The effects of contact time and coking on the catalytic fast pyrolysis of cellulose

Abstract

The effects of catalyst contact time (WHSV⁻¹) and coking on catalytic fast pyrolysis of cellulose with ZSM-5 were studied in a bubbling fluidized bed reactor. Because coke interferes with catalyst activity, the effect of catalyst contact time was studied at coke loadings known not to deactivate the catalyst. CO and CH₄ are favored at low catalyst contact times (<1000 s), oxygenated and unidentified species at medium catalyst contact times (1000 s–10 000 s), and aromatics and CO₂ at high catalyst contact times (>10 000 s). At increased time on stream, the catalyst lost activity due to coking. The majority aromatic-producing activity was lost after site turnovers of 95 (cellulose monomers to Brønsted sites) corresponding to a weight turnover of 2.0 (feed weight to catalyst weight). Accumulated coke deactivates the catalyst by both filling the micropores and blocking the acid sites.