Method for improving stability of catalyst for producing halogenated propylene

Abstract

The invention discloses a method for improving the stability of a catalyst for producing halogenated propylene, which comprises the following steps: taking chlorofluoropropane as a raw material, and carrying out dehydrochlorination reaction under the action of an activated carbon-based catalyst to obtain halogenated propylene, the activated carbon-based catalyst is obtained by roasting and constant-temperature ultrasonic pickling of activated carbon in sequence; the step of constant-temperature ultrasonic pickling comprises the steps of acid liquor preparation, constant-temperature ultrasonic dipping, washing and drying. The active carbon-based catalyst is used in the production process of halogenated propylene, can reduce the reaction temperature, improve the stability and the service life of the catalyst, keeps excellent reaction conversion rate and selectivity, and is very suitable for industrial application.

Description

Technical Field

[0001] The present invention relates to the preparation of fluoroolefins, and particularly to a method for improving the stability of a catalyst during the production of halopropene. Background Art

[0002] Common halopropenes include 2,3,3,3-tetrafluoropropene (HFO-1234yf), 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd), and 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya). Especially HCFO-1224yd and HFO-1234yf hardly damage the atmospheric ozone layer and have extremely little impact on global warming (GWP < 1). Their excellent environmental performance gives them the potential to replace existing refrigerants and has high research value.

[0003] Currently, haloolefins can be obtained by liquid-phase preparation or gas-solid phase preparation methods. In the liquid-phase preparation method, Chinese patent CN113527040A discloses a method for preparing haloolefins using a metal base catalyst and a phase transfer catalyst. This method has high conversion rate and selectivity, but does not disclose catalyst stability data. Asahi Glass patent CN108473397A discloses a method for preparing 1-chloro-2,3,3,3-tetrafluoropropene by dehydrochlorination reaction of 1,2-dichloro-2,3,3,3-tetrafluoropropane in the liquid phase in the presence of a base. Under continuous conditions, the reactant conversion rate is 95.8% and the selectivity is 95%, but this method also does not disclose catalyst stability data.

[0004] In fact, in the actual reaction process of the liquid-phase reaction, not only an additional solvent needs to be added, resulting in additional costs, but also there will be a large amount of alkaline wastewater and unreacted raw material mixtures, which is not conducive to the subsequent separation and purification of reactants and the environmental protection requirements in the industrialization process. The gas-solid phase reaction can avoid the above problems.

[0005] As a method for preparing 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd), Japanese AGC Corporation patent CN109563010A discloses a method of using an activated carbon-based catalyst simultaneously loaded with Pd and Cl to react HCFO-1214ya with H2 to generate HCFO-1224yd. During the reaction process, the temperature of the catalyst bed gradually decreases with the deterioration of the catalyst, and additional heating is required to maintain the temperature required for the reaction. Although this method reduces the selectivity of by-products, the overall yield of HCFO-1224yd is relatively low, and the catalyst activity decreases significantly in the later stage. Moreover, the catalyst contains precious metals, and hydrogen needs to be added during the reaction process, which not only causes the problem of increased production costs, but also there may be safety hazards when hydrogen participates in the reaction.

[0006] Zhejiang Sanmei Patent CN109438170A discloses a preparation method of HFO-1234yf, which includes the step of directly dehydrochlorinating 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) in the gas phase to obtain HFO-1234yf. In this step, at least one of CsCl / MgF2, SbF5 / C, and Cr2O3-Ni / C is used as the catalyst, the reaction temperature is 320-380°C, the reaction pressure is 2-10 bar, and the reaction contact time is 100-180 s. Its reaction yield at 320°C is only 78.2%, and this patent does not disclose stability data. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention proposes a method for improving the stability of a catalyst for producing halopropene, so that the halopropene has good conversion rate, selectivity, and excellent catalyst stability.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A method for improving the stability of a catalyst for producing halopropene, the method includes: using fluorochloropropane as a raw material, and obtaining halopropene through a dehydrochlorination reaction under the action of an activated carbon-based catalyst; the activated carbon-based catalyst is obtained by roasting activated carbon and then subjecting it to constant-temperature ultrasonic pickling.

[0010] When the fluorochloropropane is 3,3,3-trichloro-1,1,1,2-tetrafluoropropane, the halopropene is 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya); when the fluorochloropropane is 3,3-dichloro-1,1,1,2-tetrafluoropropane, the halopropene is 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd); when the fluorochloropropane is 1-chloro-2,3,3,3-tetrafluoropropane, the halopropene is 2,3,3,3-tetrafluoropropene (HFO-1234yf).

[0011] The present invention has found through research that: the fluorochloropropane in the present invention mainly follows the Knudsen diffusion model in activated carbon, so the pore size of the activated carbon has a significant impact on the diffusion efficiency of gas molecules. The present invention increases the pore size of the activated carbon through roasting, reduces the diffusion resistance of gas molecules in the pores of the activated carbon, thereby significantly improving the reaction activity; at the same time, it also makes the product molecules more likely to diffuse out of the pores, thereby improving the reaction stability. It should be noted that the roasting treatment also increases the specific surface area of the activated carbon, laying a foundation for the improvement of the intensity of a sufficient number of active sites during the ultrasonic pickling process.

[0012] Further research of the present invention has found that: in the dehydrochlorination reaction, the strong acidic sites present in activated carbon not only have the ability to adsorb reactants, but also show a strong affinity for the chlorine atoms in the reactants; the adsorbed chlorine atoms can promote the cleavage of C-Cl and C-H bonds in the reactants, thus promoting the progress of the dehydrochlorination reaction. By expanding the pore size and specific surface area of activated carbon and then performing constant-temperature ultrasonic pickling, the present invention has successfully enhanced a sufficient amount of strong acidic reaction sites (the desorption temperature of the basic probe molecule NH3 adsorbed on the acidic sites of the solid catalyst is greater than 400 °C), further improving the reaction activity and lifespan. Therefore, only by first calcining and then performing constant-temperature ultrasonic pickling can the strength of the active sites of activated carbon be fully enhanced, thereby achieving a more excellent reaction effect.

[0013] The activated carbon of the present invention is selected from coconut shell activated carbon, coal-based activated carbon or wood-based activated carbon, and the specific surface area is 500-1200 m 2 / g; the higher specific surface area can improve the adsorption of activated carbon for reactants, further improve the reaction conversion rate, and is more conducive to the occurrence of the reaction. Preferably, the activated carbon is selected from coconut shell activated carbon with high hardness and good adsorption performance, and the specific surface area is 1000-1200 m 2 / g.

[0014] The activated carbon treated by calcination and ultrasonic pickling in sequence has an increased specific surface area of 10%-120%, an increased pore volume of 10%-100%, and an increased pore diameter of 10%-100%. At the same time, the strength of the strong acidic sites of the catalyst is enhanced, and the strength of the strong basic sites is weakened.

[0015] The calcination of the activated carbon of the present invention is carried out in a calcination atmosphere, and the calcination atmosphere is a mixed gas of nitrogen and oxygen. By gas volume, the oxygen content is 1%-10%; preferably, the oxygen content is 5%-10%. The calcination temperature of the activated carbon is 200-500 °C, and the calcination time is 1-6 h; preferably, the calcination temperature is 300-350 °C, and the calcination time is 3-4 h. By calcining the activated carbon, not only can the specific surface area, pore volume and pore diameter of the activated carbon be effectively increased, but also the surface ash, moisture and other impurities generated during the production process can be reduced, improving the catalytic activity and stability.

[0016] The steps of the constant-temperature ultrasonic pickling in the present invention include: acid solution preparation, constant-temperature ultrasonic impregnation, water washing and drying; the acid solution is a solution obtained by mixing a hydrochloric acid solution with at least one selected from a nitric acid solution, a phosphoric acid solution or an acetic acid solution, and the molar concentration of the acid solution is 0.1-10% mol / L. Among them, the molar concentration of the hydrochloric acid solution, the nitric acid solution, the phosphoric acid solution or the acetic acid solution is 0.1-10% mol / L, preferably 0.5%-5% mol / L. Using the mixed acid solution for pickling can minimize the content of various oxygen-containing groups and other impurities, reduce the occurrence of side reactions, and improve the stability of the activated carbon catalyst.

[0017] The temperature of constant-temperature ultrasonic impregnation is 40-80°C, and the impregnation time is 2-8 h; preferably, the impregnation temperature is 50-60°C, and the impregnation time is 4-6 h; the ultrasonic power is 400 W-800 W, preferably 500-600 W. Constant-temperature ultrasonic impregnation helps to increase the specific surface area, pore volume and pore diameter of the catalyst, and can effectively change the acid-base sites on the catalyst surface, enhance the strength of acidic sites, reduce the strength of basic sites, and contribute to the uniform distribution on the activated carbon surface. During constant-temperature ultrasonic impregnation, the acid solution concentration and treatment time should be appropriate. Too high an acid solution concentration or too long a pickling time may damage the structure of the activated carbon itself and is not conducive to the occurrence of the reaction.

[0018] After the activated carbon is impregnated by constant-temperature ultrasonic, it is washed with water (such as deionized water, distilled water) until the activated carbon is neutral. Then it is dried, the drying temperature is 60-100°C, and the drying time is 6-12 h; preferably, the drying temperature is 80-100°C, and the drying time is 10-12 h. The drying method can adopt common methods, such as oven drying, etc.

[0019] In order to further improve the catalytic activity of the catalyst, an active component is loaded on the activated carbon after calcination and constant-temperature ultrasonic pickling. The active component is selected from at least one of strontium, barium, calcium, cesium or magnesium. Based on the mass of the activated carbon, the loading amount of the active component is 0.5-10 wt%, preferably 0.5-5.0 wt%.

[0020] The loading method of the active component can adopt common methods in the art, such as the impregnation method. First, a soluble salt solution of the active component is prepared, and the activated carbon after constant-temperature ultrasonic pickling is impregnated in the soluble salt solution according to the loading amount. After impregnation for a certain time (such as 10-12 h), the activated carbon is taken out and dried. The drying temperature is 60-110°C, preferably 90-110°C, to obtain an activated carbon-based catalyst for the preparation of halopropene.

[0021] Specifically, in the presence of any of the aforementioned activated carbon-based catalysts, hydrochlorofluoropropane is subjected to dehydrochlorination reaction to obtain hydrochlorofluoropropene. The reaction temperature is 250 - 350 °C, and the reaction pressure is atmospheric pressure. Preferably, the reaction temperature is 280 - 320 °C. Within this temperature range, on the basis of ensuring that the raw material conversion rate and product selectivity are ≥ 80%, excellent catalyst stability can be obtained, and the catalyst efficiency is above 90 g product / g cat.

[0022] Before the reaction, the activated carbon-based catalyst is pretreated by introducing an inert gas (such as nitrogen). The pretreatment temperature is 200 - 400 °C, preferably 320 - 350 °C, the pretreatment time is 3 - 6 h, preferably 3 - 4 h; the flow rate of the inert gas is 20 - 100 mL / min, preferably 40 - 60 mL / min. Nitrogen pretreatment can remove the moisture in the catalyst and improve the reaction activity.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The activated carbon-based catalyst obtained by roasting and constant-temperature ultrasonic pickling of activated carbon in sequence in the present invention is used in the process of producing halopropene by dehydrochlorination of hydrochlorofluoropropane. Not only is the catalyst treatment method simple, but also on the premise of ensuring the reaction conversion rate and selectivity, the catalyst stability can be significantly improved, the reaction temperature can be reduced, thereby reducing the production cost, and significantly improving the market competition advantage of the process route. Description of the Drawings

[0025] Figure 1 It is the NH3-TPD spectra of the catalysts obtained in Preparation Examples 4, 8, 10, 12 of the present invention and commercially available activated carbon;

[0026] Figure 2 It is the CO2-TPD spectra of the catalysts obtained in Preparation Examples 4, 8, 10, 12 of the present invention and commercially available activated carbon. Detailed Embodiments

[0027] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternative, improved, and equivalent solutions that may be included within the scope of the claims.

[0028] The activated carbon raw material used in the following preparation examples and embodiments of the present invention is coconut shell activated carbon purchased from Shanghai Junpeng Company, with a mesh number of 8 - 16 meshes.

[0029] The stable operation time of the catalyst of the present invention refers to the time that can be sustained when the raw material conversion rate remains above 80% (inclusive) during the process of preparing halopropene by dehydrochlorination of fluorochloropropane. When the raw material conversion rate < 80%, the catalyst is considered deactivated. The catalyst efficiency refers to the mass of halopropene produced by a unit catalyst during stable operation.

[0030] Preparation Example 1

[0031] This preparation example is for the preparation of an activated carbon catalyst, which specifically includes the following steps:

[0032] (1) Activated carbon calcination: Weigh 15 g of activated carbon and place it in a porcelain boat. Place the porcelain boat in a tube furnace. Pass a nitrogen-oxygen mixture with an oxygen volume content of 1% into the tube furnace at a flow rate of 10 mL / min, and set the heating rate to 5 °C / min to raise the temperature to 200 °C, and calcine for 2 hours;

[0033] (2) Constant-temperature ultrasonic pickling treatment of activated carbon:

[0034] 1) Acid solution preparation: ① Solution 1: Measure 30 mL of hydrochloric acid solution with a concentration of 1 mol / L, and record it as Solution 1; ② Solution 2: Measure 30 mL of nitric acid solution with a concentration of 1 mol / L, and record it as Solution 2; ③ Solution mixing: Drop Solution 2 into Solution 1 through a peristaltic pump at a speed of 1 ml / min to obtain a mixed acid solution.

[0035] 2) Weigh 10 g of the calcined activated carbon and add it to the above mixed acid solution, and carry out constant-temperature ultrasonic impregnation for 12 hours. The constant-temperature is 40 °C and the ultrasonic power is 500 W.

[0036] 3) Pour out the mixed acid solution and wash the activated carbon with deionized water under normal-temperature ultrasonic conditions until it is neutral. The washed activated carbon is dried at 100 °C for 12 h to obtain the activated carbon catalyst, denoted as Cat 1.

[0037] Preparation Example 2

[0038] The operation of this preparation example is the same as that of Preparation Example 1, except that: in step (1), the calcination temperature of the activated carbon is increased to 300 °C, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 2.

[0039] Preparation Example 3

[0040] The operation of this preparation example is the same as that of Preparation Example 1, except that: in step (1), the calcination temperature of the activated carbon is increased to 500 °C, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 3.

[0041] Preparation Example 4

[0042] The operation of this preparation example is the same as that of Preparation Example 2, except that: in step (1), the calcination atmosphere of the activated carbon is changed to a nitrogen-oxygen mixture with an oxygen volume content of 5%, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 4.

[0043] Preparation Example 5

[0044] The operation of this preparation example is the same as that of Preparation Example 2, except that: in step (1), the calcination atmosphere of the activated carbon is changed to a nitrogen-oxygen mixture with an oxygen volume content of 10%, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 5.

[0045] Preparation Example 6

[0046] The operation of this preparation example is the same as that of Preparation Example 4, except that: in step (1), the calcination time of the activated carbon is increased to 4 hours, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 6.

[0047] Preparation Example 7

[0048] The operation of this preparation example is the same as that of Preparation Example 4, except that: in step (1), the calcination time of the activated carbon is increased to 6 hours, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 7.

[0049] Preparation Example 8

[0050] The operation of this preparation example is the same as that of Preparation Example 6, except that: in step (2), 1 mol / L phosphoric acid solution is used instead of 1 mol / L nitric acid solution, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat8.

[0051] Preparation Example 9

[0052] The operation of this preparation example is the same as that of Preparation Example 6, except that: in step (2), 1 mol / L acetic acid solution is used instead of 1 mol / L nitric acid solution, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat9.

[0053] Preparation Example 10

[0054] The operation of this preparation example is the same as that of Preparation Example 6, except that: in step (2), 30 mL of 2 mol / L hydrochloric acid solution is used to replace 1 mol / L hydrochloric acid solution, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 10.

[0055] Preparation Example 11

[0056] The operation of this preparation example is the same as that of Preparation Example 6, except that in step (2), 30 mL of a nitric acid solution with a concentration of 2 mol / L is used to replace the 1 mol / L nitric acid solution, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 11.

[0057] Preparation Example 12

[0058] The operation of this preparation example is the same as that of Preparation Example 6, except that in step (2), the constant-temperature ultrasonic temperature is changed from 40 °C to 60 °C, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 12.

[0059] Preparation Example 13

[0060] The operation of this preparation example is the same as that of Preparation Example 6, except that in step (2), the constant-temperature ultrasonic temperature is changed from 40 °C to 80 °C, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 13.

[0061] Preparation Example 14

[0062] The operation of this preparation example is the same as that of Preparation Example 7, except that in step (2), the ultrasonic power is changed from 500 W to 800 W, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 14.

[0063] Preparation Example 15

[0064] This preparation example is for the preparation of an activated carbon-based catalyst, which specifically includes the following steps:

[0065] (1) The activated carbon calcination step is the same as that of Preparation Example 6;

[0066] (2) The activated carbon constant-temperature ultrasonic pickling step is the same as that of Preparation Example 6;

[0067] (3) Active component loading: Weigh 0.153 g of BaCl2 and dissolve it in 20 mL of deionized water to make a BaCl2 solution. Take 10 g of the activated carbon after constant-temperature ultrasonic acid treatment and place it in a beaker. Add the above BaCl2 solution and impregnate for 10 hours. Take out the activated carbon and dry it at 100 °C for 12 hours to obtain the Ba / AC catalyst, denoted as Cat15.

[0068] Preparation Example 16

[0069] The operation of this preparation example is the same as that of Preparation Example 15, except that in step (3), the dosage of BaCl2 is increased to 0.306 g, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 16.

[0070] Preparation Example 17

[0071] The operation of this preparation example is the same as that of Preparation Example 15, except that: in step (3), 0.126 g of CsCl is used instead of 0.153 g of BaCl2, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat 17.

[0072] Comparative Preparation Example 1

[0073] The operation of this comparative preparation example is the same as that of Preparation Example 6, except that: the activated carbon is directly subjected to constant temperature ultrasonic pickling treatment without the calcination step, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat B1.

[0074] Comparative Preparation Example 2

[0075] The operation of this comparative preparation example is the same as that of Preparation Example 6, except that: after the activated carbon is calcined, it is not subjected to the constant temperature ultrasonic acid treatment step, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as Cat B2.

[0076] Comparative Preparation Example 3

[0077] The operation of this comparative preparation example is the same as that of Preparation Example 6, except that: the activated carbon is first subjected to constant temperature ultrasonic pickling treatment, and then the activated carbon is calcined, and other operations remain unchanged. The obtained activated carbon catalyst is denoted as CatB3.

[0078] The national standard GB / T 7702.20-2008 method is used to test the macroscopic physical properties of the commercially purchased activated carbon, the catalysts prepared in Preparation Examples 1-17, and the catalysts prepared in Comparative Examples 1-3. The test results are shown in Table 1 below:

[0079] Table 1 Macroscopic Physical Properties of Different Catalysts

[0080] Catalyst <![CDATA[Specific surface area (m 2 / g)]]> Average pore diameter (nm) Pore volume (ml / g) Commercially available activated carbon 826 1.82 0.283 Cat 1 962 2.12 0.301 Cat 2 1065 2.23 0.308 Cat 3 1167 2.32 0.335 Cat 4 1467 2.35 0.375 Cat 5 1411 3.22 0.367 Cat 6 1685 2.54 0.389 Cat 7 1644 2.46 0.377 Cat 8 1566 2.39 0.356 Cat 9 1423 2.33 0.342 Cat 10 1402 2.45 0.344 Cat 11 1486 2.50 0.351 Cat 12 1788 2.45 0.376 Cat 13 1443 2.23 0.332 Cat 14 1423 2.47 0.368 Cat 15 1465 2.46 0.389 Cat 16 1388 2.43 0.409 Cat 17 1423 2.51 0.388 Cat B1 913 1.92 0.292 Cat B2 941 2.12 0.299 Cat B3 935 1.99 0.295

[0081] According to the results in Table 1 above, it shows that the specific surface area, pore volume of the catalyst after calcination and then constant temperature ultrasonic pickling treatment increase, and the pore diameter increases, indicating that the method of the present invention can effectively change the macroscopic physical properties of the original activated carbon and improve the specific surface area, pore volume and pore capacity of the catalyst.

[0082] An adsorption instrument is used to test the acid-base sites of the activated carbon-based catalyst. The experimental method is: the activated carbon-based catalyst is pretreated under a helium atmosphere, the pretreatment temperature is 300 °C, after the catalyst is cooled to room temperature, NH3 / CO2 is introduced for adsorption, after the adsorption is completed, it is purged with helium at room temperature for 1 h, and the catalyst is programmed to heat up for gas desorption and the signal is collected.

[0083] Appendix Figure 1 、 Figure 2The NH3-TPD spectra and CO2-TPD spectra of the catalysts obtained in Preparation Examples 4, 8, 10, and 12 of the present invention and commercially available activated carbon are respectively given. From Figure 1 , 2 it can be seen that compared with the commercially available activated carbon, the strongly acidic sites of the modified catalyst of the present invention are enhanced and the strongly basic sites are weakened.

[0084] Example 1

[0085] This example provides a method for preparing 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd) by dehydrochlorination of 3,3-dichloro-1,1,1,2-tetrafluoropropane, which specifically includes:

[0086] S1. Using a reaction tube made of Inconel 600 alloy with an inner diameter of 8 mm and a length of 600 mm as a fixed-bed reactor, 2 g of Cat1 is loaded into the fixed-bed reactor. First, nitrogen is introduced for catalyst pretreatment. The pretreatment temperature is 350 °C and the pretreatment time is 2 h;

[0087] S2. After the pretreatment is completed, the reaction temperature is controlled at 300 °C, the operating pressure is atmospheric pressure, the raw material 3,3-dichloro-1,1,1,2-tetrafluoropropane is introduced, the space velocity is 3 g / h, the reaction products are collected and subjected to gas chromatography analysis.

[0088] According to the chromatographic analysis results, it can be known that: the overall conversion rate of 3,3-dichloro-1,1,1,2-tetrafluoropropane is 93.4%, the selectivity of the reaction main product HCFO-1224yd is 98.2%, the stable operation time of the catalyst is 92 h, and the catalyst efficiency is 96 g 1224yd / g cat.

[0089] Examples 2 to 17, Comparative Examples 1 to 4

[0090] The operations of Examples 2 to 17 are the same as those of Example 1, except that: Cat 2 to Cat 17, commercially available activated carbon, CatB1 to CatB3 are respectively used to replace Cat 1, and other operations remain unchanged. The reaction products are collected and subjected to gas chromatography analysis. The analysis results are shown in Table 2 below:

[0091] Table 2 Reaction results of different catalysts

[0092]

[0093]

[0094] Examples 18 to 22

[0095] The operations of Examples 18 to 22 were the same as those of Example 12, except that: the reaction temperature in Step S2 was changed, and other operations remained unchanged. The reaction products were collected for gas chromatography analysis, and the analysis results are shown in Table 3 below:

[0096] Table 3 Reaction Results at Different Reaction Temperatures

[0097]

[0098] Examples 23 to 25

[0099] The operations of Examples 23 to 25 were the same as those of Examples 4, 8, and 12, except that: the reaction raw material introduced in Step S2 was changed to 1-chloro-2,3,3,3-tetrafluoropropane, and the reaction was the dehydrochlorination of 1-chloro-2,3,3,3-tetrafluoropropane to form 2,3,3,3-tetrafluoropropene. Other operations remained unchanged. The reaction products were collected for gas chromatography analysis, and the analysis results are shown in Table 4 below:

[0100] Table 4 Reaction Results of 1-chloro-2,3,3,3-tetrafluoropropane

[0101]

[0102] Examples 26 to 28

[0103] The operations of Examples 26 to 28 were the same as those of Examples 4, 8, and 12, except that: the reaction raw material introduced in Step S2 was changed to 3,3,3-trichloro-1,1,1,2-tetrafluoropropane, and the reaction was the dehydrochlorination of 3,3,3-trichloro-1,1,1,2-tetrafluoropropane to form 1,1-dichloro-2,3,3,3-tetrafluoropropene. Other operations remained unchanged. The reaction products were collected for gas chromatography analysis, and the analysis results are shown in Table 5 below:

[0104] Table 5 Reaction Results of 3,3,3-trichloro-1,1,1,2-tetrafluoropropane

[0105]

[0106] The present invention changes the macroscopic physical properties of the catalyst by the method of first roasting and then constant-temperature ultrasonic pickling, and enhances the active sites of the catalyst to optimize the catalyst performance. The method of the present invention can effectively increase the specific surface area, pore volume, and pore diameter of the catalyst, thereby increasing the active sites of the catalyst, reducing the gas molecule diffusion resistance, and thus being more conducive to the mass transfer process and improving the catalytic activity and stability.

[0107] In addition, the method of the present invention can also adjust the acid-base sites of the catalyst, reduce the strength of the basic sites and increase the strength of the strong acid sites. According to the dehydrochlorination reaction mechanism, this adjustment of the acid-base sites helps to increase a sufficient number of reactive sites, thus promoting the occurrence of the dehydrochlorination reaction. By comparing the performance of the examples and the untreated activated carbon, the catalyst treated by the method of the present invention can significantly improve the reaction activity and enhance the stability of the catalyst at the same time.

Claims

1. A method for improving the stability of a catalyst for producing halogenated propylene, characterized in that: The method includes: using fluorochloropropane as a raw material, and obtaining halogenated propene through dehydrochlorination reaction under the action of an activated carbon-based catalyst; the activated carbon-based catalyst is obtained by roasting activated carbon and then subjecting it to constant-temperature ultrasonic pickling.

2. The method for improving the stability of the catalyst for producing halopropene according to claim 1, characterized in that: The activated carbon is selected from coconut shell activated carbon, coal-based activated carbon or wood-based activated carbon.

3. The method for improving the stability of the catalyst for producing halogenated propylene according to claim 1, characterized in that: The roasting temperature of the activated carbon is 200 - 500 °C, and the roasting time is 1 - 6 h.

4. The method for improving the stability of the catalyst for producing halogenated propylene according to claim 3, characterized in that: The roasting of the activated carbon is carried out in a roasting atmosphere, and the roasting atmosphere is a mixed gas of nitrogen and oxygen. By gas volume, the oxygen content is 1% - 10%.

5. The method for improving the stability of the catalyst for producing halopropene according to claim 1, characterized in that: The steps of the constant-temperature ultrasonic pickling include: acid solution preparation, constant-temperature ultrasonic impregnation, water washing and drying. The acid solution is a mixed solution of hydrochloric acid solution and at least one selected from nitric acid solution, acetic acid solution or phosphoric acid solution.

6. The method for improving the stability of the catalyst for producing halogenated propylene according to claim 5, characterized in that: The molar concentration of the acid solution is 0.1 - 10% mol / L.

7. The method for improving the stability of the catalyst for producing halopropene according to claim 5, characterized in that: The temperature of the constant-temperature ultrasonic impregnation is 40 - 80 °C, and the impregnation time is 2 - 8 h.

8. The method for improving the stability of the catalyst for producing halogenated propylene according to claim 5, characterized in that: The ultrasonic power is 400 - 800 W.

9. The method for improving the stability of the catalyst for producing halopropene according to claim 5, characterized in that: The drying temperature is 60 - 100 °C, and the drying time is 6 - 12 h.

10. The method for improving the stability of the catalyst for producing halopropene according to claim 1, characterized in that: An active component is loaded on the activated carbon after roasting and constant-temperature ultrasonic pickling. The active component is selected from at least one of strontium, barium, calcium, cesium or magnesium. By the mass of the activated carbon, the loading amount of the active component is 0.5 - 10 wt%.

11. The method for improving the stability of the catalyst for producing halopropene according to any one of claims 1-10, characterized in that: The reaction temperature of the dehydrochlorination reaction is 250 - 350 °C, and the reaction pressure is atmospheric pressure.

12. The method for improving the stability of the catalyst for producing halogenated propylene according to claim 11, characterized in that: Before the reaction, the activated carbon-based catalyst is pretreated by introducing an inert gas. The pretreatment temperature is 200 - 400 °C, and the pretreatment time is 2 - 4 h.

13. The method for improving the stability of the catalyst for producing halogenated propylene according to claim 1, characterized in that: When the fluorochloropropane is 3,3,3-trichloro-1,1,1,2-tetrafluoropropane, the halogenated propene is 1,1-dichloro-2,3,3,3-tetrafluoropropene (CFO-1214ya); when the fluorochloropropane is 3,3-dichloro-1,1,1,2-tetrafluoropropane, the halogenated propene is 1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd); when the fluorochloropropane is 1-chloro-2,3,3,3-tetrafluoropropane, the halogenated propene is 2,3,3,3-tetrafluoropropene (HFO-1234yf).

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