Kinetic Model and Simulation Analysis for Toluene Disproportionation and C9-Aromatics Transalkylation

A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity(WHSV)into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giv- ing the guidance to select suitable operating conditions.

Disproportionation of Toluene by Modified ZSM-5 Zeolite Catalysts with High Shape-selectivity Prepared Using Chemical Liquid Deposition with Tetraethyl Orthosilicate

Shape-selective catalysts for the disproportionation of toluene were prepared by the modification of the cylinder-shaped ZSM-5 zeolite extrudates with chemical liquid deposition with TEOS （tetraethyl orthosilicate）.Various parameters for preparing catalysts were changed to investigate the suitable conditions.The resulting cata-lysts were tested in a pressured fixed bed reactor and characterized by SEM （scanning electron microscopy）.The conversion of toluene and para-xylene selectivity were influenced remarkably by the n（SiO2）/n（Al2O3） ratio of ZSM-5 zeolite,the type and amount of deposition agent,acid and solvent used,and the time and cycle of deposition treatment.TEOS was proved to be a more efficient agent than the conventional polysiloxanes when the deposition amount was low.The catalyst prepared at the suitable conditions exhibited a high para-xylene selectivity of 91.1% with considerable high conversion of 25.6%.SEM analyses confirmed the formation of a layer of amorphous silica on the external surface of ZSM-5 zeolie crystals,which was responsible for the highly enhanced shape-selectivity.

The Difference between ZSM-5 Zeolites Manufactured from Various Synthesis Systems and Their Catalytic Performances

ZSM-5 zeolites with similar St/Al ratio were synthesized successfully using various templates [n- butylamine （BTA）, tetrapropylammonium bromide （TPABr） and no template （NT）] under hydrothermal conditions, The samples were characterized by XRD, SEM, Py-IR and BET surface area measurements in order to understand the template eiTects and the differences between the ZSM-5 santples. The synthesis of ZSM-5 with organic templates was relatively easier than those with inorganic templates and withnut template. SEM results revealed that ZSM-5 synthesized with different templates had different morphologies in similar particle size. Toluene disproportiortation reaction was carried out over the catalyst samples to evaluate the catalytic properties. The results have shown that large crystals which have a correspondingly small external surface showed a high para-xylene selectivity, and the amount of C9^＋ and C5^＋ was much less than that obtained from zeolite with small crystals.