A catalyst for synthesizing acetonitrile by acetic acid ammoniation method and its preparation method
By using catalysts prepared by zinc, aluminum, hydrotalcite and other materials, the problem of low yield of synthesis of acetonitrile catalysts is solved, and efficient acetonitrile production and low-cost production process are achieved.
Patent Information
- Application Number
- CN202510422356.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2025-06-24
- Estimated Expiration
- 2045-04-07
AI Technical Summary
The current catalyst synthesis of acetonitrile by ammonization of the acetic acid method is not high, resulting in high production costs.
The catalyst consisting of zinc-aluminum hydrotalcite, γ-Al2O3, pore-generating agent and binder is used to synthesize zinc-aluminum hydrotalcite by co-precipitation of mixed salt solution and alkali liquid, and the catalyst is prepared by kneading, extrusion molding and calcining.
The acetic acid conversion rate and acetonitrile selectivity are improved, production costs are reduced, and the catalyst can be reused through the regeneration and calcination process.
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Abstract
Description
Technical Field
[0001] The present application relates to the technical field of catalyst preparation, and particularly relates to a catalyst for synthesizing acetonitrile by acetic acid ammoniation and a preparation method thereof. Background Art
[0002] Acetonitrile, also known as methyl cyanide, is an important intermediate in organic, pharmaceutical, and petrochemical syntheses. It can not only be used as the mobile phase of high-performance liquid chromatography but also as a solvent for hydrocarbon extraction and azeotropic distillation. In addition, acetonitrile is widely used as a solvent in the fields of medicine, pesticides, textiles, plastics, etc. Due to the special physical properties and excellent performance of acetonitrile, its demand as a solvent for high-performance liquid chromatography (HPLC) and semiconductor cleaning agents has been increasing year by year.
[0003] There are many production methods for acetonitrile. Currently, it is mainly produced as a by-product of the ammoxidation of propylene to acrylonitrile. However, the acetonitrile produced by this process contains impurities such as hydrocyanic acid, and the cost of its purification and subsequent target conversion is high. At the same time, due to the continuous decline in the demand for acrylonitrile, the first major market application of acrylonitrile, the by-product acetonitrile is in severe shortage. Therefore, it is urgent to research and develop a commercially convenient and low-cost production method for acetonitrile.
[0004] In the method of synthesizing acetonitrile by acetic acid ammoniation, first, acetic acid reacts with ammonia to form ammonium acetate, then dehydrates to form acetamide, and further dehydrates to form acetonitrile. This method can avoid the formation of hydrocyanic acid and is promising in reducing the operating cost of the separation and purification of the final product acetonitrile.
[0005] However, the yield of acetonitrile obtained by the acetic acid ammoniation synthesis process is not high; therefore, it is necessary to provide a suitable catalyst for synthesizing high-yield acetonitrile by acetic acid ammoniation. Summary of the Invention
[0006] In order to solve the above technical problems, the present application provides a catalyst for synthesizing acetonitrile by acetic acid ammoniation and a preparation method thereof.
[0007] The present application provides a catalyst for synthesizing acetonitrile by acetic acid ammoniation, which is prepared from the following components in parts by weight: 100 parts of zinc-aluminum hydrotalcite, 5 - 10 parts of γ-Al2O3, 1 - 3 parts of pore-forming agent, and 40 - 80 parts of binder;
[0008] The zinc-aluminum hydrotalcite is synthesized by a coprecipitation method using a mixed salt solution and an alkali solution;
[0009] The mixed salt solution is composed of the following components in concentrations: 0.1 - 0.4 mol / L soluble zinc salt, 0.6 - 0.9 mol / L soluble aluminum salt, and the solvent is water.
[0010] Preferably, the preparation method of the zinc-aluminum hydrotalcite specifically includes the following steps carried out in sequence:
[0011] Dissolve soluble zinc salt and soluble aluminum salt in deionized water respectively, mix them evenly to obtain a mixed salt solution;
[0012] Dissolve NaOH and Na2CO3 together in deionized water to obtain an alkali solution with a concentration of + 0.8 - 1.2 mol / L;
[0013] Under a constant temperature water bath at 30 - 80 °C, simultaneously drop the mixed salt solution and the alkali solution into the reactor, keep the pH value of the reaction solution between 9 - 10, stir and mix evenly, then crystallize at 30 - 80 °C for 3 - 12 h, wash, filter, and dry at 60 - 120 °C for 4 - 12 h to obtain the zinc-aluminum hydrotalcite;
[0014] Preferably, the soluble zinc salt is selected from one or more of zinc nitrate, zinc sulfate, and zinc chloride; the soluble aluminum salt is selected from one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride.
[0015] Preferably, in the mixed salt solution, the molar ratio of zinc ions to aluminum ions is 1:2 - 4; in the alkali solution, the molar ratio of NaOH to Na2CO3 is 1:3 - 5.
[0016] In a specific embodiment, in the mixed salt solution, the molar ratio of zinc ions to aluminum ions is 1:2, 1:3, or 1:4.
[0017] In a specific embodiment, in the alkali solution, the molar ratio of NaOH to Na2CO3 is 1:3, 1:4, or 1:5.
[0018] Through experimental analysis, it can be known that in this application, controlling the molar ratio of zinc ions to aluminum ions in the mixed salt solution to 1:2 - 4 and the molar ratio of NaOH to Na2CO3 in the alkali solution to 1:3 - 5 can further improve the acetic acid conversion rate and acetonitrile selectivity.
[0019] Preferably, during the dropping process, the constant temperature water bath temperature is 30 - 50 °C; the crystallization temperature is 50 - 70 °C.
[0020] Preferably, the pore-forming agent is selected from one or more of carbon powder, urea, sesbania powder, and carboxymethyl cellulose.
[0021] Preferably, the pore-forming agent is composed of a mixture of urea and sesbania powder with a weight ratio of 0.5 - 1.5:3 - 5.
[0022] In a specific embodiment, in the pore-forming agent, the weight ratio of urea to sesbania powder can be 0.5:3, 0.5:4, 0.5:5, 1:3, 1:4, 1:5, 1.5:3, 1.5:4, or 1.5:5.
[0023] Through experimental analysis, it is known that in this application, the pore-forming agent composed of urea and sesbania powder mixed in the above weight ratio is selected, which can further improve the acetic acid conversion rate and acetonitrile selectivity.
[0024] Preferably, the binder is selected from one or more of 4-8wt% aqueous nitric acid solution, pseudo-boehmite, silica sol, and aluminum sol.
[0025] In a second aspect, this application provides a preparation method of the catalyst for synthesizing acetonitrile by the above acetic acid ammoniation method, specifically including the following steps carried out in sequence:
[0026] Shaping: Weigh zinc-aluminum hydrotalcite, γ-Al2O3, binder, and pore-forming agent according to the weight parts of each raw material, put them into a kneader and knead for 1-3 h, then put them into an extrusion machine to extrude and form, and cut them into uniformly sized particles;
[0027] Subsequently, the shaped catalyst is dried and calcined to obtain the catalyst.
[0028] Preferably, the drying temperature is 80-120 °C, and the drying time is 4-12 h; the calcination temperature is 400-800 °C, and the calcination time is 3-6 h.
[0029] In summary, the technical solution of this application has the following effects:
[0030] The catalyst provided by this application is suitable for synthesizing acetonitrile by acetic acid ammoniation. In a fixed-bed reactor, using acetic acid and ammonia as raw materials, under the action of the catalyst, acetic acid is ammoniated to acetonitrile. This process has few reaction by-products, a simple separation process, relatively high acetic acid conversion rate and acetonitrile selectivity, and high product yield; it can avoid the generation of a large amount of waste water and waste gas, and has low energy consumption during the production process, thus having a relatively low cost.
[0031] At the same time, the method for preparing the catalyst in this application has a simple operation process; and the catalyst can remove the coke on the surface of the catalyst only by calcining again to realize the regeneration of the catalyst. Specific Embodiments
[0032] The following further describes this application in detail with reference to examples, comparative examples, and performance detection tests. These examples should not be construed as limiting the scope claimed by this application.
[0033] The carbon powder used in this application is purchased from Xilong Science Co., Ltd.; urea and sesbania powder are purchased from Yantai Far East Fine Chemical Co., Ltd.; carboxymethyl cellulose is purchased from Shanghai Macklin Biochemical Co., Ltd. Examples
[0034] Examples 1-3
[0035] Examples 1-3 respectively provide a catalyst for synthesizing acetonitrile by acetic acid ammoniation and a preparation method thereof.
[0036] The differences among the above examples are as follows: the dosages of each component in the catalyst are different, as specifically shown in Table 1.
[0037] The preparation method of the catalyst for synthesizing acetonitrile by acetic acid ammoniation in the above examples is specifically as follows.
[0038] (1) Preparation of zinc-aluminum hydrotalcite
[0039] Weigh 0.25 mol of Zn(NO3)2·6H2O and 0.75 mol of Al(NO3)3·9H2O respectively (the molar ratio of zinc ions to aluminum ions is 1:3), and dissolve them together in 1000 ml of deionized water to obtain a mixed salt solution with the sum of Zn 2+ and Al 3+ concentrations of 1 mol / L;
[0040] Weigh a mixture of 0.1 mol of NaOH and 0.4 mol of Na2CO3 (the molar ratio of NaOH to Na2CO3 is 1:4) and dissolve it in 900 ml of deionized water to obtain an alkali solution with a Na + concentration of 1 mol / L;
[0041] At a constant water bath temperature of 40 °C, simultaneously drop the mixed salt solution and the alkali solution into the beaker at a speed of 1 drop / second, and keep the pH of the solution between 9 and 10. After the dropping is completed, stir for 2 h; after the stirring ends, crystallize at 60 °C for 12 h. Filter the obtained reaction solution, wash it 3 times with deionized water until neutral, and dry the obtained precipitate at 100 °C for 6 h to obtain zinc-aluminum hydrotalcite.
[0042] (2) Preparation of the catalyst
[0043] According to Table 1, take the corresponding weights of zinc-aluminum hydrotalcite, γ-Al2O3, and pore-forming agent (composed of urea and sesbania powder with a weight ratio of 1:4) and put them into a kneader to mix evenly. Then add a binder of nitric acid aqueous solution with a concentration of 5 wt%, knead for 2 h, put it into an extrusion machine to extrude into a shape, and cut it into uniformly sized particles (diameter 3-6 mm); then dry at 120 °C for 12 h and calcine at 600 °C for 4 h to obtain the catalyst for synthesizing acetonitrile by acetic acid ammoniation.
[0044] Table 1 Dosages of each component in the catalysts of Examples 1-3 and Comparative Examples 1-2
[0045]
[0046] Examples 4-10
[0047] Examples 4-10 respectively provide a catalyst for synthesizing acetonitrile by acetic acid ammoniation and a preparation method thereof.
[0048] The differences between the above examples and Example 1 are specifically as follows: the preparation methods of zinc-aluminum hydrotalcite are different, as shown below.
[0049] In Example 4: The preparation method of the mixed salt solution is as follows: Weigh 0.1 mol of Zn(NO3)2·6H2O and 0.9 mol of Al(NO3)3·9H2O (the molar ratio of zinc ions to aluminum ions is 1:9) respectively, and dissolve them in 1000 ml of deionized water together to obtain a mixed salt solution with the sum of the concentrations of Zn 2+ and Al 3+ being 1 mol / L.
[0050] In Example 5: The preparation method of the mixed salt solution is as follows: Weigh 0.4 mol of Zn(NO3)2·6H2O and 0.6 mol of Al(NO3)3·9H2O (the molar ratio of zinc ions to aluminum ions is 1:1.5) respectively, and dissolve them in 1000 ml of deionized water together to obtain a mixed salt solution with the sum of the concentrations of Zn 2+ and Al 3+ being 1 mol / L.
[0051] In Example 6: The preparation method of the mixed salt solution is as follows: Weigh 0.2 mol of Zn(NO3)2·6H2O and 0.8 mol of Al(NO3)3·9H2O (the molar ratio of zinc ions to aluminum ions is 1:4) respectively, and dissolve them in 1000 ml of deionized water together to obtain a mixed salt solution with the sum of the concentrations of Zn 2+ and Al 3+ being 1 mol / L.
[0052] In Example 7: The preparation method of the mixed salt solution is as follows: Weigh 0.33 mol of Zn(NO3)2·6H2O and 0.67 mol of Al(NO3)3·9H2O (the molar ratio of zinc ions to aluminum ions is 1:2) respectively, and dissolve them in 1000 ml of deionized water together to obtain a mixed salt solution with the sum of the concentrations of Zn 2+ and Al 3+ being 1 mol / L.
[0053] In Example 8: The preparation method of the alkali solution is as follows: Weigh a mixture of 0.3 mol of NaOH and 0.3 mol of Na2CO3 (the molar ratio of NaOH to Na2CO3 is 1:1) and dissolve it in 900 ml of deionized water to obtain an alkali solution with the concentration of Na + being 1 mol / L.
[0054] In Example 9: At a constant water bath temperature of 40 °C, the mixed salt solution and the alkali solution were simultaneously dropped into a beaker at a rate of 1 drop per second, and the pH of the solution was maintained between 9 and 10. After the dropping was completed, the solution was stirred for 2 h; after the stirring ended, it was crystallized at 80 °C for 12 h. The obtained reaction solution was filtered, washed 3 times with deionized water until neutral, and the obtained precipitate was dried at 100 °C for 6 h to obtain zinc-aluminum hydrotalcite.
[0055] In Example 10: At a constant water bath temperature of 60 °C, the mixed salt solution and the alkali solution were simultaneously dropped into a beaker at a rate of 1 drop per second, and the pH of the solution was maintained between 9 and 10. After the dropping was completed, the solution was stirred for 2 h; after the stirring ended, it was crystallized at 60 °C for 12 h. The obtained reaction solution was filtered, washed 3 times with deionized water until neutral, and the obtained precipitate was dried at 100 °C for 6 h to obtain zinc-aluminum hydrotalcite.
[0056] In the above examples, all other process parameters were the same as those in Example 1.
[0057] Examples 11 - 14
[0058] Examples 11 - 14 respectively provided a catalyst for synthesizing acetonitrile by acetic acid ammoniation and a preparation method thereof.
[0059] The differences between the above examples and Example 1 were specifically as follows: The types of pore-forming agents were different, as shown below.
[0060] In Example 11: The pore-forming agent was composed of a mixture of carbon powder and sesbania powder with a weight ratio of 1:4.
[0061] In Example 12: The pore-forming agent was composed of a mixture of urea and sesbania powder with a weight ratio of 4:1.
[0062] In Example 13: The pore-forming agent was composed of a mixture of urea and sesbania powder with a weight ratio of 0.5:5.
[0063] In Example 14: The pore-forming agent was composed of a mixture of urea and sesbania powder with a weight ratio of 1.5:3.
[0064] In the above examples, all other process parameters were the same as those in Example 1. Comparative Examples
[0065] Comparative Examples 1 - 2
[0066] Comparative Examples 1 - 2 respectively provided a catalyst for synthesizing acetonitrile by acetic acid ammoniation and a preparation method thereof.
[0067] The differences between the above comparative examples and Example 1 were that: The dosages of each component in the catalyst were different, as shown in Table 1.
[0068] In the above comparative examples, all other process parameters were the same as those in Example 1.
[0069] Comparative Example 3-4
[0070] Comparative Example 3-4 respectively provided a catalyst for synthesizing acetonitrile by acetic acid ammoniation and a preparation method thereof.
[0071] The differences between the above comparative examples and Example 1 are as follows.
[0072] In Comparative Example 3: Magnesium-aluminum hydrotalcite was used instead of zinc-aluminum hydrotalcite. In the preparation method of magnesium-aluminum hydrotalcite, the preparation method of the mixed salt solution was as follows: 0.25 mol of Mg(NO3)2·6H2O and 0.75 mol of Al(NO3)3·9H2O were weighed respectively (the molar ratio of magnesium ions to aluminum ions was 1:3), and they were dissolved in 1000 ml of deionized water together to obtain a mixed salt solution with the sum of the concentrations of Mg 2+ and Al 3+ being 1 mol / L.
[0073] In Comparative Example 4: In the preparation method of zinc-aluminum hydrotalcite, the preparation method of the mixed salt solution was as follows: 0.75 mol of Zn(NO3)2·6H2O and 0.15 mol of Al(NO3)3·9H2O were weighed respectively (the molar ratio of zinc ions to aluminum ions was 3:1), and they were dissolved in 1000 ml of deionized water together to obtain a mixed salt solution with the sum of the concentrations of Zn 2+ and Al 3+ being 1 mol / L.
[0074] Other process parameters in the above comparative examples were the same as those in Example 1.
[0075] Performance detection test
[0076] Catalyst evaluation conditions: 50 ml of the catalyst prepared in the example and the comparative example was added to a fixed-bed tubular reactor. Acetic acid was fed into the top of the reactor by a feed pump and vaporized, and then mixed with ammonia and entered the fixed-bed reactor. The reaction temperature was 380 °C, the reaction pressure was 0.35 MPa, the molar ratio of acetic acid to ammonia was 3:5, and the residence time of the material in the reactor was 5 s. The reaction products were analyzed and determined by gas chromatography.
[0077] Catalyst evaluation test results: As shown in Table 2.
[0078] Table 2 Performance evaluation results of the catalysts in the example and the comparative examples
[0079]
[0080] Combined with Table 2, by comparing the detection results of the examples and the comparative examples, the present application uses zinc-aluminum hydrotalcite, γ-Al2O3, pore-forming agent, and binder as raw materials for preparing the catalyst, and uses this catalyst in the process of synthesizing acetonitrile by acetic acid ammoniation method, resulting in fewer reaction by-products, a simple product separation process, higher acetic acid conversion rate and acetonitrile selectivity, and high product yield; and it can avoid the generation of a large amount of waste water and waste gas, with lower energy consumption during the production process, and thus lower cost. At the same time, the method for preparing the catalyst in the present application has a simple operation process; and the catalyst can remove the coke on the surface of the catalyst only by roasting again to realize the regeneration of the catalyst.
[0081] In Comparative Examples 1-2, the dosages of the raw material components in the catalyst do not match. In Comparative Example 3, magnesium-aluminum hydrotalcite is used instead of zinc-aluminum hydrotalcite. In the preparation method of zinc-aluminum hydrotalcite in Comparative Example 4, the molar ratio of zinc ions to aluminum ions is 3:1. When this catalyst is used in the process of synthesizing acetonitrile by acetic acid ammoniation method, the acetic acid conversion rate and acetonitrile selectivity are relatively low.
[0082] By comparing the detection results of Examples 1, 4-10, it can be seen that in the preparation method of the catalyst in the present application, the molar ratio of zinc ions to aluminum ions in the mixed salt solution is controlled to be 1:2-4, and the molar ratio of NaOH to Na2CO3 in the alkali solution is controlled to be 1:3-5, which can further improve the acetic acid conversion rate and acetonitrile selectivity.
[0083] By comparing the detection results of Examples 1, 11-14, it can be seen that in the preparation method of the catalyst in the present application, choosing a pore-forming agent composed of a mixture of urea and sesbania powder with a weight ratio of 0.5-1.5:3-5 can further improve the acetic acid conversion rate and acetonitrile selectivity.
[0084] Although the present invention has been described in detail with general descriptions and specific embodiments above, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.
Claims
1. A catalyst for synthesizing acetonitrile by acetic acid ammoniation, characterized in that: It is prepared from the following components in parts by weight: 100 parts of zinc-aluminum hydrotalcite, 5-10 parts of γ-Al2O3, 1-3 parts of porogen, and 40-80 parts of binder; The zinc-aluminum hydrotalcite is synthesized by co-precipitation of mixed salt solution and alkali solution; The preparation method of the zinc-aluminum hydrotalcite specifically comprises the following steps in sequence: Dissolve a soluble zinc salt and a soluble aluminum salt in deionized water respectively, mix them evenly, and obtain a mixed salt solution; the mixed salt solution is composed of the following components in concentration: 0.1-0.4 mol / L soluble zinc salt, 0.6-0.9 mol / L soluble aluminum salt, the molar ratio of zinc ion to aluminum ion is 1:2-4, and the solvent is water; Dissolve NaOH and Na2CO3 in deionized water to obtain Na + An alkali solution with a concentration of 0.8-1.2 mol / L; in the alkali solution, the molar ratio of NaOH to Na2CO3 is 1:3-5; In a constant temperature water bath at 30-80°C, the mixed salt solution and the alkali solution are simultaneously added dropwise to the reactor, the pH value of the reaction solution is maintained between 9-10, and after stirring and mixing evenly, crystallization is carried out at 50-70°C for 3-12h, washing, filtering, and drying at 60-120°C for 4-12h to obtain the zinc-aluminum hydrotalcite; The porogen is composed of urea and sesbania powder mixed in a weight ratio of 0.5-1.5:3-5.
2. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 1, characterized in that: The soluble zinc salt is selected from one or more of zinc nitrate, zinc sulfate and zinc chloride; the soluble aluminum salt is selected from one or more of aluminum nitrate, aluminum sulfate and aluminum chloride.
3. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 1, characterized in that: The binder is selected from one or more of 4-8wt% nitric acid aqueous solution, pseudo-boehmite, silica sol, and alumina sol.
4. The method for preparing a catalyst for synthesizing acetonitrile by acetic acid ammoniation according to any one of claims 1 to 3, characterized in that: Specifically, the following steps are performed in sequence: Molding: according to the weight of each raw material, zinc-aluminum hydrotalcite, γ-Al2O3, binder and porogen are weighed respectively, put into a kneader and knead for 1-3 hours, then put into an extruder for extrusion molding, and cut into particles of uniform size; The shaped catalyst is then dried and calcined to obtain the catalyst.
5. The method for preparing a catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 4, characterized in that: The drying temperature is 80-120° C., and the drying time is 4-12 hours; the roasting temperature is 400-800° C., and the roasting time is 3-6 hours.
Citation Information
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