Maximizing the catalytic performance of FER zeolite in the methanol-to-hydrocarbon process by manipulating the crystal size and constructing a bifunctional system

Abstract

An unprecedented catalyst lifespan was accomplished with a preferential selectivity for C4–C7 hydrocarbons by combining Y2O3 with a unique flake-shaped FER zeolite with optimized physicochemical properties.

The synergistic interplay of hierarchy, crystal size, and Ga-promotion in the methanol-to-aromatics process over ZSM-5 zeolites

“…Therefore, the consumption and oligomerization of shorter olefin appear to be more influenced by particle size, leading directly to alkylated aromatics via subsequent cyclization/aromatization, bypassing the need for further alkylation. As recently reported by multiple research groups independently, 67,73–78 besides the effects brought by the acid distribution characteristics, Ga-promoter could induce methanol dehydrogenation and disproportionation step to yield formaldehyde, which is considered a pivotal intermediate in the MTA process. 30,81 This intermediate could readily participate in hydrogen transfer, Prins reaction with dienes, and eventually promotes the catalyst deactivation.…”

“…30,81 This intermediate could readily participate in hydrogen transfer, Prins reaction with dienes, and eventually promotes the catalyst deactivation. 67,79–81 This work demonstrates that processes involving formaldehyde are not significant promoting factors, likely due to the use of hierarchical medium-acidic zeolite. This is further confirmed by the relatively long catalytic lifespan and the low increase in the selectivity of C 2 –C 4 alkanes (see Fig.…”

“…Typically, these zeolites exhibited three NH 3 desorption peaks at ≤200 °C, 200–300 °C, and ≥300 °C, which were classified as weak (WAS), medium (MAS), and strong acid sites (SAS), respectively. 21,56,66,67 Herein, the Ga/ZSM-5 zeolites exhibited medium acid sites to some extent and diminished stronger acidity. This aspect could be attributed to substituting some of the zeolite's Brønsted acids with Ga clusters/species, resulting in additional medium acidity.…”

Assessing the effects of dealumination and bifunctionalization on 8-membered ring zeolite/zeo-type materials in the methanol-to-olefin catalytic process

“…30 To mitigate the adverse impact of HCHO, metallic scavengers such as Y 2 O 3 are typically combined with zeolites to form bifunctional catalytic systems, enhancing the reaction's durability. 30,52,72 Hence, in the second phase of our catalytic performance evaluation, we assessed MTO performance over bifunctional catalytic systems, incorporating Y 2 O 3 and untreated or dealuminated zeolites under identical reaction conditions (refer to Fig. 9 and 10 and S21–S25, and Table S1 in the ESI†).…”

“…Despite not significantly altering or promoting specific product selectivity, Y 2 O 3 , a well-known scavenger of formaldehyde (a methanol disproportionation product facilitating aromatic formation), played a crucial role in potentially mitigating aromatics' formation and slowing deactivation by preventing oxymethylene species formation. 52,72 Moreover, the lifetime of catalysts in the MTO reaction over 8-MR zeolites can be extended by dealumination-driven changes in morphology (such as increased hierarchical porosity and smaller crystal size) or acidity (such as altered acid sites distribution or Brønsted–Lewis acid synergy), which improve product diffusion and reduce coke precursor deposition. In essence, this study not only maximizes the catalyst lifetime of 8-MR zeolite/zeo-type materials for the MTO process without affecting preferential product selectivity but also advances the understanding of zeolite-catalyzed methanol conversion chemistry, contributing to the promotion of the methanol economy initiative.…”