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Controllable preparation of highly uniform γ-alumina microspheres via the sol–gel route for alkoxide in a coaxial microchannel

  • Huilin Yi
  • Yanchun Wan
  • Yang Zhang
  • Yujun WangEmail author
  • Weiyang FeiEmail author
  • Guangsheng Luo
Original Paper: Sol-gel and hybrid materials for catalytic, photoelectrochemical and sensor applications
  • 24 Downloads

Abstract

This study describes a novel and facile route for fabricating highly uniform γ-alumina microspheres with controllable size, morphology, and pore structure by integrating the sol–gel route for alkoxide with “temperature/pH-induced gelation” in a coaxial microchannel. Taking advantage of the controllability of the microfluidic devices and Al–O–Al chains formed by the sol–gel route of aluminum alkoxide, the uniformity of the microspheres was assured, and the mechanical strength of the microspheres was greatly improved to 18–27 N/mm2. The effects of the continuous phase composition and two-phase flow rate on the size, morphology, and pore structure of the obtained microspheres were investigated. When triocylamine (TOA) was added to the continuous phase and the two-phase flow rate ratio was larger than 188, the as-prepared microspheres had a smooth surface and good sphericity; otherwise, the microspheres had poor spheriticy and included many ravines on the surface, which can be explained by the mutual influence of long-lasting movements of molecular chains resulted from low gelation speed and inner circulation of the droplets. Under different continuous phase compositions, the average pore diameter, pore volume, and specific surface area ranged from 7 to 12 nm, 0.89 to 1.58 mL/g, and 293.7 to 387.7 m2/g, respectively.

Highlights

  • Sol–gel route was combined with temperature/pH-induced gelation in a microchannel.

  • The size, morphology, and pore structure were strictly controlled by preparation conditions.

  • The cause of ravines was explained by different gelation speed and inner circulation.

  • The crushing strength of the microspheres was greatly improved to 18–27 N/mm2.

Keywords

Sol–gel route Temperature/pH-induced gelation Coaxial microchannel γ-Al2O3 microspheres 

Notes

Acknowledgements

This work was financially supported by the National Basic Research Program of China (Grant No. 2013CB733600), the National Natural Science Foundation of China (Grant Nos. 21276140 and 21036002), and the PetroChina Co., Ltd. (Grant No. 2016A-1803).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.State Key Laboratory of Chemical Engineering, Department of Chemical EngineeringTsinghua UniversityBeijingPR China

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