A catalyst for preparing 3-cyanopyridine and a method for preparing the same

Abstract

The application belongs to the technical field of catalysts, and provides a catalyst for preparing 3-cyanopyridine and a preparation method thereof.The method comprises the following steps: S1, vanadium pentoxide is added into water, and oxalic acid is added, so that an active solution is obtained after dissolution; S2, modified titanium dioxide is added into the active solution, and after being soaked for 23-25 hours, the active solution is stirred and evaporated to dryness to obtain a loaded material; the mass of the vanadium pentoxide is 6-8% of the mass of the modified titanium dioxide; S3, the loaded material is heated to 480-510 DEG C, and is calcined for 4 hours, so that the catalyst is obtained; the modified titanium dioxide is prepared by double loading modification of titanium dioxide by tungsten and cerium; on the premise that the titanium dioxide is modified by double loading of tungsten and cerium, the final calcination temperature of the catalyst can be increased to 480-510 DEG C, the dispersibility of the active component is optimized in the temperature range, and the problem of deterioration of the support crystal phase at high temperature is avoided, so that the catalytic activity of the catalyst is further improved.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a catalyst for preparing 3-cyanopyridine and its preparation method. Background Technology

[0002] 3-Cyanopyridine, also known as nicotinic nitrile, has the molecular formula C6H4N2 and is a white crystalline solid. It sublimes and is soluble in ethanol, diethyl ether, chloroform, benzene, and petroleum ether, and slightly soluble in water. Its main uses are as an intermediate in pharmaceuticals, food additives, feed additives, and pesticides. 3-Cyanopyridine can be produced from 3-methylpyridine via ammoxidation. The key technology in this process lies in the catalyst; therefore, research into developing catalysts with high conversion, high selectivity, and high yield is of great significance.

[0003] A Chinese invention patent application with publication number CN101433836A discloses a catalyst for the production of 3-cyanopyridine, its preparation method, and its application. The catalyst is supported by anatase TiO2, the active component is V2O5, and the promoter is one or more transition metal oxides or alkali metal oxides. The steps for preparing the catalyst are as follows: weigh the precursors of the support, active component, and promoter according to the ratio, mix the support, active component, and promoter in an oxalic acid solution, control the pH value of the mixture, evaporate the mixture to obtain a solid powder, and calcine the solid powder to obtain the catalyst.

[0004] Chinese invention patent application CN118179481A discloses a 3-cyanopyridine catalyst and its preparation method. The catalyst includes a support and an active component. The support comprises one or more of alumina, silica, titanium dioxide, and guar gum powder. The active component is vanadium pentoxide and antimony trioxide. The preparation steps include: preparing the support; distributing the active component into a solution, then adding an additive and stirring to obtain an impregnation solution; adding the support to the impregnation solution, rotary evaporating and drying, and then calcining at a third preset temperature to obtain the catalyst.

[0005] In the preparation of the aforementioned vanadium-based catalysts, calcination is required to ultimately obtain the catalyst. Increasing the calcination temperature promotes highly dispersed, uniformly distributed, and tightly bound active components, thus enhancing catalytic activity. However, excessively high calcination temperatures cause partial agglomeration of the active components and the transformation of some TiO2 support into rutile TiO2, leading to a decrease in catalytic activity. Summary of the Invention

[0006] To address the problems existing in the background art, the present invention provides a catalyst for preparing 3-cyanopyridine and its preparation method. Under the premise of titanium dioxide being modified by tungsten and cerium dual loading, the calcination temperature of the catalyst is increased to 480-510℃. In this temperature range, the dispersion of the active component is optimized, while avoiding the problem of high-temperature crystal phase deterioration, thereby further improving the catalytic activity of the catalyst.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a catalyst for preparing 3-cyanopyridine, comprising the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution. S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 23-25 ​​hours, stir and evaporate to dryness to obtain the loaded material; the mass of the vanadium pentoxide is 6-8% of the mass of the modified titanium dioxide; S3. Place the loaded material obtained in S2 into a muffle furnace, heat it to 480-510℃, and calcine it for 4 hours to obtain the catalyst used to prepare 3-cyanopyridine. The modified titanium dioxide is prepared by modifying titanium dioxide with tungsten and cerium dual loading.

[0008] Furthermore, the preparation method of the modified titanium dioxide is as follows: A1. Dissolve ammonium metatungstate and cerium nitrate in deionized water to obtain a mixed salt solution; A2. After impregnating titanium dioxide with the mixed salt solution obtained in A1 for 11-13 hours, dry and pre-calcine to obtain the modified titanium dioxide.

[0009] Furthermore, in the mixed salt solution, the mass fraction of ammonium metatungstate is 5±0.1%, and the mass fraction of cerium nitrate is 4±0.1%.

[0010] Furthermore, the specific surface area of ​​the titanium dioxide is 110 m². 2 / g, pore volume is 0.34mL / g.

[0011] Furthermore, in A2, the drying temperature is 110±5℃, and the drying time is 9-11h.

[0012] Furthermore, in A2, the pre-firing temperature is 400-420℃, and the pre-firing time is 2.5-3h.

[0013] Furthermore, in S1, the molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0014] Furthermore, the mass of the vanadium pentoxide is 7% of the mass of the modified titanium dioxide.

[0015] Furthermore, in S3, the heating rate is 10-12℃ / min.

[0016] In a second aspect, the present invention provides a catalyst for preparing 3-cyanopyridine, which is prepared by the above-described preparation method.

[0017] This application has the following beneficial effects: In the preparation of the vanadium-based catalyst of this invention, ammonium metatungstate and cerium nitrate are simultaneously introduced to modify the titanium dioxide support. Tungsten species are highly dispersed on the surface of the TiO2 support, forming WO-Ti interfacial bonds, which inhibits the transformation of the anatase phase to the rutile phase at high temperatures (500℃) and reduces the deterioration of the support crystal structure. Tungsten oxide acts as acidic sites, which can moderately weaken the lattice oxygen activity of vanadium, inhibit deep oxidation of intermediate products, and improve selectivity. It can also increase the specific surface area of ​​the support, avoid high-temperature agglomeration of V2O5, and improve the conversion rate, thus achieving a higher yield. Cerium is used to construct Ce. 3+ / Ce 4+ The redox pair replenishes the oxygen supply to the catalyst surface lattice, accelerating the rate-limiting steps (methyl dehydrogenation and oxidation) and improving the conversion rate. It also promotes the activation of gaseous NH3 into surface -NH2 / ·NH2 through the synergistic effect of the VO-Ce interface, accelerating the cyanation reaction and improving selectivity, thereby increasing the yield.

[0018] W controls oxygen to prevent deep oxidation, stabilizes the crystal structure, and adjusts acidic sites; Ce replenishes lattice oxygen, activates ammonia, and enhances the rate-limiting step of dehydrogenation. Thus, slow hydrogen dehydrogenation is accelerated by Ce, while rapid but easily oxidized cyanide is suppressed by W. The two work synergistically to improve the catalyst's catalytic activity (final yield). Furthermore, the degree of lattice distortion is higher after dual-loading modification, doubly blocking the transformation of anatase to rutile; the dispersion of the vanadium active component is much higher than in single-modified samples; and the applicable calcination temperature threshold of the catalyst is raised. Attached Figure Description

[0019] Figure 1 This is a comparative trend chart showing the conversion and yield test data of the catalyst samples prepared in Examples 1-3 and Comparative Examples 1-5 of the present invention in the preparation of 3-cyanopyridine. Detailed Implementation

[0020] The present application will be further described in detail below with reference to the embodiments.

[0021] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0022] Example 1: (1) Preparation of modified titanium dioxide, the preparation method is as follows: A1. Dissolve ammonium metatungstate and cerium nitrate in deionized water to obtain a mixed salt solution.

[0023] In this mixed salt solution, the mass fraction of ammonium metatungstate is 5%, and the mass fraction of cerium nitrate is 4%. That is, based on the total mass of the mixed salt solution, ammonium metatungstate accounts for 5 wt%, and cerium nitrate accounts for 4 wt%.

[0024] A2. After impregnating titanium dioxide with the mixed salt solution obtained in A1 for 12 hours, it is first dried at 110℃ for 10 hours, and then pre-calcined at 410℃ for 2.8 hours to obtain modified titanium dioxide.

[0025] Among them, the specific surface area of ​​titanium dioxide is 110 m². 2 / g, pore volume 0.34mL / g, purity ≥99%, purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0026] Ammonium metatungstate was purchased from Suzhou Kangshuo Chemical Co., Ltd. Cerium nitrate was purchased from Nantong Zhonghe Chemical New Materials Co., Ltd.

[0027] (2) A method for preparing a catalyst for preparing 3-cyanopyridine, comprising the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0028] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0029] S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0030] The mass of vanadium pentoxide is 7% of the mass of modified titanium dioxide.

[0031] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 500°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0032] Example 2: The difference between this example and Example 1 is that the calcination temperature in the preparation of the catalyst used to prepare 3-cyanopyridine is 480℃.

[0033] Specifically, a method for preparing a catalyst for preparing 3-cyanopyridine includes the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0034] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0035] S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0036] The mass of vanadium pentoxide is 7% of the mass of modified titanium dioxide.

[0037] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 480°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0038] Example 3: The difference between this example and Example 1 is that the calcination temperature in the preparation of the catalyst used to prepare 3-cyanopyridine is 510°C.

[0039] Specifically, a method for preparing a catalyst for preparing 3-cyanopyridine includes the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0040] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0041] S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0042] The mass of vanadium pentoxide is 7% of the mass of modified titanium dioxide.

[0043] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 510°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0044] Comparative Example 1: The difference between this comparative example and Example 1 is that the modified titanium dioxide is replaced with titanium dioxide; and the calcination temperature in the preparation of the catalyst used to prepare 3-cyanopyridine is 450°C.

[0045] Specifically, a method for preparing a catalyst for preparing 3-cyanopyridine includes the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0046] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0047] S2. Add titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0048] The mass of vanadium pentoxide is 7% of the mass of titanium dioxide.

[0049] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 450°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0050] Comparative Example 2: The difference between this comparative example and Example 1 is that the modified titanium dioxide is replaced with titanium dioxide.

[0051] Specifically, a method for preparing a catalyst for preparing 3-cyanopyridine includes the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0052] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0053] S2. Add titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0054] The mass of vanadium pentoxide is 7% of the mass of titanium dioxide.

[0055] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 500°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0056] Comparative Example 3: The difference between this comparative example and Example 1 is that cerium nitrate is not added in the preparation of the modified titanium dioxide.

[0057] Specifically, (1) the modified titanium dioxide is prepared by the following method: A1. Dissolve ammonium metatungstate in deionized water to obtain a mixed salt solution.

[0058] The mass fraction of ammonium metatungstate in this mixed salt solution is 5%.

[0059] A2. After impregnating titanium dioxide with the mixed salt solution obtained in A1 for 12 hours, it is first dried at 110℃ for 10 hours, and then pre-calcined at 410℃ for 2.8 hours to obtain modified titanium dioxide.

[0060] (2) A method for preparing a catalyst for preparing 3-cyanopyridine, comprising the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0061] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0062] S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0063] The mass of vanadium pentoxide is 7% of the mass of modified titanium dioxide.

[0064] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 500°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0065] Comparative Example 4: The difference between this comparative example and Example 1 is that ammonium metatungstate is not added in the preparation of the modified titanium dioxide.

[0066] Specifically, (1) the modified titanium dioxide is prepared by the following method: A1. Dissolve cerium nitrate in deionized water to obtain a mixed salt solution.

[0067] The mass fraction of cerium nitrate in this mixed salt solution is 4%.

[0068] A2. After impregnating titanium dioxide with the mixed salt solution obtained in A1 for 12 hours, it is first dried at 110℃ for 10 hours, and then pre-calcined at 410℃ for 2.8 hours to obtain modified titanium dioxide.

[0069] (2) A method for preparing a catalyst for preparing 3-cyanopyridine, comprising the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0070] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0071] S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0072] The mass of vanadium pentoxide is 7% of the mass of modified titanium dioxide.

[0073] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 500°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0074] Comparative Example 5: The difference between this comparative example and Example 1 is that the calcination temperature in the preparation of the catalyst used to prepare 3-cyanopyridine is 450°C.

[0075] Specifically, a method for preparing a catalyst for preparing 3-cyanopyridine includes the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution.

[0076] The molar ratio of vanadium pentoxide to oxalic acid is 1:10.

[0077] S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 24 hours, stir and evaporate to dryness to obtain the loaded material.

[0078] The mass of vanadium pentoxide is 7% of the mass of modified titanium dioxide.

[0079] S3. Place the loaded material obtained in S2 into a muffle furnace and heat it to 450°C at a heating rate of 10°C / min. Calcine for 4 hours to obtain the catalyst for the preparation of 3-cyanopyridine.

[0080] Experimental Example: Experimental Subjects: Catalyst samples prepared in Examples 1-3 and Comparative Examples 1-5. Experimental Method: Catalytic ammonia oxidation was carried out in a fixed-bed reactor with a diameter of 25 mm and a length of 4000 mm; the molar ratio of 3-methylpyridine:ammonia:air:nitrogen was 1:1.66:12:37; the reaction temperature was approximately 345℃; the conversion rate of 3-methylpyridine and the yield of 3-cyanopyridine were tested. Experimental Results: See Table 1.

[0081] Table 1. Results data of the test cases Results Analysis: Combining the data in Table 1 and... Figure 1 Analysis of Examples 1-3 shows that the catalyst samples prepared by the present invention (Examples 1-3) have a conversion rate of over 98.6% and a yield of over 94.5% in the preparation of 3-cyanopyridine.

[0082] Combining the data in Table 1 and Figure 1 Analysis of Example 1 and Comparative Examples 1-5: Specifically, comparing Comparative Examples 1 and 2, it can be seen that compared to the calcination temperature of 450℃ in the catalyst preparation of Comparative Example 1, the calcination temperature in Comparative Example 2 was increased to 500℃, resulting in a significant decrease in conversion rate and yield. This is mainly because the calcination temperature was raised too high, causing partial agglomeration of the active components of the catalyst and the transformation of some of the TiO2 support into rutile crystal TiO2, thus reducing catalytic activity.

[0083] Specifically, by comparing Comparative Example 2 and Comparative Example 3, it can be seen that, compared with Comparative Example 2, the addition of ammonium metatungstate to modify the titanium dioxide support in the preparation of the catalyst in Comparative Example 3 can improve the conversion rate and yield of the catalyst used in the preparation of 3-cyanopyridine.

[0084] Specifically, by comparing Comparative Example 2 and Comparative Example 4, it can be seen that, compared with Comparative Example 2, the addition of cerium nitrate to modify the titanium dioxide support in the preparation of the catalyst in Comparative Example 4 can also improve the conversion rate and yield of the catalyst used in the preparation of 3-cyanopyridine.

[0085] In comparison with Example 1, it can be seen that the simultaneous introduction of ammonium metatungstate and cerium nitrate to modify the titanium dioxide support during catalyst preparation can produce a synergistic effect, synergistically improving the conversion and yield of the prepared catalyst in the preparation of 3-cyanopyridine.

[0086] Comparing with Comparative Example 5, it can be seen that the conventional TiO2 catalyst's calcination performance at 500℃ is weaker than at 450℃. However, by simultaneously modifying the titanium dioxide support with ammonium metatungstate and cerium nitrate, the calcination effect at 500℃ is superior to that at 450℃. This indicates that simultaneously modifying the titanium dioxide support with ammonium metatungstate and cerium nitrate also raises the applicable calcination temperature threshold of the catalyst, breaking through the original system's calcination temperature limitations. This is mainly because the dual modification with W and Ce improves the thermal stability of the support, offsetting the negative effects of sintering and rutile phase transformation caused by the originally excessively high temperature (500℃). At the same time, the vanadium component achieves better dispersion at this originally excessively high temperature (500℃), making the overall benefits outweigh the negative effects.

[0087] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0088] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a catalyst for the preparation of 3-cyanopyridine, characterized in that, Includes the following steps: S1. Vanadium pentoxide is added to water, then oxalic acid is added, and the solution is dissolved to obtain an active solution. S2. Add modified titanium dioxide to the active solution obtained in S1, impregnate for 23-25 ​​hours, stir and evaporate to dryness to obtain the loaded material; the mass of the vanadium pentoxide is 6-8% of the mass of the modified titanium dioxide; S3. Place the loaded material obtained in S2 into a muffle furnace, heat it to 480-510℃, and calcine it for 4 hours to obtain the catalyst used to prepare 3-cyanopyridine. The modified titanium dioxide is prepared by modifying titanium dioxide with tungsten and cerium dual loading; The modified titanium dioxide is prepared as follows: A1. Dissolve ammonium metatungstate and cerium nitrate in deionized water to obtain a mixed salt solution; A2. After impregnating titanium dioxide with the mixed salt solution obtained in A1 for 11-13 hours, dry and pre-calcine to obtain the modified titanium dioxide.

2. The method for preparing the catalyst for preparing 3-cyanopyridine according to claim 1, characterized in that, In the mixed salt solution, the mass fraction of ammonium metatungstate is 5±0.1%, and the mass fraction of cerium nitrate is 4±0.1%.

3. The method for preparing the catalyst for preparing 3-cyanopyridine according to claim 1, characterized in that, The specific surface area of ​​the titanium dioxide is 110 m². 2 / g, pore volume is 0.34mL / g.

4. The method for preparing the catalyst for preparing 3-cyanopyridine according to claim 1, characterized in that, In A2, the drying temperature is 110±5℃ and the drying time is 9-11h.

5. The method for preparing the catalyst for preparing 3-cyanopyridine according to claim 1, characterized in that, In A2, the pre-firing temperature is 400-420℃, and the pre-firing time is 2.5-3h.

6. The method for preparing the catalyst for preparing 3-cyanopyridine according to claim 1, characterized in that, In S1, the molar ratio of vanadium pentoxide to oxalic acid is 1:

10.

7. The method for preparing the catalyst for preparing 3-cyanopyridine according to claim 1, characterized in that, The mass of vanadium pentoxide is 7% of the mass of modified titanium dioxide.

8. The method for preparing the catalyst for preparing 3-cyanopyridine according to claim 1, characterized in that, In S3, the heating rate is 10-12℃ / min.

9. A catalyst for the preparation of 3-cyanopyridine, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 8.

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