Upgrading of biomass-derived pyrolytic vapours over zeolite ZSM-5 catalyst: Effect of catalyst dilution on product yields

Biomass in the form of waste wood chips was pyrolysed in a fluidized bed reactor at 550 degrees C to maximize the formation of pyrolytic vapours. The pyrolysis vapours were then upgraded by passing them over a fixed bed of ZSM-5 zeolite catalyst. The catalyst bed was diluted with stainless steel ball bearings to increase the residence time of the pyrolysis vapours in the bed and to provide additional hot surface for thermal cracking of the vapours. The pyrolytic and catalytic liquid products were analysed in detail to determine the predominant chemical classes and the identity and concentrations of the major compounds present. The presence of steel in the catalyst bed appears beneficial in the conversion of the pyrolytic vapours to hydrocarbon products, with a threefold increase in the formation of monocyclic aromatic compounds under certain process conditions. Copyright (C) 1996 Elsevier Science Ltd.