Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 5, pp. 905−910.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
F.A. Gashimov, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 5, pp. 850−855.
AND POLYMERIC MATERIALS
Densiﬁ cation Products in Conversion of Ethylene
on a High-Silica Zeolite Catalyst
F. A. Gashimov
Azerbaijani State Petroleum Academy, Baku, Azerbaijan
Received July 30, 2008
Abstract—Fundamental aspects of the conversion of ethylene on a high-silica zeolite catalyst in the temperature
range 200–400°C were studied. The methods of differential-thermal and X-ray phase analysis were employed
to examine the formation of coking products on the surface of the zeolite catalyst in the conversion of ethylene
As is known, high-silica zeolites are active catalysts
in conversion of low-molecular-weight oleﬁ ns [1–3].
These reactions occur at acid centers whose role is played
by tricoordinated lattice atoms of aluminum and silicon,
formed in high-temperature dehydroxylation of zeolites
. Adsorbed carbenium ions are conventionally regarded
as active intermediate structures in these reactions
In addition to the formation of various gaseous and
liquid products, the conversion of hydrocarbons on
catalysts is frequently accompanied by deposition of
coking products (CPs) on the catalyst surface . The
effect of these products on the occurring reactions has
not been entirely elucidated, and the available published
data are occasionally contradictory [9–14].
In this context, a study of the conversion of low-
molecular-weight olefins on zeolite catalysts and
elucidation of the nature of CPs and their role in these
reactions are a topical task.
This study is aimed to analyze the conversion of
ethylene on a high-silica zeolite catalyst and to elucidate
the nature of coking products and their role in this
As object of study served a decationated high-silica
zeolite of the Pentasil type, NVTsK (SiO
O < 0.1%). A modiﬁ ed catalyst with a ZnO content
of about 8 wt % was prepared by impregnation of the
starting H-form of the zeolite with an aqueous solution
and subsequent calcination in air at T ≈
550°C for 6 h. Prior to experiments, the zeolite catalyst
was dehydrated at 500°C in a ﬂ ow of air, with oxygen
removed by a ﬂ ow of nitrogen. To completely remove
the residual oxygen in the gas mixture, nitrogen was
passed through a reactor with a copper catalyst heated to
In the ionic mechanism of interaction between acid
OH groups of a high-silica zeolite Pentasil and ethylene
molecules, an intermediate complex with a hydrogen
bond is formed and then transformed to the ethoxyl
Further, the carbon chain grows and the oligomer is
subsequently desorbed from the catalyst surface [4, 7].
Analysis of published data shows that the mechanism
of oligomerization of low-molecular-weight oleﬁ ns on
zeolite catalysts has been studied in sufﬁ cient detail.