Using the “memory effect” of hydrotalcites for improving the catalytic reduction of nitrates in water
Using the “memory effect” of hydrotalcites for improving the catalytic reduction of nitrates in water
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DOI：
10.1016/j.jcat.2003.07.013
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发表时间：
2004
影响因子：
7.3
通讯作者：
A. E. Palomares;J. G. Prato;F. Rey;A. Corma
中科院分区：
文献类型：
--
作者：
A. E. Palomares;J. G. Prato;F. Rey;A. Corma
研究了载体在PdCu/Mg/Al水滑石催化硝酸盐液相加氢中的作用。通过x射线衍射、红外光谱、元素分析和表面积对材料进行了表征。研究表明，通过引入活性载体的新概念，使用煅烧水滑石作为载体减少了PdCu/Al2O3上观察到的传质限制相关问题。在这种情况下，利用煅烧水滑石的“记忆效应”，硝酸盐被迫位于带正电的水滑石层之间，因此靠近还原活性位点。硝酸盐被还原为亚硝酸盐，亚硝酸盐保持在相同的位置，这些亚硝酸盐进一步被还原为氮，或者在更低的程度上被还原为氨。由于电荷不足，这些最终化合物被释放到溶液中，减少了与扩散限制有关的问题，这些问题强烈影响反应的选择性。用不同的表征技术分别研究了吸附和反应步骤，证明了这一点。
The role of the support in the catalytic hydrogenation of nitrates in the liquid phase using a PdCu/Mg/Al hydrotalcite is studied. The material has been characterized by X-ray diffraction, infrared spectroscopy, elemental analysis, and surface area. It is shown that the use of calcined hydrotalcites as support reduces the problems associated with mass transfer limitations observed on PdCu/Al2O3, by introducing a new concept of active supports. In this case by taking advantage of the “memory effect” of calcined hydrotalcites, the nitrates are forced to be located between the positively charged layers of the hydrotalcite and therefore close to the reductive active sites. The nitrates are reduced to nitrites that remain in the same position, and these are further reduced to nitrogen or in a much lower extent to ammonia. These final compounds due to their inadequate charge are released to the solution, reducing the problems related with diffusion limitations that strongly affect the selectivity of the reaction. This has been proved by studying separately the adsorption and reaction steps with different characterization techniques.