Investigations in influence of different pretreatments on A. donax pyrolysis: Trends in product yield, distribution and chemical composition

This study explores the influence of chemical pretreatment on the compositional and structural properties of Arundo donax, and the consequent effects on the pyrolysis products with emphasis on chemical composition of bio-oil. A. donax samples were chemically pretreated with different concentrations of 5 media (viz. H2SO4, H3PO4, NaOH, SDS and Triton X-100) and pyrolyzed in a semi-batch pyrolysis reactor. The chemical composition of obtained bio-oils was quantitatively determined by GC–MS analysis. The primary effects of pretreatments were in terms of 10.1–49.2 % enhancement in bio-oil yield in the order: untreated biomass < H2SO4 < Triton X-100 < SDS < H3PO4 < NaOH. Acid treatment, in general, led to an increase in furan production, with H3PO4 treatment yielding the highest furan yield of 21.2 % v/v. GC–MS analysis revealed substantial reduction in oxygenates with alkali treatment. The drop in lignin fraction with all pretreatments led to generation of lower phenol and methoxyphenol bio-oil derivatives except with SDS treatment, which reported high methoxyphenol derivatives content. Although the biochar yield dropped by 11.9–32.9 %, significant improvement in its quality was indicated by lower H/C and O/C ratios and higher calorific value of 27.5–30.5 MJ/kg, which is at par with coal. Non-condensable gas yields dropped post pretreatment of biomass, signifying a favorable shift to production of bio-oil.