Hydrogenation Of Levulinic Acid Research Articles

Ru nanoclusters supported on HfO2@CN derived from NH2-UiO-66(Hf) as stable catalysts for the hydrogenation of levulinic acid to γ-valerolactone

The catalytic hydrogenation of levulinic acid to produce value-added γ-valerolactone represents a model reaction for upgrading biomass. Herein, we report the development of Ru/HfO2@CN, a ruthenium nanocluster catalyst supported on HfO2 embedded in nitrogen-doped porous carbon (HfO2@CN) derived from a Hf-based metal-organic framework [NH2-UiO-66(Hf)], as a highly efficient and stable catalyst for this transformation under mild reaction conditions. These characteristics are mainly attributed to the HfO2 embedded within the nitrogen-doped porous carbon support, which results in a high and stable dispersion of the Ru nanoclusters and also generates acidic sites that are hypothesized to promote the hydrogenation.

Green synthesis of gamma-valerolactone (GVL) through hydrogenation of biomass-derived levulinic acid using non-noble metal catalysts: A critical review

The distinct physicochemical properties and renewable origin of gamma-valerolactone (GVL) have provided opportunities for diversifying its applications, particularly as a green solvent, excellent fuel additive, and precursor to valuable chemicals. Among the related publications found in the SCOPUS database (≈172 in the last 10 years), we focused our effort to review the conversion of levulinic acid (LA) to GVL over non-noble metal catalysts and the corresponding mechanisms (≈30 publications) as well as the applications of GVL as a solvent, fuel additive, and platform chemical (≈30 publications) mostly in the last five years (some preceding publications have also been included due to their relevance and importance in the field). The use of non-noble metals (e.g., Cu and Zr) presents a greener route of GVL synthesis than the conventional practice employing noble metals (e.g., Pd and Ru), in view of their higher abundance and milder reaction conditions needed (e.g., low pressure and temperature without H2 involved). The significance of the catalyst characteristics in promoting catalytic transfer hydrogenation of LA to GVL is critically discussed. Structural features and acid-base properties are found to influence the activity and selectivity of catalysts. Furthermore, metal leaching in the presence of water in catalytic systems is an important issue, resulting in catalyst deactivation. Various endeavors for developing catalysts using well-dispersed metal particles along with a combination of Lewis acid and base sites are suggested for efficiently synthesizing GVL from LA.

Influence of surface Lewis acid sites for the selective hydrogenation of levulinic acid to γ-valerolactone over Ni–Cu–Al mixed oxide catalyst

Al2O3 interacted Cu–Ni bimetallic catalysts derived from incorporation of Cu into Ni–Al hydrotalcite were found to be efficient in the selective transformation of levulinic acid (LA) to γ-valerolactone (GVL). The promotional effect of Cu on Ni hydrogenation activity was explained due to an increased ease of NiO reduction and also enhanced surface Lewis acid sites measured by DRIFT spectroscopy. An optimum composition of Ni–Cu–Al catalyst with a mole ratio of 44:22:33 (NCA-423) exhibited a higher Ni metal surface area which demonstrated superior performance in the hydrogenation of LA to GVL with a productivity of 1.68 kgGVL kg cat −1 h−1. The physicochemical properties of Ni–Cu–Al catalysts were rationalized by XRD, H2-TPR, XPS, EPR, BET surface area, H2 chemisorption and pyridine adsorbed IR spectroscopy.

Noble and Base-Metal Nanoparticles Supported on Mesoporous Metal Oxides: Efficient Catalysts for the Selective Hydrogenation of Levulinic Acid to γ-Valerolactone

The selective hydrogenation of levulinic acid, LA to γ-valerolactone, GVL in water and solvent-free systems using mesoporous TiO2, NiO and MnO2 metal oxides supported noble and base-metal nanoparticles was investigated. BET results showed that all the synthetized materials were mesoporous with type IV isotherms and type I hysteresis. The p-XRD peaks observed in the low angle region confirm the successful formation of the meso-structured materials, whereas the wide-angle diffraction patterns show that the crystalline structure of the pure nanocatalysts is maintained upon deposition of the metal. TPR results showed that the reduced supported nanocatalysts consist of metallic Ru, Pd, Cu and Cr, and the average particle sizes obtained from HRTEM were found to be of 2 to 6 nm in diameter. The as-synthetized reusable nanocatalysts were revealed to be highly efficient for the conversion of LA to GVL. The best performance with complete conversion of LA and > 95% GVL selectivity was obtained from the TiO2 and MnO2-based nanocatalysts when water was used as a solvent. The order of reactivity of the supported metal nanoparticles was established as: Pd ≈ Ru > Cu > Cr. With an activity, TOF of up to 277273 h−1/mol, the low cost copper-based nanocatalysts could be an alternative to the high cost noble metal-based catalysts.

In-situ synthesis of single-atom Ir by utilizing metal-organic frameworks: An acid-resistant catalyst for hydrogenation of levulinic acid to γ-valerolactone

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) is a key reaction for the production of renewable chemicals and fuels, wherein acid-resistant and robust catalysts are highly desired for practical usage. Herein, an ultra-stable 0.6 wt% Ir@ZrO2@C single-atom catalyst was prepared via an in-situ synthesis approach during the assembly of UiO-66, followed by confined pyrolysis. The Ir@ZrO2@C offered not only a quantitative LA conversion and an excellent GVL selectivity (>99%), but also an unprecedented stability during recycling runs under harsh conditions (at T = 453 K, PH2 = 40 bar in pH = 3 or pH = 1 aqueous solution). By thorough spectroscopy characterizations, a well-defined structure of atomically dispersed Irδ+ atoms onto nano-tetragonal ZrO2 confined in the amorphous carbon was identified for the Ir@ZrO2@C. The strong metal-support interaction and the confinement of the amorphous carbon account for the ultra-stability of the Ir@ZrO2@C.

Phase‐Dependent Stability and Substrate‐Induced Deactivation by Strong Metal‐Support Interaction of Ru/TiO2 Catalysts for the Hydrogenation of Levulinic Acid

AbstractThe choice of support type has a profound influence on catalyst performance in liquid phase hydrogenation reactions, including the catalytic hydrogenation of biomass‐derived levulinic acid (LA) to γ‐valerolactone (GVL). Catalytic performance, including stability, of three Ru/TiO2 catalysts, having a similar mean Ru metal nanoparticle size but supported on three types of TiO2, namely P25, rutile and anatase, is evaluated by multiple reuse under batch reactor conditions. T3he catalysts’ physicochemical properties before and after recycling are characterized by XRD, STEM, TGA and FT‐IR after CO stepwise adsorption. The results show that the deactivation seen for (mixed) anatase‐supported catalysts in dioxane can be attributed to strong metal‐support interaction (SMSI) rather than coke formation or metal sintering, with the rutile‐based catalyst being more resistant against such support reduction. Notably, SMSI formation under the applied, relatively mild conditions only occurs in the presence of organic acids, such as LA or valeric acid.

Novel Cu/Al2O3-ZrO2 composite for selective hydrogenation of levulinic acid to γ-valerolactone

Novel Cu/Al2O3-ZrO2 composite catalyst was developed for the catalytic hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in water. By increasing Al2O3 content of the Cu/Al2O3-ZrO2 composite up to 5.0 wt% resulted in a nearly 3-fold increase in activity, without loss of selectivity towards GVL. This superior catalytic activity can be attributed to the dilution of Cu by Al2O3 as well as the enhanced electronic interaction between Cu and ZrO2 compared to Cu/ZrO2 catalyst. Reusability test for four consecutive runs showed a stable activity and selectivity, thus confirming the scope for practical application.

Facile synthesis of γ-valerolactone by transfer hydrogenation of methyl levulinate and levulinic acid over Ni/ZrO2

Nickel on zirconium oxide catalyst showed a high activity for the transfer hydrogenation of methyl levulinate and levulinic acid to γ-valerolactone (GVL) using 2-propanol as a hydrogen donor. The GVL yield of 94% at 373 K and 92% even at 363 K were attained for the hydrogenation of methyl levulinate. For the hydrogenation of levulinic acid, the GVL yield of 86% was attained at 393 K. The studies of the reactions on each component, i.e., nickel or ZrO2 showed that nickel in the Ni/ZrO2 catalyst largely contributed to the hydrogenation of the substrate and ZrO2 had a high activity for the lactonization of the hydrogenated product.

In situ synthesis of biomass-derived Ni/C catalyst by self-reduction for the hydrogenation of levulinic acid to γ-valerolactone

Abstract Herein, we reported in situ synthesis of biomass-derived Ni/C catalyst by self-reduction with pomelo peel. Compared with the conventional method, which includes carbonization, activation, impregnation and reduction, the entire preparation process was simplified to two steps, which was more straightforward. This synthesis method was green as Ni/C can be prepared without any additional chemical and the self-reduction process was realized in N2, which can avoid using H2 thus averting some problems such as storage, transportation and safety of H2. Meanwhile, the size and dispersion of Ni particles can be controlled by changing carbonization temperature. The synthesis mechanism of Ni/C catalyst with self-reduction was investigated, which was mainly attributed to the carbon and reducing gas produced during the carbonization process. For the catalytic performance of GVL synthesis, a high yield (94.5%) can be obtained and it exhibited good stability up to 5 cycles without obvious loss of catalytic activity.

CFD Design of Hydrogenation Reactor for Transformation of Levulinic Acid to γ-Valerolactone (GVL) by using High Boiling Point Organic Fluids

Levulinic acid (LA) has been ranked as one of the “Top 10” building blocks for future bio-refineries as proposed by the US Department of Energy. It is considered one of the most important platform molecules for the production of fine chemicals and fuels based on its compatibility with existing processes, market economics, and industrial ability to serve as a platform for the synthesis of important derivatives. Hydrogenation of LA to produce γ-valerolactone (GVL) is an active area of research due to the potential of GVL to be used as a biofuel in its own right and for its subsequent transformation into hydrocarbon fuels. This paper contains a new design for a simple, cost effective, and safe hydrogenation reactor for the transformation of levulinic acid to γ-valerolactone (GVL) by utilizing high boiling point organic fluid. The hydrogenation reactor is composed of a heating source—organic fluid (called “DOWTHERM A” or “thermex”) and the catalytic reactor. The advantages of high boiling temperature fluids, along with advances in hydrocracking and reforming technologies driven by the oil and gas industries, make the organic concept more suitable and safer (water coming in contact with liquid metal is well understood in the metallurgical industry to be a steam explosion hazard) for heating the hydrogenation reactor. COMSOL multi-physics software version 4.3b was applied in this work and simultaneously solves the continuity, Navier-Stokes (fluid flow), energy (heat transfer), and diffusion with chemical reaction kinetics equations. It was shown that the heat flux supplied by the DOWTHERM A organic fluid could provide the necessary heat flux required for maintaining the hydrogenation process. It was found that the mass fractions of hydrogen and levulinic acid decreased along the reactor axis. The GVL mass fraction increased along the reactor axis.

One-step fabrication of Ni-embedded hierarchically-porous carbon microspheres for levulinic acid hydrogenation

The facile fabrication of highly stable non-noble-supported carbonaceous catalysts for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) is still a major challenge. In an effort to address this challenge, we put forward a novel strategy to fabricate Ni and N co-decorated hierarchically-porous carbon microspheres (Ni@NCMs) through one-step synthesis. The developed micron-sized sphere catalyst possesses a hierarchically porous interior structure integrating uniform macropores and mesopores, in which Ni NPs are homogeneously located. The key to such a success is the utilization of the Pickering emulsion droplet-confined spaces, within which the co-assembly of carbon source, nitrogen source, surfactant and metal salt leads to the enhanced interactions. Moreover, such a catalyst exhibits superior activity and significantly enhanced stability in the hydrogenation of LA to GVL compared to the benchmarking catalyst, Ni-supported commercial active carbon (Ni/AC) prepared through the conventional wet impregnation. The present strategy may open up new horizons in the integration of rationally designed hierarchically porous structure with highly stable metal supported carbonaceous catalysts for various potential applications.

Microwave Irradiation-Enhanced Catalytic Transfer Hydrogenation of Levulinic Acid to γ-Valerolactone Using Ruthenium: A Comparative Study with Conventional Heating Processes

Conversion of biomass-derived levulinic acid to γ-valerolactone (GVL) via catalytic transfer hydrogenation (CTH) using conventional oven heating (COH) is associated with issues, such as long reaction time, and low yield. Microwave irradiation (MWI) appears to be a solution to address these issues as MWI can shorten reaction times and enhance yields. To explore effectiveness of MWI for LA conversion, MWI and COH are compared for LA conversion via CTH catalyzed by a model catalyst, Ru/C. Through investigating the effects of temperature and reaction time, MWI is validated to shorten the reaction time and enhance LA conversion efficiencies in comparison with COH. The optimal condition for the full LA conversion to GVL by Ru/C using MWI is 160 °C for 30 min with 10 mg (Ru/C)/mL (2-PrOH). MWI is also validated to improve conversion of several common levulinate esters (LAEs) to GVL. The regenerated Ru/C can also exhibit almost the same catalytic activity as the pristine Ru/C for LA conversion using MWI. These results indicate that Ru/C is a highly-effective catalyst for LA conversion and MWI can further enhance LA conversion by Ru/C by shortening reaction time and increasing yield of GVL. Thus, MWI is a promising process for enhancing biomass conversion.

A Remarkable Effect of Aluminum on the Novel and Efficient Aqueous-Phase Hydrogenation of Levulinic Acid into γ-Valerolactone Using Water-Soluble Platinum Catalysts Modified with Nitrogen-Containing Ligands

The catalytic performance of novel water-soluble platinum catalysts modified with various nitrogen-containing and phosphine ligands in the hydrogenation reaction of levulinic acid (LA) into γ-valerolactone (GVL) has been studied in environmentally attractive, green, aqueous monophasic systems. The presence of the Lewis acid aluminum enormously increases the catalytic activity of water-soluble platinum catalysts modified with nitrogen-containing ligands in the LA hydrogenation reaction and high catalytic activities up to 3540 TOF’s per hour with a quantitative selectivity towards GVL have been achieved using Na2PtCl6·6H2O precursors modified with the bidentate bathophenanthrolinedisulfonic acid disodium salt (BPhDS) ligand and low amounts of AlCl3·6H2O promotors (molar ratio of AlCl3·6H2O/Pt = 0.17) in aqueous media. This unprecedented increase in catalytic activity with aluminum promotors for water-soluble transition metal catalytic systems in aqueous-phase hydrogenation reactions has not been described until now in the literature. The apparent activation energy of platinum catalyst modified with the monodentate nitrilotriacetic acid trisodium salt ligand in aqueous medium was calculated and amounts to a relative low value of 73.04 kJ mol−1 when one considers that in the LA hydrogenation reaction this catalyst reduces a less reactive keto group into alcohol functionality. A recycling experiment of the Pt/BPhDS/Al catalyst from the aqueous monophasic LA hydrogenation reaction mixture followed by biphasic recovery of the catalyst in active form from organic reaction products by extraction and simple phase separation of an aqueous/organic two-phase system formed after addition of diethyl ether has shown that the Pt/BPhDS/Al catalyst is stable without loss of activity and selectivity in a consecutive run.

Water-born zirconium-based metal organic frameworks as green and effective catalysts for catalytic transfer hydrogenation of levulinic acid to γ-valerolactone: Critical roles of modulators

While zirconium (Zr)-based metal organic frameworks (MOFs) are promising for conversion of levulinic acid (LA) to γ-valerolactone (GVL) through catalytic transform hydrogenation (CTH), these reported Zr MOFs for LA conversion must be synthesized in toxic dimethylformamide (DMF). From the viewpoint of sustainability, it is preferable to avoid usage of DMF-based solvents to prepare these Zr MOFs. As water is a green solvent, the aim of this study is to develop and investigate Zr MOFs, which are prepared in water, for LA conversion to GVL. Specifically, monocarboxylic acids (e.g., formic acid, acetic acid and propanoic acid) are employed as modulators during the preparation of water-born ZrF. The role of modulators is extremely important for the well-developed formation of water-born ZrF. In addition, different monocarboxylic acid modulators also significantly influence the morphology of water-born ZrF; nevertheless, their crystalline structures and acidities are equivalent. As for LA conversion, these water-born modulated ZrF MOFs are validated to successfully convert LA to GVL. Especially, the formic acid-modulated ZrF can exhibit LA conversion = 96%, selectivity for GVL = 98% and yield of GVL = 98%. These water-born modulated ZrF also exhibit even higher catalytic activities than the typical DMF-based ZrF and reported Zr-based MOFs in LA conversion to GVL. These water-born ZrF could be also reused even without regeneration for multiple cyclic LA conversion. These results and findings prove that the water-born ZrF is not only environmentally benign but also more effective for LA conversion to GVL.

The hydrogenation of levulinic acid to γ-valerolactone over Cu–ZrO2 catalysts prepared by a pH-gradient methodology

A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr. All of the catalysts were highly selective to the desired product, γ-valerolactone, and are considerably more stable than Cu–ZrO2 catalysts prepared by other co-precipitation methods for this reaction. Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability. We consider the active site to be the interface between Cu/CuOx and ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction. This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design. As such, we conclude that the activity of Cu–ZrO2 catalysts in this reaction is dictated by the quantity of Cu–Zr interface sites.

CNF-Functionalization as Versatile Tool for Tuning Activity in Cellulose-Derived Product Hydrogenation.

Carbon nanofibers (CNFs) have been functionalized by introducing O, N, and P containing groups in order to investigate the effect of support functionalization in Ru catalysed hydroxymethyl furfural (HMF) and levulinic acid (LA) hydrogenation. In the case of HMF, despite the fact that no effect on selectivity was observed (all the catalysts produced selectively gamma-valerolactone (GVL)), the functionalization strongly affected the activity of the reaction. O-containing and N-containing supports presented a higher activity compared to the bare support. On the contrary, in HMF hydrogenation, functionalization of the support did not have a beneficial effect on the activity of a Ru-catalysed reaction with respect to bare support and only CNFs-O behaved similarly to bare CNFs. In fact, when CNFs-N or CNFs-P were used as the supports, a lower activity was observed, as well as a change in selectivity in which the production of ethers (from the reaction with the solvent) greatly increased.

Microwave-enhanced catalytic transfer hydrogenation of levulinic acid to γ-valerolactone using zirconium-based metal organic frameworks: A comparative study with conventional heating processes

Abstract Catalytic transfer hydrogenation (CTH) of levulinic acid (LA) to a versatile platform chemical, γ-valerolactone (GVL), has received increasing attention because CTH can be implemented using alcohols as H-donors and non-noble metal catalysts. While conventional heating is commonly used for LA conversion via CTH, microwave irradiation (MWI) is employed for the first time to converting LA to GVL via CTH using UiO-66 as a non-noble metal catalyst. In comparison with the conventional heating, the MWI significantly accelerates LA conversion to GVL as the yields and selectivities are much higher than those obtained by conventional heating. This enhancement may be because Zr-O cluster of UiO-66 is more catalytic active owing to the quick and intensive heat and promoting effects from the ligand of UiO-66 under MWI. Additionally, the MWI is still able to enhance LA conversion substantially in less suitable alcohols for LA and enable the unfavorable UiO-66-NH2 to work and making the effective catalyst, such as UiO-66-SO3H, even more catalytically active. These features indicate that MWI is certainly a useful and effective approach for enhancing LA conversion via CTH. The findings of this study are also an important basis for developing highly effective LA conversion via CTH with MWI.

Enhanced Production of γ‐Valerolactone with an Internal Source of Hydrogen on Ca‐Modified TiO2 Supported Ru Catalysts

Calcium-modified titania supported Ru catalysts were synthesized and evaluated for the hydrogenation of levulinic acid with formic acid as an internal hydrogen source and water as a green solvent. A new elegant photoassisted method was developed for the synthesis of uniform-size and evenly distributed Ru particles on the titania surface. Compared with the counterpart catalysts prepared by classical wet impregnation, enhanced levulinic acid conversion and γ-valerolactone yield were obtained and further improved through modification of the support by introduction of calcium into the titania support. This synthesis approach resulted in a change of the surface and bulk properties of the support, namely a decrease in the anatase crystallite size and the formation of a new calcium titanate phase. As a consequence, the properties of the catalysts were modified, and smaller ruthenium particles that had stronger interactions with the support were obtained. This affected the strength of the CO adsorption on the catalyst surface and facilitated the reaction performance. The optimum size of Ru particles that allowed for most efficient levulinic acid conversion was established.

Ni‐Al‐Ti Hydrotalcite Based Catalyst for the Selective Hydrogenation of Biomass‐Derived Levulinic Acid to γ‐Valerolactone

AbstractNi−Al‐Ti mixed oxide derived from Ni−Al‐Ti hydrotalcite precursor is identified as an efficient catalyst for the hydrogenation of levulinic acid (LA) to γ‐valerolactone (GVL). This catalyst showed high active surface Ni sites due to a higher synergy in the mixed oxide formed from the hydrotalcite precursor. These results are further supported by X‐ray diffraction analysis (XRD), electron spin resonance spectroscopy (ESR) and scanning electron microscopy (SEM) results. The higher activity of Ni−Al‐Ti compared to Ni−Al, Ni−Ti catalysts was attributed to a high ratio of Lewis to Brønsted acid sites (LAS/BAS) observed from pyridine adsorption – DRIFTS results along with high surface Ni sites on the catalyst surface measured from CO‐chemisorption studies. This contributed to the enhanced selectivity of the desired product, GVL over Ni−Al‐Ti catalyst as compared to its individual counter parts, Ni−Ti and Ni−Al catalysts.

Expression of concern: Monodisperse CuB23 nanoparticles grown on graphene as highly efficient catalysts for unactivated alkyl halide Heck coupling and levulinic acid hydrogenation

Expression of concern for ‘Monodisperse CuB23 nanoparticles grown on graphene as highly efficient catalysts for unactivated alkyl halide Heck coupling and levulinic acid hydrogenation’ by Shi Yan Fu et al., Catal. Sci. Technol., 2015, 5, 1638–1649.