Hong Yin

Poly(phenylene sulfide) (PPS) produced by the sodium sulfide method contains ionized end groups such as sodium mercaptide (‐SNa) and sodium 4‐(methylamino)butanoate​ (‐SMAB), which can be exchanged to proton or other cations by ion‐exchange process. Depending on the type of cation and the extent of replacement, PPS performances can vary significantly. In this study, PPS samples with different extents of sodium ionization are prepared by adjusting the p H of PPS aqueous dispersion, then the melt stability is systematically investigated by capillary rheometer. It is found that neutral PPS possesses the best melt stability, while melt viscosity increases with the p H. Moreover, molecular weights before and after melt stability test are compared, neutral and alkaline PPS demonstrate similar minor decrease in molecular weight, while acidic PPS suffers severe degradation. Furtherly, electron paramagnetic resonance spectroscopy (EPR), rotational rheometer, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) are applied to reveal the mechanism behind. Loss of ionized end groups weakens ionic interactions in alkaline PPS, which accounts for reduction of melt viscosity, while protonated end groups in acidic PPS accelerate the formation of free radicals, leading to severe degradation of PPS chains.

The strategic spatial positioning of ion affinity sites within biological ion channels and their cooperative binding with the targeted ions are pivotal for enhancing ion recognition and ensuring exceptional selectivity in high ionic competition scenarios. However, the application of these principles to artificial ion channels remains largely unexplored. Herein, we present a series of covalent organic framework (COF) membranes, engineered with oxygen functional groups aligned along the rims of oriented COF pore channels of varying sizes to achieve a precise spatial arrangement of ion affinity sites. A notable COF membrane, featuring subnanometer pores decorated alternately with carbonyl and amide groups, demonstrated outstanding selectivity, achieving a Li/Mg selectivity ratio of 513 under equal mole and electrodialysis conditions. Impressively, as the Mg/Li ratio in the source solution increased to 16.6, the selectivity ratio rose to 833, significantly exceeding the reductions typically seen in conventional selective electrodialysis and nanofiltration methods. Both simulation and experimental analyses indicate that this exceptional selectivity stems from the cooperative binding between the oxygen functional groups and Li⁺ ions within the confined nanochannels, facilitating the preferential transport of Li⁺ ions. These findings provide a promising approach for designing selective ion extraction systems that function effectively in highly competitive environments.

A computational fluid dynamics-population balance model (CFD-PBM)-coupled simulation method was established to simulate the Sauter mean diameter (d₃₂) in a stirred sieve-plate extraction column with Ansys Fluent 19.2. The droplet breakage and coalescence were considered, and the kernel functions were loaded into Fluent as a user-defined function (UDF). The simulated d₃₂ by different kernels was compared with the experimental values, and the results showed that the modified model considering the dispersed phase viscosity has better simulation accuracy and good applicability. In addition, the effects of different operating conditions on d₃₂ were investigated. When the stirring speed is increased, d₃₂ decreases. As the dispersed phase flow rate increases, d₃₂ increases, while the change in the continuous phase flow rate does not have a significant impact on d₃₂.

4-Hydroxy-2-butanone, an important intermediate for vitamin A and fragrances, is usually produced by aldol condensation of acetone and formaldehyde. Noncatalytic synthesis of 4-hydroxy-2-butanone in supercritical state, which was fast and had high production yield, was widely applied. Previous research on 4-hydroxy-2-butanone synthesis in the supercritical state focused on the formation and dehydration of 4-hydroxy-2-butanone while ignoring side reactions involving formaldehyde, which were studied in this paper. A reaction pathway of 4-hydroxy-2-butanone supercritical synthesis containing formaldehyde side reactions was proposed. The cross-disproportionation of formaldehyde and formic acid was found to be the main consumption of formic acid. The effects of initial formaldehyde and formic acid mass fractions in the feed on side reactions were studied. Based on the experiments conducted from 523.15 K to 563.15 K and 17 MPa, a kinetic model was suggested. The relative deviations between experimental and simulated data were less than 10%.