Isomerization of n-butane and of n-pentane in the presence of sulfated zirconia: formation of surface deposits investigated by in situ UV–vis diffuse reflectance spectroscopy

Ahmad, Rafat; Melsheimer, Jörg; Jentoft, Friederike C.; Schlögl, Robert

doi:10.1016/s0021-9517(03)00144-1

Cited by 42 publications

(14 citation statements)

References 39 publications

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“…The causes of their deactivation are still under discussion. The deactivation has been attributed to deposition of polymerized hydrocarbons on the catalyst, causing the coverage of the acid centers by carbonaceous deposits [29], to reduction of Zr 4+ to Zr 3+ on the surface of the catalysts during the reaction or to the transformation of tetragonal to monoclinic zirconia on the surface of the catalyst [30]. …”

Section: Resultsmentioning

confidence: 99%

Industrial Aplication of Catalytic Systems for n-Heptane Isomerization

et al. 2011

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The ideal gasoline must have a high pump octane number, in the 86 to 94 range, and a low environmental impact. Alkanes, as a family, have much lower photochemical reactivities than aromatics or olefins, but only the highly branched alkanes have adequate octane numbers. The purpose of this work is to examine the possibilities of extending the technological alternative of paraffin isomerization to heavier feedstocks (i.e., n-heptane) using non-conventional catalytic systems which have been previously proposed in the literature: a Pt/sulfated zirconia catalyst and a molybdenum sub-oxide catalyst. Under the experimental conditions at which these catalysts have been evaluated, the molybdenum sub-oxide catalyst maintains a good activity and selectivity to isomerization after 24 h, while the Pt/sulfated zirconia catalyst shows a higher dimethylpentanes/methylhexanes ratio, probably due to a lower operating temperature, but also a high formation of cracking products, and presents signs of deactivation after 8 h. Though much remains to be done, the performance of these catalysts indicates that there are good perspectives for their industrial application in the isomerization of n-heptane and heavier alkanes.

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Section: Resultsmentioning

confidence: 99%

Industrial Aplication of Catalytic Systems for n-Heptane Isomerization

et al. 2011

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“…It is therefore clear that the most important role of the Pt metal component is stabilizing the catalytic activity and to ensure higher selectivity for hydroisomerization. However, some general literature findings showed that the isomerisation activity of Zirconia catalysts declines rapidly at lower temperatures (Ahmad et al, 2003). This was reported to be attributed to formation of hydrocarbon surface deposits (coke), reduction of Zr 4+ to Zr 3+ by reacting hydrocarbon, H2S formation reduction of surface sulphate groups, and surface poisoning by water (Comelli et al, 1995;Li & Gonzalez, 1998;Vera et al, 1999).…”

Section: Galadima Et Al (Swj):15-22mentioning

confidence: 99%

Solid acid catalysts in heterogeneous n-alkanes hydroisomerisation for increasing octane number of gasoline

Galadima¹,

Anderson²,

Wells³

2010

Science World Journal

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As the current global environmental concerns have prompted regulations to reduce the level of aromatic compounds, particularly benzene and its derivatives in gasoline, hydroisomerisation of n-alkanes is becoming a major alternative for enhancing octane number. Series of solid acid catalysts comprising of Freidel crafts, zirconias, MoO3-based (MOB), chlorinated Al2O3, heteropoly acids and bifunctional zeolite based catalysts have been tested in this respect. This paper reviewed important studies conducted on these catalysts with the aim of identifying areas requiring further investigation(s). Freidel craft catalysts are currently abandoned due to corrosion and disposal problems. MOB and heteropoly acids have good resistance to nitrogen and sulphur in a reaction stream but have poor thermal stability, difficult to regenerate and with mechanism their action only partly resolved. Bifunctional zeolites on the other hand are increasingly becoming promising catalysts due to resulting high acidity, activity and easy regeneration properties. Both solid and gaseous acid modifiers could similarly modify their textural characteristics. The activities of all catalysts could under uncontrolled conditions lead to side reactions such as cracking, aromatisation and dehydrogenation.

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“…Scheme and picture of an in-situ DRS cell for measuring solids operating in liquid-phase reactions at elevated temperatures and pressures. the in-situ DRS cells designed by Melsheimer et al [14,15]. Their cells allow the measuring of gas-phase reactions over catalytic solids in the range of 250-2500 nm, making use of a spacer to bridge the distance between integration sphere and microreactor.…”

Section: Fil-;mentioning

confidence: 99%