A catalyst for preparing light aromatics, its preparation method and application

Abstract

This invention discloses a catalyst for preparing light aromatic hydrocarbons, its preparation method, and its application. The catalyst comprises a metal oxide and a composite molecular sieve; the composite molecular sieve includes both eight-membered ring molecular sieves and ten-membered ring molecular sieves; the weak acid content of the eight-membered ring molecular sieve is 100–800 μmol·g. ‑1 The strong acid has an acidity of 16–500 μmol·g. ‑1 The ratio of weak acid content to strong acid content is 1–6. When applied to the reaction for preparing light aromatics, the catalyst improves the selectivity of BTX in aromatics without reducing the overall aromatic selectivity.

Description

Technical Field

[0001] This invention belongs to the field of light aromatic hydrocarbon catalysts, specifically relating to a catalyst for preparing light aromatic hydrocarbons, its preparation method, and its application. Background Technology

[0002] Syngas is an important platform for producing chemicals as an alternative to petroleum. It can be derived from natural gas, coal, biomass, etc., and through different catalysts, syngas can be used to produce high-value-added basic chemicals such as oxygenated compounds, C2-C4 hydrocarbons, liquid fuels, and aromatics. Among these, aromatic products, especially BTX, are raw materials for the synthesis of styrene, polyamide resins, and terephthalic acid, possessing significant commercial value and attracting widespread attention.

[0003] CN110368984A discloses an Fe-based catalyst, its preparation method, and its application in the one-step synthesis of aromatics from syngas. The catalyst is composed of Fe-based spinel material, molecular sieve zeolite, and metal oxides, wherein the Fe-based spinel content is 9.95%–79.95%, the zeolite molecular sieve content is 20%–90%, and the oxide promoter content is 0.05%–20%. This catalyst couples the synthesis of olefins from syngas with the aromatization reaction of olefins to produce aromatics; however, it exhibits high methane selectivity but low aromatic selectivity, around 60%.

[0004] CN110201709A discloses a composite catalyst for the direct production of high-value aromatics from syngas. This catalyst is prepared by mechanically mixing a metal oxide with nano-HZSM-5 molecular sieves or metal-modified nano-HZSM-5 molecular sieves; wherein the metal oxide is at least one of sodium, potassium, iron, and manganese oxides. Using this catalyst enables the coupling of multiple reaction stages, effectively improving the driving force of intermediate reactions, increasing the conversion efficiency of syngas, and reducing the occurrence of side reactions. The CO conversion rate can reach 95%, but the selectivity for aromatics among the organic products is relatively low (<60%).

[0005] Although existing technologies have been studied in the field of syngas-to-aromatics production, the selectivity for light aromatics (benzene, toluene, xylene, abbreviated as BTX) in the coupled system, which are in high demand, is low. Therefore, it is of great significance to further develop catalysts with high activity and high BTX selectivity for one-step syngas-to-aromatics production. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a catalyst for preparing light aromatics, its preparation method, and its application. The catalyst is applied in the reaction of carbon oxides and hydrogen to prepare light aromatics, improving the selectivity of BTX in aromatics without reducing the total aromatics selectivity.

[0007] The first aspect of this invention provides a catalyst for preparing light aromatic hydrocarbons, the catalyst comprising a metal oxide and a composite molecular sieve; the composite molecular sieve comprises both an eight-membered ring molecular sieve and a ten-membered ring molecular sieve; the weak acid content of the eight-membered ring molecular sieve is 100–800 μmol·g. -1 The strong acid has an acidity of 16–500 μmol·g. -1 The ratio of weak acid concentration to strong acid concentration is 1 to 6.

[0008] According to the present invention, preferably, the weak acid content in the eight-membered ring molecular sieve is 100–800 μmol·g. -1 Preferably, the concentration is 150–600 μmol·g. -1 As a non-limiting example, the acid mass of the weak acid can be 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, or 800 μmol·g. -1 Any of the following values.

[0009] According to the present invention, preferably, the amount of strong acid in the eight-membered ring molecular sieve is 16–500 μmol·g. -1 Preferably, it is 50–400 μmol·g -1 As a non-limiting example, the strong acid mass can be 16, 20, 60, 100, 150, 200, 250, 300, 350, 400, 450, or 500 μmol·g. -1 Any of the following values.

[0010] According to the present invention, preferably, the ratio of weak acid content to strong acid content in the eight-membered ring molecular sieve is 1 to 6, more preferably 1 to 4. As a non-limiting example, the ratio of weak acid content to strong acid content can be any value among 1, 2, 3, 4, 5, 6, etc.

[0011] According to the present invention, the eight-membered ring molecular sieve includes at least one of SAPO-18 and SAPO-17 molecular sieves. Preferably, the silicon-containing eight-membered ring molecular sieve contains SiO₂. 2 / The molar ratio of Al2O3 is 0.2 to 1.8.

[0012] According to the present invention, the decacyclic molecular sieve has two-dimensional (2D) or three-dimensional (3D) decacyclic channels, more preferably at least one of ZSM-5, ZSM-11, ZSM-12, MCM-22, Silicalite-1 and Silicalite-2.

[0013] According to the present invention, in the catalyst, the metal element of the metal oxide is selected from at least one of Cr, Zr, Mn, Ce, La, In, Ga and Zn; preferably at least one of Cr, Zr, Ce, Mn and Ga.

[0014] According to the present invention, the mass ratio of metal oxide to molecular sieve in the catalyst is 0.05 to 10, preferably 1 to 5.

[0015] According to the present invention, the mass ratio of the octagonal molecular sieve to the ten-membered ring molecular sieve in the catalyst is 1:5 to 5:1.

[0016] A second aspect of the present invention provides a method for preparing the catalyst for preparing light aromatic hydrocarbons, comprising: mixing a composite molecular sieve and a metal oxide to obtain the catalyst.

[0017] According to the present invention, the mixing is a mechanical mixing method, preferably the following method, comprising: dispersing metal oxide and composite molecular sieve in a low-carbon alcohol solution, ultrasonically treating, drying and calcining to obtain the catalyst.

[0018] According to the present invention, in the method of mixing composite molecular sieves and metal oxides, the low-carbon alcohol is an alcohol with C6 or less, preferably ethanol. The mass concentration of the low-carbon alcohol solution is 50% to 90%. The mass ratio of the low-carbon alcohol to the total mass of the metal oxide and the composite molecular sieve in step (1) is (1 to 10):1, preferably (2 to 5):1. The ultrasonic treatment conditions are as follows: ultrasonic frequency of 10 to 40 kHz, ultrasonic temperature of 30 to 50 °C, and ultrasonic time of 0.5 to 3 h. The drying conditions are as follows: drying temperature of 50 to 120 °C and drying time of 2 to 12 h. The calcination conditions are as follows: calcination temperature of 400 to 600 °C and calcination time of 3 to 8 h.

[0019] According to the present invention, the acid treatment method for the eight-membered ring molecular sieve can be achieved by immersing the eight-membered ring molecular sieve in an acid solution. The acid used can be at least one of nitric acid, oxalic acid, and acetic acid, preferably acetic acid. The concentration of the acid solution is 0.1–3 mol / L. The mass ratio of the eight-membered ring molecular sieve to the acid solution is 1:1 to 1:5. The acid treatment equipment is preferably a stainless steel pressure vessel lined with polytetrafluoroethylene. The pressure is not particularly limited and is self-generated pressure. The acid treatment temperature is 150–180°C, and the time is 12–36 hours. The heating equipment can be an oven.

[0020] According to the present invention, in the method for preparing the catalyst for preparing light aromatic hydrocarbons, the metal oxide can be prepared by conventional methods, such as precipitation, preferably co-precipitation. In the precipitation method, the metal source is a metal salt. Preferably, the metal salt is at least one selected from nitrate, acetate, and sulfate. The precipitant includes at least one selected from sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and ammonia water. In the precipitation method, the molar ratio of the metal source to the precipitant is 0.5–2. After the coprecipitation reaction, aging, drying, and calcination steps can be performed to obtain the metal oxide. The aging conditions are: aging temperature of 40–80°C and aging time of 1–5 h. The drying conditions are: drying temperature of 80–120°C and drying time of 8–12 h. The calcination conditions are: calcination temperature of 400–600°C and calcination time of 1–4 h, and the calcination atmosphere is a mixed atmosphere of hydrogen and nitrogen, preferably with a hydrogen volume concentration of 10%–30% in the hydrogen-nitrogen mixture.

[0021] A third aspect of the present invention provides the application of the catalyst in the preparation of light aromatics.

[0022] According to the present invention, in the application, the light aromatic hydrocarbon includes at least one of benzene, toluene, and xylene (BTX).

[0023] According to the present invention, in the application, the feed gas includes carbon oxides and hydrogen. The carbon oxides include at least one of carbon monoxide and carbon dioxide, preferably carbon monoxide. The molar ratio of hydrogen to carbon oxides is 0.5–10:1, preferably 0.5–5:1.

[0024] According to the present invention, the reaction conditions are: a reaction temperature of 350–450°C, and / or a reaction pressure of 1–10 MPa, and / or a total volume hourly space velocity of 800–10000 h⁻¹. -1 The reaction apparatus is a fixed bed.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The inventors discovered through research that in the reaction of carbon oxides and hydrogen to prepare light aromatics, when both eight-membered ring molecular sieves and ten-membered ring molecular sieves are used simultaneously, the acid content of the eight-membered ring molecular sieve, especially the acid content of the weak acid and the strong acid, is crucial to improving the selectivity of light aromatics. Further research by the inventors revealed that when the acid content of the weak acid in the eight-membered ring is 100–800 μmol·g... -1 The strong acid has an acidity of 16–500 μmol·g. -1When the ratio of weak acid content to strong acid content is 1 to 6, it is beneficial to convert active intermediates such as methoxy and methanol generated on the surface of metal oxides and carbon oxides into olefins, which are then desorbed from the surface of the molecular sieve. This avoids further alkylation of BTX generated in the ten-membered ring channel with active intermediates such as methoxy at the acidic sites on the outer surface of the ten-membered ring molecular sieve. This can significantly improve the selectivity of BTX in aromatics without reducing the selectivity of total aromatics.

[0027] 2. The preparation method of the present invention includes: mixing a composite molecular sieve and a metal oxide to obtain the catalyst. The eight-membered ring molecular sieve needs to be acid-treated. By controlling the acid treatment conditions, the eight-membered ring molecular sieve has an appropriate acid content distribution, reducing the side reaction of hydrogenation of intermediates to alkanes at the acidic sites of the molecular sieve. Further, in a preferred embodiment, SiO2 can be simultaneously controlled. 2 / The acid content distribution is adjusted by the Al2O3 molar ratio and acid treatment conditions.

[0028] 3. When the catalyst of the present invention is applied to the reaction in the preparation of light aromatics, it can significantly improve the selectivity of BTX in aromatics without reducing the total aromatics selectivity. Detailed Implementation

[0029] The present invention will be further illustrated below through specific embodiments. The embodiments only provide some conditions for achieving this objective, but the scope of the claims of the present invention is not limited by these embodiments.

[0030] In this invention, NH3-TPD was used to determine the acidity and acid content of the sample. The test was performed on a chemisorption analyzer (Altamira AMI-3300). 100 mg of catalyst was first heated to 600 °C at 10 °C / min under a He atmosphere and purged for 60 min. After cooling to 50 °C, it was adsorbed with a mixture of NH3 and N2 containing 10% (by volume) NH3 until saturation. He purging was then used to remove the physically adsorbed NH3 from the surface. Subsequently, the temperature was increased from 50 °C to 600 °C at 10 °C / min, and the change in NH3 concentration in the exhaust gas was detected using a TCD. In the NH3-TPD spectrum, the peaks from 100 to 250 °C correspond to weak acid centers, and the peaks from 250 to 500 °C correspond to strong acid centers. The acidity and acid content were calculated based on the peak areas of the weak and strong acid peaks.

[0031] In this invention, CO conversion, aromatic selectivity, and BTX / aromatics ratio are all percentages calculated in moles.

[0032]

Example 1

[0033] Preparation of metal oxides:

[0034] MnO was prepared by precipitation method. 0.5 mol of manganese nitrate was weighed and dissolved in 1000 mL of distilled water. Then, 1.0 mol of sodium hydroxide was dissolved in 1000 mL of water. The two aqueous solutions were co-precipitated by running them in parallel. The solution was aged at 80 °C for 2 h, filtered, dried at 100 °C for 12 h, and calcined at 500 °C in a 10% hydrogen-nitrogen mixed atmosphere for 1 h to obtain MnO oxide.

[0035] Preparation of ten-membered ring molecular sieves:

[0036] 0.27 g of aluminum isopropoxide was added to a solution containing 16.27 g of tetrapropylammonium hydroxide (25%) and 11.82 g of deionized water, and stirred at room temperature for 10 h. Then, 13.89 g of tetraethyl orthosilicate was added to the mixture, and the mixture was stirred for 12 h. 5.01 g of urea was added to the above solution, and the mixture was stirred for another 1 h to form a molecular sieve mother liquor. The final composition (molar ratio) of the reaction mixture was 1 SiO2:0.01 Al2O3:0.3 TPAOH:20H2O:1.25 urea. The mother liquor was placed in a polytetrafluoroethylene-lined autoclave and hydrothermally heated in an oven at 180 °C for 48 h. After centrifugation and washing until the supernatant was neutral, the mixture was dried at 80 °C for 12 h and then calcined at 550 °C for 5 h to obtain ZSM-5 molecular sieve.

[0037] Preparation and acid treatment of octagonal ring molecular sieves:

[0038] 27.4 g of boehmite (Al₂O₃, 74.6 wt%) was added to a mixture prepared by mixing 46.1 g of H₃PO₄ (85 wt%) and 119.2 g of water, and stirred until homogeneous. Then, HCl solution (37 wt%), TEAOH (25 wt%), and silica sol were added, and the mixture was further stirred until homogeneous. The final reaction mixture composition (molar ratio) was 0.4SiO₂:0.33HCl:0.67(TEA)₂O:Al₂O₃:P₂O₅:40H₂O. The reaction mixture was sealed in a polytetrafluoroethylene stainless steel pressure vessel and heated under pressure in an oven at 170 °C for 72 h. The solid reaction product was recovered by filtration, washed with water, dried at 100 °C for 12 h, and then calcined at 550 °C for 5 h at a rate of 2 °C / min to obtain SAPO-18 molecular sieve.

[0039] 10g of SAPO-18 molecular sieve was placed in 10g of 1mol / L acetic acid and sealed in a polytetrafluoroethylene stainless steel pressure vessel. The vessel was then heated under pressure in an oven at 160℃ for 12 hours. After centrifugation and washing, low-acid SAPO-18 molecular sieve was obtained. The weak acid content of the SAPO-18 molecular sieve was 407 μmol·g. -1 The strong acid has a strength of 163 μmol·g. -1The ratio of weak acid concentration to strong acid concentration is 2.5. (This refers to the SiO2 content of SAPO-18 molecular sieve.) 2 / The molar ratio of Al2O3 is 0.4:1.

[0040] Catalyst preparation:

[0041] 1.0 g of prepared MnO oxide, 0.5 g of ZSM-5 and 0.5 g of SAPO-18 molecular sieve were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatics.

[0042] The obtained catalyst was granulated and packed into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400 °C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to enter the catalytic bed for reaction. The reaction temperature was 400 °C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0043]

Example 2

[0044] The preparation of MnO, ZSM-5, and SAPO-18 molecular sieves was the same as in Example 1. The acid treatment of SAPO-18 molecular sieve was the same as in Example 1.

[0045] Catalyst preparation:

[0046] 1.0g of the prepared MnO oxide, 0.5g of ZSM-5 and 0.5g of SAPO-18 molecular sieve were ground and mixed, and then granulated to obtain the catalyst.

[0047] The catalyst was loaded into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400°C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to react in the catalytic bed. The reaction temperature was 400°C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0048]

Example 3

[0049] The preparation of MnO and ZSM-5 is the same as in Example 1.

[0050] Preparation and acid treatment of octagonal ring molecular sieves:

[0051] 27.4 g of boehmite (Al₂O₃, 74.6 wt%) was added to a mixture prepared by mixing 46.1 g of H₃PO₄ (85 wt%) and 119.2 g of water, and stirred until homogeneous. Then, HCl solution (37 wt%), TEAOH (25 wt%), and silica sol were added, and the mixture was further stirred until homogeneous. The final composition (molar ratio) of the reaction mixture was 0.8SiO₂:0.33HCl:0.67(TEA)₂O:Al₂O₃:P₂O₅:40H₂O. The reaction mixture was sealed in a polytetrafluoroethylene stainless steel pressure vessel and heated under pressure in an oven at 170 °C for 72 h. The solid reaction product was recovered by filtration, washed with water, dried at 100 °C for 12 h, and then calcined at 550 °C for 5 h at a rate of 2 °C / min to obtain SAPO-18 molecular sieve.

[0052] 10g of SAPO-18 molecular sieve was placed in 10g of 1mol / L acetic acid and sealed in a polytetrafluoroethylene stainless steel pressure vessel. The vessel was then heated in an oven at 160℃ under pressure for 12 hours. After centrifugation and washing, low-acid SAPO-18 molecular sieve was obtained. The weak acid content of the SAPO-18 molecular sieve was 400 μmol·g. -1 The strong acid has an acid strength of 250 μmol·g. -1 The ratio of weak acid concentration to strong acid concentration is 1.6. (This refers to the SiO2 content of SAPO-18 molecular sieve.) 2 / The molar ratio of Al2O3 is 0.8:1.

[0053] Catalyst preparation:

[0054] 1.0 g of prepared MnO oxide, 0.5 g of ZSM-5 and 0.5 g of SAPO-18 molecular sieve were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatics.

[0055] The obtained catalyst was granulated and packed into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400 °C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to enter the catalytic bed for reaction. The reaction temperature was 400 °C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0056]

Example 4

[0057] The preparation of MnO and ZSM-5 is the same as in Example 1.

[0058] Preparation and acid treatment of octagonal ring molecular sieves:

[0059] 27.4 g of boehmite (Al₂O₃, 74.6 wt%) was added to a mixture prepared by mixing 46.1 g of H₃PO₄ (85 wt%) and 119.2 g of water, and stirred until homogeneous. Then, HCl solution (37 wt%), TEAOH (25 wt%), and silica sol were added, and the mixture was further stirred until homogeneous. The final reaction mixture composition (molar ratio) was 1.5SiO₂:0.33HCl:0.67(TEA)₂O:Al₂O₃:P₂O₅:40H₂O. The reaction mixture was sealed in a polytetrafluoroethylene stainless steel pressure vessel and heated under pressure in an oven at 170 °C for 72 h. The solid reaction product was recovered by filtration, washed with water, dried at 100 °C for 12 h, and then calcined at 550 °C for 5 h at a rate of 2 °C / min to obtain SAPO-18 molecular sieve.

[0060] 10g of SAPO-18 molecular sieve was placed in 10g of 1mol / L acetic acid and sealed in a polytetrafluoroethylene stainless steel pressure vessel. The vessel was then heated in an oven at 160℃ under pressure for 12 hours. After centrifugation and washing, low-acid SAPO-18 molecular sieve was obtained. The weak acid content of the SAPO-18 molecular sieve was 400 μmol·g. -1 The strong acid has a strength of 384 μmol·g. -1 The ratio of weak acid concentration to strong acid concentration is 1.04. (This refers to the SiO2 content of SAPO-18 molecular sieve.) 2 / The molar ratio of Al2O3 is 1.5:1.

[0061] Catalyst preparation:

[0062] 1.0 g of prepared MnO oxide, 0.5 g of ZSM-5 and 0.5 g of SAPO-18 molecular sieve were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatics.

[0063] The obtained catalyst was granulated and packed into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400 °C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to enter the catalytic bed for reaction. The reaction temperature was 400 °C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0064]

Example 5

[0065] The preparation of MnO, ZSM-5, and SAPO-18 molecular sieves was the same as in Example 1.

[0066] The acid treatment of SAPO-18 molecular sieve is as follows:

[0067] 10g of SAPO-18 molecular sieve was placed in 10g of 0.1mol / L acetic acid and sealed in a polytetrafluoroethylene stainless steel pressure vessel. The mixture was then heated in an oven at 180℃ under pressure for 30 hours. After centrifugation and washing, low-acid SAPO-18 molecular sieve was obtained. The weak acid content of the SAPO-18 molecular sieve was 540 μmol·g. -1 The strong acid has a strength of 142 μmol·g. -1 The ratio of weak acid concentration to strong acid concentration is 3.8.

[0068] The catalyst preparation and molding process are the same as in Example 1.

[0069] The catalyst was tested under the same conditions as in Example 1.

[0070] The results of the activity evaluation are shown in Table 1.

[0071]

Example 6

[0072] Cr₂O₃ oxide was prepared by precipitation method. 0.5 mol of chromium nitrate was weighed and dissolved in 1000 mL of distilled water. Then, 1.0 mol of sodium hydroxide was dissolved in 1000 mL of water. The two aqueous solutions were co-precipitated under parallel flow. The precipitate was then aged at 80 °C for 2 h, filtered, dried at 100 °C for 12 h, and calcined at 500 °C in a 10% hydrogen / nitrogen mixed atmosphere for 1 h to obtain Cr₂O₃ oxide.

[0073] The preparation of ZSM-5 and SAPO-18 molecular sieves was the same as in Example 1. The acid treatment of SAPO-18 molecular sieve was the same as in Example 1.

[0074] Catalyst preparation:

[0075] 1.0 g of the prepared Cr2O3 oxide, 0.5 g of ZSM-5 and 0.5 g of SAPO-18 molecular sieve were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatic hydrocarbons.

[0076] The catalyst was tested under the same conditions as in Example 1.

[0077] The results of the activity evaluation are shown in Table 1.

[0078]

Example 7

[0079] Preparation of metal oxides:

[0080] GaMn oxide was prepared by precipitation method. 0.47 mol of manganese nitrate and 0.03 mol of gallium nitrate were weighed and dissolved in 1000 mL of distilled water. Then, 1.0 mol of sodium hydroxide was dissolved in 1000 mL of water. The two aqueous solutions were co-precipitated under parallel flow. The mixture was aged at 80 °C for 2 h, filtered, dried at 100 °C for 12 h, and calcined at 500 °C in a 10% hydrogen-nitrogen mixed atmosphere for 1 h to obtain GaMn oxide.

[0081] The preparation of ZSM-5 and SAPO-18 molecular sieves was the same as in Example 1. The acid treatment of SAPO-18 molecular sieve was the same as in Example 1.

[0082] Catalyst preparation:

[0083] 1.0 g of the prepared GaMn oxide, 0.5 g of ZSM-5 and 0.5 g of SAPO-18 molecular sieve were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatic hydrocarbons.

[0084] The catalyst was tested under the same conditions as in Example 1.

[0085] The results of the activity evaluation are shown in Table 1.

[0086]

Example 8

[0087] The preparation of MnO and SAPO-18 molecular sieves was the same as in Example 1. The acid treatment of SAPO-18 molecular sieves was the same as in Example 1.

[0088] Preparation of ten-membered ring molecular sieves:

[0089] 33.05 g of silica sol, 1.16 g of tetrabutylammonium bromide, and 20 g of deionized water were added to a beaker and mixed thoroughly to form solution I. A homogeneous solution II was prepared by adding 2.26 g of aluminum sulfate, 2.54 g of sodium hydroxide, and 20 g of deionized water. Solution II was slowly added to solution I with continuous stirring, and stirring was continued for 8 hours until homogeneous. The molar ratio of the resulting reaction mixture was 9.0 Na₂O:1.0 Al₂O₃:100 SiO₂:0.53 (TBA)₂O:1300 H₂O. The resulting initial gel was transferred to a reaction vessel with a polytetrafluoroethylene liner, sealed, and placed in a hydrothermal synthesis oven. Crystallization was carried out using a two-stage method: first, a constant temperature of 90 °C for 24 hours, followed by a temperature increase to 170 °C and a constant temperature of 24 hours. After the reactor was cooled, the solid was separated from the mother liquor. The solid was washed with deionized water until neutral, dried in air at 120°C, and then calcined at 550°C for 5 hours after three ammonium exchange cycles to obtain ZSM-11 molecular sieve.

[0090] Catalyst preparation:

[0091] 1.0 g of prepared MnO oxide, 0.5 g of ZSM-11 and 0.5 g of SAPO-18 molecular sieves were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatics.

[0092] The catalyst was tested under the same conditions as in Example 1.

[0093] The results of the activity evaluation are shown in Table 1.

[0094]

Example 9

[0095] The preparation of MnO and SAPO-18 molecular sieves was the same as in Example 1. The acid treatment of SAPO-18 molecular sieves was the same as in Example 1.

[0096] ZSM-12 with a Si / Al (atomic ratio) of 50 was purchased from the catalyst factory of Nankai University.

[0097] 1.0 g of prepared MnO oxide, 0.5 g of ZSM-12 and 0.5 g of SAPO-18 molecular sieves were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatics.

[0098] The catalyst was tested under the same conditions as in Example 1.

[0099] The results of the activity evaluation are shown in Table 1.

[0100] Comparative Example 1

[0101] The preparation of MnO was the same as in Example 1. The preparation of ZSM-5 was the same as in Example 1.

[0102] 1.0 g of prepared MnO oxide and 1.0 g of ZSM-5 were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. After drying at 80 °C for 12 h and calcining at 500 °C for 1 h, a catalyst for preparing light aromatic hydrocarbons was obtained.

[0103] The obtained catalyst was granulated and packed into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400 °C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to enter the catalytic bed for reaction. The reaction temperature was 400 °C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹.-1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0104] Comparative Example 2

[0105] The preparation of MnO was the same as in Example 1. The preparation and acid treatment of SAPO-18 molecular sieve were the same as in Example 1.

[0106] 1.0 g of prepared MnO oxide and 1.0 g of SAPO-18 were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. After drying at 80 °C for 12 h and calcining at 500 °C for 1 h, a catalyst for preparing light aromatic hydrocarbons was obtained.

[0107] The obtained catalyst was granulated and packed into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400 °C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to enter the catalytic bed for reaction. The reaction temperature was 400 °C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0108] Comparative Example 3

[0109] The preparation of MnO was the same as in Example 1. The preparation of ZSM-5 was the same as in Example 1.

[0110] SSZ-13 was produced using catalysts from Nankai University, with a Si / Al molar ratio of 25. The weak acid content is 240 μmol·g. -1 The strong acid has a strength of 570 μmol·g. -1 The ratio of weak acid concentration to strong acid concentration is 0.42.

[0111] 1.0 g of prepared MnO oxide, 0.5 g of ZSM-5 and 0.5 g of SSZ-13 molecular sieve were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. The mixture was then dried at 80 °C for 12 h and calcined at 500 °C for 1 h to obtain a catalyst for preparing light aromatic hydrocarbons.

[0112] The obtained catalyst was granulated and packed into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400 °C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to enter the catalytic bed for reaction. The reaction temperature was 400 °C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0113] Comparative Example 4

[0114] The preparation of MnO is the same as in Example 1.

[0115] The preparation of ZSM-11 is the same as in Example 8.

[0116] The preparation of ZSM-5 is the same as in Example 1.

[0117] 1.0 g of prepared MnO oxide and 0.5 g of ZSM-5 and 0.5 g of ZSM-11 molecular sieves were placed in 5 g of 80% ethanol solution and ultrasonicated at 10 kHz in a water bath at 60 °C for 2 h. After drying at 80 °C for 12 h and calcining at 500 °C for 1 h, a catalyst for preparing light aromatic hydrocarbons was obtained.

[0118] The obtained catalyst was granulated and packed into a quartz reaction tube with an inner diameter of 6 mm. Before the reaction, it was reduced with hydrogen at 400 °C for 3 hours. After the reduction was completed, the feed gas (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and allowed to enter the catalytic bed for reaction. The reaction temperature was 400 °C, the reaction system pressure was 5 MPa, and the volume hourly space velocity of the feed gas was 2000 h⁻¹. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0119] Comparative Example 5

[0120] The preparation of MnO, ZSM-5, and SAPO-18 molecular sieves was the same as in Example 1. The difference was that the SAPO-18 molecular sieve was not acid-treated. In this example, the weak acid content of the SAPO-18 molecular sieve was 1230 μmol·g. -1 The strong acid has a strength of 182 μmol·g. -1 The ratio of weak acid concentration to strong acid concentration is 6.8.

[0121] The catalyst preparation and molding process are the same as in Example 1.

[0122] The catalyst was tested under the same conditions as in Example 1.

[0123] The results of the activity evaluation are shown in Table 1.

[0124] Table 1

[0125]

[0126]

[0127] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst for preparing light aromatics, comprising a metal oxide and a composite molecular sieve; wherein the composite molecular sieve comprises both an eight-membered ring molecular sieve and a ten-membered ring molecular sieve; The weak acid content of the eight-membered ring molecular sieve is 150~600 μmol·g. -1 The strong acid has an acid strength of 50~400 μmol·g. -1 The ratio of weak acid amount to strong acid amount is 1~4; The acidity was determined using the NH3-TPD method; in the NH3-TPD spectrum, the peaks at 100~250℃ correspond to weak acid centers, and the peaks at 250~500℃ correspond to strong acid centers. The eight-membered ring molecular sieve includes at least one of SAPO-18 and SAPO-17 molecular sieves; The ten-membered ring molecular sieve is at least one of ZSM-5, ZSM-11, ZSM-12, MCM-22, Silicalite-1, and Silicalite-2; The mass ratio of octagonal molecular sieves to decacyclic molecular sieves is 1:5 to 5:

1.

2. The catalyst according to claim 1, characterized in that, The metal element of the metal oxide is selected from at least one of Cr, Zr, Mn, Ce, La, In, Ga and Zn; and / or, the mass ratio of the metal oxide to the molecular sieve is 0.05 to 10.

3. The catalyst according to claim 1, characterized in that, The metal element of the metal oxide is selected from at least one of Cr, Zr, Ce, Mn and Ga; and / or, the mass ratio of the metal oxide to the molecular sieve is 1 to 5.

4. A method for preparing the catalyst according to any one of claims 1 to 3, comprising: The catalyst is obtained by mixing the composite molecular sieve and the metal oxide.

5. The preparation method according to claim 4, characterized in that, The mixing is a mechanical mixing method.

6. The preparation method according to claim 5, characterized in that, The mixing process involves dispersing metal oxides and composite molecular sieves in a low-carbon alcohol solution, followed by ultrasonic treatment, drying, and calcination to obtain the catalyst.

7. The preparation method according to claim 4, characterized in that, Eight-membered ring molecular sieves require acid treatment.

8. The preparation method according to claim 7, characterized in that, The acid treatment temperature is 150~180 °C and the time is 12~36 h.

9. The preparation method according to claim 7, characterized in that, The acid used includes at least one of nitric acid, oxalic acid, and acetic acid.

10. The preparation method according to claim 9, characterized in that, The acid used is acetic acid.

11. The preparation method according to claim 9, characterized in that, The concentration of the acid solution is 0.1~3 mol / L.

12. The use of a catalyst according to any one of claims 1 to 3 or a catalyst prepared by any one of claims 4 to 11 in the preparation of light aromatic hydrocarbons.

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