Pyrolysis of the bio-oil blended with Ni/Al2O3: Evolution of heavy components in the bio-oil.

Heavy components in bio-oils pose significant challenges for their utilisation through thermal conversion, as they are highly reactive and prone to polymerisation upon heating. This study investigates the formation and reduction of heavy components during ex-situ and in-situ catalytic pyrolysis of bio-oil over Ni/Al 2 O 3. The heavy components present in the volatile products from bio-oil pyrolysis can be cracked for ex-situ catalysis. In contrast, in-situ catalysis results in catalyst deactivation due to the polymerisation of bio-oil components. However, at temperatures >700 °C, as thermal cracking reactions dominate during bio-oil pyrolysis, in-situ catalysis can further suppress the polymerisation among bio-oil components. As a result, the tar and coke yields decrease by 9.8 wt% and 2.7 wt% at most. • Evolution of heavy components during in−/ex- situ catalysis were investigated. • Tar and coke were decreased by in-situ catalytic pyrolysis of bio-oil. • O-containing groups in heavy components tend to be cracked over Ni/Al 2 O 3. • Ni leads to more C−C- cross-linkage structures in heavy components. [ABSTRACT FROM AUTHOR]