Reduction of the Variety of Phenolic Compounds in Bio-oil via the Catalytic Pyrolysis of Pine Sawdust

The objective of this study was to evaluate phenolic compounds produced from the catalytic pyrolysis of pine sawdust by commercial catalysts. Eight types of commercial catalysts consisting of SiO2, montmorillonite, α-Fe2O3, HZSM-5 (Si:Al = 25:1), ZnO, γ-Fe2O3, HZSM-5 (Si:Al = 50:1), and nano-HZSM-5 (Si:Al = 50:1) were screened in a fixed bed reactor at a reaction temperature of 500 °C and a vapor residence time of 3 s. All the tested commercial catalysts exhibited different catalytic performances for the adjustment of the composition of the bio-oil. HZSM-5 (Si:Al = 25:1) significantly increased hydrocarbon production in the bio-oil, which is helpful for improving its heating value. The different types of phenols were reduced significantly from 17 to 7 with nano-HZSM-5 (Si:Al = 50:1); however, the phenols content also decreased from 32.6% to 23.28% compared with non-catalytic pyrolysis. Meanwhile, the addition of nano-HZSM-5 (Si:Al = 50:1) to the raw material provided the highest amount of furans (up to 38.8%) among the tested commercial catalysts. The inexpensive ZnO and γ-Fe2O3 also were surprisingly effective for the reduction of the variety of phenolic compounds detected by GC/MS, reducing that number from 17 to 10