A Sol–Gel Ruthenium–Niobium–Silicon Mixed‐Oxide Bifunctional Catalyst for the Hydrogenation of Levulinic Acid in the Aqueous Phase

Abstract

A mixed-oxide nanomaterial with composition (RuO2)0.038(Nb2O5)0.024(SiO2)0.938 was prepared by a one-pot sol–gel route. The synthesis was entirely performed at room temperature, by using easy-to-handle precursors and avoiding the employment of any toxic and/or polluting reactant. One of the samples was synthesised in the presence of a non-ionic surfactant acting as both pore directing agent and metal complexing agent, obtaining a high-specific-surface-area material characterized by a very good dispersion of the metallic species. In both cases, nanomaterials characterized by a complete reducibility of Ru species were obtained. The reduced nanomaterials acted as effective bifunctional catalysts in the hydrogenation of levulinic acid (LA) to γ-valerolactone, performed under mild conditions in the aqueous phase. The catalyst prepared without surfactant showed good stability and no activity loss during all the performed cycles. By contrast, some deactivation phenomena took place with the surfactant-templated catalyst. These phenomena were ascribed to both the partial surface oxidation and the surface adsorption of LA molecules giving deactivation during the second run

Nanostructured Metal Catalysts for Selective Hydrogenation and Oxidation of Cellulosic Biomass to Chemicals

“…Compared with other platform building blocks, levulinic acid has attracted much more attention in recent years. Mainstream efforts have primarily focused on bimetallic catalysts and metal‐solid acid hybridized nanocatalysts . The main advantage of using bimetallic catalysts is to alter the binding energy of carboxylic groups on metal surface, while for hybrid catalyst systems, the presence of acidic promoters often lowers activation barriers for H 2 and C=O bond, although unfavorable reconstruction Bronsted acidic sites ( e. g ., Al 3+ leaching) still remains a serious issue.…”

Ru Nanoparticles Embedded in Cubic Mesoporous Silica SBA-1 as Highly Efficient Catalysts for Hydrogen Generation from Ammonia Borane

“…Various materials with high surface areas, such as graphene [30], active carbon [31], carbon nanotubes [32], and mesoporous silica [33,34], have been employed as supports for immobilization of metal NPs in order to obtain homogenous dispersion of the metal NPs in the support. Mesoporous silicas, such as SBA-15, MCM-41, FDU-12, and SBA-16, have been widely used as the supports for the incorporation of the metal NPs due to their large surface areas, pore volumes, and homogenous pore structures [35][36][37][38][39][40]. In particular, 3D cubic mesoporous silicas like FDU-12, SBA-16, and SBA-1 are of great interest as the supports for the entrapment of the metallic NPs, since their interpenetrating mesoporous networks are resilient to pore blocking, and hence the catalysts can provide more active sites for the catalytic reactions [41,42].…”

Effects of Solid Acid Supports on the Bifunctional Catalysis of Levulinic Acid to γ‐Valerolactone: Catalytic Activity and Stability

“…The highest total acidity of Cu/γ-Al 2 O 3 was achieved at the Cu loading of 5 wt %, and the agglomeration of Cu particles would result in an obvious decrease in the total catalyst acidity. The optimum catalytic performance with a 98% LA conversion and a 87% GVL selectivity could be given with a 5 wt % Cu loading at 265°C < 10% LA con., < 10% GVL yield 37 RNS-a_h 0.4 g LA, 0.5 g catalyst, 200 g water 70°C, 20 bar H 2 , 1.5 h 45% LA con., 30% GVL yield [31] ( Table 1, entry 22). The effect of temperatures was significant.…”

“…At higher temperatures, an angelica lactone (AL) would be formed through the dehydration process of LA, and then be hydrogenated to generate GVL . The Al‐oriented pathway generally prevailed particularly under vapor phase conditions . In fact, the steps of hydrogenation and dehydration always take place in either pathway, and the difference lies only in the sequence of the above two processes under different control conditions.…”