Method for preparing light aromatic hydrocarbon by aromatization of catalyst system and ethanol

Abstract

The invention discloses a method for preparing light aromatic hydrocarbon through aromatization of a catalyst system and ethanol, and belongs to the technical field of energy and chemical engineering catalysts. The catalyst system comprises a CuZr / SiO2 molecular sieve and an HZSM-5 molecular sieve, and the molecular sieve is marked as CuZr / SiO2: HZSM-5; wherein the CuZr / SiO2 comprises a SiO2 carrier, a Cu element and a Zr element, and the Cu element and the Zr element are loaded on the surface of the SiO2 carrier. The method comprises the following steps: carrying out contact reaction on a raw material containing ethanol and a CuZr / SiO2: HZSM-5 catalyst system in a reaction area to generate the BTX-based aromatic hydrocarbon. Specifically, CuZr / SiO2 is mainly used for catalyzing ethanol dehydrogenation condensation to generate an intermediate product butadiene; and the HZSM-5 molecular sieve active component catalyzes aromatization of butadiene into aromatic hydrocarbon, especially BTX. The catalyst system can efficiently and directly convert ethanol into light aromatic hydrocarbon, can reduce the production cost of the product, is convenient to reuse, and is beneficial to large-scale industrial production and application. In addition, the catalyst system can effectively restrain the problems of agglomeration of the catalyst, loss of active components and carbon deposition, and the stability of the catalyst is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy chemical catalysts, and particularly to a CuZr / SiO2:HZSM-5 catalyst system with high efficiency and high stability, which is mainly applied to the field of directional catalytic synthesis of light aromatics from aqueous ethanol. Background Art

[0002] Light aromatics (a mixture of benzene, toluene and xylene, Benzene-Toluene-Xylene, abbreviated as BTX) are important chemical platform molecules, which are widely used in the production of high-value-added chemical products such as plastics, synthetic fibers, dyes, medicines and consumer goods, and play a crucial role in modern industry and human daily life. Due to the rapid expansion of the global pharmaceutical and construction industries, the market demand for BTX is increasing continuously, and it is expected that the global market size will exceed 130 million tons in 2024. At present, the production of BTX mainly relies on traditional petrochemical processes such as catalytic reforming of naphtha and steam cracking of hydrocarbons. However, these methods highly depend on non-renewable petroleum resources, and the production process has a great impact on the environment. With the gradual depletion of petroleum resources and the increasing prominence of environmental problems, the production of BTX is restricted to a certain extent. The contradiction between the growing market demand and production restrictions has become an urgent problem for researchers in this field. Therefore, it is particularly urgent to develop a new BTX synthesis route to replace the petroleum route.

[0003] In recent years, China has been actively promoting modern coal chemical technologies to promote the efficient and clean utilization of coal. Among them, manufacturing ethanol from coal-based syngas is an important direction for the current research and development of new coal chemical industries. Further preparing downstream product BTX from coal-based ethanol is a potential industrialized synthesis route for BTX. This method can fully combine the energy structure advantages of "rich in coal, poor in oil and less in gas" in China and improve the deficiency of over-relying on petroleum resources to produce basic chemicals.

[0004] Most of the existing ethanol aromatization catalytic systems use metal-modified or zeolite-modified catalysts. Patent CN101954291A discloses a zinc isomorphously substituted nanosheet crystal zeolite catalyst, which can be used for catalytic aromatization reaction of alcohols in a fixed bed. The reaction pressure is 0.1-2.0 MPa, the reaction temperature is 380-500 °C, and the liquid hourly space velocity of the raw material is 0.2-4.0 h -1 . Among them, the highest aromatic hydrocarbon yield in ethanol aromatization reaches 63.6%.

[0005] Patent CN112920006A discloses a method for catalytic aromatization reaction of ethanol and carbon monoxide as mixed raw materials using an acid zeolite catalyst without metal elements. This method can improve and stabilize the aromatic hydrocarbon selectivity, and the selectivity of aromatic hydrocarbon compounds in the product can be increased to 70.0%.

[0006] Patent CN104841473A discloses a method for preparing a catalyst by treating ZSM5 zeolite with acid or base and combining it with atomic layer deposition to load metal or metal oxide. By improving the pore shape retention of the carrier and precisely controlling the amount of loaded metal, carbon deposition, sintering and penetration of active metal of the catalyst are effectively inhibited. Using the catalyst obtained by this method for reaction, the yield of aromatics can reach 70.0%.

[0007] The literature

Green Chemistry, 2017, 19(18): 4344 - 4352

[0008] From the above - mentioned literature, it can be seen that due to the co - existence of acidic sites and suitable topological structure, ZSM - 5 zeolite has become one of the most widely studied catalysts in the ethanol aromatization reaction. At present, the main ways to improve the performance of ZSM - 5 catalyst include introducing metals (such as Ga, Zn, Mo, Pd, etc.) or modifying the topological structure (such as alkali treatment or steam treatment). Due to the strong acidity of conventional ZSM - 5 zeolite, carbon deposition is likely to occur during the reaction process, which in turn affects the stability of the catalyst. In addition, the distribution position, composition of the active metal and its interaction with the carrier are relatively complex, which easily causes blockage of the zeolite pores and loss of the active metal, resulting in a decrease in the selectivity of the target product BTX. Therefore, how to solve a series of problems such as easy carbon deposition deactivation, loss of active metal and poor selectivity of target products of the ethanol aromatization reaction catalyst at the present stage, and develop a new type of aromatization catalyst, is still an important issue faced by those skilled in the art. Summary of the Invention

[0009] In view of the above - mentioned deficiencies of the prior art, the purpose of the present invention is to provide a catalyst system and a catalytic method for preparing BTX through ethanol aromatization by a non - petroleum route, aiming to solve the problems such as easy carbon deposition deactivation, loss of active metal and poor selectivity of target products existing in the existing catalysts for preparing BTX by ethanol aromatization.

[0010] The technical solution of the present invention is as follows:

[0011] In the first aspect of the present invention, a catalyst system is provided, wherein the catalyst system includes CuZr / SiO2 and HZSM - 5 zeolite, denoted as CuZr / SiO2:HZSM - 5; wherein, the CuZr / SiO2 includes a SiO2 carrier and Cu element and Zr element loaded on the surface of the SiO2 carrier.

[0012] Optionally, the mass content of CuZr / SiO2 in CuZr / SiO2:HZSM-5 is 66.7-75.0%, and the mass content of HZSM-5 molecular sieve in CuZr / SiO2:HZSM-5 is 25.0-33.3%.

[0013] Optionally, the mass content of Cu element in CuZr / SiO2 is 1.0-5.0%, and the mass content of Zr element in CuZr / SiO2 is 10.0-50.0%.

[0014] Optionally, the SiO2 support is at least one of Q3 spherical support, Q6 spherical support, Q10 spherical support, Q15 spherical support, Q30 spherical support, and Q50 spherical support;

[0015] The atomic ratio of silicon to aluminum in the HZSM-5 molecular sieve is 40-200, and the HZSM-5 molecular sieve has a hierarchical pore structure of micropores, mesopores, and macropores.

[0016] Optionally, the CuZr / SiO2 is prepared by the following method: dissolving soluble Cu salt and soluble Zr salt in water to obtain a soluble salt solution; adding the soluble salt solution into a container containing SiO2 support, and successively performing stirring, evaporation drying, and calcination to obtain the CuZr / SiO2.

[0017] Optionally, the HZSM-5 molecular sieve is an activated HZSM-5 molecular sieve, and the activation method of the HZSM-5 molecular sieve includes the steps of: taking the HZSM-5 molecular sieve, performing programmed temperature rise at a heating rate of 1-20 °C / min to 300-900 °C, and then holding the temperature for 3-24 h to obtain the activated HZSM-5 molecular sieve.

[0018] Optionally, the CuZr / SiO2 is CuZr / SiO2 with a particle size of 20-100 mesh after granulation treatment, and the HZSM-5 molecular sieve is HZSM-5 molecular sieve with a particle size of 20-100 mesh after granulation treatment.

[0019] In the second aspect of the present invention, a method for preparing light aromatics by ethanol aromatization is provided, which includes the steps of: contacting a raw material containing ethanol with the catalyst system of the present invention in a reaction zone to obtain light aromatics.

[0020] Optionally, the reaction zone is the constant temperature zone of a single fixed bed reactor or the constant temperature zone of a series-connected double fixed bed reactor;

[0021] The reaction temperature is 300-600 °C;

[0022] The raw material containing ethanol is an ethanol aqueous solution, the mass fraction of ethanol in the ethanol aqueous solution is 1-100%, and the mass hourly space velocity of ethanol is 0.5-7 h -1 .

[0023] Optionally, the catalyst system is pretreated with hydrogen or a hydrogen-containing mixed gas before use;

[0024] Among them, the temperature of the pretreatment is 300-600 °C, the time of the pretreatment is 2-12 h, and the gas hourly space velocity of the pretreatment gas is 600-3600 h -1 .

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] 1) The catalyst system (CuZr / SiO2:HZSM-5) for preparing BTX from ethanol provided by the present invention selectively introduces Cu and Zr on the surface of the SiO2 support. Through the interaction between Cu, Zr and the SiO2 support, and through the physical combination and chemical bonding of the three, the stability of the catalyst system is greatly improved, and the service life of the catalyst system is extended.

[0027] 2) The catalyst system (CuZr / SiO2:HZSM-5) for preparing BTX from ethanol provided by the present invention uses butadiene as an intermediate product, couples the reaction of ethanol to butadiene and the reaction of butadiene to prepare BTX, promotes the reaction, and the product distribution shows high BTX selectivity.

[0028] 3) The catalyst system for preparing BTX from ethanol provided by the present invention does not require the addition of precious metal elements, greatly saves costs, and the preparation process of the catalyst system is simple and easy to repeat, and can be prepared on a large scale.

[0029] 4) The catalyst system for preparing BTX from ethanol provided by the present invention can effectively inhibit the problems of catalyst agglomeration, active component loss and carbon deposition, and significantly improves the stability of the catalyst. Description of the Drawings

[0030] Figure 1 It is a process schematic diagram for preparing BTX from ethanol through the CuZr / SiO2:HZSM-5 catalyst system.

[0031] Figure 2 It is the XRD spectra of the CuZr / SiO2 active component before and after calcination prepared in Example 1.

[0032] Figure 3 It is the XRD spectrum of HZSM-5(105) selected in Example 1.

[0033] Figure 4The chromatogram of the oil-phase product of Example 1. Detailed implementation manners

[0034] The present invention provides a method for preparing light aromatics by the aromatization of ethanol with a catalyst system. To make the objectives, technical solutions and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] In the process of producing BTX from ethanol using existing catalysts, the catalysts are prone to sintering and carbon deposition, the active metals are prone to agglomeration and loss of activity, and the single-pass selectivity stability of BTX is poor.

[0036] Research shows that introducing the dehydrogenation active component Cu element into the catalyst system can significantly promote the ethanol dehydrogenation reaction. The research on Cu-based catalysts has attracted extensive attention. In particular, the combination of Cu element and the stable SiO2 support not only helps to maintain the high activity of the ethanol dehydrogenation reaction, but also is beneficial to effectively inhibiting the dehydration reaction and reducing the formation of by-products such as diethyl ether. Although the Cu-based catalyst is a highly active and highly selective ethanol dehydrogenation catalyst, it is also accompanied by phenomena such as sintering, carbon deposition, and loss of active components during the catalytic process. Therefore, the stability of the ethanol dehydrogenation activity decreases, resulting in a shortened service life of the catalyst.

[0037] ZrO2, as an amphoteric metal oxide, is commonly used as a catalyst for the dehydration of alcohols to prepare olefins. It is closely connected with other active components of the catalyst, improving the interaction between the active center and the support, thus significantly improving the stability of the catalyst and effectively reducing the deactivation of the catalyst caused by the agglomeration of active metals. At the same time, the Zr catalyst supported on SiO2 is also a highly active aldol condensation and MPV (Meerwein–Ponndorf–Verley) reduction catalyst.

[0038] Based on this, the present invention makes full use of the synergistic effect of Cu and Zr species, loads Cu and Zr species on the SiO2 support, and then combines with the lower-layer HZSM-5 molecular sieve to construct a novel catalyst system. This catalyst system can effectively improve the catalytic activity and BTX selectivity of the ethanol aromatization reaction, and at the same time enhance the stability of the catalyst system, thus providing an efficient and stable catalytic solution for the preparation of BTX from ethanol.

[0039] Specifically, the present invention provides a catalyst system, wherein the catalyst system includes CuZr / SiO2 and HZSM-5 molecular sieve, denoted as CuZr / SiO2:HZSM-5; wherein the CuZr / SiO2 includes a SiO2 support and Cu element and Zr element loaded on the surface of the SiO2 support.

[0040] The present invention provides a catalyst system for preparing BTX by aromatization of ethanol through a non - petroleum route, specifically providing a CuZr / SiO2:HZSM - 5 catalyst system for preparing BTX by aromatization of ethanol. The CuZr / SiO2 component can improve the activity of preparing butadiene intermediate from ethanol, and stabilize the active component for ethanol - to - butadiene through the synergistic effect of Cu, Zr and the SiO2 support. Through the synergistic effect of the dual - catalyst system, the activity, stability and BTX selectivity of the catalyst system are improved. This catalyst system can effectively catalyze the reaction of ethanol to BTX, and can maintain high catalytic activity, high BTX selectivity and good thermal stability.

[0041] In one embodiment, the mass content of CuZr / SiO2 in the CuZr / SiO2:HZSM - 5 is 66.7 - 75.0%, and the mass content of the HZSM - 5 molecular sieve in the CuZr / SiO2:HZSM - 5 is 25.0 - 33.3%. When the mass content of CuZr / SiO2 is between 66.7 - 75.0%, the catalytic stability is enhanced, the catalytic activity is significantly improved, and the yield of the target product BTX reaches more than 40%. When the mass content of CuZr / SiO2 is less than 66.7%, carbon deposition is serious, and when the mass content of CuZr / SiO2 is higher than 75.0%, the aromatization efficiency decreases.

[0042] In one embodiment, the mass content of the Cu element in the CuZr / SiO2 is 1.0 - 5.0% (such as 2.0%, 3.0%, 4.0%, etc.), and the mass content of the Zr element in the CuZr / SiO2 is 10.0 - 50.0% (such as 20.0%, 30.0%, 40.0%, etc.). When the Cu content is between 1.0 - 5.0% and the Zr content is between 10.0 - 50.0%, CuZr / SiO2 shows the best selectivity for butadiene. When it is lower than this range, the stability of CuZr / SiO2 is poor and the content of by - products such as acetaldehyde from ethanol dehydration increases. When it is higher than this range, metal species agglomerate and the availability of active sites decreases.

[0043] In one embodiment, the SiO2 support is at least one of Q3 spherical support, Q6 spherical support, Q10 spherical support, Q15 spherical support, Q30 spherical support, Q50 spherical support. Among them, Q3, Q6, Q10, Q15, Q30, Q50 respectively refer to SiO2 spherical supports with pore diameters of 3, 6, 10, 15, 30 and 50 nanometers.

[0044] In one embodiment, the atomic ratio of silicon to aluminum in the HZSM-5 zeolite is 40 to 200 (such as 40, 50, 80, 100, 150, 200, etc.), and the HZSM-5 zeolite has a hierarchical pore structure with micropores, mesopores and macropores.

[0045] In one embodiment, the CuZr / SiO2 is prepared by the following method:

[0046] Step 1: Dissolve soluble Cu salts and soluble Zr salts in water (such as deionized water) to obtain a soluble salt solution;

[0047] Step 2: Add the soluble salt solution to a container (such as a beaker) containing a SiO2 support, and successively stir (specifically, continuously ultrasonically stir at room temperature until a uniform viscous gel-like substance is obtained), evaporate and dry, and calcine to obtain the CuZr / SiO2.

[0048] Among them, in Step 1, the soluble Cu salts and soluble Zr salts can be fully dissolved in water by ultrasonic treatment to obtain the soluble salt solution.

[0049] Among them, in Step 2, the conditions for evaporation and drying are drying at 60 to 120 °C (such as 70 °C, 80 °C, 90 °C, 100 °C, etc.) for 12 to 24 h (such as 15 h, 18 h, 20 h, 22 h, etc.), and the conditions for calcination are calcination at 300 to 700 °C (such as 400 °C, 500 °C, 600 °C, 650 °C, etc.) for 3 to 24 h (such as 5 h, 8 h, 10 h, 12 h, 18 h, 20 h, 22 h, etc.). During the calcination process, the loaded soluble Cu and Zr salts undergo thermal decomposition to generate CuO and ZrO2 respectively. Under high-temperature conditions, the generated oxides not only interact with each other, but also can strongly interact with the SiO2 support, thereby promoting their highly dispersed on the support surface, and further helping to improve the catalytic efficiency and durability of the catalyst.

[0050] In one embodiment, the CuZr / SiO2 is granulated CuZr / SiO2 with a particle size of 20 to 100 (such as 30, 50, 70, 80, etc.) mesh. That is, after the calcination, granulation treatment is carried out, and CuZr / SiO2 with a particle size of 20 to 100 mesh is screened.

[0051] Preferably, the soluble Cu salt can be selected from at least one of Cu(NO3)2·3H2O, CuSO4·5H2O, CuSO4, Cu2(CH3COO)4, CuCl2, CuCl2·2H2O.

[0052] Preferably, the soluble Zr salt may be selected from at least one of ZrO(NO3)2·2H2O, Zr(NO3)4, ZrCl4, ZrO(ClO4)2, Zr6O4(OH)4(O2CCH3). 12

[0053] In one embodiment, the HZSM-5 molecular sieve is an activated HZSM-5 molecular sieve. The activation method of the HZSM-5 molecular sieve includes the steps of: taking the HZSM-5 molecular sieve (which can be purchased from Mizusawa Chemical Industry Co., Ltd.), performing programmed temperature increase at a heating rate of 1-20 °C / min to 300-900 °C, and then holding the temperature for 3-24 h to obtain the activated HZSM-5 molecular sieve.

[0054] After the HZSM-5 molecular sieve is activated, it has developed pores and strong three-dimensional regular structure stability, which can significantly improve the reactivity of reactant molecules and intermediate products and the diffusivity of product molecule BTX, and greatly improve the activity stability of the catalyst system.

[0055] In one embodiment, the HZSM-5 molecular sieve is a granulated HZSM-5 molecular sieve with a particle size of 20-100 mesh (such as 30, 50, 70, 80, etc.). That is, after the activation, the activated HZSM-5 molecular sieve is granulated, and the activated HZSM-5 molecular sieve with a particle size of 20-100 mesh is screened.

[0056] The present invention provides a method for preparing light aromatics by ethanol aromatization, which includes the steps of: contacting a raw material containing ethanol with the catalyst system of the present invention in a reaction zone to obtain light aromatics.

[0057] Specifically, CuZr / SiO2 and the HZSM-5 molecular sieve are placed in the constant temperature zone of a fixed-bed reactor to construct a CuZr / SiO2:HZSM-5 catalyst system for ethanol to BTX. Hydrogen or a hydrogen-containing mixed gas is introduced to pretreat the catalyst system, and then a raw material containing ethanol (such as an ethanol aqueous solution) is pumped into a vaporization chamber by a peristaltic pump for vaporization (the vaporization temperature is 80-200 °C, such as 90 °C, 120 °C, 150 °C, 180 °C, etc.). The vaporized ethanol is mixed with N2 (the volume ratio of ethanol to N2 can be 0.5:1-5:1, such as 1:1, 2:1, 3:1, 4:1, etc.) and enters the constant temperature zone of the fixed-bed reactor for reaction to produce BTX.

[0058] The present invention provides a method for directly preparing light aromatics (Benzene-Toluene-Xylene, BTX) from a raw material containing ethanol in one step. Figure 1 ​As shown, this method involves contacting a raw material containing ethanol with a CuZr / SiO2:HZSM-5 catalyst system (including a CuZr / SiO2 catalyst and HZSM-5 zeolite) in a reaction zone to produce aromatics mainly composed of BTX. Specifically, the active components of the CuZr / SiO2 catalyst are composed of Cu and Zr active metals supported by SiO2 as the carrier, mainly used for catalyzing the dehydrogenation and condensation of ethanol to produce the intermediate product butadiene; the active components of the HZSM-5 zeolite catalyze the aromatization of butadiene into aromatics, especially BTX. This catalyst system can efficiently and directly convert ethanol into light aromatics, reduce the production cost of products, facilitate reuse, and is conducive to large-scale industrial production applications. In addition, this catalyst system can also effectively inhibit catalyst agglomeration, loss of active components, and carbon deposition problems, significantly improving the stability of the catalyst.

[0059] In one embodiment, the reaction zone is the constant temperature zone of a single fixed-bed reactor or the constant temperature zone of a series of two fixed-bed reactors. That is, the reactor is a single fixed-bed reactor or a series of two fixed-bed reactors.

[0060] When using a single fixed-bed reactor, when the catalyst system is used for producing BTX from ethanol in the single fixed-bed reactor, a two-bed catalyst state mode is adopted. Specifically, CuZr / SiO2 is loaded in the upper part of the constant temperature zone of the fixed-bed reactor, and HZSM-5 zeolite is loaded in the lower part of the constant temperature zone of the fixed-bed reactor.

[0061] When using a series of two fixed-bed reactors, when the catalyst system is used for producing BTX from ethanol in the series of two fixed-bed reactors, the series of two fixed-bed reactors sequentially includes a first fixed-bed reactor and a second fixed-bed reactor connected in series up and down. CuZr / SiO2 is placed in the constant temperature zone of the first fixed-bed reactor, and HZSM-5 zeolite is placed in the constant temperature zone of the second fixed-bed reactor.

[0062] In one embodiment, the reaction temperature is 300 - 600 °C, preferably 400 - 550 °C, such as 400 °C, 450 °C, 500 °C, 550 °C.

[0063] In one embodiment, the raw material containing ethanol is an aqueous ethanol solution, and the mass fraction of ethanol in the aqueous ethanol solution is 1 - 100% (such as 1%, 10%, 20%, 50%, 60%, 70%, 80%, 90%, 100%, etc.).

[0064] In one embodiment, the mass hourly space velocity of ethanol is 0.5 - 7 h -1 , preferably 0.5 - 4 h -1 , 2 h -1 .

[0065] In one embodiment, the catalyst system is pretreated with hydrogen or a hydrogen-containing gas mixture before use; wherein, the temperature of the pretreatment is 300 to 600 °C (preferably 400 to 600 °C, such as 500 °C), the time of the pretreatment is 2 to 12 h (such as 2 h, 4 h, 5 h, 8 h, 10 h, 12 h, etc.), and the gas hourly space velocity of the pretreatment gas is 600 to 3600 h -1 .

[0066] The present invention will be further described in detail below through specific examples.

[0067] The analysis method in the embodiments of the present invention is as follows:

[0068] Online analysis is carried out using a Shimadzu GC2014 gas chromatograph equipped with a TCD detector connected to a TDX-1 packed column and an FID detector connected to a DB-5 capillary column.

[0069] In the embodiments of the present invention, the conversion rate and selectivity are both calculated based on the carbon molar number, and the calculation formulas for the conversion rate and selectivity are as follows:

[0070] Ethanol conversion rate = [(carbon molar number of ethanol in the feed) - (carbon molar number of ethanol in the product)] ÷ (carbon molar number of ethanol in the feed) × (100%).

[0071] Selectivity of liquid hydrocarbons (hydrocarbons with more than 5 carbons) = (carbon molar number of liquid hydrocarbons in the product) ÷ (carbon molar number of all products in the product) × (100%).

[0072] Aromatic hydrocarbon selectivity = (carbon molar number of aromatic hydrocarbons in the product) ÷ (carbon molar number of all products in the product) × (100%).

[0073] BTX selectivity = (carbon molar number of BTX in the product) ÷ (carbon molar number of all products in the product) × (100%).

[0074] The catalyst performance test is as follows:

[0075] Example 1

[0076] 1) The CuZr / SiO2(Q10) component was prepared by ultrasonic-assisted impregnation method. 0.30 g of Cu(NO3)2·3H2O and 2.35 g of ZrO(NO3)2·2H2O were dissolved in 15 mL of deionized water and ultrasonicated until a mixed solution was formed. The above mixed solution was added to a beaker containing 4.01 g of Q10 support and subjected to water bath ultrasonic impregnation. The water bath temperature was set at 60 °C, and continuous stirring was carried out under ultrasonic conditions until a uniform and viscous gel-like substance was obtained, until it was evaporated to dryness. Then, the obtained sample was dried in an oven at 80 °C for 12 h. Finally, the obtained sample was transferred to a muffle furnace and calcined at a heating rate of 5 °C / min to 500 °C for 4 h to obtain the CuZr / SiO2(Q10) active component. Among them, the mass content of Cu in the calcined CuZr / SiO2(Q10) active component was 2.0 wt%, and the mass content of Zr in the calcined CuZr / SiO2(Q10) active component was 20.0 wt%.

[0077] 2) The zeolite molecular sieve was activated by air calcination method. 5.00 g of HZSM-5 molecular sieve with a silicon-aluminum atomic ratio of 105 was calcined in a muffle furnace at a heating rate of 5 °C / min to 500 °C for 3 h to obtain the activated HZSM-5(105) molecular sieve.

[0078] 3) A single fixed-bed reactor with a two-bed catalyst state mode was adopted. The above-prepared CuZr / SiO2(105) component and the activated HZSM-5(105) molecular sieve were loaded into the upper and lower parts of the isothermal zone of the fixed-bed reactor at a mass ratio of 1:1, respectively, to obtain the catalyst system for ethanol to produce BTX.

[0079] 4) The above catalyst system was reduced by passing pure hydrogen. The space velocity of the reducing gas was 1200 h -1 , the reduction temperature was 450 °C, the reduction time was 3 h, and the reduction pressure was atmospheric pressure. After the reduction process was completed, N2 gas was introduced for purging for 1 h to remove residual reducing gases. Subsequently, ethanol was pumped in and completely vaporized in the vaporization chamber. The generated ethanol vapor entered the reaction zone with the N2 carrier gas to carry out the target reaction. The reaction pressure was 0.1 MPa, the mass space velocity of ethanol was 2 h -1 , the reaction temperature was 450 °C, and the reaction results are shown in Table 1.

[0080] 5) The gas-phase products entered the gas chromatograph for on-line analysis. The liquid-phase products were collected in a cold trap, taken out after the reaction was completed, and separated to obtain an oil phase and an aqueous phase. The oil-phase products and the aqueous-phase products were respectively analyzed by gas chromatography, and the selectivity of each substance in the analysis results was carbon molar selectivity.

[0081] Example 2

[0082] The preparation steps and method are the same as those in Example 1, except that the mass of Cu(NO3)2·3H2O in step 1) of Example 1 is changed to 0.15 g, and the reaction results are shown in Table 1.

[0083] Example 3

[0084] The preparation steps and method are the same as those in Example 1, except that the mass of Cu(NO3)2·3H2O in step 1) of Example 1 is changed to 0.61 g, and the reaction results are shown in Table 1.

[0085] Example 4

[0086] The preparation steps and method are the same as those in Example 1, except that the mass of ZrO(NO3)2·2H2O in step 1) of Example 1 is changed to 1.17 g, and the reaction results are shown in Table 1.

[0087] Example 5

[0088] The preparation steps and method are the same as those in Example 1, except that the mass of ZrO(NO3)2·2H2O in step 1) of Example 1 is changed to 3.53 g, and the reaction results are shown in Table 1.

[0089] Example 6

[0090] The preparation steps and method are the same as those in Example 1, except that the reaction temperature in step 4) of Example 1 is changed to 350 °C, and the reaction results are shown in Table 1.

[0091] Example 7

[0092] The preparation steps and method are the same as those in Example 1, except that the reaction temperature in step 4) of Example 1 is changed to 400 °C, and the reaction results are shown in Table 1.

[0093] Example 8

[0094] The preparation steps and method are the same as those in Example 1, except that the reaction temperature in step 4) of Example 1 is changed to 500 °C, and the reaction results are shown in Table 1.

[0095] Example 9

[0096] The preparation steps and method are the same as those in Example 1, except that the ethanol mass space velocity in step 4) of Example 1 is changed to 1 h -1 , and the reaction results are shown in Table 1.

[0097] Example 10

[0098] The preparation steps and method are the same as those in Example 1, except that the ethanol mass space velocity in step 4) of Example 1 is changed to 3 h -1 , and the reaction results are shown in Table 1.

[0099] Example 11

[0100] The preparation steps and method are the same as those in Example 1, except that step 3) of Example 1 is changed to adopt the state mode of a series-connected dual fixed-bed reactor. The CuZr / SiO2(105) component prepared in the above steps 1) and 2) and the activated HZSM-5(105) molecular sieve are successively loaded into the constant temperature zone of the series-connected dual fixed-bed reactor according to a mass ratio of 1:1, and thus a catalyst system for ethanol to prepare BTX is obtained. The reaction is carried out according to the method in step 4) of Example 1, and the reaction results are shown in Table 1.

[0101] Example 12

[0102] The preparation steps and method are the same as those in Example 1, except that step 2) of Example 1 is changed to take 4.01 g of HZSM-5 molecular sieve with a silicon-aluminum atomic ratio of 38. After step 3) of Example 1, the reaction is carried out according to the method in step 4) of Example 1, and the reaction results are shown in Table 1.

[0103] Table 1. Ethanol aromatization reaction results

[0104]

[0105]

[0106] It can be seen from Table 1 that in the BTX synthesis reaction of ethanol through the CuZr / SiO2:HZSM-5 catalyst system, the appropriate introduction of Cu element can significantly improve the selectivity of aromatics (especially BTX); the addition of Zr element can stabilize the selectivity of aromatic hydrocarbon products; increasing the reaction temperature can promote the formation of aromatics, but too high a temperature will lead to an increase in the formation of high-molecular aromatics; the ethanol mass hourly space velocity has no obvious effect on the selectivity of the product distribution; the series-connected dual fixed-bed reactor and the single fixed-bed reactor show almost the same performance in catalytic activity; too high acidity of HZSM-5 leads to an increase in by-products, thereby reducing the selectivity of aromatics. The catalyst system of the present invention shows high catalytic activity and good aromatic selectivity. Among them, the 2% Cu10% Zr / SiO2(Q10):HZSM-5(105) catalyst system can reach a BTX selectivity of 58.5% under the reaction conditions of 450 °C.

[0107] Figure 2 XRD spectra of the CuZr / SiO2 active component prepared in Example 1 before and after calcination. The diffraction peaks of its XRD spectrum are attributed to the characteristic diffraction peaks of the amorphous SiO2 support and there are no characteristic diffraction peaks of the loaded metal elements, indicating that the active metal is evenly distributed on the support.

[0108] Figure 3XRD pattern of the HZSM-5(105) selected for Example 1. The characteristic diffraction peaks at 2θ = 8.1, 8.9, 23.2, 24.1, 30.0, 45.2, and 45.7 are attributed to the characteristic diffraction peaks of HZSM-5, indicating that the selected and activated molecular sieve has a good crystal form.

[0109] Figure 4 Gas chromatogram of the oil-phase product of Example 1. The main products in the oil phase are aromatics, especially BTX.

[0110] In summary, the present invention provides a catalyst system and a method for preparing light aromatics (Benzene-Toluene-Xylene, BTX) by a one-step method using an aqueous ethanol raw material. In this method, an aqueous solution containing ethanol is brought into contact with a CuZr / SiO2:HZSM-5 (25.0 wt% - 33.3 wt%: 66.7 wt% - 75.0 wt%) catalyst system in the reaction zone to generate aromatics mainly composed of BTX. Specifically, the active components of the CuZr / SiO2 catalyst are composed of Cu and Zr active metals supported on SiO2 as the carrier, which is mainly used to catalyze the dehydrogenation condensation of ethanol to produce the intermediate product butadiene; the HZSM-5 molecular sieve active component catalyzes the aromatization of butadiene into aromatics, especially BTX. This catalyst system can efficiently and directly convert ethanol into light aromatics, reduce the production cost of products, facilitate reuse, and is conducive to large-scale industrial production applications. In addition, this catalyst system can also effectively inhibit the agglomeration of the catalyst, the loss of active components, and the coking problem, significantly improving the stability of the catalyst.

[0111] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A catalyst system, characterized in that The catalyst system includes CuZr / SiO2 and HZSM-5 molecular sieve, which is recorded as CuZr / SiO2:HZSM-5; wherein the CuZr / SiO2 includes a SiO2 carrier and Cu elements and Zr elements loaded on the surface of the SiO2 carrier.

2. The catalyst system according to claim 1, characterized in that The mass content of the CuZr / SiO2 in the CuZr / SiO2:HZSM-5 is 66.7-75.0%, and the mass content of the HZSM-5 molecular sieve in the CuZr / SiO2:HZSM-5 is 25.0-33.3%.

3. The catalyst system according to claim 1, characterized in that The mass content of the Cu element in the CuZr / SiO2 is 1.0-5.0%, and the mass content of the Zr element in the CuZr / SiO2 is 10.0-50.0%.

4. The catalyst system according to claim 1, characterized in that The SiO2 carrier is at least one of a Q3 spherical carrier, a Q6 spherical carrier, a Q10 spherical carrier, a Q15 spherical carrier, a Q30 spherical carrier, and a Q50 spherical carrier; The atomic ratio of silicon to aluminum in the HZSM-5 molecular sieve is 40-200, and the HZSM-5 molecular sieve has a multi-level pore structure of micropores, mesopores and macropores.

5. The catalyst system according to claim 1, characterized in that The CuZr / SiO2 is prepared by the following method: dissolving a soluble Cu salt and a soluble Zr salt in water to obtain a soluble salt solution; adding the soluble salt solution into a container containing a SiO2 carrier, and sequentially stirring, evaporating and drying, and roasting to obtain the CuZr / SiO2.

6. The catalyst system according to claim 1, characterized in that The HZSM-5 molecular sieve is an activated HZSM-5 molecular sieve. The activation method of the HZSM-5 molecular sieve comprises the steps of taking the HZSM-5 molecular sieve, heating the temperature to 300-900° C. at a heating rate of 1-20° C. / min, and keeping the temperature for 3-24 hours to obtain the activated HZSM-5 molecular sieve.

7. The catalyst system according to claim 1, characterized in that The CuZr / SiO2 is CuZr / SiO2 that has been granulated and has a particle size of 20 to 100 meshes, and the HZSM-5 molecular sieve is HZSM-5 molecular sieve that has been granulated and has a particle size of 20 to 100 meshes.

8. A method for preparing light aromatics by aromatization of ethanol, characterized in that: The method comprises the steps of: contacting and reacting a raw material containing ethanol with the catalyst system according to any one of claims 1 to 7 in a reaction zone to obtain light aromatic hydrocarbons.

9. The method for preparing light aromatics by aromatization of ethanol according to claim 8, characterized in that: The reaction zone is a constant temperature zone of a single fixed bed reactor or a constant temperature zone of a series of two fixed bed reactors; The reaction temperature is 300-600°C; The raw material containing ethanol is an ethanol aqueous solution, the mass fraction of ethanol in the ethanol aqueous solution is 1-100%, and the mass space velocity of ethanol is 0.5-7h -1 .

10. The method for preparing light aromatics by aromatization of ethanol according to claim 8, characterized in that: The catalyst system is pretreated with hydrogen or a hydrogen-containing mixed gas before use; The pretreatment temperature is 300-600°C, the pretreatment time is 2-12 hours, and the pretreatment gas hourly space velocity is 600-3600h -1 .

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