417
Many companies like Daimler AG, General Motors, Hyundai are either already
launched their PEMFC-based car or planning to launch it soon. PEMFC is conceptually only an electrochemical device that takes in oxygen and hydrogen which then
reacts to produce electric power and water vapor. Although, few companies have
come up with a solution to remove water vapor from the system by continuing to run
the cell’s exhaust for a minute or two but storing gaseous hydrogen on-board persists to be a problem. For liquid hydrogen, the case is even more complex since it
would have to be stored at −253 °C in a carefully insulated tank which would
increase the weight, design complexity, and expense. Hence, the only solution to the
defined issues can hereby be suggested using an on-board ultra-pure hydrogen generator with integrated reforming and separation units.
Membrane reformers are being popular from the last two decades to use as a
device to produce the ultra-pure hydrogen for on-site/on-board applications [3–11].
However, it is still far from commercialization due to its low hydrogen recovery.
The low hydrogen recovery is mainly caused because of inappropriate integration of
hydrogen production catalysts with membrane separation units (dense palladiumbased membranes). For better integration with the membranes used in membrane
reformer, one needs to modify the traditional steam reforming process to fulfill the
requirement of membrane separation unit [6, 12]. Similarly, the membrane separation unit also needs to be modified to accommodate the requirements of the steam
reforming reaction.
2 Membrane Reformer
A membrane reformer is a process-intensified reactor in which generation and separation of hydrogen take place in a single unit. Generally, a membrane reformer is
comprised of a reforming catalyst for hydrogen generation and palladium-based
membranes for selective separation of hydrogen. A typical schematic of membrane
reformer is shown in Fig. 1. Continuous transfer of hydrogen moves the equilibrium
toward the forward direction which ultimately results in increased conversion as per
the Le Chatelier’s principle. Hence, through the membrane reformer, thermodynamic limits can be modified and higher hydrogen yield can be obtained [9–12].
This is the major advantage of membrane reformer over the traditional reformer.
Further, membrane reformer does not require traditional hydrogen separation units
like pressure swing adsorption, cryogenic distillation, etc. Hence, it is very compact
and ideal for the production of fuel cell grade ultra-pure hydrogen for on-site/onboard applications [10–13]. However, the contrary requirement of steam reforming
reaction and membrane separation makes the integration of these two processes in
a single unit more challenging [9, 12]. Steam reforming being an endothermic reaction requires high temperature and low pressure while for high hydrogen recovery
membrane requires high pressure and low temperature. There are certain other challenges too which need to be overcome for the successful operation of membrane
reformer. These are as follows: (1) production of thin dense membranes having high
Steam Reforming Catalysts for Membrane Reformer
Many companies like Daimler AG, General Motors, Hyundai are either already
launched their PEMFC-based car or planning to launch it soon. PEMFC is conceptually only an electrochemical device that takes in oxygen and hydrogen which then
reacts to produce electric power and water vapor. Although, few companies have
come up with a solution to remove water vapor from the system by continuing to run
the cell’s exhaust for a minute or two but storing gaseous hydrogen on-board persists to be a problem. For liquid hydrogen, the case is even more complex since it
would have to be stored at −253 °C in a carefully insulated tank which would
increase the weight, design complexity, and expense. Hence, the only solution to the
defined issues can hereby be suggested using an on-board ultra-pure hydrogen generator with integrated reforming and separation units.
Membrane reformers are being popular from the last two decades to use as a
device to produce the ultra-pure hydrogen for on-site/on-board applications [3–11].
However, it is still far from commercialization due to its low hydrogen recovery.
The low hydrogen recovery is mainly caused because of inappropriate integration of
hydrogen production catalysts with membrane separation units (dense palladiumbased membranes). For better integration with the membranes used in membrane
reformer, one needs to modify the traditional steam reforming process to fulfill the
requirement of membrane separation unit [6, 12]. Similarly, the membrane separation unit also needs to be modified to accommodate the requirements of the steam
reforming reaction.
2 Membrane Reformer
A membrane reformer is a process-intensified reactor in which generation and separation of hydrogen take place in a single unit. Generally, a membrane reformer is
comprised of a reforming catalyst for hydrogen generation and palladium-based
membranes for selective separation of hydrogen. A typical schematic of membrane
reformer is shown in Fig. 1. Continuous transfer of hydrogen moves the equilibrium
toward the forward direction which ultimately results in increased conversion as per
the Le Chatelier’s principle. Hence, through the membrane reformer, thermodynamic limits can be modified and higher hydrogen yield can be obtained [9–12].
This is the major advantage of membrane reformer over the traditional reformer.
Further, membrane reformer does not require traditional hydrogen separation units
like pressure swing adsorption, cryogenic distillation, etc. Hence, it is very compact
and ideal for the production of fuel cell grade ultra-pure hydrogen for on-site/onboard applications [10–13]. However, the contrary requirement of steam reforming
reaction and membrane separation makes the integration of these two processes in
a single unit more challenging [9, 12]. Steam reforming being an endothermic reaction requires high temperature and low pressure while for high hydrogen recovery
membrane requires high pressure and low temperature. There are certain other challenges too which need to be overcome for the successful operation of membrane
reformer. These are as follows: (1) production of thin dense membranes having high
Steam Reforming Catalysts for Membrane Reformer