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Optimization of Ammonium Sulfamate Nitration for the Preparation of Ammonium Dinitramide

Mandal A. K., Kunjir G. M., Singh J., Adhav S. S., Singh S. K., Pandey R. K., Bhattacharya B., Lakshmi Kantam M.

Central European Journal of Energetic Materials

2014

Vol. 11, no. 1

83--97

The reaction kinetics for the preparation of ammonium dinitramide (ADN) is described. ADN is the ammonium salt of the dinitramide anion, and belongs to the group of inorganic oxidizers, mainly useful for energetic rocket propellant formulations, particularly for underwater applications. It is also a potential candidate to replace ammonium perchlorate (AP), in order to develop chlorine-free, green propellants. At HEMRL, ADN is prepared by the nitration of ammonium sulfamate (AS) using mixed acid, followed by hydrolysis, neutralization with ammonia (g) and rectification using solvent. The nitration of ammonium sulfamate (AS) is carried out at a subzero temperature of -40 ±1 °C. The yield of ADN is reliant on the formation of dinitramidic acid, an intermediate product formed during the hydrolysis step, and its stability is predominantly dependent upon the level of acidity and temperature of the reaction medium. Prior to these kinetics studies, process optimization of the nitration of ammonium sulfamate (AS) was performed and gave the final mole ratio of AS:HNO3:H2SO4. Since the nitration of AS is sensitive to temperature, the rate of reaction was studied at fixed temperatures with variation of time, keeping all of the other parameters, such as vessel volume, agitator speed, feed rate etc., constant. During these studies, predetermined quantities of ammonium sulfamate (AS) and mixed acid were allowed to react at a fixed temperature (-40 ±1 °C) for different reaction periods to generate the concentration profile of AS. Using this concentration profile, the reaction order and reaction rate constant were evaluated. In order to find the effect of temperature on the reaction rate and yield, experiments were conducted at other temperatures such as -30 and -50 °C. In the present studies, it was found that the optimum temperature of nitration is -40 ±1 °C and that the rate of reaction follows a pseudo second order process with rate constant 0.01113 (min-1)•(mol/L)-1. The reaction time evaluated for 55 to 60% conversion is about 70-80 minutes at -40 ±1 °C, based on this kinetics. The activation energy of AS nitration was found to be -4.6 kcal/mol, using the reaction kinetic data based on the temperature dependent rate equation derived from Arrhenius’s law.

Assay of the Insensitive High Explosive 3-Nitro-1,2,4-triazol-5-one (NTO) by Acid-Base Titration

Nandi A. K., Singh S. K., Kunjir G. M., Singh J., Mandal A. K., Pandey R. K.

Central European Journal of Energetic Materials

2013

Vol. 10, no. 1

113--122

The insensitive high explosive 3-nitro-1,2,4-triazol-5-one (NTO) is a weak acid (pKa 3.76) due to the labile N–H bond. The weakly acidic character of this compound is exploited for its assay by aqueous acid-base titration. The NTO sample was dissolved in water and the resultant solution was titrated against 0.07 N NaOH solution using phenolphthalein as indicator. Regular batch samples were assayed by this method and the results were compared with those obtained by the HPLC method. The aqueous acid-base titration method was found to be suitable for the quality control of the product.