Catalytic conversion of aromatics in fixed-bed over several zeolites in the liquid phase

Xylene isomerization is an important step in the production of p-xylene. The reaction is normally conducted in the gas phase; however, the liquid-phase isomerization has attracted the attention of both industry and academia. Three MFI-type, two MOR-type, and one BEA-type zeolites with different SiO2/Al2O3 ratios were used to study the conversion of aromatics in the liquid-phase at 513 K. The catalysts were characterized through several techniques to assess their textural and acidic properties. The experiments consisted of 3 ml/min (5 x 10(-8) m(3)/s) of m-xylene fed to a fixed-bed column at 2.1 MPa to maintain liquid-phase conditions for 25-30 h. MFI-type zeolites showed high selectivity towards p-xylene and long stability, but m-xylene conversions were below 5%. Large-pore zeolites exhibited significantly higher conversion but faster deactivation due to secondary reactions. MOR-type zeolite with a SiO2/Al2O3 ratio of 40 showed the best performance with a m-xylene conversion of 45.3% with only 1.9% of secondary products.