Catalytic performance of alumina catalysts with different surface properties for the dehydrofluorination of HFC-134a (1,1,1,2-Tetrafluoroethane)

Abstract

The activated alumina with different specific surface areas and different acidity was used to catalyze the dehydrofluorination reaction of CF3CH2F (HFC-134a). The catalytic performance of the alumina catalysts was rationalized by analyzing the relationship between specific surface area and acidity before and after fluorination. A series of physiochemical techniques, including Scanning Electron Microscope (SEM), X-ray diffraction (XRD), and N2 physical adsorption (BET), were used to investigate the changes in catalyst structure and surface morphology before and after being tested for the dehydrofluorination reaction. The Al2O3 catalyst prepared from the precipitation method (Al2O3-P) demonstrated the best stability among all the Al2O3 catalysts. Results from XRD techniques showed that Al2O3 catalysts were fully or partially fluorinated into AlF3 after the dehydrofluorination reaction. Al2O3-B catalyst and Al2O3-S catalyst containing mainly α-AlF3 deactivate easier than the Al2O3-P catalyst, which has primarily β-AlF3. In addition, it can be concluded the high surface area Al2O3-P catalyst still has the highest specific surface area and pore size when fluorinated to AlF3, while forming the β-AlF3 crystalline phase. Therefore, it has the optimum catalytic performance for dehydrofluorination of HFC-134a. This provides a new idea for designing alumina catalysts with reasonable structure.