Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 4, pp. 711−714.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
V.P. Talzi, 2008, published in Khimicheskaya Promyshlennost’, 2008, Vol. 85, No. 8, pp. 388−391.
TECHNOLOGY OF ORGANIC
AND INORGANIC CHEMISTRY
To the Mechanism of the Isobutane Alkylation
V. P. Talzi
Institute of the Problems of Processing Hydrocarbons, Siberian Branch, Russian Academy of Sciences, Russia
Received October 11, 2008
Abstract—-The arguments in favor of a change in the accents at the description of the reaction mechanism of
the isobutene alkylation with butylenes in the presence of sulfuric acid are proposed. The reaction of sulfate
sulfur reduction that until now considered as the side process is proposed to suggest as just the initiation of chain
process which includes generation of tert-butyl cations. Such a concept makes it possible to explain a number of
characteristic experimental data, in particular failure of attempts of creation of the effective solid catalyst for the
alkylation on the basis of the sulfated zirconium oxides.
, is organized the continuous additional feeding
to the reaction zone of the fresh catalyst.
It is suggested that the rapid deactivation of the solid
catalysts of alkylation is connected with the blocking of
the catalytic centers by the butylenes oligomers formed
in the reaction . But even at the liquid-phase sulfuric
acid catalyzed alkylation under the industrial conditions
it is necessary to feed constantly the reaction mass with
fresh sulfuric acid or oleum. In this case at ~ 10°C the
mass ratio of organic and acidic phases can be 1:1.5,
and isobutane and butylenes ~ 1:7, and the reaction
mixture should be effectively stirred. The consumption
of sulfuric acid is 5-7 kg per 100 l of alkylate. Such
high consumption of catalyst is connected with the
side reaction leading to the reduction of sulfates with
the elimination of water which dilutes sulfuric acid .
The process of alkylation is commonly considered to
be the chain ionic process, which is conducted by tert-
Below is given a possible scheme of the reaction of
chain propagation, which is accompanied by transfer
the hydride ion and methyl anion in the initially formed
carbenium ion A with interaction of the tert-butyl cation
with the butene-1 (Scheme 1). The canceling of this
chain, which has small length, taking into account the high
comnsumption of catalyst, in essence is connected with
The process of alkylation of isobutane with butenes
resulted in formation of alkylate, which is a component
of the high-knock rating gasoline, is one of the most
important large-capacity petrochemical processes,
which acquired recently an even great significance
in connection with the introduction of more stringent
ecological requirements to the gasoline composition.
From the moment of the discovery in the thirties of past
century and industrial introduction of this process was
attempted creation of a solid catalyst of alkylation instead
of concentrated sulfuric acid (98%) and liquid hydrogen
ﬂ uoride that found industrial application. In the recent
decades the reanimation of attempts of obtaining the
solid catalyst of the alkylation was connected with the
discovery of the high catalytic activity of the systems,
obtained, for example, by treatment with sulfuric acid
of zirconium oxide, so-called sulfated zirconium .
However, in spite of obtaining on the given systems of
a catalyzate close in composition to alkylates produced
in the industrial installations of alkylation with use of
sulfuric acid, all such contact materials are too rapidly
deactivating to be considered for industrial application.
It should be also accounted for the fact that the problem
of their economically reasonable regeneration is not
solved. In the described demonstration pilot plants for
the alkylation on the solid catalysts, for example, based