Conversion of levulinic acid using CuO/WO3(x)-Al2O3 catalysts

Reductive Amination of Levulinic Acid to Pyrrolidones: Key Step in Biomass Valorization towards Nitrogen-Containing Chemicals

Nowadays, the field of biomass conversion is gradually moving towards an encouraging stage. The preparation of nitrogen-containing chemicals using various biomass resources instead of fossil resources do not only reduce carbon emissions, but also diversify the products of biomass conversion, thus increasing the economic competitiveness of biomass refining systems. Levulinic acid (LA) can be used as a promising intermediate in biomass conversion for further synthesis of pyrrolidone via reductive amination. However, there are still many critical issues to be solved. Particularly, the specific effects of catalysts on the performance of LA reductive amination have not been sufficiently revealed, and the potential impacts of key conditional factors have not been clearly elucidated. In view of this, this review attempts to provide theoretical insights through an in-depth interpretation of the above key issues. The contribution of catalysts to the reductive amination of LA as well as the catalyst structural preferences for improving catalytic performance are discussed. In addition, the role of key conditional factors is discussed. The insights presented in this review will contribute to the design of catalyst nanostructures and the rational configuration of green reaction conditions, which may provide inspiration to facilitate the nitrogen-related transformation of more biomass platform molecules.

γ-Valerolactone Production from Levulinic Acid Hydrogenation Using Ni Supported Nanoparticles: Influence of Tungsten Loading and pH of Synthesis

γ-Valerolactone (GVL) has been considered an alternative as biofuel in the production of carbon-based chemicals; however, the use of noble metals and corrosive solvents has been a problem. In this work, Ni supported nanocatalysts were prepared to produce γ-Valerolactone from levulinic acid using methanol as solvent at a temperature of 170 °C utilizing 4 MPa of H₂. Supports were modified at pH 3 using acetic acid (CH₃COOH) and pH 9 using ammonium hydroxide (NH₄OH) with different tungsten (W) loadings (1%, 3%, and 5%) by the Sol-gel method. Ni was deposited by the suspension impregnation method. The catalysts were characterized by various techniques including XRD, N₂ physisorption, UV-Vis, SEM, TEM, XPS, H₂-TPR, and Pyridine FTIR. Based on the study of acidity and activity relation, Ni dispersion due to the Lewis acid sites contributed by W at pH 9, producing nanoparticles smaller than 10 nm of Ni, and could be responsible for the high esterification activity of levulinic acid (LA) to Methyl levulinate being more selective to catalytic hydrogenation. Products and by-products were analyzed by ¹H NMR. Optimum catalytic activity was obtained with 5% W at pH 9, with 80% yield after 24 h of reaction. The higher catalytic activity was attributed to the particle size and the amount of Lewis acid sites generated by modifying the pH of synthesis and the amount of W in the support due to the spillover effect.

Ru Catalysts Supported on Commercial and Biomass-Derived Activated Carbons for the Transformation of Levulinic Acid into γ-Valerolactone under Mild Conditions

Ru catalysts (1 wt.%) supported on commercial and biomass-derived activated carbons (AC) have been prepared, thoroughly characterized, and used in the hydrogenation of levulinic acid to produce gamma-valerolactone (GVL). This is an important platform compound that plays a key role in the production of liquid fuels and that can also be used, for example, as a food flavoring agent, antifreeze, and solvent. The study focuses on the influence of the carbon support characteristics, such as porous texture and acidity, on the properties and performance (LA conversion and selectivity to GVL) of the catalysts. Catalytic activity tests have been carried out at 170 °C and also in noticeably milder conditions (70 °C) to implement a less energy-demanding process. All the catalysts show high LA conversion and GVL yield at 170 °C, while at 70 °C, important differences between them, related to the support properties, have been found. The catalysts prepared with more acidic supports show better catalytic properties: very good catalytic performance (98% LA conversion and 77% selectivity to GVL) has been obtained in mild temperature conditions.