Esterification Reaction Research Articles

Disposal of used oils as a prospective method of production of biodiesel

The article is devoted to the improvement of the production technology of diesel biofuel from waste oils, which are a significant source of environmental pollution. Environmental pollution is one of the biggest environmental problems of our time. Used oils that are not properly disposed of cause serious environmental problems, including water and soil pollution. The use of waste oils for the production of biofuel is a promising technology that allows reducing the amount of pollution and reducing dependence on fossil fuels. Biodiesel from waste oils has significant environmental, economic and sustainable advantages. The main goal of the article is a detailed analysis of modern technologies for the production of diesel biofuel from waste oils and an assessment of their improvements and impact on ecology, economy and society. The article discusses innovative approaches to the processing of used oils, their purification and preparation for further use. An analysis of the main methods of transesterification, hydrogenation, esterification and enzyme catalysis, as well as the latest technologies, such as ultrasonic and microwave intensification of biofuel production, was carried out. New technological solutions for the preliminary preparation of used oils with a high content of free fatty acids using a combination of acid catalysts are proposed, and a technological scheme of the full production cycle is developed. The rational parameters of the equipment for the preliminary preparation of used oils with a high content of free fatty acids have been determined. Recommended conditions include hydrogenation temperature not higher than 80°С, duration of the process not less than 40 minutes; separation of the water-protein part by centrifugation at a rotation frequency of the centrifuge rotor of 3000 rpm for 20 minutes; the esterification reaction temperature is no more than 60°C; molar ratio of alcohol to oil 9:1; acid catalyst concentration within 1-15%; the intensity of mixing in the reactor is 31.42 s-1; the duration of the process is not less than 120 minutes. It was established that it is advisable to use potassium hydroxide for the transesterification reaction. The use of potassium hydroxide is beneficial because the potassium salts formed during the technological process of diesel biofuel production can be used as mineral fertilizers. According to the results of the research, the optimal parameters for the transesterification reaction were chosen: the amount of methanol - 20% by mass. from the weight of the oil, the KOH 1 catalyst is 1.5%, the temperature of the process is 60°C and the duration is 60-70 minutes. Examples of successful implementation of these technologies in various countries of the world, in particular in Europe, the USA and Asia, are presented. Additionally, recommendations are provided for further research and technology development, including the need to improve waste oil purification methods, optimize transesterification processes, and integrate renewable energy sources. The prospects and challenges of the industry of biofuel production from waste oils are considered, in particular the issues of regulatory support, financial incentives and investment attraction.

Epoxy composite films of superior dielectric properties promoted by active ester hardeners for applications in electronic packaging

Epoxy composites with ultralow dielectric dissipation factors (Df) are highly desired in advanced electronic packaging architectures to cater for high-frequency signal transmission. However, Df of epoxy systems traditionally cured by amine, anhydride or phenolic resin is too high due to the generated high-polarization groups like hydroxyl moieties. Using active esters as curing agents is an effective strategy to reduce polarization of cured epoxy by replacing hydroxyl moieties with ester groups. Herein, diallyl-based active ester hardeners (DAAE) are synthesized via one-step esterification reaction with a high yield of > 90 %. When DAAE is used to cure epoxy films containing SiO2 fillers, the cured epoxy composite films (DAAE-ECFs) demonstrate low dielectric constant (Dk, ∼3.0) and low Df (∼0.005) above 5 GHz at 25 ℃. Importantly, whether immersed in room-temperature water for 24 h or in boiling water for 1 h, DAAE-ECFs absorb < 0.6 wt% water with stable Dk and slightly increased Df (<0.0085). Moreover, DAAE-ECFs show excellent thermal stability (Td5% >365 ℃), dimensional stability (CTE of ∼ 30 ppm ℃-1 below 80 ℃), high storage modulus (∼10 GPa at 30 ℃). The appealing dielectric, thermal and mechanical properties imply that DAAE-ECFs could serve as promising candidates for electronic packaging materials in high-frequency signal transmission.

Self-Produced O2 CNs-Based Nanocarriers of DNA Hydrophobization Strategy Triggers Photodynamic and Mitochondrial-Derived Ferroptosis for Hepatocellular Carcinoma Combined Treatment.

Hypoxia can aggravate tumor occurrence, development, invasion, and metastasis, and greatly inhibit the photodynamic therapy (PDT) effect. Herein, carbon nitride (CNs)-based DNA and photosensitizer co-delivery systems (BPSCNs) with oxygen-producing functions are developed to address this problem. Selenide glucose (Seglu) is used as the dopant to prepare red/NIR-active CNs (SegluCNs). The tumor-targeting unit Bio-PEG2000 is utilized to construct BPSCNs nanoparticles through esterification reactions. Furthermore, DNA hydrophobization is realized via mixing P53 gene with a positively charged mitochondrial-targeted near-infrared (NIR) emitting photosensitizer (MTTPY), which is encapsulated in non-cationic BPSCNs for synergistic delivery. Ester bonds in BPSCNs@MTTPY-P53 complexes can be disrupted by lipase in the liver to facilitate P53 release, upregulated P53 expression, and promoted HIF-1α degradation in mitochondria. In addition, the oxygen produced by the complexes improved the hypoxic microenvironment of hepatocellular carcinoma (HCC), synergistically downregulated HIF-1α expression in mitochondria, promoted mitochondrial-derived ferroptosis and enhanced the PDT effect of the MTTPY unit. Both in vivo and in vitro experiments indicated that the transfected P53-DNA, produced O2 and ROS by these complexes synergistically led to mitochondrial-derived ferroptosis in hepatoma cells through the HIF-1α/SLC7A11 pathway, and completely avoiding PDT resistance caused by hypoxia, exerting a significant therapeutic role in HCC treatment.

Synthesis of carrageenan/DFNS composite and its application in the esterification of levulinic acid with alcohols

The surface acidity of dendritic fibrous nano-silica (DFNS) was modified by a k-carrageenan biopolymer having sulfonic acid functional groups. The composite was used as a solid acid catalyst in the Fischer esterification reaction to convert levulinic acid (LA) to alkyl levulinates. The samples were characterized by analytical and instrumental techniques such as FT-IR spectroscopy, X-ray diffraction (XRD), N2 adsorption–desorption analysis, FESEM, and TEM. By using different alcohols including a short chain (ethanol), a medium chain (n-butanol), and a long chain (n-hexanol), the impact of various parameters on the esterification reaction was investigated. Under the optimum reaction conditions including 6 h as the reaction time, 10 mg catalyst amount, 12:1 ethanol: LA ratio, and 150 °C as the reaction temperature a 61 % ethyl levulinate was obtained. The selected catalyst was recycled and regenerated for use in successive runs without worthy loss in its activity.

Combination of contact ultrasound and infrared radiation for improving the quality and flavor of air-dried beef during hot air drying

Air-dried beef, a traditional dry fermented meat product in China, whose quality is largely influenced by processing conditions. In this study, contact ultrasound (CU) and infrared radiation (IR) were employed to enhance hot air drying (HAD), with an investigation into the mechanisms underlying improvements in quality and flavor. Samples subjected to CU and IR treatments during HAD (CU-IRD) demonstrated superior color (L* = 42.68, a* = 5.05, b* = −3.86) and tenderness (140.59 N) than HAD group, primarily attributed to reduced drying times and alterations in ultrastructure. Analyses utilizing SDS-PAGE and total volatile basic nitrogen (TVB-N) revealed that HAD and CU-HAD resulted in significant protein oxidation (197.85 mg TVB-N/kg and 202.23 mg TVB-N/kg, respectively), while IR treatments were associated with increased thermal degradation of proteins, producing lower molecular weight peptides. Compared with HAD group, the activities of certain lipases and proteases were enhanced by ultrasound and infrared treatments, leading to the release of greater amounts of free fatty acids and flavor amino acids. Furthermore, the thermal effects of infrared and the cavitation effects of ultrasound contributed to increased fat oxidation, amino acid Strecker degradation, and esterification reactions, thereby augmenting the diversity and concentration of volatile flavor compounds, including alkanes, ketones, aldehydes, and esters. These findings indicate that the synergistic application of CU and IR represents a promising strategy for enhancing the quality of air-dried beef.

A bio-based soy wood adhesive modified by dual-crosslinking strategy with excellent mechanical strength and water-resistance

Soy-based adhesives have garnered significant attention owing to their distinctive environmentally sustainable characteristics and low cost. However, they exhibit inadequate bonding strength and water-resistance, which can be attributed to the presence of polar groups in soy flours. Herein, a simple and eco-friendly dual-crosslinking strategy was proposed to manufacture a soy-based adhesive (SF/IO4/CA adhesive) with excellent mechanical properties and good water-resistance. Specifically, soy flours were treated with sodium periodate (NaIO4) for oxidization, which facilitated the soy flours' self-crosslinking process by converting carbohydrates into components having the cross-linking action (internal cross-linking agents). Then, incorporating the citric acid (CA) would promote to the carboxyl groups (-COOH) of CA to react with the hydrophilic hydroxyl groups (-OH) present in soy flours by esterification reaction. The findings demonstrated that a high-performance plywood using SF/IO4/CA adhesive was successfully produced, which shear strength of cold-water (20 °C for 24 h), hot-water (63 °C for 3 h), and boiling-water (93 °C for 3 h) reached 1.69 MPa, 1.68 MPa, 1.72 MPa, and 1.47 MPa, respectively. The soy-based adhesive has excellent mechanical strength and water-resistance due to its dual-crosslinking network system, which has significant promise for application use in the wood-based panels industry.

Tuning the Properties of Xylan/Chitosan-Based Films by Temperature and Citric Acid Crosslinking Agent.

Petroleum-based food packaging causes environmental problems such as waste accumulation and microplastic generation. In this work, biobased films from stable polyelectrolyte complex suspensions (PECs) of xylan and chitosan (70 Xyl/30 Ch wt% mass ratio), at different concentrations of citric acid (CA) (0, 2.5, 5, 7.5 wt%), were prepared and characterized. Films were treated at two temperatures (135 °C, 155 °C) and times (30 min, 60 min) to promote covalent crosslinking. Esterification and amidation reactions were confirmed by Fourier Transform Infrared Spectroscopy and Confocal Raman Microscopy. Water resistance and dry and wet stress-strain results were markedly increased by thermal treatment, mainly at 155 °C. The presence of 5 wt% CA tended to increase dry and wet stress-strain values further, up to 88 MPa-10% (155 °C for 60 min), and 5.6 MPa-40% (155 °C for 30 min), respectively. The UV-blocking performance of the films was improved by all treatments, as was thermal stability (up to Tonset: 230 °C). Contact angle values were between 73 and 84°, indicating partly wettable surfaces. Thus, thermal treatment at low CA concentrations represents a good alternative for improving the performance of Xyl/Ch films.

Solvent-Free Synthesis of HKUST-1 with Abundant Defect Sites and Its Catalytic Performance in the Esterification Reaction of Oleic Acid.

HKUST-1 has received increasing attention because of its potential applications in many fields, such as heterogeneous catalysis, sensors, gas storage, and separation. Herein, we report that HKUST-1 can be facilely prepared by heating a ground mixture of copper nitrate trihydrate and 1,3,5-benzenetricarboxylic acid in an autoclave at 80 °C for 10 h. The data from nitrogen sorption show that the obtained material, named HKUST-1-free, possesses a high BET specific surface area of 1671 m2/g and a pore volume of 0.8 cm3/g. The results from acid-base titration indicate that the number of defect sites in HKUST-1-free is more than that in HKUST-1-solvent prepared by the solvothermal method. As a heterogeneous catalyst, HKUST-1-free gave a high yield (91%) of methyl oleate in the esterification reaction of oleic acid with methanol at room temperature compared to HKUST-1-solvent (70%). Additionally, it is proven that HKUST-1-free is a heterogeneous catalyst and can be reused.

Fabrication of liquid-free ionic conductive elastomer (ICE) from cellulose-rosin derived poly(esterimide) towards temperature-tolerant and solvent-resistant UV shadowless adhesive and sensor

Recently, the utilization of the cellulose to fabricate the multifunctional materials with aim to replace the petroleum-based product, is receiving significant attentions. However, the development of cellulose-based multifunctional materials with high mechanical strength and temperature resistance is still a challenge. Herein, the intrinsic feature and property of cellulose and rosin were creatively employed to fabricate a novel cellulose-rosin based poly(esterimide) (PEI) by esterification reaction and imidization reaction, and the obtained cellulose-rosin derived PEI exhibits superior thermal stability. Then the as-prepared cellulose-rosin derived PEI was dissolved in polymerizable deep eutectic solvents (PDES) and in-situ formed the ionic conductive elastomer (ICE) with via UV-induced polymerization. These cellulose-rosin based ICE exhibited excellent mechanical properties, solvent resistance, and temperature tolerance. By adjusting the mass ratio of cellulose-rosin derived PEI and PDES, the as-prepared liquid-free ICE functions as UV shadowless adhesive and wearable sensors. The bonding strength of UV shadowless adhesive could 1.52 MPa, which could be applied to fix the broken glass toy models. Furthermore, wearable sensors based those ICE could monitor the large and subtle movements even under extreme environmental condition, such as being soaked in organic solvent (such as tetrahydrofuran) or at low/high temperature (−25 °C or 80 °C). This work opens a new avenue for the next-generation of multifunctional ICE.

Theoretical study on reaction kinetics of the absent HO2 concerted addition reaction on ester group of methyl esters: Case studies of methyl formate and methyl propanoate

In this work, a comprehensive study is performed to specify the contributions of H-abstraction, addition and addition-dissociation reactions of methyl esters + HO2, particularly to the low temperature oxidation. It is imperative to investigate these reactions in detail despite the generally higher bond strength of C=O compared to C=C. The two representative methyl esters, methyl formate (MF, HC(=O)OCH3) and methyl propanoate (MP, CH3CH2C(=O)OCH3), are chosen to theoretically explore the reaction kinetics of the C=O of ester group and HO2. The reaction pathways and potential energy profiles including H-abstraction, addition and addition-dissociation of MF+HO2 and MP+HO2 are investigated at the CCSD(T)/cc-pVxZ(x = T, Q)//M062X/6–311+G(2df,2p) and DLPNO-CCSD(T)/cc-pVxZ(x = T, Q)//M062X/6–311+G(2df,2p) level of theory, respectively. The rate constants of MF/MP + HO2 are determined by using the RRKM/master equation coupled with the 1-D hindered rotor approximation and Eckart tunneling correction. This work delves into the temperature and pressure-dependence of these reaction pathways, as well as the competition relationship among of them. The results indicate that for small ester (MF), the H-abstraction is more competitive across all reaction pathways, but under low temperature (≤ 700 K) and high pressure (≥ 10 atm) conditions, the collisional stabilization of peroxy-alcohol radicals (MF+HO2 = HO-ROO) becomes predominant. For larger ester (MP), this is not necessarily the case as such reactions are unimportant for combustion conditions (rates only appear at 400 K, 100 atm). Furthermore, to assess the impact of these reactions on kinetic modeling, the new rate constants of MF/MP + HO2 are incorporated into the kinetic models of MF and MP, respectively. The updated kinetic models reveal the significant role of H-abstraction reactions in ignition delay time and fuel consumption and the formation of peroxy-alcohol radicals is favorable for decomposition pathways, notably affecting fuel consumption at low temperatures. Consequently, this study highlights the important role of the HO2 addition to the C=O of ester group in the low temperature oxidation mechanism of methyl esters, which has been overlooked in previous studies.

Enhancing reactivity-controlled compression ignition engine performance: A response surface methodology approach with ammonium hydroxide-waste cooking oil biodiesel optimization

The focus on ammonium hydroxide, biodiesels and their combustion technology has garnered significant attention in pursuing carbon-neutral and carbon-free fuels to address greenhouse gas emissions (GHG) and mitigate global warming. Low-temperature combustion (LTC) has been introduced as an alternative method to conventional compression ignition (CI) combustion. Reactivity controlled compression ignition (RCCI) can be achieved by introducing highly reactive waste cooking oil methyl ester (WCOME) oil directly into the manifold in intervals of 10% energy and injecting low-reactive ammonium hydroxide at 20%–50%. Utilizing the response surface methodology (RSM) approach, it was determined that for optimal operation in RCCI mode, an ideal ammonium hydroxide energy sharing (AHES) of 43% would account for the varying parameters and their effects on emissions and performance. The results of the experiments predicted a brake thermal efficiency (BTHE) of 34.85% and a brake specific energy consumption (BSEC) of 10.69 MJ/kWh. Meanwhile, a notable decrease in exhaust emissions was observed for HC, CO, CO2, NO x and smoke by 41.54%, 38.89%, 48.89%, 51.27% and 65.80% respectively when compared to conventional biodiesel combustion (CBC). The experimental result at maximum load operation with an AHES of 50% indicates that RCCI combustion led to an increase in thermal efficiency from 30.36% to 35.42%, and the in-cylinder pressure and heat release rate dropped from 83.42 bar to 59.64 bar and 78.68 kJ to 60.92 kJ, respectively. There was a significant reduction in HC, CO, CO2, NO x and smoke emissions recorded as 58.76 ppm, 0.11%v, 1.61%v, 442 ppm and 6.64 N, respectively, compared to CBC.

Micromechanism of the effect of coal functional groups on the catalytic/esterification reaction of acetic acid

Acidification modification has proven to be a successful approach for enhancing the permeability of low-permeability coal seams and increasing coalbed methane extraction. To explore the influence of acetic acid on the organic structure of coal, a combined approach of experimental research and quantum chemical calculation is employed to examine the reaction mechanism of coal organic structure in response to acetic acid. Fourier transform infrared spectroscopy reveals a reduction in the content of hydroxyl and C–O bonds in the treated samples, along with the appearance of an absorption peak of C=C bonds. This demonstrates that the main site of acetic acid acidification modification on coal molecules is the hydroxyl functional group. Therefore, glycerol can be used as a simplified model of coal molecules for further investigation. In addition, three typical functional groups (phenyl, hydroxyl, amino) are selected as the research objects. The electronic density topological properties, molecular surface electrostatic potential, Mayer bond orders and CM5 charge of coal molecules were calculated based on quantum chemical theory. This reveals the intrinsic strength of each chemical bond between single atoms in a molecule, thereby predicting potential reaction pathways between acetic acid and coal molecules. The micro-mechanism of acetic acid catalyzing/esterifying the organic structure of coal is studied using transition state methods. The computational results show that there are two main modes of reaction between acetic acid and coal molecules: (1) acetic acid catalyzes the dehydration reaction of coal molecules; (2) acetic acid reacts with coal molecules to form ester intermediates, followed by decomposition through various reactions. Among the 14 reaction pathways, acetic acid provides protons or groups to trigger the dehydration of coal molecules. Interestingly, it is found that the overall hydroxyl group participates in the reaction is easier than the individual hydrogen atom on the hydroxyl group, and the overall carboxyl group participates in the reaction is easier than the individual hydroxyl group. This indicates that the higher the overall atomic reactivity of acetic acid, the lower the reaction barrier. Compared with catalytic reactions, acetic acid tends to undergo esterification reactions with hydroxyl groups, with the phenyl ring functional group significantly affecting the reaction barrier. The introduction of various oxygen-containing functional groups like ketone, aldehyde, and ester in the reaction products will hinder the adsorption of non-polar methane, reduce the adsorption capacity of coal seams for gas, and play an essential role in promoting gas desorption. The research findings can provide theoretical guidance for the organic acidification modification of low-permeability coal seams to enhance gas permeability and coalbed methane extraction.

Biodiesel photoelectrocatalytic synthesis employing α-Fe2O3 film decorated with Pt nanoparticles as photoanode

In this work, photoelectrochemical route for biodiesel production using an electrochemical cell configured with platinum and α-Fe2O3 modified with Pt nanoparticles as electrodes was investigated. XRD patterns registered for film prepared by modified hydrothermal method revealed a trigonal structure of the hematite (α-Fe2O3) phase. The α-Fe2O3 film surface was decorated by metallic Pt nanoparticles (PtNP) in order to reduce the charge recombination and improve the photocatalytic efficiency. The band gap energy (EBG) of the α-Fe2O3 and PtNP/α-Fe2O3 films was estimated by UV-Vis spectroscopy at approximately 2.1 eV. Electrochemical measurements showed that the oxide is an n-type semiconductor adequate to be used as a photoanode in biodiesel synthesis. Under polarization conditions, the electrochemical cell changed the pH from 7 to 14 when the system was polarized at 5.0 V. In the synthesis of biodiesel by esterification reaction, oleic acid, 300 µL of 0.1 mol L−1 aqueous KCl solution and methanol were used as precursor reagents. The reaction was carried out free of strong base, such as KOH or NaOH, as a supporting electrolyte. In this route, the reduction of the water molecule occurred on the cathode, with the formation of hydroxyl (OH-) species, methoxy, and consequently fatty acid methyl esters (FAMEs). Thermogravimetric analysis (TGA) and Gas chromatography coupled to mass spectrometry (CG-MS) were performed to evaluate the catalysis products. GC-MS analyzes show that the reaction has a yield of about 7 % with the formation of FAMEs, such as methyl 9-octadecenoate, methyl hexadecanoate and methyl hexadecanoate.

Synthesis of the acidic/magnetic catalyst x-MoO3/Ni0.5Zn0.5Fe2O4 by combustion reaction and evaluation of its catalytic potential/reuse in biodiesel production

The objective of this work was to synthesize a new catalyst x-MoO3/Ni0.5Zn0.5Fe2O4 using the combustion reaction method and to evaluate its catalytic potential and reuse in biodiesel production from waste oil, optimizing the process through experimental design. The catalysts were characterized in terms of structure by X-ray diffraction and phase quantification by Rietveld refinement, surface area by the Brunauer-Emmett-Teller technique, experimental density by helium pycnometry, acidity tests by ammonia desorption at programmed temperature, chemical analysis by X-ray fluorescence, morphology by scanning and transmission electron microscopy, and catalytic properties. The products of the simultaneous transesterification and esterification reactions were characterized by gas chromatography and acidity index. The results indicate the formation of catalysts with surface area ranging from 1.5 to 1.7 m2/g and density ranging from 4.5 to 5.1 g/cm3, composed of major crystalline phases of MoO3 in the orthorhombic configuration and cubic Ni0.5Zn0.5Fe2O4 ferrite, with total acidity ranging from 70 to 182 μmol/g of NH3. Morphological characterization revealed that the catalyst comprises irregular plates of various sizes and shapes with a wide range of cluster sizes. In the simultaneous transesterification and esterification reactions of residual oil, the catalysts were active under all conditions tested, with emphasis on the catalyst containing 50 % Mo ions and 50 % Ni0.5Zn0.5Fe2O4 presenting the best catalytic performance with a conversion of 95 % in ethyl esters and a reduction of 71 % in acidity, with a service life of 6 cycles, an average conversion of 90 % and good thermal and structural stability after use. The experimental design was significant and predictive, with a confidence level of 95 %. Statistical analysis identified that all input variables (temperature, time, and amount of catalyst) were significant for the adopted design. The new catalyst composed of molybdenum, iron, nickel, and zinc has a positive impact on biodiesel synthesis from frying oil and ethanol.

Evaluation and optimization of esterified starch and Canna edulis ker fiber films for food packaging applications

Starch-based films reinforced with Canna edulis Ker fiber were developed by a reactive extrusion process in which an esterification reaction was generated using maleic anhydride as a modifying agent and glycerin as a plasticizer. A Box-Behnken experimental design and the response surface methodology allowed modeling of the mechanical and physicochemical properties and their subsequent optimization to obtain flexible or rigid materials with different approaches in food packaging. The optimal composition for the rigid and flexible material was 10 and 2 % (w/w) lignocellulosic fibers, 30 and 30 % (w/w) glycerol, and 4 and 4 % (w/w) maleic anhydride, respectively. Glycerol and maleic anhydride were the key variables that influenced the water solubility and water absorption of the materials. The values of the rigid and flexible material properties of elastic modulus, tensile strength, elongation at break, water solubility, and water absorption were 2.58 and 1.51 GPa, 112.04 and 104.56 Mpa, 6.58 and 10.44 %, 21.63 and 21.85 %, and 139.72 and 141.06, respectively.

Enhancing the sodium storage performance of hard carbon by constructing thin carbon coatings via esterification reactions

Hard carbons derived from pitch are considered a competitive low-cost anode for sodium-ion batteries. However, the preparation of pitch-based hard carbon (PHC) requires the aid of a pre-oxidation strategy, which introduces unnecessary defects and oxygen elements, which leads to low initial Coulombic efficiency (ICE) and poor cycling stability. Herein, we demonstrate a new surface engineering strategy by grafting chemically active glucose molecules on the PHC surface via esterification reactions, which can achieve low-cost nano-scaled carbon coating. Thin glucose coating can be carbonized at a lower temperature, which results in a more closed pore structure and fewer functional groups. The as prepared PHC exhibits a high reversible capacity of 328.5 mAh/g with a high ICE of 92.08 % at 0.02 A/g. It is noteworthy that the PHC can be adapted to a variety of cathode materials for full-cell assembling without pre-sodiation, which maintains the characteristics of high capacity and excellent cycling stability. The performance of resin-based hard carbon coated with a similar method was also improved, demonstrating the universality of the technique.

Sustainable conversion of polystyrene waste into polymeric surfactants to be evaluated as pour point deperssants for waxy crude oil

Disposing of polystyrene trash is an environmental concern, and converting it into value-added products is appealing . This research study focuses on implementing a sustainable method to convert polystyrene waste into polymeric nonionic surfactants. The polymeric nonionic surfactant additives were prepared by grafting polystyrene waste (WPS) with a methacrylic monomer (MMA), followed by an esterification reaction with polyethylene glycol of different molecular weights (400 and 1000). The chemical composition of the synthesized compounds was justified by spectroscopic analysis. Interfacial tension (IFT) was investigated to gain insights into the behavior of the polymeric nonionic surfactants produced at the interface. The modified waste polymers were evaluated as pour depressants and paraffin inhibitors. Additionally, the rheological properties of the modified waste polymers were examined. The findings revealed that, the IFT between oil and water decreased from 21 to 7 mN/m for WSPA400 and even further to 4 mN/m for WSPA1000. At a concentration of 500 ppm, WPSA1000 exhibited the maximum depression effect than WPSA400, reducing the pour point temperature from 27 °C to 12 °C and 3 °C, respectively. Also, At 500 ppm, the amount of wax deposition declined from 8.5 g to 1.90 g and 0.95 g after treating the crude oil with WPSA 400 and WPSA 1000. The rheological measurements further revealed that the WPSA1000 additive outperformed the WPSA400 additive in terms of enhancing the fluidity of oil. In order to acquire a more comprehensive understanding of the mechanisms involved in pour point depression, the utilization of polarizing optical microscopy was used to explore the effect of WPSA1000 as a pour point depressant.

Bubbling insights: unveiling the true sophorolipid biosynthetic pathway by Starmerella bombicola

BackgroundThe yeast Starmerella bombicola is renowned for its highly efficient sophorolipid production, reaching titers and productivities of (over) 200 g/L and 2 g/(L h), respectively. This inherent efficiency has led to the commercialization of sophorolipids. While the sophorolipid biosynthetic pathway has been elucidated a few years ago, in this study, it is revisited and true key intermediates are revealed.ResultsRecently, Starmerella bombicola strains developed and evaluated in the past were reevaluated unveiling unexpected findings. The AT enzyme encoded in the sophorolipid biosynthetic gene cluster is the only described enzyme known to acetylate sophorolipids, while the SBLE enzyme encoded by the SBLE gene is described to catalyze the conversion of (acetylated) acidic sophorolipids into lactonic sophorolipids. A double knockout of both genes was described to result in the generation of bolaform sophorolipids. However, new experiments performed with respective S. bombicola strains Δsble, Δat Δsble, and ∆at revealed inconsistencies with the current understanding of the SL pathway. It was observed that the ∆sble strain produces mainly bolaform sophorolipids with higher acetylation degrees instead of acidic sophorolipids. Furthermore, the ∆at strain produces predominantly bolaform sophorolipids and lactonic sophorolipids with lower acetylation degrees, while the ∆at ∆sble strain predominantly produces bolaform sophorolipids with lower acetylation degrees. These results indicate that the AT enzyme is not the only enzyme responsible for acetylation of sophorolipids, while the SBLE enzyme performs an intramolecular transesterification reaction on bolaform glycolipids instead of an esterification reaction on acidic sophorolipids. These findings, together with recent in vitro data, led us to revise the sophorolipid biosynthetic pathway.ConclusionsBolaform sophorolipids instead of acidic sophorolipids are the key intermediates in the biosynthetic pathway towards lactonic sophorolipids. Bolaform sophorolipids are found in very small amounts in extracellular S. bombicola wild type broths as they are very efficiently converted into lactonic sophorolipids, while acidic sophorolipids build up as they cannot be converted. Furthermore, acetylation of sophorolipids is not exclusively performed by the AT enzyme encoded in the sophorolipid biosynthetic gene cluster and acetylation of bolaform sophorolipids promotes their transesterification. These findings led to the revision of the industrially relevant sophorolipid biosynthetic pathway.

UV-Mediated Facile Fabrication of a Robust, Fully Renewable and Controllably Biodegradable Poly(lactic acid)-Based Covalent Adaptable Network.

A robust and fully biobased covalent adaptable network (CAN) that allows recyclability, biocompatibility, and controlled biodegradability is reported. The CAN was fabricated through a simple photo-cross-linking method, wherein low-molecular-weight poly(lactic acid) (∼3 kDa) was modified with end 1,2-dithiolane rings through a one-step Steglich esterification reaction with thioctic acid (TA). These incorporated 1,2-dithiolane rings undergo photoinduced ring-opening polymerization, thus enabling the cross-linking of poly(lactic acid) with abundant dynamic disulfide bonds. The resultant CAN demonstrates excellent transparency, effective UV-blocking capabilities below 320 nm, robust tensile strength (∼39 MPa), and superior dimensional stability at 80 °C, alongside attractive biocompatibility. Moreover, owing to the dynamic exchange and redox-responsiveness of disulfide bonds, the material can be recycled by hot-pressing and a reduction-oxidation process while also being capable of controllably biodegrading at the end of its lifecycle. Furthermore, it exhibits reconfigurable shape memory properties with fast recovery. This study elucidates a straightforward approach to fabricating multifunctional and sustainable polymer materials with potential applications in diverse fields such as packaging, coating, and biomedicine.

Derivatives of (5-Oxooxazolidin-4-yl)acetic acids in aspartic acid α-carboxyl protection: a word of caution

Isomeric products could be isolated in a reaction of pentafluorophenyl ester of (S)-2-(3-((benzyloxy)-carbonyl)-5-oxooxazolidin-4-yl)acetic acid with aminoacid esters. One product is an expected dipeptide, the isomeric one is an N-hydroxymethylamino succinimide – a product of methylene bridge cleavavge. Steric bulkness of aminoacid esters favors the formation of a peptide, however the reaction selectivity is quite unpredicatable. Moreover, the precise structure assignement requires high-temperature NMR experiments.