5 Preparation of the Catalysts
205
5.5 Large-Scale Preparation of Catalysts: Examples
and Discussion
Over the past decades, with the continuous development of preparation technologies, many efficient catalysts have been successfully synthesized, including: Pt-based
bimetallic or multimetallic catalysts with tunable components (Pt–Ni, Pt–Co, Pt–
Fe, Pt–Pd, Pt–Fe–Ni, Pt–Co–Ni, etc.); catalysts with diverse shapes (sphere, rod,
wire, plate, cube, tetrahedron, octahedron, decahedron, icosahedron, etc.); catalysts
with unique structures (core–shell, hollow, framework, dendrite, branch, etc.); and
catalysts with high-index facets enclosed surface [39, 64, 102–109].
These catalysts with controllable composition, size, shape and surface enable
the study of catalytic mechanism and structure–function relationship, and provide
directions for improving the activity and stability of catalysts. Although these active
catalysts reported show great application prospects as promising candidates for the
next-generation catalysts, there is still a big gap between academic research and
industrial application of nanocatalysts, because the large-scale preparation of catalysts is challenge. In most literatures, the preparation of catalysts is carried out in
one batch, using flasks, vials and PTFE autoclave as reaction containers, and the
yield of catalysts is typically limited at milligram level. For example, in a 50-mL
flask, only 100 mg carbon-supported catalyst (metal load of 50%) can be synthesized
in the 25 mL reaction solution. Using 10 mL reaction solution in PTFE autoclave
with a volume of 25 mL, 20 mg carbon-supported catalyst (metal load of 50%)
are normally produced. As for the conventional electrochemical deposition, only
microgram catalysts could be produced in one batch. Therefore, the corresponding
large-scale preparation technologies should be seek to achieve the synthesis of efficient catalysts at gram scale by one batch or kilogram-scale daily, satisfying the great
needs of industry and market [6, 110].
At present, the main strategies for large-scale preparation are: (1) increasing the
volume of reaction, and appropriately adjusting the quantity and parameters in the
reaction system; (2) designing reactor for continuous synthesis; and (3) solid-phase
reduction. In addition, in the large-scale preparation of catalysts, green synthesis
technology should be preferred.
5.5.1 Increasing the Volume of Reaction
To realize large-scale preparation, increasing the volume of reaction is a common
strategy. For example, in the hydrothermal/solvothermal synthesis of catalysts, the
volume of reaction can be increased by more than 10 times (using a PTFE autoclave
with volume greater than 500 mL). Using a flask with volume larger than 250 mL,
the volume of reaction solution should be increased correspondingly, and a larger
magnetic stirrer should be used to stir the solution (Fig. 5.13). By increasing the
205
5.5 Large-Scale Preparation of Catalysts: Examples
and Discussion
Over the past decades, with the continuous development of preparation technologies, many efficient catalysts have been successfully synthesized, including: Pt-based
bimetallic or multimetallic catalysts with tunable components (Pt–Ni, Pt–Co, Pt–
Fe, Pt–Pd, Pt–Fe–Ni, Pt–Co–Ni, etc.); catalysts with diverse shapes (sphere, rod,
wire, plate, cube, tetrahedron, octahedron, decahedron, icosahedron, etc.); catalysts
with unique structures (core–shell, hollow, framework, dendrite, branch, etc.); and
catalysts with high-index facets enclosed surface [39, 64, 102–109].
These catalysts with controllable composition, size, shape and surface enable
the study of catalytic mechanism and structure–function relationship, and provide
directions for improving the activity and stability of catalysts. Although these active
catalysts reported show great application prospects as promising candidates for the
next-generation catalysts, there is still a big gap between academic research and
industrial application of nanocatalysts, because the large-scale preparation of catalysts is challenge. In most literatures, the preparation of catalysts is carried out in
one batch, using flasks, vials and PTFE autoclave as reaction containers, and the
yield of catalysts is typically limited at milligram level. For example, in a 50-mL
flask, only 100 mg carbon-supported catalyst (metal load of 50%) can be synthesized
in the 25 mL reaction solution. Using 10 mL reaction solution in PTFE autoclave
with a volume of 25 mL, 20 mg carbon-supported catalyst (metal load of 50%)
are normally produced. As for the conventional electrochemical deposition, only
microgram catalysts could be produced in one batch. Therefore, the corresponding
large-scale preparation technologies should be seek to achieve the synthesis of efficient catalysts at gram scale by one batch or kilogram-scale daily, satisfying the great
needs of industry and market [6, 110].
At present, the main strategies for large-scale preparation are: (1) increasing the
volume of reaction, and appropriately adjusting the quantity and parameters in the
reaction system; (2) designing reactor for continuous synthesis; and (3) solid-phase
reduction. In addition, in the large-scale preparation of catalysts, green synthesis
technology should be preferred.
5.5.1 Increasing the Volume of Reaction
To realize large-scale preparation, increasing the volume of reaction is a common
strategy. For example, in the hydrothermal/solvothermal synthesis of catalysts, the
volume of reaction can be increased by more than 10 times (using a PTFE autoclave
with volume greater than 500 mL). Using a flask with volume larger than 250 mL,
the volume of reaction solution should be increased correspondingly, and a larger
magnetic stirrer should be used to stir the solution (Fig. 5.13). By increasing the