Preparation method of chloropyridine

Abstract

The invention provides a preparation method of chloropyridine, which comprises the following steps: in an oxidizing atmosphere, pyridine and chlorine-containing gas are subjected to a chlorination reaction under the action of a catalyst, and a reaction product comprises chloropyridine; the catalyst comprises an active component and a carrier, the carrier comprises porous alumina and activated carbon, and the active component comprises ZnCl2. The preparation method of chloropyridine has the advantages of few side reactions, high yield of chloropyridine and flexible and adjustable chlorination depth, and is suitable for efficient and economic industrial production by using a continuous flow reactor.

Description

Technical Field

[0001] The present application relates to the field of chemical engineering, and in particular to a method for preparing chloropyridine. Background Art

[0002] Chloropyridines are a class of chlorine-substituted pyridine derivatives, including 2-chloropyridine, 3,5-dichloropyridine, 2,6-dichloropyridine, 2,3,5-trichloropyridine, 2,3,6-trichloropyridine, 2,3,5,6-tetrachloropyridine, and pentachloropyridine. Chloropyridines are not only important intermediates in fine chemicals such as pesticides, veterinary drugs, and pharmaceuticals, but are also in increasing demand in emerging fields such as organic optoelectronic devices and flexible electronic devices. In the gas-solid catalytic chlorination process, chlorine-containing gas in the presence of a catalyst progressively chlorinates pyridine. The catalyst's composition, physicochemical properties, and relative dosage are closely related to the reaction pathway and product yield.

[0003] Currently, there is still a lack of a method for preparing chloropyridine with high chloropyridine yield and flexible and adjustable chlorination depth, which is suitable for efficiently and conveniently preparing chloropyridine products on demand. Summary of the Invention

[0004] The present application provides a method for preparing chloropyridine, which can achieve a high yield of chloropyridine and a flexible and adjustable chlorination depth.

[0005] The preparation method of chloropyridine provided in the present application comprises: in an oxidizing atmosphere, pyridine and chlorine-containing gas are subjected to a chlorination reaction in the presence of a catalyst, and the reaction product comprises chloropyridine; the catalyst comprises an active ingredient and a carrier, the carrier comprises porous alumina and activated carbon, and the active ingredient comprises ZnCl2.

[0006] Using porous alumina or activated carbon as a carrier and a supported catalyst containing zinc chloride as the active component, a gas-solid phase catalytic chlorination reaction is carried out in an oxidizing atmosphere. A high yield of chloropyridine can be achieved, and the chlorination depth can be regulated by fine-tuning the catalyst composition to achieve different chloropyridine product selectivities. Therefore, the above-mentioned method for preparing chloropyridine has the advantages of few side reactions, a high yield of chloropyridine, and a flexible and adjustable chlorination depth. It is suitable for efficient and economical industrial production using a continuous flow reactor, and is not only cost-effective but also environmentally friendly.

[0007] In any embodiment, the loading amount of the active component in the catalyst is 4.8% to 12% based on the Zn element in the active component.

[0008] In any embodiment, the catalyst further includes a promoter, which includes one or more alkali metal elements or rare earth elements. The alkali metal elements include one or more of sodium, potassium, rubidium, and cesium. The rare earth elements include one or more of cerium and lanthanum.

[0009] In any embodiment, the loading amount of the active component in the catalyst is 4.8% to 9.6% based on the Zn element in the active component.

[0010] In any embodiment, the promoter includes an alkali metal element, and the alkali metal element includes rubidium and / or cesium. Optionally, the mass content of the promoter containing the alkali metal element in the catalyst is 1%-3%.

[0011] In any embodiment, the temperature of the chlorination reaction is 320°C to 360°C.

[0012] In any embodiment, the loading amount of the active component in the catalyst is 9.6%-12% based on the Zn element in the active component.

[0013] In any embodiment, the catalyst further includes an auxiliary agent, which includes a rare earth element and an optional alkali metal element, the rare earth element includes cerium and / or lanthanum, and the alkali metal element includes rubidium and / or cesium; optionally, the mass content of the auxiliary agent containing rare earth elements in the catalyst is 0.5%-2.5%; optionally, the mass content of the auxiliary agent containing alkali metal elements in the catalyst is 1%-2%.

[0014] In any embodiment, the temperature of the chlorination reaction is 350°C to 430°C.

[0015] In any embodiment, an oxidizing atmosphere is formed by introducing air and protective gas, and the volume fraction of oxygen in the oxidizing atmosphere is 0.3% to 1.8%.

[0016] In any embodiment, the oxidizing atmosphere comprises oxygen and a protective gas; optionally, the protective gas comprises nitrogen or an inert gas, and the inert gas comprises one or more of helium, neon or argon.

[0017] In any embodiment, the chlorine-containing gas includes chlorine and hydrogen chloride, and the molar ratio of pyridine to the chlorine element in the chlorine-containing gas is 1:(3.5-13).

[0018] In any embodiment, the weight hourly space velocity of pyridine is 0.02h -1 -0.18h -1 , optional 0.06h -1 -0.10h -1 . DETAILED DESCRIPTION

[0019] The following embodiments of the present invention are further described in detail with reference to the following examples. The detailed description of the following examples is used to illustrate the principles of the present invention, but is not intended to limit the scope of the present invention, that is, the present invention is not limited to the described examples.

[0020] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0021] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0022] Unless otherwise specifically stated, all materials and reagents used in this disclosure are commercially available.

[0023] In the present application, the term "about" means that the numerical value it defines may have a deviation within the range of ±10% of the numerical value. For example, the term "about 100° C." means the range of "100±10° C.".

[0024] In the present application, the term "room temperature" refers to 20°C-25°C, preferably 25°C.

[0025] The present application provides a method for preparing chloropyridine, comprising: in an oxidizing atmosphere, subjecting pyridine and a chlorine-containing gas to a chlorination reaction in the presence of a catalyst, wherein the reaction product comprises chloropyridine; the catalyst comprises an active ingredient and a carrier, wherein the carrier comprises porous alumina and activated carbon, and the active ingredient comprises ZnCl2.

[0026] Without wishing to be bound by any theory, the applicant has found that by using porous alumina or activated carbon as a carrier and a supported catalyst with zinc chloride as the active component, a gas-solid phase catalytic chlorination reaction is carried out under an oxidizing atmosphere, a higher chloropyridine yield can be obtained, and the chlorination depth can be regulated by fine-tuning the catalyst composition to achieve different chloropyridine product selectivities. Therefore, the preparation method of the above-mentioned chloropyridine has the advantages of few side reactions, high chloropyridine yield, and flexible and adjustable chlorination depth, and is suitable for efficient and economical industrial production using a continuous flow reactor, which not only has cost advantages but is also environmentally friendly.

[0027] In some embodiments, the chloropyridine comprises one or more of 2,6-dichloropyridine, 2,3,6-trichloropyridine, 2,3,5,6-tetrachloropyridine, and pentachloropyridine. Using the preparation method provided herein, the selectivity of a particular chloropyridine can be improved by adjusting parameters such as the temperature, pressure, and gas flow rate of the chlorination reaction.

[0028] In some embodiments, the loading amount of the active ingredient in the catalyst is 4.8%-12% based on the Zn element in the active ingredient. For example, the loading amount of the active ingredient in the catalyst can be 4.8%, or 6.4%, or 7.2%, or 8.5%, or 9.6%, or 10.2%, or 11.5%, or 12%, or a range formed by any two of the above, based on the Zn element in the active ingredient.

[0029] In some embodiments, the catalyst further comprises a promoter, which comprises one or more of an alkali metal element or a rare earth element, wherein the alkali metal element comprises one or more of sodium, potassium, rubidium, and cesium, and the rare earth element comprises one or more of cerium and lanthanum. The promoter containing an alkali metal element or a rare earth element can exhibit one or more of the following effects: regulating the acidity of the catalyst, inhibiting carbon deposition, and extending the life of the catalyst; improving the thermal stability of the catalyst; enhancing the Zn through 4f electron transfer; 2+ acidity, improving catalytic activity or chlorination depth.

[0030] In some embodiments, the active ingredient loading in the catalyst is 4.8% to 9.6% based on the Zn element in the active ingredient, for example, 4.8%, 6.4%, 7.2%, 8.5%, 9.6%, or any combination thereof. This helps improve the selectivity of 2,3,6-trichloropyridine while achieving a high yield of chloropyridine.

[0031] In some embodiments, the promoter includes an alkali metal element, including rubidium and / or cesium. Optionally, the weight content of the promoter containing the alkali metal element in the catalyst is 1% to 3%, such as 1%, 2%, or 3%. Within the above loading range, the promoter containing the alkali metal element can further improve the yield of 2,3,6-trichloropyridine.

[0032] In some embodiments, the chlorination reaction temperature is 320°C-360°C. For example, the chlorination reaction temperature can be 320°C-350°C, or 330°C-360°C, 330°C-350°C, 340°C-360°C, etc., but is not limited thereto. Chlorination reaction temperatures within the above temperature ranges can improve the selectivity of 2,3,6-trichloropyridine.

[0033] In some embodiments, the active ingredient loading in the catalyst is 9.6%-12%, calculated as the Zn element in the active ingredient, such as 9.6%, 10.2%, 11.5%, or 12%, or a range formed by any two of the above. Active ingredient loadings within these ranges not only achieve a high yield of chloropyridine, but also help increase the depth of chlorination, thereby significantly increasing the yield of pentachloropyridine.

[0034] In some embodiments, the catalyst further comprises a promoter comprising a rare earth element and optionally an alkali metal element, wherein the rare earth element comprises cerium and / or lanthanum, and the alkali metal element comprises rubidium and / or cesium. Optionally, the mass content of the rare earth promoter in the catalyst is 0.5%-2.5%; alternatively, the mass content of the alkali metal promoter in the catalyst is 1%-2%. When the promoter comprises both a rare earth element and an alkali metal element, significantly improved catalytic activity can be achieved, further increasing the yield of chloropyridine and the depth of the chlorination reaction.

[0035] In some embodiments, the chlorination reaction temperature is 350°C-430°C. For example, the chlorination reaction temperature can be 350°C-400°C, 360°C-420°C, 370°C-430°C, 380°C-410°C, 400°C-430°C, 360°C-400°C, etc., but is not limited thereto. Chlorination reaction temperatures within the above temperature range are conducive to obtaining a relatively higher yield of pentachloropyridine.

[0036] In some embodiments, an oxidizing atmosphere is formed by introducing air and a protective gas, and the volume fraction of oxygen in the oxidizing atmosphere is 0.3% to 1.8%. For example, the volume fraction of oxygen in the oxidizing atmosphere can be 0.3%, 0.6%, 1.2%, 1.8%, or a range formed by any two of the foregoing. An oxidizing atmosphere with an oxygen volume fraction within the foregoing range is more conducive to accelerating the desorption of pyridine from the catalyst while suppressing side reactions such as pyridine decomposition, thereby achieving a higher yield of chloropyridine.

[0037] In some embodiments, the oxidizing atmosphere comprises oxygen and a protective gas; optionally, the protective gas comprises nitrogen or an inert gas, and the inert gas comprises one or more of helium, neon, or argon.

[0038] In this application, the ratio of pyridine to chlorine-containing gas can be based on conventional techniques, wherein the chlorine-containing gas is relatively excessive to improve the conversion rate of pyridine. In some embodiments, the chlorine-containing gas includes chlorine and hydrogen chloride, and the molar ratio of pyridine to the chlorine element in the chlorine-containing gas is 1:(3.5-13). By way of example and not limitation, the molar ratio of pyridine to the chlorine element in the chlorine-containing gas can be 1:3.5, 1:4, 1:5, 1:6, 1:7, 1:8, 1:10, 1:13 or a range formed by any two of them.

[0039] In some embodiments, the weight hourly space velocity of pyridine is 0.02 h -1 ~0.18h -1 , optional 0.06h -1 -0.10h -1 The raw material pyridine can be preheated and vaporized before entering the reactor together with the carrier gas, or the carrier gas can be used to blow tiny droplets containing pyridine into the reactor.

[0040] The beneficial effects of the present application will be further illustrated below in conjunction with Examples and Comparative Examples, but the scope of the present invention is not limited to these Examples. Where specific techniques or conditions are not specified in the Examples, the techniques or conditions described in the literature in this area or in accordance with the product specifications are used. Unless otherwise expressly stated, all materials and reagents used are conventional products that can be obtained commercially.

[0041] Example 1

[0042] Step 1: At room temperature, 5 g of ZnCl2 (136.28 g / mol) was dissolved in 34 g of water, and 45 g of porous alumina was added. After standing for 12 hours, the mixture was dried at 80°C-90°C for 12 hours, and then placed in a muffle furnace and calcined at 400°C for 5 hours to obtain a 10% ZnCl2 / Al2O3 catalyst, where 10% represents the mass content of ZnCl2 in the catalyst (the same below). Calculated based on the Zn element in the active ingredient, the active ingredient loading of the catalyst is 4.8%;

[0043] The porous alumina has a pore volume of 0.5 mL / g, a particle size distribution in the range of 3 mm to 8 mm, and a BET specific surface area of ​​230 m 2 / g;

[0044] Step 2: Weigh 40 g of the above catalyst and load it into a fixed bed reactor. Sent pyridine into the preheater at a flow rate of 0.04 mL / min for vaporization. Then, N2 was used as a carrier gas to send the vaporized pyridine into the reactor. The flow rate of N2 was 3000 mL / min, and the weight hourly space velocity of pyridine was 0.06 h -1 , while introducing chlorine gas to react with pyridine on the catalyst bed, the flow rate of chlorine gas is 50 mL / min, the molar ratio of pyridine to chlorine gas is 1:4.86, and air is continuously introduced during the reaction to form an oxidizing atmosphere in the reactor. The volume fraction of O2 in the oxidizing atmosphere is 0.6%, the reaction temperature is 320°C-350°C, the reaction pressure is maintained at 0.5 MPa, and the reaction time is 24 h;

[0045] Step 3: After the reaction is completed, the product is cooled sufficiently, ethanol is added to dissolve it until it is clear and transparent, and it is weighed. The composition and content are analyzed by high performance liquid chromatography to calculate the pyridine conversion rate and the yield of each product.

[0046] Comparative Examples 1 to 7

[0047] Compared with Example 1, the only difference is the selection of active ingredients in step 1:

[0048] Comparative Examples 1 to 7 each used 5 g of other active ingredients to prepare catalysts, and the loading amounts of the active ingredients in the resulting catalysts were also different, calculated as metal elements.

[0049] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 1.

[0050] The results of pyridine conversion and product yields of Example 1 and Comparative Examples 1 to 7 are shown in Table 1. For the convenience of comparative analysis, the catalyst differences between Example 1 and each comparative example are recorded in Table 1.

[0051] Table 1

[0052]

[0053]

[0054] From the data in Table 1, it can be found that when the catalyst uses porous alumina as the carrier and ZnCl2 as the active ingredient, the pyridine conversion rate and the total yield of chloropyridine in the catalytic chlorination reaction are significantly better than those in the comparative examples.

[0055] Example 2

[0056] The difference between the preparation method of chloropyridine in this embodiment and that in Example 1 is only in step 1:

[0057] 2.5 g of ZnCl2 was dissolved in 34 g of water, and 47.5 g of porous alumina was added. After standing for 12 hours, the mixture was dried at 80°C-90°C for 12 hours, and then placed in a muffle furnace and calcined at 400°C for 5 hours. The remaining settings and operations were consistent with those in Example 1 to prepare a 5% ZnCl2 / Al2O3 catalyst. The active ingredient loading of the catalyst was 2.4% based on the Zn element in the active ingredient.

[0058] The pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina are the same as those in Example 1;

[0059] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 1.

[0060] Example 3

[0061] The difference between the preparation method of chloropyridine in this embodiment and that in Example 1 is only in step 1:

[0062] 7.5 g of ZnCl2 was dissolved in 34 g of water, and 42.5 g of porous alumina was added. After standing for 12 hours, the mixture was dried at 80°C-90°C for 12 hours, and then placed in a muffle furnace and calcined at 400°C for 5 hours. The remaining settings and operations were consistent with those in Example 1 to prepare a 15% ZnCl2 / Al2O3 catalyst. The active ingredient loading of the catalyst was 7.2% based on the Zn element in the active ingredient.

[0063] The pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina are the same as those in Example 1;

[0064] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 1.

[0065] Example 4

[0066] The difference between the preparation method of chloropyridine in this embodiment and that in Example 1 is only in step 1:

[0067] 10 g of ZnCl2 was dissolved in 34 g of water, and 40 g of porous alumina was added. After standing for 12 hours, the mixture was dried at 80°C-90°C for 12 hours, and then placed in a muffle furnace and calcined at 400°C for 5 hours. The remaining settings and operations were consistent with those in Example 1 to prepare a 20% ZnCl2 / Al2O3 catalyst. The active ingredient loading of the catalyst was 9.6% based on the Zn element in the active ingredient.

[0068] The pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina are the same as those in Example 1;

[0069] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 1.

[0070] Example 5

[0071] The difference between the preparation method of chloropyridine in this embodiment and that in Example 1 is only in step 1:

[0072] 12.5 g of ZnCl2 was dissolved in 34 g of water, and 37.5 g of porous alumina was added. After standing for 12 hours, the mixture was dried at 80°C-90°C for 12 hours, and then placed in a muffle furnace and calcined at 400°C for 5 hours. The remaining settings and operations were consistent with those in Example 1 to prepare a 20% ZnCl2 / Al2O3 catalyst. The active ingredient loading of the catalyst was 9.6% based on the Zn element in the active ingredient.

[0073] The pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina are the same as those in Example 1;

[0074] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 1.

[0075] The results of the catalyst differences, pyridine conversion rates, and yields of various products in Examples 1 to 5 are recorded in Table 2.

[0076] Table 2

[0077]

[0078] As can be seen from Table 2, when the loading amount of the active ingredient in the catalyst is increased from 2.4% (Example 2) to 7.2% (Example 3), calculated as Zn element, the total yield of chloropyridine increases rapidly from 63.8% to 91.05%. When the loading amount of the active ingredient is further increased to 12%, the total yield of chloropyridine no longer increases but instead decreases slightly.

[0079] Specific analysis also revealed that: (1) With the increase of the loading amount of the active ingredient in the catalyst, the yield of 2,6-dichloropyridine showed a "U-shaped" non-monotonic change trend that first decreased and then increased, but the absolute value of the yield was stable in the range of 23.5%-30%, with small fluctuations; (2) When the loading amount of the active ingredient was between 2.4% and 7.2%, the yield of 2,3,6-trichloropyridine continued to increase, reaching a peak at a loading amount of 7.2% and then declining. With the increase of the loading amount of the active ingredient in the catalyst, it showed an "inverted U-shaped" non-monotonic change trend, and the yield change trend of 2,3,5,6-tetrachloropyridine was similar to it; (3) When the loading amount of the active ingredient in the catalyst increased from 2.4% to 12%, the yield of pentachloropyridine continued to increase, especially when the loading amount of the active ingredient was between 7.2% and 12%, the yield of pentachloropyridine increased significantly faster.

[0080] Therefore, by adjusting the loading of the active ingredient in the catalyst, it is possible to achieve on-demand preparation of chloropyridines. For example, when the target product is 2,3,6-trichloropyridine, the loading of the active ingredient in the catalyst is preferably controlled between 4.8% and 9.6%; when the target product is pentachloropyridine, the loading of the active ingredient in the catalyst is preferably controlled within the range of 7.2% to 12%.

[0081] In the above examples, Example 3 has the best total yield of chloropyridine and 2,3,6-trichloropyridine. Next, based on Example 3, the progress of the catalytic chlorination reaction was explored when different components and contents of the auxiliary agents were introduced into the catalyst.

[0082] Examples 6 to 9

[0083] The only difference between the preparation methods of chloropyridines in Examples 6 to 9 and Example 3 is step 1:

[0084] At room temperature, 0.5 g of additive X and 7.5 g of ZnCl₂ were dissolved in 31 g of water, and 42 g of porous alumina was added to prepare a 1%X-15%ZnCl₂ / Al₂O₃ catalyst. The additive X was a chloride containing an alkali metal element, and the additives X used in Examples 6 to 9 were different. The pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 3.

[0085] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 3.

[0086] The results of the catalyst differences, pyridine conversion rates, and yields of various products in Examples 3, 6 to 9 are recorded in Table 3.

[0087] Table 3

[0088]

[0089]

[0090] Examples 8 and 9, respectively, employ catalysts containing RbCl and CsCl, effectively increasing the total yield of chloropyridines. Furthermore, the data in Table 3 indicate that the introduction of an alkali metal chloride-containing additive into the catalyst can enhance the depth of reaction of chloropyridines. Compared to Example 3, which does not contain an alkali metal chloride additive, the yields of polychlorinated products (2,3,5,6-tetrachloropyridine and pentachloropyridine) in Examples 6 to 9 increased to varying degrees, with the most significant increase observed in Example 9.

[0091] Furthermore, the difference in the effect of the catalyst in the catalytic chlorination reaction was explored as the amount of the auxiliary agent containing alkali metal chloride changed.

[0092] Example 10

[0093] The difference between Example 10 and Example 9 is only step 1:

[0094] At room temperature, 1 g of CsCl and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 41.5 g of porous alumina was added to prepare a 2% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 9;

[0095] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 9.

[0096] Example 11

[0097] The difference between Example 11 and Example 9 is only step 1:

[0098] At room temperature, 1.5 g of CsCl and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 41 g of porous alumina was added to prepare a 3% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 9;

[0099] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 9.

[0100] Example 12

[0101] The difference between Example 12 and Example 9 is only step 1:

[0102] At room temperature, 2 g of CsCl and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 40.5 g of porous alumina was added to prepare a 4% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 9;

[0103] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 9.

[0104] Example 13

[0105] The only difference between Example 13 and Example 9 is step 1:

[0106] At room temperature, 2.5 g of CsCl and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 40 g of porous alumina was added to prepare a 5% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 9;

[0107] In addition, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 9.

[0108] The results of the catalyst differences, pyridine conversion rates, and yields of various products in Examples 9 to 13 are recorded in Table 4.

[0109] Table 4

[0110]

[0111] Taking CsCl as an example, the results in Table 4 indicate that when the catalyst includes an alkali metal chloride as a promoter, changes in the amount of the promoter cause changes in the total yield of chloropyridine. When the mass content of the promoter CsCl in the catalyst is between 1% and 5%, this change exhibits a nonlinear trend, with the total yield of chloropyridine initially increasing and then decreasing. When the mass content of the promoter CsCl in the catalyst is greater than 3%, the total yield of chloropyridine decreases significantly. Therefore, it can be inferred that controlling the mass content of the alkali metal promoter in the catalyst within the range of 1% to 3% can achieve a better catalytic effect.

[0112] Furthermore, based on Example 10 (corresponding to 2% CsCl-15% ZnCl2 / Al2O3 catalyst) with the highest total yield of chloropyridine in Table 4, a rare earth element-containing additive was introduced into the catalyst to explore the effect of the combined use of bimetallic additives on the catalytic chlorination reaction.

[0113] Example 14

[0114] The difference between Example 14 and Example 10 is only step 1:

[0115] 0.25 g of CeCl3, 1 g of CsCl, and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 41.25 g of porous alumina was added to prepare a 0.5% CeCl3-2% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 10;

[0116] Otherwise, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 10.

[0117] Example 15

[0118] The difference between Example 15 and Example 10 is only step 1:

[0119] 0.25 g of LaCl₃, 1 g of CsCl, and 7.5 g of ZnCl₂ were dissolved in 31 g of water, and 41.25 g of porous alumina was added to prepare a 0.5% LaCl₃-2% CsCl-15% ZnCl₂ / Al₂O₃ catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 10;

[0120] Otherwise, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 10.

[0121] Example 16

[0122] The difference between Example 16 and Example 10 is only step 1:

[0123] 0.5 g of LaCl3, 1 g of CsCl, and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 41 g of porous alumina was added to prepare a 1% LaCl3-2% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 10;

[0124] Otherwise, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 10.

[0125] Example 17

[0126] The difference between Example 17 and Example 10 is only step 1:

[0127] 0.75 g of LaCl3, 1 g of CsCl, and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 40.75 g of porous alumina was added to prepare a 1.5% LaCl3-2% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 10;

[0128] Otherwise, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 10.

[0129] Example 18

[0130] The difference between Example 18 and Example 10 is only step 1:

[0131] 1 g of LaCl3, 1 g of CsCl, and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 40.5 g of porous alumina was added to prepare a 2% LaCl3-2% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 10;

[0132] Otherwise, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 10.

[0133] Example 19

[0134] The difference between Example 19 and Example 10 is only step 1:

[0135] 1.25 g of LaCl3, 1 g of CsCl, and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 40.25 g of porous alumina was added to prepare a 2.5% LaCl3-2% CsCl-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 10;

[0136] Otherwise, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 10.

[0137] Example 20

[0138] The difference between Example 20 and Example 10 is only step 1:

[0139] 0.75 g of LaCl3 and 7.5 g of ZnCl2 were dissolved in 31 g of water, and 41.75 g of porous alumina was added to prepare a 1.5% LaCl3-15% ZnCl2 / Al2O3 catalyst, wherein the pore volume, particle size distribution, and BET specific surface area of ​​the porous alumina were the same as those in Example 10;

[0140] Otherwise, the rest of the settings including the catalytic chlorination reaction remained the same as in Example 10.

[0141] The results of catalyst differences, pyridine conversion, and yield of each product in Examples 10, 14 to 20 are recorded in Table 5.

[0142] Table 5

[0143]

[0144]

[0145] The data in Table 5 indicate that the presence of both alkali metal chloride and rare earth chloride additives in the catalyst improves catalytic activity, further increasing the total yield of chloropyridines to over 98%, and significantly increasing the yield of pentachloropyridine. Therefore, compared to using only one type of additive containing either alkali metals or only one containing rare earth metals, the combined use of alkali metal and rare earth additives can yield a higher total yield of chloropyridines and improve the depth of chlorination.

[0146] By comparing the results of Examples 15 to 19, it can be found that: taking LaCl3 as an exemplary rare earth element-containing additive, when its mass content is in the range of 0.5%-2.5%, the total yield of chloropyridine can reach more than 98%. In particular, when the mass content of LaCl3 is greater than 1.5%, the yield of pentachloropyridine and the total yield of chloropyridine both show a slight decrease. It can be seen that it is preferred to control the mass content of the rare earth element-containing additive in the catalyst within the range of 0.5%-1.5%, which is sufficient to fully exert the effectiveness of the rare earth element-containing additive.

[0147] To clarify the effect of different catalyst supports on the catalytic chlorination reaction, the porous alumina in Example 1 was replaced with other support materials in Example 21 and Comparative Examples 8 to 11, respectively. The remaining settings and operations were consistent with Example 1. For the sake of brevity, the support type and physical properties (pore volume, particle size distribution range, BET specific surface area) are listed in Table 6. The pyridine conversion and product yield results of Examples 1, 21, and Comparative Examples 8 to 11 are also recorded in Table 6.

[0148] Table 6

[0149]

[0150]

[0151] According to the results in Table 6, when the active component of the catalyst is ZnCl2, porous alumina or activated carbon is used as a carrier, and the gas-solid phase catalytic chlorination reaction is used to prepare chloropyridine with both a better yield of 2,3,6-trichloropyridine and a better total yield of chloropyridine.

[0152] To clarify the effect of different reaction temperatures on the catalytic chlorination reaction, Examples 22 to 26 were set at different reaction temperatures from Example 17, while the remaining settings and operations remained consistent with Example 17. For the sake of brevity, the reaction temperatures, pyridine conversion rates, and product yields of Examples 17, 22 to 26 are presented in Table 7.

[0153] The data shown in Table 7 indicate that the reaction products exhibit varying selectivity for chloropyridines at different reaction temperatures. Therefore, this method for preparing chloropyridines allows for flexible adjustment of the reaction temperature to produce specific chloropyridines. For example, a reaction temperature between 350°C and 430°C yields relatively high pentachloropyridine yields, while a reaction temperature between 320°C and 360°C yields relatively high 2,3,6-trichloropyridine yields.

[0154] Table 7

[0155]

[0156] To clarify the effect of varying oxygen volume fractions on the catalytic chlorination reaction, Examples 27 and 28 employed different oxygen atmospheres from Example 26, using air plus an inert gas mixture to adjust the oxygen volume fraction. All other settings and operations remained consistent with Example 26. For simplicity, the reaction temperatures, pyridine conversions, and product yields of Examples 26 to 31 are presented in Table 8.

[0157] Table 8

[0158]

[0159] The results in Table 8 indicate that, when conducting the catalytic chlorination reaction, pentachloropyridine can achieve a higher relative yield under oxygen-containing conditions. Controlling the oxygen volume fraction in the oxidizing atmosphere between 0.3% and 1.8% can balance the chlorination depth and the total yield of the chloropyridine. Excessively high oxygen volume fractions can easily cause decomposition of the pyridine substrate, reducing the yield of the chloropyridine.

[0160] To clarify the effect of pyridine weight hourly space velocity (WHSV) on the catalytic chlorination reaction, Examples 31 to 34 were set with different WHSVs than those in Example 26. The remaining settings and operations remained the same as in Example 26. For the sake of brevity, the WHSVs, pyridine conversions, and product yields for Examples 26, 31 to 34 are summarized in Table 9.

[0161] Table 9

[0162]

[0163] According to the data in Table 9, when the pyridine is heavy, the space velocity is 0.02h -1 -0.10h -1 Within the range, the reaction chlorination depth is higher, and a higher pentachloropyridine yield can be obtained. When the pyridine hourly space velocity is 0.06h -1 -0.18h -1 The total yield of chloropyridine is relatively high. The pyridine weight hourly space velocity is 0.06h -1 -0.10h -1 Within this range, the yield of pentachloropyridine and the total yield of chloropyridine can be maintained at a high level.

[0164] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing chloropyridine, comprising: In an oxidizing atmosphere, pyridine and chlorine-containing gas are subjected to a chlorination reaction in the presence of a catalyst, and the reaction product includes chloropyridine; The catalyst comprises an active component and a carrier, wherein the carrier comprises porous alumina and activated carbon, and the active component comprises ZnCl2.

2. The preparation method according to claim 1, characterized in that Calculated based on the Zn element in the active component, the loading amount of the active component in the catalyst is 4.8%-12%.

3. The preparation method according to claim 1 or 2, characterized in that The catalyst also includes a promoter, which includes one or more alkali metal elements or rare earth elements. The alkali metal elements include one or more sodium, potassium, rubidium, and cesium. The rare earth elements include one or more cerium and lanthanum.

4. The preparation method according to any one of claims 1 to 3, characterized in that Calculated based on the Zn element in the active component, the loading amount of the active component in the catalyst is 4.8%-9.6%.

5. The preparation method according to claim 4, characterized in that The auxiliary agent includes an alkali metal element, and the alkali metal element includes rubidium and / or cesium; Optionally, the mass content of the additive containing alkali metal elements in the catalyst is 1%-3%.

6. The preparation method according to claim 4 or 5, characterized in that The temperature of the chlorination reaction is 320°C-360°C.

7. The preparation method according to any one of claims 1 to 3, characterized in that Calculated based on the Zn element in the active component, the loading amount of the active component in the catalyst is 9.6%-12%.

8. The preparation method according to claim 7, characterized in that The catalyst further comprises a promoter, wherein the promoter comprises a rare earth element and an optional alkali metal element, wherein the rare earth element comprises cerium and / or lanthanum, and the alkali metal element comprises rubidium and / or cesium; Optionally, the mass content of the rare earth element additive in the catalyst is 0.5%-2.5%; Optionally, the mass content of the alkali metal additive in the catalyst is 1%-2%.

9. The preparation method according to claim 7 or 8, characterized in that The temperature of the chlorination reaction is 350°C-430°C.

10. The preparation method according to any one of claims 1 to 9, characterized in that The oxidizing atmosphere is formed by introducing air and protective gas, and the volume fraction of oxygen in the oxidizing atmosphere is 0.3% to 1.8%.

11. The preparation method according to any one of claims 1 to 10, characterized in that The oxidizing atmosphere comprises oxygen and a protective gas; optionally, the protective gas comprises nitrogen or an inert gas, and the inert gas comprises one or more of helium, neon or argon.

12. The preparation method according to any one of claims 1 to 11, characterized in that The chlorine-containing gas includes chlorine and hydrogen chloride, and the molar ratio of the pyridine to the chlorine element in the chlorine-containing gas is 1:(3.5-13).

13. The preparation method according to any one of claims 1 to 12, characterized in that The weight hourly space velocity of pyridine is 0.02h -1 -0.18h -1 , optional 0.06h -1 -0.10h -1 .

Images