Method for producing 2,3,3,3-tetrafluoropropene

Abstract

This invention provides a method for producing 2,3,3,3-tetrafluoropropene or 2-chloro-1,1,1,2-tetrafluoropropane, which is a precursor of 2,3,3,3-tetrafluoropropene, in two or three reaction steps, using at least one chlorine-containing compound selected from the group consisting of 1,1,1,2,3-pentachloropropane, 2,3-dichloro-1,1,1-trifluoropropane, and 1,1,2,3-tetrachloropropene as a starting material, the reaction products of at least two of the steps being supplied to the same distillation apparatus to subject the products to a separation operation simultaneously. With this method, 2,3,3,3-tetrafluoropropene or 2-chloro-1,1,1,2-tetrafluoropropane, which is a precursor of 2,3,3,3-tetrafluoropropene, can be efficiently produced with reduced energy and equipment costs in an economically advantageous manner.

Claims

1. A method for producing 2,3,3,3-tetrafluoropropene, comprising the reaction steps of: (1) obtaining 2-chloro-3,3,3-trifluoropropene by reacting a fluorinating agent with at least one chlorine-containing compound selected from the group consisting of 1,1,1,2,3-pentachloropropane, 2,3-dichloro-1,1,1-trifluoropropane, and 1,1,2,3-tetrachloropropene; (2) obtaining 2-chloro-1,1,1,2-tetrafluoropropane by adding hydrogen fluoride to the 2-chloro-3,3,3-trifluoropropene, wherein the reaction is conducted in gas phase; and (3) obtaining 2,3,3,3-tetrafluoropropene by dehydrochlorination of the 2-chloro-1,1,1,2-tetrafluoropropane, wherein reaction step (1) is performed in a first reactor, reaction step (2) is performed in a second reactor, and reaction step (3) is performed in a third reactor, wherein the first reactor, the second reactor, and the third reactor each comprise an outlet, the method further comprising the step of supplying the products obtained from the outlet of the first reactor, the products obtained from the outlet of the second reactor, and the products obtained from the outlet of the third reactor to a single distillation apparatus to separate the products into a hydrogen chloride-containing fraction and a fraction free of hydrogen chloride which comprises 2-chloro-1,1,1,2-tetrafluoropropane as a major component, wherein at least two products selected from the group consisting of the products obtained from the outlet of the first reactor, the products obtained from the outlet of the second reactor, and the products obtained from the outlet of the third reactor are mixed prior to being supplied to the single distillation apparatus.

2. The method for producing 2,3,3,3-tetrafluoropropene according to claim 1, wherein reaction step (1) is performed by reacting anhydrous hydrogen fluoride with at least one chlorine-containing compound selected from the group consisting of 1,1,1,2,3-pentachloropropane, 2,3-dichloro- 1,1,1-trifluoropropane, and 1,1,2,3-tetrachloropropene in a gas phase in the presence of a fluorination catalyst while heating.

3. The method for producing 2,3,3,3-tetrafluoropropene according to claim 1, further comprising the step of removing hydrogen chloride from the hydrogen chloride-containing fraction.

4. The method for producing 2,3,3,3-tetrafluoropropene according to claim 3, further comprising the step of recycling all or part of the fraction from which hydrogen chloride has been removed to at least one of the reaction steps.

5. The method for producing 2,3,3,3-tetrafluoropropene according to claim 1, further comprising the step of collecting 2,3,3,3-tetrafluoropropene from the hydrogen chloride-containing fraction and/or the fraction free of hydrogen chloride.

6. The method for producing 2,3,3,3-tetrafluoropropene according to claim 1, further comprising the step of recycling all or part of the fraction free of hydrogen chloride to at least one of the reaction steps.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 shows a flow diagram of the general reaction process used in Comparative Example 1 for producing 2,3,3,3-tetrafluoropropene using in 1,1,1,2,3-pentachloropropane as a starting material.

(2) FIG. 2 is a flow diagram of the reaction process in Examples 1 to 3.

(3) FIG. 3 is a flow diagram of the reaction process in Examples 4 and 5.

DESCRIPTION OF EMBODIMENTS

(4) The present invention is described in more detail below with reference to Examples.

EXAMPLE 1

(5) According to the flow diagram shown in FIG. 2, 2,3,3,3-tetrafluoropropene was produced using 1,1,1,2,3-pentachloropropane as a starting material by a process comprising the trifluoropropene-producing step and the tetrafluoropropene-producing procedure (single-step method).

(6) A Hastelloy reactor with a capacity of 1.5 L was used as a reactor for the trifluoropropene-producing step (reactor 1), and 1.3 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. A Hastelloy reactor with a capacity of 9 L was used as a reactor for the tetrafluoropropene-producing procedure (reactor 2), and 7.7 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst.

(7) As a pretreatment before the use of these catalysts for the corresponding reactions, fluorination treatment was performed by passing anhydrous hydrogen fluoride diluted with nitrogen through the reactors and raising the temperature of each reactor from 200 C. to 360 C. The fluorinated catalysts were used for the corresponding reactions without being removed.

(8) While allowing nitrogen to flow into the reactors, the reactors and preheaters were each heated with an electric furnace. After predetermined temperatures were reached, an operation of the process shown in FIG. 2 started.

(9) The operating conditions of the reactor for the trifluoropropene-producing reaction step (reactor 1) were as follows: a pressure of 0.1 MPa and a temperature of 300 C. The operating conditions of the reactor for the tetrafluoropropene-producing reaction procedure (reactor 2) were as follows: a pressure of 0.1 MPa and a temperature of 365 C. The operating conditions of distillation column 1 (HCl separation step) were as follows: a pressure of 0.75 MPa, a column top temperature of 13 C., and a column bottom temperature of 92 C. Further, a distillation operation at a pressure of 0.75 MPa, a column top temperature of 87 C., and a column bottom temperature of 90 C. was performed using distillation column 2 as a crude purification step.

(10) 50 hours after the operation of the process started, the composition of components in each step of the reaction process was analyzed using gas chromatography. Table 1 shows the operating conditions of each step of the reaction process. Table 2 shows the results of the analysis. The circled numbers shown in Table 2 correspond to the numbers of the steps of the reaction process shown in FIG. 2.

(11) The structure of each product is as follows:
CF.sub.3CFCH.sub.2 (HFO-1234yf)
CF.sub.3CF.sub.2CH.sub.3 (HFC-245cb)
CF.sub.3CClCH.sub.2 (HCFO-1233xf)
CCl.sub.3CHClCH.sub.2Cl (HCC-240db)

(12) TABLE-US-00001 TABLE 1 Reaction Step Reaction Temperature ( C.) Pressure (MPa) Reactor 1 300 0.1 Reactor 2 365 0.1 Column Top Column Bottom Distillation Temperature Temperature Pressure Step ( C.) ( C.) (MPa) Distillation 13 92 0.75 Column 1 (HCl Separation) Distillation 87 90 0.75 Column 2 (Crude Purification)

(13) TABLE-US-00002 TABLE 2 O.sub.2 HCl HF 1234yf 245cb 1233xf 240db (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) {circle around (1)} 0.00 0.00 4.50 0.00 0.00 0.00 1.14 {circle around (2)} 0.00 0.00 23.9 0.00 0.00 0.08 1.14 {circle around (3)} 0.00 4.52 20.5 0.00 0.00 1.21 0.01 {circle around (4)} 1.02 0.00 0.00 0.00 0.00 0.00 0.00 {circle around (5)} 1.02 0.00 145 0.01 0.34 7.14 0.00 {circle around (6)} 1.02 1.13 144 1.13 0.34 6.01 0.00 {circle around (7)} 1.02 5.65 164 1.13 0.34 7.22 0.01 {circle around (8)} 1.02 5.65 0.00 1.12 0.00 0.00 0.00 {circle around (9)} 0.00 0.00 164 0.01 0.34 7.22 0.00 {circle around (10)} 0.00 0.00 145 0.01 0.34 7.14 0.00 {circle around (11)} 0.00 0.00 19.4 0.00 0.00 0.08 0.01

(14) As is clear from Table 2, it can be confirmed that separation of hydrogen chloride and collection of 2,3,3,3-tetrafluoropropene from the products can be carried out using a single distillation apparatus by supplying the components obtained from the outlet of the reactor for the trifluoropropene-producing reaction step (reactor 1) and the components obtained from the outlet of the reactor for the tetrafluoropropene-producing reaction procedure (reactor 2) to the same distillation apparatus to perform a distillation operation. Further, the results show that the unreacted starting material, intermediates, hydrogen fluoride, and the like can effectively be used by subjecting the fraction free of hydrogen chloride to a crude purification (distillation) operation.

EXAMPLE 2

(15) According to the flow diagram shown in FIG. 2, 2,3,3,3-tetrafluoropropene was produced using 2,3-dichloro-1,1,1-trifluoropropane (HCFC-243db) as a starting material by a process comprising the trifluoropropene-producing step and the tetrafluoropropene-producing procedure (single-step method).

(16) A Hastelloy reactor with a capacity of 1.3 L was used as a reactor for the trifluoropropene-producing step (reactor 1), and 1.1 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. A Hastelloy reactor with a capacity of 12 L was used as a reactor for the tetrafluoropropene-producing procedure (reactor 2), and 10 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst.

(17) Fluorination treatment of the catalysts before the reactions and heating of the reactors were performed in the same manner as in Example 1. Thereafter, an operation of the process started under the operating conditions shown in Table 3. The composition of components in each step of the reaction process was analyzed using gas chromatography in the same manner as in Example 1. Table 4 shows the results.

(18) TABLE-US-00003 TABLE 3 Reaction Step Reaction Temperature ( C.) Pressure (MPa) Reactor 1 300 0.1 Reactor 2 365 0.1 Column Top Column Bottom Distillation Temperature Temperature Pressure Step ( C.) ( C.) (MPa) Distillation 1.4 92 0.75 Column 1 (HCl Separation) Distillation 86 88 0.75 Column 2 (Crude Purification)

(19) TABLE-US-00004 TABLE 4 O.sub.2 HCl HF 1234yf 245cb 1233xf 243db (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) {circle around (1)} 0.00 0.00 1.50 0.00 0.00 0.00 1.82 {circle around (2)} 0.00 0.00 19.6 0.00 0.00 0.13 1.82 {circle around (3)} 0.00 1.82 19.6 0.00 0.00 1.94 0.01 {circle around (4)} 1.02 0.00 0.00 0.00 0.00 0.00 0.00 {circle around (5)} 1.02 0.00 134 0.01 0.46 11.4 0.00 {circle around (6)} 1.02 1.82 132 1.83 0.46 9.55 0.00 {circle around (7)} 1.02 3.64 152 1.83 0.46 11.5 0.01 {circle around (8)} 1.02 3.64 0.00 1.82 0.00 0.00 0.00 {circle around (9)} 0.00 0.00 152 0.01 0.46 11.5 0.01 {circle around (10)} 0.00 0.00 134 0.01 0.46 11.4 0.00 {circle around (11)} 0.00 0.00 18.1 0.00 0.00 0.13 0.01

(20) As is clear from Table 4, also when 2,3-dichloro-1,1,1-trifluoropropane is used as a starting material, it can be confirmed that separation of hydrogen chloride and collection of 2,3,3,3-tetrafluoropropene from the products can be carried out using a single distillation apparatus by supplying the components obtained from the outlet of the reactor for the trifluoropropene-producing reaction step (reactor 1) and the components obtained from the outlet of the reactor for the tetrafluoropropene-producing reaction procedure (reactor 2) to the same distillation apparatus to perform a distillation operation. Further, the results show that the unreacted starting material, intermediates, hydrogen fluoride, and the like can effectively be used by subjecting the fraction free of hydrogen chloride to a crude purification (distillation) operation.

EXAMPLE 3

(21) According to the flow diagram shown in FIG. 2, 2,3,3,3-tetrafluoropropene was produced using 1,1,2,3-tetrachloropropene as a starting material by a process comprising the trifluoropropene-producing step and the tetrafluoropropene-producing procedure (single-step method).

(22) A Hastelloy reactor with a capacity of 1.3 L was used as a reactor for the trifluoropropene-producing step (reactor 1), and 1.1 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. A Hastelloy reactor with a capacity of 7.7 L was used as a reactor for the tetrafluoropropene-producing procedure (reactor 2), and 6.4 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst.

(23) Fluorination treatment of the catalysts before the reactions and heating of the reactors were performed in the same manner as in Example 1. Thereafter, an operation of the process started under the operating conditions shown in Table 5. The composition of components in each step of the reaction process was analyzed using gas chromatography in the same manner as in Example 1. Table 6 shows the results.

(24) TABLE-US-00005 TABLE 5 Reaction Step Reaction Temperature ( C.) Pressure (MPa) Reactor 1 300 0.1 Reactor 2 365 0.1 Column Top Column Bottom Distillation Temperature Temperature Pressure Step ( C.) ( C.) (MPa) Distillation 8.9 92 0.75 Column 1 (HCl Separation) Distillation 88 89 0.75 Column 2 (Crude Purification)

(25) TABLE-US-00006 TABLE 6 O.sub.2 HCl HF 1234yf 245cb 1233xf 1230xa (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) {circle around (1)} 0.00 0.00 7.00 0.00 0.00 0.00 1.82 {circle around (2)} 0.00 0.00 27.2 0.00 0.00 0.13 1.82 {circle around (3)} 0.00 5.43 21.8 0.00 0.00 1.94 0.01 {circle around (4)} 1.02 0.00 0.00 0.00 0.00 0.00 0.00 {circle around (5)} 1.02 0.00 167 0.01 0.46 11.4 0.00 {circle around (6)} 1.02 1.82 165 1.83 0.46 9.55 0.00 {circle around (7)} 1.02 7.25 187 1.83 0.46 11.5 0.01 {circle around (8)} 1.02 7.25 0.00 1.82 0.00 0.00 0.00 {circle around (9)} 0.00 0.00 187 0.01 0.46 11.5 0.01 {circle around (10)} 0.00 0.00 167 0.01 0.46 11.4 0.00 {circle around (11)} 0.00 0.00 20.2 0.00 0.00 0.13 0.01

(26) As is clear from Table 6, also when 1,1,2,3-tetrachloropropene is used as a starting material, it can be confirmed that separation of hydrogen chloride and collection of 2,3,3,3-tetrafluoropropene from the products can be carried out using a single distillation apparatus by supplying the components obtained from the outlet of the reactor for the trifluoropropene-producing reaction step (reactor 1) and the components obtained from the outlet of the reactor for the tetrafluoropropene-producing reaction procedure (reactor 2) to the same distillation apparatus to perform a distillation operation. Further, the results show that the unreacted starting material, intermediates, hydrogen fluoride, and the like can effectively be used by subjecting the fraction free of hydrogen chloride to a crude purification (distillation) operation.

EXAMPLE 4

(27) According to the flow diagram shown in FIG. 3, 2,3,3,3-tetrafluoropropene was produced by a process comprising the trifluoropropene-producing step in which 2-chloro-3,3,3-trifluoropropene is obtained using 1,1,2,3-tetrachloropropene as a starting material, and comprising the tetrafluoropropene-producing procedure performed in two reaction steps in which hydrogen fluoride is added to the 2-chloro-3,3,3-trifluoropropene obtained in the trifluoropropene-producing step to produce 2-chloro-1,1,1,2-tetrafluoropropane and then a dehydrochlorination reaction is performed to produce 2,3,3,3-tetrafluoropropene.

(28) A Hastelloy reactor with a capacity of 0.5 L was used as a reactor for the trifluoropropene-producing step (reactor 1), and 0.4 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. A Hastelloy reactor with a capacity of 2.5 L was used as a reactor for the step of addition of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene (reactor 2), and 2.1 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. A Hastelloy reactor with a capacity of 2.0 L was used as a reactor for the step of dehydrochlorination of 2-chloro-1,1,1,2-tetrafluoropropane (reactor 3), and 1.6 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst.

(29) Fluorination treatment of the catalysts before the reactions and heating of the reactors were performed in the same manner as in Example 1. Thereafter, an operation of the process started under the operating conditions shown in Table 7. The composition of components in each step of the reaction process was analyzed using gas chromatography in the same manner as in Example 1. Table 8 shows the results.

(30) TABLE-US-00007 TABLE 7 Reaction Step Reaction Temperature ( C.) Pressure (MPa) Reactor 1 300 0.1 Reactor 2 365 0.1 Reactor 3 365 0.1 Column Top Column Bottom Distillation Temperature Temperature Pressure Step ( C.) ( C.) (MPa) Distillation 1.8 92 0.75 Column 1 (HCl Separation) Distillation 84 96 0.75 Column 2 (Crude Purification)

(31) TABLE-US-00008 TABLE 8 HCl HF 1234yf (kmol/ (kmol/ (kmol/ 1233xf 1230xa 244bb hr) hr) hr) (kmol/hr) (kmol/hr) (kmol/hr) {circle around (1)} 0.00 9.00 0.00 0.00 2.97 0.00 {circle around (2)} 8.91 0.09 0.00 2.97 0.00 0.00 {circle around (3)} 0.00 2.70 0.00 0.00 0.00 0.00 {circle around (4)} 0.00 12.6 0.02 14.3 0.00 9.66 {circle around (5)} 0.00 0.00 0.02 1.66 0.00 22.3 {circle around (6)} 0.00 9.50 0.00 0.00 0.00 13.6 {circle around (7)} 2.85 19.3 2.85 9.80 0.00 0.95 {circle around (8)} 11.8 19.4 2.88 14.3 0.00 23.3 {circle around (9)} 0.00 19.4 0.02 14.3 0.00 23.3 {circle around (10)} 11.8 0.00 2.86 0.00 0.00 0.00 {circle around (11)} 0.00 9.90 0.02 14.3 0.00 9.66

(32) As is clear from Table 8, also in the method comprising three steps in which the tetrafluoropropene-producing reaction procedure is performed in two steps, it can be confirmed that separation of hydrogen chloride and collection of 2,3,3,3-tetrafluoropropene from the products can be carried out using a single distillation apparatus by supplying the components obtained from the outlet of the reactor for the trifluoropropene-producing reaction step (reactor 1), the components obtained from the outlet of the reactor for the step of addition of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene (reactor 2), and the components obtained from the outlet of the reactor for the step of dehydrochlorination of 2-chloro-1,1,1,2-tetrafluoropropane (reactor 3) to the same distillation apparatus to perform a distillation operation. Further, the results show that the unreacted starting material, intermediates, hydrogen fluoride, and the like can effectively be used by subjecting the fraction free of hydrogen chloride to a crude purification (distillation) operation.

EXAMPLE 5

(33) According to the flow diagram shown in FIG. 3, 2,3,3,3-tetrafluoropropene was produced using 2,3-dichloro-1,1,1-trifluoropropane as a starting material. The tetrafluoropropene-producing procedure was carried out in the same manner as in Example 4 in two steps in which hydrogen fluoride is added to the 2-chloro-3,3,3-trifluoropropene obtained in the trifluoropropene-producing step to produce 2-chloro-1,1,1,2-tetrafluoropropane, and then a dehydrochlorination reaction is performed to produce 2,3,3,3-tetrafluoropropene.

(34) A Hastelloy reactor with a capacity of 0.12 L was used as a reactor for the trifluoropropene-producing step (reactor 1), and 0.1 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. A Hastelloy reactor with a capacity of 1.7 L was used as a reactor for the step of addition of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene (reactor 2), and 1.4 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. A Hastelloy reactor with a capacity of 1.7 L was used as a reactor for the step of dehydrochlorination of 2-chloro-1,1,1,2-tetrafluoropropane (reactor 3), and 1.4 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst.

(35) Fluorination treatment of the catalysts before the reactions and heating of the reactors were performed in the same manner as in Example 1. Thereafter, an operation of the process started under the operating conditions shown in Table 9. The composition of components in each step of the reaction process was analyzed using gas chromatography in the same manner as in Example 1. Table 10 shows the results.

(36) TABLE-US-00009 TABLE 9 Reaction Step Reaction Temperature ( C.) Pressure (MPa) Reactor 1 300 0.1 Reactor 2 365 0.1 Reactor 3 365 0.1 Column Top Column Bottom Distillation Temperature Temperature Pressure Step ( C.) ( C.) (MPa) Distillation 8.3 92 0.75 Column 1 (HCl Separation) Distillation 86 96 0.75 Column 2 (Crude Purification)

(37) TABLE-US-00010 TABLE 10 HCl HF 1234yf (kmol/ (kmol/ (kmol/ 1233xf 244bb 243db hr) hr) hr) (kmol/hr) (kmol/hr) (kmol/hr) {circle around (1)} 0.00 0.00 0.00 0.00 0.00 3.00 {circle around (2)} 3.00 0.00 0.00 3.00 0.00 0.00 {circle around (3)} 0.00 2.60 0.00 0.00 0.00 0.00 {circle around (4)} 0.00 13.0 0.03 12.5 11.7 0.00 {circle around (5)} 0.00 0.50 0.03 0.00 24.2 0.00 {circle around (6)} 0.00 10.2 0.00 0.00 13.4 0.00 {circle around (7)} 2.82 19.9 2.80 9.70 0.90 0.00 {circle around (8)} 5.82 20.4 2.83 12.7 25.1 0.00 {circle around (9)} 0.00 20.6 0.03 12.5 25.1 0.00 {circle around (10)} 5.82 0.02 2.80 0.20 0.00 0.00 {circle around (11)} 0.00 10.4 0.03 12.5 11.7 0.00

(38) As is clear from Table 10, also in the method for producing 2,3,3,3-tetrafluoropropene using 2,3-dichloro-1,1,1-trifluoropropane as a starting material in three steps in which the tetrafluoropropene-producing reaction procedure is performed in two steps, it can be confirmed that separation of hydrogen chloride and collection of 2,3,3,3-tetrafluoropropene from the products can be carried out using a single distillation apparatus by supplying the components obtained from the outlet of the reactor for the trifluoropropene-producing reaction step (reactor 1), the components obtained from the outlet of the reactor for the step of addition of hydrogen fluoride to 2-chloro-3,3,3-trifluoropropene (reactor 2), and the components obtained from the outlet of the reactor for the step of dehydrochlorination of 2-chloro-1,1,1,2-tetrafluoropropane (reactor 3) to the same distillation apparatus to perform a distillation operation. Further, the results show that the unreacted starting material, intermediates, hydrogen fluoride, and the like can effectively be used by subjecting the fraction free of hydrogen chloride to a crude purification (distillation) operation.

COMPARATIVE EXAMPLE 1

(39) As a comparative example, 2,3,3,3-tetrafluoropropene was produced using 1,1,1,2,3-pentachloropropane as a starting material by the general process shown in FIG. 1.

(40) More specifically, after the trifluoropropene-producing step in which 2-chloro-3,3,3-trifluoropropene is obtained using 1,1,1,2,3-pentachloropropane as a starting material was performed in reactor 1, a distillation operation for separating HCl, which is a by-product, was carried out in a distillation column A. Subsequently, a distillation operation for separating unreacted 1,1,1,2,3-pentachloropropane and 2-chloro-3,3,3-trifluoropropene, which is a reaction product, was performed using a distillation column B as a crude purification step. The tetrafluoropropene-producing procedure in which 2-chloro-3,3,3-trifluoropropene is fluorinated to produce 2,3,3,3-tetrafluoropropene was then performed in reactor 2. The components obtained from the outlet of the reactor of the tetrafluoropropene-producing procedure was supplied to a distillation column C, and a distillation operation was carried out to separate the components into a column top fraction containing HCl and 2,3,3,3-tetrafluoropropene as main components, and a column bottom fraction containing HF and 2-chloro-3,3,3-trifluoropropene as main components. The column bottom fraction was recycled to the reactor 2. The column top fraction can be subjected to any purification step to obtain 2,3,3,3-tetrafluoropropene.

(41) A Hastelloy reactor with a capacity of 1.2 L was used as a reactor for the trifluoropropene-producing step (reactor 1), and 1.0 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst.

(42) The operating conditions in the distillation column A (HCl separation step) were as follows: a pressure of 0.75 MPa, a column top temperature of 31 C., and a column bottom temperature of 91 C. The operating conditions in the distillation column B (crude purification step) were as follows: a pressure of 0.75 MPa, a column top temperature of 65 C., and a column bottom temperature of 92 C. The column top fraction obtained from the distillation column B (crude purification step), which contains HF and 2-chloro-3,3,3-trifluoropropene as main components, was supplied to the reactor 2 in the next tetrafluoropropene-producing procedure, and the column bottom fraction, which contains HF as a main component, was recycled to the reactor 1.

(43) A Hastelloy reactor with a capacity of 7.8 L was used as a reactor for the tetrafluoropropene-producing procedure (reactor 2), and 6.5 kg of chromium oxide containing CrO.sub.2 as a main component was placed in the reactor as a catalyst. The operating conditions in the distillation column C were as follows: a pressure of 0.75 MPa, a column top temperature of 3.7 C., and a column bottom temperature of 92 C.

(44) Fluorination treatment of the catalyst before the reaction in the reactor 1 (trifluoropropene-producing step) and the catalyst before the reaction in the reactor 2 (tetrafluoropropene-producing procedure) and heating of the reactors were performed in the same manner as in Example 1. Thereafter, an operation of the process started under the operating conditions shown in Table 11. The composition of components in each step of the reaction process was analyzed using gas chromatography in the same manner as in Example 1. Table 12 shows the results.

(45) TABLE-US-00011 TABLE 11 Reaction Step Reaction Temperature ( C.) Pressure (MPa) Reactor 1 300 0.1 Reactor 2 365 0.1 Column Top Column Bottom Distillation Temperature Temperature Pressure Step ( C.) ( C.) (MPa) Distillation 31 91 0.75 Column A Distillation 65 92 0.75 Column B Distillation 3.7 92 0.75 Column C

(46) TABLE-US-00012 TABLE 12 O.sub.2 HCl HF 1234yf 245cb 1233xf 240db (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) (kmol/hr) {circle around (1)} 0.00 0.00 5.10 0.00 0.00 0.00 1.50 {circle around (2)} 0.00 0.00 30.0 0.00 0.00 0.01 1.50 {circle around (3)} 0.00 6.00 25.5 0.00 0.00 1.51 0.00 {circle around (4)} 0.00 5.94 0.00 0.00 0.00 0.00 0.00 {circle around (5)} 0.00 0.06 25.5 0.00 0.00 1.51 0.00 {circle around (6)} 0.00 0.06 0.60 0.00 0.00 1.49 0.00 {circle around (7)} 0.00 0.00 24.9 0.00 0.00 0.01 0.00 {circle around (8)} 1.02 0.00 1.00 0.00 0.00 0.00 0.00 {circle around (9)} 1.02 0.06 93.6 0.01 0.30 9.34 0.00 {circle around (10)} 1.02 1.54 92.0 1.50 0.30 7.85 0.00 {circle around (11)} 1.02 1.54 0.00 1.49 0.00 0.00 0.00 {circle around (12)} 0.00 0.00 92.0 0.01 0.30 7.85 0.00

(47) As is clear from Tables 11 and 12, 2,3,3,3-tetrafluoropropene can be continuously obtained in the process shown in FIG. 1; however, since a distillation column for separating HCl is disposed for each of the trifluoropropene-producing step and the tetrafluoropropene-producing procedure, cooling must be performed for each distillation step. It is thus necessary to repeat heating and cooling during each reaction step and each distillation step respectively, and it is clear that this process increases energy costs and equipment costs.