NASCIMENTO JUNIOR, B. B.; http://lattes.cnpq.br/2087640695128776; NASCIMENTO JUNIOR, Baraquizio Braga do.
Resumen:
Methanol is a product with a large variety of industrial uses, such as
formaldehyde synthesis, antifreeze in motors, as solvent in a great number of
industries and production of MTBE (methyl terc-buthyl-ether). In some
synthesis, as in the MTBE production, the unreacted methanol may be recycled
after separation of the effluent by adsorption. The knowledge of equilibrium and
kinetics is essential to project and optimize adsorption equipment as well as the
correct choice of adsorbent. In order to compare the adsorption capacity of
aluminas and other adsorbents suited for the adsorption of methanol, such as
zeolites, in this work two types of activated aluminas were used: La-Roche 204-
4 spherical and Alcoa Selexsorb COS spherical. Their principal characteristics
are: specific area of 326.53m2/g and 284.61 m2/g with pore volume of 0.64 cm3/g
and 0.73 cm3/g respectively. This work deals with studies of equilibrium and
kinetics in liquid phase. The adsorption isotherms were obtained in static medium
at temperatures from 18°C to 35°C and concentration of the liquid phase varying
from 0 to 16% by weight of methanol in toluene. The adsorption capacity
determined for both types of aluminas from the experimental data, was of about
8g/100g (adsorbed methanol /adsorbent). This value is approximately one half of
the adsorption capacity found in previous works for zeolites 4A. The Langmuir
model was proposed to the isotherms, obtaining a good fitting of the experimental
data. The qs (concentration of methanol in the adsorbent at saturation) parameter
shows a slow decreasing with temperature. Nevertheless, the influence of
temperature on the Henry constant, obtained from the Langmuir parameters, is
well described by the Vant Hoff equation with correlation coefficient of 0.990.
The calculated AHa d s is in the order of = 10 kcal/mol, greater than the 6.5
kcal/mol found for the zeolites 4A. The kinetics of adsorption was studied by
mean of the finite bath method at the temperature of 30°C and initial
concentration of methanol varying from 7.2% to 13.34% by weight. It was
verified that the concentration as well as the pellet size influence the rate of
adsorption. From this evidence it was assumed that the macropore diffusion is the
controlling step. The "Shrinking Core" model was applied to the uptake curves
with satisfactory correlation. The macropore diffusion coefficient of methanol in
activated aluminas was estimated from this model with average value of 0.644E-
05 cm2/s at 30°C.