Catalytic upgrading of bio-oils derived from Giant Miscanthus with hollow HZSM-5 zeolites

In this study, a series of hollow-structured DSx/HZSM-5 zeolites were synthesized through a method of alkaline treatment with sodium hydroxide (NaOH) solution. The size of cavities and amount of acid sites in hollow zeolite can be exactly controlled by adjusting the NaOH concentration. The hollow HZSM-5 zeolites were employed for catalytic deoxygenation of bio-oils from fast pyrolysis of Giant Miscanthus via a dual-furnace-heated fix-bed reactor. Experimental results illustrated that the hollow structure enhanced the formation of deoxygenated aromatic compounds. The best hollow HZSM-5 zeolite named DS2/HZSM-5 exhibited the highest catalytic efficiency with a selectivity toward deoxygenated aromatic compounds of 75.9 ± 0.8 %. Moreover, the formation mechanism of hollow structure and possible pathways for deoxygenated compounds formation were proposed. In addition, the DS2/HZSM-5 catalyst demonstrated higher stability than the parent one. The results confirm that the hollow-structured HZSM-5 zeolite is a promising catalyst for efficient and stable upgrading of bio-oils.