Research On Fluorine And Chlorine Exchange Catalyst Based On Metal-organic Frameworks

The chlorofluoroalkane(CFCs)chemical gas fire extinguishing agent"Halon"has been widely used in various fields and places because of its excellent fire extinguishing effect.However,its use has been banned due to extremely serious damage to the ozone layer during the fire extinguishing process.Regarding the particularity of high-altitude and confined environment on civil aviation aircraft,there is no extinguishing agent that can perfectly replace"halon",so the use time of"halon"extinguishing agent in the civil aviation field has been temporarily extended.Although hydrofluoroalkane(HFCs)fire extinguishing agents solve the problem of destroying the ozone layer,they will cause a huge greenhouse effect and will soon be phased out as a transitional product.The latest generation of hydrofluoroolefin(HFOs)fire extinguishing agents has zero ozone depletion potential(ODP)and lower global warming potential(GWP)in comparison,and is recognized as an ideal alternative to"halons".The preparation is mainly based on gas phase fluorine and chlorine exchange method.However,in the face of the key core reaction of fluorine-chlorine exchange,the chromium-based catalyst based on chromium oxide prepared by the co-precipitation method currently used in industry can no longer meet the higher catalytic requirements,which greatly restricts its further development.It is necessary to carry out research on the preparation of high-performance fluorine and chlorine exchange catalysts.Metal-organic frameworks are porous materials with a periodic network structure formed by self-assembly of metal centers and organic ligands.The characteristics of this material perfectly compensate for the shortcomings of traditional chromium-based catalysts.In this paper,the metal-organic framework material MIL-101(Cr)with high specific surface area was selected,and the influence of solvothermal conditions on the crystal morphology was studied to prepare higher purity MIL-101(Cr).Using MIL-101(Cr)as the precursor,carbonized under different high temperature conditions to obtain chromium oxide nanoparticles uniformly supported porous carbon derivative composite material,after fluorination,the catalytic active component Cr O_xF_y supported porous carbon high-performance fluorine Chlorine exchange catalyst.And used SEM,TEM,XRD,XPS,TGA,Raman and other methods for characterization and analysis.Finally,the use of hexachlorobutadiene to catalyze the catalytic reaction to produce dichlorotetrafluorobutene verified its excellent catalytic performance and stability,and its catalytic performance and stability mechanism were discussed.