1070-4272/03/7605-0831$25.00C2003 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 76, No. 5, 2003, pp. 831!834. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 5,
2003, pp. 860!862.
Original Russian Text Copyright + 2003 by Pen, Mironov, Kolmakova.
AND POLYMERIC MATERIALS
A Micromethod of Estimating the Reactivity
of Cellulose to Acetylation
R. Z. Pen, P. V. Mironov, and O. A. Kolmakova
Siberian State Technological University, Krasnoyarsk, Russia
Received October 23, 2002; in final form, March 2003
Abstract-A micromethod was developed for estimating the reactivity of cellulose to acetylation by
monitoring temperature variation in the process.
Since acetylation of cellulose with acetic anhydride
is an exothermic process, a series of methods for
determining the acetylation rate and estimating the
cellulose reactivity are based on temperature meas-
urements, with the reaction being carried out under
adiabatic conditions . According to generally ac-
cepted analysis methods, cellulose acetylation is
carried out by the homogeneous procedure in a Dewar
vessel. For analysis, 10 g of air-dry cellulose and
239 ml of acetylating mixture are taken . In the
reaction of cellulose with the acetylating mixture, the
temperature of the reaction mixture increases from
To carry out of the process in a calorimeter, 3.5 g
of cellulose and 365 ml of the acetylating mixture are
taken. Cellulose placed in the calorimeter shaft is
ejected into the acetylating mixture. In the process,
the temperature of the reaction mixture increases by
Among the most significant drawbacks of this
procedure are considerable increase in the temperature
of the reaction mixture, which distorts the kinetic
parameters of the process. In addition, relatively large
amounts of cellulose required for measurements are
inconvenient for laboratory studies.
Here we studied the possibility for estimating the
rate of cellulose acetylation using a non-adiabatic
microcalorimeter under the conditions close to iso-
The measuring system consists of two batteries of
thermocouples connected by the differential scheme
and attached to an emf amplifier, which allows record-
ing of the temperature difference in the cells of micro-
calorimetric blocks. The signal from the emf amplifier
is recorded on a diagram tape in the form of the plot
time t (s)3temperature difference DT (oC). The nomi-
nal sensitivity of the device (from the diagram) was
Cellulose was activated before acetylation. For this
purpose, 0.5 g of pulverized air-dry cellulose was uni-
formly moistened in 0.5 cm
of glacial acetic acid in
bottle and placed in a thermostat at 80oC
for 1 h, after which it was kept at room temperature
for 2 h.
The acetylating mixture was prepared by mixing
acetic anhydride, acetic acid, and concentrated sulfuric
acid in the volume ratio of 50 : 100 : 1, respectively.
portion of this mixture was placed into the
reaction vessel of the measurement cell of the device.
Activated cellulose (5310 mg) was attached to the end
of the sample holder with a very thin wire and placed
into the acetylating mixture. The instant of immersion
was considered as the reaction start (t = 0).
A typical diagram of temperature variation in the
reaction mixture is shown in Fig. 1. The ascending
Fig. 1. Variation of temperature of the reaction mixture DT
in time t. The points were transferred from the recorder,
and the solid line is calculated by Eq. (12).