Carbon supports have been shown to provide better hydrothermal stability than alumina or silica supports, thus attracting more attention for aqueous-phase biomass conversion reactions. However, sintering and leaching of the metal particles still occur during condensed phase utilization of carbon supported metal catalysts. To further improve the stability of supported metal particles, a simple nitrogen-doped carbon coated SBA-15 was synthesized and systematically characterized. Better stability of supported Pd particles was found from nitrogen incorporation into the carbon support during extended hydrothermal treatment or under continuous flow reaction conditions. With these materials, leaching was negligible and sintering was suppressed. Based on solid-state ¹⁵N and ¹³C NMR analysis before and after hydrothermal treatment, the improved dispersion and stability from nitrogen doping was ascribed to pyridine, pyrrole, and imidazolium groups. Relatively small carbon fragments resulting from nitrogen incorporation rendered more silica exposure to water and concomitant hydrolysis, but the stability and activity of Pd particles were preserved. The Pd stability advantage was also observed on nitrogen-doped carbon coatings of silica gel and CMK-3 supports. The enhanced stability of Pd particles on different nitrogen-doped carbon materials was correlated with the synergistic effect of oxygen and nitrogen heteroatoms and the formation of a decorative carbon overlayer on the Pd particles.

中文翻译：

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掺氮碳载体上钯纳米颗粒的水热稳定性提高†

碳载体已显示出比氧化铝或二氧化硅载体更好的水热稳定性，因此引起了水相生物质转化反应的更多关注。然而，在碳载金属催化剂的冷凝相利用期间，仍然发生金属颗粒的烧结和浸出。为了进一步提高负载金属颗粒的稳定性，合成了简单的氮掺杂碳包覆的SBA-15并对其进行了系统表征。在延长的水热处理过程中或在连续流动反应条件下，将氮掺入碳载体中，发现负载的Pd颗粒具有更好的稳定性。使用这些材料，浸出可以忽略不计并且烧结被抑制。基于固态¹⁵ N和¹³水热处理前后的13 C NMR分析表明，氮掺杂改善的分散性和稳定性归因于吡啶，吡咯和咪唑鎓基团。氮掺入产生的相对较小的碳碎片使更多的二氧化硅暴露于水并伴随水解，但保留了Pd颗粒的稳定性和活性。在硅胶和CMK-3载体的氮掺杂碳涂层上也观察到Pd的稳定性优势。Pd颗粒在不同的氮掺杂碳材料上增强的稳定性与氧和氮杂原子的协同作用以及在Pd颗粒上形成装饰性碳覆盖层有关。