Silicalite-1 Layer Secures the Bifunctional Nature of a CO₂ Hydrogenation Catalyst

Abstract

Close proximity usually shortens the travel distance of reaction intermediates, thus able to promote the catalytic performance of CO 2 hydrogenation by a bifunctional catalyst, such as the widely reported In 2 O 3 /H-ZSM-5. However, nanoscale proximity (e.g., powder mixing, PM) more likely causes the fast deactivation of the catalyst, probably due to the migration of metals (e.g., In) that not only neutralizes the acid sites of zeolites but also leads to the reconstruction of the In 2 O 3 surface, thus resulting in catalyst deactivation. Additionally, zeolite coking is another potential deactivation factor when dealing with this methanol-mediated CO 2 hydrogenation process. Herein, we reported a facile approach to overcome these three challenges by coating a layer of silicalite-1 (S-1) shell outside a zeolite H-ZSM-5 crystal for the In 2 O 3 /H-ZSM-5-catalyzed CO 2 hydrogenation. More specifically, the S-1 layer (1) restrains the migration of indium that preserved the acidity of H-ZSM-5 and at the same time (2) prevents the over-reduction of the In 2 O 3 phase and (3) improves the catalyst lifetime by suppressing the aromatic cycle in a methanol-to-hydrocarbon conversion step. As such, the activity for the synthesis of C 2 + hydrocarbons under nanoscale proximity (PM) was successfully obtained. Moreover, an enhanced performance was observed for the S-1-coated catalyst under microscale proximity (e.g., granule mixing, GM) in comparison to the S-1-coating-free counterpart. This work highlights an effective shielding strategy to secure the bifunctional nature of a CO 2 hydrogenation catalyst.

Crystal epitaxy-confined Pd, Ti-bimetallic sites in the MFI zeolite for benzylalcohol oxidation

“…In fact, a general strategy for constructing spatially segregated multiple metallic components in a zeolite catalyst for the increasing modern demands is strongly desired. Recently, Arian 18 disclosed the epitaxial growth rules of silicalite-1 over ZSM-5, and the obtained results confirmed the growth of an epitaxial silicalite-1 layer without blocking the pore permeability of the inner zeolite core and the catalyst exhibited excellent catalytic performance.…”

Confinement-Induced Indium Oxide Nanolayers Formed on Oxide Support for Enhanced CO2 Hydrogenation Reaction

“…Indium oxide (In 2 O 3 ) and In 2 O 3 -supported catalysts have attracted extensive attention for CO 2 hydrogenation reactions. − Partially reduced In 2 O 3 with rich surface oxygen vacancies is highly active but suffers from over-reduction and sintering in the H 2 -containing atmospheres. − It is a crucial but challenging task to achieve highly dispersed CUSs of In 2 O 3 confined on supports, and they have high activity and stability. Herein, we present a study on the interface confinement effect in an In 2 O 3 –TiO 2 catalyst during the reverse water gas shift (RWGS) reaction.…”

Integration of Nano-Sized HZSM-5 with ZnZrOx as a Bifunctional Catalyst to Boost Benzene Alkylation with Carbon Dioxide and Hydrogen

“…Different metals exhibited different reducibility and migratability under reaction conditions, as reported by Wang et al and Ding et al For example, In and Zn are easily reduced and migrate into zeolite forthwith neutralizing partial BASs; on the contrary, the migration ability of Cr, Zr, and Mn is relatively weak. Xing et al recently found the S-1 layer on the HZSM-5 surface is an efficient shield for defending In migration.…”