JPH06298682A - Production of 1,1,1,2-tetrafluoroethane - Google Patents

Abstract

PURPOSE:To produce HFC-134a useful as a fluorocarbon substitute in high productivity. CONSTITUTION:HFC-134a is produced by fluoripating HCFC-133a with HF in the presence of a fluorination catalyst containing cadmium, chromium, oxygen and fluorine as essential components and having a Cd/Cr atomic ratio of 0.01-0.6.

Description

Detailed Description of the Invention

[0001]

The present invention relates to 1-chloro-2,2 in the production of 1,1,1,2-tetrafluoroethane (hereinafter, abbreviated as HFC-134a), which is an alternative CFC which does not destroy the ozone layer. , 2-trifluoroethane (hereinafter referred to as HCF
C-133a) and hydrogen fluoride (hereinafter abbreviated as HF) are reacted in the presence of a novel fluorination catalyst to obtain a target compound HFC-134a in high yield.

[0002]

H by fluorination of HCFC-133a
The synthesis reaction of FC-134a is a thermodynamically disadvantageous endothermic reaction, and an equilibrium exists. Therefore, in general, HCF
The reaction is carried out under the condition that HF of stoichiometry or higher is coexisted with C-133a to give a significant equilibrium conversion rate. As an example, in Japanese Patent Laid-Open No. 55-27138, CrF ₃ .3H ₂
O is treated with air as a catalyst under a normal pressure at a reaction temperature of 400 ° C., a molar ratio of HF and HCFC-133a (hereinafter, abbreviated as molar ratio) 8, space velocity (hereinafter, abbreviated as SV) 55
Under the reaction condition of ⁰ hr ^-1, the yield of HFC-134a is 32.
It is obtained in%. In Japanese Patent Laid-Open No. 1-268651, CoC
Using a catalyst obtained by fluorinating l ₂ / Al ₂ O ₃ , HFC under normal pressure under a reaction condition of a reaction temperature of 410 ° C., a molar ratio of 10 and a contact time of 30 seconds (SV120 hr ⁻¹ ).
The -134a yield is 32%.

When the reaction is carried out at such a low SV, the productivity is poor, and the high reaction temperature causes not only a thermal energy loss but also a decrease in the selectivity, and further, the findings of the present inventors. According to the method, the catalyst life is shortened. Therefore,
Various studies aiming at high activity and long life of the catalyst have been made so far. That is, Japanese Patent Laid-Open No. 2-1729
In 33, Al, Mg, Ca, Ba, Sr, Fe, N
It is disclosed that a catalyst composed of a halide or oxide containing at least one element selected from the group consisting of i, Co and Mn and Cr, has excellent durability (lifetime). Further, in EP502605, C supporting Zn is used.
It is disclosed that the r-based catalyst provides high activity. Further, Japanese Patent Laid-Open No. 346943/1992 asserts that a catalyst made of partially fluorinated Cr ₂ O ₃ supporting Ru or Pt has a long life.

[0004]

However, in recent years,
As described in JP-A-4-346943, when the fluorination reaction of HCFC-133a with HF is carried out using a conventional Cr-based or Al-based catalyst, the reaction rate decreases when the reaction pressure is increased. Then, it became clear that there is a new problem peculiar to this reaction that productivity decreases. That is, atmospheric pressure (hereinafter, abbreviated as normal pressure)
Even with a catalyst showing a high reaction yield below, when the reaction pressure is increased (for example, 10 kg / cm ² G (gauge pressure)), HFC-
Although the selectivity of 134a is slightly improved, HCFC-1
The yield is considerably reduced due to the reduced conversion of 33a. (At the time of comparison, the reaction temperature, the molar ratio, and the SV converted to the standard state are the same)

1 kg / c reaction in an actual manufacturing facility
Performing at a normal pressure of about m ² G is not preferable because it requires ancillary equipment for lowering the pressure, resulting in an increase in equipment cost.
Furthermore, the selectivity of the reaction is better under pressure, and in particular, the reaction rate does not decrease even when the reaction pressure is increased, because the by-product amount of a high unsaturated compound that needs to be removed can be suppressed, and more preferable. Are required to develop a catalyst whose reaction rate increases with increasing reaction pressure. As a result of intensive studies to solve the above problems, it was found that the negative effect of pressure on the reaction rate can be improved by combining Cd and Cr as metal components.
The present invention has been made based on the above-mentioned invention.
It is an object of the present invention to provide a method for producing 134a with high productivity.

[0006]

In the present invention, HC
By contacting FC-133a and HF, HFC-134
In the method for producing a, Cd, Cr, O and F are contained as essential components, and the atomic ratio of Cd to Cr is 0.01.
The solution was to use a catalyst of ˜0.6, particularly preferably 0.03 to 0.5. It is not so preferable that a large amount of alkali metal is contained as a constituent component of the catalyst (% order by weight), but other (Cd, Cr,
Elements other than O and F) may be included in the order of% or more.

The catalyst used in the present invention is a compound containing Cd and Cr (preferably an oxide or a hydroxide) as a catalyst precursor, which is HF, F ₂ , or a halogenated hydrocarbon having fluorine in the molecule. Fluorinated by such as O and O
It can be prepared by partially replacing H with fluorine. As a method for preparing the catalyst precursor, any conventionally known method such as a kneading method, an impregnation method or a coprecipitation method can be used, and a raw material for preparing the catalyst precursor can be obtained on an industrial scale. Then, any compound may be used. Among the above methods, the impregnation method and the coprecipitation method are preferable because Cd and Cr can be uniformly distributed. Among them, the coprecipitation method is more preferable because it is possible to uniformly adjust the bulk composition of the catalyst.

Therefore, as an example of a preferable method for preparing the catalyst precursor, a method in which a liquid in which the Cd and Cr compounds are dissolved is reacted with a precipitant to form a precipitate, which is filtered, washed, dried and calcined (coprecipitation) Method), a method of impregnating Cr ₂ O ₃ or chromium hydroxide with a solution of a Cd compound, and drying and firing (example of impregnation method). As a more preferred example of the preparation method, the pH of the reaction solution of the solution in which the compounds of Cd and Cr are dissolved and the precipitating agent in the coprecipitation method is in the range of 6 to 12, particularly preferably 6.5 to 10. While controlling as described above, a method in which the slurry prepared by dropping both simultaneously or alternately is filtered, washed, dried, and fired in N ₂ . If a molded article is desired as the catalyst shape, tablet molding may be performed before or after firing,
A molded product can be obtained by carrying out extrusion molding before drying.

The catalyst may be prepared by the above-mentioned method and any other known method.
Atomic ratio (hereinafter, abbreviated as Cd / Cr ratio) is 0.01 to 0.
6, preferably 0.03 to 0.5. If the Cd / Cr ratio is smaller than the above range,
The rate of decrease in the reaction rate due to an increase in the reaction pressure is large, and if the Cd / Cr ratio is too large, the reaction rate at normal pressure decreases, which is not preferable. The adjustment of the Cd / Cr ratio can be easily achieved by controlling the ratio of the powder to be mixed in the kneading method and the solution concentration or solution composition of the Cd and / or Cr compound in the impregnation method or the coprecipitation method.

The fluorination catalyst of the present invention further contains O and F as essential components. The appropriate range of the O and F contents varies depending on the Cd / Cr ratio and the method for preparing the catalyst precursor, but it is necessary that both components be 0.3% by weight or more based on the total weight of the catalyst. The preferred range of O content is 1 to 25% by weight. To include O and F in the catalyst, as described above, C
This can be achieved by fluorinating a compound containing d and Cr (preferably an oxide or hydroxide) with HF, F ₂ , a halogenated hydrocarbon having fluorine in the molecule, or the like. A preferred method for fluorinating a catalyst precursor is 30
0 to 450 ° C., preferably under pressure (2 to 10 kg / c
m ² G) is a method of fluorinating with HF.

The fluorination catalyst of the present invention containing Cd, Cr, O and F as an essential component can be applied when fluorinating a halogenated hydrocarbon with HF, but HCFC-133a
It is particularly effective when the above fluorination reaction is carried out under pressure. That is, the negative effect of the reaction pressure, which is observed when a conventional fluorination catalyst such as chromium oxyfluoride is used, is that the reaction rate is decreased when the reaction pressure is increased and the conversion rate of HCFC-133a is decreased, which can be improved. .
More specifically, the Cd, Cr, O and F of the present invention will be described.
Although the catalyst containing as an essential component is somewhat less active than conventional fluorination catalysts such as chromium oxyfluoride at atmospheric pressure, even if the reaction pressure is increased, the reaction rate (HCFC
(-133a conversion) hardly decreases. On the other hand, in a conventional fluorination catalyst such as chromium oxyfluoride, the reaction rate (HCFC-133a conversion rate) decreases as the reaction pressure increases.

Therefore, the HCFC-133a conversion rates of the two are reversed at a reaction pressure of about ² kg / cm ² G, and the difference between the conversion rates becomes larger as the reaction pressure is further increased.
That is, by using the catalyst of the present invention, the negative effect of the reaction pressure observed in the conventional fluorination catalyst can be improved, and further, by carrying out the reaction under pressure, the production amount of by-products can be reduced. Therefore, the target compound HFC-134a can be obtained in a high yield particularly in the fluorination reaction of HCFC-133a under pressure.

The fluorination reaction of HCFC-133a can be carried out by a reaction method such as a fixed bed, a fluidized bed or a moving bed, but a fixed bed is generally used. The reaction conditions are JP-A-53-105404.
Alternatively, it can be carried out within the known condition range as disclosed in JP-A-55-27138. That is, molar ratio: 3 to 20, temperature: 3
00 to 400 ° C., pressure: atmospheric pressure to 20 kg / cm ² G,
SV: 100-10000 hr ^-1 . Since the reaction rate of the fluorination catalyst of the present invention does not decrease even under pressure, the reaction pressure may be raised to atmospheric pressure or higher, and the preferable reaction pressure is 1.5.
-20 kg / cm ² G, more preferably 2-20 kg /
cm ² G.

[0014]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but it goes without saying that the present invention is not limited by such description. In the description, the Cd / Cr ratio represents the atomic ratio of each element contained in the catalyst obtained from the chemical analysis, and the molar ratio in the examples represents the molar ratio of HF to HCFC-133a. SV is a value converted into a standard state, and pressure is a gauge pressure.

Preparation Example 1 Cr (NO ₃ ) ₃ ··· was placed in a 10-liter container containing 1 liter of pure water.
9H ₂ O1257g and _{Cd (NO 3) 2 · 4H} 2 O97
pH of the reaction solution was 8. while stirring a solution prepared by dissolving 3 g of pure water in 3 l of pure water and 1.1 l of 28 wt% ammonia water.
Approximately 2 by controlling to be within the range of 5 to 9.5
It dripped over time. The obtained hydroxide slurry was filtered, washed well with pure water, and then dried at 120 ° C. The obtained solid was ground, mixed with graphite, and pelletized by a tablet molding machine. The pellets were calcined at 400 ° C. for 4 hours under N ₂ flow to obtain a catalyst precursor. 60 ml of the catalyst precursor was filled in a reaction tube made of Inconel, and at 350 ° C. under an HF gas stream diluted with N _{2 at} normal pressure, and then 100 with no N ₂ dilution.
Fluorination treatment was carried out at 4 kg / cm ² G by pressurizing at 350 ° C. under 100% HF gas flow and further under 100% HF gas flow. The composition of the pellets after the treatment is shown below. Cd: 10.5 wt% Cr: 49.1 wt% O: 14.5 wt% F: 22.5 wt% From these values, the Cd / Cr ratio was 0.1.

[0016] was prepared Comparative Preparation Example 1 Cd (NO ₃₎ except that no addition of ₂ · 4H ₂ O does not contain Cd in the same manner as in Preparation Example 1 catalyst precursor. 60 ml of this catalyst precursor was filled in a reaction tube made of Inconel and fluorinated as in Preparation Example 1. The composition of the pellets after the treatment is shown below. Cr: 56.9 wt% O: 16.3 wt% F:
23.8% by weight

Preparation Example 2 Cd (NO ₃ ) was added to 200 g of the dried product prepared in Comparative Preparation Example 1.
The ₂ · 4H ₂ O18g impregnated was dissolved in pure water, 12 again
It was dried at 0 ° C. The following method was performed in the same manner as in Preparation Example 1 up to the fluorination treatment. The composition of the pellets after the treatment is shown below. Cd: 3.7 wt% Cr: 54.6 wt% O: 15.9 wt% F: 23.7 wt%

Example 1 50 ml of the catalyst prepared in Preparation Example 1 was filled in an Inconel reaction tube, and HCFC-13 was prepared by HF under the following reaction conditions.
The fluorination reaction of 3a was performed. The outlet gas of the reaction tube was blown into an alkali trap to remove unreacted HF and generated HCl, and the gas composition was analyzed by gas chromatography.
The results are shown in Table 1. Temperature: 320 ° C., pressure: normal pressure, molar ratio: 8, SV: 15
00 hr ^-1

Example 2 The fluorination reaction of HCFC-133a was carried out in the same manner as in Example 1 except that the reaction pressure was 2 kg / cm ² G.
The results are shown in Table 1.

Example 3 The fluorination reaction of HCFC-133a was carried out in the same manner as in Example 1 except that the reaction pressure was 4 kg / cm ² G.
The results are shown in Table 1.

Example 4 The fluorination reaction of HCFC-133a was carried out in the same manner as in Example 1 except that the catalyst prepared in Preparation Example 2 was used. The results are shown in Table 1.

Example 5 The fluorination reaction of HCFC-133a was carried out in the same manner as in Example 3 except that the reaction pressure was 4 kg / cm ² G.
The results are shown in Table 1.

Comparative Example 1 HCFC-133a was subjected to a fluorination reaction in the same manner as in Example 1 except that the catalyst prepared in Comparative Preparation Example 1 was used. The results are shown in Table 1.

Comparative Example 2 HCFC-133a was fluorinated as in Comparative Example 1 except that the reaction pressure was 2 kg / cm ² G.
The results are shown in Table 1.

Comparative Example 3 The fluorination reaction of HCFC-133a was carried out in the same manner as in Comparative Example 1 except that the reaction pressure was 4 kg / cm ² G.
The results are shown in Table 1.

[0026]

[Table 1]

In the table, 134a yield and 134a selectivity are HFC-134a yield and HFC-134a, respectively.
Represents the selectivity of.

From the results shown in Table 1, the catalyst without addition of Cd gives higher yields under normal pressure, but the reaction pressure is 2
It can be seen that the results are reversed when the amount is more than kg / cm ² G and the yield is higher for the catalyst to which Cd is added, and further, the difference in the yield is increased as the reaction pressure is increased.
This indicates that the negative effect of pressure can be improved by combining Cd and Cr.

[0029]

As described above, when the fluorination reaction of HCFC-133a with HF is carried out using the fluorination catalyst according to the present invention, HFC-134a can be produced in high yield even under pressure.
Can be obtained.

Front page continuation (72) Inventor Tetsuo Nakajo 5-1 Ogimachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Denko K.K.

Claims (1)

[Claims] 1. Cadmium, chromium, oxygen and fluorine are contained as essential components, and the atomic ratio of cadmium to chromium is 0.01 to 0.6. Hydrogen chloride and 1-chloro-2,
Contact 2,2-trifluoroethane to give 1,1,
A method for producing 1,2-tetrafluoroethane.