CN101462925B - Method for preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene - Google Patents
Method for preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene Download PDFInfo
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- CN101462925B CN101462925B CN2009100288978A CN200910028897A CN101462925B CN 101462925 B CN101462925 B CN 101462925B CN 2009100288978 A CN2009100288978 A CN 2009100288978A CN 200910028897 A CN200910028897 A CN 200910028897A CN 101462925 B CN101462925 B CN 101462925B
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- tetrafluoroethylene
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- polytetrafluorethylene
- polyfluortetraethylene
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Abstract
The invention relates to a method for preparing tetrafluoroethylene by thermal cracking of polyfluortetraethylene. The thermal cracking is carried out in a cracking kettle at the temperature of 400-900 DEG C and the vacuum degree of 10-101kPa; more particularly, before the thermal cracking reaction, the polyfluortetraethylene which is taken as raw material is evenly mixed with solid particles according to the mass ratio of 1:0.1-5. A certain amount of solid particles are selected to be mixed with the polyfluortetraethylene, and the solid particles are like a plurality of small heaters in the polyfluortetraethylene, thus effectively promoting the heat transfer among the particles and obviously improving the heat transferring effect; meanwhile, the solid particles also can absorb a little bit of difluorocarbene generated by thermal cracking of the polyfluortetraethylene, so that the secondary reaction caused by the collision of the excessive difluorocarbene can be effectively avoided, the generation of perfluoroisobutylene which is noxious byproduct can be prevented, and the purity of the product is improved. In addition, the method has the advantages of being safe, simple and low in production cost.
Description
Technical field
The present invention relates to a kind of is the method for feedstock production tetrafluoroethylene with the tetrafluoroethylene.
Background technology
Tetrafluoroethylene (TFE), no color or smell gas, fusing point-142.5 ℃; Boiling point-76.3 ℃; Being the important monomer of synthetic teflon resin, also is the monomer of synthetic other Fluroplast-4, viton, perfluoro propylene, reaches and pharmaceutically all has a wide range of applications in fluorine surfactant, fine chemistry industry.
At present, the preparation of tetrafluoroethylene both at home and abroad mainly with difluorochloromethane (F22) be raw material at high temperature pyrolytic reaction make, specifically have blank pipe cracking and water vapour to dilute two kinds of methods of cracking.Difluorochloromethane can be made by chloroform, has the advantage that raw material is easy to get, but this technology is more loaded down with trivial details.U.S. Pat 3832411 has been reported the high-temperature steam heating tetrafluoroethylene that uses 405 ℃～760 ℃, and as the carrier gas of product tetrafluoroethylene, obtains the tetrafluoroethylene of purity about 90%, must separate because product purity is lower.Patent CN1398839 adopts an independent nickelalloy pipe to heat tetrafluoroethylene as the thermal source that produces superheated vapour; The heating electrode of nickelalloy pipe is processed than big area with electroconductibility and the preferable metal of thermal diffusivity; Prolong the work-ing life of nickelalloy pipe, but equipment cost is higher.The patent No. is that the Chinese invention patent of ZL96193012.8 joins metal fluoride and carbon in the plasma flame, to form a kind of gaseous mixture, then it chilling is obtained tetrafluoroethylene.Plasma flame can form from non-reactive gas or a kind of raw material wherein, but reaction conditions is higher, is unfavorable for applying.US5432259 goes into the fluidizing ptfe granules through vapor zone, and with it heating pyrolyze, has obtained about 85% tetrafluoroethylene, but owing to has used a large amount of steam, product to need aftertreatment to separate.Publication number be the U.S. Patent application of US2006/0020106 to adopt rotary oven be cracking reactor, heat tetrafluoroethylene and make its cracking through heating steam, the high-content of tetrafluoroethylene is 67%, more complicated on the equipment making.
Summary of the invention
Technical problem to be solved by this invention is in order to overcome the deficiency of prior art, to provide a kind of tetrafluoroethylene high temperature pyrolysis to prepare the method for tetrafluoroethylene, and this method is simple, heat-transfer effect good, and gained tetrafluoroethylene purity is high.
For solving above technical problem, the present invention takes following technical scheme:
A kind of method of preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene; Said thermo-cracking is carried out in the cracking still of 400 ℃～900 ℃ of temperature, vacuum tightness 10～101kPa; Particularly; Before carrying out said heat scission reaction, will mix by mass ratio 1: 0.1～5 as the tetrafluoroethylene and the solid particulate of raw material.
The solid particulate that the present invention adopts has high melt point (more than 400 ℃) and thermal conductivity (greater than 40W/ (m
2K)), particle size is between 2.5～500 orders.Solid particulate preferable alloy, MOX and sand a kind of or their mixture; Wherein metal can be one or more the alloy in copper, iron, magnesium, aluminium, gold and silver, platinum, the nickel, and MOX can be meant one or more in cupric oxide, red stone, Natural manganese dioxide, aluminum oxide, silver suboxide, quicklime, manganese oxide, zinc oxide and the nickel oxide.When solid particulate is MOX or sand, can absorb the low amount of fluorinated hydrogen (HF) that produces in the cracking process, prevent that tetrafluoroethylene is present in acidic conditions.
The mass ratio of tetrafluoroethylene and solid particulate is preferably 1: 0.1～and 2.The thermo-cracking of tetrafluoroethylene is at high temperature carried out, and preferred temperature is between 500 ℃～800 ℃.Type of heating can be electrically heated, steam indirect heating or far-infrared heating.
Described thermo-cracking is preferably carried out under vacuum tightness 80～101kPa, can avoid gathering of pyrolysis product effectively and the side reaction that causes.
The boiling point of tetrafluoroethylene is-76 ℃ under the normal pressure, and is lower under vacuum condition.Adopt liquid nitrogen condensation to collect split product and can improve the tetrafluoroethylene yield.
For the selection of tetrafluoroethylene raw material, can be purified tetrafluoroethylene, also can be waste and old tetrafluoroethylene, form is particle or powder.With waste and old tetrafluoroethylene is raw material, helps the recovery and the utilization of waste and old tetrafluoroethylene and reduces production costs.
Because the utilization of technique scheme, the present invention compared with prior art has advantage:
Select for use a certain amount of solid particulate to mix with tetrafluoroethylene, solid particulate is equivalent to one by one little well heater in tetrafluoroethylene, can promote intergranular heat transmission effectively, improves heat-transfer effect significantly; Simultaneously, solid particulate can also adsorb the difluorocarbene that the small amount of polytetrafluoroethylmay thermo-cracking produces, and effectively avoids too much difluorocarbene's collision and causes side reaction, suppresses the generation of toxic byproduct octafluoroisobutene, improves product purity.In addition, safety of the present invention, simple, production cost is low.
Embodiment
Following specific embodiments of the invention describes, but is not limited to these embodiment.
Embodiment 1
3kg polytetrafluorethylepowder powder and 1.5kg copper powder are mixed, add in the 10L stainless steel scission reaction still, vacuumize and use nitrogen replacement after the sealing, oxygen level is evacuated to-101kPa less than 20ppm then to the still.Be warming up to 550 ℃ of beginning cracking, liquid nitrogen condensation is collected product.When the still internal pressure no longer changes, finish reaction, the time is 1.8h, stratographic analysis records tetrafluoroethylene quality percentage composition 95.3%, does not detect octafluoroisobutene.
Embodiment 2
3kg polytetrafluorethylepowder powder and 1.5kg aluminum oxide are mixed, add in the 10L stainless steel scission reaction still, vacuumize and use nitrogen replacement after the sealing, oxygen level is evacuated to-80kPa less than 20ppm then to the still.Be warming up to 550 ℃ of beginning cracking, liquid nitrogen condensation is collected product.When the still internal pressure no longer changes, finish reaction, the time is 2.0h, it is 90.7% that stratographic analysis records tetrafluoroethylene quality percentage composition, does not detect octafluoroisobutene.
Embodiment 3
3kg polytetrafluorethylepowder powder and 0.3kg iron-nickel alloy powder are mixed, add in the 10L stainless steel scission reaction still, vacuumize and use nitrogen replacement after the sealing, oxygen level is evacuated to-80kPa less than 20ppm then to the still.Be warming up to 550 ℃ of beginning cracking, the condensation and collection product.When the still internal pressure no longer changes, finish reaction, the time is 2.2h, it is 89.2% that stratographic analysis records tetrafluoroethylene quality percentage composition, does not detect octafluoroisobutene.
Embodiment 4
Cupric oxide, the quicklime of 3kg polytetrafluorethylepowder powder and 1.5kg are mixed, add in the 10L stainless steel scission reaction still, vacuumize and use nitrogen replacement after the sealing, oxygen level is evacuated to-101kPa less than 20ppm then to the still.Be warming up to 800 ℃ of beginning cracking, liquid nitrogen condensation is collected product.When the still internal pressure no longer changes, finish reaction, the time is 1.5h, stratographic analysis records tetrafluoroethylene 98.8%, does not detect octafluoroisobutene.
Embodiment 5
3kg polytetrafluorethylepowder powder and 6kg fine sand are mixed, add in the 10L stainless steel scission reaction still, vacuumize and use nitrogen replacement after the sealing, oxygen level is evacuated to-101kPa less than 20ppm then to the still.Be warming up to 800 ℃ of beginning cracking, liquid nitrogen condensation is collected product.When the still internal pressure no longer changes, finish reaction, the time is 0.7h, it is 98.3% that stratographic analysis records tetrafluoroethylene content, does not detect octafluoroisobutene.
Embodiment 6
The mixture of aluminium, zinc oxide and the sand of 3kg polytetrafluorethylepowder powder and 1.5kg is mixed, add in the 10L stainless steel scission reaction still, vacuumize and use nitrogen replacement after the sealing, oxygen level is evacuated to-101kPa less than 20ppm then to the still.Be warming up to 800 ℃ of beginning cracking, liquid nitrogen condensation is collected product.When the still internal pressure no longer changes, finish reaction, the time is 1.6h, stratographic analysis records tetrafluoroethylene 98.9%, does not detect octafluoroisobutene.
Comparative Examples
The 3kg polytetrafluorethylepowder powder is added in the 10L stainless steel scission reaction still, vacuumize and use nitrogen replacement after the sealing, oxygen level is evacuated to-101kPa less than 20ppm then to the still.Be warming up to 550 ℃ of beginning cracking, the condensation and collection product.When the still internal pressure no longer changes, finish reaction, the time is 2.5h, stratographic analysis records TFE 80.8%, contains micro-octafluoroisobutene.
Can find out from embodiment 1～6 and Comparative Examples, with tetrafluoroethylene with carry out heat scission reaction again after a certain amount of solid particulate mixes, can improve the purity and the generation of avoiding the toxic byproduct octafluoroisobutene of product tetrafluoroethylene.In addition, the present invention is a rhythmic reaction, simple to operate and safety, and production cost is lower.
Claims (6)
1. the method for a preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene; Said thermo-cracking is carried out in the cracking still of 400 ℃～900 ℃ of temperature, vacuum tightness 10～101kPa; It is characterized in that: before carrying out said heat scission reaction; To mix by mass ratio 1: 0.1～5 as the tetrafluoroethylene and the solid particulate of raw material; Described solid particulate is one or more the mixture in metal, MOX and the sand, and described metal is one or more the alloy that is selected from copper, iron, aluminium, the nickel; Described MOX is to be selected from cupric oxide, aluminum oxide, quicklime and the zinc oxide one or more.
2. the method for a kind of preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene according to claim 1, it is characterized in that: the mass ratio of tetrafluoroethylene and solid particulate is 1: 0.1～2.
3. a kind of tetrafluoroethylene cracking according to claim 1 prepares the method for tetrafluoroethylene, it is characterized in that: the temperature of thermo-cracking is between 500 ℃～800 ℃.
4. the method for a kind of preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene according to claim 1, it is characterized in that: described vacuum tightness is between 80～101kPa.
5. the method for a kind of preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene according to claim 1, it is characterized in that: described tetrafluoroethylene is waste and old tetrafluoroethylene.
6. the method for a kind of preparing tetrafluoroethylene by thermal cracking polytetrafluorethylene according to claim 1 is characterized in that: collect split product through liquid nitrogen condensation.
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| CN101462925B true CN101462925B (en) | 2012-08-08 |
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Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102672968A (en) * | 2012-05-07 | 2012-09-19 | 四川久远科技股份有限公司 | Method for manufacturing ultrafine powder from polytetrafluoroethylene through irradiation cracking |
| CN107722149A (en) * | 2017-11-16 | 2018-02-23 | 四川金核高分子材料有限公司 | A kind of ptfe micropowder and preparation method thereof |
| CN109734070A (en) * | 2018-12-24 | 2019-05-10 | 天津长芦新材料研究院有限公司 | The method that waste and old PTFE cracking becomes carbonyl fluoride |
| CN109912384A (en) * | 2019-04-04 | 2019-06-21 | 浙江大学 | A kind of catalysis process recycling dichloropropylene from dichloropropylene polymer |
| CN111073186B (en) * | 2019-12-20 | 2022-05-13 | 浙江巨化技术中心有限公司 | Polytetrafluoroethylene composite material for packing and method for preparing packing by using same |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1108639A (en) * | 1993-10-06 | 1995-09-20 | 赫彻斯特股份公司 | Process for the preparation of fluorinated monomers |
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1108639A (en) * | 1993-10-06 | 1995-09-20 | 赫彻斯特股份公司 | Process for the preparation of fluorinated monomers |
Non-Patent Citations (2)
| Title |
|---|
| C. M. Simon et al.."Chemical recycling of polytetrafluoroethylene by pyrolysis".《Polymer Degradation and Stability》.1998,第62卷(第1期),1-7. |
| 张宗礼 等."废聚四氟乙烯回收生产四氟乙烯单体的研究".《环境工程学报》.2007,第1卷(第10期),141-144. |
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Owner name: TAICANG ZHONGHUA ENVIRONMENTAL PROTECTION MEDICAL Free format text: FORMER OWNER: ZHONGHUA INTERNATIONAL (SUZHOU) NEW MATERIAL R + D CO., LTD. Effective date: 20120301 |
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Effective date of registration: 20120301 Address after: 215433 No. 18 South Binjiang Road, petrochemical District, Taicang Port Development Zone, Jiangsu, China Applicant after: Sinochem Taicang Environmental Protection Chemical Co., Ltd. Address before: 215433 No. 18 South Binjiang Road, petrochemical District, Taicang Port Development Zone, Jiangsu, China Applicant before: Sinochem International (Suzhou) New Material R&D Co., Ltd. |
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Effective date of registration: 20191225 Address after: No. 18, Binjiang South Road, petrochemical District, Port Development Zone, Taicang City, Suzhou City, Jiangsu Province Co-patentee after: Sinochem Lantian Co., Ltd. Patentee after: Sinochem Taicang Environmental Protection Chemical Co., Ltd. Co-patentee after: Sinochem Corporation Address before: 215433 No. 18 South Binjiang Road, petrochemical District, Taicang Port Development Zone, Jiangsu, China Patentee before: Sinochem Taicang Environmental Protection Chemical Co., Ltd. |
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