This review covers the characteristics of pyrolysis and catalytic pyrolysis bio-oils by focusing on the fundamental factors that determine bio-oil upgradability. The abundant works on the subject of bio-oil production from lignocellulosic biomass were studied to establish the essential attributes of the bio-oils for assessment of the oil stability and upgradability. Bio-oils from catalytic pyrolysis processes relating to catalysts of different compositions and structures are discussed. A general relationship between the higher heating value and the oxygen content in the catalytic pyrolysis oils exists, but this relationship does not apply to the thermal pyrolysis oil. Reporting bio-oil yield is meaningful only when the oxygen content of the oil is measured because the pyrolytic oil stability is mainly determined by the oxygen content. Isoenergy plot that associates bio-oil yield with oxygen content is presented and discussed.
Keywords: Bio-oils; biomass; catalytic pyrolysis; higher heating value (HHV); lignocellulosic biomass; oxygen content; zeolite.
© 2019 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.