Microwave-Assisted Optimized Synthesis Conditions for the Conversion of Methanol to Olefins over Variable Content of Aluminum ZSM-5 Zeolite

The synthesis of ZSM-5 zeolite with different silicon to aluminum ratios (SAR) was performed under microwave radiation. The synthesized samples were ion-exchanged with ammonium nitrate to form the proton form of the zeolite (H-ZSM-5) and then evaluated in a fixed bed reactor for methanol conversion to light olefins. The modified ZSM-5 zeolite samples showed excellent selectivities toward light olefins (C2= , C3= , and C4=) and the selectivities were in the range of 75.2 and 82.7%. The catalyst’s lifetime was proportional to the ratio of SAR, and the lifetime was enhanced from 7 to 33 h by increasing the SAR from 30 to 150. An additional increase in the SAR from 150 to 750 led to a reduction in the lifetime from 33 to 14 h. On the other hand, the selectivity to propylene was proportional to the ratio of SAR, while the selectivity toward ethylene showed an inverse proportionality as the SAR increases. The zeolitic properties of the synthesized ZSM-5 zeolites demonstrated the influence of textural and acidity properties on the catalytic performance in the MTO reaction.