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Reaction mechanism and process optimization of hydrogenolysis of hydrodebenzylation of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazaisowurtzitane
- Zijie GUO Bin ZHANG Jie CHEN Xin FENG Guilong WANG Weipeng ZHANG Chao YANG Wanqin JIN
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The Chinese Journal of Process Engineering. 2024, 24(1):
36-46.
DOI: 10.12034/j.issn.1009-606X.223070
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The key step in the preparation of hexanitrohexaazaisowurtzitane (HNIW) is the formation of hydrogenolysis of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazaisowurtzitane (TADBIW) by hydrogenolysis of hydrodebenzylation of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazaisowurtzitane (HBIW) with a palladium-based catalyst in the presence of hydrogen. Due to the instability of HBIW, the caged structure of HBIW disintegrated easily in high temperature and acid environment, which was unable to be directly nitrified to synthesize HNIW. Therefore, hydrogenolysis debenzylation of HBIW is basically inevitable. In this process, hydrogenolysis debenzylation and acetylation occur simultaneously, the C-N bond is hydrogenated on the catalyst, and the subsequently formed amine is acetylated with the acetic anhydride. However, the process is complex and has many intermediate products. Current research is mainly focused on the development of new types of catalysts, with little knowledge of the dynamics and mechanisms of the reaction. This study established a new HPLC analysis method, and the concentration changes of raw materials and intermediates could be observed in the same chromatogram. Based on this, the effect of cosolvent and PhBr content on the hydrogenolysis reaction was studied. The reaction temperature was raised to 65℃, the reaction time was shortened to less than 1 h, and the yield reached 78.90%. Based on the optimal reaction conditions, the kinetics of the hydrogen dehumidification process at the reaction temperature of 18~45℃ were studied, and the concentration change law of each intermediate and reaction product in the reaction process was obtained through quantitative analysis and was inferred that the later stage was mainly acetylating. The process of converting raw materials into intermediates follows first-order reaction kinetics. The intermediate produces the product, following zero-order reaction kinetics; the apparent activation energies were Ea1=62.43 kJ/mol and Ea2=52.80 kJ/mol, respectively. The predigital factors were A1=6.81×109 min-1, A2=5.91×108 mmoL/min; The linear correlation coefficients were R12=0.99181, R22=0.98897. The continuous synthesis method was further developed, and the yield of TADBIW could reach 95.89% at a reaction temperature of 70℃ and a residence time of 4 min.
