Metal self-dispersed low-carbon alkane dehydrogenation catalyst as well as preparation method and application thereof

Abstract

The invention discloses a metal self-dispersed low-carbon alkane dehydrogenation catalyst as well as a preparation method and application thereof. The catalyst is composed of a molecular sieve carrier, metal particles of main active components Ru, Rh, Pd, Ir, Pt and Au, auxiliary components 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 alkali metal components Na, Mg, K, Ca and Cs. Firstly, the synthesized molecular sieve is subjected to high-temperature activation heat treatment, so that rich defect sites are generated; and mixing the activated molecular sieve with metal particles, and finally carrying out high-temperature treatment on the mixture in an oxygen atmosphere to prepare the stable molecular sieve loaded metal cluster. The obtained catalyst shows excellent catalytic activity and regeneration performance. The active metal particles are used as raw materials, the step of converting metal particle powder into salt is reduced, a physical mixing method is adopted, the preparation process of the catalyst is simpler, and the economic cost is lower.

Description

Technical Field

[0001] The present invention belongs to the field of industrial catalyst preparation, and particularly relates to a metal self-dispersed dehydrogenation catalyst for light alkanes, a preparation method thereof, and an application thereof. Background Art

[0002] Light olefins (such as ethylene, propylene, butadiene, etc.) are important basic chemicals in the chemical industry, and are the basic raw materials for manufacturing the "three major synthetic materials" of plastics, synthetic rubber, and synthetic fibers. They occupy an important position in the global economy. The wide application of their products makes the economic scale of related industries huge. The traditional olefin production route highly depends on petroleum resources, with poor resource utilization efficiency and sustainability, and problems such as high energy consumption and low selectivity of by-product olefins. Especially in recent years, due to the change of the global energy structure and the rapid consumption of non-renewable energy, the traditional olefin production route has been greatly restricted, and its output can no longer meet the market demand. The catalytic dehydrogenation technology of light alkanes is an important chemical process for converting light alkanes into corresponding olefins. It has the advantages of wide raw material sources, high olefin selectivity, low energy consumption, etc., and has been widely developed. It is considered to be one of the most promising olefin production technologies.

[0003] The catalysts commonly used in the dehydrogenation reaction of light alkanes mainly include two categories: noble metal catalysts and non-noble metal catalysts. Noble metal catalysts such as Pt-based catalysts have the advantages of high activity and good selectivity, and are the main catalysts used in industrial production; non-noble metal catalysts such as Cr-based catalysts have lower costs, but their activity and stability are poor, and more importantly, they cause great environmental pollution, so they are less used. The carrier also has an important influence on the performance of the catalyst. Common carriers include alumina, molecular sieves, and carbon materials, etc. In recent years, with the in-depth research on the catalytic dehydrogenation of light alkanes, its catalysts have been widely developed. For example, patents such as CN202111290651.5, CN202310078631.4, and CN202310777681.1, etc., load Group VIII metal compounds on modified Al 2 O 3 to utilize the confinement effect of molecular sieves to stabilize the active metal, and strategies such as preparing a core-shell structure of an alumina core-inert ceramic shell to improve the catalyst stability. These patents have greatly improved the stability of the catalyst, but in high-temperature reactions, there are still problems such as easy sintering and deactivation of the active metal.

[0004] Currently, industrially, it is mainly based on Al 2 O 3The supported noble metal Pt catalyst is produced as a dehydrogenation catalyst for light alkanes. However, the Pt supported by the traditional impregnation method has poor dispersion, and during the high-temperature conversion of dehydrogenation, the interaction between the metal and the support is weak. Small-sized Pt nanoparticles will undergo severe sintering and rapidly reduce the activity, resulting in catalyst deactivation. Molecular sieves have characteristics such as regular pore structures, excellent thermal stability, and chemical stability, and are considered ideal supports for anchoring metal nanoparticles. In Pt-based catalysts, the size of metal Pt nanoparticles is a key factor affecting dehydrogenation performance. Reducing the particle size is beneficial to exposing more metal active sites, thereby increasing the conversion rate of alkanes. Therefore, it is of great significance to develop a dehydrogenation molecular sieve catalyst with highly dispersed active metals, excellent catalytic performance, high stability, and renewable properties. Summary of the Invention

[0005] The object of the present invention is to provide a light alkane dehydrogenation catalyst with self-dispersed metal and its preparation method. The synthesis process of this preparation method is simple, economical, and efficient, and its catalyst has advantages such as high stability, high activity, and renewable properties.

[0006] To achieve the above object, the present invention adopts the following technical solutions: A light alkane dehydrogenation catalyst with self-dispersed metal, characterized in that: the catalyst includes a support, a main active component, an auxiliary component, and an alkali metal component; the support is a molecular sieve, the main active component is one of metal particles of Ru, Rh, Pd, Ir, Pt, 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, Ce, and the alkali metal component is one of Na, Mg, Ca, K, Cs; 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 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.

[0007] The preparation method of the above light alkane dehydrogenation catalyst with self-dispersed metal specifically includes the following steps: (1) Preparation of the molecular sieve support: At room temperature, a silicon source, a template agent, an auxiliary agent, an alkali metal, and water are mixed and stirred to obtain a homogeneous solution; the solution is transferred to a hydrothermal reaction kettle for hydrothermal reaction, and the reaction product is filtered, washed, dried, and calcined to obtain a heteroatom@molecular sieve support; (2) The support obtained in step (1) is subjected to high-temperature heat treatment in an active atmosphere to obtain an activated heteroatom@molecular sieve support; (3) The activated heteroatom@molecular sieve support and metal active particles are mixed evenly to obtain a catalyst precursor; (4) Subject the catalyst precursor obtained in step (3) to thermal oxidation treatment in an oxygen-containing atmosphere at a certain temperature, and reduce it under H 2 to obtain a metal self-dispersed low-carbon alkane dehydrogenation catalyst.

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

[0009] Furthermore, the molar ratio of SiO 2 in the template agent, promoter, alkali metal, water, and silicon source in step (1) is (0.1~1):(0.001~0.1):(0.001~0.1):(10~50):1; the silicon source is any one or a mixture of several of tetraethyl orthosilicate, silica sol, fumed silica, water glass, and solid silica gel; Furthermore, 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, and tetrabutylammonium bromide; Furthermore, the promoter in step (1) 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, Ce, selected from one or a mixture of several of metal chlorides, metal nitrates, metal sulfates, and metal acetates; Furthermore, the alkali metal in step (1) is one or a mixture of several of chlorides, hydroxides, sulfates, and nitrates of Na, Mg, K, Ca, and Cs; Furthermore, the temperature of the hydrothermal reaction in step (1) is 100~200 °C, and the hydrothermal reaction time is 12~144 h; Furthermore, the drying temperature in step (1) is 50~150 °C, and the drying time is 2~24 h; Furthermore, the calcination temperature in step (1) is 450~650 °C, and the calcination time is 2~24 h; Furthermore, the active atmosphere in step (2) is N 2 , O 2 , H 2 O, CO, CO 2 , NO, NO 2 or a mixture of any one or several of them; Further, the high-temperature heat treatment temperature in step (2) is 500~1000 °C, and the treatment time is 0.5~10 h; Further, the active metal particles in step (3) are one or a mixture of several of the metal particles of Ru, Rh, Pd, Ir, Pt, and Au; Further, the oxygen content of the oxygen-containing atmosphere in step (4) is 2~100%, the treatment temperature is 450~900 °C, and the treatment time is 5~600 min; Further, the reduction temperature in step (4) is 300~900 °C, and the reduction time is 0.5~10 h.

[0010] The catalyst can be used for the propane dehydrogenation to propylene reaction. The method for evaluating the activity of the catalyst in a fixed-bed tubular reactor is as follows: The catalyst raw powder is mixed with quartz sand for activity evaluation. The processes of thermal oxidation treatment and hydrogen reduction are completed on the tubular reactor. The conditions for the dehydrogenation reaction are as follows: pure alkane feed, mass space velocity of 2~20 h -1 , reaction temperature of 500~700 °C, and reaction pressure of 0.05~0.2 MPa. Among them, 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 25 mg of the catalyst 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, heat up to 700 °C for thermal oxidation for 4 h, then cool down and switch to a nitrogen atmosphere for purging for 30 min, then switch to a hydrogen atmosphere, reduce at 620 °C for 2 h, and finally switch the atmosphere to pure propane gas for dehydrogenation reaction. The products are analyzed by a gas chromatograph.

[0011] Further, the regeneration evaluation method of the catalyst is as follows: After the catalyst is deactivated, in an air (O 2 / N 2 =21 / 79) atmosphere, heat up to 600 °C and calcine for 4 h, then cool down and switch to a nitrogen atmosphere for purging for 30 min, then switch to a hydrogen atmosphere, reduce at 620 °C for 2 h, and finally switch the atmosphere to pure propane gas for dehydrogenation reaction. The products are analyzed by a gas chromatograph.

[0012] The present invention uses thermal oxidation treatment to disperse active metal particles, and then utilizes the rich defect sites formed by the activation of the molecular sieve support to anchor the active metal, forming stable and uniformly dispersed sub-nanometer metal clusters, thereby obtaining an alkane dehydrogenation catalyst with self-dispersed metal. The activation of the molecular sieve adopts a high-temperature heat treatment method. Under high temperature and active atmosphere conditions, the pore structure of the molecular sieve is reconstructed and a large number of oxygen vacancies are introduced, forming rich defect sites. These defect sites can not only effectively anchor the active metal, but also optimize the metal-support interaction. Compared with the active metal salt raw materials and impregnation methods used in the synthesis of general catalysts, the present invention directly uses active metal particles as raw materials and adopts a physical mixing method, reducing the conversion steps from metal particle powder to salt, avoiding the use of solvents, making the preparation process simpler, the economic cost lower, and the synthesis method more environmentally friendly. Moreover, due to the self-dispersion of the metal and the anchoring effect of the support defect sites in the obtained catalyst at high temperature, the sintering, agglomeration and deactivation of the catalyst under high temperature conditions can be effectively avoided, greatly improving the high-temperature stability and average service life of the catalyst.

[0013] The beneficial effects of the present invention are as follows: (1) The present invention uses an activated molecular sieve as the support and active metal particles as the raw materials. Through thermal oxidation treatment, the active metal particles are oxidized and decomposed into single-atom oxides, and then the defect sites formed by the activation of the molecular sieve support are used to anchor the active metal. Finally, through reduction, high-temperature stable and uniformly dispersed active metal clusters are formed, obtaining a low-carbon alkane dehydrogenation catalyst with self-dispersed metal; (2) Compared with the soluble active metal salts used in the synthesis of general catalysts, the present invention directly uses active metal particles as raw materials, reducing the conversion process from metal to salt, and adopting a simple physical mixing method to avoid the use of solvents. Its preparation process is simpler, the economic cost is lower, it is green and efficient, providing a new technology for the preparation of stable dehydrogenation molecular sieve catalysts.

[0014] (3) The dehydrogenation catalyst of the present invention has high conversion rate, high selectivity and recyclability. The number of times it can be regenerated reaches more than 64 times, and there is no obvious deactivation phenomenon. Description of the Drawings

[0015] Figure 1 It is the TEM image of the prepared Pt / GaK@S-1 catalyst.

[0016] Figure 2 It is the catalytic activity image of the prepared Pt / GaK@S-1 catalyst for propane dehydrogenation reaction after being regenerated 64 times.

[0017] Figure 3 It is the Pt / GaK@S-1 unactivated catalyst prepared in Comparative Example 1.

[0018] Figure 4 TEM image of the Pt / GaK@S-1-nc catalyst prepared in Comparative Example 2.

[0019] Figure 5 TEM image of the Pt / S-1 catalyst obtained in Comparative Example 3. Detailed implementation manners

[0020] To better understand the technical solution of the present invention, the following further describes it in detail with reference to specific embodiments and the accompanying drawings, but does not limit the protection scope of the present invention.

[0021] Example 1 A low-carbon alkane dehydrogenation catalyst with self-dispersed metal, loaded with active metal Pt, promoter metal Ga and alkali metal K, and the loading amounts are 0.40 wt.%, 0.44 wt.% and 0.42 wt.% respectively. The carrier is SiO 2 Calculated by, the molar ratio of Pt, Ga, K and SiO 2 is 0.13:0.40:0.68:100.

[0022] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 40 mg of Ga(NO 3 ) 3 ·xH 2 O and 20 mg of KCl and mix them in a beaker, stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, Ga, K, H 2 O and SiO in the silicon source 2 is 0.42:0.004:0.007:16.4:1.

[0023] (2) Transfer the solution to the inner lining of the hydrothermal crystallization kettle, hydrothermally crystallize in an oven at 170 °C for 72 h, cool, centrifuge, wash and dry at 100 °C for 6 h, and calcine at 550 °C for 4 h to obtain the GaK@S-1 molecular sieve carrier.

[0024] (3) Place 2.5 g of the GaK@S-1 molecular sieve carrier in a tubular furnace, introduce O 2 and perform high-temperature heat treatment at 800 °C for 2 h to obtain the activated GaK@S-1 molecular sieve carrier.

[0025] (4) Mix the activated GaK@S-1 molecular sieve carrier obtained in step (3) with 10 mg of Pt metal particles, sieve them evenly, and then place the mixture in air (O 2 / N 2=21 / 79) It was oxidized in an air stream at 700 °C for 4 h and then reduced in a hydrogen stream at 620 °C for 4 h, finally obtaining the Pt / GaK@S-1 catalyst.

[0026] Figure 1 This is the TEM image of the Pt / GaK@S-1 catalyst obtained in this example. As shown in the figure, sub-nanometer Pt clusters are uniformly dispersed on the molecular sieve support, indicating that Pt particles can spontaneously disperse and be effectively anchored to form uniform clusters on the activated GaK@S-1 support after thermal oxidation treatment; its propane dehydrogenation performance is shown in Table 1. Further, Figure 2 This is the catalytic activity diagram of it in the propane dehydrogenation reaction-regeneration cycle for 64 times. This catalyst can be successfully regenerated 64 times by simple air calcination and there is no obvious deactivation phenomenon, indicating its excellent high-temperature stability and regenerability.

[0027] Example 2 A low-carbon alkane dehydrogenation catalyst with metal self-dispersion, loaded with active metal Pt, promoter metal Ge and alkali metal K, and the loading amounts are 0.40 wt.%, 0.55 wt.% and 0.42 wt.% respectively. The carrier is SiO 2 Calculated by, the molar ratio of Pt, Ge, K and SiO 2 is 0.13:0.49:0.68:100.

[0028] (1) At room temperature, 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 20 mg of GeO 2 and 20 mg of KCl were mixed in a beaker and stirred for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, Ge, K, H 2 O and SiO 2 in the silicon source is 0.42:0.005:0.007:16.4:1.

[0029] (2) The solution was transferred to the inner lining of a hydrothermal crystallization kettle and hydrothermally crystallized in an oven at 165 °C for 72 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, and calcining at 550 °C for 4 h, the GeK@S-1 molecular sieve support was obtained.

[0030] (3) 2.5 g of the GeK@S-1 molecular sieve support was placed in a tubular furnace, and O 2 was introduced and heat-treated at 800 °C for 2 h to obtain the activated GeK@S-1 molecular sieve support.

[0031] (4) Mix the activated GeK@S-1 molecular sieve support obtained in step (3) with 10 mg of Pt metal particles, sieve and mix evenly, and then oxidize the mixture in an air (O 2 / N 2 = 21 / 79) gas stream at 680 °C for 4 h, and reduce it in a hydrogen gas stream at 620 °C for 4 h to finally obtain the Pt / GeK@S-1 catalyst.

[0032] Example 3 A low-carbon alkane dehydrogenation catalyst with metal self-dispersion, loaded with active metal Pt, promoter metal Ga and alkali metal Na, and the loadings are 0.40 wt.%, 0.44 wt.% and 0.31 wt.% respectively. The support is SiO 2 Calculated as, the molar ratio of Pt, Ga, Na and SiO 2 is 0.13:0.40:0.87:100.

[0033] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 40 mg of Ga(NO 3 ) 3 ·xH 2 O and 20 mg of NaCl and mix them in a beaker, stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, Ga, Na, H 2 O and SiO 2 in the silicon source is 0.42:0.004:0.009:16.4:1.

[0034] (2) Transfer the solution to the inner lining of the crystallization kettle, hydrothermally crystallize in an oven at 165 °C for 48 h, cool, centrifuge, wash and dry at 100 °C for 6 h, and calcine at 550 °C for 4 h to obtain the GaNa@S-1 molecular sieve support.

[0035] (3) Place 2.5 g of the GaNa@S-1 molecular sieve support in a tube furnace, introduce O 2 and heat-treat at 800 °C for 2 h to obtain the activated GaNa@S-1 molecular sieve support.

[0036] (4) Mix the activated GaNa@S-1 molecular sieve support obtained in step (3) with 10 mg of Pt metal particles, sieve and mix evenly, and then oxidize the mixture in an air (O 2 / N 2 = 21 / 79) gas stream at 700 °C for 4 h, and reduce it in a hydrogen gas stream at 620 °C for 4 h to finally obtain the Pt / GaNa@S-1 catalyst.

[0037] Example 4 A metal self-dispersed low-carbon alkane dehydrogenation catalyst, loaded with active metal Pt, promoter metal Ge and alkali metal Na, with loadings of 0.40 wt.%, 0.55 wt.% and 0.31 wt.% respectively. The carrier is SiO 2 Calculated by, the molar ratio of Pt, Ge, Na and SiO 2 is 0.13:0.49:0.87:100.

[0038] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 20 mg of GeO 2 and 20 mg of NaCl and mix them in a beaker, stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, Ge, Na, H 2 O and SiO in the silicon source 2 is 0.42:0.005:0.009:16.4:1.

[0039] (2) Transfer the solution to the inner lining of a crystallization kettle, hydrothermally crystallize in an oven at 170 °C for 48 h, cool, centrifuge, wash and dry at 100 °C for 6 h, and calcine at 550 °C for 4 h to obtain the GeNa@S-1 molecular sieve carrier.

[0040] (3) Place 2.5 g of the GeNa@S-1 molecular sieve carrier in a tubular furnace, introduce O 2 and perform high-temperature heat treatment at 800 °C for 2 h to obtain the activated GeNa@S-1 molecular sieve carrier.

[0041] (4) Mix the activated GeNa@S-1 molecular sieve carrier obtained in step (3) with 10 mg of Pt metal particles, sieve evenly, and then oxidize the mixture in an air (O 2 / N 2 =21 / 79) gas stream at 680 °C for 4 h, and reduce it in a hydrogen gas stream at 620 °C for 4 h to finally obtain the Pt / GeNa@S-1 catalyst.

[0042] Example 5 A metal self-dispersed low-carbon alkane dehydrogenation catalyst, loaded with active metal Rh, promoter metal Ga and alkali metal K, with loadings of 0.40 wt.%, 0.44 wt.% and 0.42 wt.% respectively. The carrier is SiO 2 Calculated by, the molar ratio of Rh, Ga, K and SiO 2 is 0.13:0.49:0.68:100.

[0043] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 40 mg of Ga(HNO 3 ) 2 ·xH 2 O and 20 mg of KCl and mix them in a beaker. Stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, Ga, K, H 2 O and SiO 2 in the silicon source is 0.42:0.005:0.007:16.4:1.

[0044] (2) Transfer the solution to the inner lining of a crystallization kettle and hydrothermally crystallize it in an oven at 170 °C for 48 h. After cooling, centrifuging, washing and drying at 100 °C for 6 h, calcine it at 550 °C for 4 h to obtain the GaK@S-1 molecular sieve support.

[0045] (3) Place 2.5 g of the GaK@S-1 molecular sieve support in a tubular furnace and introduce O 2 Heat-treat it at 800 °C for 2 h to obtain the activated GaK@S-1 molecular sieve support.

[0046] (4) Mix the activated GaK@S-1 molecular sieve support obtained in step (3) with 10 mg of Rh metal particles, sieve them evenly, and then oxidize the mixture in an air (O 2 / N 2 = 21 / 79) gas stream at 700 °C for 4 h and reduce it in a hydrogen gas stream at 620 °C for 4 h to finally obtain the Rh / GaK@S-1 catalyst.

[0047] Example 6 A low-carbon alkane dehydrogenation catalyst with metal self-dispersion, loaded with active metal Rh, promoter metal Ge and alkali metal K, and the loading amounts are 0.40 wt.%, 0.55 wt.% and 0.42 wt.% respectively. Based on SiO 2 , the molar ratio of Rh, Ge, K and SiO 2 is 0.13:0.49:0.68:100.

[0048] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 20 mg of GeO 2 and 20 mg of KCl and mix them in a beaker. Stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The TPAOH, Ge, K, H 2 O and SiO in the silicon source2 The molar ratio is 0.42:0.005:0.007:16.4:1.

[0049] (2) Transfer the solution to the inner lining of the crystallization kettle, hydrothermally crystallize at 170 °C in an oven for 48 h, cool, centrifuge, wash, and dry at 100 °C for 6 h, and calcine at 550 °C for 4 h to obtain the GeK@S-1 molecular sieve support.

[0050] (3) Place 2.5 g of the GeK@S-1 molecular sieve support in a tubular furnace, and introduce O 2 Perform high-temperature heat treatment at 800 °C for 2 h to obtain the activated GeK@S-1 molecular sieve support.

[0051] (4) Mix the activated GeK@S-1 molecular sieve support obtained in step (3) with 10 mg of Rh metal particles, sieve and mix evenly, and then oxidize the mixture in an air (O 2 / N 2 =21 / 79) gas stream at 680 °C for 4 h, and reduce it in a hydrogen gas stream at 620 °C for 4 h to finally obtain the Rh / GeK@S-1 catalyst.

[0052] Comparative Example 1 Same as Example 1, except that the obtained heteroatom@molecular sieve support is not subjected to high-temperature heat treatment activation (step 3). Based on SiO 2 , the molar ratio of Pt, Ga, K, and SiO 2 is 0.13:0.40:0.68:100.

[0053] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 40 mg of Ga(HNO 3 ) 2 ·xH 2 O and 20 mg of KCl and mix them in a beaker, stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, Ga, K, H 2 O, and SiO 2 in the silicon source in the solution is 0.42:0.005:0.007:16.4:1.

[0054] (2) Transfer the solution to the inner lining of the crystallization kettle, hydrothermally crystallize at 170 °C in an oven for 72 h, cool, centrifuge, wash, and dry at 100 °C for 6 h, and calcine at 550 °C for 4 h to obtain the GaK@S-1 molecular sieve support.

[0055] (3) Mix 10 mg of Pt metal particles with 2.5 g of GaK@S-1 molecular sieve, sieve and mix evenly. Then, oxidize the mixture in an air (O 2 / N 2 = 21 / 79) gas stream at 700 °C for 4 h, and reduce it in a hydrogen gas stream at 620 °C for 4 h to obtain Pt / GaK@S-1 unactivated catalyst.

[0056] Figure 3 This is the TEM image of the Pt / GaK@S-1 unactivated catalyst obtained in this comparative example. As shown in the figure, ~10 nm Pt particles are present on 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.

[0057] Comparative Example 2 Same as Example 1, except that the mixed sample was not subjected to thermal oxidation post-treatment (step 4). Based on SiO 2 , the molar ratio of Pt, Ga, K, and SiO 2 is 0.13:0.40:0.68:100.

[0058] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide, 6.5 g of deionized water, 40 mg of Ga(HNO 3 ) 2 ·xH 2 O and 20 mg of KCl and mix them in a beaker, stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, Ga, K, H 2 O, and SiO 2 in the silicon source in the solution is 0.42:0.005:0.007:16.4:1.

[0059] (2) Transfer the solution to the inner lining of a hydrothermal crystallization kettle, hydrothermally crystallize it in an oven at 170 °C for 72 h, cool, centrifuge, wash, and dry at 100 °C for 6 h, and calcine at 550 °C for 4 h to obtain the GaK@S-1 molecular sieve support.

[0060] (3) Place 2.5 g of the GaK@S-1 molecular sieve support in a tubular furnace, introduce O 2 and heat-treat it at 800 °C for 2 h to obtain the activated GaK@S-1 molecular sieve support.

[0061] (4) Mix the activated GaK@S-1 molecular sieve support obtained in step (3) with 10 mg of Pt metal particles, sieve and mix evenly, and reduce it in a hydrogen gas stream at 620 °C for 4 h to obtain the Pt / GaK@S-1-nc catalyst.

[0062] Figure 4 This is the TEM image of the Pt / GaK@S-1-nc catalyst obtained in this comparative example. As shown in the figure, Pt metal particle aggregates of ~70 nm exist on the surface of the molecular sieve, indicating that Pt species cannot be dispersed to form nanoclusters on the GaK@S-1 support without thermal oxidation treatment; its propane dehydrogenation performance is shown in Table 1.

[0063] Comparative Example 3 Same as Example 1, except that no promoter metal and alkali metal were added during catalyst synthesis. The support is SiO 2 calculated, the molar ratio of Pt to SiO 2 is 0.13:100.

[0064] (1) At room temperature, weigh 8.2 g of tetraethyl orthosilicate, 8.5 g of tetrapropylammonium hydroxide and 6.5 g of deionized water, mix them in a beaker, and stir for 8 h until complete hydrolysis to obtain a homogeneous gel-like mixed solution. The molar ratio of TPAOH, H 2 O and SiO 2 in the silicon source is 0.42:16.4:1.

[0065] (2) Transfer the solution to the inner lining of the hydrothermal crystallization kettle, hydrothermally crystallize in an oven at 170 °C for 72 h, cool, centrifuge, wash and dry at 100 °C for 6 h, and calcine at 550 °C for 4 h to obtain the S-1 molecular sieve support.

[0066] (3) Place 2.5 g of the S-1 molecular sieve support in a tubular furnace, introduce O 2 and heat-treat at 800 °C for 2 h to obtain the activated S-1 molecular sieve support.

[0067] (4) Mix the activated S-1 molecular sieve support obtained in step (3) with 10 mg of Pt metal particles, sieve and mix evenly, and then oxidize the mixture in an air (O 2 / N 2 =21 / 79) gas stream at 700 °C for 4 h, and reduce it in a hydrogen gas stream at 620 °C for 4 h to finally obtain the Pt / S-1 catalyst.

[0068] Figure 5TEM image of the Pt / S-1 catalyst obtained in this comparative example is shown as follows. Large Pt metal particles of ~60 nm exist on the surface of the molecular sieve, indicating that the Pt-based catalyst without promoters and alkali metals is prone to sintering at high temperature and has poor stability, highlighting the synergistic stabilizing effect of promoters and alkali metals on Pt clusters. Its propane dehydrogenation performance is shown in Table 1.

[0069] The catalytic performance of the catalysts obtained in the above examples and comparative examples was evaluated in the propane dehydrogenation reaction. The experimental procedure is as follows: 25 mg 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 620 °C, the reaction pressure was atmospheric pressure, and the weight hourly space velocity of propane was 10 h -1 Under the conditions, the propane conversion and propylene selectivity of the catalyst are shown in Table 1.

[0070] Table 1 Propane dehydrogenation catalytic performance of different catalysts obtained in examples and comparative examples From Comparative Example 1 and Example 1, it can be seen that although the catalyst with the unactivated support has a relatively high initial conversion, the propane conversion decreases significantly as the reaction time progresses, indicating that activating the support can significantly stabilize the catalyst activity. From Comparative Example 2 and Example 1, it can be seen that the catalyst without thermal oxidation post-treatment has almost no dehydrogenation activity, indicating that thermal oxidation treatment is a necessary step for preparing metal self-dispersed catalysts. From Comparative Example 3 and Example 1, it can be seen that the catalyst without promoters and alkali metals has poor stability, indicating that promoters and alkali metals play an important role in stabilizing Pt clusters. From Examples 1-6, it can be seen that by changing the types of promoter metals, alkali metals, and active metals, stable and efficient dehydrogenation catalysts can be obtained, indicating that this preparation method has universality and broad application prospects in the field of chemical catalysis.

[0071] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A metal self-dispersed light alkane dehydrogenation catalyst, characterized in that: The catalyst comprises a carrier, a main active component, an auxiliary component and an alkali metal component; the carrier is a molecular sieve, the main active component is one of metal particles 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; 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 the metal self-dispersed light alkane dehydrogenation catalyst according to claim 1, characterized in that: The specific steps include: (1) Preparation of molecular sieve carrier: at room temperature, silicon source, template, auxiliary agent, alkali metal and water are mixed and stirred to obtain a uniform solution; the solution is transferred to a crystallization kettle for hydrothermal reaction, and the reaction product is filtered, washed, dried and calcined to obtain a heteroatom@molecular sieve carrier; (2) subjecting the carrier obtained in step (1) to high temperature heat treatment under an active atmosphere to obtain an activated heteroatom@molecular sieve carrier; (3) uniformly mixing the activated heteroatom@molecular sieve carrier with active metal particles to obtain a catalyst precursor; (4) The catalyst precursor obtained in step (3) is subjected to thermal oxidation treatment in an oxygen-containing atmosphere at a certain temperature, and is reduced under H2 to obtain a metal self-dispersed low-carbon alkane dehydrogenation catalyst.

3. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: The molecular sieve carrier 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.

4. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: The molar ratio of the template, auxiliary agent, alkali metal, water and SiO2 in the silicon source in step (1) is (0.1-1): (0.001-0.1): (0.001-0.1): (10-50): 1; the silicon source 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 and tetrabutylammonium bromide or a mixture of several thereof.

5. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: The auxiliary agent in step (1) 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, or Ce, selected from one or a mixture of metal chlorides, metal nitrates, metal sulfates, or metal acetates; the alkali metal is one or a mixture of chlorides, hydroxides, sulfates, and nitrates of Na, Mg, K, Ca, or Cs.

6. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: The temperature of the hydrothermal reaction in step (1) is 100-200 °C, and the time of the hydrothermal reaction is 12-144 h; the drying temperature is 50-150 °C, and the drying time is 2-24 h; the roasting temperature is 450-650 °C, and the roasting time is 2-24 h.

7. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: The active atmosphere described in step (2) is one or a mixture of N2, O2, H2O, CO, CO2, NO, NO2, etc.; the high-temperature heat treatment temperature is 500~1000 °C, and the treatment time is 0.5~10 h.

8. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: The active metal particles described in step (3) are one or a mixture of metal particles selected from the group consisting of Ru, Rh, Pd, Ir, Pt and Au.

9. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: The oxygen content of the oxygen-containing atmosphere in step (4) is 2-100%, the treatment temperature is 450-900 °C, and the treatment time is 5-600 min.

10. The method for preparing the metal self-dispersed light alkane dehydrogenation catalyst according to claim 2, characterized in that: In step (4), the reduction temperature is 300-900 °C and the reduction time is 0.5-10 h.

Images