Xylene isomerization by ZSM‐5 zeolite catalyst

Abstract

The larger pore LaY zeolite catalyst resembles homogeneous metal chloride and heterogeneous silica‐alumina acid catalysts since the results are consistent with isomerization being a series of intramolecular 1,2 shifts. On the other hand, isomerization with the smaller pore zeolite, ZSM‐5, is very different and the relative rate constants appear to be influenced by diffusion and/or shape selectivity. Disproportionation is a significant reaction with LaY but not with ZSM‐5 in the temperature range used for the present study. The small amount of trimethylbenzene formed at low conversions using ZSM‐5 is 1,2,4‐trimethylbenzene, also providing evidence of shape selectivity influencing the reaction products.

Experimental Design for Catalyst Test. A Statistical Approach

“…Xylene isomerization is an industrially important reaction which allows the conversion of the less useful meta-isomer into para-and ortho-Xylene, extensively used for the plasticizer, synthetic fiber, resin, dye and paint industry. The reaction has been investigated on catalysts like zeolite Y, mordenite and ZSM-5 and is reported to occur in both the liquid and vapor phases [10,11,12,13,14,15,16].…”

Xylene Isomerization in the Liquid Phase Using Large‐Pore Zeolites

“…Since xylene isomerization is normally performed in the gas phase, the information available in the literature on xylene isomerization in the liquid phase is very scarce; the catalysts used are essentially Mordenite (a large-pore zeolite) [15] and ZSM-5 (a medium-pore zeolite) [16][17][18][19]. Nonetheless, there are examples in the industry of xylene isomerization in the liquid phase performed in the past.…”

Kinetic model for hydroisomerization reaction of C8-aromatics

“…The advantage of utilizing rigorous models as compared to empirical approaches is that the prediction accuracy of rigorous models is significantly superior over a wide operating range, hence researchers pursue the kinetic model of process industries. As to C 8 -aromatics isomerization, many kinetic models have been developed over several zeolites [2][3][4][5][6]. Normally, hydrogen is added to promote the isomerization and to prevent the coking on catalyst in the hydroisomerization process.…”