ZSM-5 composite molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a ZSM-5 composite molecular sieve as well as a preparation method and application thereof. The ZSM-5 composite molecular sieve comprises an inner core containing an MxOy-ZSM-5 molecular sieve and a shell layer containing a ZSM-5 molecular sieve, the silica-alumina ratio a of the MxOy-ZSM-5 molecular sieve in the inner core is smaller than or equal to 100, the silica-alumina ratio b of the ZSM-5 molecular sieve in the shell layer is larger than 100, and M is selected from one or more of divalent metal elements, trivalent metal elements and pentavalent nonmetal elements. The ZSM-5 composite molecular sieve disclosed by the invention shows relatively high total aromatic yield and stability.

Description

Technical Field

[0001] The invention relates to the field of porous materials, and in particular to a ZSM-5 composite molecular sieve and a preparation method and application thereof. Background Art

[0002] Aromatics are important basic organic chemical raw materials. At present, aromatics mainly come from catalytic reforming and steam cracking by-product pyrolysis gasoline (nearly 90%) - the oil route, and only about 10% comes from the coal route. From the perspective of energy distribution, my country lacks oil and gas but is rich in coal. Therefore, it is imperative to develop new technologies to replace the oil route to produce aromatics. Direct conversion of abundant coal-based methanol to produce aromatics is of strategic significance for increasing the added value of methanol downstream products and extending the coal chemical and natural gas chemical industry chain.

[0003] CN106607074B reports a fluidized bed catalyst for producing aromatics and propylene from oxygen-containing compounds. The molecular sieve of the catalyst is a physical mixture of oxides such as ZnO, P2O5, La2O3 and active components (two ZSM-5 molecular sieves with different silicon-aluminum ratios). There is almost no interaction between the two ZSM-5 molecular sieves with different silicon-aluminum ratios, and a considerable amount of propylene is produced as a by-product in the aromatics preparation reaction catalyzed by the catalyst, which reduces the yield of total aromatics in the product to a certain extent.

[0004] Oxygen-containing compound or alkane aromatization catalysts are prone to skeleton dealumination during the reaction or regeneration process under high temperature hydrothermal conditions, resulting in decreased catalyst activity. At the same time, the outer surface of the unmodified catalyst often leads to carbon deposition or side reactions such as disproportionation and alkylation to generate heavy aromatics, which results in a decrease in the total aromatic yield of the catalyst and poor stability. Summary of the invention

[0005] In order to solve one of the above technical problems existing in the prior art, the present invention provides a ZSM-5 composite molecular sieve with a core-shell structure and a preparation method and application thereof. The core phase of the composite molecular sieve of the present application contains an oxide-modified MxOy-ZSM-5 molecular sieve with a low silicon-aluminum ratio, and the shell layer contains an unmodified ZSM-5 molecular sieve with a high silicon-aluminum ratio. When the composite molecular sieve of the present invention is used as a catalyst in the aromatization process, the total aromatic yield and stability are significantly better than those of existing catalysts.

[0006] The technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a ZSM-5 composite molecular sieve, comprising an inner core containing an MxOy-ZSM-5 molecular sieve and a shell layer containing a ZSM-5 molecular sieve, wherein the silicon-to-aluminum ratio a of the MxOy-ZSM-5 molecular sieve in the inner core is ≤100, the silicon-to-aluminum ratio b of the ZSM-5 molecular sieve in the shell layer is >100, and M is selected from one or more of divalent metal elements, trivalent metal elements, and pentavalent non-metal elements.

[0008] The ZSM-5 composite molecular sieve of the present invention has a shell layer made of a ZSM-5 molecular sieve with a high silicon-aluminum ratio (>100), which can inhibit the occurrence of side reactions such as carbon deposition during aromatization.

[0009] In the core of the ZSM-5 composite molecular sieve of the present invention, the silicon-aluminum molar ratio a of the MxOy-ZSM-5 molecular sieve satisfies: 0<a≤100, for example, a can be 5, 10, 15, 20, 30, 40, 50, 60, 70, 75, 80, 90, 100 or any value therebetween. Preferably, 10≤a≤100. More preferably, 15≤a≤75.

[0010] In some embodiments, the content of MxOy in the MxOy-ZSM-5 molecular sieve is 0.1-8wt%, for example, it can be 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt% or any value therebetween.

[0011] In some embodiments, the composition of the MxOy-ZSM-5 molecular sieve is: 3-5 wt% MxOy: 1-10 wt% Al2O3: 85-95 wt% SiO2.

[0012] In some embodiments, in the shell layer of the ZSM-5 composite molecular sieve, the silicon-aluminum molar ratio b of the ZSM-5 molecular sieve satisfies: 100<b≤600, for example, b can be 101, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600 or any value therebetween. Preferably, 150≤b≤550, more preferably, 150≤b≤450.

[0013] In some embodiments, the ZSM-5 molecular sieve in the shell accounts for 10-50% of the total mass of the composite molecular sieve, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50% or any value therebetween.

[0014] In some embodiments, the content of M element in the shell layer is no more than 0.5 wt %. In some embodiments, the content of M element in the shell layer is zero.

[0015] In some embodiments, the MxOy-ZSM-5 molecular sieve in the inner core accounts for 50-90% of the total mass of the composite molecular sieve, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or any value therebetween.

[0016] In some embodiments, M is selected from one or more of Zn, Ga, P or La. In some preferred embodiments, M is selected from Zn and P.

[0017] In some embodiments, the ZSM-5 composite molecular sieve includes an inner core containing ZnO-P2O5-ZSM-5 molecular sieve and a shell containing ZSM-5 molecular sieve.

[0018] In some embodiments, the composition of the ZnO-P2O5-ZSM-5 molecular sieve in the inner core is: 1.5-2.5wt% ZnO: 1.5-2.5wt% P2O5: 1-10wt% Al2O3: 85-95wt% SiO2.

[0019] In a second aspect, the present invention provides a method for preparing the ZSM-5 composite molecular sieve described in the first aspect, comprising the following steps:

[0020] (1) subjecting a mixture I containing a first silicon source, a first template R1, a first aluminum source, an M source and water to a first crystallization reaction to obtain an MxOy-ZSM-5 molecular sieve;

[0021] (2) Mixing a mixture II containing a second silicon source, a second template R2, a second aluminum source and water with the MxOy-ZSM-5 molecular sieve obtained in step (1) and performing a second crystallization reaction to obtain a ZSM-5 composite molecular sieve.

[0022] In some embodiments, the silicon to aluminum ratio of the mixture II is greater than the silicon to aluminum ratio of the mixture I.

[0023] Since the silicon-aluminum ratio of the synthesized product molecular sieve is slightly lower than the silicon-aluminum ratio in the feed solution, the silicon-aluminum ratio in the feed solution is usually 10-20% higher than the silicon-aluminum ratio of the molecular sieve to be synthesized.

[0024] In some embodiments, in the mixture I, the molar ratio of the first silicon source calculated as silicon oxide to the first aluminum source calculated as aluminum oxide is less than or equal to 120, preferably less than or equal to 110, and more preferably less than or equal to 100.

[0025] In some embodiments, in the mixture I, the molar ratio of the first silicon source calculated as silicon oxide to the first aluminum source calculated as aluminum oxide is 10:(0.1-1.0), for example 10:0.1, 10:0.2, 10:0.3, 10:0.4, 10:0.5, 10:0.6, 10:0.7, 10:0.8, 10:0.9, 10:1.0 or any value therebetween.

[0026] In some embodiments, in the mixture II, the molar ratio of the second silicon source calculated as silicon oxide to the second aluminum source calculated as aluminum oxide is greater than 100, preferably greater than 100 and less than or equal to 600. In some embodiments, in the mixture II, the molar ratio of the second silicon source calculated as silicon oxide to the second aluminum source calculated as aluminum oxide is greater than 120 and less than or equal to 600.

[0027] In some embodiments, in the mixture II, the molar ratio of the second silicon source calculated as silicon oxide to the second aluminum source calculated as aluminum oxide is 10:(0.0167-0.099), for example, 10:0.0167, 10:0.02, 10:0.03, 10:0.04, 10:0.05, 10:0.06, 10:0.07, 10:0.08, 10:0.09, 10:0.099 or any value therebetween.

[0028] In some preferred embodiments, in the mixture II, the molar ratio of the second silicon source calculated as silicon oxide to the second aluminum source calculated as aluminum oxide is 10:(0.02-0.099).

[0029] In some embodiments, the first silicon source and the second silicon source are the same or different, and are each independently selected from at least one of silica sol, white carbon black, water glass, solid silica gel, amorphous silica, diatomaceous earth, zeolite molecular sieve and tetraalkoxysilane.

[0030] In some embodiments, the first template R1 and the second template R2 are the same or different, and are each independently selected from at least one of ethylenediamine, hexamethylenediamine, tetrapropylammonium hydroxide (TPAOH), tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide or tetrabutylammonium hydroxide.

[0031] In some embodiments, the first aluminum source and the second aluminum source are the same or different and are each independently selected from at least one of aluminum sulfate, sodium aluminate, aluminum nitrate, aluminum chloride, pseudo-boehmite, aluminum oxide, aluminum hydroxide, aluminum isopropoxide, and aluminum acetate.

[0032] In some embodiments, the M source is selected from one or more of zinc nitrate, zinc sulfate, zinc chloride, phosphoric acid, calcium nitrate, calcium chloride, and lanthanum nitrate. In some preferred embodiments, the M source is selected from phosphoric acid and at least one of zinc nitrate, zinc sulfate, and zinc chloride.

[0033] In some embodiments, in step (1), in the mixture I, the molar ratio of SiO2:R1:Al2O3:MxOy:H2O=10:(1-10):(0.1-1.0):(0.05-0.5):(100-1000).

[0034] In some embodiments, step (1) further comprises: before the first crystallization reaction, adjusting the pH value of the mixture I to 8 to 13, preferably 10 to 13, more preferably 12 to 13. In some embodiments, the pH value of the mixture I is adjusted using TPAOH.

[0035] In some embodiments, in step (1), the temperature of the first crystallization reaction is 100 to 200° C., and the time of the first crystallization reaction is 24 to 196 hours.

[0036] In some embodiments, step (1) further comprises: drying the reaction product after crystallization in the step (1) (preferably drying at 60-150°C) and removing the template agent without calcination to obtain an MxOy-ZSM-5 molecular sieve containing the template agent. It should be noted that in step (1) of the present invention, the MxOy-ZSM-5 molecular sieve obtained when the product is dried but not calcined at high temperature (200-700°C) to remove the template agent has a better total aromatic yield when catalyzing the reaction of preparing aromatic hydrocarbons. By adopting the method of not removing the template agent, in the second crystallization process, the modifying element M introduced into the molecular sieve through the first crystallization can be enclosed in the molecular sieve skeleton or pores obtained after the first crystallization. If the conventional first crystallization is followed by calcination to remove the template agent, in the second crystallization process, due to the etching effect under alkaline medium conditions, and the pores of the molecular sieve are completely unobstructed, the modifying element M introduced into the molecular sieve by the first crystallization may partially enter the shell layer of the molecular sieve obtained by the second crystallization, affecting the total aromatic yield to a certain extent.

[0037] In some embodiments, in step (2), in the mixture II, the molar ratio of SiO2:Al2O3:R2:H2O=10:(0.02-0.099):(1-10):(100-1000).

[0038] In some embodiments, step (1) further comprises: first adjusting the pH value of the mixture II to 8 to 13, preferably 10 to 13, more preferably 12 to 13, and then mixing the mixture II with the MxOy-ZSM-5 molecular sieve obtained in step (1) to perform a second crystallization reaction. In some embodiments, TPAOH is used to adjust the pH value of the mixture II.

[0039] In some embodiments, in step (2), the mixture II is mixed with the MxOy-ZSM-5 molecular sieve obtained in step (1) at a liquid-to-solid ratio of 1.25 to 20.

[0040] In some embodiments, in step (2), the temperature of the second crystallization reaction is 100 to 200° C., and the time of the second crystallization reaction is 24 to 196 hours.

[0041] In some embodiments, the method further comprises step (3): calcining the ZSM-5 composite molecular sieve prepared in step (2). Preferably, the calcination temperature in step (3) is 200-700°C.

[0042] In a third aspect, the present invention provides an aromatization catalyst, which comprises an active component and an optional matrix, wherein the active component comprises the ZSM-5 composite molecular sieve described in the first aspect of the present invention.

[0043] In some embodiments, the matrix includes at least one of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, and clay.

[0044] In some embodiments, the mass percentage of the ZSM-5 composite molecular sieve in the aromatization catalyst is 40-100%. In some embodiments, the mass percentage of the matrix in the aromatization catalyst is 0-60%.

[0045] In some embodiments, the aromatization catalyst comprises, by weight: 40-100 parts of ZSM-5 composite molecular sieve and 0-60 parts of matrix.

[0046] In some embodiments, the catalyst comprises, by weight percentage, 3-5% MxOy: 1-10% Al2O3: 85-95% SiO2, wherein M is selected from one or more of divalent metal elements, trivalent metal elements, and pentavalent non-metal elements.

[0047] In some embodiments, the catalyst comprises, by weight percentage, 3-5% MxOy: 1-10% Al2O3: 85-95% SiO2, wherein M is selected from one or more of Zn, Ga, P or La.

[0048] In some embodiments, the catalyst comprises, by weight percentage, 1.5-2.5% ZnO: 1.5-2.5% P2O5: 1-10% Al2O3: 85-95% SiO2.

[0049] In a fourth aspect, the present invention provides use of the ZSM-5 composite molecular sieve described in the first aspect, or the ZSM-5 composite molecular sieve prepared by the method described in the second aspect, or the aromatization catalyst described in the third aspect in an aromatics production reaction.

[0050] In some embodiments, the feedstock for the aromatics production reaction includes oxygen-containing compounds such as formaldehyde or hydrocarbon compounds.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. The ZSM-5 composite molecular sieve of the present invention has a MxOy-ZSM-5 molecular sieve with a lower silicon-aluminum ratio (≤100) as the core phase and a ZSM-5 molecular sieve with a higher silicon-aluminum ratio (>100) as the shell phase. When used in the aromatization process, it shows a higher total aromatic yield and stability.

[0053] 2. The method for preparing the ZSM-5 composite molecular sieve of the present invention first synthesizes an oxide-modified MxOy-ZSM-5 molecular sieve base core with a low silicon-to-aluminum ratio by a one-step method, and then wraps a layer of high-silicon ZSM-5 molecular sieve on the base core without undergoing a calcination process (without removing the template agent in the base core). The shell layer of the molecular sieve contains almost no doping element M. Compared with the composite molecular sieve prepared by the existing impregnation method, the total aromatic yield and stability are more significant. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to constitute any limitation to the present invention.

[0055] Unless otherwise specified, the "silicon to aluminum ratio" of the molecular sieve described herein refers to the molar ratio of silicon oxide to aluminum oxide in the molecular sieve, or refers to the molar ratio of the silicon source calculated as silicon oxide to the aluminum source calculated as aluminum oxide in the mixed liquid.

[0056] The "total aromatics yield (carbon basis)" of the catalyst described herein is defined as the ratio of the total mass of aromatic products in the aromatization product excluding water generated by the reaction to the weight of all hydrocarbons excluding water in the product.

[0057] The "stability" of the catalyst described in this article is expressed by the total aromatic retention rate, which is defined as the ratio of the total aromatic yield of the catalyst after 100 hours of reaction with methanol as the raw material to the total aromatic yield of the fresh catalyst (reaction time 2 hours).

[0058] The surface element distribution of the catalyst described in this article was characterized by X-ray photoemission spectroscopy XPS.

[0059] Example 1

[0060] (1) 15000 g of silica sol (40 wt% SiO2), 600 g of ethylenediamine, 1501 g of aluminum nitrate nonahydrate, 441.9 g of zinc nitrate hexahydrate, 173.0 g of phosphoric acid (85 wt%) and 62140 g of water were mixed at room temperature in a molar ratio of 10SiO2: 1.0 ethylenediamine: 0.20Al2O3: 0.15ZnO: 0.075P2O5: 400H2O, and the pH value was adjusted to 12.5 to obtain a feed solution I. The feed solution I was crystallized at 170°C for 48 h, washed, and dried at 120°C for 12 h to obtain a ZnO-P2O5-ZSM-5 molecular sieve having a composition of 2.04 wt% ZnO: 1.88 wt% P2O5: 3.47 wt% Al2O3: 92.61 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 45.4).

[0061] (2) 600.6 g of white carbon black (99.9% SiO2), 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate nonahydrate and 6292 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.025 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0062] (3) 100 g of ZnO-P2O5-ZSM-5 molecular sieve was mixed with 160 g of liquid II, and then crystallized at 170 °C for 36 h to obtain a core-shell type ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve;

[0063] XPS test results show that, in weight percentage, the contents of Zn and P elements on the surface of the ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve are 0.02wt% and 0.01wt%, respectively.

[0064] (4) The ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve obtained in step (3) was washed and calcined at 550°C to obtain 110.5 grams of molecular sieve catalyst a, whose chemical composition is: 1.85wt% ZnO: 1.70wt% P2O5: 3.19wt% Al2O3: 93.27wt% SiO2 (see Table 1).

[0065] Example 2

[0066] (1) 1500 g of silica sol (40 wt% SiO2), 60 g of ethylenediamine, 300.16 g of aluminum nitrate nonahydrate, 44.19 g of zinc nitrate hexahydrate, 17.30 g of phosphoric acid (85 wt%) and 6149 g of water were mixed at room temperature in a molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.40 Al2O3: 0.15 ZnO: 0.075 P2O5: 400 H2O, and the pH value was adjusted to 12.5 to obtain liquid I. Liquid I was crystallized at 170° C. for 48 h, washed, and dried at 120° C. for 12 h to obtain a ZnO-P2O5-ZSM-5 molecular sieve having a composition of 2.06 wt% ZnO: 1.86 wt% P2O5: 7.32 wt% Al2O3: 88.76 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 20.6).

[0067] (2) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate nonahydrate and 6292 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.025 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0068] (3) 100 g of ZnO-P2O5-ZSM-5 molecular sieve was mixed with 160 g of liquid II, and then crystallized at 170 °C for 36 h to obtain a core-shell type ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve;

[0069] XPS test results show that, in weight percentage, the contents of Zn and P elements on the surface of the ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve are 0.01wt% and 0.03wt%, respectively.

[0070] (4) The ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve obtained in step (3) was washed and calcined at 550°C to obtain 110.3 grams of molecular sieve catalyst b, whose chemical composition is 1.83wt% ZnO: 1.71wt% P2O5: 6.68wt% Al2O3: 89.78wt% SiO2 (see Table 1).

[0071] Example 3

[0072] (1) 1500 g of silica sol (40 wt% SiO2), 60 g of ethylenediamine, 71.27 g of aluminum nitrate nonahydrate, 44.19 g of zinc nitrate hexahydrate, 17.30 g of phosphoric acid (85 wt%) and 6300 g of water were mixed at room temperature in a molar ratio of 10SiO2:1.0ethylenediamine:0.095Al2O3:0.15ZnO:0.075P2O5:400H2O, and the pH value was adjusted to 12.5 to obtain liquid I. After the liquid I was crystallized at 170°C for 48 hours, it was washed and dried at 120°C for 12 hours to obtain a ZnO-P2O5-ZSM-5 molecular sieve with a composition of 2.03wt% ZnO: 1.87wt% P2O5: 1.67wt% Al2O3: 94.43wt% SiO2, which can also be written as 2.03wt% ZnO: 1.87wt% P2O5: 96.10wt% ZSM-5 (the molar ratio of silicon oxide to aluminum oxide is 96.2).

[0073] (2) 600 g of white carbon black, 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate and 6292 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.025 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0074] (3) 100 g of ZnO-P2O5-ZSM-5 molecular sieve was mixed with 160 g of liquid II and crystallized at 170 °C for 36 h to obtain a core-shell ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve; XPS test results showed that, in weight percentage, the surface Zn and P element contents of the ZSM-5@MxOy-ZSM-5 composite molecular sieve were 0.02 wt% and 0.03 wt%, respectively.

[0075] (4) The ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve obtained in step (3) was washed and calcined at 550°C to obtain 110.6 grams of molecular sieve catalyst c, whose chemical composition is 1.84wt% ZnO: 1.69wt% P2O5: 1.55wt% Al2O3: 94.92wt% SiO2 (see Table 1).

[0076] Example 4

[0077] (1) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 22.56 g of aluminum nitrate nonahydrate and 6290 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.056 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0078] (2) 100 g of the ZnO-P2O5-ZSM-5 molecular sieve prepared in step (1) of Example 1 was mixed with 160 g of liquid II and crystallized at 170°C for 36 h to obtain a core-shell ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve; XPS test results showed that, in weight percentage, the surface Zn and P element contents of the ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve were 0.03 wt% and 0.01 wt%, respectively.

[0079] (3) The ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve obtained in step (3) was washed and calcined at 550°C to obtain 110.2 grams of molecular sieve catalyst a, whose chemical composition is 1.87% ZnO: 1.68% P2O5: 3.22% Al2O3: 93.23% SiO2 (see Table 1).

[0080] Example 5

[0081] (1) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 13.53 g of aluminum nitrate nonahydrate and 6294 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.018 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0082] (2) 100 g of the ZnO-P2O5-ZSM-5 molecular sieve prepared in step (1) of Example 1 was mixed with 160 g of liquid II and crystallized at 170°C for 36 h to obtain a core-shell ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve; XPS test results showed that, in terms of weight percentage, the surface Zn and P element contents of the ZSM-5@MxOy-ZSM-5 composite molecular sieve were 0 and 0.03 wt%, respectively.

[0083] (4) The ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve obtained in step (3) was washed and calcined at 550°C to obtain 110.4 grams of molecular sieve catalyst d, whose chemical composition is 1.85wt% ZnO: 1.68wt% P2O5: 3.17wt% Al2O3: 93.31wt% SiO2 (see Table 1).

[0084] Comparative Example 1

[0085] Different from Example 1, the ZnO and P2O5 components are not introduced during the synthesis of the core phase ZSM-5 molecular sieve, but after the composite ZSM-5 molecular sieve is synthesized, ZnO and P2O5 are loaded by impregnation. The specific preparation process is as follows:

[0086] (1) 1500 g of silica sol (40 wt% SiO2), 60 g of ethylenediamine, 150.1 g of aluminum nitrate nonahydrate, and 6235 g of water were mixed at room temperature in a molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.20 Al2O3: 400 H2O, and the pH value was adjusted to 12.5 to obtain liquid I. Liquid I was crystallized at 170° C. for 48 h, washed, and dried at 120° C. for 12 h to obtain ZSM-5 / A molecular sieve, the composition of which was 3.60 wt% Al2O3: 96.40 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 45.5).

[0087] (2) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate nonahydrate and 6292 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.025 Al2O3:1.5 template:350 H2O, and the pH value was adjusted to 12.5 to obtain a mixture II.

[0088] (3) 100 g of ZSM-5 / A was mixed with 160 g of liquid II, and then crystallized at 170°C for 36 h to obtain a ZSM-5 composite molecular sieve. After washing and calcination at 550°C for 6 h, 110.4 g of ZSM-5 / B molecular sieve was obtained. The chemical composition of the molecular sieve was 3.31 wt% Al2O3: 96.69 wt% SiO2.

[0089] (4) 93.27 g of ZSM-5 / B molecular sieve was impregnated with 80 g of a solution containing 6.73 g of zinc nitrate hexahydrate and 2.76 g of phosphoric acid (85 wt%), aged at room temperature for 6 hours, then dried at 120° C. for 12 hours, and calcined at 550° C. for 6 hours to obtain catalyst x, the chemical composition of which was 1.85 wt% ZnO: 1.70 wt% P2O5: 3.19 wt% Al2O3: 93.27 wt% SiO2. XPS test results showed that, in terms of weight percentage, the surface Zn and P contents of catalyst x were 5.71 wt% and 3.45 wt%, respectively. The composition of catalyst x is listed in Table 1.

[0090] Comparative Example 2

[0091] Different from Example 1, the outer layer of the ZnO-P2O5-ZSM-5 molecular sieve particles obtained in Example 1 is not covered with a layer of ZSM-5 molecular sieve with a high silicon-aluminum ratio. The specific preparation process is as follows:

[0092] 1500 g silica sol (40 wt% SiO2), 60 g ethylenediamine, 150.1 g aluminum nitrate nonahydrate, 44.19 g zinc nitrate hexahydrate, 17.30 g phosphoric acid (85 wt%) and 6214 g water were mixed at room temperature according to the molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.20 Al2O3: 0.15 ZnO: 0.075 P2O5: 400 H2O, and the pH value was adjusted to 12.5 to obtain liquid I. Liquid I was crystallized at 170°C for 48 h, washed, and dried at 120°C for 12 h to obtain ZnO-P2O5-ZSM-5 molecular sieve, with a composition of 2.04 wt% ZnO: 1.88 wt% P2O5: 3.47 wt% Al2O3: 92.61 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 45.4). Catalyst y was obtained by calcining ZnO-P2O5-ZSM-5 molecular sieve at 550°C for 6h. XPS test results showed that the content of Zn and P elements on the surface of catalyst y was 3.57wt% and 3.32wt% respectively in weight percentage. The composition of catalyst y is listed in Table 1.

[0093] Comparative Example 3

[0094] The difference from Example 1 is that after preparing MxOy-ZSM-5 in step (1), the template agent is first removed by high-temperature calcination, and then a layer of ZSM-5 molecular sieve is covered on the outer layer of the MxOy-ZSM-5 molecular sieve particles after the template agent is removed by a synthesis method. The specific preparation process is as follows:

[0095] (1) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate nonahydrate and 6292 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.025 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0096] (2) 100 g of the ZnO-P2O5-ZSM-5 molecular sieve prepared in step (1) of Example 1 was mixed with 160 g of liquid II and crystallized at 170° C. for 36 h to obtain a core-shell ZSM-5@ZnO-P2O5-ZSM-5 composite molecular sieve.

[0097] (3) The ZSM-5@ZnO-P2O5-ZSM-5 composite molecular sieve of step (3) was washed with distilled water for 3 times, dried at 120°C for 12h and calcined at 550°C for 6h to obtain 110.8g of catalyst z, whose chemical composition was 1.80wt% ZnO: 1.62wt% P2O5: 3.19wt% Al2O3: 93.38wt% SiO2. XPS test results showed that the surface Zn and P elements of catalyst z were 3.06wt% and 2.71wt% respectively in weight percentage. The composition of catalyst z is listed in Table 1.

[0098] Comparative Example 4

[0099] The difference from Example 1 is that the supported ZnO-P2O5-ZSM-5 is first prepared by an impregnation method, and then a layer of high-silicon ZSM-5 molecular sieve is covered on the outer surface of the ZnO-P2O5-ZSM-5 molecular sieve by a synthesis method to prepare the catalyst. The specific preparation process is as follows:

[0100] (1) 1500 g of silica sol (40 wt% SiO2), 60 g of ethylenediamine, 150.1 g of aluminum nitrate nonahydrate, and 6235 g of water were mixed at room temperature in a molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.20 Al2O3: 400 H2O, and the pH value was adjusted to 12.5 to obtain liquid I. Liquid I was crystallized at 170° C. for 48 h, washed, and dried at 120° C. for 12 h to obtain a ZSM-5 / D molecular sieve having a composition of 3.60 wt% Al2O3: 96.40 wt% SiO2 (a molar ratio of silicon oxide to aluminum oxide was 45.5).

[0101] (2) 95.99 g of ZSM-5 / D molecular sieve was impregnated with 85 g of a mixture containing 9.42 g of zinc nitrate hexahydrate and 3.05 g of phosphoric acid (85 wt%), aged at room temperature for 6 h, then dried at 120°C for 12 h, and calcined at 550°C for 6 h to obtain molecular sieve K. The chemical composition of K is: 2.04 wt% ZnO: 1.88 wt% P2O5: 3.46 wt% Al2O3: 92.62 wt% SiO2.

[0102] (3) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate nonahydrate and 6292 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.025 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0103] (4) 100.1 g of molecular sieve K was mixed with 160 g of liquid II and crystallized at 170°C for 36 h to obtain a ZSM-5@ZnO-P2O5-ZSM-5 composite molecular sieve. After washing and calcination, 110.6 g of catalyst u was obtained, and its chemical composition was 1.7wt8% ZnO: 1.64wt% P2O5: 3.19wt% Al2O3: 93.39wt% SiO2. XPS test results showed that the surface Zn and P elements of catalyst u were 2.98wt% and 2.65wt% respectively in weight percentage. The composition of catalyst u is listed in Table 1.

[0104] Comparative Example 5

[0105] The difference from Example 1 is that the surface of the ZnO-P2O5-ZSM-5 molecular sieve is covered with a ZSM-5 molecular sieve with a silicon-aluminum ratio of less than 100.

[0106] (1) 1500 g of silica sol (40 wt% SiO2), 60 g of ethylenediamine, 150.1 g of aluminum nitrate nonahydrate, 44.19 g of zinc nitrate hexahydrate, 17.30 g of phosphoric acid (85 wt%) and 6214 g of water were mixed at room temperature in a molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.20 Al2O3: 0.15 ZnO: 0.075 P2O5: 400 H2O, and the pH value was adjusted to 12.5 to obtain a feed solution I. The feed solution I was crystallized at 170° C. for 48 h, washed, and dried at 120° C. for 12 h to obtain a ZnO-P2O5-ZSM-5 molecular sieve having a composition of 2.04 wt% ZnO: 1.88 wt% P2O5: 3.47 wt% Al2O3: 92.61 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 45.4).

[0107] (2) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 78.79 g of aluminum nitrate nonahydrate and 6266 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.105 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0108] (3) 100 g of ZnO-P2O5-ZSM-5 molecular sieve was mixed with 160 g of liquid II, and crystallized at 170°C for 36 h to obtain ZSM-5@ZnO-P2O5-ZSM-5 composite molecular sieve; after washing and calcination, 110.5 g of catalyst v was obtained, and its chemical composition was 1.85 wt% ZnO: 1.70 wt% P2O5: 3.31 wt% Al2O3: 93.15 wt% SiO2. XPS test results show that the surface Zn and P content of catalyst v are 0.01 wt% and 0.04 wt% respectively in weight percentage. The composition of catalyst v is listed in Table 1.

[0109] Comparative Example 6

[0110] Different from Example 1, ZnO and P2O5 components are not introduced during the synthesis of the low silicon-aluminum ratio ZSM-5 molecular sieve, and the high silicon-aluminum ratio ZSM-5 shell is not wrapped in the outer layer of the low silicon-aluminum ratio ZSM-5, but ZnO and P2O5 are directly loaded by impregnation after the low silicon-aluminum ratio ZSM-5 molecular sieve is synthesized, wherein the feed composition of the low silicon-aluminum ratio molecular sieve is the same as that of Example 1, and the loading amount of the ZnO and P2O5 modified components on the catalyst is the same as that of Example 1. The specific preparation process is as follows:

[0111] (1) 1500 g of silica sol (40 wt% SiO2), 60 g of ethylenediamine, 150.1 g of aluminum nitrate nonahydrate, and 6235 g of water were mixed at room temperature in a molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.20 Al2O3: 400 H2O, and the pH value was adjusted to 12.5 to obtain liquid I. Liquid I was crystallized at 170° C. for 48 h, washed, and dried at 120° C. for 12 h to obtain a ZSM-5 / D molecular sieve having a composition of 3.60 wt% Al2O3: 96.40 wt% SiO2 (a molar ratio of silicon oxide to aluminum oxide was 45.5).

[0112] (2) 96.38 g of ZSM-5 molecular sieve was impregnated with 84 g of an aqueous solution containing 6.73 g of zinc nitrate hexahydrate and 2.76 g of phosphoric acid (85 wt%), aged at room temperature for 6 hours, dried at 120° C. for 12 hours, and calcined at 550° C. for 6 hours to obtain catalyst w1, which had a composition of 1.85 wt% ZnO: 1.70 wt% P2O5: 3.47 wt% Al2O3: 92.98 wt% SiO2. XPS test results showed that, in terms of weight percentage, the surface Zn and P elements of catalyst w1 were 5.68 wt% and 3.40 wt% respectively.

[0113] Comparative Example 7

[0114] The difference from Example 1 is that a high silicon-aluminum ratio ZSM-5 molecular sieve (silicon-aluminum ratio greater than 100) is first synthesized, and then ZnO and P2O5 are directly loaded by impregnation method, wherein the feed composition of the high silicon-aluminum ratio molecular sieve is the same as that of step (2) of Example 1, and the loading amount of ZnO and P2O5 modified components on the catalyst is the same as that of Example 1. The specific preparation process is as follows:

[0115] (1) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate nonahydrate and 6292 g of water were mixed at room temperature in a molar ratio of 10SiO2:0.025Al2O3:1.5 hexamethylenediamine:350H2O, and the pH value was adjusted to 12.5 to obtain liquid II. Liquid II was crystallized at 170°C for 36 h to obtain ZSM-5 molecular sieve. After being washed with distilled water three times, dried at 120°C for 12 h and calcined at 550°C for 6 h, a ZSM-5 molecular sieve with the template removed was obtained, whose chemical composition was 0.50 wt% Al2O3:99.50 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 338.3).

[0116] (2) 96.45 g of the ZSM-5 molecular sieve prepared in step (1) without the template was impregnated with 84 g of a solution containing 6.73 g of zinc nitrate hexahydrate and 2.76 g of phosphoric acid (85 wt%), aged at room temperature for 6 hours, dried at 120° C. for 12 hours, and calcined at 550° C. for 6 hours to obtain a catalyst w2, which has a composition of 1.85 wt% ZnO: 1.70 wt% P2O5: 0.48 wt% Al2O3: 95.97 wt% SiO2. XPS test results show that, in terms of weight percentage, the surface Zn and P content of catalyst w2 are 5.75 wt% and 3.51 wt%, respectively.

[0117] Comparative Example 8

[0118] The difference from Example 1 is that the silicon-aluminum ratio of the ZnO-P2O5-ZSM-5 molecular sieve synthesized in step (1) is different, and the silicon-aluminum ratio of the feed solution II in step (2) is also different. The details are as follows:

[0119] (1) 1500 g of silica sol (40 wt% SiO2), 60 g of ethylenediamine, 18.8 g of aluminum nitrate nonahydrate, 44.19 g of zinc nitrate hexahydrate, 17.3 g of phosphoric acid (85 wt%) and 6300 g of water were mixed at room temperature in a molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.025 Al2O3: 0.15 ZnO: 0.075 P2O5: 400 H2O, and the pH value was adjusted to 12.5 to obtain liquid I. Liquid I was crystallized at 170° C. for 48 h, washed and dried at 120° C. to obtain a ZnO-P2O5-ZSM-5 molecular sieve having a composition of 2.05 wt% ZnO: 1.86 wt% P2O5: 0.48 wt% Al2O3: 95.61 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 338.6).

[0120] (2) 600 g of white carbon black, 174.3 g of hexamethylenediamine, 150.1 g of aluminum nitrate nonahydrate and 6235 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.20 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0121] (3) 100 g of ZnO-P2O5-ZSM-5 molecular sieve was mixed with 160 g of liquid II and crystallized at 170 °C for 36 h to obtain a ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve. XPS test results showed that, in weight percentage, the surface Zn and P element contents of the ZSM-5@MxOy-ZSM-5 composite molecular sieve were 0.01 wt% and 0.02 wt%, respectively.

[0122] (4) The ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve obtained in step (3) was washed and calcined to obtain 110.5 grams of molecular sieve catalyst w3, whose chemical composition is 1.86wt% ZnO: 1.68wt% P2O5: 0.77wt% Al2O3: 96.69wt% SiO2 (see Table 1).

[0123] Comparative Example 9

[0124] The difference from Example 1 is that the silicon-aluminum ratio of the ZnO-P2O5-ZSM-5 molecular sieve synthesized in step (1) is different. Specifically, as follows:

[0125] (1) 1500 g silica sol (40 wt% SiO2), 60 g ethylenediamine, 37.52 g aluminum nitrate nonahydrate, 44.19 g zinc nitrate hexahydrate, 17.3 g phosphoric acid (85 wt%) and 6271 g water were mixed at room temperature in a molar ratio of 10 SiO2: 1.0 ethylenediamine: 0.05 Al2O3: 0.15 ZnO: 0.075 P2O5: 400 H2O, and the pH value was adjusted to 12.5 to obtain liquid I. Liquid I was crystallized at 170° C. for 48 h, washed, and dried at 120° C. to obtain a ZnO-P2O5-ZSM-5 molecular sieve having a composition of 2.03 wt% ZnO: 1.90 wt% P2O5: 0.87 wt% Al2O3: 95.20 wt% SiO2 (the molar ratio of silicon oxide to aluminum oxide was 186).

[0126] (2) 600.6 g of white carbon black, 174.3 g of hexamethylenediamine, 18.8 g of aluminum nitrate and 6292 g of water were mixed at room temperature in a molar ratio of 10 SiO2:0.025 Al2O3:1.5 hexamethylenediamine:350 H2O, and the pH value was adjusted to 12.5 to obtain liquid II.

[0127] (3) 100 g of ZnO-P2O5-ZSM-5 molecular sieve was mixed with 160 g of liquid II and crystallized at 170 °C for 36 h to obtain a ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve. XPS test results showed that, in weight percentage, the surface Zn and P element contents of the ZSM-5@MxOy-ZSM-5 composite molecular sieve were 0.03 wt% and 0.02 wt%, respectively.

[0128] (4) The ZnO-P2O5-ZSM-5@ZSM-5 composite molecular sieve obtained in step (3) was washed and calcined to obtain 110.5 grams of molecular sieve catalyst w4, whose chemical composition is: 1.84wt% ZnO: 1.69wt% P2O5: 0.83wt% Al2O3: 95.61wt% SiO2 (see Table 1).

[0129] Catalytic effect evaluation of catalyst:

[0130] The catalysts in Examples 1-5 and Comparative Examples 1-9 were crushed into 20-40 mesh particles. The fixed bed was used for evaluation. The evaluation conditions were: catalyst loading 3.0 g, 480°C, 100% methanol, methanol weight space velocity 1.0 hour -1 , normal pressure 0.1MPa, the reaction results are listed in Table 2.

[0131] Table 1

[0132]

[0133]

[0134] Table 2

[0135]

[0136] As can be seen from Table 2, the present invention obtains a core phase with a lower silicon-aluminum ratio and loaded with modified elements (Zn, P, etc.) and a core-shell ZSM-5 composite molecular sieve with a higher silicon-aluminum ratio shell layer by controlling the silicon-aluminum ratio of the feed liquid I and the feed liquid II within a specific range, thereby improving the aromatics selectivity and stability of the ZSM-5 molecular sieve in the aromatization reaction. In particular, when preparing the core phase ZSM-5 molecular sieve, when the template is not removed by high-temperature calcination, the aromatization performance of the obtained core-shell ZSM-5 composite molecular sieve is more excellent.

[0137] In addition, compared with loading modifying elements (Zn, P, etc.) on the surface of ZSM-5 molecular sieve by traditional impregnation method, the present invention loads modifying elements in ZSM-5 molecular sieve by synthesis method, which can make the modifying elements more evenly distributed in the ZSM-5 molecular sieve body phase, rather than agglomerating on the surface of ZSM-5 molecular sieve, thereby improving the total aromatic yield and stability of the catalyst.

[0138] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A ZSM-5 composite molecular sieve, comprising an inner core containing an MxOy-ZSM-5 molecular sieve and a shell layer containing a ZSM-5 molecular sieve, wherein the silicon-to-aluminum ratio a of the MxOy-ZSM-5 molecular sieve in the inner core is ≤100, the silicon-to-aluminum ratio b of the ZSM-5 molecular sieve in the shell layer is >100, and M is selected from one or more of a divalent metal element, a trivalent metal element, and a pentavalent non-metal element.

2. The composite molecular sieve according to claim 1, characterized in that: 10≤a≤100, preferably, 15≤a≤75; 100<b≤600, preferably, 150≤b≤450.

3. The composite molecular sieve according to claim 1 or 2, characterized in that: The ZSM-5 molecular sieve in the shell layer accounts for 10-50% of the total mass of the composite molecular sieve; preferably, the content of the M element in the shell layer does not exceed 0.5wt%; and / or, the MxOy-ZSM-5 molecular sieve in the inner core accounts for 50-90% of the total mass of the composite molecular sieve; and / or, In the MxOy-ZSM-5 molecular sieve in the inner core, the content of MxOy is 0.1-8wt%; and / or, M is selected from one or more of Zn, Ga, P or La; preferably, M is selected from Zn and / or P.

4. A method for preparing the composite molecular sieve according to any one of claims 1 to 3, comprising the following steps: (1) subjecting a mixture I containing a first silicon source, a first template R1, a first aluminum source, an M source and water to a first crystallization reaction to obtain an MxOy-ZSM-5 molecular sieve; (2) Mixing a mixture II containing a second silicon source, a second template R2, a second aluminum source and water with the MxOy-ZSM-5 molecular sieve obtained in step (1) and performing a second crystallization reaction to obtain a ZSM-5 composite molecular sieve.

5. The method according to claim 4, characterized in that The silicon-to-aluminum ratio of the mixture II is greater than the silicon-to-aluminum ratio of the mixture I; Preferably, in the mixture I, the molar ratio of the first silicon source calculated as silicon oxide to the first aluminum source calculated as aluminum oxide is less than or equal to 120, preferably 10:(0.1-1.0); Preferably, in the mixture II, the molar ratio of the second silicon source calculated as silicon oxide to the second aluminum source calculated as aluminum oxide is greater than 100, preferably 10:(0.02-0.099); Preferably, step (1) further comprises: before performing the first crystallization reaction, adjusting the pH of the mixture I to 8 to 13, preferably 11 to 13; Preferably, step (2) further comprises: first adjusting the pH of the mixture II to 8-13, preferably 11-13, and then mixing the mixture II with the MxOy-ZSM-5 molecular sieve obtained in step (1).

6. The method according to claim 4 or 5, characterized in that: The first silicon source and the second silicon source are the same or different and are independently selected from at least one of silica sol, white carbon black, water glass, solid silica gel, amorphous silicon dioxide, diatomaceous earth and tetraalkoxysilane; and / or, The first template R1 and the second template R2 are the same or different and are independently selected from at least one of ethylenediamine, hexamethylenediamine, tetrapropylammonium hydroxide, tetraethylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide and tetrabutylammonium hydroxide; and / or, The first aluminum source and the second aluminum source are the same or different, and are independently selected from at least one of aluminum sulfate, sodium aluminate, aluminum nitrate, aluminum chloride, pseudo-boehmite, aluminum oxide, aluminum hydroxide, aluminum isopropoxide and aluminum acetate; and / or, The M source is selected from one or more of zinc nitrate, zinc sulfate, zinc chloride, phosphoric acid, calcium nitrate, calcium chloride, and lanthanum nitrate, preferably phosphoric acid and at least one selected from zinc nitrate, zinc sulfate, and zinc chloride.

7. The method according to any one of claims 4 to 6, characterized in that: In the mixture I, the molar ratio of SiO2:R1:Al2O3:MxOy:H2O=10:(1-10):(0.1-1.0):(0.05-0.5):(100-1000); and / or, The temperature of the first crystallization reaction is 100 to 200° C., and the time of the first crystallization reaction is 24 to 196 hours; and / or, In the mixture II, the molar ratio of SiO2:Al2O3:R2:H2O=10:(0.02-0.099):(1-10):(100-1000); and / or, The mixture II is mixed with the MxOy-ZSM-5 molecular sieve obtained in step (1) at a liquid-to-solid mass ratio of 1.25 to 20; and / or, The temperature of the second crystallization reaction is 100 to 200° C., and the time of the second crystallization reaction is 24 to 196 hours; Preferably, step (1) further comprises: drying the reaction product after the first crystallization and removing the template without calcination to obtain the MxOy-ZSM-5 molecular sieve. Preferably, the drying temperature is 60-150°C.

8. An aromatization catalyst comprising an active component and an optional matrix, wherein the active component comprises the ZSM-5 composite molecular sieve according to any one of claims 1 to 3 or the ZSM-5 composite molecular sieve prepared by the method according to any one of claims 4 to 7.

9. The aromatization catalyst according to claim 8, characterized in that The matrix includes at least one of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, and clay; and / or, In terms of weight percentage, the mass percentage of the ZSM-5 composite molecular sieve in the aromatization catalyst is 40-100%, and the mass percentage of the matrix in the aromatization catalyst is 0-60%; and / or, In parts by weight, the aromatization catalyst comprises: 40-100 parts of ZSM-5 composite molecular sieve, 0-60 parts of matrix; preferably, in weight percentage, the catalyst comprises 1.5-2.5% ZnO: 1.5-2.5% P2O5: 1-10% Al2O3: 85-95% SiO2.

10. Use of the ZSM-5 composite molecular sieve according to any one of claims 1 to 3, or the ZSM-5 composite molecular sieve prepared by the method according to any one of claims 4 to 7, or the aromatization catalyst according to any one of claims 8 to 9 in an aromatics production reaction; preferably, the raw materials for the aromatics production reaction include oxygen-containing compounds or hydrocarbon compounds.

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