Hydrogenation Of Levulinic Acid Research Articles

Highly efficient hydrogenation of levulinic acid into γ-valerolactone over modified bifunctional yolk-shell catalyst

Highly efficient hydrogenation of levulinic acid into γ-valerolactone over modified bifunctional yolk-shell catalyst

Advances in Sustainable γ-Valerolactone (GVL) Production via Catalytic Transfer Hydrogenation of Levulinic Acid and Its Esters.

γ-Valerolactone (GVL) is a versatile chemical derived from biomass, known for its uses such as a sustainable and environmentally friendly solvent, a fuel additive, and a building block for renewable polymers and fuels. Researchers are keenly interested in the catalytic transfer hydrogenation of levulinic acid and its esters as a method to produce GVL. This approach eliminates the need for H2 pressure and costly metal catalysts, improving the safety, cost effectiveness and environmental sustainability of the process. Our Perspective highlights recent advancements in this field, particularly with respect to catalyst development, categorizing them according to catalyst types, including zirconia-based, zeolites, precious metals, and nonprecious metal catalysts. We discuss factors such as reaction conditions, catalyst characteristics, and hydrogen donors and outline challenges and future research directions in this popular area of research.

Enhanced hydrothermal stability by a semi-embedded structure: An efficient Ru catalyst for levulinic acid conversion in the aqueous phase

Catalyst stability is believed to be one of the greatest challenges faced for the supported metal catalysts in the catalytic conversion of biomass and its derivatives because many biomass transformations are conducted in the aqueous phase. In this work, we report a simple yet efficient coating-impregnation-pyrolysis (CIP) strategy to fabricate Al2O3 supported Ru catalyst (Ru-Al2O3@CN) with Ru NPs (nanoparticles) semi-embedded into N-doped carbon (CN) layer for the efficient hydrogenation of levulinic acid (LA) to γ-valerolactone in the aqueous phase. Benefit from the special structure of Ru-Al2O3@CN catalyst, it possesses both high catalytic activity and stability, giving a TOF of 28,099 h-1 for LA hydrogenation at 120 °C and 2 MPa H2, which is superior to the most of reported Ru-based catalysts. More importantly, compared with conventional impregnated Ru/Al2O3 catalyst, the Ru-Al2O3@CN catalyst exhibits a remarkably improved hydrothermal stability. Based on series of catalyst characterizations and control experiments, it was found that the presence of CN can weak the interaction between Ru and Al2O3, as well as protect the Al2O3 and Ru NPs from hydrolysis and aggregation, respectively. We anticipate that such a novel strategy may provide some valuable insights into the synthesis of oxides-supported metal catalyst with high hydrothermal stability.

Hydrogen spillover on Ni@Graphene enables robust and efficient catalytic hydrogenation of aqueous levulinic acid to γ-valerolactone

Hydrogenation of biomass-derived aqueous levulinic acid (LA) to produce γ-valerolactone (GVL) is a promising approach from biomass to sustainable platform chemicals. However, the practical application of this method is limited because aqueous LA is highly corrosive to metal-based hydrogenation catalyst in high-temperature hydrothermal environments. Herein, we encapsulated metallic Ni0 particles with a few layers of graphene using a hydrothermal carbon coating method to obtain Ni@FLG-600 catalyst, which exhibited efficient catalytic activity and excellent cycling stability for the hydrogenation of aqueous LA to GVL. The defect-rich graphene shell prevents the Ni0 from acid corrosion meanwhile selectively permits the passage of small H2 molecules. The resulted active H* on Ni0 spills over to the outer surface of graphene shell and reacts with LA. Remarkably, the amount of H* on graphene shell can be the descriptor of activity. This finding presents a new strategy for the fabrication of acid-resistant catalysts for aqueous biomass hydrogenation.

Isopropanol/Water Bi‐Solvent Enhanced the Catalytic Transfer Hydrogenation of Levulinic Acid to γ‐Valerolactone over Ru‐PC Catalyst

AbstractCatalytic transfer hydrogenation of levulinic acid (LA) to γ‐valerolactone (GVL) was attractive in biomass conversions since GVL is highly useful in different applications, such as polymer synthesis, fuel, and food. Various catalytic systems were reported for the reaction, yet harsh reaction conditions were generally required, which could restrict the scaling up of the reaction. Herein, we developed an effective and green bi‐solvent system of isopropanol/water for the catalytic transfer hydrogenation of LA to GVL over a ruthenium–phosphorous carbon (Ru‐PC) catalyst. It was found that the presence of water in the solvent system promoted the production of GVL from LA. The effect of isopropanol/water ratios and other reaction conditions were investigated, exhibiting that 93.8% yield of GVL was achieved using isopropanol/water ratio of 2.5:2.5 at 140 °C for 4 h and over Ru‐PC catalyst. Combining water and organic solvent not only reduced the usage of organic solvent but also created an effective bi‐solvent system for catalytic reactions.

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.

Anchoring nickel sites on ceria-coated silica to enhance the catalytic stability for the vapor phase levulinic acid hydrogenation

The preparation of the binary metal NiCe-based catalysts involved a 2-step protocol, the ceria was first coated on SiO2 which was then utilized to disperse Ni nanoparticles. Various techniques including N2 adsorption/desorption, ICP-OES, XRD, HRTEM, XPS, H2-chemisorption, H2-TPR, NH3-TPD, and TG etc. were performed to study the microstructure, redox, acid property and deactivation. The results revealed that CeO2 and metallic Ni were well dispersed on the support surface, the synergistic effect between the two metal species was conserved well. The content of CeO2 had considerable effects on redox and metallic properties rather than the acidic property. The dispersion of metallic Ni played a dominant role in promoting the catalytic activity. The levulinic acid conversion attained 84.0 % with a γ-valerolactone selectivity of 98.8 % on Ni/SiO2@2CeO2 sample with the highest dispersion of 9.8 %. The amorphous CeO2 suppressed the sintering of metallic Ni nanoparticles and improved the coke resistance, leading to better catalytic activity within 20 h time on stream.

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.

Facile generation of unsaturated-coordinated and atomically-dispersed hafnium active sites for the highly efficient catalytic transfer hydrogenation of levulinic acid

The sluggish kinetic of the hydrogen transfer reaction pose a significant challenge in developing efficient catalytic transfer hydrogenation (CTH) system for upgrading biomass-derived platform molecules. In this contribution, for the first time, hafnium (Hf) species have been found to coordinate with the hydroxyl groups on halloysite nanotubes surface to construct a single-atom Hf catalyst (Hf@HNTs) with unsaturated-coordinated structure at room temperature. Especially, the Hf(1.7)@HNTs delivered an impressive catalytic performance for the CTH of levulinic acid (LvA) to gamma-valerolactone (GVL) with high turn-over frequency (TOF) of 43.1 h−1 at 160 °C, considerably exceeding that of coordination-saturated HfO2 and state-of-art Hf-based catalysts. Experimental and density functional theory (DFT) studies revealed that Hf(1.7)@HNTs possessed unsaturated-coordinated and atomically-dispersed Hf-O Lewis acid-base pairs, which favored the adsorption and activation of LvA. Moreover, DFT calculations explicitly demonstrated that the energy barriers for the hydrogen transfer between the LvA and hydrogen donor were significantly reduced on the Hf(1.7)@HNTs than that of HfO2.

Hybrid Magnetically Separable Catalyst for the Hydrogenation of Levulinic Acid to γ-Valerolactone

Hybrid Magnetically Separable Catalyst for the Hydrogenation of Levulinic Acid to γ-Valerolactone

Solvent‐Free Efficient Hydrogenation of Levulinic Acid over Silicotungstic Acid Promoting the Activity of CuNiAl Catalysts: A Synergistic Effect

AbstractMulti‐metallic catalysts rely on the synergistic effect between metals to perform better catalytic effect in biomass hydrogenation experiments compared with mono‐metallic catalysts. A series of CuNiAl composite metal oxide catalysts promoted by silicotungstic acid (HSiW), which were prepared by co‐precipitation and impregnation methods, were characterized by powder X‐ray diffraction (XRD), N2‐physisorption, scanning electron microscope (SEM) and NH3 program temperature desorption (NH3‐TPD) and pyridine infrared adsorption (Py‐FTIR). Their catalytic performance was evaluated in the hydrogenation of levulinic acid (LA) to prepare γ‐valerolactone (GVL). The results showed that the addition of Cu could improve the hydrogenation activity of Ni, and the addition of HSiW could further increase the amount of acid sites in the catalysts. Both of them could enhance the conversion of LA to some extent. CuNiAl‐5SiW, the par excellence catalyst, relied on the synergistic interactions between metals as well as the Brønsted and Lewis acid active sites to show efficient hydrogenation performance. The CuNiAl‐5SiW catalyst demonstrated 96.9 % conversion of LA and more than 99 % selectivity to GVL under 2 hours of reaction time, 180 °C of reaction temperature, 3.0 MPa of initial hydrogen pressure and solvent‐free conditions.

Innovative microkinetic modelling-supported structure–activity analysis of Ni/ZSM-5 during vapor-phase hydrogenation of levulinic acid

The study examines Ni/ZSM-5 catalysts in vapor phase hydrogenation of levulinic acid (LA) under continuous flow conditions (ambient pressure, 210–250 °C). Advanced characterization revealed the interplay between Al and Ni. This was further reinforced by new approach of microkinetic modeling, which demonstrates a pioneering work on mathematical description of pulse H2 sorption, TPD kinetics, DRIFT-supported determination of sorption energy barriers and (de)sorption kinetics. The Ni/ZSM-5 (3.7 wt.% Ni, Si/Al = 28) emerged as the optimal choice for obtaining γ-valerolactone (GVL) as the desired product. Al-rich catalysts with high acid site amounts and low metallic Ni active site concentrations favored esterification, reducing hydrogenation activity, and impeding further hydrogenation of GVL to pentanoic/valeric acid (PA). To enhance PA formation, Ni/ZSM-5 (4 wt.% Ni, Si/Al = 750) with a high Si/Al ratio, was identified as crucial. The combination of described experiments and modelling is demonstrated beneficial for insightful investigation of the structure–activity relationship of Ni/ZSM-5 or any other mono/bi-functional catalysts.

Effect of method of preparation of Ni and/or Cu supported on ZSM-5 catalysts for the aqueous phase hydrogenation of levulinic acid to γ-valerolactone

A series of Cu and Ni supported on ZSM-5 catalysts were synthesized by ion exchange (IE) and impregnation (IMP) techniques and examined for the aqueous phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) at atmospheric pressure. Hydrogenation of LA to GVL proceeds through LA dehydration to AL (angelica lactone) and subsequent hydrogenation of it to GVL, emphasizing the combined role of an acid and a metal site present on the catalyst surface. The interaction of Cu and/or Ni with ZSM-5 was elucidated using various characterization techniques such as powder XRD, XPS, H2-TPR, NH3-TPD, CO and/or H2 pulse chemisorption and SS NMR techniques. The CO chemisorption results indicated a lower uptake on Cu-ZSM-5(IMP) than on Cu-ZSM-5(IE). The H2 uptake was lower on Ni-ZSM-5(IE) than on Ni-ZSM-5(IMP). In the comparative analysis, the Ni-ZSM-5(IMP) catalyst exhibited a high rate of GVL formation, while the Cu-ZSM-5(IE) catalyst displayed a larger proportion of AL formation than the other catalysts prepared under similar protocols. The influence of the surface active sites on the product distribution was rationalized based on the physico-chemical characteristics of the fresh and reduced catalysts.

Precursor-Driven Catalytic Performances of Al2O3-Supported Earth-Abundant Ni Catalysts in the Hydrogenation of Levulinic Acid and Hydroxymethylfurfural into Added-Value Chemicals.

It has been shown that the nature of the metal precursor and the thermal effects during calcination determine the physicochemical properties of the catalysts and their catalytic activity in the levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) hydrogenation reactions. The endothermic effect during calcination of the inorganic nickel precursor promoted higher metal dispersion and stronger interaction with the alumina surface. In contrast, the exothermic effects during the calcination of organic nickel precursors resulted in smaller metal dispersion and lower interaction with the support surface. A clear relationship was found between the size of the metal crystallites and the yield of LA hydrogenation reaction. The smaller crystallites were more active in the LA hydrogenation reaction. In turn, the size of the metal particles and their nature of interaction with the surface of the alumina influence the hydrogenation pathways of the HMF.

Enhancing reductive conversion of levulinic acid and levulinates to γ-valerolactone: Role of oxygen vacancy in MnOx catalysts

Oxygen vacancies (Ov) in metal oxides play a crucial role in modifying the electronic and acidic properties of catalysts, thereby influencing their catalytic activity. This study explores the impact of Ov in MnOx catalysts on their acidic and catalytic properties for the Meerwein–Ponndorf–Verley reduction of levulinic acid (LA) and levulinate to γ-valerolactone (GVL). Various characterization techniques demonstrate that surface Ov significantly modulate the acidic properties of MnOx catalysts, positively correlating with Lewis/Brønsted acid ratio and GVL yield. In situ DRIFTS and DFT calculations further unveil the reaction mechanism, revealing that Ov facilitate the activation and dehydrogenation of isopropanol and subsequent hydrogen transfer and hydrogenation of LA, leading to enhanced GVL production. These insights underscore the pivotal role of Ov in MnOx catalysts for the efficient conversion of LA to GVL, highlighting their importance in improving catalytic performance.

Pivotal MoOx-decorated Ru/C with a monomeric structure boosts the room temperature and low-pressure hydrogenation of levulinic acid to γ−valerolactone

Pivotal molybdenum oxide-decorated ruthenium on charcoal catalysts exhibited high efficiency and selectivity for the room temperature and low pressure hydrogenation of levulinic acid (LA) to renewable fuel γ−valerolactone (GVL). The Ru-(y)MoOx/C (y = the amount of co-loaded Mo in wt%) catalysts were synthesised by using a one-pot coprecipitation-hydrothermal method of a solution that consisted of Ru and Mo species at 150 °C for 24 h, followed by reduction with H2 at 300–600 °C for 1.5 h. The Ru-(0.55)/MoOx/C catalyst (pre-reduced at 500 °C) exhibited high dispersion of Ru nanoparticles on the surface of MoOx/C composite support, demonstrating the highest yield of GVL (>99) with a turnover frequency (TOF) reaching up to 2730 h−1 at 30 °C, 10 bar H2, and 1 h. The Ru-(0.55)/MoOx/C also catalysed various carboxylic acids to corresponding alcohols and was reusable without any significant loss of selectivity.

Improved catalytic performance of Ru catalysts via CO2-assisted one-pot synthesis strategy for aqueous levulinic acid hydrogenation

Fabrication of metal/porous carbon catalysts with high catalytic activity and stability is highly desirable but challenging because the metal nanoparticles in these catalysts cannot have both high exposure and strong interaction with carbon support. Here, for the first time, a facile CO2-assisted one-pot pyrolysis (CAOP) strategy was developed to in situ liberate the inaccessible Ru sites without obviously affecting the size of Ru nanoparticles. The Ru@CN-700-80 prepared with the assistance of CO2 exhibits a remarkable improvement in catalytic activity for levulinic acid hydrogenation compared with that without CO2 during pyrolysis, giving a TOF of 28449 h−1 under mild conditions, which is superior to the reported Ru-based catalysts. Additionally, the Ru@CN-700-80 also demonstrates an excellent stability without activity loss after 10 cycles. We anticipate that this CAOP strategy addresses a crucial issue that currently plagues the design of metal/porous carbon catalyst with high catalytic performance applied in energy and environmental fields.

Alkaline modified Zr-loading on nanosheet zeolite towards production of γ-valerolactone from levulinic acid through catalytic transfer hydrogenation

A self-pillared nanosheet ZSM-5 zeolite (SP) loading Zr catalyst is prepared for conversion of levulinic acid (LA) to produce γ-valerolactone (GVL). The hierarchical pore by nanosheet aggregates promotes Zr dispersion with establishment of strong interaction between Zr and zeolite. Moreover, Na ions are introduced to modify the chemical environment of Zr on nanosheet zeolite (Zr/NaSP). In catalytic transfer hydrogenation of LA using isopropanol as H-donor, uniformly dispersed Zr species on SP zeolite is conducive for both conversion of LA as well as production of GVL, in comparison with samples using conventional microporous ZSM-5 as supports (Zr/CZ). More importantly, different from protonated zeolite sample (Zr/HSP), the introduction of alkali sites could attract protons in hydroxyl groups of isopropanol, which accelerates the generation rates of GVL. The as-designed Zr/NaSP catalyst delivers GVL generation rates of 31.9 mmol·g-1·h-1, which provides a potential catalyst for GVL production.

Yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres with tunable shell thickness and ultrahigh surface area for biomass-derived levulinic acid hydrogenation under mild conditions

Aiming to efficiently upgrade renewable biomass-derived levulinic acid (LA) into γ-valerolactone (GVL), we have devised yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres, featuring a tunable shell thickness (20−70 nm) and an ultrahigh surface area (4016 m2 g−1). Experimental and theoretical investigations reveal that the strategic formation of the yolk-shell structure and appropriate thinning of the carbon shell facilitate the generation of electron-rich Ru0 and a positive shift of the d-band center towards the Fermi level by increasing surface pyridinic-N species. These modifications suitably intensify Ru0−H interaction, promote reactant adsorption, stimulate electron transfer between active H and the CO group of LA, and ultimately reduce apparent activation energy. Consequently, a high LA turnover frequency (18733.4 h−1 at 30 °C) and GVL selectivity (99.9%), alongside excellent stability up to eight cycles, are achieved, markedly outperforming externally-supported analogues. These findings afford valuable insights into designing yolk-shell nanostructures for biomass upgrading through microenvironment engineering.

Interplay Between Metallicity and Acidity in the Hydrogenation of Levulinic Acid

Interplay Between Metallicity and Acidity in the Hydrogenation of Levulinic Acid