Preparation of Pd(OH)₂/C catalyst for hydrogenolytic debenzylation of hexabenzylhexaazaisowurtzitane

Pd(OH)₂/C catalyst is a key material for the preparation of hexanitrohexaazaisowurtzitane (HNIW, CL-20). Several Pd(OH)₂/C catalysts for the hydrogenolytic debenzylation of hexabenzylhexaazaisowurtzitane (HBIW) were prepared through soaking-deposition method with three types of commercial activated carbons as carriers. Effects of the surface properties and pore size distributions of activated carbons, the preparation temperature of catalyst, the kinds of base and the loading amount of palladium on the catalytic activity of Pd(OH)₂/C catalyst were investigated. The catalytic activity and the characteristics of N₂ adsorption, temperature programmed desorption (TPD), powder X-ray diffraction (XRD) and transmission electron microscope (TEM) show that the catalytic activity of Pd(OH)₂/C catalyst is strongly influenced by the surface property and pore size distribution of activated carbon, reaction temperature and the loading amount of palladium, whereas the specific surface area of activated carbon and the kinds of base used in preparation process of catalyst are not key factors affecting the properties of Pd(OH)₂/C catalyst. Using disodium carbonate as base source and 30% nitric acid pretreated granular activated carbon (produced by ACROS Organics Company) as carrier, the 9% Pd(OH)₂/C catalyst prepared under the reaction temperature of 5℃, has the best catalytic activity. When the amount of palladium used in catalyst is 0.3% (wt/wt) of HBIW substrate, the product yield of hydrogenolytic debenzylation-acetylation reaction of HBIW reaches 93%.