Research And Application Of Synthesis Of Supported Nanomaterials In Microchannel Reactors

Supported nanomaterials are widely used in catalysis,medicine and other fields due to their high dispersion,stable structure and easy recovery.The performance of nanomaterials is closely related to the morphology,In the batch reactor,the mixing of materials is not sufficient,the morphology of the prepared materials is poor,and the repeatability of the reaction process is poor.The industrial production is unstable.Microchannel reactor has large specific surface area,fast mass transfer and good controllability of the synthesis process.It can be easily applied into industrial scale and controllable synthesis of nanoparticles with uniform size distribution.In this paper,3D printing technology is combined with the microchannel reactor to study the synthesis of supported nanomaterials in the microchannel reactor.The main contents are as follows:1.A coiled flow inverter（CFI）microfluidic reactor was constructed by combining 3D printing technology with microchannel reactor technology.The traditional mesoporous material of SBA-15 was used as the support to continuously synthesize Ag/SBA-15 supported nanomaterials with a particle size of 7-11 nm.Compared with conventional batch reactor,the nanomaterials obtained by microfluidic technology have smaller particle size and better distribution.The factors such as the addition of support,flow rate,concentration of silver reagents,concentration of capping agent and structure of support were further explored and analyzed,and the effects of these factors on the size,loading contents and catalytic performance of the synthesized nanomaterials were studied.It was found that the catalytic performance of the nanoparticles was the best when the residence time was 35 s and the concentration of reactant was 0.2 mM.At this time,the particle size of supported silver nanoparticles was 9.35±2.06 nm,and the actual load content was 2.91 wt%.2.An ultrasonic field was introduced into the CFI microchannel reactor to synthesize novel Ag/g-C₃N₄ nanomaterials.Combined with fluid dynamics simulation,the influence of ultrasonic field on the morphology of the synthesized materials was further explored through the change of fluid flow field.During the experiment,the ultrasonic power,flow rate and initial concentration were analyzed and it was found that Ag/g-C₃N₄ with a theoretical loading of 7 wt%had the highest photocatalytic activity when the ultrasonic power was 60 W and the residence time was 35 s.At this time,the Ag particle size dispersed on g-C₃N₄ was 5.62± 2.25 nm,and the actual loading content was 5.83%.In addition,COMSOL Multiphysics was used to simulate the process,and the flow field and sound pressure distribution in the microchannel reactor were studied under different flow rates,ultrasonic power and ultrasonic frequencies.The influence of ultrasonic on the particle size of the synthesized nanomaterials was analyzed through the change of flow field.3.The ultrasound-assisted CFI microchannel reactor was used to synthesize supported nanomaterials with different metal components of Ag,Pt and Au.The morphology,structure,composition and photoelectron transfer performance of the catalysts were characterized.The morphology and catalytic performance of supported nanomaterials with different metal components were studied.The synthesis of g-C₃N₄ supported by Ag,Pt and Au showed that Pt had stronger hydrogen evolution ability and could effectively promote the catalytic hydrogen evolution rate.At the same time,the addition of Pt could effectively improve the catalytic performance of the bimetallic catalyst.The photocatalytic performance of Pt/g-C₃N₄ was best,and the hydrogen evolution rate of Pt/g-C₃N₄ was 2019.2 μmol/（g·h）,about 13 times that of pure g-C₃N₄.Moreover,the Ag-Pt/g-C₃N₄ supported nanomaterials with different proportions were synthesized.With the decrease of Ag:Pt ratio,the size of nanoparticles formed gradually became smaller,the distribution was more uniform,and the catalytic activity of the catalyst also gradually increased.4.3D printing technology was used to construct a multi-start spiral tube reactor,and the reactor was coupled with ultrasonic field to synthesize Ag/g-C₃N₄ supported nanomaterials.Combined with fluid dynamics simulation,the enhancement mechanism of the tube structure on the internal flow field and mixing was analyzed.The effects of flow rate,pitch,corrugation depth on the size and loading content of the synthesized nanomaterials were studied.When the flow rate was 4 mL/min,the pitch was 6 mm,and the thread depth was 0.375 mm,the particle size of Ag/g-C₃N₄ was the smallest and the distribution was the best.The particle size was 3.30±1.02 nm,and the loading content was 2.46 wt%.Furthermore,COMSOL Multiphysics was used to simulate the flow field in the multi-start spiral tube.The effect of microchannel reactors’ structure on the velocity distribution and residence time distribution was studied,so as to assist the analysis of its influence on the particle nucleation and growth rate in the synthesis process of nanoparticles.