Frontiers of Chemical Science and Engineering最新文献

Nowadays, global warming caused by the increasing levels of CO₂ has become a serious environmental problem. Membrane separation technology has demonstrated its promising potential in carbon capture due to its easy operation, energy-efficientness and high efficiency. Interfacial polymerization process, as a facile and well-established technique for preparing membranes with a thin selective layer, has been widely used for fabricating commercial reverse osmosis and nanofiltration membranes in water treatment domain. To push forward such an interfacial polymerization process in the research of CO₂ separation membranes, herein we make a review on the regulation and research progress of the interfacial polymerization membranes for CO₂ separation. First, a comprehensive and critical review of the progress in the monomers, nanoparticles and interfacial polymerization process optimization for preparing CO₂ separation membrane is presented. In addition, the potential of molecular dynamics simulation and machine learning in accelerating the screen and design of interfacial polymerization membranes for CO₂ separation are outlined. Finally, the possible challenges and development prospects of CO₂ separation membranes by interfacial polymerization process are proposed. It is believed that this review can offer valuable insights and guidance for the future advancement of interfacial polymerization membranes for CO₂ separation, thereby fostering its development.

A class of supramolecular binary hydrogels is formed from dodecylamine or tridecylamine and sparing carboxylic acids (with amine/acid molar ratio ⩾ 18). These hydrogels exhibit a remarkable thermally reversible four-phase transition. On heating, they transition from gel one (G¹)-to-sol one (Sol¹), then to gel two (G²)-to-sol two (Sol²). On cooling, they revert from Sol²-to-G²-to-Sol¹-to-G¹. Additionally, several G¹ and G² hydrogels undergo thermally reversible gel-to-gel phase transitions, which are reflected by translucent-opaque and opaque-translucent changes in their appearance. The nature of the four-phase transformation was analyzed using a range of techniques. Scanning electron microscopy images confirmed that the fibers of the opaque hydrogel at high temperatures were considerably larger than those of its translucent counterpart at low temperatures. Fluorescence emission spectra demonstrated that higher temperatures, higher amine/acid ratios, and greater acid hydrophobicity increased the hydrophobic interactions. Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopic analyses confirmed the existence of hydrogen-bonding interactions and aggregation in the hydrogels. X-ray diffraction profiles indicated that the hydrogels adopt lamellar structures. The findings advance our current understanding of the phase transition of supramolecular gels and facilitate the constitution of binary or multicomponent gels, providing a practical way to create new smart functional materials.

The urgent need for sustainable waste management has led to the exploration of upcycling waste plastics and biomass as viable solutions. In 2018, global plastic production reached 359 million tonnes, with an estimated 12000 million tonnes projected to be delivered and disposed of in landfills by 2050. Unfortunately, current waste management practices result in only 19.5% of plastics being recycled, while the rest is either landfilled (55%) or incinerated (25.5%). The improper disposal of plastics contributes to issues such as soil and groundwater contamination, air pollution, and wildlife disturbance. On the other hand, biomass has the potential to deliver around 240 exajoules of energy per year by 2060. However, its current utilization remains relatively small, with only approximately 9% of biomass-derived energy being consumed in Europe in 2017. This review explores various upcycling methods for waste plastics and biomass, including mechanical, chemical, biological, and thermal approaches. It also highlights the applications of upcycled plastics and biomass in sectors such as construction, packaging, energy generation, and chemicals. The environmental and economic benefits of upcycling are emphasized, including the reduction of plastic pollution, preservation of natural resources, carbon footprint reduction, and circular economy advancement.

Metal-organic frameworks have a wide range of applications in the field of membrane separation, but the inherent flexible structure and the difficulty for scale-up hinder their further applications. Herein, the relatively rigid zeolitic imidazolate framework-8 particles prepared under an electric field (E-ZIF-8) were used as the fillers in polysulfone (PSF) to form series of mixed matrix membranes. It was found that the introduction of E-ZIF-8 improves both the C₃H₆ permeability and C₃H₆/C₃H₈ selectivity of the membranes. Compared with the bare PSF membrane, the C₃H₆/C₃H₈ selectivity of the 30 wt % E-ZIF-8@PSF membrane increased by ∼230%, while the C₃H₆ permeability was enhanced by ∼830%. In addition, time and pressure dependence analysis demonstrated that such E-ZIF-8@PSF membranes also exhibited good long-term stability and pressure resistance, offering significant industrialization advantages.

This study investigates the detailed mechanism of CO₂ conversion to CO using the manganese(I) diimine electrocatalyst [Mn(pyrox)(CO)₃Br], synthesized by Christoph Steinlechner and coworkers. Employing density functional theory calculations, we thoroughly explore the electrocatalytic pathway of CO₂ reduction alongside the competing hydrogen evolution reaction. Our analysis reveals the significant role of diimine nitrogen coordination in enhancing the electron density of the Mn center, thereby favoring both CO₂ reduction and hydrogen evolution reaction thermodynamically. Furthermore, we observe that triethanolamine (TEOA) stabilizes transition states, aiding in CO₂ fixation and reduction. The critical steps influencing the reaction rate involve breaking the MnC(O)–OH bond during CO₂ reduction and cleaving the MnH–H–TEOA bond in the hydrogen evolution reaction. We explain the preference for CO₂ conversion to CO over H₂ evolution due to the higher energy barrier in forming the Mn-H₂ species during H₂ production. Our findings suggest the potential for tuning the electron density of the Mn center to enhance reactivity and selectivity in CO₂ reduction. Additionally, we analyze potential competing reactions, focusing on electrocatalytic processes for CO₂ reduction and evaluating “protonation-first” and “reduction-first” pathways through density functional theory calculations of redox potentials and Gibbs free energies. This analysis indicates the predominance of the “reduction-first” pathway in CO production, especially under high applied potential conditions. Moreover, our research highlights the selectivity of [Mn(pyrox)(CO)₃Br] toward CO production over HCOO⁻ and H₂ formation, proposing avenues for future research to expand upon these findings by using larger basis sets and exploring additional functionalized ligands.

Polyolefins, widely used for packaging, construction, and electronics, facilitate daily life but cause severe environmental pollution when discarded after usage. Chemical recycling of polyolefins has received widespread attention for eliminating polyolefin pollution, as it is promising to convert polyolefin wastes to high-value chemicals (e.g., fuels, light olefins, aromatic hydrocarbons). However, the chemical recycling of polyolefins typically involves high-viscosity, high-temperature and high-pressure, and its efficiency depends on the catalytic materials, reaction conditions, and more essentially, on the reactors which are overlooked in previous studies. Herein, this review first introduces the mechanisms and influencing factors of polyolefin waste upcycling, followed by a brief overview of in situ and ex situ processes. Emphatically, the review focuses on the various reactors used in polyolefin recycling (i.e., batch/semi-batch reactor, fixed bed reactor, fluidized bed reactor, conical spouted bed reactor, screw reactor, molten metal bed reactor, vertical falling film reactor, rotary kiln reactor and microwave-assisted reactor) and their respective merits and demerits. Nevertheless, challenges remain in developing highly efficient reacting techniques to realize the practical application. In light of this, the review is concluded with recommendations and prospects to enlighten the future of polyolefin upcycling.

The oxygen vacancy formation energy and chemical looping dry reforming of methane over metal-substituted CeO₂ (111) are investigated based on density functional theory calculations. The calculated results indicate that among the various metals that can substitute for the Ce atom in the CeO₂(111) surface, Zn substitution results in the lowest oxygen vacancy formation energy. For the activation of CH₄ on CeO₂ (111) and Zn-substituted CeO₂ (111) surfaces, the calculated results illustrate that the dissociation process of CH_3(ads) is very difficult on pristine surfaces and unfavorable for CHO_(ads) on substituted surfaces. Furthermore, the dissociative adsorption of CO and H₂ on the Zn-substituted CeO₂ (111) surface requires high energy, which is unfavorable for syngas production. This work demonstrates that excessive formation of oxygen vacancy can lead to excessively high adsorption energies, thus limiting the conversion efficiency of the reaction intermediates. This finding provides important guidance and application prospects for the design and optimization of oxygen carrier materials, especially in the field of chemical looping dry methane reforming to syngas.

The trend of employing machine learning methods has been increasing to develop promising biocatalysts. Leveraging the experimental findings and simulation data, these methods facilitate enzyme engineering and even the design of new-to-nature enzymes. This review focuses on the application of machine learning methods in the engineering of polyethylene terephthalate (PET) hydrolases, enzymes that have the potential to help address plastic pollution. We introduce an overview of machine learning workflows, useful methods and tools for protein design and engineering, and discuss the recent progress of machine learning-aided PET hydrolase engineering and de novo design of PET hydrolases. Finally, as machine learning in enzyme engineering is still evolving, we foresee that advancements in computational power and quality data resources will considerably increase the use of data-driven approaches in enzyme engineering in the coming decades.

The steam reforming of bio-oil can provide a sustainable means to produce hydrogen, while tar steam reforming can significantly enhance the efficiency of the biomass gasification process. Bio-oils and tars are highly complex mixtures, and while there has been extensive research on the reforming of small oxygenates and aliphatic hydrocarbons, there have been comparatively much less studies on aromatics reforming. In the current work, we present a comparative study of the steam reforming of hydroquinone, benzyl alcohol and toluene, selected as model compounds of the aromatic fraction of bio-oils and tars with different functional groups. The effect of temperature, partial pressure of reactants, and contact time is studied over a Rh catalyst supported on γ-Al₂O₃. Across the range of conditions studied, hydroquinone is found to be more reactive, followed by benzyl alcohol, and, lastly, toluene. The differences are attributed to the presence of hydroxyl groups in the case of the former two compounds, versus a methyl group in the case of toluene, effectively correlating activity with the O/C ratio in the compounds’ molecule. Nonetheless, similar pathways are observed, with methane, benzene, naphthalene and toluene (during hydroquinone and benzyl alcohol reforming) detected as products in addition to carbon oxides and hydrogen.

This study introduces an innovative screening approach to evaluate advanced oxidation processes (AOPs) as a preliminary diagnostic tool for degrading emerging contaminants (EC). It includes the design, prototyping, and cost-benefit analysis of circular photochemical reactors with flat and spiral internal geometries. Three-dimensional (3D) printing was used for reactor prototyping, providing flexibility and economy, and this stage was assisted by the hydrodynamic analysis of the prototypes based on residence time distribution (RTD) and macromixing models. The research evaluates the degradation of a model contaminant of emerging concern, fluoxetine (FLX) hydrochloride, using the solar/persulfate (PS) process in two water matrices (i.e., ultrapure water and sewage treatment plant effluent) to optimize reactor performance. The study also proposes primary theoretical pathways for fluoxetine degradation involving hydroxyl and sulfate radicals, as well as predicting the toxicity of the parent compound and its primary metabolites using quantitative structure-activity relationship (QSAR) models. The spiral reactor exhibits improved hydrodynamic behavior, closely resembling continuous stirred and plug flow reactors in series. Despite a slightly lower specific degradation rate in real wastewater, the solar/PS process remains effective for both matrices. By-products generated via the sulfate radical pathway are expected to be less toxic than those formed by hydroxyl radicals (HO·) attack.