(67a) Heat Release Analysis of Neat and Upgraded Biorenewable Thermal Deoxygenation Oils in a Diesel Engine

Thermal DeOxygenation is a non-catalytic thermochemical process which converts biomass-derived levulinic and formic acids to crude hydrocarbon oils at 450°C and atmospheric pressure. The resulting oils contain a broad boiling point distribution of hydrocarbons (75-550°C) with low oxygen content (<5 wt%) and low total acid number (TAN) compared to pyrolysis oils. Crude oil distillates (150-325°C) have been analyzed as an ultra-low sulfur diesel (ULSD) fuel blend stock at 50 vol% in a naturally-aspirated diesel engine. High aromaticity and low cetane rating of the blend delayed combustion phasing and resulted in high specific engine emissions of CO and THC compared to USLD. Hydrogenation and distillation of the crude oils over Ni/SiO₂-Al₂O₃ catalyst at 350°C improves cetane and hydrogen content of the resulting diesel fraction to meet most American Society for Testing and Materials (ASTM) D975 #2 distillate fuel specifications.

In this study, crude TDO oil is hydrogenated using a commercial Ni/SiO₂-Al₂O₃ catalyst in bench scale continuous flow tubular reactors. The crude and hydrogenated TDO oils are distilled to produce jet fuel (180-250 °C) and diesel (150-325 °C) range hydrocarbons using a fractional distillation apparatus according to ASTM standards. Four different TDO oil
blendstocks (crude TDO oil, Hydrotreated TDO oil, distilled TDO oil, and distilled Hydrotreated TDO oil) are analyzed for chemical and physicochemical properties following ASTM standard methods and used for diesel combustion analysis. Properties of the TDO fuels are compared with ASTM and military fuel standards (MIL-DTL), and blended appropriately to meet the specifications. Each TDO diesel blendstocks is blended with ULSD in four different volume percent (5 %, 10 %, 15%, and 20%) to produce sixteen total fuel blends for the analysis. Combustion and emission behaviors of the fuel blends were studied using a naturally-aspirated, air-cooled, single-cylinder diesel engine as a function of engine load at a fixed speed of 3,600 RPM. In-cylinder heat release analysis results show combustion phasing and indicated thermal efficiency can be predicted by fuel cetane rating. Quantitation of engine emission include oxygenates (aldehydes and ketones) using GCMS methods and soot which is collected on 0.45 um fiberglass filters and analyzed using thermogravimetric analysis to ascertain total emission rate and volatile fraction. Results show TDO oils are a viable renewable fuel blending agent for making finished transportation fuels.