Triisobutylaluminum additive for liquid hydrocarbon burn enhancement

Metallizing hydrocarbons has received renewed attention as a potential means to increase energy density and burn rate. Particle agglomeration however, is a significant concern, impeding both performance as well as practical implementation due to system fouling. Achieving a metallized hydrocarbon without nanoparticles in suspension would avoid particle agglomeration problems. Previous proof-of-concept work with highly reactive organometallic Al-based clusters stabilized by ligands and dissolved in a hydrocarbon showed such a scheme is not only possible, but the decreased size of the cluster molecules relative to nanoparticles substantially increases reactivity and at least an order of magnitude less active aluminum. To increase understanding of how such burning rate effects manifest with dissolved aluminum, a higher valency alkyl aluminum historically used as a hypergol, triisobutylaluminum (IBu3Al), is dissolved in toluene and isolated droplet combustion is characterized showing up to 60% burning rate increase with 810 mM IBu3Al relative to that of pure toluene attributed specifically to the aluminum content of the additive molecule. Flame emission spectroscopy observing AlO emission supports the vital role of gas eruption and droplet disruption to transport additives into the flame.