Effect of CO₂ on activity and coke formation over gallium-based catalysts for propane dehydrogenation

This work investigated the effects of support and CO₂ co-feeding on the activity and coke formation over gallium-based catalysts for propane dehydrogenation (PDH). The prepared catalysts were characterized by XRD, NH₃-TPD, CO₂-TPD, O₂-TPO, pyridine-IR, Raman and tested in CO₂ assisted propane dehydrogenation. The results revealed Ga/HZSM-5 as a highly active and carbon resistant catalyst, more so in the presence of CO₂. The structure of coke species was investigated and found to be different over these gallium based catalysts as characterized by O₂-TPO and Raman techniques. Coke formation behavior is shown to be directly related to the acid density and strength as well as the topological structure of the support. Moreover, the introduction of CO₂ leads to an increase in propane conversion and a decrease in coke selectivity over Ga/HZSM-5 catalysts, although coke species become more graphitic in nature. Lastly, PDH reaction with different co-feeding agents (H₂, CO₂ and O₂) were performed and the results indicate CO₂ co-feeding yields the highest propane conversion and lower coke deposition, exhibiting a good application prospect.