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甲烷是一种在自然界中大量存在的原材料,在取代原油和合成重要化工产品等许多领域具有潜在的应用价值.然而,由于CH4中C–H键的键能特别大(约~4.5 eV),如何实现甲烷的绿色有效转化在化学化工领域仍然是一个挑战.本文采用密度泛函理论对Co3O4(001)和(011)晶面活化甲烷C–H键的机理进行了理论研究,得到了如下结论:(1)CH4的C–H键在Co3O4晶面的解离具有很高的活性,只需要克服大约1 eV的能垒;(2)与Co2+相连的Co–O离子对是CH4活化的活性位点,其中两个带正负电荷的离子对C–H解离起着协同作用,帮助产生Co–CH3和O–H物种;(3)(011)面的反应活性明显大于(001)面,与实验的观察一致.本文的计算结果表明,Co3O4纳米晶面对CH4中C–H键的活化表现出明显的晶面效应和结构敏感效应,Co?O离子对活性中心对于活化惰性的C–H键发挥了关键作用.
Methane is a kind of raw material that exists in a large amount in nature and has potential applications in many fields, such as replacing crude oil and synthesizing important chemical products, etc. However, since the bond energy of C-H bond in CH4 is particularly large (about 4.5 eV) How to realize the green and effective conversion of methane is still a challenge in the field of chemical engineering.In this paper, the mechanism of activating methane C-H bond of Co3O4 (001) and (011) planes by using density functional theory is studied theoretically, and the following conclusions are obtained : (1) The C-H bond of CH4 is highly active in the dissociation of the Co3O4 crystal plane and only needs to overcome the energy barrier of about 1 eV. (2) The Co-O ion pair linked to Co2 + is the activity of CH4 activation Sites, of which two positively and negatively charged ions act synergistically with C-H dissociation to help produce Co-CH3 and O-H species; (3) the reactivity of (011) plane is significantly greater than that of (001) , Consistent with the experimental observations.The calculation results show that the Co3O4 nanocrystal surface on the C-H bond CH4 CH4 activation showed significant crystal face-effect and structure-sensitive effect, Co? O ion pair active center for activation of inert C -H key has played a key role.