Silicalite-2 full-silica molecular sieve, method for preparing same, and use thereof

Abstract

The application relates to the technical field of molecular sieves, and discloses a Silicalite-2 full-silicon molecular sieve, a preparation method and application thereof, the full-silicon molecular sieve method comprises the following steps: crystallizing a crystallization solution containing a silicon source, N,N,N-tri-butyl-1-butylammonium hydroxide and water, performing solid-liquid separation and calcining; wherein the molar ratio of the silicon source, the N,N,N-tri-butyl-1-butylammonium hydroxide and water is 1:0.2-0.5:6-15, and the silicon source is calculated according to SiO2; the crystallization temperature is 100-160 DEG C. The one-way service life of a catalyst can be improved when the molecular sieve is used for a propane dehydrogenation reaction by increasing the external surface area of the molecular sieve and the number of surface defect sites.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve technology, specifically to a Silicalite-2 all-silica molecular sieve, its preparation method, and its applications. Background Technology

[0002] The propane dehydrogenation to propylene process features simple feedstocks and products, a short process flow, and low separation costs, demonstrating good economic benefits and leading to rapid global capacity expansion in recent years. Currently, there are two main technologies: a moving bed process using alumina-supported Pt-based catalysts and a fixed bed process using alumina-supported Cr-based catalysts. However, both processes require frequent catalyst activation and regeneration, resulting in short catalyst lifetimes and significantly increasing costs in terms of both energy consumption and construction. Summary of the Invention

[0003] The purpose of this invention is to overcome the problem of short single-pass lifespan of propane dehydrogenation catalysts in existing technologies, and to provide a Silicalite-2 all-silica molecular sieve, its preparation method, and its application.

[0004] To achieve the above objectives, the first aspect of the present invention provides a method for preparing Silicalite-2 all-silica molecular sieves, the method comprising: crystallizing, solid-liquid separation and calcining a crystallization solution containing a silicon source, N,N,N-tributyl-1-butanium hydroxide and water; wherein the molar ratio of silicon source, N,N,N-tributyl-1-butanium hydroxide and water is 1:0.2-0.5:6-15, and the silicon source is SiO2; the crystallization temperature is 100-160℃.

[0005] A second aspect of the present invention provides a Silicalite-2 all-silica molecular sieve prepared by the method described above.

[0006] A third aspect of the present invention provides a Silicalite-2 all-silica molecular sieve, wherein the Silicalite-2 all-silica molecular sieve... 29 In the NMR spectrum of Si solid, the peak area ratio of the peaks with chemical shifts near -103 ppm and -114 ppm is 1:6-9.

[0007] The fourth aspect of this invention provides the application of the aforementioned Silicalite-2 all-silica molecular sieve as a support for a supported catalyst.

[0008] The fifth aspect of the present invention provides a catalyst with propane dehydrogenation function, the catalyst comprising a support and Pt supported on the support and optional modifying components, wherein the support is the aforementioned Silicalite-2 all-silica molecular sieve, and the modifying components include IIB and / or IIA metal elements.

[0009] A sixth aspect of the present invention provides a method for propane dehydrogenation, the method comprising contacting a propane-containing feedstock with the catalyst described above under propane dehydrogenation conditions.

[0010] The Silicalite-2 all-silica molecular sieve prepared by the method of the present invention has a large number of weakly acidic sites, a high external surface area, and a large number of surface silanol defects, which are beneficial to the dispersion of active components (e.g., Pt), and to improving the catalytic performance and anti-sintering ability of the catalyst (anti-sintering ability refers to the growth of active metal particles), thereby improving the stability of the catalyst.

[0011] The weakly acidic surface of the Silicalite-2 all-silica molecular sieve of the present invention can inhibit the isomerization of intermediate products and the occurrence of secondary hydrogenation reactions, thereby reducing the formation of carbon deposits.

[0012] The catalyst using Silicalite-2 all-silica molecular sieve as a support in this invention can improve the single-pass life of the catalyst while maintaining high propylene selectivity, thereby reducing the high energy consumption and expensive equipment construction costs caused by frequent regeneration in current processes. Attached Figure Description

[0013] Figure 1 This is a scanning electron microscope image of the Silicalite-2 all-silica molecular sieve from Example 1.

[0014] Figure 2 The Si in Silicalite-2 all-silica molecular sieve of Example 1 is... 29 -NMR solid-state nuclear magnetic resonance results. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of this invention provides a method for preparing Silicalite-2 all-silica molecular sieves, the method comprising: crystallizing, solid-liquid separation and calcining a crystallization solution containing a silicon source, N,N,N-tributyl-1-butanium hydroxide and water; wherein the molar ratio of silicon source, N,N,N-tributyl-1-butanium hydroxide and water is 1:0.2-0.5:6-15, and the silicon source is SiO2; the crystallization temperature is 100-160℃ (e.g. 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, and any two of the above).

[0017] In this invention, the molar ratio of silicon source, N,N,N-tributyl-1-butanmonium hydroxide, and water can be 1:0.2:6, 1:0.2:7, 1:0.2:8, 1:0.2:9, 1:0.2:10, 1:0.2:11, 1:0.2:12, 1:0.2:13, 1:0.2:14, 1:0.2:15, 1:0.3:6, 1:0.3:7, 1:0.3:8, 1:0.3:9, 1:0.3:10, 1:0.3:11, 1:0.3:12, 1:0.3:13, 1:0.3:14, 1:0.3:15, 1:0.4:6, 1 The ranges are 0.4:7, 1:0.4:8, 1:0.4:9, 1:0.4:10, 1:0.4:11, 1:0.4:12, 1:0.4:13, 1:0.4:14, 1:0.4:15, 1:0.5:6, 1:0.5:7, 1:0.5:8, 1:0.5:9, 1:0.5:10, 1:0.5:11, 1:0.5:12, 1:0.5:13, 1:0.5:14, 1:0.5:15, and any two of the above ranges; preferably 1:0.2-0.5:10-15, more preferably 1:0.2-0.3:10-15.

[0018] According to the present invention, the silicon source can be a substance commonly used in the art that can provide silicon, preferably, the silicon source is silica sol and / or tetraethyl orthosilicate.

[0019] According to the present invention, preferably, the method further includes stirring the crystallization solution at 15-40°C for 2-3.5 hours, followed by crystallization, solid-liquid separation, and calcination. More preferably, the stirring speed is 500-800 r / min.

[0020] According to the present invention, the crystallization conditions can be conventional crystallization conditions in the art. However, in order to obtain grains with moderate crystallinity and many surface defects, the crystallization conditions preferably include: a temperature of 100-140°C, more preferably 100-120°C, and a time of 48-120h (e.g., 48h, 50h, 60h, 70h, 80h, 90h, 100h, 110h, 120h, and any two of the above), more preferably 100-120h.

[0021] According to the present invention, preferably, the calcination conditions include: heating to 550-600°C at a heating rate of 1-2°C / min, and then calcining at this temperature for 4-6 hours. More preferably, the calcination is carried out in an oxygen-containing atmosphere (e.g., air).

[0022] According to a particularly preferred embodiment of the present invention, the method includes the following steps:

[0023] (1) Add the aqueous solution of silicon source to the aqueous solution of N,N,N-tributyl-1-butanium hydroxide, and then stir at 15-40℃ for 2-3.5h to obtain a crystallization solution. The molar ratio of silicon source, N,N,N-tributyl-1-butanium hydroxide and water in the crystallization solution is 1:0.2-0.5:6-15, and the silicon source is calculated as SiO2.

[0024] (2) Then crystallization, solid-liquid separation and calcination are carried out in sequence.

[0025] According to a particularly preferred embodiment of the present invention, the concentration of the aqueous solution of the silicon source is 28-40% by weight.

[0026] According to a particularly preferred embodiment of the present invention, the temperature at which the substance is added is 25-30°C.

[0027] According to a particularly preferred embodiment of the present invention, the solid-liquid separation includes: centrifuging the crystallized product to obtain a solid product, and then washing the solid product until neutral. The centrifugation rate can be 4000-5500 r / min, and the time can be 20-35 min.

[0028] According to a particularly preferred embodiment of the present invention, the method further includes drying before calcination, and more preferably, the drying conditions include a temperature of 80-120°C and a time of 2-4 hours.

[0029] A second aspect of the present invention provides a Silicalite-2 all-silica molecular sieve prepared by the method described above.

[0030] A third aspect of the present invention provides a Silicalite-2 all-silica molecular sieve, wherein the Silicalite-2 all-silica molecular sieve... 29 In the nuclear magnetic resonance spectrum of Si solid, the ratio of the peak areas of the peaks with chemical shifts near -103 ppm and -114 ppm is 1:6-9 (e.g., 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, and any two of the above points), more preferably 1:6-8, and even more preferably 1:6-7.

[0031] According to the present invention, preferably, the average particle size of the Silicalite-2 all-silica molecular sieve is 50-500 nm (e.g., 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, and any two of the above ranges), more preferably 200-250 nm, and the specific surface area is 600-700 m². 2 / g.

[0032] According to the present invention, preferably, the specific surface area of ​​the Silicalite-2 all-silica molecular sieve includes the microporous surface area and the external surface area, wherein the microporous surface area is 300-400 m². 2 / g, with an external surface area of ​​200-350m² 2 / g (e.g., 200m) 2 / g、220m 2 / g、240m 2 / g、250m 2 / g、260m 2 / g、280m 2 / g、300m 2 / g、320m 2 / g、330m 2 / g、340m 2 / g, 350m 2 / g, and the range consisting of any two of the above points), more preferably 250-320m 2 / g, further preferably 300-320m 2 / g. In this invention, the micropore surface area refers to the specific surface area of ​​pores with a diameter of less than 2nm, and the external surface area refers to the total surface area minus the micropore surface area.

[0033] According to the present invention, preferably, the crystallinity of the Silicalite-2 all-silica molecular sieve is 50-80%.

[0034] According to the present invention, preferably, at a desorption temperature of 90-92°C, the acid (weak acid) content of the Silicalite-2 all-silica molecular sieve is 0.1-0.13 mmol / g (e.g., 0.1 mmol / g, 0.105 mmol / g, 0.11 mmol / g, 0.115 mmol / g, 0.12 mmol / g, 0.125 mmol / g, 0.13 mmol / g, and any two of the above ranges), more preferably 0.105-0.13 mmol / g, and even more preferably 0.12-0.126 mmol / g.

[0035] The fourth aspect of this invention provides the application of the aforementioned Silicalite-2 all-silica molecular sieve as a support for a supported catalyst.

[0036] The fifth aspect of the present invention provides a catalyst with propane dehydrogenation function, the catalyst comprising a support and Pt supported on the support and optional modifying components, wherein the support is the aforementioned Silicalite-2 all-silica molecular sieve, and the modifying components include IIB and / or IIA metal elements.

[0037] According to the present invention, preferably, the content of Pt is 0.3-0.5% by weight and the content of the modified component is 0-2% by weight, preferably 0.3-1% by weight, relative to 100g of Silicalite-2 all-silica molecular sieve.

[0038] According to the present invention, preferably, the weight ratio of IIB metal elements to IIA metal elements in the catalyst is 1:0.1-2, more preferably 1:0.4-1.

[0039] In this invention, the modified active component can be Ca and / or Zn, more preferably a combination of Ca and Zn.

[0040] The present invention also provides a method for preparing a catalyst with propane dehydrogenation function, the method comprising loading Pt and optional modifying components onto a silicalite-2 all-silica molecular sieve, and then calcining it.

[0041] In this invention, the loading method can be a conventional method in the art, such as the impregnation method (vacuum rotary evaporation excess impregnation method), specifically: the above-mentioned Silicalite-2 all-silica molecular sieve is placed in an aqueous solution containing platinum precursor, zinc precursor and calcium precursor, and then vacuum impregnation is performed using a rotary evaporator at an impregnation temperature (rotary evaporation temperature) of 50-70°C and a vacuum degree of 80-100 Pa. The catalyst is obtained after the water has evaporated completely. The platinum precursor can be chloroplatinic acid, the zinc precursor can be zinc nitrate, and the calcium precursor can be calcium nitrate.

[0042] The preparation method of the catalyst with propane dehydrogenation function of the present invention further includes a step of reducing the catalyst at 550-650°C in the presence of a reducing gas (e.g., hydrogen); wherein the reduction time is 2-4 hours.

[0043] A sixth aspect of the present invention provides a method for propane dehydrogenation, the method comprising contacting a propane-containing feedstock with the catalyst described above under propane dehydrogenation conditions.

[0044] According to the present invention, preferably, the propane-containing raw material further includes a diluent gas (e.g., hydrogen), and the volume ratio of the diluent gas to propane is 1:2-4.

[0045] According to the present invention, preferably, the contact conditions include: a temperature of 590-600°C, a pressure of 0.1-1 MPa, and a propane mass hourly space velocity of 2-5 h⁻¹. -1 .

[0046] The present invention will be described in detail below through embodiments. In the following embodiments,

[0047] All raw materials are commercially available.

[0048] The room temperature is approximately 25°C.

[0049] Example 1

[0050] (1) Under stirring at room temperature, N,N,N-tributyl-1-butanium hydroxide was added dropwise to deionized water at a rate of 5 mL / min, and stirred for 5 minutes to obtain a homogeneous mixed solution. Under stirring at room temperature, 33.2846 g of tetraethyl orthosilicate (28% aqueous solution by mass) was added dropwise to the above mixed solution at a rate of 5 mL / min, and stirred at room temperature for 3 h to obtain a crystallization solution. The molar ratio of silicon source, N,N,N-tributyl-1-butanium hydroxide and water in the crystallization solution was 1:0.24:12, and the silicon source was measured as SiO2.

[0051] (2) The crystallization solution was transferred to a stainless steel high-pressure reactor with a polytetrafluoroethylene liner and placed in a muffle furnace for hydrothermal crystallization. The hydrothermal crystallization conditions were: crystallization temperature 120℃ and crystallization time 120h. After hydrothermal crystallization, the reactor was cooled and the reaction product was taken out. The reaction product was centrifuged at 5000r / min for 30min. After removing the supernatant, the solid product was washed with water until neutral and dried in a muffle furnace at 120℃ for 2h. After drying, the temperature was increased to 600℃ at a heating rate of 2℃ / min and calcined at this temperature for 6h to obtain Silicalite-2 all-silica molecular sieve, denoted as molecular sieve A.

[0052] Depend on Figure 1As can be seen, the scanning electron microscope image of the Silicalite-2 all-silica molecular sieve prepared in Example 1 is shown.

[0053] Depend on Figure 2 It can be seen that the Silicalite-2 all-silica molecular sieve prepared in Example 1 29 Nuclear magnetic resonance spectrum of Si solid.

[0054] (3) Prepare 0.09 mol / L chloroplatinic acid solution, 0.1 mol / L zinc nitrate solution, and 0.1 mol / L calcium nitrate solution. Weigh the above precursor solutions according to the loading amounts of Pt 0.3 wt%, Zn 0.7 wt%, and Ca 0.3 wt%. Then mix the weighed precursor solutions with 50 mL of deionized water to obtain a mixed solution. Weigh 4 g of molecular sieve support and place it in the mixed solution. Vacuum impregnate the support using a rotary evaporator at 60 °C and a vacuum degree of 90 Pa. After the water has evaporated, the catalyst is obtained and designated as catalyst 1.

[0055] Example 2

[0056] The method was carried out according to Example 1, except that the amount of tetraethyl orthosilicate solution used was 28.6423 g, and the molar ratio of silicon source, N,N,N-tributyl-1-butanium hydroxide and water in the crystallization solution was 1:0.5:10, with the silicon source being SiO2.

[0057] The obtained Silicalite-2 all-silica molecular sieve is designated as molecular sieve B, and the obtained catalyst is designated as catalyst 2.

[0058] Example 3

[0059] The method was carried out according to Example 1, except that the amount of tetraethyl orthosilicate solution used was 20.832 g, and the molar ratio of silicon source, N,N,N-tributyl-1-butanium hydroxide and water in the crystallization solution was 1:0.5:15, with the silicon source being SiO2.

[0060] The Silicalite-2 all-silica molecular sieve is denoted as molecular sieve C, and the catalyst is denoted as catalyst 3.

[0061] Example 4

[0062] The method was carried out according to Example 2, except that the crystallization time was 48 hours.

[0063] The obtained Silicalite-2 all-silica molecular sieve is denoted as molecular sieve D, and the obtained catalyst is denoted as catalyst 4.

[0064] Example 5

[0065] The method was carried out according to Example 1, except that the crystallization temperature was 140°C.

[0066] The obtained Silicalite-2 all-silica molecular sieve is denoted as molecular sieve E, and the obtained catalyst is denoted as catalyst 5.

[0067] Comparative Example 1

[0068] The method was carried out according to Example 1, except that the crystallization temperature was 180°C.

[0069] The obtained Silicalite-2 all-silica molecular sieve is denoted as molecular sieve DA1, and the obtained catalyst is denoted as catalyst DA1.

[0070] Comparative Example 2

[0071] The method was carried out according to Example 1, except that the molar ratio of silicon source, N,N,N-tributyl-1-butanium hydroxide and water in the crystallization solution was 1:1:30.

[0072] The obtained Silicalite-2 all-silica molecular sieve is denoted as molecular sieve DA2, and the obtained catalyst is denoted as catalyst DA2.

[0073] Test Example 1

[0074] The surface silanol defects, specific surface area, average particle size, and acid content of the molecular sieves prepared in the test examples and comparative preparation examples are shown in Table 1.

[0075] The testing method for surface silanol defects (the ratio of peak areas near -103 ppm and -114 ppm chemical shifts, where the peak area at -103 ppm represents the peak area of ​​hydroxyl groups and the peak area at -114 ppm represents the peak area of ​​hydroxyl defects): using Si 29 - Solid-state NMR was used to determine the silanol content on the surface. 29Si MAS NMR was performed on a Bruker 400MHz Avance III (9.4T) NMR spectrometer with a resonance frequency of 79.5MHz, using a high-power proton decoupling sequence, a rotation speed of 8kHz, 1024-4096 sampling times, a π / 4 pulse width of 3.2μs, and a sampling delay of 10s.

[0076] Specific surface area testing method: N2 adsorption-desorption isotherm analysis was performed using an Anton Pao Instruments IQ fully automated adsorption analyzer (USA), and the specific surface area was calculated based on the isotherms. Degassing conditions: The temperature was increased to 80℃ at a rate of 2℃ / min and held for 1 h, then increased to 150℃ at a rate of 2℃ / min and held for 1 h, then increased to 350℃ at a rate of 2℃ / min and held for 6 h. The specific surface area of ​​the sample was calculated using the BET method, and the inner and outer surface areas of the micropores were simulated using a t-plot model.

[0077] Methods for testing average particle size: The surface morphology of the catalyst was characterized by analysis using a Hitachi S4800 field emission environmental scanning electron microscope, and the average particle size was measured and calculated using SEM images.

[0078] Acidity testing method: The surface acidity of the catalyst was determined using an AUTOCHEM 2920 fully automated chemisorption analyzer from Micrometeos, USA. Experimental conditions: Approximately 0.10 g of sample was weighed and placed in a sample tube. The temperature was programmed to rise to 480 °C under a He gas flow of 10 mL / min, then switched to 10% H2-90% Ar reduction for 1 hour. The temperature was then raised to 700 °C under a He atmosphere at a rate of 10 °C / min and held for 1 hour. The temperature was then lowered to a specific adsorption temperature, and a 10% NH3-90% He mixture was adsorbed at a rate of 10 mL / min for 1 hour. The mixture was then purged with He gas at a rate of 20 mL / min for 1 hour. Finally, the temperature was raised to 700 °C at a rate of 10 °C / min, and the desorption was recorded.

[0079] XRD characterization showed that the molecular sieves prepared in Examples 1-5 and Comparative Examples 1-2 exhibited characteristic peaks of Silicalite-2 all-silica molecular sieve.

[0080] Table 1

[0081]

[0082] As can be seen from the results in Table 1, compared with the comparative example, the molecular sieve AE prepared by the present invention has a higher external specific surface area, acid content, and more surface defect sites. Particularly preferred is the molecular sieve prepared in Example 1 of the present invention, which has an even higher external specific surface area, acid content, and more surface defect sites.

[0083] Test Example 2

[0084] The catalysts prepared in the comparative examples were used for propane dehydrogenation reactions, and their performance in propane dehydrogenation to propylene was evaluated in a fixed-bed microreactor. The catalyst was loaded with 0.5 g of catalyst, the reaction tube diameter was 10 mm, the reaction temperature was 600 °C, and the propane mass hourly space velocity (WHSV) was 3 h⁻¹. -1 The reaction was conducted at atmospheric pressure (0.1 MPa) using hydrogen as a diluent gas, with a hydrogen to propane volume ratio of 1:3. Before use, the catalyst was reduced under the following conditions: H2 atmosphere, gas flow rate 30 ml / min, reduction at 600℃ for 3 h. The results are shown in Table 2. In the following test examples, the single-pass lifetime refers to the total time from the start of the reaction until the propane conversion rate could no longer maintain 90% of the initial conversion rate.

[0085] Analytical methods used for the reaction products: The composition of the reaction products was analyzed using a gas chromatograph (Agilent Technologies 7890A), with propane and propylene detected by an alumina column FID detector. The propane conversion rate was calculated using the normalization method, and the main formula is as follows:

[0086] Propane conversion rate = (Number of moles of propane converted / Number of moles of propane fed) × 100%

[0087] Propylene selectivity = (Number of moles converted to propylene / Number of moles converted to propane) × 100%

[0088] Table 2

[0089] Propane conversion rate (%) Propylene selectivity (%) Catalyst single-pass lifetime (h) Catalyst 1 38 92 350 Catalyst 2 40 90 220 Catalyst 3 40 90 160 Catalyst 4 36 91 180 Catalyst 5 38 90 180 Catalyst DA1 32 91 70 Catalyst DA2 30 92 50

[0090] As can be seen from the results in Table 2, the catalyst of the present invention can improve the single-pass life of the catalyst while increasing the propane conversion rate.

[0091] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing Silicalite-2 all-silica molecular sieve, characterized in that, The method includes: crystallizing, solid-liquid separation, and calcining a crystallization solution containing a silicon source, N,N,N-tributyl-1-butanammonium hydroxide, and water; wherein the molar ratio of silicon source, N,N,N-tributyl-1-butanammonium hydroxide, and water is 1:0.2-0.5:6-15, and the silicon source is calculated as SiO2; the crystallization temperature is 100-160℃.

2. The method according to claim 1, wherein, The silicon source is silica sol and / or tetraethyl orthosilicate.

3. The method according to claim 1, wherein, The method further includes stirring the crystallization solution at 15-40℃ for 2-3.5 hours, followed by crystallization, solid-liquid separation, and calcination.

4. The method according to claim 1, wherein, The crystallization conditions include a temperature of 100-140℃ and a time of 48-120h.

5. The method according to claim 1, wherein, The calcination conditions include: heating to 550-600℃ at a heating rate of 1-2℃ / min, and then calcining at that temperature for 4-6 hours; And / or, the calcination is carried out in an oxygen-containing atmosphere.

6. A Silicalite-2 all-silica molecular sieve, characterized in that, The Silicalite-2 all-silica molecular sieve 29 In the nuclear magnetic resonance spectrum of Si solid, the ratio of the peak areas of the chemical shifts at -103 ppm and -114 ppm is 1:6-9. The Silicalite-2 all-silica molecular sieve has an average particle size of 50-500 nm and a specific surface area of ​​600-700 m². 2 / g; At a desorption temperature of 90-92℃, the amount of acid in the Silicalite-2 all-silica molecular sieve is 0.1-0.13 mmol / g; The microporous surface area of ​​the Silicalite-2 all-silica molecular sieve is 300-400 m². 2 / g, with an external surface area of ​​200-350m² 2 / g.

7. The application of the Silicalite-2 all-silica molecular sieve prepared by the method according to any one of claims 1-5 or the Silicalite-2 all-silica molecular sieve according to claim 6 as a support for a supported catalyst.

8. A catalyst with propane dehydrogenation function, characterized in that, The catalyst comprises a support and Pt supported on the support, wherein the support is a Silicalite-2 all-silica molecular sieve prepared by the method of any one of claims 1-5 or the Silicalite-2 all-silica molecular sieve of claim 6.

9. The catalyst according to claim 8, wherein, The Pt content is 0.3-0.5% by weight per 100g of Silicalite-2 all-silica molecular sieve.

10. A catalyst with propane dehydrogenation function, characterized in that, The catalyst comprises a support and Pt and a modifying component supported on the support, wherein the support is a Silicalite-2 all-silica molecular sieve prepared by the method of any one of claims 1-5 or the Silicalite-2 all-silica molecular sieve of claim 6, and the modifying component comprises IIB and / or IIA metal elements.

11. The catalyst according to claim 10, wherein, The content of Pt is 0.3-0.5% by weight per 100g of Silicalite-2 all-silica molecular sieve, and the content of modified components is 0.3-2% by weight.

12. The catalyst according to claim 11, wherein, The content of Pt is 0.3-0.5% by weight per 100g of Silicalite-2 all-silica molecular sieve, and the content of modified components is 0.3-1% by weight.

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