Upgrading of Bio-oil from Torrefied Wheat Straw over Fe-Ni Modified HZSM-5@MCM-41: Influence of Pyrolysis Temperature and Catalyst-Feedstock Ratio

This study employed torrefied wheat straw (260°C) as feedstock to synthesise a bifunctional metal-modified composite zeolite catalyst through alkali treatment (NaOH), dual metal loading (Fe and Ni), and hierarchical MCM-41 construction. Catalytically assisted pyrolysis behaviour was investigated using a tube furnace and Py-GC/MS system, evaluating the effects of pyrolysis temperature and catalyst/feedstock mixing ratio on product distribution and bio-oil composition. Results indicate that at a catalyst/feedstock ratio of 3:2, bio-oil yield peaked at 28.41% at 500°C, concurrently achieving a maximum monocyclic aromatic content of 66.36%. Elevating pyrolysis temperature promoted aromatic formation while significantly suppressing oxygenated compounds; notably, phenolic components decreased by 13.94% at 500°C, indicating the 1Ni1FeHR@M catalyst's potent deoxygenation capability. Further optimisation of the catalyst/feedstock blending ratio revealed that a 3:2 ratio yielded the highest combined bio-oil and monocyclic aromatic hydrocarbon production (18.62%), confirming this catalytic strategy effectively shifts the product distribution towards higher-value hydrocarbon fuels.