comments on energy use in manufacturing and the recycling potential of carbon nanotubes timothy g....
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Comments on Energy Use in Manufacturing and the Recycling Potential of Carbon Nanotubes
Timothy G. GutowskiMassachusetts Institute of Technology
Chicago, IL Nov 5, 2009
Outline
• Toxicity
• Energy
• Recycling
Brian Wardle, MIT
Kripa Varanasi MIT
Energy to make SWNT
“HiPco” Process
2CO CO2 + C
Nikolaev et al 1999
HiPco Process Estimates
Gutowski & Liow 2010 IEEE
Ref: Gutowski & Liow 2010 IEEE
Theoretical minimum Electricity (Exergy) Estimates for Synthesis only.Does not include losses at process, nor other steps in the process, norinfrastructure requirements, nor losses at the utilities. Does not includeenergy cost of raw materials.
Healy et al
Estimates of actual
Th
eore
tica
l M
inim
um
Ele
ctri
city
Req
uir
em
en
ts
Ashby 2009
Estimate of embodied energy for SWNT =Synthesis + purification + infrastructure + utilities + input materials ≈ 1.0 - 0.1 TJ/kg
0
1
2
3
4
5
6
7
EAF Steel Aluminum Poly Si Wafer Si Nanotube
Material
log
10
(MJ/
kg)
Electrical energy requirements for five materials in MJ/kg.
The Energy Paradox
• One of the most energy intensive materials known to humankind
• Less than 1% of the mfg cost
(Healy, Isaacs, 2008)
Gutowski 2009
Compared to other processes
5 kW
50 kW
Gutowski & Liow 2010 IEEE
CNF energy estimates
Why so much variation?
•Many products
•Many processes
•All changing
Gutowski & Liow 2010 IEEE
1 kW
5 kW, 50 kW
QuickTime™ and a decompressor
are needed to see this picture.
Carbon source:CH4,C2H4,
CO
Metal catalyst:Ni
Mo/CoFe
Growth substrate
AJHart
T= 500-1200oC
Synthesizing CNTs: Catalytic chemical vapor deposition (CVD)
Work by Desiree PlataMt Holyoke College and MIT
Resistively heated platform for VA-MWCNT growth
Cold-wall reactor tube
Pre-heater: TURNED OFF
Tgas
Direct delivery of potential precursors
vinylacetylene
Desiree Plata 09
Deliver at equal partial pressures: 0.01 atm (1% v/v)
Desiree Plata 09
Deliver at equal partial pressures: 0.01 atm (1% v/v)
*vinyl acetylene at 0.003 atm (0.3% v/v)
*
Rapid CNT formation without thermal pre-treatment of feedstock gases:Potential 55% energetic savings
Desiree Plata 09
Recycling and Separation
• The Science of Separation
Phase separation boundary
Nanotubes in solvents, Plata 2009
Separationof Hexane fromPolybutadieneGutowski 1981
Flory 1953
Practical Recycling Issues
• Value
• Quantity
• Toxicity
• Easy of isolation
• Quality after isolation
• Down cycle
Dahmus & Gutowski 2007
Potential for Recycling
Dahmus PhD ‘07
Trends in Product Design
Dahmus & Gutowski 07
Composite materials are not recycled
Ashby 2009
End of Life for CNTs?
From an environmental protection point of view…
• Toxicity - Is what we are interested in
• Energy - Is very large and incomplete
• Recycling - Lots of Science, but…