ACS Sustainable Chemistry & Engineering最新文献

Oxygen-balanced mixotrophy (OBM) is a particular type of microalgae mixotrophic cultivation, where the supply of an organic carbon substrate is adjusted to match heterotrophic oxygen consumption with photosynthetic production. In this way, the need for aeration is eliminated due to intracellular gas recycling during daytime. After implementing this process at lab scale, we sought to explore its scalability in a tubular photobioreactor (TPBR). In this study, OBM was implemented in a two-phase tubular photobioreactor of 1700 L placed in a greenhouse and exposed to sunlight. The process was run with the polyextremophilic species Galdieria sulphuraria, using glucose as a carbon source. The gas phase was continuously recirculated, and the oxygen concentration was monitored and utilized to manage the glucose supply through a proportional-integral controller. An excessive rate of night aeration, however, resulted in CO₂ limitation issues. Subsequent tuning and optimization of controller settings and the nighttime aeration rate effectively addressed the problem. The average biomass productivity reached 0.81 g·L^-1·day^-1, a significant improvement over autotrophic productivity in the same pilot system. On the other hand, the biomass yield on the substrate was 0.68 C-mol _x ·C-mol_s ^-1, indicating that considerable carbon recycling took place but to a lower extent than at lab scale. These results provide a solid foundation for the large-scale industrial implementation of OBM.

Vanadium-based oxides with unique layered structures and multiple oxidation states have attracted considerable attention for aqueous zinc-ion batteries (AZIBs). However, the inferior conductivity and nearly nonporous structural characteristics of commercial V₂O₅ inevitably hinder the transport of electrons/ions, and the inherently narrow interlayer spacing and strong electrostatic interactions severely restrict the further development of V₂O₅ cathodes. In this work, neodymium (Nd) ions were employed as guests to intercalate into MIL-88B(V)-derived V₂O₅ (denoted as O_V-NVO) by a one-step hydrothermal process and as stable cathode materials for AZIBs. Benefiting from its well-designed honeycomb-like porous structure, large surface area, expanded interlayer spacing, abundant oxygen vacancies, and feeble electrostatic interactions, the O_V-NVO cathode delivered a prominent discharge capacity of 455.2 mAh g^–1 at 0.1 A g^–1 and exhibited satisfactory rate capability (341.5 mAh g^–1 at 5.0 A g^–1) and cycling stability (90.8% capacity retention after 2000 cycles at 5.0 A g^–1). Impressively, the assembled Zn//O_V-NVO flexible battery can operate stably under extreme bending conditions and exhibits superior electrochemical behavior. Furthermore, the reversible Zn²⁺ storage mechanism and structural evolution of the O_V-NVO cathode were further analyzed by kinetic analysis, ex situ characterizations, and density functional theory calculations. This synergistic strategy by combining Nd-ion intercalation and oxygen defect engineering provides an effective approach to the design of high-performance vanadium-based cathode materials, offering more possibilities for the practical applications of AZIBs.

This study found that the CoO_x/Ti₂O₃ catalyst showed high activity, selectivity, and stability for hydrodeoxygenation (HDO) of anisole to benzene. Due to the reductivity of Ti₂O₃, a redox reaction occurred between Ti₂O₃ and CoO_x, forming cobalt species with a low oxidation state, such as CoO and metallic Co. These cobalt species on Ti₂O₃ enhanced the catalytic performance for the HDO reaction. On the other hand, CoO_x supported on other supports, including TiO₂, Al₂O₃, SiO₂, and active carbon, was in the form of Co₃O₄ and showed only low catalytic activity. H₂-TPR and H₂-TPD experiments demonstrated that CoO_x supported on Ti₂O₃ was easily reduced to metallic Co, which had the ability to activate H₂. CoO_x/Ti₂O₃ and CoO_x/TiO₂ catalysts were deactivated more or less by partial oxidation of the cobalt species during the HDO reaction. The reduction of the partially oxidized cobalt species was promoted by the redox reaction between the cobalt species and Ti₂O₃, and therefore, CoO_x/Ti₂O₃ showed a much longer catalyst life than CoO_x/TiO₂.

Data consistency affects the robustness of machine learning-based models. Most experimental and industrial data have low consistency, leading to poor generalization performance. In this study, a hybrid Quantum Neural Network (hybrid QNN) with superior generalization capabilities, was compared with established machine learning models, including artificial neural networks and decision-tree-based methods such as CatBoost and XGBoost. We evaluated these models by predicting the catalyst performance across different data-consistency scenarios using two catalyst data sets: a low-consistency preferential oxidation of CO (PROX) catalyst and a high-consistency oxidation coupling of methane (OCM) catalyst. The hybrid QNN performed better in both low- and high-consistency environments, demonstrating robust generalization capabilities. In the regression tasks, the hybrid QNN achieved a 6.7% lower mean absolute error (MAE) for the PROX catalyst and a 35.1% lower MAE for the OCM catalyst compared with the least-performing model. Adaptability is crucial in catalysis, where data scarcity and variability are common. Our research confirms the potential of the hybrid QNN as a comprehensive tool for advancing catalyst design and selection by achieving high accuracy and predictive power under diverse conditions.

We present a new strategy for the production of a δ-lactam from glucose that integrates biological production of triacetic acid lactone (TAL, 4-hydroxy-6-methyl-2H-2-one) with catalytic transformation of TAL into 6-methylpiperidin-2-one (MPO) through metabolic engineering, isomerization, amination, and catalytic hydrogenation/hydrogenolysis. We developed a sustainable and antibiotic-free fed-batch fermentation using genetically modified Rhodotorula toruloides IFO0880. This process achieved a yield of 2-hydroxy-6-methyl-4H-pyran-4-one (2H4P) at 0.05 g/g of glucose, corresponding to a 9.9 g/L titer. By adjusting the pH of the fermentation broth to 2, 2H4P was quantitatively converted into TAL. The TAL in the fermentation broth was directly converted by aminolysis into 4-hydroxy-6-methylpyridin-2(1H)-one (HMPO), which achieved an 18.5% yield with 94.3% purity. The HMPO yield was lower in the fermentation broth than in a clean feedstock (32.2%), suggesting that the biological impurities are inhibitors in this reaction. Further investigation revealed that lower pH levels and reduced TAL concentrations in the fermentation broth significantly decreased HMPO yields. Subsequently, the precipitated HMPO was filtered and dried and then subjected to the final catalytic conversion in H₂O solvent, achieving a MPO yield of 91.8%. This integrated approach demonstrated the direct use of TAL in the filtered aqueous fermentation broth without the need to isolate TAL.

The ammoximation reaction of ketones and aldehydes is a crucial industrial process for producing oximes, which has the advantages of a short process, mild reaction conditions, high ultilization of nitrogen atoms, and environmental friendliness. Significant efforts have been made to advance this process using Ti-containing zeolites as catalysts. This review discusses the reaction mechanisms of liquid-phase ammoximation, highlighting the challenges in designing effective catalysts. Research conducted over the past decades on designing high-performance, low-cost, and easily separable catalysts has been systematically reviewed. The structure–performance relationship of the zeolite catalyst is particularly examined, aiming to offer new insights for the design and preparation of more efficient catalysts in the future. Additionally, recent advances in process optimization for ammoximation are discussed, including the influence of reaction conditions on performance, the development of new reactors, industrial examples, and life cycle assessments. Finally, based on the discussion, future perspectives for enhancing the sustainability of ammoximation industrialization are outlined.

Oxygen-balanced mixotrophy (OBM) is a particular type of microalgae mixotrophic cultivation, where the supply of an organic carbon substrate is adjusted to match heterotrophic oxygen consumption with photosynthetic production. In this way, the need for aeration is eliminated due to intracellular gas recycling during daytime. After implementing this process at lab scale, we sought to explore its scalability in a tubular photobioreactor (TPBR). In this study, OBM was implemented in a two-phase tubular photobioreactor of 1700 L placed in a greenhouse and exposed to sunlight. The process was run with the polyextremophilic species Galdieria sulphuraria, using glucose as a carbon source. The gas phase was continuously recirculated, and the oxygen concentration was monitored and utilized to manage the glucose supply through a proportional-integral controller. An excessive rate of night aeration, however, resulted in CO₂ limitation issues. Subsequent tuning and optimization of controller settings and the nighttime aeration rate effectively addressed the problem. The average biomass productivity reached 0.81 g·L^–1·day^–1, a significant improvement over autotrophic productivity in the same pilot system. On the other hand, the biomass yield on the substrate was 0.68 C-mol_x·C-mol_s^–1, indicating that considerable carbon recycling took place but to a lower extent than at lab scale. These results provide a solid foundation for the large-scale industrial implementation of OBM.

This work explores the implementation of oxygen-balanced mixotrophy at an industrially relevant scale, enhancing the sustainability and economics of microalgae cultivation by reducing aeration needs and improving biomass productivity.

Bitumen asphaltenes (AS) are investigated as promising precursors for carbon fiber due to their low cost and high concentration of aromatic compounds. However, as-received AS exhibit poor melt-spinnability, which can be significantly improved by blending them with miscible polymers. In this work, blends of AS and recycled poly(ethylene terephthalate) (rPET) were investigated for their potential as precursors for sustainable partially carbonized fibers. This process is sustainable because it redirects two waste streams into feedstock for a higher value product, does not require thermal pretreatment of the AS, and avoids the use of solvents normally required to purify AS. The effect of the blending ratio on the viscoelastic properties of the AS-rPET blends and its role in melt-spinning was investigated. AS-rPET fibers were melt-spun, stabilized via oxidation, and partially carbonized. Scanning electron microscopy indicated that the produced partially carbon fibers had diameters of 40.75 ± 5.12 μm, representing an order-of-magnitude reduction in diameter compared to fibers derived from pure AS. Tensile testing of individual partially carbonized fibers determined the maximum tensile strength and Young’s modulus to be ∼0.29 ± 0.13 GPa and 24.9 ± 6.4 GPa, respectively.