(38h) Mass Production of Nanoscale Materials with Uniform Ultralarge Mesopores Via Colloidal Solution Combustion Synthesis

Mass Production of
Nanoscale Materials with Uniform Ultralarge Mesopores via Colloidal Solution
Combustion Synthesis

Mesoporous metal oxides
are commonly synthesized via soft or hard templates. However, these multistep
laborious methods normally result in low product yield. Furthermore, mesoporous
hard templates (e.g., SBA-15, KIT-6, and CMK-3) are very expensive, and high
capital costs are needed for the production. Facile and economical synthesis of
mesoporous oxides with tailored porosity on a large scale still remains a
challenging task for commercialization.

     Here we demonstrate
a scalable, economic, energy and time efficient colloidal solution combustion
synthesis (CSCS) method to produce crystalline mesoporous materials with
tailored porosity using inexpensive colloidal silica [1,2]. CSCS utilizes the
internal chemical energy of reactants which is released in the form of the
heat, converting precursors into the products. For the proof of concept 0.5 kg
of crystalline CeO₂ with uniform 22 nm ultralarge mesopores, 130 m²/g
surface area, 0.6 ml/g pore volume and high yield has been synthesized at low
cost. Importantly, by eliminating the use of an organic solvent or surfactant,
CSCS provides relatively green chemistry route to a scalable synthesis of
nanomaterials. In addition to large-scale synthesis capability, CSCS method provides
exceptional advantages compared to other well-established template-assisted
methods. Specifically, the large surface area, uniform ultralarge mesoporosity,
high crystallinity, and small crystal size of the oxide can be achieved at the
same time, whereas prolonged high-temperature post-synthesis calcination for
crystallization usually leads to the collapse of the mesoporous structure in
other template-assisted methods. These can be achieved because the formation
and crystallization of nuclei occur almost simultaneously through the heat
generated from the exothermic reaction between the reactants in the CSCS.

[1]
A. A. Voskanyan, K.-Y. Chan, C.-Y. V. Li, Colloidal Solution Combustion
Synthesis: Toward mass production of a crystalline uniform mesoporous CeO₂
catalyst with tunable porosity. Chem. Mater. 2016, 28,
2768-2775.

[2]
A. A. Voskanyan, K.-Y. Chan, Scalable Synthesis of Three-Dimensional
Meso-Macroporous NiO with Uniform Ultralarge Randomly Packed Mesopores and High
Catalytic Activity for Soot Oxidation, ACS Appl. Nano Materials, 2018,
1, 556-563.