Transient behavior of the system ethanol-diethyl ether-water-alumina

Morávek, Vladimír

doi:10.1016/0021-9517(84)90205-7

Cited by 36 publications

(21 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It consists in a temporary increase of the reaction rate when the reactant feed is switched off and replaced by an inert gas stream with the total¯ow rate kept constant. This phenomenon was also observed by Makarova et al [3] with the dehydration of n-butanol on H-ZSM-5 and amorphous aluminosilicate, and by Moravek and Kraus [4] with the ethanol dehydration on alumina.…”

Section: Introductionsupporting

confidence: 57%

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

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionsupporting

confidence: 57%

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

View full text Add to dashboard Cite

show abstract

“…This peculiar behavior is called the ''stop effect'', and its only explanation is that the alkene precursor is stored on the catalyst surface during the previous (steady-state) period. In the pulse-flow regime, a pulse of an alcohol on alumina first yields a wave of water, followed by a wave of the alkene [62,63]. Further investigations using other transient and infra-red (IR) techniques showed [64][65][66] that the surface hydroxyl groups can be replaced by alkoxyl groups via the reactions with alcohols and ethers.…”

Section: Stop Effectmentioning

confidence: 99%

“…These transformations are reversible, and the formed surface alkoxides are intermediates in alkene or ether formation and in the hydrolysis of ethers. The general reaction scheme [62] is given in Eq. (9), while the individual reactions are explained in Table 3.…”

Section: Stop Effectmentioning

confidence: 99%

“…This failure is probably caused by the simplified assumptions adopted for the derivation of the Langmuir-Hinshelwood kinetics and the strong interactions of the reacting substances with the surface of alumina. Transient kinetic studies indicate [61][62][63][64][65][66] that the number of active sites is not constant but rather depends on the partial pressures of the alcohol, ether, and water (i.e., in a steady-state situation) on conversion.…”

Section: Kineticsmentioning

confidence: 99%

See 1 more Smart Citation

Elimination and Addition Reactions

Kraus

Knözinger

2008

Handbook of Heterogeneous Catalysis

View full text Add to dashboard Cite

The sections in this article are Scope and Thermodynamics Common Features Mechanism Influence of Reactant Structure on Rate Direction of Elimination and Addition Reactions Elimination Addition Catalysts Surface Chemistry and Reaction Mechanisms Stop Effect Catalyst Poisoning and Deactivation Kinetics Practical Applications of Elimination and Addition Reactions Dehydrochlorination Vinyl Chloride Production Trichloroethene and Tetrachloroethene Production Production of Linear Alkenes Dehydration Hydrochlorination Hydration and Amination Formation of Ethanol Formation of 2‐Propanol Addition of Alcohols and Organic Acids to Alkenes Isopropyl Acetate Methyl tert ‐Butyl Ether Alkylation and Dealkylation

show abstract

“…The ethanol dehydration to ethene on -alumina presents a stop-e!ect behaviour, i.e., a drastic increase of the reaction rate when the feed concentration of the reactant is switched to zero, with a total #ow rate kept constant (Koubek et al, 1980a, b;Moravek and Kraus, 1984). In previous studies (Golay et al, 1997 this reaction was investigated by simultaneous measurements of the gas phase composition by gas chromatography and of the concentration of adsorbed species on the catalyst surface by in situ infrared spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Influence of the catalyst acid/base properties on the catalytic ethanol dehydration under steady state and dynamic conditions. In situ surface and gas-phase analysis

Golay

Kiwi‐Minsker

Doepper

et al. 1999

Chemical Engineering Science

View full text Add to dashboard Cite

The in#uence of the acid/base properties of Mg>-modi"ed aluminas on the steady-state and transient behaviour of the ethanol to ethene dehydration has been investigated by simultaneous gas phase and in-situ surface analysis. The steady-state ethanol conversion and the ethene selectivity decrease when the catalyst basicity, i.e., the magnesium concentration, increases. The ethene transient behaviour is characterised by a stop-e!ect phenomenon, which is a drastic increase of the reaction rate measured for a step-wise decrease in the inlet concentration of ethanol. The relative augmentation of the ethene concentration under dynamic conditions is maximal for the catalyst with a Mg>/Al> atomic ratio of 2.5%. Compared to stationary experiments, transients are much more sensitive to modi"cations of the catalyst acid/base properties.The experiments were described by a model considering the existence of acid and basic sites on the catalyst surface. The magnesium concentration in#uences the kinetic parameters, whereas the site concentrations do not show any signi"cant variation.

show abstract

Transient behavior of the system ethanol-diethyl ether-water-alumina

Cited by 36 publications

References 17 publications

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

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

Elimination and Addition Reactions

Influence of the catalyst acid/base properties on the catalytic ethanol dehydration under steady state and dynamic conditions. In situ surface and gas-phase analysis

Contact Info

Product

Resources

About