CN1039118C - Improved gas-phase fluorating process for preparation of difluoromethane - Google Patents

Improved gas-phase fluorating process for preparation of difluoromethane Download PDF

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CN1039118C
CN1039118C CN 92102368 CN92102368A CN1039118C CN 1039118 C CN1039118 C CN 1039118C CN 92102368 CN92102368 CN 92102368 CN 92102368 A CN92102368 A CN 92102368A CN 1039118 C CN1039118 C CN 1039118C
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reaction
temperature
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preparation
catalyzer
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CN1076686A (en
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郭心正
叶朝珲
马鑫明
赵璇
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Zhejiang blue environmental protection hi tech Limited by Share Ltd
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Zhejiang Chemical Industry Research Institute Co Ltd
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Abstract

The present invention discloses an improved method for preparing difluoromethane by gas phase fluorination reaction between methylene chloride and anhyrous hydrogen fluoride. Pessurization reaction of 0.8 to 1.5MPa is adopted, a condensation separation device is additionally arranged behind a reactor, the cooling water temperature of the condensation separation device is from 0 to 30 DEG C, the reaction temperature is form 180 to 400 DEG C, the molar ratio of HF to CH2Cl2 is from 2.1 to 2.3, a catalyst adopts oxide or halide which uses active carbon, AlF3 or Al2O3 as a carrier to load Fe<+++>, Cr<+++>, Ni<++>, Co<+++>, Mn<++>, Bi<+++>, Cu<++>, Ag<+> and Na<+>, or Cr2O3 or AlF3-Cr2O3 which does not contain carriers. The conversion rate of CH2Cl2 is higher than 99%, and the selectivity of the difluoromethane is higher than 95%. The service life of the catalyst is greatly enhanced.

Description

Gas phase fluorination prepares improving one's methods of methylene fluoride
The present invention relates to improvement preparation method by methylene dichloride and anhydrous hydrogen fluoride gas phase fluorination system methylene fluoride.
Always, the preparation method of methylene fluoride adopts methylene dichloride and the gaseous fluoridizing method of anhydrous hydrogen fluoride in the presence of catalyzer.In the method, generate methylene fluoride by following halogen exchange reaction.
(1)
(2)
(3)
Methylene dichloride and anhydrous hydrogen fluoride gas phase fluorination in the presence of catalyzer prepares the method for methylene fluoride, existing many patent documentations records, and US2 for example, 745,886 with CrF 3Be catalyzer, 250 ℃ of temperature of reaction, HF and CH 2Cl 2Mole ratio M HF: M CH2Cl2=2.8: 1,5.9 seconds residence time, the selectivity that the transformation efficiency 52.7% of methylene dichloride, methylene dichloride are converted into methylene fluoride is 82.7%.US2,748,177 with AlF 3Be catalyzer, 400 ℃ of temperature of reaction, the mol ratio of hydrogen fluoride and methylene fluoride=1: 1.3,3.7 seconds residence time, CH 2Cl 2Transformation efficiency be 36.3%, CH 2Cl 2Be converted into CH 2F 2Selectivity be 17.0%.US3,644,454, with NaF-Cr 2O 8Be catalyzer, 200 ℃ of temperature of reaction, 10 seconds residence time, CH 2Cl 2Transformation efficiency be 62%, CH 2Cl 2Be converted into CH 2F 2Selectivity be 59.7%.US4,147,733 with CrCl 3-AlF 3Be catalyzer, 350 ℃ of temperature of reaction, the mol ratio of hydrogen fluoride and methylene fluoride=1.4: 1,3.5 seconds residence time, CH 2Cl 2Transformation efficiency be 12%, CH 2Cl 2Be converted into CH 2F 2Selectivity be 73%.Luigi Marangoni has announced Cr in the 7th European fluorine chemistry meeting 2O 3Make the result of catalyzer: 300 ℃ of temperature of reaction, the mol ratio of hydrogen fluoride and methylene fluoride=3: 1,3.0 seconds residence time, CH 2Cl 2Transformation efficiency be 76.5%, CH 2Cl 2Be converted into CH 2F 2Selectivity be 77.1%.It is clear 59,225 that the spy opens, and 131 with CrF 3Be catalyzer, 380 ℃ of temperature of reaction, the mol ratio of hydrogen fluoride and methylene fluoride=5.82: 1,15.5 seconds residence time, CH 2Cl 2Transformation efficiency be 83.6%, CH 2Cl 2Be converted into CH 2F 2Selectivity be 84.6%.The spy opens clear 59-225132 with FeCl 3/ gac is a catalyzer, 300 ℃ of temperature of reaction, the mol ratio of hydrogen fluoride and methylene fluoride=9: 1,26.4 seconds residence time, CH 2Cl 2Transformation efficiency is 85.4%, CH 2Cl 2Be converted into CH 2F 2Selectivity be 89.2%.More than existing patented technology is synthesis under normal pressure.
In sum, methylene dichloride and anhydrous hydrogen fluoride gas phase fluorination prepare methylene fluoride, although patent is a lot, but the transformation efficiency of methylene dichloride is not high, the selectivity that methylene dichloride is converted into methylene fluoride is not high yet, and what the sustained reaction time of being announced was the longest also has only 120 hours, illustrates that life of catalyst is not long yet.
The inventor's purpose is exactly at the problem on the prior art, improvement by processing condition and select more appropriate catalyst system, the transformation efficiency of methylene dichloride in the reaction and selectivity are all obtained significantly improve, and prolong catalyst life greatly, for suitability for industrialized production creates conditions.
Technical process of the present invention as shown in drawings.
Methylene dichloride and anhydrous hydrogen fluoride enter from storage tank (1) and (2) with volume pump with selected speed and give hot device (3), entering fluorination reactor (4) after the gasification reacts, reaction product enters condensation separator (5) from the bottom of fluorination reactor (4), after condensation separation, gas-phase product HCl, CH 2F 2Enter water wash column (6) from condenser overhead, soda-wash tower (7), gas holder (8), the dry back of drying device (9) (10) is pressed into thick groove (12) with compressor (11) then.The CH that condensation is got off in the condensation separator (5) 2Cl 2, HF and CH 2Overflows such as ClF are returned and are given hot device (3) and unstripped gas HF, CH 2Cl 2Enter together and continue reaction in the fluorination reactor (4).
The inventor has made two important improvement to the technology that the methylene dichloride gas phase fluorination prepares methylene fluoride, and the one, the change synthesis under normal pressure is compressive reaction, the 2nd, behind reactor, increase condensation separator.
Compressive reaction helps previous reaction (1), (2), (3) to carry out to positive dirction, thereby helps improving CH 2Cl 2Transformation efficiency and generate CH 2F 2Selectivity, at same CH 2F 2Under the output requirement condition, lower temperature of reaction in the time of can adopting than normal pressure, thus prolong catalyst life significantly.
By technology of the present invention, after the product that leaves the gas phase fluorination device enters condensation separator, under condensation and separation of double effect, the CH that boiling point is higher 2Cl 2Be condensed with the HF overwhelming majority, and the middle CH of boiling point 2The ClF major part is condensed, and they are returned the gas phase fluorination device together and continue reaction, and lower HCl and the principal product CH of boiling point 2F 2The overwhelming majority is overflowed, and leaves condenser.Like this, as long as take the pressure and the condensing temperature that suit, just can make through CH in washing, the alkali cleaning after product 2F 2Content is brought up to more than 95%, and CH 2Cl 2Be reduced to below 1%.
The cooling temperature of condensation separator and reaction pressure complement each other and interact.As require to wash CH in the alkali cleaning after product 2F 2Content reaches 95%, and selected reaction pressure is high more, and then the temperature of cooling water of condensation separator just can be higher.So just can not adopt chilled brine only to adopt common tap water to make water coolant, save the energy.But reaction pressure is too high, and the requirement of equipment and material-transporting system is also increased.Therefore suitable condensation separator temperature of cooling water is 0-30 ℃, and corresponding reaction pressure is 0.8-1.5MPa, and especially Shi Yi condensation separator temperature of cooling water is 10-25 ℃, and corresponding reaction pressure is 1.0-1.3MPa.
The inventor discovers, temperature of reaction is high more, CH 2Cl 2Be converted into CH 2F 2Speed of response accelerate, but the increase of catalyst carbon deposit speed is faster, causes catalyst life to shorten significantly.Temperature of reaction reduces, CH 2Cl 2Be converted into CH 2F 2Speed of response slow down, but the carbon deposit speed of catalyzer slows down more.Therefore catalyst life can prolong greatly.Take all factors into consideration speed of response and catalyst life, temperature of reaction of the present invention generally is controlled at 180-400 ℃, and especially suitable reaction temperature is 220-280 ℃.
HF and CH 2Cl 2The mole proportioning can have influence on CH 2Cl 2Transformation efficiency and CH 2Cl 2Be converted into CH 2F 2Selectivity.HF and CH 2Cl 2Mol ratio＜2, CH 2Cl 2Be converted into CH 2F 2Selectivity lower, HF and CH 2Cl 2Mol ratio＞2.5, in compressive reaction equipment, HF constantly accumulates, and makes CH 2Cl 2The residence time at catalyst bed shortens, and influences its transformation efficiency.Suitable HF and CH 2Cl 2Mol ratio be 2.1-2.3.
Selection of catalysts is one of key problem in technology of the present invention, and the solid acid catalyst of numerous species all is fit to the present invention, comprising with suitable property charcoal, AlF 3Or Al 2O 3As carrier, carry attached metal Fe +++, Cr +++, Ni ++, Co +++, Mn ++, Bi +++, Cu ++, Ag +, Na +Oxide compound or halogenide, metal content 0.5-10wt.%.In the metal halide, bromide, iodide can use, but secondly the general fluorochemical that uses is muriate more.Carrier-free Cr 2O 3Or AlF 3-Cr 2O 3Also can be used as the catalyzer of process of the present invention.But the optimum catalyzer of the present invention is metal content meter 0.5～10Wt.%Bi +++, Mn ++, Co +++Oxide compound or halid AlF 3Or Al 2O 3Composite catalyst and contain 2～25Wt.%Cr 2O 3AlF 3-Cr 2O 3Composite catalyst.At AlF 3Or Al 2O 3Contained Bi in the catalyzer +++, Mn ++, Co +++Halogenide, what override adopted is fluorochemical, secondly is muriate.
Catalyzer of the present invention can adopt fixed bed, also can adopt thermopnore.
By the inventive method, prepare methylene fluoride by the methylene dichloride gas phase fluorination, the transformation efficiency of methylene dichloride＞99%, methylene dichloride are converted into selectivity＞95% of methylene fluoride, and the catalyst surface coking amount reduces greatly, thereby catalyst life obtains to prolong significantly.
Specify the present invention below for example, the catalyzer component content is weight percentage in each example.
Embodiment one
Contain Bi with 0.1 kilogram 2O 3, MnCl 2AlF 3(Bi content 1%, Mn content 2%) adds gas phase fluorination device (4) (carbon steel system, cubic capacity are 2.5 liters, and shell and tube, tubulation internal diameter are 25 millimeters), per hour to heat up 50 ℃ speed heating, feeds nitrogen simultaneously and drives moisture content.Kept after rising to 230 ℃ 5 hours, and fed anhydrous hydrogen fluoride 300 grams in wherein last 1 hour; Begin fluoridation then, the feed rate of control anhydrous hydrogen fluoride is 415 Grams Per Hours, methylene dichloride is 800 Grams Per Hours, the control reaction pressure is 1.0MPa, the heat transfer area of condensation separator (5) is 0.2 square metre, number of actual plates is 3, control condenser (5) top material temperature≤15 ℃, treat to emit reaction product by condenser (5) top after fluorination reactor pressure liter reaches 1.0MPa, after washing (6), alkali cleaning (7), enter gas holder (8), form at the preceding gas chromatography analysis for sampling product of gas holder (8) simultaneously.Overflows such as the anhydrous hydrogen fluoride that the interior condensation of condensation separator (5) is got off, methylene dichloride are back to fluorination reactor (4) continuation reaction after giving hot device (3), reaction continues 1000 hours, and it the results are shown in Table one.
Table one
The reaction times Accumulative Hours or Hours Accumulated The alkali cleaning after product is formed M% CH 2F 2During output/hour CH 2Cl 2
CH 2F 2 CH 2ClF CH 2Cl 2 Transformation efficiency % Selectivity %
100 96.2 2.8 0.5 424 99.5 96.7
300 96.2 2.8 0.5 424 99.5 96.7
500 96.2 2.8 0.5 424 99.5 96.7
700 96.0 3.0 0.5 423 99.5 96.5
800 96.0 3.0 0.5 423 99.5 96.5
1000 95.8 3.2 0.5 422 99.5 96.3
Embodiment two, three, four, five, six, seven, eight
All undertaken by device and the operation steps of embodiment one, but reaction conditions is pressed table 2 Data Control, reaction pressure is 1.0MPa, and with the used Bi that contains among the embodiment 1 2O 3And MnCl 3AlF 3Catalyzer is used following various catalyzer instead:
Cat1-2:FeCl 3/ gac contains Fe 7%
Cat1-4:CrCl 3/ gac, Cr content 14%
Cat2-2:Bi 2O 3-CrCl 3/ AlF 3, Bi and Cr content are respectively 1% and 2%
Cat2-3:Bi 2O 3-CoCl 3/ AlF 3, Bi and Co content are respectively 1% and 2%
Cat3-1:Cr 2O 3/ AlF 3, contain Cr 2O 310%
Cat4-1：Cr 2O 3
Cat5-1:MnCl 2-Bi 2O 3/ Al 2O 3, Mn, Bi content are respectively 2% and 1%
React the 20th hour sampling analysis, it the results are shown in table 2
Table two
Reference examples one～eight
Adopt the single tube reactor of the long 700mm of carbon steel system internal diameter 25mm, be respectively charged into each 150 gram of eight kinds of corresponding among embodiment 1-8 catalyzer in the reactor, carry out synthesis under normal pressure by reaction conditions shown in the table three, reaction product directly enters washing, alkali cleaning without condensation separator after leaving reactor, sampling analysis the results are shown in table three.
Table three

Claims (5)

1. one kind prepares the method for methylene fluoride by methylene dichloride, anhydrous hydrogen fluoride gas phase fluorination, it is characterized in that adopting compressive reaction, and increase condensation separator behind reactor, and catalyzer adopts with gac, AlF 3Or Al 2O 3Make carrier, carry attached metal Fe +++, Cr +++, Ni ++, Co +++, Mn ++, Bi +++, Cu ++, Ag +, Na +Oxide compound or halogenide, metal content 0.5～10Wt.%, condensation separator temperature of cooling water are 0～30 ℃, reaction pressure is 0.8～1.5MPa, 180～400 ℃ of temperature of reaction, HF and CHCl 2Mol ratio be 2.1～2.3.
2. by the said preparation method of claim 1, it is characterized in that catalyzer adopts metal content meter 0.5～10Wt.%Bi +++, Mn ++, Co +++Oxide compound or halid AlF 3Or Al 2O 3Composite catalyst.
3. by the said preparation method of claim 1, it is characterized in that the catalyzer employing contains 2～25Wt.%Cr 2O 3AlF 3-Cr 2O 3Composite catalyst.
4. by claim 1,2 said preparation methods, it is characterized in that at AlF 3Or Al 2O 3In contained Bi +++, Mn ++, Co +++Halogenide be fluorochemical or muriate.
5. by the said preparation method of claim 1, it is characterized in that the condensation separator temperature of cooling water is 10～25 ℃, reaction pressure is 1.0～1.3MPa, and temperature of reaction is 220～280 ℃.
CN 92102368 1992-03-23 1992-03-23 Improved gas-phase fluorating process for preparation of difluoromethane Expired - Lifetime CN1039118C (en)

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TW200516068A (en) * 2003-09-10 2005-05-16 Showa Denko Kk Process for production of hydrofluorocarbons, products thereof and use of the products
CN100434166C (en) * 2005-09-09 2008-11-19 北京宇极科技发展有限公司 Producing art of hydroflurocarbon and producing method of special catalyst thereof
CN110204414A (en) * 2019-06-25 2019-09-06 福建省杭氟电子材料有限公司 A kind of preparation method of a fluoromethane
CN115010576A (en) * 2022-07-02 2022-09-06 浙江三美化工股份有限公司 Preparation method of difluoromethane

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