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1 Introduction
Due to limited fossil fuel sources, climate change and environmental concerns,
researchers are motivated to develop renewable energy sources for the full replacement of fossil fuel. Among all energy sources, hydrogen is now gaining attention
because it can be used in fuel cell applications to generate electricity [1, 2]. Hydrogen
is considered a clean source of energy that can be consumed without emitting
carbon- based environmental pollutants [3, 4]. Also, hydrogen has an energy density
of 143 MJ/kg, which is more than any known hydrocarbon-based fuels [5, 6].
Currently, 90% of hydrogen is obtained from reforming of nonrenewable sources—
natural gas and other fossil fuels—which are not sustainable [3, 7].
Storage and transportation of hydrogen, which is flammable, are the major challenges to commercialize hydrogen as a standard fuel for vehicles. One of the convenient ways to overcome this issue is the use of metal hydrides like MgH 2 , NaAlH 4 ,
LiH and hydrides of some transition metals to capture hydrogen. The main problems of the metal hydrides are their regeneration after the hydrogen is released,
diffusion and leakage of H 2 during storage and transportation [8]. On-site production and use of H 2 are possible solutions to mitigate the storage problem [6].
Utilization of hydrogen in different sectors such as rocket engines [9], petrochemical industry [10], ammonia production [11], fertilizer [10], and Fischer-Tropsch
synthesis [12–14] has globally bolstered future demands of hydrogen. Other popular industrial applications of hydrogen include metal production and fabrication,
methanol synthesis, food processing and electronic applications [6].
Water electrolysis, hydrocarbon reforming, photocatalysis and biocatalysis are
different routes to produce H 2 [15–17]. Steam reforming of hydrocarbons is currently used to produce highly purified H 2 [18–21]. Worldwide H 2 production mainly
comprises 48% from steam reforming of methane, 30% from reforming of naphtha/
oil, 18% from coal gasification and 3.9% from electrolysis of water [22]. The major
drawback of methane steam reforming is the high temperature required for reforming effective in the range of 800–1000 °C [23]. The steam reforming of alcohols
such as ethanol, methanol and glycerol is favoured commercially because it provides a much less endothermic (200–700 °C), less energy-intensive, hence lower
capital cost route to produce hydrogen compared to fossil fuels [4, 24]. Steam
reforming of alcohols also generates less greenhouse gases relative to fossil fuels.
This ensures that the amount of CO 2 released into the atmosphere is low enough to
be consumed by green plants via photosynthesis [25].
For steam reforming of methanol, ethanol and glycerol, researchers aim to control the effective way to cleave C–H, C–C and C–O bonds [25] in order to free the
hydrogen atoms. While the C–H and C–O bonds are broken in steam reforming of
methanol, the C–C bond is broken for higher alcohols—ethanol and glycerol, and
the process is more complex. Several catalysts with different supports have been
used for steam reforming of these three alcohols. Metals such as Cu, Ni, Co and Fe
have been used extensively for methanol steam reforming [26–28]. Among these
catalysts, Cu-based catalysts are more effective in methanol steam reforming (SRM)
due to its higher activity and selectivity [29–34]. However, these catalysts suffer
S. Bepari et al.
1 Introduction
Due to limited fossil fuel sources, climate change and environmental concerns,
researchers are motivated to develop renewable energy sources for the full replacement of fossil fuel. Among all energy sources, hydrogen is now gaining attention
because it can be used in fuel cell applications to generate electricity [1, 2]. Hydrogen
is considered a clean source of energy that can be consumed without emitting
carbon- based environmental pollutants [3, 4]. Also, hydrogen has an energy density
of 143 MJ/kg, which is more than any known hydrocarbon-based fuels [5, 6].
Currently, 90% of hydrogen is obtained from reforming of nonrenewable sources—
natural gas and other fossil fuels—which are not sustainable [3, 7].
Storage and transportation of hydrogen, which is flammable, are the major challenges to commercialize hydrogen as a standard fuel for vehicles. One of the convenient ways to overcome this issue is the use of metal hydrides like MgH 2 , NaAlH 4 ,
LiH and hydrides of some transition metals to capture hydrogen. The main problems of the metal hydrides are their regeneration after the hydrogen is released,
diffusion and leakage of H 2 during storage and transportation [8]. On-site production and use of H 2 are possible solutions to mitigate the storage problem [6].
Utilization of hydrogen in different sectors such as rocket engines [9], petrochemical industry [10], ammonia production [11], fertilizer [10], and Fischer-Tropsch
synthesis [12–14] has globally bolstered future demands of hydrogen. Other popular industrial applications of hydrogen include metal production and fabrication,
methanol synthesis, food processing and electronic applications [6].
Water electrolysis, hydrocarbon reforming, photocatalysis and biocatalysis are
different routes to produce H 2 [15–17]. Steam reforming of hydrocarbons is currently used to produce highly purified H 2 [18–21]. Worldwide H 2 production mainly
comprises 48% from steam reforming of methane, 30% from reforming of naphtha/
oil, 18% from coal gasification and 3.9% from electrolysis of water [22]. The major
drawback of methane steam reforming is the high temperature required for reforming effective in the range of 800–1000 °C [23]. The steam reforming of alcohols
such as ethanol, methanol and glycerol is favoured commercially because it provides a much less endothermic (200–700 °C), less energy-intensive, hence lower
capital cost route to produce hydrogen compared to fossil fuels [4, 24]. Steam
reforming of alcohols also generates less greenhouse gases relative to fossil fuels.
This ensures that the amount of CO 2 released into the atmosphere is low enough to
be consumed by green plants via photosynthesis [25].
For steam reforming of methanol, ethanol and glycerol, researchers aim to control the effective way to cleave C–H, C–C and C–O bonds [25] in order to free the
hydrogen atoms. While the C–H and C–O bonds are broken in steam reforming of
methanol, the C–C bond is broken for higher alcohols—ethanol and glycerol, and
the process is more complex. Several catalysts with different supports have been
used for steam reforming of these three alcohols. Metals such as Cu, Ni, Co and Fe
have been used extensively for methanol steam reforming [26–28]. Among these
catalysts, Cu-based catalysts are more effective in methanol steam reforming (SRM)
due to its higher activity and selectivity [29–34]. However, these catalysts suffer
S. Bepari et al.