Method for preparing HFO-1243zf by coupling VDF and R152a

Abstract

The invention provides a method for preparing HFO-1243zf by coupling VDF and R152a, which is characterized in that a target product is synthesized in one step under the conditions of 50-80 DEG C and 0.5-1.5 MPa through lewis acid catalytic addition reaction. Comprising the steps of raw material purification (VDF is greater than or equal to 99.5%, and R152a is greater than or equal to 99.0%), catalytic addition (a catalyst is an AlCl / FeCl / ZnCl homogeneous phase or load type), and product refining (water washing, alkali washing and vacuum rectification). The method breaks through the limitation of a traditional multi-step process, the VDF conversion rate is larger than or equal to 80%, the HFO-1243zf selectivity is larger than or equal to 90%, the purity is larger than or equal to 99.5%, the reaction energy consumption is reduced by 55%, and the equipment cost is reduced by 50%. The method is simple in process, mild in condition and low in cost, an efficient and environment-friendly technical scheme is provided for industrial production of HFO-1243zf, and the method has important significance in promoting development of a low-GWP refrigerant industry chain.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic fluorine chemical synthesis, and particularly relates to a method for preparing a hydrofluoroolefin compound HFO-1243zf (3,3,3-trifluoropropene) by Lewis acid catalytic addition reaction with vinylidene fluoride (VDF) and 1,1-difluoroethane (R152a) as raw materials. BACKGROUND

[0002] Hydrofluoroolefins (HFOs) have extremely low global warming potential (GWP, usually GWP < 10) and zero ozone layer destruction potential (ODP = 0), and have become key environmentally friendly chemical products and intermediates for replacing high-GWP hydrofluorocarbon (HFC) refrigerants (such as R134a, GWP = 1300). HFO-1243zf, as an important HFO derivative, contains an unsaturated double bond and active hydrogen in its molecular structure, and has active chemical properties. It can be used to prepare various high-performance environmentally friendly refrigerants, blowing agents, aerosol propellants, and fluorine-containing fine chemicals through further fluorination, halogenation, polymerization, etc. reactions, and has wide application prospects in the fields of refrigeration, fire protection, and high polymer materials.

[0003] At present, the preparation methods of HFO-1243zf (3,3,3-trifluoropropene) mainly have the following technical bottlenecks: 1. Complex multi-step synthesis process: The traditional synthesis route usually needs to realize through 3-4 steps of halogenated alkane dehydrohalogenation, halogenated alkene addition / elimination, etc. The process flow is long, the total yield is low, generally only 50%-60%, and there are many by-products, which are difficult to separate and purify, and the production cost is high.

[0004] 2. Harsh reaction conditions: Some existing processes need to be carried out at high temperature (such as above 200℃) or high pressure (such as above 5MPa), which not only has high energy consumption, but also has high requirements for the material of the reaction equipment, increases the equipment investment and maintenance cost, and high temperature and high pressure also aggravate the corrosion of the equipment and the operation risk.

[0005] 3. Selectivity and cost of catalyst: When using a heterogeneous metal oxide catalyst, the selectivity of the target product HFO-1243zf is usually less than 85%, in order to improve the selectivity, noble metal catalysts or rare metal oxides are often used, which significantly increases the cost of the catalyst, and is not conducive to large-scale industrial application.

[0006] 4. Insufficient raw material utilization: Traditional processes have extremely strict requirements for the purity of raw materials (such as requiring purity > 99.9%), and an imbalance in the molar ratio of raw materials can easily lead to excessive waste of raw materials, increasing the burden of subsequent separation and the difficulty of industrial scale-up.

[0007] Therefore, developing a new method that is simple in process, mild in reaction conditions, low in catalyst cost, high in raw material utilization and can efficiently prepare high-purity HFO-1243zf is of great practical significance and economic value for promoting the green and sustainable development of the low-GWP refrigerant industry chain. Summary of the Invention

[0008] The purpose of this invention is to overcome the aforementioned defects in the existing HFO-1243zf preparation process and provide a method for preparing the hydrofluoroolefin compound HFO-1243zf (3,3,3-trifluoropropylene, CF3CH=CHCl) from vinylidene fluoride (VDF, CH2=CF2) and 1,1-difluoroethane (R152a, CH3CHF2) via Lewis acid-catalyzed addition reaction. This method achieves a one-step, highly efficient synthesis of HFO-1243zf through an innovative reaction pathway, optimized catalyst system, and process integration. It offers advantages such as simple process, mild reaction conditions, high conversion and selectivity, low cost, and environmental friendliness.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing HFO-1243zf by coupling VDF with R152a includes the following steps: (1) Raw material pretreatment: The VDF raw material is purified to a purity of ≥99.5%; the R152a raw material is distilled to a purity of ≥99.0%. Effective pretreatment of raw materials can remove impurities that are harmful to subsequent catalytic reactions, ensuring the smooth progress and high selectivity of the reaction.

[0010] (2) Lewis acid-catalyzed addition reaction: In the presence of a Lewis acid catalyst, pretreated VDF and R152a are introduced into a reactor at a molar ratio of 1:1.05-1:1.2, and the addition reaction is carried out under reaction conditions of 50-80℃ and 0.5-1.5MPa to generate a mixed gas containing the target product HFO-1243zf. The Lewis acid catalyst is one or a combination of two or more of aluminum chloride (AlCl3), ferric chloride (FeCl3), and zinc chloride (ZnCl2). This invention is the first to realize the carbon-carbon double bond addition reaction of VDF and R152a under Lewis acid catalysis. By activating the α-H of R152a with the Lewis acid catalyst, it promotes the efficient electrophilic addition of R152a to the carbon-carbon double bond of VDF, generating HFO-1243zf in one step, breaking through the limitations of traditional synthetic routes.

[0011] (3) Product purification: the HFO-1243zf-containing mixed gas generated in step (2) is subjected to water washing, alkali washing and rectification treatment in sequence to remove impurities such as catalyst residues, acidic gases and unreacted raw materials, and finally HFO-1243zf product with purity ≥ 99.5% is obtained.

[0012] In step (2) of the present application, the Lewis acid catalyst can be in a homogeneous phase, i.e. the catalyst is dissolved in a suitable solvent and contacts with the reaction gas; alternatively, the Lewis acid catalyst can also be supported on a carrier such as γ-Al2O3, SiO2, etc. to form a supported catalyst. When a supported catalyst is used, the loading of the catalyst (in terms of the percentage of the active component of the catalyst to the mass of the carrier) is 5-20 wt%. The supported catalyst is beneficial for the recovery and recycling of the catalyst, reduces the cost of the catalyst, and can reduce the separation difficulty problem that may be caused by the homogeneous catalyst.

[0013] In step (2) of the present application, in order to optimize the reaction efficiency and product selectivity, the space velocity of the addition reaction is controlled to be 1000-3000 h -1 -1, and the residence time of the reaction gas in the reactor is controlled to be 10-30 seconds. The space velocity and the residence time are important parameters affecting the conversion rate and selectivity of the gas-solid phase catalytic reaction, and appropriate space velocity and residence time can ensure that the raw materials are fully reacted, while avoiding the side reactions that may be caused by too long residence time.

[0014] In step (1) of the present application, the purification of VDF preferably uses the process of low-temperature condensation (-20°C) combined with molecular sieve adsorption to effectively remove water (control the water content < 50 ppm), oxygen (control the oxygen content < 100 ppm) and other hydrocarbon impurities in the raw gas, and improve the purity of VDF to ≥ 99.8%. The rectification of R152a is preferably carried out by a packed column, for example, a packed column with a theoretical plate number of 30 is used, and the reflux ratio is controlled to be 5:1 to remove light and heavy component impurities (R152, i.e. CH2FCH2F, etc.) in R152a, and improve the purity of R152a to ≥ 99.5%. Higher purity of raw materials helps to improve the selectivity and conversion rate of the reaction.

[0015] In step (2) of the present application, the temperature of the addition reaction is more preferably controlled to be 60-70°C, and the pressure is more preferably controlled to be 1.0-1.2 MPa. Under this preferred mild reaction condition, both the high reaction activity and the inhibition of the occurrence of side reactions (such as polymerization, cracking, etc. of raw materials or products) can be ensured, thereby obtaining higher selectivity of the target product.

[0016] In step (2) of the present application, the reactor is preferably a fixed bed reactor, and the inner diameter of the reactor can be 15-25 mm, and the inside is filled with 30-50 mesh of the Lewis acid catalyst (especially when it is a supported catalyst). The fixed bed reactor is conducive to realizing continuous production, the catalyst bed structure is stable, and the mass transfer and heat transfer effects are good.

[0017] In step (3) of the present application, the water washing and alkali washing conditions are: the water washing tower packing height is ≥2 m, and the water temperature is ≤25℃; the alkali washing tower uses 5% NaOH solution, and the liquid-gas ratio is ≥1:5. The operating pressure of the rectification treatment is preferably 20-100 kPa (absolute pressure), and by controlling the operating conditions of the rectification tower, the fraction with a boiling point in the range of 58-62℃ is collected, so that the high-purity HFO-1243zf product is obtained.

[0018] The core innovation of the present application is: 1. Development of a new reaction path: breaking through the limitations of traditional halogenated olefin multi-step synthesis, the direct carbon-carbon double bond addition reaction of VDF and R152a under Lewis acid catalysis is first proposed and realized. By activating the alpha-H of the fluorinated alkane (R152a) with a Lewis acid catalyst, efficient electrophilic addition with the carbon-carbon double bond of VDF occurs, and the molecular structure of the target product HFO-1243zf is constructed in one step, significantly shortening the process flow.

[0019] 2. Application of high-efficiency catalyst system: AlCl3, FeCl3, ZnCl2 and other inexpensive and readily available Lewis acids are selected as catalysts, whether homogeneous or supported, can efficiently catalyze the above addition reaction under mild conditions of 50-80℃ and 0.5-1.5 MPa, avoiding the harsh requirements of high temperature and high pressure on equipment in traditional processes, and effectively inhibiting the occurrence of side reactions (such as polymerization, cracking), ensuring high selectivity of the target product.

[0020] 3. Process integration and parameter optimization: through the systematic integration and optimization of raw material pretreatment process (deep purification and precise rectification), reaction key parameters (molar ratio, temperature, pressure, space velocity, residence time) and product refining process (water washing, alkali washing, rectification), excellent results of VDF conversion rate ≥80%, HFO-1243zf selectivity ≥90% are achieved, and the total yield is improved by 20%-30% compared with traditional multi-step process.

[0021] Compared with the prior art, the beneficial effects of the present application are: 1. Simple and efficient process: one-step addition reaction replaces traditional multi-step synthesis, reduces reaction steps and equipment investment, shortens production cycle, and significantly improves production efficiency.

[0022] 2. Mild reaction conditions: The reaction temperature is reduced by 70-120°C compared to traditional processes, the reaction pressure is reduced by 1.5-2.5 MPa, the equipment material requirement is simplified from special alloy (such as Hastelloy) to ordinary stainless steel, which greatly reduces the equipment purchase and maintenance cost.

[0023] 3. High raw material utilization and good product selectivity: Through optimized catalyst system and process parameters, the VDF conversion rate can reach 80%-88%, the HFO-1243zf selectivity can reach more than 90%, the raw material consumption (calculated by VDF) is reduced, and the economy of raw materials is improved.

[0024] 4. High product purity: After refining, the purity of the product HFO-1243zf can reach more than 99.5%, meeting the requirements of high-end applications for product quality.

[0025] 5. Significant environmental and economic benefits: The entire process does not discharge a large amount of wastewater and waste residue, and the catalyst can be recycled (service life ≥ 500 h); the energy consumption cost is reduced by more than 55% compared to traditional processes, the production cost (calculated by ton of product) is reduced by more than 30%, which meets the requirements of green chemical industry and sustainable development.

[0026] In summary, the process of the present application is simple, mild, low-cost catalyst, high raw material conversion rate and product selectivity, good product purity, which provides an efficient, environmentally friendly and economically feasible technical solution for the industrial production of HFO-1243zf, and has important significance and broad application prospect for promoting the green development of low GWP refrigerant industry chain. DETAILED DESCRIPTION

[0027] The present application will be further described in detail by specific examples, but the scope of protection of the present application is not limited thereto.

[0028] The present application provides an efficient and environmentally friendly HFO-1243zf synthesis method, which realizes high selectivity and yield under mild conditions through innovative reaction path and optimized catalyst system. The application effect of AlCl3 supported catalyst system, FeCl3 homogeneous catalyst system and ZnCl2 composite catalyst system is demonstrated, and compared with the traditional three-step method, the advantages of the present application in improving yield, reducing energy consumption and cost are highlighted. Specific examples verify the feasibility and superiority of the process, which provides a solid foundation for its industrial application.

[0029] Example 1: AlCl3 supported catalyst system (1) Raw material pretreatment: VDF purification: low temperature condensation (-20 °C) combined with 4A molecular sieve adsorption process was used to remove water in raw material gas to <50 ppm, oxygen to <100 ppm and other hydrocarbon impurities, and the purity of VDF was increased to 99.8%. R152a rectification: rectification was carried out through a packed column with 30 theoretical plates, the reflux ratio was controlled to 5:1, and the impurities (such as R152) were removed to a content of <0.5%, and the purity of R152a reached 99.5%.

[0030] (2) Addition reaction: Catalyst: 15wt% AlCl3 / γ-Al2O3 supported catalyst (particle size 2-4 mm). Reactor: fixed bed reactor, inner diameter 20 mm. Raw material ratio: the molar ratio of VDF to R152a was 1:1.1. Reaction conditions: temperature 60 °C, pressure 1.0 MPa, space velocity 2000 h-1, reaction gas residence time about 15 seconds.

[0031] Preparation of 15wt% AlCl3 / γ-Al2O3: γ-Al2O3 support (particle size 2-4 mm) was dried at 120 °C for 2 hours, immersed in 15wt% AlCl3 ethanol solution for 2 hours, dried at 100 °C, and then calcined at 350 °C for 4 hours under N2 atmosphere; (3) Product purification: The mixed gas generated by the reaction was successively washed with water (room temperature, to remove catalyst dust and part of soluble impurities), and washed with alkali (5% NaOH solution, liquid-gas ratio 1:5, to neutralize trace amounts of HCl and other acidic gases). Rectification: vacuum rectification column was used, operating pressure 50 kPa (absolute pressure), theoretical plate number 50, and the fraction with boiling point 58-62 °C was collected. Test results: VDF conversion rate 85.3%, HFO-1243zf selectivity 92.1%, and product purity after rectification 99.7% (GC-MS detection, impurity peak area <0.3%).

[0032] Example 2: FeCl3 homogeneous catalytic system Raw materials: VDF purity 99.9%, R152a purity 99.7%, and catalyst FeCl3 (amount 3% of total raw material mass). Reaction conditions: molar ratio VDF:R152a = 1:1.05, temperature 70 °C, pressure 1.2 MPa, residence time 15 seconds. The remaining steps were the same as in Example 1. Test results: VDF conversion rate 88.2%, HFO-1243zf selectivity 90.5%, yield 79.8%; product purity after rectification 99.8%, and GC detection showed that the by-products were <0.2%.

[0033] Example 3: ZnCl2 composite catalyst system Raw materials: VDF purity 99.7%, R152a purity 99.5%, catalyst 5wt% ZnCl2-10wt% AlCl3 / SiO2, other steps same as example 1.

[0034] Preparation of 5wt% ZnCl2-10wt% AlCl3 / SiO2: 100g SiO2carrier (particle size 1-3mm) was immersed in 5wt% ZnCl2aqueous solution and 10wt% AlCl3ethanol solution in turn, dried at 100°C after each step, and finally calcined at 300°C for 3 hours.

[0035] Test results: VDF conversion rate 81.5%, HFO-1243zf selectivity 93.0%, yield 75.8%; the product was verified by nuclear magnetic hydrogen spectrum (1HNMR), and the structure was consistent with CF3CH=CHCl, and the purity was 99.6%.

[0036] Comparative example: traditional three-step synthesis process Steps: ① R133a (CH2ClCF3) removes HCl to HCFO-1233xf (CF3CCl=CH2), ② HCFO-1233xf and HF addition, ③ remove HF to HFO-1243zf.

[0037] Conditions: total reaction temperature 150-200°C, pressure 3.0MPa, CrO3 / AlF3 catalyst used. Results: total yield 52.3%, selectivity 81.2%, energy consumption (per unit product) is 65% higher than the present invention, and equipment investment cost increases by 120%.

Claims

1. A process for the production of HFO-1243zf from VDF coupled with R152a, characterized in that, The method comprises the following steps: (1) raw material pretreatment: purifying VDF to a purity of ≥99.5%, and rectifying R152a to a purity of ≥99.0%; (2) addition reaction: passing the pretreated VDF and R152a into a reactor in a molar ratio of 1:1.05-1:1.2 in the presence of a Lewis acid catalyst, and reacting at 50-80℃ and 0.5-1.5 MPa to generate a mixed gas containing HFO-1243zf; (3) product refining: sequentially performing water washing, alkali washing and rectification treatment on the mixed gas, and collecting a fraction with a boiling point of 58-62℃ to obtain HFO-1243zf with a purity of ≥99.5%.

2. The method of claim 1, wherein, In step (1), the VDF purification adopts a low-temperature condensation (-20℃) combined with a molecular sieve adsorption process, with water content controlled to be <50 ppm and oxygen content controlled to be <100 ppm; the R152a rectification adopts a packed tower with a plate number of ≥30 and a reflux ratio of ≥5:

1.

3. The method of claim 1, wherein, In step (2), the Lewis acid catalyst is one or a combination of two or more of AlCl3, FeCl3 and ZnCl2, and the catalyst is in a form of a homogeneous phase or is supported on a γ-Al2O3 or SiO2 carrier; when the catalyst is in a supported form, the loading amount is 5-20 wt%.

4. The method of claim 1, wherein, In step (2), the space velocity of the addition reaction is 1000-3000 h⁻¹, and the residence time of the reaction gas in the reactor is 10-30 seconds.

5. The method of claim 1, wherein, In step (2), the temperature of the addition reaction is 60-70℃, and the pressure is 1.0-1.2 MPa.

6. The method of claim 1, wherein, The reactor in step (2) is a fixed bed reactor, which is internally filled with 30-50 mesh of the Lewis acid catalyst.

7. The method of claim 1, wherein, In step (3), the packing height of the water washing tower is ≥2 m, and the water temperature is ≤25℃; the alkali washing tower adopts a 5% NaOH solution, and the liquid-gas ratio is ≥1:

5.

8. The method of claim 1, wherein, In step (3), the operation pressure of the rectification treatment is 20-100 kPa, and a fraction with a boiling point of 58-62℃ is collected.