Investigation On Synthesis Of 1H,1H,2H-Heptafluorocyclopentane

This thesis belongs to the field of environmental chemical engineering technology,which aims to develop the most promising synthetic route of environmentally friendly high-end cleaning agent 1H,1H,2H-heptafluoro-cyclopentane?F7A or c-HFC-447?with independent intellectual property rights.It will provide a technical support for the implementation of the"Montreal Protocol"and the"Kigali agreement",and for the upgrading of the cleaning agent in China.On the basis of their environmental parameters and product characteristics as weel as course of development,fluorine containing cleaning agents are divided into four generation as following:The first generation is the chlorofluorocarbons?CFCs?or hydrofluorocarbon?HCCs?cleaning agent including 1,2,2-trichloro-trifluoroethane?CFC-113?;The second generation is hydrochlorofluorocarbons?HCFCs?cleaning agent including 1,1-dichloro-1-fluoroethane?HCFC-141b?with a nonzero ODP value;The third generation is hydrofluorocarbons?HFCs?including 1,1,1,3,3-pentafluorobutane?HFC-365mfc?with a zero ODP value and a high GWP value;The fourth generation is cyclic hydrofluorocarbons?c-HFCs?or cyclic hydrofluoroolefins?c-HFOs?with a zero ODP value and a low GWP value.F7A belongs to the fourth generation of cleaning agent with an ODP value of 0and a GWP₁₀₀ value of 195,which is a new generation of environmentally friendly and high-end cleaning agent.In order to solve the existing technical problems in the open literatures as following:unclear structure and performance of intermediate,low catalytic activity of catalyst,and short lifetime of catalyst,in this thesis,three most promising synthetic routes of F7A from the starting material hexachlorocyclopentadiane?HCCPD?are investigated.In the above process,high-valence chromium-based catalyst and hydrodechlorination catalyst with high activity and long lifetime are developed,and the structures of the main intermediates are determined as well as the mechanisms in fluorine-chlorine exchange,chlorine-fluorine exchange and isomerization of them are investigated.This provides a technical support for the industrialization of F7A.?1?Three synthetic routes of F7A were studied,and their process parameters were optimized.These routes contained fluorination process and hydrogenation process,as described next:?1-1?In the fluorination process in the first synthetic route,F7-1was synthesized by three steps of the liquid-phase fluorine-chlorine exchange from starting material HCCPD.The optimal reaction conditions in the liquid-phase fluorine-chlorine exchange were shown as follows:In the reaction of HCCPD?1,3,3-trichloropentafluorocyclopentene?F5-133?,DMF solvent,reation temperature 150?,n?KF?/n?HCCPD?=6,reaction time=24h;In the reaction of F5-133?1,2-dichlorohexafluorocyclopentene?F6-12?,DMF solvent,reation temperature 130?,n?KF?/n?F5-133?=2,reaction time=6h;In the reaction of F5-133?F6-12,DMF solvent,reation temperature130?,n?KF?/n?F6-12?=2,reaction time=6h.?1-2?In the fluorination process in the second synthetic route,F7-1was synthesized by two steps of the gas-phase fluorine-chlorine exchange from starting material HCCPD.The optimal reaction conditions in the gas-phase fluorine-chlorine exchange were shown as follows:In the reaction of HCCPD?F6-12,high-valence chromium-based composite catalyst?Co/Cr?,T=420?,n?AHF?/n?HCCPD?/n?Cl₂?=10/1/1,contact time=10 s;In the reaction of F6-12?F7-1,high-valence chromium-based composite catalyst?Co/Cr?,T=390?,n?AHF?/n?F6-12?=20,contact time=12 s,mean particle diameter=1.7-4.0mm.?1-3?In the fluorination process in the third synthetic route,F7-1was synthesized by two steps of the gas-phase fluorine-chlorine exchange from starting material F5-133.The optimal reaction conditions in the gas-phase fluorine-chlorine exchange were shown as follows:In the reaction of F5-133?F6-13,high-valence chromium-based composite catalyst?Co/Cr?,T=220?,n?AHF?/n?F5-133?=10/1,contact time=15 s,mean particle diameter=1.7-4.0mm;In the reaction of F6-13?F7-1,high-valence chromium-based composite catalyst?Co/Cr?,T=290?,n?AHF?/n?F6-13?=20,contact time=15 s,mean particle diameter=1.7-4.0mm.In the same hydrogenation process in the above three routes,the optimal reaction conditions in the gas-phase hydrodechlorination of F7-1 were shown as follows:In the reaction of F7-1?F7A,hydrodechlorination catalyst?Pd+Bi/AlF₃?,T=160?,n?H₂?/n?F7-1?=10,contact time=22 s.In the first synthetic route,liquid-phase fluorination process can be controlled under mild reaction condition,but can produce a large number of waste liquid pollution environment due to the use of a large amount of solvent.And in the second synthetic route,F7A is synthesized with lower yield at much higher temperature,which leads to high energy consumption.Therefore,the above routes are not ideal methods for the industrial production of F7A.While in the third synthetic route,F7A is synthesized with higher yield at much lower temperature.It is a new approach with independent intellectual property rights.Thus,the third synthetic route is an ideal method for the continuous production of F7A.?2?Two kinds of process catalysts were designed and investigated,like the following:?2-1?High-valence chromium-based composite catalystThe chromium-based catalyst modified by by titanium,vanadium,scandium,iron,cobalt,nickel,copper or zinc was prepared by coprecipitation,and then oxidized by chlorine after activation with AHF,the high-valence chromium-based composite catalyst was obtained.The opmized catalyst is Co/Cr,which showed a high activity and a long lifetime in the fluorine-chlorine exchange of F6-12,HCCPD,F5-133 or F6-13 for 500-hour life test.?2-2?Hydrodechlorinating catalystThe palladium catalyst modified by bismuth,platinum,copper or zinc was prepared on the different porous metal fluorides by impregnation method,and then activated with H₂,the hydrodechlorination catalyst was obtained.The opmized catalyst was Pd+Bi/AlF₃,which showed a high activity and a long lifetime in the hydrodechlorination of F7-1 in 500-hour life test.?3?The strctures of the main intermediates in the liquid-phase or gas-phase fluorine-chlorine exchange of HCCPD were comprehensively confirmed for the first time.And the mechanisms of fluorine-chlorine exchange,chlorine-fluorine exchange and isomerization of the main intermediates were investigated as well as the isomerization of hydrofluorineted cyclopentenes,as follows:?3-1?Inliquidphase,thefluorine-chlorineexchangeof chlorofluoirnted cyclopentene with KF occurred mainly on C?sp²?.While in gas phase,the fluorine-chlorine exchange with AHF occurred mianly on C?sp³?in the presence of fluorination catalyst.?3-2?In DMF,the chlorine-fluorine exchange of chlorofluorinated cyclopentene with AlCl₃ occurred mainly on C?sp²?.While in 1,1,1,3,3-pentachloropropane?HCC-240fa?,thechlorine-fluorineexchangeof chlorofluorinated cyclopentene with AlCl₄^–occurred mainly on C?sp³?.?3-3?In DMF,the migration of fluorine atom in chlorofluorinated cyclopentene from position 3 on C?sp³?to position 4 on C?sp³?promoted by NH₄F was a chemical equilibrium other than the migration of fluorine atom from position 2 on C?sp²?to position 3 on C?sp³?.?3-4?In DMF,the migration of fluorine atom or hydrogen atom in hydrofluorinated cylopentene promoted by alkali fluoride contained two processes as follows:an allylic syn-addition/elimination of fluorine anion that did not change the mutual positions of hydrogen atoms but was responsible for transfers of fluorine atoms,and a fluorine anion-assisted deprotonation/protonation which did not change the mutual positions of fluorine atoms but was responsible for transfers of hydrogen atoms.