Fe-Mo Catalyst for High-Yield Carbon Nanotube Synthesis
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Solution Overview
Problem
Existing catalyst compositions for synthesizing multi-walled carbon nanotubes face challenges in achieving high yield due to non-uniform dispersion of metal catalysts and support materials, leading to low catalytic efficiency and high costs in commercially available scales.
Innovation Solution
A catalyst composition comprising Fe and Mo as main catalysts, Al as an inactive support, and co-catalysts like Co, Ni, Ti, Mn, W, or Cu, prepared through co-precipitation and spray-drying processes, which results in a uniformly dispersed fine powder form, enhancing the synthesis of multi-walled carbon nanotubes with high apparent density and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional metal catalyst compositions are used for synthesizing multi-walled carbon nanotubes, then the synthesis process can be carried out, but the catalytic yield is low and production costs are high
Solution Approach 1:
The patent employs a composite catalyst system comprising Fe and Mo as main catalysts, Al as support, and co-catalysts from groups 8-11 transition metals. This composite structure enhances catalytic activity and yield while reducing the quantity of expensive catalyst materials needed, directly addressing the contradiction between productivity and production cost.
Solution Approach 2:
The patent optimizes the molar ratios of catalyst components (Fe:Mo ratio between 7.9:2.1 to 9.9:0.1, co-catalyst content between 0.1-3.0 mol%) and preparation parameters (calcination temperature 400-1200°C, spray-drying conditions) to achieve maximum catalytic yield. These parameter optimizations enable high productivity with reduced material costs.
2Productivity
If metal catalysts are used in thermal chemical vapor deposition, then carbon nanotube synthesis can proceed, but the metal catalyst components are slowly consumed due to encapsulation by carbon atoms
Solution Approach 1:
The Al support acts as an intermediary that disperses and stabilizes the Fe-Mo catalyst particles, preventing direct contact and encapsulation by carbon atoms. The co-catalysts from groups 8-11 metals serve as mediators that enhance catalytic activity while resisting carbon encapsulation, thereby reducing catalyst consumption and maintaining productivity.
Solution Approach 2:
The catalyst system creates local quality differences through the Fe-Mo binary catalyst system with specific molar ratios (7.9:2.1 to 9.9:0.1), where Fe provides catalytic activity and Mo provides structural stability and resistance to encapsulation. This local optimization at the catalyst particle level reduces overall catalyst consumption.
3Ease of manufacture
If existing catalyst preparation methods are used, then catalyst composition can be obtained, but uniform dispersion of metal catalysts and support materials cannot be achieved
Solution Approach 1:
The patent employs preliminary action through co-precipitation of Fe and Mo salts before spray-drying, ensuring uniform distribution of metal species throughout the support matrix. This preliminary mixing at the molecular level ensures uniform dispersion after calcination, achieving high manufacturing precision while maintaining ease of manufacture through a straightforward two-step process.
Solution Approach 2:
The patent replaces conventional mechanical mixing methods with a chemical co-precipitation approach followed by spray-drying. This substitution of mechanical processes with chemical and aerosol-based methods achieves superior uniformity in catalyst dispersion while simplifying the manufacturing process and improving scalability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The catalyst composition achieves a 3 to 5 times higher yield of multi-walled carbon nanotubes with 5-15 nm diameter and 0.5-4 µm bundle diameter, reducing production costs and eliminating the need for additional catalyst removal steps, while maintaining high purity and efficiency.
Implementation Method 1
the growth of carbon nanotube can be made by the direct reaction between carbon source gas and metal catalyst
Implementation Method 2
synthesizing carbon nanotube by thermal decomposition of supplied carbon source on the surface of a catalyst composition
Implementation Method 3
co-precipitating the catalyst composition by adjusting pH, temperature, and/or amount of ingredients
Implementation Method 4
spray-drying the solution containing the multi component metal salt
Implementation Method 5
spray pyrolysis of the solution containing the multi component metal salt
Implementation Method 6
calcinating the milled catalyst composition by thermal oxidation at 400∼1,200
Data Source
Figure 1~3
AI summary
The present invention relates to a catalyst composition for the synthesis of multi-walled carbon nanotube having high apparent density in a manner of high yield. More particularly, this invention relates to a multi-component metal catalyst composition comprising i) main catalyst of Fe and Mo, ii) inactive support of Al and iii) optional co-catalyst at least one selected from Co, Ni, Ti, Mn, W, Sn or Cu. Further, the present invention affords multi-walled carbon nanotube having 5~15 nm of fibrous diameter and 0.5~4 ㎛ bundle diameter.