One pot selective transformation of biomass derived chemicals towards alkyl levulinates over titanium exchanged heteropoly tungstate catalysts

Steady states and kinetic modelling of the acid-catalysed ethanolysis of glucose, cellulose, and corn cob to ethyl levulinate

Ethyl levulinate is a promising advanced biofuel and platform chemical that can be derived from lignocellulosic biomass by ethanolysis processes. It can be blended with both diesel and gasoline and, thus, used in conventional engines and infrastructure. Previously, it has been shown that alkyl levulinate/alcohol/alkyl ether mixtures exhibit significantly enhanced fuel properties relative to any of the individual fuel components, particularly when blended with conventional hydrocarbon liquid fuels. Consequently, this study specifically quantifies the three primary components of the alcoholysis reaction mixture: ethyl levulinate, diethyl ether, and ethanol. The steady state and kinetic phase fractions of ethyl levulinate and diethyl ether produced from glucose, cellulose, and corn cob with 0.5-2 mass% sulphuric acid in ethanol are determined for 5, 10, and 20 mass% of feedstock at 150 °C. Knowledge of the steady state equilibrium mixture fraction is specifically targeted due to its importance in assessing commercial-scale production and in modelling analysis as: (i) it defines the maximum yield possible at a given condition, and (ii) it is equitable to the minimum free energy state. Maximum steady state yields (mass%) of ethyl levulinate of (46.6 ± 3.7), (50.2 ± 5.4), and (27.0 ± 1.9)% are determined for glucose, cellulose, and corn cob, respectively. The conversion of glucose and cellulose to ethyl levulinate in the presence of ethanol and sulphuric acid is shown to be a catalytic process, where the ethyl levulinate yield is not dependent on the acid concentration. For corn-cob biomass, in a new and contrasting finding, the ethyl levulinate yield is shown to strongly depend on the acid concentration. This effect is also observed in the fractions of diethyl ether formed, providing strong evidence that the hydrogen cation is not being replenished in the ethanolysis process and the overall reaction with corncob is not wholly catalytic. Thus, for the acid catalysed alcoholysis of lignocellulosic biomass, acid concentration must be scaled with feedstock concentration. The critical corn cob-to-acid ratio that maximises ethyl levulinate yields while minimizing the formation of undesired co-products (diethyl ether) is in the range 10-20 : 1 at 150 °C. A detailed, hierarchical, mass-conserved chemical kinetic model capable of accurately predicting the relative abundance of the three primary components of the ethanolysis reaction: ethyl levulinate, diethyl ether, and ethanol, from the biochemical composition of the feedstock, is elucidated and validated.

2,5-Dimethylfuran Production by Catalytic Hydrogenation of 5-Hydroxymethylfurfural Using Ni Supported on Al2O3-TiO2-ZrO2 Prepared by Sol-Gel Method: The Effect of Hydrogen Donors

5-Hydroxymethylfurfural (5-HMF) has been described as one of the 12 key platform molecules derived from biomass by the US Department of Energy, and its hydrogenation reaction produces versatile liquid biofuels such as 2,5-dimethylfuran (2,5-DMF). Catalytic hydrogenation from 5-HMF to 2,5-DMF was thoroughly studied on the metal nickel catalysts supported on Al2O3-TiO2-ZrO2 (Ni/ATZ) mixed oxides using isopropanol and formic acid (FA) as hydrogen donors to find the best conditions of the reaction and hydrogen donor. The influence of metal content (wt%), Ni particle size (nm), Nickel Ni0, Ni0/NiO and NiO species, metal active sites and acid-based sites on the catalyst surface, and the effect of the hydrogen donor (isopropanol and formic acid) were systematically studied. The structural characteristics of the materials were studied using different physicochemical methods, including N2 physisorption, XRD, Raman, DRS UV-Vis, FT-IR, SEM, FT-IR Pyad, H2-TPD, CO2-TPD, H2-TPR, TEM and XPS. Second-generation 2,5-DMF biofuel and 5-HMF conversion by-products were analyzed and elucidated using 1H NMR. It was found that the Ni0NiO/ATZ3WI catalyst synthesized by the impregnation method (WI) generated a good synergistic effect between the species, showing the best catalytic hydrogenation of 5-HMF to 2,5-DMF using formic acid as a hydrogen donor for 24 h of reaction and temperature of 210 °C with 20 bar pressure of Argon (Ar).

Cascade Upgrading of Biomass-Derived Furfural to γ-Valerolactone Over Zr/Hf-Based Catalysts

Biomass feedstocks are promising candidates of renewable clean energy. The development and utilization of biological energy is in line with the concept of sustainable development and circular economy. As an important platform chemical, γ-valerolactone (GVL) is often used as green solvent and biofuel additive. Regarding this, the efficient synthesis of GVL from biomass derivative furfural (FF) has attracted wide attention recently, However, suitable catalyst with appropriate acid-base sites is required due to the complex reaction progress. In this Mini Review, the research progress of catalytic synthesis of GVL from furfural by Zr/Hf-based catalysts was reviewed. The different effects of Lewis acid-base and Brønsted acid sites in the catalysts on each steps in the reaction process were discussed firstly. Then the effects of regulation of acid-base sites in the catalysts was also studied. Finally, the advantages and challenges of Zr/Hf-based catalysts in FF converted to GVL system were proposed.

Hydrophobic species-enabled acid–base multi-catalysis for stereoselective access to renewable trans-anethole

A green and sustainable route was developed to stereoselectively produce biomass-based trans-AN (90% selectivity) over an acid–base bifunctional catalyst through cascade transfer hydrogenation and dehydration.

Recyclable Zr/Hf-Containing Acid-Base Bifunctional Catalysts for Hydrogen Transfer Upgrading of Biofuranics: A Review

The massive burning of a large amount of fossil energy has caused a lot of serious environmental issues (e.g., air pollution and climate change), urging people to efficiently explore and valorize sustainable alternatives. Biomass is being deemed as the only organic carbon-containing renewable resource for the production of net-zero carbon emission fuels and fine chemicals. Regarding this, the selective transformation of high-oxygen biomass feedstocks by catalytic transfer hydrogenation (CTH) is a very promising strategy to realize the carbon cycle. Among them, the important Meerwein-Ponndorf-Verley (MPV) reaction is believed to be capable of replacing the traditional hydrogenation strategy which generally requires high-pressure H2 and precious metals, aiming to upgrade biomass into downstream biochemical products and fuels. Employing bifunctional heterogeneous catalysts with both acidic and basic sites is needed to catalyze the MPV reaction, which is the key point for domino/cascade reaction in one pot that can eliminate the relevant complicated separation/purification step. Zirconium (Zr) and hafnium (Hf), belonging to transition metals, rich in reserves, can demonstrate similar catalytic efficiency for MPV reaction as that of precious metals. This review introduced the application of recyclable heterogeneous non-noble Zr/Hf-containing catalysts with acid-base bifunctionality for CTH reaction using the safe liquid hydrogen donor. The corresponding catalysts were classified into different types including Zr/Hf-containing metal oxides, supported materials, zeolites, metal-organic frameworks, metal-organic hybrids, and their respective pros and cons were compared and discussed comprehensively. Emphasis was placed on evaluating the bifunctionality of catalytic material and the key role of the active site corresponding to the structure of the catalyst in the MPV reaction. Finally, a concise summary and prospect were also provided centering on the development and suggestion of Zr/Hf-containing acid-base bifunctional catalysts for CTH.

Versatile Coordination Polymer Catalyst for Acid Reactions Involving Biobased Heterocyclic Chemicals

The chemical valorization/repurposing of biomass-derived chemicals contributes to a biobased economy. Furfural (Fur) is a recognized platform chemical produced from renewable lignocellulosic biomass, and furfuryl alcohol (FA) is its most important application. The aromatic aldehydes Fur and benzaldehyde (Bza) are commonly found in the slate of compounds produced via biomass pyrolysis. On the other hand, glycerol (Gly) is a by-product of the industrial production of biodiesel, derived from fatty acid components of biomass. This work focuses on acid catalyzed routes of Fur, Bza, Gly and FA, using a versatile crystalline lamellar coordination polymer catalyst, namely [Gd(H4nmp)(H2O)2]Cl·2H2O (1) [H6nmp=nitrilotris(methylenephosphonic acid)] synthesized via an ecofriendly, relatively fast, mild microwave-assisted approach (in water, 70 °C/40 min). This is the first among crystalline coordination polymers or metal-organic framework type materials studied for the Fur/Gly and Bza/Gly reactions, giving heterobicyclic products of the type dioxolane and dioxane, and was also effective for the FA/ethanol reaction. 1 was stable and promoted the target catalytic reactions, selectively leading to heterobicyclic dioxane and dioxolane type products in the Fur/Gly and Bza/Gly reactions (up to 91% and 95% total yields respectively, at 90 °C/4 h), and, on the other hand, 2-(ethoxymethyl)furan and ethyl levulinate from heterocyclic FA.

The selective conversion of furfuryl alcohol to ethyl levulinate over Zr-modified tungstophosphoric acid supported on β-zeolites

Catalysts of zirconium-exchanged proton-containing tungstophosphoric acid (TPA) supported on β-zeolites were prepared by an impregnation method for the selective alcoholysis of furfuryl alcohol into ethyl levulinate.

Direct Alcoholysis of Carbohydrate Precursors and Real Cellulosic Biomasses to Alkyl Levulinates: A Critical Review

Alkyl levulinates (ALs) represent outstanding bio-fuels and strategic bio-products within the context of the marketing of levulinic acid derivatives. However, their synthesis by acid-catalyzed esterification of pure levulinic acid, or by acid-catalyzed alcoholysis of furfuryl alcohol, although relatively simple, is still economically disadvantageous, due to the high costs of the pure precursors. The direct one-pot alcoholysis of model C6 carbohydrates and raw biomass represents an alternative approach for the one-step synthesis of ALs. In order to promote the market for these bio-products and, concurrently, the immediate development of new applications, it is necessary to speed up the intensification of their production processes, and this important achievement is onlypossible by using low-cost or, even better, waste biomasses, as starting feedstocks. This review provides an overview of the most recent and promising advances on the one-pot production of ALs from model C6 carbohydrates and real biomasses, in the presence of homogeneous or heterogeneous acid catalysts. The use of model C6 carbohydrates allows for the identification of the best obtainable ALs yields, resulting in being strategic for the development of new smart catalysts, whose chemical properties must be properly tuned, taking into account the involved reaction mechanism. On the other hand, the transition to the real biomass now represents a necessary choice for allowing the next ALs production on a larger scale. The improvement of the available synthetic strategies, the use of raw materials and the development of new applications for ALs will contribute to develop more intensified, greener, and sustainable processes.

Novelty of iron-exchanged heteropolyacid encapsulated inside ZIF-8 as an active and superior catalyst in the esterification of furfuryl alcohol and acetic acid

Metal-exchanged dodecatungstophosphoric acids encapsulated inside ZIF-8 framework were synthesized to produce a variety of active catalysts M-DTP@ZIF-8 for the formation of furfuryl acetate from the esterification of furfuryl alcohol and acetic acid.

Catalytic Processes from Biomass-Derived Hexoses and Pentoses: A Recent Literature Overview

Biomass is a plentiful renewable source of energy, food, feed and chemicals. It fixes about 1–2% of the solar energy received by the Earth through photosynthesis in both terrestrial and aquatic plants like macro- and microalgae. As fossil resources deplete, biomass appears a good complement and eventually a good substitute feedstock, but still needs the development of relatively new catalytic processes. For this purpose, catalytic transformations, whether alone or combined with thermal ones and separation operations, have been under study in recent years. Catalytic biorefineries are based on dehydration-hydrations, hydrogenations, oxidations, epimerizations, isomerizations, aldol condensations and other reactions to obtain a plethora of chemicals, including alcohols, ketones, furans and acids, as well as materials such as polycarbonates. Nevertheless, there is still a need for higher selectivity, stability, and regenerability of catalysts and of process intensification by a wise combination of operations, either in-series or combined (one-pot), to reach economic feasibility. Here we present a literature survey of the latest developments for obtaining value-added products using hexoses and pentoses derived from lignocellulosic material, as well as algae as a source of carbohydrates for subsequent transformations.

Efficient synthesis of butyl levulinate from furfuryl alcohol over ordered mesoporous Ti-KIT-6 catalysts for green chemistry applications

Here we describe the synthesis of butyl levulinate by alcoholysis of furfuryl alcohol with n-butanol over a series of titanium incorporated mesoporous KIT-6 molecular sieve catalysts prepared by a simple sol–gel treatment.