ESTUDIO COMPARATIVO DE LA HIDROCONVERSIÓN DE AROMÁTICOS C8 SOBRE CATALIZADORES Pt/MORDENITA Y Pt/SiO2-Al2O3 COMPARATIVE STUDY OF THE HYDROCONVERSION OF C8 AROMATICS OVER Pt/MORDENITE AND Pt/SiO2-Al2O3 CATALYSTS

The C8 aromatics fraction in a refinery consists mainly of four isomers i.e. ortho-, meta-, para-xylene and ethylbenzene, being para-xylene the one with major industrial importance. Since the equilibrium amount of paraxylene at the outlet of the catalytic reformer is only ∼24 %, a separation of this isomer is performed, and the orthoand meta- rich fraction is selectively isomerized. The reaction system is highly complex and besides isomerization, hydrogenolysis, disproportionation, trans-alkylation and hydrocracking might also occur during the reaction. In the past, a Pt/silica-alumina catalyst was used in the industrial reactor for this process, however lately zeolitic catalysts have gained importance due to their better activity and selectivity. In this work, the catalytic behavior (selectivity) of Pt/Mordenita and Pt/SiO2-Al2O3 commercial catalysts in the hydroconversion of C8 aromatics was analyzed through a mathematical reaction model. A pseudo-heterogeneous one-dimensional model was used to represent the behavior of the reactor. The proposed model represents well the product distribution and outlet temperature of the industrial reactor. The results of the parametric sensitivity analysis indicated that temperature, pressure and space velocity were the most influential variables for the yield of para-xylene, while for the loss of xylenes, pressure and space velocity were more important than temperature. Intermediate values of temperature (377-427 °C), pressure (10-15 atm) and W/Fo (5-10 kgcat/kgmol/h) favored the para-xylene yield and decreased the loss of xylenes.