Synthesis And Properties Of Azido-Containing Energetic Fuels

Azido amine is a new and low-toxic liquid fuel propellant which can be used to replace hydrazine and its derivatives.The reaction kinetics of three azido amines(DMAZ、BAZ and DEAZ) with sodium azide in aqueous solution was studied using ultraviolet absorption spectrometry. The results show the order reaction and the reaction rate constants at several temperatures.Furthermore, the apparent activation energy (Ea) and the pre-exponential factor (ko) can be calculated. For kinetics of synthesizing DMAZ hydrochloride, the results show that the reaction can be considered as a second-order reaction.The reaction rate constants are1.848×10-3、4.382x10-3and9.195×10-3L·mol-1·min-1, respectively, at337K,347K and357K. The apparent activation energy (Ea) is80.3kJ·mol-1and the pre-exponential factor (ko) is5.24×109L·mol-1·min-1. For kinetics of synthesizing DEAZ hydrochloride, the results show that the reaction can be considered as a second-order reaction,too.The reaction rate constants (k) were2.445×10-2、7.992×10-2and0.138L·mol-1·min-1, respectively, at337K,347K and353K. The apparent activation energy (Ea) was118.5kJ·mol-1and the pre-exponential factor (k0) was5.75×1016L·mol-1·min-1.For kinetics of synthesizing BAZ hydrochloride, the results show that the reaction can be considered as a third-order reaction. The reaction rate constants at333K,338K,343K and348K were0.4206,0.5860,0.7609and1.0302L2·mol-2·min-1, respectively. The apparent activation energy (Ea) was56.9kJ·mol-1and the pre-exponential factor(k0) was3.52×108L2·mol-2·min-1.Five target ionic liquids were synthesized by two-step method, alkylation and anion exchange. And the raw material was azido amine DMAZ and dicyanamide anion.Ionic liquids were characterized by FT-IR、1H NMR、13C NMR. A variety of physical and chemical properties of ionic liquids were measured, including the density, viscosity, melting point(the glass transition temperature) and thermal decomposition temperature, and heat of combustion, and enthalpy of formation. Combined with its characterization results of analysis, the cation (alkyl chain length) in the series of ionic liquid of DMAZ has impacts on properties such as density, viscosity, thermal decomposition temperature, the glass transition temperature, combustion heat and the enthalpy of formation.The results show that with the growth of carbon chain of cationic group and temperature, in terms of those the density of ILs decreases. The viscosity of [edmaz][N (CN)2] is very low (5.3mPa·s, T=25℃), and the others’increase with the growth of carbon chain of cationic group. The ionic liquids of [edmaz][N(CN)2],[bdmaz][N(CN)2],[C6dmaz][N(CN)2] and [Cgdmaz][N(CN)2])have only glass transition temperatures (Tg) without melting points, whereas [C12dmaz][N(CN)2] displays several phase changes during-90℃and30℃. Decomposition temperatures are similar (234-242℃) and irrespective of the alkyl chain length. Heat capacities increase with alkyl chain length of [Rdmaz][N(CN)2] at the same temperature. Heat capacities increase gradually with temperature, which can be correlated with a quadratic equation.The enthalpy of formation of the six ionic liquids can be calculated with combustion heat, and we find that the enthalpy of formation decreases with increasing alkyl chain length.