Acetone/hexane recrystallization of HNAB

In the manufacturing process for hexanitroazobenzene (HNAB), the final step prior to heat treatment is a recrystallization of HNAB from an acetonitrile/tetrachlorethane mixture. The possibility that the above solvents might become unavailable at some future date and the toxicities of these solvents indicate a need for a new solvent system. Initial work using acetone/hexane in place of acetonitrite/tetrachloroethane indicated its feasibility (D. M. O'Keefe, Sandia Laboratories, Private Communication). The objective of the present work was to confirm the feasibility of the use of acetone/hexane system and then to scale-up the recrystallization to the size and type of equipment used in the manufacturing process. A 7.2 kg batch of HNAB was produced with the final recrystallization from the acetone/hexane system. The analysis of the HNAB-II compared favorably with that from the production process. A 50 g sample was furnished to Sandia Laboratory.