Selective fast pyrolysis of biomass impregnated with ZnCl2 to produce furfural: Analytical Py-GC/MS study

A new technique was proposed to produce furfural (FF) through low-temperature fast pyrolysis of biomass impregnated with ZnCl2. Analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were performed in this study to reveal the ZnCl2-catalyzed biomass pyrolysis and FF formation characteristics. The results revealed that the presence of ZnCl2 decreased the temperature for the complete decomposition of biomass, inhibited the devolatilization of lignin and pyrolytic ring scission of holocellulose. Meanwhile, it promoted the depolymerization and dehydration of holocellulose to form the FF and three anhydrosugars (levoglucosenone (LGO), 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one (LAC) and 1,4:3,6-dianhydro-α-d-glucopyranose (DGP)) as the major primary pyrolytic products. With the increase of the ZnCl2 content, the three anhydrosugars were firstly increased and then decreased, while the FF was increased steadily. Moreover, these anhydrosugars could be converted to FF through the secondary catalysis by ZnCl2, leaving the FF as the predominant product. In addition, the acetic acid (AA), which was not inhibited by the ZnCl2, was formed as the only important liquid by-product.