Study of Deactivation of Pd(OH)₂/C Catalyst in Reductive Debenzylation of Hexabenzylhexaazaisowurtzitane

Abstract

The conversion of hexabenzylhexaazaisowurtzitane (HBIW) to 2,6,8,12‐tetraacetyl‐4,10‐dibenzyl‐2,4,6,8,10,12‐hexaazaisowurtzitane (TADB) is the major challenge in the production of hexanitrohexaazaisowurtzitane (HNIW) which only proceeds over supported palladium catalyst in a reductive debenzylation reaction. The catalyst is quickly deactivated during the debenzylation reaction. In this study, the change in Pd content in the catalyst during the reaction was measured. It was demonstrated that a portion of the palladium particles in the catalyst was leached during the reaction. The H2 chemisorption isotherm on the catalyst at 303 K showed that the volume of chemisorbed H2 on spent catalyst was significantly less than that on fresh catalyst. The N2 physisorption isotherm on the catalyst at 77 K revealed that the surface area of spent catalyst was less than that of fresh catalyst. Moreover, the FESEM‐EDS and TEM images and also wide‐angle XRD patterns demonstrated that the mean sizes of palladium crystallites and particles in spent catalyst were larger than those in the fresh catalyst. These results demonstrated that the leaching of palladium particles and the aggregation of palladium particles in catalyst play active roles in the deactivation of catalyst in the debenzylation of HBIW.

The Use of Laser Induced Breakdown Spectroscopy (LIBS) to Study Catalyst Deactivation of V2O5/γ‐Al2O3 as Compared to Inductively Coupled Plasma Optical Emission Spectrometry

“…The fresh catalyst of Pd(OH) 2 /C with 10 % of Pd was prepared via deposition precipitation method. The spent Pd/C catalyst was obtained after the debenzylation reaction of HBIW to produce CL‐20 (Figure ) …”

“…V 2 O 5 /γ‐Al 2 O 3 and Pd(OH) 2 /C are two important catalysts where their activities can be decreased during dehydration of glycerol and reductive debenzylation of HBIW, respectively. [14a], , [17a], …”

Research Progress and Key Issues of Hydrodebenzylation of Hexabenzylhexaazaisowurtzitane (HBIW) in the Synthesis of High Energy Density Material Hexanitrohexaazaisowurtzitane (HNIW)

“…I. L. Simakova et al [39] discovered that the rapid deactivation of a Pd/C catalyst in the HBIW hydrodebenzylation process was not determined by the preparation method, but the agglomeration of metal particles and the blocking of activated carbon particles by oligomer products inside the carbon pores. Hadis Bashiri et al [74] found that the loading amount of Pd decreased in the HBIW hydrodebenzylation process, and believed that the leaching and aggregation of Pd particles was responsible for the deactivation of the catalyst. To reduce the loading amount of Pd and improve the stability of the Pd-based catalyst, JunYang and Shuang Liu, from the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, studied [11,12,16] the application of bimetallic catalysts in HBIW hydrodebenzylation reactions, and found that when the amount of the catalyst was the same, the yield of a bimetallic catalyst (PdFe) was significantly higher than that of the Pd mono-metal catalyst, and was 4% higher than that of the commercial Pd/C catalyst.…”

Role of the Bromide on the Hydrodebenzylation of 2,4,6,8,10,12‐Hexabenzyl‐2,4,6,8,10,12‐hexaazaisowurtzitane (HBIW)

“…The conversion from HBIW into TADBIW is the key challenge of HNIW synthesis because high reaction temperature and acid medium are favorite for the debenzylation process but detrimental for preserving the high-strained polycyclic structure of HBIW. [16][17] Moreover, the nitrogen-rich by-product generated by ring-opening may also complex with palladium and thus poisoned the catalysts. [18][19] Consequently, the novel catalysts can catalyze the debenzylation at low temperature are significant for improving the yield and reducing the cost of HNIW.…”