This paper investigated the interactions between volatiles and char during pyrolysis of biomass with an emphasis on those between the reactive compounds in volatiles and the oxygen-containing functional groups in char. On the basis of a comparative study on the products from biomass pyrolysis with and without heavy oil (HO) recycling, which represented a maximization and minimization of the volatile char interactions, respectively, levoglucosan (LG) was selected as the typical reactive compound in the volatiles. The interactions between LG and functionalized graphitized multiwalled carbon nanotubes with hydroxyl and carboxyl groups (HGMCN and CGMCN, respectively) as char models were surveyed at 300, 350, 400, and 450 degrees C. The results show that temperature plays an important role in the interactions between LG and GMCNs. HGMCN interacted with LG only at 400 degrees C, while the LG CGMCN interactions started at 400 degrees C and intensified at 450 degrees C with a significant increase in gas yield. The GC MS analyses indicated that the liquid products from the LG GMCNs interactions were predominant in furfural and 5-methyl-2-furancarboxaldehyde.