JPH07324044A - Production of 1,1,1,2,2-pentafluoroethane - Google Patents

Abstract

PURPOSE:To obtain the compound through a simplified process at a markedly reduced cost by reaction between tetrachloroethylene and HF as feedstocks. CONSTITUTION:A reaction between tetrachloroethylene and HF is conducted in a 1st reaction vessel 1 to produce a chlorofluoroethane intermediate, which is then reacted with HF in a 2nd reaction vessel 2 to form 1,1,1,2,2- pentafluoroethane; the products in both the reaction vessels are joined and fed into a distillation column 3, and a 1,1,1,2,2-pentafluoroethane-rich overhead product 17 is delivered via the column top, while the vapor fractions from two side cut tiers 27, 28 are circulated to the 2nd reaction vessel 2 and bottoms 20 are circulated to the 1st reaction vessel.

Description

Detailed Description of the Invention

[0001]

The present invention relates to 1,1,1,2,2-pentafluoroethane (CF ₃ --CHF ₂ , hereinafter referred to as "HFC1".
25 "), and particularly to a method for efficiently producing HFC125 in a simplified process from a product obtained by reacting tetrachloroethylene with HF.

[0002]

2. Description of the Related Art In recent years, ozone layer depletion in the stratosphere by chlorofluorocarbons has been raised as a serious problem, and its use has been internationally prohibited. Furthermore,
Chlorodifluoromethane (CHClF ₂ , commonly known as “HCF
Hydrochlorofluorocarbons such as C22 ") have an extremely low ozone depletion potential compared to chlorofluorocarbons, but their production and use are regulated because the possibility of depleting the ozone layer increases as the amount used increases. It is targeted. Therefore, there is a strong international demand for the development of an HCFC22 substitute that can be used as it is by substituting it for an air conditioner using HCFC22 without affecting the ozone layer. Hydrofluorocarbons have a zero ozone depletion potential and a low global warming potential, so they are not subject to regulation. Therefore, it is desired to find a substitute for HCFC22 from these compounds, but it is difficult to meet with a single component, and a mixture of a plurality of components is being investigated to meet this demand. HFC125 is one of the promising components.

Generally, HFC125 contains tetrachloroethylene (CCl ₂ = CCl ₂ , hereinafter referred to as “PCE”) and H.
It is produced from F with a gas phase two-step reaction. That is, in the first reaction, as shown in the following formula (1), PCE and H
A product mainly containing 1,1-dichloro-2,2,2-trifluoroethane (hereinafter, referred to as “HCFC123”) was obtained from F and then, in the second reaction, as shown by the following formula (2), HCFC123 and HF and mainly the target HF
A product containing C125 is obtained.

[0004]

[Chemical 1]

However, it is known that the reactions represented by the following formulas (3) and (4) also proceed in parallel with the above respective reactions. That is, in the first reaction represented by the formula (3), 1-chloro-1,2,2,2-tetrafluoroethane (hereinafter, referred to as “H
CFC124 ”) is generated, and this is further reacted with HF as in the formula (4) in the second reaction, and finally becomes the target HFC125.

[0006]

[Chemical 2]

Since both HCFC123 and HCFC124 are intermediates in the HFC125 producing reaction, one or both of them will be generically referred to as "intermediate" hereinafter. The first reaction for producing the intermediates represented by the formulas (1) and (3) is, for example, a pressure of 4 kg / cm.
HFC12 represented by formula (2) and formula (4) under the conditions of ² G, temperature 300 ° C., and HF / PCE molar ratio of 4
The second reaction producing 5 is, for example, a pressure of 4 kg / cm
² G, temperature 330 ° C., HF / HCFC123 molar ratio 4 to
Since the reaction proceeds under the condition of 8, it is not possible to combine both reaction steps into a one-step reaction.

Therefore, in the conventional manufacturing process, for example, as shown in FIG. 3, raw materials PCE and HF and the second distillation column 3 are used.
The combined product 30 of PCE and the recovered distillate 40 rich in HF, which is recovered from No. 8, is introduced into the first reactor 31 and reacted therewith, and the intermediate product produced here is introduced into the first deoxidation column 32. Then, HCl, which is a by-product, is removed from the top of this column, and the bottom liquid 33 rich in the intermediate is combined with the intermediate recovered in the second distillation column 38 and the circulating distillate 39 rich in HF to produce the second Reactor 3
4, and then reacted with HF again, the produced product is introduced into the second deoxidation column 35 to remove HCl from the top of the column, and the bottom liquid 36 is introduced into the first distillation column 37. A distillate rich in HFC125 is distilled off from the top of the column, a bottom liquid is introduced into the second distillation column 38 to obtain a circulating distillate 39 rich in the intermediate and HF as a top distillate, and PCE as a bottom liquid. A recovered fraction 40 rich in HF was obtained, a circulating fraction 39 was circulated to the second reactor 34 together with the first deoxidizer bottom liquid 33, and a recovered fraction 40 was circulated to the first reactor 31 together with the raw materials. It was

[0009]

However, this manufacturing process is long and complicated, not only requires at least two distillation columns and two deoxidation columns, but also has a low energy efficiency and a high process cost. It was a problem. The present invention has been made to solve the above problems, and therefore its purpose is to
Efficient and simple HFC125 from CE and HF
It is to provide a method of manufacturing.

[0010]

[Means for Solving the Problems] The above-mentioned problems are solved by dividing the reaction into a first reactor and a second reactor, and in the first reactor, PCE and HF are reacted to form a first reactor containing an intermediate. A product is produced, and at least a part of the first product is reacted with HF in the second reactor to produce a second product containing HFC125, and the products obtained from both reactors are combined. At least a part of the combined product thus obtained is distilled using a distillation column to distill a HFC125-rich overhead fraction from the top of the column, and at least a part of the remainder is circulated separately in each of the above reactors. It can be solved by the method.

In the above, at least a part of the combined product obtained by combining the products obtained from both reactors is supplied to an intermediate feed stage of the distillation column, and two stages different in stage below the feed stage are provided. The first side cut and the second side cut, which are rich in intermediates, are distilled out as gas from the side cut stage, and both side cuts are combined and circulated to the second reactor, and the distillation column bottom from the bottom. The liquid is preferably circulated in the first reactor. The HCl produced by the above reaction is obtained by distilling the combined product and then introducing the overhead fraction of the distillation column into the deoxidizing column to remove it as the overhead fraction, or supplying the combined product to the distillation column. Prior to this, it can be introduced into the deoxidation column and removed as the overhead fraction. In the latter case, the bottom liquid of the deoxidizing column will be supplied to the distillation column.

Next, the present invention will be specifically described with reference to the drawings. FIG. 1 shows a preferred embodiment of the present invention. In FIG. 1, PCE12 and HF11 as feed materials are first introduced into the first reactor 1 in a gas phase. In the first reactor 1,
According to the above formula (1) or formula (3), mainly HCF
Intermediate consisting of C123 and HCFC124, and H
A first product 24 containing Cl is produced.

On the other hand, in the second reactor 2, the first product 24
The first side-cut 18 and the second side-cut 19 rich in the intermediate from the distillation column 3, which is a part of the above, are combined, and HF11 as a feed material is further added and introduced as the second reaction material 14, and the formula (2 ) Or a second product 25 mainly containing HFC125 and HCl by the reaction according to formula (4)
Is generated.

The first product 24 and the second product 25 are combined to form a combined product 15. The combined product 15 is further combined with the recovery intermediate 23 from the refining step 5 and introduced as a combined product 16 into the intermediate supply stage 26 of the distillation column 3. In addition to the top and bottom of this distillation column 3, distillation outlets are provided in two side-cut stages 27 and 28 below the supply stage 26 and having different stages. The combined product 16 introduced from the supply stage 26 is distilled in this distillation column 3, and a column top fraction 17 rich in HFC125 and HCl is distilled from the column top. H from the upper stage 27 of the two side cut stages
The first side cut 18 rich in CFC124 and HF is distilled, and the second side cut 19 rich in HCFC123 and HF is distilled from the lower stage 28. Further, from the bottom, the bottom liquid 20 of the distillation column rich in unreacted PCE and HF
Is obtained.

The first side cut 18 and the second side cut 19 are merged as described above, and a suitable reaction amount of the raw material HF11 is added to this and introduced into the second reactor 2. The bottom liquid 20 of the distillation column is composed of PCE12 and H
It is merged with F11 and circulated in the first reactor 1 as the first reaction raw material 13.

The overhead fraction 17 obtained here is HFC1
25 with HCl and a small amount of unreacted material. The overhead fraction 17 is then introduced into the deoxidizing column 4, the HCl fraction 21 is removed from the overhead, and the deoxidizing column bottom liquid 22 obtained from the bottom is purified in a purification step 5 provided separately. H
FC125, unreacted HF, and a small amount of recovered intermediate 23 are separated. The recovery intermediate 23 is combined with the combined product 15 and circulated as a combined product 16 in the distillation column 3.

According to the method of this embodiment, it is not necessary to add a product separation step to each reactor, the products of these reactors are collectively distilled, and the reaction products containing HFC125 are removed from the column. It is recovered as a top fraction, and the residue is separated into a side-cut fraction rich in intermediates and a bottom liquid of a distillation column rich in unreacted raw materials, which are respectively the second reactor and the first reactor.
Since it is circulated in the reactor, the process conditions in continuous operation are stable, the process control is simple, the equipment is simplified, and the energy consumption rate is lower than in the conventional manufacturing method.

The main substances involved in the above steps and their boiling points under atmospheric pressure are as follows. PCE 121.0 ° C HF 19.5 ° C HCFC123 27.1 ° C HCFC124 -12.0 ° C HFC125 -48.5 ° C HCl -84.9 ° C The HFC125-rich fraction is removed from the confluent 16 containing all of these. At the same time, the residual unreacted material was efficiently separated, and PCE was fed to the first reactor, where HCFC123 and HCF
C124 is required to be circulated in the second reactor. At this time, since HF serves as a raw material for both the first reaction and the second reaction, it may be appropriately distributed to both and circulated.

The present inventors have found that there is a minimum azeotropic relationship between HCFC123 and HF, and between HCFC124 and HF, respectively, and arrived at the present invention. These azeotropes have a pressure of, for example, 4 kg / cm ² G
At an HCFC123 / HF azeotrope (A): molar ratio of 78 /
22, azeotropic point 52 ° C. HCFC124 / HF azeotrope (B): molar ratio 67 /
33, azeotropic point 26 ° C. That is, when the vapor phase of these azeotropes is taken out from the intermediate stage below the feed stage of the distillation column, this vapor phase component is HCFC123 or HCFC124 and H with high purity.
Since it is a mixture with F, it can be suitably used as the second reaction raw material.

Therefore, when one distillation column 3 is used and the combined product 16 is fed as a gas or liquid or a gas / liquid mixed phase to the intermediate feed stage 26, the boiling point is sufficiently low from the top of the column. Product system HFC125 (pressure 4 kg
(About −13 ° C. under C / cm ² G) and an overhead fraction 17 rich in HCl are distilled off, and HCFC123 / which is a second reaction raw material system is fed from the side cut stages below the feed stage 26, respectively.
Gas phase component of HF azeotrope (A) and HCFC124 / H
The vapor phase component of the F azeotropic mixture (B) can be distilled off, and the bottom liquid of the distillation column rich in PCE and HF which is the first reaction raw material system can be taken out from the bottom.

At this time, since the difference in boiling points between the azeotropic mixture (A) and the azeotropic mixture (B) is relatively large, if both gas phase components are simultaneously taken out from the same side-cut stage, they will be removed in the distillation column. It becomes difficult to maintain the gas-liquid equilibrium relationship, and the operation is unstable and the separation ability of each component decreases. Therefore, as shown in FIG. 1, the side cut stages are divided into two upper and lower stages (27 and 2).
8), the upper side 27 is used as the first side cut 18 for the gas phase component of the azeotrope (B), and the lower side 28 is used as the second side cut 18.
If the gas phase component of the azeotropic mixture (A) is taken out as the side cut 19, the gas-liquid equilibrium relationship in the distillation column is stabilized and good separation can be achieved.

The overhead fraction 17 separated by this distillation
Is rich in HFC125 and HCl which are reaction products. However, since both have a sufficiently large boiling point difference and do not form an azeotrope, HCl is removed from the top of the column by distillation in the deoxidation column 4 in the subsequent step. It can be easily separated by distilling. The first side cuts 18 and the second side cuts 19 join together, and the additional H required for the second reaction is added.
It can be introduced into the second reactor 2 together with F11 to cause a reaction for producing HFC125. Distillation tower bottom liquid 2
Since 0 contains substantially no intermediate component and is rich in PCE and HF, it can be recycled and used as a part of the reaction raw material of the first reactor 1.

Since the reaction product HCl has a sufficiently large boiling point difference from other components and does not form an azeotropic mixture, it may be removed using the deoxidation column 4 prior to the above-mentioned distillation. . FIG. 2 shows an example of this method. In the process of FIG. 2, the combined product 16 including the first product 24, the second product 25, and the recovery intermediate 23 is first introduced into the deoxidizing tower 4, where the HCl fraction 21 and the deoxidizing tower bottom are provided. It is separated into liquid 22. The deoxidizing tower bottom liquid 22 contains PCE, HF,
HCFC123, HCFC124, and HFC125
Is included. This deoxidizer bottoms liquid 22 is then fed to a distillation column 3 similar to that described in FIG. 1, where it is distilled and separated to a top fraction 17 which is rich in HFC125 and mainly composed of HCFC124 and HF. 1 side cut 18
And a second side cut 19 mainly composed of HCFC 123 and HF, and a distillation column bottom liquid 20 rich in PCE and HF.

The overhead fraction 17 obtained here is refined in a purification step 5 provided separately, the separated HF is recovered, the recovered intermediate 23 is combined with the combined product 15, and the deoxidation tower 4 is obtained. Is circulated to. The first side cut 18 and the second side cut 19 are merged and introduced into the second reactor 2 as the second reaction raw material 14 together with additional HF. The bottom liquid 20 of the distillation column is circulated to the first reactor 1 as the first reaction raw material 13 together with new PCE and HF.

In both cases, with or without separation of HCl in advance, the internal pressure of the distillation column is preferably in the range of atmospheric pressure to 20 atm. Operation is possible even below atmospheric pressure, but distillation is required to be performed in a low-temperature refrigerant system, which is not desirable in terms of equipment. On the other hand, if the pressure exceeds 20 atm, high pressure equipment is required, which is not preferable.

The production method of HFC125 of the present invention is PCE,
As long as it is a step of reacting HCFC123, HCFC124, or a mixture of any two or more of these with HF, it can be applied to any composition, and HCFC123 or HCF can be used as the above side cut.
It is also possible to withdraw C124, or both, from the process for other purposes.

[0027]

EXAMPLES The present invention will be described in more detail by way of examples. Example 1 HFC125 was produced from PCE and HF using the process shown in FIG. The pressure in the first reactor 1 is 4 kg
/ Cm ² G, operating at a temperature of 300 ° C, and supplying H to this
The F / PCE molar ratio was 4. 2nd reactor 2 pressure 4k
It was operated at g / cm ² G and a temperature of 330 ° C., and the HF / intermediate molar ratio supplied thereto was 4. Distillation column 3 pressure is 4 kg
It was operated at / cm ² G. At this time, the temperature of each part of the distillation column was about 0 ° C at the top of the column, about 44 ° C at the first side cut, about 68 ° C at the second side cut, and about 89 ° C at the bottom. Table 1 shows the flow rate of each component in each step of the process and the weight ratio (wt%) of each component when the flow rate of the combined product 16 is 100 (kg / hr).

[0028]

[Table 1]

From the results of Table 1, the following facts are clear. (1) The overhead fraction 17 is rich in HFC125 and HCl which are reaction products, and is dehydrochlorinated in the deoxidation column 4, whereby the deoxidation column bottom liquid containing HFC125 at a concentration of 87.4% by weight. 22 is obtained. (2) The first side cut 18 is made of HCFC124 and HF, and the second side cut 19 is made of HCFC123.
And HF. Therefore, these merge and the second
It can be suitably used as a reaction raw material of the reactor 2. (3) Since the distillation column bottom liquid 20 does not contain an intermediate component, it can be suitably circulated as a reaction raw material for the first reactor 1. (4) As described above, the HFC125 can be smoothly produced by using only one distillation tower and one deoxidizer tower.

Example 2 A PC was manufactured using the process shown in FIG.
HFC125 was produced from E and HF. First reactor 1
The operating conditions of the second reactor 2 were the same as in Example 1. The distillation column 3 and the deoxidation column 4 were operated at a pressure of 4 kg / cm ² G. At this time, the temperature of each part of the deoxidizer 4 is about −39 ° C. at the top and about 20 ° C. at the bottom, and the temperature of each part of the distillation tower 3 is about 8 ° C. at the top of the tower, about 44 ° C. at the first side cut, and the second side. The cut was about 68 ° C and the bottom was about 89 ° C. Table 2 shows the flow rate of each component in each part of the process and the weight ratio (wt%) of each component when the flow rate of the combined product 16 is 100 (kg / hr).

[0031]

[Table 2]

From the results of Table 2, the following facts are clear. (1) The overhead fraction 17 of the distillation column 3 does not contain HCl, but contains the target product, HFC125, at a concentration of 87.4% by weight. (2) The first side cut 18 is made of HCFC124 and HF, and the second side cut 19 is made of HCFC123.
And HF. Therefore, these merge and the second
It can be suitably used as a reaction raw material of the reactor 2. (3) Since the distillation column bottom liquid 20 does not contain an intermediate component, it can be suitably circulated as a reaction raw material for the first reactor 1. (4) As described above, the HFC125 can be smoothly produced by using only one distillation tower and one deoxidizer tower.

[0033]

As described above in detail, in the method for producing HFC125 of the present invention, the products obtained from both the first reactor and the second reactor are combined, and the combined product is obtained. At least a part of the above is distilled to distill an HFC125-rich overhead fraction from the top of the column, and at least a part of the remaining fraction is separately circulated to the first reactor and the second reactor described above, respectively. Therefore, not only the distillation process is simplified and the process cost can be significantly reduced, but also process loss is reduced and the energy consumption rate can be reduced.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of the present invention.

FIG. 2 is a process drawing showing another embodiment of the present invention.

FIG. 3 is a process drawing showing an example of a conventional manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st reactor, 2 ... 2nd reactor, 3 ... Distillation column, 4 ... Deoxidization column, 17 ... Top fraction, 20 ... Distillation column bottom liquid, 27, 28 ... Side cut stage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Oi 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Denko KK Kawasaki Plant

Claims (6)

[Claims] 1. When producing 1,1,1,2,2-pentafluoroethane by reacting tetrachloroethylene with HF, tetrachloroethylene and HF are reacted in the first reactor to produce 1,1-dichloro. An intermediate-rich first product consisting of -2,2,2-trifluoroethane or 1-chloro-1,2,2,2-tetrafluoroethane is produced and in the second reactor, this first production is produced. At least some of the things and HF
To produce a second product containing 1,1,1,2,2-pentafluoroethane, and at least a part of the combined product obtained by combining the products obtained from both reactors is distilled. Distilling using a column to distill a 1,1,1,2,2-pentafluoroethane-rich overhead fraction from the column top, and at least a part of the remainder is fractionated into each of the above reactors. A method for producing 1,1,1,2,2-pentafluoroethane which is characterized in that it is circulated. 2. At least a part of the combined product is supplied to an intermediate feed stage of the distillation column, and first side cuts rich in intermediates are obtained from each of two side cut stages having different stages below the feed stage. And a second side cut are distilled as a gas, and both of these side cuts are combined to form a second
The method for producing 1,1,1,2,2-pentafluoroethane according to claim 1, wherein the distillation column bottom liquid obtained from the bottom is circulated to the first reactor. 3. The above-mentioned overhead fraction is introduced into a deoxidizing column, and HCl generated by the reaction is distilled off from the top of this deoxidizing column to obtain a bottom liquid of the deoxidizing column from this bottom. A 1,1,1,2,2-pentafluoroethane according to any one of claims 1 to 2, characterized in that a fraction rich in 1,1,1,2,2-pentafluoroethane is obtained. Manufacturing method. 4. The deoxidizing tower bottom liquid obtained by introducing the above combined product into a deoxidizing tower, distilling off and removing HCl generated by the reaction from the top of this deoxidizing tower. Is supplied to the distillation column.
Or 1, 1, 1, 2, 2 according to any one of claims 2 to 4.
-A process for producing pentafluoroethane. 5. The 1,1,1,2,2-pentafluoroethane according to any one of claims 1 to 4, wherein the bottom liquid of the distillation column contains tetrachloroethylene and HF as main components. Manufacturing method. 6. The 1,1,1,2,2-pentafluoroethane of claim 1, wherein the pressure in the distillation column is in the range of atmospheric pressure to 20 atmospheres. Manufacturing method.