Hydrogen production by catalytic cracking of methane over nickel gauze under periodic reactor operation

Monnerat, B.; Kiwi‐Minsker, Lioubov; Renken, Albert

doi:10.1016/s0009-2509(00)00270-0

Cited by 97 publications

(39 citation statements)

References 7 publications

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“…First, carbon can form as a result of reactions over a catalyst. This process has been very well studied over Ni, Fe, and Co, both for catalytic applications [9][10][11][12][13][14][15][16] and for "dusting", also known as "dry corrosion", the problem of pitting when steels are exposed to hydrocarbons at high temperatures [17,18]. The mechanism on each of these metals involves deposition of a carbon source onto the metal surface, dissolution of the carbon into the bulk of the metal, and finally precipitation of carbon as a graphite fiber at some surface of the metal particle.…”

Section: Introductionmentioning

confidence: 99%

A study of carbon formation and prevention in hydrocarbon-fueled SOFC

Kim

Liu

Boaro

et al. 2006

Journal of Power Sources

178

120

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The formation and removal of the carbonaceous deposits formed by n-butane and liquid hydrocarbons, such as n-decane and proprietary light and heavy naphthas, between 973 and 1073 K on YSZ and ceria-YSZ, has been studied to determine conditions for stable operation of direct-utilization SOFC. First, it is shown that deactivation of SOFC with Cu-ceria-YSZ anodes operating on undiluted n-decane, a mixture of 80% n-decane and 20% toluene, or light naphtha at temperatures above 973 K is due to filling of the pores with polyaromatic compounds formed by gas-phase, free-radical reactions. Formation of these compounds occurs at a negligible rate below 973 K but increases rapidly above this temperature. The rate of formation also depends on the residence time of the fuel in the anode compartment. Because steam does not participate in the gas-phase reactions, carbonaceous deposits could form even at a H 2 O:C ratio of 1.5, a value greater than the stability threshold predicted by thermodynamic calculations. Temperature-programmed-oxidation (TPO) measurements with 20% H 2 O in He demonstrated that carbon deposits formed in pure YSZ were unreactive below 1073 K, while deposits formed on ceria-YSZ could be removed at temperatures as low as 923 K. Based on these results, we discuss strategies for avoiding carbon formation during the operation of direct-utilization anodes on oil-based liquid fuels. KeywordsSolid-oxide fuel cell, Hydrocarbon fuels, Carbon Formation, Gas-phase pyrolysis, Ceria, Yttira-stabilized zirconia AbstractThe formation and removal of the carbonaceous deposits formed by n-butane and liquid hydrocarbons, such as n-decane and proprietary light and heavy naphthas, between 973 and 1073 K on YSZ and ceria-YSZ, has been studied to determine conditions for stable operation of directutilization SOFC. First, it is shown that deactivation of SOFC with Cu-ceria-YSZ anodes operating on undiluted n-decane, a mixture of 80% n-decane and 20% toluene, or light naphtha at temperatures above 973 K is due to filling of the pores with polyaromatic compounds formed by gas-phase, free-radical reactions. Formation of these compounds occurs at a negligible rate below 973 K but increases rapidly above this temperature. The rate of formation also depends on the residence time of the fuel in the anode compartment. Because steam does not participate in the gas-phase reactions, carbonaceous deposits could form even at a H 2 O:C ratio of 1.5, a value greater than the stability threshold predicted by thermodynamic calculations. Temperatureprogrammed-oxidation (TPO) measurements with 20% H 2 O in He demonstrated that carbon deposits formed in pure YSZ were unreactive below 1073 K, while deposits formed on ceria-YSZ could be removed at temperatures as low as 923 K. Based on these results, we discuss strategies for avoiding carbon formation during the operation of direct-utilization anodes on oilbased liquid fuels.

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Section: Introductionmentioning

confidence: 99%

A study of carbon formation and prevention in hydrocarbon-fueled SOFC

Kim

Liu

Boaro

et al. 2006

Journal of Power Sources

178

120

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“…In this case, the methane decomposition step was performed for 1 h following which the catalyst was regenerated using an oxidation-reduction cycle. There was no apparent decrease in catalytic activity throughout the 12 cycles studied at 723 K. Similarly, Monnerat et al [51] have investigated the cyclic process (methane decomposition and air regeneration) over a Ni gauze catalyst (Ni-grid with Raney type outer layer). Their studies revealed an optimal reaction performance when the cycle consisted of 4 min of reaction period followed by 4 min of regeneration period.…”

Section: Step-wise Reforming Of Hydrocarbonsmentioning

confidence: 94%

CO-free fuel processing for fuel cell applications

2003

Fuel and Energy Abstracts

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In view of the stringent CO intolerance of the state-of-the-art proton exchange membrane (PEM) fuel cells, it is desirable to explore CO-free fuel processing alternatives. In recent years, step-wise reforming of hydrocarbons has been proposed for production of CO-free hydrogen for fuel cell applications. The decomposition of hydrocarbons (first step of the step-wise reforming process) has been extensively investigated. Both steam and air have been employed for catalyst regeneration in the second step of the process. Since, PEM is poisoned by very low (ppm) levels of CO, it is essential to eliminate even trace amounts of CO from the reformate stream. Preferential oxidation of CO (PROX) is considered to be a promising method for trace CO clean up. Related studies along with a discussion of catalytic ammonia decomposition (for applications in alkaline fuel cells) will be included in this review.

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“…The main advantages of this kind of catalyst are the regular open structure and the exibility that enables to use them in structured catalytic beds . In order to increase the speciÿc surface area of bulk nickel, a Raney-type outer layer was formed on the metal surface (Wainwright, 1997;Monnerat et al, 2001;Kiwi-Minsker, 2002). Experiments were performed with the modiÿed nickel gauze (∼ 210 mg), placed in the middle part of the reactor in a rolled form (length 20 -30 mm) between two inert packings of quartz beads.…”

Section: Methodsmentioning

confidence: 99%

“…Recently, we reported an attractive method to produce carbon oxide-free hydrogen by catalytic cracking of methane over nickel gauze (Monnerat, Kiwi-Minsker, & Renken, 2001). The catalyst deactivates due to intensive coke deposition.…”

Section: Introductionmentioning

confidence: 99%

Mathematical modelling of the unsteady-state oxidation of nickel gauze catalysts

Monnerat

Kiwi‐Minsker

Renken

2003

Chemical Engineering Science

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The oxidation of nickel gauze catalysts by O2 was investigated by transient response methods. Qualitative description of the experimental transient responses have shown that the oxidation of metallic nickel proceeds in two stages. The ÿrst step is a fast dissociation of gaseous oxygen on the catalytic surface, followed by oxygen di usion from the surface into the bulk. This slow second step explains the long tailing observed from the experimental transient responses. Furthermore, a rise of temperature was observed during the nickel oxidation. A kinetic model has been developed on the basis of the experimental results in order to provide quantitative information about this reaction. For nickel gauze oxidation, a non-isothermal model combining the subsurface oxygen di usion with an exponential distribution for the activity of surface sites gave a good agreement with experimental transient data. As a result, the activation energies and the pre-exponential factors of the rate constants as well as the characteristic oxygen di usion times were determined. ?

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Hydrogen production by catalytic cracking of methane over nickel gauze under periodic reactor operation

Cited by 97 publications

References 7 publications

A study of carbon formation and prevention in hydrocarbon-fueled SOFC

A study of carbon formation and prevention in hydrocarbon-fueled SOFC

CO-free fuel processing for fuel cell applications

Mathematical modelling of the unsteady-state oxidation of nickel gauze catalysts

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