On-board fuel reforming

All fuel cells for use in vehicles are based on proton-exchange-membrane fuel cell (PEMFC) technology. The methanol fuel-processor fuel cell (FPFC) vehicle comprises an on-board fuel processor with downstream PEMFC. On-board methanol reforming was a development focus of industry for a number of years until around 2002. Direct-methanol fuel cells (DMFC) are no longer considered for the propulsion of commercial vehicles in the industry (see also Chapter 13). 

These are reasonable questions. Several additional questions need to be answered before we pursue a path of generating large volumes of hydrogen from gasoline reformers on board fuel cell vehicles ... 

PEM fuel cells use a solid proton-conducting polymer as the electrolyte at 50-125 °C. The cathode catalysts are based on Pt alone, but because of the required tolerance to CO a combination of Pt and Ru is preferred for the anode [8]. For low-temperature (80 °C) polymer membrane fuel cells (PEMFC) colloidal Pt/Ru catalysts are currently under broad investigation. These have also been proposed for use in the direct methanol fuel cells (DMFC) or in PEMFC, which are fed with CO-contaminated hydrogen produced in on-board methanol reformers. The ultimate dispersion state of the metals is essential for CO-tolerant PEMFC, and truly alloyed Pt/Ru colloid particles of less than 2-nm size seem to fulfill these requirements [4a,b,d,8a,c,66j. Alternatively, bimetallic Pt/Ru PEM catalysts have been developed for the same purpose, where nonalloyed Pt nanoparticles <2nm and Ru particles <1 nm are dispersed on the carbon support [8c]. From the results it can be concluded that a Pt/Ru interface is essential for the CO tolerance of the catalyst regardless of whether the precious metals are alloyed. For the manufacture of DMFC catalysts, in... 

Methanol and ethanol have been considered as promising fuels for generating H2, especially for on-board fuel cell applications due to their easy availability, ability to transport, and reaction simplicity.52 121 159 169 For example, both alcohols have high H2-to-carbon ratio (H/C) of 4 and 3, respectively (Table 2.1). They could be synthesized from renewable sources such as biomass and thus the ability to close the carbon cycle.161 166 Unlike hydrocarbon fuels, methanol and ethanol are free from sulfur, and this avoids additional sulfur removal step in the fuel processing. In addition, methanol can be reformed at a lower temperature, around 300 °C, and this makes the fuel processing relatively simple and less complicated. Furthermore, unlike natural gas, which produces primarily syngas, reforming of methanol and ethanol can in principle produce a mixture of H2 and C02, and this would also simplify the downstream CO cleanup for fuel cells such as PEMFCs where CO is a poison. 

Argonne National Laboratory has developed a POX reformer suitable for use in vehicles. The U.S. Department of Energy (DOE) supports work on POX systems for on-board fuel processors for fuel cell vehicles through the Office of Transportation Technologies Fuel Cell Program.17... 

Adapt proven technologies for on-board fuel processing to be capable of reducing the H2S concentration to <1 ppm in reformate. 

Gas-phase desulfurization using ZnO is the approach that we have pursued in past years. ZnO is an attractive adsorbent for on-board fuel processing because of its favorable sulfidation thermodynamics (<1 ppmv). The sulfidation equilibrium for ZnO (ZnO + H2S o ZnS + H2O) is a function of the temperature and the ratio of the partial pressure of H2O/H2S. To reduce the H2S concentration to <0.1 ppmv requires a temperature of 300-350°C based on the typical range of H2O concentrations present in the reformate (Carter et al. 2001). However, it has been observed that although the equilibrium becomes more favorable as the... 

Evaluate the viability of autothermal NH3 reformation on-board fuel cell vehicles. 

Methanol is a liquid fuel that is readily dispensed and stored but, compared with conventional liquid fuels, is by no means ideal it is both toxic and water-miscible and has an energy content per litre that is well below that of petrol see Table 1.4, Chapter 1. A further drawback of incorporating a reformer into the vehicle is the need to supply heat for its operation. At 80-90 °C, the waste heat from the fuel cell would be inadequate and it would be necessary to burn some of the methanol to provide the heat or to use electrical heating. Either of these two options would obviously reduce the effective efficiency of the fuel-cell system. Altogether, on-board methanol reformers pose as many engineering problems as on-board hydrogen storage. Furthermore, the combined cost of a reformer and a fuel cell is likely to prove prohibitive, at least for small vehicles such as cars. 

Also in Germany, Mercedes-Benz has been developing electric vehicles for over 30 years. Many of the later vehicles utilized advanced sodium—nickel chloride (ZEBRA) batteries. By 1997, over 1 million km of road testing of these batteries had been accumulated, much of it in the electric version of the Mercedes-Benz A-Class car. In 1994, the company commenced its research on fuel cell vehicles - the New Electric Car (NECAR) programme. Following the evaluation of a series of prototypes, the NECAR 5 was launched in November 2000. This, too, was based on the A-Class car. Power was supplied by a 75 kW fuel-cell system that was fed by an on-board methanol reformer. The car featured a cold-start facility to remove the need for the reformer to... 

We leave to specialists the task to describe the desired new approaches in the preparation of zeolites and mesoporous materials. Much work remains to be done for the scale-up of fabrication of MCM and similar materials. The manufacture of specially structured catalysts for very compact devices, like on-board fuel cells and automobile reforming units, is certainly able to bring much information valuable for the fabrication of many specific catalysts in environmental protection, especially for reverse-flow reactors. The demands of photocatalysis also impose constraints. 

Boettner D and Moran M J (2004), Proton exchange membrane (PEM) fuel cell-powered vehicles performance using direct-hydrogen fueling and on-board methanol reforming. Energy, 29,2317-2330. 

Karakaya M. Avci AK. Comparison of compact reformer configurations for on-board fuel processing. International Journal of Hydrogen Energy 2010 35 2305-2316. 

Darwish, N.A., et al. 2004. Feasibility of the direct generation of hydrogen for fuel-cell-powered vehicles by on-board steam reforming of naphtha. Fuel 83 409 17. 

In addition, some fuel cells will require deep-desulfiuized fuels. For example, methanol-based fuels for on-board fuel cell applications require the use of a fuel with sulfur content <1 ppmw in order to avoid poisoning and deactivation of the reformer catalyst. To use gasoline or diesel commercial fuels, which are the ideal fuels for fuel cells because of their high energy density, ready... 

As a constituent of synthesis gas, hydrogen is a precursor for ammonia, methanol, Oxo alcohols, and hydrocarbons from Fischer Tropsch processes. The direct use of hydrogen as a clean fuel for automobiles and buses is currently being evaluated compared to fuel cell vehicles that use hydrocarbon fuels which are converted through on-board reformers to a hydrogen-rich gas. Direct use of H2 provides greater efficiency and environmental benefits. ... 

If fuel cell technology were introduced on a large scale for automotive transportation, would you prefer a fuel distribution system in which gasoline fuel remains the major energy carrier but is reformed on-board to hydrogen or one in which hydrogen is provided at fuel stations Explain your choice. 

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