A Simple Method to Prepare the High Performance Pd(OH)2/C for C–N Bond Cleavage
The debenzylation reaction of hexabenzylhexaazaisowurtzitane (HBIW) and 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazaisowurtzitane (TADBIW) to synthesize 2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (TAIW) is the major challenge in the production of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW). This is primarily attributed to the reaction needing a lot of palladium catalysts, which tend to deactivate rapidly during the process. In this work, a series of Pd(OH)2/C catalysts were successfully prepared through a convenient deposition-precipitation method by controlling the flow rate of the PdCl2 solution. Employing the 10% Pd(OH)2/C–F0.5 sample, the debenzylation reaction was successfully completed with a lower usage of Pd and shorter time of reaction. For the HBIW debenzylation reaction, the yield of TADBIW was 87.4% at low temperature (25 °C) when 1‰ Pd/HBIW was used, and the higher yield was 89.8% at high temperature (45 °C) when 3‰ Pd/HBIW was used. The TADBIW/Pd/h values of them were 42.5 and 95.7, respectively. For the TADBIW debenzylation reaction, the complete conversion of the reactant was realized when Pd/TADBIW was 2‰. The value of TAIW/Pd/h was 154.6 when Pd/TADBIW was 4‰, which was higher than the reports. Compared to the reported catalysts, the dosage of Pd used in the debenzylation reactions of HBIW and TADBIW was significantly decreased. Furthermore, the 10% Pd(OH)2/C–F0.5 sample was recycled six times with similar performance, demonstrating excellent stability. Based on the analysis of characterization results, it is effortless to find that the flow rate of the PdCl2 solution plays a key role in controlling the adsorption behavior of palladium species on activated carbon. The lower flow rate is beneficial to obtaining Pd nanoparticles with a smaller size, a higher proportion of Pd2+, and a higher metal distribution. This study may provide a simple way to develop palladium catalysts with high performance for related applications.
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