Scale-up of ultrasonic microreactor systems and their applications in the preparation of nanomaterials

doi:10.11949/0438-1157.20240598

Abstract

Abstract:

The combination of ultrasonics and microreactor can solve the problems of conventional microreactors that can frequently be blocked by solid particles, poor operational elasticity, and difficult scale-up so that ultrasonic microreactor is expected to become a new generation of microreactor technology, which will be widely used in reaction processes, involving solid blockage and limited mass transfer of mixing, especially the synthesis of nanomaterials. Although there are many research reports on ultrasonic microreactors, most of them are limited to small reactors for laboratory use, and there are few studies on the amplification of ultrasonic microreactors. This review systematically introduces the structural composition of the ultrasonic microreactor system and the resonance matching and scale-up strategies between the components. Generally, the ultrasonic microreactor system consists of four parts: ultrasonic power supply, ultrasonic transducer, microchannel reactor, and fluid in the channel. The ultrasonic energy is generated by the power supply and transmitted to the fluid through the transducer and microchannel. To ensure the high energy transfer efficiency of the system, the resonant frequency corresponding to these four parts needs to be consistent and the impedance should be matched. The scale-up of the ultrasonic microreactor is divided into three aspects: ultrasonic power amplification, reactor radiation surface enlargement, and microchannel size expansion, and the core problems and solutions encountered in the magnification of each part are systematically expounded. Finally, the applications of ultrasonic microreactors in the field of nanomaterial synthesis are introduced in detail, and according to the mechanism of the synthesis process, it is divided into three types of nanomaterial synthesis: reaction nucleation growth control, molecular self-assembly control, emulsion and interface confinement control.

Key words: ultrasonic microreactor, micro-chemical, ultrasonic chemistry, process scale-up, flow chemistry

摘要：

将超声波与微反应器结合能解决常规微反应器易被固体颗粒堵塞、操作弹性欠佳、放大困难等问题，使超声微反应器（USMR）成为新一代微反应器技术，广泛应用于涉及固体堵塞和混合传质受限的反应过程，特别是纳米材料的合成。虽然目前有不少关于USMR的研究报道，但大多局限于实验室用的小型反应器，鲜有关于USMR放大的研究。系统地介绍了USMR系统的结构组成以及各组成部件之间的谐振匹配和放大策略。一般来说，USMR系统包括超声波电源、超声波换能器、微通道反应器、通道中的流体四部分，超声波能量由电源产生并经换能器、微通道传输到流体中。要保证该系统较高的能量传输效率，需要这四个部分对应的谐振频率保持一致、阻抗实现匹配。将USMR系统的放大分成超声波电源放大、反应器辐射面放大、微通道尺寸放大三个方面，系统阐述每个方面放大遇到的核心关键问题和解决思路。最后重点介绍了USMR在纳米材料合成领域的应用，并根据合成过程的机理将其分为反应成核生长控制、分子自组装控制、乳液及界面限域控制三种纳米材料合成类型。综合结果表明，USMR在控制纳米材料尺寸形貌均一性方面展现了巨大的优势。

关键词: 超声微反应器, 微化工, 超声波化学, 过程放大, 流动化学

CLC Number:

TQ 028.8

Zhengya DONG, Xiaojing ZHU, Jingfu JIA, Jie ZHANG, Zhuotao ZHENG, Xiaolin LIU, Zhilin WU. Scale-up of ultrasonic microreactor systems and their applications in the preparation of nanomaterials[J]. CIESC Journal, 2024, 75(11): 4095-4119.

董正亚, 朱晓晶, 贾竞夫, 张杰, 郑卓韬, 刘晓霖, 武志林. 超声微反应器系统的放大及其在纳米材料制备中的应用[J]. 化工学报, 2024, 75(11): 4095-4119.

Figures/Tables 20

Fig.1 Composition of the ultrasonic microreactor system

Fig.2 (a) Schematic diagram of the structure of the sandwich piezoelectric ceramic ultrasonic transducer; (b) Physical diagram of the ultrasonic transducer of various structures[27]

Fig.3 Reported direct-contact ultrasonic microreactors[34-35]

Fig.4 (a) Schematic of the ultrasonic cavitation-based micromixer design; (b) Geometric information of the glass capillary-based microchannel; (c) Schematic of the ultrasonic setup using co-flow and impinge flow microchannel

Fig.5 Series tuning and parallel tuning[39]

Fig.6 (a) Vibration system consisting of a capillary microreactor; (b) Vibration system consisting of a cylindrical luffing rod and a sandwich transducer

Fig.7 (a) Acoustic cavitation under ultrasound[41]; Cavitation behavior of free bubbles at the microscale: (b) vibrational behavior,(c) confinement effect[38]; (d) Acoustic flow from vibration[42]; Two important cavitation bubble oscillation phenomena observed in ultrasonic microreactor: (e) bubble arrays (or bubble cluster arrays) in straight channels and (f) strongly oscillating bubble clouds in curved channels[43]

Fig.8 (a) The number of cavitation bubbles and mixing behavior under different solvent systems[22]; The effect of ultrasonic power on cavitation bubble formation rate (b) and mixing performance under different solvent systems (c); (d) Cavitation behavior and bubble distribution in the ultrasonic reactor with different channel sizes[57]; (e) Mixing time as a function of ultrasonic power for 0.5—2.0 mm channel sizes[22]

Fig.9 Typical cavitation modes: (a) cavitation modes at different channel sizes and frequencies: array mode, elastic cluster mode and cluster mode; (b) Under different ultrasonic powers and flows: cavitation modes and microscopic cavitation behaviors; (c) Cavitation modes under different relative positions of coaxial casings and channels: bubble tailing, satellite, surround and cluster; (d) Cavitation pattern diagram in the ultrasonic microreactor[57]

Fig.10 Schematic diagram of the scale-up strategy of the antisolvent precipitation process of the ultrasonic microreactor[57]

Fig.11 Schematic diagram of the reaction nucleation growth process in the microchannel: (a) Nucleation growth in diffusion mixed mode; (b) Nucleation growth in ultrasound-enhanced mass transfer mode

Fig.12 Scanning electron microscopy of silica microspheres: (a) An average particle size of 155 nm and a CV value of 6.77%; (b) An average particle size of 300 nm and a CV value of 4.33%; (c) An average particle size of 409 nm and a CV value of 6.90%; (d) An average particle size of 550 nm and a CV value of 5.87%; (e) An average particle size of 730 nm and a CV value of 4.17%; (f) An average particle size of 840 nm and a CV value of 4.05%

Fig.13 Suspension stability of silicon-based nanomagnetic microspheres

Fig.14 SEM images of scale-up preparation of nanomaterials by ultrasonic microreactor[57]

Fig.15 (a) Schematic illustration of USMR approach for synthesis biomedical organic NPs; (b) Size distribution and (c) mRNA encapsulation efficiency of mRNA-LNPs synthesized by different approaches; (d) Cryo-TEM micrographs of mRNA-LNP synthesized via this approach[22]

Fig.16 (a) Preparation of liposomes by USMR with different flow patterns; (b),(c) Effect of ultrasonic power on DS and PDI of liposomes prepared with USMR-IF; (d) Comparison of liposomes prepared by different methods； (e) Cryo-TEM image of liposomes prepared with USMR-IF under the optimal condition[25]

Fig.17 Emulsification observed in ultrasonic microreactor: (a) bubble shuttle emulsification[110], (b) two-phase emulsification[41],(c) bubble oscillation-induced interface deformation and emulsification, (d) shockwave-induced emulsification[112]; (e) Effect of different cavitation behaviors on emulsion size distribution[114]

Fig.18 The influence of the main factors on the particle size and PDI of the emulsions: (a) the ratio of aqueous phase to soybean oil, (b) the residence time of the feedstocks, (c) ultrasonic power; (d) Photographs of emulsion samples[26]

Table 1 DS and PDI of nanoemulsions prepared with different USMR（A∶O ratio：9∶1）［26］

USMR	Residence time/min	Ultrasonic power/W	Total flow rate/(ml/min)	DS/nm	PDI
umFlow-D×1	1	40	0.66	119.8	0.211
	1	40	1.32	121.3	0.239
	1	40	2.64	119.7	0.225
	0.7	160	20	120.5	0.219

Fig.19 Photographs of magnetic polymer nanosphere: (a) photographs of scanning electron microscope; (b) photographs of transmission electron microscope and EDS

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