MESOPOROUS HZN-ZSM-5 FOR METHANOL TO AROMATICS WITH HIGH YIELD AND HIGH STABILITY

摘要

MTA process with ZSM-5 modified by Ag~+, Ga~(2+), Zn~(2+) and Mo~(2+) as the catalysts attracted much attention. Incorporating Zn to ZSM-5 framework can increase aromatics yield to 64%, however, the space time yield still kept low since the WHSV was just 0.8 h~(-1), and no obvious improved lifetime was observed. The catalysts suffer from low space tune yield of aromatics and short lifetime, which mainly due to coke formation in the micropores of ZSM-5. Though the deactived catalysts can be regenerated, the activity can not be recovered totally since the irreversible dealumination of ZSM-5 caused by water at high temperature. Alkali-treatment can create mesopores in ZSM-5 besides the micropores, which may be an effective way to improve the lifetime since the carbon capacity can be enlarged a lot. Here we prepared mesoporous HZn-ZSM-5 by direct synthesis method followed by alkali-treatment. The resultant catalyst exhibited high aromatics space time yield and satisfactory stability.