Abstract
Over the past 30 years, the methanol-to-olefin (MTO) process on acidic zeolites has been subject to a vast number of studies from both industrial and academic researchers, leading to numerous controversies regarding the most probable reaction mechanism. Improvement of computational facilities during the past decade led to a sudden boost of theoretical contributions that, when considered individually, all seemed to provide reasonable evidence for partial pathways of the commonly proposed direct mechanisms. Not only the reactions suggested by experimental studies were investigated, but in addition novel potential routes were discovered by theoreticians as well. However, when all of the individual reactions scattered throughout the literature were recently combined, theoretically obtained rate coefficients turned out to show the exact opposite, that is, the complete failure of the direct mechanisms to produce ethylene from methanol only. In this paper, we give a detailed overview of the theoretical contributions that initially supported the direct mechanism proposal, but which finally culminated in its demise.