Acid‐Functionalized Mesoporous Carbon: An Efficient Support for Ruthenium‐Catalyzed γ‐Valerolactone Production

Abstract

The hydrogenation of levulinic acid has been studied using Ru supported on ordered mesoporous carbons (OMCs) prepared by soft-templating. P- and S-containing acid groups were introduced by postsynthetic functionalization before the addition of 1 % Ru by incipient wetness impregnation. These functionalities and the reaction conditions mediate the activity and selectivity of the levulinic acid hydrogenation. The presence of S-containing groups (Ru/OMC-S and Ru/OMC-P/S) deactivates the Ru catalysts strongly, whereas the presence of P-containing groups (Ru/OMC-P) enhances the activity compared to that of pristine Ru/OMC. Under mild conditions (70 °C and 7 bar H2 ) the catalyst shows high selectivity to γ-valerolactone (GVL; >95 %) and high stability on recycling. However, under more severe conditions (200 °C and p H 2=40 bar) Ru/OMC-P is particularly able to promote GVL ring-opening and the consecutive hydrogenation to pentanoic acid.

Controlling the Incorporation of Phosphorus Functionalities on Carbon Nanofibers: Effects on the Catalytic Performance of Fructose Dehydration

“…In particular vapor-grown carbon nanofibers treated at 700 • C (Pyrolytically Striped Carbon Nanofibers, PS-CNFs), 1500 • C (Low-temperature Heat Treated Carbon Nanofibers, LHT-CNFs), and 3000 • C (High-temperature Heat Treated Carbon Nanofibers, HHT-CNFs) were used as pristine materials to study the influence of CNF structural properties on the incorporation of P groups. To introduce P-functionalities, carbon materials were treated with a H 3 PO 4 -HNO 3 mixture at 150 • C following a modified procedure from [31]. The functionalized carbon materials, labelled as P-PS-CNFs, P-LHT-CNFs, and P-HHT-CNFs, were tested in the fructose dehydration reaction, in a batch reactor at 120 • C under diffusional control (Scheme 1).…”

“…The introduction of heteroatoms (N, O, P, and S) has been reported to confer higher hydrophilicity, enhanced metal-support interactions, and additional acidic or basic sites [23][24][25][26][27][28][29][30][31][32]. Obviously, the distribution, the amount, the location, and the specific binding forms of the heteroatoms on the surface strictly depend on the nature of the carbonaceous substrate.…”

“…From this point of view, using a HNO 3 -H 3 PO 4 mixture represents a suitable strategy to promote the phosphorylation in mild conditions without affecting the original morphology of the samples. Indeed, the co-presence of HNO 3 results in the introduction of O-functionalities on the surface, acting as preferential anchoring sites for phosphate groups [31]. As known from the literature, P-containing materials are effective catalysts in the selective dehydration of fructose to 5-hydroxymethylfurfural (HMF) in water [34][35][36][37][38].…”

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

“…This method usually involves immobilization of surface functional groups on solid support and subsequent anchoring of in situ formed NPs in a second pot. P and S containing molecules were immobilized using such methodology on OMC (ordered mesoporous carbon) . For example, APTS (3‐aminopropyltriethoxysilane) agent was immobilized on Al 2 O 3 support using a similar approach.…”

“…Ru particles are well distributed due to strong interaction with well dispersed amine groups on the surface of solid support. Although they do not show significantly higher activity, the resultant materials are found to display remarkable selectivity (98+%, entry#7 in Table ) …”