A highly efficient multi-metallic catalyst for the synthesis of hexafluoroisopropanol

Abstract

The application discloses a kind of high-efficiency multi-metal catalyst for synthesizing hexafluoropropylene oxide, and belongs to the field of catalyst preparation.The multi-metal catalyst of the application is Cu, Ce, Mo ternary metal catalyst, comprising: 1wt%-5wt% of Cu, 0.5wt%-3wt% of Ce, 0.1wt%-1wt% of Mo and 85wt%-95wt% of phosphoric acid modified mesoporous silica carrier, wherein, Cu is loaded in the form of nanoparticle with particle size of 5-20nm, Ce exists in the form of cerium oxide, and Mo exists in the form of molybdate.The multi-metal catalyst plays catalytic activity through the oxidation activity of Cu 0 , the oxygen storage capacity of CeO2 and the electronic regulation effect of MoO4 2‑ , is suitable for preparing hexafluoropropylene oxide from hexafluoropropylene gas phase oxidation, has high raw material conversion rate, and can reduce reaction temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts for the gas-phase preparation of hexafluoropropylene oxide and specifically relates to a high-efficiency multi-metal catalyst for synthesizing hexafluoropropylene oxide. BACKGROUND

[0002] Hexafluoropropylene oxide (HFPO) is a key intermediate in the fluorine chemical industry. The epoxy group in its molecular structure gives it extremely high chemical reactivity, making it a key raw material for the synthesis of high-end products such as perfluoropolyether, fluororubber, fluorine-containing surfactants, and medical anesthetics (such as sevoflurane). For example, its downstream product, perfluoropolyether lubricating oil, has irreplaceable lubricating properties in aerospace and semiconductor manufacturing, while fluorine-containing vinyl ether monomers are the basis for the production of high-performance fluoropolymers. However, the existing gas-phase oxidation process for preparing HFPO has long been plagued by the difficulty in balancing conversion rate and selectivity, which has restricted industrial production efficiency and product quality.

[0003] Currently, its preparation method mainly relies on gas-phase catalytic oxidation technology. In existing technologies, silver-based catalysts (such as Ag / α-Al2O3) can improve selectivity, but have problems such as high silver loading (20%~40%), high cost, and easy sintering at high temperatures. Chinese patent CN118304925A discloses a method for reducing metal loading through the synergistic effect of a bimetallic catalyst (such as Cu-Ce / HZSM-5), but is limited by insufficient adjustment of carrier acidity and relatively high reaction temperature (140~220℃), resulting in a high amount of byproduct generation. In addition, traditional barium-based catalysts are being phased out due to environmental concerns, while silica gel-based catalysts face the bottleneck of insufficient selectivity (<70%).

[0004] In summary, the existing hexafluoropropylene oxide catalysts mainly have the following technical problems: 1. Insufficient activity of single metal: traditional Ag-based catalysts require high loading (>20%), which is costly and prone to deactivation; 2. Limitations of bimetallic synergistic effect: existing Cu-Ce bimetallic systems have strong dependence on carrier acidity, with a narrow reaction temperature range (140~220℃); 3. Insufficient control of byproducts: high temperatures easily generate byproducts such as carbon oxyfluoride (COF2), making it difficult to break through 90% selectivity; 4. Poor carrier adaptability: traditional molecular sieves (such as HZSM-5) have too small pore sizes (0.53~0.58nm), limiting mass transfer efficiency. SUMMARY

[0005] To solve the problems in the prior art, the application provides a high-efficiency multi-metal catalyst for synthesizing hexafluoropropylene oxide. By optimizing the catalyst components (valence state synergy of ternary metals Cu, Ce and Mo) and the carrier structure, the limitations of the existing catalysts in low-temperature oxygen activation efficiency, byproduct inhibition and mass transfer stability are broken, and key problems such as difficulty in balancing conversion rate and selectivity, excessively high reaction temperature, high metal loading cost and insufficient catalyst service life in the prior art are solved, thereby providing technical support for green and efficient industrial production of HFPO.

[0006] The technical scheme of the application is as follows:

[0007] The application first provides a multi-metal catalyst for synthesizing hexafluoropropylene oxide, which is a ternary metal catalyst of Cu, Ce and Mo, and contains the following components in percentage by mass:

[0008] Cu: 1wt%-5wt%, loaded in the form of nanoparticles with a particle size of 5-20nm;

[0009] Ce: 0.5wt%-3wt%, in the form of cerium oxide;

[0010] Mo: 0.1wt%-1wt%, in the form of molybdate;

[0011] Phosphoric acid modified mesoporous silica carrier: 85wt%-95wt%.

[0012] According to a preferred scheme of the application, the pore size of the phosphoric acid modified mesoporous silica carrier is 10-30nm, and the surface acid amount is 0.5-1.2mmol / g.

[0013] According to a preferred scheme of the application, in the multi-metal catalyst, the mass ratio of Cu, Ce and Mo is (1-4.5):(0.5-2.2):(0.1-0.8).

[0014] According to a preferred scheme of the application, the ratio of the pore size of the phosphoric acid modified mesoporous silica carrier to the particle size of the Cu nanoparticles is 2:1-6:1.

[0015] The application also provides a preparation method of the multi-metal catalyst, which comprises the following steps:

[0016] 1) carrier modification: immerse the mesoporous silica carrier in a 0.1-0.5M phosphoric acid solution, dry and calcine to obtain a phosphoric acid modified mesoporous silica carrier;

[0017] 2) metal loading: dissolve copper nitrate, cerium nitrate and ammonium molybdate in an ethanol-water mixture, immerse the carrier obtained in step 1), ultrasonically disperse the immersed carrier, and then dry;

[0018] 3) Gradient reduction of the product obtained in step 2) drying, comprising:

[0019] First stage: the product obtained in step 2) drying is heated to 300-320℃ at 5℃ / min under hydrogen atmosphere, and kept for 1-3 hours;

[0020] Second stage: the atmosphere is switched to a mixed gas with a H2:N2 molar ratio of 1:4, and heated to 450-500℃ at 2℃ / min, and kept for 2-4 hours;

[0021] 4) Passivation treatment: the product obtained in step 3) is passed through nitrogen containing 1% O2, and passivated at room temperature for 2-6 hours to obtain a multi-metallic catalyst.

[0022] According to a preferred scheme of the present application, the calcination temperature of step 1) is 350-450℃, and the calcination time is 1-4h. More preferably, in step 2), the mesoporous silica is impregnated in a phosphoric acid solution, dried at 80℃, and calcined at 400℃ for 2 hours.

[0023] According to a preferred scheme of the present application, the volume ratio of ethanol and water is 1:1; and the drying temperature of step 2) is 110-130℃. More preferably, in step 2), the ultrasonic dispersion is performed for 30 minutes, and the drying is performed at 120℃ for 12 hours.

[0024] The present application further provides a preparation method of hexafluoropropylene oxide, which uses the multi-metallic catalyst, and the method comprises: passing hexafluoropropylene and oxygen into a fixed bed reactor filled with the multi-metallic catalyst, with a molar ratio of 3:1-5:1, and controlling the reaction temperature to be 100-150℃; the reaction pressure is 0.1-0.5MPa; the space velocity is 20-200h -1 , and the gas phase catalytic oxidation is used to prepare hexafluoropropylene oxide.

[0025] Compared with the prior art, the present application has at least the following beneficial effects:

[0026] 1. Ternary metal synergistic system: Cu-Ce-Mo ternary combination is introduced for the first time, and through the oxidation activity of Cu 0 , the oxygen storage capacity of CeO2, and the electronic regulation of MoO4 2- , the conversion rate is increased by 20%-30% compared with the bimetallic catalyst (such as Cu-Ce);

[0027] 2. Precise regulation of carrier acidity: the acid amount (0.5-1.2mmol / g) of the mesoporous silica modified by phosphoric acid is significantly better than that of the traditional HZSM-5 (the acid amount is >2mmol / g), and the excessive cracking of hexafluoropropylene HFP caused by strong acid is avoided;

[0028] 3. Low temperature and high efficiency: the reaction temperature is reduced to 100-150℃, which is 40% lower than the prior art (such as CuO / SiO2 requires 230℃), and the amount of by-product is less than 3%;

[0029] 4. Innovation in preparation process: the gradient reduction process controls the valence state of the metal in stages, avoids the competitive reduction of Cu and Ce / Mo, and ensures uniform distribution of active sites. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 SEM electron micrograph of the catalyst synthesized under the conditions of Example 1;

[0031] Figure 2 SEM electron micrograph of the catalyst prepared under the conditions of Comparative Example 3. DETAILED DESCRIPTION

[0032] The present application will be further described and explained with specific embodiments. The examples are merely exemplary and do not circumscribe the scope of the disclosure. The technical features of each embodiment in the present application can be combined accordingly without conflict.

[0033] The present application exemplarily provides a method for preparing the multi-metal catalyst proposed in the present application using a "co-impregnation-gradient reduction" process. The preparation method mainly includes the following steps:

[0034] (1) Carrier pretreatment: immerse mesoporous silica in a 0.1-0.5M phosphoric acid solution, dry at 80℃, and then calcine at 400℃ for 2h to form a phosphoric acid modification layer;

[0035] (2) Metal loading: dissolve copper nitrate, cerium nitrate and ammonium molybdate in ethanol-water mixture (volume ratio 1:1) according to the proportion, immerse the carrier, and then ultrasonic dispersion for 30min, dry at 120℃ for 12h;

[0036] (3) Gradient reduction: the first stage is to heat to 300℃ at 5℃ / min under hydrogen atmosphere (flow rate 50mL / min), and keep for 2h, so that Cu 2 ⁺ is reduced to Cu 0 ; the second stage is to switch to nitrogen-hydrogen mixed gas (H2:N2=1:4), and heat to 500℃ at 2℃ / min, and keep for 3h, to promote Ce 3+ and Mo 6+ to form stable oxides;

[0037] (4) Passivation treatment: pass in nitrogen containing 1% O2, and passivate at room temperature for 4h to prevent oxidation of metal particles.

[0038] The catalyst prepared by the above method is a ternary metal composite system, which contains, by mass percentage:

[0039] Active layer: Copper (Cu) 1%~5% in the form of nanoparticles (particle size 5~20 nm); Cerium (Ce) 0.5%~3% to regulate surface oxygen vacancies through cerium oxide (CeO2); Molybdenum (Mo) 0.1%~1% in the form of molybdate (MoO4 2- ) to enhance electron transfer ability;

[0040] Support layer: Modified mesoporous silica 85%~95% with pore size 10~30 nm and specific surface area 800~1000 m 2 / g, treated with phosphoric acid to enhance surface acidity (acid amount 0.5~1.2 mmol / g).

[0041] Synergistic mechanism: The Cu-Ce-Mo ternary system promotes oxygen activation through electron coupling effect (Cu 0 -Ce 3+ -Mo 6+ ), reduces the activation energy of epoxidation, CeO2's oxygen vacancies accelerate oxygen dissociation, MoO4 2- inhibits deep oxidation side reactions, and phosphoric acid modified mesoporous silica provides moderate Bronsted acid sites to optimize HFP adsorption orientation.

[0042] The above obtained multi-metal catalyst is applied to the process parameters for synthesizing hexafluoropropylene oxide as follows:

[0043] The multi-metal catalyst is loaded in a fixed bed reactor:

[0044] Raw material ratio: HFP to oxygen molar ratio 1.5:1~5:1 (preferably 4:1), and excess oxygen will promote the occurrence of side reactions;

[0045] Reaction conditions: temperature 100~150℃ (preferably 120℃), pressure 0.1~0.5 MPa, and space velocity 20~200 h -1 . By matching the reactant diffusion rate with the 10~30 nm pore size of the support, internal diffusion limitation is avoided.

[0046] Example 1:

[0047] 1. Catalyst composition

[0048] Cu 3.0wt%, Ce 1.5wt%, Mo 0.5wt%, phosphoric acid modified mesoporous silica support 95wt% (acid amount 0.8 mmol / g, pore size 20 nm).

[0049] 2. Preparation method

[0050] Support modification: immerse mesoporous silica in 0.3M phosphoric acid solution, dry at 80℃, and calcine at 400℃ for 2h.

[0051] Metal loading: Copper nitrate, cerium nitrate and ammonium molybdate were dissolved in an ethanol-water solution (1:1) in a certain proportion, impregnated with the carrier, and then sonicated for 30 min and dried at 120℃ for 12 h.

[0052] Gradient reduction: The first stage is in H2 atmosphere (50 mL / min), with the temperature increased to 300℃ at 5℃ / min and held for 2 hours (reducing Cu). 2 ⁺→Cu 0 The second stage involves switching to an H2 / N2 mixture (1:4), increasing the temperature to 500℃ at a rate of 2℃ / min, and holding for 3 hours (to stabilize Ce). 3+ / Mo 6+ The passivation conditions were 1% O2 / N2 atmosphere, and passivation at room temperature for 4 hours.

[0053] 3. Oxidation reaction

[0054] HFP:O2 = 4:1 (molar ratio), temperature 120℃, pressure 0.3MPa, space velocity 30h -1 .

[0055] 4. Results Analysis

[0056] The catalyst morphology was characterized using SEM (Self-Electron Microscopy). (See attached image.) Figure 1 As shown, the active metal catalyst is basically uniformly supported on a mesoporous silica support, with a total diameter distribution between approximately 500 and 800 nm. Gas chromatography analysis of the products and calculations showed that the HFP conversion was 85.7% and the HFPO selectivity was 90.3%. After 1000 hours of continuous operation, the HFP conversion remained at 83.5%, the selectivity at 89.1%, and the decay rate was <3%.

[0057] Example 2

[0058] 1. Catalyst composition

[0059] Cu 1.5wt%, Ce 0.8wt%, Mo 0.3wt%, phosphoric acid modified mesoporous silica support 97.4wt% (acidity 0.5mmol / g, pore size 30nm).

[0060] 2. Preparation method

[0061] Same as in Example 1, but the gradient reduction conditions are adjusted as follows: first stage 300℃ / 2h (H2), second stage 450℃ / 3h (H2 / N2).

[0062] 3. Oxidation reaction

[0063] HFP:O2 = 5:1, temperature 100℃, pressure 0.1MPa, space velocity 50h -1 .

[0064] 4. Result analysis

[0065] The product was analyzed by gas chromatography and calculated, HFP conversion rate 78.4%, HFPO selectivity 89.6%, conversion rate 76.2% after continuous operation for 1000 hours, selectivity 88.3%, decay rate <3%.

[0066] Example 3

[0067] 1. Catalyst composition

[0068] Cu 4.5wt%, Ce 2.2wt%, Mo 0.8wt%, phosphoric acid modified mesoporous silica support 92.5wt% (acid amount 1.2mmol / g, pore size 10nm).

[0069] 2. Preparation method

[0070] The same as example 1, the gradient reduction condition is adjusted to: the first stage 320℃ / 2h (H2), the second stage 480℃ / 3h (H2 / N2)

[0071] 3. Oxidation reaction

[0072] HFP:O2=3:1, temperature 150℃, pressure 0.5MPa, space velocity 45h -1 .

[0073] 4. Result analysis

[0074] The product was analyzed by gas chromatography and calculated, HFP conversion rate 82.1%, HFPO selectivity 90.5%, conversion rate 79.3% after continuous operation for 1500 hours, selectivity 89.1%, decay rate 3.4%.

[0075] Comparative example 1

[0076] 1. Catalyst composition

[0077] Cu 4.6wt% (total metal amount ≈ Cu+Ce+Mo of example 1), phosphoric acid modified mesoporous silica support 95.4wt% (acid amount 0.8mmol / g, pore size 20nm).

[0078] 2. Preparation method:

[0079] The carrier is phosphoric acid modified as in example 1 (0.3M phosphoric acid, calcination at 400℃ for 2h), immersed in copper nitrate solution, ultrasonic for 30min, dried at 120℃ for 12h, one-step reduction: H2atmosphere (50mL / min), directly increased to 500℃ at 5℃ / min, and kept for 5h (no gradient reduction). Passivation treatment is the same as example 1.

[0080] 3. Oxidation reaction

[0081] Example 1: HFP:O2=4:1, temperature 120℃, pressure 0.3MPa, space velocity 30h -1 .

[0082] 4. Result analysis

[0083] The product was analyzed by gas chromatography and calculated, the conversion rate of HFP was 68.3%, the selectivity of HFPO was 69.7%, after continuous operation for 1500 hours, the conversion rate was 51.2%, and the selectivity was 62.1%. It is shown that the lack of CeO2 oxygen vacancies leads to insufficient oxygen activation, and the lack of Mo inhibiting layer leads to uncontrolled deep oxidation.

[0084] Comparative Example 2

[0085] 1. Catalyst composition

[0086] Cu 3.0wt%, Ce 1.5wt%, HZSM-5 molecular sieve carrier 95.5wt% (acid amount 2.5mmol / g, pore size 0.55nm)

[0087] 2. Preparation method

[0088] The carrier directly uses unmodified HZSM-5, co-impregnated with copper nitrate + cerium nitrate solution, ultrasonic for 30min, dried at 120℃ for 12h; one-step reduction conditions are H2 atmosphere (50mL / min), 400℃ for 4h (traditional process); passivation treatment is the same as example 1.

[0089] 3. Oxidation reaction

[0090] Same as example 1: HFP:O2=4:1, temperature 120℃, pressure 0.3MPa, space velocity 3000h -1

[0091] 4. Result analysis

[0092] The product was analyzed by gas chromatography and calculated, the conversion rate of HFP was 63.8%, the selectivity of HFPO was 74.1%, after continuous operation for 1500 hours, the conversion rate was 47.5%, and the selectivity was 68.3%, and there was slight carbon deposition in the channel. It is shown that strong acid carrier (2.5mmol / g) initiates partial cracking, and lack of Mo electronic regulation leads to poor selectivity.

[0093] Comparative Example 3:

[0094] 1. Catalyst composition

[0095] Cu 10.0wt%, Ce 5.0wt%, Mo 1.5wt%, phosphoric acid modified mesoporous silica carrier 83.5wt% (acid amount 0.8mmol / g, pore size 20nm).

[0096] 2. Preparation method

[0097] Support modification: same as example 1.

[0098] Metal loading: copper nitrate, cerium nitrate, ammonium molybdate were dissolved in ethanol-water solution (1:1) in proportion, the support was immersed and ultrasonic treated for 50 min, and then dried at 120℃ for 12 h.

[0099] Gradient reduction: same as example 1.

[0100] 3. Oxidation reaction

[0101] Same as example 1, HFP:O2=4:1 (molar ratio), temperature 120℃, pressure 0.3 MPa, space velocity 30 h -1 .

[0102] 4. Result analysis

[0103] The catalyst morphology was characterized by SEM. As shown in the attached Figure 2 , the active metal of the catalyst was basically loaded on the mesoporous silica support, and the total diameter was distributed between 500-800 nm. However, due to the excessive loading, the metal particles were not uniformly dispersed and agglomerated, which greatly reduced the specific surface area of the catalytically active component. Gas chromatography analysis of the product showed that the HFP conversion rate was 68.2%, and the HFPO selectivity was 76.6%. This was due to the uneven dispersion of the active metal caused by excessive loading, which reduced the specific surface area and led to a decrease in catalytic performance.

[0104] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent of the present application. For ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A method for preparing a multimetallic catalyst, characterized in that, The method comprises the following steps: 1) carrier modification: immerse mesoporous silica carrier in 0.1-0.5M phosphoric acid solution, dry and calcine to obtain phosphoric acid modified mesoporous silica carrier; 2) metal loading: dissolve copper nitrate, cerium nitrate and ammonium molybdate in ethanol-water mixture, immerse the carrier obtained in step 1), ultrasonic dispersion after the carrier is immersed, and then dry; 3) gradient reduction on the product obtained after drying in step 2), comprising: first stage: the product obtained after drying in step 2) is heated to 300-320℃ at 5℃ / min under hydrogen atmosphere, and kept for 1-3 hours; second stage: switch the atmosphere to H2:N2 mixed gas with a molar ratio of 1:4, heat to 450-500℃ at 2℃ / min, and keep for 2-4 hours; 4) passivation treatment: pass 1% O2-containing nitrogen into the product obtained in step 3), passivate at room temperature for 2-6 hours, and obtain a multi-metal catalyst; the multi-metal catalyst is a Cu, Ce and Mo ternary metal catalyst, which comprises the following components in mass percentage: Cu: 1wt%-5wt%; Ce: 0.5wt%-3wt%; Mo: 0.1wt%-1wt%; phosphoric acid modified mesoporous silica carrier: 85wt%-95wt%.

2. The production method according to claim 1, characterized by, The mesoporous silica carrier in step 1) is mesoporous silica; the calcination temperature in step 1) is 350-450℃, and the calcination time is 1-4h.

3. The production method according to claim 1, characterized by, The volume ratio of ethanol to water in the ethanol-water mixture in step 2) is 1:1; the drying temperature in step 2) is 110-130℃.

4. A process for the preparation of hexafluoropropylene oxide, characterized in that, The multi-metallic catalyst is prepared by the preparation method in any one of claims 1-3, and the method comprises: passing hexafluoropropylene and oxygen into a fixed bed reactor filled with the multi-metallic catalyst at a molar ratio of 3:1-5:1, controlling the reaction temperature to be 100-150 ℃, the reaction pressure to be 0.1-0.5 MPa, and the space velocity to be 20-200 h -1 -1, and preparing hexafluoropropylene oxide by gas phase catalytic oxidation.

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