The mechanism for catalytic fast pyrolysis of levoglucosan, furfural and furan over HZSM-5: An experimental and theoretical investigation

In this work, we have investigated the complicated reaction network of biomass catalytic fast pyrolysis, particularly the decomposition of the key cellulose pyrolysis intermediate, levoglucosan. Fast pyrolysis of levoglucosan using a Py-GC-MS-FID system in the presence of HZSM-5 suggested that furan and furfural are key intermediates to aromatic hydrocarbons. This was followed by theoretical modelling adopting density functional theory (DFT) to unravel the details of the catalytic reaction mechanism from levoglucosan to furan. Our investigations revealed for the first time a direct route from levoglucosan to furan without furfural as an intermediate, with the highest energy barrier along the most favourable pathway to be 2.15 eV. Combined with previously reported mechanisms in the literature, we provide here a detailed reaction network for the conversion of cellulose-derived intermediates to aromatic hydrocarbons.