Continuous Production Of Carbon Nanotubes Over Easily-Washable Co-Mo/Mgo Catalyst Using Rotary Reactor
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Date
2014-08
Authors
Yeoh, Wei Ming
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Since the groundbreaking report of carbon nanotubes (CNTs) by Iijima in
year 1991, extensive research activities were conducted in their synthesis and
applications credited to their superior physical and chemical properties. In order to
realize the potential applications, CNTs need to be available in large quantity and
with much greater control over the key characteristics. Mass synthesis of high
quality, high purity and uniform properties CNTs can be realized via the
development of a rotary reactor for continuous production of CNTs, and optimization
of both the easily-washable catalyst system and process conditions of catalytic
decomposition of methane (CDM). Bimetallic Co-Mo was supported on MgO for the
development of an easily-washable catalyst. Catalyst 10Co-20Mo/70MgO prepared
using citric acid and calcined at 700oC was found to be the best catalyst for growing
CNTs. Single-step purification by mild nitric acid treatment was effective in
removing most of the catalyst particles giving high purity CNTs (99.28wt%). In
CDM process, another aspect affecting the performance of catalyst, in view of
carbon yield and the morphology of CNTs, is the process condition. Among the
numerous process parameters, reaction temperature, reaction time, methane partial
pressure and catalyst amount were the four CDM process parameters chosen for
catalytic performance study of the developed easily-washable catalyst in fixed-bed
reactor. The study was done by using central composite design (CCD) of response
surface methodology (RSM) approach. The main effect of each process parameter
emerged as the major effects over the carbon content and there was no interaction
exists between process parameters. Meanwhile, it was found that only reaction
temperature had significant effect on morphology and structural properties of
reaction product over the range of process parameters selected in the present
experimental study. A horizontal rotary reactor system was assembled for continuous
synthesis of CNTs. The optimum CDM process condition for continuous rotary
reactor obtained was a reaction temperature of 833oC, catalyst residence time of
165minutes, methane partial pressure of 0.54atm and catalyst feed rate of
260mg/min. The carbon deposits synthesized under suggested optimum process
condition for continuous rotary reactor had high carbon content of 95.21wt%,
equivalent to carbon yield of 1987.7%, and high selectivity toward the synthesis of
solely multi-walled CNTs (MWCNTs) with diameter distribution of 10.18±1.02nm
and ID/IG ratio of 1.262. The carbon deposition rate of approximately 310gCNTs/hr
based on the catalyst feeding rate of 260mg/min was achieved. These results
demonstrated that coupling the optimized easily-washable catalyst, the optimized
process condition of continuous rotary reactor and simple purification process
provides the way of mass synthesis of CNTs with high purity and high quality.
Description
Keywords
Production of carbon nanotubes , catalyst using rotary reactor