Supported MWW molecular sieves, their preparation methods and applications

Abstract

This invention relates to the field of molecular sieve preparation, and discloses a supported MWW molecular sieve, its preparation method, and its applications. A supported MWW molecular sieve comprises an active metal and an MWW molecular sieve; wherein the ratio of pyridine infrared L-acid content to total acid content of the supported MWW molecular sieve is 0.4-0.9:1; and the pyridine infrared spectrum of the supported MWW molecular sieve is in the range of 1430-1473 cm⁻¹. ‑1 Two L-acid absorption peaks are present, and the ratio of the area of ​​the L-acid absorption peak to the total area of ​​the two L-acid absorption peaks at the top wavenumber position is 0.3-0.7:1. This supported MWW molecular sieve has a specific content of L-acid, and the amount of strong acid in the L-acid also has a specific proportion. The combination of the two can improve the conversion rate of low-carbon olefins and the selectivity of target products.

Description

Technical Field

[0001] This invention relates to the technical field of molecular sieve preparation, specifically to supported MWW molecular sieves, their preparation methods, and applications. Background Technology

[0002] Propylene oligomerization is a crucial process in the petroleum refining industry for producing nonene and dodecene. Nonene, a trimerized product of propylene, serves as an intermediate and can be further alkylated to produce nonylphenol, used in the production of nonionic surfactants, plasticizers, antioxidants, petroleum additives, and agricultural emulsifiers. Alkylation of dodecene, a tetramer of propylene, can synthesize branched dodecylbenzene and tridecyl alcohol. Sulfonation and neutralization of branched dodecylbenzene yield the calcium salt of ABS emulsifier, while tridecyl alcohol can be used as a raw material for various solvents such as lubricants, surfactants, pesticides, and inks. Currently, solid phosphoric acid catalysts are commonly used in the industrial production of nonene and dodecene through propylene oligomerization. Due to their low cost and less stringent requirements for raw materials, they have long dominated the domestic process for producing propylene trimer and tetramers. However, solid phosphoric acid catalysts require steam treatment to generate free phosphoric acid before catalyzing the reaction. Strict control of water volume is necessary during the reaction, and they suffer from drawbacks such as easy mud formation, short lifespan, and environmental pollution. Furthermore, because the reaction occurs on the catalyst surface, the oligomerized products have a narrow distribution and are highly branched. Aluminosilicate molecular sieves, as a type of green catalyst, are widely used in acid catalysis due to their abundant acidic sites and unique pore structures. Commonly used aluminosilicate molecular sieves include MCM-22, Y, ZSM-5, MOR, and Beta, which have different acid properties and regular pore structures, and can effectively catalyze the oligomerization of propylene. The confinement effect of their pore structure can produce products with high linearity. Modifying molecular sieves to adjust their acidity and thus regulate product distribution is a key research focus.

[0003] In the field of propylene oligomerization, ZSM-5 molecular sieve and its modified forms are the most widely used. Patent application CN111229304A modifies HZSM-5 molecular sieve using Fenton's reagent, introducing metallic Fe into the sieve channels and framework, achieving an initial conversion rate of 95% and an oil recovery rate of 90%. However, C9 and C... 12The product yield is low, the catalyst stability is poor, and it is prone to coking and deactivation. Patent application CN111617799A describes metal-modified HZSM-5 molecular sieves, using transition metal oxide NiO as the active component to catalyze propylene oligomerization. The propylene conversion rate is 60%-73%, and the nonene selectivity is 40%-55%, indicating low propylene conversion and poor catalyst stability. This demonstrates that ZSM-5 molecular sieves suffer from small pore size and are prone to coking and deactivation. Patent application US20080064911 A1 uses MCM-22 zeolite in a distillation column reactor at a pressure of 1.4-3.1 MPa and a temperature of 70-85°C, achieving a propylene conversion rate of 70-75%. The product includes approximately 20% hexene and 55% nonene, exhibiting good stability, but further improvements in activity and selectivity for high-carbon-number products are needed.

[0004] Based on the above, current catalysts suffer from environmental pollution, easy carbon deposition and deactivation, low conversion rate of low-carbon olefins, and low selectivity of high-carbon products, necessitating the development of new, highly efficient catalysts. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of existing technologies, such as catalysts easily polluting the environment, carbon deposition and deactivation, low conversion rate of low carbon olefins, and low selectivity of high carbon number products. This invention provides a supported MWW molecular sieve, its preparation method, and its application. The supported MWW molecular sieve has a specific content of L acid, and the strong acid content in the L acid also has a specific proportion. The combination of the two can improve the conversion rate of low carbon olefins and the selectivity of target products.

[0006] To achieve the above objectives, a first aspect of the present invention provides a supported MWW molecular sieve, wherein the supported MWW molecular sieve comprises an active metal and an MWW molecular sieve; wherein the ratio of the amount of pyridine infrared L-acid to the total amount of acid in the supported MWW molecular sieve is 0.4-0.9:1; and the pyridine infrared spectrum of the supported MWW molecular sieve is in the range of 1430-1473 cm⁻¹. -1 There are two L-acid absorption peaks. The ratio of the area of ​​the L-acid absorption peak at the front wavenumber position to the total area of ​​the two L-acid absorption peaks is 0.3-0.7:1.

[0007] A second aspect of the present invention provides a method for preparing a supported MWW molecular sieve, wherein the method includes:

[0008] MWW molecular sieves are impregnated in an active metal precursor solution, and then dried, shaped, and activated in two stages to obtain supported MWW molecular sieves. The two stages of activation are carried out independently under a flowing activation atmosphere.

[0009] The third aspect of this invention provides an application of the supported MWW molecular sieve described in the first aspect or the preparation method described in the second aspect in the propylene oligomerization reaction.

[0010] The supported MWW molecular sieve provided by this invention has an active metal loaded on it, which gives the MWW molecular sieve a specific ratio of L acid content and a specific proportion of strong acid content in the L acid. The combination of the two can improve the conversion rate of low carbon olefins and the selectivity of target products.

[0011] The preparation method provided by the present invention can easily achieve the modulation of the acidity of the molecular sieve and prepare a supported MWW molecular sieve with a specific acid content by loading an active metal onto the MWW molecular sieve by impregnation and performing two-stage activation under a flowing atmosphere.

[0012] The application provided by this invention, using the supported MWW molecular sieve with a specific acid content ratio of this invention, can provide activity and stability for catalytic propylene oligomerization reaction, and facilitate the control of product distribution. Attached Figure Description

[0013] Figure 1 These are the pyridine infrared spectra of the molecular sieves in Examples 1, 3, and Comparative Example 1. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] The first aspect of this invention provides a supported MWW molecular sieve, wherein the supported MWW molecular sieve comprises an active metal and an MWW molecular sieve; wherein the ratio of the pyridine infrared L-acid content to the total acid content of the supported MWW molecular sieve is 0.4-0.9:1; and the pyridine infrared spectrum of the supported MWW molecular sieve is in the range of 1430-1473 cm⁻¹. -1 There are two L-acid absorption peaks. The ratio of the area of ​​the L-acid absorption peak at the front wavenumber position to the total area of ​​the two L-acid absorption peaks is 0.3-0.7:1.

[0016] The supported MWW molecular sieve provided by this invention has active metals loaded on it, which gives the MWW molecular sieve a specific ratio of L acid content and a specific proportion of strong acid content in the L acid, resulting in strong anti-coking ability. The combination of the two can improve the conversion rate of low carbon olefins and the selectivity of target products.

[0017] In this invention, the pyridine infrared acidity of the supported MWW molecular sieve is determined by pyridine adsorption infrared spectroscopy (Py-IR). The specific test conditions are as follows: a Bruker Tensor II Fourier transform infrared spectrometer is used. The test procedure is as follows: approximately 15 mg of sample is pressed at 20 MPa for 5 min to obtain a self-supporting pellet, which is then sealed in the in-situ cell of the infrared spectrometer. The temperature is increased to 450 °C at a rate of 10 °C / min, and a vacuum is drawn to 10 °C. -6 The sample was kept at approximately 2 Pa for 2 hours to desorb impurities such as water molecules physically adsorbed by the molecular sieve. After cooling to room temperature, the sample background was measured and stored. The pyridine valve was opened, and static saturation adsorption of pyridine was allowed to equilibrate for 10 minutes. Then, the temperature was raised to 200°C, and a vacuum was drawn again to 10°C. -6 Pa, hold for 30 min, cool to room temperature, scan 1000-4000 cm⁻¹ -1 Infrared spectra were obtained within the specified range for calculating the total acid content. The sample was then heated to 350°C and evacuated to a vacuum of 10... -6 Pa, maintain for 30 min, cool to room temperature, scan at 1400-1700 cm⁻¹ -1 Infrared spectra within the specified range are used to calculate the amount of strong acid. Among them, 1540 cm⁻¹... -1 The infrared absorption peak at 1450 cm⁻¹ corresponds to the Brønsted acid site. -1 The infrared absorption peak at that location is the L acid site. Using the integrated area and extinction coefficient of the absorption peaks, the amounts of B acid, L acid, and L acid / (L+B) acid can be calculated. The ratio of the two absorption peaks in the L acid peak can then be obtained through peak fitting.

[0018] In this invention, preferably, the ratio of the amount of pyridine infrared L-acid to the total acid amount in the supported MWW molecular sieve is 0.5-0.8:1. The advantage of this preferred embodiment is that when the ratio of L-acid to the total acid amount is within the aforementioned range, the propylene oligomerization reaction is mainly catalyzed by the L-acid center, which can significantly reduce side reactions initiated by the propylene oligomerization catalyzed by the Brønsted acid center, such as cracking and aromatization reactions, and improve the C-axis... 3n With improved selectivity, reduced coking, and extended catalyst life, the inventors have discovered that when the ratio of L-acid content to total acid content is within the aforementioned range, the metal centers and the acid centers of the molecular sieve can achieve a synergistic effect, which is more conducive to improving the activity and selectivity of the catalyst. The L-acid centers introduced by the loaded metal can also effectively increase the selectivity of the polymer.

[0019] In this invention, preferably, the ratio of the absorption peak area at the upper wavenumber position to the total area of ​​the two absorption peaks is 0.3-0.6:1, more preferably 0.35-0.55:1. The advantage of this preferred embodiment is that when the ratio of the L-acid centers introduced by the supported metal to the L-acid centers of the molecular sieve is close to 1, the L-acid centers of the metal and the acid centers of the molecular sieve can achieve a better synergistic effect, which is more conducive to improving the activity and selectivity of the catalyst. The L-acid centers introduced by the supported metal can also effectively increase the selectivity of the polymer.

[0020] In this invention, the range of types of active metals is relatively wide. Preferably, the active metal is selected from at least one of Group IIB, Group IIIB, Group IVB, and Group VB transition metals; more preferably, it is selected from at least one of Group IIIB, Group IVB, and Group VB transition metals; further preferably, it is selected from at least one of Group IIIB, Group IVB, and Group VB transition metals with valence states of divalent, trivalent, tetravalent, and pentavalent; even more preferably, it is selected from at least one of transition metals with valence states of trivalent, tetravalent, and pentavalent; even more preferably, it is selected from at least one of Zr, Zn, Y, Nb, La, and Ce; and still more preferably, it is selected from at least one of Zr, Y, and Nb. The advantage of this preferred embodiment is that when a high-valence metal is loaded, the active metal center can effectively adsorb olefins such as C6 and C9 or carbocations. The olefins can be further protonated to form carbocations, and propylene can further add to the carbocation to generate C9 and C2 olefins. 12 Products with equal chain lengths, i.e., those supported by metals, are more conducive to the formation of high-polymer target products.

[0021] In this invention, by adjusting the loading of the active metal in conjunction with the MWW molecular sieve, the proportion of L-acid in the supported MWW molecular sieve and the proportion of strong acid in the L-acid can be effectively controlled, thereby improving the activity and stability of the supported MWW molecular sieve. Preferably, based on the total amount of the supported MWW molecular sieve, the loading of the active metal, in elemental terms, is 0.1-15% by weight, more preferably 0.1-10% by weight.

[0022] In this invention, the loading of the active metal was determined by X-ray fluorescence spectroscopy (XRF). A Rigaku ZSX100E XRF spectrometer was used to characterize the elemental composition of the molecular sieve bulk phase. The testing conditions were: tungsten target, excitation voltage 40 kV, and excitation current 250 mA. The sample powder was pressed into tablets, with an applied pressure typically between 500 and 1000 kPa.

[0023] In this invention, preferably, the MWW molecular sieve is selected from at least one of HMCM-22 molecular sieve, HMCM-36 molecular sieve, HMCM-49 molecular sieve, and HMCM-56 molecular sieve, with HMCM-22 molecular sieve being the most preferred. The advantage of this preferred embodiment is that HMCM-22 has two independent multi-ring pore systems, a ten-membered ring and a twelve-membered ring, and possesses suitable amounts of Brønsted acid and Lewis acid. The Brønsted acid centers are uniformly distributed, resulting in a suitable Brønsted acid density, which can reduce side reactions such as aromatication and cracking.

[0024] In this invention, preferably, the silicon-to-aluminum molar ratio of the MWW molecular sieve is 2-40, more preferably 2-20, and even more preferably 5-20. Here, the silicon-to-aluminum molar ratio refers to the silicon-to-aluminum molar ratio of the MWW molecular sieve without loaded active metal.

[0025] In this invention, preferably, the total content of Al2O3 and SiO2 in the MWW molecular sieve accounts for 99% by weight of the total MWW molecular sieve, and the content of sodium oxide does not exceed 0.5% by weight, preferably not exceeding 0.2% by weight.

[0026] In this invention, the source of the MWW molecular sieve is not particularly limited; for example, it can be obtained commercially or prepared using conventional methods in the prior art. According to a specific embodiment of the invention, the MWW molecular sieve is prepared by the following method: aluminum hydroxide is dissolved in a strong alkali of sodium hydroxide as an aluminum source, and silica gel is used as a silicon source. The aluminum source, silicon source, and template agent are mixed, stirred, and crystallized in a stirred tank according to a certain proportion. After crystallization, a sodium-type molecular sieve is obtained, which is then subjected to ammonium exchange and calcination to obtain a hydrogen-type MWW molecular sieve. This invention does not particularly limit the specific operating conditions and the amount of each substance used in the preparation of the MWW molecular sieve; those skilled in the art can select the appropriate methods according to actual needs.

[0027] A second aspect of the present invention provides a method for preparing a supported MWW molecular sieve, wherein the method includes:

[0028] MWW molecular sieves are impregnated in an active metal precursor solution, and then dried, shaped, and activated in two stages to obtain supported MWW molecular sieves. The two stages of activation are carried out independently under a flowing activation atmosphere.

[0029] The preparation method provided by this invention can uniformly distribute the active metal load in the molecular sieve using a conventional impregnation method. This effectively controls the proportion of L-acid and the proportion of strong L-acids in the supported MWW molecular sieve, increasing the selectivity of the target product and improving the molecular sieve's resistance to coking. Furthermore, the flowing atmosphere roasting greatly affects the quality and performance of the catalyst, and can adjust the structure of the catalyst's active center. During the roasting process, the flowing oxygen-containing atmosphere roasting can fully oxidize the catalyst, allowing each element in the molecular sieve composition to exist in the form of single oxides with high valence states. High valence metals are more conducive to the formation of high-polymer target products. The combined roasting of the flowing oxygen-containing atmosphere and the inert atmosphere can make the metal, acid radicals, and molecular sieve more stable, introducing new strong L-acid sites to catalyze oligomerization reactions.

[0030] In this invention, a flowing activation atmosphere refers to an activation atmosphere that is in a flowing state.

[0031] In this invention, the range of active metals selected is relatively wide. Preferably, the active metal is selected from at least one transition metal from Group IIB, Group IIIB, Group IVB, and Group VB; more preferably, it is selected from at least one transition metal from Group IIIB, Group IVB, and Group VB; further preferably, it is selected from at least one transition metal from Group IIIB, Group IVB, and Group VB with a valence state of divalent, trivalent, tetravalent, and pentavalent; even more preferably, it is selected from at least one transition metal with a valence state of trivalent, tetravalent, and pentavalent; even more preferably, it is selected from at least one of Zr, Zn, Y, Nb, La, and Ce; and still more preferably, it is selected from at least one of Zr, Y, and Nb.

[0032] In this invention, there is no particular limitation on the type of active metal precursor, as long as an active metal element can be provided. Preferably, the active metal precursor is selected from soluble salts containing active metals, more preferably from at least one of sulfates, nitrates, and chlorides of active metals, and even more preferably from sulfates and / or nitrates.

[0033] In this invention, preferably, the active metal precursor solution is prepared by dissolving the active metal precursor in a solvent. This invention does not particularly limit the type of solvent, as long as it can dissolve the active metal precursor; water is preferred. In this invention, the range of solvent dosage is relatively wide. Preferably, the mass ratio of the solvent to the MWW molecular sieve is 0.5-1.5:1, more preferably 0.7-1.2:1.

[0034] In this invention, the types, properties and sources of MWW molecular sieves have been described in the first aspect and will not be repeated here.

[0035] In this invention, by controlling the amounts of the active metal precursor and the MWW molecular sieve, the acid content distribution of the supported MWW molecular sieve can be effectively regulated, thereby improving the reactivity of the supported MWW molecular sieve. Preferably, the mass ratio of the active metal precursor to the MWW molecular sieve, calculated by element, is 0.01-0.3:1, more preferably 0.02-0.15:1.

[0036] In this invention, the range of conditions for impregnation is relatively wide. Preferably, the impregnation conditions include: a temperature of 10-30°C and a time of 1-5 hours.

[0037] In this invention, the specific operation method of impregnation is not particularly limited, and those skilled in the art can choose according to the actual situation. According to a specific embodiment of the present invention, the impregnation includes: placing the MWW molecular sieve in an active metal precursor solution, mixing the two evenly under stirring conditions, and then impregnating at a temperature of 10-30℃ for 1-5 hours. The present invention does not specifically limit the stirring conditions, as long as the mixing of MWW molecular sieve and active metal precursor can be achieved.

[0038] In this invention, the range of drying conditions is relatively wide. Preferably, the drying conditions include: a temperature of 100-130℃ and a time of 10-15 hours.

[0039] In this invention, in a preferred embodiment, a supported MWW molecular sieve precursor is obtained after molding. This invention does not particularly limit the molding process, and molding methods conventionally defined in the art are applicable to this invention.

[0040] In this invention, the shape of the supported MWW molecular sieve precursor is not particularly limited; for example, it can be spherical, strip-shaped, or butterfly-shaped. Similarly, the particle size of the supported MWW molecular sieve precursor is not particularly limited; for example, it can be 10-40 mesh. It should be noted that the subsequent two activation stages do not change the shape and particle size of the supported MWW molecular sieve; therefore, the shape and particle size of the supported MWW molecular sieve are the same as those of the supported MWW molecular sieve precursor.

[0041] In this invention, the interaction force between the active metal and the MWW molecular sieve is enhanced through a two-stage activation process, thereby increasing the activity of the supported MWW molecular sieve. Preferably, the two-stage activation includes a first-stage activation and a second-stage activation.

[0042] In this invention, there is no particular limitation on the operation method of the first-stage activation. Preferably, the first-stage activation includes: performing a first-stage activation on the shaped supported MWW molecular sieve precursor under a flowing first activation atmosphere.

[0043] In this invention, the range of types of the first activating atmosphere is relatively wide. Preferably, the first activating atmosphere is an oxygen-containing atmosphere, and is preferably selected from at least one of air, a nitrogen-oxygen mixture, an argon-oxygen mixture, and a helium-oxygen mixture. The advantage of this preferred embodiment is that calcination in a flowing oxygen-containing atmosphere allows for complete oxidation of the catalyst, ensuring that each element in the molecular sieve composition exists in the form of a single oxide in a high valence state. This high-valence metal-catalyzed propylene oligomerization reaction is more conducive to the formation of the target polymer product.

[0044] In this invention, the oxygen content in the oxygen-containing atmosphere is not particularly limited. Preferably, based on the total amount of the oxygen-containing atmosphere, the oxygen content in the oxygen-containing atmosphere is 3-30% by volume, more preferably 10-30% by volume.

[0045] In this invention, the selection range for the activation conditions is relatively wide. Preferably, the activation conditions include: a temperature of 300-600℃, a time of 2-10h, and a flow rate of 5-20mL / min / gcats for the first activation atmosphere; more preferably, the activation conditions include: a temperature of 350-550℃, a time of 2-8h, and a flow rate of 8-15mL / min / gcats for the first activation atmosphere. The advantage of this preferred embodiment is that by controlling the flow rate of the oxygen-containing atmosphere, the oxygen content is ensured, allowing the catalyst to be fully oxidized, ensuring that each element in the molecular sieve composition exists in the form of a single oxide in a high valence state. By controlling the temperature and calcination time, water evaporation can be controlled, retaining some acid radicals, which is beneficial to improving the quality and performance of the catalyst.

[0046] In this invention, there are no particular limitations on the operation method of the two-stage activation. Preferably, the two-stage activation includes: performing a two-stage activation on the product of the first-stage activation under a flowing second activation atmosphere.

[0047] In this invention, the range of types of the second activating atmosphere is relatively wide. Preferably, the second activating atmosphere is an inert atmosphere, preferably selected from at least one of nitrogen, argon, helium, and neon, and more preferably nitrogen. The advantage of this preferred embodiment is that the combined roasting of the flowing oxygen-containing atmosphere and the inert atmosphere can make the metal, acid radical, and molecular sieve more stable, which is beneficial for introducing new strong L-acid sites to catalyze oligomerization reactions.

[0048] In this invention, the selection range for the two-stage activation conditions is relatively wide. Preferably, the two-stage activation conditions include: a temperature of 300-600℃, a time of 2-10h, and a flow rate of 5-20mL / min / gcats for the first activation atmosphere; more preferably, the two-stage activation conditions include: a temperature of 350-550℃, a time of 2-6h, and a flow rate of 10-18mL / min / gcats for the first activation atmosphere. The advantage of this preferred embodiment is that by controlling the flow rate of the inert component, the temperature, and the calcination time, it facilitates the combination of metals, acid radicals, and molecular sieves, introducing strong L-acid sites, which is more conducive to the propylene oligomerization reaction.

[0049] The third aspect of this invention provides an application of the supported MWW molecular sieve described in the first aspect or the preparation method described in the second aspect in the propylene oligomerization reaction.

[0050] The inventors of this invention discovered that during the propylene oligomerization reaction catalyzed by MWW molecular sieves, an excessively strong Brønsted acid content easily leads to side reactions such as cracking and aromatization, which is detrimental to obtaining the target product. Using the supported MWW molecular sieve provided by this invention can effectively reduce the occurrence of side reactions such as cracking and aromatization, and effectively increase C... 3n (n is a positive integer) Product selectivity and regulation of reaction product distribution.

[0051] The present invention will be described in detail below through embodiments. Unless otherwise specified, all embodiments described below are derived from commercially available products.

[0052] In this invention, the loading of active metals is determined by X-ray fluorescence spectroscopy (XRF).

[0053] In this invention, the pyridine infrared acidity of the supported MWW molecular sieve is determined by pyridine adsorption infrared spectroscopy (Py-IR).

[0054] In this invention, room temperature refers to 25±5℃.

[0055] Example 1

[0056] (1) Weigh 2.06g Y2(SO4)3·8H2O and mix it with 18mL of deionized water. Stir to dissolve the metal solution.

[0057] (2) Weigh 20g of HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), pour the metal solution from step (1) into the molecular sieve, and obtain a mixture;

[0058] (3) After the mixture is thoroughly stirred, it is soaked at room temperature for 1 hour, dried in an oven at 120°C for 12 hours, and then pressed into tablets and crushed into 20-40 mesh catalysts.

[0059] (4) The catalyst was loaded into a tube furnace. The first stage of activation was carried out in a flowing air atmosphere with an air flow rate of 11 mL / min / gcats and a temperature of 450℃ for 8 hours. The second stage of activation was carried out in a flowing nitrogen atmosphere with a nitrogen flow rate of 15 mL / min / gcats and a temperature of 450℃ for 4 hours.

[0060] Figure 1 This is the pyridine infrared spectrum of the supported MWW molecular sieve from Example 1. Figure 1 It can be seen that the pyridine infrared spectrum of the supported MWW molecular sieve is in the range of 1430-1473 cm⁻¹. -1 There are two L-acid absorption peaks, at 1447 cm⁻¹. -1 The ratio of the absorption peak area of ​​the L acid at the location to the total area of ​​the two L acid absorption peaks is 0.48, indicating that the supporting metal introduced a new L acid site.

[0061] Example 2

[0062] (1) Weigh 1.99g Nb2(SO4)5 and mix it with 18mL of deionized water, stir to dissolve it and obtain a metal solution;

[0063] (2) Weigh 20g of HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), pour the metal solution from step (1) into the molecular sieve, and obtain a mixture;

[0064] (3) After the mixture is thoroughly stirred, it is soaked at room temperature for 1 hour, dried in an oven at 120°C for 12 hours, and then pressed into tablets and crushed into 20-40 mesh catalysts.

[0065] (4) The catalyst was loaded into a tube furnace. The first stage of activation was carried out in a flowing air atmosphere at a flow rate of 8 mL / min / gcats and a temperature of 350°C for 3 hours. The second stage of activation was carried out in a flowing nitrogen atmosphere at a flow rate of 12 mL / min / gcats and a temperature of 350°C for 2 hours. The supported MWW molecular sieve in Example 2 has a similar infrared spectrum to that of pyridine in Example 1, ranging from 1430 to 1473 cm⁻¹. -1 There are two L-acid absorption peaks.

[0066] Example 3

[0067] (1) Weigh 2.82g Zr(NO3)4·5H2O and mix it with 18mL of deionized water, stir to dissolve it and obtain a metal solution;

[0068] (2) Weigh 20g of HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), pour the metal solution from step (1) into the molecular sieve, and obtain a mixture;

[0069] (3) After the mixture is thoroughly stirred, it is soaked at room temperature for 1 hour, dried in an oven at 120°C for 12 hours, and then pressed into tablets and crushed into 20-40 mesh catalyst.

[0070] (4) The catalyst was loaded into a tube furnace. The first stage of activation was carried out in a flowing air atmosphere with an air flow rate of 15 mL / min / gcats and a temperature of 550℃ for 8 hours. The second stage of activation was carried out in a flowing nitrogen atmosphere with a nitrogen flow rate of 18 mL / min / gcats and a temperature of 450℃ for 6 hours.

[0071] Figure 1 This is the pyridine infrared spectrum of the supported MWW molecular sieve from Example 3. Figure 1 It can be seen that the pyridine infrared spectrum of MWW molecular sieve is in the range of 1430-1473 cm⁻¹. -1 There are two L-acid absorption peaks, at 1447 cm⁻¹. -1 The ratio of the absorption peak area of ​​L acid at position 0.35 to the total absorption peak area of ​​the two L acid peaks is 0.35.

[0072] Example 4

[0073] The method of Example 1 was followed, except that HMCM-49 molecular sieve (silicon-aluminum molar ratio of 12.6) was used instead of HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), while all other conditions remained the same. The supported MWW molecular sieve of Example 4 exhibited a similar infrared spectrum to that of pyridine in Example 1, ranging from 1430 to 1473 cm⁻¹. -1 There are two L-acid absorption peaks.

[0074] Example 5

[0075] (1) Weigh 2.64g ZnSO4·7H2O and mix it with 18mL of deionized water, stir to dissolve it and obtain a metal solution;

[0076] (2) Weigh 20g of HMCM-22 molecular sieve, pour the metal solution from step (1) into the molecular sieve, and obtain a mixture;

[0077] (3) After the mixture is thoroughly stirred, it is soaked at room temperature for 1 hour, dried in an oven at 120°C for 12 hours, and then pressed into tablets and crushed into 20-40 mesh catalysts.

[0078] (4) The catalyst was loaded into a tube furnace. The first stage of activation was carried out in a flowing air atmosphere at a flow rate of 11 mL / min / gcats and a temperature of 450°C for 8 hours. The second stage of activation was carried out in a flowing nitrogen atmosphere at a flow rate of 11 mL / min / gcats and a temperature of 450°C for 2 hours. The supported MWW molecular sieve in Example 5 has a similar infrared spectrum to that of pyridine in Example 1, ranging from 1430 to 1473 cm⁻¹. -1 There are two L-acid absorption peaks.

[0079] Example 6

[0080] The method of Example 1 was followed, except that in step (4), the first stage of activation was carried out in a flowing air atmosphere at a flow rate of 5 mL / min / gcats and a temperature of 300°C for 2 hours; the second stage of activation was carried out in a flowing nitrogen atmosphere at a flow rate of 5 mL / min / gcats and a temperature of 300°C for 2 hours. The supported MWW molecular sieve of Example 6 has a similar infrared spectrum to that of pyridine in Example 1, ranging from 1430 to 1473 cm⁻¹. -1 There are two L-acid absorption peaks.

[0081] Comparative Example 1

[0082] The unmodified HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4) from Example 1 was selected. Figure 1 The image shows the pyridine infrared spectrum of the comparative example 1 MWW molecular sieve. Figure 1 It can be seen that the pyridine infrared spectrum of MWW molecular sieve is in the range of 1430-1473 cm⁻¹. -1 There is only one L-acid absorption peak.

[0083] Comparative Example 2

[0084] The method is the same as in Example 1, except that step (4) only performs the second stage of activation, and the activation conditions are the same as the second stage activation conditions in Example 1.

[0085] Comparative Example 3

[0086] The method is the same as in Example 1, except that the activation method is muffle furnace calcination, in which the catalyst is placed in a muffle furnace and calcined at 550°C for 2 hours.

[0087] The characterization results of the supported MWW molecular sieves in the above embodiments and comparative examples are shown in Table 1.

[0088] Table 1

[0089]

[0090] As can be seen from the results in Table 1, the supported MWW catalyst of the embodiment of the present invention with an L acid content ratio of 0.5-0.8:1 and an absorption peak ratio of 0.4-0.6:1 has a better acidity ratio.

[0091] Test case

[0092] The supported MWW-type molecular sieves prepared in the above examples and comparative examples were subjected to propylene oligomerization in a tubular fixed-bed reactor. The reaction conditions were: reaction temperature 80°C, reaction pressure 3.3 MPa, and propylene mass hourly space velocity (MHV) 1.5 h⁻¹. -1The reaction results are shown in Table 2.

[0093] Table 2

[0094] propylene conversion rate / % <![CDATA[C9 selectivity / %]]> <![CDATA[C 12 Selectivity / % <![CDATA[C 9+12 Selectivity % <![CDATA[C 3n Selectivity % Example 1 96.5 56.2 15.2 71.4 80.2 Example 2 95.5 54.8 15.9 70.7 82.1 Example 3 93.8 52.4 12.4 64.8 79.4 Example 4 91.3 46.3 13.4 59.7 73.5 Example 5 92.4 45.9 17.2 63.1 74.5 Example 6 91.8 46.8 15.2 62.0 72.6 Comparative Example 1 89.1 38.5 16.2 54.7 65.8 Comparative Example 2 90.2 40.5 15.9 56.4 66.9 Comparative Example 3 89.4 39.5 15.7 55.2 66.5

[0095] Note: C 3n For C6, C9, C 12 C 15 C 18 C 21 The sum of the components.

[0096] As can be seen from the results in Table 2, the catalyst provided by this invention has high activity and high selectivity for C9 and C12.

[0097] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A supported MWW molecular sieve, characterized in that, The supported MWW molecular sieve comprises an active metal and an MWW molecular sieve; wherein, the ratio of pyridine infrared L acid content to total acid content of the supported MWW molecular sieve is 0.4-0.9:1; the pyridine infrared spectrum of the supported MWW molecular sieve is in the range of 1430-1473 cm⁻¹. -1 There are two L-acid absorption peaks, and the ratio of the area of ​​the L-acid absorption peak at the front wavenumber position to the total area of ​​the two L-acid absorption peaks is 0.3-0.7:

1. The active metal is selected from at least one of Zr, Zn, Y, Nb, La and Ce; The MWW molecular sieve is selected from at least one of HMCM-22 molecular sieve, HMCM-36 molecular sieve, HMCM-49 molecular sieve, and HMCM-56 molecular sieve; The method for preparing the supported MWW molecular sieve includes: impregnating the MWW molecular sieve in an active metal precursor solution, followed by drying, molding, and two-stage activation to obtain the supported MWW molecular sieve. The first stage of activation is carried out in an oxygen-containing atmosphere, and the second stage of activation is carried out in an inert atmosphere.

2. The molecular sieve according to claim 1, wherein, The ratio of pyridine infrared L acid content to total acid content in the supported MWW molecular sieve is 0.5-0.8:

1.

3. The molecular sieve according to claim 2, wherein, The ratio of the absorption peak area at the first wavenumber position to the total area of ​​the two absorption peaks is 0.3-0.6:

1.

4. The molecular sieve according to claim 1, wherein, The active metal is selected from at least one of Zr, Y and Nb.

5. The molecular sieve according to claim 1, wherein, Based on the total amount of the supported MWW molecular sieve, the loading of the active metal in terms of elements is 0.1-15% by weight.

6. The molecular sieve according to claim 5, wherein, Based on the total amount of the supported MWW molecular sieve, the loading of the active metal in terms of elements is 0.1-10% by weight.

7. The molecular sieve according to any one of claims 1-6, wherein, The MWW molecular sieve is HMCM-22 molecular sieve.

8. A method for preparing a supported MWW molecular sieve according to any one of claims 1-7, wherein, The method includes: MWW molecular sieves are impregnated in an active metal precursor solution, and then dried, shaped and activated in two stages to obtain supported MWW molecular sieves. The two stages of activation are carried out independently under a flowing activation atmosphere. After the first stage of activation, a second stage of activation is performed.

9. The method according to claim 8, wherein, The active metal precursor is selected from soluble salts containing active metals.

10. The method according to claim 9, wherein, The active metal precursor is selected from at least one of the sulfate, nitrate and chloride salts of active metals.

11. The method according to claim 10, wherein, The active metal precursor is a sulfate and / or nitrate.

12. The method according to claim 8, wherein, The mass ratio of the active metal precursor to the MWW molecular sieve, calculated by element, is 0.01-0.3:

1.

13. The method according to claim 12, wherein, The mass ratio of the active metal precursor to the MWW molecular sieve, calculated by element, is 0.02-0.15:

1.

14. The method according to claim 8, wherein, The impregnation conditions include a temperature of 10-30°C and a time of 1-5 hours.

15. The method according to claim 8, wherein, The drying conditions include a temperature of 100-130℃ and a time of 10-15 hours.

16. The method according to claim 8, wherein, The activation process includes: performing a first activation on the shaped supported MWW molecular sieve precursor under a flowing first activation atmosphere; wherein the first activation atmosphere is selected from at least one of air, nitrogen-oxygen mixture, argon-oxygen mixture and helium-oxygen mixture.

17. The method according to claim 16, wherein, Based on the total amount of oxygen-containing atmosphere, the oxygen content in the oxygen-containing atmosphere is 3-30% by volume.

18. The method according to claim 17, wherein, Based on the total amount of oxygen-containing atmosphere, the oxygen content in the oxygen-containing atmosphere is 10-30% by volume.

19. The method of claim 16, wherein, The activation conditions include: a temperature of 300-600℃, a time of 2-10h, and a flow rate of 5-20mL / min / gcats for the first activation atmosphere.

20. The method according to claim 19, wherein, The activation conditions include: a temperature of 350-550℃, a time of 2-8h, and a flow rate of 8-15mL / min / gcats for the first activation atmosphere.

21. The method according to any one of claims 16-20, wherein, The two-stage activation includes: performing a two-stage activation on the product of the first-stage activation under a flowing second activation atmosphere; wherein the second activation atmosphere is selected from at least one of nitrogen, argon, helium and neon.

22. The method according to claim 21, wherein, The second activation atmosphere is nitrogen.

23. The method according to claim 21, wherein, The conditions for the two-stage activation include: a temperature of 300-600℃, a time of 2-10h, and a flow rate of 5-20mL / min / gcats for the second activation atmosphere.

24. The method according to claim 23, wherein, The conditions for the two-stage activation include: a temperature of 350-550℃, a time of 2-6h, and a flow rate of 10-18mL / min / gcats for the second activation atmosphere.

25. The application of the supported MWW molecular sieve according to any one of claims 1-7 in the propylene oligomerization reaction.

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