Vanadium-doped TS-1 molecular sieve catalyst as well as preparation method and application thereof

Abstract

The invention provides a vanadium-doped TS-1 molecular sieve catalyst as well as a preparation method and application thereof. According to the catalyst, a novel V / TS-1 catalyst is formed by doping vanadium metal heteroatoms with a unique electronic structure and catalytic characteristics into a TS-1 molecular sieve framework. According to the method, the doped vanadium atoms have multiple oxidation states, and the reaction can be effectively promoted through the oxidation-reduction characteristic in the catalysis process. Meanwhile, titanium (Ti) and vanadium (V) atoms in the catalyst can generate a synergistic effect in the molecular sieve structure, and the effect can significantly enhance the catalytic ability of the catalyst, especially the catalytic application in olefin oxidation reaction. Tests show that the V / TS-1 molecular sieve catalyst shows excellent catalytic performance in the olefin oxidation process, and has high activity and high selectivity.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and in particular relates to a vanadium-doped TS-1 molecular sieve catalyst and a preparation method and application thereof. Background Art

[0002] TS-1 molecular sieve is a solid acid catalyst with a regular microporous structure. Its pores are composed of a three-dimensional ten-membered ring pore system formed by the intersection of Z-shaped ten-membered ring pores (pore diameter 0.51×0.55 nm) and straight ten-membered ring pores (pore diameter 0.53×0.56 nm).

[0003] Generally, the isolated tetracoordinated framework titanium in TS-1 molecular sieve acts as the active center of catalytic oxidation, mainly located in the pores of the molecular sieve. Therefore, TS-1 molecular sieve exhibits excellent activity and product selectivity in the reaction of olefins and linear alkanes with smaller molecular diameters. However, due to the rapid hydrolysis of titanium, it is difficult to increase the titanium content in the framework, and the catalytic capacity of a single framework titanium is limited. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a vanadium-doped TS-1 molecular sieve catalyst and its preparation method and application. The catalyst exhibits excellent catalytic performance in the olefin oxidation process, with high activity and high selectivity.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a vanadium-doped TS-1 molecular sieve catalyst, comprising a TS-1 molecular sieve framework and vanadium doped on the TS-1 molecular sieve framework.

[0007] Preferably, the vanadium doping amount is 3-5 mol % based on the molar amount of Si in the vanadium-doped TS-1 molecular sieve catalyst.

[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned vanadium-doped TS-1 molecular sieve catalyst, comprising the following steps:

[0009] S1: mixing a mixed solution of a vanadium source and a silicon source solution with a titanium source solution to obtain a mixture; the silicon source solution comprises a silicon source and a template; the titanium source solution comprises a titanium source and a solvent;

[0010] S2: The mixture is mixed with a crystallization regulator, subjected to hydrothermal crystallization treatment, and calcined to obtain a vanadium-doped TS-1 molecular sieve catalyst.

[0011] Preferably, the silicon source comprises tetraethyl orthosilicate.

[0012] Preferably, the templating agent comprises tetrapropylammonium hydroxide.

[0013] Preferably, the solvent comprises isopropanol.

[0014] Preferably, the molar ratio of the solvent to tetrabutyl titanate is (60-80):1.

[0015] Preferably, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate is (0.3-0.5):1.

[0016] Preferably, the mass fraction of the tetrapropylammonium hydroxide is 20-25%.

[0017] Preferably, the vanadium source is selected from any one or more of vanadyl sulfate, vanadium trichloride, ammonium metavanadate, vanadyl isopropoxide, vanadyl oxalate or vanadyl acetylacetonate.

[0018] Preferably, the titanium source is selected from any one or more of tetrabutyl titanate, titanium tetrachloride or titanyl sulfate. Preferably, the crystallization regulator is selected from any one or more of ammonium carbonate, ammonium nitrate, ammonium sulfate or ammonium citrate.

[0019] Preferably, the molar ratio of the titanium source, the vanadium source, the crystallization regulator and the silicon source is (0.02~0.05):(0.03~0.05):(0.05~0.2):1.

[0020] Preferably, the temperature of the hydrothermal crystallization treatment is 150-180° C., and the time is 72-96 h.

[0021] Preferably, the calcination atmosphere is air, the calcination temperature is 500-560° C., the heating rate is 2-3° C. / min, and the calcination time is 2-10 h.

[0022] In a second aspect, the present invention provides an application of the above-mentioned vanadium-doped TS-1 molecular sieve catalyst in catalyzing olefin reactions.

[0023] Preferably, the olefin is selected from one or more of 1-pentene, 1-hexene, 1-heptene or 1-octene.

[0024] Preferably, the ratio of the olefin to the vanadium-doped TS-1 molecular sieve catalyst is (20-40) mmol: (0.4-0.6) g.

[0025] Preferably, the reaction is carried out in the presence of a solvent and an oxidizing agent.

[0026] Preferably, the oxidant is selected from a hydrogen peroxide solution, and the mass fraction of the hydrogen peroxide solution is 20-50%; the molar ratio of the oxidant to the olefin is (1-1.5):2.

[0027] Preferably, the solvent is selected from methanol.

[0028] Preferably, the reaction temperature is 50-70° C., the reaction pressure is 0.1-0.3 MPa, and the reaction time is 0.5-6 h.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention provides a vanadium-doped TS-1 molecular sieve catalyst, which is formed by doping vanadium metal heteroatoms with unique electronic structure and catalytic properties onto the TS-1 molecular sieve framework to form a new type of V / TS-1 catalyst. In the present invention, the doped vanadium atoms have multiple oxidation states, and can effectively promote the reaction through redox characteristics during the catalytic process. At the same time, the titanium (Ti) and vanadium (V) atoms in the catalyst can produce a synergistic effect in the molecular sieve structure, which can significantly enhance the catalytic ability of the catalyst, especially in the catalytic application of olefin oxidation reactions.

[0031] The test showed that the V / TS-1 molecular sieve catalyst exhibited excellent catalytic performance in the olefin oxidation process, with high activity and high selectivity, wherein the olefin conversion rate was above 20%, and the corresponding alkylene oxide selectivity was above 70%.

[0032] It can be seen that this discovery not only expands the application range of TS-1 molecular sieve, but also provides new ideas and methods for the development of efficient olefin oxidation catalysts. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The present invention provides a vanadium-doped TS-1 molecular sieve catalyst, which comprises a TS-1 molecular sieve framework and vanadium doped on the TS-1 molecular sieve framework.

[0035] In some embodiments of the present invention, the vanadium doping amount is 3-5 mol%, preferably 4 mol%, based on the molar amount of Si in the vanadium-doped TS-1 molecular sieve catalyst.

[0036] In the present invention, the titanium in TS-1 molecular sieve is mainly in the form of Ti 4+It exists in the form of vanadium and has good oxidation properties. After being doped with vanadium, V and Ti can enhance the activation ability of reactants by changing the electron distribution and local environment, thereby improving the catalytic activity. The redox properties of vanadium help to improve the catalytic efficiency in reactions such as H2O2 decomposition. At the same time, the ionic radius of vanadium is similar to that of titanium. When it is doped into the TS-1 molecular sieve framework, it has little effect on the lattice and is not easy to cause significant lattice distortion, but it can effectively adjust the electronic properties of the molecular sieve, thereby optimizing the catalytic ability of the catalyst. Furthermore, vanadium has a variety of oxidation states (such as V 2+ 、V 3+ 、V 4+ 、V 5+ ), in its actual use in olefin catalysis, can effectively promote the reaction through its redox properties.

[0037] The present invention also provides a method for preparing the vanadium-doped TS-1 molecular sieve catalyst, comprising the following steps:

[0038] S1: mixing a mixed solution of a vanadium source and a silicon source solution with a titanium source solution to obtain a mixture; the silicon source solution comprises a silicon source and a template; the titanium source solution comprises a titanium source and a solvent;

[0039] S2: The mixture is mixed with a crystallization regulator, subjected to hydrothermal crystallization treatment, and calcined to obtain a vanadium-doped TS-1 molecular sieve catalyst.

[0040] In the present invention, the silicon source is usually used as the main body of the molecular sieve framework during the synthesis of the molecular sieve. The vanadium source is preferentially added to the silicon source solution to ensure that the vanadium and the silicon oxygen framework are better combined to form a stable VO-Si bond, thereby uniformly introducing the vanadium into the molecular sieve structure to play a role in doping modification. In addition, since the titanium source will hydrolyze, if the vanadium source, the titanium source and the silicon source are directly mixed, the hydrolysis of titanium and the doping of vanadium will produce a complex competitive reaction, affecting the uniformity and catalytic activity of the final product. Therefore, according to the present invention, the vanadium source and the silicon source solution are first mixed to obtain a mixed solution of the two (referred to as solution 1), and then mixed with the titanium source solution to obtain a mixture (referred to as solution 2).

[0041] In the present invention, the silicon source solution is preferably obtained by mixing a silicon source and a template, and the titanium source solution is preferably obtained by mixing a titanium source and a solvent. The silicon source includes tetraethyl orthosilicate, the template includes tetrapropylammonium hydroxide, the titanium source is selected from any one or more of tetrabutyl titanate, titanium tetrachloride or titanyl sulfate, preferably tetrabutyl titanate; and the solvent includes isopropanol. The mixing is preferably performed under stirring conditions.

[0042] Specifically, in some embodiments of the present invention, tetraethyl orthosilicate is preferably added dropwise into a tetrapropylammonium hydroxide solution and stirred to obtain a silicon source solution. The stirring temperature is 30-45°C, preferably 40°C.

[0043] In some embodiments of the present invention, tetrabutyl titanate is preferably added dropwise into isopropanol and stirred to obtain a titanium source solution. The stirring temperature is 30-45°C, preferably 40°C.

[0044] The molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate is (0.3-0.5):1, preferably (0.35-0.45):1; the mass fraction of tetrapropylammonium hydroxide is 20-25%, preferably 22%. The stirring temperature is 30-45°C, preferably 40°C.

[0045] In some embodiments of the present invention, the vanadium source is preferably added to the silicon source solution and stirred to obtain solution 1. The vanadium source is selected from any one or more of vanadyl sulfate, vanadium trichloride, ammonium metavanadate, vanadyl isopropoxide, vanadyl oxalate or vanadyl acetylacetonate, and the molar ratio of the vanadium source to the silicon source (preferably tetraethyl orthosilicate) is (0.03-0.05):1, preferably (0.035-0.045):1. The stirring is preferably performed at room temperature.

[0046] Then, according to the present invention, the titanium source solution is added dropwise to solution 1 to form solution 2. The process is preferably stirred at room temperature until clear.

[0047] After obtaining solution 2, according to the present invention, it is mixed with a crystallization regulator to obtain a precursor solution. The mixing is preferably carried out under stirring conditions, and the stirring conditions are 40-50°C, preferably 40-45°C; the rotation speed is 300-500 rpm, preferably 400-500°C; and the time is 30-60 min, preferably 30-50 min.

[0048] In the present invention, the crystallization regulator is selected from any one or more of ammonium carbonate, ammonium nitrate, ammonium sulfate or ammonium citrate. The molar ratio of the crystallization regulator to the silicon source is (0.05-0.2):1, preferably (0.08-0.15):1.

[0049] Then, the precursor solution is subjected to a hydrothermal crystallization treatment, in which silicon and titanium release silicon ions and titanium ions during the hydrothermal process. The titanium ions partially replace the silicon atoms in the silicon framework by coordinating with the silicon ions to form a framework structure containing Ti-O-Si bonds. In this process, titanium and silicon ions gradually polymerize to form a three-dimensional network structure. As the reaction proceeds, the crystal nuclei gradually grow and eventually form stable titanium silicon molecular sieve crystals. The temperature of the hydrothermal crystallization treatment is 150-180°C, preferably 155-170°C; the time is 72-96 h, preferably 75-80 h.

[0050] In some preferred embodiments of the present invention, after hydrothermal crystallization treatment, the product is preferably centrifuged, washed, dried, and then calcined to obtain a vanadium-doped TS-1 molecular sieve catalyst.

[0051] In the above calcination, high temperature can remove the template, form an open pore structure, and promote the stabilization of the crystal framework, and enhance the strength of Si-O and Ti-O bonds. In addition, calcination can also remove by-products, improve the size and morphology of the grains, and may lead to the adjustment of the pores and the densification of the crystals, thereby improving the structural stability, purity and catalytic performance of the titanium silicon molecular sieve.

[0052] The present invention has no particular limitation on the centrifugal separation, washing and drying methods, which can be carried out according to methods well known to those skilled in the art.

[0053] In the present invention, the calcination atmosphere is air, and the calcination temperature is 500~560℃, preferably 510~550℃. It should be noted that the heating rate during the calcination process has an important influence on the structure and performance of the titanium silicon molecular sieve. Too fast a heating rate may lead to incomplete removal of the template, resulting in irregular pore structure or uneven crystal morphology. On the contrary, a relatively slow heating rate is conducive to the thorough decomposition of the template, promoting the uniform stabilization of the crystal framework, and is conducive to obtaining a more uniform pore structure and better catalytic performance. Therefore, reasonable control of the heating rate can optimize the pore structure and catalytic performance of the titanium silicon molecular sieve. The present invention preferably has a heating rate of 2~3℃ / min in the calcination, preferably 2.2~2.5℃ / min; the time is 2~10 h, preferably 3~5 h.

[0054] In some specific embodiments of the present invention, the method for preparing the vanadium-doped TS-1 molecular sieve catalyst comprises the following steps:

[0055] Adding tetraethyl orthosilicate dropwise into the tetrapropylammonium hydroxide solution, stirring to obtain a silicon source solution;

[0056] Adding the vanadium source into the silicon source solution and stirring to obtain solution 1;

[0057] Tetrabutyl titanate is added dropwise into isopropanol and stirred to obtain a titanium source solution;

[0058] Adding the titanium source solution dropwise into solution 1 to form solution 2;

[0059] Adding a crystallization regulator to solution 2 to obtain a precursor solution;

[0060] The precursor solution is placed in a hydrothermal reactor for crystallization. After crystallization, the product is centrifuged, washed, dried, and calcined to obtain a molecular sieve catalyst containing titanium and vanadium active sites, that is, a vanadium-doped TS-1 molecular sieve catalyst (which can be recorded as V / TS-1 molecular sieve).

[0061] In summary, the preparation method provided by the present invention is simple, convenient, easy to implement, and conducive to large-scale production.

[0062] The present invention also provides an application of the vanadium-doped TS-1 molecular sieve catalyst in catalyzing olefin reactions.

[0063] Based on the above application, the present invention provides a method for olefin catalysis, comprising the following steps:

[0064] The product is obtained by reacting V / TS-1 molecular sieve and olefin in the presence of an oxidant and a solvent.

[0065] Wherein, the olefin is selected from one or more of 1-pentene, 1-hexene, 1-heptene or 1-octene.

[0066] The oxidant is selected from a hydrogen peroxide solution, and the mass fraction of the hydrogen peroxide solution is 20-50%, preferably 30-40%.

[0067] The solvent is preferably methanol.

[0068] In the above method, the amount of methanol used is preferably 30 mL, the amount of olefin added is 20-40 mmol, preferably 25-35 mmol; the amount of catalyst added is 0.4-0.6 g, preferably 0.45-0.5 g. The molar ratio of the oxidant to the olefin is (1-1.5):2, preferably (1.1-1.3):2.

[0069] In the invention, the above reaction is preferably carried out under stirring conditions, the reaction temperature is 50~70°C, preferably 55~60°C; the reaction pressure is 0.1~0.3 MPa, preferably 0.1~0.2 MPa; the reaction time is 0.5~6 h, preferably 1~4 h.

[0070] The test showed that the V / TS-1 molecular sieve catalyst exhibited excellent catalytic performance in the olefin oxidation process, with high activity and high selectivity, wherein the olefin conversion rate was above 20%, and the corresponding alkylene oxide selectivity was above 70%.

[0071] In the present invention, vanadium has various oxidation states (such as V 2+ 、V 3+ 、V 4+ 、V 5+ ), in its actual use in olefin catalysis, it can effectively promote the reaction through its redox properties. At the same time, the redox properties of vanadium help to improve the catalytic efficiency in reactions such as H2O2 decomposition.

[0072] In order to further illustrate the present invention, the following examples are provided for detailed description. The experimental raw materials used in the following examples of the present invention are all common commercially available products.

[0073] Example 1

[0074] Tetraethyl orthosilicate was added dropwise into a 20% by mass tetrapropylammonium hydroxide solution, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate was 0.4:1, and stirred at 40°C for 2 h to obtain a clear and transparent solution;

[0075] Adding vanadyl sulfate to the silicon source solution, stirring to obtain solution 1, wherein the molar ratio of vanadyl sulfate to tetraethyl orthosilicate is 0.03:1, stirring at room temperature for 2 h;

[0076] Titanyl sulfate was added to the isopropanol solution, stirred at room temperature for 30 min, and then transferred to solution 1, the molar ratio of isopropanol to titanyl sulfate was 60:1, the molar ratio of titanyl sulfate to tetraethyl orthosilicate was 0.05:1, and stirred at 80°C until clear, to obtain solution 2;

[0077] Add ammonium nitrate as a crystallization regulator to solution 2, with a molar ratio of ammonium nitrate to tetraethyl orthosilicate of 0.15:1, stir at room temperature for 3 h to obtain a uniform precursor solution, and transfer to a hydrothermal reactor for crystallization at a crystallization temperature of 150°C and a crystallization time of 84 h;

[0078] The product in the hydrothermal autoclave was separated, dried, and calcined in an air atmosphere at a calcination temperature of 560°C, a heating rate of 2°C / min, and a calcination time of 8 h to obtain a V / TS-1 catalyst with vanadium-titanium synergistic effects.

[0079] Example 2

[0080] Tetraethyl orthosilicate was added dropwise into a 25% by mass tetrapropylammonium hydroxide solution, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate was 0.3:1, and stirred at 40°C for 4 h to obtain a clear and transparent solution;

[0081] Add vanadium trichloride to the silicon source solution, stir to obtain solution 1, wherein the molar ratio of vanadium trichloride to tetraethyl orthosilicate is 0.03:1, and stir at room temperature for 4 h;

[0082] Titanium tetrachloride was added to the isopropanol solution, stirred at room temperature for 30 min, and then transferred to solution 1, the molar ratio of isopropanol to titanium tetrachloride was 70:1, the molar ratio of titanium tetrachloride to tetraethyl orthosilicate was 0.03:1, and stirred at 95°C until clear, to obtain solution 2;

[0083] Add ammonium citrate, a crystallization regulator, to solution 2, with a molar ratio of ammonium citrate to tetraethyl orthosilicate of 0.2:1, stir at room temperature for 3 h to obtain a uniform precursor solution, and transfer to a hydrothermal reactor for crystallization at a crystallization temperature of 160 °C and a crystallization time of 72 h;

[0084] The product in the hydrothermal autoclave was separated, dried, and calcined in an air atmosphere at a calcination temperature of 550°C, a heating rate of 3°C / min, and a calcination time of 6 h to obtain a V / TS-1 catalyst with vanadium-titanium synergistic effects.

[0085] Example 3

[0086] Tetraethyl orthosilicate was added dropwise into a 23% tetrapropylammonium hydroxide solution, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate was 0.5:1, and stirred at 40°C for 4 h to obtain a clear and transparent solution.

[0087] Adding vanadium isopropoxide to the silicon source solution, stirring to obtain solution 1, wherein the molar ratio of vanadium isopropoxide to tetraethyl orthosilicate is 0.05:1, and stirring at room temperature for 4 h;

[0088] Tetrabutyl titanate was added to the isopropanol solution, stirred at room temperature for 30 min, and then transferred to solution 1, the molar ratio of isopropanol to tetrabutyl titanate was 80:1, and the molar ratio of tetrabutyl titanate to tetraethyl orthosilicate was 0.04:1, and stirred at room temperature until clear to obtain solution 2;

[0089] Add ammonium carbonate, a crystallization regulator, to solution 2, with a molar ratio of ammonium carbonate to tetraethyl orthosilicate of 0.05:1, stir at 90°C for 3 h to obtain a uniform precursor solution, and transfer to a hydrothermal reactor for crystallization at a crystallization temperature of 170°C for 96 h.

[0090] The product in the hydrothermal autoclave was separated, dried, and calcined in an air atmosphere at a calcination temperature of 520°C, a heating rate of 2.5°C / min, and a calcination time of 10 h to obtain a V / TS-1 catalyst with vanadium-titanium synergistic effect.

[0091] Example 4

[0092] Tetraethyl orthosilicate was added dropwise into a 25% by mass tetrapropylammonium hydroxide solution, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate was 0.3:1, and stirred at 40°C for 4 hours to obtain a clear and transparent solution;

[0093] Add ammonium metavanadate to the silicon source solution, stir to obtain solution 1, wherein the molar ratio of ammonium metavanadate to tetraethyl orthosilicate is 0.04:1, and stir at room temperature for 4 h;

[0094] Tetraethyl titanate was added to the isopropanol solution, stirred at room temperature for 30 min, and then transferred to solution 1, the molar ratio of isopropanol to tetrabutyl titanate was 70:1, and the molar ratio of tetraethyl titanate to tetraethyl orthosilicate was 0.03:1, and stirred at room temperature until clear to obtain solution 2;

[0095] Add ammonium nitrate as a crystallization regulator to solution 2, the molar ratio of ammonium nitrate to tetraethyl orthosilicate is 0.15:1, stir at 90°C for 3 h to obtain a uniform precursor solution, and transfer to a hydrothermal reactor for crystallization at a crystallization temperature of 160°C and a crystallization time of 72 h;

[0096] The product in the hydrothermal autoclave was separated, dried, and calcined in an air atmosphere at a calcination temperature of 540°C, a heating rate of 3°C / min, and a calcination time of 8 h to obtain a V / TS-1 catalyst with vanadium-titanium synergistic effects.

[0097] Example 5

[0098] Tetraethyl orthosilicate was added dropwise into a 20% by mass tetrapropylammonium hydroxide solution, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate was 0.4:1, and stirred at 40°C for 4 hours to obtain a clear and transparent solution;

[0099] Adding vanadyl acetylacetonate to the silicon source solution, stirring to obtain solution 1, wherein the molar ratio of vanadyl acetylacetonate to tetraethyl orthosilicate is 0.05:1, and stirring at room temperature for 4 h;

[0100] Titanium tetrachloride was added to the isopropanol solution, stirred at room temperature for 30 min, and then transferred to solution 1, the molar ratio of isopropanol to titanium tetrachloride was 80:1, and the molar ratio of titanium tetrachloride to tetraethyl orthosilicate was 0.04:1, and stirred at room temperature until clear to obtain solution 2;

[0101] Add ammonium sulfate, a crystallization regulator, to solution 2, with a molar ratio of ammonium sulfate to tetraethyl orthosilicate of 0.10:1, stir at 90°C for 3 h to obtain a uniform precursor solution, and transfer to a hydrothermal reactor for crystallization at a crystallization temperature of 150°C and a crystallization time of 84 h;

[0102] The product in the hydrothermal autoclave was separated, dried, and calcined in an air atmosphere at a calcination temperature of 560°C, a heating rate of 3°C / min, and a calcination time of 6 h to obtain a V / TS-1 catalyst with vanadium-titanium synergistic effect.

[0103] Example 6

[0104] Tetraethyl orthosilicate was added dropwise into a 23% by mass tetrapropylammonium hydroxide solution, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate was 0.3:1, and stirred at 40°C for 4 hours to obtain a clear and transparent solution;

[0105] Adding vanadyl oxalate to the silicon source solution, stirring to obtain solution 1, wherein the molar ratio of vanadyl oxalate to tetraethyl orthosilicate is 0.03:1, stirring at room temperature for 4 h;

[0106] Titanyl sulfate was added to the isopropanol solution, stirred at room temperature for 30 min, and then transferred to solution 1, the molar ratio of isopropanol to titanyl sulfate was 75:1, the molar ratio of titanyl sulfate to tetraethyl orthosilicate was 0.05:1, and stirred at room temperature until clear to obtain solution 2;

[0107] Add ammonium carbonate, a crystallization regulator, to solution 2, with a molar ratio of ammonium carbonate to tetraethyl orthosilicate of 0.2:1, stir at 90°C for 3 h to obtain a uniform precursor solution, and transfer to a hydrothermal reactor for crystallization at a crystallization temperature of 160°C for 96 h.

[0108] The product in the hydrothermal autoclave was separated, dried, and calcined in an air atmosphere at a calcination temperature of 540°C, a heating rate of 2°C / min, and a calcination time of 6 h to obtain a V / TS-1 catalyst with vanadium-titanium synergistic effect.

[0109] Comparative Example 1

[0110] This comparative example provides a method for preparing an olefin oxidation catalyst, which is different from Example 1 only in that no vanadyl sulfate is added to obtain a TS-1 catalyst.

[0111] Comparative Example 2

[0112] This comparative example provides a method for preparing an olefin oxidation catalyst, which is different from Example 2 only in that no titanium tetrachloride is added, and Catalyst 1 is obtained.

[0113] Comparative Example 3

[0114] This comparative example provides a method for preparing an olefin oxidation catalyst, which is different from Example 3 only in that ammonium metavanadate and tetraethyl titanate are not added, and Catalyst 2 is obtained.

[0115] Comparative Example 4

[0116] This comparative example provides a method for preparing an olefin oxidation catalyst, which differs from Example 4 only in that ammonium metavanadate is replaced with manganese nitrate (the manganese element in the manganese nitrate and the vanadium element in the ammonium metavanadate are equimolar), to obtain Catalyst 3.

[0117] Comparative Example 5

[0118] This comparative example provides a method for preparing an olefin oxidation catalyst, which differs from Example 3 only in that vanadium acetylacetonate is replaced by chromium chloride (the chromium element in the chromium chloride and the vanadium element in the vanadium acetylacetonate are in equimolar amounts), to obtain Catalyst 4.

[0119] Comparative Example 6

[0120] This comparative example provides a method for preparing an olefin oxidation catalyst, which differs from Example 3 only in that the vanadium oxalate is replaced by aluminum nitrate (the aluminum element in the aluminum nitrate and the vanadium element in the vanadium oxalate are in equimolar amounts), to obtain Catalyst 5.

[0121] Performance Testing

[0122] This test is used to illustrate the reaction effect of the molecular sieve obtained by the method provided by the present invention and the molecular sieve obtained by the comparative example method in olefin oxidation reaction.

[0123] The molecular sieve catalyst samples prepared in the above examples and comparative examples were tested according to the following steps:

[0124] 30 mL of methanol was added as solvent to a three-necked flask, followed by 0.40 g of catalyst, the stirrer was started, 30 mmol of olefin was measured and added as reactant, the olefin included one of 1-pentene, 1-hexene, 1-heptene, and 1-octene, and the molar ratio of hydrogen peroxide to olefin was 1:2. The mixture was stirred and mixed evenly in a three-necked flask with condensation reflux, the temperature was raised to 60°C, the reaction was carried out at a reaction temperature of 60°C and a reaction pressure of 0.1 MPa for 4 h, and the distribution of each product was determined on an Agilent 7890A chromatograph, and the results are shown in Table 1.

[0125] Among them, olefin conversion rate % = ×100%;

[0126] Product selectivity % = ×100%;

[0127] Table 1

[0128]

[0129] It can be seen from the data in Table 1 that the vanadium-doped titanium silicon molecular sieve provided by the present invention has high catalytic activity. When used in olefin oxidation reactions, the olefin conversion rate and epoxide selectivity are significantly higher than those of the titanium silicon molecular sieve not doped with vanadium in Comparative Example 1, the catalyst containing vanadium but no titanium in Comparative Example 2, and the catalyst without vanadium and titanium in Comparative Example 3. At the same time, manganese, chromium and aluminum were used to replace vanadium for doping in Comparative Examples 4 to 6, respectively, and the effects were found to be unsatisfactory, indicating that vanadium and titanium play a synergistic role in the catalyst and improve the catalytic ability of the catalyst.

[0130] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A vanadium-doped TS-1 molecular sieve catalyst, characterized in that: The invention comprises a TS-1 molecular sieve framework and vanadium doped on the TS-1 molecular sieve framework.

2. The vanadium-doped TS-1 molecular sieve catalyst according to claim 1, characterized in that: The vanadium doping amount is 3 to 5 mol % based on the molar amount of Si in the vanadium-doped TS-1 molecular sieve catalyst.

3. A method for preparing a vanadium-doped TS-1 molecular sieve catalyst as claimed in claim 1 or 2, characterized in that: The following steps are involved: S1: mixing a mixed solution of a vanadium source and a silicon source solution with a titanium source solution to obtain a mixture; the silicon source solution comprises a silicon source and a template; the titanium source solution comprises a titanium source and a solvent; S2: The mixture is mixed with a crystallization regulator, subjected to hydrothermal crystallization treatment, and calcined to obtain a vanadium-doped TS-1 molecular sieve catalyst.

4. The preparation method according to claim 3, characterized in that: The silicon source includes tetraethyl orthosilicate; The template agent includes tetrapropylammonium hydroxide; The solvent includes isopropanol; the molar ratio of the solvent to tetrabutyl titanate is (60-80):1; The molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate is (0.3-0.5):1; The mass fraction of the tetrapropylammonium hydroxide is 20-25%.

5. The preparation method according to claim 3 or 4, characterized in that: The vanadium source is selected from any one or more of vanadyl sulfate, vanadium trichloride, ammonium metavanadate, vanadyl isopropoxide, vanadyl oxalate or vanadyl acetylacetonate; The titanium source is selected from any one or more of tetrabutyl titanate, titanium tetrachloride or titanyl sulfate; The crystallization regulator is selected from any one or more of ammonium carbonate, ammonium nitrate, ammonium sulfate or ammonium citrate.

6. The preparation method according to any one of claims 3 to 5, characterized in that The molar ratio of the titanium source, the vanadium source, the crystallization regulator and the silicon source is (0.02-0.05):(0.03-0.05):(0.05-0.2):

1.

7. The preparation method according to any one of claims 3 to 6, characterized in that The hydrothermal crystallization treatment is performed at a temperature of 150 to 180° C. and a time of 72 to 96 h. The calcination atmosphere is air, the calcination temperature is 500-560°C, the heating rate is 2-3°C / min, and the calcination time is 2-10 h.

8. Use of the vanadium-doped TS-1 molecular sieve catalyst according to claim 1 or 2 or the vanadium-doped TS-1 molecular sieve catalyst prepared by the preparation method according to any one of claims 3 to 7 in catalyzing olefin reactions.

9. The use according to claim 8, characterized in that: The olefin is selected from one or more of 1-pentene, 1-hexene, 1-heptene or 1-octene; The ratio of the olefin to the vanadium-doped TS-1 molecular sieve catalyst is (20-40) mmol: (0.4-0.6) g.

10. The use according to claim 8 or 9, characterized in that: The reaction is carried out in the presence of a solvent and an oxidant; The oxidant is selected from a hydrogen peroxide solution, the mass fraction of the hydrogen peroxide solution is 20-50%; the molar ratio of the oxidant to the olefin is (1-1.5):2; The solvent is selected from methanol; The reaction temperature is 50-70° C., the reaction pressure is 0.1-0.3 MPa, and the reaction time is 0.5-6 h.

Images