JPS59225131A - Preparation of difluoromethane - Google Patents

Abstract

PURPOSE:To obtain the titled substance economically in high yield, by subjecting dishloromethane and HF to gaseous-phase reaction at a specific temperature in the presence of a catalyst consisting of chromium fluoride or obtained by mixing chromium fluoride with a carrier followed by molding the blend, or supporting it on the carrier. CONSTITUTION:CH2Cl2 is reacted with HF in a gaseous phase at 200-500 deg.C (preferably at 300-450 deg.C) in the presence of a catalyst consisting of chromium fluoride or obtained by blending it with a carrier(e.g., active carbon) followed by molding, or supporting it on the carrier, to give the titled substance. CrF3 is used as chromium fluoride, or it is obtained by fluorinating a chrominum compound(e.g., chromium oxide, chromium hydroxide, chromium chloride) and used, and, when the compound contains a chromiun compound except CrF3, it is necessary to fluorinate the compound after molding or supporting on the carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing difluoromethane, and more particularly to a method for producing difluoromethane in which difluoromethane is brought into contact with a catalyst comprising a mixture of dichloromethane and hydrogen fluoride.

Conventionally, aliphatic halogenated hydrocarbons and hydrogen fluoride (HF)
Many methods have been published for producing fluorocarbons (fluorocarbons) by reacting them. However, the halogenated hydrocarbons used in the above reaction are those with two or more carbon atoms, and in the case of methane, carbon tetrachloride (CCl2), chloroform (CHCL3), and dichloromethane (CH2CL2).
There is almost no publication regarding the method for producing difluoromethane (CH2F2t or Freon 32) using CH2F2t and HF.

Generally, by reaction of dichloromethane and hydrogen fluoride,
The difficulty in efficiently producing difluoromethane is described in the report by Ryogo. For example, in "Chemistry and Industry of Fluorine Compounds 1, p. 267, published by CMC Co., Ltd., December 1977, the -cct3 group has very high reactivity, and -CC72F N CCI
Although it is substituted with F2, it is difficult to fluorinate up to CF3, and -CHCl2 group has low reactivity, and it is substituted with -CHCtF, but -CHF2
It is also stated that the more hydrogen in the molecule, the lower the reactivity and the more likely it is that decomposition or side reactions will occur.

In fact, difluoromethane is produced by a gas phase reaction from dichloromethane and hydrogen fluoride using dichromium trioxide as a catalyst (Japanese Patent Publication No. 42-3
004).

Moreover, the result was ≠3% with respect to the raw material CH2Cl2.
Not only was only 100% of CH2F2 obtained, but a large amount of CH2Cl2 was lost, presumably due to side reactions and other factors.

However, as a result of extensive and detailed research into a production method in which dichloromethane and hydrogen fluoride are reacted in the gas phase, the present inventors have found that chromium fluoride or chromium fluoride is mixed with a carrier or molded with fluoride. It was discovered that by using a catalyst consisting of chromium chloride supported on a carrier and carrying out the reaction under appropriate conditions, the desired difluoromethane could be obtained in high yield with extremely few side reactions. ,
An economically extremely advantageous method for producing difluoromethane has been invented.

The present invention has been made based on the above findings, and the gist thereof is to form a catalyst in which CH2C42 and HF are mixed and molded with chromium fluoride or chromium fluoride with a carrier, or chromium fluoride is supported on a carrier. and the reaction temperature: zo
C M 2 F subjected to gas phase reaction under one condition of o-joθ°C
It is in the manufacturing method of 2.

The present invention will now be celebrated in detail.

The fluorinated chromium catalyst used in the present invention is chromium trifluoride (CrF3) and is used as it is, mixed with a porous carrier such as activated carbon, or supported on the carrier.

In addition, when using chromium fluoride, which is a fluorinated chromium compound, examples of the chromium compound include chromium oxide, chromium hydroxide, chromium chloride, chromium nitrate, etc., which have anhydrous or crystal water, or Chromates are used.

The above chromium compound may be used alone or in a mixture.
A portion of F3 may be mixed. However, when containing a chromium compound other than CrFa, it is necessary to perform a fluorination treatment after molding or supporting it on a porous carrier such as activated carbon.

The above-mentioned method of fluorination treatment includes using fluorinated lower aliphatic hydrocarbons (so-called fluorocarbons) containing or not containing salts, or HF as it is or diluting it with an inert gas such as N2 to form a chromium compound or HF. Contact with the supported material or the material mixed with the carrier and molded. The above-mentioned fluorination treatment is preferably carried out at /30 to J-00° C. until consumption of the introduced HF or fluorocarbons is substantially eliminated.

Although the chemical composition and physical structure of the catalyst obtained by fluorination treatment are not clear, at least a portion of it is fluoride, and as a result, an excellent catalyst that is active and has very few side reactions can be obtained. think about something.

It should be noted that when CrF3 is used as a catalyst, fluorination treatment is not necessary, but there is no problem in using it as a catalyst even if fluorination treatment is performed.

The above-mentioned catalyst can be used alone or by being supported on a carrier, and does not require a co-catalyst. Furthermore, if a fluorination treatment is required, the reaction apparatus can be used as is, which is industrially advantageous.

Further, the reaction temperature varies depending on conditions such as the ratio of the raw materials HF and CN2C12 and the contact time with the catalyst, but if it is too low, the reaction rate will decrease and the production rate of CH2F2 will decrease. Moreover, if it is too high, problems such as deterioration of the catalyst and corrosion of reactor structural materials may occur. The reaction temperature range is 1.
200~SOO℃ is good, especially 3θO-≠! θ°C is preferred.

In addition, regarding the ratio of raw materials HF and CH2Cl2, when HF is small, less CH2F2 is produced. Increasing the proportion of HF increases the production rate of CH2F2.

However, although an increase to a certain degree is effective, even if it increases beyond that, the production rate of CH2F2 does not increase significantly. Furthermore, excess or unreacted HF must be disposed of or recovered, so increasing the proportion of HF will complicate the process and cause economic disadvantage. Gatte HF / CH2Ct
2 tD molar ratio id / ~, 20.

In particular, it is preferably 2 to 10.

Since this reaction is a gas phase reaction, it is necessary to gasify the raw material in advance using a vaporizer or the like. In addition, as long as the operating pressure is within a range where the raw materials and products do not liquefy,
Although there is no particular restriction Fi, it is preferable to carry out the reaction at normal pressure or slightly increased pressure for reasons of simplicity and economy.

The method of contact between the catalyst and the raw material is not particularly limited, such as fluidized bed or fixed bed, but the fixed bed method is preferable because of the simplicity of the equipment 1. As mentioned above, the CH2F2 according to the present invention The production method is an extremely excellent industrial method that allows CH2F2 to be obtained in high yield with almost no Ail or I production.

Next, examples will be shown to specifically explain the present invention.

Example 1 Commercially available CrFs, 3H2〇23009, was Arrrrn'
2:) After forming into a pellet shape of 4mmH, it was gradually heated and dried in a N2 stream, and kept at about μOO℃ for 1 hour.
It was used as a CrF3 catalyst.

This catalyst 100- was packed into a reactor made of 71 Steroid C with an inner diameter of 20 mm and a length of 7 m, and CH2Cl2:Pug1i'/
h r and HF: 'Z4 (f/hr) were introduced into the reactor in the gas phase while being evaporated in a vaporizer. Unreacted HF and generated HCl were collected by alkali, acid content was removed, and the remaining organic matter was condensed and recovered.

The composition of the recovered organic matter was analyzed by gas chromatography, and the following values were obtained.

CH2F2:it, 1. ? CHzCAF: Yu♂1C
H2C12: 2F? As a result, the production rate for the supplied CH2Cl2 is:
It can be seen that CH2Fz near 091r, CI (2ctF:/Jchi).

Example 2 A chromium chloride aqueous solution was prepared by dissolving CrCta 6H207jf in 100Vc of water, and separately dried in a N2 atmosphere at 300°C for 2 hours.
After immersing and mixing 1 in the above aqueous solution, Cr CL 3 was supported on activated carbon by drying it under reduced pressure in an evaporator.
was filled into a Hastelloy C reactor having an inner diameter of θwn and a length of 17n.

Next, while flowing N2 gas at a flow rate of 30ml/-, the temperature inside the reactor was gradually raised to 330°C by a heater.
The catalyst was dried by holding for a period of time. After drying, this is KHF
While gradually stopping the N2 supply, the internal temperature was lowered to ≠
After heating to oo'C and no consumption of HF passing through the tube was observed, the supply of ①-IF was stopped and the tube was cooled in a N2 stream.

Next, while maintaining the reactor internal temperature at aOO℃,
CH2Cl2Yu II? / h r 1 and I(F
3 t/hr was vaporized in a vaporizer and fed to the reactor. After the system became sufficiently stable, the acid content in the gas coming out of the reactor was collected with an alkali for 5 hours, and the organic matter after deoxidation was condensed and liquefied and recovered.

The composition of the recovered organic matter was analyzed by gas chromatography, and the following values were obtained.

CH2F1 Yog2, CHzCAF: t, of, CH2
Cl2: l≠1, This result shows that the production rate for the supplied CH2Ct2 is CH2F2 near Hirochi, CH2CtF'/0chi.

Example 3 [Chromium trioxide 100H] formed into pellets with a μ scale of φ×l/−1 lanH] was packed into a Hastelloy C reactor having an inner diameter of −θ and a length of 7 m.

Next, while flowing N2 gas at a flow rate of J Orttl / ytx, the temperature inside the reactor was gradually raised by a heater, and after drying at 200 ° C., HF gas was added thereto, and while N2 gas was gradually stopped, Check the internal temperature
After heating to Q'C and no consumption of 1-IF was observed, the supply of f(F was stopped, and a fluorination catalyst of dichromium trioxide was obtained.

Next, while maintaining the internal temperature of the reactor at 3jO℃, C.
HzCt2Q7P/hr, HF3. It/hr was evaporated in a vaporizer and supplied to the reactor.

After the system became sufficiently stable, the acid content in the gas coming out of the reactor was collected with an alkali for 3 hours, and the organic matter after deoxidation was condensed and liquefied and recovered.

The composition of the recovered organic matter was analyzed by gas chromatography, and the following values were obtained.

CH2F2: Ma7? N CH2C/-F:lg1,C
H2Cl2:Yukog The above results show that the production rate with respect to the supplied CH2C1F is CH2F2:69CH)C)tzcAF:i 3%.

Example 4 Commercially available CrF3.3H! After adding 0 powder/jOtllc and activated carbon powder 2009 and mixing well, it was molded into a cylindrical shape with a diameter of φ×μm+nH using a molding machine, and then thoroughly dried. A pellet was obtained which was mixed and molded in proportions of parts by weight.

These pellets 100- were filled into a Hastelloy C reactor having an inner diameter of 20 rtrmφ and a height of 7 m.

Next, while flowing nitrogen gas at a flow rate of j Orttl/ttM, the reactor was heated by a heater to raise the internal temperature of the reactor to 370°C, and the nitrogen gas was stopped.

Next, CH2C was added while maintaining the reactor internal temperature at 370°C.
42: &! f/hr and HF:'lAf/br were fed to the reactor in the gas phase while being evaporated in a vaporizer. After the system became sufficiently stable, the acid content in the reactor outlet gas was collected with an alkali over a period of 5 hours, and the organic matter after deoxidation was condensed and liquefied and recovered.

The composition of the recovered organic matter was analyzed by gas chromatography, and the following values were obtained.

CH2F2: / If CH2C1F: Qt
fCH2C42: 'A/lii' This result indicates that CI(2F
2 and CH2C1F were produced by 7% and 1%, respectively. Is it possible to obtain it with high yield?

Applicant Showa Tunko Co., Ltd.

Claims (4)

[Claims] (1) Dichloromethane and hydrogen fluoride are mixed with chromium fluoride, chromium fluoride is mixed with a carrier, or chromium fluoride is supported on a carrier, using a catalyst other than that, at a reaction temperature of roo ℃ to 200 ℃. A method for producing difluoromethane, characterized by carrying out a gas phase reaction. (2) The method for producing difluoromethane according to claim 1, wherein the chromium fluoride is chromium trifluoride. (3) The method for producing difluoromethane according to claim 7, wherein the chromium fluoride is obtained by fluorinating a chromium compound. (4) The method for producing difluoromethane according to claim 7, wherein the carrier is activated carbon.