Carbon nanotube production from greenhouse gases during syngas synthesis
Date
2010-06-08T10:05:58Z
Authors
Moothi, Kapil
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Abstract
The impact of climate change around the world has led governments, institutions and
industries to increase their efforts to combat it by seeking new and innovative
technologies. Carbon dioxide (CO2) is believed to be the primary reason for global
warming. Therefore, the capture and transformation of some of the billions of tons of
CO2 produced annually by burning fossil fuels into useful products such as carbon
nanotubes (CNTs) and carbon nanofibers (CNFs) is one of the methods being pursed in
current research activities. The conversion of two major greenhouse gases, CO2 and
methane (CH4), into CNTs and synthesis gas, which is a mixture of carbon monoxide
(CO) and hydrogen (H2) has been studied experimentally by passing a CO2/CH4 mixture
through a vertically orientated Chemical Vapour Deposition (CVD) reactor at
temperatures ranging from 650°C to 950°C . Two different catalysts were used, a
lanthanum nickel alloy (LaNi5) and a mischmetal nickel alloy. Transmission electron
microscopy (low and high magnification), Raman spectroscopy and gas chromatography
were used to analyze the products from the experiment. The apparent activation energy
for CH4 and CO2 consumption, and H2 and CO production were estimated to be 41.7,
47.5, 54.5 and 47.5 kJ/ mol, respectively in the temperature range 1023 – 1123K. The
CO2 and CH4 were decomposed, forming CNFs and CNTs as shown by the transmission
electron microscope images. The findings showed that as the temperature increased the
CNFs and CNTs became, less defined and fewer in number. The mischmetal nickel alloy
had a smaller amount of amorphous carbon deposit compared to the lanthanum nickel
alloy.