Vapor-phase Fluorination Of1,1,2,3-tetrachloropropene To Synthesis Tetrafluoropropene

For its superior environment parameters such as lower GWP and ODP, and less life climate performance (LCCP),2,3,3,3-tetrafluoropropene (HFC-1234yf) is considered as a potential substitution for HFC-134a and could be a promising candidate for the fourth generation of refrigerants. In this thesis, vapor-phase fluorination of1,1,2,3-tetrachloropropene(HCC-1230xf) was conducted to synthesize2-chloro-3,3,3-trifluoropropene(HCFC-1233xf) and tetrafluoropropene(HFC-1234). This process is divided into two consecutive steps, the first step is vapor phase fluorination of1,1,2,3-tetrachloropropene to synthesize2-chloro-3,3,3-trifluoropropene, the second step is fluorination2-chloro-3,3,3-trifluoropropene to synthesize HFC-1234. In this work, various Cr-based catalysts were synthesized and tested for vapor-phase fluorination of HCC-1230xf. The catalysts were characterized by various techniques such as XRD, XRF, H2-TPR, XPS and BET to investigate the phase structures and surface acid properties of the catalysts.The detailed contents of this work are as follows:1. A series of M-Cr2O3catalysts with different promoters M (M=La, Y, Co, Ni) were prepared by a co-precipitation method and tested for vapor-phase fluorination of HCC-1230xf to synthesize HCFC-1233xf. Experimental results showed that the Y-doped catalyst (YF3-Cr2O3) was stable during the reaction. The highest activity was obtained on a YF3-Cr2O3catalyst with a HCC-1230xf conversion of99%and a HCFC-1233xf selectivity of98.1%at280℃. It was also found that the presence of surface CrOxFy species was beneficial to the stability, and the carbon deposit may be the main reason for the deactivation of the catalyst during the reaction.2. A series of Y-doped Cr2O3catalysts were prepared and tested for the vapor phase fluorination of HCC-1230xf to HCFC-1233xf. It was found that HCC-1230xf conversion hardly changed with increasing Y contents, but the selectivity of HCFC-1233xf first increased and then decreased. The highest selectivity (98.1%) was obtained on a1YF3-Cr2O3(F) catalyst, and the catalyst was stable during the long-term testing. The bulk phase CrF3and CrOxFy content of catalysts could effect the selectivity of HCFC-1233xf, and the surface CrOxFy species was beneficial to the stability.3. Cr2O3, Pt/C and Pd/C catalysts were prepared and tested for the vapor phase fluorination of HCFC-1233xf to HFC-1234ze. It was found that HFC-1234yf was the main product over the Cr2O3catalyst, while HFC-1234ze was the main product over the Pt/C and Pd/C catalysts. Based on these results, the reaction mechanisms on these catalysts were discussed.