Study On The Separation Of Trifluoromethane/Hydrochloride Gas Mixture And Conversion Of Trifluoromethane

In order to treat the greenhouse gas trifluoromethane (CHF₃) viaincineration process, CHF₃ has to be separated from its hydrochloride(HCl)gas mixture. This thesis is focused on the separation technology for the gasmixture of trifluoromethans/hydrochloride by using organic solvent absorptionprocess, and on the study of feasible approaches for the conversion ofthrifluoromethane under mild conditions. The thesis is composed of three partsthat follows.Firstly, solubility of CHF₃ and HCI in such organic solvents as alkane,chlorinated solvents, alcohol, ketone, ether and ester was measuredexperimentally, their solubility difference in different solvents was compared,and the feasibility of separating the gas mixture via absorption was discussed.The experimental results show that the alcohol solvents such as n-butanol andglycerol are possibly viable for the separation of CHF₃ and HCl and especiallythe latter, since CHF₃ is insoluble in glycerol while HCl is highly soluble andthermal desorptive, meanwhile the corrosivity of organic solution of hydrochloride is much lower than the corresponding aqueous solution.Secondly, solubility of HCl in such electrolyte solutions as hydrochloricacid, aluminium chloride, zinc chloride, titanium chloride, titanyl sulfate,stannum chloride and calcium chloride of different concentration wasmeasured experimentally, the dissolving rate of HCl in calcium chloride andstannum chloride aqueous solution was determined, and their solubilitydifference as well as desorption ratio as pressure reduced from 0.8MPa to0.2MPa were compared, whereby the feasibility of separating the gas mixturevia absorption was discussed. The results show that calcium chloride ispossibly viable for the separation of CHF₃ and HCl, since the presence of saltcan not only suppress the solubility of CHF₃ but also lower the vapor pressureof water, which is good for reducing the water content of HCl gas. Meanwhile,calcium chloride is cheap and commercially available.Lastly, hydrolysis performance of CHF3 on the catalyst ofγ-Al2O₃/ZnCl₂and granular active carbon/ZnO was investigated experimentally. Besides, thepossibility of converting CHF₃ to some high value-added chemicals undermild conditions was studied. The experimental results show that neither ZnCl₂nor ZnO can catalyze the hydrolysis of CHF₃ in a high conversion rate undertemperatures below 500℃. In addition, it is very hard to convert CF3H tosome high value added chemicals using conventional reaction due to the highstability of CHF₃. Therefore, more efficient approaches for converting CF3Hto other chemicals need to be explored in the future.