Mechanistic Insights into Solution-Phase Oxidative Esterification of Primary Alcohols on Pd(111) from First-Principles Microkinetic Modeling

Abstract

We present an ab initio microkinetic model for the oxidative esterification of 1-propanol to methyl propionate over Pd(111). The model fully accounts for solvation of solution-phase species and added catalytic base and provides key insights into the factors that limit the activity of unpromoted Pd aerobic oxidation catalysts. In particular, we find that the activity is limited by the large steady-state surface H coverage, which destabilizes other adsorbed intermediates via lateral interactions, and substantial barriers governing the formation of O−H bonds, which is required for the reduction of O 2 and removal of H byproducts from the catalyst surface.

Quantized Electrodes: Atomic Palladium and Gold in Polyaniline

“…DFT calculations were performed to compute the binding energies of hydroxyl radicals with the Pd m Au n /Em(base) model catalyst structures. Hydroxyl radical was chosen due to both the presumed generation of these species (Eq 1) during the anodic sweep (Figure 6, point 1) and because of the demonstrated importance of surface oxygen promotors in the elementary bond scission during alcohol oxidation [43] . Calculations were performed for the four atomic metal catalysts PdPdAu, PdAuPd, AuPdAu, and PdPdPd.…”

“…[37,38] This is a relatively complex electrochemical reaction that has been studied on bare solid electrodes, [38,39] on activated carbon electrode, [40] and also on Pt electrodes coated with a thin layer of polyaniline (PANI). [24,41] We note that recent ab initio studies have elucidated alcohol oxidation mechanisms on model heterogeneous catalysts, [42][43][44] but it is unknown how mechanisms are altered for the Pd m Au n catalysts in presence of the PANI support. While oxidation of all lower aliphatic alcohols up to butanol have been studied, [16][17][18][19][20]24] only oxidation of npropanol is discussed here for particular electrocatalysts of structure Pd m Au n /PANI/Pt for (m + n = 3).…”

“…Hydroxyl radical was chosen due to both the presumed generation of these species (Eq 1) during the anodic sweep (Figure 6, point 1) and because of the demonstrated importance of surface oxygen promotors in the elementary bond scission during alcohol oxidation. [43] Calculations were performed for the four atomic metal catalysts PdPdAu, PdAuPd, AuPdAu, and PdPdPd. Figure 8 compares the experimental catalytic activity from Jonke et al [22] vs the hydroxyl radical binding energy for the model catalyst structures.…”

Photocatalytic hot-carrier chemistry

“…For example, selective oxidation of primary alcohol to aldehyde with ambient-pressure oxygen molecules (O 2 ) is kinetically difficult at room temperature, although it is thermodynamically spontaneous (or exergonic). 15 The slow oxidation kinetics can be overcome in the presence of silica-supported platinum (Pt) nanocrystals under photoillumination. 16 Photoexcitation of the Pt nanocrystals generates hot electrons that are injected into O 2 adsorbed on the Pt surface, leading to the formation of freestanding superoxide radicals (O 2…”

Plasmon‐Induced Radical‐Radical Heterocoupling Boosts Photodriven Oxidative Esterification of Benzyl Alcohol over Nitrogen‐Doped Carbon‐Encapsulated Cobalt Nanoparticles

“…Directly heating the metal‐based catalysts without light irradiation can generate oxygen‐containing free radicals (e.g. ⋅O 2 − , ⋅OH), which facilitate the dehydrogenation of the alcohol and oxidative cleavage of C−S bonds [11–13] . When metals are exposed to light irradiation, the excited plasmons on the metal surface can activate target molecules in organic synthesis, leading to the generation of corresponding free radicals [14] .…”