Insights into the methanol to olefins (MTO) performance of SAPO-34 under the stripper conditions of fluid catalytic cracking (FCC)

FCC is an important process for light olefins production, but it's a challenge to enhance the ethylene selectivity. In view of the high selectivity of ethylene and propylene (SEP) of MTO and the similar process of FCC and MTO, methanol may be co-fed from the stripper units to improve the selectivity of light olefins (SLO), especially ethylene, of a conventional FCC process. Herein, the MTO performance of SAPO-34 under the stripper conditions was studied, and the influences of the coke from heavy oil cracking were analyzed. When MTO was performed following the conditions (500 degrees C, 7.5-35 h-1) in the FCC stripper, the SEP and SLO achieved 83-86% and 91-96%, respectively, the weight ratio of ethylene to propylene (mEe:mPe) was about 1.2-1.6, and dimethyl ether was not detected. Although more complicated coke was introduced by heavy oil, the active polymethylbenzenes can help retaining the SEP (82.2%) and SLO (89.3%), and the methanol utilization efficiency and mEe:mPe were enhanced from 92.5% to 1.21 to 95.3-95.9% and 1.34, respectively. More importantly, the SEP, SLO and mEe:mPe can further be enhanced to 85.6%, 91.6%, and 1.52, respectively when SAPO-34 with less strong acid sites was applied. Consequently, SAPO-34 may be used as an FCC catalysts promoter for the development of a modified FCC process with significantly enhanced SLO.

Automated summary

This study investigates the co-feeding of methanol from stripper units to enhance the ethylene selectivity in the conventional FCC process. The results show that the use of SAPO-34 catalyst under specific conditions can significantly improve the yield of ethylene and light olefins.