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Continuous Flow Recrystallization of Energetic Nitramines



OBJECTIVE: Design, develop and demonstrate a continuous process for direct recrystallization of energetic materials.

DESCRIPTION: Energetic materials are dual-use materials used in private industry, recreational sport, and military applications. Energetic materials are extremely dangerous to handle. Unfortunately the manufacturing processes used today are decades-old using antiquated equipment. This has resulted in catastrophic events leading to injury and death over the years. The design and engineering capabilities available today, along with innovative technologies that were not available decades ago, offer a unique opportunity for the implementation of safer and sustainable manufacturing processes for energetics.The main steps include the reaction, filtration, and recrystallization while extraction and distillation processes are also utilized depending on the material. These steps typically include an operator interfacing with sometimes dangerous intermediates and products. The main reaction can be done in batch or continuous reactors.Development of continuous flow synthetic approaches applied to energetic materials have demonstrated several advantages including reduced waste, material in process, process control and product quality.In order to fully realize the potential of continuous flow synthesis it needs to be paired with complementary continuous flow technologies including filtration, recrystallization, extraction, and distillation.Continuous flow recrystallization presents one of the largest challenges and opportunities in continuous flow preparation of nitramines including RDX and HMX.The pharmaceutical industry has demonstrated use of continuous flow recrystallization to result in improved purity, particle size control and particle size distribution.This topic desires continuous flow recrystallization strategies for direct recrystallization to each of the RDX/HMX class sizes (eliminating grinding steps) with tighter particle size, greater process control and improved process waste profiles while retaining the desired polymorph for each.

PHASE I: The small business will investigate innovative strategies for lab-scale continuous flow recrystallization of RDX and HMX with tunable particle size distribution within the range specified for various class sizes and their respective desired polymorph.This lab-scale work will develop models based off of experimental work to better understand process kinetics and viability.The phase I output will be a prototype process for energetic material recrystallization that results in a tunable system for the direct production of Class 1-5 nitramines with their desired polymorph.This prototype process will result in a 20% tighter particle size distribution, eliminated operator exposure and developed strategies for inline process monitoring.While initial process development may be on surrogate compounds, the final prototype and evaluation must be on either RDX or HMX.A Phase 2 effort must be on the energetic materials.

PHASE II: Development and demonstration of a pilot scale process for continuous nitramine recrystallization.The process models generated in Phase 1 should be validated, optimized for affordability and robustness, and developed into a physical pilot process.This pilot scale process should produce final product at a rate of at least 1 g/min.The demonstration should exhibit polymorph and particle size control to each of the class sizes and be transition-able to manufacturing environments.It should show reduced particle size distribution, operator exposure, hazardous waste generation, and greater process control.A 20 g sample of each class size must be shipped to CCDC-Armaments Center for further evaluation of product quality.Phase 2 will conclude with a full process design and transition plan.

PHASE III: The process developed in Phase 2 should be scalable to production capacity.This capability will allow greater flexibility in meeting warfighter needs for nitramine-based end items in times of high demand with lower infrastructure costs than large scale batch recrystallization process equipment.It will also result in greater control of nitramine explosive properties (due to tighter control of particle size distribution) for improved end item reliability.

KEYWORDS: Continuous Flow, Recrystallization, Nitramines, Process Analytical Technology


K.A. Powell, A.N. Saleemi, C.D. Rielly, Z.K. Nagy.“Periodic steady-state flow crystallization of a pharmaceutical drug using MSMPR operation.”Chemical Engineering and Processing: Process Intensification, Volume 97, November 2015, pp 195-212; P.B. Palde, T.F. Jamison.“Safe and Efficient Tetrazole Synthesis in a Continuous-Flow Microreactor.” Angewandte Chemie International Edition, Volume 50, 15, April 2011, pp 3525-3528.; “DETAIL SPECIFICATION RDX (CYCLOTRIMETHYLENETRINITRAMINE).”MIL-DTL-398D.1996.; S. Lawton, G. Steel, P. Shering, L. Zhao, I. Laird, X.W. Ni."Continuous Crystallization of Pharmaceuticals Using a Continuous Oscillatory Baffled Crystallizer." Org. Process Res. Dev., Volume 13, October 2009, pp 1357-1363

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