Phenol Hydroxylation over Cu-Containing LDHs and Their Calcined Forms: Profound Cobivalent Metal Influence
Phenol Hydroxylation over Cu-Containing LDHs and Their Calcined Forms: Profound Cobivalent Metal Influence
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DOI：
10.1021/ie100399j
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发表时间：
2010-07-07
影响因子：
4.2
通讯作者：
Kannan, S.
中科院分区：
文献类型：
--
作者：
Antonyraj, Churchil A.;Gandhi, Mohini;Kannan, S.
以（Cu+M（II））/Al原子比为3.0，合成了含铜的层状双氢氧化物（LDHs），其中Cu沿着含量小于1原子%，并含有不同的二价离子，如镁、锌、镍或钴。这些材料的煅烧提供了没有任何离散氧化铜相的混合金属氧化物（在此称为CLDH），如通过PXRD和STEM分析所证实的。以苯酚为原料，采用羟基化法合成邻苯二酚（CAT）和对苯二酚（HQ）。在共二价离子中，合成态和煅烧态的含锌样品均显示出非常高的活性，而钴显示出最低活性。CuZnAl三元体系（0.009原子%至0.056原子%）的铜含量的变化显示具有0.038原子%（CuZnAl-5-CLDH）的样品的最大活性。高活性是由于更好的分散孤立的铜物种推断通过TPR测量。高活性的CuZnAl-5-CLDH可以重复使用多达三个循环，而活性没有任何显著变化。当反应在CuZnAl-5-CLDH上放大到200倍时，没有注意到转化率的显著变化，这使得有希望将其探索到下一个水平。
Copper containing layered double hydroxides (LDHs) with less than 1 atom % Cu along with different cobivalent ions such as magnesium, zinc, nickel or cobalt at (Cu+M(II))/Al atomic ratio 3.0 were synthesized. Calcination of these materials offered mixed metal oxides (refereed here as CLDHs) without any discrete copper oxide phase as confirmed by PXRD and STEM analysis. Hydroxylation of phenol to catechol (CAT) and hydroquinone (HQ) was carried out over both as-synthesized and calcined materials. Among the cobivalent ions, zinc containing samples both in the as-synthesized and calcined forms showed very high activity while cobalt showed the minimum. Variation of copper content for CuZnAl ternary system (0.009 atom % to 0.056 atom %) showed a maximum activity for the sample with 0.038 atom % (CuZnAl-5-CLDH). High activity was attributed to better dispersion of isolated copper species as inferred through TPR measurements. Highly active CuZnAl-5-CLDH can be reused up to three cycles without any significant change in the activity. No significant variation in the conversion was noted when the reaction was scaled up to 200 times over CuZnAl-5-CLDH renders the promise of exploring it to the next level.