Mechanistic Complexity of Methane Oxidation with H(2)O(2) by Single-Site Fe/ZSM-5 Catalyst.
Mechanistic Complexity of Methane Oxidation with H(2)O(2) by Single-Site Fe/ZSM-5 Catalyst.
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DOI：
10.1021/acscatal.8b01672
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发表时间：
2018-09-07
期刊：
影响因子：
12.9
通讯作者：
Pidko EA
中科院分区：
文献类型：
--
作者：
Szécsényi Á;Li G;Gascon J;Pidko EA
采用周期密度泛函理论（DFT）方法研究了Fe/ZSM-5分子筛中Fe位上H2 O2氧化甲烷的反应机理.初始Fe位被模拟为[（H2O）2-Fe（III）-（μO）2-Fe（III）-（H2O）2]2+骨架外原子簇沉积在沸石孔中，并由两个阴离子晶格位进行电荷补偿。该簇与H2 O2的活化引起形成的各种Fe（III）-氧代和Fe（IV）-氧代络合物的潜在反应对甲烷解离。这些位点都能通过以下三种可能的反应机制促进甲烷中第一个C-H键的断裂：（a）异裂甲烷解离和（B）均裂甲烷解离以及（c）以自由OH自由基为催化物种的Fenton型反应。C-H活化步骤之后是MeOH和MeOH的形成和活性位点的再生。芬顿型路径被发现进行最低的激活势垒。尽管发现替代异裂和均裂途径的障碍略高，但它们仍然是相当有利的，并且预计在反应条件下是可行的，最终产生MeOH和MeOH产物。H2 O2氧化剂与CH 4底物竞争相同的位点。由于H2 O2氧化成O2和两个[H+]在能量上比C-H氧代官能化更有利，后一目标方法的总体效率仍然较低。
Periodic density functional theory (DFT) calculations were carried out to investigate the mechanism of methane oxidation with H2O2 over the defined Fe sites in Fe/ZSM-5 zeolite. The initial Fe site is modeled as a [(H2O)2–Fe(III)–(μO)2–Fe(III)–(H2O)2]2+ extraframework cluster deposited in the zeolite pore and charge-compensated by two anionic lattice sites. The activation of this cluster with H2O2 gives rise to the formation of a variety of Fe(III)-oxo and Fe(IV)-oxo complexes potentially reactive toward methane dissociation. These sites are all able to promote the first C–H bond cleavage in methane by following three possible reaction mechanisms: namely, (a) heterolytic and (b) homolytic methane dissociation as well as (c) Fenton-type reaction involving free OH radicals as the catalytic species. The C–H activation step is followed by formation of MeOH and MeOOH and regeneration of the active site. The Fenton-type path is found to proceed with the lowest activation barrier. Although the barriers for the alternative heterolytic and homolytic pathways are found to be somewhat higher, they are still quite favorable and are expected to be feasible under reaction conditions, resulting ultimately in MeOH and MeOOH products. H2O2 oxidant competes with CH4 substrate for the same sites. Since the oxidation of H2O2 to O2 and two [H+] is energetically more favorable than the C–H oxofunctionalization, the overall efficiency of the latter target process remains low.
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影响因子：
4.5
作者：
Hammond, Ceri;Hermans, Ive;Dimitratos, Nikolaos
通讯作者：
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影响因子：
12.9
作者：
Hammond, Ceri;Dimitratos, Nikolaos;Hutchings, Graham J.
通讯作者：
Hutchings, Graham J.
影响因子：
12.9
作者：
Hammond, Ceri;Dimitratos, Nikolaos;Hutchings, Graham J.
通讯作者：
Hutchings, Graham J.
影响因子：
2.9
作者：
Belanzoni, Paola;Bernasconi, Leonardo;Baerends, Evert Jan
通讯作者：
Baerends, Evert Jan
DOI：
10.1039/ct9028100535
发表时间：
1902-01-01
期刊：
JOURNAL OF THE CHEMICAL SOCIETY
影响因子：
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作者：
Bone, WA;Wheeler, RV
通讯作者：
Wheeler, RV