Partial oxidation of hydrocarbons on nickel: from surface science mechanistic studies to catalysis1Presented at the 9th International Symposium on Relations Between Homogeneous and Heterogeneous Catalysis.1

Thermal chemistry of diiodomethane on Ni(110) surfaces II. Effect of coadsorbed oxygen

“…Since experiments with CD 2 I 2 result in the desorption of large quantities of D 2 O and HDO, it is clear that at least some of the hydrogen atoms required to hydrogenate surface oxygen to OH ads originate from dehydrogenation of methylene groups. In fact, hydroxide surface groups have been previously shown to facilitate both oxygen insertion and b-hydride elimination steps [9,35,36,38]. Similar chemistry has also been reported for both water [43,44] and ammonia [73,74] coadsorbed with oxygen on nickel surfaces.…”

“…Moreover, both passivation of the surface and formaldehyde formation have been reported for methylene on oxygen-treated Rh-(1 1 1) [26,31], Pd(1 0 0) [32], and Ru(0 0 1) [33]. On Ni(1 0 0), past work in our lab has highlighted the ease with which oxygen atoms are inserted into metal-alkyl bonds [34][35][36][37][38]. Here, the results of temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) studies on the thermal chemistry of diiodomethane moieties with oxygen on Ni(1 1 0) are discussed.…”

Bond Forming Reactions Involving C1 Moieties: Late Versus Early Transition Metal Surfaces

“…With methyl groups, on the other hand, formaldehyde formation is significantly more facile, and must therefore involve an initial oxygen insertion into the nickel-methyl bond (followed by b-hydride elimination) rather than the reverse sequence, methyl dehydrogenation to methylene followed by oxygen insertion into the nickel-methylene bond [63]. The ease with which the oxygen insertion step takes place, as implied here, has also been documented by us on Ni(100) [67][68][69][70][71], in that case by using branched alkyl groups to produce ketones (which are more stable and do not rapidly decompose further upon their formation). It should also be pointed out that an alternative alkyl-oxygen bond formation mechanism via an Eley-Rideal step involving gas-phase methyl radicals has been reported on Mo(110) [51,72].…”

Catalytic Partial Oxidation of Methanol and Ethanol for Hydrogen Generation

“…Zaera and collaborators [102] studied the mechanism of partial oxidation of methanol on a nickel (100) wire. This reaction mechanism is related to the oxygen coverage of the Ni surface.…”