Synergistic catalysis of carbon-partitioned LaF 3 –BaF 2 composites for the coupling of CH 4 with CHF 3 to VDF

• Published in: Catalysis science & technology 2019-03, Vol.9 (6), p.1338-1348
• Main Authors: Wang, Jinchao, Han, Wenfeng, Wang, Shucheng, Tang, Haodong, Liu, Wucan, Li, Ying, Lu, Chunshan, Zhang, Jianjun, Kennedy, Eric M., Li, Xiaonian
• Format: Article
• Language: English
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/C8CY02376J

Catalytic coupling of CH 4 with potent greenhouse gas CHF 3 to vinylidene fluoride (VDF) was investigated over composite catalysts. Carbon-partitioned LaF 3 –BaF 2 catalysts were prepared by PVDF (polyvinylidene fluoride)-mediated calcination. During catalyst preparation, PVDF functions as the fluorine source and carbon source. Compared with the catalysts prepared by the conventional HF co-precipitation method, the transformation of LaF 3 and BaF 2 to Ba 1−x La x F 2+x solid solution is inhibited as Ba and La are separated by carbon layers derived from the decomposition of PVDF. The Ba 1−x La x F 2+x phase is not favorable for the coupling of CH 4 with CHF 3 to VDF. In addition, PVDF-mediated calcination facilitates the formation of LaOF which is one of the key species for coupling of CH 4 with CHF 3 to VDF. O − species, which is the most active oxygen species for the activation of CH 4 , increases significantly following PVDF-mediated calcination due to the formation of LaOF. Consequently, the formation rate of VDF over the catalyst derived from PVDF-mediated calcination is 3.6 times higher than the HF co-precipitation catalyst at a reaction temperature of 700 °C. The formation rate of the HF co-precipitated catalyst declines to nearly half of the initial rate in a time-on-stream of 15 h. By contrast, only slight deactivation is observed over the catalyst prepared by PVDF-mediated calcination. The present work provides a promising strategy for the preparation of composite catalysts.