1070-4272/04/7711-1877C2004 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 77, No. 11, 2004, pp. 1877!1882. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11,
2004, pp. 1895!1900.
Original Russian Text Copyright + 2004 by Yu. Kuznetsov, Khripunov, Kruchinina, V. Kuznetsov, Turkova, Pen’kova.
AND POLYMERIC MATERIALS
Transport Properties of Cellulose Ester Membranes
for Separating Gas and Liquid Mixtures
Yu. P. Kuznetsov, A. K. Khripunov, E. V. Kruchinina, V. M. Kuznetsov,
L. D. Turkova, and A. V. Pen’kova
Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
St. Petersburg State University, St. Petersburg, Russia
Received April 29, 2004
Abstract-Mass-exchange characteristics of cellulose myristate or acetomyristate membranes in separating
aqueous-organic, organic, or gas mixtures, particularly, in recovering aromatic hydrocarbons from binary
mixtures with aliphatic alcohols, and also ethyl acetate from a mixture of esterification products, are studied.
There is a steady scientific and practical interest in
cellulose-based membranes in recent six decades,
which is caused by easy availability of cellulose raw
material, and also by the possibility of directed syn-
thesis of homologous series of various cellulose
derivatives with desired physicochemical character-
istics. Therefore, cellulose-based membranes with
desired transport properties can be prepared as well.
Microporous (diffusion) membranes are mostly
formed on the basis of cellulose esters or mixed esters
(diacetates, triacetates, acetobutyrates), regenerated
cellulose, and chitosan . Previously we demon-
strated the possibility of using cellulose acetomyri-
state diffusion membranes for separating aromatic and
aliphatic hydrocarbons using the pervaporation tech-
nique . In this work we studied the transport prop-
erties of cellulose myristate (CM) and acetomyristate
(CAM) membranes of different composition in sepa-
rating gas, aqueous-organic, and organic mixtures.
Cellulose myristate and acetomyristates were
prepared according to the standard procedure .
Membranes as nonporous films of a fixed thickness
were formed from chloroform solutions of the poly-
mers on a cellophane support. The pervaporation
experiments were carried out using a laboratory cell of
the autonomous type (effective area of the membrane
) with stirring the mixtures over the membrane
at a residual pressure under the membrane of 0.2 mbar.
The permeate vapor (flow passed across the mem-
brane) was condensed in a receiving vessel at the
liquid nitrogen temperature and weighed, and the total
flow P (kg m
) was estimated. In the experi-
ments we used binary mixtures ethanol3water, tolu-
ene3methanol, and benzene3ethanol of various com-
positions, and also a mixture of ethyl acetate, acetic
acid, ethanol, and water. The compositions of per-
meates were analyzed on a refractometer or chroma-
tographically using Porapak-Q or Reoplex columns.
The partition factor a was estimated as
are the concentrations of A and B
in the initial binary mixture (wt %), and X
in the permeate (wt %).
The gas-permeability coefficient P and selectivity
of vapors were determined chromato-
graphically using a column filled with 5A molecular
sieve as a stationary phase at an excess pressure over
the membrane of 10 mbar. The compositions of liquid
permeates and gas-permeability coefficients were
determined to within 5 and 10%, respectively.
To study the selectivity of CM membranes, we
prepared a 1 m long chromatographic column with the
CM stationary phase supported on Celite 22. The
evolution of the chemical structure of cellulose esters
on passing from cellulose diacetate to CM is accom-
panied by decreasing packing density of the polymer
chains and increasing fraction of the free volume in
the polymer matrix. This is caused by weakening of
the network of the hydrogen bonds and disordering of
the supramolecular structure, being reflected in a
regular increase in the gas permeability with parallel
decrease in the selectivity. These trends are illustrated