Upgrading crude bio-oil by in situ and ex situ catalytic pyrolysis through ZSM-5, Ni2Fe3, and Ni2Fe3/ZSM-5: Yield, component, and quantum mechanism

Abstract

Crude bio-oil was upgraded using in situ and ex situ catalysts (Ni2Fe3, ZSM-5, and Ni2Fe3/ZSM-5) in order to reduce the bio-oil oxygen content. The Ni2Fe3 catalyst powder was specifically designed for this research using materials' simulations, and it showed good activity in improving the bio-oil quality by increasing the heating value. Furthermore, a fixed bed reactor was used for comparing in situ catalytic pyrolysis (ISCP) with ex situ catalytic pyrolysis (ESCP). The results indicated that the Ni2Fe3 catalyst showed greater activity for the ISCP experiments resulting in increased bio-oil yield and improved the bio-oil quality. The bio-oil consisted of higher heating value compounds including a small number of hydrocarbon compounds. However, the results showed that the bio-oil yield with the Ni2Fe3/ZSM-5 catalyst was low for both cases of ISCP and ESCP while the sugar content decreased during the pyrolysis process. Different reaction pathways and mechanisms are proposed for ISCP and ESCP. ESCP reactions transformed 1-hydroxy-2-butanone completely to 2-propanone, 1-hydroxy-, but ISCP converted only 55% of 1-hydroxy-2-butanone to 2-propanone, 1-hydroxy- to the final product. ISCP and ESCP methods showed different reaction pathways for the 1,2-cyclopentanedione compound, and the final product was 2-cyclopenten-1-one and 1,2-cyclopentanedione, 3-methyl-, respectively. These results indicated that the catalysts showed different reactions for ISCP vs ESCP, while the Ni2Fe3 catalyst was effective for ISCP catalytic pyrolysis. Ni2Fe3 showed better activity when compared to ZSM-5 and when supported by ZSM-5 as an ESCP catalyst. These results indicated that the Ni2Fe3 metal catalyst has potential to replace the current catalysts for industrial use to upgrade bio-oil.