Catalyst, process for its preparation and process for the preparation of aromatic compounds

Abstract

The present application relates to a kind of catalyst and its preparation method, and the method for preparing aromatic compound.The catalyst includes molecular sieve and active component, the active component contains at least one of Ta, Nb, Ti, Ga, Ni, Zn, V, Co, Cr and Fe element;Wherein, the specific surface area of the catalyst is 500~700m 2 / g;The content of the active component is 0.1wt%~10wt% in terms of oxide.The catalyst provided by the present application has the advantages of good thermal stability, strong shape selection effect, and ideal acid distribution, suitable for benzene ring related catalytic reactions.

Description

Technical Field

[0001] This invention relates to the field of catalysts, and more specifically, to a catalyst, a method for preparing the same, and a method for preparing aromatic compounds. Background Technology

[0002] Benzene, toluene, and xylene, collectively known as the "three benzenes," are among the most important basic organic raw materials in modern chemical engineering, widely used in solvents, fuel oils, pharmaceuticals, dyes, and synthetic materials. In addition, there are other aromatic compounds with similar properties and large π-bonded aromatic rings, such as pyridine and methylpyridine, which also have extremely important applications in the fine chemical industry. Currently, aromatics are mainly produced through petrochemical processes, while heterocyclic methyl aromatics, represented by 2-methylpyridine, are prepared through the separation of coal tar components. However, given the current situation of gradually depleting petroleum resources and high oil prices, the corresponding production costs are gradually increasing. Therefore, developing new processes for the preparation of aromatics is of significant economic importance.

[0003] Aromatic hydrocarbons can be prepared through a cyclotrimerization reaction of three alkyne molecules containing carbon-carbon triple bonds. Furthermore, as a derivative, the carbon-nitrogen triple bond in the cyano group can also undergo cyclotrimerization with alkyne molecules to obtain high-value-added fine chemical raw materials such as 2-methylpyridine. Currently known cyclotrimerization processes include heterogeneous reactions supported by active metals such as Ti, Nb, and Ni, as well as batch reactions catalyzed by organic cobalt, but based on known reports, these reactions have low yields of the target products, low synthesis efficiency, and complex recovery processes. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the inventors of this invention, through extensive and in-depth research, have provided a catalyst and its preparation method, as well as a method for preparing aromatic compounds. For example, one objective of this invention is to provide a catalyst with advantages such as good thermal stability, strong shape selectivity, and further, an ideal acidity distribution, suitable for benzene ring-related catalytic reactions. Another objective of this invention is to provide a preparation method corresponding to the catalyst.

[0005] To achieve the above objectives, a first aspect of the present invention provides a catalyst comprising a molecular sieve and an active component, wherein the active component contains at least one element selected from Ta, Nb, Ti, Ga, Ni, Zn, V, Co, Cr, and Fe; wherein,

[0006] The catalyst has a specific surface area of ​​500–700 m². 2 / g; In the catalyst, the content of the active component, calculated as oxide, is 0.1wt% to 10wt%. That is, the oxide of at least one of the elements Ta, Nb, Ti, Ga, Ni, Zn, V, Co, Cr and Fe accounts for 0.1wt% to 10wt% of the total mass of the catalyst, preferably 0.5wt% to 1.5wt%.

[0007] In some embodiments of the present invention, the active component contains at least one of Nb, Ti and Zn elements.

[0008] In some embodiments of the present invention, the molar ratio of SiO2 / Al2O3 (silicon-aluminum ratio) in the molecular sieve is 25-80:1, preferably 30-40:1; preferably, the molecular sieve has an MFI structure, a MOR structure or a MEL structure.

[0009] Compared to non-molecular sieve catalysts, the catalyst of this invention has better shape selectivity, larger specific surface area, better thermal stability, more reasonable distribution of active phase, and is easier to regenerate after deactivation.

[0010] A second aspect of the present invention provides a method for preparing a catalyst, comprising the steps of:

[0011] S1. Mix the dispersion I containing silicon source and aluminum source with the solution I containing active component source to obtain a mixed gel;

[0012] S2. Obtain a gel precursor containing a template agent and the mixed gel;

[0013] S3. The gel precursor is subjected to aging and hydrothermal crystallization treatments in sequence to obtain intermediate product I.

[0014] S4. The intermediate product I is filtered, and the solid phase obtained after filtration is dried and then subjected to ammonium ion exchange treatment to obtain intermediate product II.

[0015] S5. The intermediate product II is calcined to obtain the catalyst.

[0016] In some embodiments of the present invention, step S1 includes the step of mixing the active component source with an auxiliary agent to obtain the solution I.

[0017] In some embodiments of the present invention, the source of the active component is selected from one or more of oxides, acids, bases, salts and organic compounds containing the active component;

[0018] In some embodiments of the present invention, the adjuvant is selected from one or more of ethylenediaminetetraacetic acid (EDTA), ammonium fluoride, hydrofluoric acid, triethanolamine, oxalic acid, tartaric acid, citric acid, and sulfosalicylic acid.

[0019] In some embodiments of the present invention, the molar ratio of the active ingredient source to the auxiliary agent is 0.5 to 2:1.

[0020] In this invention, the active component source is mixed with an auxiliary agent to obtain solution I, and then a subsequent reaction is carried out; in the prior art, organic salts of active components such as Co are used to carry out a batch reaction in solvents such as acetic acid.

[0021] In some embodiments of the present invention, in step S1, the silicon source is silica sol and / or water glass;

[0022] And / or, the aluminum source is selected from at least one of boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide.

[0023] In some embodiments of the present invention, in step S2, the template agent is selected from at least one of isopropylamine, n-butylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0024] In some embodiments of the present invention, the molar ratio of the active component source, silicon source, aluminum source, and template agent is 0.5–2.5:30–150:1:0–2.0. A template agent value of 0 indicates that no template agent is added.

[0025] In some embodiments of the present invention, in step S1, the silicon source and the aluminum source are dispersed in water to obtain their respective dispersions, which are then mixed to obtain dispersion I. In other words, dispersion I also includes water, and the molar ratio of the active component source, silicon source, aluminum source, template agent, and water (water contained in dispersant I) in dispersion I is 0.5–2.5:30–150:1:0–2.0:25–200.

[0026] In some embodiments of the present invention, in step S1, the dispersion I is added dropwise (dropwise) to solution I to obtain the mixed gel. The dropping time for adding the dispersion I to solution I is 1 to 6 hours, and the dropping rate can be set accordingly.

[0027] In some embodiments of the present invention, in step S2, the template agent is added dropwise (dropwise) to the mixed gel to obtain the gel precursor. The time for adding the template agent to the mixed gel is 1 to 6 hours, and the dropping rate can be set accordingly.

[0028] In some embodiments of the present invention, in step S3, the aging treatment conditions include: a temperature of 60°C to 90°C and a time of 1 to 8 hours.

[0029] In some embodiments of the present invention, in step S3, the conditions for the hydrothermal crystallization treatment include: a pressure of 1.2 to 2.5 MPa, a temperature of 150°C to 240°C, and a time of 1 to 8 hours.

[0030] In this invention, the hydrothermal crystallization treatment can be carried out in a hydrothermal crystallization kettle with a polytetrafluoroethylene liner.

[0031] According to the present invention, there are no strict limitations on the filtration process, and those skilled in the art can choose according to the specific circumstances.

[0032] According to the present invention, after the product of hydrothermal crystallization is filtered, the resulting solid phase is subjected to subsequent steps such as drying and ammonium ion exchange.

[0033] In some embodiments of the present invention, in step S4, the drying conditions include: a temperature of 100°C to 150°C and a time of 2 to 24 hours.

[0034] In some embodiments of the present invention, in step S4, the ammonium ion exchange treatment is carried out in an ammonium ion-containing solution of 1–5 mol / L at 80°C–95°C.

[0035] According to the present invention, there is no strict limitation on the ammonium solution used for ammonium ion exchange treatment, such as 1 to 5 mol / L NH4Cl.

[0036] In some embodiments of the present invention, an ammonium ion exchange treatment can be performed several times (e.g., at least 3 times) using an ammonium ion-containing solution, each time for 1 to 3 hours.

[0037] In this invention, the product obtained after ammonium ion exchange treatment can also be filtered and washed, and the solid obtained after filtration and washing can be roasted.

[0038] In some embodiments of the present invention, in step S5, the conditions for the calcination treatment include: a temperature of 450°C to 650°C and a time of 2 to 8 hours.

[0039] In this invention, during catalyst preparation, molecular sieve seeds (such as ZSM-5 molecular sieve) may be added in step S2. The amount of molecular sieve seeds added is 0-15 wt% of the gel precursor. The molecular sieve seeds added in this invention can be commercially available or synthesized using conventional experimental methods.

[0040] A third aspect of the present invention provides a method for preparing an aromatic compound, the method comprising contacting a raw material containing an alkyne with a catalyst described in the first aspect or a catalyst prepared by the preparation method described in the second aspect above to undergo a cyclotrimerization reaction to prepare the aromatic compound.

[0041] In this invention, the cyclotrimerization reaction is carried out in a fixed bed, which allows for continuous production and eliminates the need to recover the catalyst after the reaction stops. Since the reactants and products have a long residence time in a batch reaction, the reaction in a fixed bed can improve the reaction performance.

[0042] Compared to the batch reaction in existing technologies, the method for preparing aromatic compounds of the present invention uses the catalyst described in the first aspect above. The high activity of this catalyst enables the aromatic compounds to be prepared by continuous fixed-bed reaction. Specifically, firstly, it achieves continuous reaction preparation of aromatic compounds, avoiding complex loading and multiple temperature increases and decreases, thus improving reaction efficiency; secondly, compared to the batch reaction which requires the addition of solvents, the reaction system of the present invention does not contain solvents, reducing equipment corrosion and lowering production costs; thirdly, the fixed-bed reaction is a plug flow reaction, where the residence time of reactants / products in the catalyst bed is relatively short, while the residence time of reactants and products in the batch reaction is longer, which is more conducive to improving reaction selectivity.

[0043] In some embodiments of the present invention, the reaction conditions for the cyclotrimerization reaction include: a reaction pressure of 0.5 MPa to 2 MPa; and / or a reaction temperature of 400°C to 600°C; and / or an alkyne volume hourly space velocity of 2600 to 3000 h⁻¹. -1 .

[0044] In some embodiments of the present invention, the alkyne is a C2-C6 alkyne; preferably acetylene and / or butyne.

[0045] In some embodiments of the present invention, the raw material further contains C2-C6 nitrile compounds.

[0046] In some embodiments of the present invention, the aromatic compound is selected from one or more of aromatic hydrocarbons and aromatic heterocyclic compounds, wherein the aromatic hydrocarbon has 5-10 skeletal cyclic carbon atoms; the aromatic heterocyclic compound has 5-10 cyclic atoms, wherein at least one cyclic atom is N.

[0047] In some embodiments of the present invention, the aromatic compound is selected from one or more of benzene, toluene, xylene, pyridine, and methylpyridine.

[0048] In some embodiments of the present invention, when preparing aromatic heterocyclic compounds such as pyridine and methylpyridine, the reaction raw materials also include C2-C6 nitrile compounds (such as acetonitrile, propionitrile, and butyronitrile), and the molar ratio of the reactants to the alkynes is 0.5-3:1.

[0049] In some embodiments of the present invention, the steps of the method for preparing aromatic compounds may include:

[0050] The prepared catalyst was loaded into a tableting mold and pressed into tablets under a pressure of 10–20 MPa. After pressing, the tablets were crushed and ground in a mortar. 20–40 mesh particles were selected and packed into a 6 mm diameter tubular fixed-bed reactor at a loading rate of 1 g. Hydrogen gas was introduced at a flow rate of 10–40 mL / min, and reduction was carried out at 300–600 °C for 1–4 h. Pure nitrogen gas was then introduced at a flow rate of 10–40 mL·min⁻¹ for purging at 300–600 °C for 10–60 min. Finally, a reaction gas containing 25% vol of feed gas and 75% vol of nitrogen was introduced at a space velocity of 2600–3000 h⁻¹. -1 Aromatic compounds are prepared by continuous reaction under the conditions of 400–600℃ and 0.5–2MPa.

[0051] In this invention, during the reaction process, the mixed gas exiting the tubular fixed-bed reactor enters the tail gas absorption device via a condenser. After the reaction stabilizes for 2 hours, the product in the condenser is collected and analyzed by gas chromatography (catalyst evaluation).

[0052] Compared with the prior art, the present invention includes at least one of the following beneficial effects:

[0053] 1) Compared with organometallic compound catalysts and homogeneous catalysts, the catalyst provided by this invention can realize heterogeneous reactions, reduce the cost of separating the catalyst from the product, and enable long-term application of the catalyst, significantly improving production efficiency and demonstrating significant cost advantages.

[0054] 2) Compared with non-molecular sieve catalysts (non-molecular sieve catalysts need to be dissolved and reacted in the presence of a stirred tank and solvent, and the solvent needs to be distilled after the reaction, resulting in losses), the catalyst provided by the present invention has better shape selectivity, larger specific surface area, better thermal stability, more reasonable distribution of active phase, and easier regeneration of deactivated catalyst.

[0055] 3) The catalyst preparation method provided by this invention uses a one-pot method (crystallizing the active component together with the molecular sieve) to prepare a highly dispersed active component during the molecular sieve crystallization process. This allows the active component to be more evenly distributed in the molecular sieve framework, channels, and other positions, achieving better coupling with acidic centers. When applied to the preparation of aromatic compounds, it can further improve the reaction performance of cyclotrimerization, thereby achieving the efficient synthesis of aromatic compounds with π-bonded molecules such as aromatic hydrocarbons and pyridine.

[0056] 4) The catalyst preparation method provided by this invention employs a one-pot hydrothermal synthesis, which, compared to catalysts prepared by impregnation, achieves high dispersion of the active components, significantly reduces the influence of the active components on the molecular sieve channels and specific surface area, and also enables more efficient utilization of the metallic active components.

[0057] 5) When the catalyst provided by this invention is used to prepare aromatic compounds, a fixed-bed continuous reaction can be used, which can significantly improve production efficiency compared with the batch reaction of the prior art and has great potential for industrial application. Attached Figure Description

[0058] The present invention will now be described in further detail with reference to the accompanying drawings.

[0059] Figure 1 The image shows the XRD pattern of the catalyst AI prepared in Example 1 of this invention. Detailed Implementation

[0060] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0061] Unless otherwise specified in the examples, the conditions shall be performed under conventional conditions or conditions recommended by the manufacturer. Raw materials, reagents, or instruments whose manufacturers are not specified are all commercially available products or prepared according to publicly disclosed methods.

[0062] In this invention, the molar ratio of silicon source to aluminum source is a common descriptive method for molecular sieve synthesis, calculated using framework element oxides (i.e., SiO2 and Al2O3).

[0063] In this invention, the crystal structure of the catalyst was determined by X-ray diffraction (XRD) using a Bruker D8 X-ray powder diffractometer (XRD) from Germany, with a Cu-Kα ray source and a Kα1 wavelength λ = 1.5405980 angstroms. Nickel filter, operating voltage 40kV, current 40mA, scanning range 2θ=5~80°.

[0064] In the following examples, the specific surface area was measured using a Micrometritics ASAP 2020M analyzer. The adsorbate was N2, adsorbed at liquid nitrogen temperature. The specific surface area of ​​the catalyst was calculated using the BET equation.

[0065] In the following examples, the elemental composition of the catalyst was determined by inductively coupled plasma atomic emission spectrometry (ICP) using an Avio 200 ICP spectrometer manufactured by Perkin Elmer, USA. The samples were digested with HF solution.

[0066] In the catalysts obtained in the following examples and comparative examples, the catalyst evaluation adopted... The reaction was carried out in a fixed-bed reactor with a length of 1000 mm, with a catalyst loading of 1 g and a reaction system pressure of 0.5-2 MPa.

[0067] In the following embodiments, the product yield and raw material conversion rate are calculated using the following methods:

[0068]

[0069]

[0070] In the following examples, the silica sol concentration was 30wt% SiO2 and the Na content was ≤0.1%; tetraethylammonium hydroxide was an aqueous solution of disodium EDTA (0.25mol / L) and a 25wt% aqueous solution; for other reagents not specified, commercially available reagents of analytical grade were used directly.

[0071] Example 1

[0072] In the catalyst preparation method of this embodiment, Nb2O5 is selected as the active component source, silica sol is selected as the silicon source, aluminum sulfate is selected as the aluminum source, hydrofluoric acid is selected as the auxiliary agent, and tetraethylammonium hydroxide is selected as the template agent; the molar ratio of active component source to auxiliary agent is 1:1; and the gel precursor is prepared according to the molar ratio of active component source: silicon source: aluminum source: template agent: H2O of 1:50:1:0.5:150.

[0073] 1. Catalyst Preparation

[0074] 1) Mix Nb2O5 and hydrofluoric acid in the above proportion to obtain solution I; mix silica sol, aluminum sulfate and water in the above proportion to obtain dispersion I; add dispersion I dropwise to solution I at a rate of 50 g / h to obtain mixed gel; then add tetraethylammonium hydroxide in the above proportion to the mixed gel at a rate of 50 g / h to obtain gel precursor;

[0075] 2) The gel precursor was stirred and aged at 80°C for 4 hours; the aged product was transferred to a hydrothermal crystallization vessel with a PTFE liner and hydrothermally crystallized at 160°C for 32 hours to obtain intermediate product I.

[0076] 3) Filter the intermediate product I and dry the solid phase obtained after filtration at 120°C for 4 hours; exchange the dried product with ammonium ions in 2 mol / L NH4Cl solution at 80°C for 1 hour, repeat 3 times; to obtain intermediate product II.

[0077] 4) The intermediate product II was filtered and washed with water to obtain a solid, which was dried at 120°C for 4 hours and then calcined in a muffle furnace at 550°C for 4 hours to obtain catalyst AI.

[0078] The specific surface area of ​​catalyst AI was determined to be 570.3 m². 2 ·g -1 The SiO2 / Al2O3 molar ratio (silicon-to-aluminum ratio) is 35, and the Nb oxide (Nb2O5) content is 0.83 wt%. Figure 1 It can be seen that the catalyst AI mainly exhibits the MFI crystalline phase and does not have diffraction peaks of aggregated oxides, etc.

[0079] 2. Catalyst Evaluation

[0080] One gram (1g) of 20-40 mesh compressed Al catalyst particles were loaded into a fixed-bed reactor. The feed gas was acetylene, and the reaction conditions were: reaction pressure 1 MPa, reaction temperature 500℃, and acetylene volume hourly space velocity (VHSV) 2900 h⁻¹. -1 Gas chromatography analysis of the reaction product showed that the conversion rate of acetylene was 90.2% and the yield of benzene was 57.5%.

[0081] Example 2

[0082] In the catalyst preparation method of this embodiment, niobium oxalate is selected as the active component source, silica sol is selected as the silicon source, aluminum sulfate is selected as the aluminum source, hydrofluoric acid is selected as the auxiliary agent, and tetraethylammonium hydroxide is selected as the template agent; the molar ratio of active component source to auxiliary agent is 1:1; and the gel precursor is prepared according to the molar ratio of active component source: silicon source: aluminum source: template agent: H2O of 1.5:50:1:0.5:150.

[0083] 1. Catalyst Preparation

[0084] 1) Mix Nb2O5 and hydrofluoric acid in the above proportion to obtain solution I; mix silica sol, aluminum sulfate and water in the above proportion to obtain dispersion I; add dispersion I dropwise to solution I at a rate of 40 g / h to obtain mixed gel; add tetraethylammonium hydroxide in the above proportion dropwise to mixed gel at a rate of 40 g / h to obtain gel precursor I; add 2 wt% of ZSM-5 molecular sieve seed crystals by weight of gel precursor to gel precursor I to obtain gel precursor II;

[0085] 2) The gel precursor II was stirred and aged at 80°C for 4 hours; the aged product was transferred into a hydrothermal crystallization vessel with a PTFE liner and hydrothermally crystallized at 170°C for 48 hours to obtain intermediate product I.

[0086] 3) Filter the intermediate product I and dry the solid phase obtained after filtration at 120°C for 4 hours; exchange the dried product with ammonium ions in 2 mol / L NH4Cl solution at 80°C for 1 hour, repeat 3 times; to obtain intermediate product II.

[0087] 4) Filter and wash the intermediate product II, and dry the solid at 120°C for 4 hours. After drying, calcine it in a muffle furnace at 550°C for 4 hours to obtain catalyst AII.

[0088] The specific surface area of ​​catalyst AII was determined to be 586.0 m². 2 ·g -1 The SiO2 / Al2O3 molar ratio (silicon-aluminum ratio) is 32, and the content of Nb as Nb oxide (Nb2O5) is 0.98 wt%. The catalyst AII is in the MFI crystalline phase.

[0089] 2. Catalyst Evaluation

[0090] One gram (1g) of 20-40 mesh compressed catalyst AII particles was loaded into a fixed-bed reactor. The feed gas was acetylene, and the reaction conditions were: reaction pressure 1 MPa, reaction temperature 500℃, and acetylene volume hourly space velocity (VHSV) 2900 h⁻¹. -1 Gas chromatography analysis of the reaction product showed that the conversion rate of acetylene was 92.2% and the benzene yield was 59.4%.

[0091] Example 3

[0092] In the catalyst preparation method of this embodiment, Nb2O5 and TiCl4 are selected as active component sources, silica sol is selected as silicon source, aluminum sulfate is selected as aluminum source, disodium EDTA is selected as auxiliary agent, and tetraethylammonium hydroxide is selected as template agent; the molar ratio of active component source (the sum of Nb2O5 and TiCl4) to auxiliary agent is 1:1; the molar ratio of Nb source:Ti source:silica sol:aluminum sulfate:tetraethylammonium hydroxide:H2O is 1:0.5:50:1:0.5:150, and a gel precursor is prepared.

[0093] 1. Catalyst Preparation

[0094] 1) Nb2O5 and TiCl4 were mixed with disodium EDTA in the above proportions to obtain solution I; silica sol, aluminum sulfate and water were mixed in the above proportions to obtain dispersion I; dispersion I was added dropwise to solution I at a rate of 40 g / h to obtain a mixed gel; tetraethylammonium hydroxide in the above proportions was then added dropwise to the mixed gel at a rate of 40 g / h to obtain a gel precursor;

[0095] 2) The gel precursor II was stirred and aged at 80°C for 4 hours; the aged product was transferred into a hydrothermal crystallization vessel with a PTFE liner and hydrothermally crystallized at 170°C for 48 hours to obtain intermediate product I.

[0096] 3) Filter the intermediate product I and dry the solid phase obtained after filtration at 120°C for 4 hours; exchange the dried product with ammonium ions in 2 mol / L NH4Cl solution at 80°C for 1 hour, repeat 3 times; to obtain intermediate product II.

[0097] 4) Filter and wash the intermediate product II, and dry the solid at 120°C for 4 hours. After drying, calcine it in a muffle furnace at 550°C for 4 hours to obtain catalyst AIII.

[0098] The specific surface area of ​​catalyst AIII was determined to be 565.1 m². 2 ·g -1 The SiO2 / Al2O3 molar ratio (silicon-aluminum ratio) is 30, and the content of Nb as Nb oxide (Nb2O5) is 0.77 wt%; the content of Ti as Ti oxide (TiO2) is 0.32 wt%. The catalyst AIII is in the MFI crystalline phase.

[0099] 2. Catalyst Evaluation

[0100] One gram (1g) of 20-40 mesh tableted catalyst AIII particles was packed into a fixed-bed reactor. The feed gas was acetylene, and the reaction conditions were: reaction pressure 1 MPa, reaction temperature 500℃, and acetylene volume hourly space velocity (VHSV) 2900 h⁻¹. -1 Gas chromatography analysis of the reacted product showed a conversion rate of 91.4% and a benzene yield of 60.7%.

[0101] Example 4

[0102] In the catalyst preparation method of this embodiment, zinc nitrate is selected as the active component source, silica sol is selected as the silicon source, aluminum sulfate is selected as the aluminum source, hydrofluoric acid is selected as the auxiliary agent, and tetraethylammonium hydroxide is selected as the template agent; the molar ratio of zinc nitrate to auxiliary agent is 1:1; the mass ratio / molar ratio of zinc nitrate: silica sol: aluminum sulfate: tetraethylammonium hydroxide: H2O is 0.8:0.3:50:1:0.5:150, and a gel precursor is prepared.

[0103] 1. Catalyst Preparation

[0104] 1) Zinc nitrate and disodium EDTA were mixed in the above proportion to obtain solution I; silica sol, aluminum sulfate and water were mixed in the above proportion to obtain dispersion I; dispersion I was added dropwise to solution I at a rate of 30 g / h to obtain a mixed gel; tetraethylammonium hydroxide in the above proportion was added dropwise to the mixed gel at a rate of 50 g / h to obtain a gel precursor;

[0105] 2) The gel precursor was stirred and aged at 80°C for 4 hours; the aged product was transferred to a hydrothermal crystallization vessel with a PTFE liner and hydrothermally crystallized at 170°C for 24 hours to obtain intermediate product I.

[0106] 3) Filter the intermediate product I, and dry the solid phase obtained after filtration at 120°C for 4 h; the dried product is then exchanged with ammonium ions in 2 mol / L NH4Cl solution at 80°C for 1 h, and repeated 3 times to obtain intermediate product II;

[0107] 4) Filter and wash the intermediate product II, and dry the solid at 120°C for 4 hours. After drying, calcine it in a muffle furnace at 550°C for 4 hours to obtain the catalyst AIV.

[0108] The specific surface area of ​​the AIV catalyst was measured to be 523.1 m². 2 ·g -1 The SiO2 / Al2O3 molar ratio (silicon-aluminum ratio) is 40, and the content of Zn as Zn oxide (ZnO) is 0.77 wt%. The catalyst AIV is in the MFI crystalline phase.

[0109] 2. Catalyst Evaluation

[0110] One gram (1g) of AIV catalyst particles (20-40 mesh size, compressed into tablets) was loaded into a fixed-bed reactor. The feed gas was acetylene, and the reaction conditions were: reaction pressure 1 MPa, reaction temperature 500℃, and acetylene volume hourly space velocity (VHSV) 2900 h⁻¹. -1 Gas chromatography analysis of the product after the reaction showed a conversion rate of 88.6% and a benzene yield of 54.9%.

[0111] Example 5

[0112] Catalyst AIII, prepared in Example 3, was used for catalyst evaluation.

[0113] One gram (1g) of catalyst AIII particles, compressed into tablets with a size of 20-40 mesh, was loaded into a fixed-bed reactor. The feed gas consisted of acetylene and acetonitrile in a molar ratio of 2:1. The reaction conditions were: reaction pressure 1.5 MPa, reaction temperature 480℃, and space velocity 2900 h⁻¹. -1 Gas chromatography analysis of the reaction product showed a conversion rate of 93.5%, a 2-methylpyridine yield of 43.6%, and a benzene yield of 18.3%.

[0114] Example 6

[0115] Catalyst AIII, prepared in Example 3, was used for catalyst evaluation.

[0116] One gram (1g) of 20-40 mesh tableted catalyst AIII particles was packed into a fixed-bed reactor. The feed gas consisted of acetylene and butyne in a molar to volume ratio of 2:1. The reaction conditions were: a reaction pressure of 1.8 MPa, a reaction temperature of 520 °C, and a volume hourly space velocity (VHSV) of 2900 h⁻¹ for acetylene and butyne. -1 Gas chromatography analysis of the reaction product showed a conversion rate of 91.7%, a toluene yield of 45.5%, and a benzene yield of 15.0%.

[0117] Example 7

[0118] Catalyst AIII, prepared in Example 3, was used for catalyst evaluation.

[0119] One gram (1g) of 20-40 mesh tableted catalyst AIII particles was packed into a fixed-bed reactor. The feed gas consisted of acetylene and acetonitrile in a molar to volume ratio of 1:1.5. The reaction conditions were: a reaction pressure of 2.5 MPa, a reaction temperature of 520 °C, and a volume hourly space velocity (VHSV) of 2700 h⁻¹ for acetylene and acetonitrile. -1 Gas chromatography analysis of the product after the reaction showed a conversion rate of 90.0% and a pyridine yield of 46.2%.

[0120] Example 8

[0121] Catalyst AIII, prepared in Example 3, was used for catalyst evaluation.

[0122] One gram (1g) of 20-40 mesh tableted catalyst AIII particles was packed into a fixed-bed reactor. The feed gas consisted of acetylene and acetonitrile in a molar ratio of 2:1; the reaction conditions were a reaction pressure of 1.8 MPa, a reaction temperature of 500 °C, and a volume hourly space velocity (VHSV) of 2700 h⁻¹ for acetylene and butyne. -1Gas chromatography analysis of the reaction product showed a conversion rate of 89.8%, a benzene yield of 24.5%, and a 2-methylpyridine yield of 22.6%.

[0123] Comparative Example 1

[0124] 1. Catalyst Preparation

[0125] Commercially available H-type ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 35 was selected. The niobium oxalate solution was used as the impregnation liquid to impregnate the sieve with an Nb2O5 content of 1%. After impregnation, the sieve was dried at 120°C for 4 hours and then calcined in a muffle furnace at 550°C for 4 hours to obtain catalyst BI.

[0126] The specific surface area of ​​catalyst BI was determined to be 476.6 m². 2 ·g -1 The SiO2 / Al2O3 molar ratio (silicon-aluminum ratio) is 34, and the content of Nb as Nb oxide (Nb2O5) is 0.96 wt%. The catalyst BI is in the MFI crystalline phase.

[0127] 2. Catalyst Evaluation

[0128] One gram (1g) of BI catalyst particles (20-40 mesh size, compressed into tablets) was loaded into a fixed-bed reactor. The feed gas was acetylene, and the reaction conditions were: reaction pressure 1 MPa, reaction temperature 500℃, and volumetric hourly space velocity (VHSV) 2900 h⁻¹. -1 Gas chromatography analysis of the reaction product showed that the conversion rate of acetylene was 86.2% and the benzene yield was 54.0%.

[0129] Comparative Example 2

[0130] In the catalyst preparation method of this comparative example, Nb2O5 was selected as the active component source, silica sol was selected as the silicon source, aluminum sulfate was selected as the aluminum source, hydrofluoric acid was selected as the auxiliary agent, and tetraethylammonium hydroxide was selected as the template agent; the molar ratio of active component source to auxiliary agent was 1:1; and the gel precursor was prepared according to the molar ratio of active component source:silicon source:aluminum source:template agent:H2O of 0.2:20:1:0.5:150.

[0131] 1. Catalyst Preparation

[0132] 1) Mix Nb2O5 and hydrofluoric acid in the above proportion to obtain solution I; mix silica sol, aluminum sulfate and water in the above proportion to obtain dispersion I; add dispersion I dropwise to solution I at a rate of 50 g / h to obtain mixed gel; then add tetraethylammonium hydroxide in the above proportion to the mixed gel at a rate of 50 g / h to obtain gel precursor;

[0133] 3) The gel precursor was stirred and aged at 80°C for 4 hours; the aged product was transferred to a hydrothermal crystallization kettle with a PTFE liner and hydrothermally crystallized at 160°C for 32 hours to obtain intermediate product I.

[0134] 4) Filter the intermediate product I and dry the solid phase obtained after filtration at 120°C for 4 hours; exchange the dried product with ammonium ions in 2 mol / L NH4Cl solution at 80°C for 1 hour, repeat 3 times; to obtain intermediate product II.

[0135] 5) After filtration, the intermediate product II was washed with water, and the solid was dried at 120°C for 4 hours. After drying, it was calcined in a muffle furnace at 550°C for 4 hours to obtain catalyst BII.

[0136] The specific surface area of ​​the catalyst BII was determined to be 505.3 m². 2 ·g -1 The SiO2 / Al2O3 molar ratio (silicon-aluminum ratio) is 15, and the Nb oxide (Nb2O5) content is 0.79 wt%. The catalyst BII is in the MFI crystalline phase.

[0137] 2. Catalyst Evaluation

[0138] One gram (1g) of 20-40 mesh compressed Al catalyst particles were loaded into a fixed-bed reactor. The feed gas was acetylene, and the reaction conditions were: reaction pressure 1 MPa, reaction temperature 500℃, and acetylene volume hourly space velocity (VHSV) 2900 h⁻¹. -1 Gas chromatography analysis of the reaction product showed that the conversion rate of acetylene was 80.1% and the benzene yield was 47.2%.

[0139] Comparative Example 3

[0140] In the catalyst preparation method of this embodiment, niobium oxalate is selected as the active component source, silica sol is selected as the silicon source, aluminum sulfate is selected as the aluminum source, and tetraethylammonium hydroxide is selected as the template agent; a gel precursor is prepared according to the molar ratio of active component source: silicon source: aluminum source: template agent: H2O of 1.5:50:1:0.5:150.

[0141] 1. Catalyst Preparation

[0142] 1) Niobium oxalate was dissolved in water to obtain solution I; silica sol, aluminum sulfate and water were mixed in the above proportion to obtain dispersion I; dispersion I was added dropwise to solution I at a rate of 40 g / h to obtain mixed gel; tetraethylammonium hydroxide in the above proportion was added dropwise to mixed gel at a rate of 40 g / h to obtain gel precursor I; and 2 wt% of ZSM-5 molecular sieve seed crystals by weight of gel precursor were added to gel precursor I to obtain gel precursor II.

[0143] 2) The gel precursor II was stirred and aged at 80°C for 4 hours; the aged product was transferred into a hydrothermal crystallization vessel with a PTFE liner and hydrothermally crystallized at 170°C for 48 hours to obtain intermediate product I.

[0144] 3) Filter the intermediate product I and dry the solid phase obtained after filtration at 120°C for 4 hours; exchange the dried product with ammonium ions in 2 mol / L NH4Cl solution at 80°C for 1 hour, repeat 3 times; to obtain intermediate product II.

[0145] 4) Filter and wash the intermediate product II, and dry the solid at 120°C for 4 hours. After drying, calcine it in a muffle furnace at 550°C for 4 hours to obtain catalyst BIII.

[0146] The specific surface area of ​​catalyst BIII was determined to be 506.3 m². 2 ·g -1 The SiO2 / Al2O3 molar ratio (silicon-aluminum ratio) is 29, and the content of Nb as Nb oxide (Nb2O5) is 0.76 wt%. Catalyst BIII is in the MFI crystalline phase.

[0147] 2. Catalyst Evaluation

[0148] One gram (1g) of 20-40 mesh compressed catalyst AII particles was loaded into a fixed-bed reactor. The feed gas was acetylene, and the reaction conditions were: reaction pressure 1 MPa, reaction temperature 500℃, and acetylene volume hourly space velocity (VHSV) 2900 h⁻¹. -1 Gas chromatography analysis of the reaction product showed that the conversion rate of acetylene was 86.4%, and the benzene yield was 40.3%.

[0149] Comparative Example 4

[0150] Using a batch reactor:

[0151] Acetonitrile liquid was added to a high-pressure reactor. A catalyst prepared by reacting CoCl2 with cyclopentadiene at a 1:2 ratio was added to the reactor at a catalyst-to-acetonitrile mass ratio of 1:800. After the reactor was closed, acetylene gas was introduced through a gas pipeline at a acetonitrile-to-acetylene molar ratio of 1:3 to maintain the reaction system pressure at approximately 1.5 MPa. The reaction temperature was 120℃, and the reaction time was 3 hours. After the reaction, the reactor was shut down, and the liquid product was extracted for analysis.

[0152] Gas chromatography analysis of the product after the reaction showed a conversion rate of 95.5%, a benzene yield of 36.2%, and a 2-methylpyridine yield of 18.6%.

[0153] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing aromatic compounds, characterized in that, The method includes contacting a raw material containing alkynes with a catalyst to induce a cyclotrimerization reaction in order to prepare an aromatic compound; The catalyst comprises a molecular sieve and an active component, wherein the active component contains at least one element selected from Nb, Ti, Ga, Ni, Zn, V, Co, Cr, and Fe; wherein, The catalyst has a specific surface area of ​​500~700 m². 2 / g; In the catalyst, the content of the active component, calculated as oxide, is 0.1wt%~10wt%; The molar ratio of SiO2 / Al2O3 in the molecular sieve is 25~80:1; The molecular sieve has an MFI structure, a MOR structure, or a MEL structure; The method for preparing the catalyst includes the following steps: S1. Mix the dispersion I containing silicon source and aluminum source with the solution I containing active component source to obtain a mixed gel; S2. Obtain a gel precursor containing a template agent and the mixed gel; S3. The gel precursor is subjected to aging and hydrothermal crystallization treatments in sequence to obtain intermediate product I. S4. The intermediate product I is filtered, and the solid phase obtained after filtration is dried and then subjected to ammonium ion exchange treatment to obtain intermediate product II. S5. The intermediate product II is calcined to obtain the catalyst.

2. The method according to claim 1, characterized in that, In step S1, the preparation of solution I includes the following steps: mixing the active ingredient source with the auxiliary agent to obtain solution I; wherein, The active component source is selected from one or more of oxides, salts, and organic compounds containing the active component; And / or, the adjuvant is selected from one or more of ethylenediaminetetraacetic acid, ammonium fluoride, hydrofluoric acid, triethanolamine, oxalic acid, tartaric acid, citric acid and sulfosalicylic acid; And / or, the molar ratio of the active ingredient source to the adjuvant is 0.5 to 2:

1.

3. The method according to claim 1, characterized in that, In step S1, the silicon source is silica sol and / or water glass; and / or, the aluminum source is selected from at least one of boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide. And / or, in step S2, the template agent is selected from at least one of isopropylamine, n-butylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

4. The method according to claim 1, characterized in that, The molar ratio of the active component source, silicon source, aluminum source and template agent is 0.5~2.5:30~150:1:0~2.

0.

5. The method according to claim 1, characterized in that, In step S3, the aging treatment conditions include: a temperature of 60°C to 90°C and a time of 1 to 8 hours; and / or, the hydrothermal crystallization treatment conditions include: a pressure of 1.2 to 2.5 MPa, a temperature of 150°C to 240°C, and a time of 1 to 8 hours. And / or, in step S4, the drying conditions include: a temperature of 100°C to 150°C and a time of 2 to 24 hours; and / or, the ammonium ion exchange treatment is carried out in a 1 to 5 mol / L ammonium ion-containing solution at 80°C to 95°C. And / or, in step S5, the calcination conditions include: a temperature of 450°C to 650°C and a time of 2 to 8 hours.

6. The method according to any one of claims 1-5, characterized in that, The cyclotrimerization reaction is carried out in a fixed bed; And / or, the reaction conditions for the cyclotrimerization reaction include: a reaction pressure of 0.5 MPa to 2 MPa; and / or, a reaction temperature of 400°C to 600°C; and / or, a volume hourly space velocity (VHSV) of 2600 to 3000 h⁻¹. -1 .

7. The method according to any one of claims 1-5, characterized in that, The alkyne is a C2-C6 alkyne; and / or, the raw material also contains a C2-C6 nitrile compound; And / or, the aromatic compound is selected from one or more of aromatic hydrocarbons and aromatic heterocyclic compounds, wherein the aromatic hydrocarbon has 5-10 skeletal cyclic carbon atoms; the aromatic heterocyclic compound has 6-8 cyclic atoms, wherein at least one cyclic atom is N.

8. The method according to any one of claims 1-5, characterized in that, The alkyne is acetylene and / or butyne; And / or, the aromatic compound is selected from one or more of benzene, toluene, xylene, pyridine and methylpyridine.

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