CN111495387B - Chloropyridine hydrodechlorination catalyst and preparation method and application thereof - Google Patents
Chloropyridine hydrodechlorination catalyst and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to the technical field of catalysis, in particular to a chloropyridine hydrodechlorination catalyst and a preparation method and application thereof. The chloropyridine hydrodechlorination catalyst comprises a carrier and an active component loaded on the carrier, wherein the carrier comprises alumina, and the active component is Co oxide and/or Pt oxide. The catalyst of the invention takes alumina as a carrier and takes Co oxide and/or Pt oxide as active components, and the obtained catalyst not only has good stability, catalytic activity and selectivity, but also can realize the continuous production of 2, 3-dichloropyridine and 2,3,5, 6-tetrachloropyridine in a fixed bed reactor.
Description
Technical Field
The invention relates to the technical field of catalysis, in particular to a chloropyridine hydrodechlorination catalyst and a preparation method and application thereof.
Background
2,3,5, 6-tetrachloropyridine and 2, 3-dichloropyridine are important fine chemical intermediates, are widely applied to the fields of medicines and pesticides, are mainly used for synthesizing a pesticide intermediate, namely chlorantraniliprole, and have large market demand.
At present, catalysts for preparing 2,3,5, 6-tetrachloropyridine and 2, 3-dichloropyridine mostly use noble metal Pd as a hydrogenation active component, and have the advantages of high price and large using amount; the catalyst carrier is usually selected from active carbon, and although the specific surface area is large, the stability is poor and the catalyst carrier is easy to inactivate. Therefore, the catalyst is basically used in an autoclave reactor and cannot be used for continuous production of a fixed bed reactor. In the kettle-type liquid phase reaction, reactants need to be dissolved in a certain solvent, NaOH, liquid ammonia and the like are added as acid-binding agents to absorb hydrogen chloride gas generated by the reaction, a large amount of waste salt and waste liquid can be generated, and the environmental protection property is poor.
Disclosure of Invention
The catalyst has good stability, catalytic activity and selectivity, can realize continuous production of 2, 3-dichloropyridine and 2,3,5, 6-tetrachloropyridine in a fixed bed reactor, and is free of solvent and acid binding agent in the whole process, thereby being more environment-friendly.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a chloropyridine hydrodechlorination catalyst which comprises a carrier and an active component loaded on the carrier, wherein the carrier comprises alumina, and the active component is Co oxide and/or Pt oxide.
Preferably, the loading amount of Co in the active component is below 30 wt%, and the loading amount of Pt in the active component is below 5 wt%.
Preferably, the loading amount of Co in the active component is below 15 wt%, and the loading amount of Pt in the active component is below 3 wt%.
Preferably, when the active components are Co oxide and Pt oxide, the mass ratio of the Co to the Pt is (2-20): 1.
Preferably, the alumina is unmodified alumina or modified alumina, and the modified alumina is obtained by modifying calcium, magnesium or potassium.
The invention provides a preparation method of a chloropyridine hydrodechlorination catalyst in the scheme,
A. when the active component is Co oxide, the method comprises the following steps:
dipping an alumina carrier into a Co precursor solution, and sequentially drying and roasting the alumina carrier obtained after dipping to obtain a chloropyridine hydrodechlorination catalyst;
B. when the active component is an oxide of Pt, the method comprises the following steps:
dipping an alumina carrier into a chloroplatinic acid solution, and sequentially drying and roasting the alumina carrier obtained after dipping to obtain a chloropyridine hydrodechlorination catalyst;
C. when the active components are Co oxide and Pt oxide, the method comprises the following steps:
(1) dipping an alumina carrier into a Co precursor solution, and drying and roasting the alumina carrier obtained after dipping in sequence to obtain a Co-loaded catalyst precursor;
(2) and (3) dipping the Co-loaded catalyst precursor into a chloroplatinic acid solution, and drying and roasting the solid obtained after dipping in sequence to obtain the chloropyridine hydrodechlorination catalyst.
Preferably, the roasting temperature in A, B, C is 300-600 ℃, and the heat preservation time is 1-5 hours.
Preferably, the precursor solution of Co in A, B, C includes a cobalt chloride solution or a cobalt nitrate solution.
The invention provides an application of chloropyridine in a hydrodechlorination reaction catalyzed by the chloropyridine hydrodechlorination catalyst or the chloropyridine hydrodechlorination catalyst prepared by the preparation method in the scheme.
Preferably, the hydrodechlorination reaction is carried out in a fixed bed reactor.
Preferably, the application mode comprises:
activating the chloropyridine hydrodechlorination catalyst in a fixed bed reactor to obtain an activated catalyst;
mixing hydrogen and chloropyridine, and vaporizing the obtained mixture to obtain a mixed gas;
and introducing the mixed gas into a fixed bed reactor filled with an activated catalyst, carrying out hydrodechlorination reaction, and carrying out gas-liquid separation to obtain a chloropyridine hydrodechlorination product.
Preferably, the temperature of the hydrodechlorination reaction is 140-300 ℃, the pressure is 0.1-5 MPa, and the mass space velocity is 0.05-0.1 h-1。
Preferably, the temperature of the hydrodechlorination reaction is170-260 ℃, the pressure of 0.5-1 MPa and the mass space velocity of 0.06-0.85 h-1。
Preferably, the vaporization rate of the chloropyridine during vaporization is 80-100%.
The invention provides a chloropyridine hydrodechlorination catalyst which comprises a carrier and an active component loaded on the carrier, wherein the carrier comprises alumina, and the active component is Co oxide and/or Pt oxide. The catalyst provided by the invention takes alumina as a carrier and takes Co oxide and/or Pt oxide as active components, so that the obtained catalyst has good stability, catalytic activity and selectivity, and can realize continuous production of 2, 3-dichloropyridine and 2,3,5, 6-tetrachloropyridine in a fixed bed reactor, and the whole process is free of solvent and acid-binding agent and is more environment-friendly.
The invention provides a preparation method of a chloropyridine hydrodechlorination catalyst, which has simple process and easy operation.
The invention provides an application of chloropyridine in a hydrodechlorination reaction catalyzed by a chloropyridine hydrodechlorination catalyst, and the catalyst has high catalytic activity and selectivity for preparing 2, 3-dichloropyridine and 2,3,5, 6-tetrachloropyridine from chloropyridine.
Detailed Description
The invention provides a chloropyridine hydrodechlorination catalyst which comprises a carrier and an active component loaded on the carrier, wherein the carrier comprises alumina, and the active component is Co oxide and/or Pt oxide.
The chloropyridine hydrodechlorination catalyst comprises a carrier, wherein the carrier comprises alumina. In the present invention, the alumina is preferably unmodified alumina or modified alumina, and the modified alumina is preferably modified from calcium, magnesium or potassium.
When the alumina is modified with calcium, magnesium or potassium, the method for preparing the modified alumina preferably comprises the following steps: the method comprises the steps of dipping alumina into a water solution of calcium salt, magnesium salt or potassium salt, and then drying and roasting the alumina obtained after dipping in sequence to obtain the modified alumina.
In the present invention, theThe shape of the alumina is preferably gear-shaped, and the gear-shaped alumina has larger specific surface area, more pore diameters and higher strength, thereby being beneficial to the loading and dispersion of active components on the surface of the carrier and further being beneficial to improving the catalytic performance of the catalyst. In the invention, the specific surface area of the alumina is preferably 200-300 m2A concentration of 220 to 280 m/g is more preferable2G, most preferably 230m2(ii) in terms of/g. The present invention does not require specific types of such calcium, magnesium and potassium salts, and soluble calcium, magnesium and potassium salts well known in the art are all suitable. The invention has no special requirement on the dosage of the aqueous solution, and preferably meets the requirement that the aqueous solution can completely immerse the alumina carrier and can be completely absorbed by alumina. In the present invention, the amount of the calcium salt, magnesium salt or potassium salt is preferably determined according to the content of calcium, magnesium or potassium in the modified alumina; the mass content of calcium, magnesium or potassium in the modified alumina is preferably 0.1-3%. In the invention, the temperature of the impregnation is preferably room temperature, and the time of the impregnation is preferably that the alumina can completely absorb the aqueous solution; the drying temperature is preferably 110 ℃, and the drying time is preferably 4 h; the roasting temperature is preferably 450 ℃, and the time is preferably 3 hours. The invention can improve the catalytic activity and selectivity of the catalyst by modifying the alumina.
When the carrier is unmodified alumina, the shape of the alumina is preferably gear-shaped, and the gear-shaped alumina has large specific surface area, more pore diameters and higher strength, so that the loading and dispersion of active components on the surface of the carrier are facilitated, and the catalytic performance of the catalyst is further improved. . In the invention, the specific surface area of the alumina is preferably 200-300 m2A concentration of 220 to 280 m/g is more preferable2G, most preferably 230m2/g。
Compared with the existing activated carbon carrier, the unmodified alumina or the modified alumina is adopted as the carrier, so that the stability is better, the inactivation is not easy, and the selectivity of the product is higher.
The chloropyridine hydrodechlorination catalyst comprises an active component, wherein the active component is Co oxide and/or Pt oxide. The oxide of Co is not particularly required in the present invention, and any oxide of Co known in the art may be used; the oxide of Pt is not particularly required in the present invention, and any oxide of Pt known in the art can be used.
In the present invention, the loading amount of Co in the active component is preferably 30 wt% or less, more preferably 15 wt% or less; the supported amount of Pt in the active component is preferably 15 wt% or less, more preferably 3 wt% or less. In the present invention, the loading amount refers to the mass percentage of Co and/or Pt in the support. When the active components are Co oxide and Pt oxide, the mass ratio of the Co to the Pt is preferably (2-20): 1, more preferably (5-18): 1, and most preferably (6-15): 1.
The catalyst of the invention takes alumina as a carrier and takes Co oxide and/or Pt oxide as active components, and the obtained catalyst not only has good stability, catalytic activity and selectivity, but also can realize the continuous production of 2, 3-dichloropyridine and 2,3,5, 6-tetrachloropyridine in a fixed bed reactor.
The invention provides a preparation method of a chloropyridine hydrodechlorination catalyst in the scheme,
A. when the active component is Co oxide, the method comprises the following steps:
dipping an alumina carrier into a Co precursor solution, and sequentially drying and roasting the alumina carrier obtained after dipping to obtain a chloropyridine hydrodechlorination catalyst;
B. when the active component is an oxide of Pt, the method comprises the following steps:
dipping an alumina carrier into a chloroplatinic acid solution, and sequentially drying and roasting the alumina carrier obtained after dipping to obtain a chloropyridine hydrodechlorination catalyst;
C. when the active components are Co oxide and Pt oxide, the method comprises the following steps:
(1) dipping an alumina carrier into a Co precursor solution, and drying and roasting the alumina carrier obtained after dipping in sequence to obtain a Co-loaded catalyst precursor;
(2) and (3) dipping the Co-loaded catalyst precursor into a chloroplatinic acid solution, and drying and roasting the solid obtained after dipping in sequence to obtain the chloropyridine hydrodechlorination catalyst.
The preparation process of the chloropyridine hydrodechlorination catalyst when the active component is an oxide of Co, discussed below, comprises the following steps:
and (3) dipping the alumina carrier into a Co precursor solution, and drying and roasting the alumina carrier obtained after dipping in sequence to obtain the chloropyridine hydrodechlorination catalyst.
In the invention, the precursor solution of Co is preferably a cobalt chloride solution or a cobalt nitrate solution, and the content of Co in the precursor solution of Co corresponds to the content of Co in the active component in the final catalyst. The concentration of the Co precursor solution is not particularly required, and the Co precursor solution preferably satisfies the condition that the alumina carrier can be completely immersed in the Co precursor solution and can be completely absorbed by the alumina carrier. In the present invention, when the alumina carrier needs to be modified, the alumina carrier is preferably modified before impregnation, and the modification method is already described in the section of the chloropyridine hydrodechlorination catalyst, and is not described herein again.
In the present invention, the temperature of the impregnation is preferably room temperature, and the time of the impregnation is preferably such that the alumina can completely absorb the Co precursor solution.
In the invention, the drying temperature is preferably 110 ℃, and the drying time is preferably 3-8 h; the roasting temperature is preferably 300-600 ℃, more preferably 350-550 ℃, and most preferably 400-500 ℃; the roasting heat preservation time is preferably 1-5 hours, and more preferably 2-4 hours. The present invention preferably performs the firing in an air atmosphere. In the roasting process, a precursor of Co is decomposed and forms an oxide form of Co; in addition, crystal water in the catalyst can be removed by roasting, a certain specific surface area, pore structure and strength are obtained, the interaction between the carrier and the active component is enhanced, and a stable active center is obtained.
The preparation process of the chloropyridine hydrodechlorination catalyst when the active component is an oxide of Pt, discussed below, comprises the following steps:
and (3) dipping the alumina carrier into a chloroplatinic acid solution, and sequentially drying and roasting the alumina carrier obtained after dipping to obtain the chloropyridine hydrodechlorination catalyst.
In the present invention, the content of Pt in the chloroplatinic acid solution corresponds to the content of Pt in the active component in the final catalyst. The concentration of the chloroplatinic acid solution is not particularly required, and the chloroplatinic acid solution preferably meets the requirement that the alumina carrier can be completely immersed and can be completely absorbed by the alumina carrier. The pH value of the chloroplatinic acid solution is not particularly required, and is preferably 0.5. In the present invention, when the alumina carrier needs to be modified, the alumina carrier is preferably modified before impregnation, and the modification method is already described in the section of the chloropyridine hydrodechlorination catalyst, and is not described herein again.
In the present invention, the temperature of the impregnation is preferably room temperature, and the time of the impregnation is preferably such that the alumina can completely absorb the chloroplatinic acid solution.
In the invention, the drying temperature is preferably 110 ℃, and the drying time is preferably 3-8 h; the roasting temperature is preferably 300-600 ℃, more preferably 350-550 ℃, and most preferably 400-500 ℃; the roasting heat preservation time is preferably 1-5 hours, and more preferably 2-4 hours. The present invention preferably performs the firing in an air atmosphere. In the roasting process, the chloroplatinic acid solution is decomposed into an oxide form of Pt; in addition, crystal water in the catalyst can be removed by roasting, a certain specific surface area, pore structure and strength are obtained, the interaction between the carrier and the active component is enhanced, and a stable active center is obtained.
The preparation process of the chloropyridine hydrodechlorination catalyst, when the active components are Co oxide and Pt oxide, is discussed below, comprises the following steps:
(1) dipping an alumina carrier into a Co precursor solution, and drying and roasting the alumina carrier obtained after dipping in sequence to obtain a Co-loaded catalyst precursor;
(2) and (3) dipping the Co-loaded catalyst precursor into a chloroplatinic acid solution, and drying and roasting the solid obtained after dipping in sequence to obtain the chloropyridine hydrodechlorination catalyst.
In the present invention, the preparation conditions in the step (1) are the same as those in the case where the active component is an oxide of Co, and thus, the details thereof are not repeated.
In the present invention, the preparation conditions in the step (2) are the same as those in the case where the active component is an oxide of Pt, and thus, the details thereof are omitted.
When the alumina support needs to be modified, the modification is only performed before the impregnation in step (1), and the additional modification in step (2) is not required.
The invention provides an application of chloropyridine in a hydrodechlorination reaction catalyzed by the chloropyridine hydrodechlorination catalyst or the chloropyridine hydrodechlorination catalyst prepared by the preparation method in the scheme.
In the present invention, the hydrodechlorination reaction is preferably carried out in a fixed bed reactor. The fixed bed reactor is not particularly limited in the present invention, and any fixed bed reactor known in the art may be used.
In the present invention, the manner of application preferably includes:
activating the chloropyridine hydrodechlorination catalyst in a fixed bed reactor to obtain an activated catalyst;
mixing hydrogen and chloropyridine, and vaporizing the obtained mixture to obtain a mixed gas;
and introducing the mixed gas into a fixed bed reactor filled with an activated catalyst, carrying out hydrodechlorination reaction, and carrying out gas-liquid separation to obtain a chloropyridine hydrodechlorination product.
The invention carries out activation treatment on the chloropyridine hydrodechlorination catalyst in a fixed bed reactor to obtain the activated catalyst.
In the present invention, before the activation treatment, the present invention preferably further comprises purging the air in the fixed bed reactor with nitrogen. In the present invention, the process of the activation treatment is preferably: and filling the chloropyridine hydrodechlorination catalyst into a fixed bed reactor, introducing hydrogen into the fixed bed reactor, wherein the hydrogen flow is over 400-2000 mL/min, heating the chloropyridine hydrodechlorination catalyst to 200-400 ℃, and keeping the temperature for 3-5 h. The loading amount of the chloropyridine hydrodechlorination catalyst is not particularly required, and is preferably determined according to the space velocity of the hydrodechlorination reaction.
In the activation treatment process, the Co oxide and/or the Pt oxide in the catalyst is reduced into simple substance Co and/or Pt by hydrogen and is used as an active substance for catalytic hydrodechlorination reaction.
The invention mixes hydrogen and chloropyridine, and vaporizes the mixture to obtain the mixed gas.
Before mixing, the invention preferably also comprises preheating the hydrogen and melting the chloropyridine respectively to obtain preheated hydrogen and melted chloropyridine. In the invention, the preheating temperature is preferably 100-250 ℃. The method has no special requirement on the melting temperature, and can ensure that the chloropyridine is completely melted. In the present invention, the chloropyridine is preferably 2,3, 6-trichloropyridine, 2,3, 5-trichloropyridine or pentachloropyridine. In the invention, the molar ratio of the hydrogen to the chloropyridine is preferably 10-30: 1, more preferably 10 to 20: 1.
In the present invention, the vaporization is preferably carried out in a vaporizer. In the present invention, the vaporization rate of the chloropyridine is preferably 80 to 100%, and more preferably 100%.
After the mixed gas is obtained, the mixed gas is introduced into a fixed bed reactor filled with an activated catalyst to carry out hydrogenation dechlorination reaction, and the chloropyridine hydrogenation product is obtained after gas-liquid separation.
In the invention, the temperature of the hydrodechlorination reaction is preferably 140-300 ℃, and more preferably 170-260 ℃; the mass space velocity of the hydrodechlorination reaction is preferably 0.05-0.1 h-1More preferably 0.06-0.85 h-1(ii) a The pressure of the hydrodechlorination reaction is preferably 0.1-5 MPa, and more preferably 0.5-1 MPa. The space velocity of the hydrodechlorination reaction of the present invention refers to the feed amount per mass of catalyst. The inventionIn the process of the hydrogenation and dechlorination reaction, the chloropyridine is subjected to the hydrogenation and dechlorination reaction under the action of hydrogen and a catalyst to obtain a liquid chloropyridine hydrogenation and dechlorination product.
After the hydrodechlorination reaction is finished, the gas-liquid separation is preferably carried out on the obtained system in the invention, so that a chloropyridine hydrodechlorination product is obtained. The present invention preferably performs gas-liquid separation in a gas-liquid separator. The present invention has no special requirement on the gas-liquid separation conditions, and the gas-liquid separation conditions known in the art can be adopted. After the gas-liquid separation is completed, the invention preferably also comprises purifying the obtained liquid to obtain a chloropyridine hydrodechlorination product. The purification process is not particularly required in the present invention, and a purification process well known in the art may be used. In the invention, when the chloropyridine is 2,3, 6-trichloropyridine or 2,3, 5-trichloropyridine, the hydrodechlorination product is 2, 3-dichloropyridine; when the chloropyridine is pentachloropyridine, the hydrodechlorination product is 2,3,5, 6-tetrachloropyridine.
The chloropyridine hydrodechlorination catalyst provided by the present invention, the preparation method and the application thereof are described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
The carrier of the catalyst is unmodified alumina, the active component is oxide of Pt, and the mass loading of Pt is 1.1%.
The preparation method comprises the following steps:
dissolving 1.335g of chloroplatinic acid in deionized water to prepare 50mL of chloroplatinic acid solution, then adding 0.65g of hydrochloric acid to adjust the pH value of the chloroplatinic acid solution to 0.5, uniformly mixing 44g of gear-shaped alumina carrier and the chloroplatinic acid solution, soaking at room temperature for 20min, drying the soaked solution in a drying oven at 110 ℃ for 4h after the soaked solution is completely absorbed, and then roasting the dried solution, wherein the specific roasting process is as follows: raising the temperature from room temperature for 4h to 450 ℃, preserving the temperature for 3h, and then naturally cooling to obtain the chloropyridine hydrodechlorination catalyst which is marked as catalyst 1.
Example 2
The carrier of the catalyst is unmodified alumina, the active components are Pt oxide and Co oxide, the mass percentage of Pt is 1.1%, and the loading amount of Co is 15 wt%.
The preparation method comprises the following steps:
step one, dissolving 37.34g of cobalt chloride hexahydrate in deionized water to prepare 50mL of Co precursor solution, uniformly mixing 44g of gear-shaped alumina carrier and the Co precursor solution, soaking at room temperature for 20min, drying the impregnated solution in a drying oven at 110 ℃ for 4h after the impregnated solution is completely absorbed, and then roasting the dried impregnated solution, wherein the specific roasting process is as follows: raising the temperature from room temperature to 450 ℃ for 4h, preserving the temperature for 3h, and then naturally cooling to obtain a Co-loaded catalyst precursor;
step two, dissolving 1.335g of chloroplatinic acid in deionized water to prepare 40mL of chloroplatinic acid solution, uniformly mixing the Co-loaded catalyst precursor prepared in the step one with the chloroplatinic acid solution, soaking at room temperature for 20min, drying the impregnated solution in a drying oven at 110 ℃ for 4h after the impregnated solution is completely absorbed, and then roasting the dried impregnated solution, wherein the specific roasting process is as follows: raising the temperature to 450 ℃ within 4h, preserving the heat for 3h, and then naturally cooling to obtain the chloropyridine hydrodechlorination catalyst which is marked as catalyst 2.
Example 3
The carrier of the catalyst is unmodified alumina, the active component is Co oxide, and the load of Co is 15 wt%.
The preparation method comprises the following steps:
dissolving 37.34g of cobalt chloride in deionized water to prepare 50mL of Co precursor solution, uniformly mixing 44g of gear-shaped alumina carrier and the Co precursor solution, soaking at room temperature for 20min, drying the impregnated solution in a drying oven at 110 ℃ for 4h after the impregnated solution is completely absorbed, and then roasting the impregnated solution, wherein the specific roasting process is as follows: raising the temperature from room temperature for 4h to 450 ℃, preserving the temperature for 3h, and then naturally cooling to obtain the chloropyridine hydrodechlorination catalyst which is marked as catalyst 3.
Example 4
The carrier of the catalyst is modified alumina, the active components are Pt oxide and Co oxide, the mass percentage of Pt is 3%, and the load of Co is 15 wt%.
The preparation method comprises the following steps:
weighing 0.78g of calcium nitrate, dissolving in deionized water to prepare 50mL of solution, uniformly mixing 44g of gear-shaped alumina carrier and the calcium nitrate solution, standing at room temperature for 30min, drying in a 110 ℃ oven for 4h, roasting, heating to 450 ℃ for 4h, keeping the temperature for 3h, and naturally cooling to obtain the calcium-modified alumina carrier;
step two, performing; dissolving 3.64g of chloroplatinic acid in deionized water to prepare 50mL of chloroplatinic acid solution, uniformly mixing the alumina carrier modified by calcium and the precursor solution of Pt, soaking at room temperature for 20min, drying the impregnation solution in a drying oven at 110 ℃ for 4h after the impregnation solution is completely absorbed, and then roasting the impregnation solution, wherein the specific roasting process is as follows: raising the temperature to 450 ℃ for 4h, preserving the temperature for 3h, and then naturally cooling to obtain a catalyst precursor loaded with Pt;
step three, dissolving 37.34g of cobalt chloride hexahydrate in deionized water to prepare a precursor solution of 50mL of Co, uniformly mixing the catalyst precursor loaded with Pt prepared in the step one with the cobalt chloride solution, soaking at room temperature for 20min, drying the catalyst precursor in a drying oven at 110 ℃ for 4h after the soaking solution is completely absorbed, and then roasting the catalyst precursor, wherein the specific roasting process is as follows: raising the temperature from room temperature for 4h to 450 ℃, preserving the temperature for 3h, and then naturally cooling to obtain the chloropyridine hydrodechlorination catalyst which is marked as catalyst 4.
Example 5
The difference from example 4 is that the alumina has not been modified and the chloropyridine hydrodechlorination catalyst obtained is designated as catalyst 5.
Application example 1
2, 3-dichloropyridine is continuously produced by using the catalyst 1 prepared in the example 1 to catalyze and reduce 2,3, 6-trichloropyridine, and the method comprises the following steps:
filling a catalyst 1 into a fixed bed reactor, and then introducing nitrogen into the fixed bed reactor filled with the catalyst until air in the fixed bed reactor is completely exhausted;
step two, activating the catalyst filled in the fixed bed reactor in the step one to obtain an activated catalyst, wherein the activating process is as follows: and (3) introducing hydrogen into the fixed bed reactor, and heating the catalyst to 250 ℃ and preserving the temperature for 4h under the condition that the hydrogen flow is 2000 mL/min.
Step three, adopting 2,3, 6-trichloropyridine as a raw material, mixing a molten raw material solution with hydrogen (the molar ratio of the hydrogen to the raw material is 16:1) preheated to 130 ℃, heating to completely vaporize the mixture to obtain a mixed gas, then continuously introducing the mixed gas into the fixed bed reactor filled with the activated catalyst in the step two, wherein the gas pressure in the fixed bed reactor is 0.8MPa, the reaction temperature is 240 ℃, and the reaction mass space velocity is 0.07h-1Under the condition of (1), carrying out hydrodechlorination reaction on the raw material by using a catalyst to obtain a reaction material. And step four, feeding the reaction materials into a gas-liquid separator for gas-liquid separation, and purifying the separated liquid to obtain the 2, 3-dichloropyridine.
Application example 2
The difference from application example 1 is that the gas pressure in the fixed bed reactor in the third step is 1.6MPa, and the reaction temperature is 233 ℃.
Application example 3
The difference from application example 1 is that the gas pressure in the fixed bed reactor in the third step is 1.8MPa, and the reaction temperature is 233 ℃.
Application example 4
The difference from application example 1 is that the gas pressure in the fixed bed reactor in the third step is 0.1 MPa.
Application example 5
The difference from application example 1 is that the gas pressure in the fixed bed reactor in the third step is 2.0MPa, and the reaction temperature is 233 ℃.
Application example 6
2, 3-dichloropyridine is continuously produced by using the catalyst 2 prepared in the example 2 to catalyze and reduce 2,3, 6-trichloropyridine, and the method comprises the following steps:
filling a catalyst 2 into a fixed bed reactor, and then introducing nitrogen into the fixed bed reactor filled with the catalyst until air in the fixed bed reactor is completely exhausted;
step two, activating the catalyst filled in the fixed bed reactor in the step one to obtain an activated catalyst, wherein the activating process is as follows: and (3) introducing hydrogen into the fixed bed reactor, and heating the catalyst to 308 ℃ and preserving the temperature for 4 hours under the condition that the hydrogen flow is 400 mL/min.
Step three, adopting 2,3, 6-trichloropyridine as a raw material, mixing a molten raw material solution with hydrogen (the molar ratio of the hydrogen to the raw material is 12:1) preheated to 150 ℃, heating to 190 ℃ to completely vaporize the mixture to obtain a mixed gas, continuously introducing the mixed gas into the fixed bed reactor filled with the activated catalyst in the step two, wherein the gas pressure in the fixed bed reactor is 0.1MPa, the reaction temperature is 205 ℃, and the reaction mass space velocity is 0.07h-1Under the condition of (1), carrying out hydrodechlorination reaction on the raw material by using a catalyst to obtain a reaction material.
And step four, feeding the reaction materials into a gas-liquid separator for gas-liquid separation, and purifying the separated liquid to obtain the 2, 3-dichloropyridine.
Application example 7
The difference from application example 6 is that the activation temperature in step one is 250 ℃, the hydrogen flow rate is 2000mL/min, and the reaction temperature in the fixed bed reactor in step three is 170 ℃.
Application example 8
The difference from application example 6 is that the activation temperature in step one is 250 ℃, the hydrogen flow rate is 2000mL/min, and the reaction temperature in the fixed bed reactor in step three is 200 ℃.
Application example 9
The difference from application example 6 is that the catalyst used was catalyst 3.
Application example 10
2, 3-dichloropyridine is continuously produced by catalytic reduction of 2,3, 5-trichloropyridine by using the catalyst 4 prepared in example 4, and the method comprises the following steps:
filling a catalyst 4 into a fixed bed reactor, and then introducing nitrogen into the fixed bed reactor filled with the catalyst until air in the fixed bed reactor is completely exhausted;
step two, activating the catalyst filled in the fixed bed reactor in the step one to obtain an activated catalyst, wherein the activating process is as follows: and (3) introducing hydrogen into the fixed bed reactor, and heating the catalyst to 250 ℃ and preserving the temperature for 4h under the condition that the hydrogen flow is 2000 mL/min.
Step three, adopting 2,3, 5-trichloropyridine as a raw material, mixing the molten raw material liquid with hydrogen (the molar ratio of the hydrogen to the raw material is 10:1) preheated to 200 ℃, heating to 200 ℃ to completely vaporize the hydrogen to obtain mixed gas, then continuously introducing the mixed gas into the fixed bed reactor filled with the activated catalyst in the step two, wherein the gas pressure in the fixed bed reactor is 2.0MPa, the reaction temperature is 240 ℃, and the reaction mass space velocity is 0.07h-1Under the condition of (1), carrying out hydrodechlorination reaction on the raw material by using a catalyst to obtain a reaction material.
And step four, feeding the reaction materials into a gas-liquid separator for gas-liquid separation, and purifying the separated liquid to obtain the 2, 3-dichloropyridine.
Application example 11
The difference from application example 10 was that catalyst 5 was used.
Application example 12
The catalyst 2 prepared in the example 2 is used for catalyzing and reducing pentachloropyridine to continuously produce 2,3,5, 6-tetrachloropyridine, and the method comprises the following steps:
filling a catalyst 2 into a fixed bed reactor, and then introducing nitrogen into the fixed bed reactor filled with the catalyst until air in the fixed bed reactor is completely exhausted;
step two, activating the catalyst filled in the fixed bed reactor in the step one to obtain an activated catalyst, wherein the activating process is as follows: and (3) introducing hydrogen into the fixed bed reactor, and heating the catalyst to 250 ℃ and preserving the temperature for 4h under the condition that the hydrogen flow is 2000 mL/min.
Step three, adopting pentachloropyridine as a raw material, mixing the melted raw material liquid with hydrogen (the molar ratio of the hydrogen to the raw material is 30:1) preheated to 220 ℃, heating to 198 ℃ to completely vaporize to obtain mixed gas, and then adding the mixed gas into the step twoContinuously introducing mixed gas into a fixed bed reactor filled with the activated catalyst, wherein the gas pressure in the fixed bed reactor is 0.5MPa, the reaction temperature is 250 ℃, and the reaction mass space velocity is 0.1h-1Under the condition of (1), carrying out hydrodechlorination reaction on the raw material by using a catalyst to obtain a reaction material.
And step four, sending the reaction materials into a gas-liquid separator for gas-liquid separation, and purifying the separated liquid to obtain the 2,3,5, 6-tetrachloropyridine.
Application example 13
The difference from application example 12 is that the reaction pressure in the fixed bed reactor in the third step was 3.5 MPa.
Application example 14
The difference from application example 12 is that the reaction temperature in the fixed bed reactor in the third step was 240 ℃.
Application example 15
The difference from application example 12 is that the reaction temperature in the fixed bed reactor in the third step was 220 ℃.
The conversion of the reactant (chloropyridine) and the selectivity to the product in application examples 1 to 15 are specifically shown in Table 1.
TABLE 1 conversion of reactants and selectivity to product for application examples 1-15
| Numbering | Conversion of reactants/%) | Product selectivity/%) |
| Application example 1 | 85.03 | 84.04 |
| Application example 2 | 85.68 | 82.76 |
| Application example 3 | 86.74 | 78.72 |
| Application example 4 | 83.53 | 84.04 |
| Application example 5 | 98.06 | 66.00 |
| Application example 6 | 88.30 | 72.06 |
| Application example 7 | 98.45 | 62.04 |
| Application example 8 | 99.31 | 60.94 |
| Application example 9 | 88.12 | 71.77 |
| Application example 10 | 84.39 | 85.05 |
| Application example 11 | 80.22 | 74.38 |
| Application example 12 | 86.95 | 80.26 |
| Application example 13 | 85.79 | 82.30 |
| Application example 14 | 85.01 | 83.04 |
| Application example 15 | 83.95 | 85.76 |
As can be seen from Table 1, the catalyst of the present invention is used for catalyzing the hydrodechlorination of chloropyridine, and the conversion rate of the reactants is high, which indicates that the catalyst has high catalytic activity and high selectivity to the product.
Catalysts 2 and 4 were selected and used in a life test, and 2,3, 6-trichloropyridine was used as a starting material to carry out a reaction under the conditions of application example 1, and the results are shown in table 2.
TABLE 2 service life of the catalyst
| Numbering | Life/h |
| Catalyst 2 | 1700 |
| Catalyst 4 | 1000 |
As can be seen from Table 2, the chloropyridine hydrodechlorination catalyst provided by the invention has a long service life, which indicates that the catalyst has good stability.
The embodiments show that the catalyst provided by the invention has good stability, catalytic activity and selectivity, can realize continuous production of 2, 3-dichloropyridine and 2,3,5, 6-tetrachloropyridine in a fixed bed reactor, has no solvent or acid binding agent in the whole process, has high selectivity to the 2, 3-dichloropyridine and the 2,3,5, 6-tetrachloropyridine, has long service life, and is suitable for industrial scale-up production.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. The application of the chloropyridine in the hydrodechlorination reaction under the catalysis of the chloropyridine hydrodechlorination catalyst is characterized in that the chloropyridine hydrodechlorination catalyst comprises a carrier and an active component loaded on the carrier, wherein the carrier comprises alumina, and the active component is Co oxide;
the application mode comprises the following steps:
activating the chloropyridine hydrodechlorination catalyst in a fixed bed reactor to obtain an activated catalyst;
mixing hydrogen and chloropyridine, and vaporizing the obtained mixture to obtain a mixed gas;
introducing the mixed gas into a fixed bed reactor filled with an activated catalyst, carrying out hydrodechlorination reaction, and carrying out gas-liquid separation to obtain a chloropyridine hydrodechlorination product;
the temperature of the hydrodechlorination reaction is 140-300 ℃, the pressure is 0.1-5 MPa, and the mass space velocity is 0.05-0.1 h-1。
2. The use according to claim 1, wherein the loading of Co in the active component is below 30 wt%.
3. The use according to claim 2, wherein the loading of Co in the active component is below 15 wt%.
4. The use according to any one of claims 1 to 3, wherein the alumina is unmodified alumina or modified alumina, and the modified alumina is obtained by modifying calcium, magnesium or potassium.
5. Use according to claim 1, characterized in that the preparation process of the chloropyridine hydrodechlorination catalyst comprises the following steps:
and (3) dipping the alumina carrier into a Co precursor solution, and drying and roasting the alumina carrier obtained after dipping in sequence to obtain the chloropyridine hydrodechlorination catalyst.
6. The application of claim 5, wherein the roasting temperature is 300-600 ℃, and the holding time is 1-5 h.
7. Use according to claim 5, wherein the Co precursor solution comprises a cobalt chloride solution or a cobalt nitrate solution.
8. Use according to claim 1, characterized in that the hydrodechlorination reaction is carried out in a fixed bed reactor.
9. Use according to claim 1, characterized in thatCharacterized in that the temperature of the hydrodechlorination reaction is 170-260 ℃, the pressure is 0.5-1 MPa, and the mass space velocity is 0.06-0.85 h-1。
10. The use according to claim 1, wherein the vaporization rate of the chloropyridine during vaporization is 80 to 100%.
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