Ultrasmall Pd Nanoparticles Supported on TiO₂ for Catalytic Debenzylation via Hydrogenative C–N Bond Cleavage

Heterogeneous Pd has been developed as a well-known catalyst for debenzylation reactions via hydrogenative C–N bond cleavage. However, the extensive applications are still limited owing to a high loading and usage amount of the noble metal. Herein, well-dispersed Pd nanocatalysts over TiO2 were explored with a deposition–precipitation method and characterized by FESEM, physical adsorption, XRD, TEM, and XPS. It was proposed that the ultrasmall and electron-rich Pd nanoparticles can be enhanced over TiO2 rather than C, Al2O3, or SiO2. As representatives, the debenzylations of hexabenzylhexaazaisowurtzitane (HBIW) and tetraacetyldibenzylhexaazaisowurtzitane (TADBIW), which are key steps for the synthesis of CL-20 with the highest energy and density, were selected to evaluate the catalytic performances. It was found that Pd/TiO2 exhibited considerably low usage with high yields in the debenzylation processes of not only HBIW (1 wt ‰) but also TADBIW (4 wt ‰). Meanwhile, the superior catalytic activities can be maintained in the different reaction scales and can be repeated for TADBIW hydrodebenzylation. Hence, Pd nanoparticles supported on TiO2 can be considered to be suitable catalysts for highly efficient catalytic synthesis for hydrogenative C–N bond cleavage.