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Performance of edges on carbon for the catalytic hydroxylation of benzene to phenol†
Catalysis Science & Technology ( IF 5 ) Pub Date : 2017-11-01 00:00:00 , DOI: 10.1039/c7cy01648d
Ya-Jing Lyu 1, 2, 3, 4, 5 , Ting Qi 4, 5, 6, 7 , Hua-Qing Yang 4, 5, 6, 7 , Chang-Wei Hu 1, 2, 3, 4, 5
Affiliation  

Carbon catalyst is regarded as an efficient and environment-friendly material for the direct oxidation of benzene to phenol. However, the essence and detailed performances of the active sites are still unclear at the molecular level. In the present study, the role of typical defect sites on carbon for benzene hydroxylation to phenol with hydrogen peroxide as the oxidant was theoretically investigated at M06-2x/6-311++G(d, p) level in acetonitrile solution. The carbon with defect sites was modeled with armchair and zigzag edges. The turnover frequency analysis indicated that the rate-controlling step was associated with the HO–OH bond cleavage in the H2O2 moiety for the formation of hydroxyl radical. For both the armchair and zigzag edges on carbon material, the defect site plays an essential role in the hydroxyl radical formation from H2O2. In the presence of water, the defect site of carbon could readily be hydrated, where the zigzag defect site could be more easily hydrated to hydroquinone than the defect armchair site. Furthermore, the zigzag defect carbon exhibits better catalytic performance than the armchair defect carbon. Based on activation strain analysis, there is a stronger stabilizing transition state interaction in the zigzag defect carbon than that in the defect armchair carbon, which arises from a narrower HOMO–LUMO gap. The present study could shed some light on the essence and function of active sites on carbon for the benzene hydroxylation to phenol.

中文翻译:

碳边缘对苯催化羟基化为苯酚的性能

碳催化剂被认为是将苯直接氧化为苯酚的有效且环境友好的材料。但是,活性位点的本质和详细性能在分子水平上仍不清楚。在本研究中,从理论上研究了乙腈溶液中M06-2x / 6-311 ++ G(d,p)浓度下典型缺陷位点对过氧化氢作为氧化剂将苯羟基化为苯酚的碳的作用。用扶手椅和锯齿形边缘对带有缺陷部位的碳进行建模。周转频率分析表明,速率控制步骤与H 2 O 2中HO-OH键的裂解有关用于形成羟基的部分。对于碳材料上的扶手椅和锯齿形边缘,缺陷部位在由H 2 O 2形成的羟基自由基中起着至关重要的作用。。在水的存在下,碳的缺陷位点很容易被水合,而之字形缺陷位点比缺陷扶手椅位点更容易被水合为对苯二酚。此外,之字形缺陷碳表现出比扶手椅缺陷碳更好的催化性能。根据活化应变分析,之字形缺陷碳中的稳定过渡态相互作用比缺陷扶手椅碳中的稳定过渡态相互作用强,这是由于HOMO-LUMO间隙变窄所致。本研究可能为苯上的羟基化为苯酚的碳上的活性位点的本质和功能提供一些启示。
更新日期:2017-11-01
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