Fabrication of high-silica Cu/ZSM-5 with confinement encapsulated Cu-based active species for NH3-SCR

Boosting the catalytic performance of Cu-SAPO-34 in NOx removal via hydrothermal treatment

Phosphate ions promoted Cu-SAPO-34 (P-Cu-SAPO-34) were prepared using bulk CuO particles as Cu2+ precursor by a solid-state ion exchange technique for the selective catalytic reduction of NOx with NH3 (NH3-SCR). The effects of high temperature (H-T) hydrothermal aging on the NOx removal (de-NOx) performance of Cu-SAPO-34 with and without phosphate ions were systematically investigated at atomic level. The results displayed that both Cu-SAPO-34 and P-Cu-SAPO-34 presented relatively poor NOx removal activity with a low conversion (< 30%) at 250-500°C. However, after H-T hydrothermal treatment (800°C for 10 hr at 10% H2O), these two samples showed significantly satisfied NOx elimination performance with a quite high conversion (70%-90%) at 250-500°C. Additionally, phosphate ions decoration can further enhance the catalytic performance of Cu-SAPO-34 after hydrothermal treatment (Cu-SAPO-34H). The textural properties, morphologies, structural feature, acidity, redox characteristic, and surface-active species of the fresh and hydrothermally aged samples were analyzed using various characterization methods. The systematical characterization results revealed that increases of 28% of the isolated Cu2+ active species (Cu2+-2Z, Cu (OH)+-Z) mainly from bulk CuO and 50% of the Brønsted acid sites, the high dispersion of isolated Cu2+ active component as well as the Brønsted acid sites were mainly responsible for the accepted catalytic activity of these two hydrothermally aged samples, especially for P-Cu-SAPO-34H.

Encapsulation of CuO nanoparticles within silicalite-1 as a regenerative catalyst for transfer hydrogenation of furfural

Catalytic transfer hydrogenation (CTH) of biomass-derived furfural (FAL) to furfuryl alcohol is recognized as one of the most versatile techniques for biomass valorization. However, the irreversible sintering of metal sites under the high-temperature reaction or during the coke removal regeneration process poses a serious concern. Herein, we present a silicalite-1-confined ultrasmall CuO structure (CuO@silicalite-1) and then compared its catalytic efficiency against conventional surface-supported CuO structure (CuO/silicalite-1) toward CTF of FAL with alcohols. Characterization results revealed that CuO nanoparticles encapsulated within the silicalite-1 matrix are ∼1.3 nm in size in CuO@silicalite-1, exhibiting better dispersion as compared to that in the CuO/silicalite-1. The CuO@silicalite-1, as a result, exhibited nearly 100-fold higher Cu-mass-based activity than the CuO/silicalite-1 counterpart. More importantly, the activity of the CuO@silicalite-1 catalyst can be regenerated via facile calcination to remove the surface-bound carbon deposits, unlike the CuO/silicalite-1 that suffered severe deactivation after use and cannot be effectively regenerated.

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Ultrasmall CuO NPs are encapsulated in silicalite-1 matrix for CTH of furfural

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Encapsulated CuO catalyst shows impressive Cu-mass-based activity of ∼130 hr⁻¹

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Carbon deposits can be easily removed without the obvious increase in CuO size

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Strong Cu-Si interactions exist in silicalite-1-encapsulated CuO structure