Towards ‘bio-based’ Nylon: conversion of γ-valerolactone to methyl pentenoate under catalytic distillation conditions

Unlocking Enhanced Butadiene Selectivity: The Crucial Role of Zeolite Channel Confinement in the Selective Decarbonylation of γ-Valerolactone

Herein, we report a highly selective production route for butadiene from γ-valerolactone over zeolite catalysts. The catalytic performance of eight zeolites with different framework topologies were compared, revealing that zeolites with narrower 10-membered ring channels exhibit enhanced selectivity of butadiene. Specifically, ZSM-35 and ZSM-22, featuring the narrowest 10-membered ring channels, demonstrate the highest butadiene selectivity to 61 % and 59 %, respectively. Notably, surface passivation of ZSM-35 leads to a remarkable increase in butadiene selectivity to 82 %, maintaining a 99 % conversion. Additionally, we propose a reaction network and identify cyclopentenone as a key intermediate in the transformation of γ-valerolactone to butadiene. Both experimental and theoretical results conclude that confinement effect of 10-membered ring channels improves the selectivity of butadiene.

Valeric Biofuels from Biomass-Derived γ-Valerolactone: A Critical Overview of Production Processes

This review analyzes critically the production of valeric biofuels from γ-valerolactone, a relevant biomass-derived platform molecule. Initially, the main properties of valeric esters as fuels for spark- and compression-ignition engines are summarized. Then, catalytic routes to valeric esters from γ-valerolactone are meticulously analyzed, describing the acid- and metal-catalyzed reactions taking part in the tandem catalysis. Only works focused on the production of the valeric biofuels were considered, excluding the cases where these esters were observed in minor amounts or as byproducts. The role of the appropriate selection of the support, catalytic species, catalyst preparation and experimental conditions on the valeric ester productivity are thoroughly commented. Finally, some concluding remarks and perspectives are given, mentioning the areas where additional efforts must be done in order to turn the dream of a massive and renewable valeric biofuel production into a reality.

Microwave-Assisted One Pot Cascade Conversion of Furfural to γ-Valerolactone over Sc(OTf)3

γ-Valerolactone (GVL) is considered as a star biochemical which can be used as a green solvent, fuel additive and versatile organic intermediate. In this study, metal triflate (M(OTf)n ) was utilized as the catalyst for one-pot transformation of furfural (FF) to GVL in alcohol media under microwave irradiation. Alcohol plays multiple functions including solvent, hydrogen donor and alcoholysis reagent in this cascade reaction process. And process efficiency of GVL production from FF upgrading is strongly related to the effective charge density of selected catalyst and the reduction potential of selected alcohol. Complex (OTf)n -M-O(H)R, presenting both Brønsted acid and Lewis acid, is the real catalytic active species in this cascade reaction process. Among various catalysts, Sc(OTf)3 exhibited the best catalytic activity for GVL production. Various reaction parameters including the Sc(OTf)3 amount, reaction temperature and time were optimized by the response surface methodology with the central composite design (RSM-CCD). Up to 81.2 % GVL yield and 100 % FF conversion were achieved at 143.9 °C after 8.1 h in the presence of 0.16 mmol catalyst. This catalyst exhibits high reusability and can be regenerated by oxidative degradation of humins. In addition, a plausible cascade reaction network was proposed based on the distribution of product.

Ru-Catalyzed Direct Asymmetric Reductive Amination of Bio-Based Levulinic Acid and Ester for the Synthesis of Chiral Pyrrolidinone

Direct asymmetric reductive amination of bio-based levulinic acid (LA) to the enantioenriched 5-methylpyrrolidinone is achieved by using a readily available chiral Ru/bisphosphine catalyst with excellent enantioselectivity (up to 96 % ee) and high isolated yield (up to 89 %). Methyl levulinate (ML), a byproduct from the industrial production of 2,5-furandicarboxylic acid (FDCA), can be used instead of LA with similar reactivity and selectivity. Mass spectrometry and isotope labelling studies indicate that the chiral lactam is formed via imine-enamine tautomerization/cyclization followed by asymmetric hydrogenation of the cyclic enamide.

Ru-MnOx Interaction for Efficient Hydrodeoxygenation of Levulinic Acid and Its Derivatives

Metal-oxide interaction was widely observed in supported metal catalysts, playing a significant role in tuning the catalytic performance. Here, we reported that the interaction of Ru and MnO_x was able to facilitate the hydrodeoxygenation of levulinic acid (LA) to 2-butanol with a high turnover frequency (1.99 × 10⁶ h^-1), turnover number (4411), and yield (98.8%). Moreover, this catalyst was capable of removing the hydroxymethyl group of lactones and diol with high yields of products. The high activity of the Ru-MnO_x catalyst was due to the strong Ru-MnO_x interaction, which facilitated reduction of Ru oxide to Ru⁰ and Mn oxide to Mn²⁺. The increased fractions of Ru⁰ and Mn²⁺ provided metal and Lewis acid sites, respectively, and therefore facilitated LA hydrodeoxygenation. A linear correlation between the hydrodeoxygenation activity of the Ru-MnO_x catalyst and [Mn²⁺]ln([Ru⁰]) was observed.

Critical review on microfibrous composites for applications in chemical engineering

Microfibrous composites (MCs) are novel materials with unique structures and excellent functional properties, showing great potential in industrial applications. The investigation of the physicochemical properties of MCs is significant for accommodating the rapid development of high-efficiency chemical engineering industries. In this review, the characteristics, synthesis and applications of different types of previously reported MCs are discussed according to the constituent fibres, including polymers, metals and nonmetals. Among the different types of MCs, polymer MCs have a facile synthesis process and adjustable fibre composition, making them suitable for many complex situations. The high thermal and electrical conductivity of metal MCs enables their application in strong exothermic, endothermic and electrochemical reactions. Nonmetallic MCs are usually stable and corrosion resistant when reducing and oxidizing environments. The disadvantages of MCs, such as complicated synthesis processes compared to those of particles or powders, high cost, insufficient thorough study, and unsatisfactory regeneration effects, are also summarized. As a result, a more systematic investigation of MCs remains necessary. Despite the advantages and great application potential of microfibrous composites, much effort remains necessary to advance them to the industrial level in the chemical engineering industry.

Continuous Flow Upgrading of Selected C2-C6 Platform Chemicals Derived from Biomass

The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C₂ to C₆ bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethylfurfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.

Ni Supported on Natural Clays as a Catalyst for the Transformation of Levulinic Acid into γ-Valerolactone without the Addition of Molecular Hydrogen

γ-Valerolactone (GVL) is a valuable chemical that can be used as a clean additive for automotive fuels. This compound can be produced from biomass-derived compounds. Levulinic acid (LA) is a compound that can be obtained easily from biomass and it can be transformed into GVL by dehydration and hydrogenation using metallic catalysts. In this work, catalysts of Ni (a non-noble metal) supported on a series of natural and low-cost clay-materials have been tested in the transformation of LA into GVL. Catalysts were prepared by a modified wet impregnation method using oxalic acid trying to facilitate a suitable metal dispersion. The supports employed are attapulgite and two sepiolites with different surface areas. Reaction tests have been undertaken using an aqueous medium at moderate reaction temperatures of 120 and 180 °C. Three types of experiments were undertaken: (i) without H2 source, (ii) using formic acid (FA) as hydrogen source and (iii) using Zn in order to transform water in hydrogen through the reaction Zn + H2O → ZnO + H2. The best results have been obtained combining Zn (which plays a double role as a reactant for hydrogen formation and as a catalyst) and Ni/attapulgite. Yields to GVL higher than 98% have been obtained at 180 °C in the best cases. The best catalytic performance has been related to the presence of tiny Ni particles as nickel crystallites larger than 4 nm were not present in the most efficient catalysts.

Rhodium porphyrin molecule-based catalysts for the hydrogenation of biomass derived levulinic acid to biofuel additive γ-valerolactone

RhTPP and RhTCPP were prepared and utilized for the conversion of levulinic acid to γ-valerolactone and the reaction mechanism was proposed.

An Alcohol Dehydrogenase from the Short-Chain Dehydrogenase/Reductase Family of Enzymes for the Lactonization of Hexane-1,6-diol

Biocatalytic production of lactones, and in particular ϵ-caprolactone (CL), have gained increasing interest as a greener route to polymer building blocks, especially through the use of Baeyer-Villiger monooxygenases (BVMOs). Despite several advances in the field, BVMOs, however, still suffer several practical limitations. Alcohol dehydrogenase (ADH)-mediated lactonization of diols in turn has received far less attention and very few enzymes have been identified for the conversion of diols to lactones, with horse-liver ADH (HLADH) remaining the catalyst of choice. Screening of a diverse panel of ADHs, AaSDR-1, a member of the short-chain dehydrogenase/reductase family, was found to produce ϵ-caprolactone from hexane-1,6-diol. Moreover, cofactor regeneration by an NADH oxidase eliminated the requirement of co-substrates, yielding water as the sole by-product. Despite lower turnover frequencies as compared to HLADH, higher selectivity was found for the production of CL, with HLADH forming significant amounts of 6-hydroxyhexanoic acid and adipic acid through aldehyde dehydrogenation/oxidation of the gem-diol intermediates. Also, CL yield were shown to be dependent on buffer choice, as structural elucidation of a Tris adduct confirmed the buffer amine to react with aliphatic aldehydes forming a Schiff-base intermediate which through further ADH oxidation, forms a tricyclic acetal product.

How Catalysts and Experimental Conditions Determine the Selective Hydroconversion of Furfural and 5-Hydroxymethylfurfural

Furfural and 5-hydroxymethylfurfural stand out as bridges connecting biomass raw materials to the biorefinery industry. Their reductive transformations by hydroconversion are key routes toward a wide variety of chemicals and biofuels, and heterogeneous catalysis plays a central role in these reactions. The catalyst efficiency highly depends on the nature of metals, supports, and additives, on the catalyst preparation procedure, and obviously on reaction conditions to which catalyst and reactants are exposed: solvent, pressure, and temperature. The present review focuses on the roles played by the catalyst at the molecular level in the hydroconversion of furfural and 5-hydroxymethylfurfural in the gas or liquid phases, including catalytic hydrogen transfer routes and electro/photoreduction, into oxygenates or hydrocarbons (e.g., furfuryl alcohol, 2,5-bis(hydroxymethyl)furan, cyclopentanone, 1,5-pentanediol, 2-methylfuran, 2,5-dimethylfuran, furan, furfuryl ethers, etc.). The mechanism of adsorption of the reactant and the mechanism of the reaction of hydroconversion are correlated to the specificities of each active metal, both noble (Pt, Pd, Ru, Au, Rh, and Ir) and non-noble (Ni, Cu, Co, Mo, and Fe), with an emphasis on the role of the support and of additives on catalytic performances (conversion, yield, and stability). The reusability of catalytic systems (deactivation mechanism, protection, and regeneration methods) is also discussed.

Influence of Sulfuric Acid on the Performance of Ruthenium-based Catalysts in the Liquid-Phase Hydrogenation of Levulinic Acid to γ-Valerolactone

The presence of biogenic or process-derived impurities poses a major problem on the efficient catalytic hydrogenation of biomass-derived levulinic acid to γ-valerolactone; hence, studies on their influence on catalyst stability are now required. Herein, the influence of sulfuric acid as feed impurity on the performance of Ru-based heterogeneous catalysts, including Ru/ZrO₂ and mono- and bimetallic Ru-on-carbon catalysts in dioxane as solvent, was investigated. The carbon-supported Ru catalysts proved to be very sensitive to minor amounts of sulfuric acid. In stark contrast, Ru/ZrO₂ showed a remarkable stability in the presence of the same impurity, which is attributed to the sulfate-ion adsorption capacity of the support. Preferential sulfate adsorption onto the surface of ZrO₂ effectively protects the Ru active phase from deactivation by sulfur poisoning. A simple catalyst regeneration strategy was effective in removing adsorbed impurities, allowing efficient catalyst recycling.

Synthesis of γ-Valerolactone from Carbohydrates and its Applications

γ-Valerolactone (GVL) is a valuable chemical intermediate that can be obtained by catalytic reduction of levulinic acid (LA) or alkyl levulinates (AL). There are many reports on the synthesis of GVL from LA or AL. However, the demand for the large-scale synthesis of GVL requires more environmentally friendly and cost-effective production processes. This article focuses on the recent advance in the synthesis of GVL from carbohydrates or lignocellulosic biomass. In addition, application of GVL as the reaction solvents, fuel additives, and as precursor for the synthesis of jet fuel and polymer monomers is also discussed.

Potential and challenges of zeolite chemistry in the catalytic conversion of biomass

This review emphasizes the progress, potential and future challenges in zeolite catalysed biomass conversions and relates these to concepts established in existing petrochemical processes.

Transfer hydrogenation of biomass-derived levulinic acid to γ-valerolactone over supported Ni catalysts

A bifunctional Ni/MMT catalyst for catalytic transfer hydrogenation of levulinic acid to γ-valerolactone with complete conversion and selectivity.

Efficient hydrogenation of levulinic acid in water using a supported Ni–Sn alloy on aluminium hydroxide catalysts

Efficient hydrogenation of levulinic acid (LA) into γ-valerolactone (GVL) in water using supported Ni–Sn(1.4)/AlOH consisting of Ni₃Sn₂ alloy species was achieved with high selectivity towards GVL and the catalyst could be reused without any significant loss of activity and selectivity.

A practical and efficient synthesis of methyl levulinate from cellulosic biomass catalyzed by an aluminum-based mixed acid catalyst system

A combination of aluminum compounds and organic sulfonic acids was an efficient catalyst system for direct methyl levulinate synthesis from both microcrystalline cellulose and wood powder.

Catalytic distillation for ethyl acetate synthesis using microfibrous-structured Nafion–SiO2/SS-fiber solid acid packings

We present a microfibrous-structured Nafion–SiO₂/SS-fiber solid acid catalyst and demonstrate its separation and reaction efficiency as catalytic distillation (CD) packings for esterification to produce ethyl acetate from acetic acid and ethanol.

Acid-functionalized mesoporous carbon: an efficient support for ruthenium-catalyzed γ-valerolactone production

The hydrogenation of levulinic acid has been studied using Ru supported on ordered mesoporous carbons (OMCs) prepared by soft-templating. P- and S-containing acid groups were introduced by postsynthetic functionalization before the addition of 1 % Ru by incipient wetness impregnation. These functionalities and the reaction conditions mediate the activity and selectivity of the levulinic acid hydrogenation. The presence of S-containing groups (Ru/OMC-S and Ru/OMC-P/S) deactivates the Ru catalysts strongly, whereas the presence of P-containing groups (Ru/OMC-P) enhances the activity compared to that of pristine Ru/OMC. Under mild conditions (70 °C and 7 bar H2 ) the catalyst shows high selectivity to γ-valerolactone (GVL; >95 %) and high stability on recycling. However, under more severe conditions (200 °C and p H 2=40 bar) Ru/OMC-P is particularly able to promote GVL ring-opening and the consecutive hydrogenation to pentanoic acid.

In Situ Catalytic Hydrogenation of Biomass-Derived Methyl Levulinate to γ-Valerolactone in Methanol

In this work, the hydrocyclization of methyl levulinate (ML) to γ-valerolactone (GVL) was performed in MeOH over an in situ prepared nanocopper catalyst without external H2 . This nanocopper catalyst served as a dual-functional catalyst for both hydrogen production by MeOH reforming and hydrogenation of ML. Nearly quantitative ML conversion with a GVL selectivity of 87.6 % was achieved at 240 °C in 1 h in MeOH under a nitrogen atmosphere. ML in the methanolysis products of cellulose also could be hydrogenated effectively to GVL over this nanocopper catalyst even in the presence of humins to give an ML conversion of 94.1 % and a GVL selectivity of 73.2 % at 240 °C in 4 h. The absorption behavior of humins on the surface of the nanocopper catalyst was observed, which resulted in a pronounced increase in the acidic sites of the nanocopper catalyst that facilitate ring-opening and the hydrocarboxylation/alkoxycarbonylation of GVL to byproducts.