David Kubička

The platform molecule 5‐Hydroxymethylfurfural (HMF) can be derived from biomass feedstocks and catalytically hydrogenated into various high value molecules. Its conversion to 5‐methylfurfural (5‐MF), a versatile synthetic intermediate and perfuming agent is challenging as the selective hydrodeoxygenation of the C–OH group in HMF is far less favorable kinetically and thermodynamically than the hydrogenation of the C═O group, which leads to 2,5‐bis(hydroxymethyl)furan (BHMF). Herein, for the first time we demonstrate that Ni/TiO₂ catalysts can be tuned to promote the selective removal of a hydroxyl group in the presence of an aldehyde moiety, achieving a high 5‐MF yield. Among various synthesis approaches, the direct ion‐exchange incorporation of Ni into a TiO₂ network prepared via an alginate synthesis route enabled identifying key factors directing the reaction selectivity toward 5‐MF. The highest 5‐MF selectivity (86%) at nearly full conversion was favored by high acidity and ultra‐high dispersion of Ni atoms on the surface, while the crucial role of titania was discussed. By contrast, increasing the reduction temperature to 700 °C significantly lowered acidity and led to the formation of larger Ni particles, which favored C═O activation and in turn promoted a selectivity shift toward BHMF achieving 86% selectivity at nearly full conversion.

The simple hydration of physically mixed Mg and Al oxides results in the formation of solids with an LDH phase, but hydration conditions need to be optimized to obtain resulting catalysts with the optimal performance in aldol condensation.

The 5-Hydroxymethylfurfural (HMF) platform molecule can be derived from biomass feedstocks and catalytically hydrogenated into various added-value molecules. Its conversion to 5-methylfurfural (5-MF), a versatile synthetic intermediate and perfuming agent, is particularly challenging, the selective hydrodeoxygenation of the C–OH group in HMF being by far less favourable kinetically and thermodynamically than the hydrogenation of the C=O group that gives 2,5-bis-hydroxymethylfuran (BHMF). Herein, for the first time we showed that Ni/TiO2 catalysts can be tuned to promote the selective removal of a hydroxy group in the presence of an aldehyde moiety, and give high 5-MF yield. Among various synthesis approaches, the direct ion exchange incorporation of Ni into a TiO2 network prepared by an alginate synthesis route allowed the key-factors orientating the reaction selectivity towards 5-MF to be identified. The highest 5-MF selectivity (86%) at nearly full conversion was favoured by high acidity and ultra-high dispersion of Ni atoms at the surface, while the prime role of titania was discussed. By contrast, increasing the reduction temperature up to 700°C strongly lowered the acidity and formed larger Ni particles, which favour the C=O activation, and is thereby promoting the selectivity switch towards BHMF at 86% also at nearly full conversion.

Two supports (ZnO, ZrO ₂ ) and four promoters (Al ₂ O ₃ , ZnO, CoO _x , NiO) were investigated to design environmentally-friendly Cu-based hydrogenolysis catalysts.