CN1313423C - Method for preparing difluoromethane by stage continuous fluorination - Google Patents
Method for preparing difluoromethane by stage continuous fluorination Download PDFInfo
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- CN1313423C CN1313423C CNB2005100492558A CN200510049255A CN1313423C CN 1313423 C CN1313423 C CN 1313423C CN B2005100492558 A CNB2005100492558 A CN B2005100492558A CN 200510049255 A CN200510049255 A CN 200510049255A CN 1313423 C CN1313423 C CN 1313423C
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Abstract
The present invention relates to a method for preparing difluoromethane by sectionally continuous fluorination. When the method of the present invention is used, the technology is improved, the device is simplified, the reaction temperature is lowered, the production cost is lowered, and the quality of the difluoromethane is enhanced. The present invention is characterized in that the gas-phase reaction is carried out in the first section, the batch charging molar ratio of hydrogen fluoride to methylene chloride is from 2 to 4:1 in the presence of a composite catalyst which is composed of chloride, hydroxide, oxide or fluoride of Al and Cr, the reaction temperature is from 180 to 320 DEG C, and the pressure is from 0.5 to 1.5MPa; the liquid phase reaction is carried out in the second section; in the presence of a catalyst which is composed of Sb chloride or a chloride mixture of Sb and Sn, the product of the first section is directly led into a liquie-phase reactor, the reaction temperature is from 50 to 120 DEG C, and the reaction pressure is from 0.5 to 1.2MPa.
Description
Technical field
The present invention relates to a kind of method for preparing methylene fluoride, specifically is a kind of method of preparing difluoromethane by stage continuous fluorination.
Background technology
Methylene fluoride (be called for short R32), boiling point-51.7 ℃, its ozone layer destroying potential value (ODP) is zero, forms the substitute that the mixture that forms has been used as HCFC22 etc. with other, its application will be extensive all the more.Prepare the existing many patent documentation reports of methylene fluoride by fluorination of dichloromethane, gaseous fluoridizing method is wherein promptly arranged, disclosing gas phase fluorination as Chinese patent literature CN1172097 " process for manufacture of difluoromethane " carries out in the presence of chlorine and fluorination catalyst, temperature is 240～350 ℃, and material is circulated repeatedly.Liquid-phase fluorination process is also arranged,, use chlorofluorination antimony to make catalyzer, 50～150 ℃ of temperature, pressure 1～10kg/cm as Chinese patent literature CN 1168660 " methylene fluoride manufacture method "
2In the above-mentioned existing document, gas phase fluorination, material need circulation repeatedly, and device is complicated, be not very economic manufacture method, and temperature of reaction is higher, have more by product to generate.And the muriate that liquid-phase fluorination adopts antimony is during as catalyzer, often need to feed continuously or off and on a small amount of chlorine, to keep activity of such catalysts, chlorine is contacted with methylene dichloride, thereby produce a certain amount of trichloromethane, and cause the generation of a certain amount of R21 (a fluorine monochloro methane), R22 (difluorochloromethane), thereby influence the quality of methylene fluoride.
Summary of the invention
The technical issues that need to address of the present invention are, improve technology, and simplification device reduces temperature of reaction, reduces production costs, and improves the methylene fluoride product quality.
The method of preparing difluoromethane by stage continuous fluorination of the present invention, it is characterized in that being gas-phase reaction at first section, under the condition that the composite catalyst that muriate, oxyhydroxide, oxide compound or the fluorochemical of Al, two kinds of metals of Cr are formed exists, the molar ratio 2～4: 1 of hydrogen fluoride and methylene dichloride, be preferably as 2～3: 1,180～320 ℃ of temperature of reaction are preferably 180～250 ℃ of pressure 0.5～1.5Mpa; Second section is liquid phase reaction, does directly to feed Liquid-phase reactor from first section product, 50～120 ℃ of temperature of reaction, reaction pressure 0.5～1.2Mpa under the condition of catalyzer existence at Sb muriate or its chloride mix that contains Sn.
First section composite catalyst prepares as follows:
1) commercially available or homemade AlF
3Ointment washs to neutral with pure water, and oven dry is pulverized, and gets AlF
3Powder;
2) in the compound solution that contains chromium (III) 1～10%, add solution of ammonium hydroxide, wherein NH
3Content is 1～25%, be stirred to pH value reach 9.0 hydration Cr
2O
3Precipitation is filtered, and washs NH to the filter cake
4 +The anion-content of content and chromium (III) compound is less than 0.05%, oven dry, grind Cr
2O
3Powder; It is described that to contain chromium (III) compound can be CrCl
36H
2O, Cr (NO
3)
39H
2O, KCr (SO
4)
212H
2A kind of among the O.
3) will contain Cr
2O
3With AlF
3Two powders add water and are mixed into the wet-milling shape with 10: 90～95: 5 weight ratio, granulate, oven dry, bulk density be the 0.7kg/L catalyst prod.
Add the anhydrous hydrogen fluoride thinner in second section reaction, dilution dosage is 0.1～1.5 times of catalyst weight; Its preferred weight is 0.1～1 times of catalytic amount.The consumption of reacting middle catalyst can be determined by general test.
Prepare methylene fluoride by methylene dichloride and anhydrous hydrogen fluoride reaction, generally comprise two step fluorine chlorine permutoid reactions:
(R30) (R31)
(R31) (methylene fluoride)
The present invention is directed to the problem that prior art exists, utilize methylene dichloride and anhydrous hydrogen fluoride reaction to generate the mechanism of methylene fluoride dexterously, adopt segmentation continuous catalysis fluorination method, add selection of catalysts, the air-flow that makes first section gas phase fluorination generation is based on R31, in second section liquid-phase fluorination, make methylene dichloride have with a small amount of state that (R30 is at R30, R31, account for about 20% in the R32 mixture), significantly reduce R21, the generation of R22, promote carrying out smoothly of fluoridation, suppressed the generation of side reaction effectively, prolonged life of catalyst, improve plant efficiency, and obtained very high reaction conversion ratio and selectivity.
One of key of the present invention just is that selected catalyzer and processing condition help reaction (A) and carrying out smoothly (B), and can effectively suppress the generation of other side reaction.
The present invention discovers that temperature of reaction is an important factor, and temperature of reaction is high more, and by product is many more in fluoridizing, and temperature of reaction reduces, and then helps improving the selectivity of reaction (A), (B).Therefore, the present invention is in order to reduce the generation of by product as far as possible, and first important measures of making be adopt the manufacturing of wet mixing extrusion process the composite catalyst formed of the muriate, oxyhydroxide, oxide compound or the fluorochemical that contain Al, two kinds of metals of Cr, the gas-phase reaction temperature is reduced.And the present invention carries out reaction (A) major control by adopting segmentation continuous catalysis flaorination process in first reactor, and reaction (B) major control is carried out in second section reactor.Two-stage reaction adopts different catalyst systems, controls different reaction process conditions, thereby makes reaction more help effectively suppressing the generation of by product again towards reaction (A) and (B) acceleration.
Technology novelty of the present invention has device and relatively simplifies, and temperature of reaction is lower, and production cost descends, and the methylene fluoride product quality is characteristics preferably.
Description of drawings
Fig. 1 is a process flow sheet of the present invention.
Raw material methylene dichloride and anhydrous hydrogen fluoride are with selected speed, after the vaporizer vaporization, enter first section gas phase fluorination device 3 from storage tank 1 and 2 after metering, the R31 mixture that generates directly enters second section Liquid-phase reactor 4, methylene fluoride enters snubber 5, water wash column 6, soda-wash tower 7, gas holder 8 by the evaporator overhead condenser of Liquid-phase reactor 4, the drying device 9 then, are pressed into crude product storage tank 11 with compressor 10.
First section composite catalyst that the gas phase fluorination device selects for use the muriate, oxyhydroxide, oxide compound or the fluorochemical that contain Al, two kinds of metals of Cr of extrusion process manufacturing to form, this catalyzer can quicken the fluorine chlorine permutoid reaction of methylene dichloride and anhydrous hydrogen fluoride, and suppress the generation of other by product, thereby prolong life of catalyst.
The temperature of reaction of first section reactor is high more, and the formation speed of R31 is fast more, but other by product increase is faster, causes catalyst regeneration frequent, and catalyst life shortens.Temperature of reaction reduces, and the R31 formation speed slows down, and other by product formation speed slows down more.Therefore reduce temperature of reaction and can prolong the catalyzer need regenerated time, prolong catalyst life greatly.Take all factors into consideration speed of response and catalyst life, gas phase fluorination temperature of the present invention generally is controlled at 180～320 ℃, especially the temperature of reaction of Shi Heing is 180～250 ℃, the molar ratio of hydrogen fluoride and methylene dichloride can have influence on the transformation efficiency of methylene dichloride and be converted into the selectivity of R31, generally be controlled at 2～4: 1, especially the mol ratio of Shi Heing is 2～3: 1.The suitable catalyzer of subordinate phase liquid phase fluorination reaction is that Sb muriate or its contain the chloride mix of Sn, select suitable temperature of reaction and catalyst concn, can strengthen the catalytic fluorination ability, prolong catalyst life, for keeping second section catalyst reactor concentration moderate, need to add a certain amount of material and make thinner, make thinner as hydrogen fluoride, suitable thinner weight is 0.1～1.5 times of catalytic amount, and especially suitable weight is 0.1～1 times of catalyst weight.
The temperature of second section liquid phase fluorination reactor is high more, and then the formation speed of methylene fluoride is fast more, but the catalyst life shortening, temperature of reaction reduces, and the formation speed of methylene fluoride slows down, but catalyst life prolongs.Take all factors into consideration the formation speed and the catalyst life of methylene fluoride, the optimum range of temperature of reaction is 50～120 ℃, and especially suitable temperature is 60～100 ℃.
It is one of key problem in technology of the present invention that the pressure of second section reaction is selected, can compressive reaction, but also synthesis under normal pressure.Compressive reaction can be accelerated the formation speed of methylene fluoride, and under identical condensing temperature, pressure is high more, and the methylene fluoride content in the product of effusion reactor is high more, and hydrogen fluoride content is low more, thereby helps reaction.But pressure is high more, and to the technical requirements increase of equipment and material-transporting system, suitable reaction pressure is 0.1～1.0Mpa, and especially suitable pressure is 0.5～1.2Mpa.
By the inventive method, adopt segmentation continuous catalysis fluorination method, the generation of by product is effectively suppressed, catalyst life obtains significantly to prolong, and the transformation efficiency of methylene dichloride reaches more than 99%, escaping gas after the segmentation continuous catalysis is fluoridized reaches more than 99% by methylene fluoride content in the crude product of washing, alkali cleaning.
Embodiment
Below by embodiment technology contents of the present invention is described further.
Catalyst production example 1:
1) one section composite catalyst:
Commercially available AlF
3Ointment, is dried in 120 ℃ of baking ovens to neutral with the pure water washing, through grinding, gets mean particle size 160 purpose AlF
3Powder is standby.
In addition, in 10% chromium chloride solution, adding concentration is 20% solution of ammonium hydroxide, fully stirs, and stops when pH value reaches 9.0, obtains hydration Cr
2O
3Precipitation is filtered, with pure water washing, NH in filter cake
4 +Content and Cl
-Content is less than till 0.05%.Filter cake is dried in 120 ℃ baking oven, and grind average 160 purpose Cr
2O
3Powder is standby.
With above-mentioned Cr
2O
3With AlF
3Two powders are with 40: 60 weight ratio, and add the suitable quantity of water high-speed mixing and become the wet-milling shape, send tablets press to granulate.The particle of making is put into 110 ℃ baking oven, dried 10 hours, the bulk density of institute's controlling catalyst is 0.7kg/L.
2) two sections catalyzer: commercially available SbCl
5
Catalyst production example 2:
1) one section composite catalyst:
Commercially available γ-Al
2O
3, same 40%BHF (water hydrofluoric acid is arranged) reaction makes γ-AlF
3,, dry in 120 ℃ of baking ovens to neutral with the pure water washing, through grinding, get mean particle size 160 purpose AlF
3Powder is standby.
In addition, in 20% chromium nitrate solution, adding concentration is 10% solution of ammonium hydroxide, fully stirs, and stops when pH value reaches 9.0, obtains hydration Cr
2O
3Precipitation is filtered, with pure water washing, NH in filter cake
4 +Content and NO
3 -Content is less than till 0.05%.Filter cake is dried in 120 ℃ baking oven, and grind average 160 purpose Cr
2O
3Powder is standby.
With above-mentioned Cr
2O
3With AlF
3Two powders are with 50: 50 weight ratio, and add the suitable quantity of water high-speed mixing and become the wet-milling shape, send tablets press to granulate.The particle of making is put into 10 ℃ baking oven, dried 10 hours, the bulk density of institute's controlling catalyst is 0.7kg/L.
2) two sections catalyzer: SbCl
5With SnCl
410: 1 in molar ratio, in the liquid phase reaction still, mix.
Reaction example 1:
In technical process as shown in drawings, first section gas phase fluorination device 3 is caliber 57 * 3mm, the Steel Vessel of long 1200mm, in one section catalyzer is housed in the 1.5kg catalyst production example 1, be connected with the preheater of caliber 57 * 3mm before the reaction tubes.Before the reaction, lead to nitrogen earlier in preheater, flow is 400L/h, be heated to 120 ℃, keep 12 hours, be warming up to 200 ℃ again to drive away moisture in the catalyzer, the preheater temperature is 150 ℃, keeps changing logical hydrogen fluoride after 6 hours, flux is 1mol/h, after 24 hours activation treatment of hydrogen fluoride, control preheater temperature is at 150 ℃, and temperature of reaction transfers to 200 ℃ of predetermined temperature of reaction, feed reaction raw materials again, 0.6Mpa keep-ups pressure.The molar ratio of hydrogen fluoride and methylene dichloride is controlled at 2.5, and the charging capacity of methylene dichloride is 500g/h.
The reactor volume of second section liquid phase fluorination reactor 4 is 6L, and the condenser area is 0.3m
2The tetrafluoro filler is equipped with at the middle part, number of actual plates is 5, add two sections catalyzer 2kg in the catalyst production example 1 in the reactor 4, thereafter add AHF (anhydrous hydrogen fluoride) 2Kg, in 4 reacting kettle jacketing, feed steam, keep 80 ℃ of temperature in the kettle, feed chilled brine in the condenser chuck, keep 4 condenser overhead temperature of charge and be-10 ℃, mixture from first section enters reactor, after question response device pressure liter reaches 0.5Mpa, emit reaction product, enter gas holder 8 through washing 6 alkali cleanings 7 by condenser 4 tops, sampling before gas holder 8 is simultaneously analyzed with gas chromatograph.Reaction result sees the following form:
Table one
| Reaction pressure (Mpa) | Temperature of reaction (℃) | The product of alkali cleaning is formed M% | CH 2Cl 2 | CH 2F 2The output Grams Per Hour | ||||
| One section | Two sections | One section | Two sections | R31 | Methylene fluoride | Transformation efficiency % | Selectivity % | 305 |
| 0.6 | 0.5 | 200 | 60 | 0.61 | 99.50 | ＞99.9 | 99.6 | |
Reaction example 2,3:
In said apparatus, use the catalyzer of Production Example 2, pre-treatment remains unchanged, and inlet amount remains unchanged, and changes different temperature of reaction, pressure, and its reaction result is as follows:
Table two
| Reaction pressure (Mpa) | Temperature of reaction (℃) | The product of alkali cleaning is formed M% | CH 2Cl 2 | CH 2F 2The output Grams Per Hour | ||||
| One section | Two sections | One section | Two sections | R31 | Methylene fluoride | Transformation efficiency % | Selectivity % | |
| 0.8 | 0.7 | 250 | 80 | 0.50 | 99.30 | ＞99.9 | 99.4 | 304 |
| 1.0 | 0.9 | 300 | 100 | 0.35 | 99.10 | ＞99.9 | 99.2 | 303 |
Claims (8)
1, a kind of method of preparing difluoromethane by stage continuous fluorination, it is characterized in that being gas-phase reaction at first section, under the condition that the composite catalyst that muriate, oxyhydroxide, oxide compound or the fluorochemical of Al, two kinds of metals of Cr are formed exists, the molar ratio 2～4: 1 of hydrogen fluoride and methylene dichloride, 180～320 ℃ of temperature of reaction, pressure 0.5～1.5Mpa; Second section is liquid phase reaction, does directly to feed Liquid-phase reactor from first section product, 50～120 ℃ of temperature of reaction, reaction pressure 0.5～1.2Mpa under the condition of catalyzer existence at Sb muriate or its chloride mix that contains Sn.
2, the method for preparing methylene fluoride according to claim 1 is characterized in that described first section composite catalyst prepares as follows:
1) commercially available AlF
3Ointment washs to neutral with pure water, and oven dry is pulverized, and gets AlF
3Powder;
2) in the compound solution that contains chromium (III) 1～10%, add solution of ammonium hydroxide, wherein NH
3Content is 1～25%, be stirred to pH value reach 9.0 hydration Cr
2O
3Precipitation is filtered, and washs NH to the filter cake
4 +The anion-content of content and chromium (III) compound is less than 0.05%, oven dry, grind Cr
2O
3Powder;
3) will contain Cr
2O
3With AlF
3Two powders add water and are mixed into the wet-milling shape with 10: 90～95: 5 weight ratio, granulate, oven dry, bulk density be the 0.7kg/L catalyst prod.
3, the method for preparing methylene fluoride according to claim 1 is characterized in that described second section catalyzer is that Sb muriate or its contain the muriatic mixture of Sn, and the Sn weight content is 1～10% in the mixture.
4,, it is characterized in that the molar ratio 2～3: 1 of described first section hydrogen fluoride and methylene dichloride, 180～250 ℃ of temperature of reaction according to claim 1 or the 2 or 3 described methods that prepare methylene fluoride.
5, according to claim 1 or the 2 or 3 described methods that prepare methylene fluoride, it is characterized in that adding in second section reaction the anhydrous hydrogen fluoride thinner, its amount is 0.1～1.5 times of catalyst weight.
6, the method for preparing methylene fluoride according to claim 4 is characterized in that adding in second section reaction the anhydrous hydrogen fluoride thinner, and its amount is 0.1～1.5 times of catalyst weight.
7, the method for preparing methylene fluoride according to claim 5, the weight that it is characterized in that the thinner that adds in described second section reaction are 0.1～1 times of catalytic amount.
8, the method for preparing methylene fluoride according to claim 6, the weight that it is characterized in that adding thinner in described second section reaction are 0.1～1 times of catalytic amount.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100492558A CN1313423C (en) | 2005-01-27 | 2005-01-27 | Method for preparing difluoromethane by stage continuous fluorination |
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|---|---|---|---|
| CNB2005100492558A CN1313423C (en) | 2005-01-27 | 2005-01-27 | Method for preparing difluoromethane by stage continuous fluorination |
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| CN1313423C true CN1313423C (en) | 2007-05-02 |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102527414B (en) * | 2011-12-28 | 2013-01-02 | 临海市利民化工有限公司 | Fluorination catalyst for preparing difluoromethane or monochlorodifluoromethane, preparation method and application |
| CN110627612A (en) * | 2019-09-26 | 2019-12-31 | 江苏三美化工有限公司 | Method for producing fluorinated alkane in pipeline mode by improving selectivity of reaction process |
| CN113698270A (en) * | 2021-08-24 | 2021-11-26 | 聊城氟尔新材料科技有限公司 | Process and system for stable production of difluoromethane |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1168660A (en) * | 1994-06-20 | 1997-12-24 | 大金工业株式全社 | Process for producing difluoromethane |
| CN1201446A (en) * | 1995-09-20 | 1998-12-09 | 联合讯号公司 | Process for production of difluromethane |
-
2005
- 2005-01-27 CN CNB2005100492558A patent/CN1313423C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1168660A (en) * | 1994-06-20 | 1997-12-24 | 大金工业株式全社 | Process for producing difluoromethane |
| CN1201446A (en) * | 1995-09-20 | 1998-12-09 | 联合讯号公司 | Process for production of difluromethane |
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