In-Line Esterification of Pyrolysis Vapor with Ethanol Improves Bio-oil Quality

A simple reactive condensation technique was developed to decrease the concentration of reactive species ill the oily phase of two-phase pyrolysis oil its it means to increase the storage stability, heating value, and overall quality of the oil. Bio-oil vapor was esterified from the reaction of in situ organic acids with ethanol during condensation resulting ill the production of water and esters. The research compared the quality of slow pyrolysis-produced bio-oils collected by condensing pyrolysis vapor using atomized ethanol (EtOH) at various weight hourly space velocity (WHSV). The resultant bio-oil exhibited two phases at room temperature, which were separated to obtain an oily and,in aqueous phase. WHSV was varied from 8.3 to 33 (kg h(-1) biomass per kg h(-1) ethanol), which produced bio-oils with ethanol content ranging from 7.3 to 23.2 wt % of total oil. Increasing EtOH from 0 to 23% (w/w) decreased water content and viscosity ill the oily phase by 16% and 56%, respectively, while also increasing pH from 2.48 to 3.05. Results were consistent with the formation of esters. The concentration of a carboxylic acid, acetic acid, and all ester, ethyl acetate, were determined Using quantitative GC-MS analysis and indicated it maximum 40% (v/v) conversion of acetic acid with 19% (v/v) being converted to ethyl acetate. Other reactions predicted included acetalizations of formaldehyde and acetaldehyde with ethanol to form diethoxymethane and 1,1-diethoxyethane, respectively.