(632d) Process Scale-up for Production of  Bis-Tetrazol-Amine  and N,N'-Bis-(1H-tetrazol-5-yl)-Hydrazine

Two nitrogen-rich materials, namely 5,5’-bis(1H-tetrazolyl)amine (BTA) and 5,5’-hydrazinebistetrazole (HBT) were found to be excellent burning rate modifiers in nitrocellulose based propellant formulations. These two nitrogen-rich energetic materials were also found to be compatible with nitrocellulose and nitrated ester plasticizers according to the STANAG 4147 guidelines. These results demonstrated that pursuing the characterization of the impact of these materials on propellants further was worthwhile. However, in order to do so, large quantities of materials are required. A scale-up of the synthesis of BTA and HBT to the pilot scale in a 30 L CSTR was undertaken. The scale-up of the synthesis of BTA proved easy to perform and followed the previously published synthesis protocols for quantities at the gram scale. The enthalpy of mixing of adding acid to the reactive media proved to be a non-issue and was the only exothermic step of this reaction. The scale-up of the synthesis of HBT however proved more challenging. The synthesis of HBT involves the synthesis of an intermediary, sodium 5,5’-azotetrazolate pentahydrate (NaZT). Due to volume constraints, concentrations of reactants were increased for the synthesis of NaZT. This proved a challenge due to the exothermal nature of the step of adding one of the reactants to reactive mixture in the CSTR reactor. Isolating the synthesized NaZT also proved challenging due to the high amount of water needed to be removed to isolate the product in satisfactory yields. To circumvent this, it was decided to minimize the amount of water to be evaporated by reusing the reactive media for the subsequent synthesis step after filtering out the MnO₂ by-product resulting from the synthesis of NaZT. This permitted a significant reduction of the amount of water to be evaporated. However, this choice of re-using the reactive media from the synthesis of NaZT for the subsequent synthesis of HBT proved challenging for two reasons. Firstly, the synthesis of HBT requires an initial pH of around 7 to be performed in a timely manner which required the neutralization of the reactive media as the synthesis of NaZT requires a highly alkaline media. This was an unknown as to our knowledge, this has never been attempted as fully isolating NaZT was not a challenge at the laboratory scale. Secondly, the addition of acid to neutralize the reactive media could incur the degradation of NaZT. The second challenge was tackled by carefully adding the neutralizing acid at a flow rate of 30 mL∙min^-1 and by isolating part of the NaZT through partial recrystallization of the product prior to the neutralization step. The final step of the synthesis of HBT which was performed with ease in the laboratory also proved more challenging at the pilot scale. Exothermal effects from the addition of magnesium to the CSTR which were a non-issue at the laboratory scale proved to be of a high importance in the 30 L CTSR during the first synthesis at the pilot scale. As a result, the heat release associated with each reaction step were measured experimentally. Both reactions for the synthesis of HBT are performed at high temperatures. A batch process design taking advantage of the exothermal nature of part of the synthesis is proposed to minimize the energy requirements for the synthesis of HBT. A batch process design for the synthesis of BTA is also presented.