CN85105080A - The improvement preparation method of trifluoromethane - Google Patents

Abstract

A kind of improvement preparation method of trifluoromethane is by CF ₂ClH and anhydrous HF are in the presence of aluminum fluoride catalyst, and the Fixed Bed Gas Phase reaction forms.Catalyzer also contains the oxide compound or the halogenide of 1-20% (weight) bismuth, lanthanum, nickel, cobalt, chromium etc.200～350 ℃ of temperature of reaction, HF and CF ₂The mol proportioning of ClH is 1.0～2.0, CF ₂ClH air speed 50～1000ml/ gram catalyzer hour.This law reaction conditions gentleness, a step is finished fluoridation and disproportionation reaction, CF simultaneously ₂The transformation efficiency of ClH, CHF ₃Selectivity and content all up to more than 99%, product need not rectifying and can directly use as industrial goods.

Description

The improvement preparation method of trifluoromethane

The invention relates to the improvement preparation method of trifluoromethane, promptly gas-phase reaction in the presence of catalyzer generates trifluoromethane by difluorochloromethane and anhydrous hydrogen fluoride.

Trifluoromethane is mainly as the raw material of cooling agent with preparation high-efficiency low-toxicity fire-fighting medium bromotrifluoromethane.Up to the present, the method for preparing trifluoromethane mainly contains following two kinds:

One, chloroform fluorination method:

Two, difluorochloromethane discrimination method:

It is higher that the advantage of chloroform fluorination method is that chloroform is converted into the selectivity of trifluoromethane, and shortcoming is to need harsh reaction conditions and catalyst life short etc.As United States Patent (USP) 2744148, adopt to contain CuF ₂Activated alumina be catalyzer, 400 ℃ of temperature of reaction were reacted three hours 2.9 seconds duration of contact, resultant through washing, dry after CHF ₃Content is 95%.United States Patent (USP) 2745886 adopts CrF ₃Be catalyzer, 400 ℃ of temperature of reaction, were reacted CHF 42 minutes at 20.5 seconds duration of contact ₃Content is 96.7%.United States Patent (USP) 2744147 adopts to contain NiCl respectively ₂, CoCl ₂Activated alumina be catalyzer, temperature of reaction is respectively 278 ℃ and 284 ℃, CHF ₃Yield be that benchmark is respectively 73.0% and 83.7% with HF.English Patent 816622, adopting the gac that contains 12.7% Fe is catalyzer, 350 ℃ of temperature of reaction, CHF ₃Content is 87.0%.

The difluorochloromethane discrimination method has been delivered many patents in recent years.Its advantage is that temperature of reaction is lower, does not use hydrogen fluoride again.Through updating, catalyst life is also longer, CHF in the resultant ₃Content is also higher.As the clear 53-87303 of day disclosure special permission communique, adopt the disproportionation reaction in two stages, after the resultant that obtains is removed chloroform, CHF ₃Content 96-98%.The clear 56-53290 of Japan's special permission communique adopts fs pressurization disproportionation reaction, subordinate phase normal pressure disproportionation reaction for another example.After removing chloroform, CHF ₃Content 90-95%.Catalyzer used 90 days, and activity drops to 0.964 from 0.994.But the shortcoming of present method is a methylene dichloride, and to change into the selectivity of trifluoromethane low, and every generation two molecule trifluoromethanes at least just have the chloroform of a part to generate.This is the fatal shortcoming that present method can't overcome.

In view of all there is bigger shortcoming in above-mentioned two kinds of methods, the present inventor attempts to seek the method that another prepares trifluoromethane.Expect that this method has the selectivity height that reactant changes into trifluoromethane, the content of trifluoromethane is near 100% in the resultant, and reaction conditions is relatively gentleer, and catalyst life is than advantages such as length.

The present inventor is through comparing repeatedly and exploring, fluoridize according to chloroform and to generate dichlorofluoromethane and dichlorofluoromethane, difluorochloromethane disproportionation reaction generate the fact that difluorochloromethane, trifluoromethane can be carried out respectively under comparatively gentle reaction conditions, selecting difluorochloromethane dexterously is reactant, use a class not only can carry out gas phase fluorination but also can carry out the catalyzer of disproportionation reaction, achieve the above object finally.

Method of the present invention can be represented with following chemical equation:

Its major ingredient of catalyzer that the present invention uses is the different aluminum fluorides of various crystalline forms, uses or add simultaneously the oxide compound or the halogenide of one or more metallic compounds such as bismuth, lanthanum, nickel, cobalt, chromium etc. separately.Addition is the 1-20% of aluminum fluoride weight, and catalyzer is processed into strip or sheet, the fixed-bed reactor of packing into, before the use,, feed small amount of nitrogen simultaneously and drive moisture content earlier at 260～275 ℃ of heat-activated 3-5 hours, thereafter feed anhydrous hydrogen fluoride, its amount is the 5-10% of catalyst weight.

After finishing above-mentioned activation act step, just can feed difluorochloromethane and anhydrous hydrogen fluoride and carry out gas phase fluorination.

The catalyzer that adopts among the present invention, its active beginning is relatively poor, rises gradually later on, reach optimum regime after, can keep the long period.The catalyzer that wherein has is through after 1106 hours, and temperature of reaction is low during still than the reaction beginning, and specific activity initial reaction stage height, the transformation efficiency of difluorochloromethane and resultant through wash dry after the content of trifluoromethane all remain on about 99%.

The temperature of reaction that the present invention uses is 200-350 ℃, is preferable with 260-320 ℃.Temperature of reaction is lower than 260 ℃, and the transformation efficiency of difluorochloromethane is difficult to reach more than 99%; Temperature is higher than 350 ℃, and catalyst surface carbon deposit speed speeds, and catalyst activity reduces rapidly, and difluorochloromethane is converted into the selectivity reduction of trifluoromethane simultaneously.

In reaction of the present invention, the mol proportioning of hydrogen fluoride and difluorochloromethane is 1.0-2.0, is preferable with 1.2-1.8.The hydrogen fluoride proportioning reduces, and dichlorofluoromethane and chloroform content increase in the resultant; The hydrogen fluoride proportioning increases, and dichlorofluoromethane and chloroform content reduce in the resultant.The mol proportioning of hydrogen fluoride and difluorochloromethane is 1.2-1.8,260 ℃ of temperature of reaction, and the mol content of dichlorofluoromethane and chloroform is lower than 0.1%.

In reaction of the present invention, the air speed of difluorochloromethane can be in (50-1000 milliliter difluorochloromethane/gram catalyzer hour) change in a big way.Generally hour be advisable with 200-500 milliliter difluorochloromethane/gram catalyzer.

The present invention compares with the technology of existing preparation trifluoromethane, has following superiority:

The present invention compares with the difluorochloromethane discrimination method, and it does not need the such two-stage compressive reaction of discrimination method, as long as adopt one section reaction of normal pressure, the content of trifluoromethane all can reach 99% in the transformation efficiency of difluorochloromethane and the resultant.Especially difluorochloromethane be converted into trifluoromethane selectivity also up to 99%, the corresponding selectivity 66% than discrimination method has improved 33%.In addition, the content of the resultant of the inventive method trifluoromethane after washing, drying can reach 99%, can directly use as industrial goods without rectifying.Therefore, according to domestic existing price, the cost for preparing trifluoromethane with the inventive method will significantly be lower than the difluorochloromethane discrimination method.

The present invention compares with the chloroform fluorination method, it does not need the such severe condition of chloroform fluorination method, as long as comparatively gentle reaction conditions, trifluoromethane content in the resultant, the selectivity that the transformation efficiency of difluorochloromethane and it are converted into trifluoromethane all can reach 99%.Especially the catalyzer that uses among the present invention uses 1106 hours activity not fall as follows.In addition, the content of the resultant of the inventive method trifluoromethane after washing, drying can reach 99%, can directly use as industrial goods without rectifying.All these is that the chloroform fluorination method did not reach so far.

The following method of the present invention of implementing that illustrates.

Example one

The vertical carbon steel reaction tubes of placing, 21 millimeters of internal diameters, long 750 millimeters, 700 millimeters of electrically heated segment lengths, in adorn 100 gram aluminum fluoride catalysts (strip, 3 * 10 millimeters of φ).Slowly be warming up to 270 ℃, under the situation that feeds nitrogen (flow is 5 liters/hour), kept 3 hours, fed anhydrous hydrogen fluoride (20 Grams Per Hour) thereafter 15 minutes.Then, stop to feed nitrogen, change logical difluorochloromethane and anhydrous hydrogen fluoride, the mol proportioning of keeping anhydrous hydrogen fluoride and difluorochloromethane is 1.6-1.7, the flow of difluorochloromethane is 22 liters/hour, and the conditioned reaction temperature is 99% with the transformation efficiency of keeping difluorochloromethane.Resultant of reaction is through water and 3%NaOH solution washing, remove HF and HCl after, through solid caustic soda and molecular sieve drying, sampling is analyzed with gas chromatograph.Reaction conditions and result are as follows:

Reaction tubes outside wall temperature: 318 ℃

The mol proportioning $M_{\mathrm{HF}}/M_{{\mathrm{CF}}_3}$ 1.67

Difluorochloromethane air speed: 210 milliliters of CF ₂ClH/ gram catalyzer hour

Resultant composition: M% after the drying when reacting 16 hours

CF ₃H 99.1%

CF ₂ClH 0.7%

CFCl ₂H 0.1%

CHCl ₃0.1%

CF ₂ClH transformation efficiency: 99.3%

CF ₂ClH changes into CF ₃The selectivity of H: 99.8%

Example two, three, four

Operation steps is with example one, and example two is used the self-control aluminum fluoride, and (φ 5 * 10m/m), and example three is used the aluminum fluoride (strip, 3 * 10 millimeters of φ) that contains 2% bismuth oxide, lanthanum trioxide.Example four is used and is contained 10%CoCl ₂Aluminum fluoride (strip, 3 * 10 millimeters of φ), activation temperature is 260 ℃.Reaction conditions and the results are shown in following table.

Example five

Operation steps is used to contain 10%NiCl with example one ₂Aluminum fluoride (strip, 3 * 10 millimeters of φ) make catalyzer.260 ℃ of activation temperatures.Following table provides the result and the reaction conditions of long period long run test.

Claims (4)

1, a kind ofly prepares the method for trifluoromethane, it is characterized in that making difluorochloromethane and anhydrous hydrogen fluoride gas-phase reaction in the presence of catalyzer by difluorochloromethane.

2, by the described method for preparing trifluoromethane of claim 1, the major ingredient that it is characterized in that catalyst system therefor is the different aluminum fluorides of various crystal formations, use separately or add simultaneously the oxide compound or the halogenide of one or more metallic compounds such as bismuth, lanthanum, nickel, cobalt, chromium, addition is the 1-20% of aluminum fluoride weight.

3, by the described method for preparing trifluoromethane of claim 1, it is characterized in that the reaction conditions that is adopted is: temperature of reaction 200-350 ℃, the mol proportioning of hydrogen fluoride and difluorochloromethane is 1.0-2.0, and the air speed of difluorochloromethane is 50-1000 milliliter/gram catalyzer hour.

4, by the described method for preparing trifluoromethane of claim 2, it is characterized in that catalyst system therefor earlier at 260-275 ℃ of heat-activated 3-5 hour, feeds small amount of nitrogen simultaneously and drives moisture content, feed the anhydrous hydrogen fluoride of catalyst weight 5-10% again.