The effect of zeolite ZSM-5 catalyst deactivation during the upgrading of biomass-derived pyrolysis vapours

摘要

A mixed biomass waste was flash pyrolysed in a fluidised bed reactor at 550℃ to maximise the formation of pyrolysis vapours. The pyrolysis products were then characterised using a number of analytical techniques. The pyrolysis vapours were passed on-line over a fixed bed of zeolite ZSM-5 catalyst which had an operational temperature of 500℃. The catalyst was exposed to the pyrolysis vapours for a total of 3 h, with samples of the catalysis products and the catalyst being taken periodically. The gaseous catalysis products were identified and quantified using gas chromatography. The catalysis oil samples were analysed to determine their elemental composition, molecular mass range using size exclusion chromatography and individual constituents using capillary column gas chromatography/mass spectrometry. Elemental analysis of the coked catalyst was also carried out. The results showed that the presence of the catalyst dramatically alters the original pyrolysis product slate. As the catalysis run time increased so the deactivation of the catalyst became apparent, with a loss in the selectivity of the catalysis products. The formation of monocyclic aromatic hydrocarbons was reduced and there was an increase in the formation of oxygenated products as the catalysis run time was extended.