1070-4272/02/7504-0585 $27.00 C 2002 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 75, No. 4, 2002, pp. 585!588. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 4, 2002,
Original Russian Text Copyright + 2002 by Mamedov, Gagarin, Kharlampidi.
AND INDUSTRIAL ORGANIC CHEMISTRY
Effect of Acetophenone on Liquid-Phase Dehydration
E. M. Mamedov, M. A. Gagarin, and Kh. E. Kharlampidi
Kazan State Technological University, Kazan, Tatarstan, Russia
Received September 25, 2001
Abstract-The acid-catalyzed liquid-phase dehydration of dimethylphenylmethanol to a-methylstyrene was
considered. The scheme and mathematical model of liquid-phase dehydration of dimethylphenylmethanol
were proposed, and the effect of acetophenone on the reaction kinetic parameters was studied.
Combined production of phenol and acetone by the
cumene method is a widely used process of chemi-
cal technology . It yields, along with the target
products, many by-products, including dimethylphen-
ylmethanol (DMPM). DMPM is formed through non-
selective consumption of cumene hydroperoxide in
the stages of cumene oxidation and acid decomposi-
tion of hydroperoxide into phenol and acetone. The
presence of DMPM in the reaction mixture leads to
formation of products impairing the quality of com-
As noted in , DMPM can be dehydrated to
obtain a-methylstyrene (a-MS), which is the ini-
tial monomer for production of various polymeric
At present, a-MS is prepared in Russia mainly by
high-temperature catalytic dehydrogenation of cumene
. This process is very power-consuming. Therefore,
development and promotion of a process for a-MS
production from DMPM, which finds no commercial
application yet, is of practical interest.
Dehydration of DMPM to a-MS can be performed
in both gas and liquid phases. We consider here the
liquid-phase process as the most cost-efficient.
DMPM obtained by base decomposition of cumene
hydroperoxide was used as a raw material . The
sample contained (wt %) DMPM 91.7, acetophenone
(ACP) 7.6, a-MS 0.53, cumene 0.28, and cumene
hydroperoxide 0.50. A 0.5 M solution of sulfuric acid
in acetic acid was taken as catalyst. Kinetic studies
were performed in a temperature-controlled glass
cell equipped with a magnetic stirrer. During the re-
action, an inert gas (nitrogen) was bubbled through
the reaction mixture. The reaction course was mon-
itored chromatographically by the concentrations of
the initial substances and reaction products .
Initially cumene was taken as a reaction medium,
since it was the initial substance in DMPM synthesis,
which eliminates the stage of additional purification
It is commonly believed [10, 11] that the acid-cat-
alyzed dehydration of alcohols in the liquid phase
proceeds via formation of carbocation by the scheme
ROH + H
Olefin + H
where R is a hydrocarbon radical.
It was found experimentally that DMPM dehy-
dration in cumene decelerates in the course of time
(Fig. 1), which is probably due to inhibition of the
catalyst by water formed, rather than to attainment of
a chemical equilibrium. Special experiments showed
that a-MS is not hydrated under these conditions.
Since water exhibits higher proton affinity than the
other reaction components, its accumulation in the
system can cause resolvation of protons with water
and, as a result, a decrease in the catalyst activity.
In experiments with various initial DMPM concen-
trations (Fig. 1), we found that the DMPM dehydra-
tion is first-order with respect to the substrate and that
the reaction selectivity with respect to a-MS is 100%.
The use of special procedures  and analysis of the