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Process Optimization for the Gas-Liquid Heterogeneous Reactive Crystallization Process Involved in the Preparation of the Insensitive High Explosive TATB

Nandi A. K., Kshirsagar A. S., Thanigaivelan U., Bhattacharyya S. C., Mandal A. K., Pandey R. K., Bhattacharya B.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 1

31--57

EN

The thermally stable, insensitive, high explosive 1,3,5-triamino-2,4,6- trinitrobenzene (TATB) is manufactured by amination of 1,3,5-trichloro-2,4,6- trinitrobenzene (TCTNB) in toluene with NH3 gas. It is an isothermal, single-feed, semi-batch, gas-liquid heterogeneous, reaction crystallization process. The amination process is discussed by applying the chemical engineering methodology of mass transfer and reactive crystallization processes based on Two-Film Mass- Transfer (TFMT) theory. Kinetic expressions have been developed to define the chemical reactions as well as the physical phenomena (mass transfer) associated with this process. A single expression has been derived to explain the dependence of the ammonia consumption rate on various process parameters. Subsequently, the influence of various process parameters on the product quality (particle size and chloride impurity content) has been studied on the laboratory scale. Finally, the process has been established in the pilot plant, with optimized process conditions, to realize TATB of desired particle size and chloride content. The effects of feeding excess ammonia, and the presence of mercaptans/hydrogen sulphide impurities in poor quality toluene on the formation of certain undesirable by-products in TATB, are also discussed.

2

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

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2014

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Vol. 11, no. 1

83--97

EN

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.

3

Assay of the thermally stable, insensitive, high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)

Nandi A. K., Thirupathi N., Mandal A. K., Pandey P. K.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 2

295--305

EN

An aqueous titration method is described to assay the insensitive, high explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). TATB is initially quantitatively converted to the weak acid 1,3,5-trihydroxy-2,4,6-trinitrobenzene (THTNB) by base catalysed hydrolysis. Subsequently THTNB is assayed by acidbase titration. TATB samples obtained from regular batch operations are assayed by this method, and the results are compared with those obtained by the total amino functional group estimation method using a modified Kjeldhal apparatus. The method is simple and has good accuracy and precision.

4

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

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2013

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Vol. 10, no. 1

113--122

EN

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.

5

Assay of the Insensitive High Explosive FOX-7 by Non-Aqueous Titration

Nandi A. K., Paramasivan P., Singh S. K., Mandal A. K., Pandey R. K.

Central European Journal of Energetic Materials

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2012

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Vol. 9, nr 4

343-352

EN

A non-aqueous titration method was developed to assay the insensitive high explosive 1,1-diamino-2, 2-dinitroethene (FOX-7). The weak acidic nature of FOX-7 (pKa 10.6) was exploited in the assay method. The sample was dissolved in the protophilic solvent N, N-dimethylformamide and titrated against sodium methoxide solution in benzene/methanol using azo violet as indicator. FOX-7 samples obtained from regular batch operations were assayed by this method and the results were compared with that of a recrystallized sample. The method is simple, rapid and has good accuracy and precision.