Asia-Pacific Journal of Chemical Engineering最新文献

Hollow fibre membrane (HFM) is favourable for carbon dioxide (CO₂) due to its high packing density and high volume to area ratio. In this study, the effect of air gap and bore fluid ratio is explored to study its influence on the morphology and separation performance. With high dope extrusion rate (DER), the shear-induced polymer orientation can be preserved with low air gap which come with the cost of deformed lumen. As such, the coagulant activity of the bore fluid can be reduced by introducing solvent, which in turn reduces rate of phase inversion to prevent sudden contraction of polymer at low air gap, thus allowing proper formation of lumen. With the presence of solvent, the flowability of the dope solution increased due to reduced viscosity as the bore fluid with high solvent content make contact the external coagulant. HFM spun with low air gap with the presence of solvent in the bore fluid shows increased stretched ratio due to the influence of gravitational pull upon being extruded from the spinneret. This in turn improved the polymer chain orientation due to the stretch across the spinning line. Subsequently, HFM spun with 80 wt.% of N-methyl-2-pyrollidone (NMP) in the bore fluid using narrow gap spinneret with 5-cm air gap shows the highest ideal CO₂/N₂ and CO₂/CH₄ selectivity at 23.4 and 28 respectively, even though it also exhibit the lowest CO₂ permeance at only 3.1 GPU which was ascribed to the formation of dense skin layer. Meanwhile, when HFM was spun with a bigger annulus gap, the ideal CO₂/N₂ and CO₂/CH₄ selectivity slightly dropped, however the CO₂ permeance exhibit increment.

The jet impingement–negative-pressure reactor (JI-NPR) is a continuous and efficient technology designed to remove ammonia without clogging. Prior research has discovered that the changing movement of a porous jet impinging under negative-pressure conditions is distinguished by a more pronounced distribution over many regions. This study utilizes the CFD numerical simulation method in conjunction with the MATLAB platform to investigate the fractal characteristics of water phase distribution, velocity, turbulence intensity, vortex amount, and other parameters at various locations. The fractal dimension is employed as a criterion to analyze the chaotic characteristics of this multi-area distribution phenomenon. The study demonstrates that the effectiveness of deamination removal can be enhanced by quantitatively assessing the complex characteristics in the fluid flow using the chaotic fractal theory, which facilitates the identification of the ideal parameter settings. The optimal deamination effect can be achieved in the reactor when the jet velocity is set to 3.45 m/s and the negative pressure is maintained at 20 400 Pa.

In recent years, there has been growing interest in using polymer nanocomposite membranes as a more advanced method for removing pollutants from water and treating wastewater for various purposes. In this study, thin-film nanocomposite (TFN) membranes of polycarbonate/polyvinyl alcohol–titanium dioxide thin-film (PC/PVA–TiO₂) were fabricated by dip-coating a PC substrate in a PVA/TiO₂ solution. Various methods, including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and water contact angle were utilized to assess the structural characteristics of the produced membranes. The PC/PVA thin-film composite (TFC) and PC/PVA–TiO₂ TFN membranes were then examined in a submerged membrane system to evaluate their effectiveness in filtering humic acid (HA) under various vacuum transmembrane pressure (0.3 and 0.6 bar) condition. The FTIR-ATR results confirmed the formation of the active layer of PVA/TiO₂ nanoparticles (NPs). It was observed that adding 1 wt.% of TiO₂ NPs to the active layer of PVA/TiO₂ significantly enhanced the water contact angle from 77.5° for PC support to 55.3° for PC/PVA–TiO₂ (0.1) TFN membranes. Furthermore, the FE-SEM results confirmed the formation of an active layer of PVA/TiO₂ with a thickness of 237.87 nm. The pure water flux increased from 101.64 L/m²h for the PC/PVA TFC membrane to 144.02 L/m²h and 199.09 L/m²h for the PC/PVA–TiO₂ (0.05) and PC/PVA–TiO₂ (0.1) TFN membranes, respectively. Also, the results revealed that at lower transmembrane pressure, all membranes showed higher value in HA removal as compared to when higher transmembrane pressure was used.

The idea of a hybrid nanofluid (HNF) has sparked curiosity among many scientists because of its ability to enhance thermal characteristics, leading to elevated rates of heat transfer (HT). These HNFs are utilized in various engineering and industrial settings, such as electronics cooling, manufacturing, naval structures, biomedical applications, and drug delivery. The current study investigates the analysis of irreversibility in EMHD [Cu + TiO₂/H₂O]^h flow over a stretching sheet with radiation and viscous dissipation. The governing PDEs are converted into ODEs using similarity variables. These ODEs are then solved using the RKF method along with a shooting technique. The effects of different physical parameters on the velocity and temperature distributions of the HNF, as well as on HT and surface drag force, are thoroughly examined and presented in graphs. The velocity of [TiO₂/water]ⁿ flow declines as the magnetic field strength rises, but it rises with greater electric field values for [Cu + TiO₂/water]^h. The temperature of the [Cu + TiO₂/water]^h increases with elevated levels of radiation, Eckert number, and heat generation strength. Higher Reynolds and Brinkman numbers result in a rise in entropy generation for [Cu + TiO₂/H₂O]^h, whereas the Bejan number decreases to the same extent. The HT rate in [Cu + TiO₂/H₂O]^h increases by 3.05% as the Eckert number rises, while it drops by 4.01% when there is significant thermal radiation. Skin friction reduces by 3.21% in [TiO₂/water]ⁿ as the electric field strength increases, whereas it decreases by 4.05% with an increase in magnetic field strength. These discoveries offer valuable perspectives on furthering the utilization of HNFs in engineering and industrial operations.

The synthesis of high-efficiency magnetic composite photocatalyst by doping magnetic cobalt ferrite and compounding single semiconductor photocatalyst is a promising strategy to improve the oxidation ability of photocatalytic systems. In this paper, CoFe_1.95Dy_0.05O₄ (CFDO) was prepared by doping Dy element into magnetic CoFe₂O₄, and Ag₂S (AS)/CFDO with high-efficiency magnetic photocatalyst was synthesized by compounding AS with CFDO as the substrate. The photocatalytic samples were characterized by different advanced characterization methods, and their photocatalytic degradation of methylene blue (MB) was studied. The results show that AS/CFDO exhibits higher visible light response, excellent photogenerated charge separation ability and migration efficiency, and excellent catalytic performance in the catalytic degradation system. The photocatalytic activity of AS/CFDO was the highest, and its photocatalytic degradation kinetic constant K was 2.48 and 1.54 times that of AS and CFDO, respectively. In addition, the catalyst contained in the catalytically contaminated solution can be effectively separated by an external magnetic field to achieve multiple cycles of degradation and recycling. The cyclic degradation experiments showed that AS/CFDO exhibited high degradation stability during the photodegradation process. After the fifth reuse, the degradation efficiency was still more than 88.0%. Finally, the possible photocatalytic mechanism of the samples was discussed. Therefore, this work provides an effective solution for the construction of photocatalysts with high efficiency, magnetic recovery, and cyclic degradation stability and avoids the secondary pollution of catalysts to organic wastewater. It is of great significance to create an environmentally friendly catalytic method for efficient cyclic degradation of organic wastewater.

MoV-based composites stand out as the most promising potential catalysts targeted for direct production of acrylic acid from alkane/alkene substances. Herein, MoVTeNbO powder was synthesized and successfully fabricated by adding graphite as an appropriate tableting agent. Without employing graphite as lubricant, the fabrication of tablets was not practicable. The physicochemical effects of graphite on the catalyst properties were investigated via characterization by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), ammonia temperature-programmed desorption (NH₃-TPD), and thermal gravimetric analysis (TGA) methods. In addition to the easy and operative formation of tablets by consisting graphite, TGA results indicated better thermal stability compared to the bare powder. No harmful impact of graphite on the catalyst crystalline phases and morphology was detected by XRD and SEM analysis. The SEM images proved the graphite incorporation as a binder in the physical combination of the catalyst particles along the compression process, resulting in the desired physical resistance. Graphite caused a slight decrease in the BET surface area and final catalyst acidity. Despite the effect of reducing propene conversion, interestingly, a substantial improvement in the yield of acrylic acid was found by tableting. The graphite as an inert agent suppressed hot spots on the catalyst surface, leading to superior consistency in activity over time as well as lower selectivity to undesirable CO_x.

Self-excited thermoacoustic instability (SETAI) is a dangerous phenomenon in combustion equipment. While it is widely acknowledged that SETAI behavior is determined by the couple between pressure and heat release oscillation, their phase difference is difficult to predict, which impedes the development of SETAI control technology. With the aim of passive control technology development, this paper conducted experiment on a premixed hedge combustor to explore the mechanism whereby premixed chamber length (L_P) and equivalence ratio (φ) collaboratively influence SETAI behavior. Results showed L_P mainly affects the pressure mode shape within premixed chamber and consequently alters the phase difference between pressure and flowrate oscillation at combustion chamber inlet. Changing φ gives rise to different reaction time-lag (τ), thus altering the phase difference between flowrate and reaction heat release oscillation. By introducing this flowrate oscillation, how L_P and φ collaboratively determine phase difference between pressure oscillation and heat release oscillation was clarified. The mechanisms identified in this study are consistent with the emerging rationalization of the factors contributing to SETAI, and also provides better understanding on Rayleigh criterion and guidance for SETAI control. With further work on heat release and flow rate measurement, as well as the development on τ description, SETAI can be better predicted and controlled.

Due to excellent performance, hydrogen is treated as the most promising energy carrier. However, during the storage of liquid hydrogen, there are still some thorny issues that need to be addressed urgently, such as fluid thermal stratification and sloshing phenomenon. To efficiently grasp fluid sloshing mechanical characteristics, a simple visual sloshing experiment rig was established by using a rectangle transparent water vessel. The variations of the interface shape and the impact force during sloshing were monitored and analyzed. The effects of sloshing frequency, horizontal acceleration, and initial liquid height on fluid sloshing mechanical mechanism were investigated. The results show that when the external sloshing excitation is close to the first order natural frequency, obvious interface fluctuation and large amplitude sloshing force variation are observed. The present work is of significance to strengthen the understanding of fluid sloshing mechanical performance and may lay a solid foundation for fluid sloshing suppression and long-term storage of cryogenic fuels.

Deep eutectic solvents (DESs) are increasingly recognized as sustainable alternatives suitable for a range of industrial applications. A precise comprehension of their properties is important for progress in science and engineering. In this study, we synthesized four novel ternary DESs using mandelic acid and measured their densities and viscosities at temperatures ranging from 298 to 353 K. Subsequently, an artificial neural network model was developed to predict DES density and viscosity based on temperature, critical properties, acentric factor, and molar ratio. The neural network parameters were optimized using experimental data from synthesized DESs and literature sources, both collectively over 500 data points for density and viscosity. Additionally, we investigated the influence of input parameters on model accuracy and assessed their significance. The results show that the average percentage relative error was 0.501 for density and 4.81 for viscosity. This research helps advance science and engineering applications of DESs.

High expansion (Hi-Ex) foam is recommended to suppress the leakage and diffusion of cryogenic liquid due to its light weight and large volume. However, the disadvantages of low stability and high break rate under environmental conditions are all limited the further application in vapor mitigation and fire extinguishing. So that, this paper focus on the effect and mechanism of nanoparticles in stabilizing Hi-Ex foam. Three kinds of nanoparticles with different concentration were selected to evaluate the effect of foam half-life and the mechanism of particles on improving the foam stability. The results indicated that different particle concentrations can improve the foam stability to a specific extent, and the maximum improving of half-life can increase by 95.4% in the presence of the hydrophilic SiO₂ at .5 wt%. Meanwhile, the hydrophilicity, size, and morphology of the particles have a specific impact on the foam stability. The foam expansion rate first increased and then decreased. From the microscopic point of view, the bubble size gradually increases with time by two processes of ripening and coalescence and satisfied in a logarithmic distribution. While, the liquid film thickness remarkably decreases due to foam drainage without particles and the adsorption and accumulation of nanoparticles on foam lamella can provide a spatial barrier for the film thinning and the inter bubble diffusion. Finally, the microscopic interaction mechanism on improving the foam stability has been further explored and revealed in these two aspects.