1. Introduction Methanol-to-olefins (MTO) conversion is an unsteady state fluidized bed process in which catalyst lifetime is a key metric for economical process operation. In this study, we present two examples (seeding and water cofeeds) in which we exploit a mechanistic understanding of chemistries mediating deactivation to develop strategies for improving catalyst lifetime in methanol-to-olefins conversion. 2. Experimental Reaction products were quantified using an Agilent 7890A GC system with a HP-PLOT Q column connected to a thermal conductivity detector (He as reference gas) and an HP-1 column connected to a flame ionization detector. 3. Results & Discussion Cumulative carbon loss decreased monotonically with seed loading (Figure 1), consistent with the hypothesis that incorporation of the seed leads to the introduction of chain propagation steps that compete with methanol transfer dehydrogenation reactions. Both initiation and termination rates decreased monotonically with increasing water pressure, resulting in a 2.5X enhancement in HSSZ-13 turnover capacity (Figure 2). Enhancement in turnover capacity at a certain temperature was found to correlate with the fraction of formaldehyde formed present as methanediol, suggesting that the scavenging of formaldehyde as methanediol has a major impact on catalyst lifetime. 4. Conclusions Two strategies for improving methanol-to-olefins turnover capacity were developed: one by inhibiting and the other by scavenging formaldehyde formed in methanol transfer dehydrogenation events.

Improving methanol-to-olefins turnover capacity of CHA materials by controlling methanol transfer dehydrogenation rates

256th National Meeting (2018)

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