(218a) Applications of a Micropyrolysis Index (MPI) towards Molecular Engineering of Fuels

A new sooting tendency measurement was developed to give an estimate of the pyrolytic sooting tendency of a particular fuel on a lab scale. This measurement has been coined the micropyrolysis index (MPI), as it involves pyrolyzing 20μL of fuel across a hot bed of α-Al₂O₃ in a flow reactor in a He environment. The α-Al₂O₃ bed is then removed, and the deposited carbon is quantified via temperature programmed oxidation (TPO) in order to obtain a kinetic measurement of the fuel to form soot via pyrolysis. SEM, Raman, and same spot TEM images were used to characterize the deposited soot. The MPI compliments similar techniques, such as threshold sooting indices (TSI) or yield sooting indices (YSI), which introduce oxygen into the system. By comparing the two methods, one can separate the tendency of a compound to form soot based on pyrolysis alone with other factors that will vary from compound to compound such as flame temperatures and oxygen/fuel ratios.

Because such small sample volumes are used, several pure compounds were tested. A database was constructed, and quantitative structure-property relationships (QSPR) were created in order to predict the MPI of a pure compound based on its molecular structure. These measured and predicted values were used to provide direction for several important issues in catalytic conversion, including selective ring opening for diesel fuels, reduction of aromatics in gasoline while maintaining octane number, and enhancing fungibility of several renewable fuels.