三氟甲烷/氯化氢气体的分离及三氟甲烷的转化技术研究/STUDY ON THE SEPARATION OF TRIFLUOROMETHANE /HYDROCHLO
In order to treat the greenhouse gas trifluoromethane (CHF3) via incineration process, CHF3 has to be separated from its hydrochloride(HCl) gas mixture. This thesis is focused on the separation technology for the gas mixture of trifluoromethans/hydrochloride by using organic solvent absorption process, and on the study of feasible approaches for the conversion of thrifluoromethane under mild conditions. The thesis is composed of three parts that follows.
Firstly, solubility of CHF3 and HCl in such organic solvents as alkane, chlorinated solvents, alcohol, ketone, ether and ester was measured experimentally, 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 and glycerol are possibly viable for the separation of CHF3 and HCl and especially the latter, since CHF3 is insoluble in glycerol while HCl is highly soluble and thermal 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 hydrochloric acid, aluminium chloride, zinc chloride, titanium chloride, titanyl sulfate, stannum chloride and calcium chloride of different concentration was measured experimentally, the dissolving rate of HCl in calcium chloride and stannum chloride aqueous solution was determined, and their solubility difference as well as desorption ratio as pressure reduced from 0.8MPa to 0.2MPa were compared, whereby the feasibility of separating the gas mixture via absorption was discussed. The results show that calcium chloride is possibly viable for the separation of CHF3 and HCl, since the presence of salt can not only suppress the solubility of CHF3 but also lower the vapor pressure of 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 of γ-Al2O3/ZnCl2 and granular active carbon/ZnO was investigated experimentally. Besides, the possibility of converting CHF3 to some high value-added chemicals under mild conditions was studied. The experimental results show that neither ZnCl2 nor ZnO can catalyze the hydrolysis of CHF3 in a high conversion rate under temperatures below 500℃. In addition, it is very hard to convert CF3H to some high value added chemicals using conventional reaction due to the high stability of CHF3. Therefore, more efficient approaches for converting CF3H to other chemicals need to be explored in the future.