Catalyst for synthesizing acetonitrile by acetic acid ammoniation method and preparation method thereof

Abstract

The invention relates to the technical field of catalyst preparation, and particularly discloses a catalyst for synthesizing acetonitrile by an acetic acid ammoniation method and a preparation method of the catalyst. The catalyst disclosed by the invention is prepared from the following components in parts by weight: 100 parts of zinc-aluminum hydrotalcite, 5-10 parts of gamma-Al2O3, 1-3 parts of a pore-foaming agent and 40-80 parts of a binder, the zinc-aluminum hydrotalcite is synthesized by adopting a mixed salt solution and alkali liquor co-precipitation method; the mixed salt solution is prepared from the following components in concentration: soluble zinc salt with the concentration of 0.2 to 0.4 mol / L, soluble aluminum salt with the concentration of 0.6 to 0.8 mol / L and water as a solvent. The catalyst provided by the invention is suitable for synthesizing acetonitrile by an acetic acid ammoniation method, so that the acetic acid conversion rate and the acetonitrile selectivity are relatively high, and the product yield is high; generation of a large amount of wastewater and waste gas can be avoided, and energy consumption is low. The preparation method of the catalyst is simple in operation process; the regeneration of the catalyst is easy to realize.

Description

Technical Field

[0001] The present application relates to the technical field of catalyst preparation, and in particular to a catalyst for synthesizing acetonitrile by acetic acid ammoniation method and a preparation method thereof. Background Art

[0002] Acetonitrile, also known as methyl nitrile, is an important intermediate in organic, pharmaceutical and petrochemical synthesis. It can be used not only as a mobile phase for high-performance liquid chromatography, but also as a solvent for hydrocarbon extraction and azeotropic distillation. In addition, acetonitrile is also 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 high-performance liquid chromatography HPLC solvent and semiconductor cleaning agent is increasing year by year.

[0003] There are many methods for producing acetonitrile. At present, it is mainly produced as a by-product of acrylonitrile produced by the ammoniolysis of propylene. However, the acetonitrile produced by this process contains impurity hydrocyanic acid, and the cost required for its purification and subsequent target conversion is large. At the same time, due to the continuous decline in the demand for acrylic fiber, the first market for acrylonitrile, its by-product acetonitrile is in serious shortage. Therefore, it is urgent to study and develop a commercially convenient and low-cost acetonitrile production method.

[0004] The method for synthesizing acetonitrile by ammoniation of acetic acid is to first react acetic acid with ammonia to form ammonium acetate, which is then dehydrated to form acetamide, and then further dehydrated to form acetonitrile. This method can avoid the formation of hydrocyanic acid and is very promising in reducing the operating cost of separation and purification of the final product acetonitrile.

[0005] However, the acetonitrile yield obtained by the acetic acid ammoniation synthesis process is not high; therefore, it is necessary to provide a suitable catalyst for the acetic acid ammoniation method to synthesize high-yield acetonitrile. 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 method and a preparation method thereof.

[0007] The present application provides a catalyst for synthesizing acetonitrile by acetic acid ammoniation method, 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 porogen, and 40-80 parts of binder; The zinc-aluminum hydrotalcite is synthesized by co-precipitation of mixed salt solution and alkali solution; The mixed salt solution consists of components with the following concentrations: 0.1-0.4 mol / L soluble zinc salt, 0.6-0.9 mol / L soluble aluminum salt, and the solvent is water.

[0008] Preferably, the method for preparing the zinc-aluminum hydrotalcite specifically comprises sequentially performing the following steps: Dissolving a soluble zinc salt and a soluble aluminum salt in deionized water respectively, and mixing them evenly to obtain a mixed salt solution; Dissolve NaOH and Na2CO3 in deionized water to obtain Na + Alkali solution with a concentration of 0.8-1.2 mol / L; 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 30-80°C for 3-12h, washing, filtering, and drying at 60-120°C for 4-12h to obtain the zinc-aluminum hydrotalcite; 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.

[0009] 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.

[0010] 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.

[0011] In a specific embodiment, the molar ratio of NaOH to Na2CO3 in the alkali solution is 1:3, 1:4, or 1:5.

[0012] Through experimental analysis, it can be known that the present application controls the molar ratio of zinc ions to aluminum ions in the mixed salt solution to 1:2-4, and controls the molar ratio of NaOH to Na2CO3 in the alkali solution to 1:3-5, which can further improve the acetic acid conversion rate and acetonitrile selectivity.

[0013] Preferably, during the dropping process, the temperature of the constant temperature water bath is 30-50°C; and the temperature of the crystallization is 50-70°C.

[0014] Preferably, the porogen is selected from one or more of carbon powder, urea, sesbania powder, and hydroxymethyl cellulose.

[0015] Preferably, the porogen is composed of a mixture of urea and sesbania powder in a weight ratio of 0.5-1.5:3-5.

[0016] In a specific embodiment, in the porogen, 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, 1.5:5.

[0017] Through experimental analysis, it can be known that the present application selects a porogen composed of a mixture of urea and sesbania powder in the above weight ratio, which can further improve the acetic acid conversion rate and acetonitrile selectivity.

[0018] Preferably, the binder is selected from one or more of 4-8wt% nitric acid aqueous solution, pseudo-boehmite, silica sol, and alumina sol.

[0019] In a second aspect, the present application provides a method for preparing the catalyst for synthesizing acetonitrile by the above-mentioned acetic acid ammoniation method, which specifically comprises the following steps 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.

[0020] Preferably, 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.

[0021] In summary, the technical solution of this application has the following effects: The catalyst provided in the present application is suitable for synthesizing acetonitrile by the acetic acid ammoniation method. In a fixed bed reactor, acetic acid and ammonia are used as raw materials, and acetonitrile is ammoniation by acetic acid under the action of the catalyst. The process has few reaction by-products, a simple separation process, a high acetic acid conversion rate and acetonitrile selectivity, and a high product yield; it can avoid the generation of a large amount of wastewater and waste gas, and the energy consumption in the production process is low, so the cost is low.

[0022] At the same time, the method for preparing the catalyst of the present application has a simple operation process; and the catalyst only needs to be roasted again to remove the coke on the catalyst surface and achieve catalyst regeneration. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with examples, comparative examples and performance testing experiments. These examples should not be construed as limiting the scope of protection claimed in the present application.

[0024] The carbon powder used in this application was purchased from Xilong Science Co., Ltd.; urea and sesbania powder were purchased from Yantai Yuandong Fine Chemical Co., Ltd.; and hydroxymethyl cellulose was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. Example Examples 1-3

[0025] Examples 1-3 respectively provide a catalyst for synthesizing acetonitrile by ammoniation of acetic acid and a preparation method thereof.

[0026] The difference between the above embodiments is that the dosage of each component in the catalyst is different, as shown in Table 1.

[0027] The preparation method of the catalyst for synthesizing acetonitrile by acetic acid ammoniation method in the above embodiment is specifically as follows.

[0028] (1) Preparation of zinc-aluminum hydrotalcite Weigh 0.25 mol of Zn(NO3)2·6H2O and 0.75 mol of Al(NO3)3·9H2O (the molar ratio of zinc ion to aluminum ion is 1:3) respectively and dissolve them in 1000 ml of deionized water to obtain Zn 2+ and Al 3+ A mixed salt solution with a concentration of 1 mol / L; Weigh 0.1 mol of NaOH and 0.4 mol of Na2CO3 mixture (the molar ratio of NaOH to Na2CO3 is 1:4) and dissolve them in 900 ml of deionized water to obtain Na + Alkali solution with a concentration of 1 mol / L; In a constant temperature water bath at 40°C, the mixed salt solution and alkali solution are simultaneously added to the beaker at a rate of 1 drop / second, and the pH value of the solution is maintained between 9-10. After the addition is completed, it is stirred for 2 hours. After the stirring is completed, it is crystallized at 60°C for 12 hours. The obtained reaction solution is filtered and washed with deionized water for 3 times until it is neutral. The obtained precipitate is dried at 100°C for 6 hours to obtain zinc-aluminum hydrotalcite.

[0029] (2) Preparation of catalyst According to Table 1, corresponding weights of zinc-aluminum hydrotalcite, γ-Al2O3, and a porogen (composed of a mixture of urea and sesbania powder in a weight ratio of 1:4) were taken together in a kneader and mixed evenly, and then a 5wt% nitric acid aqueous solution binder was added, kneaded for 2 hours, put into an extruder for extrusion molding, and cut into particles of uniform size (diameter 3-6mm); then dried at 120°C for 12 hours, and calcined at 600°C for 4 hours to obtain a catalyst for synthesizing acetonitrile by acetic acid ammoniation method.

[0030] Table 1 Amount of each component in the catalyst in Examples 1-3 and Comparative Examples 1-2 Embodiment 4-10

[0031] Examples 4-10 respectively provide a catalyst for synthesizing acetonitrile by ammoniation of acetic acid and a preparation method thereof.

[0032] The difference between the above embodiment and embodiment 1 is that the preparation method of zinc-aluminum hydrotalcite is different, as shown below.

[0033] In Example 4, the preparation method of the mixed salt solution is: weigh 0.1 mol of Zn(NO3)2·6H2O and 0.9 mol of Al(NO3)3·9H2O (the molar ratio of zinc ion to aluminum ion is 1:9), dissolve them in 1000 ml of deionized water, and obtain Zn 2+ and Al 3+ A mixed salt solution with a concentration of 1 mol / L.

[0034] In Example 5, the mixed salt solution was prepared by weighing 0.4 mol of Zn(NO3)2·6H2O and 0.6 mol of Al(NO3)3·9H2O (the molar ratio of zinc ion to aluminum ion was 1:1.5) and dissolving them in 1000 ml of deionized water to obtain Zn 2+ and Al 3+ A mixed salt solution with a concentration of 1 mol / L.

[0035] In Example 6, the preparation method of the mixed salt solution is as follows: 0.2 mol of Zn(NO3)2·6H2O and 0.8 mol of Al(NO3)3·9H2O (the molar ratio of zinc ion to aluminum ion is 1:4) are weighed and dissolved in 1000 ml of deionized water to obtain Zn 2+ and Al 3+ A mixed salt solution with a concentration of 1 mol / L.

[0036] In Example 7, the mixed salt solution was prepared by weighing 0.33 mol of Zn(NO3)2·6H2O and 0.67 mol of Al(NO3)3·9H2O (the molar ratio of zinc ion to aluminum ion was 1:2) and dissolving them in 1000 ml of deionized water to obtain Zn 2+ and Al 3+ A mixed salt solution with a concentration of 1 mol / L.

[0037] In Example 8, the alkali solution was prepared by weighing 0.3 mol of NaOH and 0.3 mol of a mixture of Na2CO3 (the molar ratio of NaOH to Na2CO3 was 1:1) and dissolving them in 900 ml of deionized water to obtain Na + Alkali solution with a concentration of 1 mol / L.

[0038] In Example 9: In a constant temperature water bath at 40°C, the mixed salt solution and the alkali solution are simultaneously added dropwise to a beaker at a rate of 1 drop / second, and the pH value of the solution is maintained between 9 and 10. After the addition is completed, the solution is stirred for 2 hours. After the stirring is completed, the solution is crystallized at 80°C for 12 hours, the reaction solution is filtered, washed with deionized water three times until it is neutral, and the precipitate is dried at 100°C for 6 hours to obtain zinc-aluminum hydrotalcite.

[0039] In Example 10: In a constant temperature water bath at 60°C, the mixed salt solution and the alkali solution are simultaneously added dropwise to a beaker at a rate of 1 drop / second, and the pH value of the solution is maintained between 9 and 10. After the addition is completed, the solution is stirred for 2 hours. After the stirring is completed, the solution is crystallized at 60°C for 12 hours, the reaction solution is filtered, washed with deionized water three times until it is neutral, and the precipitate is dried at 100°C for 6 hours to obtain zinc-aluminum hydrotalcite.

[0040] The other process parameters in the above embodiment are the same as those in embodiment 1. Examples 11-14

[0041] Examples 11-14 respectively provide a catalyst for synthesizing acetonitrile by the acetic acid ammoniation process and a preparation method thereof.

[0042] The difference between the above embodiment and embodiment 1 is that the types of porogens are different, as shown below.

[0043] In Example 11: the porogen is composed of a mixture of carbon powder and sesbania powder in a weight ratio of 1:4.

[0044] In Example 12: the porogen is composed of a mixture of urea and sesbania powder in a weight ratio of 4:1.

[0045] In Example 13: the porogen is composed of a mixture of urea and sesbania powder in a weight ratio of 0.5:5.

[0046] In Example 14: the porogen is composed of a mixture of urea and sesbania powder in a weight ratio of 1.5:3.

[0047] The other process parameters in the above embodiment are the same as those in embodiment 1. Comparative Example Comparative Example 1-2

[0048] Comparative Examples 1-2 respectively provide a catalyst for synthesizing acetonitrile by the acetic acid ammoniation method and a preparation method thereof.

[0049] The difference between the comparative example and Example 1 is that the amounts of the components in the catalyst are different, as shown in Table 1.

[0050] The other process parameters in the above comparative example are the same as those in Example 1. Comparative Examples 3-4

[0051] Comparative Examples 3-4 respectively provide a catalyst for synthesizing acetonitrile by the acetic acid ammoniation method and a preparation method thereof.

[0052] The difference between the above comparative example and Example 1 is as follows.

[0053] 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 (the molar ratio of magnesium ion to aluminum ion was 1:3) were weighed respectively, and dissolved in 1000 ml of deionized water to obtain Mg(NO3)2·6H2O. 2+ and Al 3+ A mixed salt solution with a concentration of 1 mol / L.

[0054] In comparative example 4: In the preparation method of zinc-aluminum hydrotalcite, the preparation method of the mixed salt solution is: weigh 0.75 mol of Zn(NO3)2·6H2O and 0.15 mol of Al(NO3)3·9H2O (the molar ratio of zinc ion to aluminum ion is 3:1), dissolve them in 1000 ml of deionized water, and obtain Zn 2+ and Al 3+ A mixed salt solution with a concentration of 1 mol / L.

[0055] The other process parameters in the above comparative example are the same as those in Example 1. Performance testing

[0056] Catalyst evaluation conditions: 50 ml of the catalyst prepared in the examples and comparative examples 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 product was determined by gas chromatography.

[0057] Catalyst evaluation test results: as shown in Table 2.

[0058] Table 2 Performance evaluation results of catalysts in Examples and Comparative Examples

[0059] Combined with Table 2, by comparing the test results of the embodiment and the comparative example, the present application uses zinc-aluminum hydrotalcite, γ-Al2O3, porogen, and binder as raw materials for preparing the catalyst, and uses the catalyst in the process of synthesizing acetonitrile by acetic acid ammoniation, so that there are few reaction by-products, the product separation process is simple, the acetic acid conversion rate and acetonitrile selectivity are high, and the product yield is high; and the generation of a large amount of waste water and waste gas can be avoided, the energy consumption in the production process is low, and thus the cost is low. At the same time, the method for preparing the catalyst in the present application has a simple operation process; and the catalyst only needs to be roasted again to remove the coke on the surface of the catalyst to achieve the regeneration of the catalyst.

[0060] The amounts of the raw material components in the catalysts in Comparative Examples 1-2 are not matched, magnesium aluminum hydrotalcite is used instead of zinc aluminum hydrotalcite in Comparative Example 3, and in the preparation method of zinc aluminum hydrotalcite in Comparative Example 4, the molar ratio of zinc ion to aluminum ion is 3:1. When the catalyst is used in the process of synthesizing acetonitrile by acetic acid ammoniation method, the acetic acid conversion rate and acetonitrile selectivity are low.

[0061] By comparing the test results of Examples 1 and 4-10, it can be seen that in the catalyst preparation method of the present application, the molar ratio of zinc ions to aluminum ions in the mixed salt solution is controlled to 1:2-4, and the molar ratio of NaOH to Na2CO3 in the alkali solution is controlled to 1:3-5, which can further improve the acetic acid conversion rate and acetonitrile selectivity.

[0062] By comparing the test results of Examples 1 and 11-14, it can be seen that in the catalyst preparation method of the present application, the pore-forming agent is selected by mixing urea and sesbania powder in a weight ratio of 0.5-1.5:3-5, which can further improve the acetic acid conversion rate and acetonitrile selectivity.

[0063] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed 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 mixed salt solution consists of components with the following concentrations: 0.1-0.4 mol / L soluble zinc salt, 0.6-0.9 mol / L soluble aluminum salt, and the solvent is water.

2. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 1, characterized in that: The preparation method of the zinc-aluminum hydrotalcite specifically comprises the following steps in sequence: Dissolving a soluble zinc salt and a soluble aluminum salt in deionized water respectively, and mixing them evenly to obtain a mixed salt solution; Dissolve NaOH and Na2CO3 in deionized water to obtain Na + Alkali solution with a concentration of 0.8-1.2 mol / L; At a constant temperature water bath of 30-80° C., the mixed salt solution and the alkali solution are simultaneously added dropwise into the reactor, the pH value of the reaction solution is maintained between 9-10, and after stirring and mixing evenly, the mixture is crystallized at 30-80° C. for 3-12 hours, washed, filtered, and dried at 60-120° C. for 4-12 hours to obtain the zinc-aluminum hydrotalcite.

3. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 2, 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.

4. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 2, characterized in that: 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.

5. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 2, characterized in that: During the dropping process, the temperature of the constant temperature water bath is 30-50°C; the temperature of the crystallization is 50-70°C.

6. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 1, characterized in that: The porogen is selected from one or more of carbon powder, urea, sesbania powder and hydroxymethyl cellulose.

7. The catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 6, characterized in that: The porogen is composed of urea and sesbania powder mixed in a weight ratio of 0.5-1.5:3-5.

8. 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.

9. The method for preparing a catalyst for synthesizing acetonitrile by acetic acid ammoniation according to any one of claims 1 to 8, 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.

10. The method for preparing a catalyst for synthesizing acetonitrile by acetic acid ammoniation according to claim 9, 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.

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