Highly efficient CuNi-ZrO2 nanocomposites for selective hydrogenation of levulinic acid to γ-valerolactone

CuNi-ZrO2 nanocomposites were prepared by a simple coprecipitation technique of copper, nickel and zirconium ions with potassium carbonate. The structures of the nanocomposites were characterized by N2 physical adsorption, XRD, H2-TPR and STEM-EDS. The Cu0.05Ni0.45-ZrO2 nanocomposite showed outstanding catalytic performance in hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL), especially NaOH solution (0.5 mol L-1) as a solvent. 100% LA conversion and > 99.9% GVL selectivity are achieved over Cu0.05Ni0.45-ZrO2 catalyst at 200 °C, 3 MPa for 1.5 h. Characterization results suggest that the excellent reactivity of the Cu0.05Ni0.45-ZrO2 may be due to a better reducibility of nickel oxide in the CuONiO-ZrO2, dispersion of Ni in the Cu0.05Ni0.45-ZrO2 compared to nickel oxide in the NiO-ZrO2 and Ni in the Ni0.5-ZrO2 and promotion of OH-. The results demonstrate that the Cu0.05Ni0.45-ZrO2 nanocomposite has potential to realize high efficiency and low-cost synthesis of liquid fuels from biomass.

Kinetics Driven by Hollow Nanoreactors: An Opportunity for Controllable Catalysis

As a novel class of catalytic materials, hollow nanoreactors offer new opportunities for improving catalytic performance owing to their higher controllability on molecular kinetic behavior. Nevertheless, to achieve controllable catalysis with specific purposes, the catalytic mechanism occurring inside hollow nanoreactors remains to be further understood. In this context, this Review presents a focused discussion about the basic concept of hollow nanoreactors, the underlying theory for hollow nanoreactor-driven kinetics, and the intrinsic correlation between key structural parameters of hollow nanoreactors and molecular kinetic behaviors. We aim to provide in-depth insights into understanding kinetics occurred within typical hollow nanoreactors. The perspectives proposed in this paper may contribute to the development of the fundamental theoretical framework of hollow nanoreactor-driven catalysis.

Ruthenium-Nanoparticle-Loaded Hollow Carbon Spheres as Nanoreactors for Hydrogenation of Levulinic Acid: Explicitly Recognizing the Void-Confinement Effect

As a typical class of man-made nanoreactors, metal-loaded hollow carbon nanostructures (MHC nanoreactors) exhibit competitive potentials in the heterogeneous catalysis due to their tailorable microenvironment effects, in which the void-confinement effect is one of the most fundamental functions in boosting the catalytic performance. Herein this paper, Ru-loaded hollow carbon spheres are employed as nanoreactors with a crucial biomass hydrogenation process, levulinic acid (LA) hydrogenation into γ-valerolactone, as the probe reaction to further recognize the forming mechanism of this pivotal effect. We demonstrated that the void-confinement effect of the selected MHC nanoreactors is essentially driven by an integrating action of electronic metal-support interaction, reactant enrichment and diffusion, which are mainly ascribed to peculiar properties of hollow nanoreactors both in electronic and structural aspects, respectively. This work offers a distinct case for interpreting the catalytic behaviour of MHC nanoreactors, which could potentially promise broader insights into the microenvironment engineering strategies of hollow nanostructures.

A Biorefinery Cascade Conversion of Hemicellulose-Free Eucalyptus Globulus Wood: Production of Concentrated Levulinic Acid Solutions for γ-Valerolactone Sustainable Preparation

Eucalyptus globulus wood samples were subjected to preliminary aqueous processing to remove water-soluble extractives and hemicelluloses, and the resulting solid (mainly made up of cellulose and lignin) was employed as a substrate for converting the cellulosic fraction into mixtures of levulinic and formic acid through a sulfuric acid-catalyzed reaction. These runs were carried out in a microwave-heated reactor at different temperatures and reaction times, operating in single-batch or cross-flow modes, in order to identify the most favorable operational conditions. Selected liquid phases deriving from these experiments, which resulted in concentrated levulinic acid up to 408 mmol/L, were then employed for γ-valerolactone production by levulinc acid hydrogenation in the presence of the commercial 5% Ru/C catalyst. In order to assess the effects of the main reaction parameters, hydrogenation experiments were performed at different temperatures, reaction times, amounts of ruthenium catalyst and hydrogen pressure. Yields of γ-valerolactone in the range of 85–90 mol % were obtained from the hydrogenation of the wood-derived solutions containing levulinic acid, obtained by single-batch operation or by the cross-flow process. The negative effect of co-produced formic acid present in crude levulinic acid solutions was evidenced and counteracted efficiently by allowing the preliminary thermal decomposition of formic acid itself.