Study on key technologies for resource recovery and high-value transformation of main charge in decommissioned explosive tear gas grenades

Abstract

To enable the sustainable and harmless treatment of decommissioned explosive tear gas grenades (DTGG), a holistic resource-oriented strategy was developed, which prioritizes the effective recovery of ortho-chlorobenzylidene malononitrile (CS) and its transformation into value-added chemical products. Through a systematically developed separation process, CS and RDX were recovered with exceptional efficiency and high purity. The average recovered rate of CS and RDX reached 90.92% and 94.42% respectively, with a purity of more than 98%. The recovered CS was then successfully transformed into 2-(2-chlorophenyl)-benzimidazole (2-CPBZ) via an optimized one-pot synthesis achieving an impressive 86.2% yield with 98% purity. Comprehensive characterization and complementary analytical techniques confirmed the structural integrity of both the recovered CS and the synthesized 2-CPBZ. Mechanistic investigations through density functional theory calculations revealed a sophisticated reaction pathway involving sequential nucleophilic addition, acid–base neutralization, nucleophilic substitution, proton transfer, elimination, intramolecular cyclization, and oxidative aromatization. By demonstrating a complete value chain from decommissioned munitions to pharmaceutical intermediates, the research provides both fundamental insights and practical methodologies for green chemical transformation of hazardous materials, opening new avenues for environmentally responsible disposal and resource utilization in defense and security sectors.