Microwave-assisted conversion of microcrystalline cellulose to 5-hydroxymethylfurfural catalyzed by ionic liquids

A simple and efficient synthesis of 5-hydroxymethylfurfural from carbohydrates using acidic ionic liquid grafted on silica gel

The catalytic application of 3-(4-sulfobutyl)-1H-imidazole-3-ium chloride immobilized on activated silica gel (SiO2-Imi-SO3H) for the production of 5-hydroxymethylfurfural is described here for the first time. This material was synthesized using a three-step method involving the grafting of chloropropyl groups onto activated silica gel, the substitution of zwitterions, and the acidification of zwitterions to form silica-supported ionic liquid. The successful immobilization of the IL on silica gel was confirmed through energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and elemental mapping. SiO2-Imi-SO3H-2 demonstrated good catalytic activity and recycling ability in fructose dehydration to 5-HMF. Several conditions for reaction were investigated, and an excellent 5-HMF yield (94.1%) was obtained after 4 h at 160 °C in dimethyl sulfoxide (DMSO) from fructose. Furthermore, a mechanism was proposed, the catalyst's reusability was investigated, and the catalyst was applied for the conversion of glucose to 5-HMF with other metal salts.

Microwave Encounters Ionic Liquid: Synergistic Mechanism, Synthesis and Emerging Applications

Progress in microwave (MW) energy application technology has stimulated remarkable advances in manufacturing and high-quality applications of ionic liquids (ILs) that are generally used as novel media in chemical engineering. This Review focuses on an emerging technology via the combination of MW energy and the usage of ILs, termed microwave-assisted ionic liquid (MAIL) technology. In comparison to conventional routes that rely on heat transfer through media, the contactless and unique MW heating exploits the electromagnetic wave-ions interactions to deliver energy to IL molecules, accelerating the process of material synthesis, catalytic reactions, and so on. In addition to the inherent advantages of ILs, including outstanding solubility, and well-tuned thermophysical properties, MAIL technology has exhibited great potential in process intensification to meet the requirement of efficient, economic chemical production. Here we start with an introduction to principles of MW heating, highlighting fundamental mechanisms of MW induced process intensification based on ILs. Next, the synergies of MW energy and ILs employed in materials synthesis, as well as their merits, are documented. The emerging applications of MAIL technologies are summarized in the next sections, involving tumor therapy, organic catalysis, separations, and bioconversions. Finally, the current challenges and future opportunities of this emerging technology are discussed.

Evaluating the potential of a novel hardwood biomass using a superbase ionic liquid

Lignocellulosic biomass, being ubiquitous and easily accessible, bears a huge potential for sustainable energy and other products.

Engineering of sustainable biomaterial composites from cellulose and silk fibroin: Fundamentals and applications

This review addresses composites prepared from cellulose (Cel) and silk fibroin (SF) to generate multifunctional, biocompatible, biodegradable materials such as fibers, films and scaffolds for tissue engineering. First, we discuss briefly the molecular structures of Cel and SF. Their structural features explain why certain solvents, e.g., ionic liquids, inorganic electrolyte solutions dissolve both biopolymers. We discuss the mechanisms of Cel dissolution because in many cases they also apply to (much less studied) SF dissolution. Subsequently, we discuss the fabrication and characterization of Cel/SF composite biomaterials. We show how the composition of these materials beneficially affects their mechanical properties, compared to those of the precursor biopolymers. We also show that Cel/SF materials are excellent and versatile candidates for biomedical applications because of the inherent biocompatibility of their components.

Microwave-assisted catalytic conversion of glucose to 5-hydroxymethylfurfural using “three dimensional” graphene oxide hybrid catalysts

High glucose → 5-HMF conversion was yielded with conversion of 99% and yield of 95% by 3D structured NiGO-FD and microwave-assisted reaction.

New Developments in Material Preparation Using a Combination of Ionic Liquids and Microwave Irradiation

During recent years, synthetic methods combining microwaves and ionic liquids became accepted as a promising methodology for various materials preparations because of their high efficiency and low energy consumption. Ionic liquids with high polarity are heated rapidly, volumetrically and simultaneously under microwave irradiation. Hence, combination of microwave irradiation as a heating source with ionic liquids with various roles (e.g., solvent, additive, template or reactant) opened a completely new technique in the last twenty years for nanomaterials and polymers preparation for applications in various materials science fields including polymer science. This review summarizes recent developments of some common materials syntheses using microwave-assisted ionic liquid method with a focus on inorganic nanomaterials, polymers, carbon-derived composites and biomass-based composites. After that, the mechanisms involved in microwave-assisted ionic-liquid (MAIL) are discussed briefly. This review also highlights the role of ionic liquids in the reaction and crucial issues that should be addressed in future research involving this synthesis technique.

Chemocatalytic Conversion of Cellulose into Key Platform Chemicals

Chemocatalytic transformation of lignocellulosic biomass to value-added chemicals has attracted global interest in order to build up sustainable societies. Cellulose, the first most abundant constituent of lignocellulosic biomass, has received extensive attention for its comprehensive utilization of resource, such as its catalytic conversion into high value-added chemicals and fuels (e.g., HMF, DMF, and isosorbide). However, the low reactivity of cellulose has prevented its use in chemical industry due to stable chemical structure and poor solubility in common solvents over the cellulose. Recently, homogeneous or heterogeneous catalysis for the conversion of cellulose has been expected to overcome this issue, because various types of pretreatment and homogeneous or heterogeneous catalysts can be designed and applied in a wide range of reaction conditions. In this review, we show the present situation and perspective of homogeneous or heterogeneous catalysis for the direct conversion of cellulose into useful platform chemicals.

Recent Advances in the Microwave-Assisted Production of Hydroxymethylfurfural by Hydrolysis of Cellulose Derivatives-A Review

The concepts of sustainable development, bioeconomy, and circular economy are being increasingly applied for the synthesis of molecules of industrial interest. Among these molecules, hydroxymethylfurfural as a platform molecule is the subject of various research approaches to improve its synthesis and productivity, and extend its potential uses. Accordingly, this review paper aims essentially at outlining recent breakthroughs obtained in the field of hydroxymethylfurfural production from sugars and polysaccharide feedstocks under microwave-assisted technology. The review discusses advances obtained via microwave activation in major production pathways recently explored, split into the following categories: (i) use of various homogeneous catalysts like mineral or organic acids, metal salts, or ionic liquids; (ii) feedstock dehydration making use of various solid acid catalysts; and (iii) non-catalytic routes.

Recent Advances in Solvents for the Dissolution, Shaping and Derivatization of Cellulose: Quaternary Ammonium Electrolytes and their Solutions in Water and Molecular Solvents

There is a sustained interest in developing solvents for physically dissolving cellulose, i.e., without covalent bond formation. The use of ionic liquids, ILs, has generated much interest because of their structural versatility that results in efficiency as cellulose solvents. Despite some limitations, imidazole-based ILs have received most of the scientific community’s attention. The objective of the present review is to show the advantages of using quaternary ammonium electrolytes, QAEs, including salts of super bases, as solvents for cellulose dissolution, shaping, and derivatization, and as a result, increase the interest in further investigation of these important solvents. QAEs share with ILs structural versatility; many are liquids at room temperature or are soluble in water and molecular solvents (MSs), in particular dimethyl sulfoxide. In this review we first give a historical background on the use of QAEs in cellulose chemistry, and then discuss the common, relatively simple strategies for their synthesis. We discuss the mechanism of cellulose dissolution by QAEs, neat or as solutions in MSs and water, with emphasis on the relevance to cellulose dissolution efficiency of the charge and structure of the cation and. We then discuss the use of cellulose solutions in these solvents for its derivatization under homogeneous and heterogeneous conditions. The products of interest are cellulose esters and ethers; our emphasis is on the role of solvent and possible side reactions. The final part is concerned with the use of cellulose dopes in these solvents for its shaping as fibers, a field with potential commercial application.

Microwave-Assisted Conversion of Fructose to 5-Hydroxymethylfurfural Using Sulfonated Porous Carbon Derived from Biomass

In this study, a series of sulfonated carbon solid acid catalysts was prepared by a template method using fructose as the carbon source and zinc chloride as the catalyst and template. The reaction involving fructose dehydration to 5-hydroxymethylfurfural (5-HMF) was investigated using these catalysts with microwave assistance in dimethyl sulfoxide. The influence of different catalysts, catalyst amount, microwave power, fructose content, and reaction temperature, as well as the reusability of the catalyst, were investigated. The prepared catalysts were characterised by X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy, nitrogen adsorption–desorption measurement, and temperature-programmed desorption of ammonia gas, and the total numbers of surface acid sites of these carbon-based solid acid catalysts were analysed by chemical adsorption–desorption of ammonia along with the standard curve for ammonia. The results revealed that the C2-SO3H catalyst exhibited the best activity. A 5-HMF yield of 87 % and fructose conversion of 99 % were achieved at 170°C in DMSO after 3 min. The microwave-assisted synthetic strategy was advantageous compared with the traditional method because this approach could shorten the total reaction time.

Catalytic valorization of starch-rich food waste into hydroxymethylfurfural (HMF): Controlling relative kinetics for high productivity

This study aimed to maximize the valorization of bread waste, a typical food waste stream, into hydroxymethylfurfural (HMF) by improving our kinetic understanding. The highest HMF yield (30mol%) was achieved using SnCl₄ as catalyst, which offered strong derived Brønsted acidity and moderate Lewis acidity. We evaluated the kinetic balance between these acidities to facilitate faster desirable reactions (i.e., hydrolysis, isomerization, and dehydration) relative to undesirable reactions (i.e., rehydration and polymerization). Such catalyst selectivity of SnCl₄, AlCl₃, and FeCl₃ was critical in maximizing HMF yield. Higher temperature made marginal advancement by accelerating the undesirable reactions to a similar extent as the desirable pathways. The polymerization-induced metal-impregnated high-porosity carbon was a possible precursor of biochar-based catalyst, further driving up the economic potential. Preliminary economic analysis indicated a net gain of USD 43-236 per kilogram bread waste considering the thermochemical-conversion cost and chemical-trading revenue.

Facile synthesis of hierarchical pore foam catalysts with Brønsted–Lewis acid sites for the one-pot conversion of cellulose to 5-hydroxymethylfurfural

The Whole process of synthesis of HPFCs by Pickering high internal phase emulsions and application in conversion of cellulose to HMF.

Pretreatment by NaOH swelling and then HCl regeneration to enhance the acid hydrolysis of cellulose to glucose

A simple pretreatment method, NaOH swelling at a low temperature and then HCl regeneration, was developed for depolymerization of cellulose to glucose. Cellulose was transformed into amorphous hydrogel during the treatment; and due to the easy diffusion of H(+) and Cl(-) ions into the cellulose hydrogel network as well as the strong ability of Cl(-) to disrupt the massive hydrogen bond, the hydrolysis rate was greatly enhanced. The method is effective for α-cellulose, microcrystalline cellulose, filter paper, ramie fiber and absorbent cotton. Even at a high α-cellulose concentration of 50g/L, 29.1% yield of glucose was still obtained within 10min at 160°C under microwave irradiation, where up to 16.2g/L of glucose solution was given. The influence of NaOH concentration, HCl concentration, hydrolysis temperature and time on the hydrolysis rate was investigated. The structure of cellulose hydrogel was also studied to confirm the reaction mechanism.

Efficient production of glucose by microwave-assisted acid hydrolysis of cellulose hydrogel

To improve the production of glucose from cellulose, a simple and effective route was developed. This process uses a combination of a step of cellulose dissolution in aqueous NaOH/urea solution and then regeneration with water, followed by an acid hydrolysis step under microwave irradiation. The method is effective to obtain glucose from α-cellulose, microcrystalline cellulose, filter paper, ramie fiber and absorbent cotton. Increased with the acid concentration the glucose yield from hydrogel hydrolysis increased from 0.42% to 44.6% at 160 °C for 10 min. Moreover, the ozone treatment of cellulose in NaOH/urea solution before regeneration significantly enhanced the hydrolysis efficiency with a glucose yield of 59.1%. It is believed that the chains in cellulose hydrogel are relatively free approached, making that the acids easily access the β-glycosidic bonds.

From lignocellulosic biomass to lactic- and glycolic-acid oligomers: a gram-scale microwave-assisted protocol

The conversion of lignocellulosic biomass into platform chemicals is the key step in the valorization of agricultural waste. Of the biomass-derived platform chemicals currently produced, lactic acid plays a particularly pivotal role in modern biorefineries as it is a versatile commodity chemical and building block for the synthesis of biodegradable polymers. Microwave-assisted processes that furnish lactic acid avoid harsh depolymerization conditions while cutting down reaction time and energy consumption. We herein report a flash catalytic conversion (2 min) of lignocellulosic biomass into lactic and glycolic acids under microwave irradiation. The batch procedure was successfully adapted to a microwave-assisted flow process (35 mL min(-1) ), with the aim of designing a scalable process with higher productivity. The C2 and C4 units recovered from the depolymerization were directly used as the starting material for a solvent and catalyst-free microwave-assisted polycondensation that afforded oligomers in good yields.

A kinetic study on microwave-assisted conversion of cellulose and lignocellulosic waste into hydroxymethylfurfural/furfural

Native cellulose, lignocellulosic materials from Brazil (carnauba palm leaves and macauba pulp and shell) and pine nut shell from Spain have been studied as substrates for the production of HMF and furfural in a conventional microwave oven. In order to promote the dissolution of native cellulose, several ionic liquids, catalysts, organic solvents and water doses have been assessed. The most suitable mixture (5mL of choline chloride/oxalic acid, 2mL of sulfolane, 2mL of water, 0.02g of TiO2 and 0.1g of substrate) has been chosen to conduct kinetic studies at different reaction times (5-60min) and various temperatures (120-200°C) and to evaluate the best conditions for HMF+furfural production according to Seaman's model. The best production yields of HMF+furfural have been attained for native cellulose, with a yield of 53.24% when an ultrasonic pretreatment was used prior to a microwave treatment with stirring.

Microwave assisted rapid conversion of fructose into 5-HMF over solid acid catalysts

Microwave assisted efficient conversion of fructose into 5-hydroxymethylfurfural over solid acid catalysts in a very short reaction time.

Fabrication of a micellar heteropolyacid with Lewis–Brønsted acid sites and application for the production of 5-hydroxymethylfurfural from saccharides in water

Supramolecular complexes (C_nH_2n+1N(CH₃)₃)H₄PW₁₁TiO₄₀ (n = 4, 8, 12, 14, 16, and 18) consisting of heteropolyacids (HPAs) and amphiphilic quaternary ammonium were fabricated through self-assembly.

Absorption degree analysis on biogas separation with ionic liquid systems

For biogas upgrading, present work mainly focuses on either thermodynamics or mass transfer properties. A systematical study on these two aspects is important for developing a new biogas separation process. In this work, a new criterion "absorption degree", which combines both thermodynamics and mass transfer properties, was proposed for the first time to comprehensively evaluate the absorption performance. Henry's law constants of CO2 and CH4 in ionic liquids-polyethylene glycol dimethyl ethers mixtures were investigated. The liquid-side mass transfer coefficients (kL) were determined. The results indicate that IL-NHD mixtures exhibit not only a high CO2/CH4 selectivity, but also a fast kL for CO2 absorption. The [bmim][NO3]+NHD mixtures present a high absorption degree value for CO2 but a low value for CH4. For presenting a highest relative absorption degree value, the 50wt% [bmim][NO3]+50wt% NHD mixture is recommended for biogas upgrading.

Porous solid acid with high Surface area derived from emulsion templating and hypercrosslinking for efficient one-pot conversion of cellulose to 5-hydroxymethylfurfural

This work addressed efficient one-pot conversion of cellulose to 5-hydroxymethylfurfural by porous solid acid in the presence of [Emim]Cl.