Bromine-substituted nitrogen heterocyclic coordinated zinc-based catalyst as well as preparation method and application thereof
By preparing a zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination, the problems of low catalyst activity and poor stability in the acetylene acetylene reaction were solved, achieving a highly efficient acetylene acetylene reaction with significantly improved conversion and selectivity, while inhibiting the loss of active components and carbon deposition.
Patent Information
- Application Number
- CN202511642989.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-11
- Publication Date
- 2026-02-17
AI Technical Summary
The existing acetylene acetylene esterification reaction suffers from low catalyst activity, poor stability, easy loss of active components, and easy carbon deposition.
A novel zinc-based catalyst, employing bromine-substituted nitrogen heterocyclic coordination, was prepared by mixing the bromine-substituted nitrogen heterocyclic ligand with zinc acetate and activated carbon support. This catalyst weakens the adsorption of acetylene while enhancing the adsorption of acetic acid, thus inhibiting the loss of active components and carbon deposition.
It improved the conversion rate and selectivity of the catalyst, significantly enhanced the activity and stability of the reaction, with a conversion rate of 91% and a selectivity of 99%, and effectively suppressed the loss of active components and carbon deposition.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of vinyl acetate synthesis technology, specifically relating to a zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination, its preparation method, and its application. Background Technology
[0002] Vinyl acetate (VAc), a product of the acetylene acetylation reaction, is an important industrial organic raw material, mainly used in the production of polyvinyl alcohol (PVOH), polyethylene-vinyl acetate copolymer (EVA), vinyl acetate-ethylene copolymer emulsion (VAE), and polyvinyl acetate (PVAc), all of which have applications in construction, textiles, machinery, medicine, and soil conditioners. Among these, polyethylene-vinyl acetate copolymer (EVA) is an important photoelectrode separator material in photovoltaic systems, offering good transparency, low cost, and excellent water and oxygen barrier properties; polyvinyl alcohol (PVOH) is a crucial raw material for photoresists used in chip manufacturing.
[0003] Currently, the main industrial production methods for vinyl acetate are the ethylene process and the acetylene process. In the industrial application of the acetylene process for producing vinyl acetate, zinc acetate (Zn(OAc)₂) is used as the active component and activated carbon as the support to catalyze the acetylene acetylation reaction. This catalyst is simple, inexpensive, and readily available; however, it still suffers from low reactivity (conversion rate <70%) and limited production capacity (space velocity <100 h⁻¹). -1 It also suffers from problems such as insufficient activity and stability, including easy carbon buildup and easy loss of Zn components.
[0004] To address this issue, this invention designs and develops a novel, highly efficient Zn-based catalyst, its preparation method, and its applications. In this system, non-metallic atoms, halogen atoms, and heterocyclic compounds are introduced to alter the electronic structure of the active component, anchor the active component, and suppress the loss of the active component and carbon deposition. Summary of the Invention
[0007] The purpose of this invention is to provide a zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination, which solves the problems of low catalyst activity, poor stability, loss of active components, and carbon deposition in the acetylene acetate reaction process.
[0008] To achieve the above objectives, the technical solution adopted is as follows:
[0009] A zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination is prepared using the following raw materials: solvent, bromine-substituted nitrogen heterocyclic ligand, zinc acetate, and activated carbon support.
[0010] Furthermore, the solvent is water and anhydrous ethanol.
[0011] Furthermore, the bromine-substituted nitrogen heterocyclic ligand is a monobromine-substituted N-containing heterocyclic compound or a dibromine-substituted N-containing heterocyclic compound.
[0012] Furthermore, the monobromosubstituted N-containing heterocyclic compound is 2-bromopyridine or 2-bromopyrrole;
[0013] Furthermore, the 2-bromopyridine has the molecular formula C5H4BrN and the CAS number 109-04-6; the 2-bromopyrrole has the molecular formula C4H4BrN and the CAS number 38480-28-3.
[0014] The dibromo-substituted N-containing heterocyclic compounds are 2,6-dibromopyridine and 2,5-dibromopyrrole.
[0015] Further, 2,6-dibromopyridine has the molecular formula C5H3Br2N and the CAS number 626-05-1; 2,5-dibromopyrrole has the molecular formula C4H3Br2N and the CAS number 56454-25-2.
[0016] Furthermore, the bromine-substituted nitrogen heterocyclic ligand in the catalyst comprises 20%-52% by mass;
[0017] The zinc acetate in the catalyst has a mass percentage of 10%-20%.
[0018] Another objective of this invention is to provide a method for preparing the above-mentioned zinc-based catalyst, which is simple, efficient, and can be widely used in industrial applications.
[0019] To achieve the above objectives, the technical solution adopted is as follows:
[0020] The preparation method of the above-mentioned zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination is as follows: after uniformly mixing the solvent, bromine-substituted nitrogen heterocyclic ligand and zinc acetate, an activated carbon support is added, impregnated, and then dried to obtain the zinc-based catalyst.
[0021] Furthermore, the impregnation treatment is either over-volume impregnation or equal-volume impregnation;
[0022] The drying temperature is 40℃-120℃, and the time is 5h-24h.
[0023] Another objective of this invention is to provide applications of the aforementioned zinc-based catalyst.
[0024] To achieve the above objectives, the technical solution adopted is as follows:
[0025] Application of the above-mentioned zinc-based catalysts with bromine-substituted nitrogen heterocyclic coordination, or zinc-based catalysts prepared by the above-mentioned preparation method, in the acetylene acetylene reaction.
[0026] Furthermore, the application involves the acetylene-acetic acid reaction of acetylene and acetic acid under anaerobic conditions at 120℃-300℃. The reaction equation is as follows:
[0027] C2H2 + CH3COOH → H2C = CHOCOCH3
[0028] Furthermore, the space velocity for the acetylene reaction is 60 h⁻¹. -1 -600h -1 ;
[0029] The molar ratio of acetylene to acetic acid is 1:1 to 5:1.
[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0031] 1. In the technical solution of the present invention, the catalyst comprises a mixture of Zn element as active component, multidentate nitrogen ligand as ligand, and activated carbon as support. This catalyst weakens the adsorption of acetylene by the active site, while increasing the adsorption of acetic acid.
[0032] The catalyst developed in this invention has improved activity to 91% conversion and 99% selectivity (space velocity 360 h⁻¹). -1 Conversion rate 81%, selectivity 95% (space velocity 480 h⁻¹); -1 Compared to the same conditions, the Zn(OAc)2 / AC ratio was significantly improved (conversion rate 47%, selectivity 90%) (space velocity 480 h⁻¹). -1 Furthermore, this catalyst effectively inhibits the loss of active components and carbon deposition during the reaction process. (At 1200 h⁻¹ (space velocity 360 h⁻¹)...) -1 In the test, the Zn component loss rate was as low as 9.2%, and the carbon deposition was only 5.24%.
[0033] 2. The catalyst preparation method of the present invention is simple and efficient, and can be widely used in industrial applications, thus having good practicality. Attached Figure Description
[0034] Figure 1 Diagram of an acetylene acetic acid reaction apparatus;
[0035] Figure 2 XRD data for catalyst No. 3 and Zn(OAc)2 / AC catalyst.
[0036] Figure 3 The performance of catalyst No. 3 and Zn(OAc)2 / AC catalyst in adsorbing acetic acid.
[0037] Figure 4The ability of catalyst No. 3 and Zn(OAc)2 / AC catalyst to adsorb acetylene.
[0038] Figure 5 A comparison of conversion rates between catalyst No. 3 and Zn(OAc)2 / AC catalyst.
[0039] Figure 6 A comparison of selectivity between catalyst No. 3 and Zn(OAc)2 / AC catalyst.
[0040] Figure 7 A comparison of the conversion rates of catalyst No. 3 and Zn(OAc)2 / AC catalyst over 150 h.
[0041] Figure 8 The selectivity of catalyst No. 3 and Zn(OAc)2 / AC catalyst was compared over 150 h.
[0042] Figure 9 The stability of catalyst No. 3 was tested for 1200 hours.
[0043] Figure 10 Thermogravimetric analysis of catalyst No. 3. Detailed Implementation
[0044] To further illustrate the bromine-substituted nitrogen heterocyclic coordinated zinc-based catalyst, its preparation method, and its applications according to the present invention, and to achieve the intended objectives of the invention, the following detailed description, in conjunction with preferred embodiments, details the specific implementation methods, structures, features, and effects of the bromine-substituted nitrogen heterocyclic coordinated zinc-based catalyst, its preparation method, and its applications. In the following description, different "one embodiment" or "example" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.
[0045] The following will provide a detailed description of the zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination, its preparation method, and its applications, using specific embodiments as examples:
[0046] This invention relates to a zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination, its preparation method, and its applications. The catalyst comprises a support, an active component, and a halogenated heterocyclic ligand. The catalyst comprises a mixture of Zn element as the active component, a multidentate nitrogen ligand, and activated carbon as the support. This catalyst weakens the adsorption of acetylene at the active sites while increasing the adsorption of acetic acid. Furthermore, it effectively inhibits the loss of the active component during the reaction process, thereby significantly improving the activity and stability of the reaction. The preparation method of this catalyst is simple and efficient, and it can be widely used in industrial applications, demonstrating good practicality.
[0047] The technical solution of this invention is as follows:
[0048] A zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination is prepared using the following raw materials: solvent, bromine-substituted nitrogen heterocyclic ligand, zinc acetate, and activated carbon support.
[0049] Preferably, the solvent is water and anhydrous ethanol.
[0050] In the above technical solution, water is used to dissolve zinc acetate, and ethanol is used to dissolve the bromine-substituted nitrogen heterocyclic ligand. In specific operations, the bromine-substituted nitrogen heterocyclic ligand and zinc acetate can be dissolved separately in ethanol and water and then mixed, or they can be dissolved together in an aqueous ethanol solution, or they can be dissolved separately in an aqueous ethanol solution and then mixed.
[0051] Preferably, the bromine-substituted nitrogen heterocyclic ligand is a monobromine-substituted N-containing heterocyclic compound or a dibromine-substituted N-containing heterocyclic compound.
[0052] More preferably, the monobromosubstituted N-containing heterocyclic compound is 2-bromopyridine or 2-bromopyrrole.
[0053] The dibromo-substituted N-containing heterocyclic compounds are 2,6-dibromopyridine and 2,5-dibromopyrrole.
[0054] Preferably, the bromine-substituted nitrogen heterocyclic ligand in the catalyst has a mass percentage of 20%-52%;
[0055] The zinc acetate in the catalyst has a mass percentage of 10%-20%.
[0056] In the above technical solution, the amount of ligand used should be greater than the amount of zinc acetate used.
[0057] The preparation method of the above-mentioned zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination is as follows: after uniformly mixing the solvent, bromine-substituted nitrogen heterocyclic ligand and zinc acetate, an activated carbon support is added, impregnated, and then dried to obtain the zinc-based catalyst.
[0058] Preferably, the impregnation treatment is over-volume impregnation or equal-volume impregnation.
[0059] The drying temperature is 40℃-120℃, and the time is 5h-24h.
[0060] Application of the above-mentioned zinc-based catalysts with bromine-substituted nitrogen heterocyclic coordination, or zinc-based catalysts prepared by the above-mentioned preparation method, in the acetylene acetylene reaction.
[0061] Preferably, the application is: acetylene and acetic acid are subjected to an acetylene acetate reaction in an oxygen-free environment at 120℃-300℃.
[0062] More preferably, the space velocity of the acetylene reaction is 60 h⁻¹. -1 -600h-1 .
[0063] The molar ratio of acetylene to acetic acid is 1:1 to 5:1.
[0064] Preferably, the bromine-substituted nitrogen heterocyclic ligand in the catalyst has a mass percentage of 20%-52%;
[0065] The zinc acetate in the catalyst has a mass percentage of 10%-20%.
[0066] Example 1: 2-bromopyridine (its structural formula is C5H4BrN, CAS number is 109-04-6) was used as a ligand (denoted as L1).
[0067] The specific steps for preparing catalyst No. 1 are as follows:
[0068] S1: Weigh 2.26g of zinc acetate and dissolve it in 7.51g of ultrapure water to obtain solution 1.
[0069] S2: Weigh 3.89g of L1 and dissolve it in 7.51g of anhydrous ethanol to obtain solution 2.
[0070] S3: Mix solution 1 and solution 2, and heat and stir at 80°C for 10 minutes to obtain solution 3.
[0071] S4: Weigh 4.27g of activated carbon and 9.39g of solution 3 into a 100mL beaker, and soak for 10h to obtain the precursor.
[0072] S5: Dry the precursor in an 80℃ forced-air drying oven for 8 hours, and stir it every 10 minutes during the first hour of heating to ensure it is fully and evenly dried, thus obtaining catalyst No. 1.
[0073] Example 2: Using 2-bromopyrrole (structural formula C4H4BrN, CAS number: 38480-28-3) as a ligand (denoted as L2).
[0074] The specific steps for preparing catalyst No. 2 are as follows:
[0075] S1: Weigh 2.26g of zinc acetate and dissolve it in 7.77g of ultrapure water to obtain solution 1.
[0076] S2: Weigh 3.59g of L2 and dissolve it in 7.68g of anhydrous ethanol to obtain solution 2.
[0077] S3: Mix solution 1 and solution 2, and heat and stir at 80°C for 10 minutes to obtain solution 3.
[0078] S4: Weigh 4.41g of activated carbon and 9.71g of solution 3 into a 100mL beaker, and soak for 10h to obtain the precursor.
[0079] S5: Dry the precursor in an 80℃ forced-air drying oven for 8 hours, and stir it every 10 minutes during the first hour of heating to ensure it is fully and evenly dried, thus obtaining catalyst No. 2.
[0080] Example 3: Using 2,6-dibromopyridine (structural formula C5H3Br2N, CAS number: 626-05-1) as a ligand (denoted as L3).
[0081] The specific steps for preparing catalyst No. 3 are as follows:
[0082] S1: Weigh 2.26g of zinc acetate and dissolve it in 5.8g of ultrapure water to obtain solution 1.
[0083] S2: Weigh 5.83g of L3 and dissolve it in 7.99g of anhydrous ethanol to obtain solution 2.
[0084] S3: Mix solution 1 and solution 2, and heat and stir at 180°C for 10 minutes to obtain solution 3.
[0085] S4: Weigh 3.29g of activated carbon and 7.25g of solution 3 into a 100mL beaker, and soak for 10h to obtain the precursor.
[0086] S5: The precursor was dried in an 80℃ forced-air drying oven for 8 hours, and stirred every 10 minutes during the first hour of heating to ensure thorough and uniform drying, thus obtaining catalyst No. 3.
[0087] Example 4: Using 2,5-dibromopyrrole (structural formula C4H3Br2N, CAS number: 56454-25-2) as a ligand (denoted as L4).
[0088] The specific steps for preparing catalyst No. 4 are as follows:
[0089] S1: Weigh 2.26g of zinc acetate and dissolve it in 6.06g of ultrapure water to obtain solution 1.
[0090] S2: Weigh 5.54g of L4 and dissolve it in 6.06g of anhydrous ethanol to obtain solution 2.
[0091] S3: Mix solution 1 and solution 2, and heat and stir at 180°C for 10 minutes to obtain solution 3.
[0092] S4: Weigh 3.29g of activated carbon and 7.25g of solution 3 into a 100mL beaker, and soak for 10h to obtain the precursor.
[0093] S5: The precursor was dried in an 80℃ forced-air drying oven for 8 hours, and stirred every 10 minutes during the first hour of heating to ensure thorough and uniform drying, thus obtaining catalyst No. 4.
[0094] Example 5: Using 2,6-dibromopyridine (structural formula C5H3Br2N, CAS number: 626-05-1) as a ligand (denoted as L3).
[0095] The specific steps for preparing catalyst No. 3 are as follows:
[0096] S1: Weigh 2.26g of zinc acetate and dissolve it in 5.8g of ultrapure water to obtain solution 1.
[0097] S2: Weigh 5.83g of L3 and dissolve it in 7.99g of anhydrous ethanol to obtain solution 2.
[0098] S3: Mix solution 1 and solution 2, and heat and stir at 180°C for 10 minutes to obtain solution 3.
[0099] S4: Weigh 3.29g of activated carbon into a 100mL beaker and weigh 21.88g of the solution 3 prepared above. Soak for 10h to obtain the precursor.
[0100] S5: The precursor was dried in an 80℃ forced-air drying oven for 8 hours, and stirred every 10 minutes during the first hour of heating to ensure thorough and uniform drying, thus obtaining catalyst No. 5.
[0101] Example 6: Testing the performance of the catalyst.
[0102] (1) Catalyst
[0103] Catalyst No. 3 prepared in Example 3, catalyst No. 5 prepared in Example 5, and control catalyst Zn(OAc)2 / AC.
[0104] Preparation method of catalyst Zn(OAc)2 / AC:
[0105] S1: Weigh 2.26g of zinc acetate and dissolve it in 13.63g of ultrapure water to obtain solution 1.
[0106] S2: Weigh 7.74g of activated carbon into a 100mL beaker and weigh 17.03g of solution 1. Soak for 10h to obtain the precursor.
[0107] S3: The precursor was dried in an 80℃ forced-air drying oven for 8 hours, and stirred every 10 minutes during the first hour of heating to ensure thorough and uniform drying, thus obtaining the zinc-based catalyst Zn(OAc)2 / AC.
[0108] (2) Test method
[0109] Combination Figure 1 The specific operating steps are as follows:
[0110] S1: Fill 2.5 mL of catalyst into each reaction tube. The reaction tube is located in the middle of the heating zone of the reactor. Purge the entire reaction system with N2 to remove impurity gases from the reaction device.
[0111] S2: The gasification zone, insulation zone, and reaction zone are heated. The gasification zone is set to 150℃, the insulation zone to 150℃, and the reaction zone to 220℃. When the reaction zone temperature reaches 200℃, the catalyst in the fixed-bed reactor is activated with acetic acid for 30 minutes using a peristaltic pump.
[0112] S3: Turn off the N2 switch. After the nitrogen flow meter reading reaches zero, turn on the C2H2 switch. According to the acetylene space velocity of the reaction feed: 480 h⁻¹ -1 The reaction conditions of acetylene:acetic acid = 3:1 are used to inject acetylene and acetic acid into the reactor;
[0113] The content of the product was detected by manual injection via gas chromatography every hour to analyze its composition and selectivity.
[0114] The products obtained from the acetylene acetylene reaction were quantitatively analyzed using the calibrated area normalization method. The conversion rate (C) of acetic acid and the selectivity (S) of vinyl acetate were used as standards to evaluate the performance of the zinc-based catalyst in the acetylene acetylene reaction. The main product of the acetylene reaction was vinyl acetate, and the byproducts included acetone and other impurities.
[0115] The formulas for calculating the conversion rate of acetic acid and the selectivity of vinyl acetate are as follows:
[0116]
[0117] in, This indicates the volume fraction of vinyl acetate in gas chromatography. This indicates the volume fraction of acetone in the gas chromatography. This indicates the volume fraction of acetic acid in the gas chromatography. This indicates the volume fraction of other impurities in the product after the reaction in gas chromatography.
[0118] (3) Results
[0119] ①XRD data
[0120] Figure 2 The figure shows the XRD data of the catalysts. As can be seen from the figure, both catalysts exhibit characteristic peaks of activated carbon at 002 and 100.
[0121] ②Adsorption
[0122] The adsorption performance of the catalyst on acetic acid and acetylene was determined. The results are as follows: Figures 3-4 As shown.
[0123] Depend on Figures 3-4 As can be seen from the figure, the introduction of ligands with bromine substituents will improve the catalyst's adsorption performance of acetic acid, but conversely, it will reduce the catalyst's adsorption performance of acetylene.
[0124] ③ Conversion rate
[0125] Figure 5 The conversion rates of the catalysts are compared. As shown in the figure, the conversion rate of catalyst No. 3 after the addition of the bromine-substituent ligand reached 81%, while the conversion rate of the control group Zn(OAc)2 / AC catalyst was 47%.
[0126] ④ Selectivity
[0127] Figure 6 This figure shows a comparison of the selectivity among the catalysts. As can be seen from the figure, catalyst #3 has a selectivity of over 95%, while the Zn(OAc)₂ / AC catalyst has a selectivity of 91%.
[0128] ⑤ 150h stability comparison test
[0129] Figure 7 The stability of the catalysts was compared over 150 hours. As shown in the figure, the stability of the Zn(OAc)2 / AC catalyst decreased significantly after 120 hours, while the reaction activity of catalyst No. 3 remained stable with no significant change after 150 hours.
[0130] Figure 8 The selectivity test was used to assess catalyst stability. As shown in the figure, catalyst #3 exhibited a selectivity of over 95% in the stability test, while the Zn(OAc)₂ / AC catalyst showed a selectivity of 89%.
[0131] ⑥ Aperture structure analysis
[0132] The changes in the physical adsorption pore size structure of the catalyst before and after the reaction were measured, and the results are shown in Table 1. The pore size structure revealed a significant change compared to the Zn(OAc)2 / AC catalyst, indicating substantial carbon deposition that blocked the catalyst pores. In contrast, catalyst No. 3 showed a smaller change in pore size after the reaction, which also corresponds to a small amount of carbon deposition.
[0133] Table 1. Comparison of pore structure between catalyst No. 3 and Zn(OAc)2 / AC catalyst
[0134] <![CDATA[Zn(OAc)2 / AC]]> Catalyst No. 3 Pore size before reaction (nm) 2.72 2.56 Pore size (nm) after 10 hours of reaction 3.56 2.73
[0135] ⑦ 1200h Long-Term Stability Test
[0136] Figure 9 For the stability test of catalyst No. 3, the conversion rate was 91% and the selectivity was 99% after 1200 h.
[0137] ⑧ Thermogravimetric analysis
[0138] Thermogravimetric analysis was performed on catalyst No. 3 before and after 1200 h of reaction, and the results are as follows: Figure 10 As shown in the figure, the carbon deposition of catalyst No. 3 is 5.24%. This indicates that the introduction of the Br group reduces the carbon deposition, which is one of the important reasons for the improved stability of this catalyst.
[0139] ⑨ Zn content analysis
[0140] The Zn content before and after the catalyst reaction for 1200 h was analyzed, and the results are shown in Table 2.
[0141] Based on Table 2, the experiment found that the introduction of ligands inhibited the loss of Zn, with a Zn loss rate of 9.2%.
[0142] Table 2. Zinc loss test results for catalyst No. 3 and Zn(OAc)2 / AC catalyst.
[0143]
[0144] Example 7: Using 2,5-dibromopyrrole as a ligand (denoted as L4)
[0145] The specific steps are as follows:
[0146] (1) Preparation of catalyst No. 4
[0147] S1: Weigh 2.0g of zinc acetate and dissolve it in 6.0g of ultrapure water to obtain solution 1.
[0148] S2: Weigh 4.0g of L4 and dissolve it in 8.0g of anhydrous ethanol to obtain solution 2.
[0149] S3: Mix solution 1 and solution 2, and heat and stir at 180°C for 20 minutes to obtain solution 3.
[0150] S4: Weigh 7.0g of activated carbon and 10.0g of solution 3 into a 100mL beaker, and soak for 10h to obtain the precursor.
[0151] S5: The precursor was dried in a 40°C forced-air drying oven for 24 hours, and stirred every 10 minutes during the first hour of heating to ensure thorough and uniform drying, thus obtaining a zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination.
[0152] (2) Catalyst No. 4 was used in the fixed-bed reaction of acetylene acetylene acidification.
[0153] S6: Fill 2.5 mL of catalyst into the reaction tube, which is located in the middle of the heating zone of the reactor. Purge the entire reaction system with N2 to remove impurity gases from the reaction apparatus.
[0154] S7: Heat the gasification zone, insulation zone, and reaction zone. Set the gasification zone temperature to 100℃, the insulation zone temperature to 100℃, and the reaction zone temperature to 150℃. When the reaction zone temperature reaches 120℃, activate the catalyst in the fixed-bed reactor with acetic acid for 40 minutes using a peristaltic pump.
[0155] S8: Turn off the N2 switch. After the nitrogen flow meter reading reaches zero, turn on the C2H2 switch. According to the acetylene space velocity of the reaction feed: 60 h⁻¹ -1 The reaction conditions of acetylene and acetic acid = 1:1 were used to inject acetylene and acetic acid into the reactor.
[0156] Example 8: Using 2,5-dibromopyrrole as a ligand (denoted as L4)
[0157] The specific steps are as follows:
[0158] (1) Preparation of catalyst No. 4
[0159] S1: Weigh 2.0g of zinc acetate and dissolve it in 6.0g of ultrapure water to obtain solution 1.
[0160] S2: Weigh 4.0g of L4 and dissolve it in 8.0g of anhydrous ethanol to obtain solution 2.
[0161] S3: Mix solution 1 and solution 2, and heat and stir at 180°C for 10 minutes to obtain solution 3.
[0162] S4: Weigh 4.00g of activated carbon into a 100mL beaker and weigh 20.0g of solution 3. Soak for 10h to obtain the precursor.
[0163] S5: The precursor was dried in a 120℃ forced-air drying oven for 5 hours, and stirred every 10 minutes during the first hour of heating to ensure thorough and uniform drying, thus obtaining a zinc-based catalyst with bromine-substituted nitrogen heterocyclic coordination.
[0164] (2) Catalyst No. 4 was used in the fixed-bed reaction of acetylene acetylene acidification.
[0165] S6: Fill 2.5 mL of catalyst into the reaction tube, which is located in the middle of the heating zone of the reactor. Purge the entire reaction system with N2 to remove impurity gases from the reaction apparatus.
[0166] S7: Heat the gasification zone, insulation zone, and reaction zone. Set the gasification zone to 200℃, the insulation zone to 200℃, and the reaction zone to 320℃. When the reaction zone temperature reaches 300℃, activate the catalyst in the fixed-bed reactor with acetic acid for 30 minutes using a peristaltic pump.
[0167] S8: Turn off the N2 switch. After the nitrogen flow meter reading reaches zero, turn on the C2H2 switch. According to the acetylene space velocity of the reaction feed: 600 h⁻¹ -1 The reaction conditions of acetylene:acetic acid = 5:1 were used to inject acetylene and acetic acid into the reactor.
[0168] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.
Claims
1. A zinc-based catalyst complexed with a bromo-substituted nitrogen heterocycle, characterized in that, The following raw materials are used for preparation: solvent, bromine-substituted nitrogen heterocyclic ligand, zinc acetate, activated carbon carrier.
2. The zinc-based catalyst according to claim 1, characterized in that, the solvent is water and anhydrous ethanol.
3. The zinc-based catalyst according to claim 1, characterized in that, the bromine-substituted nitrogen heterocyclic ligand is a monobromine-substituted N-containing heterocyclic compound or a dibromine-substituted N-containing heterocyclic compound.
4. The zinc-based catalyst according to claim 3, characterized in that, the monobromine-substituted N-containing heterocyclic compound is 2-bromopyridine and 2-bromopyrrole; and the dibromine-substituted N-containing heterocyclic compound is 2,6-dibromopyridine and 2,5-dibromopyrrole.
5. The zinc-based catalyst according to claim 1, characterized in that, the mass percentage of the bromine-substituted nitrogen heterocyclic ligand in the catalyst is 20%-52%; and the mass percentage of the zinc acetate in the catalyst is 10%-20%.
6. A preparation method of the zinc-based catalyst with bromine-substituted nitrogen heterocyclic ligand according to any one of claims 1-5, characterized in that, the preparation method comprises the following steps: uniformly mixing the solvent, the bromine-substituted nitrogen heterocyclic ligand and the zinc acetate, adding the activated carbon carrier, performing impregnation treatment, and drying to obtain the zinc-based catalyst.
7. The preparation method according to claim 6, characterized in that, the impregnation treatment is volume impregnation or equal volume impregnation; and the drying temperature is 40-120°C, and the drying time is 5-24h.
8. Application of the zinc-based catalyst with bromine-substituted nitrogen heterocyclic ligand according to any one of claims 1-5 or the zinc-based catalyst prepared by the preparation method according to any one of claims 6-7 in acetylene acetylation reaction.
9. The application according to claim 8, characterized in that, the application is that acetylene and acetic acid are subjected to acetylene acetylation reaction under the action of the catalyst in an anaerobic environment at 120-300°C to generate product vinyl acetate, and the reaction equation is as follows, 10. The application according to claim 9, characterized in that, the molar ratio of acetylene to acetic acid is 1:1-5:
1. C2H2 + CH3COOH → H2C=CHOCOCH 3。 The space velocity of the acetylene reaction is 60 h -1 -600 h -1 ;