Methanol conversion over SAPO-34 catalysts; Systematic study of temperature, space–time, and initial gel composition on product distribution and stability

Abstract

The effect of temperature, space–time and the molar ratio of morphine to alumina over the SAPO-34 catalyst in methanol to olefin (MTO) process and catalytic stability were studied. Response surface methodology coupled with central composite design (CCD) was used to investigate the exact effect of main factor and their interactions. From the CCD studies, the effects of temperature and space–time were concluded to be the key factors influencing initial light olefins yield, while the molar ratio of morpholine to alumina had the most important role in catalytic stability compared with the other two variables. It was found that an optimum for initial propylene yield resulted from increasing temperature and space–time. However, increasing temperature and space time resulted in increasing initial ethylene yield. Furthermore, optimum points were found for the reduced ethylene and reduced propylene (catalytic stability). The best conditions for simultaneous maximization of initial ethylene and initial propylene yields are at T=466°C, space–time=12.08 gcathrmolMeOH and the molar ratio of morphine to alumina=0.94. The optimal set, T=411°C, space–time=12.24 gcathrmolMeOH and the molar ratio of morphine to alumina=0. 92, with the goal of minimizing both the reduction of ethylene and propylene after processing 8g of methanol per unit weight of catalyst (M=8) was achieved.