Catalytic fast pyrolysis of Geodae-Uksae 1 over zeolites

Three microporous zeolites with different structures, HZSM-5 (Si/Al2 = 23), Hβ (Si/Al2 = 25) and HY (Si/Al2 = 30), were assessed for the first time for the catalytic fast pyrolysis of Geodae-Uksae-1, a variety of Miscanthus sacchariflorus. In non-catalytic pyrolysis, the temperature for the maximum bio-oil yield was 500 °C, which allowed sufficient conversion of the solid to the vapor phase and suppressed the decomposition reactions in the vapor phase. Using the catalysts, the bio-oil yield decreased with significant changes in composition as a result of active deoxygenation and cracking reactions. This led to the release of CO2, CO and C1-C4 hydrocarbons to the gas phase. In the bio-oil composition, the proportions of phenolics, mono-aromatics and polycyclic aromatic hydrocarbons (PAHs) increased, whereas those for acids, oxygenates and furans decreased. In particular, the use of HZSM-5 led to the largest proportion of mono-aromatics with a minimized coke production, since it had higher acidity, higher shape selectivity, and smaller pore size than the other catalysts. With both Hβ and HY catalysts, the formation of PAHs in the bio-oil and coke on the catalyst surface was significantly high. The proportion of light phenolics, such as alkyl phenolics, also increased with the HY catalyst.