Green Chemical Engineering最新文献

Metal-organic frameworks (MOFs) are favored in the fields of adsorption, separation, catalysis, electrochemistry, and magnetism due to their advantages of large specific surface area, high porosity, controllable pore size adjustment, and dispersion of metal active sites. The application of MOFs involves multiple fields, which requires that MOFs have good water stability, as gaseous and liquid water inevitably exist in industrial processes. In this paper, the research status of the stability of MOFs in aqueous solutions was reviewed in recent years, including the design and synthesis, the influencing factors, and the applications of MOFs in water stability.

The development of ultrafine particles provided a new way to solve problems in the fields of energy, environment, and medicine, and had become one of the most promising technologies. Therefore, the application of ultrafine particles required the development of cleaner, greener, and more efficient preparation methods. The new freeze-dissolving technology has been applied in manufacturing of KHCO₃ ultrafine particles, with an aqueous solution of 0.02–0.1 g KHCO₃/g water. Frozen ice particles were formed after dripping the solution into liquid nitrogen. The antisolvent ethanol was used to dissolve the ice spherical template at a temperature below 273.15 K, and the pre-formed KHCO₃ ultrafine particles inside the ice template remained in the ethanol aqueous solution. The ice particles were put into the freeze dryer to isolate the ultrafine KHCO₃ particles. Compared with the particles produced with traditional freeze-drying technology, the ultrafine powder/particles produced by the freeze-dissolving technology were smaller with narrower size distribution. The freeze-dissolving technology has demonstrated a much more sustainable and efficient manufacturing process than the traditional freeze-drying process. In addition, the influence of the concentrations of KHCO₃ and the sizes of ice particles were investigated with the discussions of mechanisms.

Dendritic mesoporous silica nanoparticles (DMSNs) are a new class of solid porous materials used for enzyme immobilization support due to their intrinsic characteristics, including their unique open central–radial structures with large pore channels and their excellent biocompatibility. In this review, we review the recent progress in research on enzyme immobilization using DMSNs with different structures, namely, flower-like DMSNs and tree-branch-like DMSNs. Three DMSN synthesis methods are briefly compared, and the distinct characteristics of the two DMSN types and their effects on the catalytic performance of immobilized enzymes are comprehensively discussed. Possible directions for future research on enzyme immobilization using DMSNs are also proposed.

Waste plastics are serious environmental threats due to their low degradability and low recycling rate. Rapid and efficient waste plastics recycling technologies are urgently demanded for a sustainable future. Herein, we report a rapid, closed-loop, and streamlined process to convert polyesters such as poly(ethylene terephthalate) (PET) back to its purified monomers. Using trifluoromethanesulfonic acid or metal triflates as the recyclable catalyst, polyesters such as PET can be completely depolymerized by simple carboxylic acids within 1 h. By coupling this acidolysis with a subsequent hydrogenolysis process, the consumed carboxylic acid was recovered and the closed-loop of PET depolymerization could be established. All catalysts and depolymerization agents are fully recycled while only PET and hydrogen are consumed.

Non-methane hydrocarbons (NMHCs) are a common type of volatile organic compounds (VOCs) pollutant in the petrochemical industry and have attracted widespread attention because of their adverse health effects and environmental impacts. In this paper, we report a new porous slurry formed with zeolitic imidazolate framework-8 (ZIF-8) and iso-hexadecane to capture the low-concentration and multi-component NMHCs (mainly ethane (C₂H₆), propane (C₃H₈), and n-butane (n-C₄H₁₀)) from the oil field exhaust. The sorption capacity of C₂H₆ in the slurry is significantly higher than that of nitrogen (N₂) and methane (CH₄). Moreover, the slurry demonstrated a clear advantage for C₂H₆ over N₂ and CH₄ in competitive adsorption through the pressure-drop curves. In the NMHCs capture experiments, the C₃H₈ and n-C₄H₁₀ concentrations after purification can be reduced to below 100 ppm, while the C₂H₆ concentration can reach approximately 180 ppm. More encouragingly, in the breakthrough tests, the slurry exhibits a perfect kinetic separation selectivity for multi-component NMHCs. Furthermore, to avoid structural collapse of ZIF-8 material during long-term use in acidic and wet environments, a certain amount of 2-methylimidazole was retained in the slurry as a protective agent in the material synthesis process. In this way, the ZIF-8 materials in the slurry can retain the stable characteristic structure in an aqueous and acidic environment and keep the capture capacity for NMHCs without degradation. We believe the porous ZIF-8/iso-hexadecane slurry is a promising capture agent for low-concentration and multi-component NMHCs with strong purification capacity and stability.

In the chemical synthesis of L-syn-p-methylsulfoxide phenylserine ethyl ester (D-ethyl ester), l-tartaric acid or enzymatic resolution is employed to resolve the racemate, and thus obtain the target compound, and the remaining isomer can be recycled to obtain the raw material. In this study, high-purity L-syn-p-methylsulfoxide phenylserine (L-syn-MPS) was obtained. The kinetics of the d-threonine aldolase enzymatic hydrolysis reaction reveals that D-syn-p-sulfoxylphenylserine resolves well in [BMIM][BF₄] ionic solvents. The D/L-syn-MPS racemate was resolved using a two-phase ionic solvent [BMIM][NTf₂] to afford L-syn-MPS (ee (enantiomeric excess) > 99%) and a white solid in 41.7% yield. Therefore, this system is suitable for the separation of insoluble aldehydes and successfully avoids the condensation of hydroxyl aldehydes to form D-anti-MPS.

The genomic scale metabolic networks of the microorganisms can be constructed based on their genome sequences, functional annotations, and biochemical reactions, reflecting almost all of the metabolic functions. Mathematical simulations of metabolic fluxes could make these functions be visualized, thereby providing guidance for rational engineering design and experimental operations. This review summarized recently developed flux simulation algorithms of microbial systems. For the single microbial systems, the optimal planning algorithm has low complexity because there is no interaction between microorganisms, and it can quickly simulate the stable metabolic states through the pseudo-steady hypothesis. Besides, the experimental conditions of single microbial systems are easier to reach or close to the optimal states of simulation, compared with polymicrobial systems. The polymicrobial culture systems could outcompete the single microbial systems as they could relieve metabolic pressure through metabolic division, resource exchange, and complex substrate co-utilization. Besides, they provide varieties of intracellular production environments, which render them the potential to achieve efficient bioproduct synthesis. However, due to the quasi-steady hypothesis that restricts the simulation of the dynamic processes of microbial interactions and the algorithm complexity, there are few researches on simulation algorithms of polymicrobial metabolic fluxes. Therefore, this review also analyzed and combed the microbial interactions based on the commonly used hypothesis of maximizing growth rates, and studied the strategies of coupling interactions with optimal planning simulations for metabolism. Finally, this review provided new insights into the genomic scale metabolic flux simulations of polymicrobial systems.