Frontiers of Chemical Science and Engineering最新文献

Eucalyptus species are extensively cultivated trees commonly used for timber production, firewood, paper manufacturing, and essential nutrient extraction, while lacking consumption of the leaves increases soil acidity. The objective of this study was to recover bio-oil through microwave pyrolysis of eucalyptus camaldulensis leaves. The effects of microwave power (450, 550, 650, 750, and 850 W), pyrolysis temperature (500, 550, 600, 650, and 700 °C), and silicon carbide amount (10, 25, 40, 55, and 70 g) on the products yields and bio-oil constituents were investigated. The yields of bio-oil, gas, and residue varied within the ranges of 19.8–39.25, 33.75–46.7, and 26.0–33.5 wt %, respectively. The optimal bio-oil yield of 39.25 wt % was achieved at 650 W, 600 °C, and 40 g. The oxygenated derivatives, aromatic compounds, aliphatic hydrocarbons, and phenols constituted 40.24–74.25, 3.25–23.19, 0.3–9.77, and 1.58–7.75 area % of the bio-oils, respectively. Acetic acid (8.17–38.18 area %) was identified as a major bio-oil constituent, and hydrocarbons with carbon numbers C₁ and C₂ were found to be abundant. The experimental results demonstrate the potential of microwave pyrolysis as an eco-friendly and efficient way for converting eucalyptus waste into valuable bio-oil, contributing to the sustainable utilization of biomass resources.

Broadening spectral response range to realize the full spectrum photocatalysis is crucial to develop photocatalysts with satisfactory light-energy conversion ability. A full-spectrum driven p-n heterojunction photocatalytic system was rationally designed through introducing the Er³⁺/Yb³⁺ co-doped BiOBr with up-conversion effect as the collector of near infrared light and photocatalysts substrate. Meanwhile, Cu₃Mo₂O₉ with the photothermal effect as a heat source to accelerate the reaction at the surface through absorbing the near infrared light. The photocatalytic activity of BiOBr:Yb³⁺,Er³⁺/Cu₃Mo₂O₉ composite was markedly strengthened under visible and near infrared light irradiation, and the BiOBr:Yb³⁺,Er³⁺/Cu₃Mo₂O₉-5 composite displayed the optimal photodegradation activities for 0.03372 min⁻¹ and 0.058 h⁻¹, being 2.3-folds and 2.4-folds than that of pure BiOBr:Yb³⁺,Er³⁺ under the visible and near infrared light, respectively. The position of doped ions (Yb³⁺ and Er³⁺) in BiOBr:Yb³⁺,Er³⁺ was determined from the X-ray absorption fine structure spectra. And the reasonable mechanism of p-n heterojunction was proposed base on the results of experimental and density functional theory calculation. This work provides a rational strategy for the design and development of full-spectrum heterojunction photocatalysts with the up-conversion and photothermal effects to increase the photocatalytic performance.

The precise engineering of surface active sites is deemed as an efficient protocol for regulating surfaces and catalytic properties of catalysts. Defect engineering is the most feasible option to modulate the surface active sites of catalysts. Creating specific active sites on the catalyst allows precise modulation of its electronic structure and physicochemical characteristics. Here, we outlined the engineering of several types of defects, including vacancy defects, void defects, dopant-related defects, and defect-based single atomic sites. An overview of progress in fabricating structural defects on catalysts via de novo synthesis or post-synthetic modification was provided. Then, the applications of the well-designed defective catalysts in energy conversion and environmental remediation were carefully elucidated. Finally, current challenges in the precise construction of active defect sites on the catalyst and future perspectives for the development directions of precisely controlled synthesis of defective catalysts were also proposed.

Single-atom catalysts (SACs), characterized by exceptionally high atom efficiency, have garnered significant attention across various catalytic reactions. Recent studies have showcased SACs with robust capabilities for precise catalysis, specifically targeting reactions along designated pathways. This review focuses on the advances in the precise activation and reconstruction of chemical bonds on SACs, including precise activation of C–O and C–H bonds and selective couplings involving C–C and C–N bonds. Our discussion begins with a thorough exploration of the factors that render SACs skilled in precise catalytic processes, encompassing the narrow d-band electronic state of single atom site resulting in the adsorption tendency, isolate site resulting in unique adsorption structure, and synergy effect of a single atom site with its neighbors. Subsequently, we elaborate on the applications of SACs in electrocatalysis and thermocatalysis including four prominent reactions, namely, electrochemical CO₂ reduction, urea electrochemical synthesis, CO₂ hydrogenation, and CH₄ activation. Then the concept of rational design of SACs for precisely controlling reaction pathways is discussed from the aspects of pore structure design, support-metal strong interaction, and support hydrophilic/hydrophobic. Finally, we summarize the challenges encountered by SACs in the field of precise catalytic processes and outline prospects for their further development in this domain.

The traditional separation of bicyclic and tricyclic aromatics from coal tar involves complicated multi-steps and consumes significantly more energy. Previous work accomplished the separation between anthracene-phenanthrene isomers using electrostatic interaction, but for the separation between bicyclic and tricyclic aromatics, electrostatic interactions are difficult to produce a recognizable effect. Naphthalene-based solvents, named as naphthaleneacetamide, naphthaleneethanol, naphthalenemethanol, naphthol, naphthylacetic acid, naphthylacetonitrile, and naphthylamine, respectively, were used for the efficient separation of naphthalene and phenanthrene via dispersion interaction. Results showed that the pre-studied structural parameters are the key factors in selecting an efficient solvent. And the substituents on the intermolecular interactions involved in the separation processes had an important impact, which were evaluated. Naphthalenemethanol exhibited a superior performance with a purity of 96.3 wt % naphthalene products because its electron-donating substituent enables the selective recognition of naphthalene via the dispersion interaction. The used naphthalene-based solvents can be regenerated and recycled via back extraction with a purity of over 90 wt % naphthalene products, suggesting solvent structural stability during the regeneration processes. Notably, the naphthalene-based solvents also demonstrated better separation performance for polycyclic aromatics from coal tar with a purity of over 80 wt % for bicyclic aromatics. This study would enhance the utilization of coal tar as a valuable source of polycyclic aromatics besides broadening the knowledge for applying non-bonded interaction in the separation of polycyclic aromatics technologies.

The cost-effective separation of ethylene (C₂H₄), ethyne (C₂H₂), and ethane (C₂H₆) poses a significant challenge in the contemporary chemical industry. In contrast to the energy-intensive high-pressure cryogenic distillation process, zeolite-based adsorptive separation offers a low-energy alternative. This review provides a concise overview of recent advancements in the adsorptive separation of C₂H₄, C₂H₂, and C₂H₆ using zeolites or zeolite-based adsorbents. It commences with an examination of the industrial significance of these compounds and the associated separation challenges. Subsequently, it systematically examines the utilization of various types of zeolites with diverse cationic species in such separation processes. And then it explores how different zeolitic structures impact adsorption and separation capabilities, considering principles such as cation-π interaction, π-complexation, and steric separation concerning C₂H₄, C₂H₂, and C₂H₆ molecules. Furthermore, it discusses methods to enhance the separation performance of zeolites and zeolite-based adsorbents, encompassing structural design, modifications, and ion exchange processes. Finally, it summarizes current research trends and future directions, highlighting the potential application value of zeolitic materials in the field of C₂H₄, C₂H₂, and C₂H₆ separation and offering recommendations for further investigation.

Regulation of aluminum distribution in zeolite framework is an effective method for improving its catalytic performance for propane aromatization. Herein, we found that recrystallization and post-realuminization of ZSM-5 cannot only create hollow structures to enhance the diffusion ability, but also adjust the content and position of paired aluminum species in its framework. Various characterizations results confirmed that increase of paired aluminum content and inducement of more aluminum atoms sited in the intersection cavity are beneficial to the formation of aromatic products in propane aromatization. As a result, the hollow-structured ZSM-5 zeolite with more paired aluminum (H-200-hollow) showed higher propane conversion and aromatics selectivity than other samples at the same conditions. The catalytic performance of H-200-hollow can be further improved by ion-exchanging with a small amount of Ga(III) species. The propane conversion and aromatics selectivity of Ga-200-hollow reached as high as 95% and 70%, respectively, at 540 °C and 1 atm.

With the rapid iteration and update of wearable flexible devices, high-energy-density flexible lithium-ion batteries are rapidly thriving. Flexibility, energy density, and safety are all important indicators for flexible lithiumion batteries, which can be determined jointly by material selection and structural design. Here, recent progress on high-energy-density electrode materials and flexible structure designs are discussed. Commercialized electrode materials and the next-generation high-energy-density electrode materials are analyzed in detail. The electrolytes with high safety and excellent flexibility are classified and discussed. The strategies to increase the mass loading of active materials on the electrodes by designing the current collector and electrode structure are discussed with keys of representative works. And the novel configuration structures to enhance the flexibility of batteries are displayed. In the end, it is pointed out that it is necessary to quantify the comprehensive performance of flexible lithium-ion batteries and simultaneously enhance the energy density, flexibility, and safety of batteries for the development of the next-generation high-energy-density flexible lithium-ion batteries.

With the advancement of social process, the resource problem is becoming more prominent, biomass materials come into being, and it is becoming more and more important to explore and prepare efficient and multifunctional biomass materials to alleviate the problems of energy storage and water pollution. In this paper, nitrogen-doped hierarchical porous carbon materials (NRRC) were produced by one-step carbonization of withered rose as raw material and melamine as nitrogen source with KOH-activated porosification. The resulting nitrogen-doped porous carbon material had the most abundant pores and the best microspherical graded pore structure, with a specific surface area of up to 1393 m²·g⁻¹, a pore volume of 0.68 cm³·g⁻¹, and a nitrogen-doped content of 5.52%. Electrochemical tests showed that the maximum specific capacitance of NRRC in the three-electrode system was 346.4 F·g⁻¹ (0.5 A·g⁻¹), which was combined with favorable capacitance retention performance and cycling stability. The NRRC//NRRC symmetric supercapacitors were further assembled, and the maximum energy density of a single device was 23.88 Wh·kg⁻¹, which still maintains excellent capacitance retention and cyclic charging/discharging stability. For example, the capacitance retention rate was always close to 96.27% with almost negligible capacitance loss after 10000 consecutive charge/discharge cycles (current density: 10 A·g⁻¹). Regardless of the three-electrode or two-electrode system, the super capacitive performance of NRRC porous carbon materials was comparable to the electrochemical performance of many reported biomass porous carbon materials, which showed better energy storage advantages and practical application potential. In addition, NRRC porous carbon materials had excellent water purification ability. The dye adsorption test confirmed that NRRC had a high adsorption capacity (491.47 mg·g⁻¹) for methylene blue. This undoubtedly also showed a potential and promising avenue for high value-added utilization of this material.

A significant reaction in the synthesis of biomass-based chemicals is the catalyst-based and targeted oxidation of monosaccharides into valuable sugar acids. In this study, an activated carbon supported gold catalyst was used to oxidize glucose and xylose to gluconic acid and xylonic acid under neutral condition. Optimization of reaction conditions for the catalysts was performed using both a batch reactor and a flow-through reactor. In a batch reactor, the yields of gluconic and xylonic acid reached 93% and 92%, respectively, at 90 °C within 180 min. In a flow reactor, both reactions reached a similar yield at 80 °C with the weight hourly space velocity of 47.1 h⁻¹. The reaction kinetics were explored in the flow reactor. The oxidation of glucose and xylose to gluconic and xylonic acid followed a first-order kinetics and the turnover frequency was 0.195 and 0.161 s⁻¹, respectively. The activation energy was evaluated to be 60.58 and 59.30 kJ·mol⁻¹, respectively. This study presents an environmentally friendly and feasible method for the selective oxidation of monosaccharides using an activated carbon supported gold catalyst, benefiting the high-value application of carbohydrates.