Asia-Pacific Journal of Chemical Engineering最新文献

Understanding the mechanisms of shale–water interaction by water vapour adsorption is crucial for predicting shale gas productivity. In this study, equilibrium adsorption data of water vapour on four different shales of the Sichuan Basin at three temperatures (298, 308, and 318 K) were measured using static gravity techniques. The water vapour adsorption isotherms were simulated by three statistical physics models. Steric parameters, including the number of water vapour molecules adsorbed per site (n), monolayer adsorption amount (q₀), and adsorption energy (ΔE^a), and thermodynamic parameters such as configuration entropy (S_a), internal energy (E_int), and free energy (G_a) derived from the selected model were used to explain the adsorption mechanism. The model analyses suggest that the adsorbed water vapour molecules are attached to the shale surface in a multi-anchorage manner. The adsorption of the first layer shows a Type I characteristics, while the adsorption of the subsequent layer is of Type III. The calculated adsorption energies indicate that the physical adsorption takes place on the water vapour molecules on the shale, and the main interaction forces are hydrophilic bonding forces and van der Waals forces. Negative E_int and G_a values indicate that the spontaneous properties are for water vapour adsorption and that the system requires the release of energy to capture the water vapour molecules.

To solve the high heat dissipation problem of lithium ion battery, the air-cooled heat dissipation with fins is adopted for the thermal management. Heat dissipation characteristics of two types of air inlets and outlets (single air inlet and outlet, and double air inlet and outlet) and two types of surfaces (smooth and fin structure) were simulated and compared. When the air inlet and outlet are single inlet and single outlet, compared with smooth battery packs, finned construction packs can increase the Nusselt number by 24.9%. When the air inlet and outlet are double inlet and double outlet, compared with smooth battery packs, finned construction packs can increase the Nusselt number by 13.3%. The double-air inlet and outlet battery pack can significantly reduce the average temperature of the battery pack compared with the single-air inlet and outlet battery pack. Compared with the single-inlet and single-outlet solar smooth battery pack, it can increase the Nu by 131.6%, and the comprehensive performance index can reach 1.66.

Direct air capture (DAC) of CO₂ is an important technology to mitigate mobile carbon emissions, reduce atmospheric CO₂ concentration, and cope with climate change. Moisture-swing adsorption is regarded as one of the most promising technologies in DAC due to its low energy consumption and ease of operation. In this work, a cheap and easily available moisture-swing adsorbent of potassium carbonate loaded on porous supports (i.e., activated carbon, magnesium oxide, and zeolite) was prepared for CO₂ capture from ambient air. The composite adsorbent of potassium carbonate on activated carbon showed the best performance with a DAC capacity of 0.562 mmol/g at 25°C and 5% relative humidity. The effects of temperature, relative humidity, and CO₂ concentration on the adsorption performance were investigated systematically, as well as the cyclic DAC performance. In 50 adsorption–desorption cycles, the adsorption capacity of the composite adsorbent decreased by ~40% due to potassium carbonate leaching loss during water evaporation but can be fully recovered simply by re-impregnating with potassium carbonate again.

Kinetics of antimony production via carbothermal reduction of Sb₂O₃–carbon powder–NaCl mixture using microwave and conventional heating was investigated to identify the dominant controlling mechanism. Results of conventional heating revealed the temperature range of conventional carbothermal reduction reaction is 500°C to 800°C, with the average activation energy of each stage being 81.97 kJ/mol (α = 0.1–0.5), 65.17 kJ/mol (α = 0.5–0.75), and 69.86 kJ/mol (α = 0.75–1.0), respectively. In the microwave field, the carbothermal reduction reaction of raw materials can be completed at 600°C to obtain antimony, and the weight loss data of the carbothermal reduction process were recorded for the first time. The above results show that the microwave field enhanced the interfacial chemical effect, accelerated the interfacial diffusion from the metal phase to the oxide phase, and reduced the activation energy of the carbon thermal reduction process to 6.85 kJ/mol. The growth index of antimony grain growth process is estimated to be 4.33, controlled by the surface diffusion. These data provide a reliable theoretical basis for studying the reduction reactions of minerals in microwave fields.

The purpose of this investigation was to determine whether pyriproxyfen (PPF), a synthetic juvenile hormone analog (JHA), could be encapsulated in supercritical carbon dioxide (scCO₂) using the process particles from the gas-saturated solutions (PGSS) for a controlled-release system. The PGSS process represents a promising two-step production system especially suited for the encapsulation and controlled-release system (CRS). In contrast to traditional encapsulation methods that often involve the use of harsh organic solvents or high temperatures, the PGSS process offers a gentler approach employing scCO₂ as an alternative. The solubility of scCO₂ in polymer (poly-ϵ-caprolactone [PCL]) allowed for the formation of PPF microparticles, and the particle size distribution could be controlled by adjustment of operating pressure and temperature. The obtained particles had a mean particle size of 73.6 ± 2 μm and encapsulation efficiency of 78.8 ± 9% at 60°C and 10 MPa. Furthermore, the in vitro dissolution profiles of PPF–PCL particles showed a low-level release pattern (42.5 ± 5 ppb/d) in water, followed by zero-order kinetics indicating a high-performance CRS. Finally, the in vivo bioassay using microparticles treated water exhibited 95%–100% emergence inhibition of mosquitoes, suggesting the effectiveness of PPF–PCL particles as a mosquito control agent.

Hydrocarbon resin (HR) is an essential fine chemical. The preparation and application process of HR involves lots of gas–liquid heterogeneous reactions, and the bubbly flow behavior influences them significantly. Using high-speed photography and digital image processing techniques, the motion and interaction of in-line bubbles in non-aqueous solutions of HR are examined in this article. The results show a critical gas flow rate that can change the bubbling regime. It can be observed that viscosity features prominently in changing the shape of bubbles and their motion. As the viscosity increases, the bubbles are more prone to coalescence, and the bubble coalescence process gradually changes from connected slip-rising coalescence to connected-rising coalescence. The viscosity transition region between non-coalescent and coalescent systems in non-aqueous solutions of HR occurs at 3.6–9.2 mPa·s. Further, a force analysis shows that in paired bubbles, the leading bubble can be viewed as an individual bubble unaffected by trailing bubble before the two bubbles collide, but in the wake of the leading bubble, the drag force on the trailing bubble decreases and the added mass force increases.

The turbulence observed in the stirred tank is a result of the superposition of flows at different scales, each exerting various influences on the operational processes. To understand the flow characteristics associated with stirring, this paper undertakes particle image velocimetry (PIV) experimental research on an unbaffled tank stirred by an open turbine featuring four distinct blade deflection angles. The flow field in the unbaffled tank manifests as a double-circulation flow pattern; however, it is worth noting that the blade deflection angle exerts a significant impact on the stirring process. Specifically, when the blade deflection angle reached 90°, the flow discharge aligned closely with the radial direction, accompanied by pronounced fluctuations in the high-velocity region. The Lagrangian coherent structures (LCS) formed were subsequently extracted and subjected to finite-time Lyapunov exponent (FTLE) analysis. Notably, a more regular wake pattern emerged in proximity to the blade tip, while a larger scale flow structure persisted along the flow direction. To systematically analyze the flow field stirred by the open turbine, modal analysis was employed. By reconstructing the flow field based on the principle of 50% energy content, the decomposition of flows at different scales was achieved. The turbulent kinetic energy (TKE) generated by the various scale flows was subsequently calculated, revealing that the high TKE values primarily originate from the large-scale flow structure. Conversely, the TKE generated by the small-scale flow exhibits a uniform distribution across different regions. Notably, in regions characterized by higher velocities, the peak TKE associated with the small-scale flow also manifests; however, it is significantly smaller in magnitude compared to that generated by the original flow or the large-scale flow.

The aim of this study was to use different proportions (1% to 20% by weight) of γ-alumina to modify sugarcane bagasse ash (SCBA) for the production of dimethyl ether (DME) through the dehydration of methyl alcohol. A simple precipitation method was utilized to fabricate (1–20 wt.%) Al₂O₃/SCBA catalysts. X-ray fluorescence, X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and N₂ sorption were used to explore the structural, spectroscopic, morphological, and textural features. The XRD pattern of Al₂O₃/SCBA catalysts showed a new peak that corresponded to the formation of γ-Al₂O₃. In addition, the average crystallite sizes of pure SCBA and 10% and 20%Al₂O₃/SCBA catalysts were calculated and found to be 20.1, 21.6, and 22.6 nm, respectively. To evaluate the acidity of these catalysts, the dehydration of isopropyl alcohol and the chemisorption of basic probe molecules were employed. The acidity test results displayed that these catalysts have weak to moderate acidic sites. The 10% Al₂O₃/SCBA catalyst calcined at 400°C showed high efficiency for the conversion of methyl alcohol to DME, attaining 89% conversion with 100% selectivity. This observation can be attributed to the even distribution of active sites and the acid–base equilibrium on the surface. Moreover, its catalytic activity and selectivity remain unchanged over a continuous 2-week operation without coke formation, demonstrating its extremely high stability. A strong correlation was observed between the catalytic activity and both the surface area and acidity of the catalysts.

Hollow carbon nanospheres (HCNS) were prepared from carbon black (CB) derived from spent tyre pyrolysis oil. The pristine CB produced by partial oxidation of the pyrolysis oil in a drop tube furnace was subsequently oxidised in air in a fixed bed reactor to yield HCNS. The effect of oxidation temperature (300 to 700°C) and time (1 to 8 h) on the burn-off (B_t) of the sample over the duration (t) of oxidation and average reaction rate (R_t) was assessed. The BET surface area and pore volume and the nanostructure of the HCNS samples obtained were characterised using N₂ adsorption–desorption and high-resolution transmission electron microscope (HRTEM) techniques, respectively. Higher temperature and longer oxidation time led to higher B_t. As B_t increased, the BET surface area and pore volume initially increased linearly due to the removal of the amorphous core and then decreased because of the collapse of the shell of the carbon nanostructure. At B_t of ~56%, the maximum BET surface area and pore volume of the HCNS were 383.2 m² g⁻¹ and 0.39 cm³ g⁻¹, respectively, compared to ~19.5 m² g⁻¹ and 0.033 cm³ g⁻¹ of the pristine CB. The HRTEM images indicate that the change in BET surface area corresponds to the formation of the HCNS, as the core of the CB particle was preferentially consumed to create a hollow structure. The formation of HCNS follows an internal oxidation model, which is characterised by rapid core consumption and relatively slow shell consumption.

3D simulations have been achieved on a flow-focusing geometry employing the VOF method to study the consequence of viscosity, surface tension, wettability, and geometry on drop generation for the dripping regime. Here the dispersed phase is the PDMS oil (polydimethylsiloxane), and the continuous phase is the water. Simulations were performed at different oil-to-water viscosity ratios $�\left(\frac{{\mu }_o}{{\mu }_w}\right)$ of 3, 12, 27, and 50. The interfacial tension between PDMS oil and water is 0.0118 N/m. It has been abridged to 0.008 N/m, 0.005 N/m, and 0.002 N/m, and simulations were performed. The walls of the microchannel are considered to be PMMA surfaces. The contact angle of an oil droplet on the PMMA surface in the presence of water is 140°. The effect of wettability was shown at various contact angles (angle created by water droplet on the PMMA surface in the presence of oil) of 0°, 40°, 90°, 135° and 180°. The frequency of droplet generation (1/s), non-dimensional droplet length (L/W_c), droplet volume (nl), and droplet velocity (m/s) have been calculated for each of the cases. A flow pattern map has been industrialized classifying the dripping and jetting regimes. A comparison between normal geometry and two constricted geometries (having different orifice lengths) based on the frequency of droplet, non-dimensional drop length, drop volume, and drop velocity has been made for both dripping and jetting regimes. Prediction of simulated non-dimensional droplet length has also been made using dimensional analysis.