Low-carbon olefin oligomerization reaction method

Abstract

The invention relates to the field of olefin oligomerization reaction, and discloses a low-carbon olefin oligomerization reaction method. The invention relates to a low-carbon olefin oligomerization reaction method. The method comprises the following step: carrying out contact reaction on a mixture containing low-carbon olefin and a diluent and a solid acid catalyst, the solid acid catalyst is 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. According to the method, the low-carbon olefin oligomerization reaction is catalyzed by selecting the catalyst with specific acid amount, so that the conversion rate of reaction raw materials and the selectivity of a target product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of olefin polymerization reaction, and in particular to a low-carbon olefin polymerization reaction method. Background Art

[0002] Olefin polymerization refers to the reaction process in which certain olefin monomers are polymerized under the action of catalysts to form compounds with one or more structural units repeatedly connected. The significant difference from general polymerization reactions is that the products of polymerization reactions are high molecular weight polymers, while oligomerization reactions mainly produce di-, tri- and tetramers. Olefin polymerization can transform cheap low molecular weight olefins into products with high added value, and the development and optimization of catalysts is the core content of propylene polymerization research.

[0003] At present, the catalytic reactions for synthesizing olefin oligomers are mainly divided into homogeneous reactions and heterogeneous reactions. Homogeneous reactions mainly use complex catalysts such as Ziegler-Natta type, which have the outstanding advantages of high activity and selectivity. For example, the selective oligomerization process of France IFP: using nickel complexes dispersed in ionic liquids as catalysts, the conversion rate of low-carbon olefins is over 80%, and the dimer selectivity can reach 95%. However, the olefin products generated by this type of reaction have a high degree of branching and a low content of high-carbon number products, and the catalyst needs to be separated from the reaction system after the reaction; for heterogeneous reactions, the catalyst is easier to separate from the reaction system, and solid acid catalysts are commonly used catalysts for liquid phase reactions such as low-carbon olefin polymerization.

[0004] Solid acid catalysts can be divided into molecular sieve type and non-molecular sieve type catalysts, among which solid phosphoric acid catalysts (SPAC) and molecular sieve catalysts are the two most important solid acid catalysts. Solid phosphoric acid catalyst is one of the industrial catalysts for the polymerization of propylene and butene. This type of catalyst is also the most widely used catalyst for the polymerization of propylene and butene. For example, the non-selective olefin polymerization SPAC process developed by UOP is a medium-strong acid. When catalyzing butene polymerization, the product is mainly dimer, and when catalyzing propylene polymerization, the main product is trimer. However, solid phosphoric acid catalysts have the disadvantages of easy mudification, short life, and environmental pollution. Molecular sieve catalysts are a type of aluminosilicate system with molecular-sized pores. They act in the form of proton acid in olefin polymerization reactions. The unique pore structure has a strong screening ability for olefin molecules, thus having high catalytic activity and shape-selective catalytic effect. Among them, ZSM-5 molecular sieve is the most widely used in the field of low-carbon olefin polymerization, and the MOGD process technology was developed in the 1980s. This process uses medium-pore ZSM-5 molecular sieve (silicon / aluminum molar ratio is about 70) and 35% Al2O3 by mass. 2 O 3The catalyst kneaded into strips can effectively convert low-carbon olefins into gasoline and diesel, but the product distribution is wide, and it is difficult to achieve high selectivity for a certain component. The relatively small pore structure is also prone to carbon deposition and deactivation. To this end, researchers modified the ZSM-5 molecular sieve. Patent application CN111229304A used Fenton reagent to modify HZSM-5 molecular sieve to catalyze propylene polymerization, and introduced metal Fe into the molecular sieve pores and skeleton. The initial olefin conversion rate can reach 95%, and the oil yield can reach 90%, but there are few high-carbon products, the catalyst stability is poor, and it is easy to be carbonized and deactivated. Patent application CN111617799A modified the HZSM-5 molecular sieve with metal loading, and used transition metal oxides and NiO as active components to catalyze propylene polymerization. The propylene conversion rate was 60%-73%, the nonene selectivity was 40%-55%, the propylene conversion rate was low, and the catalyst stability was poor. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of complex catalyst preparation process and low selectivity of high carbon number target products in the light olefin polymerization reaction in the prior art, and to provide a light olefin polymerization reaction method. The method uses a catalyst with a specific acid amount to catalyze the light olefin polymerization reaction, thereby improving the conversion rate of the reaction raw materials and the selectivity of the target product.

[0006] In order to achieve the above object, the present invention provides a method for oligomerization of light olefins, wherein the method comprises: contacting a mixture containing light olefins and a diluent with a solid acid catalyst for reaction;

[0007] The solid acid catalyst is a supported MWW molecular sieve, which includes 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.

[0008] The inventors of the present invention have found in their research that in molecular sieve-catalyzed polymerization of low-carbon olefins, ZSM-5 molecular sieve is usually used for metal loading modification and catalytic reaction, but its excessive Br acid content and relatively small pore structure can easily lead to carbon deposition and deactivation.

[0009] The method provided by the present invention selects a supported MWW molecular sieve having a specific amount of L-acid and a specific proportion of strong acid in the L-acid to catalyze the polymerization reaction of light olefins. The supported MWW molecular sieve has good activity and stability, and the side reactions such as cracking and aromatization are less, which can effectively increase the target products with high carbon numbers such as C3n , C 4n (n is a positive integer) products, and regulate the distribution of reaction products to increase the proportion of high carbon number reaction products.

[0010] The method provided by the present invention introduces a diluent to mix with low-carbon olefins. The introduction of the diluent can reduce the coking of the molecular sieve caused by excessive heat release. The introduction of the diluent can also increase the distance between the low-carbon olefin molecules, so that they have more space to generate long-chain target products. On the other hand, olefins with too high carbon numbers are prone to side reactions such as cracking and aromatization, which is not conducive to improving the selectivity of the target product. The diluent reduces the probability of high-activity low-carbon olefins continuing to react with the product to a certain extent, thereby reducing the generation of olefins with a carbon number of more than 18. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is the pyridine infrared spectrum of the molecular sieve in Example 1, Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0012] 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.

[0013] The present invention provides a method for oligomerization of light olefins, wherein the method comprises: contacting a mixture containing light olefins and a diluent with a solid acid catalyst for reaction;

[0014] The solid acid catalyst is a supported MWW molecular sieve, which includes 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.

[0015] 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.

[0016] 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. -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.

[0017] In the present invention, preferably, the ratio of the pyridine infrared L-acid amount to the total acid amount of 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 L-acid amount to the total acid amount is within the aforementioned range, the L-acid center catalyzes the polymerization reaction, which can greatly reduce the side reactions caused by the B-acid center catalyzing the polymerization of propylene, such as cracking, aromatization reaction, etc., improve the selectivity of the target product, reduce carbon deposition, and extend the life of the catalyst; the inventors have found that when the ratio of the L-acid amount to the total acid amount 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, and the L-acid center introduced by the supported metal can also effectively increase the polymer selectivity.

[0018] 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 loaded 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 loaded metal can also effectively increase the polymer selectivity.

[0019] 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, it is more conducive to the generation of a high-polymer target product.

[0020] In the present invention, by regulating the loading amount of the active metal and cooperating 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 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] In the present invention, preferably, in the MWW molecular sieve, Al 2 O 3 and SiO 2 The total content of accounts for 99 weight % of the total amount of 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 %.

[0025] 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.

[0026] In the present invention, preferably, the preparation method of the supported MWW molecular sieve comprises: impregnating the MWW molecular sieve in an active metal precursor solution, and then drying, molding and two-stage activation to obtain the supported MWW molecular sieve, wherein the two-stage activation is performed independently under a flowing activation atmosphere.

[0027] 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.

[0028] In the present invention, the flowing activation atmosphere means that the activation atmosphere is in a flowing state.

[0029] In the present invention, the types of active metals have been described in the above content and will not be repeated here.

[0030] 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.

[0031] 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.

[0032] In the present invention, the types, properties and sources of the MWW molecular sieve have been described above and will not be repeated here.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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 catalytic polymerization reaction is more conducive to the formation of a high-polymer target product.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] In the present invention, the range 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.

[0047] In the present invention, the range of selection of low-carbon olefins is relatively wide, and all low-carbon olefins conventionally defined in the art are applicable to the present invention. Preferably, the low-carbon olefin is selected from C3-C6 olefins, preferably at least one selected from propylene, butene and hexene, more preferably propylene and / or butene, and even more preferably propylene.

[0048] In the present invention, the diluent has a wide range of choices. Preferably, the diluent is selected from C3-C6 alkanes, more preferably at least one selected from propane, isobutane, n-hexane and cyclohexane, and more preferably propane and / or isobutane. The advantages of adopting this preferred embodiment are that the conversion rate of olefins can be guaranteed and the selectivity of the target product can be improved.

[0049] In the present invention, preferably, based on the total amount of the mixture containing light olefins and diluents, the content of the light olefins is 30-99% by mass, and the content of the diluent is 1-70% by mass; further preferably, based on the total amount of the mixture containing light olefins and diluents, the content of the light olefins is 50-80% by mass, and the content of the diluent is 20-50% by mass. With this preferred embodiment, on the one hand, propylene accounts for a high proportion, which ensures the activity of the reaction to a certain extent; on the other hand, the introduction of the diluent can ensure the conversion rate of the olefins and improve the selectivity of the target product.

[0050] In the present invention, the contact reaction conditions can be selected in a wide range. Preferably, the contact reaction conditions include: temperature 60-240°C, pressure 0.5-6MPa, feed mass space velocity 0.5-5h -1 Further preferably, the contact reaction conditions include: temperature 60-120°C, pressure 1-5MPa, feed mass space velocity 0.5-3h -1 In the present invention, the feed mass space velocity refers to the feed mass space velocity of a mixture containing light olefins and a diluent.

[0051] In the present invention, preferably, the olefin polymerization product obtained by the reaction method provided by the present invention has a carbon number greater than 4, preferably greater than 8.

[0052] The inventors of the present invention have found that during the polymerization reaction catalyzed by MWW molecular sieve, an excessive amount of B acid can easily lead to 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, effectively increase the selectivity of high-carbon polymerization products, and regulate the distribution of reaction products.

[0053] The present invention will be described in detail by way of examples. In the following examples, all products are commercially available unless otherwise specified.

[0054] In the present invention, the amount of active metal supported is measured by X-ray fluorescence spectrometry (XRF).

[0055] 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.

[0056] In the present invention, normal temperature refers to 25±5°C.

[0057] Example 1

[0058] (1) Weigh 2.06 g Y 2 (SO4) 3 8H 2 O is mixed with 18 mL of deionized water and stirred to dissolve the metal to obtain a metal solution;

[0059] (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;

[0060] (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.

[0061] (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.

[0062] 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.

[0063] The above-mentioned supported MWW molecular sieve was subjected to polymerization reaction in a tubular fixed bed reactor. The reaction conditions were: reaction temperature of 80°C, reaction pressure of 3.3 MPa, mass ratio of propylene to propane of 2:1, feed mass space velocity of propylene to propane of 1.5 h -1 The reaction results are shown in Table 2.

[0064] Example 2

[0065] (1) Weigh 1.99 g Nb 2 (SO4) 5 Mix with 18 mL of deionized water and stir to dissolve to obtain a metal solution;

[0066] (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;

[0067] (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.

[0068] (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 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.

[0069] The infrared spectrum of the supported MWW molecular sieve in Example 2 is similar to that of pyridine in Example 1, with a range of 1430-1473 cm -1 There are two L acid absorption peaks.

[0070] The above-mentioned supported MWW molecular sieve was subjected to polymerization reaction in a tubular fixed bed reactor. The reaction conditions were: reaction temperature of 60°C, reaction pressure of 1 MPa, mass ratio of propylene to propane of 1:1, feed mass space velocity of propylene to propane of 0.5 h -1 The reaction results are shown in Table 2.

[0071] Example 3

[0072] (1) Weigh 2.82 g Zr(NO 3 ) 4 ·5H 2 O is mixed with 18 mL of deionized water and stirred to dissolve the metal to obtain a metal solution;

[0073] (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;

[0074] (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.

[0075] (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.

[0076] 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 -1The ratio of the absorption peak area of ​​L acid at position to the total area of ​​two L acid absorption peaks is 0.35.

[0077] The above-mentioned supported MWW molecular sieve was subjected to polymerization reaction in a tubular fixed bed reactor. The reaction conditions were: reaction temperature of 120°C, reaction pressure of 5 MPa, mass ratio of propylene to propane of 4:1, feed mass space velocity of propylene to propane of 3 h -1 The reaction results are shown in Table 2.

[0078] Example 4

[0079] The method of Example 1 was followed, except that HMCM-49 molecular sieve (silicon to aluminum molar ratio of 12.6) was used to replace HMCM-22 molecular sieve (silicon to aluminum molar ratio of 11.4), and the other conditions remained unchanged.

[0080] The infrared spectrum of the supported MWW molecular sieve in Example 4 is similar to that of pyridine in Example 1, with a range of 1430-1473 cm -1 There are two L acid absorption peaks.

[0081] According to the method and conditions of the polymerization reaction in Example 1, the reaction results are shown in Table 2.

[0082] Example 5

[0083] (1) Weigh 2.64 g ZnSO 4 7H 2 O is mixed with 18 mL of deionized water and stirred to dissolve the metal to obtain a metal solution;

[0084] (2) Weighing 20 g of HMCM-22 molecular sieve, pouring the metal solution in step (1) into the molecular sieve to obtain a mixture;

[0085] (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.

[0086] (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.

[0087] According to the method and conditions of the polymerization reaction in Example 1, the reaction results are shown in Table 2.

[0088] Example 6

[0089] The method of Example 1 is followed, except that in step (4), the first stage of activation is 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; and the second stage of activation is 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.

[0090] The infrared spectrum of the supported MWW molecular sieve in Example 6 is similar to that of pyridine in Example 1, with a range of 1430-1473 cm -1 There are two L acid absorption peaks.

[0091] According to the method and conditions of the polymerization reaction in Example 1, the reaction results are shown in Table 2.

[0092] Example 7

[0093] The supported MWW molecular sieve of Example 1 was selected.

[0094] The method and conditions of the oligomerization reaction were the same as in Example 1, except that the mass ratio of propylene to propane was 2:3, and the feed mass space velocity of propylene to propane was 1.5 h -1 The reaction results are shown in Table 2.

[0095] Example 8

[0096] The supported MWW molecular sieve of Example 1 was selected.

[0097] The above-mentioned supported MWW molecular sieve was subjected to polymerization reaction in a tubular fixed bed reactor. The reaction conditions were: reaction temperature of 120°C, reaction pressure of 3.3 MPa, mass ratio of butene to isobutane of 1:1, and feed mass space velocity of butene to isobutane of 1.5 h -1 The reaction results are shown in Table 3.

[0098] Comparative Example 1

[0099] 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.

[0100] According to the method and conditions of the polymerization reaction in Example 1, the reaction results are shown in Table 2.

[0101] Comparative Example 2

[0102] 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.

[0103] According to the method and conditions of the polymerization reaction in Example 1, the reaction results are shown in Table 2.

[0104] Comparative Example 3

[0105] 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.

[0106] According to the method and conditions of the polymerization reaction in Example 1, the reaction results are shown in Table 2.

[0107] Comparative Example 4

[0108] The unmodified HMCM-22 molecular sieve (silicon to aluminum molar ratio of 11.4) in Example 1 was selected.

[0109] According to the polymerization method of Example 8, the reaction results are shown in Table 3.

[0110] The characterization results of the MWW molecular sieves in the above examples and comparative examples are shown in Table 1.

[0111] Table 1

[0112]

[0113] 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.

[0114] Table 2

[0115]

[0116]

[0117] Note: C 3n C 6 , C 9 , C 12 , C 15 , C 18 , C 21 The sum of the components.

[0118] Table 3

[0119] Butene conversion rate / % <![CDATA[C 8 Selectivity / %]]> <![CDATA[C 12 Selectivity / %]]> <![CDATA[C 16 Selectivity %]]> <![CDATA[C 4n Selectivity %]]> Example 8 96.85 58.9 15.8 12.8 89.4 Comparative Example 4 88.52 51.8 12.5 6.8 74.6

[0120] Note: C 4n C 8 , C 12, C 16 , C 20 The sum of the components.

[0121] It can be seen from Table 2 and Table 3 above that the method of the present invention can effectively reduce the occurrence of side reactions such as cracking and aromatization, effectively increase the selectivity of high-carbon oligomerization products, and regulate the distribution of reaction products.

[0122] 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 method for oligomerization of light olefins, characterized in that: The method comprises: contacting a mixture containing low-carbon olefins and a diluent with a solid acid catalyst for reaction; The solid acid catalyst is a supported MWW molecular sieve, and the supported MWW molecular sieve includes 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 method 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 method 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 state 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 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, 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 method 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. The method according to any one of claims 1 to 4, wherein: The preparation method of the supported MWW molecular sieve 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 precursor is selected from soluble salts containing active metals, preferably at least one selected from sulfates, nitrates and chlorides of active metals, preferably sulfates and / or nitrates; 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.

7. The method according to claim 5, 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.

8. The method according to claim 7, 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 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 2-6 h, and flow rate of the first activation atmosphere of 10-18 mL / min / gcats.

9. The method according to any one of claims 1 to 8, wherein: The low-carbon olefin is selected from C3-C6 olefins, preferably at least one selected from propylene, butene and hexene, and more preferably propylene and / or butene; Preferably, the diluent is selected from C3-C6 alkanes, further preferably selected from at least one of propane, isobutane, n-hexane and cyclohexane, and further preferably propane and / or isobutane; Preferably, based on the total amount of the mixture containing light olefins and diluents, the content of the light olefins is 30-99% by mass, and the content of the diluent is 1-70% by mass; More preferably, based on the total amount of the mixture containing the light olefins and the diluent, the content of the light olefins is 50-80% by mass, and the content of the diluent is 20-50% by mass.

10. The method according to any one of claims 1 to 9, wherein: The contact reaction conditions include: temperature 60-240°C, pressure 0.5-6MPa, feed mass space velocity 0.5-5h -1 ; Preferably, the contact reaction conditions include: temperature 60-120°C, pressure 1-5MPa, feed mass space velocity 0.5-3h -1 .

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