Weakly acidic mww molecular sieves, methods of making and using the same, and methods of making aromatic compounds

Abstract

The application relates to the field of catalytic chemistry, and discloses a weakly acidic MWW molecular sieve, a preparation method and application thereof, and a preparation method of aromatic hydrocarbon compounds. Taking the total aluminum content in the MWW molecular sieve as a benchmark, the proportion of four-coordinated Al in the MWW molecular sieve is A, and taking the total acid content of the MWW molecular sieve as a benchmark, the proportion of strong acid content of the MWW molecular sieve is B, wherein the ratio of A to B is not less than 450%. By using the weakly acidic MWW molecular sieve or a catalyst containing the weakly acidic MWW molecular sieve, hydrolysis and polymerization of raw materials are effectively reduced, and high selectivity to products is ensured.

Description

Technical Field

[0001] This invention relates to the field of catalytic chemistry, specifically to a weakly acidic MWW molecular sieve, its preparation method and application, and a method for preparing aromatic compounds. Background Technology

[0002] The MWW topological molecular sieve has two independent, non-interconnected ten-membered ring channel systems: one set of two-dimensional sinusoidal channels with an approximately elliptical cross-section and a pore size of [missing information]. Another set of ten-element ring channels contains a size of An approximately cylindrical twelve-membered ring supercage, which passes through a slightly distorted ten-membered ring window. It is connected to the outside world. Furthermore, the MWW topology also features a bowl-shaped twelve-membered ring semi-supercage located on the outer surface of the crystal. CN104511271B discloses an SCM-1 molecular sieve with an MWW topology. This molecular sieve has a two-dimensional layered structure with a huge external specific surface area of ​​185 m². 2 Above / g, the exposed large number of bowl-shaped twelve-membered ring semi-supercages on the outer surface of the crystal give it the potential for catalytic applications in larger molecules.

[0003] With the development of human society, petroleum resources are becoming increasingly scarce, and the massive emissions of CO2 exacerbate the greenhouse effect. Under the pressure of carbon emission reduction, countries are seeking new technologies to replace petroleum-based chemical products with bio-based chemical products. Among them, the reaction with promising potential is the preparation of bio-based benzene, toluene, and p-xylene from furan compounds and ethylene, namely, furan and ethylene to prepare benzene, 2-methylfuran and ethylene to prepare toluene, and 2,5-dimethylfuran and ethylene to prepare p-xylene. This type of reaction has two main characteristics. First, because furan reactants are relatively reactive, strong acids easily induce self-polymerization, hydrolysis, and condensation side reactions of furan molecules. However, suitable acidity satisfies the dehydration after Diels-Alder addition, which can yield the product with high selectivity. Therefore, the reaction does not require catalysis by strong acid sites, and the catalytic material should selectively eliminate strong acid sites. Second, this type of reaction is prone to carbon deposition, and the catalytic material will quickly deactivate due to carbon deposition. Therefore, the catalyst is required to have excellent mass transfer performance and anti-carbon deposition ability. Traditional silica-alumina molecular sieves face significant challenges in such reactions due to their typically small external surface area and high acidity, containing numerous strong acid sites. While SCM-1 materials offer a large external surface area providing abundant reaction interfaces and excellent mass transfer performance, they also contain a large number of strong acid sites. Although CN113831238A and CN113831308A successfully prepared Sn-Al-SCM-1 or Zr-Al-SCM-1, their catalytic materials still retain a large number of strong acid sites. This strong acidity can cause a series of serious side reactions, such as alkylation, isomerization, and polymerization, leading to the self-consumption of reactive furan-based feedstocks and very low selectivity for the target product.

[0004] US20190344252A1 reports the use of phosphoric acid-modified Beta zeolites in the reaction of 2,5-dimethylfuran and ethylene to prepare p-xylene (PX). Although it achieves 97% PX selectivity, its active sites are hydroxyl vacancies in the phosphoric acid-modified zeolite, resulting in poor chemical stability and difficulty in repeated recycling. Furthermore, the three-dimensional structure of Beta zeolites leads to insufficient mass transfer performance and resistance to carbon deposition. If metal atoms are introduced into the modified Beta zeolite, the introduction of new sites can easily block its three-dimensional channels, resulting in poor accessibility of the active sites and hindering the reaction.

[0005] In summary, existing technologies mainly suffer from problems such as unsuitable catalyst structure, insufficient catalyst mass transfer performance, poor stability, or unsuitable catalyst acidity leading to low product selectivity, which pose challenges to practical industrial applications. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of unsuitable acidity and poor carbon deposition resistance of existing molecular sieves, such as their difficulty in application to the field of biomass catalysis. Specifically, when used in the field of biomass catalysis, they suffer from poor mass transfer, poor carbon deposition resistance, and low selectivity of bio-based aromatic products. This invention provides a weakly acidic MWW molecular sieve, its preparation method, and its application.

[0007] Through extensive research and experimentation, the inventors of this invention discovered a weakly acidic MWW molecular sieve that differs from existing technologies. Specifically, when the proportion of tetracoordinated Al in the weakly acidic MWW molecular sieve has a specific ratio to the proportion of strong acid, the weakly acidic MWW molecular sieve possesses both weak acidity and a high proportion of tetracoordinated Al. This results in good catalytic activity and resistance to carbon deposition. Furthermore, when this weakly acidic MWW molecular sieve is used as the active component of a catalyst for the directional catalytic conversion of furan feedstocks and ethylene to prepare aromatic compounds, the catalyst exhibits high selectivity in catalyzing the reaction of furan feedstocks and ethylene to produce aromatic compounds. The catalyst also demonstrates strong resistance to carbon deposition and high cycle stability.

[0008] Based on the above findings, the first aspect of the present invention provides a weakly acidic MWW molecular sieve, wherein the proportion of four-coordinated Al in the MWW molecular sieve is A, and the proportion of strong acid in the MWW molecular sieve is B, based on the total aluminum content in the MWW molecular sieve, wherein the ratio of A to B is not less than 450%.

[0009] A second aspect of the present invention provides a method for preparing the MWW molecular sieve described in the first aspect of the present invention, the method comprising:

[0010] (1) Hydrogen-type MWW molecular sieve raw powder is subjected to steam hydrothermal treatment;

[0011] (2) Acid pickling removes aluminum.

[0012] The third aspect of this invention provides the application of the MWW molecular sieve described in the first aspect of this invention in the preparation of aromatic compounds from furan compounds and ethylene.

[0013] A fourth aspect of the present invention provides a method for preparing an aromatic compound, the method comprising:

[0014] Using the MWW molecular sieve described in the first aspect of the present invention as the active component of the catalyst, in the presence of the catalyst and in an ethylene atmosphere, a material containing furan compounds undergoes a Diels-Alder addition followed by a dehydration reaction.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] Existing molecular sieves, especially MWW molecular sieves, have a high proportion of strong acids when they contain a large amount of four-coordinated Al. However, the weakly acidic MWW molecular sieve of this invention not only has weak acidity but also a high proportion of four-coordinated Al. By using the weakly acidic MWW molecular sieve of this invention or a catalyst containing the weakly acidic MWW molecular sieve of this invention, the occurrence of raw material hydrolysis and polymerization reactions is effectively reduced, ensuring high selectivity for products. Furthermore, its excellent structural features, such as its two-dimensional layered structure, endow the catalyst with good mass transfer performance, which is conducive to the smooth progress of the reaction. It also has strong anti-carbon deposition ability, which keeps the catalyst highly active. Furan raw materials and ethylene can be efficiently converted into their corresponding aromatic products, and the conversion rate and product selectivity of aromatic products are very high. Attached Figure Description

[0017] Figure 1 This is the NH3-TPD diagram of the acid distribution of the hydrogen-form SCM-1 molecular sieve raw powder in Example 1;

[0018] Figure 2 This is the NH3-TPD spectrum of the hydrogen-form SCM-1 molecular sieve raw powder after hydrothermal treatment with steam in step (1) of Example 1;

[0019] Figure 3 It is the hydrogen-form SCM-1 molecular sieve raw powder after hydrothermal treatment with steam in step (1) of Example 1. 27 Al-NMR spectrum;

[0020] Figure 4 This is the XRD pattern of the weakly acidic MWW molecular sieve in Example 1;

[0021] Figure 5 This is the pyridine infrared spectrum of the weakly acidic MWW molecular sieve in Example 1;

[0022] Figure 6 This is the NH3-TPD spectrum of the weakly acidic MWW molecular sieve in Example 1. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The first aspect of the present invention provides a weakly acidic MWW molecular sieve, wherein, based on the total aluminum content in the MWW molecular sieve, the proportion of tetracoordinated Al in the MWW molecular sieve is A, and based on the total acid content in the MWW molecular sieve, the proportion of strong acid content in the MWW molecular sieve is B, wherein the ratio of A to B is not less than 450%.

[0025] In this invention, the inventors discovered that when the proportion of tetracoordinated Al and the proportion of strong acid in the weakly acidic MWW molecular sieve of this invention have a specific ratio relationship, it has both weak acidity and a high proportion of tetracoordinated Al, which makes the weakly acidic MWW molecular sieve of this invention have good catalytic activity. When used, the conversion rate and product selectivity of the target product are very high, and the weakly acidic MWW molecular sieve also has strong anti-carbon deposition ability.

[0026] In this invention, the content of tetracoordinated Al is determined by solid... 27 Al nuclear magnetic resonance ( 27 The Al-NMR spectrum was obtained on a Varian 400MHz NMR solid-state nuclear magnetic resonance spectrometer with a magnetic field strength of 9.4T and a proton resonance frequency of 400MHz.

[0027] In this invention, the NH3 temperature-programmed desorption (NH3-TPD) experiment was conducted on a TPD / TPR Altamira AMI-3300 instrument. The total acid content was calculated by fitting and peaking the obtained spectrum. Acids with desorption temperatures of 100-240℃ were defined as weak acids, acids with desorption temperatures of 240-320℃ were defined as medium-strong acids, and acids with desorption temperatures of 320-500℃ were defined as strong acids. The proportion of strong acids was then calculated.

[0028] According to the present invention, exemplified ratios of A to B include 450%, 455%, 543%, 690%, 870%, 900%, 1000%, 1138%, 1300%, 1500%, and any range of any two of the above values. In some preferred embodiments, the ratio of A to B is not less than 500%, preferably 500-1500%. The molecular sieve of the aforementioned embodiments not only possesses good catalytic activity and anti-carbon deposition ability, but also exhibits high selectivity for aromatic compounds when used to prepare aromatic compounds from furan compounds and ethylene.

[0029] According to the present invention, in some preferred embodiments, the value of A is not less than 60%, for example, 60%, 75%, 82%, 83%, 85%, 88%, 90%, 91%, 93%, or 95%, and any combination of two of the above values. Preferably, the proportion of tetracoordinated Al in the MWW molecular sieve is not less than 75%. The molecular sieves in the aforementioned embodiments have good catalytic activity and anti-carbon deposition ability, and when used to prepare aromatic compounds from furan compounds and ethylene, they also have high selectivity for aromatic compounds.

[0030] According to the present invention, in some preferred embodiments, the value of B is not greater than 20%, for example, 5%, 8%, 10%, 12%, 13%, 16%, 18%, 20%, and any range of two of the above values. Preferably, the strong acid content of the MWW molecular sieve is not greater than 15%, and more preferably 5-15%. The molecular sieve in the aforementioned embodiments has a small number of strong acid sites, which reduces the occurrence of side reactions during use. When used to prepare aromatic compounds from furan compounds and ethylene, it also has high furan compound conversion rate and aromatic compound selectivity.

[0031] According to the present invention, in some embodiments, the total acidity of the MWW molecular sieve is 300-800 μmol / g, for example, 300 μmol / g, 336 μmol / g, 400 μmol / g, 460 μmol / g, 500 μmol / g, 587 μmol / g, 600 μmol / g, 630 μmol / g, 700 μmol / g, 750 μmol / g, or 800 μmol / g, and any range of the above values. The molecular sieves in the aforementioned embodiments exhibit good catalytic activity and resistance to carbon deposition, and when used to prepare aromatic compounds from furans and ethylene, they also exhibit high selectivity for aromatic compounds.

[0032] According to the present invention, in some preferred embodiments, the total acidity of the MWW molecular sieve is 400-700 μmol / g, more preferably 500-600 μmol / g. The molecular sieves in the aforementioned preferred embodiments exhibit good catalytic activity and resistance to carbon deposition, and when used to prepare aromatic compounds from furans and ethylene, they also exhibit high selectivity for aromatic compounds.

[0033] According to the present invention, it is understood that the MWW molecular sieve includes at least Si and Al elements. As long as the purpose of the present invention is achieved, the content of Si and Al elements in the MWW molecular sieve is not particularly limited. In some preferred embodiments, the Si / Al molar ratio of the MWW molecular sieve is 25-180, preferably 30-100. Existing MWW molecular sieves, even with low aluminum content (i.e., a higher Si / Al molar ratio), exhibit strong acidity. The MWW molecular sieve of the aforementioned preferred embodiments of the present invention, with a wide range of adjustable Si / Al molar ratios, also exhibits weak acidity. When used to prepare benzene compounds from furans and ethylene, it can maintain high catalytic activity and target product selectivity.

[0034] According to the present invention, in some embodiments, the Lewis / The ratio is greater than 2:1, for example, 2.2:1, 2.5:1, 3.1:1, 3.6:1, 4.5:1, 6.1:1, or 7:1, as well as any range of two of the above ratios. The MWW molecular sieve of the aforementioned preferred embodiments of the present invention has good catalytic activity and resistance to carbon deposition.

[0035] In this invention, the pyridine adsorption infrared (py-FTIR) method is used to determine the type of catalyst acid. The py-FTIR spectrum is obtained on a Nicolet Model 710 spectrometer. The specific operation steps are as follows: a) Sample preparation and pretreatment: Approximately 15 mg of sample is compressed into a thin disc with a diameter of 13 mm and placed in the infrared sample cell; then the sample is pretreated at 400℃ in a vacuum cell for 2 h; the background spectrum of the sample is obtained by scanning at 150℃, 250℃, and 400℃; b) After the sample cell cools to room temperature, pyridine is adsorbed for 10 min; vacuum desorption is performed at 150℃ for 10 min, and the infrared absorption spectrum is scanned and recorded; the infrared absorption spectra are scanned and recorded sequentially at 250℃ and 400℃. The difference spectrum before and after pyridine adsorption is the obtained Py-FTIR spectrum.

[0036] According to the present invention, in some embodiments, the MWW molecular sieve is selected from pure MWW molecular sieves and / or metal heteroatom-doped MWW molecular sieves, wherein M is selected from at least one of Ti, Zr, Nb, Ta, W, Ga, and Sn. The foregoing embodiments further broaden the application range of MWW molecular sieves, enabling them to maintain high catalytic activity and target product selectivity when used in the preparation of benzene compounds from furan compounds and ethylene.

[0037] According to the present invention, in some preferred embodiments, M is Ga and / or Sn. The MWW molecular sieves described in the aforementioned preferred embodiments exhibit good catalytic performance and resistance to carbon deposition.

[0038] According to the present invention, in some preferred embodiments, the MWW molecular sieve is a metal heteroatom-doped MWW molecular sieve. The MWW molecular sieves in the aforementioned preferred embodiments exhibit good catalytic performance and resistance to carbon deposition.

[0039] According to the present invention, as long as the purpose of the present invention can be achieved, the doping amount of M is not particularly limited. In some preferred embodiments, the Si / M molar ratio of the MWW molecular sieve is 20-100, for example 20, 30, 40, 50, 60, 70, 80, 90 or 100, and any range of the above values, preferably 30-70.

[0040] In this invention, the elemental composition of the molecular sieve was determined by an Agilent 725-ES inductively coupled plasma atomic emission spectrometer (ICP). The molecular sieve sample was digested with hydrofluoric acid, and the elemental content was expressed in moles.

[0041] According to the present invention, the specific type of the MWW molecular sieve is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the MWW molecular sieve is selected from at least one of MCM molecular sieves, ITQ molecular sieves, and SCM molecular sieves.

[0042] According to some preferred embodiments of the present invention, the MWW molecular sieve is an SCM type molecular sieve.

[0043] According to some preferred embodiments of the present invention, the SCM molecular sieve is an SCM-1 molecular sieve and / or an SCM-2 molecular sieve.

[0044] In this invention, those skilled in the art will know that existing SCM-1 and SCM-2 molecular sieves have a two-dimensional layered structure with a large external surface area, exposing a large number of bowl-shaped twelve-membered ring semi-supercages on the outer surface of the crystals, which gives them potential for catalytic applications in larger molecules. However, when they are directly used as active components of catalysts, the selectivity of the products is very low. For example, when furan compounds and ethylene are used to prepare benzene compounds, using them as catalyst components will cause a series of serious side reactions. In contrast, the SCM-1 and SCM-2 molecular sieves of this invention, after introducing heteroatoms, have weak acidity and a high proportion of tetracoordinated Al. They not only have good catalytic activity, but also good selectivity of the target product when used in catalytic reactions, and they also have excellent carbon resistance.

[0045] In this invention, SCM-1 molecular sieve is used as an example to illustrate the advantages of the invention, but the invention is not limited thereto.

[0046] According to the present invention, in some embodiments, the internal specific surface area of ​​the MWW molecular sieve is 150-400 m².2 / g, for example, 150m 2 / g、200m 2 / g、205m 2 / g、225m 2 / g、259m 2 / g、289m 2 / g、325m 2 / g or 400m 2 / g, and any range of the above values, preferably 200-400m 2 / g. The MWW molecular sieve described in the above embodiments exhibits good catalytic performance and resistance to carbon deposition.

[0047] According to the present invention, in some embodiments, the external specific surface area of ​​the MWW molecular sieve is 50-200 m². 2 / g, for example, 50m 2 / g, 100m 2 / g、117m 2 / g、134m 2 / g、142m 2 / g、157m 2 / g、178m 2 / g、186m 2 / g or 200m 2 / g, and any range of the above values, preferably 100-200m 2 / g. The MWW molecular sieve described in the above embodiments exhibits good catalytic performance and resistance to carbon deposition.

[0048] A second aspect of the present invention provides a method for preparing the MWW molecular sieve described in the first aspect of the present invention, the method comprising:

[0049] (1) Hydrogen-type MWW molecular sieve raw powder is subjected to steam hydrothermal treatment;

[0050] (2) Acid pickling removes aluminum.

[0051] In this invention, the hydrogen-form MWW molecular sieve raw powder is subjected to hydrothermal treatment with steam to achieve a low proportion of strong acid in the weakly acidic MWW molecular sieve while maintaining a high proportion of tetracoordinated Al. By using the weakly acidic MWW molecular sieve of this invention or a weakly acidic MWW molecular sieve containing this invention as a catalyst, the occurrence of raw material hydrolysis and polymerization reactions can be effectively reduced, ensuring high selectivity for the product.

[0052] According to the present invention, in some embodiments, the hydrothermal treatment conditions are controlled such that after water vapor hydrothermal treatment, the proportion of tetracoordinated Al is not less than 60%, preferably not less than 75%. The inventors have found that using the aforementioned embodiments can not only increase the proportion of tetracoordinated aluminum in the prepared MWW molecular sieve, but also reduce the amount of strong acid in the MWW molecular sieve.

[0053] In this invention, hydrogen-form MWW molecular sieve raw powder can be prepared by ion exchange and calcination of MWW molecular sieve raw powder; wherein, calcination after ion exchange is a conventional method for preparing hydrogen-form molecular sieve raw powder from molecular sieve raw powder in the art, and its specific operation will not be described in detail in this invention.

[0054] As mentioned above, in this invention, SCM-1 molecular sieve is used as an example to illustrate the advantages of the invention. That is, in the preparation of the corresponding SCM-1 molecular sieve, the corresponding SCM-1 molecular sieve raw powder is used as the raw material. In this invention, the preparation method described in CN104511271B is used to synthesize SCM-1 molecular sieve raw powder as an example to illustrate the advantages of the invention, but the invention is not limited thereto.

[0055] According to some preferred embodiments of the present invention, the conditions for the water vapor hydrothermal treatment include: an inert gas atmosphere.

[0056] In this invention, inert gases that may be listed include nitrogen and / or argon.

[0057] According to the present invention, in some preferred embodiments, the conditions for the water vapor hydrothermal treatment include: a water vapor partial pressure of 10-100%, for example, 10%, 30%, 50%, 70%, 80%, or 100%, and any range of the above values, preferably 30-70%. By employing the aforementioned embodiments, strong acid sites can be reduced without causing a large amount of Al to be removed from the framework, thus preserving a larger proportion of tetracoordinated aluminum in the molecular sieve. The resulting MWW molecular sieve exhibits good catalytic activity and resistance to carbon deposition.

[0058] According to the present invention, in some preferred embodiments, the conditions for the steam hydrothermal treatment include: a treatment temperature of 600-900℃, for example, 600℃, 700℃, 800℃, or 900℃, or any combination thereof, preferably 700-800℃. By employing the aforementioned embodiments, strong acid sites can be reduced without causing a large amount of Al to be removed from the framework, thus preserving a larger proportion of tetracoordinated aluminum in the molecular sieve. The resulting MWW molecular sieve exhibits good catalytic activity and resistance to carbon deposition.

[0059] According to some preferred embodiments of the present invention, the conditions for the steam hydrothermal treatment include: a treatment time of 1-72 h, for example, 1 h, 3 h, 6 h, 10 h, 12 h, 18 h, 24 h, 30 h, 48 h, 66 h, or 72 h, and any range of the above values, preferably 6-12 h. Using the aforementioned embodiments, the MWW molecular sieve finally prepared exhibits good catalytic activity and resistance to carbon deposition.

[0060] According to the present invention, in order to obtain a metal heteroatom M-doped MWW molecular sieve, in some embodiments, the preparation method of the MWW molecular sieve further includes: contacting a metal M salt with a molecular sieve obtained after partial dealuminization by acid washing, followed by calcination; wherein the metal M in the metal M salt is selected from at least one of Ti, Zr, Nb, Ta, W, Ga, and Sn.

[0061] In this invention, the water vapor hydrothermal and M-doped MWW molecular sieve after the introduction of heteroatoms not only has weak acidity but also a high proportion of tetracoordinated Al. It not only has good catalytic activity but also good selectivity of the target product when used in catalytic reactions, and it also has excellent carbon resistance.

[0062] According to some preferred embodiments of the present invention, the metal M is Ga and / or Sn.

[0063] According to some preferred embodiments of the present invention, the molar ratio of Si in the molecular sieve obtained after acid washing and partial dealuminization to the metal M in the metal M salt is 20-100, preferably 30-70. Using the aforementioned embodiments, the prepared MWW molecular sieve exhibits good catalytic activity and resistance to carbon deposition.

[0064] According to the present invention, those skilled in the art can select appropriate metal salts as needed, such as gallium acetylacetonate, tris(dimethylamino)gallium dimer, dimethyltin dichloride, etc.

[0065] According to the present invention, there are no particular limitations on the method of contacting the metal M salt with the molecular sieve obtained after acid washing and partial dealuminization, as long as the doping of metal M can be achieved in the end. In order to enable the metal M salt and the molecular sieve obtained after acid washing and partial dealuminization to be more fully mixed and contacted, in some embodiments, the contact includes dynamic contact.

[0066] According to some preferred embodiments of the present invention, the contact is mechanical grinding.

[0067] In this invention, mechanical grinding is a conventional method in the art, and there are no specific limitations on its conditions. Those skilled in the art only need to ensure that the material is fully mixed and in contact during mechanical grinding to achieve the final doping.

[0068] According to the present invention, there are no special restrictions on the calcination conditions. In some embodiments, the calcination conditions include a calcination temperature of 500-650°C.

[0069] According to the present invention, there are no special restrictions on the calcination conditions. In some embodiments, the calcination conditions include a calcination time of 3-12 hours.

[0070] According to the present invention, it is understood that when metal heteroatom M doping is not required, those skilled in the art may choose to dry and optionally calcine after partial dealuminization in the acid washing process to obtain the desired MWW molecular sieve.

[0071] According to the present invention, in some embodiments, in step (2), the endpoint of the acid pickling dealuminization is: the Si / Al ratio of the molecular sieve after acid pickling dealuminization is 25-180, for example, 25, 23.4, 30, 45.5, 50, 60, 70, 80, 90, 100, 120, 150 or 180, and any two of the above values.

[0072] According to the present invention, it is understood that pickling for partial aluminum removal refers to washing with an acid solution. As long as the purpose of the present invention can be achieved, there are no special restrictions on the acid solution used in step (2). In some preferred embodiments, the acid solution used in pickling is selected from one or more of hydrochloric acid solution, oxalic acid solution, nitric acid solution, sulfuric acid solution and phosphoric acid solution.

[0073] In this invention, acid solution refers to a mixed solution of the corresponding acid and water, for example, concentrated nitric acid refers to an aqueous solution of nitric acid with a mass fraction of about 68%.

[0074] In some preferred embodiments, in step (2), the acid solution used for pickling is a nitric acid solution.

[0075] According to the present invention, as long as the purpose of the present invention can be achieved, the pickling conditions in step (2) are not particularly limited. In some preferred embodiments, the pickling conditions for partial aluminum removal include: a washing temperature of room temperature to 120°C; wherein, room temperature refers to any temperature between 15°C and 30°C.

[0076] According to some preferred embodiments of the present invention, the conditions for partial aluminum removal by pickling include: a rinsing time of more than 10 hours, preferably 12-48 hours.

[0077] The third aspect of this invention provides the application of the MWW molecular sieve described in the first aspect of this invention in the preparation of aromatic compounds from furan compounds and ethylene.

[0078] In this invention, when the MWW molecular sieve of this invention is used to prepare aromatic compounds from furan compounds and ethylene, it can not only efficiently convert them into their corresponding aromatic products with very high conversion rate and product selectivity, but also has strong anti-carbon deposition ability, so that it maintains high activity during use.

[0079] A fourth aspect of the present invention provides a method for preparing an aromatic compound, the method comprising:

[0080] Using the MWW molecular sieve described in the first aspect of the present invention as the active component of the catalyst, in the presence of the catalyst and in an ethylene atmosphere, a material containing furan compounds undergoes a Diels-Alder addition followed by a dehydration reaction.

[0081] In this invention, the MWW molecular sieve is used as the active component of the catalyst, which can selectively catalyze the reaction of furan compounds and ethylene to prepare aromatic compounds, and the catalyst has strong resistance to carbon deposition and high cycle stability.

[0082] In this invention, it is understood that the active component of the catalyst described in the first aspect of this invention, MWW molecular sieve, can be used alone as a catalyst, or it can be compounded or molded with other additives as a catalyst.

[0083] According to the present invention, those skilled in the art can select the corresponding furan compounds according to the specific needs of the aromatic compounds. In some embodiments, the furan compounds are selected from at least one of furan, 2-methylfuran and 2,5-dimethylfuran, that is, furan reacts with ethylene to prepare benzene, 2-methylfuran reacts with ethylene to prepare toluene, and 2,5-dimethylfuran reacts with ethylene to prepare p-xylene.

[0084] According to the present invention, it is understood that the furan-containing material may contain an auxiliary agent that facilitates the reaction, and in some embodiments, the furan-containing material contains an organic solvent, preferably selected from one or more of n-hexane, cyclohexane, n-heptane, n-octane, and tetrahydrofuran.

[0085] According to some embodiments of the present invention, the mass concentration of furan compounds in the material containing furan compounds is greater than 5%.

[0086] According to the present invention, in some embodiments, the mass ratio of furan compound to catalyst is (5-50):1, preferably (5-8):1.

[0087] According to the present invention, in some embodiments, the pressure of ethylene is 1-6 MPa, preferably 2-4 MPa.

[0088] According to the present invention, in some embodiments, the conditions for the dehydration reaction after Diels-Alder addition include: a reaction temperature of 200-300°C, preferably 230-280°C.

[0089] According to the present invention, in some embodiments, the conditions for the dehydration reaction after Diels-Alder addition include: a reaction time of 3-24 h, preferably 6-12 h.

[0090] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples:

[0091] XRD patterns were obtained using a Bruker D8 Advance X-ray diffractometer in Germany, using a CuKα ray source.

[0092] (1) The method for preparing benzene using the prepared MWW molecular sieve as a catalyst is as follows: 0.5g of catalyst, 3.0g of furan and 17g of n-heptane are added to a high-pressure reactor with magnetic stirring, and 3.0MPa of ethylene is introduced. The reaction is carried out at 250℃ for 12h to obtain the reaction solution.

[0093] (2) The method for preparing toluene using the prepared MWW molecular sieve as a catalyst is as follows: 0.5g of catalyst, 3.0g of 2-methylfuran and 17g of n-heptane are added to a high-pressure reactor with magnetic stirring, and 3.0MPa of ethylene is introduced. The reaction is carried out at 250℃ for 12h to obtain the reaction solution.

[0094] (3) The method for preparing para-xylene using the prepared MWW molecular sieve as a catalyst is as follows: 0.5g of catalyst, 3.0g of 2,5-dimethylfuran and 17g of n-heptane are added to a high-pressure reactor with magnetic stirring, and 3.0MPa of ethylene is introduced. The reaction is carried out at 250℃ for 12h to obtain the reaction solution.

[0095] If the catalyst is to be reused, the used catalyst must be regenerated by calcining in air at 550°C for 6 hours before being put into the next cycle.

[0096] The components of the reaction solution were qualitatively analyzed using an Agilent 7890A gas chromatography-mass spectrometry (GC-MS) system (Agilent Technologies, Inc.) with a Wax polar capillary column. Quantitative analysis was performed using an Agilent 7890B gas chromatograph (GC) system (Agilent Technologies, Inc.), equipped with a flame ionization detector (FID) and a Wax polar capillary column. The conversion rate and selectivity of the substances were calculated based on the molar amounts of the substances determined by gas chromatography.

[0097] The formula for calculating the raw material conversion rate is: Raw material conversion rate % = (Initial molar amount of raw material added - Remaining molar amount of raw material) / (Initial molar amount of raw material added) × 100%.

[0098] The formula for calculating product selectivity is: Product selectivity % = (molar amount of product generated in the reaction) / (molar amount of initial added raw material - molar amount of remaining raw material) × 100%.

[0099] Example 1

[0100] Preparation of SCM-1 molecular sieve raw powder:

[0101] SCM-1 raw powder was prepared according to the preparation method in Example I-1 of patent CN104511271B. 12.64 g of sodium aluminate (Al₂O₃ 43.0 wt%, Na₂O 35.0 wt%, balance water) was dissolved in 362.40 g of water, then 39.68 g of hexamethyleneimine aqueous solution (hexamethyleneimine content 80.0 wt%) and 101.54 g of dicyclohexylamine were added, and finally 240 g of silica sol (SiO₂ 40.0 wt%, balance water) were added. The final gel formed had a molar ratio of SiO₂, Al₂O₃, NaOH, hexamethyleneimine, dicyclohexylamine, and H₂O of 1:0.033:0.09:0.20:0.35:18. The gel was placed in a reaction vessel and crystallized at 150 °C for 4 days under stirring. The solid product was then obtained by centrifugation, washing, and drying. This solid product was calcined in air at 550 °C for 5 hours to obtain SCM-1 molecular sieve powder.

[0102] SCM-1 molecular sieve raw powder was subjected to ion exchange and calcination to obtain hydrogen-form SCM-1 molecular sieve raw powder.

[0103] The silica-alumina ratio (atomic ratio) of the hydrogen-form SCM-1 molecular sieve powder was determined to be 15.2 by ICP; the acidity distribution (NH3-TPD) of the hydrogen-form SCM-1 molecular sieve powder is shown in the figure below. Figure 1 As shown;

[0104] Preparation of weakly acidic MWW molecular sieves:

[0105] (1) In a nitrogen atmosphere, the above-mentioned hydrogen-type SCM-1 molecular sieve raw powder was subjected to hydrothermal treatment with steam at 900°C and 10% water vapor partial pressure for 10 hours.

[0106] (2) The hydrogen-form SCM-1 molecular sieve raw powder after steam hydrothermal treatment was partially dealuminized by washing with concentrated nitric acid at 110℃ for 48 hours.

[0107] (3) Add gallium acetylacetonate to the partially dealuminized molecular sieve, control the Si / Ga atomic ratio to 40, perform thorough mechanical grinding, and then calcine at 550℃ for 6 hours to obtain weakly acidic MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0108] The NH3-TPD spectrum of the hydrogen-form SCM-1 molecular sieve raw powder after hydrothermal treatment with steam in step (1) is shown below. Figure 2 As shown, through Figure 2 After hydrothermal treatment with steam, the number of strong acid sites is significantly reduced; 27 Al-NMR such as Figure 3 As shown, its tetracoordinated Al content accounts for 78%;

[0109] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured by ICP to be 45.8.

[0110] XRD patterns of weakly acidic MWW molecular sieves, such as Figure 4 As shown, through Figure 4 The MWW structure remains intact;

[0111] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 259 m². 2 / g, with an external specific surface area of ​​142m² 2 / g;

[0112] The pyridine infrared spectrum of the weakly acidic MWW molecular sieve is as follows: Figure 5 As shown, through Figure 5 It can be seen that most of the pyridine has been desorbed at 350℃, indicating that there are relatively few strong acid sites. Lewis / The ratio is 3.6;

[0113] The NH3-TPD spectrum of the weakly acidic MWW molecular sieve is as follows: Figure 6 As shown, the total acid content is 587 μmol / g, and the calculated percentage of strong acid content is 16%.

[0114] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 87%.

[0115] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the initial reaction showed a furan conversion rate of 92% and a benzene selectivity of 41%; after 5 catalyst cycles, the furan conversion rate remained at 91% and the benzene selectivity remained at 41%.

[0116] When using the prepared MWW molecular sieve as a catalyst to prepare toluene, the initial reaction showed a 93% conversion rate of 2-methylfuran and a 72% selectivity for toluene. After five catalyst cycles, the conversion rate of 2-methylfuran remained at 93%, and the selectivity for toluene remained at 71%.

[0117] When using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the initial reaction showed a conversion rate of 93% for 2,5-dimethylfuran and a selectivity of 92% for the product p-xylene. After five catalyst cycles, the conversion rate of 2,5-dimethylfuran remained at 93%, and the selectivity for the product p-xylene remained at 92%.

[0118] Example 2

[0119] The method of Example 1 differs in that: in step (1), a water vapor hydrothermal treatment is performed at 600°C and 50% water vapor partial pressure for 70 hours.

[0120] The tetracoordinated Al content of the hydrogen-type SCM-1 molecular sieve raw powder after water vapor hydrothermal treatment in step (1) is 82%.

[0121] XRD patterns of weakly acidic MWW molecular sieves Figure 4 similar;

[0122] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured by ICP to be 42.1.

[0123] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 245 m². 2 / g, with an external specific surface area of ​​178m² 2 / g;

[0124] Lewis / weakly acidic MWW molecular sieve The ratio is 3.1;

[0125] The total acid content of the weakly acidic MWW molecular sieve is 598 μmol / g, and the calculated strong acid content accounts for 13%.

[0126] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 90%.

[0127] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan was 98% and the selectivity of benzene was 42%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran was 95% and the selectivity of toluene was 74%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran was 95% and the selectivity of p-xylene was 93%.

[0128] Example 3

[0129] The method of Example 1 differs in that: in step (1), a water vapor hydrothermal treatment is performed at 900°C and 80% water vapor partial pressure for 1 hour.

[0130] The tetracoordinated Al content of the hydrogen-type SCM-1 molecular sieve raw powder after water vapor hydrothermal treatment in step (1) is 64%.

[0131] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured by ICP to be 49.2.

[0132] XRD patterns of weakly acidic MWW molecular sieves Figure 4 similar;

[0133] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 205 m². 2 / g, with an external specific surface area of ​​157m² 2 / g;

[0134] Lewis / weakly acidic MWW molecular sieve The ratio is 4.5;

[0135] The total acid content of the weakly acidic MWW molecular sieve is 460 μmol / g, and the calculated strong acid content is 12%.

[0136] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 83%.

[0137] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan was 87% and the selectivity of the product benzene was 41%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran was 90% and the selectivity of the product toluene was 70%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran was 91% and the selectivity of the product p-xylene was 91%.

[0138] Example 4

[0139] The method of Example 1 differs in that: in step (2), the hydrogen-type SCM-1 molecular sieve raw powder after water vapor hydrothermal treatment is eluted with concentrated nitric acid at 120°C for 48 hours.

[0140] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured to be 176 by ICP.

[0141] XRD patterns of weakly acidic MWW molecular sieves Figure 4 similar;

[0142] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 289 m². 2 / g, with an external specific surface area of ​​186m² 2 / g;

[0143] Lewis / weakly acidic MWW molecular sieve The ratio is 6.1;

[0144] The total acid content of the weakly acidic MWW molecular sieve is 336 μmol / g, and the calculated strong acid content is 8%.

[0145] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 91%.

[0146] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan is 90% and the selectivity of benzene is 44%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran is 91% and the selectivity of toluene is 74%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran is 90% and the selectivity of p-xylene is 94%.

[0147] Example 5

[0148] The method of Example 1 differs in that: in step (2), the hydrogen-type SCM-1 molecular sieve raw powder after water vapor hydrothermal treatment is eluted with 1M oxalic acid solution at room temperature for 24 hours.

[0149] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured by ICP to be 23.4.

[0150] XRD patterns of weakly acidic MWW molecular sieves Figure 4 similar;

[0151] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 208 m². 2 / g, with an external specific surface area of ​​134m² 2 / g;

[0152] Lewis / weakly acidic MWW molecular sieve The ratio is 2.2;

[0153] The total acid content of the weakly acidic MWW molecular sieve is 630 μmol / g, and the calculated strong acid content is 18%.

[0154] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 82%.

[0155] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan is 99% and the selectivity of benzene is 40%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran is 96% and the selectivity of toluene is 70%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran is 98% and the selectivity of p-xylene is 91%.

[0156] Example 6

[0157] The method of Example 1 is different in that: in step (3), dimethyltin dichloride is used to replace gallium acetylacetonate, and the Si / Sn atomic ratio is controlled to be 40, and finally weakly acidic MWW molecular sieve (Sn-Al-SCM-1 molecular sieve) is obtained.

[0158] XRD patterns of weakly acidic MWW molecular sieves Figure 4 similar;

[0159] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 225 m². 2 / g, with an external specific surface area of ​​117m² 2 / g;

[0160] Lewis / weakly acidic MWW molecular sieve The ratio is 4.5;

[0161] The total acid content of the weakly acidic MWW molecular sieve is 587 μmol / g, and the calculated strong acid content is 10%.

[0162] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 87%.

[0163] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan is 95% and the selectivity of benzene is 42%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran is 93% and the selectivity of toluene is 73%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran is 95% and the selectivity of p-xylene is 93%.

[0164] Example 7

[0165] The method of Example 1 differs in that: in step (1), a water vapor hydrothermal treatment is performed at 750°C and 40% water vapor partial pressure for 36 hours.

[0166] The tetracoordinated Al content of the hydrogen-type SCM-1 molecular sieve raw powder after water vapor hydrothermal treatment in step (1) is 84%.

[0167] XRD patterns of weakly acidic MWW molecular sieves Figure 4 similar;

[0168] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured by ICP to be 43.5.

[0169] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 256 m². 2 / g, with an external specific surface area of ​​189m² 2 / g;

[0170] Lewis / weakly acidic MWW molecular sieve The ratio is 2.9;

[0171] The total acid content of the weakly acidic MWW molecular sieve is 623 μmol / g, and the calculated strong acid content is 10%.

[0172] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 93%.

[0173] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan was 99% and the selectivity of benzene was 44%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran was 96% and the selectivity of toluene was 74%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran was 97% and the selectivity of p-xylene was 94%.

[0174] Comparative Example 1

[0175] The method of Example 1 is the same, except that the hydrogen-type SCM-1 molecular sieve powder is not subjected to water vapor hydrothermal treatment, while the other steps are kept the same to obtain MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0176] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured by ICP to be 44.5.

[0177] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 259 m². 2 / g, with an external specific surface area of ​​182m² 2 / g;

[0178] Lewis / weakly acidic MWW molecular sieve The ratio is 1.8;

[0179] The total acid content of the weakly acidic MWW molecular sieve is 688 μmol / g, and the calculated strong acid content accounts for 27%.

[0180] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 85%.

[0181] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan was 98% and the selectivity of the product benzene was 25%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran was 98% and the selectivity of the product toluene was 53%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran was 99% and the selectivity of the product p-xylene was 61%.

[0182] Comparative Example 2

[0183] The method of Example 1 is different in that the hydrogen-type SCM-1 molecular sieve raw powder is not subjected to water vapor hydrothermal treatment, and in step (2), the hydrogen-type SCM-1 molecular sieve raw powder is eluted with concentrated nitric acid at 120°C for 48 hours. Other steps are kept the same to obtain MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0184] After partial dealuminization, the Si / Al atomic ratio of the molecular sieve was measured to be 158 by ICP.

[0185] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 254 m². 2 / g, with an external specific surface area of ​​185m² 2 / g;

[0186] Lewis / weakly acidic MWW molecular sieve The ratio is 2.5;

[0187] The total acid content of the weakly acidic MWW molecular sieve is 378 μmol / g, and the calculated strong acid content accounts for 21%.

[0188] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 88%.

[0189] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan was 97% and the selectivity of benzene was 29%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran was 96% and the selectivity of toluene was 57%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran was 97% and the selectivity of p-xylene was 79%.

[0190] Comparative Example 3

[0191] The method of Example 1 is the same, except that partial dealuminization is not performed after water vapor hydrothermal treatment, while the other steps are kept the same to obtain MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0192] The Si / Al atomic ratio of the molecular sieve was measured to be 15.2 by ICP.

[0193] BET measured the internal specific surface area of ​​the weakly acidic MWW molecular sieve to be 186 m². 2 / g, with an external specific surface area of ​​104m² 2 / g;

[0194] Lewis / weakly acidic MWW molecular sieve The ratio is 4.6;

[0195] The total acid content of the weakly acidic MWW molecular sieve is 522 μmol / g, and the calculated strong acid content accounts for 24%.

[0196] The four-coordinated Al content of the weakly acidic MWW molecular sieve is 78%.

[0197] When using the prepared MWW molecular sieve as a catalyst to prepare benzene, the conversion rate of furan was 79% and the selectivity of benzene was 12%; when using the prepared MWW molecular sieve as a catalyst to prepare toluene, the conversion rate of 2-methylfuran was 82% and the selectivity of toluene was 34%; when using the prepared MWW molecular sieve as a catalyst to prepare p-xylene, the conversion rate of 2,5-dimethylfuran was 78% and the selectivity of p-xylene was 51%.

[0198] The results from the examples and comparative examples show that using the weakly acidic MWW molecular sieve of the present invention, which has both a high proportion of tetracoordinated aluminum and a low amount of strong acid, as a catalyst in the preparation of aromatic compounds from furans and ethylene not only results in a good conversion rate of furans, but also a high conversion rate of aromatic compounds.

[0199] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A weakly acidic MWW molecular sieve, characterized in that, Based on the total aluminum content in the MWW molecular sieve, the proportion of tetracoordinated Al in the MWW molecular sieve is A, and based on the total acid content in the MWW molecular sieve, the proportion of strong acid in the MWW molecular sieve is B, wherein the ratio of A to B is not less than 450%.

2. The MWW molecular sieve according to claim 1, wherein, The ratio of A to B is not less than 500%; and / or The value of A is not less than 60%; and / or The value of B is no greater than 20%.

3. The MWW molecular sieve according to claim 2, wherein, The ratio of A to B is 500-1500%; and / or The value of A is not less than 75%; and / or The value of B is no greater than 15%.

4. The MWW molecular sieve according to claim 3, wherein, The value of B is 5-15%.

5. The MWW molecular sieve according to claim 1, wherein, The total acidity of the MWW molecular sieve is 300-800 µmol / g; and / or The Si / Al molar ratio of the MWW molecular sieve is 25-180; and / or The Lewis / Brønsted ratio of the MWW molecular sieve is greater than 2:

1.

6. The MWW molecular sieve according to claim 5, wherein, The total acidity of the MWW molecular sieve is 400-700 µmol / g; and / or The Si / Al molar ratio of the MWW molecular sieve is 30-100.

7. The MWW molecular sieve according to claim 6, wherein, The total acidity of the MWW molecular sieve is 500-600 µmol / g.

8. The MWW molecular sieve according to claim 1, wherein, The MWW molecular sieve is selected from pure MWW molecular sieve and / or metal heteroatom M-doped MWW molecular sieve, wherein M is selected from at least one of Ti, Zr, Nb, Ta, W, Ga, and Sn; and / or The MWW molecular sieve is selected from at least one of MCM molecular sieves, ITQ molecular sieves, and SCM molecular sieves.

9. The MWW molecular sieve according to claim 8, wherein, M is Ga and / or Sn; The MWW molecular sieve is selected from metal heteroatom M-doped MWW molecular sieves; The MWW molecular sieve is an SCM type molecular sieve.

10. The MWW molecular sieve according to claim 9, wherein, The Si / M molar ratio of the metal heteroatom M-doped MWW molecular sieve is 20-100; The SCM-type molecular sieve is SCM-1 molecular sieve and / or SCM-2 molecular sieve.

11. The MWW molecular sieve according to claim 10, wherein, The Si / M molar ratio of the metal heteroatom M-doped MWW molecular sieve is 30-70.

12. The MWW molecular sieve according to claim 1, wherein, The MWW molecular sieve has an internal specific surface area of ​​150-400 m². 2 / g; and / or The MWW molecular sieve has an external specific surface area of ​​50-200 m². 2 / g.

13. The MWW molecular sieve according to claim 12, wherein, The MWW molecular sieve has an internal specific surface area of ​​200-400 m². 2 / g; and / or The MWW molecular sieve has an external specific surface area of ​​100-200 m². 2 / g.

14. A method for preparing the MWW molecular sieve according to any one of claims 1-13, characterized in that, The preparation method includes: (1) The hydrogen-form MWW molecular sieve raw powder was subjected to steam hydrothermal treatment; (2) Acid pickling dealuminization.

15. The preparation method according to claim 14, wherein, Control the hydrothermal treatment conditions so that the proportion of tetracoordinated Al is not less than 60% after steam hydrothermal treatment.

16. The preparation method according to claim 15, wherein, Control the hydrothermal treatment conditions so that the proportion of tetracoordinated Al is not less than 75% after steam hydrothermal treatment; The conditions for the steam hydrothermal treatment include: In an inert gas atmosphere; and / or The partial pressure of water vapor is 10-100%; and / or The processing temperature is 600-900℃; and / or Processing time is 1-72 hours.

17. The preparation method according to claim 16, wherein, The conditions for the steam hydrothermal treatment include: The partial pressure of water vapor is 30-70%; and / or The processing temperature is 700-800℃; and / or The processing time is 6-12 hours.

18. The preparation method according to claim 14, wherein, The preparation method further includes: contacting the metal M salt with the molecular sieve obtained after acid washing and partial dealuminization, followed by calcination; wherein the metal M in the metal M salt is selected from at least one of Ti, Zr, Nb, Ta, W, Ga, and Sn; The contact includes dynamic contact.

19. The preparation method according to claim 18, wherein, The metal M in the metal M salt is Ga and / or Sn; The molar ratio of Si in the molecular sieve obtained after acid washing and partial dealuminization to metal M in the metal M salt is 20-100; and / or The contact includes mechanical grinding.

20. The preparation method according to claim 19, wherein, The molar ratio of Si in the molecular sieve obtained after acid washing and partial dealuminization to metal M in the metal M salt is 30-70.

21. The preparation method according to claim 14, wherein, In step (2), the endpoint of the acid pickling dealuminization is: the Si / Al ratio of the molecular sieve after acid pickling dealuminization is 25-180. In step (2), the conditions for partial aluminum removal during pickling include: Elution temperature: room temperature - 120°C; and / or The elution time is greater than 10 hours.

22. The preparation method according to claim 21, wherein, In step (2), the endpoint of the acid pickling dealuminization is: the Si / Al ratio of the molecular sieve after acid pickling dealuminization is 30-100. In step (2), the acid solution used during pickling is selected from one or more of hydrochloric acid solution, oxalic acid solution, nitric acid solution, sulfuric acid solution and phosphoric acid solution; and / or In step (2), the conditions for aluminum removal in the pickling part include: the rinsing time is 12-48h.

23. The preparation method according to claim 22, wherein, In step (2), the acid solution used during pickling is nitric acid solution.

24. The use of the MWW molecular sieve according to any one of claims 1-13 in the preparation of aromatic compounds from furan compounds and ethylene.

25. A method for preparing an aromatic compound, characterized in that, The preparation method includes: Using the MWW molecular sieve described in any one of claims 1-13 as the active component of the catalyst, in the presence of the catalyst and in an ethylene atmosphere, a material containing furan compounds undergoes a Diels-Alder addition followed by a dehydration reaction.

26. The preparation method according to claim 25, wherein, The furan compound is selected from at least one of furan, 2-methylfuran, and 2,5-dimethylfuran; and / or Materials containing furan compounds contain organic solvents; and / or Materials containing furan compounds have a mass concentration of furan compounds greater than 5%; and / or The mass ratio of furan compounds to catalysts is (5-50):1; and / or The pressure of ethylene is 1-6 MPa; and / or The conditions for the dehydration reaction following Diels-Alder addition include: a reaction temperature of 200-300℃; and / or a reaction time of 3-24h.

27. The preparation method according to claim 26, wherein, The organic solvent is selected from one or more of n-hexane, cyclohexane, n-heptane, n-octane, and tetrahydrofuran; and / or The mass ratio of furan compounds to catalysts is (5-8):1; and / or The pressure of ethylene is 2-4 MPa; and / or The conditions for the dehydration reaction following Diels-Alder addition include: a reaction temperature of 230-280℃; and / or a reaction time of 6-12 h.

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