JP2007084481A - Preparation method of pentafluoroethane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel preparation method of pentafluoroethane. <P>SOLUTION: In reaction process (a), a reaction product containing pentafluoroethane (HFC-125) is prepared by reacting 1,1,1-trifluoro-2,2-dichloroethane (HCFC-123) with HF in a gas phase in the presence of a catalyst by using a reaction material which contains 1,1,1-trifluoro-2,2-dichloroethane and practically does not contain 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene and 1,1,1,4,4,4-hexafluoro-2-fluoro-2-butene. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing pentafluoroethane (hereinafter also referred to as HFC-125), and more specifically from 1,1,1-trifluoro-2,2-dichloroethane (hereinafter also referred to as HCFC-123) to HFC- It relates to a method of manufacturing 125.

  HFC-125 is useful as an alternative chlorofluorocarbon compound containing no chlorine, and is used, for example, in refrigerants, mixed refrigerants (R-410A, R-407C, R-404A), blowing agents, propellants, and the like.

  HFC-125 can be produced by reacting HCFC-123 with HF. As a method for producing HFC-125 including such a reaction, trichloroethylene (hereinafter also referred to as TrCE) is used as a starting material, 1,1,1-trifluoro-2-chloroethane (hereinafter also referred to as HCFC-133a) and HCFC. The manufacturing method comprised by the three-step reaction process which passes through -123 in order and obtains HFC-125 is mentioned.

  In the method for producing HFC-125 as described above, the reaction step of obtaining HCFC-123 from HCFC-133a is performed by contacting HCFC-133a with chlorine at a temperature of 150 to 320 ° C. in the presence of HF and a catalyst. It is known to produce 1,1,1-trifluoro-2,2,2-trichloroethane (hereinafter also referred to as CFC-113a) as a by-product (see Patent Document 1).

Although not related to a method for producing HFC-125, several other methods are known for the reaction of obtaining HCFC-123 from HCFC-133a.
For example, in one method, HCFC-133a is contacted with chlorine in the presence or absence of a catalyst and in the absence of HF, usually at a temperature of 250 to 500 ° C. (see Patent Document 2). .
For example, in another method, HCFC-133a is brought into contact with chlorine at a temperature of 350 to 450 ° C. in the absence of a catalyst and HF (see Patent Document 3).
A reaction for obtaining HCFC-123 from HCFC-133a by photochlorination is also known, but such a reaction is not preferable because the conversion rate of HCFC-133a and the selectivity of HCFC-123 are low.

JP 2001-240566 A JP-A-1-290638 JP-A-3-24026 JP-A-11-171806

  In the conventionally known reaction for obtaining HCFC-123 from HCFC-133a (refer to Patent Documents 1 to 3), 1,1,1,4,4,4-hexafluoro in addition to CFC-113a as a by-product We have found that 2-chloro-2-butene (hereinafter also referred to as HCFC-1326) can also be produced.

It can be said that the above-mentioned reaction conventionally known aims at or copes with any of the following (1) to (3):
(1) HCFC-133a conversion rate improvement,
(2) Improved selectivity of HCFC-123 compared to CFC-113a, which is a byproduct, and (3) mild and simple reaction conditions.
However, conventionally, it has not been recognized that HCFC-1326 is produced as a by-product in the reaction of obtaining HCFC-123 from HCFC-133a, and moreover, the presence of HCFC-1326 by-product is considered in the production of HFC-125. It was never done.

  In contrast, the present inventors examined the influence of the HCFC-1326 by-product on the production of HFC-125. As a result, HCFC-1326 (boiling point: 30 to 32 ° C.) has a boiling point close to that of HCFC-123 (boiling point: 27.1 ° C.), so that it is difficult to separate and remove by distillation, and HCFC-123 to HFC HCFC-1326 and 1,1,1,4,4,4-hexafluoro-2-fluoro-2-butene that may be derived from HCFC-1326 It has been found that the reaction efficiency (or catalytic activity for the production of HFC-125) is significantly reduced due to (hereinafter also referred to as HFC-1327). These are findings obtained independently by the present inventors. As a result of intensive studies based on such findings, the present invention has been completed.

According to one aspect of the present invention, there is provided a process for producing pentafluoroethane,
(A) 1,1,1-trifluoro-2,2-dichloroethane (HCFC-123) and 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene (HCFC) -1326) and 1,1,1,4,4,4-hexafluoro-2-fluoro-2-butene (HFC-1327) (hereinafter also referred to as HCFC-123-containing reaction raw material). ), 1,1,1-trifluoro-2,2-dichloroethane (HCFC-123) is reacted with HF in the gas phase in the presence of a catalyst to produce a reaction containing pentafluoroethane (HFC-125) A production method including a reaction step for obtaining a product is provided.

  Traditionally, HCFC-123 containing reaction feedstock that can be used to produce HFC-125 also contained HCFC-1326. When such a reaction raw material containing HCFC-123 is used in the catalytic reaction step for obtaining HFC-125 from HCFC-123, the catalytic activity is reduced by HCFC-1326 and HFC-1327 that may be derived therefrom. Need to be replaced or regenerated frequently. Alternatively, it is necessary to change the reaction conditions to more severe conditions in order to compensate for the decrease in catalyst activity, and specifically, it is necessary to gradually increase the reaction temperature. Considering the heat resistance of the reactor and the corrosion resistance of the reactor material at high temperatures against HF and HCl present in the reaction system, there is a limit to raising the reaction temperature. Alternatively, it may be considered that HCFC-1326 is separated and removed in advance from the reaction raw material containing HCFC-123, but such separation is difficult by a conventional distillation operation, the production process is complicated, and the production cost is reduced. It will increase.

  On the other hand, according to the production method of the present invention, since the HCFC-123-containing reaction raw material substantially not containing HCFC-1326 and HFC-1327 is used, it is caused by HCFC-1326 and HFC-1327. Catalyst poisoning can be significantly reduced and desirably eliminated. As a result, the catalytic activity can be maintained high for a relatively long period of time, and thus the conversion rate of HCFC-123 can be maintained high, and the final target product HFC-125 can be efficiently produced. .

  1,1,1,4,4,4-hexafluoro-2-chloro-2-butene (HCFC-1326) and 1,1,1,4,4,4 in the reaction raw material used in the reaction step (a) The total concentration of hexafluoro-2-fluoro-2-butene (HFC-1327) (collectively referred to herein simply as olefins) should be sufficiently low that catalyst poisoning is not a problem, For example, it is less than 100 molppm, preferably about 40 molppm or less (of course, the lower limit is 0 molppm for all). The olefin concentration can be determined by gas chromatographic analysis (the analysis sample is in the gas phase, so the molar basis ratio (molppm) is the same as the volume basis ratio (volppm)).

  In the reaction step (a), HCFC-1326 and HFC-1327 are in an equilibrium state on the catalyst, and they are not converted into other substances. Therefore, the olefin concentration is substantially the same before and after the reaction step (a), and the olefin concentration in the reaction raw material can be regarded as the olefin concentration in the organic matter of the reaction system. The “reaction system” means a reaction mixture in which the reaction proceeds and includes a reaction raw material and a product (target product, intermediate and by-product), and specifically for carrying out the reaction. Gas mixture in the reactor. As described above, HCFC-1326 can be generated in the reaction step for obtaining HCFC-123, and HFC-1327 is generated in the reaction step for obtaining HFC-125 from HCFC-123 by contacting HCFC-1326 with the catalyst. However, the present invention is not limited to this.

  According to the study by the present inventors, there is no quantitative relationship between the concentration of the olefins present in the reaction raw material and thus the reaction system and the degree of catalyst poisoning, and the olefin concentration is present in the range of 100 molppm or more. It has been confirmed that catalyst poisoning occurs and the catalytic activity decreases.

In one embodiment, the production method of the present invention is performed before the reaction step (a).
(B) 1,1,1-trifluoro-2-chloroethane (HCFC-133a) is reacted with Cl ₂ in the gas phase in the absence of a catalyst and HF at a temperature of 200 to 420 ° C. The method further includes a reaction step of obtaining a preliminary reaction product containing 1-trifluoro-2,2-dichloroethane (HCFC-123).
Thus, by applying the absence of catalyst and HF and temperature conditions of 200-420 ° C., the production of HCFC-1326 can be effectively reduced and the pre-reaction product substantially free of olefins. From the preliminary reaction product, the reaction raw material can be obtained. The pressure in the reaction step (b) is not particularly limited. For example, the pressure in the first reaction step (a) may be about 0.3 to 0.7 MPa, typically about 0.6 MPa and the pressure in the vicinity thereof.

In order to obtain the reaction raw material of the reaction step (a) from the preliminary reaction product obtained in the reaction step (b), for example, between the reaction steps (a) and (b),
(P) A distillation step of subjecting the preliminary reaction product obtained in the reaction step (b) to a distillation operation to separate a first fraction containing 1,1,1-trifluoro-2,2-dichloroethane. The first fraction thus obtained is used as a reaction raw material in the reaction step (a).

  This distillation step (p) includes separating a second fraction containing 1,1,1-trifluoro-2-chloroethane (HCFC-133a) by a distillation operation, and the obtained second fraction is subjected to a reaction step ( You may return to b). Thereby, the unreacted HCFC-133a can be recycled and reused in the reaction step (b).

Also, HCl produced by the reaction and optionally unreacted Cl ₂ may be separated in the distillation step (p) or by an additional operation.

  As described above, an HCFC-123-containing reaction raw material used in the reaction step (a) may be obtained.

The said reaction process (a) can be implemented at the temperature of about 250-400 degreeC, for example. The pressure in the reaction step (a) is not particularly limited, and may be, for example, about 0.1 to 1 MPa, typically about 0.3 MPa and a pressure in the vicinity thereof. The pressure in the reaction step (a) may be equal to or different from the pressure in the reaction step (b) when carried out.
Moreover, reaction process (a) can be implemented using the catalyst containing chromium.

In one embodiment, the production method of the present invention comprises, after the reaction step (a),
(Q) The method further includes a distillation step of subjecting the reaction product obtained in the reaction step (a) to a distillation operation to separate a third fraction containing pentafluoroethane (HFC-125). Thereby, HFC-125 which is a final target substance can be obtained by distillation operation.

  This distillation step (q) includes separating a fourth fraction containing 1,1,1-trifluoro-2,2-dichloroethane (HCFC-123) by a distillation operation, and reacting the obtained fourth fraction. You may return to a process (a). Thereby, unreacted HCFC-123 can be recycled to the reaction step (b) and reused.

  The distillation step (q) was obtained by separating a fifth fraction containing 1,1,1,2-tetrafluoro-2-chloroethane (hereinafter also referred to as HCFC-124) by distillation operation. The fifth fraction may be returned to reaction step (a) to react 1,1,1,2-tetrafluoro-2-chloroethane with HF in the gas phase in the presence of a catalyst to produce pentafluoroethane. . Thereby, HCFC-124 which is a by-product can be effectively used as a raw material different from HCFC-123 for obtaining HFC-125 in the reaction step (a).

  In addition, in the distillation step (q) or by an additional operation, HCl produced by the reaction and optionally unreacted HF may be separated.

  The production method of the present invention as described above is preferably applied when continuously carried out, and in particular, at least one of the fourth fraction containing HCFC-123 and the fifth fraction containing HCFC-124 is used in the reaction step (a). This is especially effective when returning. Separating HCFC-123 (boiling point: 27.1 ° C.) and HCFC-1326 (boiling point: 30 to 32 ° C.) and HCFC-124 (boiling point: −12 ° C.) and HFC-1327 (boiling point: −13 to − 14 ° C.), it is difficult to separate the HCFC-1326 in the case of using the reaction raw material containing HCFC-1326 as in the prior art and returning the fraction containing HCFC-123 to the reaction system. In addition, when the fraction containing HCFC-124 is returned to the reaction system, HFC-1327 is also returned together, and HCFC-1326 / HCFC-1327 is accumulated in the reaction system, and the catalyst coverage by olefins is increased. Poison problems can be significant. On the other hand, according to the production method of the present invention, since the reaction raw material containing HCFC-123 substantially free of olefin is used, the fourth and / or fifth fractions are returned to the reaction step (a). However, olefin accumulation in the reaction system can be kept sufficiently low so as not to cause a problem over a long period of time, and preferably the olefin concentration in the reaction system can be maintained at less than 100 molppm. However, this invention is not limited to this, You may implement the said manufacturing method of this invention by a batch type.

  According to the production method of the present invention, in the reaction step (a) for obtaining pentafluoroethane (HFC-125) from 1,1,1-trifluoro-2,2-dichloroethane (HCFC-123) in the presence of a catalyst. Thus, since the HCFC-123-containing reaction raw material substantially free of olefins (HCFC-1326 and HFC-1327) is used, catalyst poisoning due to olefins can be remarkably reduced, and the catalyst can be used for a relatively long period of time. Since the activity can be maintained high, pentafluoroethane can be efficiently produced.

  In addition, according to the production method of the present invention, the catalyst activity can be maintained high for a relatively long period of time, so that the replacement or regeneration frequency of the catalyst can be reduced, and the decrease in the catalyst activity due to the olefin is compensated. There is an advantage that it is not necessary to change the reaction conditions to harsher conditions or to add a complicated process for removing the olefin.

  One embodiment of the present invention will be described in detail below with reference to the drawings. It should be noted that in the description of the fraction throughout this specification, the phrase “comprising (one or more components)” consists essentially of such components, or consists essentially of such components. Furthermore, it shall mean that other components may be contained in a small amount.

1. First reaction step (corresponding to reaction step (b))
First, as shown in FIG. 1, HCFC-133a and Cl ₂ are supplied to the first reactor 1. HCFC-133a can be obtained by, for example, reacting trichlorethylene (TrCE) with HF under appropriate conditions and fluorinating the HFFC (provided that HF is not entrained when fed to the first reactor 1). Unreacted HF is removed in advance). However, the present invention is not limited to this, and HCFC-133a may be prepared by other methods.

またこのとき一般に副反応も起こってＣＦＣ−１１３ａおよびＨＣＦＣ−１３２６を生じ得る。但し、上記反応条件では、ＨＣＦＣ−１３２６の生成量は無視可能な程度に極めて少量である。 In the first reactor 1 HCFC-133a and Cl ₂ are vapor phased in the absence of catalyst and HF at a temperature of about 200-420 ° C., preferably about 350-420 ° C., more preferably about 350-400 ° C. React with. As a result, the following reaction of formula (I) occurs to produce HCFC-123.

At this time, side reactions generally also occur to yield CFC-113a and HCFC-1326. However, under the above reaction conditions, the amount of HCFC-1326 produced is extremely small enough to be ignored.

Thereby, a preliminary reaction product (gas mixture) containing HCFC-123, HCFC-133a, CFC-113a, HCFC-1326, HCl and Cl ₂ is obtained.

2. First distillation step (corresponding to distillation step (p))
The preliminary reaction product obtained as described above is subjected to a distillation operation to obtain a first fraction comprising HCFC-123.

More specifically, first, the preliminary reaction product is supplied from the first reactor 1 to the fractionation tower 3 and separated into a high volatile component fraction and a low volatile component fraction. The highly volatile fraction comprises HCl and unreacted Cl ₂ and is removed from the top of fractionator 3 and removed. On the other hand, the low-volatile component fraction taken out from the fractionation tower 3 as the bottoms is supplied to the rectification tower 5 and is divided into a second fraction comprising HCFC-133a, which is a low-boiling component, and a high-boiling component fraction. To separate. The second fraction taken out from the column top side of the rectifying column 5 is returned to the first reactor 1 in order to recycle the HCFC-133a. On the other hand, the high-boiling component fraction taken out as the bottoms of the rectification column 5 is supplied to the rectification column 7. And the 1st fraction which contains HCFC-123 which is a low boiling point component is taken out from the column top side of the rectification column 7, and the fraction which contains CFC-113a which is a high boiling point component as a bottom liquid. It is taken out.

  As a result, the first fraction is obtained. In addition to HCFC-123, the first fraction contains HCFC-1326 if present. The concentration of HCFC-1326 in the first fraction is less than about 100 molppm, preferably about 40 molppm or less, and can be about 10 molppm or less.

3. Second reaction step (corresponding to reaction step (a))
Next, as shown in FIG. 2, the first fraction containing HCFC-123 obtained above is used as a reaction raw material, and the first fraction (reaction raw material) and HF are supplied to the second reactor 11. A catalyst is put in the second reactor 11 in advance. As this catalyst, one containing chromium can be used, for example, chromium, chromium oxide, chromium fluoride and chromium oxide fluoride, and metal elements (indium, gallium, cobalt, nickel, zinc, aluminum, and the like). It is possible to use chromium-based catalysts including those to which at least one selected from the above is added. Examples of the chromium-based catalyst include a catalyst described in Patent Document 4. Such a chromium-based catalyst may be used as it is, but for example, chromium may be supported on a support such as activated carbon and aluminum fluoride.

このとき式（ＩＩ−ａ）により生じるＨＣＦＣ−１２４の一部はそのまま存在し得る。またこのとき一般に副反応も起こってＣＦＣ−１１５を生じ得る。 In the second reactor 11, HCFC-123 and HF are reacted in the gas phase in the presence of a catalyst at a temperature of about 250 to 400 ° C, preferably about 300 to 350 ° C. As a result, the following reactions of formulas (II-a) and (II-b) occur continuously to yield HFC-125.

At this time, a part of HCFC-124 produced by the formula (II-a) may exist as it is. At this time, a side reaction generally occurs and CFC-115 can be generated.

  By this second reaction step, HCFC-1326 contained in the first fraction comes into contact with the catalyst, and HCFC-1326 and HFC-1327 are equilibrated on the catalyst, and both are contained in the reaction mixture. It will be. Since HCFC-1326 and HFC-1327 are not converted into other substances, the olefin concentration in the reaction mixture in the reactor 11 (concentration of HCFC-1326 and HFC-1327 combined) is before and after the second reaction step. It is essentially the same. However, as will be described later, it should be noted that the olefin concentration increases as the operation time increases when the operation is performed continuously.

  Thereby, a reaction product (gas mixture) containing HFC-125, HCFC-124, HCFC-123, CFC-115, HCFC-1326, HFC-1327, HF and HCl is obtained.

4). Second distillation step (corresponding to distillation step (q))
The reaction product obtained above is subjected to a distillation operation to obtain a third fraction comprising HFC-125.

  More specifically, first, the reaction product is supplied from the second reactor 11 to the fractionation tower 13 and separated into a high volatile component fraction and a low volatile component fraction. The low-volatile component fraction withdrawn from the fractionator 13 as bottoms comprises unreacted HCFC-123 and HF, and is a fourth fraction that may further contain HCFC-1326, which is HCFC-123 and HF. To the second reactor 11 for recycling. On the other hand, the highly volatile component fraction taken out from the top of the fractionation tower 13 is subjected to deoxidation treatment 15 by washing with water to remove HCl, and then subjected to dehydration treatment 17 which is passed through a suitable adsorbent to remain. After removing the water content, it is supplied to the rectifying column 19 and separated into a low boiling point component fraction and a high boiling point component fraction. The high-boiling component fraction withdrawn from the rectification column 19 as the bottoms comprises HCFC-124, and is the fifth fraction that may further contain HFC-1327, which is the second reaction to recycle HCFC-124. Return to vessel 11. On the other hand, the low-boiling component fraction taken out from the top of the rectifying column 19 comprises HFC-125 and CFC-115 having close boiling points, and the product fraction having higher HFC-125 purity by removing CFC-115. In order to obtain this, an extractant is added and supplied to the extractive distillation column 21. In the case of the present embodiment, the extractant has a higher affinity for HFC-125 than CFC-115 and lowers volatility, such as methanol, but is not limited thereto. Not. The extractive distillation column 21 is separated into a fraction containing CFC-115 and a fraction containing an extractant and HFC-125. The fraction comprising CFC-115 is removed from the top of extractive distillation column 21 and removed. On the other hand, the fraction containing the extractant and HFC-125 is taken out from the extractive distillation tower 21 as a bottoms and supplied to the rectifying tower 23, and contains the third fraction containing HCFC-125 and the extractant. Separated into fractions consisting of The collected fraction containing the extractant may be recycled and used as shown in FIG.

  Thereby, the product fraction of HFC-125 which is the final target substance is obtained as the third fraction.

  Throughout this embodiment, the pressure can be about 0.1 to 1.0 MPa. However, the present invention is not limited to this, and the pressure may be set as appropriate, and the pressures in the first reaction step and the second reaction step may be the same or different.

  The manufacturing method as described above is continuously performed. According to this embodiment, since the 4th fraction and the 5th fraction which can respectively contain HCFC-1326 and HFC-1327 are returned to the 2nd reactor 11, HCFC-1326 and HFC-1327 are not removed, but operation As time goes on, it accumulates in the second reactor 11 and thus the olefin concentration in the reaction mixture increases. However, according to this embodiment, since the amount of HCFC-1326 produced in the first reaction step is sufficiently reduced, the olefin concentration in the reaction mixture in the second reactor 11 is less than 100 molppm, preferably about 40 molppm. It is possible to maintain the following low levels for a relatively long period of time.

  Although one embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made.

For example, in this embodiment, Cl ₂ and HCl are separated and removed in the same fraction, but these are separated as separate fractions, and the fraction comprising Cl ₂ is recycled to the first reactor 1 for recycling. You may make it return to. In this embodiment, HCFC-123 and HF are separated and removed in the same fraction, but these may be separated as separate fractions and returned to the second reactor 11 respectively.

  Furthermore, in this embodiment, in order to recycle HCFC-133a, HCFC-123, HF and HCFC-124, the second fraction is returned to the first reaction step, and the fourth and fifth fractions are returned to the second reaction step. However, these are not essential to the present invention, and some or all of these operations may be omitted.

  In this embodiment, extractive distillation technology is used to obtain high-purity HFC-125. However, this is not essential to the present invention. If the desired purity is not so high, extractive distillation is used. And subsequent operations for separating the extractant may be omitted.

  In addition, the distillation operation described in detail in the present embodiment is merely an example, and the number, configuration, arrangement, and the like of the distillation column including the fractionation column and the rectification column may be appropriately changed.

  The reaction steps (a) and (b) in the production method of the present invention were tested.

(Test 1) Reaction step (b) (First reaction step)
A tubular nickel reaction tube having an inner diameter of 2 mm and a length of 12.1 m was maintained at about 0.6 MPa and various temperatures shown in Table 1. HCFC-133a and Cl ₂ were heated to about 200 ° C. at a flow rate of 180 cc / min and 30 cc / min, respectively, and were circulated through the reaction tube.
The reaction product (gas mixture) coming out of the reaction tube was washed with a dilute alkaline aqueous solution previously heated to 70 ° C. to remove HCl and Cl ₂ . The composition of the mixture thus obtained was analyzed with a gas chromatograph using a flame ionization detector (FID), the conversion of HCFC-133a, the selectivity of HCFC-123 compared to CFC-113a, and the The HCFC-1326 concentration was determined. The selectivity of HCFC-123 compared to CFC-113a was determined as the ratio of HCFC-123 to the total amount of HCFC-123 and CFC-113a.
The results are also shown in Table 1.

  As can be seen from Table 1, in Examples 1 to 3 in which the temperature condition was 200 to 420 ° C., the HCFC-133a conversion rate was maintained to an acceptable level, and high HCFC-123 selectivity was achieved, while HCFC The concentration of −1326 could be reduced to 40 molppm or less. On the other hand, in Comparative Examples 1 and 2 in which the temperature condition was 430 ° C. or higher, the HCFC-1326 concentration was 100 mol ppm or higher, and in particular, the temperature condition of 450 ° C. or higher exceeded 500 mol ppm.

(Test 2) Reaction step (a) (second reaction step)
First, by adding HCFC-1326 to HCFC-123, simulated first fractions containing HCFC-1326 at various concentrations shown in Table 1 were prepared.
4.0 g of a catalyst obtained by subjecting chromium oxide to a fluorination treatment (fluorine content: about 15.0%) was charged into a tubular Hastelloy reaction tube having an inner diameter of 20 mm and a length of 1 m. The reaction tube was maintained at about 0.1 MPa and 320 ° C., and the first fraction and hydrogen fluoride prepared above were circulated through the reaction tube at a flow rate of 60 cc / min and 180 cc / min, respectively.
The reaction product (gas mixture) that came out of the reaction tube at a predetermined reaction time was washed with water preliminarily heated to 60 ° C. to remove HCl and HF. The composition of the mixture thus obtained was analyzed with a gas chromatograph using a thermal conductivity detector (TCD) to determine the conversion of HCFC-123 and the selectivity of HFC-125. In addition, the selectivity of HFC-125 was calculated | required as a ratio of HFC-125 with respect to the total amount of organic substances (including HCFC-123, HCFC-124, and HFC-125).
The results are also shown in Table 2.

  Referring to Table 2, in Example 1 using the ideal first fraction without HCFC-1326, the HCFC-123 conversion was the same at 50 hours and 250 hours. The HFC-125 selectivity of Example 1 is slightly different between 50 hours and 250 hours, but this is because the production amounts of HCFC-124 and HFC-125 are in a reciprocal relationship and may slightly vary depending on the reaction state. It can be considered that they are substantially equivalent. Further, in Examples 2 and 3 using the first fraction containing HCFC-1326 at less than 100 molppm, specifically 40 molppm or less, the same results as in Example 1 were obtained and the catalytic activity was maintained. confirmed. On the other hand, in Comparative Examples 1 to 4 using the first fraction containing HCFC-1326 at 100 molppm or more, both the HCFC-123 conversion rate and the HFC-125 selectivity were lowered in 250 hours from 50 hours, A decrease in catalyst activity was observed. In particular, catalyst poisoning was significant in Comparative Example 4 using the first fraction containing HCFC-1326 at 5000 molppm or more.

It is a schematic diagram for demonstrating the first half part of the manufacturing method of the pentafluoroethane in one embodiment of this invention. It is a schematic diagram for demonstrating the second half part of the manufacturing method of the pentafluoroethane in one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11 Reactor 3,13 Fractionation tower 5,7 Fractionation tower 15 Deoxidation treatment 17 Dehydration treatment 19,23 Fractionation tower 21 Extractive distillation tower

Claims (11)

A method for producing pentafluoroethane, comprising:
(A) 1,1,1-trifluoro-2,2-dichloroethane and 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene and 1,1,1, Using a reaction raw material substantially free of 4,4,4-hexafluoro-2-fluoro-2-butene, 1,1,1-trifluoro-2,2-dichloroethane and HF in the presence of a catalyst A production method comprising a reaction step of obtaining a reaction product containing pentafluoroethane by reacting in a gas phase.   1,1,1,4,4,4-hexafluoro-2-chloro-2-butene and 1,1,1,4,4,4-hexafluoro-2 in the reaction raw material used in the reaction step (a) The production method according to claim 1, wherein the total concentration of -fluoro-2-butene is less than 100 molppm. Prior to reaction step (a),
(B) 1,1,1-trifluoro-2-chloroethane is reacted with Cl ₂ in the gas phase in the absence of a catalyst and HF at a temperature of 200 to 420 ° C. The production method according to claim 1 or 2, further comprising a reaction step of obtaining a preliminary reaction product containing 2,2-dichloroethane, wherein the reaction raw material in the reaction step (a) is obtained from the preliminary reaction product. . During reaction steps (a) and (b),
(P) A distillation step of subjecting the preliminary reaction product obtained in the reaction step (b) to a distillation operation to separate a first fraction containing 1,1,1-trifluoro-2,2-dichloroethane. Furthermore, the manufacturing method of Claim 3 which uses the 1st fraction obtained by this as a reaction raw material of a reaction process (a).   The distillation step (p) includes separating a second fraction containing 1,1,1-trifluoro-2-chloroethane by a distillation operation, and returning the second fraction thus obtained to the reaction step (b). The manufacturing method of Claim 4.   The manufacturing method in any one of Claims 1-5 which implements reaction process (a) at the temperature of 250-400 degreeC.   The manufacturing method in any one of Claims 1-6 using the catalyst containing chromium as a catalyst in reaction process (a). After reaction step (a)
(Q) The reaction product obtained in the reaction step (a) is subjected to a distillation operation to further include a distillation step of separating a third fraction containing pentafluoroethane. The manufacturing method as described.   The distillation step (q) includes separating a fourth fraction containing 1,1,1-trifluoro-2,2-dichloroethane by a distillation operation, and the fourth fraction obtained thereby is reacted in the reaction step (a). The manufacturing method according to claim 8, wherein   The distillation step (q) includes separating a fifth fraction containing 1,1,1,2-tetrafluoro-2-chloroethane by a distillation operation, and the resulting fifth fraction is 1,1,1, 10. The process according to claim 8 or 9, wherein 1,2-tetrafluoro-2-chloroethane is returned to reaction step (a) to react with HF in the gas phase in the presence of a catalyst to produce pentafluoroethane. .   The manufacturing method in any one of Claims 1-10 performed continuously.

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