Upgrading of biomass fast pyrolysis oil over a moving bed of coal char

Abstract

Fast pyrolysis of sawdust (SD) and upgrading of the derived bio-oil* (water-free basis) over Shenmu bituminous coal char (SMC) were conducted in an integrated free fall pyrolyzer and moving bed upgrading reactor. The water soluble and heavy bio-oil* (THF soluble) yields decrease and the content of light bio-oil* (CH2Cl2 soluble) increases significantly compared that without SMC despite the decrease of light bio-oil* yield. Chemical analyses of the light bio-oil* were performed using GC–MS and 1H NMR techniques. The results show that during volatiles-char interaction, the SMC plays important roles in deoxygenation and denitrogenation. The role of SMC in the upgrading process was explored by BET, FT-IR and XRD characterization. The porous structure provides reaction active sites for the bio-oil upgrading. After volatiles-char interaction, the specific surface area of SMC decreases significantly and the carbon crystallite size increases. With increasing the char updating rate from 1 g/min to 4 g/min, the relatively fresh SMC surface leads to the increased active sites, the conversion of heavy bio-oil* is slightly promoted and the removal effects of heteroatoms (O, N) compounds in the light bio-oil* are enhanced. The changes in SMC specific surface area and microcrystalline size are weakened accordingly.