Identification of alcohol adsorption sites on $gamma;-alumina

DeCanio, E.C.; Nero, Vincent P.; Bruno, Joseph W.

doi:10.1016/0021-9517(92)90046-k

Cited by 54 publications

(36 citation statements)

References 19 publications

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“…The O±H group vibration at 3725 cm À1 belongs to a g-alumina hydroxyl group, [12,15] whereas the two bands ca. 3500 cm À1 belong to stabilised alcoholic-hydroxyl group [11,13]. The two bands at 1480 and 1560 cm À1 are those of an acetate structure.…”

Section: Resultsmentioning

confidence: 98%

In-situ characterisation of the surface intermediates for the ethanol dehydration reaction over γ-alumina under dynamic conditions

Golay

Doepper

Renken

1998

Applied Catalysis A: General

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The dynamic behavior of the ethanol adsorption on g-alumina were investigated at 180 and 2008C by the transient-response method coupled with FT±IR data of the catalyst surface. The existence of three adsorbates was demonstrated: a reacting species which is the precursor for the formation of the gas-phase ethene; an inhibiting species responsible for the low steadystate reaction rate; and a spectator species accumulating on the catalyst surface. Their infrared spectra indicate an ethoxidelike structure for the three adsorbates. Their C±H stretching bands can be depicted by four Lorentzians whose parameters indicate different surface environments. The surface concentration of the reacting species was determined on the basis of the transient ethene response. A value of 0.77AE0.07 mol/kg cat was found at 1808C. The surface concentration of the spectator species was determined by ex-situ thermogravimetric experiments. A value of 0.13AE0.01 mol/kg cat was found at 1808C. The most likely structure of this species corresponded to an ethanol molecule coordinated in a bidentate manner on Al 3 cations, with stabilisation of the alcoholic-hydroxyl group via lateral hydrogen bonding with an adjacent surface hydroxyl. # 1998 Elsevier Science B.V. All rights reserved.

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Section: Resultsmentioning

confidence: 98%

In-situ characterisation of the surface intermediates for the ethanol dehydration reaction over γ-alumina under dynamic conditions

Golay

Doepper

Renken

1998

Applied Catalysis A: General

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“…3b). According to the proposals made by NatalSantiago et al [25] and Decanio et al [26], these bands could be caused by weakly physisorbed ethanol and easily removed from the acid surface with the increase of temperature. In addition, the intensity of the 3,555 cm -1 band decreased, accompanied by the appearance of one new band at 1,350 cm -1 due to the formation of H 2 O at 100°C [27,28].…”

Section: Ft-ir Studies Of the Adsorption Of Ethanol On The Activated mentioning

confidence: 98%

Mechanistic Studies on the Coupled Reaction of n-Hexane and Ethanol Over HZSM-5 Zeolite Catalyst

et al. 2008

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The coupled reaction of n-hexane and ethanol over HZSM-5 zeolite has been, for the first time, investigated with a pulse-reaction system. The catalytic reaction results showed an improvement of the initial conversion activity of n-hexane when ethanol was introduced as co-reactant. The FT-IR analysis revealed that the ethanol molecules adsorbed on Brønsted acidic sites were immediately transformed into surface ethoxy groups, which were active species for converting n-hexane and improving the initial conversion activity of n-hexane by a bimolecular hydride transfer mode. Also, the catalytic tests suggested that alkenes resulting from the transformation of ethanol could not enhance the initial conversion of n-hexane compared to active ethoxy groups at the shortest contact time. A mechanism involving the ethoxy groups was proposed to understand the coupled reaction of ethanol and n-hexane.

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“…The conclusion that ether disproportionation is the primary ether consumption pathway on ␥-Al 2 O 3 is consistent with the 1:1 stoichiometric production of ethanol and ethylene at low conversions from DEE conversion over ␥-Al 2 O 3 at 523-616 K observed previously by Knözinger and Köhne Table 1 Kinetic parameters corresponding to models for unimolecular and bimolecular dehydration shown in Eqs. (12) and (13) for the synthesis of propylene, DPE, and DME from alcohol dehydration on ␥-Al2O3 at 623 K estimated from the data presented in Figs. 1 and 2.…”

Section: Kinetic Measurements Of Mpe Conversionmentioning

confidence: 99%

“…Alcohols dehydrate over acid catalysts, such as gamma-alumina (␥-Al 2 O 3 ) [1][2][3][4][5][6][7], to form olefins and water through a unimolecular pathway or ethers and water through a bimolecular pathway [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In previous investigations, pyridine inhibition measurements identified that these parallel alcohol dehydration pathways occur on non-equivalent pools of catalytic sites.…”

Section: Introductionmentioning

confidence: 99%