CN111135854B - Preparation method of high-selectivity catalyst for preparing aromatic hydrocarbon from methanol and catalyst - Google Patents

Preparation method of high-selectivity catalyst for preparing aromatic hydrocarbon from methanol and catalyst Download PDF

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CN111135854B
CN111135854B CN202010054493.2A CN202010054493A CN111135854B CN 111135854 B CN111135854 B CN 111135854B CN 202010054493 A CN202010054493 A CN 202010054493A CN 111135854 B CN111135854 B CN 111135854B
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付廷俊
李忠
王玉杰
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Taiyuan University of Technology
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Abstract

The invention provides a preparation method of a catalyst for preparing aromatic hydrocarbon from high-selectivity methanol. The catalyst for preparing the aromatic hydrocarbon from the high-selectivity methanol has the particle size of 100-650nm, the silicon-aluminum molecular ratio of 25-100, the external part of the catalyst is ZSM-5 with high silicon-aluminum ratio and presents a hierarchical pore structure, and the external specific surface area is large. The catalyst obtained by the invention has simple synthesis method, and can embody excellent catalytic stability and product selectivity. The yield of liquid hydrocarbon for catalyzing methanol to prepare aromatic hydrocarbon is 19-27 wt%, wherein the selectivity of the aromatic hydrocarbon reaches 65-90%, and the reaction life is 1.5-3 times of that of a conventional catalyst.

Description

Preparation method of high-selectivity catalyst for preparing aromatic hydrocarbon from methanol and catalyst
Technical Field
The invention belongs to the technical field of aromatic hydrocarbon preparation from coal, and particularly relates to a high-selectivity catalyst for preparing aromatic hydrocarbon from methanol and a preparation method thereof.
Background
Aromatic hydrocarbons, especially benzene (B), toluene (T) and xylene (X), are basic raw materials for synthetic resins, rubber, fibers and the like in China, and are in great demand. In 2017, China has become the largest global consumption country for benzene and paraxylene, and in recent years, the consumption has a rapidly increasing trend and the dependence on the outside is gradually increased. The production of aromatic hydrocarbon mainly comes from naphtha cracking, catalytic reforming and the like in a petroleum route, which further aggravates the dependence of petroleum in China on the outside. Based on the relatively abundant coal resources and the large-scale synthesis gas methanol preparation technology in China, the conversion of methanol into aromatic hydrocarbons (MTA) can reduce the dependence of the aromatic hydrocarbons on petroleum routes, and is also an important choice for efficient and clean conversion of coal.
The catalyst which is most widely applied in the current MTA technology is ZSM-5 with MFI topological structure, and shows good shape-selective performance in the reaction due to unique ordered micropore pore channel structure, adjustable acidity and good hydrothermal stability. However, the microporous structure also makes the diffusion of macromolecular products difficult in the reaction, and carbon deposition is easy to deactivate. In addition, a plurality of complex acid sites are involved in micropores of the ZSM-5 molecular sieve, so that the reaction process is complex and the selectivity of aromatic hydrocarbon is low. The shape and size of the catalyst can be regulated, mesoporous structure can be constructed, and the selectivity of aromatic hydrocarbon can be optimized to a certain extent. However, the current modification means are difficult to effectively improve the catalytic performance, and particularly difficult to consider both the selectivity and the catalytic stability of the aromatic hydrocarbon product. For example, although the pore structure can improve the catalytic stability, the framework of the molecular sieve is damaged, and a non-framework structure is introduced, so that the product selectivity is easily reduced. As another example, the introduction of an auxiliary agent can improve product selectivity, but the stability is significantly reduced due to the blockage of micropores. The invention provides a simple method and a formula for constructing a composite catalyst based on a dual-cycle microscopic reaction mechanism of aromatization reaction of methanol to olefin and low-carbon olefin, realizes the step-by-step conversion of methanol to aromatic hydrocarbon on a single catalyst, and promotes the synchronous promotion of product selectivity and catalytic stability.
Disclosure of Invention
In order to solve the problems of low reaction stability and low aromatic selectivity in the reaction of preparing aromatic hydrocarbon from methanol at present, the invention adopts a method for carrying out xerogel solid phase conversion based on desiliconization recrystallization, utilizes TPAOH solution to carry out hydrothermal treatment on ZSM-5, removes silicon in a molecular sieve based on aluminum descending distribution gradient from outside to inside, retains a ZSM-5 low silicon-aluminum ratio structure and forms mesopores, and simultaneously, the removed silicon further grows to be a ZSM-5 structure with a high silicon-aluminum ratio from outside, and finally obtains the hierarchical pore ZSM-5 with obvious silicon-aluminum distribution gradient and good diffusivity; the catalyst is applied to the reaction of preparing aromatic hydrocarbon from methanol, can realize the coupling of two reaction processes of the reaction of preparing olefin from methanol and aromatization of low-carbon olefin, and has excellent catalytic stability and aromatic hydrocarbon selectivity.
The preparation method of the high-selectivity methanol-to-aromatics catalyst provided by the invention comprises the following steps:
1) preparation of Na-ZSM-5 molecular sieve:
TEOS as silicon source, Al (NO) 3 ) 3 Is an aluminum source, TPAOH is used as a template agent, and deionized water is used as a solvent; dissolving silicon source and template agent in solvent, stirring at 80 deg.C for 24 hr, dropwise adding NaOH solution and Al (NO) 3 ) 3 Dropwise adding a certain amount of metal X salt solution after the solution is dissolved, uniformly mixing to form gel, transferring the gel into a crystallization kettle, and crystallizing for 1-6d at 110-170 ℃, wherein the final molar ratio of the materials is as follows: 60SiO 2 :15 TPAOH:0.6-2.4 Al 2 O 3 :5 Na 2 O:400-3600 H 2 O is 0.28 to 1.62X; then centrifugally washing and drying the crystallized product, and roasting the powder for 6 hours at 550 ℃ to obtain SiO 2 /Al 2 O 3 A Na-ZSM-5 molecular sieve sample with the grain size of 25-100 and 80-500 nm;
2) preparing hierarchical pore H-ZSM-5 with high silica-alumina ratio ZSM-5 outside:
dispersing the Na-ZSM-5 prepared in the step 1) into a TPAOH solution with the concentration of 0.1-0.5mol/L according to the liquid-solid ratio of 10-30ml/g, fully stirring for 0.5-15h at the temperature of 25-80 ℃, drying, uniformly grinding, transferring to a special crystallization kettle with a proper amount of deionized water at the bottom, wherein the mass ratio of water to a dried sample is 3-5:1, and performing the crystallization process for 12h-7d at the temperature of 110-; the obtained product is roasted for 6h at 550 ℃ to remove the template agent, and the hierarchical pore Na-ZSM-5 with the size of 100-650nm and the external gathering high silica-alumina ratio ZSM-5 is obtained. Dissolving the Na type molecular sieve in 0.5-2mol/L NH according to the liquid-solid ratio of 10-30ml/g 4 Stirring in Cl solution at 50-90 deg.C for 2-5 hr, repeating the centrifugal washing process several times, and drying overnight. And roasting the obtained molecular sieve at 550 ℃ for 6 hours to remove ammonia, thereby obtaining the acidified ZSM-5.
In the preparation method, the specially-made crystallization kettle is a crystallization kettle with a vertical stainless steel hollow cylinder at the kettle bottom, a porous polytetrafluoroethylene sheet layer is placed on the vertical stainless steel hollow cylinder, and the dried Na-ZSM-5 molecular sieve sample is paved on the upper surface of the porous polytetrafluoroethylene sheet layer.
By the preparation method, the H-ZSM-5 molecular sieve with the hierarchical pores, the exterior of which is high in silica-alumina ratio, and the interior of which is low in silica-alumina ratio, can be obtained. Said hierarchical pore H-ZSM-5 molecule as a wholeSiO of sieve 2 /Al 2 O 3 Still 25-100.
After the high-selectivity hierarchical pore H-ZSM-5 molecular sieve is subjected to tabletting and crushing, particles with the mesh number in the range of about 80 are screened, and then a reaction is carried out in a fixed bed reactor, wherein the reaction conditions are as follows: the reaction temperature is 380-450 ℃, the reaction pressure is 0.1-2MPa, N 2 The flow rate is 20-80ml/min, and the mass space velocity is 1-15h -1 。
The product is separated into a gas phase product and a liquid phase product after passing through a condenser and a gas-liquid separator, the gas product is collected by a gas bag, and the gas phase product is analyzed by a GC-7890 gas phase chromatographic analyzer. And the liquid phase product enters a liquid storage tank for storage, and is subjected to liquid hydrocarbon product analysis by a GC-7820 gas chromatography analyzer (configured with PONA software). The data in the examples of examples 1 to 10 show that the multistage pore H-ZSM-5 obtained by solid phase conversion of the desilicated recrystallized xerogel has a liquid hydrocarbon yield of 19-27%, with an aromatics selectivity of 65-90% and a lifetime of 1.5-3 times that of conventional catalysts.
Compared with the existing methanol aromatization catalyst, the hierarchical pore H-ZSM-5 with the high silica-alumina ratio outside prepared by the invention has the following advantages:
(1) based on a desiliconization recrystallization xerogel solid phase conversion mechanism, the ZSM-5 is hydrothermally treated by TPAOH solution, based on the aluminum descending distribution gradient from outside to inside, the silicon in the molecular sieve is removed, a ZSM-5 structure with low silica alumina ratio is reserved, and mesopores are formed, meanwhile, the removed silicon further grows to be a ZSM-5 structure with high silica alumina ratio on the outside, and finally, a fine structure with high silica alumina ratio on the outside, low silica alumina ratio on the inside and mesopores is obtained. The whole catalyst is simple to prepare, fine and controllable, no raw material is wasted, and the yield is 100%.
(2) Based on the fine silicon-aluminum structure of the catalyst, when the catalyst is used for catalyzing methanol to prepare aromatic hydrocarbon, the stepwise efficient coupling of two reaction processes of a methanol to olefin reaction and low-carbon olefin aromatization is realized on a single catalyst, the selectivity of the aromatic hydrocarbon can be effectively improved, and the catalyst is excellent in stability based on the multi-level pore structure.
Drawings
FIG. 1 is a TEM schematic of a nano ZSM-5 molecular sieve (a) and a subsequently synthesized hierarchical pore H-ZSM-5 (b) with a high silica alumina ratio ZSM-5 exterior in example 1 of the present invention.
FIG. 2 is the nitrogen adsorption desorption isotherm of the nano ZSM-5 molecular sieve and the subsequently synthesized hierarchical porous H-ZSM-5 having a high silica alumina ratio ZSM-5 exterior in example 1 of the present invention.
Detailed Description
And characterizing the morphology and the particle size of the molecular sieve by adopting a JEOL-LEM-2100F field emission transmission electron microscope. During sample preparation, a powder sample is placed in ethanol for 30 min of ultrasonic treatment, and then the obtained suspension is dropped on a copper mesh carbon film. The test was conducted by taking a photograph under the condition that the acceleration voltage was 200 kV.
The specific surface area and pore volume of the molecular sieve were measured by using a Bezid 3H-2000 PS2 model static capacity method specific surface area pore size analyzer. Firstly, pretreating a sample for 4 hours at 250 ℃, and then adsorbing and desorbing the sample at-196 ℃ to obtain an adsorption-desorption curve.
In order to make the objects and advantages of the present invention more clearly understood, the following detailed description is given for illustrative purposes only and is not intended to limit the present invention.
Example 1
1) Preparation of Na-ZSM-5 molecular sieve:
TEOS is used as silicon source, Al (NO) 3 ) 3 Is an aluminum source, TPAOH is a template agent, and deionized water is a solvent; dissolving a silicon source and a template agent in a solvent, fully stirring for 24 hours at 80 ℃, and dropwise adding a NaOH solution and Al (NO) 3 ) 3 After the solution 2 wt% Zn (NO) is added dropwise 3 ) 2 Uniformly mixing the solution to form gel, transferring the gel into a crystallization kettle, and crystallizing for 1d at 170 ℃, wherein the final molar ratio of the materials is as follows: 60SiO 2 :15 TPAOH:1 Al 2 O 3 :5 Na 2 O:500 H 2 O is 1.14 Zn; then centrifugally washing and drying the crystallized product, and roasting the powder at 550 ℃ for 6 hours to obtain SiO 2 /Al 2 O 3 60, Na-ZSM-5 molecular sieve with grain size of 100 nm;
2) preparing hierarchical pore H-ZSM-5 with high silica-alumina ratio ZSM-5 outside:
dispersing the Na-ZSM-5 prepared in the step 1) in a TPAOH solution with the concentration of 0.3 mol/L according to the liquid-solid ratio of 10 ml/g, fully stirring for 10 hours at 50 ℃, drying, uniformly grinding, and transferring to a special crystallization kettle with a proper amount of deionized water at the bottom, wherein the mass ratio of water to a dried sample is 5: 1. The crystallization process is carried out for 2 days at 170 ℃; roasting the obtained product at 550 ℃ for 6h to remove the template agent, and obtaining the hierarchical pore Na-ZSM-5 with the size of 150 nm and the external aggregation nano-level high silica-alumina ratio ZSM-5. Dissolving the Na-type molecular sieve in 1 mol/L NH according to the liquid-solid ratio of 20 ml/g 4 In the Cl solution, the mixture is stirred for 3 hours at 80 ℃, and the centrifugal washing operation process is repeated for a plurality of times and then dried overnight. And roasting the obtained molecular sieve at 550 ℃ for 6 hours to remove ammonia, thereby obtaining the acidified ZSM-5.
Tabletting and crushing the hierarchical porous H-ZSM-5 molecular sieve, screening particles with the mesh number of about 80, and then carrying out a reaction for preparing aromatic hydrocarbon from methanol in a fixed bed reactor. The reaction conditions are as follows: the reaction temperature is 430 ℃, the reaction pressure is 0.5 MPa, N 2 The flow rate is 32 ml/min, and the mass space velocity is 10 h -1 . The product is separated into a gas phase product and a liquid phase product after passing through a condenser and a gas-liquid separator, the gas product is collected by a gas bag, and the gas phase product is analyzed by a GC-7890 gas phase chromatographic analyzer. And the liquid phase product enters a liquid storage tank to be stored, and a GC-7820 gas chromatography analyzer (configured with PONA software) is used for analyzing the liquid hydrocarbon product. The results are shown in Table 1.
The transmission electron microscope detection analysis of figure 1 shows that the average grain diameter of the prepared Na-ZSM-5 molecular sieve is about 100 nm. For the H-ZSM-5 molecular sieve with the multilevel pores, the particle size is further increased to about 150 nm due to the aggregation growth of the external nanometer level high-silica-alumina ratio ZSM-5.
As can be seen from FIG. 2, the warp N 2 The hierarchical pore H-ZSM-5 of the ZSM-5 with the external aggregation nanometer level high silica-alumina ratio measured by the adsorption and desorption characterization shows obvious H 4 The type hysteresis loop shows that the Na-ZSM-5 is introduced into a mesoporous structure after desilication recrystallization solid phase conversion. Further analysis shows that the mesoporous volume is 0.43 cm 3 Per g, external specific surface area of 116 m 2 /g。
Example 2
1) Preparation of Na-ZSM-5 molecular sieve:
TEOS as silicon source, Al (NO) 3 ) 3 Is an aluminum source, TPAOH is a template agent, and deionized water is a solvent; dissolving a silicon source and a template agent in a solvent, fully stirring for 24 hours at 80 ℃, and dropwise adding a NaOH solution and Al (NO) 3 ) 3 After the solution, 3 wt% Ga (NO) is added dropwise 3 ) 3 Uniformly mixing the solution to form gel, transferring the gel into a crystallization kettle, and crystallizing for 6d at 110 ℃, wherein the final molar ratio of the materials is as follows: 60SiO 2 :15 TPAOH:1.6 Al 2 O 3 :5 Na 2 O:1800 H 2 O is 1.62 Ga; then centrifugally washing and drying the crystallized product, and roasting the powder for 6 hours at 550 ℃ to obtain SiO 2 /Al 2 O 3 Na-ZSM-5 molecular sieve with 38 and 250 nm of grain size;
2) a hierarchical pore H-ZSM-5 molecular sieve having a size of 360 nm and a high silica-alumina ratio ZSM-5 as an outer portion was obtained according to the step 2) in example 1. The method is applied to the reaction for preparing aromatic hydrocarbon from methanol, and specific obtained results are shown in table 1.
Example 3
1) Preparation of Na-ZSM-5 molecular sieve:
TEOS is used as silicon source, Al (NO) 3 ) 3 Is an aluminum source, TPAOH is a template agent, and deionized water is a solvent; dissolving a silicon source and a template agent in a solvent, fully stirring for 24 hours at 80 ℃, and dropwise adding a NaOH solution and Al (NO) 3 ) 3 After the solution, 0.5 wt% Zn (NO) is added dropwise 3 ) 2 Uniformly mixing the solution to form gel, transferring the gel into a crystallization kettle, and crystallizing for 1d at 210 ℃, wherein the final molar ratio of the materials is as follows: 60SiO 2 :15 TPAOH:0.6 Al 2 O 3 :5 Na 2 O:360 H 2 O is 0.28 Zn; then centrifugally washing and drying the crystallized product, and roasting the powder at 550 ℃ for 6 hours to obtain SiO 2 /Al 2 O 3 100, and the grain size is 80 nm of Na-ZSM-5 molecular sieve;
2) hierarchical pore H-ZSM-5 with a size of 100 nm and a high silica to alumina ratio ZSM-5 outside was obtained according to step 2) of example 1. The method is applied to the reaction for preparing aromatic hydrocarbon from methanol, and specific obtained results are shown in table 1.
Example 4
1) Preparation of Na-ZSM-5 molecular sieve:
TEOS is used as silicon source, Al (NO) 3 ) 3 An aluminum source, TPAOH as a template agent and deionized water as a solvent; dissolving a silicon source and a template agent in a solvent, fully stirring for 24 hours at 80 ℃, and dropwise adding a NaOH solution and Al (NO) 3 ) 3 After the solution 2 wt% Zn (NO) is added dropwise 3 ) 2 Uniformly mixing the solution to form gel, transferring the gel into a crystallization kettle, and crystallizing for 4d at 140 ℃, wherein the final molar ratio of the materials is as follows: 60SiO 2 :15 TPAOH:2.4 Al 2 O 3 :5 Na 2 O:3600 H 2 O is 1.24 Zn; then centrifugally washing and drying the crystallized product, and roasting the powder for 6 hours at 550 ℃ to obtain SiO 2 /Al 2 O 3 25, and the grain size is 500 nm;
2) a hierarchical pore H-ZSM-5 molecular sieve having a size of 650nm and a high silica-alumina ratio ZSM-5 as an outer portion was obtained according to step 2) of example 1. The method is applied to the reaction for preparing aromatic hydrocarbon from methanol, and specific obtained results are shown in table 1.
Example 5
1) Synthesis of SiO according to step 1) of example 1 2 /Al 2 O 3 60, Na-ZSM-5 molecular sieve with grain size of 100 nm;
2) adjustment example 1, step 2) was carried out under the following conditions: Na-ZSM-5 is dispersed in TPAOH solution with the concentration of 0.1 mol/L according to the liquid-solid ratio of 30ml/g, fully stirred for 4 hours at the temperature of 80 ℃, dried and ground uniformly, and then transferred to a special crystallization kettle with a proper amount of ionized water at the bottom, wherein the mass ratio of water to a dried sample is 4: 1. The sample was laid flat on a porous teflon sheet, which was supported by cylindrical stainless steel. The crystallization process is carried out at 140 ℃ for 4 d; roasting the obtained product at 550 ℃ for 6h to remove the template agent, and obtaining the product with the size of 150 nm and high external aggregation nano-scale Si/Al ratioHierarchical pore Na-ZSM-5 of ZSM-5. Dissolving the Na type molecular sieve in 2mol/L NH according to the liquid-solid ratio of 10 ml/g 4 In Cl solution, stirring at 50 ℃ for 5 hours, repeating the centrifugal washing operation for several times, and then drying overnight. And roasting the obtained molecular sieve at 550 ℃ for 6 hours to remove ammonia to obtain acidified ZSM-5. The rest conditions are unchanged, and the specific obtained results are shown in table 1 when the catalyst is applied to the reaction for preparing the aromatic hydrocarbon from the methanol.
Example 6
1) Synthesis of SiO according to step 1) of example 1 2 /Al 2 O 3 60, Na-ZSM-5 molecular sieve with grain size of 100 nm;
2) adjustment example 1, step 2) was carried out under the following conditions: Na-ZSM-5 is dispersed in TPAOH solution with the concentration of 0.5mol/L according to the liquid-solid ratio of 20 ml/g, fully stirred for 15 hours at the temperature of 25 ℃, dried and ground uniformly, and then transferred to a special crystallization kettle with a proper amount of deionized water at the bottom, wherein the mass ratio of water to a dried sample is 3: 1. The sample was laid flat on a porous teflon sheet, which was supported by hollow cylindrical stainless steel. The crystallization process is carried out at 110 ℃ for 6 days; roasting the obtained product at 550 ℃ for 6h to remove the template agent, and obtaining the hierarchical pore Na-ZSM-5 with the size of 150 nm and the external aggregation nano-level high silica-alumina ratio ZSM-5. Dissolving the Na type molecular sieve in 0.5mol/L NH according to the liquid-solid ratio of 30ml/g 4 In the Cl solution, the solution is stirred for 2 hours at 90 ℃, and the centrifugal washing operation process is repeated for a plurality of times and then dried overnight. And roasting the obtained molecular sieve at 550 ℃ for 6 hours to remove ammonia to obtain acidified ZSM-5. The rest conditions are unchanged, and the specific obtained results are shown in table 1 when the catalyst is applied to the reaction for preparing the aromatic hydrocarbon from the methanol.
Example 7
1) Synthesis of SiO according to step 1) of example 1 2 /Al 2 O 3 60, Na-ZSM-5 molecular sieve with grain size of 100 nm;
2) adjustment example 1, step 2) was carried out under the following conditions: dispersing Na-ZSM-5 in TPAOH solution with concentration of 0.3 mol/L according to liquid-solid ratio of 20 ml/g, stirring thoroughly at 25 deg.C for 15h, drying, grinding, transferring to the bottom with appropriate amount of ionized waterIn the crystallization kettle, the mass ratio of water to the dried sample is 5: 1. The sample was laid flat on a porous teflon sheet, which was supported by hollow cylindrical stainless steel. The crystallization process is carried out for 12 hours at 210 ℃; the obtained product is roasted for 6 hours at 550 ℃ to remove the template agent, and the hierarchical pore Na-ZSM-5 with the size of 150 nm and the external aggregation nano-level high silica alumina ratio ZSM-5 is obtained. Dissolving the Na-type molecular sieve in 0.5mol/L NH according to the liquid-solid ratio of 30ml/g 4 In Cl solution, stirring at 90 deg.C for 2 hr, repeating the centrifugal washing process several times, and drying overnight. And roasting the obtained molecular sieve at 550 ℃ for 6 hours to remove ammonia, thereby obtaining the acidified ZSM-5. The rest conditions are unchanged, and the specific obtained results are shown in table 1 when the catalyst is applied to the reaction for preparing the aromatic hydrocarbon from the methanol.
Example 8
1) Synthesis of SiO according to step 1) of example 1 2 /Al 2 O 3 60 and the grain size of the Na-ZSM-5 molecular sieve is 100 nm.
2) The evaluation conditions of the methanol to aromatics reaction in step 2) of example 1 were adjusted as follows: the reaction temperature is 380 ℃, the reaction pressure is 0.1 MPa, N 2 The flow rate is 80ml/min, and the mass space velocity is 15h -1 . The remaining conditions were unchanged and the specific results obtained are shown in Table 1.
Example 9
1) Synthesis of SiO according to step 1) of example 1 2 /Al 2 O 3 60 and the grain size of the Na-ZSM-5 molecular sieve is 100 nm.
2) The reaction evaluation conditions in step 2) of example 1 were adjusted to: the reaction temperature is 400 ℃, the reaction pressure is 2MPa, N 2 The flow rate is 32 ml/min, and the mass space velocity is 4h -1 . The remaining conditions were unchanged and the results obtained are shown in Table 1.
Example 10
1) Synthesis of SiO according to step 1) of example 1 2 /Al 2 O 3 60 and the grain size of the Na-ZSM-5 molecular sieve is 100 nm.
2) The reaction evaluation conditions in step 2) of example 1 were adjusted to: the reaction temperature is 450 ℃, the reaction pressure is 0.5 MPa, N 2 Flow rate of 20 ml/min, massSpace velocity of 1 h -1 . The remaining conditions were unchanged and the results obtained are shown in Table 1.
Table 1 examples 1-10 catalytic performance of catalysts in MTA reaction
Figure DEST_PATH_IMAGE001
Note: the liquid hydrocarbon yield in table 1 refers to the maximum liquid hydrocarbon yield in the MTA reaction catalyzed by the catalyst, the aromatic hydrocarbon selectivity is the selectivity of the aromatic hydrocarbon in the MTA reaction liquid hydrocarbon, and the lifetime is the reaction time elapsed when the catalytic liquid hydrocarbon yield is reduced to 1%.
Based on the preparation method of the invention, SiO with the particle size of 100-650nm is obtained 2 /Al 2 O 3 The catalyst is 25-100, the outer part of the catalyst is a hierarchical pore H-ZSM-5 structure with high silica-alumina ratio ZSM-5, and the catalyst is applied to the reaction of preparing aromatic hydrocarbon from methanol, so that the stepwise high-efficiency conversion of the reaction of preparing olefin from methanol and aromatizing the low-carbon olefin on a single catalyst is realized, and the catalytic stability and the product selectivity of MTA are remarkably improved. From the overall results in Table 1, the invention achieves good catalytic effect, wherein the liquid hydrocarbon yield of the methanol-to-aromatics is 19-27 wt%, the aromatics selectivity is as high as 65-90%, and the reaction life is 131-300 h. The conventional nano-catalyst is evaluated according to the reaction conditions of the example 1, and the aromatic selectivity of the conventional nano-catalyst is only 54 wt%, which is obviously lower than 80.1 wt% of the conventional nano-catalyst in the example 1; the catalytic reaction lifetime was only 95 h, which was 0.59 times the lifetime obtained in example 1. Therefore, the catalyst for preparing aromatic hydrocarbon from methanol has superior performance.

Claims (8)

1. A preparation method of a high-selectivity methanol-to-aromatics catalyst comprises the following steps:
1) preparation of Na-ZSM-5 molecular sieve: TEOS as silicon source, Al (NO) 3 ) 3 An aluminum source, TPAOH as a template agent and deionized water as a solvent; dissolving a silicon source and a template agent in a solvent, fully stirring for 24 hours at 80 ℃, and dropwise adding a NaOH solution and Al (NO) 3 ) 3 Dripping a certain amount of metal X salt solution after the solution is dissolved, mixing uniformly to form gel, and then transferring the gel to a crystallization kettleIn the method, crystallization is carried out for 1-6d at the temperature of 110-: 60SiO 2 :15TPAOH:0.6-2.4Al 2 O 3 :5Na 2 O:400-3600H 2 O is 0.28 to 1.62X; then centrifugally washing and drying the crystallized product, and roasting the powder for 6 hours at 550 ℃ to obtain SiO 2 /Al 2 O 3 25-100 and the grain size is 80-500 nm;
2) preparing hierarchical pore H-ZSM-5 with high silica-alumina ratio ZSM-5 outside: dispersing the Na-ZSM-5 molecular sieve sample prepared in the step 1) into TPAOH solution with the concentration of 0.1-0.5mol/L according to the liquid-solid ratio of 10-30ml/g, fully stirring for 0.5-15h at the temperature of 25-80 ℃, transferring the sample into a special crystallization kettle with a proper amount of deionized water at the bottom after drying and grinding, and crystallizing for 12h-7d at the temperature of 110-; in the specially-made crystallization kettle, the mass ratio of deionized water to a dried Na-ZSM-5 molecular sieve sample is 3-5: 1; then roasting the crystallized product at 550 ℃ for 6h to remove the template agent, and obtaining hierarchical pore Na-ZSM-5 with the size of 100-650nm and high silica-alumina ratio ZSM-5 gathered outside; then dissolving the hierarchical pore Na-ZSM-5 in 0.5-2mol/L NH according to a certain liquid-solid ratio 4 Stirring for 2-5H at 50-90 ℃ in a Cl solution for acidification, centrifugally washing for a plurality of times, and drying overnight, wherein the obtained molecular sieve is roasted for 6H at 550 ℃ to obtain a final product, namely the hierarchical pore H-ZSM-5;
the special crystallization kettle in the step 2) is a crystallization kettle with a vertical stainless steel hollow cylinder at the kettle bottom, a porous polytetrafluoroethylene sheet layer is placed on the vertical stainless steel hollow cylinder, and a dried and ground sample is flatly laid on the upper surface of the porous polytetrafluoroethylene sheet layer.
2. The method for preparing the catalyst for preparing aromatic hydrocarbons from methanol with high selectivity according to claim 1, wherein the metal auxiliary agent X in the metal X salt solution in the step 1) is one of Zn and Ga.
3. The method for preparing a catalyst for preparing aromatic hydrocarbon from methanol with high selectivity according to claim 2, wherein the loading amount of the metal promoter X in the metal X salt solution in the step 1) is 0.5-3 wt%.
4. The method for preparing the catalyst for preparing aromatic hydrocarbon from methanol with high selectivity as claimed in claim 1, wherein the stirring process in the step 2) is carried out at 25-80 ℃ for 0.5-15 h.
5. The method for preparing the catalyst for preparing aromatic hydrocarbons from methanol with high selectivity according to claim 1, wherein the hierarchical pore Na-ZSM-5 and 0.5-2mol/L NH are added during the acidification of the molecular sieve in the step 2) 4 The liquid-solid ratio of the Cl solution is 10-30 ml/g.
6. The high selectivity methanol-to-aromatics catalyst prepared by the preparation method of claim 1, which is characterized in that the catalyst is a hierarchical pore H-ZSM-5 molecular sieve with high silica-alumina ratio H-ZSM-5 particles attached to the outside, and the size of the hierarchical pore H-ZSM-5 molecular sieve is 650 nm.
7. The high selectivity methanol to aromatics catalyst of claim 6, wherein the hierarchical pore H-ZSM-5 molecular sieve is SiO 2 /Al 2 O 3 Is 25-100.
8. The application of the high-selectivity methanol to aromatics catalyst of claim 6 or 7 in a methanol to aromatics reaction is characterized in that the catalyst is subjected to a reaction in a fixed bed reactor after being subjected to tablet forming, and the reaction conditions are as follows: the reaction temperature is 380 ℃ and 450 ℃, the reaction pressure is 0.1-2MPa, N 2 The flow rate is 20-80ml/min, and the mass space velocity is 1-15h -1 。
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