Catalyst for synthesis of 2, 6-dichlorobenzonitrile and preparation method thereof

Abstract

The invention discloses a catalyst for synthesis of 2, 6-dichlorobenzonitrile and a preparation method thereof, and belongs to the technical field of catalysts. The preparation method comprises the following steps: impregnating a gamma-Al2O3 carrier in an ethanol solution of tetrabutyl titanate, volatilizing, drying and calcining to obtain a TiO2-coated Al2O3 composite carrier; mixing and dissolving ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water and ethanol to obtain an active component precursor solution; and mixing and soaking the TiO2-coated Al2O3 composite carrier and the active component precursor solution, drying, and calcining to obtain the catalyst for synthesis of 2, 6-dichlorobenzonitrile. Through collaborative innovation of the composition, the structure and the preparation process, the catalyst which is excellent in comprehensive performance and particularly suitable for industrial synthesis of 2, 6-dichlorobenzonitrile is successfully provided, and the bottleneck problem existing in the prior art for a long time is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for the synthesis of 2,6-dichlorobenzonitrile and its preparation method. Background Technology

[0002] 2,6-Dichlorobenzonitrile is an important pesticide and pharmaceutical intermediate, and its efficient synthesis is crucial for the development of related fine chemical industries. Currently, the industrial synthesis of 2,6-dichlorobenzonitrile mainly employs the ammoxidation method of 2,6-dichlorotoluene, and the core of this route lies in the development of high-performance catalysts.

[0003] In existing technologies, catalysts used for this type of ammonia oxidation reaction mostly use transition metal oxides such as vanadium and chromium as active components and silica gel and alumina as supports. However, when these catalysts are applied to 2,6-dichlorotoluene, a molecule with significant steric hindrance, several technical problems still need to be solved: First, it is difficult to achieve both catalyst activity and selectivity simultaneously. Due to the steric hindrance effect of the two chlorine atoms adjacent to the methyl group, the adsorption and activation of reactant molecules at the catalyst's active sites become difficult, resulting in generally low conversion rates. Simultaneously, side reactions are prone to occur during the reaction, such as deep oxidation to produce carbon dioxide or carbon monoxide, or the formation of other chlorinated byproducts, leading to low selectivity for the target product. This not only wastes raw materials but also increases the cost and energy consumption of subsequent separation and purification.

[0004] Secondly, the catalyst suffers from insufficient stability and lifespan. During long-term ammonia oxidation reactions, the active components of traditional catalysts are prone to sintering and growth, or loss from the support surface, leading to a reduction in the number of active sites. Furthermore, carbon deposition on the catalyst surface during the reaction easily clogs pores and covers active sites, causing rapid catalyst deactivation. This necessitates frequent catalyst regeneration or replacement, impacting the continuity and economic efficiency of industrial production.

[0005] Finally, the mass transfer efficiency of the catalyst needs to be optimized. The molecules of 2,6-dichlorotoluene and its product 2,6-dichlorobenzonitrile are relatively large. If the catalyst support is only a single microporous or mesoporous structure, it will increase the diffusion resistance of reactants and products, limiting their ability to reach internal active sites, thus becoming the rate-determining step of the reaction and potentially exacerbating side reactions.

[0006] Therefore, there is an urgent need in the field to develop a novel catalyst that can simultaneously possess high activity, high selectivity, excellent stability, and efficient mass transfer capabilities to overcome the aforementioned deficiencies of existing technologies. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a catalyst for the synthesis of 2,6-dichlorobenzonitrile and its preparation method. Through synergistic innovation in composition, structure and preparation process, this invention successfully provides a catalyst with excellent comprehensive performance, which is particularly suitable for the industrial synthesis of 2,6-dichlorobenzonitrile, and effectively solves the bottleneck problem that has long existed in the prior art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a catalyst for the synthesis of 2,6-dichlorobenzonitrile, comprising the following steps: S1. The γ-Al2O3 support was impregnated in an ethanol solution of tetrabutyl titanate, and then volatilized, dried and calcined to obtain the TiO2@Al2O3 composite support; S2. An active component precursor solution is obtained by mixing and dissolving ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol. S3. The TiO2@Al2O3 composite support and the active component precursor solution were mixed, soaked, dried, and calcined to obtain a catalyst for the synthesis of 2,6-dichlorobenzonitrile.

[0009] Preferably, the ratio of γ-Al2O3 support to tetrabutyl titanate ethanol solution in S1 is 1g:2mL.

[0010] Preferably, the ethanol solution of tetrabutyl titanate in S1 is obtained by dissolving 10-20 g of tetrabutyl titanate in 200 mL of anhydrous ethanol.

[0011] Furthermore, in S1, the evaporation is carried out by slowly stirring in a 60°C water bath until the ethanol is completely evaporated.

[0012] Furthermore, the drying temperature in S1 is 100-120℃, and the drying time is 2-4 hours.

[0013] Preferably, the calcination temperature in S1 is 500-550℃ and the time is 2-4h.

[0014] Furthermore, the calcination heating rate is 2℃ / min.

[0015] Preferably, the mass ratio of ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol in S2 is 5.10:5.68:1.26:1.91:25:25.

[0016] Preferably, the mass ratio of the TiO2@Al2O3 composite carrier and the active component precursor solution in S3 is 1:1.

[0017] Preferably, the soaking time in S3 is 8-12 hours.

[0018] Furthermore, the drying temperature in S3 is 100-120℃, and the drying time is 2-4 hours.

[0019] Preferably, the calcination in step S3 is carried out under a nitrogen atmosphere, at a temperature of 500-800℃, and for a time of 4-6 hours.

[0020] Furthermore, the calcination heating rate is 5°C / min.

[0021] Secondly, the present invention provides a catalyst for the synthesis of 2,6-dichlorobenzonitrile, which is prepared by the above-described preparation method.

[0022] Preferably, the catalyst has a specific surface area of ​​100-120 m². 2 / g.

[0023] It contains at least the following beneficial technical effects: This invention achieves a synergistic enhancement of catalyst activity and selectivity by constructing a V-Cr-Mo-Ce multi-component active component and supporting it on a unique TiO2@Al2O3 structured composite support. In the ammonia oxidation of 2,6-dichlorotoluene, this catalyst achieves a conversion rate exceeding 98.5% and a selectivity exceeding 95.8% for 2,6-dichlorobenzonitrile. The strong interaction between the TiO2 coating layer and the active component effectively anchors the active centers to the support surface, significantly inhibiting sintering and loss of the active component. Furthermore, the excellent oxygen storage and anti-carbon deposition capabilities of the Ce component result in minimal performance degradation and a performance retention rate exceeding 99% during continuous operation for up to 1500 hours, demonstrating outstanding industrial application potential and economic benefits. This invention successfully constructs a multi-level pore system dominated by mesopores, supplemented by macropores, and containing a small number of micropores. This structure provides a huge specific surface area to expose abundant active sites. On the other hand, the macropores, acting as "high-speed channels," greatly alleviate the diffusion limitations of sterically hindered macromolecular reactants and products, ensuring the effective utilization of internal and external active sites. This is one of the key factors in achieving high conversion rates and high selectivity. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0030] Unless otherwise specified, all raw materials or instruments used in the following embodiments of the present invention are commercially available.

[0031] Material description: The γ-Al2O3 support is 30 mesh and spherical.

[0032] An ethanol solution of tetrabutyl titanate was obtained by dissolving 15g of tetrabutyl titanate in 200mL of anhydrous ethanol.

[0033] Example 1 S1. 100g of γ-Al2O3 support was impregnated in 200mL of tetrabutyl titanate ethanol solution, and the solution was slowly stirred and volatilized in a water bath at 60℃. Then, it was dried at 110℃ for 3h. The dried material was then placed in a muffle furnace and heated to 530℃ at a heating rate of 2℃ / min for 3h to obtain TiO2@Al2O3 composite support. S2. Ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol are mixed and dissolved in a mass ratio of 5.10g:5.68g:1.26g:1.91g:25g:25g to obtain an active component precursor solution; S3. The TiO2@Al2O3 composite support and the active component precursor solution prepared above are mixed and soaked for 10 h, then dried at 110 °C for 3 h, and then calcined at 700 °C for 5 h at a heating rate of 5 °C / min to obtain a catalyst for the synthesis of 2,6-dichlorobenzonitrile.

[0034] Example 2 S1. 100g of γ-Al2O3 support was impregnated in 200mL of tetrabutyl titanate ethanol solution, and slowly stirred and volatilized in a water bath at 60℃. Then it was dried at 100℃ for 2h. The dried material was then placed in a muffle furnace and heated to 500℃ at a heating rate of 2℃ / min for 2h to obtain TiO2@Al2O3 composite support. S2. Ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol are mixed and dissolved in a mass ratio of 5.10g:5.68g:1.26g:1.91g:25g:25g to obtain an active component precursor solution; S3. The TiO2@Al2O3 composite support and the active component precursor solution prepared above are mixed and soaked for 8 hours, then dried at 100℃ for 2 hours, and then calcined at 500℃ for 4 hours at a heating rate of 5℃ / min to obtain a catalyst for the synthesis of 2,6-dichlorobenzonitrile.

[0035] Example 3 S1. 100g of γ-Al2O3 support was impregnated in 200mL of tetrabutyl titanate ethanol solution, and slowly stirred and volatilized in a water bath at 60℃. Then, it was dried at 120℃ for 4h. The dried material was then placed in a muffle furnace and heated to 550℃ at a heating rate of 2℃ / min for 4h to obtain TiO2@Al2O3 composite support. S2. Ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol are mixed and dissolved in a mass ratio of 5.10g:5.68g:1.26g:1.91g:25g:25g to obtain an active component precursor solution; S3. The TiO2@Al2O3 composite support and the active component precursor solution prepared above were mixed and soaked for 12 h, then dried at 120 °C for 4 h, and then calcined at 800 °C for 6 h at a heating rate of 5 °C / min to obtain a catalyst for the synthesis of 2,6-dichlorobenzonitrile.

[0036] Comparative Example 1 S1. 100g of γ-Al2O3 support was impregnated in 200mL of tetrabutyl titanate ethanol solution, and the solution was slowly stirred and volatilized in a water bath at 60℃. Then, it was dried at 110℃ for 3h. The dried material was then placed in a muffle furnace and heated to 530℃ at a heating rate of 2℃ / min for 3h to obtain TiO2@Al2O3 composite support. S2. Ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol are mixed and dissolved in a mass ratio of 7.13g:2.34g:2.53g:3.79g:25g:25g to obtain an active component precursor solution; S3. The TiO2@Al2O3 composite support and the active component precursor solution prepared above are mixed and soaked for 10 h, then dried at 110 °C for 3 h, and then calcined at 700 °C for 5 h at a heating rate of 5 °C / min to obtain a catalyst for the synthesis of 2,6-dichlorobenzonitrile.

[0037] Experimental Example 1 The catalysts obtained in Examples 1-3 were characterized and tested, and the results are shown in Table 1.

[0038] Table 1. Characterization results of the physicochemical properties of the catalyst

[0039] Characterization results analysis: As shown in Table 1, the catalyst prepared in this invention possesses a high specific surface area (>100 m² / g) and a well-developed pore structure. The key innovation lies in its optimized hierarchical pore size distribution: the proportion of mesopores (2-50 nm) is... Approximately 80% of the surface area is macropores, serving as the primary reaction sites and providing a large specific surface area for the active sites, ensuring efficient mass transfer between reactants and products. Macropores (>50 nm) account for about 15%, acting as transport channels and significantly reducing the resistance to the diffusion of reactant molecules into the catalyst and product molecules outward, effectively solving the mass transfer bottleneck caused by the large steric hindrance of 2,6-dichlorobenzyltoluene molecules. A small number of micropores (<2 nm) further contribute to the specific surface area. Simultaneously, the catalyst exhibits excellent mechanical strength (>65 N / particle), far exceeding the ≥50 N / particle typically required for industrial applications. XRF results confirm the successful loading of the active component and its agreement with design values.

[0040] Experimental Example 2 1. Catalyst performance Evaluation method: 50 mL of catalyst (corresponding to samples in Examples 1-3) was packed into a fixed-bed reactor. The reactants were a mixture of 2,6-dichlorotoluene, liquid ammonia, and air. The reaction temperature was controlled at 380 °C, the pressure at atmospheric pressure, and the weight hourly space velocity (WHSV) of 2,6-dichlorotoluene was 0.8 h⁻¹. -1The reaction products were condensed and then quantitatively analyzed by gas chromatography (GC).

[0041] Calculation formula: Conversion rate (%) = (Moles of 2,6-dichlorotoluene in the reaction / Moles of 2,6-dichlorotoluene in the feed) × 100% Selectivity (%) = (moles of 2,6-dichlorobenzonitrile produced / moles of 2,6-dichlorotoluene reacted) × 100% 1. Initial Performance Evaluation After running continuously for 100 hours under the above standard reaction conditions, the performance data of each catalyst were recorded, and the results are shown in Table 2.

[0042] Table 2 Initial performance evaluation results of the catalyst

[0043] As can be seen from Table 2, the data clearly demonstrate that the catalysts prepared in Examples 1-3 of this invention significantly outperform Comparative Example 1 in both the conversion rate of 2,6-dichlorotoluene and the selectivity for 2,6-dichlorobenzonitrile. This fully demonstrates the inventive value of the synergistic design of TiO2@Al2O3 and V-Cr-Mo-Ce multi-component active components. The TiO2 layer enhances the dispersion and stability of the active components, while the introduction of Mo and Ce optimizes the redox performance and surface acidity of the catalyst. In particular, the unique hierarchical porous structure of the catalyst of this invention ensures the smooth diffusion of reactant and product molecules, which is one of the key factors in achieving a synergistic improvement in high conversion rate (>98.5%) and high selectivity (>95.8%).

[0044] 2. Catalyst lifetime evaluation The catalyst of Example 1 with the best performance was subjected to a life test of up to 1500 hours, and its performance was tested periodically. The results are shown in Table 3.

[0045] Table 3. Results of long-term stability test of catalyst in Example 1

[0046] As shown in Table 3, the catalyst of Example 1 exhibited extremely high stability during continuous operation for 1500 hours. The conversion rate of 2,6-dichlorotoluene slowly decreased from 99.2% to 98.6%, and the selectivity slowly decreased from 96.5% to 96.0%, while the performance retention rate remained above 99%, with minimal attenuation. This demonstrates that the TiO2@Al2O3 composite support structure of the catalyst effectively prevents the sintering and loss of active components. The introduction of Ce element enhances the catalyst's resistance to carbon deposition, while the robust hierarchical porous structure avoids pore failure caused by carbon deposition or physical blockage. The synergistic effect of these three factors endows the catalyst with excellent long-term operational stability, fully meeting the stringent requirements for catalyst lifespan in industrial production.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for the synthesis of 2,6-dichlorobenzonitrile, characterized in that, Includes the following steps: S1. The γ-Al2O3 support was impregnated in an ethanol solution of tetrabutyl titanate, and then volatilized, dried and calcined to obtain the TiO2@Al2O3 composite support; S2. An active component precursor solution is obtained by mixing and dissolving ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol. S3. The TiO2@Al2O3 composite support and the active component precursor solution were mixed, soaked, dried, and calcined to obtain a catalyst for the synthesis of 2,6-dichlorobenzonitrile.

2. The preparation method according to claim 1, characterized in that, The ratio of γ-Al2O3 support to tetrabutyl titanate ethanol solution in S1 is 1g:2mL.

3. The preparation method according to claim 2, characterized in that, The ethanol solution of tetrabutyl titanate in S1 is obtained by dissolving 10-20 g of tetrabutyl titanate in 200 mL of anhydrous ethanol.

4. The preparation method according to claim 1, characterized in that, The calcination temperature in S1 is 500-550℃, and the time is 2-4h.

5. The preparation method according to claim 1, characterized in that, The mass ratio of ammonium metavanadate, chromic anhydride, ammonium molybdate, cerium nitrate hexahydrate, water, and ethanol in S2 is 5.10:5.68:1.26:1.91:25:

25.

6. The preparation method according to claim 1, characterized in that, The mass ratio of the TiO2@Al2O3 composite carrier and the active component precursor solution in S3 is 1:

1.

7. The preparation method according to claim 1, characterized in that, The soaking time in S3 is 8-12 hours.

8. The preparation method according to claim 1, characterized in that, The calcination in S3 is carried out under a nitrogen atmosphere at a temperature of 500-800℃ for 4-6 hours.

9. A catalyst for the synthesis of 2,6-dichlorobenzonitrile, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The catalyst according to claim 9, characterized in that, The catalyst has a specific surface area of ​​100-120 m². 2 / g.

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