Methanol steam reforming for hydrogen production

Methanol steam reforming for hydrogen production continues to be an active area of research. With much progress already achieved, there are still many problems yet to solve. While interest in methanol as a PEM fuel cell fuel has remained strong, there seems to be a shift of focus away from automotive applications and a sustained emphasis on portable and small power applications. In the higher power range (≫ 1 kW), methanol has several disadvantages relative to logistics fuels (e.g., JP-8, diesel) or infrastructure fuels (gasoline, LPG, NG), especially with regard to distribution network and energy density. On the low power side (< 100 W), where the simplicity of methanol provides an advantage, RMFCs must compete with advanced battery technology and DMFCs, both of which are further developed than RMFC units in general. Furthermore, at these low power levels, BOP considerations become increasingly important. As a result, RMFC units are likely to make their mark on the portable power space in the 100-1000 W power range, where the fuel can be treated like a prepackaged consumable and where BOP availability is not as limited. The military will continue to show interest in RMFC devices, even if only as a short-term solution, with the longer-term focus being on heavy fuels like JP-8 and diesel. Commercial markets may accept RMFCs (and DMFCs, for that matter) only if price points can be brought down considerably. Continued technical advancements will be needed in either case. As seen in section 3, catalyst development has been a big focus area for methanol reforming researchers, but much more work remains. If Cu-based catalysts are to be used successfully in the long term, the deactivation and sintering issues need to be addressed. Alternatively, the Pd alloy formulations being developed could solve many of these problems. However, regardless of the catalyst formulation used, other tangential factors need to be addressed, such as potential poisoning or passivation of the catalyst due to trace contaminants over long operational times. These contaminants could come from several sources, including the methanol fuel, the water (carried or recycled), and even the environment in which these devices are stored and operated. Reactor and system development activities by groups around the world have demonstrated the ability to conduct methanol reforming at small and large scale, at high efficiencies, and for a host of applications. Consequently, material selection and system design vary widely, from the very small metal, glass, or ceramic microreactors to the large-scale, high pressure, membrane-based hydrogen generators. Catalyst deployment methods used have included traditional packed-bed reactors, monolith reactors, and wall-coated channels, each with its demonstrated advantages and disadvantages. In this case, one size does not fit all. For each application, the method of catalyst deployment will depend on a number of factors, including price, application, user, reactor type, power output, and the developer's predispositions. Efforts in developing microchannel-based devices for methanol steam reforming and its associated unit operations have proven successful. The interleaving of combustion and reforming channels has been shown to provide a very compact device with high efficiency. In this type of deployment, though, fabrication can become quite complex and expensive if not designed for manufacturing from the early stages. Likewise, several developers have shown the promise of methanol reforming in a Pd-membrane reactor configuration, with the resultant pure H2 to feed to the fuel cell. These developers will need to address cost and weight issues before full deployment and acceptance can be expected, but they have definitely made an impression through the public demonstration of prototype units at the various conferences and expos that relate to fuel cell power. Methanol reforming will continue to be an active area of research, even if it only serves as an initial step on the road to fuel cells powered by gasoline, diesel, or JP-8. Military interest continues to be driven by a need for higher energy density power sources, as they must provide the soldier with more power without increasing his already large burden. Methanol reforming is a step to get there. Commercial applications, if successful, could see methanol become the next "propane", where it is sold in single-use containers at retail outlets for use in portable fuel cell units. This scenario is still years away, but if developers can establish an acceptance of methanol as a useful fuel and can establish a market for personal and recreational fuel cell power systems, then this is not an outlandish idea. Ultimately, the market, both military and commercial, will determine where methanol reforming goes from here. In the meantime, researchers and developers will continue to explore the possibilities, hoping to hit upon an additional breakthrough that will bring this important technology closer to commercial application. © 2007 American Chemical Society.