CORE-SHELL STRUCTURED COMPOSITE ZEOLITE FOR SELECTIVE FORMATION OF P-XYLENE IN TOLUENE METHYLATION WITH METHANOL

摘要

The selective formation of p-xylene is a challenging process, because p-xylene is one of the most valuable aromatic compounds as the raw materials of terephthalate and polyester. One of the industrialized technologies for p-xylene production was the selective formation of p-xylene through toluene methylation. The catalyst used in the technique is mainly concerned to varied acid formed zeolites. ZSM-5 was considered as the particularly interesting object among various microporous zeolites in study. Its pore size is supported suitable for separating p-xylene from the other xylene isomers. However, modification to ZSM-5 zeolite is necessary to achieve the highly p-xylene selectivity. Such as impregnation of phosphorous, MgO, or boron; deposition of inert silica on the pore mouth by chemical liquid deposition (CLD) , and chemical vapor deposition (CVD) and other techniques.