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  • Mechanistic insights into t...
    Gyngazova, Maria S.; Grazia, Lorenzo; Lolli, Alice; Innocenti, Giada; Tabanelli, Tommaso; Mella, Massimo; Albonetti, Stefania; Cavani, Fabrizio

    Journal of catalysis, 04/2019, Letnik: 372
    Journal Article

    Display omitted •Furfural can be reduced to furfuryl alcohol using methanol as H-transfer and alkaline earth metal oxides catalysts.•The reduction occurs in the liquid-phase under mild conditions with high yield.•The specific activity of catalysts follows the rank SrO > CaO > MgO.•The activity rank is parallel to the basic strength rank of catalysts.•The stronger basicity leads to different mechanisms for methanol activation. DRIFT characterization and DFT calculation were carried out to clarify the previously unexplored use of methanol as a H-transfer agent for the liquid-phase Meerwein-Ponndorf-Verley reduction of biomass-derived furfural using alkaline earth oxide catalysts (MgO, CaO, SrO). Methanol adsorption mechanism has been studied in detail and the energy correlated to the process has been theoretically calculated for each of the prepared catalyst to investigate the relative performances of the three basic oxides. Although, the higher-surface-area MgO displayed an exceptionally high activity for the H-transfer process at low temperatures, CaO and SrO were found to be the catalysts with the highest specific productivity per unit surface area and unit basic site. The different specific productivities of the three catalysts was explained by DRIFT with different adsorption mode selectivities (3 different modes for MgO versus only 1 for CaO and SrO, with the production of only the active methoxide), which may indicate a different methanol activation with regard to the H-transfer toward the carbonyl moiety of FAL. Furthermore, higher SrO than CaO productivity can be explained by the different basicity, which in turn leads to differences in the main methanol activation pathways. DFT calculations make it possible to gain further insight into the role of the basic strength on methanol activation and H-transfer reaction suggesting the increased ability of activating the alcohol via formation of the methoxide ion being the key factor in modulating the catalyst activity rather than the polarization of the aldehydic carbonyl group due to the coordination onto the M3C site.