The effects of hydrodynamics on the droplet adsorption at the parallel flow interface in a microchannel are studied. A stably moving liquid–liquid interface is generated expediently, and uniform droplets of the third phase is formed easily in each phase of parallel flow. The Laplace pressure on the interface of parallel flow makes the droplet volume distribution different when the droplets adsorb from different phase of parallel flow. The shape of droplets at the interface deviates from the theoretical result of the Neumann triangle, and becomes asymmetric under shear force. The increase of the interfacial velocity heightens the lubrication force in the liquid film between the droplet and the parallel flow interface, and prevents the film rupture accordingly. Meanwhile, the distribution of lubrication force is changed and the liquid film tends to rupture downstream. This paper provides a reference for the study of droplet adsorption on the interface of parallel flow.
Gang Fu,Lei Ni,Dan Wei,Juncheng Jiang,Zhiquan Chen,Yong Pan
In this study, toluene nitration was scaled up in a meso-scale flow reactor and safety was considered. The exothermic characteristic was demonstrated in a batch calorimeter . Parallel flow was observed in the flow channel and numerical simulation was carried out to show the hydrodynamics . Mass transfer coefficient of the reactor mixer was determined. The effects of flow rates, temperatures and molar ratios on toluene nitration in the flow reactor were analyzed. The conversion of toluene increased from 26% to 86% with the increase of flow rates while the impacts of temperatures and molar ratios were comparatively small. A productivity of 2572 kg/a could be achieved by this meso-scale flow reactor but the highest overtemperature inside the channel was more than 21.3 ∘ C. A comparison between performances of the batch calorimeter and the flow reactor was also presented. The finding of this study can serve as a reference to design inherently safer meso-scale flow reactors for kinetically fast and highly-exothermic reactions.
Electrochemical ozone production (EOP) is an intrinsically safe technology compared to Corona discharge methods for ozone generation. However, EOP technology exhibits higher electrical utility demand. Herein, a square-shaped lead oxide (PbO x -CTAB-120) electrocatalyst with outstanding EOP activity has been successfully prepared by a simple method. Then the PbO x -CTAB-120 was assembled into a newly visualized EOP electrolyzer (with parallel flow field) at 1.0 A cm −2 in ultrapure water. The gaseous ozone yield reached 588 mg h −1 g −1 catalyst , corresponding to a specific energy consumption (P EOP ) of 56 Wh g −1 gaseous ozone . In-situ 18 O isotope-labelled differential electrochemical mass spectrometry reveals that PbO x -CTAB-120 undergoes phase shuttling to β-PbO 2 via the lattice oxygen oxidation mechanism pathway. Furthermore, density functional theory calculations for multiple reaction pathways on the Pb 3 O 4 (110) surface also demonstrated the participance of lattice oxygen in the EOP process, with the results show that the oxygen vacancy generated from lattice oxygen migration could effectively stabilize the OOH* and O 2 * reaction intermediate in contrast to the adsorbate evolution mechanism. Therefore, the presence of highly stabilized surfaces Pb 3 O 4 (110) on PbO x -CTAB-120 before phase shuttling and the stabilization of β-PbO 2 (101) and β-PbO 2 (110) crystalline surfaces after phase shuttling allowed PbO x -CTAB-120 to maintain its excellent EOP activity and stability. Moreover, based on computational fluid dynamics simulations and experimental observations, the parallel flow field design facilitated efficient mass transfer of the gaseous product (O 2 +O 3 ) and effective thermal dissipation of the system. In addition, the high activity electrocatalyst coupled with the optimized EOP electrolyzer enabled efficient in-situ degradation of organic species.
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