Exploring the reaction chemistry of biomass upgrading over HZSM-5 catalyst through model compounds

•Catalytic pyrolysis of biomass-derived model compounds was studied with SPI-MS.•Real-time monitoring the dynamics of volatiles as catalyst deactivates was achieved.•Roles of some intermediates in catalytic conversion of biomass were discussed.•Reaction chemistry of biomass upgrading over HZSM-5 was proposed. The catalytic fast pyrolysis of 17 biomass-derived model compounds over HZSM-5 was conducted in double microfixed-bed reactors (DFBRs) at 500 °C. Our single photoionization mass spectrometer (SPI-MS) allows the real-time monitoring the dynamics of volatiles formation as a function of catalyst deactivation, which provides interesting information on reaction chemistry of biomass catalytic upgrading. The roles of some important intermediates (e.g., benzofurans, benzaldehydes, benzenediols etc.) and their conversion in biomass upgrading are comprehensively discussed. The network of reaction pathways for the conversion of chosen model compounds is also proposed based on the release trend of different products. Strikingly, the favorite formation pathways of large aromatic hydrocarbons in catalytic upgrading are considered to be different between carbohydrate- and lignin-derived model compounds. The level of HZSM-5 deactivation is closely associated with their ability to remove the number of oxygen atoms in feeding model compounds. Besides, the impact fact on the catalyst deactivation in the upgrading of lignin model compounds is discussed. Overall, the performance of commercial HZSM-5 in biomass upgrading is unsatisfactory and has limited relevance to the type of model compounds except for oxygen-free intermediates.