The overall research objective of this international research group is the energy efficient production of hydrogen within ultra-compact and scalable multifunctional membrane reactors for on-site and on-demand hydrogen production. This involves the investigation of new nanostructured catalysts as powder materials or coatings with improved activity and long-term stability as well as the study of novel supported palladium alloy membranes and the development of integrated devices using advanced microfabrication technology.
Energy efficiency can be maximized by application of micro structured reaction devices, because of the minimized thermal and mass transfer resistances in microchannel systems. Read more about its advantages here. Furthermore, the in situ hydrogen removal through a permselective membrane enables high conversion already at much lower temperature, due to thermodynamic and kinetic reasons. Together with the elimination of subsequent process steps required in conventional hydrogen production technology to increase the conversion and purify the hydrogen, this can enhance the energy efficiency on the process level substantially.
Scalability is of great importance for addressing the growing number of small-scale industrial uses of hydrogen, which are currently being served via rather costly and energy-inefficient truck delivery of compressed or liquefied hydrogen from central production facilities. Scalability is achieved through modularization and is important here for two reasons, i.e., (i) being able to address with little effort different capacities and to adapt more easily the capacity to changes that might be desired throughout the lifetime of the plant, and (ii) minimizing through modularity the effort both in time and in cost for replicating a plant (concept of “row housing”).
Compactness through multifunctionality is embracing several features. Multifunctionality is achieved by in situ coupling of the catalytic reactions with a permselective separation process. The integrated separation of pure hydrogen improves the reaction kinetics and reduces the number of process steps, thus greatly reducing plant complexity and footprint. Furthermore, an ultra-compact construction is obtained by combining both processes in a microstructured reaction device intimately in small space. This guarantees that both processes actually have a direct influence on each other, and it allows for minimizing dead spaces.
On demand production is a prerequisite for linking hydrogen production with fluctuating energy supplies, e.g., from renewables. Moreover, on demand production is necessary for coupling with on-site processes that have discontinuous hydrogen consumption, e.g., due to frequent plant shutdown at places with limited hydrogen storage capacity.
On-site production of hydrogen is advantageous in many situations for cost and energy efficiency reasons.
Durability is one of the main objectives, i.e., guaranteeing a long system life in steady-state and, more importantly, with realistic temperature cycling and frequent startup and shutdown. The latter is indispensable for on demand production. It means retaining the catalysts in highly active state as well as the membranes, their sealing and the reactor material itself intact under such working conditions. This is a very challenging task, which will be investigated by adopting novel preparation strategies for catalysts and membranes, highly precise micro fabrication techniques, proper reactor material choice and by using advanced synchrotron characterization methods to enable better understanding of all associated phenomena.
Investigation of Novel ultra-thin Pd-alloy membranes is one important working package within the project. Alloying of the membrane can enhance its performance, temperature working area and its poisoning resistance. Therefore, research on PdAu- and PdAg-based alloy membranes, e.g., to be supported on high-quality porous metal substrates that are chemically and thermally compatible with Pd alloy membrane layers as well as with optional intermediate layers is in focus. Furthermore, the influence of the porous metal support on mechanical stability of the membrane and the durability of the sealing is also subject to examination.
Improving activity and long-term stability of catalysts is one major research concern referring durability of the reforming reactor. Therefore, concepts such as confinement of noble metals within pores and preparation of novel core-shell structures with the metal nanoparticles surrounded by the support for deceleration of sinter processes are considered. Furthermore, application of oxide supports such as ceria with redox properties that can further enhance catalytic activity is taken into account. Studies on catalyst dispersions and performances of nanoparticles and coatings that are deposited within microchannels via inkjet-printing will be performed under reforming conditions, also in long-term.
In situ synchrotron characterization methods, namely XAS, RFA, and XRD will be applied close to real process conditions and will enable better understanding of all associated altering phenomena that take place in the membrane, membrane support, catalyst, catalyst support as well as the reactor material itself.
The applied production route of hydrogen is Methane Steam and Dry Reforming in combination with Water Gas Shift reaction. These simultaneous catalytic reactions are combined with in situ removal of hydrogen from the reaction gas via a Palladium alloy membrane.
In situ separation of hydrogen through the palladium-based membrane causes a shift of the chemical equilibrium to the product side during the reforming process. Due to this effect relevant conversion levels can be achieved at drastically reduced reaction temperatures, e.g. 550 °C instead of 800 °C.