Role of dolomite as an in-situ CO2 sorbent and deoxygenation catalyst in fast pyrolysis of beechwood in a bench scale fluidized bed reactor

Abstract

The dual effect of dolomite as a CO2 sorbent and deoxygenation catalyst in fast pyrolysis of beechwood was investigated. Investigation was performed on a bench scale fluidized bed reactor at an pyrolysis temperature of 500 °C and at different WHSV. CO2 breakthrough curves and bio-oil samples were produced simultaneously. The results show that dolomite is both a feasible catalyst and a CO2 sorbent as it produced a moderately deoxygenated bio-oil and a CO2 free and H2 rich gas. Acids were eliminated, whereas the concentration of methylated phenols and methylated cyclopentanones were enhanced. These results were achieved when rapid carbonation stage was prevailing throughout the experimental run. An organic rich bio-oil with 9.46 wt% yield and a HHV of 28.0 MJ/kg (as received) was obtained. The pH of the catalytic bio-oil increased from 3.2 to 6.0 and the oxygen content reduced to 21.5 wt% from 47.3 wt%. Moreover, the moderately deoxygenated bio-oil is of interest as it can undergo downstream reforming into wide range of liquid fuels with reduced H2 consumption. Calculations show that the H2 generated as a result of CO2 sorption can suffice the requirement for hydrodeoxygenation. In addition the catalysts were also characterized by BET, XRD and SEM analysis.