Effect of temperature of ceramic hot vapor filter in a fluidized bed reactor on chemical composition and structure of bio-oil and reaction mechanism of pine sawdust fast pyrolysis

Abstract The chemical composition, structure of bio-oil and reaction mechanism of pine sawdust pyrolysis by fluidized-bed reactor at 500 °C with hot vapor filter (HVF) at temperatures of 350 °C, 400 °C, 450 °C and 500 °C were investigated. According to elemental and GPC analysis, the average formula of HVF bio-oils at HVF temperature 350 °C, 400 °C, 450 °C, 500 °C and non-HVF bio-oil were expressed as C 36.60 H 54.17 O 15.37 , C 17.11 H 25.50 O 9.07 , C 15.22 H 22.53 O 7.61 , C 15.80 H 22.43 O 8.37 and C 15.23 H 21.47 O 8.99 , respectively. Quantitative NMR result showed that the aromatic carbon fraction and the hydroxyl and alkyl carbons in carbohydrate fraction increased, but the C O bonds in phenolic-methoxy fraction and the methoxyl-aromatic fraction decreased with the increased HVF temperature. GC × GC-TOFMS analysis showed that the contents of phenols, aldehydes and alcohols in HVF bio-oils and non-HVF bio-oil had a similar increasing tendency. In contrast, ketones, furans and carbohydrates had a similar decreasing tendency. Tentative chemical transformation pathways showed that guaiacol-type compounds with side chains of two carbons or longer were decreased. The Ar OH bonds in catechol-type were more stable than the Ar OCH 3 bonds when HVF temperature was between 400 °C and 500 °C. Experimental results showed that hot vapor filter had a positive effect on the composition and structure of bio-oil, and more stable and higher quality bio-oil can be produced.