Phosphate catalyst, method for preparing the same, and use thereof

Abstract

The application discloses a phosphate catalyst and a preparation method and application thereof, and belongs to the field of catalysis technology. The preparation method comprises the following steps: S1. mixing a rare earth metal salt, an alkaline earth metal salt and a soluble phosphate salt, heating, and reacting to obtain a composite metal phosphate carrier; S2. dipping the composite metal phosphate carrier in a noble metal salt solution, and drying to obtain a precursor; and S3. calcining, reducing and activating the precursor to obtain the phosphate catalyst. In the process of preparing 1,2,3,3,3-pentafluoropropene by defluorination of hexafluoropropene, the phosphate catalyst provided by the application has high raw material conversion rate and target product selectivity. The proportion of cis structure of 1,2,3,3,3-pentafluoropropene in the product is improved, and the phosphate catalyst has excellent carbon deposition resistance, so that the catalyst can maintain stable catalytic activity in a long-time process. The phosphate catalyst can be used as a catalyst for preparing 2,3,3,3-tetrafluoropropene by defluorination of 1,2,3,3,3-pentafluoropropene, and has high 1,2,3,3,3-pentafluoropropene conversion rate and high 2,3,3,3-tetrafluoropropene selectivity.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, specifically to a phosphate catalyst, its preparation method, and its application. Background Technology

[0002] 2,3,3,3-Tetrafluoropropylene (HFO-1234yf) is a novel fluorinated olefin compound. As a typical fourth-generation hydrofluoroolefin, it has an ozone depletion potential (ODP) of 0 and a gas volatile protein (GWP) of <1, exhibiting excellent environmental performance. It also has good compatibility with existing automotive air conditioning, commercial refrigeration, foaming agents, and thermal management systems. It is an ideal replacement for the third-generation refrigerant 1,1,1,2-tetrafluoroethane (HFC-134a) and has been widely used in automotive air conditioning, cold chain logistics, heat pumps, and other fields, showing broad application prospects. Currently, the industrial preparation routes for 2,3,3,3-tetrafluoropropylene are mainly divided into the following categories: multi-step hydrogenation-defluorination routes using hexafluoropropylene (HFP) as raw material; for example, the existing technology CN104710275B uses 1,1,2,3,3,3-hexafluoropropylene HFP as raw material to prepare 2,3,3,3-tetrafluoropropylene, which involves multiple conversion steps such as hydrogenation, defluorination, re-hydrogenation, and re-defluorination. The steps are lengthy and the hydrogen consumption is high. In addition, the conversion rate of HFP and 1,2,3,3,3-pentafluoropropylene (R1225ye) reactants is low during the hydrogenation process. The process of defluorination of 1,1,2,3,3,3-hexafluoropropane (R236ea) and 1,2,3,3,3-pentafluoropropane (R245eb) using Zn-Cr2O3 catalyst is difficult to achieve high conversion rate and high selectivity at the same time. Moreover, the defluorination process generally relies on chromium-based, aluminum-based, or fluoride catalysts. These catalysts are prone to carbon deposition and deactivation at high temperatures, have poor catalyst stability, low selectivity for the target product, and high selectivity for by-products, which in turn leads to low yield of the target product.

[0003] Existing technology discloses a method for preparing 1,2,3,3,3-pentafluoropropylene, in which hexafluoropropylene undergoes a one-step reaction in the presence of a solid mixture catalyst to prepare 1,2,3,3,3-pentafluoropropylene. This method is simple and can provide guidance for the preparation of 2,3,3,3-tetrafluoropropylene. However, this solid mixture catalyst exhibits low selectivity for 1,2,3,3,3-pentafluoropropylene and high selectivity for byproducts.

[0004] In summary, developing a defluorination catalyst with excellent catalytic activity and resistance to carbon deposition is of great significance. Summary of the Invention

[0005] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing a phosphate catalyst.

[0006] Another object of the present invention is to provide a phosphate catalyst.

[0007] Another object of the present invention is to provide the application of the above-mentioned phosphate catalyst in the defluorination of fluorinated olefins to prepare 2,3,3,3-tetrafluoropropylene.

[0008] Another object of the present invention is to provide a method for the continuous preparation of 2,3,3,3-tetrafluoropropylene.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a phosphate catalyst includes the following steps: S1. Mix rare earth metal salts, alkaline earth metal salts, and soluble phosphates, heat, and react to obtain a composite metal phosphate carrier; S2. The composite metal phosphate support is immersed in a noble metal salt solution and dried to obtain the precursor; S3. The precursor is calcined, reduced, and activated to obtain the phosphate catalyst.

[0010] This invention utilizes the reaction of rare earth metal salts, alkaline earth metal salts, and phosphates to obtain a composite metal phosphate support. Noble metals are then loaded onto this composite metal phosphate support, followed by calcination, reduction, and activation to obtain a phosphate catalyst. The phosphate support exhibits structural stability, a large specific surface area, and good dispersion of active sites. The oxygen storage capacity of rare earth metals further enhances the resistance to carbon deposition, while also providing Lewis acid-base sites. Rare earth metal cations act as strong acid sites to capture sulfur dioxide (F). - Alkaline earth metals regulate Lewis acidity and phosphate structure, while phosphate acts as a base site to assist in proton / hydrogen transfer to complete defluorination. Through the synergistic effect of these three factors, in the process of defluorinating hexafluoropropylene to prepare 1,2,3,3,3-pentafluoropropylene, the phosphate catalyst of this invention can improve the conversion rate of raw materials, the selectivity of the target product, and the cis-structure ratio of 1,2,3,3,3-pentafluoropropylene, as well as enhance the catalyst's resistance to carbon deposition, enabling it to maintain stable catalytic activity over long-term processes.

[0011] Furthermore, the phosphate catalyst of the present invention can be used as a catalyst in the one-step defluorination process of 1,2,3,3,3-pentafluoropropylene to 2,3,3,3-tetrafluoropropylene, and has high conversion rate of 1,2,3,3,3-pentafluoropropylene and high selectivity of 2,3,3,3-tetrafluoropropylene.

[0012] It should be noted that in this invention, R1225ye refers to 1,2,3,3,3-pentafluoropropene; R1234yf refers to 2,3,3,3-tetrafluoropropene; R236ea refers to 1,1,2,3,3,3-hexafluoropropane; and R245eb refers to 1,1,1,2,3-pentafluoropropane.

[0013] Preferably, in step S1, the rare earth metal salt is selected from at least one of the nitrates and / or chlorides of La, Ce, Y, Pr, Nd, Sm, and Gd.

[0014] More preferably, in step S1, the rare earth metal salt is selected from at least one of the nitrates and / or chlorides of La and Ce.

[0015] Preferably, in step S1, the alkaline earth metal salt is selected from at least one of the nitrates and / or chlorides of Mg, Ca, Sr, and Ba.

[0016] More preferably, in step S1, the alkaline earth metal salt is selected from at least one of nitrates and / or chlorides of Mg and Ca.

[0017] Preferably, in step S1, the soluble phosphate is at least one of monohydrogen phosphate, dihydrogen phosphate, or orthophosphate.

[0018] More preferably, in step S1, the soluble phosphate is at least one of disodium hydrogen phosphate, dipotassium hydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, potassium phosphate, sodium phosphate, and ammonium phosphate.

[0019] Preferably, in step S1, the reaction temperature is 60~150℃.

[0020] Preferably, in step S1, the reaction time is 2 to 12 hours.

[0021] Preferably, in step S1, the molar ratio of alkaline earth metal elements in the alkaline earth metal salt to rare earth metal elements in the rare earth metal salt is (0.05~0.30):1.

[0022] More preferably, in step S1, the molar ratio of alkaline earth metal elements in the alkaline earth metal salt to rare earth metal elements in the rare earth metal salt is (0.1~0.25):1.

[0023] Preferably, in step S1, the ratio of the total molar amount of alkaline earth metal elements in the alkaline earth metal salt and the total molar amount of rare earth metal elements in the rare earth metal salt to the molar amount of phosphate in the soluble phosphate is 1:(1.05~1.4).

[0024] More preferably, in step S1, the ratio of the total molar amount of alkaline earth metal elements in the alkaline earth metal salt and the total molar amount of rare earth metal elements in the rare earth metal salt to the molar amount of phosphate in the soluble phosphate is 1:(1.1~1.3).

[0025] Preferably, in step S2, the noble metal salt is selected from at least one of the nitrates and / or chlorides of Pd, Pt, Ir, Ru, and Rh.

[0026] Preferably, in step S2, the mass of the noble metal element in the noble metal salt is 1 to 10% of the mass of the composite metal phosphate carrier.

[0027] More preferably, in step S2, the mass of the noble metal element in the noble metal salt is 1 to 7% of the mass of the composite metal phosphate carrier.

[0028] Preferably, in step S2, the soaking time is 1 to 6 hours.

[0029] Preferably, in step S2, the specific surface area of ​​the composite metal phosphate support is 400~500 m². 2 / g, average pore size 3~7nm.

[0030] Preferably, in step S3, the calcination temperature is 300~400℃.

[0031] Preferably, in step S3, the roasting time is 1 to 10 hours.

[0032] Preferably, in step S3, the reduction temperature is 100~300℃.

[0033] Preferably, in step S3, the reduction time is 2 to 10 hours.

[0034] Preferably, in step S3, the reduction is carried out in an atmosphere containing hydrogen.

[0035] More preferably, the atmosphere containing hydrogen is a mixture of an inert gas and hydrogen.

[0036] More preferably, the volume ratio of the inert gas to hydrogen is (0~10):1. More preferably, it is (1~5):1.

[0037] Preferably, in step S3, the activation is performed in an atmosphere containing hydrogen fluoride.

[0038] More preferably, the atmosphere containing hydrogen fluoride is a mixture of an inert gas and hydrogen fluoride gas.

[0039] More preferably, the volume ratio of the inert gas to the hydrogen fluoride gas is (0.5~5):1.

[0040] Preferably, in step S3, the activation temperature is 250~400℃.

[0041] Preferably, in step S3, the activation time is 2 to 16 hours.

[0042] This invention also protects the phosphate catalyst prepared by the above preparation method.

[0043] Preferably, the specific surface area of ​​the phosphate catalyst is 120-150 m². 2 / g, average pore size 7~10nm.

[0044] This invention also protects the use of the above-mentioned phosphate catalyst in the defluorination of fluoroolefins to prepare 2,3,3,3-tetrafluoropropylene.

[0045] A method for preparing 2,3,3,3-tetrafluoropropylene includes the following steps: 1,2,3,3,3-Pentafluoropropylene reacts with hydrogen in the presence of the above-mentioned phosphate catalyst to yield 2,3,3,3-Tetrafluoropropylene.

[0046] Preferably, the 1,2,3,3,3-pentafluoropropylene is obtained by reacting hexafluoropropylene with hydrogen in the presence of the above-mentioned phosphate catalyst.

[0047] In this invention, unreacted hydrogen can be separated and recycled to the defluorination reactor; the hydrogen fluoride produced by defluorination can be separated, purified and collected in a storage tank, or recycled to the defluorination reactor to prevent over-defluorination.

[0048] In this invention, the reaction conditions for preparing 1,2,3,3,3-pentafluoropropylene from hexafluoropropylene can be the same as or different from the reaction conditions for preparing 2,3,3,3-tetrafluoropropylene from 1,2,3,3,3-pentafluoropropylene.

[0049] More preferably, the reaction temperature is 150~400°C.

[0050] More preferably, the reaction temperature is 200~350°C.

[0051] More preferably, the reaction pressure is 0.1~0.5 MPa.

[0052] More preferably, the contact time of the reaction is 1 to 30 seconds. More preferably, it is 3 to 10 seconds.

[0053] More preferably, in the reaction, the molar ratio of hydrogen to hexafluoropropylene or 1,2,3,3,3-pentafluoropropylene is (0.5~10):1. More preferably, it is (1~5):1.

[0054] In this invention, the reaction byproducts for preparing 1,2,3,3,3-pentafluoropropene from hexafluoropropene include 1,1,2,3,3,3-hexafluoropropane; and the reaction byproducts for preparing 2,3,3,3-tetrafluoropropene from 1,2,3,3,3-pentafluoropropene include 1,1,1,2,3-pentafluoropropane.

[0055] More preferably, the method for preparing 2,3,3,3-tetrafluoropropylene further includes reacting byproduct 1,1,2,3,3,3-hexafluoropropane and byproduct 1,1,1,2,3-pentafluoropropane under the action of a first catalyst to obtain 1,2,3,3,3-pentafluoropropylene and 2,3,3,3-tetrafluoropropylene respectively.

[0056] More preferably, the 1,2,3,3,3-pentafluoropropylene can be used as a raw material to react with hydrogen under the action of the above-mentioned phosphate catalyst to obtain 2,3,3,3-tetrafluoropropylene.

[0057] More preferably, the first catalyst is at least one of activated carbon, alumina, fluorinated alumina, chromium oxide, and fluorinated chromium oxide.

[0058] More preferably, the first catalyst is fluorinated chromium oxide.

[0059] More preferably, the first reaction is a reaction to remove hydrogen fluoride.

[0060] More preferably, the temperature of the first reaction is 250~450°C. More preferably, it is 300~400°C.

[0061] More preferably, the time for the first reaction is 1 to 30 seconds. More preferably, it is 5 to 15 seconds.

[0062] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes the reaction of rare earth metal salts, alkaline earth metal salts, and phosphates to obtain a composite metal phosphate support. Noble metals are then loaded onto this support, followed by calcination, reduction, and activation to obtain a phosphate catalyst. In the process of defluorinating hexafluoropropylene to prepare 1,2,3,3,3-pentafluoropropylene, the phosphate catalyst provided by this invention exhibits high feed conversion rate, target product selectivity, and improves the cis-structure ratio of 1,2,3,3,3-pentafluoropropylene in the product. Furthermore, it possesses excellent resistance to carbon deposition, allowing it to maintain stable catalytic activity over extended processing times. In addition, it can be used as a catalyst for the one-step defluorination of 1,2,3,3,3-pentafluoropropylene to prepare 2,3,3,3-tetrafluoropropylene, exhibiting high conversion rates of 1,2,3,3,3-pentafluoropropylene and high selectivity for 2,3,3,3-tetrafluoropropylene. Attached Figure Description

[0063] Figure 1 This is a technical roadmap for the continuous preparation of 2,3,3,3-tetrafluoropropylene according to the present invention. Detailed Implementation

[0064] The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0065] Example 1 This embodiment provides a phosphate catalyst, the preparation method of which includes: 1.1 mol of Ce(NO3)3·6H2O and 0.25 mol of Mg(NO3)2·6H2O (relative Ce content 25 mol%) were dissolved in deionized water until fully dissolved. While stirring, 1.5 mol of NH4H2PO4 was added. The ratio of the total molar amount of Mg and Ce to the molar amount of phosphate in NH4H2PO4 was 1:1.2. After thorough mixing, the mixture was heated to 120℃ in an oil bath and reacted for 6 hours. After cooling to room temperature, the precipitate was filtered, washed multiple times with deionized water, and dried in a 110℃ oven for 12 hours to obtain a composite metal phosphate carrier. Its specific surface area was determined to be 440.1 m². 2 / g, average pore size 4.5nm.

[0066] S2. Take 50g of the above composite metal phosphate carrier powder, weigh PdCl2 according to a 3% Pd element loading (loading = mass of Pd element / mass of composite metal phosphate carrier × 100%) and fully dissolve it in 100ml of deionized water. While sonicating, immerse the carrier powder in the PdCl2 solution. After sonicating for 3 hours, transfer it together with the PdCl2 solution to a rotary evaporator. Set the temperature to 80℃ and the rotation speed to 60r / min until the water evaporates. Then transfer it to a forced-air drying oven and dry it at 110℃ for 12 hours to obtain the precursor.

[0067] S3. The precursor was ground into particles of approximately 3-6 mm and calcined in a muffle furnace at 350°C for 4 hours. Then, it was transferred to a Hastelloy reaction tube in a fixed-bed reactor, with the temperature set at 200°C and the N2 flow rate adjusted to 150 sccm. H2 was introduced at 150 sccm for reduction for 6 hours (N2 to H2 volume ratio 1:1). H2 was then stopped, and the temperature was raised to 350°C under an N2 atmosphere. An N2 / HF (volume ratio 2:1, total 300 sccm) mixed gas was introduced for activation for 10 hours. The resulting phosphate catalyst had a specific surface area of ​​141.6 m². 2 / g, average pore size 8.7nm.

[0068] Example 2 This embodiment provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that Ce(NO3)3·6H2O is replaced with an equimolar amount of La(NO3)3·6H2O. The specific surface area of ​​the composite metal phosphate support was measured to be 405.7 m². 2 / g, with an average pore size of 5.0 nm. The specific surface area of ​​the phosphate catalyst was measured to be 127.6 m². 2 / g, average pore size 9.1nm.

[0069] Example 3 This embodiment provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that Mg(NO3)2·6H2O is replaced with an equimolar amount of Ca(NO3)2·4H2O. The specific surface area of ​​the composite metal phosphate support was measured to be 421.2 m². 2 / g, with an average pore size of 4.4 nm. The specific surface area of ​​the phosphate catalyst was measured to be 135.5 m². 2 / g, average pore size 8.0nm.

[0070] Example 4 This embodiment provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that the Pd loading is 7 wt%. The specific surface area of ​​the phosphate catalyst was measured to be 120.8 m². 2 / g, average pore size 7.4nm.

[0071] Example 5 This embodiment provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that 1.14 mol of Ce(NO3)3·6H2O and 0.11 mol of Mg(NO3)2·6H2O (relative Ce content of 10 mol%) are dissolved in deionized water until fully dissolved, and 1.5 mol of NH4H2PO4 is added while stirring. The ratio of the total molar amount of Mg and Ce to the molar amount of phosphate in NH4H2PO4 is 1:1.2. The specific surface area of ​​the phosphate catalyst was measured to be 139.4 m². 2 / g, average pore size 8.1nm.

[0072] Example 6 This embodiment provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that 0.96 mol of Ce(NO3)3·6H2O and 0.29 mol of Mg(NO3)2·6H2O (relative Ce content of 30 mol%) are dissolved in deionized water until fully dissolved, and 1.5 mol of NH4H2PO4 is added while stirring. The ratio of the total molar amount of Mg and Ce to the molar amount of phosphate in NH4H2PO4 is 1:1.2. The specific surface area of ​​the phosphate catalyst is 123.5 m². 2 / g, average pore size 7.0nm.

[0073] Comparative Example 1 This comparative example provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that Mg(NO3)2·6H2O is not added in S1. The specific surface area of ​​cerium phosphate was measured to be 376.2 m². 2 / g, with an average pore size of 3.9 nm. The final phosphate catalyst had a specific surface area of ​​116.5 m². 2 / g, average pore size 6.9nm.

[0074] Comparative Example 2 This comparative example provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that Ce(NO3)3·6H2O is not added in S1. The specific surface area of ​​magnesium phosphate was measured to be 298.2 m². 2 / g, with an average pore size of 3.5nm. The final phosphate catalyst had a specific surface area of ​​99.4m². 2 / g, average pore size 5.9nm.

[0075] Comparative Example 3 This comparative example provides a catalyst, the preparation method of which includes the following steps: S1. Dissolve 1 mol of Al(NO3)3·9H2O and 0.25 mol of Zn(NO3)2·6H2O (relative Al content of 25 mol%) in deionized water until fully dissolved. While stirring, add ammonia water until pH=8. After mixing evenly, age overnight, filter, wash, and place the filter cake in a forced-air drying oven at 120℃ for 12 h. Then, calcine it in a muffle furnace at 350℃ for 4 h to obtain Zn-Al2O3 support.

[0076] S2. Take 50g of the above metal oxide carrier powder, weigh PdCl2 according to a 3% Pd element loading (loading = mass of Pd element / mass of carrier × 100%) and fully dissolve it in 100ml of deionized water. While sonicating, immerse the carrier powder in the PdCl2 solution. After sonicating for 3 hours, transfer it to a forced-air drying oven and dry it at 110℃ for 12 hours to obtain the precursor.

[0077] S3. The precursor was ground into particles of approximately 3-6 mm and calcined in a muffle furnace at 400°C for 6 hours. Then, it was transferred to a Hastelloy reaction tube in a fixed-bed reactor, with the temperature set at 200°C and the N2 flow rate adjusted to 150 sccm. H2 was introduced at 150 sccm for reduction for 6 hours. H2 was then stopped, and the temperature was raised to 350°C under an N2 atmosphere. An N2 / HF (volume ratio 2:1, total 300 sccm) mixed gas was introduced for activation for 10 hours. The resulting metal oxide-supported noble metal catalyst had a specific surface area of ​​82.3 m². 2 / g, average pore size 5.9nm.

[0078] Comparative Example 4 This comparative example provides a phosphate catalyst, the preparation method of which differs from that of Example 1 in that Ce(NO3)3·6H2O in Example 1 is replaced with Cr(NO3)3·9H2O. The specific surface area of ​​the phosphate catalyst is 109.2 m². 2 / g, average pore size 6.2nm.

[0079] Application examples This application example provides a series of methods for the continuous preparation of 2,3,3,3-tetrafluoropropylene, including the following steps: (1) Hexafluoropropylene (HFP) reacts with H2 in the presence of a phosphate catalyst in any of the above examples or comparative examples to give 1,2,3,3,3-pentafluoropropylene (R1225ye).

[0080] (2) The 1,2,3,3,3-pentafluoropropylene (R1225ye) obtained in step (1) is reacted with H2 under the action of the phosphate catalyst in any of the above embodiments to obtain 2,3,3,3-tetrafluoropropylene (R1234yf).

[0081] (3) The byproducts 1,1,2,3,3,3-hexafluoropropane (R236ea) and 1,1,1,2,3-pentafluoropropane (R245eb) generated in steps (1) and (2) respectively undergo a dehydrofluorination step under the action of chromium oxide fluoride to obtain products 1,2,3,3,3-pentafluoropropene (R1225ye) and 2,3,3,3-tetrafluoropropene (R1234yf). After separation, 1,2,3,3,3-pentafluoropropene (R1225ye) enters the fixed bed reactor in step (2), and 2,3,3,3-tetrafluoropropene (R1234yf) enters the product collection process.

[0082] (4) The unreacted hexafluoropropylene (HFP) and 1,2,3,3,3-pentafluoropropylene (R1225ye) from steps (1) and (2) are recycled to their respective reactors to continue the reaction.

[0083] The unreacted H2 can be separated and recycled to the defluorination reactor in steps (1) and (2); the HF generated during defluorination can be separated, purified and collected in a storage tank, or recycled to the defluorination reactor to prevent excessive defluorination of fluorinated olefins.

[0084] For step (1) HFP→R1225ye 20 ml of the catalysts from Examples 1-6 and Comparative Examples 1-3 were placed in a Hastelloy reaction tube of a fixed-bed reactor. The temperature was set at 250 °C, the reaction pressure at 0.3 MPa, and 100 sccm of HFP and 160 sccm of H2 (H2 / HFP = 1.6:1) were introduced. The reaction contact time was 4.4 s. The product was washed with water, alkali, and dried before being analyzed by gas chromatography. The results are shown in Table 1. In Table 1, the Z / E ratio is the molar ratio of (Z)-1,2,3,3,3-pentafluoropropylene to (E)-1,2,3,3,3-pentafluoropropylene.

[0085] Table 1. Results of Examples 1-6 and Comparative Examples 1-3 after 20h and 720h of reaction.

[0086] As shown in Table 1, after 20 h of reaction in Examples 1-6, the HFP conversion rate was ≥90%, the R1225ye selectivity was ≥91%, the Z / E ratio was ≥11, and the R236ea selectivity was ≤8.3%; after 720 h of reaction, the HFP conversion rate was ≥85%, the R1225ye selectivity was ≥91%, the Z / E ratio was ≥10, and the R236ea selectivity was ≤8.8%. This indicates that in the one-step defluorination of hexafluoropropylene to prepare 1,2,3,3,3-pentafluoropropylene (R1225ye), the phosphate catalyst of the present invention has a high HFP conversion rate and R1225ye selectivity, and can increase the proportion of the cis structure of R1225ye in the product.

[0087] The carbon content and specific surface area of ​​the catalyst after 720 h of reaction were measured using an infrared carbon-sulfur analyzer and a fully automated specific surface area analyzer and compared with those before the reaction. The results are shown in Table 2.

[0088] Table 2. Carbon content, specific surface area, and rate of change of specific surface area of ​​the catalyst after 720 h of reaction in Examples 1-6 and Comparative Examples 1-3.

[0089] As shown in Table 2, after 720 h of reaction, the carbon content of the catalyst in Examples 1-6 was ≤4.11%, and the change rate of specific surface area was ≤18.0%. This indicates that the phosphate catalyst of the present invention has excellent anti-carbon deposition performance.

[0090] As shown in Tables 1 and 2, in Comparative Example 1, without the addition of alkaline earth metal Mg, the prepared phosphate catalyst exhibited lower selectivity for 1,2,3,3,3-pentafluoropropylene (R1225ye) and a lower Z / E ratio in the product during the defluorination of hexafluoropropylene. After 720 h of reaction, the HFP conversion, R1225ye selectivity, and Z / E ratio were all lower than those of the Example. The selectivity of the byproduct 1,1,2,3,3,3-hexafluoropropane (R236ea) was higher than that of the Example, and the carbon content of the catalyst was also higher, with a larger change in specific surface area. Comparative Example 1 and Example 1 demonstrate that the doping of alkaline earth metals is beneficial for improving the catalyst's resistance to carbon deposition and stability, thereby increasing the proportion of (Z)1,2,3,3,3-pentafluoropropylene in the product.

[0091] In Comparative Example 2, the support did not incorporate rare earth metal Ce. After 20 h and 720 h of reaction, the HFP conversion, R1225ye selectivity, and Z / E ratio of the prepared phosphate catalyst were significantly lower than those in the Example. The selectivity for the byproduct 1,1,2,3,3,3-hexafluoropropane (R236ea) was higher than in the Example. Furthermore, after 720 h of reaction, the HFP conversion and R1225ye selectivity decreased significantly, the catalyst had a higher carbon content, and the specific surface area change rate was larger. Comparative Example 2 and Example 1 show that rare earth metals mainly provide defluorination activity for phosphate-supported catalysts, and can significantly improve HFP conversion, R1225ye selectivity, and cis ratio, reduce the selectivity of the byproduct 1,1,2,3,3,3-hexafluoropropane (R236ea), and improve the catalyst's resistance to carbon deposition.

[0092] Comparative Example 3, using zinc aluminum oxide as a support, showed that after 20 hours of reaction, the catalyst prepared had low selectivity for 2,3,3,3-pentafluoropropylene (R1225ye), a low Z / E ratio in the product, and high selectivity for the byproduct 1,1,2,3,3,3-hexafluoropropane (R236ea). After 720 hours of reaction, the HFP conversion, R1225ye selectivity, and Z / E ratio were all lower than those of the example, while the selectivity for the byproduct 1,1,2,3,3,3-hexafluoropropane (R236ea) was higher than that of the example. Furthermore, the catalyst had a higher carbon content and a larger specific surface area change rate. Comparative Example 3 demonstrates that using oxides of non-alkaline earth metals and non-rare earth metals as supports results in catalysts with significantly lower catalytic activity than the phosphate catalyst of this invention. Moreover, these catalysts are prone to carbon deposition and deactivation under high temperature and long reaction conditions, exhibiting poor catalyst stability.

[0093] In Comparative Example 4, the rare earth metal Ce was replaced with the transition metal Cr in the support. During the defluorination of hexafluoropropylene to prepare 1,2,3,3,3-pentafluoropropylene, the Z / E ratio in the product was low after 20 hours of reaction. After 720 hours, the HFP conversion rate decreased significantly. The selectivity and Z / E ratio of R1225ye were lower than in the example. The selectivity of the byproduct 1,1,2,3,3,3-hexafluoropropane (R236ea) was higher than in the example, and the catalyst had a higher carbon content and a larger rate of change in specific surface area. Comparative Example 4 and Example 1 show that replacing the rare earth metal with other transition metals does not improve the cis-structure ratio of R1225ye in the product during the defluorination of hexafluoropropylene to prepare 1,2,3,3,3-pentafluoropropylene. This is detrimental to the one-step defluorination of R1225ye to prepare 2,3,3,3-tetrafluoropropylene, and the catalyst has poor resistance to carbon deposition, resulting in poor stability.

[0094] For step (2) R1225ye→R1234yf 20 ml of the defluorination catalysts from the examples and comparative examples were placed in a Hastelloy tubular reactor. The temperature was set at 330 °C, the reaction pressure at 0.2 MPa, and R1225ye gas with different cis / trans structure ratios (Z / E = 12.5 or Z / E = 7) was introduced at 45.7 sccm and H2 at 114.3 sccm (H2 to R1225ye volume ratio was 2.5). The reaction contact time was 7.5 s. After 20 h of reaction, the product was washed with water, alkali, and dried before being analyzed by gas chromatography. The results are shown in Table 3 below. Other substances in Table 3 refer to the selectivity of byproducts other than R245eb.

[0095] Table 3. Results of the reactions of each embodiment and comparative example after 20 h at different Z / E ratios.

[0096]

[0097] As shown in Table 3, after 20 hours of reaction in Examples 1-6, under a Z / E ratio of 12.5, the conversion rate of R1225ye was ≥93.9%, the selectivity of R1234yf was ≥89.5%, and the selectivity of R245eb was ≤10.3%. Under a Z / E ratio of 7, the conversion rate of R1225ye was ≥81.0%, the selectivity of R1234yf was ≥84.1%, and the selectivity of R245eb was ≤13.1%. This indicates that in the one-step defluorination of 1,2,3,3,3-pentafluoropropylene (R1225ye) to prepare 2,3,3,3-tetrafluoropropylene, the catalyst of the present invention has high R1225ye conversion and high 2,3,3,3-tetrafluoropropylene selectivity.

[0098] Furthermore, a comparison of different Z / E ratios shows that increasing the proportion of (Z)-R1225ye in the raw material is beneficial to the defluorination reaction, which can improve the conversion rate of the raw material and the selectivity of R1234yf, and reduce the generation of other by-products.

[0099] In Comparative Example 1, the support was not doped with alkaline earth metal Mg. In the defluorination of 1,2,3,3,3-pentafluoropropylene (R1225ye) to prepare 2,3,3,3-tetrafluoropropylene (R1234yf), when the Z / E ratio was 12.5, the catalyst prepared in Comparative Example 1 showed low selectivity for R1234yf but high selectivity for other products. When the Z / E ratio was 7, the catalyst in Comparative Example 1 showed low selectivity for R1234yf but high selectivity for the byproduct 1,1,1,2,3-pentafluoropropane (R245eb).

[0100] In Comparative Example 2, no rare earth metal Ce was introduced into the support. When the Z / E ratio was 12.5 or 7, the R1225ye conversion and R1234yf selectivity of the prepared phosphate catalyst were far inferior to those of the embodiments of the present invention, and the selectivity for R245eb and other substances was relatively high.

[0101] In Comparative Example 3, zinc aluminum oxide was used as the support. When the Z / E ratio was 12.5, its selectivity for R1234yf was relatively low, while its selectivity for R245eb and other substances was relatively high. When the Z / E ratio was 7, the catalyst in Comparative Example 3 showed low conversion of R1225ye and low selectivity for R1234yf, but high selectivity for R245eb and other substances.

[0102] In Comparative Example 4, rare earth metal Ce was replaced with transition metal Cr. When the Z / E ratio was 12.5 or 7, the R1225ye conversion and R1234yf selectivity of the prepared phosphate catalyst were far inferior to those of the embodiments of the present invention, and the selectivity for R245eb and other substances was relatively high.

[0103] Comparative Example 5 The 3% Pd / C catalyst used in this comparative example was purchased from Xi'an Kaili New Materials Co., Ltd.

[0104] The preparation method of the Cr2O3 catalyst used in this comparative example includes the following steps: a certain amount of chromium chloride hexahydrate is fully dissolved in deionized water, and ammonia water is added while stirring until the pH=9. After aging for 2 hours, the catalyst is filtered, washed, and the filter cake is placed in a forced-air drying oven and dried at 120℃ for 12 hours. Then, it is calcined in a muffle furnace at 350℃ for 4 hours. The catalyst is obtained by crushing and granulating.

[0105] This comparative example provides a conventional method for preparing 2,3,3,3-tetrafluoropropylene, the specific steps of which are shown below: Step 1: HFP → R236ea → R1225ye: Hexafluoropropene (HFP) undergoes an addition reaction with hydrogen to give 1,1,2,3,3,3-hexafluoropropane (R236ea). After removing hydrogen fluoride from 1,1,2,3,3,3-hexafluoropropane (R236ea), 1,2,3,3,3-pentafluoropropene (R1225ye) is obtained.

[0106] The Hastelloy reaction tube of the first fixed-bed reactor was packed with 20 ml of 3% Pd / C catalyst. The reactor was first purged with 120 sccm of N2 at 100°C for 2 h. The temperature was then raised to 200°C, the N2 flow rate was adjusted to 60 sccm, and 60 sccm of H2 was introduced, maintaining this temperature for 6 h. The reactor was then cooled to 85°C, and a reaction was carried out with 100 sccm of HFP and 160 sccm of H2 (H2 / HFP = 1.6:1) for a contact time of 4.4 s. The effluent was analyzed by gas chromatography, yielding a 100% conversion of HFP and a 95.3% selectivity for R236ea. The product flowed directly into the second fixed-bed reactor.

[0107] 20 ml of Cr2O3 catalyst was packed into a Hastelloy reaction tube in the second fixed-bed reactor. The catalyst was purged with 100 sccm of N2 at 100 °C for 2 h, then the temperature was raised to 350 °C, and an N2 / HF (volume ratio 2:1, total 300 sccm) mixture was introduced for activation for 10 h. The effluent from the second fixed-bed reactor was washed with water and alkali before being analyzed by gas chromatography. The conversion rate of R236ea was 79.1%, and the selectivity of R1225ye was 94.6%, with Z / E = 6.9. After continuous operation for 720 h, the conversion rate dropped below 30%, indicating that the Cr2O3 catalyst was essentially deactivated.

[0108] The results indicate that the cis-structure proportion of R1225ye obtained by the two-step method of catalytic hydrogenation and defluorination of HFP is lower than that obtained by the one-step method of this invention. Furthermore, under the action of the catalyst provided by this invention, the long-term stability and yield (yield = conversion × selectivity) of the operating cycle are significantly higher than those of the two-step process.

[0109] The second step, R1225ye → R245eb → R1234yf, involves an addition reaction between 1,2,3,3,3-pentafluoropropene (R1225ye) and hydrogen to yield 1,2,3,3,3-pentafluoropropane (R245eb). After removing hydrogen fluoride from 1,2,3,3,3-pentafluoropropane (R245eb), 2,3,3,3-tetrafluoropropene (R1234yf) is obtained.

[0110] The Hastelloy reaction tube of the first fixed-bed reactor was packed with 20 ml of 3% Pd / C catalyst. The reactor was first purged with 100 sccm of N2 at 100 °C for 2 h. The temperature was then raised to 200 °C, the N2 flow rate was adjusted to 50 sccm, and 50 sccm of H2 was introduced, maintaining this temperature for 6 h. The reactor was then cooled to 105 °C, and 45.7 sccm of R1225ye gas with different cis / trans structure ratios (Z / E = 12.5 or Z / E = 7) and 114.3 sccm of H2 (H2 / R1225ye = 2.5) were introduced, with a contact time of 7.5 s. The effluent was analyzed by gas chromatography. The results showed that at Z / E = 12.5, the conversion rate of R1225ye was 90.1%, and the selectivity of R245eb was 97.5%. At Z / E = 7, the conversion rate of R1225ye was 99.2%, and the selectivity of R245eb was 90.9%. The product flows directly into the second fixed-bed reactor.

[0111] 20 ml of Cr2O3 catalyst was packed into the Hastelloy reaction tube of the second fixed-bed reactor. The catalyst was purged with 100 sccm of N2 at 100 °C for 2 h, then the temperature was raised to 350 °C, and an N2 / HF (volume ratio 2:1, total 300 sccm) mixture was introduced for activation for 10 h. The effluent from the second fixed-bed reactor was washed with water and alkali before being analyzed by gas chromatography. The results showed that at Z / E = 12.5, the conversion rate of R245eb was 85.1%, and the selectivity of R1234yf was 84.9%. At Z / E = 7, the conversion rate of R245eb was 76.3%, and the selectivity of R1234yf was 80.2%.

[0112] The process route for obtaining R1234yf from R1225ye via a two-step method involving catalytic hydrogenation and defluorination has many steps, and the catalyst has low stability and a fast deactivation rate, resulting in a short operating cycle.

[0113] As can be seen from this pair, the higher the proportion of cis structure in R1225ye, the higher the conversion rate of R245eb, which in turn leads to a higher selectivity of R1234yf.

[0114] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a phosphate catalyst, characterized in that, Includes the following steps: S1. Mix rare earth metal salts, alkaline earth metal salts, and soluble phosphates, heat, and react to obtain a composite metal phosphate carrier; S2. The composite metal phosphate support is immersed in a noble metal salt solution and dried to obtain the precursor; S3. The precursor is calcined, reduced, and activated to obtain the phosphate catalyst.

2. The preparation method according to claim 1, characterized in that, The preparation method satisfies at least one of the following conditions: (a) In step S1, the rare earth metal salt is selected from at least one of the nitrates and / or chlorides of La, Ce, Y, Pr, Nd, Sm, and Gd; (b) In step S1, the alkaline earth metal salt is selected from at least one of the nitrates and / or chlorides of Mg, Ca, Sr, and Ba; (c) In step S2, the noble metal salt in the noble metal salt solution is selected from at least one of the nitrates and / or chlorides of Pd, Pt, Ir, Ru, and Rh.

3. The preparation method according to claim 1, characterized in that, The preparation method satisfies at least one of the following conditions: (d) In step S1, the molar ratio of alkaline earth metal elements in the alkaline earth metal salt to rare earth metal elements in the rare earth metal salt is (0.05~0.30):1; (e) In step S1, the ratio of the total molar amount of alkaline earth metal elements in the alkaline earth metal salt and the total molar amount of rare earth metal elements in the rare earth metal salt to the molar amount of phosphate in the soluble phosphate is 1:(1.05~1.4). (f) In step S2, the mass of the noble metal element in the noble metal salt solution is 1 to 10% of the mass of the composite metal phosphate carrier.

4. The preparation method according to claim 1, characterized in that, In step S3, the calcination temperature is 300~400℃.

5. The preparation method according to claim 1, characterized in that, In step S3, the reduction temperature is 100~300℃.

6. The preparation method according to claim 1, characterized in that, In step S3, the activation temperature is 250~400℃.

7. The phosphate catalyst prepared by any one of the preparation methods described in claims 1 to 6.

8. The application of the phosphate catalyst according to claim 7 in the defluorination of fluoroolefins to prepare 2,3,3,3-tetrafluoropropylene.

9. A method for preparing 2,3,3,3-tetrafluoropropylene, characterized in that, Includes the following steps: 1,2,3,3,3-Pentafluoropropylene reacts with hydrogen in the presence of the phosphate catalyst described in claim 7 to yield 2,3,3,3-Tetrafluoropropylene.

10. The method for preparing 2,3,3,3-tetrafluoropropylene according to claim 9, characterized in that, The 1,2,3,3,3-pentafluoropropylene is obtained by reacting hexafluoropropylene with hydrogen in the presence of the phosphate catalyst described in claim 7.

Images