M / h-zsm-5 catalyst, 2-cyanopyridine and preparation method and application thereof

Abstract

The application provides an M / H-ZSM-5 catalyst, 2-cyanopyridine and a preparation method and application thereof, and the catalyst is prepared through the following steps: S1, a precursor containing a transition metal M is dissolved in water to obtain a metal solution; S2, an H-ZSM-5 molecular sieve carrier is mixed with the metal solution obtained in step S1; S3, the mixture obtained in step S2 is subjected to ultrasonic treatment and sealed and placed; S4, the product obtained in step S3 is dried, ground and optionally subjected to calcination treatment to obtain the M / H-ZSM-5 catalyst; the transition metal M is at least one selected from Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce and Pd. The above process is simple, the energy consumption is low, and the catalyst for synthesizing 2-cyanopyridine can be obtained.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to an M / H-ZSM-5 catalyst, 2-cyanopyridine, its preparation method, and its applications. Background Technology

[0002] 2-Cyanopyridine is a key dehydrating agent in the synthesis of green chemicals such as dimethyl carbonate (DMC). Since it absorbs water and transforms into 2-pyridinecarboxamide during the reaction, efficiently regenerating 2-cyanopyridine through dehydration with 2-pyridinecarboxamide is a core step in building a low-cost, sustainable DMC industrial chain.

[0003] Currently, the catalytic dehydration reaction of 2-pyridinecarboxamide faces two major technical bottlenecks: First, high-performance catalysts are expensive and rely on precious metals. Existing catalytic systems achieving high conversion rates primarily use precious metals such as palladium (Pd) as active centers. Precious metals are scarce, expensive, and easily lost during industrial applications, significantly increasing production costs. Although some studies have attempted to use inexpensive transition metals such as iron (Fe) and copper (Cu) as substitutes, these non-precious metal catalysts typically exhibit low activity, making it difficult to achieve the yields required for industrial applications. Second, constructing active sites for non-precious metal catalysts is challenging. Unlike precious metals, the dispersion state and coordination environment of non-precious metals (such as Fe) on molecular sieve supports are extremely sensitive to the preparation process. Non-precious metal catalysts prepared using traditional impregnation-heat treatment processes often suffer from agglomeration of active components or the formation of inactive crystalline phase structures (such as large-particle oxides), resulting in catalytic performance far inferior to precious metals, or even complete deactivation. How to construct highly active non-noble metal centers on molecular sieve supports such as H-ZSM-5 by controlling the preparation process, so that they can be comparable to noble metal catalysts, is a huge challenge currently facing this field. Summary of the Invention

[0004] This invention provides an M / H-ZSM-5 catalyst, 2-cyanopyridine, its preparation method, and its application, to provide a simple, energy-efficient catalyst for the synthesis of 2-cyanopyridine and its preparation method that facilitates the dispersion of active components.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing an M / H-ZSM-5 catalyst, the method comprising the following steps: S1, Dissolve the precursor containing transition metal M in water to obtain a metal solution; S2, mix the H-ZSM-5 molecular sieve support with the metal solution obtained in step S1; S3, subject the mixture obtained in step S2 to ultrasonic treatment, and then seal and let it stand; S4. The product obtained in step S3 is dried, ground, and optionally calcined to obtain the M / H-ZSM-5 catalyst. The transition metal M is selected from at least one of Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce, and Pd.

[0006] To achieve the above objectives, the present invention also provides the following technical solutions: An M / H-ZSM-5 catalyst prepared by the above method, wherein the catalyst is an H-ZSM-5 molecular sieve supported on a transition metal M, wherein the transition metal M is selected from at least one of Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce, and Pd.

[0007] To achieve the above objectives, the present invention also provides the following technical solutions: A method for synthesizing 2-cyanopyridine involves dehydrating the reactant 2-pyridinecarboxamide in an organic solvent under the presence of a catalyst obtained by the method described above or as described above, to obtain the 2-cyanopyridine.

[0008] To achieve the above objectives, the present invention also provides the following technical solutions: The catalyst obtained by the above method or the above catalyst is used as a regeneration dehydrating agent in the dimethyl carbonate synthesis process; The regenerating dehydrating agent is 2-cyanopyridine, and the application includes dehydrating 2-pyridine carboxamide, a byproduct generated in the dimethyl carbonate synthesis reaction, into 2-cyanopyridine under the action of the catalyst.

[0009] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. Reduced preparation costs and energy consumption; 2. Promote dispersion: Introduce ultrasonic-assisted impregnation, and use the cavitation effect of ultrasound to promote the uniform dispersion and penetration of metal precursors in the molecular sieve channels. Compared with traditional static impregnation, it helps to form more effective active site precursors. 3. Environmentally friendly: Water is used as a solvent, avoiding the use of organic solvents, which is in line with the principles of green chemistry. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other solutions can be obtained based on these drawings without creative effort.

[0011] Figure 1This is a comparison chart showing the catalytic performance of the catalysts obtained in Examples 1-10 and Comparative Example 1 for the synthesis reaction of 2-cyanopyridine. Detailed Implementation

[0012] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0013] Any specific numerical values ​​disclosed herein (including the endpoints of numerical ranges) are not limited to their exact values, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0014] The terminology used in this invention is for the purpose of describing specific exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” as used herein are intended to include the plural forms as well. The terms “comprising,” “including,” “containing,” and “having” are inclusive and thus describe the presence of said features, elements, compositions, steps, integers, operations, and / or components, but do not exclude the presence or inclusion of one or more other features, integers, steps, operations, elements, components, and / or sets thereof. Although the open-ended term “comprising” should be understood as a non-limiting term used to describe and claim the various embodiments described in this invention, in some aspects it may instead be understood as a more restrictive and limiting term, such as “consisting of” or “essentially composed of.” Thus, for any given embodiment describing a composition, material, component, element, feature, integer, operation, and / or process step, the invention also particularly includes embodiments consisting of or substantially consisting of such compositions, materials, components, elements, features, integers, operations, and / or process steps. In the case of “consisting of…”, the alternative embodiments exclude any additional compositions, materials, components, elements, features, integers, operations and / or process steps. In the case of “essentially composed of…”, any additional compositions, materials, components, elements, features, integers, operations and / or process steps that substantially affect the essential and novel characteristics are excluded from such embodiments. However, any compositions, materials, components, elements, features, integers, operations and / or process steps that do not substantially affect the essential and novel characteristics may be included in the embodiments.

[0015] Any method steps, processes, and operations described in this invention should not be construed as necessarily requiring them to be performed in the specific order discussed or shown, unless explicitly specified. It should also be understood that, unless otherwise stated, additional or alternative steps may be used.

[0016] In this invention, except where expressly stated, any matters or issues not mentioned are directly applicable to those known in the art without any modification. Furthermore, any embodiment described in this invention can be freely combined with one or more other embodiments described in this invention, and the resulting technical solutions or concepts are considered part of the original disclosure or original record of this invention, and should not be regarded as new content not disclosed or anticipated by this invention, unless those skilled in the art consider the combination to be clearly unreasonable.

[0017] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0018] First aspect The preparation process of catalysts used in the synthesis of 2-cyanopyridine in the prior art is complicated and energy-intensive, and conventional impregnation methods are difficult to achieve uniform dispersion of active components in molecular sieve channels.

[0019] In view of this, the present invention provides a method for preparing an M / H-ZSM-5 catalyst, comprising the following steps: S1, dissolving a precursor containing a transition metal M in water to obtain a metal solution; S2, mixing an H-ZSM-5 molecular sieve support with the metal solution obtained in step S1; S3, subjecting the mixture obtained in step S2 to ultrasonic treatment and sealing for standing; S4, drying and grinding the product obtained in step S3, and optionally calcining it to obtain the M / H-ZSM-5 catalyst; wherein the transition metal M is selected from at least one of Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce, and Pd. The present invention employs ultrasonic-assisted impregnation, utilizes water as a green solvent, and combines the flexible process of "optional calcination," simplifying the preparation process. The cavitation effect generated by ultrasonic treatment can effectively assist metal ions in overcoming diffusion resistance and entering the interior of the H-ZSM-5 pores, promoting high dispersion of the active components.

[0020] It is worth noting that in some embodiments of the present invention, in step S4, after drying and grinding the product obtained in step S3, the above-mentioned catalyst can be obtained without high-temperature calcination. This treatment method can provide process space for some special metals, such as iron (Fe), by retaining the highly active precursor species of the specific metal, and can avoid the problems of active site sintering or structural collapse that may be caused by traditional high-temperature calcination, thereby obtaining a heterogeneous catalyst with excellent performance.

[0021] It is understandable that the "water" in step S1 above can be any one of pure water, deionized water, or distilled water.

[0022] In some embodiments of the present invention, the transition metal M is Fe. Choosing Fe as the active metal center not only significantly reduces the raw material cost of the catalyst and breaks the dependence on noble metals, but also demonstrates experimentally that in the M / H-ZSM-5 system, Fe exhibits catalytic activity far exceeding that of other non-noble metals (Cu, Ni, Co, etc.), making it the optimal metal choice for this reaction system that combines low cost and high activity. Clearly, the above approach solves the problem of high cost of noble metal (such as Pd) catalysts and also addresses the insufficient activity of conventional non-noble metals (such as Cu, Ni, etc.) in dehydration reactions.

[0023] It should be noted that the above-mentioned catalyst containing transition metal M and supported by H-ZSM-5 molecular sieve participates in the synthesis reaction of 2-cyanopyridine as shown below: .

[0024] It should be noted that, as shown in the following examples, the catalyst prepared by the above-described method of this invention using iron and H-ZSM-5 molecular sieve as raw materials exhibits superior catalytic activity for the synthesis reaction of 2-cyanopyridine, making it a better choice for the dehydration of 2-pyridinecarboxamide to 2-cyanopyridine. Furthermore, iron is a relatively inexpensive raw material, allowing the use of inexpensive iron salts to replace the precious metals used in traditional technologies, thereby significantly reducing catalyst costs. Moreover, the catalyst obtained by this invention is heterogeneous, making it easy to separate and recover, which aligns with green chemistry principles.

[0025] In some embodiments of the present invention, in step S4, the product obtained in step S3 is not calcined after drying and grinding. It is worth noting that high-temperature calcination can lead to phase inversion or agglomeration of specific metal (especially Fe) active species, resulting in complete catalyst deactivation; simultaneously, high-temperature calcination consumes a huge amount of energy. For Fe-based catalysts, omitting the calcination step not only significantly saves energy and preparation time, but more importantly, it preserves the highly catalytically active iron-containing species (possibly hydroxylated iron ions), preventing their transformation into inactive iron oxide crystalline phases. Experiments show that the yield of the uncalcined Fe catalyst is significantly better than that of the calcined catalyst, turning "waste" into a valuable resource.

[0026] In some embodiments of the present invention, in step S1, the mass ratio of the precursor containing the transition metal M to water is 0.15:1 to 0.85:1.

[0027] In some embodiments of the present invention, in step S2, the loading amount of the precursor containing the transition metal M on the H-ZSM-5 molecular sieve support is 0.4–1.2 mmol / g. By precisely controlling the amount of precursor and water, the metal loading is ensured to be within the optimal range, maintaining sufficient catalytic active center density while preserving the pore unobstructedness of the molecular sieve, thus achieving a balance between atom economy and catalytic efficiency. Clearly, the above solution solves the problems of insufficient active sites due to excessively low loading of the active component, and pore blockage or metal agglomeration due to excessively high loading. Exemplarily, the loading amount can be any one of 0.5 mmol / g, 0.6 mmol / g, 0.7 mmol / g, 0.8 mmol / g, 0.9 mmol / g, 1.0 mmol / g, or 1.1 mmol / g, or a range consisting of any two of the above values, or any value within that range.

[0028] In some embodiments of the present invention, in step S2, the metal solution and the H-ZSM-5 molecular sieve support are mixed in equal volumes. It is worth noting that by employing the equal-volume impregnation method, the capillary force of the molecular sieve itself is used to completely draw the metal solution into the pores, ensuring a near 100% utilization rate of the metal components and facilitating the uniform distribution of the active components within the micropores of the support. Clearly, the above solution solves the problems of raw material waste and uneven distribution caused by the traditional excessive impregnation method.

[0029] In some embodiments of the present invention, the silica-to-alumina ratio of the H-ZSM-5 molecular sieve support is (10–60):1. Limiting the silica-to-alumina ratio to within the range of (10–60):1 controls the density and intensity of Brønsted acid sites on the support surface. A suitable acidic environment not only helps anchor metal ions but also generates a synergistic effect with the metal centers, promoting the amide dehydration reaction. Clearly, the above limitation solves the problem that excessively strong or weak acidity of the support is detrimental to synergistic catalysis or may trigger side reactions.

[0030] In some embodiments of the present invention, in step S3, the duration of ultrasonic treatment is 5–30 min, and the duration of settling is 4–18 h. The optimized ultrasonic duration (5–30 min) is sufficient to achieve dispersion without damaging the molecular sieve framework; combined with a suitable settling time (4–18 h), sufficient ion exchange and adsorption equilibrium are achieved between the metal ions and the support framework, further stabilizing the active centers. It is understood that insufficient ultrasonic treatment or settling time leads to uneven dispersion, while excessive time reduces production efficiency or damages the crystal structure.

[0031] In some embodiments of the present invention, in step S4, the drying temperature is 90–120°C, and the drying time is 4–24 hours. Mild drying conditions can smoothly remove moisture, "fixing" the active components on the carrier surface to form a solid precursor with a certain mechanical strength, laying the foundation for subsequent applications or processing. It is worth noting that incomplete solvent removal or excessively rapid drying can lead to component migration.

[0032] In some embodiments of the present invention, in step S4, if calcination is performed, the calcination temperature is 200–500°C, and the calcination time is greater than 0 and less than or equal to 6 hours. It is worth noting that this provides process flexibility for the preparation method. For metal components that must be calcined for activation, these mild calcination conditions are sufficient to decompose the precursor ligands and form a stable oxide active phase, ensuring the universality of the method. This is also suitable for other metals besides Fe that may require oxidation-state activity (such as Pd), or for cases where heat treatment is needed to enhance metal-support interactions.

[0033] It is worth noting that this invention, through systematic catalyst screening, has confirmed that among transition metals such as Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce, and Pd, the non-noble metal Fe is the metal center with the highest catalytic activity in the dehydration reaction of 2-pyridinecarboxamide. Its performance is significantly better than that of the noble metal Pd, which is traditionally considered to be potentially superior, thus breaking the path dependence of this field on noble metal catalysts.

[0034] Furthermore, the present invention employs an ultrasonic-assisted equal-volume impregnation method to promote the high dispersion of the metal active components on the molecular sieve support, forming more active sites, and improving the conversion rate by 5% compared to catalysts that have not undergone ultrasonic treatment.

[0035] It should be noted that acetonitrile solvent is not absolutely inert in the above reaction, and the reaction solvent has a certain impact on the catalytic effect.

[0036] Furthermore, this invention uses inexpensive iron salts to replace precious metals, significantly reducing catalyst costs; the catalyst is heterogeneous, making it easy to separate and recover, which aligns with green chemistry principles.

[0037] Second aspect This invention provides an M / H-ZSM-5 catalyst prepared by the method described in the first aspect. The catalyst is an H-ZSM-5 molecular sieve supported on a transition metal M, wherein the transition metal M is selected from at least one of Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce, and Pd. The catalyst provided by this invention is a heterogeneous solid catalyst with good structural stability. After the reaction, it is easily separated from the product by simple filtration, facilitating catalyst recovery and recycling, and meeting the requirements of green chemistry for catalyst engineering. Clearly, the above solution solves the problems of high preparation cost and difficulty in recycling existing catalysts (such as homogeneous catalysts).

[0038] In some embodiments of the present invention, the transition metal M is Fe. It should be noted that Fe-based catalysts are not only abundant and inexpensive raw materials, but also exhibit excellent dehydration performance after being prepared using the specific process of the present invention, making them high-performance, cost-effective products with great industrial application potential. Clearly, the above approach reduces the cost of catalyst raw materials and improves activity.

[0039] In some embodiments of the present invention, the catalyst is an uncalcined Fe / H-ZSM-5 catalyst. This catalyst with its specific structure retains specific iron species active sites crucial for the dehydration reaction, resulting in a significantly improved yield in the dehydration reaction of 2-pyridinecarboxamide compared to calcined catalysts. This is the core advantage of the present invention. Clearly, the above approach solves the problem of low or even non-active activity in traditional calcined Fe catalysts.

[0040] Third aspect Existing methods for synthesizing 2-cyanopyridine (such as ammonia oxidation) have harsh conditions and produce many byproducts, or existing dehydration processes rely on expensive catalysts.

[0041] In view of this, the present invention provides a method for synthesizing 2-cyanopyridine, wherein the reactant 2-pyridinecarboxamide is dehydrated in an organic solvent in the presence of a catalyst obtained by the method described in the first aspect or a catalyst as described in the second aspect, to obtain the 2-cyanopyridine. It is worth noting that this method utilizes an M / H-ZSM-5 (especially Fe-based) catalyst to achieve a one-step, highly efficient catalytic dehydration. This method has advantages such as high atom economy, water as the only byproduct, and relatively mild reaction conditions. Furthermore, the catalyst is easily separated, providing a clean and low-cost synthetic route.

[0042] In some embodiments of the present invention, the reaction is carried out under sealed conditions. It is understood that a sealed reaction prevents the evaporation and loss of the organic solvent at the reaction temperature, maintains the system pressure and reactant concentration, and simultaneously prevents moisture from the air from entering the system and inhibiting the forward dehydration reaction.

[0043] In some embodiments of the present invention, the reaction temperature is 80–120°C. This temperature range is sufficient to provide the activation energy required for the reaction, ensuring a high reaction rate; at the same time, it avoids carbonization, polymerization, or catalyst deactivation caused by excessively high temperatures, thus achieving an optimal solution between energy consumption and efficiency.

[0044] In some embodiments of the present invention, the reaction time is 2 to 8 hours. A reaction time of 2 to 8 hours is sufficient to achieve a high conversion rate, ensuring production efficiency and avoiding energy waste and byproduct accumulation that may result from prolonged reactions.

[0045] In some embodiments of the present invention, the metal M in the catalyst is Fe. Using an Fe catalyst in this method exhibits the highest catalytic active center efficiency, significantly improving the yield of the target product while reducing catalyst cost.

[0046] In some embodiments of the present invention, the organic solvent is acetonitrile. As an aprotic polar solvent, acetonitrile exhibits good solubility for the reactant 2-pyridinecarboxamide and is inherently stable, providing a favorable medium environment for the dehydration reaction. Experiments show that the reaction achieves optimal catalytic performance in acetonitrile solvent.

[0047] In some embodiments of the present invention, the selectivity of the 2-cyanopyridine obtained from the reaction is above 99%. This extremely high selectivity (>99% or even 100%) means that almost no byproducts are generated, greatly simplifying the post-processing and purification of the product, reducing the overall production cost, and improving product quality. The above solution solves the problems of "difficult product separation and purification, and high costs of subsequent processes" in the prior art.

[0048] Fourth aspect This invention provides the application of a catalyst obtained by the method described in the first aspect or a catalyst as described in the second aspect in the regeneration of a dehydrating agent in the dimethyl carbonate (DMC) synthesis process; wherein the regenerated dehydrating agent is 2-cyanopyridine, and the application includes dehydrating the byproduct 2-pyridinecarboxamide generated in the DMC synthesis reaction into 2-cyanopyridine under the action of the catalyst. It is worth noting that the catalyst provided by this invention can efficiently reduce the water-absorbing byproduct (2-pyridinecarboxamide) to the dehydrating agent (2-cyanopyridine), thereby achieving closed-loop regeneration of the dehydrating agent. This not only solves the dehydration problem in DMC synthesis, breaks the thermodynamic equilibrium limitation, and improves the DMC yield, but also reduces the operating cost of the entire DMC production process through a low-cost catalyst, demonstrating significant industrial application value.

[0049] Example Unless otherwise stated, the raw materials, equipment, devices, and instruments mentioned in the embodiments of this invention can all be obtained through general commercial channels.

[0050] The main experimental reagents used in the embodiments and comparative examples of this invention are shown in Table 1.

[0051] Table 1. Main experimental reagents used in the embodiments and comparative examples of this invention.

[0052] The main instruments and equipment used in the embodiments and comparative examples of this invention are shown in Table 2.

[0053] Table 2. Instruments and equipment used in the embodiments and comparative examples of the present invention.

[0054] Example 1 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (ferric nitrate nonahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0055] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0056] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0057] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is denoted as Fe / H-ZSM-5(U).

[0058] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Fe / H-ZSM-5(U) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions, with the reaction temperature set at 100 °C, the reaction time at 4 h, and the stirring rate at 800 rpm.

[0059] Quantitative analysis by gas chromatography (with methanol as internal standard) showed that the yield of 2-cyanopyridine obtained from the reaction was 33.4%, with a selectivity of 100%.

[0060] Example 2 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (copper nitrate trihydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0061] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0062] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0063] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is denoted as Cu / H-ZSM-5(U).

[0064] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Cu / H-ZSM-5(U) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 3.28%, with a selectivity of 100%.

[0065] Example 3 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (nickel nitrate hexahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0066] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0067] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0068] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is denoted as Ni / H-ZSM-5(U).

[0069] 2. Synthesis of 2-cyanopyridine: 0.2 g of the Ni / H-ZSM-5(U) catalyst prepared above, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine obtained was 1.56%, with a selectivity of 100%.

[0070] Example 4 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (cobalt nitrate hexahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0071] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0072] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0073] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is designated as Co / H-ZSM-5(U).

[0074] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Co / H-ZSM-5(U) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 0.91%, with a selectivity of 100%.

[0075] Example 5 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (zinc nitrate hexahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0076] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0077] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0078] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is designated as Zn / H-ZSM-5(U).

[0079] 2. Synthesis of 2-cyanopyridine: 0.2 g of the Zn / H-ZSM-5(U) catalyst prepared above, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (with methanol as an internal standard) showed that the yield of 2-cyanopyridine obtained was 0.82%, with a selectivity of 100%.

[0080] Example 6 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (magnesium nitrate hexahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0081] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0082] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0083] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is designated as Mg / H-ZSM-5(U).

[0084] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Mg / H-ZSM-5(U) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 2.31%, with a selectivity of 100%.

[0085] Example 7 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (chromium nitrate nonahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0086] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0087] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0088] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is designated as Cr / H-ZSM-5(U).

[0089] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Cr / H-ZSM-5(U) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 2.66%, with a selectivity of 100%.

[0090] Example 8 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (cerium nitrate hexahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0091] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0092] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0093] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is designated Ce / H-ZSM-5(U).

[0094] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Ce / H-ZSM-5(U) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 2.32%, with a selectivity of 100%.

[0095] Example 9 1. Preparation of catalysts: Step S1 (solution preparation): At 25°C, take 0.76 ml of 10 wt% palladium nitrate solution, add water to make up to 1 ml, and the metal solution will be obtained.

[0096] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0097] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0098] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is designated as Pd / H-ZSM-5(U).

[0099] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Pd / H-ZSM-5(U) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 5.97%, with a selectivity of 100%.

[0100] Comparative Example 1 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (ferric nitrate nonahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0101] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0102] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is ultrasonically treated in an ultrasonic instrument at 100W and 20kHz for 10 minutes; then the mixture is sealed and left to stand at room temperature for 12 hours.

[0103] Step S4 (Drying and Post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh and calcined at 300°C for 3 hours at a heating rate of 2°C / min to obtain a catalyst, which is designated as Fe / H-ZSM-5(R).

[0104] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Fe / H-ZSM-5(R) catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 0%. The calcined catalyst caused highly dispersed Fe agglomerates to aggregate into large particles, and decomposed the hydroxyl species on the catalyst, preventing the formation of (Fe-OH). + The active site is lost, resulting in a conversion rate of 0%.

[0105] Comparative Example 2 1. Preparation of catalysts: Step S1 (solution preparation): Weigh 0.8 mmol of the precursor containing transition metal M (ferric nitrate nonahydrate) at 25 °C, dissolve it in 1 mL of water, and stir evenly until completely dissolved to obtain a metal solution.

[0106] Step S2 (mixing): Add 1g of H-ZSM-5 molecular sieve support to the metal solution obtained in step S1 and mix thoroughly.

[0107] Step S3 (Ultrasound and Settling): The mixture obtained in step S2 is not subjected to ultrasonic treatment; the mixture is then sealed and left to stand at room temperature for 12 hours.

[0108] Step S4 (drying and post-treatment): The product obtained in step S3 is dried at 100°C for 4 hours to obtain a hard solid medium; it is then ground to 60 mesh without calcination to obtain a catalyst, which is designated as Fe / H-ZSM-5.

[0109] 2. Synthesis of 2-cyanopyridine: 0.2 g of the prepared Fe / H-ZSM-5 catalyst, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 27.5%, with a selectivity of 100%.

[0110] Comparative Example 3 Synthesis of 2-cyanopyridine: 0.2 g of the Fe / H-ZSM-5(U) catalyst prepared in Example 1, 0.249 g of the reactant 2-pyridinecarboxamide, and 15 mL of organic solvent (high-purity HPLC-grade acetonitrile) were added to a 25 mL high-pressure reactor (PTFE-lined). The reactor was sealed, and nitrogen gas was introduced to 1 MPa and purged three times to ensure a nitrogen atmosphere and atmospheric pressure. The reaction was carried out under sealed conditions at a temperature of 100 °C for 4 h and a stirring rate of 800 rpm. Quantitative analysis by gas chromatography (using methanol as an internal standard) showed that the yield of 2-cyanopyridine was 0%. Proton transfer is difficult in highly purified acetonitrile solutions, and proton transfer on the surfaces of reactants, intermediates, and catalysts is challenging. Analytical-grade acetonitrile contains trace amounts of water and impurities, which can promote proton transfer. The reaction is difficult to proceed in an absolutely anhydrous environment. An appropriate amount of water is necessary for the reaction to proceed.

[0111] The yield and selectivity data of the catalysts obtained in the above examples and comparative examples in the synthesis of 2-cyanopyridine are summarized in Table 3 below.

[0112] Table 3. Yields and selectivity of 2-cyanopyridine for the catalysts obtained in the various embodiments and comparative examples of this invention.

[0113] As shown in Table 3 and Examples 1-9, among the catalysts prepared from M / H-ZSM-5 molecular sieves, the Fe-based catalyst (Example 1) exhibits significantly superior performance. Its yield for 2-cyanopyridine is much higher than that of the noble metal Pd and other non-noble metals tested. The Fe-based catalyst Fe / H-ZSM-5(U) obtained in Example 1 achieves a 2-cyanopyridine yield as high as 33.4%, demonstrating that Fe possesses a significantly high active site for the synthesis reaction of 2-cyanopyridine. Comparative Examples 1 and 3 show that the (M-OH)+ active site of the catalyst is crucial to the 2-cyanopyridine synthesis reaction system, while the quality of the solvent also significantly affects the reaction results.

[0114] By comparing Example 1 and Comparative Example 3, it can be found that introducing an ultrasonic treatment step in the preparation process of the catalyst provided by the present invention can significantly improve the catalytic activity of the obtained catalyst in the subsequent synthesis of 2-cyanopyridine, increasing the yield of 2-cyanopyridine from 27.5% to 33.4%. This result indicates that ultrasonic treatment is crucial for achieving high dispersion of the metal active component on the molecular sieve support, thereby forming more active sites, and is an indispensable key step in the preparation of this highly efficient catalyst.

[0115] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims. Furthermore, specific examples have been used in the specification to illustrate the principles and implementation methods of the present invention. The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention, and the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing M / H-ZSM-5 catalyst, characterized in that, The method includes the following steps: S1, Dissolve the precursor containing transition metal M in water to obtain a metal solution; S2, mix the H-ZSM-5 molecular sieve support with the metal solution obtained in step S1; S3, subject the mixture obtained in step S2 to ultrasonic treatment, and then seal and let it stand; S4. The product obtained in step S3 is dried, ground, and optionally calcined to obtain the M / H-ZSM-5 catalyst. The transition metal M is selected from at least one of Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce, and Pd.

2. The method as described in claim 1, characterized in that, The transition metal M is Fe; And / or, in step S4, the product obtained in step S3 is not subjected to calcination after drying and grinding.

3. The method as described in claim 1, characterized in that, It has at least one of the following characteristics: In step S1, the mass ratio of the precursor containing transition metal M to water is 0.15:1 to 0.85:

1. In step S2, the loading amount of the precursor containing transition metal M on the H-ZSM-5 molecular sieve support is 0.4 to 1.2 mmol / g; In step S2, the metal solution and the H-ZSM-5 molecular sieve support are mixed in equal volumes; The silicon-to-aluminum ratio of the H-ZSM-5 molecular sieve support is (10-60):

1.

4. The method as described in claim 1, characterized in that, It has at least one of the following characteristics: In step S3, the duration of the ultrasonic treatment is 5 to 30 minutes, and the duration of the settling period is 4 to 18 hours. In step S4, the drying temperature is 90–120°C, and the drying time is 4–24 hours. In step S4, if a calcination process is performed, the calcination temperature is 200–500°C, and the calcination time is greater than 0 and less than or equal to 6 hours.

5. An M / H-ZSM-5 catalyst prepared by the method according to any one of claims 1 to 4, characterized in that, The catalyst is an H-ZSM-5 molecular sieve supported on a transition metal M, wherein the transition metal M is selected from at least one of Fe, Cu, Ni, Co, Zn, Mg, Cr, Ce, and Pd.

6. The catalyst as described in claim 5, characterized in that, The transition metal M is Fe; And / or, the catalyst is an uncalcined Fe / H-ZSM-5 catalyst.

7. A method for synthesizing 2-cyanopyridine, characterized in that, The reactant 2-pyridinecarboxamide is dehydrated in an organic solvent in the presence of a catalyst obtained by the method of any one of claims 1 to 4 or a catalyst as described in claims 5 or 6 to obtain the 2-cyanopyridine.

8. The method as described in claim 7, characterized in that, It has at least one of the following characteristics: The reaction was carried out under sealed conditions; The reaction temperature is 80–120℃; The reaction time is 2 to 8 hours.

9. The method as described in claim 7, characterized in that, The catalyst contains Fe as the metal M, the organic solvent is acetonitrile, and the selectivity of the 2-cyanopyridine obtained from the reaction is above 99%.

10. The application of the catalyst obtained by the method of any one of claims 1 to 4 or the catalyst of claim 5 or 6 in the dimethyl carbonate synthesis process as a regeneration dehydrating agent; in, The regenerating dehydrating agent is 2-cyanopyridine, and the application includes dehydrating 2-pyridine carboxamide, a byproduct generated in the dimethyl carbonate synthesis reaction, into 2-cyanopyridine under the action of the catalyst.

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