(630b) The Production of CO2-Free Hydrogen and Carbon Materials By Methane Decomposition: Self-Sustained Production without Using Externally Added Catalyst

The
Production of CO₂-Free Hydrogen and Carbon Materials by Methane
Decomposition: Self-Sustained Production without using Externally Added Catalyst

I-Wen Wang, and Jianli
Hu*

Department of Chemical and Biomedical Engineering,
West Virginia University, Morgantown, WV 26506

Abstract

The
long-term legislative trends, both nationally and globally, show a preference
for non-fossil fuel based sources of energy. Indeed,
hydrogen appears to be one of the most promising and environmentally benign
energy sources, since it can be converted into transportation fuel, electricity
and other energy forms with less pollution and high efficiency. In the U.S. and the rest of the
world, there are many stranded gas resources that are not utilized because it
is too expensive to build pipelines. Most commercially viable method for
hydrogen production is from natural gas via steam methane reforming (SMR), producing
large amounts of carbon dioxide through the following reaction: CH₄ +
2H₂O ¡÷ 4H₂ + CO₂. Our CO₂-free
hydrogen production by catalytic methane decomposition leads to advanced forms
of carbon as a by-product, which could benefit a number of industrial sectors
including carbon nanofiber based composites. However, the recycle of commonly used Al₂O₃
or SiO₂ oxide supported metal catalysts is a challenge due to the
difficulty of separation and purification process which requires multiple process
steps and complex unit operation. In this study, carbon materials (carbon
nanotubes (CNTs) and carbon nanofibers (CNFs)) produced from methane
decomposition were used as supports. Ni and Pd were introduced onto CNTs/CNFs
by facile solvothermal synthesis method. The catalytic performance was
evaluated for five consecutive reaction-regeneration cycles.

In each
cycle, methane decomposition reaction was performed for 6 hours followed by acid
treatment to recover pure carbon materials. A portion of the harvested CNTs/CNFs
were used as the catalyst supports. Using the carbon materials made from the
first cycle, Ni and Pd were introduced to synthesize Ni-Pd/CNTs and CNFs
catalyst for the next cycle. After 5 cycles of operation, the Ni-Pd/CNTs and
CNFs catalyst maintained the same level of activity and selectivity to CNTs/CNFs
and H₂. Characterization by instruments including TEM, XRD, Raman,
and TGA was carried out to elucidate the CNTs and CNFs¡¦ growth mechanism. This
study demonstrates the economic and environmental advantages of sustained
production of carbon materials and H₂ from natural gas.