(205f) Optimization of Energetics Crystallization Via Quality-By-Control Direct Design Approaches

Crystallization is an essential process of solids manufacturing and is left unoptimized in several fields, including energetics manufacturing. Unoptimized crystallization protocols can lead to solid material with undesired physical and chemical characteristics, such as particle morphology, stability, detonation potential, manufacturability, and overall crystal quality. Although researchers have extensively studied the solubility of the common energetic materials, Research Department/Royal Demolition Explosive (RDX) and High Melting Explosive (HMX), little work has been completed on the optimization of both batch and continuous crystallization processes for RDX and HMX.

In this work we demonstrate the application of the Quality-by-Control (QbC) framework for the rapid design of the crystallization of energetic compounds. QbC allows for the minimization of experiments and experimental exposure by utilizing feedback control strategies for the critical quality attributes (CQAs).¹ Using the QbC-based direct design approach an optimized method for the industrial manufacturing of crystallized RDX and HMX could be suggested. Our direct design approaches require initial solubility and solvent selection data. Small-scale experiments completed with Crystal16 showed that RDX and HMX have high solubility in γ-Butyrolactone and a sizeable metastable zone width (MSZW), which is desirable for crystallization control. The two applied direct design approaches are direct nucleation control (DNC) and supersaturation control (SSC). DNC applies particle counts measurements collected with an in-situ focused beam reflectance measurement (FBRM) probe to a model-free closed feedback control loop which introduces temperature cycling to a saturated solution, stimulating controlled nucleation and crystal growth.² SSC applies solution concentration measurements collected with an in-situ infrared (IR) probe to a model-free closed feedback control loop which introduces temperature cycling to a saturated solution, stimulating controlled solution concentrations.³ In application with in-situ process analytical technology (PAT) tools, DNC and SSC allowed for the optimization and selection of crystallization techniques for RDX and HMX at the research-scale. Understanding an optimal method for the industrial crystallization of common energetic materials, such as RDX and HMX, will help improve the quality and effectiveness of manufactured energetic materials and enable future process development for the manufacturing of energetic materials.

References

1. Su, Q.; Ganesh, S.; Moreno, M.; Bommireddy, Y.; Gonzalez, M.; Reklaitis, G. V.; Nagy, Z. K. A Perspective on Quality-by-Control (QbC) in Pharmaceutical Continuous Manufacturing. Chem. Eng. 2019, 125, 216–231.

2. Bakar, M. R. A.; Nagy, Z. K.; Saleemi, A. N.; Rielly, C. D. The Impact of Direct Nucleation Control on Crystal Size Distribution in Pharmaceutical Crystallization Processes. Growth Des. 2009, 9 (3), 1378–1384.

3. Saleemi, A. N.; Rielly, C. D.; Nagy, Z. K. Comparative Investigation of Supersaturation and Automated Direct Nucleation Control of Crystal Size Distributions Using ATR-UV/Vis Spectroscopy and FBRM. Growth Des. 2012, 12 (4), 1792–1807.