HETEROGENEOUS MODELS OF TUBULAR REACTORS PACKED WITH ION-EXCHANGE RESINS - SIMULATION OF THE MTBE SYNTHESIS

The study of the behavior of fixed-bed reactors using ion-exchange res ins as catalysts was carried out by making use of a complete bidimensi onal heterogeneous model for the reactor, which included the resistanc es inside the ion-exchange resin particles, considered with a macroret icular structure. The active sites were located inside the gel phase o f the resin, represented by microspheres, and on the macropores walls. The overall efficiency of such heterogeneous catalyst particles was d efined by the macroeffectiveness and microeffectiveness factors accoun ting for the process behavior on the macropores and inside the microsp heres. The synthesis of methyl tert-butyl ether, MTBE, a liquid-phase reversible exothermic reaction between methanol and isobutene, was con sidered as a reference case. This system was studied in the temperatur e range of 313-338 K, and the effect of the thermodynamic equilibrium conditions was examined. The results predicted by the complete heterog eneous model were compared with those obtained with the simple pseudoh omogeneous model, which revealed higher hot spots. Moreover, a compari son between bidimensional and unidimensional models was also performed . The orthogonal collocation method was used for the discretization of he differential equations inside the catalyst particles, which were r educed from three (corresponding to the three mass balances for the th ree compounds, isobutene, methanol, and MTBE) to only; one differentia l equation, by using the concept of the generalized variable.