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. 2018 Oct 26;9(11):549.
doi: 10.3390/mi9110549.

Micromixing Study of a Clustered Countercurrent-Flow Micro-Channel Reactor and Its Application in the Precipitation of Ultrafine Manganese Dioxide

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Free PMC article

Micromixing Study of a Clustered Countercurrent-Flow Micro-Channel Reactor and Its Application in the Precipitation of Ultrafine Manganese Dioxide

Kun-Peng Cheng et al. Micromachines (Basel). .
Free PMC article

Abstract

A clustered countercurrent-flow micro-channel reactor (C-CFMCR) has been assembled by the numbering-up of its single counterpart (S-CFMCR). Its micromixing performance was then studied experimentally using a competitive parallel reaction system, and the micromixing time was calculated as the micromixing performance index. It was found that the micromixing time of C-CFMCR was ranged from 0.34 to 10 ms according to its numbering-up times and the operating conditions of the reactor, and it was close to that of S-CFMCR under the same operating conditions, demonstrating a weak scaling-up effect from S-CFMCR to C-CFMCR. The C-CFMCR was then applied to prepare ultrafine manganese dioxide in a continuous manner at varying micromixing time. It showed that the micromixing time had a major effect on the particle structure. More uniform and smaller MnO₂ particles were obtained with intensified micromixing. By building a typical three electrode system to characterize their performance as a supercapacitor material, the MnO₂ particles prepared by both S-CFMCR and C-CFMCR under optimal conditions displayed a specific capacitance of ~175 F·g-1 at the current density of 1 A·g-1, with a decline of ~10% after 500 charge-discharge cycles. This work showed that C-CFMCR will have a great potential for the continuous and large-scale preparation of ultrafine particles.

Keywords: clustered countercurrent-flow micro-channel reactor; manganese dioxide; micromixing time; preparation; ultrafine particle.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
C-CFMCR: (a) appearance of C-CFMCR: 1. main inlet; 2. buffer zone; 3. shell; 4. S-CFMCRs; 5. main outlet; (b) middle cross-section of C-CFMCR.; (c) S-CFMCR; (d) schematic illustration of S-CFMCR.
Figure 2
Figure 2
Relationship between micromixing time and segregation index.
Figure 3
Figure 3
Estimated micromixing time at varying inlet volumetric flow rate.
Figure 4
Figure 4
XRD patterns of MnO2 prepared at different operating conditions (Note: Please refer to the reactor Ref. # in Table 2).
Figure 5
Figure 5
Average crystallite size variation with micromixing time.
Figure 6
Figure 6
SEM images of MnO2 samples prepared under different conditions: (a) S(01); (b) C(01); (c) C(02); (d) C(03).
Figure 7
Figure 7
N2 adsorption/desorption isotherms of MnO2 obtained in S-CFMCR and C-CFMCR, respectively.
Figure 8
Figure 8
Pore size distributions of MnO2 obtained in S-CFMCR and C-CFMCR, respectively.
Figure 9
Figure 9
Cycle-life of MnO2 prepared under different operating conditions at 1 A·g−1.

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