Supported MWW molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the field of molecular sieve preparation and discloses a supported MWW molecular sieve as well as a preparation method and application thereof. The invention relates to a supported MWW molecular sieve, and the supported MWW molecular sieve comprises an active metal and an MWW molecular sieve, wherein the ratio of the pyridine infrared L acid amount of the supported MWW molecular sieve to the total acid amount is (0.4-0.9): 1; the pyridine infrared spectrum of the supported MWW molecular sieve has two L acid absorption peaks at 1430-1473cm <-1 >, and the ratio of the absorption peak area of the L acid at the front wave number position to the total area of the two L acid absorption peaks is (0.3-0.7): 1. The supported MWW molecular sieve has a specific amount of L acid, and the amount of strong acid in the L acid also has a specific proportion, so that the conversion rate of low-carbon olefins and the selectivity of a target product can be improved by combining the L acid and the strong acid.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieve preparation, and in particular to a supported MWW molecular sieve and a preparation method and application thereof. Background Art

[0002] Propylene oligomerization is an important process for producing nonene and dodecene in the petroleum refining industry. The product of propylene trimerization, nonene, as an intermediate product, can be further alkylated to prepare nonylphenol, which is used to produce nonionic surfactants, plasticizers, antioxidants, petroleum additives and agricultural emulsifiers. Alkylation of propylene tetramer dodecene can synthesize branched dodecylbenzene and tridecanol. Branched dodecylbenzene can be prepared into emulsifier ABS calcium salt after sulfonation and neutralization. Tridecanol can be used as a raw material for various solvents such as lubricants, surfactants, pesticides, and inks. At present, the commonly used catalyst for the industrial application of propylene oligomerization to prepare nonene and dodecene production process is solid phosphoric acid catalyst. Due to its low cost and undemanding requirements for raw materials, it has always dominated the domestic process for preparing propylene trimerization and tetramerization products. However, solid phosphoric acid catalyst needs to be treated with water vapor to produce free phosphoric acid, and then catalyze the reaction. The amount of water needs to be strictly controlled during the reaction. It has the disadvantages of easy mud, short life and environmental pollution. In addition, since the reaction is carried out on the catalyst surface, the distribution of the oligomerization product is narrow and highly branched. As a green catalyst, aluminosilicate molecular sieves are widely used in the field of acid catalysis due to their abundant acid sites and unique pore structure. Commonly used aluminosilicate molecular sieves include MCM-22, Y, ZSM-5, MOR, Beta, etc. They have different acid properties and regular pore structures and can effectively catalyze propylene polymerization reactions. The confining effect of their pore structure can produce products with higher linearity. The focus of the research is to modify the molecular sieve, adjust its acidity and then regulate the product distribution.

[0003] In the field of propylene polymerization, ZSM-5 molecular sieve and its modified products are the most widely used. Patent application CN111229304A uses Fenton reagent to modify HZSM-5 molecular sieve, introduces metal Fe into the molecular sieve pores and framework, and the initial conversion rate can reach 95%, and the oil yield can reach 90%, but C9 and C 12There are few products, poor catalyst stability, and easy carbon deposition and deactivation. In patent application CN111617799A, HZSM-5 molecular sieve is loaded with metal modification, and transition metal oxide NiO is used as the active component to catalyze propylene polymerization reaction. The propylene conversion rate is 60%-73%, the nonene selectivity is 40%-55%, the propylene conversion rate is low, and the catalyst stability is poor. It can be seen that ZSM-5 molecular sieve has the disadvantages of small pores and easy carbon deposition and deactivation. Patent application US20080064911 A1 uses MCM-22 zeolite, operates at a pressure of 1.4-3.1MPa and a temperature of 70-85°C in a distillation tower reactor, and the propylene conversion rate can reach 70-75%. The products include about 20% hexene and 55% nonene, with good stability, but it is necessary to further improve its activity and selectivity for high carbon number products.

[0004] Based on the above, the current catalysts have problems such as environmental pollution, easy carbon deposition and deactivation, low conversion rate of low-carbon olefins, and low selectivity of high-carbon number products. It is urgent to develop new and efficient catalysts. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of the prior art that the catalyst is easy to pollute the environment, deactivate due to carbon deposition, have a low conversion rate of light olefins and a low selectivity for high carbon number products, and to provide a supported MWW molecular sieve and a preparation method and application thereof. The 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 light olefins and the selectivity of target products.

[0006] In order to achieve the above-mentioned object, the 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 pyridine infrared L acid content to the 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 1430-1473cm -1 There are two L acid absorption peaks, and the ratio of the absorption peak area of ​​L acid at the front wave number 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 comprises:

[0008] The MWW molecular sieve is impregnated in an active metal precursor solution, and then dried, formed and activated in two stages to obtain a supported MWW molecular sieve, wherein the two stages of activation are each independently performed under a flowing activation atmosphere.

[0009] The third aspect of the present invention provides a use of the supported MWW molecular sieve described in the first aspect or the supported MWW molecular sieve prepared by the preparation method described in the second aspect in a propylene polymerization reaction.

[0010] The loaded MWW molecular sieve provided by the present invention loads active metals on the MWW molecular sieve, so that the MWW molecular sieve has a specific proportion 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 light olefins and the selectivity of target products.

[0011] The preparation method provided by the present invention can simply adjust the acidity of the molecular sieve and prepare a loaded MWW molecular sieve with a specific acid content by loading active metals on the MWW molecular sieve through an impregnation method and performing two-stage activation under a flowing atmosphere.

[0012] The application provided by the present invention uses the supported MWW molecular sieve with a specific acid content ratio of the present invention to provide activity and stability in catalyzing propylene polymerization reactions, making it easy to regulate product distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the pyridine infrared spectrum of the molecular sieve in Example 1, Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0014] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0015] The 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 pyridine infrared L acid content to the 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 1430-1473cm -1 There are two L acid absorption peaks, and the ratio of the absorption peak area of ​​L acid at the front wave number position to the total area of ​​the two L acid absorption peaks is 0.3-0.7:1.

[0016] The loaded MWW molecular sieve provided by the present invention loads active metals on the MWW molecular sieve, so that the MWW molecular sieve has a specific proportion of L acid, and the amount of strong acid in the L acid also has a specific proportion, and has strong anti-carbon deposition ability. The combination of the two can improve the conversion rate of light olefins and the selectivity of target products.

[0017] In the present invention, the pyridine infrared acid content of the supported MWW molecular sieve is determined by pyridine adsorption infrared spectroscopy (Py-IR) analysis, and the specific test conditions are: using a Bruker TensorⅡ Fourier transform infrared spectrometer for testing. Test process: Take about 15 mg of sample and press it at 20 MPa for 5 minutes to make a self-supporting sheet, then place it in the in-situ cell of the infrared spectrometer and seal it, heat it to 450°C at a rate of 10°C / min, and evacuate it to 10 -6 Pa for 2 hours to desorb water molecules and other impurities physically adsorbed by the molecular sieve. After cooling to room temperature, measure the sample background and save it. Open the pyridine valve, statically saturate adsorb pyridine for 10 minutes, then heat to 200 ° C and evacuate to 10 -6 Pa, hold for 30 min, cool to room temperature, scan 1000-4000 cm -1 The infrared spectrum was obtained within the range and used to calculate the total acid content. Then the sample was heated to 350°C and vacuumed to 10 -6 Pa, hold for 30 min, cool to room temperature, scan 1400-1700 cm -1 Infrared spectrum within the range is used to calculate the amount of strong acid. Among them, 1540cm -1 The infrared absorption peak at 1450cm -1 The infrared absorption peak at is the L acid site. The B acid amount, L acid amount and L acid amount / (L+B) acid amount are calculated using the integral area and extinction coefficient of the above absorption peaks, and the ratio of the two absorption peaks in the L acid peak can be obtained by peak fitting.

[0018] In the present invention, preferably, the ratio of the amount of pyridine infrared L-acid to the total amount of acid in the supported MWW molecular sieve is 0.5-0.8:1. The advantage of adopting this preferred embodiment is that when the ratio of the amount of L-acid to the total amount of acid is within the aforementioned range, the propylene polymerization reaction is mainly catalyzed by the L-acid center, which can greatly reduce the side reactions caused by the propylene polymerization catalyzed by the B-acid center, such as cracking, aromatization reaction, etc., and improve C 3n Selectivity, reduce carbon deposition, and extend catalyst life. The inventors have found that when the ratio of the amount of L-acid to the total amount of acid is within the aforementioned range, the metal center and the acid center 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 center introduced by the loaded metal can also effectively increase the polymer selectivity.

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

[0020] In the present invention, the selection range of the types of active metals is relatively wide. Preferably, the active metal is selected from at least one of the transition metals of Group IIB, Group IIIB, Group IVB and Group VB, preferably selected from at least one of the transition metals of Group IIIB, Group IVB and Group VB, further preferably selected from at least one of the transition metals of Group IIIB, Group IVB and Group VB with a valence state of divalent, trivalent, tetravalent and pentavalent, further preferably selected from at least one of the transition metals of Group IIIB, Group IVB and Group VB with a valence state of trivalent, tetravalent and pentavalent, further further selected from at least one of Zr, Zn, Y, Nb, La and Ce, and further preferably selected from at least one of Zr, Y and Nb. The advantage of adopting this preferred embodiment is that when a high-valent metal is loaded, the metal active center can effectively adsorb olefins or positive carbon ions such as C6 and C9, the olefins can be further protonated to form positive carbon ions, and propylene can further add to positive carbon ions to generate C9, C 12 Equal-length chain products, that is, loaded metals are more conducive to the generation of high-polymer target products.

[0021] In the present invention, by regulating the loading amount of the active metal and cooperating with the MWW molecular sieve, the L acid ratio of the supported MWW molecular sieve and the ratio of the strong acid in the L acid can be effectively regulated to improve the activity and stability of the supported MWW molecular sieve. Preferably, based on the total amount of the supported MWW molecular sieve, the loading amount of the active metal in terms of element is 0.1-15% by weight, more preferably 0.1-10% by weight.

[0022] In the present invention, the loading amount of the active metal is determined by X-ray fluorescence spectrometry (XRF), and the molecular sieve bulk phase elements are characterized (XRF) using a ZSX100E X-ray fluorescence spectrometer produced by Rigaku Company, and the test conditions are: tungsten target, excitation voltage 40kV, excitation current 250Ma. The sample powder is pressed into tablets, and the applied pressure is generally 500-1000kPa.

[0023] In the present 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, preferably HMCM-22 molecular sieve. The advantage of adopting this preferred embodiment is that HMCM-22 has two independent polycyclic pore systems of ten-membered rings and twelve-membered rings, and has a suitable amount of B acid and L acid, the B acid center is evenly distributed, has a suitable B acid density, and can reduce side reactions such as aromatization and cracking.

[0024] In the present invention, preferably, the silicon-aluminum molar ratio of the MWW molecular sieve is 2-40, more preferably 2-20, and even more preferably 5-20. The silicon-aluminum molar ratio here refers to the silicon-aluminum molar ratio of the MWW molecular sieve not loaded with active metals.

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

[0026] In the present invention, there is no particular limitation on the source of the MWW molecular sieve, for example, it can be obtained commercially, or it can be prepared by conventional preparation methods in the prior art. According to a specific embodiment of the present invention, the MWW molecular sieve is prepared by the following method: aluminum hydroxide is dissolved in a strong base of sodium hydroxide as an aluminum source, and silica gel is used as a silicon source, and the aluminum source, silicon source, and template agent are mixed, stirred, and crystallized in a stirred tank in a certain proportion. After the crystallization of the MWW molecular sieve is completed, a sodium-type molecular sieve is obtained, and a hydrogen-type MWW molecular sieve is obtained after ammonium exchange and roasting. The present invention does not particularly limit the specific operating conditions and the amount of each substance used in the preparation process of the MWW molecular sieve, and those skilled in the art can make a selection 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 comprises:

[0028] The MWW molecular sieve is impregnated in an active metal precursor solution, and then dried, formed and activated in two stages to obtain a supported MWW molecular sieve, wherein the two stages of activation are each independently performed under a flowing activation atmosphere.

[0029] The preparation method provided by the present invention can evenly distribute the active metal load in the molecular sieve by using a common impregnation method, can effectively regulate the proportion of L acid in the loaded MWW molecular sieve and the proportion of strong acid in the L acid, increase the selectivity of the target product, and improve the molecular sieve's ability to resist carbon deposition and coking; further, the flowing atmosphere roasting will greatly affect the quality and performance of the catalyst, and the catalyst active center structure can be adjusted by the flowing atmosphere roasting. During the roasting process, the flowing oxygen-containing atmosphere roasting can fully oxidize the catalyst, so that each element in the molecular sieve composition exists in the form of a single oxide in a high-valent state, and the high-valent metal is more conducive to the generation of a high-polymer target product; the flowing oxygen-containing atmosphere and the inert atmosphere combined roasting can make the metal, acid radical and molecular sieve more stably combined, and introduce a new strong L acid site catalytic polymerization reaction.

[0030] In the present invention, the flowing activation atmosphere means that the activation atmosphere is in a flowing state.

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

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

[0033] In the present invention, preferably, the active metal precursor solution is prepared by dissolving the active metal precursor in a solvent. The present invention does not particularly limit the type of solvent, as long as it can dissolve the active metal precursor, preferably water. In the present invention, the amount of solvent used can be selected in a wide range. Preferably, the mass ratio of the solvent to the MWW molecular sieve is 0.5-1.5:1, and more preferably 0.7-1.2:1.

[0034] In the present invention, the type, properties and source of the MWW molecular sieve have been described in the first aspect and will not be repeated here.

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

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

[0037] In the present invention, there is no particular limitation on the specific operation mode of impregnation, and those skilled in the art can select it according to the actual situation. According to a specific embodiment of the present invention, the impregnation includes: placing the MWW molecular sieve in the active metal precursor solution, mixing the two evenly under stirring conditions, and then impregnating at a temperature of 10-30°C for 1-5h. The present invention does not specifically limit the stirring conditions, as long as the mixing of the MWW molecular sieve and the active metal precursor can be achieved.

[0038] In the present invention, the drying conditions can be selected in a wide range. Preferably, the drying conditions include: a temperature of 100-130° C. and a time of 10-15 hours.

[0039] In the present invention, preferably, a supported MWW molecular sieve precursor is obtained after molding. The present invention does not particularly limit the molding treatment method, and the molding methods conventionally defined in the art are applicable to the present invention.

[0040] In the present 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. The particle size of the supported MWW molecular sieve precursor is also not particularly limited in the present invention, for example, it can be 10-40 mesh. It should be noted that the subsequent two-stage activation will not change the shape and particle size of the supported MWW molecular sieve, so the shape and particle size of the supported MWW molecular sieve are the same as the shape and particle size of the supported MWW molecular sieve precursor.

[0041] In the present invention, the interaction between the active metal and the MWW molecular sieve is increased by two-stage activation, thereby increasing the activity of the supported MWW molecular sieve. Preferably, the two-stage activation includes one-stage activation and two-stage activation.

[0042] In the present invention, there is no particular limitation on the operation mode of the one-stage activation. Preferably, the one-stage activation comprises: subjecting the supported MWW molecular sieve precursor obtained after molding to one-stage activation under a flowing first activation atmosphere.

[0043] In the present invention, the first activation atmosphere has a wide range of choices. Preferably, the first activation atmosphere is an oxygen-containing atmosphere, preferably selected from at least one of air, nitrogen-oxygen mixed gas, argon-oxygen mixed gas, and helium-oxygen mixed gas. The advantage of adopting this preferred embodiment is that the calcination in a flowing oxygen-containing atmosphere can fully oxidize the catalyst, so that each element in the molecular sieve composition exists in the form of a single oxide in a high-valent state, and the high-valent metal-catalyzed propylene polymerization reaction is more conducive to the formation of a high-polymer target product.

[0044] In the present invention, there is no particular limitation on the content of oxygen in the oxygen-containing atmosphere. Preferably, based on the total amount of the oxygen-containing atmosphere, the content of oxygen in the oxygen-containing atmosphere is 3-30% by volume, more preferably 10-30% by volume.

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

[0046] In the present invention, there is no particular limitation on the operation mode of the second-stage activation. Preferably, the second-stage activation comprises: subjecting the first-stage activation product to a second-stage activation under a flowing second activation atmosphere.

[0047] In the present invention, the second activation atmosphere has a wide range of choices. Preferably, the second activation atmosphere is an inert atmosphere, preferably selected from at least one of nitrogen, argon, helium and neon, and more preferably nitrogen. The advantage of using this preferred embodiment is that the combined calcination of the flowing oxygen-containing atmosphere and the inert atmosphere can make the combination of metal, acid radical and molecular sieve more stable, which is conducive to the introduction of new strong L acid site catalytic polymerization reaction.

[0048] In the present invention, the range of selection of conditions for the second stage activation is relatively wide. Preferably, the conditions for the second stage activation include: a temperature of 300-600°C, a time of 2-10h, and a flow rate of the first activation atmosphere of 5-20mL / min / gcats; further preferably, the conditions for the second stage activation include: a temperature of 350-550°C, a time of 2-6h, and a flow rate of the first activation atmosphere of 10-18mL / min / gcats. The advantage of adopting this preferred embodiment is that by controlling the flow rate, temperature and calcination time of the inert component, it helps to combine the metal, acid radical and molecular sieve, introduce strong L acid sites, and is more conducive to the polymerization reaction of propylene.

[0049] The third aspect of the present invention provides a use of the supported MWW molecular sieve described in the first aspect or the supported MWW molecular sieve prepared by the preparation method described in the second aspect in a propylene polymerization reaction.

[0050] The inventors of the present invention have found that in the process of propylene polymerization catalyzed by MWW molecular sieve, excessive B acid content is likely to cause side reactions such as cracking and aromatization, which is not conducive to obtaining the target product. The use of the supported MWW molecular sieve provided by the present 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 regulate the distribution of reaction products.

[0051] The present invention will be described in detail below by way of examples. In the following examples, all products are commercially available unless otherwise specified.

[0052] In the present invention, the loading amount of the active metal is measured by X-ray fluorescence spectrometry (XRF).

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

[0054] In the present invention, normal temperature refers to 25±5°C.

[0055] Example 1

[0056] (1) Weigh 2.06 g of Y2(SO4)3·8H2O and mix with 18 mL of deionized water, stirring to dissolve the mixture and obtain a metal solution;

[0057] (2) Weighing 20 g of HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), pouring the metal solution in step (1) into the molecular sieve to obtain a mixture;

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

[0059] (4) The catalyst was loaded into a tubular 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°C for 8 h. 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°C for 4 h.

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

[0061] Example 2

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

[0063] (2) Weighing 20 g of HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), pouring the metal solution in step (1) into the molecular sieve to obtain a mixture;

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

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

[0066] Example 3

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

[0068] (2) Weighing 20 g of HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), pouring the metal solution in step (1) into the molecular sieve to obtain a mixture;

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

[0070] (4) The catalyst was loaded into a tubular 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°C for 8 h. 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°C for 6 h.

[0071] Figure 1 This is the pyridine infrared spectrum of the supported MWW molecular sieve of Example 3. Figure 1 It can be seen that the pyridine infrared spectrum of MWW molecular sieve is 1430-1473cm -1 There are two L acid absorption peaks, 1447 cm -1 The ratio of the absorption peak area of ​​L acid at position to the total area of ​​two L acid absorption 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 to replace HMCM-22 molecular sieve (silicon-aluminum molar ratio of 11.4), and the other conditions remained unchanged. Example 4 The supported MWW molecular sieve had a similar infrared spectrum to that of Example 1, with a pyridine infrared spectrum of 1430-1473 cm -1 There are two L acid absorption peaks.

[0074] Example 5

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

[0076] (2) Weighing 20 g of HMCM-22 molecular sieve, pouring the metal solution in step (1) into the molecular sieve to obtain a mixture;

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

[0078] (4) The catalyst was loaded into a tubular furnace, and 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°C for 8 h; the second stage of activation was carried out in a flowing nitrogen atmosphere with a nitrogen flow rate of 11 mL / min / gcats and a temperature of 450°C for 2 h. The infrared spectrum of the supported MWW molecular sieve in Example 5 was similar to that of pyridine in Example 1 at 1430-1473 cm -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 with an air flow rate of 5 mL / min / gcats and a temperature of 300°C for 2 h; the second stage of activation was carried out in a flowing nitrogen atmosphere with a nitrogen flow rate of 5 mL / min / gcats and a temperature of 300°C for 2 h. Example 6 The supported MWW molecular sieve had a similar infrared spectrum to that of Example 1 with pyridine at 1430-1473 cm -1 There are two L acid absorption peaks.

[0081] Comparative Example 1

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

[0083] Comparative Example 2

[0084] The method of Example 1 is followed, except that in step (4), only the second stage activation is performed, and the activation conditions are consistent with the second stage activation conditions in Example 1.

[0085] Comparative Example 3

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

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

[0088] Table 1

[0089]

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

[0091] Test Case

[0092] The supported MWW molecular sieves prepared in the above examples and comparative examples were subjected to propylene polymerization in a tubular fixed bed reactor under the following reaction conditions: reaction temperature of 80°C, reaction pressure of 3.3 MPa, and propylene mass space velocity of 1.5 h -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] It can be seen from the results in Table 2 that the catalyst provided by the present invention has high activity and high carbon nine and carbon twelve selectivity.

[0097] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to 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 the pyridine infrared L acid content of the supported MWW molecular sieve to the total acid content is 0.4-0.9:1; the pyridine infrared spectrum of the supported MWW molecular sieve is 1430-1473cm -1 There are two L acid absorption peaks, and the ratio of the absorption peak area of ​​L acid at the front wave number position to the total area of ​​the two L acid absorption peaks is 0.3-0.7:

1.

2. The molecular sieve according to claim 1, wherein The ratio of the pyridine infrared lyophilic acid content to the total lyophilic acid content of the supported MWW molecular sieve is 0.5-0.8:1; Preferably, the ratio of the absorption peak area at the front wave number position to the total area of ​​the two absorption peaks is 0.3-0.6:

1.

3. The molecular sieve according to claim 1 or 2, wherein: The active metal is selected from at least one of transition metals of Group IIB, Group IIIB, Group IVB and Group VB, preferably selected from at least one of transition metals of Group IIIB, Group IVB and Group VB, further preferably selected from at least one of transition metals of Group IIIB, Group IVB and Group VB with a valence of divalent, trivalent, tetravalent and pentavalent, further preferably selected from at least one of transition metals of Group IIIB, Group IVB and Group VB with a valence of trivalent, tetravalent and pentavalent, further further selected from at least one of Zr, Zn, Y, Nb, La and Ce, further preferably selected from at least one of Zr, Y and Nb; Preferably, based on the total amount of the supported MWW molecular sieve, the loading amount of the active metal in terms of element is 0.1-15 wt %, more preferably 0.1-10 wt %.

4. The molecular sieve according to any one of claims 1 to 3, wherein The MWW molecular sieve is at least one selected from HMCM-22 molecular sieve, HMCM-36 molecular sieve, HMCM-49 molecular sieve and HMCM-56 molecular sieve, preferably HMCM-22 molecular sieve.

5. A method for preparing a supported MWW molecular sieve, wherein: The method comprises: The MWW molecular sieve is impregnated in an active metal precursor solution, and then dried, formed and activated in two stages to obtain a supported MWW molecular sieve, wherein the two stages of activation are each independently performed under a flowing activation atmosphere.

6. The method according to claim 5, wherein: The active metal is selected from at least one of the transition metals of Group IIB, Group IIIB, Group IVB and Group VB, preferably selected from at least one of the transition metals of Group IIIB, Group IVB and Group VB, further preferably selected from at least one of the transition metals of Group IIIB, Group IVB and Group VB with a valence state of divalent, trivalent, tetravalent and pentavalent, further preferably selected from at least one of the transition metals of Group IIIB, Group IVB and Group VB with a valence state of trivalent, tetravalent and pentavalent, further further selected from at least one of Zr, Zn, Y, Nb, La and Ce, and further preferably selected from at least one of Zr, Y and Nb; Preferably, the active metal precursor is selected from soluble salts containing active metals, more preferably selected from at least one of sulfates, nitrates and chlorides of active metals, and even more preferably sulfates and / or nitrates.

7. The method according to claim 5 or 6, wherein the MWW molecular sieve is at least one of HMCM-22 molecular sieve, HMCM-36 molecular sieve, HMCM-49 molecular sieve and HMCM-56 molecular sieve, preferably HMCM-22 molecular sieve; Preferably, the mass ratio of the active metal precursor to the MWW molecular sieve is 0.01-0.3:1, more preferably 0.02-0.15:

1. Preferably, the immersion conditions include: temperature of 10-30°C, time of 1-5h; Preferably, the drying conditions include: a temperature of 100-130° C. and a time of 10-15 hours.

8. The method according to any one of claims 5 to 7, wherein: The two-stage activation includes a first-stage activation and a second-stage activation; Preferably, the one-stage activation comprises: subjecting the supported MWW molecular sieve precursor obtained after forming to one-stage activation under a flowing first activation atmosphere; Preferably, the first activation atmosphere is an oxygen-containing atmosphere, preferably at least one selected from air, a nitrogen-oxygen mixture, an argon-oxygen mixture, and a helium-oxygen mixture; 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; Preferably, the conditions of the one-stage activation include: temperature of 300-600°C, time of 2-10h, flow rate of the first activation atmosphere of 5-20mL / min / gcats; Further preferably, the conditions of the one-stage activation include: temperature of 350-550° C., time of 2-8 h, and flow rate of the first activation atmosphere of 8-15 mL / min / gcats.

9. The method according to claim 8, wherein: The two-stage activation comprises: subjecting the first-stage activation product to a second-stage activation under a flowing second activation atmosphere; Preferably, the second activation atmosphere is an inert atmosphere, preferably at least one selected from nitrogen, argon, helium and neon, more preferably nitrogen; Preferably, the conditions of the second stage activation include: temperature of 300-600°C, time of 2-10h, flow rate of the second activation atmosphere of 5-20mL / min / gcats; Further preferably, the conditions of the second stage activation include: temperature of 350-550° C., time of 2-6 h, and flow rate of the second activation atmosphere of 10-18 mL / min / gcats.

10. Use of the supported MWW molecular sieve according to any one of claims 1 to 4 or the supported MWW molecular sieve prepared by the preparation method according to any one of claims 5 to 9 in propylene polymerization reaction.

Images