Mechanisms of catalytic cleavage of benzyl phenyl ether in aqueous and apolar phases
Mechanisms of catalytic cleavage of benzyl phenyl ether in aqueous and apolar phases
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DOI：
10.1016/j.jcat.2013.10.024
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发表时间：
2014-03-01
影响因子：
7.3
通讯作者：
Lercher, Johannes A.
中科院分区：
文献类型：
--
作者：
He, Jiayue;Lu, Lu;Lercher, Johannes A.
探讨了镍基催化剂和沸石基催化剂在液相中裂解苯并苯基醚（BPE）中醚键的催化途径。在没有催化剂的情况下，C-O键在水中被选择性水解，形成苯酚和苯甲醇作为中间体，然后烷基化。催化反应的水合氢离子是由水在523k下的解离提供的。加入HZSM-5后，水解和烷基化的速率随质子浓度的增加而显著增加。在Ni/SiO2存在下，c-脂肪- o键的裂解以选择性氢解为主。在双官能团Ni/HZSM-5的催化下，氢解是主要途径而非水解（次要途径）。在极性十一烷中，非催化热裂解途径占主导地位。在Ni/SiO2或Ni/HZSM-5的存在下，BPE的氢解反应是十一烷的主要反应途径，几乎完全抑制了自由基反应。密度泛函理论（DFT）计算有力地支持了在水相和极性相中BPE的C-O键裂解机制。这些计算表明，BPE最初是质子化的，随后在水相中水解。DFT计算表明，非极性溶剂中的自由基反应导致十一烷产生伯苄基和苯氧基自由基，只要不存在提供解离氢的金属，就会导致更重的缩合产物。(C) 2013爱思唯尔公司版权所有。
Catalytic pathways for the cleavage of ether bonds in benzyl phenyl ether (BPE) in liquid phase using Ni- and zeolite-based catalysts are explored. In the absence of catalysts, the C-O bond is selectively cleaved in water by hydrolysis, forming phenol and benzyl alcohol as intermediates, followed by alkylation. The hydronium ions catalyzing the reactions are provided by the dissociation of water at 523 K. Upon addition of HZSM-5, rates of hydrolysis and alkylation are markedly increased in relation to proton concentrations. In the presence of Ni/SiO2, the selective hydrogenolysis dominates for cleaving the C-aliphatic-O bond. catalyzed by the dual-functional Ni/HZSM-5, hydrogenolysis occurs as the major route rather than hydrolysis (minor route). In apolar undecane, the non-catalytic thermal pyrolysis route dominates. Hydrogenolysis of BPE appears to be the major reaction pathway in undecane in the presence of Ni/SiO2 or Ni/HZSM-5, almost completely suppressing radical reactions. Density functional theory (DFT) calculations strongly support the proposed C-O bond cleavage mechanisms on BPE in aqueous and apolar phases. These calculations show that BPE is initially protonated and subsequently hydrolyzed in the aqueous phase. DFT calculations suggest that the radical reactions in non-polar solvents lead to primary benzyl and phenoxy radicals in undecane, which leads to heavier condensation products as long as metals are absent for providing dissociated hydrogen. (C) 2013 Elsevier Inc. All rights reserved.