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Dehydration of butanol to butene over solid acid catalysts in high water environments

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Abstract.
The effects were studied of high water concentrations on the kinetics of alcohol dehydration, as
encountered in aqueous-phase processing of biomass-derived oxygenated hydrocarbons. These studies
were carried out for dehydration of an aqueous solution of 10 wt% 2-butanol at 513 K, and at a total
pressure of 52 bar to maintain the water in the liquid state. Under these high pressures of water, silicaalumina, niobium phosphate and niobic acid are found to be stable and active for the dehydration
of butanol. These three catalysts showed an increase in rate after contact with liquid water, caused
by an increase in the concentration of Brønsted acid sites. Zeolite catalysts (Beta, USY, H-ZSM-5) and
zirconia based catalysts (WOx/ZrO2, MoOx /ZrO2, and MgO/ZrO2) were ineffective due to deactivation or
low catalytic activity. The flow rate of inert gas at constant aqueous flow rate had a significant effect
on the rate of butene production, due to vaporization of butanol and water. At low flow rates of gas,
increasing the gas flow rate causes the preferential vaporization of butanol, leading to a decrease in the
butanol pressure in the reactor and a corresponding decrease in the rate of dehydration. Above a critical
gas flow rate, the liquid feed becomes completely vaporized in the reactor, and increasing the gas flow
rate further leads to a decrease in the pressure of water and a corresponding increase in the rate of
dehydration. In the vapor–liquid equilibrium regime, kinetic models predict that most of the catalyst is
covered with multiple layers of water, and dehydration takes place by reaction of hydrated–adsorbed
butanol with a hydrated surface site. In the vapor-only regime, kinetic models suggest that the fraction
of vacant active sites increases with increasing gas flow rate, and dehydration takes place by reaction of
adsorbed butanol with a vacant surface site.

Keywords:
2-Butanol
Dehydration
Water
Aqueous phase processing
Silica-alumina
Niobium phosphate
Niobic acid
Butene

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Informasi Detail

Judul Seri

Journal of Catalysis

No. Panggil

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Penerbit

London : Elsevier Inc.., 2009

Deskripsi Fisik

Journal of Catalysis 262 (2009) 134–143

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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