Aging of Silica and Alumina Gels

Schlaffer, W. G.; Adams, Chris; Wilson, Jeff

doi:10.1021/j100889a016

Cited by 22 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…(i) It is possible that alkali hydroxide (or alkali carbonate) adsorbs on the surface of the support (e.g. on the alumina) and has an effect similar to that of adsorbed H 20 [24,29,30]; both the alkali-hydroxide (or alkali-carbonate) species and the H20 molecule have a dipole moment and contain negatively charged oxygen. Because the alkali species are much more strongly adsorbed than is H20, the effect of alkali on the sintering may be much stronger.…”

Section: Discussionmentioning

confidence: 99%

Nickel catalysts for internal reforming in molten carbonate fuel cells

Berger

Doesburg

Ommen

et al. 1996

Applied Catalysis A: General

View full text Add to dashboard Cite

Natural gas may be used instead of hydrogen as fuel for the molten carbonate fuel cell (MCFC) by steam reforming the natural gas inside the MCFC, using a nickel catalyst (internal reforming). The severe conditions inside the MCFC, however, require that the catalyst has a very high stability. In order to find suitable types of nickel catalysts and to obtain more knowledge about the deactivation mechanism(s) occurring during internal reforming, a series of nickel catalysts was prepared and subjected to stability tests at 973 K in an atmosphere containing steam and lithium and potassium hydroxide vapours. All the catalysts prepared showed a significant growth of the nickel crystallites during the test, especially one based on c~-Al203 and a coprecipitated Ni/AI20 3 sample having a very high nickel content. However, this growth of nickel crystallites only partially explained the very strong deactivation observed in most cases. Only a coprecipitated nickel/alumina catalyst with high alumina content and a deposition-precipitation catalyst showed satisfactory residual activities. Addition of magnesium or lanthanum oxide to a coprecipitated nickel/alumina catalyst decreased the stability.Adsorption and retention of the alkali was the most important factor determining the stability of a catalyst in an atmosphere containing alkali hydroxides. This is because the catalyst bed may remain active if a small part of the catalyst bed retains all the alkali.

show abstract

Section: Discussionmentioning

confidence: 99%

Nickel catalysts for internal reforming in molten carbonate fuel cells

Berger

Doesburg

Ommen

et al. 1996

Applied Catalysis A: General

View full text Add to dashboard Cite

show abstract

“…There are different possible explanations given in the literature for the surface area reduction of oxides under steam. The most important ones are (i) evaporation condensation of metal cations; 14,15 (ii) anion exchange mechanism; 16 (iii) enhanced surface diffusion; 17,18 and (iv) bridging and condensation of surface hydroxyls. 19 In the present case, the equilibrium amount of surface hydroxyls is very low because of the higher calcination temperatures (1300°and 1400°C), and this may be the possible explanation for the observed equal stability under air and steam.…”

Section: (1) Textural Stabilitymentioning

confidence: 99%

Pore Structure Evolution of Lanthana–Alumina Systems Prepared through Coprecipitation

Nair¹,

Nair²,

Mizukami³

et al. 2000

Journal of the American Ceramic Society

View full text Add to dashboard Cite

show abstract

“…Good agreement is found between the curves and the experimental data. Equations (17) to (19) can be simplified to Eqs. (20) to (22), respectively, in which the changes in acidic properties and the deactivation function are well correlated in terms of the change in surface area of the catalyst.…”

Section: Comparisons Between Calculated and Experimental Resultsmentioning

confidence: 99%

“…(20) to (23) as well as Eqs. (17) to (19) hold over a wide range of sintering temperatures irrespective of the power n in Eq. (5).…”

Section: Simplification Of Model Equationsmentioning

confidence: 99%

Change in catalytic activity of silica-alumina catalysts during sintering.

Hashimoto

Masuda

Isobe

1988

J. Chem. Eng. Japan

View full text Add to dashboard Cite

The deactivation function of silica-alumina catalysts during steam sintering is presented. Silica-alumina catalysts sinter rapidly at high temperature in steam atmosphere, undergoing irreversible changes in both pore structure and acidic properties that result in deactivation. Change in acid strength distribution during sintering was well represented by a population balance equation. By combining this equation with the previous two models developed by the authors, one for the rate of decrease in surface area during sintering, the other for the relationship between catalytic activity and acidic properties, the deactivation function of the catalyst during sintering was found to be expressible in terms of its surface area. Changesin acidic properties and catalytic activity were well predicted by the model equations.

show abstract

Aging of Silica and Alumina Gels

Cited by 22 publications

References 0 publications

Nickel catalysts for internal reforming in molten carbonate fuel cells

Nickel catalysts for internal reforming in molten carbonate fuel cells

Pore Structure Evolution of Lanthana–Alumina Systems Prepared through Coprecipitation

Change in catalytic activity of silica-alumina catalysts during sintering.

Contact Info

Product

Resources

About