Why is metallic Pt the best catalyst for methoxy decomposition?

Synergetic Behavior of TiO2‐Supported Pd(z)Pt(1−z) Catalysts in the Green Synthesis of Methyl Formate

“…From the literature, one might analyze some key factors on the subject and thus try to correlate them with the behavior of the TiO 2 ‐supported Pd( z )Pd(1− z ) catalysts nonetheless. Particularly, DFT calculations have shown that the energy of adsorption of CH 3 O over Pt(1 1 1) is lower, −1.80 eV, compared with that over Pd(1 1 1), −1.99 eV . This implies that platinum is more effective than palladium for CH 3 O ads decomposition; a fact that is in agreement with the catalytic trends presented herein.…”

“…Particularly,D FT calculations have shown that the energy of adsorptiono fC H 3 Oo ver Pt(111)i sl ower, À1.80 eV, compared with that over Pd(111), À1.99 eV. [61] This implies that platinum is more effective than palladium for CH 3 O ads decomposition; af act that is in agreementw ith the catalytic trends presented herein.I na ddition, Ren et al [61] also showed that CH 3 Oi sp referentially adsorbed on af ace-centered cubic (fcc)h 2 (C,O) configurationo nP t(111), that is, with the oxygen www.chemcatchem.org bound to one Pt atom, whereas an h 1 (O) configuration, in which the oxygen atom of CH 3 Oi st riply bound to the surface and at shorter distance compared with the fcc-h 2 (C,O) configuration, is favored for CH 3 Oa dsorption on Pd(111). The reactivity of methanol over the bimetallicc atalysts would be given by acompetition between both mechanisms and by acompetitive adsorption and transformation of the reactioni ntermediates over the availables urface palladiuma nd platinum atoms.…”

“…This implies that platinum is more effective than palladium for CH 3 O ads decomposition; a fact that is in agreement with the catalytic trends presented herein. In addition, Ren et al . also showed that CH 3 O is preferentially adsorbed on a face‐centered cubic (fcc)‐η 2 (C,O) configuration on Pt(1 1 1), that is, with the oxygen bound to one Pt atom, whereas an η 1 (O) configuration, in which the oxygen atom of CH 3 O is triply bound to the surface and at shorter distance compared with the fcc‐η 2 (C,O) configuration, is favored for CH 3 O adsorption on Pd(1 1 1).…”

From Static to Reacting Systems on Transition-Metal Surfaces

“…CO þ 2H 2 , which may take place parallel with MSR, is an endothermic process with the reaction enthalpy DH ¼ 91 kJ mol À1 . The activation energy of the second dehydrogenation step of CH 3 O to formaldehyde also appears to be high, [187][188][189][190][191]193,194 and in many studies it is concluded to be the rate-limiting step of the reaction. Note that methanol and formaldehyde are often weakly bound to the metal substrate and may desorb from the surface before reacting.…”

“…In fact, as shown in Section 7.18.3.4, these two reactions have the same rate-limiting steps, methanol dehydrogenation to formaldehyde through CH 3 O or CH 2 OH. In Gu and Li 189 also the alternative path of formaldehyde formation through CH 2 OH was predicted to be unfavorable due to 12 kJ mol À1 higher activation energy of the first dehydrogenation step than in the case of CH 3 187,188,195 However, while CHO is a strongly adsorbed species, E ads ¼ 111-167 kJ mol À1 , 187,189,192,195 formaldehyde is prone to desorb, [187][188][189][190]192,[194][195][196] E ads ¼ 1-17 kJ mol À1 before further dehydrogenation. Thus, their adsorption energies are also important to determine the reactivity of a given surface.…”