Rational Design of Synergistic Active Sites for Catalytic Ethene/2-Butene Cross-Metathesis in a Rhenium-Doped Y Zeolite Catalyst

Abstract

Synthesizing atomically dispersed synergistic active pairs is crucial yet challenging in developing highly active heterogeneous catalysts for various industrially important reactions. Here, a single molecular Re species is immobilized on the inner surface of a Y zeolite with Brønsted acid sites (BASs) within atomic proximity to form Re OMS–BAS active pairs for the efficient catalysis of olefin metathesis reactions (OMS: olefin metathesis site). The synergy within the active pairs is revealed by studying the coadsorption geometry of the olefin substrates over the active pairs by synchrotron X-ray and neutron powder diffraction. It is shown that the BAS not only facilitates olefin adsorption but also aligns the olefin molecule to the Re OMS for efficient intermediate formation. Consequently, for the cross-metathesis of ethene and trans-2-butene to propene, this catalyst shows high activity under mild reaction conditions without observable deactivation. The catalyst outperforms not only traditional ReO x -based catalysts but also the best industrially applicable WO x -based catalyst thus far that we discovered previously. The concept of using two isolated active sites of different functionalities within atomic proximity in a confined cavity can provide opportunities for designing synergistically catalytic materials.

First-Generation Organic Reaction Intermediates in Zeolite Chemistry and Catalysis

“…Furthermore, Michorczyk et al recently showed that carbene-like species formed on Mo sites enhance the metathesis performance when Mo-loaded SBA-15 catalyst is treated with methane at 650 °C prior to propene metathesis at 50 °C. Also because Fe incorporated ZSM-5 shows significant activity for MDA, some researchers have suggested the possible formation of carbenes (C–FeCH 2 ) on carburized iron sites, considering the “Fischer-type” metal–carbene complexes. , Moreover, there are various other reactions (i.e., alkane isomerization, olefin metathesis) in which zeolite supported/assisted metal–carbene (i.e., PtCH 2 , ReCH 2 , ReCHCH 3 ) catalysts can play an effective role. − Essentially, carbenes exist in zeolite chemistry catalysis, albeit their identification depends primarily on indirect evidence, or their catalytic impact has not been completely studied. Like the radical section (cf.…”

Enhancing the activity of a supported rhenium catalyst for cross-metathesis of ethene and 2-butene via promotion of boron

“…[1][2][3] In this process, catalysts based on supported transition metals Re, molybdenum, and tungsten are normally employed to achieve decent efficiency for propene production. [4][5][6] In particular, Re-based catalysts stand out and set themselves apart from the others due to their high activity at mild temperatures (<100 °C). 7 However, it has been observed that only a small proportion of Re species within supported Re-based catalysts actually participate in the olefin metathesis reaction, while the majority of Re remains inactive.…”

Enhancement of Propylene Metathesis Performance of MoO3/Al2O3 with Promotion of Phosphoric Acid

“…[5] In addition, this promotion effect would be particularly pronounced when the Brønsted acidic site is highly dispersed and located adjacent to the metallic sites. [5][6] Due to similar physiochemical properties between Mo and W, it is reasonable to deduce that a comparable principle would also be feasible for the Mo-based counterparts. Therefore, we anticipate that constructing an appropriate Brønsted acidic site adjacent to the MoO x sites might facilitate its activation and conversion into active Mo-carbene species, and further promote its intrinsic activity.…”

“…Recently, the Brønsted acidic OH group has been found effective in promoting W‐carbene formation by alignment of the olefins toward WO x sites, which enables facile cycloaddition between C=C and WO x to generate active W=CHR intermediates [5] . In addition, this promotion effect would be particularly pronounced when the Brønsted acidic site is highly dispersed and located adjacent to the metallic sites [5–6] . Due to similar physiochemical properties between Mo and W, it is reasonable to deduce that a comparable principle would also be feasible for the Mo‐based counterparts.…”