Efficient Vapor-Phase Selective Hydrogenolysis of Bio-Levulinic Acid to γ-Valerolactone Using Cu Supported on Hydrotalcite Catalysts

A Comparative Study of Electrochemical Reduction of Levulinic Acid on Various Electrodes in Organic Solvents

Studies on the electrochemical hydrogenation (ECH) of levulinic acid (LA) to valeric acid (VA) or γ-valerolactone (GVL) have mainly focused on the electrochemical reduction of LA in acidic aqueous solutions. However, the narrow range of applied potentials has hindered understanding of some mechanistic aspects of LA electrochemical conversion. Earlier, we discovered that employing proton-deficient non-aqueous reaction media provides more comprehensive insights into the mechanism of LA electrochemical reduction. Here, we conducted further investigations into the LA electroreduction process using cyclic voltammetry in various organic solvents on a Pt electrode and on various electrode materials in acetonitrile, both with and without the addition of proton donors. The products of the ECH processes were identified using HPLC. The solvent nature, the presence of proton donors, the electrode material, and the applied potential strongly influence the LA electroreduction process. This study reveals that LA, in the presence proton donors, can undergo electrochemical reduction through different pathways, depending on the difference (ΔE1/2) between the reduction half-wave potential of protons and LA on a certain electrode. When the difference is large, the LA reduction is incomplete and the formation of GVL is observed. Under the close reduction potentials of protons and LA, LA can be completely reduced to VA.

Earth-abundant 3d-transition-metal catalysts for lignocellulosic biomass conversion

Transformation of biomass to chemicals and fuels is a long-term goal in both science and industry. However, high cost is one of the major obstacles to the industrialization of this sustainable technology. Thus, developing catalysts with high activity and low-cost is of great importance for biomass conversion. The last two decades have witnessed the increasing achievement of the use of earth-abundant 3d-transition-metals in catalysis due to their low-cost, high efficiency and excellent stability. Here, we aim to review the fast development and recent advances of 3d-metal-based catalysts including Cu, Fe, Co, Ni and Mn in lignocellulosic biomass conversion. Moreover, present research trends and invigorating perspectives on future development are given.

Highly monodispersed palladium-ruthenium alloy nanoparticles assembled on poly(N-vinyl-pyrrolidone) for dehydrocoupling of dimethylamine-borane: An experimental and density functional theory study

This study reports on one of the best heterogeneous catalysts for the dehydrogenation of dimethylamine-borane (DMAB). This new catalytic system consists of highly monodisperse Pd and Ru alloy nanoparticles supported by poly(N-vinyl-pyrrolidone) (PdRu@PVP). The prepared heterogeneous catalyst can be reproducibly formed using an ultrasonic reduction technique for DMAB dehydrogenation under mild conditions. For the characterization of PdRu@PVP nanomaterials, several spectroscopic and microscopic techniques were used. The prepared PdRu@PVP nanomaterials with an average particle size of 3.82 ± 1.10 nm provided an 808.03 h^-1 turnover frequency (TOF) in the dehydrogenation of DMAB and yielded 100% of the cyclic product (Me₂NBH₂)₂ under mild conditions. Furthermore, the activities of catalysts were investigated theoretically using DFT-B3LYP calculations. The theoretical results based on density functional theory were in favorable agreement with the experimental data.

Efficient Vapor-Phase Selective Hydrogenolysis of Bio-Levulinic Acid to γ-Valerolactone Using Cu Supported on Hydrotalcite Catalysts

In this work, Cu nanoparticles (Cu NPs, 2-20 nm) supported on Hydrotalcite catalysts exhibit enhanced selectivity for γ-valerolactone (GVL) during hydrogenolysis of levulinic acid (LA). At 260 °C, over 3 wt% Cu achieved 87.5% of LA conversion with a maximum GVL selectivity (95%). In contrast, LA hydrogenolysis over 3Cu/Hydrotalcite catalyst is highly active and stable toward the production of GVL due to balanced acido-basicity and higher Cu dispersion with ultrasmall particle sizes, which are investigated through the temperature programmed desorption (TPD) of ammonia, N2O titration, and transmission electron microscopy (TEM) analysis. Hydrotalcite in combination with inexpensive Cu catalyst is found to be an efficient and environmentally benign for LA hydrogenolysis.