Development of Promoters for Hypergolic Reactions with Hydrogen Peroxide

Energetic Ionic Liquids (EILs) were reported as promising hydrazine-replacement fuels for hypergolic rocket propulsion. However, many of these EILs were ignited by corrosive and hazardous concentrated fuming nitric acid. Significant efforts were recently made to utilize highly-concentrated H$_{2}$O$_{2}$ as a "green" alternative to the fuming nitric acid and N$_{2}$O$_{4}$ oxidizers. Although "rocket grade" H$_{2}$O$_{2}$ is more challenging for use and less safe for storage than commercially-available H$_{2}$O$_{2}$ (70%), the latter was not considered as a viable oxidizer for hypergolic propulsion. In our work, we focused on the development of novel iodine-rich promoters, capable to initiate hypergolic ignition reactions between a typical EIL fuel – 3-ethyl-1-methyl-1H-imidazol-3-ium cyanotrihydroborate and H$_{2}$O$_{2}$. Among prepared and evaluated promoters, the top performing [FcCH$_{2}$NEtMe$_{2}$$^{+}$]$_{2}$[B$_{12}$I$_{12}$$^{2–}$] showed ignition delay times of 45 msec in reaction of the tested EIL with H$_{2}$O$_{2}$ (70%) and 17 msec with H$_{2}$O$_{2}$ (95%). We also developed four novel iodocuprate-containing ionic liquids (CuILs), which exhibited capability to efficiently promote hypergolic reactions between EIL fuels and H$_{2}$O$_{2}$. The most promising promoter of CuIL-type has high decomposition temperature, was found to be stable in promoter-in-fuel formulation for weeks and showed ignition delay times of 14 msec. We believe that our findings provide a platform for the development and utilization of H$_{2}$O$_{2}$ as potential "green" oxidizer for space propulsion.