Russian Journal of Applied Chemistry, Vol. 75, No. 4, 2002, pp. 585 588. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 4, 2002,
pp. 599 602.
Original Russian Text Copyright
2002 by Mamedov, Gagarin, Kharlampidi.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Effect of Acetophenone on Liquid-Phase Dehydration
of Dimethylphenylmethanol
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 -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 [1]. 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-
mercial phenol.
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 [9].
Initially cumene was taken as a reaction medium,
since it was the initial substance in DMPM synthesis,
which eliminates the stage of additional purification
of alcohol.
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
As noted in [2 7], DMPM can be dehydrated to
obtain -methylstyrene ( -MS), which is the ini-
tial monomer for production of various polymeric
materials.
ROH + H+
ROH2
R+ + H2O
Olefin + H2O + H+,
(1)
At present, -MS is prepared in Russia mainly by
high-temperature catalytic dehydrogenation of cumene
[8]. This process is very power-consuming. Therefore,
development and promotion of a process for -MS
production from DMPM, which finds no commercial
application yet, is of practical interest.
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 -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.
Dehydration of DMPM to -MS can be performed
in both gas and liquid phases. We consider here the
liquid-phase process as the most cost-efficient.
EXPERIMENTAL
DMPM obtained by base decomposition of cumene
hydroperoxide was used as a raw material [1]. The
sample contained (wt %) DMPM 91.7, acetophenone
(ACP) 7.6, -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
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 -MS is 100%.
were performed in a temperature-controlled glass The use of special procedures [12] and analysis of the
1070-4272/02/7504-0585 $27.00 2002 MAIK Nauka/Interperiodica