Silica-magnesia modified alumina support and propane dehydrogenation catalyst

Abstract

The present application relates to a kind of silicon-magnesium modified alumina carrier and propane dehydrogenation catalyst.A kind of silicon-magnesium modified alumina carrier, the content of SiO2 in the carrier is 0.01-20wt%, the content of MgO is 0.01-20wt%, the rest is Al2O3;The carrier is prepared by calcining silicon-magnesium modified pseudo-boehmite phase precursor synthesized at pH 10-12, and the preparation method comprises the following steps: respectively preparing cation material, anion material 1 and anion material 2, the cation material is the mixed solution of aluminum sulfate and magnesium sulfate, the anion material 1 is sodium metaaluminate solution, and the anion material 2 is sodium silicate solution;Three materials are added into the reaction container containing water in parallel flow, the alkaline material is slightly excessive, hydrolysis reaction is carried out by hydrothermal stirring, then aging, washing and drying, and calcining.The present application solves the problems of existing dehydrogenation catalyst in prior art, such as easy to occur side reaction and carbon deposition at high temperature, and easy to sinter platinum ion.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a silicon-magnesium modified alumina support and a propane dehydrogenation catalyst. Background Technology

[0002] Propylene is an important chemical raw material that can be further used to produce high-value-added chemical products such as polypropylene, polyacrylonitrile, and propylene oxide. Currently, the main global propylene production routes include steam cracking, catalytic cracking, and propane selective dehydrogenation. Among these, propane selective dehydrogenation has advantages such as fewer byproducts and a shorter production route, and it has great application prospects.

[0003] Currently, the main industrialized propane dehydrogenation processes are the Catofin process developed by Lummus and the Oleflex process developed by UOP. The Catofin process primarily uses chromium-based catalysts, whose waste catalysts are highly toxic and difficult to recycle in an environmentally friendly manner. The Oleflex process, on the other hand, primarily uses platinum-based catalysts, which are characterized by low toxicity and high activity. This process uses a moving bed reactor, allowing for easy online catalyst replacement, and the precious metals in the old catalyst can be repeatedly recovered and reused. Currently, most propane dehydrogenation plants in China adopt this process.

[0004] Propane dehydrogenation processes generally employ a low-pressure, high-temperature reaction strategy. The Oleflex process typically uses reaction pressures of 1–3 bar and reaction temperatures of 525–700°C. At high temperatures, side reactions easily occur, leading to catalyst deactivation due to carbon buildup. Furthermore, the active component, platinum, migrates and aggregates under high-temperature conditions, increasing its size and reducing reaction activity. Currently, developing catalysts with high activity, high selectivity, and high stability is crucial for propane dehydrogenation technology.

[0005] Alumina, due to its good thermal stability, abundant porosity, low price, and high mechanical strength, has become the main support for platinum-based catalysts. Phobospore is commonly used to prepare γ-alumina with a large specific surface area by calcination at appropriate temperatures. Studies have shown that the acidic centers provided by the support have a certain impact on the loading of active components and even the reaction activity. Unmodified alumina has a large number of L-acid centers, which, when supported on platinum, easily result in large active centers, thus affecting the reaction activity. Magnesium aluminate spinel is a common magnesium-aluminum composite material, often synthesized from magnesium and aluminum salts at higher pH levels. Its properties differ from traditional alumina, possessing abundant acid-base active sites and resistance to agglomeration. However, its surface area is far smaller than that of γ-alumina, which may lead to lower catalyst activity.

[0006] Chinese patent (CN108325523A) describes the preparation of magnesium aluminum spinel by adding aluminum alkoxide ethanol solution to magnesium nitrate ethanol solution, and the subsequent preparation of a PtBK-MgAl2O4 catalyst. The resulting active component clusters have a particle size of less than 1 nm, and the selectivity is greater than 99% after 100 h of reaction. No significant aggregation (less than 1.4 nm) was observed at the active component centers, but the conversion rate was only 16%. Chinese patent (CN201210150485.3) discloses a method for preparing alkali-modified alumina by co-precipitation of inorganic aluminum salts and alkali metals (Ca, Mg, Ba, Sr, etc.). During precipitation, the pH of the mother liquor is controlled between 8 and 12 by adding ammonia. When the pH is controlled at 8, a catalyst with active center clusters of 1.1 nm is obtained, but at pH 12, the active center clusters significantly increase in size (2.8 nm). Currently, there are no reports in the literature on the preparation of magnesium-modified pseudoboehmite using high pH and its application in the preparation of platinum-tin catalyst supports for low-carbon propane dehydrogenation. Summary of the Invention

[0007] The purpose of this invention is to provide a silicon-magnesium modified alumina support, which can be prepared under high pH (>10) conditions by simply controlling the total amount of anions and cations of the added components, in order to solve the problems of side reactions and carbon deposition and sintering of metal platinum ions in the dehydrogenation catalyst under high temperature conditions in the prior art.

[0008] Another object of the present invention is to provide a noble metal propane selective dehydrogenation catalyst prepared from the aforementioned silicon-magnesium modified alumina support, which has the advantages of anti-sintering, high activity, and high selectivity.

[0009] The technical solution adopted by this invention to solve its technical problem is:

[0010] A silica-magnesium modified alumina support, wherein the support contains 0.01–20 wt% SiO2, 0.01–20 wt% MgO, and the balance is Al2O3; the support is prepared by calcining a silica-magnesium modified pseudoboehmite phase precursor synthesized at pH 10–12, and the preparation method includes the following steps:

[0011] S1. Adding materials: Prepare cationic material, anionic material 1, and anionic material 2 respectively. The cationic material is a mixed solution of aluminum sulfate and magnesium sulfate, the anionic material 1 is a sodium aluminate solution, and the anionic material 2 is a sodium silicate solution.

[0012] The three materials are added in parallel to a reaction vessel containing water, with a slight excess of alkaline material. The hydrolysis reaction is carried out by hydrothermal stirring. The hydrothermal synthesis temperature is controlled at 60–90°C, and the stirring reaction time is 5–8 hours.

[0013] S2, aging, washing and drying: Subsequently, hydrothermal aging is carried out at a temperature of 60-90℃ for 1-2 hours. The obtained product is filtered, washed and dried to obtain magnesium silicate-modified pseudoboehmite. The solid product is dried at a temperature of 100-120℃ for more than 12 hours.

[0014] S3. Calcination: The obtained Mg-modified pseudoboehmite is calcined, crushed, and sieved to obtain the Mg-modified alumina carrier; the calcination temperature is 400-700℃ and the calcination time is 2-3h.

[0015] This invention first synthesizes silica-magnesium modified boehmite using a co-precipitation method under pH>10 conditions. The precursor is then calcined to obtain a silica-magnesium modified alumina support. The resulting support exhibits reduced acidity and a larger specific surface area. Propane dehydrogenation catalysts prepared using this support and loaded with platinum and tin components demonstrate high selectivity, strong activity, and strong resistance to sintering.

[0016] The method described in this invention is used to prepare a silica-magnesium modified alumina support. To achieve magnesium ion precipitation, excess sodium silicate and sodium aluminate are added according to the feeding method, making the turbid liquid during the hydrothermal synthesis process strongly alkaline (pH > 10). The resulting silica-magnesium modified hydrated alumina exhibits a pseudoboehmite phase. At high pH ( Figure 1 The hydrothermal synthesis of conventional alumina (without aluminum as a supporting element and no modifying agents added) yields gibbsite (a precursor of alumina with low specific surface area) rather than boehmite (a precursor of γ-alumina with high specific surface area). The inclusion of cationic, anionic (1), and anionic (2) raw materials eliminates the need for additional pH adjustment during the preparation of the silicon-magnesium modified alumina support in this invention. The appropriate addition of silicon and magnesium to the raw materials offers significant advantages over conventional hydrothermal alumina synthesis.

[0017] In S1, the preferred hydrothermal synthesis temperature is 85℃; in S2, the preferred aging temperature is 75℃; and in S3, the preferred calcination temperature is 500-700℃, with the optimal temperature being 500℃ for 2 hours.

[0018] Preferably, the support contains 1%–12 wt% SiO2, 1%–12 wt% MgO, and the balance is Al2O3. Further, the support contains 4%–12 wt% SiO2, 4%–12 wt% MgO, and the balance is Al2O3. The optimal formulation is that the support contains 8 wt% SiO2, 12 wt% MgO, and the balance is Al2O3.

[0019] As a preferred embodiment, the preparation method of cationic material and anionic material 1 is as follows: 3.40g of aluminum sulfate (Al2(SO4)3·18H2O) and 7.64g of magnesium sulfate (MgSO4·7H2O) are dissolved in 200g of water to obtain cationic material; 11.83g of sodium aluminate is dissolved in 200g of water to obtain anionic material 1.

[0020] The volume ratio of cationic material to anionic material 1 is 1:1.

[0021] Preferably, the molar ratio of aluminum ion content to magnesium ion content and aluminate content to silicate content in the three materials is 1:4, resulting in a hydrothermal synthesis pH > 9; the molar ratio of magnesium to aluminum is < 0.3:1, and the molar ratio of silicon to aluminum is < 0.4:1. More preferably, the molar ratio of magnesium to aluminum is 0.2:1. An excessively high magnesium-aluminum ratio can easily lead to the formation of a spinel phase after precursor calcination (significantly reducing the specific surface area of ​​the support and decreasing activity); experiments have shown that excessive silicon content reduces the specific surface area of ​​the support, potentially leading to excessive formation of silica crystals rather than a silica-alumina framework. Small amounts of magnesium and silicon have a positive effect on catalyst activity.

[0022] A propane dehydrogenation catalyst, wherein the catalyst uses the silica-magnesium modified alumina support described in this invention as a support, and the catalyst contains 0.05–1.2 wt% platinum and 0.05–1.2 wt% tin, based on 100% of the total catalyst mass. The catalyst is prepared by the following method:

[0023] A mixed solution of chloroplatinate and tin soluble salts was prepared to obtain an impregnation solution; a silicon-magnesium modified alumina support was immersed in the impregnation solution for thorough impregnation, dried, and reduced to obtain a propane dehydrogenation catalyst.

[0024] Preferably, the catalyst contains 0.1–0.6 wt% platinum and 0.1–0.6 wt% tin, based on 100% of the total catalyst mass. The optimal condition is Pt:Sn = 1:2 mol, meaning the catalyst contains approximately 0.4 wt% Pt and approximately 0.49 wt% Sn.

[0025] Preferably, the impregnation time is 4 to 5 hours, the drying temperature is 60℃ ± 5℃, the reduction is carried out in a hydrogen atmosphere, the reduction temperature is 500℃, and the reduction time is 4 to 8 hours.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention introduces magnesium by combining the generation characteristics of hydrated silicon-aluminum oxide. No spinel phase is generated in the hydrated silicon-magnesium-aluminum oxide obtained at high pH. Instead, a small-grained pseudo-boehmite phase is generated. By calcining this hydrated silicon-magnesium-aluminum oxide, a silicon-magnesium-aluminum oxide carrier with large specific surface area, reduced acidity and good thermal stability can be obtained.

[0028] 2. This invention does not require the addition of acid or alkali reagents to adjust the pH value, thus eliminating the pH adjustment process, making it easy to industrialize and saving costs. Attached Figure Description

[0029] Figure 1 It is the thermal conversion process of alumina hydrate;

[0030] Figure 2 The image shows the XRD patterns of hydrated oxides with different magnesium-aluminum ratios when the silicon content is 12wt%. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below through specific embodiments. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0032] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0033] Unless otherwise specified, the reagents used in the following examples can be purchased from a regular biochemical reagent store.

[0034] Working principle:

[0035] Alumina is an important support in heterogeneous catalysis. It is inexpensive, easy to produce, and its inherent acidity allows it to catalyze certain reactions. For specific applications, the specific surface area, pore size, and pore volume of the support significantly influence the catalytic effect. Alumina is usually obtained by dehydrating aluminum hydroxide. Currently, eight alumina structures have been discovered, and different types of alumina are obtained by calcining aluminum hydroxide under different temperature conditions. Commonly used mesoporous alumina generally refers to γ-alumina, an amorphous, low-temperature transition state alumina that can be obtained by dehydrating pseudoboehmite (false monohydrate boehmite).

[0036] Silicon is a commonly used carrier modifier, and its addition can improve the thermal stability of alumina. When alumina is prepared by co-precipitation without additional additives, boehmite is formed at pH > 9. This hydrated alumina has a dense structure, which is an undesirable product when preparing alumina with a large specific surface area. Research and experiments have shown that even with an appropriate amount of silicon additive, the resulting hydrated alumina retains a pseudoboehmite structure at pH > 10.

[0037] Without additional additives, calcination temperature affects the dehydration products of hydrated alumina. As the calcination temperature increases, the alumina undergoes further dehydration and sintering, causing its pore structure to collapse and its specific surface area to decrease. The addition of silicon increases the thermal stability of hydrated alumina, allowing silicon-modified alumina to remain stable at higher temperatures. Because the temperature range used for propane dehydrogenation is between 500℃ and 700℃, a calcination temperature within this range is recommended. Excessively high calcination temperatures can affect the pore structure of the support and may weaken the reaction.

[0038] γ-alumina possesses abundant L-acid sites, which easily lead to carbon deposition when used as a propane dehydrogenation catalyst support. Therefore, magnesium additives are added to reduce its acidity. Magnesium ions precipitate within a pH range of approximately 9–12. If magnesium and aluminum salts are co-precipitated, a spinel phase is easily formed during precipitation. Although the acidity of the resulting support is somewhat reduced after calcination, the specific surface area also decreases significantly. The thermal conversion process of alumina hydrate is as follows: Figure 1 As shown.

[0039] The method used in this invention to prepare silicon-magnesium modified alumina is a co-precipitation method, employing a co-flow feeding method with three feed streams:

[0040] Cationic materials, including aluminum and magnesium salts;

[0041] Anionic material 1 is sodium aluminate;

[0042] Anionic material 2 is a silicate;

[0043] No additional acid or base reagents are added to adjust the pH value;

[0044] The ratio of anions to cations used is anion:cation = 4:1 (mol), wherein the anions are aluminate and silicate, and the cations are aluminum and magnesium ions;

[0045] When preparing the solution, the cationic material and anionic material 1 use an equal amount of water, while the amount of water used for anionic material 2 is not required and can be less than that of the former.

[0046] The preparation process is as follows:

[0047] 1. Feeding: Leave a small amount of water in the constant temperature reactor, turn on the stirrer, maintain the reaction temperature at 60-90℃, add three streams into the reactor in parallel, and add all three streams at the same time. The feeding time is 60-90 minutes. After the feeding is completed, continue stirring and react for 6 hours.

[0048] 2. Aging: After the reaction is complete, turn off the stirring, adjust the aging temperature to 60-90℃, and age for 1 hour;

[0049] 3. Washing: After filtering the aged precursor, add water to make a pulp, filter again, and wash 3 times with water.

[0050] 4. Drying: Dry the washed filter cake at 100-120℃ for more than 12 hours to obtain silica-magnesium modified pseudoboehmite.

[0051] 5. Calcination: The aforementioned modified boehmite was calcined at 400–700℃ for 2 hours to obtain a silicon-magnesium modified alumina support, denoted as Si. x Al y Mg z The carrier, x, y, and z are denoted as the mass percentages of the oxides corresponding to the three components in the carrier.

[0052] The method used in this invention to prepare the propane dehydrogenation catalyst is the excess impregnation method, and the preparation method is as follows:

[0053] 1. Preparation of active component solution: Prepare a mixed solution of chloroplatinate and soluble salt of tin, stir and set aside; 2. Loading: Add the silicon-magnesium modified alumina support to the active component solution and stir to impregnate for 0.5-12 hours, then dry to obtain the catalyst precursor;

[0054] 3. Reduction: The catalyst precursor is reduced in a hydrogen atmosphere for 4–8 hours at a reduction temperature of 400–700℃ to obtain PtSn-Si. x Al y Mg z catalyst.

[0055]

Example 1

[0056] a) Dissolve 3.40g of aluminum sulfate (Al2(SO4)3·18H2O) and 7.64g of magnesium sulfate (MgSO4·7H2O) in 200g of water to obtain cationic material; dissolve 11.83g of sodium aluminate in 200g of water to obtain anionic material 1; dissolve 6.10g of sodium silicate (Na2SiO3·9H2O) in 30g of water to obtain anionic material 2. Add the three materials in parallel to a reaction vessel containing water, and add them while stirring at 85℃. After 70 minutes, add all three materials and continue stirring for 6 hours. After stirring, adjust the water bath temperature to 75℃, age for 1 hour, filter to obtain filter cake, wash with water 3 times, and dry at 110℃ to obtain magnesium silicate modified boehmite.

[0057] b) The obtained modified support was calcined at 500℃ for 2 hours, then pulverized and sieved to obtain the silicon-magnesium modified alumina support Si. 12.0 Al 75.6 Mg 12.4 .

[0058] c) Dissolve 0.21 g of chloroplatinic acid (H2PtCl6·6H2O) and 0.28 g of tin chloride (SnCl4·5H2O) in 20 g of water to prepare an impregnation solution (platinum loading 0.4 wt%, Pt:Sn = 1:2 (mol)). Add 1.83 g of the modified support to the impregnation solution and stir for 4 h. Dry at 60 °C and reduce at 500 °C for 5 h in a hydrogen stream to obtain catalyst A.

[0059]

Example 2

[0060] The support and catalyst were prepared according to the method of Example 1, except that the silica content in the support was 12% and no magnesium was added. The resulting catalyst was designated as B.

[0061]

Example 3

[0062] The support and catalyst were prepared according to the method of Example 1, except that the silica content in the support was 12% and the magnesium oxide content was 4%, and the resulting catalyst was denoted as C.

[0063]

Example 4

[0064] The support and catalyst were prepared according to the method of Example 1, except that the silica content in the support was 12% and the magnesium oxide content was 8%, and the resulting catalyst was denoted as D.

[0065]

Example 5

[0066] The support and catalyst were prepared according to the method of Example 1, except that the Mg:Al ratio in the support was 0.2:1 (mol) and the silica content was 4%. The resulting catalyst was denoted as E.

[0067]

Example 6

[0068] The support and catalyst were prepared according to the method of Example 1, except that the Mg:Al ratio in the support was 0.2:1 (mol) and the silica content was 8%, and the resulting catalyst was denoted as F.

[0069]

Example 7

[0070] The support and catalyst were prepared according to the method of Example 1, except that the Mg:Al ratio in the support was 0.2:1 (mol) and the silica content was 16%. The resulting catalyst was denoted as G.

[0071] Comparative Example 1

[0072] a) Dissolve 2.24g of aluminum sulfate (Al2(SO4)3·18H2O) and 8.51g of magnesium sulfate (MgSO4·7H2O) in 200g of water to obtain cationic material; dissolve 13.59g of sodium aluminate in 200g of water to obtain anionic material 1. Add the two materials concurrently to a reactor containing water, stirring at 85℃. After 70 minutes, all three materials are added, and stirring continues for 6 hours. After stirring is completed, the water bath temperature is adjusted to 75℃. After aging for 1 hour, filter to obtain filter cake, wash with water 3 times, and dry at 110℃ to obtain magnesium-modified hydrated alumina (without adding silicon source).

[0073] b) The obtained modified carrier was calcined at 500℃ for 2 hours, then pulverized and sieved to obtain the magnesium-modified alumina carrier SiOAl. 86.3 Mg 13.7 .

[0074] c) Dissolve 0.21 g of chloroplatinic acid (H2PtCl6·6H2O) and 0.28 g of tin chloride (SnCl4·5H2O) in 20 g of water to prepare an impregnation solution (platinum loading 0.4%, Pt:Sn = 1:2 (mol)). Add 1.83 g of the modified support to the impregnation solution and stir for 4 h. Dry at 60 °C and reduce at 500 °C for 5 h in a hydrogen stream to obtain catalyst H.

[0075] Comparative Example 2

[0076] a) Dissolve 3.40g of aluminum sulfate (Al2(SO4)3·18H2O) and 7.64g of magnesium sulfate (MgSO4·7H2O) in 200g of water to obtain cationic material; dissolve 11.83g of sodium aluminate in 200g of water to obtain anionic material 1; dissolve 6.10g of sodium silicate (Na2SiO3·9H2O) in 30g of water to obtain anionic material 2. Add the three materials in parallel to a reaction vessel containing water, and add them while stirring at 85℃. After 70 minutes, add all three materials and continue stirring for 6 hours. After stirring, adjust the water bath temperature to 75℃, age for 1 hour, filter to obtain filter cake, wash with water 3 times, and dry at 110℃ to obtain magnesium silicate modified boehmite.

[0077] b) The obtained modified support was calcined at 500℃ for 2 hours, then pulverized and sieved to obtain the silicon-magnesium modified alumina support Si. 12.0 Al 75.6 Mg 12.4 .

[0078] c) Dissolve 0.21 g of chloroplatinic acid (H₂PtCl₆·6H₂O) in 20 g of water to prepare an impregnation solution (platinum loading 0.4%, no tin source added). Add 1.92 g of the modified support to the impregnation solution and stir for 4 h, then dry at 60 °C. Reduce at 500 °C for 5 h in a hydrogen stream to obtain catalyst I. (No tin additive added)

[0079] Table 1 shows the textural properties of catalysts with different silicon contents in the magnesium-aluminum modified alumina support when the magnesium-aluminum molar ratio is 0.2.

[0080] Table 1. Texture properties of catalysts with different silicon contents at a magnesium-aluminum molar ratio of 0.2.

[0081]

[0082] Table 1 shows that the catalyst support area is very small when no silicon is added or only a small amount of silicon is added. Adding an appropriate amount of silicon improves the surface properties of the support. Excessive silicon addition can expand the pore volume and pore size of the support, but it decreases the BET specific surface area. Therefore, the preferred solution is that the SiO2 content in the silicon-magnesium modified alumina support is 4–12 wt%, the MgO content is 4–12 wt%, and the balance is Al2O3. The optimal solution is that the SiO2 content in the support is 8 wt%, the MgO content is 12 wt%, and the balance is Al2O3.

[0083] XRD patterns of hydrated oxides with different magnesium-aluminum ratios when silicon content is 12wt% are shown below. Figure 2 As shown, by Figure 2 It can be seen that after adding an appropriate amount of magnesium, the prepared hydrated oxide exhibits pseudoboehmite crystallization. As the magnesium content increases, the pseudoboehmite grains become finer. After adding excessive magnesium, the hydrated oxide obtained transforms into other crystalline phases.

[0084] Catalyst performance comparison: Reaction conditions: 620℃, atmospheric pressure, propane mass hourly space velocity (WHSV): 4.6 h⁻¹ -1 Under the condition that H2:C3H8 is 1:2, after reacting for 72 hours, the catalyst was regenerated by air burning at 500℃ for 60 minutes. The performance is shown in Table 2.

[0085] Table 2 Catalytic performance of the examples and comparative examples

[0086]

[0087]

[0088] As shown in Table 2, the propane dehydrogenation catalyst prepared in this invention exhibits slightly higher selectivity than conventional catalysts (20%-30%) across multiple regeneration cycles, indicating improved side reaction rates and reduced carbon deposition. Furthermore, the size of the active component did not significantly increase after multiple regeneration cycles, suggesting that the active centers of this catalyst are less prone to sintering. The catalyst prepared in Example 6 is the optimal one, exhibiting high conversion rate, high selectivity, and high stability. This solves the problems of easy side reaction and carbon deposition, and easy sintering of platinum ions, in existing dehydrogenation catalysts under high-temperature conditions.

[0089] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0090] The foregoing has provided a detailed description of the silicon-magnesium modified alumina support and propane dehydrogenation catalyst provided by this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A silicon-magnesium modified alumina carrier, characterized in that: The support contains 4%~12wt% SiO2, 4%~12wt% MgO, and the balance is Al2O3. This support is prepared by calcining a silicon-magnesium modified pseudo-boehmite phase precursor synthesized at pH 10~12. The preparation method includes the following steps: S1. Adding materials: Prepare cationic material, anionic material 1, and anionic material 2 respectively. The cationic material is a mixed solution of aluminum sulfate and magnesium sulfate, the anionic material 1 is a sodium aluminate solution, and the anionic material 2 is a sodium silicate solution. The three materials are added in parallel to a reaction vessel containing water, with a slight excess of alkaline material. The hydrolysis reaction is carried out by hydrothermal stirring. The hydrothermal synthesis temperature is controlled at 60~90℃, and the stirring reaction time is 5h~8h. S2, aging, washing and drying: Subsequently, hydrothermal aging is carried out at a temperature of 60~90℃ for 1h~2h. The obtained product is filtered, washed and dried to obtain magnesium silicate modified pseudoboehmite. The solid product is dried at a temperature of 100~120℃ for more than 12h. S3. Calcination: The obtained Mg-modified pseudoboehmite is calcined, crushed, and sieved to obtain the Mg-modified alumina carrier; the calcination temperature is 400~700℃, and the calcination time is 2h~3h.

2. The silicon-magnesium modified alumina carrier according to claim 1, characterized in that: The preparation methods for cationic material and anionic material 1 are as follows: 3.40g of Al2(SO4)3•18H2O and 7.64g of MgSO4•7H2O are dissolved in 200g of water to obtain cationic material; 11.83g of sodium aluminate is dissolved in 200g of water to obtain anionic material 1. The volume ratio of cationic material to anionic material 1 is 1:

1.

3. The silicon-magnesium modified alumina carrier according to claim 1, characterized in that: The molar ratio of aluminum ion content to magnesium ion content and aluminate content to silicate content in the three materials is 1:4; the molar ratio of magnesium to aluminum is <0.3:1, and the molar ratio of silicon to aluminum is <0.4:

1.

4. A propane dehydrogenation catalyst, characterized in that: The catalyst uses the silicon-magnesium modified alumina support as described in claim 1 as a support. Based on the total mass of the catalyst (100%), the catalyst contains 0.05~1.2 wt% platinum and 0.05~1.2 wt% tin. The catalyst is prepared by the following method: A mixed solution of chloroplatinate and tin soluble salts was prepared to obtain an impregnation solution; a silicon-magnesium modified alumina support was immersed in the impregnation solution for thorough impregnation, dried, and reduced to obtain a propane dehydrogenation catalyst.

5. The propane dehydrogenation catalyst according to claim 4, characterized in that: Based on the total mass of the catalyst (100%), the catalyst contains 0.1-0.6 wt% platinum and 0.1-0.6 wt% tin.

6. The propane dehydrogenation catalyst according to claim 4, characterized in that: The impregnation time is 4-5 hours, the drying temperature is 60℃±5℃, and the reduction is carried out in a hydrogen atmosphere at a temperature of 500℃ for 4-8 hours.

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