Dehydrogenation of Methanol by Vanadium Oxide and Hydroxide Cluster Cations in the Gas Phase
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- 作者：Sandra Feyel ; Ludwig Scharfenberg ; Charles Daniel ; Hans Hartl ; Detlef Schrö ; der ; Helmut Schwarz
- 刊名：Journal of Physical Chemistry A
- 出版年：2007
- 出版时间：May 3, 2007
- 年：2007
- 卷：111
- 期：17
- 页码：3278 - 3286
- 全文大小：233K
- 年卷期：v.111,no.17(May 3, 2007)
- ISSN：1520-5215
文摘
Bare vanadium oxide and hydroxide cluster cations, VmOn+ and VmOn-1(OH)+ (m = 1-4, n = 1-10), generatedby electrospray ionization, were investigated with respect to their reactivity toward methanol using massspectrometric techniques. Several reaction channels were observed, such as abstraction of a hydrogen atom,a methyl radical, or a hydroxymethyl radical, elimination of methane, and adduct formation. Moreover,dehydrogenation of methanol to generate formaldehyde was found to occur via four different pathways.Formaldehyde was released as a free molecule either upon transfer of two hydrogen atoms to the cluster orupon transfer of an oxygen atom from the cluster to the neutral alcohol concomitant with elimination ofwater. Further, formaldehyde was attached to VmOn+ upon loss of H2 or neutral water to produce the cationVmOn(OCH2)+ or VmOn-1(OCH2)+, respectively. A reactivity screening revealed that only high-valent vanadiumoxide clusters are reactive with respect to H2 uptake, oxygen transfer, and elimination of H2O, whereas smallerand low-valent cluster cations are capable of dehydrogenating methanol via elimination of H2. For comparison,the reactivity of methanol with the corresponding hydroxide cluster ions, VmOn-1(OH)+, was studied also,for which dominant pathways lead to both condensation and association products, i.e., generation of the ionsVmOn-1(OCH3)+ and VmOn-1(OH)(CH3OH)+, respectively.