Synthesis of asymmetric [bis(imidazolyl)-BH2]+-cation-based ionic liquids as potential rocket fuels?

RSC Advances Pub Date: 2021-11-25 DOI: 10.1039/D1RA07149A

Abstract

As potential hypergolic fuels, hypergolic ionic liquids have attracted much attention since their development. Herein, a series of hypergolic ionic liquids based on asymmetric [bis(imidazolyl)-BH2]+ cations were synthesized. The asymmetric structure of these hypergolic ionic liquids was further confirmed by NMR, infrared (IR), and high-resolution mass spectrometry-electron spray ionization (HRMS-ESI). Moreover, these hypergolic ionic liquids possess a high density of over 1.00 g cm?3, a comprehensive liquid range from ?60 °C to 20 °C, and a density-specific impulse performance ranging from 305.4 to 357.8 s g cm?3, which is superior to that of unsymmetrical dimethylhydrazine. Remarkably, (1-allyl-1H-imidazol-3-ium-1-yl)(1-methyl-1H-imidazol-3-ium-1-yl) dihydroboronium dicyandiamide had the best ignition-delay time (18 ms), a high density (1.114 g cm?3), and a high value for heat of formation (400 kJ mol?1/1.48 kJ g?1). This work provides the possibility of a promising and green hypergolic fuel as rocket propellant.

Graphical abstract: Synthesis of asymmetric [bis(imidazolyl)-BH2]+-cation-based ionic liquids as potential rocket fuels
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