Study on ethylbenzene and xylene conversion over modified ZSM-5

The effects of modification of H-ZSM-5 on its catalytic performance in the conversion of ethylbenzene (EB) and m-xylene were studied. The methods of silica chemical vapor deposition and 5,6-benzoquinoline adsorption can inactivate the external surface of ZSM-5, thus suppressing disproportionation and transalkylation side reactions with which isomerization selectivity and xylene yield increase at the expense of EB conversion and p-xylene yield. In contrast, platinum impregnation cannot only retard the side reactions but can also enhance EB conversion, pxylene yield and catalyst stability. Combining those simple techniques into a multiple modification procedure provoked a synergistic effect enabling optimum design of a Pt/Si/ZSM-5 catalyst. According to reaction mechanisms, the present paper also briefly reviews different generations of commercial isomerization processes. (c) 2007 Elsevier B.V. All rights reserved.