Synthesis of 2,4,6-Trinitrotoluene (TNT) Using Flow Chemistry

Abstract

This paper describes the nitration of 2,4-dinitrotoluene (DNT) and its conversion to 2,4,6-trinitrotoluene (TNT) at a gram scale with the use of a fully automated flow chemistry system. The conversion of DNT to TNT traditionally requires the use of highly hazardous reagents like fuming sulfuric acid (oleum), fuming nitric acid (90–100%), and elevated temperatures. Flow chemistry offers advantages compared to conventional syntheses including a high degree of safety and simpler multistep automation. The configuration and development of this automated process based on a commercially available flow chemistry system is described. A high conversion rate (>99%) was achieved. Unlike established synthetic methods, ordinary nitrating mixture (65% HNO3/98% H2SO4) and shorter reaction times (10–30 min) were applied. The viability of flow nitration as a means of safe and continuous synthesis of TNT was investigated. The method was optimized using an experimental design approach, and the resulting process is safer, faster, and more efficient than previously reported TNT synthesis procedures. We compared the flow chemistry and batch approaches, including a provisional cost calculation for laboratory-scale production (a thorough economic analysis is, however, beyond the scope of this article). The method is considered fit for purpose for the safe production of high-purity explosives standards at a gram scale, which are used to verify that the performance of explosive trace detection equipment complies with EU regulatory requirements.

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“…2.1. Materials 2-Aminoterephthalic-1,4-terephthaloylhydrazide [38] and TNT [39] were synthesized following previously reported procedures. 1,3,5-Triformylbenzene was purchased from Acros Organics (Geel, Belgium).…”

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“…Danilo et al [6] compared the performance of liquid/liquid biphasic benzaldehyde nitration in conventional batch reactor and continuous-flow microreactor and developed kinetic model under homogeneous conditions are validated and extended for heterogeneous liquid-liquid systems. Dimitris et al [7] described the nitration of 2,4-dinitrotoluene (DNT) and its conversion to 2,4,6-trinitrotoluene (TNT) at a gram scale with the use of a fully automated flow chemistry system and the resulting process is safer, faster, and more efficient than previously reported TNT synthesis procedures. Zhenghui et al [8] investigated the continuous-flow nitration of trifluoromethoxybenzene in a microchannel reactor and presented a scale-up strategy combining microreactor with distributed packed tubular reactor was presented.…”