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recognition. “Hydrogen” yet leads to be a driving force toward a potential replacement to fossil fuels, complemented with high energy content and also as a clean-efficient energy carrier [1]. It can be utilized as a power source (feed) to proton exchange
membrane fuel cells (PEMFC), to meet most of the necessary energy needs for the
stationary power, automobiles, industrial, and residential sectors. Compared to the
conventional internal combustion engine, other benefits of hydrogen utilization in
PEMFCs are low noise, no formation of particulate matter, and no NO x and SO x emission. Hence, the use of hydrogen as an energy career helps in providing a clean environment that greatly impacts human life and health. However, the “holy grail” of
hydrogen usage as an energy carrier lies in its storage and transportation. Traditionally
stored in compressed cylinders or as a liquid in cryogenic containers, hydrogen poses
a safety threat due to its low volumetric density. Besides, it is highly challenging to
compress hydrogen gas from 5000 to 10,000 psi which is required for liquefying it
[2]. Hydrogen combustion though does not release any carbon dioxide; but it brings
high capital costs, low energy content per unit volume, elevated storage vessel weights,
and high storage pressures. To abate these, on- board/on-site generation of hydrogen
using lightweight, high energy density alcohols seems to provide a feasible solution to
storage problems as well as effective utilization of these alcohols. Negligible dependence on any fossil fuel, these alcohols can be easily produced using any biological
matter usually known as fermented wastes “molasses” from sugarcane, corn, wheat
straw, etc. The problem with these biofuels is its heavy content of sulfur and other
impurities that need to be processed before being used for hydrogen generation. It
should be noted that along with increasing hydrogen generation with higher hydrocarbons, the amount of carbon formation also increases in the same proportion. It can
also be pointed out that amongst the processes used for hydrogen generation, steam
reforming is affected by its strong endothermic nature and its by-product formation
[3], while cracking, on the other hand, is highly expensive with the standard by-product distribution as in the case of steam reforming. Coking also forms the bases of
unalterable damage to the process and system, thereby causing difficulty to sustain the
system as well as auxiliaries such as fuel cells it is connected with. But with all its pros
and cons, steam reforming yet remains the only process that can provide high hydrogen yield [3–5]. However, as PEMFC required ultra-pure hydrogen (purity greater
than 99.999%) and CO content less than 1 ppm, separation of hydrogen from reformate gases is inevitable.
Separation of hydrogen from the reformate mixture underlines the root of any process in terms of efficiency, yield, and thereby applicability. Talking of higher yield,
adsorption-based techniques such as pressure swing adsorption and temperature swing
adsorption are widely applied on an industrial scale but show a varying selectivity chart.
Besides, it is a highly expensive and bulky process to be handled for on-board applications. Membrane separation nonetheless shows higher selectivity corresponding to the
membrane and operating conditions applied. To be precise, dense (non-porous) membranes are the ones with enhanced selectivity to hydrogen over increasing pressure gradients [4–8]. Therefore, balanced synchrony of operating conditions with the catalyst
for reforming and membranes for separation purposes is of utmost importance.
R. K. Upadhyay
recognition. “Hydrogen” yet leads to be a driving force toward a potential replacement to fossil fuels, complemented with high energy content and also as a clean-efficient energy carrier [1]. It can be utilized as a power source (feed) to proton exchange
membrane fuel cells (PEMFC), to meet most of the necessary energy needs for the
stationary power, automobiles, industrial, and residential sectors. Compared to the
conventional internal combustion engine, other benefits of hydrogen utilization in
PEMFCs are low noise, no formation of particulate matter, and no NO x and SO x emission. Hence, the use of hydrogen as an energy career helps in providing a clean environment that greatly impacts human life and health. However, the “holy grail” of
hydrogen usage as an energy carrier lies in its storage and transportation. Traditionally
stored in compressed cylinders or as a liquid in cryogenic containers, hydrogen poses
a safety threat due to its low volumetric density. Besides, it is highly challenging to
compress hydrogen gas from 5000 to 10,000 psi which is required for liquefying it
[2]. Hydrogen combustion though does not release any carbon dioxide; but it brings
high capital costs, low energy content per unit volume, elevated storage vessel weights,
and high storage pressures. To abate these, on- board/on-site generation of hydrogen
using lightweight, high energy density alcohols seems to provide a feasible solution to
storage problems as well as effective utilization of these alcohols. Negligible dependence on any fossil fuel, these alcohols can be easily produced using any biological
matter usually known as fermented wastes “molasses” from sugarcane, corn, wheat
straw, etc. The problem with these biofuels is its heavy content of sulfur and other
impurities that need to be processed before being used for hydrogen generation. It
should be noted that along with increasing hydrogen generation with higher hydrocarbons, the amount of carbon formation also increases in the same proportion. It can
also be pointed out that amongst the processes used for hydrogen generation, steam
reforming is affected by its strong endothermic nature and its by-product formation
[3], while cracking, on the other hand, is highly expensive with the standard by-product distribution as in the case of steam reforming. Coking also forms the bases of
unalterable damage to the process and system, thereby causing difficulty to sustain the
system as well as auxiliaries such as fuel cells it is connected with. But with all its pros
and cons, steam reforming yet remains the only process that can provide high hydrogen yield [3–5]. However, as PEMFC required ultra-pure hydrogen (purity greater
than 99.999%) and CO content less than 1 ppm, separation of hydrogen from reformate gases is inevitable.
Separation of hydrogen from the reformate mixture underlines the root of any process in terms of efficiency, yield, and thereby applicability. Talking of higher yield,
adsorption-based techniques such as pressure swing adsorption and temperature swing
adsorption are widely applied on an industrial scale but show a varying selectivity chart.
Besides, it is a highly expensive and bulky process to be handled for on-board applications. Membrane separation nonetheless shows higher selectivity corresponding to the
membrane and operating conditions applied. To be precise, dense (non-porous) membranes are the ones with enhanced selectivity to hydrogen over increasing pressure gradients [4–8]. Therefore, balanced synchrony of operating conditions with the catalyst
for reforming and membranes for separation purposes is of utmost importance.
R. K. Upadhyay