Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol by using Ultrasmall Rh Nanoparticles Embedded on Diamine‐Functionalized KIT‐6

Abstract

A Rh/ED‐KIT‐6 catalyst comprised of Rh nanoparticles embedded on mesoporous silica (KIT‐6) functionalized with N1‐[3‐(trimethoxysilyl)propyl]ethane‐1,2‐diamine was synthesized by Rh3+ adsorption and chemical reduction in the liquid phase. The structure of ED‐KIT‐6 and textural properties of the pristine and supported Rh catalysts, as well as particle size and chemical state of the Rh species were examined by various analytical methods. The homogeneous dispersion of ultrasmall Rh nanoparticles, approximately 1.2 nm in size, stabilized by the grafted diamine (ED) species was confirmed. Rh/ED‐KIT‐6 was applied to the transfer hydrogenation of furfural (FFR) to furfuryl alcohol (FAL) by using formic acid (FA) as the hydrogen source. The effect of the solvent and reaction parameters, such as temperature, reaction time, and FA/FFR ratio, were investigated. The Rh‐embedded catalyst exhibited a significantly high turnover frequency (TOF≈204 h−1) to that of Ru, Pd, or Ni‐based catalysts on KIT‐6. A plausible reaction mechanism was proposed after examining an independent FA decomposition reaction over the same Rh‐ED‐KIT‐6 catalyst. The heterogeneity of the catalyst was verified by a hot filtration experiment. The Rh/ED‐KIT‐6 could be reused for up to three cycles without any decrease in catalytic activity and selectivity, but the slow oxidation of Rh species was detected.

Metal Catalysts for the Efficient Transformation of Biomass‐derived HMF and Furfural to Value Added Chemicals

“…Similarly, Rh‐based catalysts have also been explored for hydrogenating upgradation of biomass‐derived furans . Recently, Neeli et al.…”

“…[125] Similarly,R h-basedc atalystsh ave also been explored for hydrogenating upgradation of biomass-derivedf urans. [126][127][128] Recently,Neeli et al explored Rh nanoparticles embedded on diaminefunctionalized KIT-6 (Rh/ED-KIT-6) for the catalytic hydrogenationo ff urfural. [126] The study revealed the necessity of reduced metal to decompose formic acida nd hydrogenation reaction, as the precursor Rh III /ED-KIT-6 (unreduced)w as found to be inactive for the conversion of furfural, while an efficient conversion (98 %) of furfural to furfuryl alcohol (99 %s electivity) was achieved with Rh/ED-KIT-6 using formic acid as ah ydrogen donor in 2-propanol at 100 8C.…”

“…[126][127][128] Recently,Neeli et al explored Rh nanoparticles embedded on diaminefunctionalized KIT-6 (Rh/ED-KIT-6) for the catalytic hydrogenationo ff urfural. [126] The study revealed the necessity of reduced metal to decompose formic acida nd hydrogenation reaction, as the precursor Rh III /ED-KIT-6 (unreduced)w as found to be inactive for the conversion of furfural, while an efficient conversion (98 %) of furfural to furfuryl alcohol (99 %s electivity) was achieved with Rh/ED-KIT-6 using formic acid as ah ydrogen donor in 2-propanol at 100 8C. Resultss uggested that amino groups of the support has as ignificant promotional effect for the hydrogenation of furfural, as Rh/KIT-6 (withoutdiamine) resultedi nv ery lowf urfural conversion (19 %).…”

Catalytic Transfer Hydrogenation of Biomass‐Derived Substrates to Value‐Added Chemicals on Dual‐Function Catalysts: Opportunities and Challenges

“…The nature of C−H and O−H bond activation is still not clear. Similarly, Rh/KIT‐6 catalysts decorated with N 1‐[3‐(trimethoxysilyl)propyl]ethane‐1,2‐diamine as a basic center also show good activity (TOF=204 h −1 ) for furfural conversion to FAL; thus suggesting that the acidic and basic centers contribute to ring activation for C=C cleavage …”

“…The nature of CÀHa nd OÀHb ond activation is still not clear.S imilarly,R h/KIT-6 catalysts decorated with N1-[3-(trimethoxysilyl)propyl]ethane-1,2-diamine as a basic center also show good activity (TOF = 204 h À1 )f or furfural conversion to FAL; thus suggesting that the acidic and basic centers contribute to ring activation for C=Ccleavage. [71] Lewis/Brønsted acidm ediated metallicc atalysts are very popularf or furfural conversion. Lu and co-workersa lso proposed as imilarm echanism for CTH-II of furfural to FALo ver Cu/MgOÀAl 2 O 3 catalysts ( Figure 10).…”