LIMA, V. E.; http://lattes.cnpq.br/0261762822034500; LIMA, Verônica Evangelista de.
Abstract:
Adsorption has been a promising alternative to replace conventional
separation process because it presents high efficiency and low energetic/environmental
cost. The biggest petrochemical industrial interest is to separate and purificate xylene
isomer using selective adsorption over type Y zeolites. The separation process occurs in
liquid phase at high temperatures and generally utilizes a dessorbent to improve the
separation (nowadays, /wra-diethylbenzene). In this work, studies of thermodynamic
equilibrium and adsorption kinetics were accomplished for orfo-xylene, para-xylene,
toluene and /?#ra-diethylbenzene over commercial Y zeolites pellets. The experimental
data were obtained in gas phase by gravimetric method in temperatures between 150-
210°C. In the study of thermodynamic equilibrium, rectangular shape isotherms were
obtained and adjusted by Langmuir model. At the same temperature, toluene showed the
highest adsorption capacity, followed by para-xylene, orto-xy\ene and paradiethylbenzene.
It was also observed that the increase of temperature reduces the sorbate
retention for all substances studied. About adsorption kinetics, the uptake curves
denoted that the diffusion rate rises when temperature increases. Two diffusional models
(for micropore diffusion control and shrinking core) were proposed in order to predict
the experimental behavior. Nevertheless the results pointed a more complex transport
mechanism, probably involving the simultaneous effects of micropore and macropore
resistences. In addition, preliminary experiments were made using xylenes over A1P04-11
molecular sieve at 60°C. The results revealed the existence of equilibrium selectivity for
orto-xylene and kinetic selectivity for para-xilene.