Effect of Torrefaction on Bio-oil Upgrading over HZSM-5. Part 2: Byproduct Formation and Catalyst Properties and Function

Abstract

A three-step bio-oil production process involving torrefaction pretreatment (225, 250, or 275 °C at 20 min hold time), pyrolysis (500 °C, two heating rates), and secondary catalytic processing over HZSM-5 (at 400, 450, or 500 °C) was studied to determine how treatments affected byproduct formation and catalyst properties and function. Torrefaction pretreatment significantly reduced average yields (%, w/w of feed) of reactor char (100% reduction), catalyst coke (21.4%), and catalyst tar (8.1%) relative to the best-case conditions using non-torrefied feedstock. The yields of chemical components, including levoglucosan, formic acid, acetic acid, and 5-hydroxymethylfurfural (5-HMF), were significantly reduced in intermediate fast-pyrolysis bio-oil (FPO) derived from torrefied feedstock, while for intermediate slow-pyrolysis bio-oil (SPO), yields of levoglucosan, acetic acid, and 5-HMF were reduced. However, in terms of concentration, only furfural showed a significant correlation with the torrefaction tempera...