Evolution Pathway and Role of Intermediates Acetaldehyde and Acetone Formed During the Methanol-to-Olefins Reaction

In this work, we found that besides formaldehyde, an important intermediate in methanol-to-olefins (MTO) conversion, acetaldehyde and acetone were also formed in the MTO reaction and accurately quantified their contents in the reaction system with time on stream. The formation of formaldehyde, acetaldehyde, and acetone follows a sequential reaction. Acetaldehyde could induce the formation of aromatic species, promoting the conversion of lighter aromatic species across cages to polycyclic aromatics and further promoting the formation of insoluble coke, resulting in rapid catalyst deactivation. In addition, acetaldehyde enhances the propagation of the aromatic-based cycle, which leads to the formation of ethylene, thus resulting in the high ethylene selectivity. In contrast, acetone has little effect on the working lifetime of the catalyst and the product distribution of the MTO reaction, although it can be converted to light hydrocarbons similar to that of MTO under the circumstance of the MTO reaction.