Over 99.6 wt%-pure, sub-millimeter-long carbon nanotubes realized by fluidized-bed with careful control of the catalyst and carbon feeds

• Published in: Carbon (New York) Vol. 80; pp. 339 - 350
• Main Authors: ZHONGMING CHEN, DONG YOUNG KIM, HASEGAWA, Kei, OSAWA, Toshio, NODA, Suguru
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier 2014
• Subjects: Beads; Carbon; Carbon nanotubes; Catalysis; Catalysts; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Chemistry; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; General and physical chemistry; Heat exchangers; Heating; Iron; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Nanoscale materials and structures: fabrication and characterization; Nanotubes; Physics; Reactors; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; CVD; Aluminium oxide; Catalysts; Reactors; Carbon nanotubes; Alumina; Carbon; Conversion; Fluidized beds; Space heating; Acetylene
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2014.08.072

To establish a method for sub-second conversion of acetylene to sub-millimeter-long carbon nanotubes (CNTs), we have proposed and developed an internal heat-exchange reactor for fluidized-bed chemical vapor deposition (FBCVD). This reactor enabled sufficient heating of the reaction gas and uniform heating of the bed of alumina beads at a space velocity as high as 3600 h super(-1). The direct feeding of the catalyst vapors (aluminum isopropoxide for the alumina support layer and ferrocene for the iron particles) to the bed separately from the other gases, which were fed through the heat-exchange and preheating zone and the distributer, enabled the careful control of the catalyst particles deposited on the beads. By decreasing the acetylene feed concentration and preventing the deactivation of small Fe particles, we realized semi-continuous production of 99.6-99.8 wt%-pure, sub-millimeter-long, few-wall CNTs with an average diameter of 6.5 nm at a carbon yield of 42%. The FBCVD reactor with an internal heat-exchanger can be scaled-up for practical mass production with uniform and energy-saving heating.