Investigation of the aromatization of C6+ hydrocarbons on chromia/lanthana-zirconia catalyst

Klepel, Olaf; Breitkopf, Cornelia; Standke, Mirko

doi:10.1016/j.molcata.2003.09.019

Cited by 4 publications

(2 citation statements)

References 30 publications

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“…The distribution of the products obtained on LZ shows that oxylen and ethylbenzene are the main products among aromatics ( figure 2). This suggests a DHC mechanism based on a stepwise dehydrogenation, alkane fi alkene fi alkadiene fi alkatrienen fi cyclohexadiene fi aromatics, which had been found to be characteristic for the DHC of alkanes on catalysts of non-acidic nature [14][15][16][17]. The n-octane conversion on Cr/LZ is high at the very beginning, in agreement with the results reported in [2,3], but it decreases rapidly.…”

Section: Dhc Of N-octanesupporting

confidence: 84%

“…However, at 180 min TOS, aromatics still were the predominating products, mainly consisting of ethylbenzene and o-xylene as shown in figure 2. This suggests that the presence of Cr 3+ species does not significantly affect the stepwise dehydrogenation mechanism assumed above for the DHC of n-octane on LZ [14][15][16][17]. Further, while the product distribution is only moderately influenced by modification of the Cr/LZ catalyst with Mg, activity and deactivation behaviour are strongly affected.…”

Section: Dhc Of N-octanementioning

confidence: 97%

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Studies on CrO x /La2O3/ZrO2 catalysts modified by Mg

et al. 2006

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Lanthana-zirconia supported chromium oxide and magnesium chromium mixed oxide catalysts were studied in the dehydrocyclization of n-octane and characterized by temperature-programmed desorption of NH3, temperature-programmed reduction, XPS and DRIFTS. The Mg-free catalyst shows the highest activity, but suffers from rapid deactivation due to coke formation. The addition of Mg decreases the initial activity of the supported chromium oxide and retards its deactivation. The characterization results reveal that the deactivation retarding effect of Mg species not only consists in the deletion of strong acid sites but also in the decoration and/or dilution of Cr3+ oxide cluster, supposedly due to the formation of Mg-Cr surface compounds and, thus, in preventing the formation of coke.

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Section: Dhc Of N-octanesupporting

confidence: 84%

Section: Dhc Of N-octanementioning

confidence: 97%

Studies on CrO x /La2O3/ZrO2 catalysts modified by Mg

et al. 2006

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Dehydrocyclization—Heterogeneous

Paál¹

2010

Encyclopedia of Catalysis

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The formation of aromatic rings from alkanes such as hexane, heptane, octane, and so on (aromatization or dehydrocyclization) on oxide catalysts: chromia, lanthana, metals, such as platinum, palladium, and so on, and nonacidic (Na‐ or Ba‐L zeolite) supports is a “monofunctional” route, catalyzed by the active ingredient itself. A bifunctional route prevails in naphtha reforming (platforming) over Pt on acidic supports (eg, alumina). Interactions of Pt with acidic or alkaline support can be important for aromatization. The metallic function can also catalyze the formation of five‐membered ring(s): C5‐cyclization. The effect of added metallic components resulting in bimetallic catalysts (such as PtRe, PtSn, and so on) as well as the effect of nonmetallic components (Cl, S, C, H) is discussed. Aromatization requiring skeletal rearrangement (eg, of alkylpentane feeds) can also take place. Cyclic hydrocarbons may undergo ring enlargement and ring contraction. The same catalyst may promote the formation of a second ring in alkylcyclopentanes. The buildup of aromatic rings is also possible from smaller molecules (ethane, propane, butane) by dehydrocyclodimerization over bifunctional catalysts, such as ZSM 5 zeolites containing Pt, Zn, but first of all Ga (eg, in the CYCLAR process). Aromatics can be produced even from methane (Mo carbide‐ZSM‐5 or Pd‐Co catalysts).

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