Pd on carbon nanotubes for liquid phase alcohol oxidation
Pd on carbon nanotubes for liquid phase alcohol oxidation
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DOI：
10.1016/j.cattod.2009.06.009
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发表时间：
2010-02
期刊：
影响因子：
5.3
通讯作者：
A. Villa;Di Wang;N. Dimitratos;D. Su;V. Trevisan;L. Prati
中科院分区：
文献类型：
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作者：
A. Villa;Di Wang;N. Dimitratos;D. Su;V. Trevisan;L. Prati
在苯甲醇液相氧化制苯甲醛过程中，碳纳米管负载的钯纳米粒子比活性炭负载的钯纳米粒子具有更高的选择性。在无溶剂条件下，Pd/CNTs的选择性显著提高，而使用Pd/AC时，苯甲醛发生了相当大的过氧化。与其他溶剂不同，环己烷对两种催化剂对苯甲醛的选择性都有显著提高。通过透射电子显微镜的表征揭示了钯/AC和钯/碳纳米管之间金属分散的差异，这可归因于活性炭和碳纳米管之间的结构、化学和物理差异。与碳纳米管相比，钯在AC上的活性更高，这可归因于第一种情况下钯的分散性得到改善。在循环使用时，Pd/CNTs比Pd/AC更稳定（7次循环损失50%的活性），甚至反应后催化剂的结构也发生了变化。钯的浸出和粒子聚结是导致活性丧失的主要原因。钯纳米颗粒与金的合金化可以显著提高催化剂的寿命。当使用碳纳米管作为载体时，可以极大地限制钯的强浸出，并且活性/选择性至少保持8次。
Pd nanoparticles supported on carbon nanotubes (CNTs) showed a higher selectivity than Pd nanoparticles supported on activated carbon (AC) in the liquid phase oxidation of benzylic alcohol to benzaldehyde. Under solventless conditions a significant improvement in selectivity was observed for Pd/CNTs, whereas using Pd/AC a considerable over-oxidation of benzaldehyde was observed. Differently from other solvents cyclohexane improved significantly the selectivity to benzaldehyde for both catalysts. Characterisation by means of transmission electron microscopy revealed differences in metal dispersion between Pd/AC and Pd/CNTs that can be ascribed to textural, chemical and physical differences between active carbon and carbon nanotubes. The higher activity in the case of Pd on AC than on CNTs can be attributed to the improved Pd dispersion in the first case. On recycling Pd/CNTs resulted more stable (activity loss 50% in 7 runs) than Pd/AC (activity loss 70% in 7 runs) even a structural change of catalysts after reaction is observed. The Pd leaching and particle coalescence are the main reasons for the loss of activity. An extraordinary improving of catalyst life has been observed by alloying the Pd nanoparticles with Au, When CNTs are used as support the strong Pd leaching can be greatly limited and the activity/selectivity maintained at least for 8 runs.