Fabrication of −SO3H functionalized aromatic carbon microspheres directly from waste Camellia oleifera shells and their application on heterogeneous acid catalysis

Sucrose-derived porous carbon catalyzed lignin depolymerization to obtain a product with application in type 2 diabetes mellitus

As the most important phenolic biopolymer in nature, lignin shows promising application potentialities in various bioactivities in vivo and in vitro, mainly including antioxidant, anti-inflammatory, hypolipidemic, and antidiabetic control. In this work, several carbon-based solid acids were synthesized to catalyze the fragmentation of organosolv lignin (OL). The generated lignin fragments, with controllable molecular weight and functional groups, were further evaluated for their application in the prevention and treatment of type 2 diabetes mellitus (T2DM). The results suggested that the urea-doped catalyst (SUPC) showed a more excellent catalytic performance in producing diethyl ether insoluble lignin (DEIL) and diethyl ether soluble lignin (DESL). In addition, the lignin fragments have a good therapeutic effect on the cell model of T2DM. Compared with the insulin resistance model, DEIL obtained by catalytic depolymerization of OL with SUPC could improve the glucose consumption of insulin-resistant cells. Moreover, low-concentration samples (50 μg/mL) can promote glucose consumption (19.7 mM) more than the traditional drug rosiglitazone (17.5 mM). This work demonstrates the prospect of depolymerized lignin for the prevention and treatment of T2DM and provides a new application field for lignin degradation products.

Extraction of cellulose nanocrystalline from Camellia oleifera Abel waste shell: Study of critical processes, properties and enhanced emulsion performance

Cellulose nanocrystals (CNCs) extracted from the waste shell of Camellia oleifera Abel (C. oleifera) are gaining attention as valuable materials. In this study, CNCs were extracted from the agricultural waste shell of C. oleifera through phosphoric acid and sulfuric acid hydrolysis, respectively. Firstly, we optimized the alkaline treatment process for cellulose isolation by using response surface methodology. Furthermore, the properties of CNCs were investigated by neutralizing them with NaOH and NH3·H2O, and by dialysis in water. In addition, the characterization methods including FT-IR, TGA, AFM and TEM were used to analysis the properties of the synthesized CNCs. Finally, CNCs were studied for their application in essential oil-based Pickering emulsions. CNCs obtained from sulfuric acid showed the smallest particle size and good dispersibility. Moreover, the release profiles of essential oils in the emulsions were followed by Peppa's kinetic release model. The antibacterial activity of the emulsions against E. coli and S. aureus showed that CNCs-stabilized emulsions enhanced the antibacterial activity of essential oils. Therefore, neutralization treatments may enhance the properties of CNCs, and CNCs stabilized Pickering emulsions can enhance antibacterial activity of essential oil. This study provides insight into the potential application of CNCs derived from C. oleifera waste shells.

A Comprehensive Review on Graphitic Carbon Nitride for Carbon Dioxide Photoreduction

Inspired by natural photosynthesis, harnessing the wide range of natural solar energy and utilizing appropriate semiconductor-based catalysts to convert carbon dioxide into beneficial energy species, for example, CO, CH₄ , HCOOH, and CH₃ COH have been shown to be a sustainable and more environmentally friendly approach. Graphitic carbon nitride (g-C₃ N₄ ) has been regarded as a highly effective photocatalyst for the CO₂ reduction reaction, owing to its cost-effectiveness, high thermal and chemical stability, visible light absorption capability, and low toxicity. However, weaker electrical conductivity, fast recombination rate, smaller visible light absorption window, and reduced surface area make this catalytic material unsuitable for commercial photocatalytic applications. Therefore, certain procedures, including elemental doping, structural modulation, functional group adjustment of g-C₃ N₄ , the addition of metal complex motif, and others, may be used to improve its photocatalytic activity towards effective CO₂ reduction. This review has investigated the scientific community's perspectives on synthetic pathways and material optimization approaches used to increase the selectivity and efficiency of the g-C₃ N₄ -based hybrid structures, as well as their benefits and drawbacks on photocatalytic CO₂ reduction. Finally, the review concludes a comparative discussion and presents a promising picture of the future scope of the improvements.

Carbon Quantum Dots-Functionalized UiO-66-NH2 Enabling Efficient Infrared Light Conversion of 5-Hydroxymethylfurfuryl with Waste Ethanol into 5-Ethoxymethylfurfural

The catalytic etherification of 5-hydroxymethylfurfural (HMF) with the waste ethanol into high-energy-density 5-ethoxymethylfurfural (EMF) has been considered as a promising way to simultaneously alleviate the energy crisis and environmental pollution. However, the energy consumption is rather high as the synthesis of EMF requires a high temperature to open the etherification reaction. Herein, we demonstrate a clever design and construction of acidified biomass-derived carbon quantum dots (BCQDs)-modified UiO-66-NH₂ that is immobilized on cermasite (H⁺/BCQDs/UiO-66-NH₂@ceramsite), which can use the IR light as driven energy and wasted ethanol to trigger the catalytic conversion of HMF into EMF. The temperature on the surface of the immobilized catalyst could reach as high as 139 °C within 15 min IR irradiation. Due to the aforementioned advantages, the as-prepared catalyst exhibited excellent IR-triggered catalytic performance toward EMF production, where the EMF yields and selectivity were as high as 45% and 65%, respectively. The high catalytic performance originates from the outstanding photo-to-thermal conversion by the introduction of BCQDs, as well as the strong interactions between BCQDs and UiO-66-NH₂ that boosts the etherification reactions. The immobilization of catalyst on cermasite not only benefits catalyst recycling, but more importantly reduces catalyst loss during practical applications. The conceptual study shown here provides new viewpoints in designing energy-effective materials for the conversion of wastes into high-value-added resources.

Applications of Chinese Camellia oleifera and its By-Products: A Review

Camellia oleifera is a woody oil tree species unique to China that has been cultivated and used in China for more than 2,300 years. Most biological research on C. oleifera in recent years has focused on the development of new varieties and breeding. Novel genomic information has been generated for C. oleifera, including a high-quality reference genome at the chromosome level. Camellia seeds are used to process high-quality edible oil; they are also often used in medicine, health foods, and daily chemical products and have shown promise for the treatment and prevention of diseases. C. oleifera by-products, such as camellia seed cake, saponin, and fruit shell are widely used in the daily chemical, dyeing, papermaking, chemical fibre, textile, and pesticide industries. C. oleifera shell can also be used to prepare activated carbon electrodes, which have high electrochemical performance when used as the negative electrode of lithium-ion batteries. C. oleifera is an economically valuable plant with diverse uses, and accelerating the utilization of its by-products will greatly enhance its industrial value.

One-step fabrication of dual functional Tb3+ coordinated polymeric micro/nano-structures for Cr(VI) adsorption and detection

Hexavalent chromium Cr(VI) has been considered as one of the most hazardous heavy metals because of its strong and persistent toxicity to the ecosystem and human beings. Herein, we have synthesized a double hydrophilic block co-polyarylene ether nitriles (abbreviated as dhPEN) bearing aromatic backbone as well as pendent carboxyl and sulfonate groups. Afterward, the synthesized dhPEN has been co-assembled with the lanthanide Tb³⁺ via a one-step solvent exchange protocol, leading to generation of Tb³⁺ coordinated dhPEN (Tb-dhPEN) micro/nano-structures that exhibit good adsorption capacity and detection sensitivity towards Cr(VI). More specifically, the direct self-assembly of dhPEN and Tb³⁺ in mixed H₂O/DMF solvents resulted to Tb-dhPEN microparticles with lamellar structures, which exhibited a high Cr(VI) adsorption capacity approaching to 402 mg/g. The detailed characterization confirm that Cr(VI) is adsorbed and partially reduced to Cr(III) by the Tb-dhPEN microparticles via chemical interaction. Furthermore, the self-assembly of dhPEN with Tb³⁺ in the H₂O/DMF mixed solvents containing NaOH contributed to the generation of spherical nanoparticles showing green emission at 545 nm, which can be selectively quenched by the Cr(VI), leading to the specific detection of trace concentration of Cr(VI) down to 0.12 nM as well as reliable determination of Cr(VI) presented in real environmental samples.

Investigation into the performance decay of proton-exchange membranes based on sulfonated heterocyclic poly(aryl ether ketone)s in Fenton's reagent

Sulfonated N-heterocyclic poly(aryl ether) proton-exchange membranes have potential applications in the fuel-cell field due to their favorable proton conduction capacity and stability. This paper investigates the changes in mass and performance decay, such as proton conduction and mechanical strength, of sulfonated poly(ether ether ketone)s (SPEEKs) and three sulfonated N-heterocyclic poly(aryl ether ketone) (SPPEK, SPBPEK-P-8, and SPPEKK-P) membranes in Fenton's oxidative experiment. The SPEEK membrane exhibited the worst oxidative stability. The oxidative stability of the SPPEK membrane is enhanced due to the introduction of phthalazinone units in the chains. The SPPEKK-P and SPBPEK-P-8 membranes exhibit better radical tolerance than the SPPEK membrane, with proton conductivity retention rates of 66% and 73% for 1 h oxidative treatment, respectively. In addition, the molecular chains of SPPEKK-P and SPBPEK-P-8 exhibit relatively little disruption. The pendant benzenesulfonic groups enhance the steric effects for reducing radical attacks on the ether bonds and reduce the hydration of molecular chains. The introduction of phthalazinone units decreases the rupture points in the main chain. Therefore, the radical tolerance of the membranes is improved. These results provide a reference for the design of highly stable sulfonated heterocyclic poly(aryl ether) membranes.

Catalytic Synthesis of the Biofuel 5-Ethoxymethylfurfural (EMF) from Biomass Sugars

A new generation of bioplatform molecule 5-ethoxymethylfurfural (EMF) has excellent energy density and combustion performance, which makes it a potential fuel additive. This article reviews the factors that affect the production of EMF from different feedstocks, including platform compounds, monosaccharides, polysaccharides, and raw lignocellulosic biomass. Focus is placed on discussing the catalytic efficiency with pros and cons of different acid catalysts, including homogeneous catalysts (i.e., liquid acids and metal salts), heterogeneous catalysts (i.e., zeolites, heteropolyacid-based hybrids, and SO3H-based catalysts), ionic liquids, mixed acid catalysts, and deep eutectic solvents (DESs). Except for the commonly used ethanol solvent, this review also summarizes the influence of the cosolvent system (e.g., ethanol/dimethylsulfoxide (DMSO), ethanol/tetrahydrofuran (THF), and ethanol/γ-valerolactone (GVL)) on the EMF yield.

Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Background:

Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been used to accelerate organic transformations. With the development of environmental awareness, to obtain highly efficient scaffolds, scientists have directed their studies towards synthetic methodologies that minimize or preferably eliminate the formation of waste, avoid toxic solvents and reagents and use renewable starting materials as far as possible.

Methods:

In this connection, the organocatalytic reactions providing efficiency and selectivity for most of the transformations have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts contributing to the transformation of reactants into products with the least possible waste production, have been serving the concept of green chemistry.

Results and Conclusion:

Organocatalysts have been classified based on their binding capacity to the substrate with covalent or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol, and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

Influence of Dimethylsulfoxide and Dioxygen in the Fructose Conversion to 5-Hydroxymethylfurfural Mediated by Glycerol's Acidic Carbon

Both the catalytic production of 5-hydroxymethylfurfural (5-HMF) from carbohydrates and the use of a catalyst obtained from residues stand out for adding value to by-products and wastes. These processes contribute to the circular economy. In this work it was evaluated optimized conditions for 5-HMF production from fructose with high yield and selectivity. The reaction was catalyzed by an acidic carbon obtained from glycerol, a byproduct of the biodiesel industry. Special attention has been given to the use of dimethyl sulfoxide (DMSO) as a solvent and its influence on system activity, both in the presence and absence of O₂. Glycerol's carbon with acidic properties can be effectively used as catalyst in fructose dehydration, allowed achieving conversions close to 100% with 5-HMF selectivities higher than 90%. The catalyst can be reused in consecutive batch runs. The influence of DMSO in the presence of O₂ should be considered in the catalytic activity, as the stabilization of a reaction intermediate by the [O₂:DMSO] complex is favored and, both fructose conversion and 5-HMF yield increase.

Recent progress in the development of advanced biofuel 5-ethoxymethylfurfural

Biomass-derived 5-ethoxymethylfurfural (EMF) with excellent energy density and satisfactory combustion performance holds great promise to meet the growing demands for transportation fuels and fuel additives to a certain extent. In this review, we summarized the relative merits of the EMF preparation from different feedstocks, such as platform chemicals, biomass sugars and lignocellulosic biomass. Advances for EMF synthesis over homogeneous (i.e. inorganic acids and soluble metal salts), heterogeneous catalysts (i.e. zeolites, heteropolyacid-based hybrids, sulfonic acid-functionalized catalysts, and others) or mixed-acid catalysts were performed as well. Additionally, the emerging development for the EMF production was also evaluated in terms of the different solvents system (i.e. single-phase solvents, biphasic solvents, ionic liquids, and deep eutectic solvents). It is concluded with current challenges and prospects for advanced biofuel EMF preparation in the future.

Thermal Characteristics and Kinetics of Waste Camellia oleifera Shells by TG-GC/MS

There is a large amount of Camellia oleifera shells generated as a waste product from industrial processes. Therefore, the high-value utilization of C. oleifera shells is a hotspot of current research. The thermal characteristics and kinetics of waste Camellia shells (WCOSs) were analyzed by thermogravimetry with gas chromatography-mass spectrometry (TG-GC/MS). The thermal behavior of WCOSs was studied at 10, 20, 40, and 60 °C/min, and the distributed activation energy model (DAEM) was used to research the kinetics and activation energies. The activation energies of WCOSs based on the DAEM ranged from 68.64 to 244.49 kJ/mol, corresponding to the conversion rate from 0.10 to 0.90. The correlation coefficient (R 2) shows the best fit, and it ranged from 0.921 to 0.994. Pyrolysis products at four key temperature points (228, 296, 492, and 698 °C) were studied via GC/MS. Many compounds were detected at the different temperatures. With the increase of temperature, furans, benzene, and long-chain alkanes were produced successively. This data will help to expand the utilization of WCOSs.

Natural Nanofibrous Cellulose-Derived Solid Acid Catalysts

Solid acid catalysts (SACs) have attracted continuous research interest in past years as they play a pivotal role in establishing environmentally friendly and sustainable catalytic processes for various chemical industries. Development of low-cost and efficient SACs applicable to different catalysis processes are of immense significance but still very challenging so far. Here, we report a new kind of SACs consisting of sulfonated carbon nanofibers that are prepared via incomplete carbonization of low-cost natural nanofibrous cellulose followed by sulphonation with sulfuric acid. The prepared SACs feature nanofibrous network structures, high specific surface area, and abundant sulfonate as well as hydroxyl and carboxyl groups. Remarkably, the nanofibrous SACs exhibit superior performance to the state-of-the-art SACs for a wide range of acid-catalyzed reactions, including dimerization of α-methylstyrene, esterification of oleic acid, and pinacol rearrangement. The present approach holds great promise for developing new families of economic but efficient SACs based on natural precursors via scalable and sustainable protocols in the future.

Camellia oleifera shell as an alternative feedstock for furfural production using a high surface acidity solid acid catalyst

This paper focuses on the high-value transformation of camellia oleifera shell, which is an agricultural waste enriched in hemicellulose. An efficient catalytic route employing sulfonated swelling mesoporous polydivinylbenzene (PDVB-SO₃H) as catalyst in monophasic or biphasic solvents was developed for the conversion of raw camellia oleifera shell into furfural. The reaction parameters were evaluated and optimized for improving the furfural yield. It was found that the solvent greatly influenced the hydrolysis of camellia oleifera shells, and the highest furfural yield of 61.3% was obtained in "γ-butyrolactone + water" system when the feedstock-to-catalyst ratio was 2 for 30 min at 443 K. Camellia oleifera shell exhibited a high potential as feedstock to produce furfural in high yields. The outcome of this study provides an attractive utilization option to camellia oleifera shell, which is currently burned or discarded for producing a bio-based chemical.