing 2 g of spherical alumina (particle size 0.5 mm, specific surface area 150 m²). 2 In a polytetrafluoroethylene (PTFE) liner (g), the PTFE liner is placed in a shaker and shaken for 2 hours, crystallized at 110°C for 12 hours, filtered and washed, washed with deionized water until neutral, and finally washed with acetone and dried.

[0063] Step B: Vacuum the container containing 2.4g of ZnAl-LDHs@Al2O3 synthesized in step A, inject In(NO3)2·xH2O solution (0.1g In(NO3)2·xH2O dissolved in 2mL deionized water), shake at room temperature for 1h, let stand, and dry in a vacuum drying oven at 60℃ for 12h.

[0064] Step C: The In(NO3)2·xH2O / ZnAl-LDHs@Al2O3 precursor prepared in step B was calcined at 550℃ with a heating rate of 5℃ / min; the calcination time after isothermal treatment was 4h; the calcination atmosphere was air; and the flow rate of the atmosphere was 40mL / min.

[0065] The In2O3 / ZnAl-LDO@Al2O3 catalyst was thus prepared, with an actual In content of 1.2 wt%.

[0066] Comparative Example 5

[0067] Step A: Dissolve Mg(NO3)2·6H2O and urea together in 1 mL of deionized water, wherein Mg 2+ The molar ratio of urea to urea is 1:4. The amount of Mg in the mixed solution... 2+ The molar concentration was 1.2 mol / L; the above mixed solution was added to a container containing 1 g of spherical alumina (particle size 0.5 mm, specific surface area 150 m²). 2 In a polytetrafluoroethylene (PTFE) liner (g), the PTFE liner is placed in a shaker and shaken for 2 hours, crystallized at 120°C for 12 hours, filtered and washed, washed with deionized water until neutral, and finally washed with acetone and dried.

[0068] Step B: Vacuum the container containing 1g of MgAl-LDH@Al2O3 synthesized in step A, inject [Pt(NH3)4](NO3)2 solution (7mg [Pt(NH3)4](NO3)2 dissolved in 0.9mL deionized water), shake at room temperature for 2h, and then dry in a vacuum drying oven at 60℃ for 12h.

[0069] Step C: The [Pt(NH3)4](NO3)2 / MgAl-LDH@Al2O3 precursor prepared in step B was calcined at 550℃ with a heating rate of 5℃ / min; the calcination time after isothermal treatment was 4h; the calcination atmosphere was air; and the flow rate of the atmosphere was 40mL / min.

[0070] Step D: After calcining the PtO2 / MgAl-LDO@Al2O3 sample in step C, purge it with N2 at 20 mL / min for 10 min, then switch to H2 and reduce it at 550℃ for 2.5 h; the flow rate of H2 is 40 mL / min.

[0071] The Pt / MgAl-LDO@Al2O3 catalyst was prepared, and the actual content of Pt in the catalyst was 0.3wt%.

[0072] Comparative Example 6

[0073] Step A: MgGaAl-LDH was prepared by a coprecipitation method, and the total concentration of metal cations [M 2+ ]+[M 3+ ] was 0.1 mol / L, the concentration of the alkali solution NaOH was 1.8([M 2+ ]+[M 3+ ]), the concentration of the buffer solution Na2CO3 was 0.5[M 3+ ], 0.045 mol of Mg(NO3)2·6H2O, 0.0015 mol of Ga(NO3)3·xH2O and 0.0135 mol of Al(NO3)3·9H2O were weighed and dissolved in 200 mL of deionized water, which was denoted as a salt solution; 0.11 mol of NaOH was weighed and dissolved in 200 mL of deionized water, which was denoted as an alkali solution; 0.0075 mol of Na2CO3 was dissolved in 200 mL of deionized water and placed in a 1000 mL four-necked flask, and the four-necked flask was placed in a water bath at room temperature. The salt solution and the alkali solution were simultaneously and slowly added into the four-necked flask, and the pH of the system was maintained at 10±0.2, and after the addition was completed, the solution was crystallized at 800 rpm under mechanical stirring and 65℃ in a water bath for 12 h. After crystallization, the solution was repeatedly washed with deionized water until it was neutral, and finally washed with acetone, and dried to obtain a catalyst precursor. The prepared MgGaAl-LDHs were ground into powder in a mortar and dried for storage.

[0074] Step B: The MgGaAl-LDHs precursor obtained in step A was calcined at 550℃, the temperature rising rate was 5℃ / min, the calcination time after constant temperature was 4 h, the calcination atmosphere was air, and the flow rate of the atmosphere was 40 mL / min.

[0075] The MgGaAl-LDO catalyst was prepared, and the actual content of Ga in the catalyst was 1.12wt%.

[0076] The catalysts prepared in each example and comparative example were used to catalyze the dehydrogenation reaction of propane, the reaction temperature was 550℃, the reaction pressure was 0.1 MPa, the reaction feed composition was C3H8:Ar=14:90 (molar ratio), the mass space velocity of C3H8 was 2.36h -1 , and the catalyst dosage was 0.70 g. The performance data are shown in Table 1.

[0077] Table 1

[0078]

[0079] From Table 1, it can be seen that the propane conversion is higher using the catalyst of the present application, close to the thermodynamic equilibrium conversion under the conditions. Compared with the corresponding supported catalyst, the activity is higher while the propylene selectivity is at least equivalent, the initial propylene formation rate is higher, and can even be 2 times. The performance of the catalyst of the present application is even close to that of the supported noble metal Pt catalyst. Compared with the catalyst without using spherical alumina, the activity and selectivity are both improved, and the spherical alumina has a synergistic effect with the composite metal oxide (LDO). In addition, the catalyst of the present application has good reaction-regeneration performance, the activity is not lost, and can still reach the initial evaluation performance after three times of regeneration, and has good regeneration stability.

[0080] The foregoing description of the various embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the application be limited not with this detailed description, but rather by the claims appended hereto.

Claims

1. A method for producing propylene by propane dehydrogenation, characterized in that, The method includes: performing a dehydrogenation reaction on propane in the presence of a propane dehydrogenation catalyst; The propane dehydrogenation catalyst is obtained by calcining a catalyst precursor, which consists of spherical alumina and hydrotalcite grown in situ on it. The spherical alumina is γ-alumina, and the hydrotalcite is a laminate containing Ga. 3+ or In 3+ Tripartite hydrotalcite; M, which makes up the hydrotalcite slab 2+ Mg 2+ Zn 2+ Co 2+ Mn 2+ or Ca 2+ ; The method for preparing the catalyst precursor includes the following steps: 1) M, which makes up the hydrotalcite slab 2+ M 3+ And urea dissolved in water to make a mixed solution, M 3+ For Ga 3+ or In 3+ M 2+ :M 3+ The molar ratio is 3-8:1, (M 2+ +M 3+ The molar ratio of urea to urea is 1:4-4.5, and the M in the mixed solution... 2+ and M 3+ The total molar concentration is 0.8-1.2 mol / L; 2) Mix the mixed solution with spherical alumina at a ratio of 0.7-1.5 mL: 1 g and shake for 2 h, then crystallize at 100-130 °C for 12 h; 3) Filter the reaction product, wash it with deionized water until neutral, wash it with acetone, and dry it to obtain the catalyst precursor.

2. The method for propane dehydrogenation to propylene according to claim 1, wherein, The spherical alumina has a particle size of 0.2-2 mm and a specific surface area of ​​100-200 m². 2 / g.

3. The method for propane dehydrogenation to propylene according to claim 1, wherein, M, which makes up the hydrotalcite slab 2+ Mg 2+ or Zn 2+ .

4. The method for propane dehydrogenation to propylene according to claim 1, wherein, The calcination conditions include: a calcination temperature of 500-600℃, a heating rate of 2-10℃ / min; a calcination time of 2-6h after constant temperature; a calcination atmosphere of 10% O2 / N2, Ar, or air; and an atmosphere flow rate of 20-80mL / min.

5. The method for propane dehydrogenation to propylene according to claim 4, wherein, The calcination conditions include: a calcination temperature of 500-550℃, a heating rate of 2-5℃ / min; a calcination time of 2-6h after constant temperature; a calcination atmosphere of air; and an atmosphere flow rate of 20-80mL / min.

6. The method for propane dehydrogenation to propylene according to claim 1, wherein, The content of Ga or In in the catalyst is 0.5-2.0 wt%.

7. The method for propane dehydrogenation to propylene according to claim 1, wherein, The conditions for the dehydrogenation reaction include: a reaction temperature of 500-650℃; a reaction pressure of 0.1 MPa; a feed composition of C3H8, Ar, and optional H2, with molar ratios of C3H8:Ar = 5-20:80-95 and C3H8:H2 = 1:1; and a propane mass hourly space velocity of 1-4 h⁻¹. -1 The catalyst dosage is 0.10-2.0g.

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