Deoxygenation mechanisms on Ni-promoted MoS2 bulk catalysts: A combined experimental and theoretical study
Deoxygenation mechanisms on Ni-promoted MoS2 bulk catalysts: A combined experimental and theoretical study
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DOI：
10.1016/j.jcat.2011.10.022
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发表时间：
2012-02-01
影响因子：
7.3
通讯作者：
Raybaud, P.
中科院分区：
文献类型：
--
作者：
de Brimont, M. Ruinart;Dupont, C.;Raybaud, P.
通过结合实验和密度泛函研究，我们研究了三种相关的非负载（本体）过渡金属硫化物催化剂：MoS2，Ni3S2和Ni促进的MoS2（具有不同的Ni/Mo比）催化庚酸乙酯的脱氧反应.两种途径竞争该反应：加氢脱氧（HDO）和脱羧/脱羰基（DCO）。实验表明，Ni的存在下，无论是在NiMoS混合相或在Ni的单硫化物相可以改变HDO和DCO途径之间的选择性。为了了解这种选择性的起源，我们研究了两个相关中间体的脱氧途径：羧酸和醛。特别是，DFT计算强调，醛脱羰发生通过其脱氢成烷酰基和/或烯酮中间体的Ni3S2（111）表面上。这些途径被发现是更有利的Ni3S2比MoS2为基础的催化剂。这一趋势是由于Ni3S2（111）上Ni-3三角形小面的存在促进了不饱和烷酰基和/或烯酮中间体以及CO产物的形成。最后，我们提出了一个详细的分析Ni对MoS2的促进作用，当存在于NiMoS结构。(C)2011 Elsevier Inc. All rights reserved.
Through a combined experimental and density functional study, we investigate the deoxygenation of ethyl heptanoate catalyzed by three relevant unsupported (bulk) transition metal sulfide catalysts: MoS2, Ni3S2 and Ni-promoted MoS2 (with various Ni/Mo ratio). Two pathways compete for this reaction: hydrodeoxygenation (HDO) and decarboxylation/decarbonylation (DCO). It is shown experimentally that the presence of Ni either in the NiMoS mixed phase or in the Ni monosulfide phase may change the selectivity between the HDO and DCO pathway. To understand the origin of this selectivity, we study the deoxygenation pathways of two relevant intermediates: carboxylic acid and aldehyde. In particular, DFT calculations highlight that the aldehyde decarbonylation occurs via its dehydrogenation into the alkanoyl and/or ketene intermediates on the Ni3S2 (111) surface. These pathways are found to be more favorable on Ni3S2 than on MoS2-based catalysts. This trend is explained by the presence of Ni-3 triangular facets on Ni3S2 (111) enhancing the formation of the unsaturated alkanoyl and/or ketene intermediates as well as the CO product. We finally propose a detailed analysis of the promoting effect of Ni on MoS2, when present in the NiMoS structure. (C) 2011 Elsevier Inc. All rights reserved.