JPH01262946A - Activation of chromium-based fluorinated catalyst - Google Patents

Abstract

PURPOSE:To recover activity of a catalyst without affecting hydrogen atoms contained in a raw material by stopping feed of the raw material at a point of time when reduction of catalyst activity is recognized in a fluorinating reac tion process and feeding the gas incorporating oxygen. CONSTITUTION:In activation of a catalyst in the fluorinating reaction of hydrogen-contg. halogenated hydrocarbon, especially of chromium-based fluorinated catalyst, activity reduction of the fluorinated catalyst is recognized in a reaction process. At this time, feed of a raw material such as CCl2=CHCl and hydrogen fluoride is stopped. The catalyst is activated by feeding the gas incorporating oxygen to the reaction system. After activation, feed of the gas incorporating oxygen is stopped and the raw material is refed. By such a way, activity of the catalyst is completely recovered without affecting hydrogen atom contained in the raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for activating a catalyst, particularly a chromium-based fluorination catalyst, in a fluorination reaction of a hydrogen-containing halogenated hydrocarbon.

[Prior Art] Fluorine-containing halogenated hydrocarbons are generally called fluorocarbon gases and are widely used as propellants, blowing agents, refrigerants, solvents, and other uses.

In recent years, it has been pointed out that chlorofluorocarbon gases containing chlorine may destroy the ozone layer in the stratosphere, and an international decision has been made to reduce their consumption. For this reason, hydrogen-containing fluoroalkane, which is expected to decompose in the atmosphere, is seen as a promising alternative, and its industrialization is eagerly awaited.

When trying to synthesize hydrogen-containing fluoroalkane by gas phase reaction, the catalyst used is a conventionally known chromium-based catalyst, which shows sufficient activity, but compared to the case of fluorinating raw materials that do not contain hydrogen, It has been found that this is a problem industrially because the catalyst life is extremely short.

For example, Japanese Patent Publication No. 52-33604 and Japanese Patent Publication No. 56-23407 have conventionally proposed methods for extending and activating the catalyst life in order to deal with the decrease in catalyst activity as described above.
There are methods described in Japanese Patent Publication No. 52-30477, etc.

[Problems to be Solved by the Invention] Japanese Patent Publication No. 52-33604 describes a method for supplying chlorine residue during the reaction, but since raw materials containing hydrogen are chlorinated, it is difficult to apply this method. Have difficulty.

Further, Japanese Patent Publication No. 56-23407 describes a method of fluorination in the coexistence of oxygen gas, but when this method is applied to hydrogen-containing raw materials, Although no effect was observed with the amount of oxygen gas supplied, and an effect of sustaining the catalytic activity was observed when the amount of oxygen gas supplied was greater than the amount stated in the claims, the oxychlorination reaction caused the same chlorination reaction as before. This has the disadvantage that the selectivity decreases due to the occurrence of oxidation (see Comparative Example! and Comparative Example 2, which will be described later). Furthermore, in the comparative example of the above-mentioned publication, it is stated that in the fluorination of carbon tetrachloride, even if the supply of raw materials is stopped and treatment with oxygen gas is performed when the catalyst activity decreases, the catalyst activity will not be sufficiently recovered. There is.

Further, Japanese Patent Publication No. 52-30477 describes a method of treating with hydrogen fluoride gas when the catalyst activity decreases, but no effect was found.

[Means for solving the problem] The above problem is to solve the above problem when activating the fluorination catalyst in the fluorination reaction of hydrogen-containing halogenated hydrocarbons. The supply of oxygen is stopped, oxygen-containing gas is supplied to the reaction system, and after activation,
It has been found that the problem can be solved by a catalyst activation method characterized by stopping the supply of oxygen-containing gas and restarting the supply of raw materials.

When the catalyst activation method of the present invention is applied, the activity of the catalyst is completely recovered without affecting the hydrogen atoms contained in the raw material.

The catalyst activation method of the present invention includes hydrogen-containing halogenated hydrocarbon,
For example, C(Jl, = CI-I CI2, cr',
cc-c11Cρ2, CF, -CHCr1, CF
3-CHffi Cr or CF, -C1-13 or a mixture thereof is treated with a chromium-based catalyst, typically a trivalent chromium compound such as chromium oxyfluoride, which is prepared by treating chromium oxide (CRTO3) and CrF2 with oxygen gas. It can be applied to fluorination with hydrogen fluoride using a catalyst containing as the main component.

When signs of a decrease in catalyst activity are observed during the fluorination reaction process, the supply of raw materials is stopped, and if necessary, after purging the reaction system with nitrogen gas, the catalyst can be improved by supplying an oxygen-containing gas to the reaction system. Perform the activation process.

The oxygen-containing gas used for activation treatment has an oxygen concentration of 01~
Preference is given to lOO% by volume, preferably from 1 to 30% by volume of an inert gas, such as nitrogen, so it is also possible to use air as such.

The activation treatment temperature is usually within the range of 200 to 450°C, but it is preferable from the viewpoint of productivity to perform the treatment at the same temperature as the fluorination reaction temperature.

Since pot spots usually exist in the catalyst bed, it is preferable to supply oxygen at such a rate that the temperature of the catalyst bed does not rise by more than 30°C.

The activation treatment time is until the pot spots have completely passed through the catalyst bed, and usually about 4 hours is sufficient.

The activation treatment pressure is not particularly limited and may normally be normal pressure, but the activation treatment may be carried out under pressure, for example, several kg/cm2.

By the method of the present invention in which the supply of raw materials is stopped and the fluorinated chromium catalyst is activated with oxygen gas, it is possible to overcome the shortcoming of the short life of the catalyst.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
It was compressed into a cylindrical tablet with a thickness of 4JIJ+.

40cc of this catalyst was packed into a Hastelloy C reaction tube with an inner diameter of 18Rx and a length of 400xm, and heated to 400°C under a nitrogen stream.
The mixture was heated and maintained for 1 hour. Thereafter, the temperature was lowered to 320° C., and anhydrous hydrogen fluoride was supplied at a rate of 400 cc/min for treatment for 1 hour. Next, gasified trichlorethylene was supplied at a rate of 80 cc/min to carry out a fluorination reaction.

After 300 hours had passed, the supply of trichlene and hydrogen fluoride was stopped, and air was supplied to the reaction tube at a rate of 400 cc/min.

The internal temperature rose to 340°C. After 3 hours, when the temperature returned to 320°C, the raw materials were supplied again to start the fluorination reaction. After a further 400 hours, oxygen treatment with air was performed again in the same manner as above. The results are shown in Table 1.

From this result, it is clear that the catalyst activity is sufficiently recovered by the catalyst activation treatment using oxygen according to the present invention.

Example 2 Fluorination was carried out using the same catalyst and equipment as in Example 1, except that CF3-CHte12 was used instead of trichlene.

The reaction temperature was 400°C, and CF3-CH,Cff was 1
At 75 cc/min, hydrogen fluoride was continuously fed at 525 cc/min.

After 160 hours, the supply of raw materials was stopped and 400cc of air was added.
/min to activate the catalyst. After 4 hours, the reaction was restarted.

Thereafter, similar operations were carried out.

The results of this series of experiments are shown in Table 2.

Example 3 Commercially available CrF3.3H*O was molded into a pellet with a diameter of 4 u+ and a thickness of 4 mm, and the inner diameter was 18 x 71 mm. Length 400mx
400 cc was filled into a Hastelloy reaction tube.

Air was supplied to this catalyst bed at a rate of 500 cc/min.
It was kept at ℃ for 5 hours. The temperature was raised to 500°C and held for an additional 3 hours, and then the temperature was lowered to 300°C to prepare Example 1.
Trichlene was fluorinated in the same manner as above.

This series of results is shown in Table 3.

Example 4 A chromium catalyst supported on aluminum fluoride was prepared by the method described in Japanese Patent Publication No. 62-44973.

A fluorination reaction was carried out using the obtained catalyst in the same apparatus and under the same conditions as in Example 2.

The results obtained are shown in Table 4.

Comparative Example 1 In Example 2, the reaction was carried out while supplying oxygen gas at 0.75 cc/min in addition to CF3-Cl-1, CQ and hydrogen fluoride.

The results are shown in Table 5.

Table 5 In this comparative example, the amount of oxygen relative to the halogenated hydrocarbon is 1 mol%, which is the maximum amount of oxygen stated in the claims of Japanese Patent Publication No. 56-23407. , no effect on maintaining catalyst activity was observed.

Comparative Example 2 Fluorination was carried out in the same manner as in Comparative Example 1, except that the oxygen gas supply rate was increased to 7.5 cc/min.

The results are shown in Table 6 below.

Table 6 From this result, it is preferable to increase the amount of oxygen supplied because compounds substituted with hydrogen or chlorine (compounds marked with * in Table 6) are formed and the selectivity of the target product decreases. It turns out there isn't.

Patent applicant Daikin Industries, Ltd.

Claims (1)

[Scope of Claims] 1. In the fluorination reaction of hydrogen-containing halogenated hydrocarbons with hydrogen fluoride, when activating the chromium-based fluorination catalyst, when a decrease in the activity of the catalyst is observed during the reaction process, the raw material A method for activating a catalyst, which comprises stopping supply of oxygen-containing gas, supplying oxygen-containing gas to a reaction system, and after activation, stopping supply of oxygen-containing gas and restarting supply of raw materials. 2. Hydrogen-containing halogenated hydrocarbon is CCl_2=CHC
l, CF_2Cl-CHCl_2, CF_3-CHCl
_2, CF_3-CH_2Cl or CF_3-CH
The activation method according to claim 1, which is _3 or a mixture thereof. 3. The activation method according to claim 1 or 2, wherein the chromium-based catalyst is a catalyst whose main component is a trivalent chromium compound, such as chromium oxide or chromium oxyfluoride. 4. The activation method according to any one of claims 1 to 3, wherein the oxygen-containing gas is an inert gas containing 1 to 30% by volume of oxygen.