02902nas a2200289   4500008004100000022001400041245012300055210006900178260000800247300001100255490000800266520195400274653001802228653000802246653003102254653001302285653002902298653001902327100001902346700002202365700001902387700002302406700001602429700001902445700001802464856013002482       2025                        eng d  a1385-894700aFacet dependence for solvent-modulated proton-coupled electron transfer in furfural acetalization on Pd nanostructures0 aFacet dependence for solventmodulated protoncoupled electron tra  cJUN  a1631590 v5143 a<p>
	Furfural dialkyl acetals prepared via acetalization reaction of furfural and alcohols are promising biofuels. Using defined experiments and density functional theory (DFT) simulations, the structure-dependent activity and selectivity for furfural acetalization reaction in the presence of alcohols (methanol, ethanol, propanol and butanol) as solvents was studied over well-defined supported Pd nanostructures (octahedra (111), cubes (100) and spheres (both (111) and (100)). Pd cubes supported over TiO2 in the presence of ethanol as a solvent (at 303 K and balloon pressure H-2) exhibited 78 % conversion and 100 % selectivity for furfural diethyl acetal product in a short time (similar to 180 min). In contrast, Pd octahedra (111) and Pd spheres showed low conversions (18 % and 6 %) at the same reaction conditions. Interestingly, when used as a solvent, methanol showed the highest conversion (90 %) and selectivity (100 %) for furfural acetalization over Pd cubes. DFT simulations provided mechanistic insight into the reactivity of the two different Pd facets (111) and (100) in the presence of alcohol molecules towards furfural acetalization reaction. A three-step reaction mechanism was proposed for furfural acetalization with alcohols: (i) alcohol hydroxyl-dehydrogenation (ii) hydrogenation of furfural carbonyl oxygen, and (iii) formation of hemiacetal product. For all three steps, Pd (100) exhibited low activation barriers (51.6, 26.7 and 76.2 kJ/mol) compared to Pd (111) surface (78.6, 35.8 and 92.2 kJ/mol) in the presence of ethanol. The activation barriers for the above steps were further reduced to 47.8, 23.9 and 64.6 kJ/mol on Pd (100) in the presence of methanol, explaining the experimental high reactivity aided by methanol. DFT calculations elucidated the role of the hydrogen bonding network between the solvent molecules and adsorbate, enabling proton-coupled electron transfer for accelerated reactions.</p>
10aAcetalization10aDFT10afacet-dependent reactivity10afurfural10aFurfural dialkyl acetals10asolvent effect1 aPorwal, Govind1 aDandekar, Pallavi1 aGorai, Twinkle1 aKhan, Tuhin, Suvra1 aHaider, Ali1 aGupta, Shelaka1 aVinod, C., P.  uhttps://library.ncl.res.in/content/facet-dependence-solvent-modulated-proton-coupled-electron-transfer-furfural-acetalization