Characterization of Aqueous Phase Bio-Oil Derived from Switchgrass Pyrolysis

Bio-oil is carbon based liquid product from biomass pyrolysis. Bio-oil is considered to be a promising substitute of crude oil in the applications as source of chemicals and fuels. However, bio-oil has high water content, high viscosity, low heating value, low pH value, and high oxygen content, leading to poor and inconsistent physicochemical properties. Bio-oil consists of hundreds of chemicals with wide range of molecular weight, some of which are water-soluble. Addition of water to bio-oil results in phase separation. The aqueous phase of bio-oil accounts for about 60% of crude bio-oil and has higher oxygen content. Conventional analytic method of GC-FID or HPLC only can quantify a small portion of the aqueous phase bio-oil as it contains volatile and non-volatiles compounds. The lack of adequate norms and standards for bio-oil and the bio-oil aqueous phase analysis have inhibited their industrialized production and application. In this study, the physical properties of bio-oil and aqueous phase from swichgrass pyrolysis were investigated and a combination technique of organic solvent extraction, GC/MS, GC-FID and HPLC-PDA was used to identify and quantify chemicals in aqueous phase bio-oil in order to comprehensively understand the chemical distribution in aqueous phase bio-oil. Three organic solvents, hexane, ethyl acetate, and chloroform were investigated as solvent to extract chemicals from aqueous phase and extracted chemicals were identified by GC/MS. The main chemicals in aqueous phase were classified into 7 categories including acids, aldehydes, ketones, furans, phenols, ethers, and alcohols.The aqueous phase bio-oil was analyzed by both GC-FID and HPLC-PDA at the wave length range of 190nm to 350nm. At least 2 predominant chemicals were quantified in GC-FID and HPLC-PDA using external standard chemicals.