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

Abstract

Summary 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.

Recent advances in the catalytic transfer hydrogenation of furfural to furfuryl alcohol over heterogeneous catalysts

“…Weng et al fabricated silicalite-1 confined ultrasmall CuO catalysts (CuO@silicalite-1) for the CTH of FF to FFA. 65 93.2% FF conversion and 88.3% FFA yield were obtained over 3CuO@sil-1 in ethanol at 513 K for 1.5 hours. Good stability was demonstrated with 84.1% FFA yield still being obtained after six cycles.…”

Zeolite confinement-catalyzed cleavage of C–O/C–C bonds in biomass

“…104 The feasibility of PVP-stabilized metals in one-pot dry-gel conversion has also been further demonstrated by the encapsulation of base metals within zeolites, such as CuO@S-1. 105 In addition, the one-pot hydrothermal synthesis method of dry-gel conversion further inhibits the potential precipitation of metals at higher pH because they crystallize in solvent-free conditions compared to the one-pot hydrothermal method. Based on this, the encapsulation of Pt or Pd in all-silica ZSM-22 zeolite, a zeolite with a TON topology, was achieved using (3-mercaptopropyl) trimethoxysilane as the metal stabilizer (Fig.…”

“…19b). 105 Notably, the catalytic activity of CuO@S-1 can be recovered by removing carbon deposition after calcination at 550 °C. However, CuO/S-1 suffers from irreversible sintering of CuO during both the reaction and the regeneration process due to poorer stability, resulting in the permanent activity loss (Fig.…”

“…19 (a) Schematic diagram of the reaction and regeneration process of encapsulated and loaded catalysts. 105 (b) Yield of furfuryl alcohol over fresh, spent, and regenerated 3CuO@sil-1, 23CuO/SiO 2 and 3CuO/ sil-1. 105 (c) Regenerability of Ni/H-ZSM-5 and Ni@H-ZSM-5.…”

“…105 (b) Yield of furfuryl alcohol over fresh, spent, and regenerated 3CuO@sil-1, 23CuO/SiO 2 and 3CuO/ sil-1. 105 (c) Regenerability of Ni/H-ZSM-5 and Ni@H-ZSM-5. 178 metals encapsulated in mesoporous zeolite have also been developed, showing high catalytic stability because of the combination of the ability to reduce coke formation and metal sintering provided by the mesoporous and encapsulation effects, respectively.…”