Chemical Engineering and Processing - Process Intensification最新文献

The oxygen reduction reaction (ORR) is fundamental in numerous electrochemical energy conversion technologies, necessitating efficient catalysts to enhance reaction kinetics and reduce precious metal usage. This study focuses strategic clustering of Pt-Ni on Calcium Oxide/activated carbon (C/Ca) aerogels. Electrochemical analyses confirmed that incorporating Ni into Pt matrices significantly enhanced ORR activities with Pt₂₅Ni₇₅-C/Ca composition emerged as optimum. A positive shift in half-wave potential (905 mV vs. RHE) and impressive mass activity (72.50 Ag⁻¹ at 85 V) highlight the potential of this composite as a highly effective and stable ORR catalyst. Pt-C/Ca demonstrated performance fluctuation, while Pt₂₅Ni₇₅-C/Ca showed remarkable stability after 40,000 cycles. Furthermore, C/Ca aerogels exhibited a significantly increased BET surface area, and the presence of Pt-Ni/pyridinic-N species on its surface C/Ca aerogel provided supplementary active sites that facilitated the adsorption and reduction of O₂ during ORR.

In this paper, we propose a micromixer with the combination of a flow-focusing region and sawtooth structures, to study the mixing performance of electrokinetic (EK) flow under the impact of an alternating current (AC) electric field by means of numerical simulations. The Helmholtz-Smoluchowski theory is applied to approximate the electric double layer (EDL) effect. Focusing on the effects of sawtooth structures and AC electric field frequencies on mixing efficiency of electrokinetic micromixers, the concentration distributions and velocity distributions within micromixers have been studied. The numerical simulation results demonstrate that this micromixer has an excellent mixing performance for Newtonian solutions. Additionally, a proper sawtooth structure is conducive to enhancing the mixing efficiency of an electrokinetic micromixer, which is due to the generation of vortices at the junction edges. The presence of vortices leads to the enhancement of fluid disturbance and the enlarged contact area between fluids, contributing to a more complete mixing for electrokinetic flows. Moreover, it is found that as the AC electric frequency is reduced, the mixing efficiency is enhanced for such novel electrokinetic micromixer. The low electric frequency causes the velocity of electro-osmotic flow to decrease, promoting the molecular diffusion as the primary mixing mechanism, which improves the mixing efficiency. This work provides important insights for the application of sawtooth structure on electrokinetic micromixers, and serves as a crucial reference for the integration of active and passive techniques in microfluidic technology.

With the depletion of traditional fossil fuel and the increasingly severe problem of carbon emissions, the world urgently seeks alternative energy sources. Biodiesel, with its clean and renewable characteristics, has become an ideal alternative to fossil fuel. The “temperature difference driven heating-mechanical stirring-heterogeneous catalytic transesterification” process is supposed to be an ideal technology for biodiesel production, but there is a large resistance to heat and mass transfer in this way, which leads to slow catalytic reaction rate and low biodiesel yield. To solve this process, researchers have innovatively introduced external field-enhanced technologies such as microwave and ultrasound, aiming to enhance heat and mass transfer processes, optimize reaction conditions and significantly improve biodiesel yield. This article deeply analyzes the principles of heterogeneously catalyzed transesterification reaction enhanced by external fields and their positive effect on reaction kinetics and thermodynamics. Furthermore, the performance of external field-enhanced technologies is comprehensively analyzed in terms of techno-economic, environmental and bibliometric mapping. Finally, the future application of external field-enhanced technologies in biodiesel production is prospectively discussed.

In recent years, the demand for phosphoric acid, a key raw material for lithium iron phosphate batteries, has surged. However, current phosphoric acid extraction equipment faces challenges such as low mass transfer efficiency and difficulty in phase separation, leading to reduced production efficiency, bulky equipment, and scaling issues. To address these problems, this study introduces a T-type central plug-in microreactor (TCPM) designed to enhance mass transfer efficiency and facilitate rapid phase separation. The extraction of phosphoric acid from the water phase to the organic phase (volume ratio of tributyl phosphate to kerosene is 4:1) was chosen as the experimental system. We investigated the effects of various parameters on liquid-liquid flow and mass transfer characteristics in the TCPM. Visualization techniques identified slug and parallel flow as the primary liquid-liquid flow patterns within the TCPM. Notably, the central plug-in promotes the formation of parallel flow, improving phase separation compared to conventional T-type microreactors. The volume mass transfer coefficient of the TCPM ranges from 0.023 to 0.074 s^-1, and the optimal phosphoric acid extraction efficiency and volume mass transfer coefficient can reach up to 90.5% and 0.074 s^-1, respectively, outperforming conventional T-type microreactors. Predictive model for extraction efficiency was developed, showing deviations within 10%. These findings demonstrate the TCPM's potential as an efficient phosphoric acid extraction device with rapid phase separation, holding significant promise for liquid-liquid extraction applications.

Wave-rotor-based gas pressure dividing (GPD) is a potential technology that can synchronously conduct gas compression and expansion. This study, proposes a novel curving flow channel of wave rotor (C-FCWR) for the three-port GPD device, aiming to settle the technical problem of traditional width-constant straight flow channels (WS-FCWR). A series of comparative hydrodynamics and thermodynamic analyses are conducted. For the optimized C-FCWR with a forward-curving angle of +10°, the flow vortex generation in the medium-pressure (MP) and low-pressure (LP) ports is rather limited, the shaft power is as low as -0.45 kW, the shock wave efficiency is beyond 99.8 %, and the expansion depth remains above 26.4 K, proving a great technical advantage. For the application feasibility of the optimized C-FCWR to working conditions, a compression ratio below 1.2 and an expansion ratio of 1.8 are conducive to the overall performance of the GPD device.