Catalysts For Pyrolysis Of Tetrafluoroethane To Trifluoroethylene

Trifluoroethylene (TrFE) is an important fluorinated alkene, which has been widely used to fluorine resin production. In this thesis, various catalysts were synthesized and tested for pyrolysis of1,1,1,2-tetrafluoroethane (HFC-134a) to trifluoroethylene, which was found to be more environmental friendly and efficient compared to the conventional process. Also, the catalysts were characterized by various techniques.The detailed contents of this work are as follows:1. A series of Y-Mg-Al-F catalysts were prepared by a deposition-precipitation method and tested for pyrolysis of HFC-134a to trifluoroethylene, and their catalytic performances were compared with an AIF3catalyst. The results showed that the Y-Mg-Al-F catalysts calcined at1100℃exhibited higher activity and stability than those calcined at low temperatures, with a HFC-134a conversion of higher than25%at400℃. The surface acidity and carbon deposits on the catalyst surface had important influences on the activity and stability of the catalysts. The Mg and Y-doped catalyst was more stable and selective to TrFE compared with the AIF3catalyst.2. A series of MOx/Al2O3(M=Ni, Mg, Co and Ce) catalysts were prepared by a deposition-precipitation method, and the effects of different additives on the catalytic pyrolysis were investigated. The transformation of Al species in the MOx/Al2O3catalysts after pre-fluorination was investigated using XRD technique. The catalysts were employed in pyrolysis of HFC-134a to trifluoroethylene, and the results showed that the addition of Ni, Co and Ce to AIF3could improve the catalytic performance, while the addition of Mg suppressed the activity. The best performance was obtained on a NiFx/AlF3catalyst, with a HFC-134a conversion of higher than21.4%and a trifluoroethylene selectivity of99.1%at the reaction temperature of400℃. It was found that the surface acidity of the catalysts played a dominant role in the catalytic performance of these catalysts.3. The effects of calcination temperature and N-doping on pyrolysis of HFC-134a to TrFE over Ni-Al-F catalysts. It was found that the calcination process could not only change the catalyst structures but also modify the surface acidity of the catalysts. The catalysts calcined at300℃exhibited the least carbon deposits while that calcined at1100℃exhibited the highest conversion of HFC-134a. And with increasing amount of Ni-doping, the conversion of HFC-134a conversion increased. In addition, pyrolysis of HFC-134a to TrFE over Ni, Ce and Ce-doped Al2O3was also investigated.