Weakly acidic MWW molecular sieve, preparation method and application thereof, and preparation method of aromatic hydrocarbon compound

Abstract

The invention 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 an aromatic compound. The total aluminum amount in the MWW molecular sieve is taken as a reference, the proportion of tetra-coordinated Al in the MWW molecular sieve is A, the total acid amount of the MWW molecular sieve is taken as a reference, the proportion of strong acid amount of the MWW molecular sieve is B, and the ratio of A to B is not less than 450%. By adopting the weakly acidic MWW molecular sieve or the catalyst containing the weakly acidic MWW molecular sieve, the occurrence of raw material hydrolysis and polymerization reaction is effectively reduced, and the high selectivity of products is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic chemistry, and in particular to a weakly acidic MWW molecular sieve and a preparation method and application thereof, and a preparation method of an aromatic compound. Background Art

[0002] The molecular sieve with MWW topology has two independent and unconnected ten-membered ring pore systems: one set of two-dimensional sinusoidal pores with an elliptical cross section and a pore size of Another set of ten-membered ring channels contains The approximately cylindrical twelve-membered ring supercage is formed by a slightly distorted ten-membered ring window. In addition, the MWW topological structure also has 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 topological structure. The molecular sieve is a two-dimensional layered structure with a huge external specific surface area of ​​185m 2 / g or more, exposing a large number of bowl-shaped twelve-membered ring semi-supercages on the outer surface of the crystal, giving it the potential for catalytic application in larger molecules.

[0003] With the development of human society, oil resources are becoming increasingly scarce, and the huge amount of CO2 emitted has aggravated the greenhouse effect. Under the pressure of carbon emission reduction, countries are looking for new technologies to replace petroleum-based chemical products with bio-based chemical products. Among them, the reaction with bright prospects is to prepare bio-based benzene, toluene and p-xylene from furan compounds and ethylene, that is, 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 major characteristics. One is that since furan reactants are relatively active, strong acids can easily cause self-polymerization, hydrolysis and condensation side reactions of furan molecules. The appropriate acidity satisfies the Diels-Alder addition and then dehydrates to obtain the product with high selectivity. Therefore, the reaction does not require the catalysis of strong acid sites, and the strong acid sites should be selectively eliminated in the catalytic material. The second is that this type of reaction is prone to carbon deposition, and the catalytic material will be rapidly deactivated due to the carbon deposition problem, so the catalyst is required to have excellent mass transfer performance and anti-carbon deposition ability. Traditional silicon aluminum molecular sieves face great challenges in such reactions because they usually have a small external specific surface area and strong acidity, and contain a large number of strong acid sites. The huge external specific surface area of ​​SCM-1 material can provide a rich reaction interface and excellent mass transfer performance, but the material contains 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 have a large number of strong acid sites, and their strong acidity will cause a series of serious side reactions, such as alkylation, isomerization, and polymerization reactions, resulting in the self-consumption of active furan raw materials, and the selectivity of the target product is very low.

[0004] US20190344252A1 reported that phosphoric acid-modified Beta molecular sieves were used to react 2,5-dimethylfuran and ethylene to prepare paraxylene (PX). Although 97% PX selectivity can be achieved, its active site is a phosphorus-modified molecular sieve hydroxyl hole, which has poor chemical stability and is difficult to achieve multiple recycling. In addition, the Beta molecular sieve has a three-dimensional structure and is insufficient in mass transfer performance and anti-carbon deposition. If the Beta molecular sieve is modified, such as the introduction of metal atoms, the introduction of new sites is likely to block its three-dimensional pores, resulting in unsatisfactory accessibility of the active sites, which is unfavorable to the reaction.

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

[0006] The purpose of the present invention is to overcome the problems of inappropriate acidity and poor carbon deposition resistance of the prior art molecular sieves, such as the difficulty in applying them to the field of biomass catalysis. Specifically, when used in the field of biomass catalysis, they have problems of poor mass transfer and carbon deposition resistance and low selectivity of bio-based aromatic products. A weakly acidic MWW molecular sieve and a preparation method and application thereof are provided.

[0007] After a lot of research and experiments, the inventors of the present invention have discovered a weakly acidic MWW molecular sieve that is different from the prior art, that is, when the proportion of tetracoordinated Al and the proportion of strong acid in the weakly acidic MWW molecular sieve have a specific ratio relationship, the weakly acidic MWW molecular sieve has a high proportion of tetracoordinated Al while having weak acidity, and the weakly acidic MWW molecular sieve has good catalytic activity and resistance to carbon deposition, and when the weakly acidic MWW molecular sieve is used as the active component of the catalyst to directional catalyze the conversion of furan raw materials and ethylene to prepare aromatic compounds, the catalyst can highly selectively catalyze the furan raw materials and ethylene to prepare aromatic compounds, and the catalyst has strong resistance to carbon deposition and high cyclic 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 tetracoordinated Al in the MWW molecular sieve is A based on the total aluminum content in the MWW molecular sieve, and the proportion of strong acid in the MWW molecular sieve is B based on the total acid content of the MWW molecular sieve, wherein the ratio of A to B is not less than 450%.

[0009] The 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 preparation method comprising:

[0010] (1) subjecting hydrogen-type MWW molecular sieve raw powder to water vapor hydrothermal treatment;

[0011] (2) Dealumination of the pickled part.

[0012] The third aspect of the present invention provides the use of the MWW molecular sieve described in the first aspect of the present 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, a material containing furanic compounds is subjected to a Diels-Alder addition followed by a dehydration reaction in the presence of the catalyst and in an ethylene atmosphere.

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

[0016] The molecular sieves in the prior art, especially the MWW molecular sieves, have a large amount of strong acid when they have more tetracoordinated Al, while the weakly acidic MWW molecular sieve in the present invention has a high proportion of tetracoordinated Al while having weak acidity. By using the weakly acidic MWW molecular sieve of the present invention or the weakly acidic MWW molecular sieve containing the present invention as a catalyst, the occurrence of raw material hydrolysis and polymerization reactions is effectively reduced, and high selectivity for products is ensured. In addition, its excellent structural characteristics such as the two-dimensional layered structure give the catalyst good mass transfer performance, which is conducive to the smooth progress of the reaction and has a strong resistance to carbon deposition, so that the catalyst maintains high activity. Furan raw materials and ethylene can be efficiently converted into their corresponding aromatic products, and the conversion rate and product selectivity of the aromatic products are very high. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0019] Figure 3 The hydrogen-type SCM-1 molecular sieve raw powder after the steam hydrothermal treatment in step (1) of Example 1 is 27 Al-NMR graph;

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

[0021] Figure 5 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 DESCRIPTION

[0023] 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.

[0024] The first aspect of the present invention provides a weakly acidic MWW molecular sieve. Based on the total aluminum amount in the MWW molecular sieve, the proportion of tetracoordinated Al in the MWW molecular sieve is A, and based on the total acid amount of 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%.

[0025] In the present invention, the inventors found that when the proportion of tetracoordinated Al and the proportion of strong acid in the weakly acidic MWW molecular sieve of the present invention have a specific ratio relationship, it has weak acidity and a high proportion of tetracoordinated Al, so that the weakly acidic MWW molecular sieve of the present invention has good catalytic activity, and the conversion rate and product selectivity of the target product are very high when used, and the weakly acidic MWW molecular sieve also has a strong resistance to carbon deposition.

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

[0027] In the present invention, the NH3 temperature programmed desorption (NH3-TPD) experiment is carried out on a TPD / TPR Altamira AMI-3300 instrument, and the total acid amount is calculated by fitting and peak separation of the obtained spectrum, and the acid corresponding to the desorption temperature of 100-240°C is defined as a weak acid, the acid corresponding to the desorption temperature of 240-320°C is defined as a medium-strong acid, and the acid corresponding to the desorption temperature of 320-500°C is defined as a strong acid, thereby calculating the proportion of strong acid.

[0028] According to the present invention, the ratio of A to B can be 450%, 455%, 543%, 690%, 870%, 900%, 1000%, 1138%, 1300%, 1500%, and the 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 above embodiment not only has good catalytic activity and anti-carbon deposition ability, but also has high selectivity for aromatic compounds when it is used for preparing aromatic compounds from furanic 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 a combination of any two of the above values, preferably, the proportion of tetracoordinated Al in the MWW molecular sieve is not less than 75%. The molecular sieve under the aforementioned embodiment has good catalytic activity and anti-carbon deposition ability, and when it is used for preparing aromatic compounds from furan compounds and ethylene, it also has high selectivity for aromatic compounds.

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

[0031] According to the present invention, in some embodiments, the total acid content 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 the range composed of any of the above numerical values. The molecular sieve under the above embodiment has good catalytic activity and anti-carbon deposition ability, and when it is used for preparing aromatic compounds from furanic compounds and ethylene, it also has high selectivity for aromatic compounds. .

[0032] According to the present invention, in some preferred embodiments, the total acid content of the MWW molecular sieve is 400-700 μmol / g, and more preferably 500-600 μmol / g. The molecular sieve under the aforementioned preferred embodiment has good catalytic activity and anti-carbon deposition ability, and when it is used to prepare aromatic compounds from furanic compounds and ethylene, it also has high selectivity for aromatic compounds.

[0033] According to the present invention, it can be understood that the MWW molecular sieve includes at least Si and Al elements. As long as the purpose of the present invention can be 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. The existing MWW molecular sieve has a strong acidity when it has a low aluminum content, that is, a high silicon-aluminum molar ratio. The MWW molecular sieve of the aforementioned preferred embodiment of the present invention has a weak acidity when it has a wide range of adjustable silicon-aluminum molar ratio. When it is used for preparing benzene compounds from furan compounds and ethylene, it can also 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, and the range of any two of the above ratios. The MWW molecular sieve of the above preferred embodiment of the present invention has good catalytic activity and carbon deposition resistance.

[0035] In the present invention, the pyridine adsorption infrared (py-FTIR) method is used to determine the type of catalyst acid, and the py-FTIR spectrum is obtained on a Nicolet Model 710 spectrometer. The specific operation steps are as follows: a. Sample preparation and pretreatment, about 15 mg of sample is pressed into a thin disc with a diameter of 13 mm and loaded into an infrared sample tank; then the sample is pretreated at 400°C in a vacuum cell for 2 hours; the sample is scanned at 150°C, 250°C, and 400°C to obtain a background spectrum; b. After the sample tank is cooled to room temperature, pyridine is adsorbed for 10 minutes; vacuum desorption is performed at 150°C for 10 minutes, and the infrared absorption spectrum is scanned and recorded, and the infrared absorption spectrum is scanned and recorded at 250°C and 400°C in sequence. 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 sieve and / or MWW molecular sieve doped with metal heteroatom M, and the M is selected from at least one of Ti, Zr, Nb, Ta, W, Ga, and Sn. The above embodiments further broaden the scope of use of the MWW molecular sieve, and when it is used for preparing benzene compounds from furan compounds and ethylene, it can also maintain high catalytic activity and target product selectivity.

[0037] According to the present invention, in some preferred embodiments, M is Ga and / or Sn. The MWW molecular sieve in the aforementioned preferred embodiments has good catalytic performance and anti-carbon deposition ability.

[0038] According to the present invention, in some preferred embodiments, the MWW molecular sieve is selected from MWW molecular sieves doped with metal heteroatom M. The MWW molecular sieves in the aforementioned preferred embodiments have good catalytic performance and anti-carbon deposition ability.

[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 a range consisting of any of the above values, preferably 30-70.

[0040] In the present invention, the element content composition of the molecular sieve is measured by an Agilent 725-ES inductively coupled plasma atomic emission spectrometer (ICP), the molecular sieve sample is digested with hydrofluoric acid, and the element content is measured in moles.

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

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

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

[0044] In the present invention, those skilled in the art know that the existing SCM-1 molecular sieve and SCM-2 molecular sieve are two-dimensional layered structures with huge external specific surface areas, exposing a large number of bowl-shaped twelve-membered ring semi-supercages on the outer surface of the crystal, which makes them have catalytic application potential 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. The SCM-1 molecular sieve and SCM-2 molecular sieve after the introduction of heteroatoms in the present invention have weak acidity and a high proportion of four-coordinated Al. They not only have good catalytic activity, but also have good selectivity for the target product when used in catalytic reactions, and they themselves have excellent carbon resistance.

[0045] In the present invention, SCM-1 molecular sieve is used as an example to illustrate the advantages of the present invention, but the present 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 150-400m2 / 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 The MWW molecular sieve in the above-mentioned embodiment has good catalytic performance and anti-carbon deposition ability.

[0047] According to the present invention, in some embodiments, the external specific surface area of ​​the MWW molecular sieve is 50-200m 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 The MWW molecular sieve in the above-mentioned embodiment has good catalytic performance and anti-carbon deposition ability.

[0048] The 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 preparation method comprising:

[0049] (1) subjecting hydrogen-type MWW molecular sieve raw powder to water vapor hydrothermal treatment;

[0050] (2) Dealumination of the pickled part.

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

[0052] According to the present invention, in some embodiments, the hydrothermal treatment conditions are controlled so that after the steam hydrothermal treatment, the proportion of tetracoordinated Al is not less than 60%, preferably not less than 75%. The inventors have found that the use of the aforementioned embodiment 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 the present invention, hydrogen-type 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-type molecular sieve raw powder from molecular sieve raw powder in the art, and its specific operation will not be elaborated in the present invention.

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

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

[0056] In the present invention, the inert gas that can be cited includes nitrogen and / or argon.

[0057] According to the present invention, in some preferred embodiments, the conditions of 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 numerical values, preferably 30-70%. The above embodiment can reduce strong acid sites without causing a large amount of Al to be removed from the framework, and the proportion of tetracoordinated aluminum in the molecular sieve is largely retained. Finally, the prepared MWW molecular sieve has good catalytic activity and carbon deposition resistance.

[0058] According to the present invention, in some preferred embodiments, the conditions of the water vapor hydrothermal treatment include: a treatment temperature of 600-900° C., for example, 600° C., 700° C., 800° C. or 900° C., and a range of any of the above values, preferably 700-800° C. By adopting the above embodiment, the strong acid sites can be reduced without causing a large amount of Al to be removed from the framework, and the proportion of tetracoordinated aluminum in the molecular sieve is largely retained. Finally, the prepared MWW molecular sieve has good catalytic activity and carbon deposition resistance.

[0059] According to the present invention, in some preferred embodiments, the conditions of the water vapor hydrothermal treatment include: a treatment time of 1-72 hours, for example, 1 hour, 3 hours, 6 hours, 10 hours, 12 hours, 18 hours, 24 hours, 30 hours, 48 ​​hours, 66 hours or 72 hours, and a range of any of the above values, preferably 6-12 hours. Using the above embodiment, the MWW molecular sieve finally prepared has good catalytic activity and anti-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 the molecular sieve obtained after partial dealumination by acid washing, and then calcining; 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 the present invention, the M-doped MWW molecular sieve after steam hydrothermal treatment and introduction of heteroatoms has weak acidity and a high proportion of tetra-coordinated Al. It not only has good catalytic activity, but also has good selectivity for the target product when used in catalytic reactions, and it itself has excellent carbon resistance.

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

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

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

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

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

[0067] In the present invention, the mechanical grinding method is a conventional method in the art, and its specific conditions are not limited. Those skilled in the art only need to make them fully mixed and contacted during mechanical grinding to achieve the final doping.

[0068] According to the present invention, there is no particular limitation 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 is no particular limitation 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 the acid-washed part after dealumination to obtain the desired MWW molecular sieve.

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

[0072] According to the present invention, it can be understood that the acid wash partial dealumination refers to washing with an acid solution. As long as the purpose of the present invention can be achieved, in step (2), the acid solution used for pickling is not particularly limited. In some preferred embodiments, the acid solution used for 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 the present invention, the acid solution refers to a mixed solution of a corresponding acid and water, for example, concentrated nitric acid refers to a nitric acid aqueous solution 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, in step (2), the conditions for pickling are not particularly limited. In some preferred embodiments, the conditions for partial dealumination by pickling include: an elution temperature of room temperature to 120° C.; wherein room temperature refers to any temperature between 15° C. and 30° C.

[0076] According to the present invention, in some preferred embodiments, the conditions for dealumination of the acid-washed part include: the elution time is greater than 10 hours, preferably 12-48 hours.

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

[0078] In the present invention, when the MWW molecular sieve of the present invention is used to prepare aromatic compounds from furan compounds and ethylene, it can not only be efficiently converted into its corresponding aromatic products with very high conversion rate and product selectivity, but also has strong resistance to carbon deposition, 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, a material containing furanic compounds is subjected to a Diels-Alder addition followed by a dehydration reaction in the presence of the catalyst and in an ethylene atmosphere.

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

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

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

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

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

[0086] According to the present invention, in some embodiments, the mass ratio of the furan compound to the 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: the reaction temperature is 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: the reaction time is 3-24h, preferably 6-12h.

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

[0091] The XRD spectra were obtained on a Bruker D8 Advance X-ray diffractometer from Germany using a CuKα radiation source.

[0092] (1) A method for preparing benzene using the prepared MWW molecular sieve as a catalyst is as follows: 0.5 g of the catalyst, 3.0 g of furan and 17 g of n-heptane are added to a magnetically stirred high-pressure reactor, and 3.0 MPa of ethylene is charged, and the reaction is carried out at 250° C. for 12 h to obtain a reaction solution;

[0093] (2) A method for preparing toluene using the prepared MWW molecular sieve as a catalyst is as follows: 0.5 g of the catalyst, 3.0 g of 2-methylfuran and 17 g of n-heptane are added to a magnetically stirred high-pressure reactor, and 3.0 MPa of ethylene is charged, and the reaction is carried out at 250° C. for 12 h to obtain a reaction liquid;

[0094] (3) The method for preparing paraxylene using the prepared MWW molecular sieve as a catalyst is as follows: 0.5 g of the catalyst, 3.0 g of 2,5-dimethylfuran and 17 g of n-heptane are added to a magnetically stirred high-pressure reactor, and 3.0 MPa of ethylene is charged, and the reaction is carried out at 250° C. for 12 hours to obtain a reaction liquid.

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

[0096] The reaction solution components were analyzed qualitatively by Agilent 7890A gas chromatograph (GC-MS) of Agilent, USA, with a Wax polar capillary column as the chromatographic column, and quantitatively by Agilent 7890B gas chromatograph (GC) of Agilent, USA, equipped with a hydrogen ion flame detector (FID) and a Wax polar capillary column. The conversion rate and selectivity of the substance were calculated based on the molar amount of the substance measured by gas chromatography.

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

[0098] The product selectivity is calculated as follows: product selectivity % = (molar amount of product generated by the reaction) / (molar amount of raw material initially added - molar amount of raw material remaining) × 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 described in patent CN104511271B. 12.64g of sodium aluminate (Al2O3 43.0wt%, Na2O 35.0wt%, the balance is water) is dissolved in 362.40g of water, then 39.68g of hexamethyleneimine aqueous solution (hexamethyleneimine content is 80.0wt%), 101.54g of dicyclohexylamine are added, and finally 240g of silica sol (SiO2 40.0wt%, the balance is water) is added, and the molar ratio of SiO2, Al2O3, NaOH, hexamethyleneimine, dicyclohexylamine, and H2O in the final gel is 1:0.033:0.09:0.20:0.35:18; it is loaded into a reactor and crystallized at 150°C for 4d under stirring; then centrifuged, washed, and dried to obtain a solid product, and the solid product is calcined at 550°C in air for 5h to obtain SCM-1 molecular sieve raw powder.

[0102] SCM-1 molecular sieve raw powder is ion exchanged and calcined to obtain hydrogen-type SCM-1 molecular sieve raw powder;

[0103] The silicon-aluminum ratio (atomic ratio) of the hydrogen-type SCM-1 molecular sieve raw powder was measured by ICP to be 15.2; the acidity distribution NH3-TPD diagram of the hydrogen-type SCM-1 molecular sieve raw powder is shown in Figure 1 As shown;

[0104] Preparation of weakly acidic MWW molecular sieve:

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

[0106] (2) The hydrogen-type SCM-1 molecular sieve raw powder after steam hydrothermal treatment was eluted with concentrated nitric acid at 110°C for 48h to partially dealuminate;

[0107] (3) Gallium acetylacetonate was added to the partially dealuminated molecular sieve, the Si / Ga atomic ratio was controlled to be 40, and after sufficient mechanical grinding, the mixture was calcined at 550°C for 6h to obtain a weakly acidic MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0108] The NH3-TPD spectrum of the hydrogen-type SCM-1 molecular sieve raw powder after steam hydrothermal treatment in step (1) is as follows: Figure 2 As shown, through Figure 2 It can be found that after steam hydrothermal treatment, the strong acid sites are greatly reduced; 27 Al-NMR Figure 3 As shown, it shows that the content of tetracoordinated Al accounts for 78%;

[0109] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 45.8 as measured by ICP;

[0110] XRD characteristics of weakly acidic MWW molecular sieves Figure 4 As shown, through Figure 4 It can be seen that the MWW structure is still well maintained;

[0111] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 259 m 2 / g, external specific surface area is 142m 2 / g;

[0112] The pyridine infrared spectrum of 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 fewer strong acid sites, Lewis / The ratio is 3.6;

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

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

[0115] When the prepared MWW molecular sieve was used as a catalyst to prepare benzene, in the initial reaction, the conversion rate of furan was 92%, and the selectivity of the product benzene was 41%; after the catalyst was recycled 5 times, the conversion rate of furan was 91%, and the selectivity of the product benzene was 41%;

[0116] When the prepared MWW molecular sieve was used as a catalyst to prepare toluene, in the initial reaction, the conversion rate of 2-methylfuran was 93%, and the selectivity of the product toluene was 72%; after the catalyst was circulated 5 times, the conversion rate of 2-methylfuran was 93%, and the selectivity of the product toluene was 71%;

[0117] When the prepared MWW molecular sieve is used as a catalyst to prepare para-xylene, in the initial reaction, the conversion rate of 2,5-dimethylfuran is 93%, and the selectivity of the product para-xylene is 92%; after the catalyst is circulated 5 times, the conversion rate of 2,5-dimethylfuran is 93%, and the selectivity of the product para-xylene is 92%.

[0118] Example 2

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

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

[0121] XRD and Figure 4 similar;

[0122] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 42.1 as measured by ICP;

[0123] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 245 m 2 / g, external specific surface area is 178m 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 strong acid content is calculated to be 13%.

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

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

[0128] Example 3

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

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

[0131] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 49.2 as measured by ICP;

[0132] XRD and Figure 4 similar;

[0133] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 205 m 2 / g, external specific surface area is 157m 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 strong acid content is calculated to be 12%.

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

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

[0138] Example 4

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

[0140] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 176 as measured by ICP;

[0141] XRD and Figure 4 similar;

[0142] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 289 m 2 / g, external specific surface area is 186m 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 accounts for 8%.

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

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

[0147] Example 5

[0148] The method of Example 1 is followed, except that in step (2), the hydrogenated SCM-1 molecular sieve raw powder after the steam hydrothermal treatment is eluted with 1 M oxalic acid solution at room temperature for 24 h.

[0149] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 23.4 as measured by ICP;

[0150] XRD and Figure 4 similar;

[0151] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 208 m 2 / g, external specific surface area is 134m 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 strong acid content is calculated to be 18%.

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

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

[0156] Example 6

[0157] The method of Example 1 is followed, except 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 a weakly acidic MWW molecular sieve (Sn-Al-SCM-1 molecular sieve) is obtained.

[0158] XRD and Figure 4 similar;

[0159] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 225 m 2 / g, external specific surface area is 117m 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 strong acid content is calculated to be 10%.

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

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

[0164] Example 7

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

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

[0167] XRD and Figure 4 similar;

[0168] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 43.5 as measured by ICP;

[0169] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 256 m 2 / g, external specific surface area is 189m 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 strong acid content is calculated to be 10%.

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

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

[0174] Comparative Example 1

[0175] The method of Example 1 is followed, except that the hydrogen-type SCM-1 molecular sieve raw powder is not subjected to steam hydrothermal treatment, and the other steps remain the same to obtain the MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0176] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 44.5 as measured by ICP;

[0177] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 259 m 2 / g, external specific surface area is 182m 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 tetracoordinated Al content of the weakly acidic MWW molecular sieve is 85%.

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

[0182] Comparative Example 2

[0183] The method of Example 1 is followed, except that the hydrogen-type SCM-1 molecular sieve raw powder is not subjected to steam 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 h, and the other steps remain the same to obtain the MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0184] After partial dealumination, the Si / Al atomic ratio of the molecular sieve was 158 as measured by ICP;

[0185] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 254 m 2 / g, external specific surface area is 185m 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 tetracoordinated Al content of the weakly acidic MWW molecular sieve is 88%.

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

[0190] Comparative Example 3

[0191] The method of Example 1 is followed, except that partial dealumination is not performed after the steam hydrothermal treatment, and the other steps remain the same to obtain the MWW molecular sieve (Ga-Al-SCM-1 molecular sieve).

[0192] The Si / Al atomic ratio of the molecular sieve was 15.2 as measured by ICP;

[0193] The internal specific surface area of ​​the weakly acidic MWW molecular sieve measured by BET is 186 m 2 / g, external specific surface area is 104m 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 tetracoordinated Al content of the weakly acidic MWW molecular sieve is 78%.

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

[0198] It can be seen from the results of the embodiments and comparative examples that the weakly acidic MWW molecular sieve having a high proportion of tetracoordinated aluminum and a small amount of strong acid in the present invention is used as a catalyst for preparing aromatic compounds from furan compounds and ethylene, which not only has a good conversion rate of furan compounds, but also has a conversion rate of aromatic compounds.

[0199] 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 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 of 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%, preferably 500-1500%; and / or The value of A is not less than 60%, preferably not less than 75%; and / or The value of B is not more than 20%, preferably not more than 15%, and more preferably 5-15%.

3. The MWW molecular sieve according to claim 1 or 2, wherein: The total acid content of the MWW molecular sieve is 300-800 μmol / g, preferably 400-700 μmol / g, and more preferably 500-600 μmol / g; and / or The Si / Al molar ratio of the MWW molecular sieve is 25-180, preferably 30-100; and / or The Lewis / The ratio is greater than 2:

1.

4. The MWW molecular sieve according to any one of claims 1 to 3, 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, Sn, preferably Ga and / or Sn; Preferably, the MWW molecular sieve is selected from metal heteroatom M doped MWW molecular sieve; More preferably, the Si / M molar ratio of the metal heteroatom M doped MWW molecular sieve is 20-100, preferably 30-70; and / or The MWW molecular sieve is at least one selected from MCM molecular sieves, ITQ molecular sieves, and SCM molecular sieves, preferably SCM molecular sieves; Preferably, the SCM type molecular sieve is SCM-1 molecular sieve and / or SCM-2 molecular sieve.

5. The MWW molecular sieve according to any one of claims 1 to 4, wherein: The internal specific surface area of ​​the MWW molecular sieve is 150-400m 2 / g, preferably 200-400m 2 / g; and / or The external specific surface area of ​​the MWW molecular sieve is 50-200m 2 / g, preferably 100-200m 2 / g.

6. A method for preparing the MWW molecular sieve according to any one of claims 1 to 5, characterized in that: The preparation method comprises: (1) subjecting hydrogen-type MWW molecular sieve raw powder to water vapor hydrothermal treatment; (2) Dealumination of the pickled part.

7. The preparation method according to claim 6, wherein: Controlling the hydrothermal treatment conditions so that after the steam hydrothermal treatment, the proportion of tetracoordinated Al is not less than 60%, preferably not less than 75%; Preferably, the conditions of the water vapor hydrothermal treatment include: in an inert gas atmosphere; and / or The water vapor partial pressure is 10-100%, preferably 30-70%; and / or The treatment temperature is 600-900°C, preferably 700-800°C; and / or The treatment time is 1-72 hours, preferably 6-12 hours.

8. The preparation method according to claim 6 or 7, wherein: The preparation method further comprises: contacting a metal M salt with a molecular sieve obtained after acid washing and partial dealumination, and then calcining; the metal M in the metal M salt is selected from at least one of Ti, Zr, Nb, Ta, W, Ga, and Sn, preferably Ga and / or Sn; Preferably, the molar ratio of Si in the molecular sieve obtained after the acid-washed partial dealumination to the metal M in the metal M salt is 20-100, preferably 30-70; and / or The contacting comprises dynamic contacting, preferably mechanical grinding.

9. The preparation method according to any one of claims 6 to 8, wherein: In step (2), the end point of the acid-washed partial dealumination is: the Si / Al ratio of the molecular sieve after the acid-washed partial dealumination is 25-180, preferably 30-100; Preferably, in step (2), the acid solution used for pickling is selected from one or more of hydrochloric acid solution, oxalic acid solution, nitric acid solution, sulfuric acid solution and phosphoric acid solution, preferably nitric acid solution; and / or In step (2), the conditions for dealumination of the pickling portion include: Elution temperature room temperature - 120 ° C; and / or The elution time is greater than 10 h, preferably 12-48 h.

10. Use of the MWW molecular sieve according to any one of claims 1 to 5 in the preparation of aromatic compounds from furan compounds and ethylene.

11. A method for preparing an aromatic compound, characterized in that: The preparation method comprises: Using the MWW molecular sieve described in any one of claims 1 to 5 as the active component of the catalyst, a material containing furanic compounds is subjected to a Diels-Alder addition and subsequent dehydration reaction in the presence of the catalyst and in an ethylene atmosphere.

12. The preparation method according to claim 11, wherein The furan compound is selected from at least one of furan, 2-methylfuran and 2,5-dimethylfuran; and / or The material containing furanic compounds contains an organic solvent, preferably the organic solvent is selected from one or more of n-hexane, cyclohexane, n-heptane, n-octane and tetrahydrofuran; and / or The mass concentration of furan compounds in the material containing furan compounds is greater than 5%; and / or The mass ratio of the furan compound to the catalyst is (5-50):1, preferably (5-8):1; and / or The pressure of ethylene is 1-6MPa, preferably 2-4MPa; and / or The conditions for the post-Diels-Alder addition dehydration reaction include: a reaction temperature of 200-300° C., preferably 230-280° C.; and / or a reaction time of 3-24 h, preferably 6-12 h.

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