Method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene

Abstract

Disclosed in the present invention is a method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene. The method comprises: introducing 1,1,1,3-tetrachloropropane, 1,1,1,2,3-pentachloropropane, and hydrogen fluoride into a first reactor, and reacting under the action of a first catalyst to obtain a first reactor reaction product; performing rectification on the first reactor reaction product to obtain a 3,3,3-trifluoropropene product and a tower kettle product, mixing the tower kettle product with hydrogen fluoride, and then introducing the mixture into a second reactor, and reacting under the action of a second catalyst to obtain a second reactor reaction product; and separating the second reactor reaction product from hydrogen chloride, water washing, alkaline washing, and drying to obtain a 2,3,3,3-tetrafluoropropene product. The present invention has the advantages of simple process, high efficiency, flexible operation, low investment, and low energy consumption.

Description

A method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene Technical Field

[0001] The present invention relates to a method for preparing fluorine-containing olefins, in particular to a method for co-producing 3,3,3-trifluoropropylene and 2,3,3,3-tetrafluoropropylene. Background Art

[0002] On September 15, 2021, China officially announced its accession to the Kigali Amendment. The Kigali Amendment aims to regulate HFCs (third-generation refrigerants, primarily hydrofluorocarbons) worldwide, requiring A5 countries, including China, to freeze HFC production and consumption in 2024, begin reducing HFCs in 2029, and achieve an 80% reduction by 2045. Therefore, the development and research of green, efficient, and low-GWP refrigeration technologies is urgent.

[0003] Fourth-generation refrigerants primarily refer to fluoroolefins (HFOs), which boast advantages such as zero ODP and extremely low GWP. A representative product is 2,3,3,3-tetrafluoropropene (HFO-1234yf, also known as R1234yf). HFO-1234yf has a boiling point of -29°C, an ODP of 0, a GWP of 4, and an atmospheric lifetime of 11 days. It can be used as a refrigerant to replace HFC-134a in automotive air conditioning systems. Three main methods for the industrialization of HFO-1234yf are available: the 3,3,3-trifluoropropene method, the hexafluoropropene method, and the 1,1,2,3-tetrachloropropene (TCP) method. The 3,3,3-trifluoropropene method has a long route, produces a lot of waste, and has high product costs; the 1,1,2,3-tetrachloropropene method has fewer reaction steps and offers high raw material utilization; and the hexafluoropropene method has a long route but low overall yields. All other production processes are derived from intermediate raw materials from these three routes.

[0004] 3,3,3-Trifluoropropene (HFO-1243zf, also known as R1243zf) has a boiling point of -22°C, an ODP of 0, a GWP of 1, and an atmospheric lifetime of 7 days. R1243zf is primarily used as a low-GWP refrigerant and a pharmaceutical intermediate. Depending on the starting material, its synthesis methods include fluorination of 1,1,1,3-tetrachloropropane, fluorination of trichloropropene (1,1,1-trichloropropene, 1,1,3-trichloro-1-propene), addition of chlorotrifluoromethane to ethylene, and carbene reaction. Fluorination of 1,1,1,3-tetrachloropropane is currently the most common method used in industrial production.

[0005] Because industrial equipment for producing HFO-1234yf and HFO-1243zf requires large investment and has high operating costs, while general equipment for simultaneously producing HFO-1234yf and HFO-1243zf requires less investment, can flexibly adjust the output of the two products, and has great operational flexibility, the technology for simultaneously preparing HFO-1234yf and HFO-1243zf has become a research hotspot.

[0006] For example, CN115322071A discloses a method for co-producing trifluoropropene and tetrafluoropropene using 1,1,1,2,3-pentafluoropropane as a raw material. This method uses 1,1,1,2,3-pentafluoropropane as a raw material and a metal ion-modified Mg-Al composite metal oxide as a catalyst. The reaction is carried out in a fixed bed reactor, and H2 is introduced during the reaction. The feed space velocity is 400-450 h -1 The reaction temperature is 330-350°C and the reaction pressure is atmospheric pressure. This invention provides a new method for preparing fluoroolefins, enabling the simultaneous production of 3,3,3-trifluoropropene, 1,3,3,3-tetrafluoropropene, and 2,3,3,3-tetrafluoropropene in a single step. However, its disadvantages are that the product is primarily tetrafluoropropene, trifluoropropene selectivity is low, production flexibility is limited, and the addition of hydrogen increases the difficulty and cost of subsequent separation.

[0007] Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides a method for co-producing HFO-1243zf and HFO-1234yf with simple process, high yield, good selectivity and low energy consumption.

[0009] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene, comprising the following steps:

[0010] (a) introducing 1,1,1,3-tetrachloropropane (HCC-250fb), 1,1,1,2,3-pentachloropropane (HCC-240db) and hydrogen fluoride (HF) into a first reactor, reacting them under the action of a first catalyst to obtain a first reactor reaction product;

[0011] (b) passing the reaction product of the first reactor into a first distillation tower for separation to obtain a first distillation tower top component and a first distillation tower bottom component;

[0012] (c) passing the top component of the first distillation tower into a second distillation tower for separation to obtain a 3,3,3-trifluoropropene product and hydrogen chloride (HCl); passing the bottom component of the first distillation tower and hydrogen fluoride into a second reactor, reacting them under the action of a second catalyst to obtain a reaction product of the second reactor;

[0013] (d) passing the reaction product of the second reactor into a third distillation tower for separation to obtain a third distillation tower top component and a third distillation tower bottom component;

[0014] (e) passing the top component of the third distillation tower into a fourth distillation tower for separation to obtain hydrogen chloride and a bottom component of the fourth distillation tower;

[0015] (f) washing the bottom components of the fourth distillation tower with water, alkali washing, and drying to obtain a 2,3,3,3-tetrafluoropropene product.

[0016] As a preferred embodiment of the present invention, the first catalyst is a supported metal catalyst, wherein the supported metal catalyst is at least one of CrCl3, SbCl3, SnCl4, TiCl4, and SbCl5 supported on a carrier, and the carrier is one of activated carbon, silica, alumina, and molecular sieve.

[0017] As a preferred embodiment of the present invention, the first catalyst is one of CrCl3 / C, SbCl3 / SiO2, SnCl4 / Al2O3, TiCl4 / molecular sieve, and SbCl5 / C.

[0018] As a preferred embodiment of the present invention, the second catalyst is a supported antimony-based or chromium-based catalyst, wherein the mass percentage of antimony or chromium is 5 to 25%.

[0019] As a preferred embodiment of the present invention, the second catalyst is one of SbCl5 / SiO2, Cr2O3 / Al2O3, CrCl3 / C, and SbCl5 / molecular sieve.

[0020] As a preferred embodiment of the present invention, the molar ratio of 1,1,1,3-tetrachloropropane to 1,1,1,2,3-pentachloropropane in step (a) is 0.5-2:1, the molar ratio of hydrogen fluoride to 1,1,1,2,3-pentachloropropane is 7.5-60:1, the reaction temperature is 50-280°C, and the pressure is 0.1-1.5 MPa.

[0021] As a preferred embodiment of the present invention, the amount of hydrogen fluoride used in step (c) is 3 to 10 times the molar number of 1,1,1,2,3-pentachloropropane described in step (a), the reaction temperature is 100 to 350° C., and the pressure is 0.1 to 1.5 MPa.

[0022] As a preferred embodiment of the present invention, the first reactor and the second reactor are liquid phase reactors or gas phase fixed bed reactors.

[0023] As a preferred embodiment of the present invention, the bottom components of the third distillation tower obtained in step (d) are circulated to the first reactor to continue the reaction.

[0024] The present invention realizes the co-production of HFO-1243zf and HFO-1234yf through two reactors. The first reactor mainly undergoes the fluorination reaction of 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane. The main equation is as follows: CCl3CH2CH2Cl(HCC-250fb)+3HF→CF3CH=CH2(HFO-1243zf)+4HCl CCl3CHClCH2Cl(HCC-240db)+3HF→CF3CCl=CH2(HCFO-1233xf)+4HCl CCl3CHClCH2Cl(HCC-240db)+2HF→CF2ClCCl=CH2(HCFO-1232xf)+3HCl CF3CH=CH2(HFO-1243zf)+HF→CF3CHFCH3(HFC-254eb) CF3CCl=CH2(HCFC-1233xf)+HF→CF3CFClCH3(HCFC-244bb)

[0025] The boiling points of some substances in the present invention are as follows:

[0026] In the present invention, the first reactor can be a liquid-phase or gas-phase reactor. 1,1,1,3-tetrachloropropane, 1,1,1,2,3-pentachloropropane, and hydrogen fluoride are introduced into the first reactor to produce a mixture containing CF3CH=CH2 (HFO-1243zf), CF3CCl=CH2 (HCFO-1233xf), CF2ClCCl=CH2 (HCFO-1232xf), CF3CHFCH3 (HFC-254eb), and CF3CFClCH3 (HFC-244bb). Rectification is performed based on the boiling points of the various substances. The material exiting the first reactor is passed through a first distillation tower for separation. HFO-1243zf and HCl are separated at the top of the tower. HFO-1243zf and HCl are then separated in a second distillation tower to obtain the target product, HFO-1243zf. The material at the bottom of the first distillation tower directly enters the second reaction process.

[0027] The second reactor of the present invention mainly undergoes the fluorination reaction of CF3CCl=CH2, and the main equations are as follows: CF3CCl=CH2(HCFO-1233xf)+HF→CF3CF=CH2(HFO-1234yf)+HCl CF3CF=CH2(HFO-1234yf)+HF→CF3CF2CH3(HFC-245cb)+HCl

[0028] The material exiting the bottom of the first distillation column is fed into a second reactor along with HF to produce a mixture containing CF3CF=CH2 (HFO-1234yf), CF3CF2CH3 (HFC-245cb), and HCl. Rectification is performed based on the boiling points of the various substances. The material exiting the second reactor is fed into a third distillation column, where HFO-1234yf and HCl are separated at the top. The material at the bottom of the column is returned to the first reactor for a cyclic reaction. The HFO-1234yf and HCl are separated in a fourth distillation column, where HCl is separated at the top and crude HFO-1234yf is obtained at the bottom. This crude HFO-1234yf product is then washed with water, rinsed with alkali, and dried as is conventional practice in the art to yield the 2,3,3,3-tetrafluoropropene product.

[0029] The main raw materials of the present invention are 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane. 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane can be fed into the first reactor separately or mixed before feeding into the first reactor. The mixture of 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane can be prepared by physically mixing 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane, or by liquid-phase chlorination of 1,1,1,3-tetrachloropropane. For example, by controlling the conversion rate of 1,1,1,3-tetrachloropropane, mixtures of 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane with different molar ratios can be obtained.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. High yield and good selectivity. The total conversion rate of raw materials 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane is above 96.8%, and the total selectivity of products 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene is above 98.2%;

[0032] 2. The process is simple and the cost is low. The present invention improves the reaction efficiency by optimizing the reaction process, catalyst and material ratio, reaction temperature and pressure, etc. The reaction temperature and reaction pressure are relatively low, the reaction conditions are mild and easy to control, the production process is significantly simplified, and energy consumption is reduced. The raw materials 1,1,1,3-tetrachloropropane and 1,1,1,2,3-pentachloropropane are inexpensive and widely available, further reducing the production cost.

[0033] 3. Green and environmentally friendly, with less three wastes. The unreacted raw materials and intermediate products of the present invention can be recycled into the reactor to continue the reaction, which significantly reduces the discharge of three wastes;

[0034] 4. Small investment and high operational flexibility. One set of equipment can simultaneously produce HFO-1243zf and HFO-1234yf. The product ratio can be flexibly adjusted according to market needs, significantly reducing equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a process flow chart of the present invention.

[0036] As shown in the figure: 1 is the first reactor, 2 is the first distillation tower, 3 is the second distillation tower, 4 is the mixer, 5 is the second reactor, 6 is the third distillation tower, and 7 is the fourth distillation tower. DETAILED DESCRIPTION

[0037] The process of the present invention is shown in FIG1 . A mixture of raw materials HCC-250fb and HCC-240db and HF are introduced into a first reactor 1 filled with a first catalyst for reaction. The obtained reaction product is introduced into a first distillation tower 2 to obtain a first distillation tower top component and a first distillation tower bottom liquid containing unreacted raw materials and other heavy components. The first distillation tower top component is introduced into a second distillation tower 3 to obtain 3,3,3-trifluoropropene product in the bottom of the tower and hydrogen chloride at the top of the tower. The first distillation tower bottom liquid and hydrogen fluoride are introduced into a mixer 4 for mixing and then are subjected to a filtration step. The reaction product is then introduced into a second reactor 5 filled with a second catalyst, where it reacts under the action of the second catalyst to produce a second reactor reaction product. The second reactor reaction product is passed into a third distillation tower 6 for separation to produce a third distillation tower overhead component and a third distillation tower bottom component. The third distillation tower overhead component is passed into a fourth distillation tower 7 for separation to produce hydrogen chloride at the top and crude 2,3,3,3-tetrafluoropropene in the bottom. The crude 2,3,3,3-tetrafluoropropene is then washed with water, washed with alkali, and dried to produce a 2,3,3,3-tetrafluoropropene product. HCl separated from the top of the second distillation tower 3 and the top of the fourth distillation tower 7 can be sent to other devices for utilization. The bottom component of the third distillation tower can be returned to the first reactor 1 for recycling.

[0038] The following examples further clearly and completely describe the technical solutions of the present invention. Obviously, the described examples are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0039] Example 1

[0040] A mixture of the raw materials HCC-250fb and HCC-240db and HF were introduced into a first reactor (liquid-phase reactor) filled with a first catalyst, CrCl3 / C. The temperature and pressure were set, and the reaction was carried out under the action of the first catalyst. The reaction product was passed into a first distillation column for separation. The bottom product of the first distillation column was mixed with HF and then introduced into a second reactor (liquid-phase reactor) filled with a second catalyst, SbCl5 / SiO2 (Sb loading of 5 wt%), for reaction. The temperature and pressure were set, and the reaction was carried out under the action of the second catalyst. The reaction product was passed into a third distillation column for separation. The reaction parameters for the first and second reactors are shown in Table 1, and the composition of the organic matter at the outlet is shown in Table 2.

[0041] Example 2

[0042] A mixture of the raw materials HCC-250fb and HCC-240db and HF were introduced into a first reactor (gas-phase fixed-bed reactor) filled with a first catalyst, SbCl3 / SiO2. The temperature and pressure were set, and the reaction was carried out under the action of the first catalyst. The reaction product was introduced into a first distillation tower for separation. The bottom product of the first distillation tower and HF were mixed and introduced into a second reactor (liquid-phase reactor) filled with a second catalyst, Cr2O3 / Al2O3 (Cr loading of 10 wt%), for reaction. The temperature and pressure were set, and the reaction was carried out under the action of the second catalyst. The reaction product was introduced into a third distillation tower for separation. The reaction parameters for the first and second reactors are shown in Table 1, and the composition of the organic matter at the outlet is shown in Table 2.

[0043] Example 3

[0044] A mixture of the raw materials HCC-250fb and HCC-240db and HF were introduced into a first reactor (liquid phase reactor) filled with a first catalyst, SnCl4 / Al2O3. The temperature and pressure were set, and the reaction was carried out under the action of the first catalyst. The reaction product was introduced into a first distillation column for separation. The bottom product of the first distillation column and HF were mixed and introduced into a second reactor (gas phase fixed bed reactor) filled with a second catalyst, CrCl3 / activated carbon (Cr loading of 15 wt%). The temperature and pressure were set, and the reaction was carried out under the action of the second catalyst. The reaction product was introduced into a third distillation column for separation. The reaction parameters for the first and second reactors are shown in Table 1, and the composition of the organic matter at the outlet is shown in Table 2.

[0045] Example 4

[0046] A mixture of the raw materials HCC-250fb and HCC-240db and HF were introduced into a first reactor (gas-phase fixed-bed reactor) filled with a first catalyst, TiCl4. The temperature and pressure were set, and the reaction was carried out under the action of the first catalyst. The reaction product was introduced into a first distillation column for separation. The bottom product of the first distillation column and HF were mixed and introduced into a second reactor (gas-phase fixed-bed reactor) filled with a second catalyst, SbCl5 / molecular sieve (Sb loading of 20 wt%). The temperature and pressure were set, and the reaction was carried out under the action of the second catalyst. The reaction product was introduced into a third distillation column for separation. The reaction parameters for the first and second reactors are shown in Table 1, and the composition of the organic matter at the outlet is shown in Table 2.

[0047] Example 5

[0048] A mixture of the raw materials HCC-250fb and HCC-240db and HF were introduced into a first reactor (gas-phase fixed-bed reactor) filled with a first catalyst, SbCl5. The temperature and pressure were set, and the reaction was carried out under the action of the first catalyst. The reaction product was passed into a first distillation column for separation. The bottom product of the first distillation column and HF were mixed and introduced into a second reactor (gas-phase fixed-bed reactor) filled with a second catalyst, Cr2O3 / alumina (Cr loading of 25 wt%), for reaction. The temperature and pressure were set, and the reaction was carried out under the action of the second catalyst. The reaction product was passed into a third distillation column for separation. The reaction parameters for the first and second reactors are shown in Table 1, and the composition of the organic matter at the outlet is shown in Table 2.

[0049] Table 1 Reaction parameters of Examples 1-5

[0050] Table 2 Reaction results of Examples 1-5

Claims

1. A method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene, characterized in that: The following steps are involved: (a) introducing 1,1,1,3-tetrachloropropane, 1,1,1,2,3-pentachloropropane and hydrogen fluoride into a first reactor, reacting them under the action of a first catalyst to obtain a reaction product of the first reactor; (b) passing the reaction product of the first reactor into a first distillation tower for separation to obtain a first distillation tower top component and a first distillation tower bottom component; (c) passing the top component of the first distillation tower into a second distillation tower for separation to obtain a 3,3,3-trifluoropropene product and hydrogen chloride; passing the bottom component of the first distillation tower and hydrogen fluoride into a second reactor, reacting under the action of a second catalyst to obtain a reaction product of the second reactor; (d) passing the reaction product of the second reactor into a third distillation tower for separation to obtain a third distillation tower top component and a third distillation tower bottom component; (e) passing the top component of the third distillation tower into a fourth distillation tower for separation to obtain hydrogen chloride and a bottom component of the fourth distillation tower; (f) washing the bottom components of the fourth distillation tower with water, alkali washing, and drying to obtain a 2,3,3,3-tetrafluoropropene product.

2. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 1, characterized in that: The first catalyst is a supported metal catalyst, which is at least one of CrCl3, SbCl3, SnCl4, TiCl4, and SbCl5 supported on a carrier, and the carrier is one of activated carbon, silica, alumina, and molecular sieve.

3. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 2, characterized in that: The first catalyst is one of CrCl3 / C, SbCl3 / SiO2, SnCl4 / Al2O3, TiCl4 / molecular sieve, and SbCl5 / C.

4. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 1, characterized in that: The second catalyst is a supported antimony-based or chromium-based catalyst, wherein the mass percentage of antimony or chromium is 5-25%.

5. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 4, characterized in that: The second catalyst is one of SbCl5 / SiO2, Cr2O3 / Al2O3, CrCl3 / C, and SbCl5 / molecular sieve.

6. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 1, characterized in that: The molar ratio of 1,1,1,3-tetrachloropropane to 1,1,1,2,3-pentachloropropane in step (a) is 0.5-2:1, the molar ratio of hydrogen fluoride to 1,1,1,2,3-pentachloropropane is 7.5-60:1, the reaction temperature is 50-280° C., and the pressure is 0.1-1.5 MPa.

7. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 1, characterized in that: The amount of hydrogen fluoride used in step (c) is 3 to 10 times the molar number of 1,1,1,2,3-pentachloropropane in step (a), the reaction temperature is 100 to 350° C., and the pressure is 0.1 to 1.5 MPa.

8. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 1, characterized in that: The first reactor and the second reactor are liquid phase reactors or gas phase fixed bed reactors.

9. The method for co-producing 3,3,3-trifluoropropene and 2,3,3,3-tetrafluoropropene according to claim 1, characterized in that: The bottom component of the third distillation tower obtained in step (d) is recycled to the first reactor to continue the reaction.

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