Production and Characterization of Straight-Run Thermal Deoxygenation (TDO) Fuels
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Thermal DeOxygenation (TDO) refers to a simple , non-catalytic , process which produces highly deoxygenated crude oils from levulinic and formic acids formed by acid hydrolysis of biomass feedstocks. The TDO reaction is a single-step decomposition reaction which converts the neutralized acids to crude hydrocarbons , chars , CO2 , water and volatiles at 450°C and at ambient pressure. The TDO crude oils have long-term shelf-stability and very low water miscibility compared to fast pyrolysis oils. Successful TDO scale-up to 50L semi-batch operation has produced crude oils with broad boiling point distribution , between 75° and 585°C , and oxygen content of 1-8 wt.%. Choice of basic cation is important in TDO reactions as it controls reaction temperatures and product mass distributions. In this work , calcium and magnesium are compared to understand their influence on crude oil composition. Straight-run crude oils obtained using each cation underwent fractionation and material and fuel property characterizations to explore suitability in gasoline , diesel and residual fuel applications. The products showed high aromaticity , low H/C ratios at about 1.3/1 and higher heating values of 38-40 MJ/kg. Crude oil oxygen content , total acid number and final boiling points were all higher for the magnesium case. In the distillate region , fuel density and cetane index were equivalent. Diesel combustion properties were characterized by comparing a 100% straight-run TDO distillate cut to specification ultra-low sulfur diesel in a single-cylinder research engine. Combustion was maintained over the entire operating window under intake air heating with measured increases in hydrocarbon and CO emissions.