Synthesis of Fe-Al catalysts to boost CNTs formation from polymer wastes via the improved two-stage system

Carbon nanotubes (CNTs) has been considering as a high-value product from polymer wastes via the coupled thermal-catalytic technology, and how to improve the yield and quality of CNTs is the key to the further industrialization. Herein, a series of Fe-Al catalysts with different Fe-loading and calcination temperature were prepared and expected to boost CNTs formation from low-density polyethylene (LDPE) in the improved twostage reaction system. The fresh and spent Fe-Al catalysts were characterized in detail by SEM-EDX, XRD, N2 physisorption, NH3-TPD, H2-TPR, TG-DSC, Raman, and TEM to explore the effects of Fe-loading (5-20%) and calcination temperature (450-650 degrees C) on the physicochemical properties of Fe-Al catalysts as well as the quantity and quality of CNTs. An increase of Fe-loading generated more active sites for CNTs growth while intensified the competition for the carbon source, promoting the yield while reducing the length of CNTs. A decrease of calcination temperature reduced the interaction between Fe sites and Al2O3 support, promoting both the yield and the length of CNTs. This work provided a promising strategy for optimizing Fe-Al catalysts to boost CNTs production from polymer wastes.