Monolithic fuel processors

Main origin of the start-up time demand was the subsequent heating of a consecutive chain of reactors. Electrical preheating of the inlet section of the reformer monolith reduced the time demand for preheating. The prototype fuel processor had a weight of 18 kg and a volume of 401 (without insulation). 

Lindermeir et aL [172] described the development work of the German company Webasto for an SOFC-based CHP system. Partial oxidation of methane was chosen as reforming technology. In a two-staged process, part of the fuel was completely oxidized generating carbon dioxide and steam followed by a 

---

Present catalysts are developed for process plant service where transient conditions are not a concern. Typical shift catalysts, such as copper-zinc oxide, are reduced in place and must be isolated from air. There is a need for smaller, high surface area catalyst beads on low-density monolith substrate to be developed without reducing activity. This need applies to all fuel processor catalyst, not just the shift catalysts. There is also a need to demonstrate that the low-temperature, PROX catalysts have high selectivity toward CO and long term stability under operating conditions. 

ScHUESSLER, M., PoRTSCHER, M., LIMBECK, U., Monolithic integrated fuel processor for the conversion of liquid methanol, Catal. Today 2003, 79-80, 511-520. 

Designed, fabricated, and installed a generic fuel processor and test stand to study the heat transfer characteristics of monolith loaded reaction zones. 

Conduct extensive sampling of Pt/ceria catalyst powders, pellets, and washcoated monoliths for evaluation by Sud-Chemie, HydrogenSource, and other fuel processor developers. 

Washcoating of monoliths with Pt/ceria catalysts provides a viable path for achieving rugged and volumetrically efficient packaging of catalysts in WGS reactors of automotive fuel processors. 

The focus of Phase II of this project is to optimize formulations for the carbide catalysts and produce monolith supported prototype catalysts that substantially out-perform the commercial catalysts. In addition, we will evaluate the cost competitiveness of the monolith supported carbide catalysts. The performance of new monolith supported catalysts demonstrated in this effort will be confirmed by independent evaluations by established fuel processor developers. 

Adachi et al. [168] developed a model for a natural gas fuel processor composed of an ATR designed as metallic foam monolith coated with catalyst and two-stage WGS reactors also designed as foam monoliths followed by two-stage ceramic monoliths for the preferential oxidation of carbon monoxide as shown in Figure 14.27. Figure 14.28 shows the course of temperature and gas composition of feed and reformate as calculated for... 

In this particular unit, the reforming reaction was carried out at an absolute pressure of approximately 2 bar, since the plant was conceived as a fuel processor for a PEM fuel cell that would operate at slightly above atmospheric pressure. The reformer catalyst was a proprietary monolith-supported, noble metal catalyst (Engelhard). The combustion side operated at atmospheric pressure and employed a proprietary palladium-based, monolith-supported catalyst (Engelhard). Heatric states that the MAB PCR offers improved selectivity or productivity on a broader basis through ... 

However, monolithic reactors and plate heat-exchangers are more suitable than fixed-beds for the rapid start-up and transient operation requirements of fuel processors on the smaller scale [57]. 

A microstructured monolith for autothermal reforming of isooctane was fabricated by Kolb et cd. from stainless steel metal foils, which were sealed to a monohthic stack of plates by laser welding [73]. A rhodium catalyst developed for this specific application was coated by a sol-gel technique onto the metal foils prior to the sealing procedure. The reactor carried a perforated plate in the inlet section to ensure flow equi-partition. At a weight hourly space velocity of 316 L (h gcat). S/C 3.3 and O/C 0.52 ratios, more than 99% conversion of the fuel was achieved. The temperature profile in the reactor was relatively flat. It decreased from 730 °C at the inlet section to 680 °C at the outlet. This was attributed to the higher wall thickness of the plate monolith compared with conventional metallic monolith technology. The reactor was later incorporated into a breadboard fuel processor (see Section 9.5). 

Catalyst cost may play a significant role in the overall fuel processor cost and could reach values as high as 38% [633]. In this situation, tailor-made catalyst formulations of enhanced activity are required along with meastues to increase the utilisation of the catalyst. This may be achieved by coating the catalyst into small channel systems of ceramic or metallic monoliths or into microstructured plate heat-exchangers, which improves the mass transfer, as described in Chapter 6. 

---