A bifunctional catalyst for synthesizing aromatic hydrocarbons from syngas, a preparation method and application thereof

Abstract

The application discloses a bifunctional catalyst for synthesizing aromatic hydrocarbons from synthesis gas as well as a preparation method and application thereof. The catalyst comprises a metal oxide and a molecular sieve, the amount of B acid obtained by 2,6-di-tert-butylpyridine adsorption infrared testing of the catalyst is X, the amount of B acid obtained by pyridine adsorption infrared testing is Y, and the ratio of X to Y is 0-0.5, and 0 is not included. The catalyst has higher CO conversion rate and aromatic hydrocarbon selectivity when used for synthesizing aromatic hydrocarbons from synthesis gas.

Description

Technical Field

[0001] This invention relates to the field of aromatic hydrocarbon preparation technology, and in particular to a bifunctional catalyst for the synthesis of aromatic hydrocarbons from syngas, its preparation method, and its application. Background Technology

[0002] Syngas is an important platform for producing chemicals as an alternative to petroleum routes. It can be derived from natural gas, coal, biomass, etc., and with different catalysts, syngas can be used to produce oxygen-containing compounds, carbon dioxide, and other chemicals. 2-4 Hydrocarbons, liquid fuels, and aromatics are high-value-added basic chemicals. Among them, aromatic products, especially BTX, are raw materials for the synthesis of styrene, polyamide resins, terephthalic acid, etc., and have significant commercial value, attracting widespread attention.

[0003] CN112473727A discloses a method for preparing a metal oxide / zeolite molecular sieve composite catalyst by solution combustion. The method includes: 1) preparing an aqueous solution of a nitrate of a suitable metal according to the preparation requirements, obtaining solution A; 2) adding organic fuel to solution A, obtaining solution B; 3) adding a measured amount of zeolite molecular sieve to solution B, dispersing it to obtain suspension C; 4) preheating the heating equipment to reach the ignition temperature of the solution, then transferring suspension C to the preheated heating equipment for ignition and combustion; 5) grinding and calcining the product obtained in step 4), the resulting product being the metal oxide / zeolite molecular sieve composite catalyst. This catalyst is suitable for the hydrogenation catalytic preparation of light aromatics from syngas or carbon dioxide.

[0004] CN111420701A discloses a catalyst for the production of aromatics from syngas and its application. The catalyst comprises the following components in mass percentage: a composite oxide containing 20%–70% CoMn spinel structure and 30%–80% zeolite molecular sieve. Its characteristic is that this bifunctional catalyst can be used in both dual-bed catalyst mode and single-bed mixed catalyst mode, and can also be used in a series of dual reactors.

[0005] Although existing technologies have been studied in the field of syngas-to-aromatics production, problems such as easy catalyst deactivation, low aromatic selectivity, and low catalytic activity still exist in coupled systems. Therefore, further development of catalysts with high activity and aromatic selectivity for one-step syngas-to-aromatics production is of great significance. Summary of the Invention

[0006] To address the problems of low aromatic selectivity and poor catalytic activity in existing technologies, this invention provides a bifunctional catalyst for syngas-to-aromatics production, its preparation method, and its applications. The catalyst of this invention exhibits higher CO conversion and aromatic selectivity when used for syngas-to-aromatics production.

[0007] The first aspect of the present invention provides a bifunctional catalyst for the synthesis of aromatics from syngas, comprising a metal oxide and a molecular sieve, wherein the amount of Brønsted acid obtained by infrared spectroscopy using 2,6-di-tert-butylpyridine adsorption is X, and the amount of Brønsted acid obtained by infrared spectroscopy using pyridine adsorption is Y, and the ratio of X to Y is 0 to 0.5, excluding 0.

[0008] Furthermore, the ratio of X to Y can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc.

[0009] Furthermore, in the catalyst, the weight ratio of metal oxide to molecular sieve is 1 to 10, preferably 1 to 5.

[0010] Furthermore, the metal oxides are ZnO, Cr2O3, ZrO2, and MnO. x At least one of CeO2, Ga2O3, ZnTi, ZnZr, ZnCr, MnCe, MnZr, and GaZr, preferably Cr2O3, ZrO2, or MnO x At least one of CeO2, MnCe, MnZr, and GaZr.

[0011] Furthermore, the molecular sieve is at least one of ZSM-5, ZSM-11, and ZSM-12, preferably at least one of ZSM-5 and ZSM-11.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, comprising:

[0013] (1) Prepare a metal salt solution by mixing the molecular sieve raw material with the metal salt solution evenly, and then drying and calcining to obtain the catalyst precursor;

[0014] (2) The catalyst precursor is dispersed in a mixed solution of TPAOH and water, and then subjected to hydrothermal treatment, solid-liquid separation, washing, drying and calcination to obtain the catalyst.

[0015] Further, in step (1), the precursor of the metal salt solution is selected from at least one of the metal nitrate, acetate, sulfate and chloride salts, preferably at least one of the chloride and nitrate salts.

[0016] Furthermore, in step (1), the concentration of the metal salt solution is 0.5 mol / L to 4.0 mol / L, preferably 1.0 mol / L to 3.0 mol / L.

[0017] Furthermore, in step (1), the Si / Al molar ratio of the molecular sieve raw material is 20 to 500, preferably 40 to 300.

[0018] Furthermore, in step (1), the mixing temperature is 30–70°C, preferably 40–65°C, and the mixing time is 5–24 h, preferably 8–15 h. The mixing method can be stirring.

[0019] Furthermore, in step (1), the drying temperature is 40-100℃, preferably 50-85℃, and the drying time is 5-15h, preferably 6-12h.

[0020] Furthermore, in step (1), the calcination temperature is 500-600℃ and the calcination time is 1-8h, preferably 1-6h.

[0021] Further, in step (2), the mass ratio of TPAOH aqueous solution to catalyst precursor is 5 to 30, preferably 10 to 20.

[0022] Furthermore, in step (2), the concentration of the TPAOH aqueous solution is 0.1 mol / L to 2 mol / L, preferably 0.2 mol / L to 1.2 mol / L.

[0023] Furthermore, in step (2), the temperature of the hydrothermal treatment is 110-200℃, preferably 150-180℃, and the time of the hydrothermal treatment is 24-120h, preferably 36-96h.

[0024] Furthermore, in step (2), centrifugation is used for solid-liquid separation and washing.

[0025] Furthermore, in step (2), the drying temperature is 60-120°C, preferably 80-110°C, and the drying time is 3-15 hours, preferably 6-10 hours.

[0026] Furthermore, in step (2), the calcination temperature is 500-600℃ and the calcination time is 1-8h, preferably 1-6h.

[0027] A third aspect of the present invention provides the application of the above-described catalyst in the preparation of aromatics using syngas as a feedstock.

[0028] Furthermore, the syngas is a mixture of carbon monoxide / hydrogen or carbon monoxide / carbon dioxide / hydrogen.

[0029] Furthermore, the preparation of aromatics is preferably carried out in a fixed bed reaction.

[0030] Furthermore, the reaction temperature for preparing aromatics is 350–450 °C, the reaction pressure is 1–10 MPa, and the volume hourly space velocity is 800–10000 h⁻¹. -1 The hydrogen-to-carbon atomic ratio is 0.5 to 5.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The bifunctional catalyst of this invention comprises two parts: a metal oxide and a molecular sieve. The metal oxide is characterized by its small particle size and uniform dispersion on the molecular sieve. Due to the interaction between the oxide and the molecular sieve, the growth of the metal oxide particles during the reaction process is prevented. Simultaneously, the active metal sites and acid sites are mutually matched. The catalyst of this invention also possesses advantages such as high activity, good selectivity, resistance to deactivation, and good stability.

[0033] The preparation method of this invention requires no modification of the molecular sieve, nor does it require the addition of additional silicon and aluminum sources. Furthermore, the preparation method of this invention can simultaneously modulate the amount of Brønsted acid on the outer surface of the molecular sieve during the preparation process, demonstrating promising application prospects. Detailed Implementation

[0034] The present invention will be further described in detail below through embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0035] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0036] In this invention, the 2,6-di-tert-butylpyridine adsorption infrared spectroscopy (DTBPy-IR) of the catalyst was performed on a Nicolet 5700FT-IR spectrometer. The testing procedure is as follows: First, the catalyst was prepared into a self-supporting thin sheet and vacuum-treated at 400℃ for 2 hours. After the temperature was reduced to 200℃, background samples were collected, and DTBPy was adsorbed to saturate the catalyst. After vacuuming for 30 minutes, the spectrum was collected. The amount of β-acid in the catalyst was obtained based on the spectrum at 200℃, denoted by X.

[0037] In this invention, the pyridine adsorption infrared spectroscopy (Py-IR) of the catalyst was performed on a Nicolet 5700FT-IR spectrometer. The testing procedure is as follows: First, the catalyst was prepared into a self-supporting thin sheet, placed in an infrared cell with CaF2 as the window, and vacuum-treated at 400℃ for 2 hours. After the temperature dropped to 200℃, the spectrum was acquired. Pyridine vapor was injected to saturate the catalyst adsorption, and the vacuum was evacuated for 30 minutes. The amount of β-acid in the catalyst was obtained based on the spectrum at 200℃, denoted as Y.

[0038] In this invention, the Si / Al molar ratio is obtained by ICP-AES testing, which is performed using a Varian 725-ES plasma emission spectrometer.

[0039]

Example 1

[0040] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 60) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and then calcined at 550 °C for 5 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.15.

[0041] 1.5g of the prepared Cr-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0042]

Example 2

[0043] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 40) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.09.

[0044] 1.5g of the prepared Cr-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0045]

Example 3

[0046] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 80) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.18.

[0047] 1.5g of the prepared Cr-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -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 4

[0049] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 100) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.24.

[0050] 1.5g of the prepared Cr-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0051]

Example 5

[0052] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 200) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.36.

[0053] 1.5g of the prepared Cr-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0054]

Example 6

[0055] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 300) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.54.

[0056] 1.5g of the prepared Cr-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0057]

Example 7

[0058] 0.05 mol of chromium chloride was weighed and dissolved in 20 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 60) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.17.

[0059] 1.5g of the prepared Cr-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0060]

Example 8

[0061] 0.022 mol of gallium nitrate was weighed and dissolved in 22 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 60) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain a catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Ga-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.15.

[0062] 1.5g of the prepared Ga-ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into the catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0063]

Example 9

[0064] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-12 (Si / Al = 60) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain the catalyst precursor. 2 g of the precursor was dispersed in 20 g of a 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the sample was dried at 80 °C for 12 h and calcined at 550 °C for 5 h to obtain Cr-ZSM-12. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.43.

[0065] 1.5g of the prepared Cr-ZSM-12 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into the catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0066] Comparative Example 1

[0067] 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of HZSM-5 (Si / Al = 60) was added to the solution, and the mixture was stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 1 h to obtain Cr-ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.53.

[0068] 1.5g of the prepared Cr / ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into the catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0069] Comparative Example 2

[0070] 0.02 mol of chromium chloride was dissolved in 20 mL of distilled water, and 0.06 mol of sodium hydroxide was dissolved in 60 mL of water. The two aqueous solutions were co-precipitated under parallel flow, aged at 70 °C for 2 h, filtered, washed several times, dried at 100 °C overnight, and calcined at 500 °C in air atmosphere for 1 h to obtain Cr₂O₃ oxide. 1 g of the prepared Cr₂O₃ oxide and 1.0 g of HZSM-5 (Si / Al = 60) were ground and mixed, granulated, and denoted as Cr+ZSM-5. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using probe molecule analysis, and the ratio X / Y = 0.64.

[0071] 1.5g of the prepared Cr+ZSM-5 was placed in a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into a catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0072] Comparative Example 3

[0073] 5 g of HZSM-5 (Si / Al = 60) was dispersed in 50 g of 0.5 mol / L TPAOH aqueous solution and hydrothermally treated at 180 °C for 84 h. After centrifugation and washing, the solution was dried at 80 °C for 12 h and calcined at 550 °C for 1 h to obtain TPAOH-treated HZSM-5. 0.028 mol of chromium chloride was weighed and dissolved in 28 mL of distilled water. Then, 2 g of the treated HZSM-5 (Si / Al = 60) was added to the solution and stirred at 50 °C for 8 h until viscous. The solution was then dried in an oven at 80 °C for 12 h. The dried sample was then calcined at 550 °C for 5 h. The Brønsted acid content (X) and (Y) of the catalyst in this state were determined using a probe molecule assay, and the ratio X / Y = 0.57.

[0074] 1.5g of the prepared Cr / ZSM-5 was granulated and loaded into a quartz reaction tube with an inner diameter of 6mm. Before the reaction, it was reduced with hydrogen at 400℃ for 3h. After the reduction was completed, (n hydrogen:n carbon monoxide = 50:50) was introduced into the reaction tube and placed into the catalytic bed for reaction. The reaction temperature was 400℃, the reaction system pressure was 5MPa, and the gas hourly space velocity was 1800h. -1 The synthesis of aromatics from syngas was carried out under the specified conditions. The activity evaluation results are shown in Table 1.

[0075] Table 1

[0076]

[0077] 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 technical concept of the present invention, 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 bifunctional catalyst for the synthesis of aromatics from syngas, comprising a metal oxide and a molecular sieve, wherein the amount of Brønsted acid obtained by infrared spectroscopy using 2,6-di-tert-butylpyridine adsorption is X, and the amount of Brønsted acid obtained by infrared spectroscopy using pyridine adsorption is Y, wherein the ratio of X to Y is 0 to 0.5, excluding 0; The metal oxide is at least one of Cr2O3, ZrO2, MnO x , CeO2, MnCe, MnZr, GaZr.

2. The bifunctional catalyst according to claim 1, characterized in that, In the catalyst, the weight ratio of metal oxide to molecular sieve is 1 to 10.

3. The bifunctional catalyst according to claim 2, characterized in that, In the catalyst, the weight ratio of metal oxide to molecular sieve is 1 to 5.

4. The bifunctional catalyst according to claim 1, characterized in that, The molecular sieve is at least one of ZSM-5, ZSM-11, and ZSM-12.

5. The bifunctional catalyst according to claim 4, characterized in that, The molecular sieve is at least one of ZSM-5 and ZSM-11.

6. A method for preparing the bifunctional catalyst according to any one of claims 1-5, comprising: (1) Prepare a metal salt solution by mixing the molecular sieve raw material with the metal salt solution evenly, and then drying and calcining to obtain a catalyst precursor; (2) The catalyst precursor is dispersed in a mixed solution of TPAOH and water, and then subjected to hydrothermal treatment, solid-liquid separation, washing, drying and calcination to obtain the catalyst; In step (2), the temperature of the hydrothermal treatment is 110~200 ℃ and the time of the hydrothermal treatment is 24~120 h.

7. The preparation method according to claim 6, characterized in that, In step (1), the Si / Al molar ratio of the molecular sieve raw material is 20~500.

8. The preparation method according to claim 7, characterized in that, In step (1), the Si / Al molar ratio of the molecular sieve raw material is 40~300.

9. The preparation method according to claim 6, characterized in that, In step (1), the mixing temperature is 30~70 ℃ and the mixing time is 5~24 h; and / or, the calcination temperature is 500~600 ℃ and the calcination time is 1~8 h.

10. The preparation method according to claim 9, characterized in that, In step (1), the mixing temperature is 40~65 ℃ and the mixing time is 8~15 h.

11. The preparation method according to claim 6, characterized in that, In step (2), the mass ratio of TPAOH aqueous solution to catalyst precursor is 5~30; and / or, the concentration of TPAOH aqueous solution is 0.1 mol / L~2 mol / L.

12. The preparation method according to claim 11, characterized in that, In step (2), the mass ratio of TPAOH aqueous solution to catalyst precursor is 10~20; and / or, the concentration of TPAOH aqueous solution is 0.2 mol / L~1.2 mol / L.

13. The preparation method according to claim 6, characterized in that, In step (2), the temperature of the hydrothermal treatment is 150~180 ℃ and the time of the hydrothermal treatment is 36~96 h.

14. The preparation method according to claim 6, characterized in that, In step (2), the roasting temperature is 500~600 ℃ and the roasting time is 1~8 h.

15. The application of the bifunctional catalyst according to any one of claims 1-5 in the preparation of aromatics using carbon monoxide / hydrogen or a mixture of carbon monoxide / carbon dioxide / hydrogen as raw materials.

16. The application according to claim 15, characterized in that, The preparation of aromatic hydrocarbons is carried out in a fixed bed, the reaction temperature is 350-450 ℃, and / or the reaction pressure is 1-10 MPa, and / or the volume space velocity is 800-10000 h -1 , and / or the hydrogen-carbon molar ratio is 0.5-5.

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