Surface modified alumina carrier and preparation method and application thereof

Abstract

The invention relates to the technical field of aluminum oxide production, in particular to a surface modified aluminum oxide carrier as well as a preparation method and application thereof. The surface modified alumina carrier is of a core-shell structure and comprises an alumina core and a surface modified shell layer, and the surface modified shell layer is alumina of a fibrous structure; the surface-modified aluminum oxide carrier is prepared by reacting a surface modifier with aluminum oxide to generate an aluminum oxide precursor on the surface of the aluminum oxide and then roasting, and the surface modifier is selected from one or more than two of ammonium bicarbonate, ammonium carbonate and ammonium carbamate. By using the surface modified aluminum oxide as a carrier, the catalytic activity and the catalytic stability of the catalyst in a catalytic reaction can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of alumina production, and in particular to a surface-modified alumina carrier and a preparation method and application thereof. Background Art

[0002] Alumina is widely used in the field of industrial catalyst carriers because of its large specific surface area, developed pore structure, high mechanical strength and excellent thermal stability. At present, the industrial preparation methods of alumina mainly include acid method, alkali method, acid-base combined method and thermal method. The differences in preparation methods determine the diversity of alumina structure, especially the surface properties of alumina, which is the main site of catalytic reaction and directly affects the activity of the catalyst.

[0003] There are many types of commercial alumina carriers available, with different preparation processes, and the surface properties (especially surface acidity) are difficult to accurately control. In addition, the precursors of alumina come from various sources, such as aluminum hydroxide, pseudo-boehmite, ammonium aluminum carbonate, ammonium aluminum sulfate, and aluminum dry glue. The surface properties of alumina formed after calcination vary greatly, thus affecting the catalytic performance after loading the active components.

[0004] Commonly used alumina has a strong surface acidity, which easily leads to the formation of carbon deposits in catalytic reactions. Researchers have done a lot of work to regulate the surface properties of alumina. Among them, adding alkali metals is a common method to improve the acidity of alumina. In existing patents such as CN1668555A, CN104209123A and CN102123790A, the alkali metals selected include any one from lithium to cesium. Alkali metals can eliminate the acidic sites formed by Al-OH, thereby reducing side reactions and inhibiting the formation of carbon deposits. However, under certain reaction conditions, especially in aqueous environments, alkali metal ions are easily lost or dissolved, resulting in a decrease in the long-term stability of the catalyst.

[0005] In addition, alkali metals may interact adversely with other active components in the catalyst, affecting the overall catalytic performance. Chinese patent CN105251486A discloses a technology for preparing a modified alumina carrier by introducing alkali metals such as La, Ce, Cs, K, and Na during the preparation of an alumina precursor. The catalyst performs well in selectivity, but there is still room for improvement in stability. Chinese patent CN101414073A prepared a chromium-based alumina catalyst for propane dehydrogenation to propylene with chromium metal as an active component and rare earth metals and alkaline earth metals as additives, although it showed a high conversion rate. However, the selectivity is insufficient and the life is short. The catalyst conversion rate drops rapidly within tens of minutes, and frequent regeneration is required to maintain the continued reaction.

[0006] Chinese patent CN111715200A discloses a core-shell structure alumina carrier, which uses alumina and / or silicon oxide particles as core seeds, and grows a layer of L-acid-rich alumina carrier on its surface. The liquid phase preparation method of the core-shell structure alumina carrier includes dispersing the seeds in water to obtain solution A, dissolving aluminum salt to obtain solution B, adding a precipitant to solution B to obtain solution C, and then mixing solution A and solution C, aging and high-temperature roasting. Although the catalyst obtained by using the alumina carrier as a carrier is applied to the propane dehydrogenation catalytic reaction, its stability is improved, but it still needs to be improved; and the preparation method of the alumina carrier has more process steps and low process efficiency. Summary of the invention

[0007] The technical problem to be solved by the present invention is: how to reduce the acidity of the surface of alumina and improve the surface performance of alumina, reduce the formation of carbon deposits when it is used as a carrier in catalysts, and improve the activity and stability of the catalyst.

[0008] In view of the shortcomings of the prior art, the present invention provides a preparation method for growing a layer of aluminum oxide in situ on the surface of commercial aluminum oxide or aluminum oxide hydrate as the core material. Based on the dissolution-reprecipitation theory, a layer of aluminum oxide with controllable thickness is constructed on the surface of the core material by a normal pressure liquid phase method. The prepared new (low acidity) aluminum oxide has uniform surface properties, abundant weak acid sites and fewer strong acid sites, and the preparation process is simple, economical and environmentally friendly.

[0009] Specifically, in order to solve the problems in the prior art, the present invention provides the following technical solutions:

[0010] In a first aspect, the present application provides a surface-modified alumina carrier, which is a core-shell structure, comprising an alumina core and a surface-modified shell layer, wherein the surface-modified shell layer is alumina with a fibrous structure; the surface-modified alumina carrier is obtained by reacting a surface modifier with alumina to generate an alumina precursor on the surface of the alumina, and then calcining the alumina carrier, wherein the surface modifier is selected from one or more of ammonium bicarbonate, ammonium carbonate and ammonium carbamate.

[0011] In some embodiments of the present application, the thickness of the surface modified shell layer is 0.005-4 μm, and preferably, the particle size of the alumina core is 0.01-8 μm.

[0012] In some embodiments of the present application, the specific surface area of ​​the surface-modified alumina carrier is 130-350 m 2 / g;

[0013] And / or, the total pore volume of the surface modified alumina carrier is 0.20-1.00 cm 3 / g;

[0014] And / or, the surface acid amount of the surface modified alumina support is 50-300 μmol NH3g -1 ;

[0015] And / or, the peak pore diameter of the surface modified alumina carrier is 3-22 nm.

[0016] In some embodiments of the present application, it is prepared by dispersing aluminum oxide in water, adding a surface modifier, aging, drying and calcining, wherein the surface modifier is selected from one or more of ammonium bicarbonate, ammonium carbonate and ammonium carbamate.

[0017] In a second aspect, the present application provides a method for preparing a surface-modified alumina carrier, which comprises the following steps:

[0018] (1) dispersing aluminum oxide in water to obtain solution A;

[0019] (2) adding a surface modifier to the solution A obtained in step (1) to obtain a solution B, wherein no aluminum salt is added to the solution B;

[0020] (3) subjecting the solution B obtained in step (2) to aging treatment, filtering, and drying to obtain a precursor;

[0021] (4) Calcining the precursor obtained in step (3) to obtain a surface-modified alumina carrier.

[0022] In some embodiments of the present application, step (1) is controlled at 15-40° C.;

[0023] and / or, the concentration of the surface modifier in solution B in step (2) is 0.5-6 mol / L, preferably, the molar ratio of the aluminum oxide to the surface modifier is 1:0.5-10, preferably 1:2-8, more preferably 1:4-8;

[0024] And / or, the aging temperature in step (3) is 25-150° C., preferably 50-100° C.; preferably, the aging time is 1-120 h, preferably 20-100 h;

[0025] And / or, the calcination temperature in step (4) is 500-700° C., and the preferred calcination time is 2-4 hours.

[0026] In some embodiments of the present application, the alumina is selected from one or more of pseudo-boehmite, boehmite, SB powder and gibbsite, or is obtained by calcining one or more of pseudo-boehmite, boehmite, SB powder and gibbsite; preferably, the calcination temperature is 300-1000°C, preferably 300-600°C.

[0027] In a third aspect, the present application also provides a surface-modified alumina carrier, which is prepared by the above-mentioned preparation method.

[0028] In a fourth aspect, the present application also provides the application of the above-mentioned surface modified alumina carrier in the field of catalysts.

[0029] In a fifth aspect, the present application also provides a catalyst for catalyzing propane dehydrogenation reaction, the catalyst comprising the above-mentioned surface-modified alumina carrier and an active component;

[0030] Preferably, the active component includes a Pt active component and a Sn active component;

[0031] Further preferably, the Pt active component exists in the catalyst in the form of single substance Pt, and the mass ratio of the single substance Pt to the core-shell structure alumina carrier is 0.3-0.5:100;

[0032] Further preferably, the Sn active component exists in the form of tin oxide, and the mass ratio of the tin oxide to the core-shell structure alumina carrier is 1-2.5:100.

[0033] In a sixth aspect, the present application provides a method for preparing a catalyst for catalyzing a propane dehydrogenation reaction, comprising the following steps:

[0034] S1. Preparing a surface-modified alumina support;

[0035] S2. impregnating the surface-modified alumina support described in S1 with an active component precursor solution in equal volumes to obtain a catalyst precursor;

[0036] S3. calcine the catalyst precursor obtained in S2 to obtain a catalyst.

[0037] In some embodiments of the present application, the active component precursor solution in S2 is a mixed solution of a Pt element solution and a Sn element solution;

[0038] Preferably, the Pt element solution is selected from one or a mixed solution of two or more of chloroplatinic acid, platinum nitrate, tetraammine platinum nitrate, and platinum trichloride, and further preferably, the mass concentration of the Pt element solution is 0.2-0.7%;

[0039] Preferably, the Sn element solution is selected from one or a mixed solution of two or more of tin dichloride, tin tetrachloride, tin nitrate, and tin acetate, and further preferably, the mass concentration of the Sn element solution is 0.4-0.9%;

[0040] Preferably, the calcination temperature in step S3 is 300-500°C;

[0041] More preferably, the calcination time is 3-6 hours.

[0042] In a seventh aspect, the present application provides a catalyst for catalyzing propane dehydrogenation reaction, which is prepared by the above-mentioned preparation method.

[0043] In an eighth aspect, the present application provides a method for catalyzing propane dehydrogenation reaction, which uses the above-mentioned catalyst to catalyze propane dehydrogenation reaction.

[0044] In some embodiments of the present application, the propane feed mass space velocity is 1-20h -1 .

[0045] In some embodiments of the present application, the reaction temperature is 550-600°C.

[0046] In some embodiments of the present application, the feed gas for the catalytic propane dehydrogenation reaction includes propane, hydrogen and nitrogen; preferably, the volume percentages of the propane, hydrogen and nitrogen are 10-20%, 15-25% and 60-70%, respectively.

[0047] Beneficial effects of the present invention:

[0048] 1. Compared with alumina, the surface-modified alumina carrier provided by the present invention has concentrated pore distribution, uniform surface properties, few strong acid sites, and abundant weak acid sites;

[0049] 2. The preparation method provided by the present invention is simple to operate, has low energy consumption, high yield, and is economical and environmentally friendly;

[0050] 3. The supported catalyst prepared by the present invention using surface modified alumina as a carrier has excellent activity and stable performance in the catalytic reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is the XRD spectrum of the precursor before calcination in Example 2;

[0052] Figure 2 This is the XRD spectrum of the precursor before calcination in Example 5;

[0053] Figure 3 This is the XRD spectrum of the precursor before calcination in Example 8;

[0054] Figure 4 is a SEM picture of commercial alumina 1;

[0055] Figure 5 This is a SEM photo of the surface alumina support prepared in Example 2;

[0056] Figure 6 This is a SEM photo of the surface alumina support prepared in Example 5;

[0057] Figure 7 This is a SEM photo of the surface alumina support prepared in Example 8;

[0058] Figure 8 NH3-TPD test spectra of the surface alumina support prepared in Example 7 and commercial alumina 2;

[0059] Fig. 9 The pore size distribution diagrams of the surface alumina carrier prepared in Example 4, the alumina carrier prepared in Comparative Example 4, and commercial alumina 1. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and technical effect of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention is described clearly and completely. The embodiments described below are part of the embodiments of the present invention, not all of them. In combination with the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] The present application provides a surface-modified alumina carrier and a preparation method thereof, which specifically includes: using alumina or alumina hydrate as a core material, in situ constructing a layer of precursor on the surface of the core material through a dissolution and reprecipitation mechanism, and obtaining surface-modified alumina by calcination, as well as the use of the surface-modified alumina as a carrier in a supported catalyst (dehydrogenation of propane to propylene).

[0062] In a specific embodiment of the present application, the present application provides a surface modified alumina carrier, which is a core-shell structure, including an alumina core and a surface modified shell layer, and the surface modified shell layer is alumina with a fibrous structure; the surface modified alumina carrier is obtained by reacting a surface modifier with alumina to generate an alumina precursor on the surface of alumina, and then calcining, wherein the surface modifier is selected from one or more of ammonium bicarbonate, ammonium carbonate and ammonium carbamate.

[0063] In the present application, the surface modifier reacts with alumina to form a layer of fibrous ammonium aluminum carbonate on the surface of the alumina, and a surface modified shell layer with a fibrous structure is obtained after calcination. The present invention does not require the addition of aluminum salt, simplifies the process, saves costs, and also improves the conversion efficiency when used to prepare the catalyst, reduces the amount of carbon deposition, and improves the activity and stability of the catalyst.

[0064] In some embodiments of the present application, the thickness of the surface modified shell layer is 0.005-4 μm, and preferably, the particle size of the alumina core is 0.01-8 μm. In some embodiments of the present application, the thickness of the surface modified shell layer can be 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm or a range formed by any two of the above values ​​as endpoints. In some embodiments of the present application, the particle size of the alumina core can be 0.01μm, 0.05μm, 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm or 8μm or a range formed by any two of the above values ​​as endpoints.

[0065] In some embodiments of the present application, the specific surface area of ​​the surface-modified alumina carrier is 130-350 m 2 / g; and / or, a total pore volume of 0.20-1.00cm 3 / g, preferably 0.29-0.94cm 3 / g; and / or, the surface acid amount of the carrier is 50-300 μmol NH3 g -1 ; and / or, the peak pore size of the surface modified alumina carrier is 3-22nm.

[0066] In some embodiments of the present application, the specific surface area of ​​the surface-modified alumina support may be 130 m 2 / g,135m 2 / g,140m 2 / g,145m 2 / g,148m 2 / g,149m 2 / g,150m 2 / g,152m 2 / g,155m 2 / g,159m 2 / g,160m 2 / g,165m 2 / g,170m 2 / g,175m 2 / g, 180m 2 / g,185m 2 / g, 190m 2 / g,195m 2 / g,200m 2 / g,205m 2 / g, 210m2 / g,215m 2 / g,220m 2 / g,225m 2 / g, 230m 2 / g,235m 2 / g,240m 2 / g,244m 2 / g,245m 2 / g,250m 2 / g,255m 2 / g, 256m 2 / g,260m 2 / g,261m 2 / g,265m 2 / g,268m 2 / g,270m 2 / g,275m 2 / g,280m 2 / g,285m 2 / g,290m 2 / g,295m 2 / g,295m 2 / g,300m 2 / g,305m 2 / g,310m 2 / g,315m 2 / g,319m 2 / g, 320m 2 / g,325m 2 / g or 330m 2 / g or a range formed by any two of the above values ​​as endpoints.

[0067] In some embodiments of the present application, the total pore volume of the surface-modified alumina support may be 0.2 cm 3 / g, 0.25cm 3 / g, 0.29cm 3 / g,0.3cm 3 / g,0.31cm 3 / g, 0.33cm 3 / g,0.35cm 3 / g,0.4cm 3 / g, 0.45cm 3 / g,0.5cm 3 / g,0.55cm 3 / g,0.6cm 3 / g,0.65cm 3 / g,0.7cm 3 / g, 0.75cm3 / g,0.8cm 3 / g,0.81cm 3 / g,0.82cm 3 / g, 0.85cm 3 / g,0.89cm 3 / g,0.9cm 3 / g,0.92cm 3 / g,0.94cm 3 / g,0.95cm 3 / g or 1.00cm 3 / g or a range formed by any two of the above values ​​as endpoints.

[0068] In some embodiments of the present application, the surface acidity of the carrier is 50 μmol NH3 g -1 , 55 μmol NH3 g -1 , 60 μmol NH3 g -1 , 65 μmol NH3 g -1 , 70 μmol NH3g -1 , 75 μmol NH3 g -1 , 80 μmol NH3g -1 , 85 μmol NH3 g -1 , 90 μmol NH3 g -1 , 95 μmol NH3g -1 , 100 μmol NH3 g -1 , 121 μmol NH3 g -1 , 122 μmol NH3 g -1 , 150 μmol NH3 g -1 , 178 μmol NH3 g -1 , 185 μmol NH3 g -1 , 187 μmol NH3 g -1 , 200 μmol NH3g -1 , 209 μmol NH3 g -1 , 241 μmol NH3 g -1 , 250 μmol NH3 g -1 , 262 μmol NH3 g -1 , 278 μmol NH3 g -1 , 295 μmol NH3 g -1 , or 300 μmol NH3 g -1 Or a range formed by any two of the above values ​​as endpoints.

[0069] In some embodiments of the present application, the peak pore size of the surface modified alumina carrier can be 3nm, 3.9nm, 4nm, 4.4nm, 4.5nm, 5nm, 5.3nm, 6nm, 6.9nm, 7nm, 7.5nm, 8nm, 9nm, 10nm, 10.1nm, 10.5nm, 10.6nm, 12nm, 14nm, 16nm, 18nm, 20nm or 22nm or a range formed by any two of the above values ​​as endpoints.

[0070] Peak pore size, total pore volume, and surface acid content are all factors that affect the decline in catalyst conversion rate and stability. Among them, the surface acid content is particularly important. The reason is that the acid sites on the surface of alumina, especially the strong acid sites, are the sites where side reactions such as cracking occur. Therefore, the amount of carbon deposits during the reaction is affected by the acid content of the carrier. Carriers with less acid content, especially strong acid, often have less carbon deposits and better stability of the catalytic reaction. Weak acid sites usually promote the activation of CH bonds during alkane reactions and anchor precious metals. Therefore, carriers rich in weak acid sites often show better activity and stability.

[0071] The shell thickness of the surface modified aluminum oxide described in the present application can be calculated by scanning electron microscopy (SEM). The shell thickness can be controlled by adjusting the amount of the surface modifier, the aging time and the aging temperature.

[0072] The present application provides a method for preparing a surface-modified alumina carrier, which comprises dispersing alumina in water, adding a surface modifier, aging, drying and calcining, wherein the surface modifier is selected from one or more of ammonium bicarbonate, ammonium carbonate and ammonium carbamate.

[0073] Through this method, a surface-modified alumina carrier with controllable surface properties and abundant weak acid sites is synthesized by a liquid phase method with the participation of a small amount of solvent.

[0074] Specifically, the method comprises the following steps:

[0075] S1. Disperse the alumina core material in water and stir in a water bath until uniformly dispersed to obtain solution A;

[0076] S2. The surface modifier is added to solution A to obtain solution B, wherein no aluminum salt is added to solution B;

[0077] S3. placing solution B in a container for aging, filtering, and drying to obtain a precursor;

[0078] S4. The precursor obtained in step S3 is calcined to obtain a surface-modified alumina carrier.

[0079] The present invention uses commercial alumina or alumina hydrate as the core, and does not require the addition of additional aluminum salts, which not only simplifies the process steps but also reduces costs. In addition, the present invention method can reduce the total acid content, while reducing the proportion of strong acid sites and enriching weak acid sites, thereby helping to inhibit carbon deposition and improve the stability and activity of the catalyst.

[0080] In some embodiments of the present application, the alumina core material is alumina or alumina hydrate, wherein the alumina hydrate is selected from one or more of pseudo-boehmite, boehmite, SB powder, and gibbsite; preferably one or more of pseudo-boehmite or gibbsite; the alumina is selected from one or more of pseudo-boehmite, boehmite, SB powder, and gibbsite and is obtained by calcination, and the calcination temperature is preferably 300-1000°C. In some embodiments of the present application, the calcination temperature can be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C or a range formed by any two of the above values ​​as endpoints, preferably 300-600°C.

[0081] In some embodiments of the present application, the calcination time is appropriately selected according to the intended purpose without any limitation, but it is preferably 2-4 hours.

[0082] In some embodiments of the present application, the water bath temperature in step S1 is 15°C-40°C.

[0083] In some embodiments of the present application, the concentration of the surface modifier in step S2 is 0.5-6 mol / L, and preferably the molar ratio of the alumina core material to the surface modifier is 1:0.5-1:10.

[0084] In some embodiments of the present application, the molar ratio of the surface modifier to the alumina core material can be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1, 5.0:1, 5.5:1, 6.0:1, 6.5:1, 7.0:1, 7.5:1, 8.0:1, 8.5:1, 9.0:1, 9.5:1 or 10.0:1 or a range formed by any two of the above values ​​as endpoints.

[0085] In some embodiments of the present application, the aging temperature in step S3 is 25-150° C., the aging time is 1-120 h, and after washing and drying, a white powder precursor is obtained. This step directly affects the morphology, crystal form and particle size of the product.

[0086] In some embodiments of the present application, the aging temperature of step S3 can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C or a range formed by any two of the above values ​​as endpoints, preferably 25-75°C.

[0087] In some embodiments of the present application, the aging time of step S3 can be 1h, 5h, 10h, 20h, 24h, 30h, 40h, 50h, 60h, 70h, 80h, 90h, 100h, 110h or 120h, preferably 20-120h.

[0088] In some embodiments of the present application, the calcination temperature in step S4 is 500-700°C, and the calcination time is 2-4h. The calcination treatment removes C, H, and O elements in the alumina precursor to form a porous structure. Therefore, the calcination process has a positive effect on the synthesis of the alumina carrier.

[0089] The present application also provides a method for preparing a catalyst for catalyzing propane dehydrogenation reaction, comprising the following steps:

[0090] Q1. Take 100-300 parts by weight of alumina carrier and dry it in a drying oven at a temperature of 100-200°C for 2-4h;

[0091] Q2. Immerse in a mixed solution containing Pt and Sn elements in equal volumes, wherein the mass concentration of the Pt element solution is 0.2-0.7%, and the mass concentration of the Sn element solution is 0.4%-1.0%, stir for 5-15 minutes, stand at room temperature for 2-4 hours, and dry at 50°C for 12 hours;

[0092] Q3. The catalyst obtained in step Q2 was calcined at 300-500°C for 3-6 hours with flowing air (10-100 mL / min).

[0093] The active material in the catalyst is a dual component. The Pt active component in the catalyst exists in the form of single substance Pt, and the Pt: surface modified alumina carrier (mass ratio) is 0.3-0.5:100.

[0094] The Sn active component in the catalyst exists in the form of tin oxide (SnO2), and the ratio of SnO2: surface modified alumina carrier (mass ratio) is 1-2.5:100.

[0095] The present invention uses alumina core material as a structural skeleton, and based on the dissolution reprecipitation theory, an active shell is uniformly constructed on the surface of the core material. The obtained surface-modified alumina carrier has the advantages of highly uniform surface properties, abundant weak acid sites, few strong acid sites, high yield, economy and environmental protection. The obtained surface-modified alumina catalyst as a carrier is applied to propane dehydrogenation reaction, and has excellent activity and stable performance.

[0096] The present application provides a method for catalyzing propane dehydrogenation reaction, which uses the above-mentioned catalyst to catalyze propane dehydrogenation reaction.

[0097] In some embodiments of the present application, the propane feed mass space velocity is 1-20h -1 .

[0098] In some embodiments of the present application, the reaction temperature is 550-600°C.

[0099] In some embodiments of the present application, the feed gas for the catalytic propane dehydrogenation reaction includes propane, hydrogen and nitrogen; preferably, the volume percentages of the propane, hydrogen and nitrogen are 10-20%, 15-25% and 60-70%, respectively.

[0100] The preparation method and technical effects of the surface-modified aluminum oxide of the present application will be specifically described below through specific examples.

[0101] The sources of raw materials and equipment used in the examples and comparative examples of the present invention are shown in Table 1.

[0102] Table 1 Sources of raw materials and equipment used in the examples and comparative examples of the present invention

[0103]

[0104]

[0105] Example 1

[0106] The preparation of surface modified alumina comprises the following specific steps:

[0107] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining pseudo-boehmite at 300° C. for 2 h.

[0108] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0109] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0110] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0111] Example 2

[0112] The preparation of surface modified alumina comprises the following specific steps:

[0113] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25°C, stirring rate 400 rpm. The alumina core material was alumina obtained by calcining pseudo-boehmite at 600°C for 2 h, and was marked as commercial alumina 1.

[0114] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0115] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0116] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0117] Example 3

[0118] The preparation of surface modified alumina comprises the following specific steps:

[0119] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining pseudo-boehmite at 1000° C. for 2 h.

[0120] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0121] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0122] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0123] Example 4

[0124] The preparation of surface modified alumina comprises the following specific steps:

[0125] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining pseudo-boehmite at 600° C. for 2 h.

[0126] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0127] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 1 h, then washed and dried;

[0128] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0129] Example 5

[0130] The preparation of surface modified alumina comprises the following specific steps:

[0131] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining pseudo-boehmite at 600° C. for 2 h.

[0132] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0133] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 120 h, then washed and dried;

[0134] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0135] Example 6

[0136] The preparation of surface modified alumina comprises the following specific steps:

[0137] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining pseudo-boehmite at 600° C. for 2 h.

[0138] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0139] (3) Solution B was transferred into a normal pressure reactor and aged at 30° C. for 24 h, then washed and dried;

[0140] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0141] Example 7

[0142] The preparation of surface modified alumina comprises the following specific steps:

[0143] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25°C, stirring rate 400 rpm. The alumina core material was alumina obtained by calcining gibbsite at 600°C for 2 h, and was marked as commercial alumina 2

[0144] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0145] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0146] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0147] Example 8

[0148] The preparation of surface modified alumina comprises the following specific steps:

[0149] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining gibbsite at 600° C. for 2 h.

[0150] (2) Add 13.2 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0151] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0152] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0153] Example 9

[0154] The preparation of surface modified alumina comprises the following specific steps:

[0155] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining gibbsite at 600° C. for 2 h.

[0156] (2) Add 7.9 g of ammonium bicarbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0157] (3) Solution B was transferred into a hydrothermal reactor and aged at 140° C. for 24 h, then washed and dried;

[0158] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0159] Example 10

[0160] The preparation of surface modified alumina comprises the following specific steps:

[0161] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining gibbsite at 600° C. for 4 h.

[0162] (2) Add 0.85 g of ammonium carbonate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0163] (3) Solution B was transferred into a normal pressure reactor and aged at 75° C. for 24 h, then washed and dried;

[0164] (4) The obtained precursor was calcined in a muffle furnace at 500° C. for 4 h to obtain a white powdery surface-modified alumina carrier.

[0165] Embodiment 11

[0166] The preparation of surface modified alumina comprises the following specific steps:

[0167] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining gibbsite at 600° C. for 3 h.

[0168] (2) Add 13 g of ammonium carbamate to solution A and continue stirring for 10 min until it is completely dissolved. The solution is labeled B.

[0169] (3) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0170] (4) The obtained precursor was calcined in a muffle furnace at 700° C. for 3 h to obtain a white powdery surface-modified alumina carrier.

[0171] Comparative Example 1

[0172] Compared with Example 2, the difference is that no ammonium bicarbonate is added. The specific preparation method is as follows:

[0173] (1) 1.7 g of aluminum oxide was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring speed 400 rpm. The aluminum oxide was obtained by calcining pseudo-boehmite at 600° C. for 2 h.

[0174] (2) Solution A was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0175] (3) The obtained precursor was calcined in a muffle furnace at 600°C for 2 h.

[0176] Comparative Example 2

[0177] Compared with Example 7, the difference is that no ammonium bicarbonate is added. The specific preparation method is as follows:

[0178] (1) 1.7 g of aluminum oxide was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The aluminum oxide was obtained by calcining gibbsite at 600° C. for 2 h.

[0179] (2) Solution B was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0180] (3) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0181] Comparative Example 3

[0182] The preparation method of patent CN 106673033 is cited. 12.45g AlCl3﹒6H2O, 10g urea, and 0.75g propylene oxide are placed in a beaker. 50ml anhydrous ethanol is added to the beaker. The solid matter is completely dissolved by magnetic stirring. The obtained solution is transferred to a high-pressure reactor, and the reactor is placed in an oven for heat treatment at 160℃ for 24 hours. After cooling naturally to room temperature, the precipitate is filtered, washed, dried at 120℃ for 6 hours, and calcined at 500℃ for 4 hours to obtain an alumina carrier with a specific surface area of ​​205m 2 / g, and the total pore volume is 0.69cm3 / g.

[0183] Comparative Example 4

[0184] Weigh 3.437g Al(NO3)3·9H2O and 6.276g (NH2)2CO and dissolve them in 100mL water, stir for 15min, and place in a 25℃ water bath; transfer the mixed solution to a hydrothermal kettle and react at 100℃ for 24h; after the reaction, filter to neutrality and dry at 50℃ for 12h. Take 1g of commercial Al2O3 and mix it directly with the above precursor, and calcine it in a muffle furnace at 600℃ for 2h to obtain an alumina carrier with a specific surface area of ​​187m 2 / g, with a total pore volume of 0.70 cm 3 / g.

[0185] Comparative Example 5

[0186] The preparation of surface modified alumina comprises the following specific steps:

[0187] (1) 1.7 g of alumina core material was placed in deionized water and stirred for 10 min until it was completely dispersed. The solution was marked as A. The water bath conditions were: temperature 25° C., stirring rate 400 rpm. The alumina core material was alumina obtained by calcining pseudo-boehmite at 600° C. for 2 h.

[0188] (2) Dissolve 9.4 g aluminum nitrate nonahydrate in deionized water and stir for 10 min until completely dissolved. The solution is labeled B.

[0189] (3) Mix A and B and stir for 10 min, add 7.9 g of ammonium bicarbonate, and continue stirring for 10 min until completely dissolved. The solution is marked as C.

[0190] (3) Solution C was transferred into a normal pressure reactor and aged at 50° C. for 24 h, then washed and dried;

[0191] (4) The obtained precursor was calcined in a muffle furnace at 600° C. for 2 h to obtain a white powdery surface-modified alumina carrier.

[0192] The surface modified alumina carriers prepared in the examples and comparative examples were tested using the following method:

[0193] 1. Peak pore diameter and total pore volume test:

[0194] Instruments used: Micromeritics TriStar 3000 from Micromeritics Instruments, USA;

[0195] Vacuum atmosphere, degassing at 200℃ for 6h;

[0196] Liquid nitrogen temperature, nitrogen adsorption and desorption test;

[0197] The specific surface area (S) was calculated according to the Brunauer-Emmett-Teller (BET) method at a relative pressure of 0.05-0.30. BET ), the pore size distribution (PDS) and peak pore size were calculated from the desorption branch of the adsorption isotherm according to Barrett-Joyner-Halenda (BJH), where the peak pore size refers to the pore size when the distribution curve reaches the maximum value in the pore size distribution, that is, the pore size at the peak of the distribution curve, and the total pore volume (V) was calculated using the adsorption amount when P / P0 = 0.99. total ).

[0198] 2. The shell thickness of the surface modified alumina carrier was tested by SEM test. The specific test and calculation methods include: measuring its thickness through the SEM software ruler; the microscopic morphology and structure of the sample were observed by FEINavaNanoSEM450 ultra-high resolution field emission scanning electron microscope (SEM) at 20kV.

[0199] 3. X-ray diffraction (XRD) analysis

[0200] The calcined precursor powder was analyzed by X-ray diffraction using an X-ray diffractometer (model: X'Pert-3Powder, manufacturer: PANalytical, the Netherlands). Cu target Kα diffraction was used in the experiment, and the incident wavelength was 50 KV and the tube current and tube pressure were 150 mA. The scanning step was 0.02, the scanning speed was 10° / min, and the scanning range 2θ was 10° to 90°.

[0201] 4.NH3-TPD test

[0202] The instrument used was AutoChemII 2920 from Micromeritics Instruments, USA.

[0203] The surface acidity of the raw material alumina as the alumina core material and the surface modified alumina prepared in the embodiment was tested by ammonia temperature programmed desorption (NH3-TPD), and the specific steps included:

[0204] (1) He atmosphere, program heating to 500°C at 10°C / min, hold for 1 h, and cool to 100°C;

[0205] (2) Pulse ammonia 6 times;

[0206] (3) He purge for 1 hour; temperature is 100°C

[0207] (4) Desorption by temperature program at 10 °C / min to 600 °C;

[0208] In order to more clearly illustrate the performance of different carriers obtained in the examples and comparative examples, the performance of the alumina carriers obtained in the above examples 1-11 and comparative examples 1-5 is summarized as shown in Table 2:

[0209] Table 2 Summary of alumina carrier performance

[0210]

[0211] From the above-mentioned examples and comparative examples, it can be seen that:

[0212] (1) XRD test analysis: The XRD test results of Example 2, Example 5 and Example 8 are as follows Figures 1 to 3 As shown, the characteristic peaks at diffraction angles 2θ=15.3°, 21.8°, and 26.9° indicate that basic ammonium aluminum carbonate is successfully generated on the surface of the alumina core.

[0213] (2) Surface performance test: According to the test results in Table 2, the surface modified alumina supports synthesized in Examples 1-6 of the present invention exhibit the following properties: peak pore diameter of 6.9-12.0 nm, total pore volume of 0.75-0.94 cm 3 / g, surface acid content is 121-295μmolNH3 g -1 In comparison, the peak pore size of commercial alumina 1 prepared by calcining commercial pseudoboehmite at 600 °C for 2 h was 5.3 nm and the total pore volume was 0.73 cm 3 / g, the surface acid content is 308μmol NH3 g -1 The surface performance of the alumina carrier synthesized by the method of the present invention is significantly lower than that of the surface modified alumina carrier synthesized by the method of the present invention. The alumina prepared by the preparation method of the patent CN 106673033 in comparative example 3 has a pore diameter of 5.7 nm and a pore volume of 0.69 cm3 / g, and its surface performance is also inferior to that of the surface modified alumina carrier synthesized by the present invention.

[0214] The peak pore diameter of the surface-modified alumina carrier synthesized in Examples 7-11 of the present invention is 3.9-5.3 nm, and the total pore volume is 0.25-0.33 cm 3 / g, surface acid content 122-209μmolNH3 g -1 The peak pore size of commercial alumina 2 obtained by calcining commercial gibbsite at 600°C is 3.4 nm and the pore volume is 0.22 cm 3 / g, surface acid content is 218μmolNH3 g -1 The surface performance is also inferior to that of the surface-modified alumina carrier synthesized by the method of the present invention.

[0215] Figure 4 This is the SEM image of commercial alumina 1. It can be seen that the morphology of commercial alumina 1 is a cluster structure of irregular particles stacked together. Figure 5 This is a SEM image showing the modified alumina support obtained in Example 2. Figure 6 This is a SEM image showing the modified alumina support obtained in Example 5. Figure 7 The SEM image of the modified alumina support prepared in Example 8 is shown in FIG. Figure 5-7 It can be seen that after modification, a fibrous alumina structure with regular morphology is formed, and the surface is obviously more uniform.

[0216] Figure 8 The results of NH3-TPD of commercial alumina 2 and the surface-modified alumina carrier synthesized in Example 7 are compared. It is found that after the commercial alumina 2 is modified, its total acid content is reduced, the proportion of strong acid sites is reduced, and the proportion of weak acid sites is increased. This proves that after modification, not only the total acid content can be reduced, but also the proportion of strong acid sites can be reduced, which is beneficial to inhibit carbon deposition and improve the stability of the catalyst.

[0217] Fig. 9 The pore size distribution diagram of the surface modified alumina support synthesized in Example 4, the surface modified alumina support synthesized in Comparative Example 4 and the commercial alumina 1 is shown in FIG. Fig. 9 It can be seen that after the commercial alumina 1 is modified, the pore size increases and the pore size distribution becomes more concentrated. At the same time, compared with the comparative example 4, the pore size distribution of the embodiment 4 is also more concentrated.

[0218] Compared with Comparative Example 5, Example 2 of the present application does not add aluminum nitrate, and directly uses ammonium bicarbonate to surface-modify the aluminum oxide to obtain a surface-modified aluminum oxide carrier, and its surface properties are significantly better than those of the aluminum oxide carrier obtained in Comparative Example 5.

[0219] Experimental example

[0220] In order to further demonstrate the application of the alumina carriers prepared in the above examples in the field of propane dehydrogenation to propylene catalysts, the alumina carriers obtained in Examples 1-11 and Comparative Examples 3-5 were made into precious metal catalysts (the catalysts prepared using the alumina carriers of Examples 1-11 were denoted as C1-C11, and the catalysts prepared using the alumina carriers of Comparative Examples 3-5 were denoted as D1-3), and commercial Al2O3 was used as a control (the catalysts prepared using commercial alumina 1 and commercial alumina 2 were denoted as B1 and B2), and applied to the propane dehydrogenation to propylene reaction.

[0221] The PtSn catalyst supported on alumina was prepared as follows:

[0222] (1) Taking 200 mg of the surface-modified alumina supports prepared in Examples 1-11 and Comparative Examples 3-5, respectively, and drying them in an oven at 120° C. for 2 h;

[0223] (2) preparing a mixed ethanol solution containing 0.5 wt% chloroplatinic acid and 0.8 wt% tin dioxide, and then impregnating the alumina support dried in step (1) with an equal volume of the mixed ethanol solution, stirring for 5 min, and then standing at room temperature for 4 h, and drying at 50° C. for 12 h;

[0224] (3) The product obtained in step (2) was calcined at 500° C. for 4 h with flowing air (48 ml / min) to obtain a PtSn catalyst supported on an alumina carrier.

[0225] Catalytic propane dehydrogenation experiment:

[0226] 100 mg of the PtSn catalyst supported on the alumina carrier was placed in a tubular reactor, propane and diluent gas were introduced into the tubular reactor for reaction, and the activity of the catalyst was detected by chromatography.

[0227] The reaction temperature is 590°C, the heating rate is 10°C / min, and the mass space velocity of propane is 9.4h -1 , raw gas volume ratio: 16% propane + 20% hydrogen + 64% nitrogen.

[0228] Among them: the fixed bed reactor used is built in the laboratory: open tubular resistance furnace + YUDIAN intelligent temperature controller + Qixing flow controller; among them, tubular resistance furnace: Yuanbang Circuit Manufacturing Co., Ltd.; intelligent temperature controller: Yudian Automation Technology Co., Ltd. KY-20A; flow controller: Qixing Huachuang Flowmeter Co., Ltd. D07-7C.

[0229] Product analysis: A GC7900 gas chromatograph was used to analyze the alkane and olefin content in the dehydrogenation product online and calculate the reaction conversion rate, selectivity, etc. The product was calculated using the area normalization method;

[0230] Among them, the gas chromatograph is GC7900 produced by Tianmei (China) Scientific Instrument Co., Ltd., and the specific operation is as follows:

[0231] (1) Chromatographic column model: Al2O3 packed column and 5A molecular sieve;

[0232] (2) Detector temperature: 200°C;

[0233] (3) Column oven program: initial temperature 70°C, hold for 3 min, then increase the temperature to 170°C at 10°C / min and hold for 6 min.

[0234] (4) Gas flow rate: 20 ml / min.

[0235] The test data is shown in Table 3.

[0236] Table 3 Catalytic effect of different reaction times in propane dehydrogenation reaction of the embodiments and comparative examples

[0237]

[0238]

[0239] When the catalysts C1-C11 prepared in the present application are used to catalyze propylene, the propane conversion rate decreases by 2.3%-8.6% from 30 minutes to 180 minutes of reaction, among which the catalysts C1, C2, C5, C7, C9 and C11 have better effects, with a propane conversion rate decrease of 2.3%-4.9%. In contrast, when catalysts B1 and B2 are used for catalysis, the propane conversion rate decreases by 12.5% ​​and 11.4%, which is significantly higher than the catalyst of the present invention. This proves that the catalyst prepared by the present invention has good activity and higher stability in the dehydrogenation of propane to propylene.

[0240] Compared with Comparative Example 5, Example 2 of the present application does not add aluminum nitrate. The catalyst prepared using the surface-modified alumina carrier prepared in Example 2 catalyzes the propane dehydrogenation to propylene reaction, and its propane conversion rate decrease rate is lower than that of Comparative Example 5, and the amount of carbon deposition is also reduced. This shows that the surface-modified alumina carrier prepared by directly using ammonium bicarbonate to surface-modify alumina as a catalyst carrier in the present application can improve the conversion efficiency and stability of the catalyst. In addition, compared with Comparative Example 5, the present application does not add aluminum salts, and can be synthesized at a lower temperature, does not require a closed reaction vessel, and exhibits higher process efficiency and product performance.

[0241] In summary, compared with the prior art, this application uses commercial alumina as the processing core. After modification, the surface modified alumina prepared has highly uniform surface properties, abundant weak acid sites, and fewer strong acid sites. Using this surface modified alumina as a carrier, Pt as an active component, and Sn as an additive, a highly active and highly stable catalyst was successfully prepared, which has a good application effect in the field of propane dehydrogenation to propylene.

[0242] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A surface-modified alumina carrier, characterized in that: It is a core-shell structure, including an alumina core and a surface-modified shell layer, wherein the surface-modified shell layer is alumina with a fibrous structure; The surface modified alumina carrier is obtained by reacting a surface modifier with alumina to generate an alumina precursor on the surface of the alumina, and then calcining the alumina precursor, wherein the surface modifier is selected from one or more of ammonium bicarbonate, ammonium carbonate and ammonium carbamate.

2. The surface-modified alumina carrier according to claim 1, characterized in that The thickness of the surface modified shell layer is 0.005-4 μm. Preferably, the particle size of the alumina core is 0.01-8 μm.

3. The surface-modified alumina carrier according to claim 1 or 2, characterized in that: The specific surface area of ​​the surface modified alumina carrier is 130-350m 2 / g; And / or, the total pore volume of the surface modified alumina carrier is 0.20-1.00 cm 3 / g; And / or, the surface acid amount of the surface modified alumina carrier is 50-300 μmol NH3 g -1 ; And / or, the peak pore diameter of the surface modified alumina carrier is 3-22 nm.

4. The method for preparing a surface-modified alumina carrier according to any one of claims 1 to 3, characterized in that: The method comprises dispersing aluminum oxide in water, adding a surface modifier, aging, drying and calcining, wherein the surface modifier is selected from one or more of ammonium bicarbonate, ammonium carbonate and ammonium carbamate.

5. The preparation method according to claim 4, characterized in that: It includes the following steps: (1) dispersing aluminum oxide in water to obtain solution A; (2) adding a surface modifier to the solution A obtained in step (1) to obtain a solution B, wherein no aluminum salt is added to the solution B; (3) subjecting the solution B obtained in step (2) to aging treatment, filtering, and drying to obtain a precursor; (4) Calcine the precursor obtained in step (3) to obtain a surface-modified alumina carrier.

6. The preparation method according to claim 5, characterized in that: Step (1) is controlled at 15-40°C; and / or, the concentration of the surface modifier in solution B in step (2) is 0.5-6 mol / L, preferably, the molar ratio of the aluminum oxide to the surface modifier is 1:0.5-10, preferably 1:2-8, more preferably 1:4-8; And / or, the aging temperature in step (3) is 25-150° C., preferably 50-100° C.; preferably, the aging time is 1-120 h, preferably 20-100 h; And / or, the calcination temperature in step (4) is 500-700° C., and the preferred calcination time is 2-4 hours.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The alumina is selected from one or more of pseudo-boehmite, boehmite, SB powder and gibbsite, or is obtained by calcining one or more of pseudo-boehmite, boehmite, SB powder and gibbsite; preferably, the calcination temperature is 300-1000°C, preferably 300-600°C.

8. A surface-modified alumina carrier, characterized in that: It is prepared by the preparation method described in any one of claims 4 to 7.

9. Use of the surface-modified alumina carrier according to any one of claims 1 to 3 or the surface-modified alumina carrier according to claim 8 in the field of catalysts.

10. A catalyst for catalyzing propane dehydrogenation reaction, characterized in that: The catalyst comprises the surface-modified alumina carrier according to any one of claims 1 to 3 or the surface-modified alumina carrier according to claim 8 and an active component; Preferably, the active component includes a Pt active component and a Sn active component; Further preferably, the Pt active component exists in the catalyst in the form of single substance Pt, and the mass ratio of the single substance Pt to the core-shell structure alumina carrier is 0.3-0.5:100; Further preferably, the Sn active component exists in the form of tin oxide, and the mass ratio of the tin oxide to the core-shell structure alumina carrier is 1-2.5:

100.

11. A method for preparing the catalyst for catalyzing propane dehydrogenation reaction according to claim 10, characterized in that: The steps include: S1. Preparing a surface-modified alumina support; S2. impregnating the surface-modified alumina support described in S1 with an active component precursor solution in equal volumes to obtain a catalyst precursor; S3. calcine the catalyst precursor obtained in S2 to obtain a catalyst.

12. The preparation method according to claim 11, wherein The active component precursor solution in S2 is a mixed solution of a Pt element solution and a Sn element solution; Preferably, the Pt element solution is selected from one or a mixed solution of two or more of chloroplatinic acid, platinum nitrate, tetraammine platinum nitrate, and platinum trichloride, and further preferably, the mass concentration of the Pt element solution is 0.2-0.7%; Preferably, the Sn element solution is selected from one or a mixed solution of two or more of tin dichloride, tin tetrachloride, tin nitrate, and tin acetate, and further preferably, the mass concentration of the Sn element solution is 0.4-0.9%; Preferably, the calcination temperature in step S3 is 300-500°C; More preferably, the calcination time is 3-6 hours.

13. A catalyst for catalyzing propane dehydrogenation reaction, prepared by the preparation method according to claim 11 or 12.

14. A method for catalyzing propane dehydrogenation reaction, characterized in that: The catalyst according to claim 10 or 13 is used to carry out catalytic propane dehydrogenation reaction.

15. The method according to claim 14, wherein: Propane feed mass space velocity is 1-20h -1 .

16. The method according to claim 14 or 15, wherein: The reaction temperature is 550-600°C.

17. The method according to any one of claims 14 to 16, wherein: The raw gas for the catalytic propane dehydrogenation reaction includes propane, hydrogen and nitrogen; preferably, the volume percentages of the propane, hydrogen and nitrogen are 10-20%, 15-25% and 60-70% respectively.

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