Continuous pyrolysis and catalytic upgrading of corncob hydrolysis residue in the combined system of auger reactor and downstream fixed-bed reactor

Continuous pyrolysis of corncob hydrolysis residue, coupled with ex situ catalytic upgrading of the pyrolysis vapor, was investigated in the combined system of an auger reactor and a downstream fixed-bed reactor. The effect of the zeolite catalyst, USY (ultrastable Y) and HZSM-5 (Si/Al = 25, 38) and catalytic temperature on the raw bio-oil upgrading were discussed. The results showed the strong acidity of porous zeolite was essential for catalytic deoxygenation during upgrading pyrolysis vapor. HZSM-5 (25), with the strong acidity and acidic sites, had favored the deoxygenation conversion of carbonyl/carboxyl-containing oxygenates in the pyrolysis vapor, which decreased its content to 2.3 area% via the GC-MS analysis of the upgraded bio-oil. Mono-phenols (phenol and alkylphenols) were enhanced to 53.2 area% over HZSM-5 (25), as compared with that of 17.3 area% during non-catalysis process. The addition of ex situ catalytic upgrading had improved the quality of organic bio-oil at the expense of its yield. Coke formation on the strong acidic sites by condensation of intermediates is detrimental to organic bio-oil yield. The increase of catalysis temperature at the fixed-bed reactor decreased oxygenate compounds to 7.1 area%, 2.3 area% and 1.9 area% at 450 °C, 550 °C and 650 °C, respectively, with 0.75 s of vapor residence time. The TG/DTG/DSC characterization of the used HZSM-5 (25) implied that the coke had deposited on the surface of HZSM-5 (25), which could be removed by combustion to recover its activity.