One-Pot Cascade Conversion of Renewable Furfural to Levulinic Acid over a Bifunctional H₃PW₁₂O₄₀/SiO₂ Catalyst in the Absence of External H₂

Abstract

The conversion of biomass-derived furfural (FUR) to levulinic acid (LA), a versatile platform chemical, involves catalytic hydrogenation of FUR followed by acid hydrolysis to LA. However, this two-step process demands expensive separation and purification of the furfuryl alcohol (FAL) intermediate. Herein, we demonstrate an ingenious catalytic strategy for the one-pot cascade conversion of FUR to LA over a bifunctional catalyst without using pure external H2. Isopropyl alcohol (IPA) served a dual role as a hydrogen donor and solvent while inhibiting the side reactions. Catalysts with a tunable surface area and acidity were synthesized by impregnating different percentages of H3PW12O40 (heteropolyacid) over a SiO2 support. The bifunctionality of the H3PW12O40/SiO2 catalyst is ascribed to the mutual coexistence of Lewis and Bro̷nsted acid sites. The Lewis acid sites imparted by active W metal sites adsorb hydrogen proton for catalytic transfer hydrogenation of FUR to FAL, while the predominant Bro̷nsted acid sites catalyze the hydrolysis of FAL to LA. Consequently, H3PW12O40/SiO2 revealed to be a potential catalyst producing an ∼51% LA yield under optimized reaction conditions. Moreover, the catalyst was found to be reusable for three catalytic cycles. This study paves the way to develop future biorefinery, particularly direct conversion of FUR to LA over a bifunctional catalyst with a liquid H-donor, in an environmentally benign manner and comply with the green chemistry principles.

Role of lattice strain in bifunctional catalysts for tandem furfural hydrogenation–esterification

“…2,5,[20][21][22] Combining the esterification and hydrogenation steps, SiO 2 -supported bifunctional metal catalysts have been widely investigated to convert furfural through tandem hydrogenation-esterification reactions. [23][24][25][26][27][28] For instance, furfural, and acetic acid conversion were found to produce furfuryl acetate using Pd supported on acidmodified SBA-15. 25 The atomic structure of the active metal, in synergy with the Brønsted acid sites is significant in governing the catalytic activity during the tandem hydrogenation-esterification of fufural.…”

“…2,22 Distortion in the atomic structure of the active metal can limit the hydrogenation step that produces an in situ furfuryl alcohol substrate during the tandem hydrogenation-esterification reaction. 21,[23][24][25][26][27][28][29][30][31] Therefore, the role of structural distortion of metal-supported bifunctional catalysts in activity has not been reported for the tandem hydrogenation-esterification system. In essence, the MSI properties such as charge transfer between the metal, particularly in the nano-regime and the support material, 9,14,32 interfacial reactions, 5 including lattice strain, are essential aspects of the underlying chemistry in tandem reactions.…”

Soft nanobrush-directed multifunctional MOF nanoarrays

“…These findings demonstrated the presence of a synergistic catalytic effect between the MPVA2 and MIL-100 (Fe), where the abundant Fe 3+ active sites on the highly aligned MIL-100 (Fe) nanoarray dominate the oxidative dehydrogenation of CH 3 OH, while the doped MPAV2 moieties provide additional redox catalytic sites (V 5+ ) and acid sites involved in the acetalization reactions. On the contrary, the phosphotungstic acid PW 12 only provided the acid sites 27 and hence the PW 12 (18.6 wt%)-doped MIL-100 (Fe) nanoarray only led to the formation of MF (methyl formate) as the major product (Supplementary Fig. 21).…”

“…6b,c and Supplementary Figs. [26][27][28][29][30][31] 31 . Compared to the pristine HKUST-1 nanoarray (16 µL), the HKUST-1 nanoarray (16 µL) loaded with 0.36 wt% of Pt nanoparticles [HKUST-1 nanoarray (16 µL)/Pt-0.36] displayed a remarkably higher sensitivity and cycling reversibility to 1 ppm H 2 S at 200 °C and the resistance quickly recovered to the baseline within 17.9 s (Fig.…”

Design of Heterogeneous Catalysts for the Conversion of Furfural to C5 Derivatives: A Brief Review

“…Nandiwale et al [52] developed silica-supported heteropoly acid catalysts to achieve the onepot conversion of FF to LA. With the optimized reaction conditions, a yield of 51% was achieved.…”