Research And Development Of A Next Generation Environment-Friendly Refrigerant 2,3,3,3-Tetrafluoropropene With Zero Odp Value And Low GWP Value

Ozone depletion and global warming are both man-made and serious environmental crises.The restriction use of refrigerants HFC-134a（1,1,1,2-tetrafluoroethane,GWP=1300）is necessary in order to improve the survival of the human environment.HFO-1234yf（2,3,3,3-tetrafluoropropene,GWP=4）is considered as an ideal substitute due to its similar chemical and physiochemical properties to HFC-134a.This paper presents a new methodology for synthesis of HFO-1234yf based on basic chemical raw materials,the main results are as follows:HCC-250fb（1,1,1,3-tetrachloropropane）was synthesized by liquid-phase telomerization of ethylene（CH₂=CH₂）with carbon tetrachloride（CCl₄）in the presence of initiator systems,where the initiator systems were comprised of Fe-FeCl₃ and TBP.And the influence of various parameters was studied,including the molar ratio of CCl₄ to CH₂=CH₂,reaction temperature,reaction pressure and solvent content.It was found that the kinetic equation of synthesis for HCC-250fb process fitted first order linear relation,and the mechanism of formation of HCC-250fb was a chain oxidation reduction reaction.Density functional theory（DFT）has been employed to investigate liquid-phase telomerization of ethylene with CCl₄ in acetonitrile solution.HCC-240db（1,1,1,2,3-pentachloropropane）was synthesized by liquid-phase catalytic chlorination of HCC-250fb with chlorine promoted by FeCl₃ catalyst.And the influence of various parameters was studied,including the molar ratio of HCC-250fb to Cl₂,catalyst content,reaction temperature and reaction pressure.DFT has been employed to investigate the liquid-phase catalytic chlorination of HCC-250fb with chlorine in CCl₄solution.It was found that the reaction paths were strongly exothermic reaction process.Temperature control was one of the most important factors in this reaction.HCFO-1233xf（2-chloro-3,3,3-trifluoropropene）was synthesized by gas-phase catalytic fluorination of HCC-240db with hydrogen fluoride（HF）promoted by Cr-based catalyst.And the influence of various parameters was studied,including the reaction conditions,the molar ratio of HCC-240db to HF,reaction temperature and space velocity.DFT has been employed to investigate the gas-phase catalytic fluorination of HCC-240db with hydrogen fluoride.It was found that the reaction paths processed F/Cl exchange reaction first,then the olefin was generated by the elimination of hydrogen chloride.HFO-1234yf was synthesized by gas-phase catalytic fluorination of HCFO-1233xf with HF promoted by Cr-based catalyst,a series of single-and multi-component catalysts X（X=Zn,Co,Ni,Cu）were prepared by means of coprecipitation for this reaction.The superiorities of fluorinated catalysts were considered,such as modifying acidity,surface composition and,subsequently,changing activity for acid-catalyzed F/Cl exchange.And the influence of various parameters were studied,including the molar ratio of HCFO-1233xf and HF,reaction temperature and space velocity.DFT has been employed to investigate the gas-phase catalytic fluorination of HCFO-1233xf with hydrogen fluoride.It indicated that HFO-1234yf was synthesized by an F/Cl exchange reaction of HCFO-1233xf with HF,and the main products were HFO-1234yf and HFC-245cb（1,1,1,2,2-Pentapropane）.It also showed that the elimination and addition of HF between HFC-245cb and HFO-1234yf were a reversible reaction process,and the conversion reaction between HFO-1234yf and HCFC-244bb was difficult to occur at less than 350℃.The deactivation and regeneration of Cr-based catalyst was studied.Cr-based catalysts treated with chlorine and oxygen were carried out for the preparation HCFO-1233xf and HFO-1234yf for 100 hours,respectively.The research showed that coke was the main reason leading to catalyst deactivation during the vapor phase catalytic reactions.In a sense,this synthesis route provided a potential method for industrial production of HFO-1234yf due to its many advantages,which included cheaper raw materials,higher catalytic efficiency,smaller environmental pollution and simpler separation of products than the prior art.