Renewable alkane dehydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention discloses a renewable alkane dehydrogenation catalyst as well as a preparation method and application thereof. The preparation method of the catalyst comprises the following steps: activating the molecular sieve carrier by adopting high-temperature heat treatment, mechanically and uniformly mixing the activated carrier with the active metal salt, the auxiliary metal salt and the alkali metal salt, and finally carrying out high-temperature oxidation treatment. And through high-temperature activation heat treatment, the pore structure of the molecular sieve is reconstructed, oxygen vacancies are introduced, rich defect sites are formed, then active metal is effectively anchored, and the metal-carrier interaction is optimized. Meanwhile, auxiliary metal and alkali metal are added to achieve a synergistic effect, sintering agglomeration of active metal is further inhibited, and the high-temperature stability and the recyclability of the catalyst are remarkably improved. The method is simple in process route, less in wastewater discharge and low in investment cost, the obtained catalyst is not inactivated after 50 times of circulation in propane dehydrogenation high-temperature reaction-regeneration, long-time sustainable use and recycling can be realized, and a new technical reference is provided for synthesis of novel industrial catalysts.

Description

Technical Field

[0001] The present invention belongs to the field of industrial catalyst preparation, and particularly relates to a renewable alkane dehydrogenation catalyst and a preparation method thereof, and its application in alkane dehydrogenation and dehydrogenation reactions of organic hydrogen storage materials. Background Art

[0002] As an important basic raw material for petrochemical industry, olefins are widely used in the preparation of products such as plastics, synthetic rubbers, and fibers, and the global market demand is increasing day by day. In recent years, due to the change of the global energy structure and the rapid consumption of non-renewable energy, traditional olefin production routes, such as steam cracking of naphtha and catalytic cracking of light diesel, have been greatly restricted. The alkane dehydrogenation technology has the characteristics of simple process, high olefin selectivity, by-product hydrogen, and good atom economy, and has better industrial application prospects. However, this technology is limited by the thermodynamic equilibrium. Generally, the reaction is carried out at high temperature in industry. High temperature not only aggravates side reactions such as C-C cracking, but also causes sintering and agglomeration of active metals, resulting in reduced catalyst selectivity, carbon deposition or coking deactivation.

[0003] Currently, industrially, mainly based on Al 2 O 3Supported noble metal Pt catalysts are produced as alkane dehydrogenation catalysts. However, during the high-temperature dehydrogenation conversion process, the interaction between the metal and the support is weak, and the active metal Pt clusters will undergo severe sintering and rapidly lose their activity. Zeolites, with their regular pore structures, excellent thermal stability, and chemical stability, are considered ideal supports for anchoring metal nanoparticles. In recent years, research on low-carbon alkane dehydrogenation catalysts has been continuously deepened, and many catalyst preparation methods have been developed successively. Patent CN202311360587.2 prepares Silicalite-1 zeolite by hydrothermal crystallization, impregnates the active metal Pt and additives, and then performs dry gel crystallization to obtain an S-1 zeolite-encapsulated metal catalyst, which exhibits good dehydrogenation stability; Patent CN201910954574.5 uses the vacuum impregnation method to load the active metal, transition metal, and alkali metal onto the MFI zeolite, and the obtained dehydrogenation catalyst has good activity and selectivity; Patent CN202211217438.6 treats the deactivated low-carbon alkane dehydrogenation noble metal catalyst with an oxygen-supplying solvent under an inert gas atmosphere, and then introduces carbon dioxide for treatment to obtain a regenerated catalyst with good regeneration effect, but the oxygen-supplying solvent used will produce a large amount of waste liquid; Patent CN201510241371.3 gradually uses a CO gas, a low-carbon oxygen-containing hydrocarbon mixture with HCl to treat the waste catalyst, and finally uses a mixed gas containing low-concentration oxygen to effectively remove carbon deposition at low temperature, but this method introduces HCl, which is highly acidic and corrosive to the reactor, and still requires dechlorination and carbon burning treatment. The above catalysts still have problems such as inability to be regenerated, complex regeneration processes, and introduction of Cl during regeneration. Although the problems of carbon deposition and metal aggregation are solved to a certain extent, they often bring other side effects, inevitably causing a decline in the performance and shortening of the lifespan of the dehydrogenation regenerated catalyst. Therefore, developing a catalyst that can be completely regenerated with a simple and pollution-free regeneration method is the key to extending the lifespan of the catalyst.

[0004] Currently, the preparation methods of metal-loaded zeolite catalysts mainly include the impregnation method, ion exchange method, and in-situ hydrothermal method, etc. Generally, the industrial synthesis of catalysts mainly uses the impregnation method, which is simpler than the ion exchange method and in-situ hydrothermal method and is more suitable for large-scale industrial production. However, the impregnation method still has problems such as the use of a large amount of organic solvents, poor dispersion of active metals, high-temperature instability, and difficulty in regeneration. Industrially, oxygen mixed with chlorine is usually used to regenerate the deactivated Pt catalyst, so that the sintered and agglomerated Pt particles are redispersed to form Pt clusters with high catalytic activity. However, the chlorine in the oxygen-chlorine regeneration not only corrodes the equipment but also causes serious environmental pollution. Therefore, it is of great significance to develop a metal dehydrogenation zeolite catalyst with a green and simple preparation method, excellent catalytic performance, and regenerability through simple calcination.

[0005] In view of the above problems, the present invention provides a renewable alkane dehydrogenation catalyst and a preparation method thereof, which can be used for the dehydrogenation reaction of alkanes and organic hydrogen storage materials. The design idea of the present invention is to first activate the molecular sieve support by high-temperature heat treatment to generate defect sites, then directly mix the activated support with active metal salts, promoter metal salts, and alkali metal salts by mechanical mixing method, and finally perform high-temperature oxidation post-treatment to decompose, disperse, and anchor the metal salts at the defect sites of the support. The synergistic effect of the promoter metal and the alkali metal further stabilizes the active metal, thereby obtaining a dehydrogenation catalyst with highly dispersed sub-nanometer active metal clusters. The obtained catalyst has excellent high-temperature stability and can achieve complete regeneration through simple air calcination. In the actual propane dehydrogenation to propylene reaction, it is confirmed that the conversion rate of this catalyst is ~42% and the selectivity is ~98%, and successful regeneration can reach 50 times. The catalyst prepared by the present invention has great industrial application prospects, and its preparation method is simple, efficient, green and environmentally friendly, providing a new technical reference for the synthesis of new industrial catalysts. Summary of the Invention

[0006] The object of the present invention is to provide a renewable alkane dehydrogenation catalyst and a preparation method thereof, to solve the problems of complex traditional preparation methods of catalysts, poor catalyst stability, and inability to be completely regenerated. The preparation method has a simple process route, less wastewater discharge, and low investment cost; its catalyst has the advantages of high dispersion of active metals, high catalytic activity, excellent high-temperature stability, and outstanding renewable performance. To achieve the above object, the present invention adopts the following technical solutions: A renewable alkane dehydrogenation catalyst and a preparation method thereof, which can be used for the dehydrogenation reaction of alkanes and hydrogen storage materials. The catalyst mainly consists of a support, an active component, a promoter component, and an alkali metal component. Among them, the support is a molecular sieve, the main active component is one of Ru, Rh, Pd, Ir, Pt, Au, the promoter component is one of Fe, Co, Ni, Cu, Zn, Ga, In, Ge, Sn, Mn, Zr, V, Cr, Ti, Nb, Mo, Y, W, Pb, Sc, Bi, Sb, La, Ce, and the alkali metal component is one of Na, Mg, Ca, K, Cs. Based on the total weight of the catalyst, the support accounts for 90.0 - 99.0 wt.% of the total weight of the catalyst, the active component accounts for 0.1 - 10.0 wt.% of the total weight of the catalyst, the promoter component accounts for 0.1 - 10.0 wt.% of the total weight of the catalyst, and the alkali metal component accounts for 0.1 - 10.0 wt.% of the total weight of the catalyst. First, synthesize the molecular sieve support by hydrothermal method, activate it by high-temperature heat treatment, then mechanically mix it with active metal salts, promoter metal salts, and alkali metal salts, and perform high-temperature oxidation treatment on the mixture to obtain a highly dispersed, highly stable, and renewable catalyst.

[0007] The specific preparation process includes the following four steps: (1)Preparation of molecular sieve support: At room temperature, mix the silicon source, template agent and water in proportion and stir to obtain a homogeneous solution; transfer the solution to a hydrothermal reaction kettle and carry out hydrothermal crystallization at a certain temperature and time. The reaction product is filtered, washed, dried and calcined to obtain the molecular sieve support; (2)Perform high-temperature heat treatment on the molecular sieve support obtained in step (1) in an active atmosphere to obtain an activated molecular sieve support; (3)Mechanically mix the activated molecular sieve support, active metal salt, promoter metal salt and alkali metal salt evenly to obtain a catalyst precursor; (4)Perform high-temperature oxidation treatment on the catalyst precursor obtained in step (3) in an oxygen-containing atmosphere at a certain temperature and time, and reduce it under H 2 to obtain the renewable alkane dehydrogenation catalyst.

[0008] Among them, the molecular sieve in step (1) is any one or a mixture of several of Silicalite-1, ZSM-5, ZSM-11, Beta, MCM-11, SSZ-13, ITQ-1.

[0009] The silicon source in step (1) is any one or a mixture of several of tetraethyl orthosilicate, silica sol, fumed silica, water glass, solid silica gel; The template agent in step (1) is any one or a mixture of several of tetramethylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetrabutylammonium hydroxide, tetrabutylammonium bromide; In the solution in step (1), the molar ratio of SiO 2 in the silicon source, the template agent and water is 1: (0.1~1): (10~50).

[0010] The crystallization temperature in step (1) is 100~200 °C, and the crystallization time is 6~144 h; The drying temperature in step (1) is 50~150 °C, and the drying time is 2~24 h; The calcination temperature in step (1) is 450~650 °C, and the calcination time is 2~24 h; The active atmosphere in step (2) is any one or a mixture of several of N 2 , O 2 , H 2 O, CO, CO 2 , NO, NO 2 ; The high-temperature heat treatment temperature in step (2) is 500~1000 °C, and the treatment time is 0.5~10 h; The active metal salt described in step (3) is one or a mixture of several of oxides, hydroxides, chlorides, nitrates, and sulfates of Ru, Rh, Pd, Ir, Pt, and Au.

[0011] The promoter metal salt described in step (3) is a soluble salt or oxide of Fe, Co, Ni, Cu, Zn, Ga, In, Ge, Sn, Mn, Zr, V, Cr, Ti, Nb, Mo, Y, W, Pb, Sc, Bi, Sb, La, and Ce. The soluble salt is selected from one or a mixture of several of chlorides, nitrates, sulfates, and acetates. The alkali metal salt described in step (3) is one or a mixture of several of chlorides, hydroxides, sulfates, and nitrates of Na, Mg, K, and Cs. In step (4), the volume percentage of oxygen in the oxygen-containing atmosphere is 2 - 100%, the high-temperature oxidation treatment temperature is 450 - 900 °C, and the treatment time is 5 - 600 min. In step (4), the reduction temperature is 300 - 900 °C, and the reduction time is 0.5 - 10 h.

[0012] Application: The catalyst can be used in the reaction of dehydrogenating alkanes to olefins and the dehydrogenation reaction of organic hydrogen storage materials. The method for evaluating the activity of the catalyst in a fixed-bed tubular reactor is as follows: The catalyst precursor raw powder is mixed with quartz sand for activity evaluation, and the processes of high-temperature oxidation treatment and hydrogen reduction are completed on the tubular reactor. The conditions for the dehydrogenation reaction are: pure alkane feed, mass space velocity of 2 - 200 h -1 The reaction temperature is 500 - 900 °C, and the reaction pressure is 0.05 - 0.2 MPa.

[0013] Among them, as a specific implementation method for catalyst evaluation, the propane dehydrogenation reaction is used as a model reaction to evaluate the performance of the dehydrogenation catalyst. The inner diameter of the tubular reactor is 6 mm, the catalyst loading height is about 10 cm, and the loading method is to mix 0.25 g of the catalyst precursor with 2.0 g of quartz sand and load them into the tubular reactor, and fix them with quartz wool at the top and bottom. In an air atmosphere, it is heated to 700 °C for oxidation for 4 h, then cooled and switched to a nitrogen atmosphere for purging for 30 min, and then switched to a hydrogen atmosphere. It is reduced at 580 °C for 2 h, and finally the atmosphere is switched to pure propane gas for dehydrogenation reaction. The products are analyzed by a gas chromatograph.

[0014] Furthermore, the regeneration evaluation method of the catalyst is as follows: after the catalyst is deactivated, it is calcined in an air atmosphere at 600 °C for 4 h to remove carbon, then cooled down and switched to a nitrogen atmosphere for purging for 30 min, and then switched to a hydrogen atmosphere, reduced at 580 °C for 2 h, and finally the atmosphere is switched to pure propane gas for dehydrogenation reaction. The products are analyzed by a gas chromatograph.

[0015] The beneficial effects of the present invention are as follows: 1) The present invention uses a high-temperature heat treatment method to activate the molecular sieve support, forming rich defect sites, effectively anchoring active metals, and optimizing the metal-support interaction. At the same time, the addition of promoter metals and alkali metals acts synergistically to further inhibit the sintering and agglomeration of active metals, significantly improving the high-temperature stability and recyclability of the catalyst.

[0016] 2) The dehydrogenation catalyst of the present invention has excellent high-temperature stability and renewable performance, and can be successfully regenerated more than 50 times in the cycle of propane dehydrogenation reaction at 580 °C and regeneration at 600 °C, realizing long-term sustainable use and recycling. 3) The preparation method of the dehydrogenation catalyst of the present invention has the advantages of simple operation, green economy, good repeatability, etc., providing a new technical reference for the synthesis of industrial new catalysts. Description of the Drawings

[0017] Figure 1 TEM image of the PtGeK / S-1 catalyst prepared in Example 1; Figure 2 Catalytic activity diagram of the PtGeK / S-1 catalyst prepared in Example 1 for propane dehydrogenation reaction and regeneration 50 times; Figure 3 TEM image of the PtGeK / S-1 catalyst prepared in Comparative Example 1; Figure 4 TEM image of the Pt / S-1 catalyst prepared in Comparative Example 2; Table 1 shows the catalytic activity of the prepared catalysts for propane dehydrogenation reaction. Specific Embodiments In order to better understand the technical solution of the present invention, the following further details are described in conjunction with specific embodiments and drawings, but it does not limit the protection scope of the present invention.

[0018] Example 1 (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide and 6.5 g of deionized water were weighed and mixed in a beaker, and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, and calcining at 550 °C for 4 h, an S-1 molecular sieve support was obtained.

[0019] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated water vapor was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain an activated S-1 molecular sieve support.

[0020] (3) The activated S-1 molecular sieve support obtained in step (2) was mechanically mixed and sieved with 25 mg of H 2 PtCl 6 ·6H 2 O, 20 mg of GeO 2 , and 20 mg of KCl to obtain a homogeneous mixture.

[0021] (4) Then, the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h to finally obtain a PtGeK / S-1 catalyst (Pt = 0.38 wt.%, Ge = 0.55 wt.%, K = 0.42 wt.%).

[0022] Figure 1 This is the TEM image of the PtGeK / S-1 catalyst obtained in this example. As shown in the figure, sub-nanometer Pt clusters (<1 nm, indicated by the arrows in the figure) are uniformly dispersed on the molecular sieve support, indicating that the defect sites generated by the activation of the molecular sieve and the synergistic effect of the promoter metal and the alkali metal can effectively anchor the active metal to form highly dispersed Pt clusters; its propane dehydrogenation performance is shown in Table 1, with high propane conversion, propylene selectivity and reaction stability. Further, Figure 2 This is the initial activity change diagram during the propane dehydrogenation reaction-regeneration cycle. The catalyst can be successfully regenerated 50 times by simple air calcination without obvious deactivation, indicating its excellent renewable performance and high-temperature stability.

[0023] Example 2 (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide and 6.5 g of deionized water were weighed and mixed in a beaker, and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, and calcining at 550 °C for 4 h, an S-1 molecular sieve support was obtained.

[0024] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated steam was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain an activated S-1 molecular sieve support.

[0025] (3) The activated S-1 molecular sieve support obtained in step (2) was mechanically mixed and sieved with 10 mg of PtO 2 , 20 mg of GeO 2 , and 20 mg of KCl to obtain a homogeneous mixture.

[0026] (4) Then, the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h to finally obtain a PtGeK / S-1 catalyst (Pt = 0.34 wt.%, Ge = 0.55 wt.%, K = 0.42 wt.%).

[0027] Example 3 (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide and 6.5 g of deionized water were weighed and mixed in a beaker, and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, and calcining at 550 °C for 4 h, an S-1 molecular sieve support was obtained.

[0028] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated steam was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain an activated S-1 molecular sieve support.

[0029] (3) The activated S-1 molecular sieve support obtained in step (2) was mechanically mixed and sieved with 25 mg of H 2 PtCl 6 ·6H 2 O, 50 mg of SnCl 4 ·5H 2 O, and 20 mg of KCl to obtain a homogeneous mixture.

[0030] (4) Then, the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h to finally obtain the PtSnK / S-1 catalyst (Pt = 0.38 wt.%, Sn = 0.68 wt.%, K = 0.42 wt.%).

[0031] Example 4 (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, and 6.5 g of deionized water were mixed in a beaker and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifugation, washing, and drying at 100 °C for 6 h, it was calcined at 550 °C for 4 h to obtain the S-1 molecular sieve support.

[0032] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated water vapor was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain the activated S-1 molecular sieve support.

[0033] (3) The activated S-1 molecular sieve support obtained in step (2) was mechanically mixed and sieved with 25 mg of H 2 PtCl 6 ·6H 2 O, 20 mg of GeO 2 , and 20 mg of NaCl to obtain a homogeneous mixture.

[0034] (4) Then, the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h to finally obtain the PtGeNa / S-1 catalyst (Pt = 0.38 wt.%, Ge = 0.55 wt.%, Na = 0.31 wt.%).

[0035] Example 5 (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, and 6.5 g of deionized water were mixed in a beaker and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifugation, washing, and drying at 100 °C for 6 h, it was calcined at 550 °C for 4 h to obtain the S-1 molecular sieve support.

[0036] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated water vapor was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain the activated S-1 molecular sieve support.

[0037] (3) Mix the activated S-1 molecular sieve support obtained in step (2) with 25 mg of RhCl 3 ·3H 2 O, 20 mg of GeO 2 , and 20 mg of KCl mechanically, then sieve them to obtain a homogeneous mixture.

[0038] (4) Then oxidize the mixture in an air stream at 700 °C for 2 h and reduce it in a hydrogen stream at 580 °C for 4 h to finally obtain the RhGeK / S-1 catalyst (Rh = 0.39 wt.%, Ge = 0.55 wt.%, K = 0.42 wt.%).

[0039] Example 6 (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetraethylammonium hydroxide, and 6.5 g of deionized water, mix them in a beaker, stir for 8 h until complete hydrolysis, then add 0.1 g of Beta molecular sieve seeds and 0.8 g of 50 wt% HF solution and continue stirring. Transfer the final gel solution to the inner lining of a crystallization kettle, crystallize it in an oven at 140 °C for 72 h, cool, centrifuge, wash, and dry at 100 °C for 6 h, then calcine at 550 °C for 4 h to obtain the Beta molecular sieve support.

[0040] (2) Place 2.5 g of the Beta molecular sieve support in a tubular furnace, introduce saturated water vapor, and heat-treat it at 800 °C for 3 h to obtain the activated Beta molecular sieve support.

[0041] (3) Mix the activated Beta molecular sieve support obtained in step (2) with 25 mg of H 2 PtCl 6 ·3H 2 O, 20 mg of GeO 2 , and 20 mg of KCl mechanically, then sieve them to obtain a homogeneous mixture.

[0042] (4) Then oxidize the mixture in an air stream at 700 °C for 2 h and reduce it in a hydrogen stream at 580 °C for 4 h to finally obtain the PtGeK / Beta catalyst (Pt = 0.38 wt.%, Ge = 0.55 wt.%, K = 0.42 wt.%).

[0043] Comparative Example 1 Same as Example 1, except that the molecular sieve support was not activated.

[0044] (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide and 6.5 g of deionized water were weighed and mixed in a beaker, and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, and calcining at 550 °C for 4 h, an S-1 molecular sieve support was obtained.

[0045] (2) 2.5 g of the S-1 molecular sieve support was mixed with 25 mg of H 2 PtCl 6 ·6H 2 O, 20 mg of GeO 2 , 20 mg of KCl were mechanically mixed and sieved to obtain a homogeneous mixture.

[0046] (3) Then the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h, and finally PtGeK / S-1 unactivated catalyst (Pt = 0.38 wt.%, Ge = 0.55 wt.%, K = 0.42 wt.%) was obtained.

[0047] Figure 3 This is the TEM image of the PtGeK / S-1 unactivated catalyst obtained in this comparative example. As shown in the figure, Pt particles of 2 - 10 nm exist on the surface of the molecular sieve, indicating that the unactivated molecular sieve support cannot effectively anchor the active metal Pt; its propane dehydrogenation performance is shown in Table 1.

[0048] Comparative Example 2 Same as Example 1, except that no promoter metal and alkali metal were added to the obtained catalyst.

[0049] (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide and 6.5 g of deionized water were weighed and mixed in a beaker, and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, and calcining at 550 °C for 4 h, an S-1 molecular sieve support was obtained.

[0050] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated water vapor was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain an activated S-1 molecular sieve support.

[0051] (3) The activated S-1 molecular sieve support obtained in step (2) was mixed with 25 mg of H 2PtCl 6 ·6H 2 O were mechanically mixed and sieved to obtain a homogeneous mixture.

[0052] (4) Then, the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h to finally obtain a Pt / S-1 catalyst (Pt = 0.38 wt.%).

[0053] Figure 4 This is the TEM image of the Pt / S-1 catalyst obtained in this comparative example. As shown in the figure, Pt metal particles of 10 - 20 nm exist on the surface of the molecular sieve, indicating that a pure Pt catalyst without promoter metal and alkali metal is prone to sintering and agglomeration at high temperatures; its propane dehydrogenation performance is shown in Table 1.

[0054] Comparative Example 3 Same as Example 1, except that no alkali metal was added to the obtained catalyst.

[0055] (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, and 6.5 g of deionized water were mixed in a beaker and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifuging, washing, and drying at 100 °C for 6 h and calcining at 550 °C for 4 h, an S-1 molecular sieve support was obtained.

[0056] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated water vapor was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain an activated S-1 molecular sieve support.

[0057] (3) The activated S-1 molecular sieve support obtained in step (2) was mixed with 25 mg of H 2 PtCl 6 ·6H 2 O, 20 mg of GeO 2 were mechanically mixed and sieved to obtain a homogeneous mixture.

[0058] (4) Then, the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h to finally obtain a PtGe / S-1 catalyst (Pt = 0.38 wt.%, Ge = 0.55 wt.%).

[0059] Comparative Example 4 Same as Example 1, except that no promoter metal was added to the obtained catalyst.

[0060] (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide and 6.5 g of deionized water were weighed and mixed in a beaker, and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The solution was transferred to the inner lining of a crystallization kettle and crystallized in an oven at 170 °C for 72 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, and calcining at 550 °C for 4 h, an S-1 molecular sieve support was obtained.

[0061] (2) 2.5 g of the S-1 molecular sieve support was placed in a tubular furnace, and saturated water vapor was introduced for high-temperature heat treatment at 800 °C for 3 h to obtain an activated S-1 molecular sieve support.

[0062] (3) The activated S-1 molecular sieve support obtained in step (2) was mechanically mixed and sieved with 25 mg of H 2 PtCl 6 ·6H 2 O and 20 mg of KCl to obtain a homogeneous mixture.

[0063] (4) Then, the mixture was oxidized in an air stream at 700 °C for 2 h and reduced in a hydrogen stream at 580 °C for 4 h to finally obtain a PtK / S-1 catalyst (Pt = 0.38 wt.%, K = 0.42 wt.%).

[0064] The catalysts obtained in the above examples and comparative examples were evaluated for catalytic performance in the propane dehydrogenation reaction. The experimental process was as follows: 0.25 g of the catalyst was mixed with 2 g of quartz sand and loaded into a fixed-bed tubular reactor. The reactant was propane, the reaction temperature was 580 °C, the reaction pressure was atmospheric pressure, and the weight hourly space velocity of propane was 15 h -1 Under the conditions, the propane conversion and propylene selectivity of the catalyst are shown in Table 1.

[0065] Table 1 Propane dehydrogenation catalytic performance of different catalysts obtained in examples and comparative examples As can be seen from the results in Table 1, the catalysts obtained in Examples 1-6 have higher activity and stability than the catalysts obtained in Comparative Examples 1-4, which reflects the significant stabilizing effect of support activation and metal synergy on dehydrogenation catalysts; from Comparative Examples 1-4, it can be seen that unactivated supports, unadded promoter metals, and unadded alkali metals cannot significantly stabilize the catalyst; from Examples 1-6, it can be seen that changing the types of active metals, promoter metals, alkali metals, and molecular sieve supports can all obtain stable and efficient dehydrogenation catalysts. Therefore, this preparation method has the advantages of universality, simple operation, green economy, and excellent performance of the obtained catalyst, and has broad application prospects in the fields of petrochemical industry, environmental catalysis, etc.

[0066] The above are only the preferred embodiments of the present invention, which are intended to help understand the content of the present invention and implement it accordingly. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A regenerable alkane dehydrogenation catalyst, characterized in that: The catalyst is mainly composed of a carrier, an active component, an auxiliary component and an alkali metal component; wherein the carrier is a molecular sieve, the main active component is one of Ru, Rh, Pd, Ir, Pt and Au, the auxiliary component is one of Fe, Co, Ni, Cu, Zn, Ga, In, Ge, Sn, Mn, Zr, V, Cr, Ti, Nb, Mo, Y, W, Pb, Sc, Bi, Sb, La and Ce, and the alkali metal component is one of Na, Mg, Ca, K and Cs; based on the total weight of the catalyst, the carrier accounts for 90.0-99.0 wt.% of the total weight of the catalyst, the active component accounts for 0.1-10.0 wt.% of the total weight of the catalyst, the auxiliary component accounts for 0.1-10.0 wt.% of the total weight of the catalyst, and the alkali metal component accounts for 0.1-10.0 wt.% of the total weight of the catalyst.

2. The method for preparing a regenerable alkane dehydrogenation catalyst according to claim 1, characterized in that: First, a molecular sieve carrier is synthesized by a hydrothermal method and activated by high-temperature heat treatment. The activated molecular sieve carrier is mechanically mixed with an active metal salt, an auxiliary metal salt and an alkali metal salt, and the mixture is subjected to a high-temperature oxidation treatment to obtain a highly dispersed, highly stable and renewable catalyst.

3. The preparation method according to claim 2, characterized in that: The specific steps include: (1) Preparation of molecular sieve carrier: at room temperature, silicon source, template agent and water are mixed and stirred in proportion to obtain a uniform solution; the solution is transferred to a hydrothermal reactor and hydrothermally crystallized at a certain temperature and time; the reaction product is filtered, washed, dried and calcined to obtain a molecular sieve carrier; (2) subjecting the molecular sieve carrier obtained in step (1) to high-temperature heat treatment under an active atmosphere to obtain an activated molecular sieve carrier; (3) Mechanically mixing the activated molecular sieve carrier with the active metal salt, the auxiliary metal salt and the alkali metal salt to obtain a catalyst precursor; (4) The catalyst precursor obtained in step (3) is subjected to high-temperature oxidation treatment in an oxygen-containing atmosphere at a certain temperature and time, and is reduced under H2 to obtain the regenerable alkane dehydrogenation catalyst.

4. The preparation method according to claim 3, characterized in that: The molecular sieve is any one of Silicalite-1, ZSM-5, ZSM-11, Beta, MCM-41, SSZ-13, and ITQ-1, or a mixture of several of them.

5. The preparation method according to claim 3, characterized in that: The silicon source in step (1) is any one of tetraethyl orthosilicate, silica sol, white carbon black, water glass, solid silica gel, or a mixture of several thereof; the template is any one of tetramethylammonium hydroxide, tetramethylammonium bromide, tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetrabutylammonium hydroxide, or a mixture of several thereof; in the solution, the molar ratio of SiO2 in the silicon source, the template, and water is 1:(0.1~1):(10~50).

6. The preparation method according to claim 3, characterized in that: The crystallization temperature in step (1) is 100-200 °C, and the crystallization time is 6-144 h; the drying temperature is 50-150 °C, and the drying time is 2-24 h; the calcination temperature is 450-650 °C, and the calcination time is 2-24 h.

7. The preparation method according to claim 3, characterized in that: The active atmosphere in step (2) is one or a mixture of N2, O2, H2O, CO, CO2, NO, NO2; the high temperature heat treatment temperature is 500-1000 °C, and the treatment time is 0.5-10 h.

8. The preparation method according to claim 3, characterized in that: The active metal salt described in step (3) is one or a mixture of oxides, hydroxides, chlorides, nitrates, and sulfates of Ru, Rh, Pd, Ir, Pt, and Au; the auxiliary metal salt is a soluble salt of Fe, Co, Ni, Cu, Zn, Ga, In, Ge, Sn, Mn, Zr, V, Cr, Ti, Nb, Mo, Y, W, Pb, Sc, Bi, Sb, La, and Ce; and the alkali metal salt is a soluble salt of Na, Mg, K, Ca, and Cs.

9. The preparation method according to claim 3, characterized in that: The oxygen content of the oxygen-containing atmosphere in step (4) is 2-100% by volume, the high-temperature oxidation treatment temperature is 450-900 °C, and the treatment time is 5-600 min.

10. The preparation method according to claim 3, characterized in that: In step (4), the reduction temperature is 300-900 °C and the reduction time is 0.5-10 h.

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