Literature Review of Fuel Processing 

by Ivan C. Lee and Deryn Chu 

ARL-TR-2946 March 2003 

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Army Research Laboratory 

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ARL-TR-2936 March 2003 

Literature Review of Fuel Processing 

Ivan C. Lee and Deryn Chu 

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14. ABSTRACT 

Technology is available for the development of hydrogen-fueled polymer electrolyte membrane (PEM) fuel cell systems of small and 

intermediate sizes. For the indirect use of organic fuels, such require the development of compact fuel processors to provide high purity 

hydrogen. Methanol fuel processors are under intensive research and development for that purpose. The associated technical challenges and 

approaches to their solutions are discussed. Integrated prototype systems of methanol processor and PEM fuel cell systems have been built for 

portable, mobile, and stationary applications. 

The additional technical barriers to be overcome for diesel or JP-8 reformers are much more formidable. Carbon and sulfur managements have 

to be addressed to develop a durable and high-performance logistic fuel reformer for Army applications. In addition, better carbon monoxide 

removal strategy is necessary, because logistic fuel reformers produce reformate gases containing high carbon monoxide concentration. Stateof-the-art logistic fuel reformers are reviewed. 

15. SUBJECT TERMS

Fuel processing, reformation, reforming, reformer, CO removal, methanol, JP-8 diesel 

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Content 

1. Introduction 1

2. Reformer 2

3. CO Removal Sub-System 5

3.1 Water-Gas Shift Reaction................................................................................................5 

3.2 Membrane Separator and Reactor ...................................................................................6 

3.3 Preferential Oxidation .....................................................................................................8 

4. Putting Them Together 10

5. Challenges for Using Diesel or JP-8 as Fuel 12

5.1 Carbon Management .....................................................................................................13 

5.2 Sulfur Management .......................................................................................................14 

6. State-of-the-Art JP-8 and Diesel Reformers 16

7. Conclusion 17

8. References 19

Appendix A. Chemical and Physical Properties of Methanol, Diesel, and JP-8 25
vi

List of Figures 

Figure 1. Permeation of hydrogen through a Pd-based membrane, in which (1) represents 

reversible dissociative chemisorption of hydrogen, (2) represents dissolution of atomic 

hydrogen, and (3) represents bulk diffusion of atomic hydrogen through the membrane.........7 

Figure 2. Conceptual block diagrams for fuel processing: A) A conventional fuel processing 

for diesel or JP-8, and B) Fuel processing for methanol..........................................................11 

Figure 3. Carbon and sulfur balances for JP-8 or diesel fuel processing.......................................13 

Figure 4. Families of sulfur compounds in the JP-8 and diesel fuel..............................................16 

List of Tables 

Table 1. Characteristics of various fuels for fuel reformation.........................................................2 

Table 2. Partial oxidation offering compact size and steam reforming offering a high 

concentration of hydrogen .........................................................................................................3 

Table 3. Water-gas shift kinetic data over various metal-ceria catalysts.........................................6 

Table 4. Comparison of adiabatic and isothermal PROX reactors ..................................................9 

Table 5. Key performance results of a 2% Pt/alumina sol-gel catalyst during PROX reaction 

with realistic post-water-gas shift reformate compositions [64]..............................................10 

Table 6. Selected qualities of low-sulfur crude [80]......................................................................15 

Table 7. The reformer is robust to fluctuating sulfur content in the hydrocarbon feed stream 

[88]...........................................................................................................................................17 

Table 8. Testing of sulfur-tolerant catalysts for diesel and JP-8 steam reforming [74].................17 

Table A-1. Selected chemical properties for methanol, JP-8, and diesel .....................................25 
1

1. Introduction 

Recently, Ball Aerospace has developed an advanced portable polymer electrolyte membrane 

(PEM) fuel cell system (4.2 by 7 by 7.8 inches, 6.5 lb) under the U.S. Army, Defense Advanced 

Research Project Agency (DARPA) and the Office of Special Technology (OST) [1]. With pure 

hydrogen fuel, this PEM fuel system can provide a normal 50-W power output for Army 

applications. Another PEM fuel cell power module (Nexa1) is volume produced and is 

commercially available from Ballard. This state-of-the-art PEM fuel cell (22 by 10 by 13 inches, 

29 lb) also converts high purity hydrogen fuel and oxygen to generate as much as 1200 W of 

unregulated electric power. One of the main drawbacks of using compressed hydrogen gas fuel is 

its low energy density compared with hydrocarbons. Another drawback is the source of 

hydrogen. An overview of several strategies of hydrogen generation and storage for PEM fuel 

cell has been reported previously [2]. Meanwhile, hydrogen is industrially produced by steam 

reforming of hydrocarbons such as methane, methanol, naphtha oil, etc [3–5]. The common goal 

for fuel processing research in many laboratories is to modify and miniaturize these industrial 

plants into fuel processors so that high purity hydrogen is produced on demand for fuel cells in 

portable, mobile, or stationary applications. 

Unfortunately, a fuel reformer usually produces an appreciable amount of carbon monoxide 

(CO); therefore, a CO removal sub-system becomes an integral part of the fuel processor. At the 

operating temperature (<85 oC) of PEM fuel cell, CO adsorbs relatively strongly onto and thus 

poisons the fuel cell anode catalyst. Since the tolerable CO concentration is less than 10 parts per 

million (ppm), a fuel processor usually consists of both a reformer and a carbon monoxide 

removal sub-system. 

At present, prototypes of complete fuel processor/fuel cell systems for portable, automobile, or 

residential applications have been developed, but none is ready to be commercialized. For 

example, Ballard and XCELLSiS have developed a methanol fuel processor that generates 

hydrogen on board the Mercedes-Benz (NECAR 52

). This fuel processor is compact enough to 

fit under the floor of the vehicle. In June 2002, DaimlerChrysler and Ballard announced that this 

fuel cell vehicle had completed an endurance drive from San Francisco, CA, to Washington, DC. 

The main objective of this report is to discuss the challenges and the progress for the state-of-theart fuel processor. This report focuses on hydrogen generation from reforming processes, and it 

is organized as follows. First, we demonstrate the general principles of fuel processing with 

state-of-the-art methanol fuel reformers as examples. Since the PEM fuel cell is the only kind of 

fuel cell that is being mass produced at this moment, research and development of carbon 

monoxide removal is important. Different approaches and recent efforts for carbon monoxide 

cleanup are included in this report. Finally, we address additional challenges and current status of 

logistic fuel (diesel and JP-8) reformers. 

 1

Nexa is a trademark of a PEM fuel cell module from Ballard. 

2

NECAR 5 is a fuel cell car from DaimlerChrysler. 
2

2. Reformer 

Considered as on-demand hydrogen generators for PEM fuel cells, fuel reformers have attracted 

lots of attentions. At this moment, details of methanol reforming [6–16] are better studied than 

other hydrocarbon fuels. There are reports on hydrogen generation from methane [17], ammonia 

[18], ethanol [19], kerosene [20] and diesel [21]. As the power need for soldiers becomes more 

demanding, diesel and JP-8 are good candidates as the main reforming fuels for Army 

applications because of logistics, transportability, flammability, and energy densities (see 

Table 1). 

Table 1. Characteristics of various fuels for fuel reformation 

Fuel Energy 

Density 

(kWh/kg, 

Lower 

Heating 

Value) 

Logistics Transportability Flammability (Flash 

point in o

F) 

H2 Storage (4-

5wt%, compressed) 

0.7-0.9 [22] No Gas Explosive 

Methanol 5.6 [23] No Liquid 52 

JP-8 11.1 [24] Yes Liquid 100 

Diesel 11.8 [22] Yes Liquid 160 - 210 

n-Octane 12.3 [23] No Liquid 56 

n-Dodecane 12.3 [23] No Liquid 160 

Propane 12.8 [22] No Gas -156 

Although the infrastructure of the methanol supply is a problem, the potential of methanol fuel 

processing as an alternate supply of hydrogen is recognized for several reasons. First, methanol 

has a much higher specific energy than military primary and secondary batteries. Second, high 

conversion of methanol can be achieved at a relatively low temperature (250 to 300 o

C). Finally, 

it is a bulk chemical produced in large quantities in chemical industry (12.5 billion gallons 

worldwide in year 2000). 

Hydrogen generation from hydrocarbon or alcohol, e.g., methanol, can proceed by partial 

oxidation reforming (Equation 1) or by steam reforming (Equation 2). 

 CH3OH(l) + 0.5 O2 → 2 H2 + CO2 ∆Ho

 = –155 kJ/mol (1) 

 CH3OH(l) + H2O(l) → CO2 + 3H2 ∆Ho

 = 131 kJ/mol (2) 

In partial oxidation reforming, the air-to-fuel ratio for combustion is substochiometric. This 

exothermic process can be performed in a catalytic manner or a non-catalytic manner. Catalytic 

partial oxidation is operated at lower temperature than non-catalytic partial oxidation. Catalytic 

partial oxidation also has a lower tendency for soot formation. Meanwhile, steam reforming is an 

endothermic process. The heat required for this process is provided by external sources. The 

advantages and disadvantages of partial oxidation reforming and steam reforming are shown in 

Table 2. 
3

Table 2. Partial oxidation offering compact size and steam reforming offering a high 

 concentration of hydrogen 

 Partial oxidation Steam reforming 

Advantages Compact in size High hydrogen concentration 

 Fast start 

 Rapid transient response 

Disadvantages Low H2 concentration in product 

gas, even when pure oxygen is 

used. Using air will further lower 

H2 concentration. 

Strongly endothermic and 

typically limited by heat transfer 

(poor transient operation) 

 Overall efficiency can suffer 

because of waste heat production. 

Water supply and recycling 

required 

 Catalyst deactivation because of 

excess heat. 

Energy required to vaporize water 

with fuel 

Partial oxidation offers compactness, fast start, and rapid transient response, while steam 

reforming produces a higher concentration of hydrogen and thus higher system efficiencies. To 

improve the heat transfer properties for steam reformer, radial flow fuel processor [25], ceramic 

multiplayer fuel processor (1We) [26] and microchannel reactor [23] have been designed. In case 

of catalytic partial oxidation, steam is added into the reformer to control the temperature of the 

reforming process. This approach is very similar to autothermal reforming. 

Autothermal reforming combines the heat effect of partial oxidation reforming and steam 

reforming so that autothermal reforming is operating under thermoneutrality (∆Hr = 0) [27]. 

Therefore, once the reactions are initiated during starting, no external heat is required. A small 

amount of precious metal catalyst (e.g., Pd/SiO2) can provide the auto-ignition [28]. 

Thermodynamic calculations indicate that the autothermal reforming is the most efficient process 

[27,29]. In some cases, the autothermal reformer is usually configured into two compartments so 

that partial oxidation reaction occurs at the front and steam reforming occurs at the back [30]. 

Alternatively, the catalysts are designed so that steam reforming catalyst is close to the partial 

oxidation catalyst. For example, a layer of partial oxidation catalyst is deposited on the top of 

another layer of steam reforming catalyst on the monolithic substrate [31]. 

Meanwhile, several criteria apply to the catalysts. First, compact and lightweight reformers 

require very active catalysts. Second, high selectivity is important in order to simplify the carbon 

monoxide removal step. Moreover, the catalysts must be mechanically durable in order to 

withstand vibrations, especially for Army applications. Finally, long life span is advantageous to 

avoid frequent regeneration or recharging of catalysts. 

Hydrogen generation by catalytic partial oxidation of methanol has been studied over Cu-Znbased catalysts [12,14,15] and supported Pd catalysts [13]. A copper-based catalyst for this 

reaction is the most cost effective, but this kind of catalyst suffers from catalyst deactivation. 

Excessive heating causes copper particles to sinter, resulting in the loss of metal surface area 

[32]. 

Kinetic models and surface mechanisms for methanol steam reforming on Cu/ZnO/Al2O3

catalysts have been investigated [7,9,10,11,16]. Peppley, Amphlett, and others found that all 
4

three reactions (steam reforming [Equation 2], methanol decomposition [Equation 3], and watergas shift reaction [Equation 4]) must be included in the rate expression [10,11]. Although the 

methanol decomposition is much slower than the steam reforming, a small amount of CO can 

impede the performance of PEM fuel cell. Therefore, the methanol decomposition is included in 

the kinetic model. 

 CH3OH(l) → 2H2 + CO ∆Ho

 = 128 kJ/mol (3) 

 CO + H2O ↔ H2 + CO2 ∆Ho = –41.2 kJ/mol (4) 

In addition to kinetics for methanol steam reforming over a Cu/ZnO/Al2O3 catalyst, Agrell et al. 

have also explored the strategies for minimizing CO formation [7]. They found that increasing 

the steam-to-methanol ratio or adding oxygen/air effectively decreases CO formation. They also 

found that shortening the contact time and lowering the reactor temperature could suppress the 

reverse water-gas shift reaction. 

Johnson Matthey has developed a modular methanol fuel processor (HotSpot3) [8]. In each 

module, both exothermic partial oxidation and endothermic steam reforming of methanol occur. 

By combining the appropriate number of individual reactors in parallel, the modular processor 

can be enlarged. A 245-cm3

 processor can achieve steady state production 750 L of hydrogen per 

hour in 50 seconds from a cold start. Then the carbon monoxide level is reduced to < 10 ppm by 

a multistage catalytic microreactor (40% of the size of processor). 

Battelle has recently developed a portable methanol steam reformer for the U.S. Army [23]. The 

reactor train includes a catalytic combustor, two vaporizers, and a microchannel steam reformer. 

Typically, fuel processor is operating at a temperature of 350 o

C and a contact time of 140 ms. 

The estimated system energy density of the resulting fuel processor/fuel cell system is 

720 Wh/kg for a 14-day mission. 

Schuessler et al. have developed an autothermal methanol reformer with power density of 

4 kWe/kg or 10 kWe/L [33]. The Cu/ZnO-based catalyst is deposited onto copper porous disks. 

Stacking these disks forms a monolithic radial flow reformer and enlarges the power requirement 

simultaneously. Since an isothermal temperature profile and a constant flow distribution are 

achieved, heat and mass transfers are not limiting with this reactor design. This design also offers 

a fast start. Within a minute, a temperature of 300 o

C could be reached. 

Membrane reactors [34,35] for methanol steam reforming have been tested. For example, 

Wieland, Melin and Lamm have developed membrane reactors using Pd75Ag25, Pd60Cu40 and 

Pd/V/Pd membranes [35]. The methanol and CO conversions in a membrane reactor are higher 

than equilibrium conversions in a conventional reactor because hydrogen is selectively removed 

in a membrane reactor. Membrane reactors are discussed in more details later. 

 3

 HotSpot is a trademark of a methanol fuel processor from Johnson Matthey. 
5

3. CO Removal Sub-System 

Since low temperature operation of the PEM fuel cell favors CO adsorption on anode catalysts, 

resulting in catalyst poisoning, a CO removal sub-system is an important component of a fuel 

processor. When the CO level in the hydrogen-rich reformate4 is on the order of 10%, the CO is 

usually removed by a water-gas shift reaction to a level of 1% or less. Then the CO level is 

further decreased to less than 10 ppm by preferential oxidation or by hydrogen-selective 

membrane separation. 

3.1 Water-Gas Shift Reaction 

The goal for a water-gas shift reactor is to reduce the CO level to less than 1% so that hot spots 

in the preferential oxidation unit can be avoided [36]. The water-gas shift reaction (Equation 5) is 

independent of pressure, and it is thermodynamically favored at low temperature. 

 CO + H2O ↔ CO2 + H2 ∆Ho

 = –41.2 kJ/mol (5) 

Since the kinetics of the current catalyst are usually so slow at low temperature, a large catalyst 

volume is needed. The common practice is a two-stage shift reactor for high temperature shift 

reaction and low temperature shift reaction [4]. The high temperature shift step reduces the CO 

level to 2% to 3% at about 350 oC with iron and chromium oxide catalysts. Then the gas stream 

is cooled to about 200 oC for the low temperature shift reaction, which further reduces the CO 

concentration to about 1% or less. Cu/ZnO/Al2O3 is the most common commercial low 

temperature shift catalyst. 

Although the water-gas shift reaction is well studied for reducing CO levels in a hydrogen stream 

in industrial applications, on-demand hydrogen generations in Army applications pose an 

entirely different set of challenges. In an industrial plant, the water-gas shift reactor continues to 

run most of the time. However, for on-demand hydrogen generation by a fuel processor, the 

water-gas shift catalysts go through lots of thermal cycles and on-off situations in which steam 

condenses. It is well known that water condensation deactivates the copper-based catalysts. The 

deactivation of Cu-based catalysts was discussed in detail recently [38]. 

Deactivation of commercial Cu/ZnO/Al2O3 water-gas shift catalysts is a major technical barrier. 

The state-of-the-art water-gas shift reactor consists of a long pre-reduction section to prevent 

metal agglomeration of copper-based catalyst. The volume of the shift reactors can occupy 50% 

of the volume of the entire fuel processor [37]. The state-of-the-art water-gas shift reactor for a 

50-kW fuel processor is about 20 to 40 kg and 20 to 40 L [39]. Unless the size of water-gas shift 

reactor is reduced through the development of a better catalyst, it is impractical to use fuelprocessing technology to provide power for Army applications. In addition, the pyrophoric 

nature of these high and low temperature catalysts in their active states is a safety issue for the 

users [37]. Replacing catalysts or any accidental exposure to air at an unsafe temperature will 

endanger soldiers’ lives. 

 4

 Reformate refers to the product stream from a reformer. 
6

In literature, there are some recent attempts to develop better water-gas shift catalysts, and metalbased cerium oxide catalysts are promising candidates [40–44]. Activation energy, Ea, for some 

kinetic studies are summarized in Table 3. 

Table 3. Water-gas shift kinetic data over various metal- 

 ceria catalysts 

Metal Loading Support Ea, kJ/mol Reference 

None Ceria 63 ±4 [40] 

Pt Ceria 46 ±4 [40] 

Rh Ceria 46 ±4 [40] 

1% Pd Ceria 38 [41] 

1% Ni Ceria 44 [41] 

None Ce(La)Ox 58.5 [42] 

5% Ni Ce(La)Ox 38.2 [42] 

5% Cu Ce(La)Ox 30.4 [42] 

The enhancement of water-gas shift activity by base metals has been attributed to a synergistic 

redox reaction. The metal components increase the oxygen storage capacity and reducibility of 

pure ceria [40,42]. 

Recently, there have been many studies of the catalysis by nanosized gold particles, including 

water-gas shift reaction [45]. Andreeva et al. [46] have studied the catalytic activity of Au/ZnO, 

Au/ZrO2, Au/Fe2O3, Au/Fe2O3-ZnO, and Au/Fe2O3-ZrO2 catalysts for water-gas shift reaction 

between 140 and 360 o

C. The catalysts are prepared by deposition-precipitation method. The 

results have shown that the water-gas shift activity strongly depends on the dispersion of gold 

particles, as well as the state and the structure of the supports. In another study, water-gas shift 

activities of gold, silver, and copper particles nano-dispersed on TiO2 have been compared [47]. 

The order of activities has determined to be gold > copper > silver (no activity). The Fourier 

transform infrared (FTIR) data indicate that the differences in activities are attributable to the 

ability to adsorb CO. In addition, a high water-gas shift activity by Au/CeO2 with loading of 1% 

to 8% has been demonstrated at low temperature [43,44]. The transmission electron microscopy 

(TEM) results indicate that the nanosized gold particles are stable and preserved after the 

reaction [44]. The temperature-programmed reduction (with 20% H2/N2) results show that the 

addition of gold drastically increases the oxygen reducibility of ceria [43]. 

Since many of the recent water-gas shift research efforts are driven by the need for a better threeway catalyst (TWC), irreversible reducibility of the catalyst was not an issue. However, 

hydrogen concentration is as high as 75% for fuel processing applications. It is important to have 

a water-gas shift catalyst that can function properly at this high hydrogen concentration regime. 

Recently, Zalc, and others [36] have tested the activity and the stability of several Pt-based ceria 

catalysts with typical reformate compositions. Low activity and rapid first order deactivation are 

observed. These results suggest that a high hydrogen concentration in reformate leads to 

irreversible over-reduction of the ceria in these Pt-based catalysts. 

3.2 Membrane Separator and Reactor 

Membrane reactors couple chemical reaction with membrane separation. They have received 

growing attention for fuel processing in recent years. A monograph [48], reviews [49–51] and 

conferences such as the International Conference on Catalysis in Membrane Reactors (ICCMR) 
7

have been dedicated to this subject. The most attractive feature is that membranes can potentially 

surpass the equilibrium conversion by removing one of the reaction products, usually hydrogen, 

selectively. 

Among several types of membrane, the Pd-based membrane has the highest selectivity for 

hydrogen. The membrane separation process is based on the selective diffusion of hydrogen 

through a high temperature metal membrane. An elevated pressure is required on the “feed” side. 

The hydrogen permeation rate is directly proportional to the difference in the square roots of 

hydrogen pressures between the feed and permeation sides of the membrane. One of the major 

challenges is the trade-off between mass transfer resistance and structural integrity. A thin 

membrane has a lower mass transfer resistance and therefore requires lower pressure difference 

between the high pressure side and low pressure side of the membrane. However, the membrane 

will become brittle during thermal cycling as the thickness decreases. Therefore, durability has 

been one of the main issues. Also, the fact that the high hydrogen is usually generated at the low 

pressure from the reformer reduces the advantage of using this process. Usually, a compressor or 

a sweep gas is needed. 

The permeation of hydrogen through the Pd membrane is a multi-step process [49]: 

1. reversible dissociative chemisorption of hydrogen on the membrane surface; 

2. reversible dissolution of surface atomic hydrogen in the bulk layers of Pd; and 

3. diffusion of atomic hydrogen in the membrane. 

Figure 1 illustrates this multi-step process. 

Figure 1. Permeation of hydrogen through a Pd-based membrane, in which (1) represents 

 reversible dissociative chemisorption of hydrogen, (2) represents dissolution 

 of atomic hydrogen, and (3) represents bulk diffusion of atomic hydrogen 

 through the membrane. 

With regard to fuel-processing applications, the membranes need to have high hydrogen 

permeability and selectivity, combined with good chemical, mechanical and thermal long-term 

stability [52]. For example, a few cycles of α ↔ β phase transition of pure Pd result in severe 

H-H 

H H H H 

H H H H 

H H H H 

H H H H 

H-H 

H-H H-H 

(1) 

(1) 

(2) 

(2) 

(3) Pd-based 

Membrane 
8

lattice strains. Therefore, Pd alloy membranes such as Pd-Ag have been studied extensively as a 

membrane candidate to reduce the strains. Other current limitations for commercial use of Pd 

membranes have been discussed elsewhere [52]. Composite membranes are believed to be the 

most reasonable choice for producing high purity hydrogen [53,54]. These membranes consist of 

1) a thin metallic layer that is only permeable to hydrogen, and 2) a porous substrate that 

provides mechanical support to the thin metal. In some cases, the porous material also prevents 

the direct contact of the metal layer and the water-gas shift catalyst [55]. 

The effect of the feed composition on the membrane reactor efficiency has been studied by 

Criscuoli et al. [55]. Their cylindrical reactor is 28 cm long with a 15-cm-long inner tube (70- to 

75-μm thick palladium membrane) and stainless steel outer tubes (4 cm inner diameter). The 

water-gas shift catalyst from Topsøe was packed in the inner tube with porous alumina 

separating the membrane and the catalyst. Criscuoli et al. have tested mixtures of different 

compositions with traditional fixed bed, mesoporous ceramic membrane and palladium 

membrane reactors. With the palladium membrane, it is possible to reach higher conversions 

than the equilibrium values. For example, the CO conversion for reformate composition (12% 

CO, 12% CO2, 75% H2, and 1% CH4) at 595 K is about 51% (about 2% higher than equilibrium 

value). 

However, the applications of membrane reactor in fuel reforming are limited by the quality of the 

reactant stream available [56]. The influences of CO [35,57], sulfur [58,59] and steam [57] on 

permeability have been studied. Note that CO, H2S, and steam are usually present in the 

reformate from diesel or JP-8 reformer. The effect of CO on permeability is flow rate dependent. 

The presence of steam has a pronounced effect on the hydrogen permeability [57]. 

3.3 Preferential Oxidation 

A typical gas stream following the water-gas shift reaction still contains about 1.0% CO, which 

is still too high for the low temperature PEM fuel cell. Therefore, preferential oxidation (PROX) 

is performed to reduce the CO in the feed to 10 ppm or less. However, hydrogen oxidation 

competes with CO oxidation: 

 H2 + 0.5 O2 → H2O ∆H = –242 kJ/mol (6) 

 CO + 0.5 O2 → CO2 ∆H = –283 kJ/mol (7) 

Since the enthalpies of these reactions are highly exothermic, heat removal from the reactor is 

important. In order to reduce CO concentration and to minimize the undesirable hydrogen 

oxidation, highly selective (preferential oxidation) catalysts are necessary. Since CO adsorbs 

more strongly to the Pt surface than hydrogen does, this fact can be used for selective oxidation. 

Low Pt loading on γ-alumina is commonly used because of its low tendency for hot spots [32]. 

Preferential oxidation reactors may be either adiabatic or isothermal [60]. The characteristics of 

these reactors are compared in Table 4. 
9

Table 4. Comparison of adiabatic and isothermal PROX reactors 

 Adiabatic Isothermal 

Temperature of Catalyst Allowed to rise during CO oxidation. Maintained constant during CO 

oxidation. 

Number of Stages A number of sequential stages 

progressively reduce the CO content. 

One or two stages. 

Concern of Reverse 

Water-Gas Shift (RWGS) 

Temperature control is important to 

prevent RWGS which forms more 

CO. 

No concern on this issue. 

Noble metal-based catalysts are the most common PROX catalysts. For example, Engelhard has 

started commercializing a highly selective Pt containing catalyst (Selectroxo5

) for H2 production 

plants in 1960s. During steady state conditions (50 oC, 10,000 h–1 and 200 to 400 psig), the 

present catalyst reduces the CO level from 1% to less than 5 ppm [61]. Although the PROX 

catalyst is well developed in industrial scale, a new catalyst needs to be developed for fuel cell 

applications. Ambient pressure, low temperature, and small residence time (i.e., fast space 

velocity) are preferred in fuel cell applications. Smaller residence time corresponds to more 

compact PROX reactor. 

Engelhard has recently developed an iron oxide promoted Pt(5%)/γ-alumina catalyst for 

preferential oxidation of CO [61,62]. The promoted Pt catalyst on the monolith reduces the CO 

level (1000 ppm inlet CO) with 90% conversion and 65% selectivity at 90 o

C and 120,000h–1. 

The results also indicate that iron oxide changes the electronic properties of Pt metal particles. 

The iron oxide also creates a dual site non-competitive mechanism for CO oxidation [62]. 

In a previous study, Watanabe et al. have shown that 6% Pt-supported zeolite can oxidize CO 

much more selectively in 78% to 98% hydrogen than can a conventional Pt-supported alumina 

catalyst [63]. With 0.5% O2 and 1% CO, the selectivity is affected by type of zeolite supports, in 

the order A type zeolite (88%) > mordenite (84%) > X type zeolite (64%)> alumina (41%). 

Watanabe et al. have designed a two-stage Pt-mordenite PROX reactor that uses 0.7% oxygen to 

remove 1% CO with a loss of 0.4% H2. 

In contrast to aforementioned studies [61,62,63], Gulari et al. [64], and General Motors [60] have 

tested the PROX catalysts using a realistic reformate composition with the presence of both CO2

and H2O. Gulari et al. argue that a realistic composition of reformate from water-gas shift reactor 

contains CO2, CO, H2, and H2O, and all these species tie together by the (reverse) water-gas shift 

reaction [64]. Gulari et al. have shown that a 2% Pt/alumina sol-gel catalyst can selectively 

oxidize CO to less than 5 ppm. Gulari et al. results also indicate that CO2 in the feed retards the 

CO oxidation, but water in the reformate promotes the CO oxidation. More importantly, Gulari 

et al. have shown that the combination of 20% CO2 and 10% water in the reformate increases the 

 5

 Selectroxo is a trademark of a PROX catalyst from Engelhard. 
10

CO conversion. Some of their results are summarized in Table 5. Based on the results in Table 5, 

Gulari et al. have proposed an optimal design for a PROX reactor that removes more than 0.5% 

CO. Their proposed design has several stages with an injection port for air or oxygen at each 

stage. 

Table 5. Key performance results of a 2% Pt/alumina sol-gel catalyst during PROX reaction with 

 realistic post-water-gas shift reformate compositions [64] 

 Case I Case II 

Feed Composition 1% CO, 20% CO2, 60% H2, 10% 

H2O and He as balance 

0.5% CO, 20% CO2, 60% H2, 

10% H2O and He as balance 

O2-to-CO ratio 1 1 

Optimal Temperature 160 oC 140 to 150 oC 

Conversion 99% 100% (sensitivity of 5 ppm) 

Selectivity 48% 50% 

Investigators at General Motors have developed an iridium-based catalyst to oxidize CO 

selectively in hydrogen-rich feed gas [60]. About 2% iridium is dispersed on a refractory oxide 

washcoat such as alumina. Then a mixture of methanol and hydrogen activates the catalyst. An 

activation method is developed to lower the binding energy and oxidation state of the iridium. At 

a temperature of about 230 oC and O2-to-CO of 2 (excess O2), 0.55% CO was decreased to 

10 ppm. The residence time is on the order of 50 milliseconds, which is much smaller than 

360 milliseconds (corresponds to 10,000 h–1) in industrial scale. 

4. Putting Them Together 

The integration of reforming reaction and water-gas shift reaction in a methanol reformer 

eliminates the need for a separate water-gas reactor. This simplifies the process flow sheet and 

potentially improves the dynamic response of the system (see Figure 2). 
11

A) 

B) 

Figure 2. Conceptual block diagrams for fuel processing: A) A conventional fuel processing for diesel or JP-8, 

 and B) Fuel processing for methanol. 

Development of the integration of a fuel cell and fuel processor into a complete functional unit is 

very active [26,29,65]. As aforementioned, DaimlerChrysler, Ballard, and XCELLSiS have 

jointly developed the NECAR 5 by using a compact size methanol reformer underneath the seats. 

This 75-kW fuel processor (ME 75-5) consists of three integrated components [65]: 1) vaporizer 

and superheater in a combined catalytic burner/vaporizer, 2) a combined reformer and 

preferential oxidation reactor, and 3) a novel reactor allowing exothermic, autothermal, and 

endothermic operations. All these components operate around 250 to 300 o

C. 

One of the major technical challenges is the dynamic or transient response of the system. When 

there is a load change in power usage, the fuel processor has to respond appropriately to maintain 

a low level of CO. In other words, CO spikes should be prevented. For instance, the fuel flow 

rate will be slow until the power usage decreases. The gas compositions of the reformate feeding 

into the PEM fuel cell will change dramatically unless (1) the system is properly controlled, (2) 

the reactor is designed appropriately as well as (3) the catalyst composition in each unit is 

optimized for different feed compositions. At a very low output (<10% of maximum), the use of 

a low fuel feed rate to the reactor can result in methanol slip and above average CO 

concentration [8]. Vandeborgh, Springer, and Huff at Los Alamos National Laboratory, NM, 

have described a recycle steam reforming reactor to achieve quick start and to address the 

transient operation [66]. 

The modular feature of Johnson Matthey HotSpot fuel processor described earlier can provide an 

extra control option during transient operation [8]. The hydrogen output can be increased or 

decreased by the use of more or fewer active reactors, instead of increasing or decreasing the 

reactant feed rates. 

Ford researchers have proposed using metal hydride bed as a load-leveling device and gaseous 

hydrogen supply for start [67,68]. One of the designs includes a single metal hydride bed and 

Reformer

PEM 

Fuel Cell 

PROX 

Reactor 

Fuel 

Reformer

SulfurRemoval 

 Bed

WGS 

Reactor 

PEM 

Fuel Cell 

PROX 

Reactor 

Fuel 
12

two hydrogen purification units in series [67]. The metal hydride bed stores hydrogen at high 

hydrogen concentration while the bed discharges hydrogen at low hydrogen concentration. Each 

hydrogen purification unit consists of a highly selective membrane that preferentially passes 

hydrogen molecules. The first hydrogen purification unit receives a supply of high pressure 

reformate, and the permeated portion supplies hydrogen to the metal hydride bed. The nonpermeated portion enters the second hydrogen purification unit. The fuel cell receives hydrogen 

from both the second purification unit and the metal hydride bed in a parallel fashion. 

In another study, a fuel cell drive system was constructed by the integration of a 16-kW catalytic 

burner, a 50-kW methanol reformer, and a PEM fuel cell [67]. The performance and dynamic 

behavior were tested. Stationary performance shows hydrogen production of 6.7 m3

/(kgcat h) with 

95% methanol conversion at 280 oC. Several peak load storage systems were also compared. A 

gas storage system was selected and integrated in the system. The transient behavior was 

measured, and the response time for reaching 99% hydrogen demand was about 20 s. 

Since methanol is usually not steam reformed completely, unreacted methanol is undesirably fed 

to the anode side of PEM fuel cell operating at low temperature. For this reason, the starting 

voltage is greatly reduced. Okamoto at Honda [70] has suggested that either the unreacted 

methanol is selectively oxidized via a noble catalyst, or the unreacted methanol is oxidized 

together with carbon monoxide. He also proposed that the unreacted methanol can be condensed 

and then be returned to the methanol tank. 

Thermal management is another challenge in system integration. General Motors has thermally 

integrated a two-stage methanol reformer [71]. The stream from the first stage reformer acts as 

the heat transfer medium, which carries heat from the heat exchanger into the reactors. The heat 

exchanger and two reactors are co-located in a common housing. In another study, Daimler-Benz 

(now DaimlerChrysler) assembled a three-stage fuel processor with thermal coupling [72]. 

CuO/ZnO/Al2O3 pellets are packed inside all three stages of the steam reformer. The center stage 

is heated externally to 280 to 350 o

C but the inlet stage and the outlet stage are not. The inlet 

stage and the outlet stage are divided by a highly heat-conducting but gas-tight wall. This design 

has three main advantages for transient response during load changes. First, temperature 

fluctuations in center reactor stage are dampened because of heating capacity of the outlet-side 

stage. Second, the fluctuations of CO content in the reformate are also reduced. Third, a selfregulating heat transfer is implemented because of thermal coupling of the inlet side with the 

outlet side. 

5. Challenges for Using Diesel or JP-8 as Fuel 

Unlike methanol, diesel and jet fuels consist of numerous components. These fuels, which are 

obtained by petroleum refinery of crude oil, have many grades with different properties. Selected 

chemical and physical properties of methanol, JP-8, and diesel are summarized in Appendix A. 

Diesel or JP-8 reforming requires a higher temperature (usually about 1000 o

C) than methanol 

reforming (200 to 300 oC). Higher temperature favors hydrogen production, but it also enhances 

catalyst deactivation (through thermal sintering of catalyst) and formation of carbonaceous 

species. Higher temperature also requires better thermal management strategies such as a 
13

sophisticated integration of heat exchanger network and/or novel insulation materials so that the 

fuel processor can be built compact enough for portable and mobile applications. This report 

focuses on two main challenges using logistic fuel reformers to generate hydrogen for PEM fuel 

cells: 1) carbon management, and 2) development of sulfur-tolerant catalysts. Figure 3 shows the 

conversion pathways of carbon- and sulfur-containing compounds during fuel processing. We 

emphasize that all these carbon-containing species from the reformer originate from the reaction 

and are not generally impurities. Meanwhile, the sulfur species come from the impurities, such as 

benzothiophenes (BT) and dibenzothiophenes (DBT), in the refinery products after 

hydrodesulfurization (HDS). 

CxHy C CO2

CO 

 CO2

CO 

 CO2

DBT, 

BT 

 H2S ZnS 

Figure 3. Carbon and sulfur balances for JP-8 or diesel fuel processing. 

5.1 Carbon Management 

Carbon management involves minimization of carbonaceous species accumulation, as well as 

optimization and removal of carbon-containing gaseous species. After reforming, the 

hydrocarbons in diesel fuel or JP-8 can become CO, CO2, CH4, coke, and soot. 

The CO, CO2, and CH4 management is similar to methanol reforming, which has been discussed 

earlier. The main difference is the level of CO concentration. Brown at Los Alamos National 

Laboratory has compared methanol, JP-8, and diesel for the utility as hydrogen source [73]. 

Thermodynamic calculations indicate that high temperature produces a large amount of CO. The 

equilibrium CO level from diesel or JP-8 reformer can be as high as 25%, which is much higher 

than 0.8% CO from methanol reformer [73]. Experimental results show that diesel steam 

reforming gives 16% CO in the reformate [74]. Therefore, separate water-gas shift reactors are 

required. The issue here is about the fuel-reforming thermodynamics that control the proportion 

of these gases. The level of CO needs to be minimized without forming too much CH4 so that the 

CO removal process is simplified. Recall that the CO tolerance level for anode catalyst in low 

temperature PEM fuel cell is about 10 ppm. The common strategy is to optimize the operating 

conditions such as space velocity, steam-to-C ratio and air-to-C ratio. 

Reformer

SulfurRemoval 

Bed

CO-Removal 

Subunits 

Fuel Cell Fuel 
14

Carbon formation, including formations of coke and soot, can arise from the thermal cracking of 

hydrocarbons (pyrolysis) or can be promoted by a catalyst [75]. Coke that deposits on the 

catalyst will deactivate the catalyst. Carbon deposition on the wall of the reactor affects the 

reactor performance by limiting heat transfer and ultimately blocking the flow. During start, 

autothermal reformers produce soot particles. Soot (smoke) prevention is an important practical 

issue for Army applications. Soldiers do not like to lose their camouflage because of smoke. 

When diesel contacts a hot surface in the reformer, it has tendency to form coke. Non-ideal 

mixing of fuel with the air and the steam also enhances coke formation, and fuel injection 

through an atomizer is often used to avoid this problem. The formation of solid carbon has been 

investigated from a thermodynamic point of view [29]. Formations of coke and soot depend on 

the ratio of carbon and hydrogen in the fuel, air-to-carbon ratio, steam-to-carbon ratio. Docter 

and Lamm at Daimler-Benz performed thermodynamic calculations to find the optimal operating 

conditions for gasoline reformers. Their results indicate that a high steam-to-carbon ratio shifts 

the coking boundary to a lower air-to-carbon ratio. 

Trimm [75] has also reviewed various approaches to minimize coke accumulation. The coke 

accumulation is a balance between coke formation and coke gasification. The first approach is 

the ensemble size control. It is believed that the ensemble size of surface sites for coke formation 

is larger than that for steam reforming. Therefore, controlling the ensemble size can minimize 

polymerization of monatomic carbon species. This can be done by adsorption of a trace amount 

(ppm level) of sulfur. For example, an H2S-to-H2 ratio that is greater than 7.5×10–7 was sufficient 

to control the coke formation. The second approach is to prevent the carbide formation by the 

addition of small amount of dopants. For example, 0.5% tin to nickel reduces coke formation 

significantly while steam reforming is not affected. The third approach is to accelerate the coke 

gasification. On a nickel steam-reforming catalyst, coke forms when carbon fibers (whiskers) 

grow with a nickel crystal at the top. When noble metals are used, the whisker growth 

mechanism is blocked simply because carbon is not dissolved [76]. Excess steam is usually fed 

into the steam reformer to enhance gasification. In industries, Topsøe uses magnesia as catalyst 

support materials because magnesia enhances the adsorption of steam. Adding rare earth oxides 

such as ceria to the support materials also appears to favor coke gasification. 

5.2 Sulfur Management 

Unlike methanol, diesel and JP-8 are mixtures of many organic compounds including sulfurcontaining compounds. Sulfur in fuel poisons and deactivates the reforming catalysts [77]. 

Typically, catalytic steam reforming of hydrocarbon is achieved by a nickel catalyst. But nickel 

catalysts are very sensitive to sulfur-containing compounds. Therefore, the fuel is usually prereformed to reduce sulfur to less than 1 ppm. An alternative is to allow the nickel catalyst to be 

poisoned, but the reformer operates at a higher temperature and with a larger volume of catalysts. 

Another choice is to use more expensive noble metal such as platinum, palladium, or rhodium 

instead of nickel. These noble metal catalysts are better than nickel, but sulfur poisoning is still 

an issue. 
15

During reforming, these sulfur compounds are converted to mainly H2S and possibly COS, 

which are commonly removed by a ZnO scrubber. 

 H2S + ZnO → ZnS + H2O (8) 

Equation (8) explains why Cu/ZnO/Al2O3 methanol reforming catalyst cannot be a good catalyst 

for diesel or JP-8 reforming. However, the reducibility or regenerative ability of ZnO above 

400 o

C has been a major issue for this adsorbent. Therefore, Cu-containing cerium oxide has 

been examined as an alternative [78]. 

It is noteworthy that H2S is an irreversible poison for Pd membrane separator and fuel cell. The 

use of membranes in enhancing H2 production from diesel or JP-8 is limited by the quality of the 

reactant stream. Several recent reviews indicate that the reactants containing CO and H2S or 

aromatics are “unacceptable” because of their tendency to poison Pd surfaces [79]. In a previous 

study [58], the effect of carbon or sulfur on the permeation rate of hydrogen through a palladium 

membrane was investigated. These impurity atoms block the surface adsorption site of hydrogen. 

It has been determined that the permeation rates of hydrogen vary by a factor of ~104

 as sulfur or 

carbon coverage increases from 0.06 to 0.65 at 625 K. 

In another study [20], the Ru/CeO2-Al2O3 catalyst shows high sulfur resistance during steam 

reforming of kerosene (C10H22). JP-8 is a kerosene-type aviation turbine fuel. The addition of 

CeO2 to Ru/Al2O3 increases the sulfur tolerance from 0.1 to 50 wt ppm of sulfur. Both Ru/Al2O3

and Ru/CeO2-Al2O3 start with 100% conversion of kerosene (with 50 wt ppm sulfur) at 800 o

C 

and steam/carbon = 3.5. After 25 hours, the conversion using Ru/Al2O3 decreases to 60% while 

the conversion using Ru/CeO2-Al2O3 was 66%. 

The sulfur content and sulfur-containing components of crude oil depend on the geographic 

location of the oil field. Some crude oils are more “sour” than others. As a result, sulfur contents 

in fuel products are also different [80]. 

Table 6. Selected qualities of low-sulfur crude [80] 

Crude Oil (Region) Crude Sulfur (wt%) Sulfur in middle distillates, 175 

to 350 o

C (wt%) 

Arab Light (Middle East) 1.9 0.9 

Bonny Medium (West Africa) 0.2 0.1 

Brega (North Africa) 0.2 0.1 

Minas (Far East) 0.1 0.0 

Government regulations often dictate sulfur content in diesel products [81,82]. In the European 

Union, the sulfur content is limited to 350 wt ppm today and will be lowered to 50 wt ppm by 

2005 [77,81]. In America, the current sulfur content limit is 500 wt ppm [83], and the 

Evironmental Protection Agency target by mid 2006 is 15 wt ppm. The specifications for sulfur 

content in jet fuels are given by military specifications MIL-DTL-5624 and MIL-DTL-83133E. 
16

Hydrodesulfurization (HDS) reduces the sulfur content in the crude oil to the acceptable level in 

diesel products. The remaining sulfur compounds are usually alkylbenzothiophenes (alkyl BT) 

and alkyldibenzothiophenes (alkyl DBT) (see Figure 4) because they are the most difficult sulfur 

compounds to be removed [84,85]. 

 Benzothiophene (BT) Dibenzothiophene (DBT) 

Figure 4. Families of sulfur compounds in the JP-8 and diesel fuel. 

For example, sulfur-containing compounds in D-2 diesel from America are present as 33 to 35 

wt% BT and 65 to 67 wt% DBT [86]. The weight percent of sulfur-containing compounds and 

the proportion of BT and DBT in diesel products depend on the origin of the crude and the 

refinery processes. If the Army fuel processor is robust enough to tolerate the sulfur-containing 

compounds in diesel fuels from global wartime suppliers, the logistic burden for fuel supply 

during wars will be improved. 

6. State-of-the-Art JP-8 and Diesel Reformers 

Jet fuel reformation for fuel cell system has been the subject of investigation as early as 1960’s 

[87]. The steam reformer with 25 cm3 of catalyst was tested on stream for 28 hours. A high 

steam-to-hydrocarbon ratio (>5) was used to avoid coking. At 972 o

F (522 oC), JP-4 with 80 ppm 

of sulfur was steam reformed to 65% hydrogen in product gas. However, there is no information 

regarding the nature of the catalyst. 

In a recent patent assigned to Allied Signal, a catalytic partial oxidation reformer was developed 

for JP-8 [88]. With the method of incipient wetness, 5 to 30 wt% rhodium is supported on the 

100 mg of alumina monolith support. The finished catalyst was held in a 0.5-inch quartz tube and 

was tested for partial oxidation reforming of heavy hydrocarbons. Some of the operating 

conditions and results are summarized in Table 7. 

In another patent, steam reforming reformer was developed for diesel and JP-8 [74]. The catalyst 

extrudates (1/16 inch outer diameter, 4 cm long) consist of three components: 

• active catalyst phase such as Ag, Co, Cu, Fe, Pd, Pt, V 

• promoter such as Bi2O3, CaO, La2O3, MgO, Pr6O11, and 

• support such as CeO2, Mullite, ZrO2. 

S S
17

Table 7. The reformer is robust to fluctuating sulfur content in the hydrocarbon feed stream [88] 

Hydrocarbon feed JP-8 without alternation JP-8 with addition of 1000 ppm 

dibenzothiophene 

Loading of Rh (wt%) 21 25 

C/O ratio 0.8 0.8 

Catalytic Temperature (oC) 1150 1220 

Contact Time (ms) 100 100 

Hydrogen gas yield(%) 80-85 70 

Carbon monoxide gas yield (%) 90-93 70-80 

Run time for stable Operation 

(hrs) 

500 300 

The packed bed reactor with these extrudates has been tested with JP-8 jet fuel and DF-2 diesel 

fuel. There is a temperature gradient along the catalyst bed. During the operating conditions 

shown in Table 8, the catalyst is sulfur tolerant and exhibits stable performance until 500 hours 

(for JP-8) without coking. Complete conversions of both fuels are observed. The composition of 

the product gas (dry basis) from the diesel steam reformer is 63% H2, 20% CO2, 16% CO, and 

1% CH4. The residence time of 1 to 2 seconds implies that the reformer size is quite large. 

Table 8. Testing of sulfur-tolerant catalysts for diesel and 

 JP-8 steam reforming [74] 

Hydrocarbon feed DF-2 JP-8 

Fuel flow rate (ml/hr) 6.1 6.8 

H2O/C ratio 3.8 4.7 

Residence Time (ms) 1654 1182 

Inlet catalyst temperature (oC) 370 360 

Outlet catalyst temperature(oC) 1000 1000 

Run time (hrs) 276 504 

7. Conclusion 

Fuel reformer can generate hydrogen from methanol, JP-8, and diesel. Since the PEM fuel cell 

anode catalyst has low CO tolerance (10 ppm), the reformate from the fuel reformer is fed into 

CO removal units before PEM fuel cell. At this moment, the development of a methanol fuel 

processor is more advanced than that of JP-8 or diesel. This report has provided examples that 

show that methanol fuel processor can be combined with PEM fuel cell to generate power (1 W 

to 75 kW) for Army applications. Although the reforming catalysts and the operation parameters 

will be different for different feedstock, the concepts and the general principles of processing 

different fuels are very similar in many aspects. The principles of fuel reforming, the applications 

of thermodynamics as guidance, the options for carbon monoxide removal, the ideas of reactor 

design and enlargement, as well as the system integration strategies for start and transient 

response are usually fuel independent. Therefore, the experience gained during the development 

of methanol fuel processors is very helpful for the development of diesel and JP-8 fuel 

processors. However, the chemical nature of JP-8 or diesel is significantly different from that of 
18

methanol. This difference poses additional challenges. Carbon and sulfur managements have to 

be addressed to advance the technology of JP-8 and diesel fuel processors for Army applications. 

In addition, better CO removal strategy is necessary because logistic fuel reformers produce 

reformate gases containing high CO concentration. 
19

8. References 

1. Chu, D., Jiang, R., Gardner, K., Jacobs, R., Schmidt, J., Quakenbush, T. and Stephens, J., 

“Polymer Electrolyte Membrane Fuel Cells for Communication Applications,” J. Power 

Sources 96 (2001) 174. 

2. Walker, C. W. Jr., Jiang, R. and Chu, D., “An Overview of Hydrogen Generation and 

Storage for Low-Temperature PEM Fuel Cells,” ARL-TR-2091, Army Research Laboratory 

(1999). 

3. Farrauto, R. J. and Bartholomew, C. H., Fundamentals of Industrial Catalytic Processes, 

Blackie Academic and Professional, London (1997). 

4. Twigg, M. V. (Ed.) Catalyst Handbook, 2nd Edition, Wolf Publishing, London (1989). 

5. Gates, B. C., Katzer, J. R. and Schuit, G. C. A., Chemistry of Catalytic Processes, McGrawHill, New York (1979). 

6. Geissler, K, Newson, E., Vogel, F., Truong, T., Hottinger, P. and Wokaun, A., “Autothermal 

Methanol Reforming for Hydrogen Production in Fuel Cell Applications,” Phys. Chem. 

Chem. Phys. 3 (2001) 289. 

7. Agrell, J., Birgersson, H. and Boutonnet, M., “Steam Reforming of Methanol over a 

Cu/ZnO/Al2O3 Catalyst: A Kinetic Analysis and Strategies for Suppression of CO 

Formation,” J. Power Sources 106 (2002) 249. 

8. Edwards, N., Ellis, S. R., Frost, J. C., Golunski, S. E., van Keulen, A. N. J., Lindewald, N. G. 

and Reinkingh, J. G., “On-Board Hydrogen Generation for Transport Applications: the 

HotSpotTM Methanol Processor,” J. Power Sources 71 (1998) 123. 

9. Lindström, B. and Pettersson, L, “Hydrogen Generation by Steam Reforming of Methanol 

over Copper-Based Catalysts for Fuel Cell Applications,” Int. J. Hydrogen Energy 26 (2001) 

923. 

10. Peppley, B. A., Amphlett, J. C., Kearns, L. M. and Mann, R. F., “Methanol-Steam 

Reforming on Cu/ZnO/Al2O3 Catalysts. Part 1: The Reaction Network,” Applied Catalysis 

A: General 179 (1999) 21. 

11. Peppley, B. A., Amphlett, J. C., Kearns, L. M. and Mann, R. F., “Methanol-Steam 

Reforming on Cu/ZnO/Al2O3 Catalysts. Part 2. A Comprehensive Kinetic Model,” Applied 

Catalysis A: General 179 (1999) 31. 

12. Alejo, L., Lago, R., Pena, M. A. and Fierro, J. L. G., “Partial Oxidation of Methanol to 

Produce Hydrogen over Cu-Zn-Based Catalysts,” Applied Catalysis A: General 162 (1997) 

281. 

13. Cubeiro, M. L. and Fierro, J. L. G., “Partial oxidation of Methanol over Supported Palladium 

Catalyst,” Applied Catalysis A: General 168 (1998) 307. 
20

14. Velu, S., Suzuki, K. and Osaki, T., “Selective Production of Hydrogen by Partial Oxidation 

of Methanol over Catalysts Derived from CuZnAl-Layered Double Hydroxides,” Catalysis 

Letters 62 (1999) 159. 

15. Agrell, J., Hasselbo, K., Jansson, K., Jaras, S. G. and Boutonnet, M., “Production of 

Hydrogen by Partial Oxidation of Methanol over Cu/ZnO Catalysts Prepared by 

Microemulsion Technique,” Applied Catalysis A: General 211 (2001) 239. 

16. Asprey, S. P., Wojciechowski, B. W. and Peppley, B. A., “Kinetic Studies using 

Temperature-Scanning: The Steam-Reforming of Methanol,” Applied Catalysis A: General

179 (1999) 51. 

17. Krumpelt, M, Kumar, R. And Myles, K. M., “Fundamentals of Fuel Cell System 

Integration,” J. Power Sources 49 (1994) 37. 

18. Choudhary, T. V., Sivadinarayana, C. and Goodman, D. W., “Catalytic Ammonia 

Decomposition: COx-Free Hydrogen Production for Fuel Cell Applications,” Catalysis 

Letters 72 (2001) 197. 

19. Rampe, T., Heinzel, A. And Vogel, B., “Hydrogen Generation from Biogenic and Fossil 

Fuels by Autothermal Reforming,” J. Power Sources 86 (2000) 536. 

20. Suzuki, T., Iwanami, H. and Yoshinari, T., “Steam Reforming of Kerosene on Ru/Al2O3 

Catalyst to Yield Hydrogen,” International Journal of Hydrogen Energy 25 (2000) 119. 

21. Amhlett, J. C., Mann, R. F., Peppley, B. A., Roberge, P. R., Rodrigues, A. And Salvador, J. 

P., “Simulation of a 250kW Diesel Fuel Processor/ PEM Fuel Cell System,” J. Power 

Sources 71 (1998) 179. 

22. Voss, H. and Huff, J., “Portable Fuel Cell Power Generator,” J. Power Sources 65 (1997) 

155. 

23. Palo, D. P., Holladay, J. D., Rozmiarek, R. T., Guzman-Leong, C. E., Wang, Y., Hu, J., 

Chin, Y-H., Dagle, R. A. and Baker E. G., “Development of a Soldier-Portable Fuel Cell 

Power System Part I: A Bread-Board Methanol Fuel Processor,” J. Power Sources 108 

(2002)28. 

24. Wohlwend, K., Maurice, L. Q. and Edwards, T., “Thermal Stability of Energetic 

Hydrocarbon Fuels for Use in Combined Cycle Engines,” J. Propulsion and Power 17 

(2001) 1258. 

25. Baumert, R. M., Epp, D. G. and Peters, E. J., “Radial Flow Fuel Processor,” US Patent 

5,676,911 (1997). 

26. Rogers, S., Gervasio, D., Koripella, R., Samms, S., and Tasic, S., “Multi-Layered Ceramic 

Fuel Cell System Based on Steam Reforming Methanol to H2-Enriched Gas,” Proc. 40th

Power Sources Conference (2002) 269. 

27. Ahmed, S. and Krumpelt, M., “Hydrogen from Hydrocarbon Fuels for Fuel Cells,” 

International Journal of Hydrogen Energy 26 (2001) 291. 
21

28. Edwards, N, Frost, J. S., Jones, A. and Pignon, J. F., “Self-Sustaining Hydrogen Generator,” 

US Patent 5,762,658 (1998). 

29. Docter, A. and Lamm, A., “Gasoline Fuel Cell Systems,” J. Power Sources 84 (1999) 194. 

30. Clawson, L. G., Mitchell, W. L., Bentley, J. M. B. and Thijssen, J. H. J., “Method and 

Apparatus for Converting Hydrocarbon Fuel into Hydrogen Gas and Carbon Dioxide,” US 

Patent 6,126,908 (2000). 

31. Farrauto, R. et al. AIChE Spring conference, New Orleans (2002). 

32. Pettersson, L. J. and Westerholm, R., “State of the Art of Multi-fuel Reformers for Fuel Cell 

Vehicles: Problem Identification and Research Needs,” Int. J. of Hydrogen Energy 26 (2001) 

243. 

33. Schuessler, M., Lamla, O., Stefanovski, T., Klein, C. and zur Megede, D., “Autothermal 

Reforming of Methanol in a Isothermal Reactor-Concept and Realisation,” Chem. Eng. 

Technol. 24 (2001) 11. 

34. Buxbaum, R. B., “Membrane Reactor Advantages for Methanol and Similar Reactions,” 

Separation Science and Technology 34 (1999) 2113. 

35. Wieland, S., Melin, S. and Lamm, A., “Membrane Reactors for Hydrogen Production,” 

Chemical Engineering Science 57 (2002) 1571. 

36. Zalc, J. M., Sokolovskii, V. and Loffler, D. G., “Are Noble Metal-Based Water-Gas Shift 

Catalysts Practical for Automotive Fuel Processing?” J. Catalysis 206 (2002) 169. 

37. Heck, R. M. and Farrauto, Catalytic Air Pollution Control: Commercial Technology, 2nd

Edition Wiley, New York (2002). 

38. Twigg, M. V. and Spencer, M. S., “Deactivation of Supported Copper Metal Catalysts for 

Hydrogenation Reactions,” Applied Catalysis A: General 212 (2001) 161. 

39. http://www.fuelcellmaterials.com/water_gas_shift_catalysts.htm, viewed on 7/26/02. 

40. Bunluesin, T., Gorte, R. J., Graham, G. W., “Studies of the Water-Gas-Shift Reaction on 

Ceria-Supported Pt, Pd, and Rh: Implications for Oxygen-Storage Properties,” Applied 

Catalysis B: Environmental 15 (1998) 107. 

41. Hilaire, S., Wang, X., Luo, T., Gorte, R. J. and Wagner, J., “A Comparative Study of WaterGas-Shift Reaction over Ceria Supported Metallic Catalysts,” Applied Catalysis A: General

215 (2001) 271. 

42. Li, Y., Fu, Q. and Flytzani-Stephanopoulos, M., “Low-Temperature Water-Gas Shift 

Reaction over Cu- and Ni-loaded Cerium Oxide Catalysts,” Applied Catalysis B: 

Environmental 27 (2000) 179. 

43. Low-Temperature Water-Gas Shift,” Catalysis Letters 77 (2001) 87. 

44. Andreeva, D., Idakiev, V., Tabakova, T., Ilieva, L., Falaras, P., Bourlinos, A., Travlos, A., 

“Low Temperature Water-Gas Shift Reaction over Au/CeO2 Catalysts,” Catalysis Today 72 

(2002) 51. 
22

45. Bond, G. C. and Thompson, D. T., “Catalysis by Gold,” Catal. Rev. – Sci. Eng. 41 (1999) 

319. 

46. Tabakova, T., Idakiev, V., Andreeva, D. and Mitov, I., “Influence of the Microscopic 

Properties of the Support on the Catalytic Activity of Au/ZnO, Au/ZrO2, Au/Fe2O3, 

Au/Fe2O3-ZnO, Au/Fe2O3-ZrO2 Catalysts for the WGS Reaction,” Applied Catalysis A: 

General 202 (2000) 91. 

47. Boccuzzi, F., Chiorino, A., Manzoli, M., Andreeva, D., Tabakova, T., Ilieva, L. and 

Iadakiev, V., “Gold, Silver and Copper Catalysts Supported on TiO2 for Pure Hydrogen 

Production,” Catalysis Today 75 (2002) 169. 

48. Sanchez, J. G. and Tsotsis, T. T., Catalytic Membranes & Catalytic Membrane Reactors, 

VCH Verlagsgesellschaft Mbh, (2002). 

49. Shu, J., Grandjean, B. P. A., Vanneste, A. and Kaliaguine, S., “Catalytic Palladium-Based 

Membrane Reactors-A Review,” Canadian Journal of Chemical Engineering 69 (1991) 

1036 

50. Coronas, J. and Santamaria, J., “Catalytic Reactors Based on Porous Membranes,” Catal. 

Today 25 (1999) 377. 

51. Julbe, A., Farrusseng, D., Guizard, C., “Porous Ceramic Membranes for Catalytic Reactors - 

Overview and New Ideas,” J. Membrane Science 181 (2001) 3. 

52. Armor, J. N., “Applications of Catalytic Inorganic Membrane Reactors to Refinery 

Products,” J. Membrane Science 147 (1998) 217. 

53. Edlund, D. J., Newbold, D. D. and Frost, C. B., “Composite Hydrogen Separation Element 

and Module,” US Patent 5,645,626 (1997). 

54. Buxbaum, R. E., “Composite Metal Membrane for Hydrogen Extraction,” US Patent 

5,215,729 (1993). 

55. Criscuoli, A., Basile, A. and Drioli, E., “An Analysis of the Performance of Membrane 

Reactors for the Water-Gas Shift Reaction using Gas Feed Mixtures,” Catalysis Today 56 

(2000) 53. 

56. Armor, J. N., “The Multiple Roles for Catalysis in the Production of H2,” Applied Catalysis 

A: General 176 (1999) 159. 

57. Li, A., Liang, W. and Hughes, R., “The Effect of Carbon Monoxide and Steam on the 

Hydrogen Permeability of a Pd/Stainless Steel Membrane,” J. Membrane Science 165 (2000) 

135. 

58. Antoniazzi, A. B., Haasz, A. A. and Stangeby, P. C., “The Effect of Adsorbed Carbon and 

Sulfur on Hydrogen Permeation through Palladium,” J. Nuclear Materials 162 (1989) 1065. 

59. Peden, C. H., Kay, B. D. and Goodman, D. W., “Kinetics of Hydrogen Adsorption by 

Chemically Modified Pd(110),” Surface Science 175 (1986) 215. 

60. Borup, R. L., Skala, G. w., Brundage, M. A. and LaBarge, W. J., “Method and Apparatus for 

Selective Removal of Carbon Monoxide,” US Patent 6,162,558 (2000). 
23

61. Korotkikh, O. and Farrauto, R., “Selective Catalytic Oxidation of CO in H2: Fuel Cell 

Applications,” Catalysis Today 62 (2000) 249. 

62. Liu, X., Korotkikh, O. and Farrauto, R., “Selective Catalytic Oxidation of CO in H2: 

Structural Study of Fe Oxide-Promoted Pt/Alumina Catalyst,” Applied Catalysis A: General

226 (2002) 293. 

63. Igarashi, H., Uchida, H., Suzuki, M., Sasaki, Y. and Watanabe, M., “Removal of Carbon 

Monoxide from Hydrogen-Rich Fuels by Selective Oxidation over Platinum Catalyst 

Supported on Zeolite,” Applied Catalysis A: General 159 (1997) 159. 

64. Manasilp, A. and Gulari, E., “Selective CO oxidation over Pt/Alumina Catalysts for Fuel 

Cell Applications,” Applied Catalysis B: Environmental 37 (2002) 17. 

65. zur Megede, D., “Fuel Processors for Fuel Cell Vehicles,” J. Power Sources 106 (2002) 35. 

66. Vanderborgh, N. E., Springer, T. E. and Huff, J. R., “Fuel Processor for Fuel-Cell Power 

System,” US Patent 4,650,727 (1987). 

67. James, B. D., “Fuel Reformer System for a Fuel Cell,” US Patent 6,329,091 (2001). 

68. Lomax, F. D. and Ijaz, M. I., “Fuel Cell Power Generation System and Method for Powering 

an Electric Vehicle,” US Patent 6,368,735 (2002). 

69. Emonts, B., Bogild Hansen, J., Schmidt, H., Grube, T., Hohlein, B., Peters, R. and 

Tschauder, A., “Fuel Cell Drive System with Hydrogen Generation in Test,” J. Power 

Sources 86 (2000) 228. 

70. Okamoto, T., “Method for Supplying Fuel Gas to Fuel Cell Assembly,” US Patent 

5,714,276. 

71. Skala, G. W., Hart-Predmore, D. J., Pettit, W. H. and Borup, R. L., “Thermally Integrated 

Staged Methanol Reformer and Method,” US Patent 6,238,815 (2001). 

72. Autenrieth, R. and Heil, D., “Reforming Reactor, Particularly for the Water Vapor 

Reforming of Methanol,” US Patent 5,928,614 (1999). 

73. Brown, L. F., “A Comparative Study of Fuels for On-Board Hydrogen Production for FuelCell-Powered Automobile,” International Journal of Hydrogen Power 26 (2001) 381. 

74. Cable; T. L.; Brakas; A. B.; Ruhl; R. C. and Milliken; C. E. “Method for Steam Reforming 

Hydrocarbons using a Sulfur-Tolerant Catalyst,” US Patent 6,238,816 (2001). 

75. Trimm, D. L., “Catalysts for the Control of Coking during Steam Reforming,” Catalysis 

Today 49 (1999) 3. 

76. Rostrup-Nielsen, J. R. and Alstrup, I., “Innovation and Science in the Process Industry Steam 

Reforming and Hydrogenolysis,” Catalysis Today 53 (1999) 311. 

77. Palm, C., Cremer, P., Peters, R. and Stolten, D., “Small-Scale Testing of a Precious Metal 

Catalyst in the Autothermal Reforming of Various Hydrocarbon Feeds,” J. Power Sources

106 (2002) 231. 
24

78. Kobayashi, M and Flytzani-Stephanopoulos, M., “Reduction and Sulfidation Kinetics of 

Cerium Oxide and Cu-Modified Cerium Oxide,” submitted. 

79. Arakawa, H., Aresta, M., armor, J. N., Barteau, M. A., Beckman, E. J., Bell, T. T., Bercaw, 

J. E., Creutz, C., Dinjus, E., Dixon, D. A., Domen, K., DuBois, D. L., Eckert, J., Fujita, E., 

Gibson, D. H., Goddard, W. A., Goodman, D. W., Keller, J., Kubas, G. J., Kung, H. H., 

Lyons, J. E., Manzer, L. E., Marks, T. J., Morokuma, K., Nicholas, K. M., Periana, R., Que, 

L., Rostrup-Nielson, J., Sachtler, W. M. H., Schmidt, L. D., Sen, A., Somorjai, G. A., Stair, 

P. C., Stults, B. R. and Tumas, W., “Catalysis Research Relevance to Carbon Management: 

Progress, Challenges, and Opportunities,” Chem. Rev. 101 (2001) 953. 

80. World Bank Report on Pakistan Clean Fuels: October 2001, 

http://www.worldbank.org/html/fpd/esmap/pdfs/pakistan_cleanfuels.pdf, viewed on 7/11/02. 

81. EPA, “Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle 

Standards and Highway Diesel Fuel Sulfur Control Requirements,” Federal Register 66 

(2001) 5002. 

82. Franz, N., “Court Upholds Sulfur Limits for Diesel,” Chemical Week 164 (2002) 38. 

83. “Standard Specification for Diesel Fuel Oils,” ASTM D975-02. 

84. Ma, X., Sakanishi, K. and Mochida, I., “Hydrodesulfurization Reactivities of Various Sulfur 

Compounds in Diesel Fuel,” Ind. Eng. Chem. Res. 33 (1994) 218. 

85. Gates, B. C. and Topsøe, H., “Reactivities in Deep Hydrodesulfurization: Challenges, 

Opportunities, and the Importance of 4-Methyldibenzothiophene and 4,6-

Dimethyldibenzothiophene,” Polyhedron 16 (1997) 3213. 

86. Lee, S. H. D., Kumar, R. and Krumpelt, M., “Sulfur Removal from Diesel FuelContaminated Methanol,” Separation and Purification Technology 26 (2002) 247. 

87. Khan, A. R., Meek, J. and Baker, B. S., “Jet Fuel as a Feedstock,” Chemical Engineering 

Progress 62 (1966) 74. 

88. Anumakonda, A., Yamanis, J. and Ferrall, J., “Catalytic Partial Oxidation of Hydrocarbon 

Fuels to Hydrogen and Carbon Monoxide,” US Patent 6,221,280 (2001). 

89. MSDS for 100% Methanol, www.alfa.com. 

90. MSDS for ARCO Emission Control Diesel #2, www.ecdiesel.com. 

91. MSDS for JP-8, www.caltex.com. 

92. Amphlett, J. C., Mann, R. F. and Peppley, B. A., “On Board Hydrogen Purification for 

Steam Reformation / PEM Fuel Vehicle Power Plants,” Int. J. Hydrogen Energy 21 (1996) 

673. 
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Appendix A. Chemical and Physical Properties of Methanol, Diesel, and JP-8 

Table A-1. Selected chemical properties for methanol, JP-8, and diesel 

 Methanol [89] Diesel [90] JP-8 [24,91] 

Molecular Formula CH3OH Mixture of Compounds, 

C13.57H27.14 [73] 

Mixture of Compounds, 

C10.9H20.9

Energy Density (LHV), 5.6 11.1 11.8 

Molecular Weight 32 190 [73] 152 

Density 0.79 (20 oC) 0.81 to 0.84 0.8 

Vapor Pressure 129 hPa (20 oC) 0.04 Reid Psia (100oF) < 7 mmHg (25 oC) 

Explosion Limits, vol% 6.7 – 36 0.7 – 5.0 0.6 - 4.5 

Boling Point, K 338 450–643 448-543 

Flash Point, K 284 344–371 311 

Ignition Temperature, K 658 530 653 
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