Hydrocarbons for Hydrogen Generation - Hydrogen Generation, Storage, and Utilization - page 24

FIGURE 2.10 Proposed mechanism of reaction. Source : Reproduced from Wang et al. [21].
Compared with the reforming process, the hydrocarbon direct decomposi-
tion process produces CO-free hydrogen, does not emit CO 2 to environment,
generates useful carbon powder, and is also an energy-saving approach for
hydrogen preparation. To form each mole of hydrogen by methane, direct
decomposition only consumes about 65.1% of the energy as that needed in
the steam reforming of methane. The reaction is also proved to be useful in
the decomposition of waste polyolefins, such as poly olefin plastic and
rubber.
2.7 SUMMARY
Hydrocarbons are important carriers and sources of hydrogen. Due to their
high chemical stability, generation of hydrogen from hydrocarbons is gener-
ally an energy-consuming process, and usually requires heating and catalysis
for high efficiency. Compared with other methods of hydrogen generation,
using hydrocarbons has some pros and cons. The main limitation is that it
uses fossil-based chemicals. One major advantage is that the major infra-
structure is already in existence for handling and delivering hydrocarbons.
At least for the foreseeable future, hydrocarbons will still be expected to be
the major source for hydrogen. The need for small-scale reformers for por-
table or mobile applications is expected to grow, and further research and
development are needed in these areas.