Selectivity Control in Tandem Catalytic Furfural Upgrading on Zeolite-Encapsulated Pt Nanoparticles through Site and Solvent Engineering

Abstract

Selectivity control is a pressing challenge in developing selective tandem catalytic processes. In this work, we demonstrate that tailoring types of acid sites of zeolite-encapsulated Pt nanoparticles (NPs) and choosing solvents provide a compelling strategy to manipulate product distribution in tandem catalysis. The model tandem furfural conversion with acetone and ethanol (EtOH) is investigated in cyclohexane and EtOH solvents. Pt NPs encapsulated in ZSM-5 with Brønsted acid sites (BAS) only located in intracrystalline mesopores selectively mediate the tandem aldol condensation and subsequent hydrogenation of furfural and acetone by limiting the access of furfural to Pt sites and promoting the aldol condensation. A combined yield of 69% toward hydrogenated aldol adducts is achieved. In contrast, furfural hydrogenation to valeric acid (VA) and ethyl valerate (EV) dominates with a combined yield of 80% on Pt NPs encapsulated in ZSM-5 with Lewis acid sites (LAS) and BAS in both zeolitic micropores and intracrystalline mesopores. The concentration of EtOH in the reaction system is identified as another key parameter in selectivity control: (1) low EtOH concentrations (EtOH to furfural ratio of <5) suppress the catalytic transfer hydrogenation pathway and favor the formation of 2methylfuran (MF) from furfural, as most hydrogenation and hydrogenolysis steps occur on Pt NPs, (2) modest EtOH concentrations (EtOH to furfural ratio of 5−10) favor VA/EV by enabling the catalytic transfer hydrogenation pathway in zeolitic micropores and exposing intermediates to BAS prior to Pt NPs, and (3) high EtOH concentrations (EtOH to furfural ratio of >10) suppress the production of VA/EV by excessive water formation via acid-catalyzed etherification of EtOH. Therefore, tailoring the nature of active sites and changing the solvent composition are both effective strategies in manipulating the product distribution in tandem catalysis.

Incorporation of Active Metal Species in Crystalline Porous Materials for Highly Efficient Synergetic Catalysis

“…In the further work, Xu's group ulteriorly investigated the influences of the nature and density of acid sites in ZSM-5-encapsulated Pt NP catalysts (Pt@ZSM-5) on the product distribution in a tandem catalytic upgrade of furfural (Figure 18f). [185] The Pt@Na-ZSM-5 catalyst was also synthesized by the cationic polymer-assisted method and followed by completely exchanging of Na + with H + to obtain a H-type Pt@H-ZSM-5. The solidstate NMR and spectroscopy experiments confirmed that the Pt@H-ZSM-5 has both distinct Lewis acid sites and Brønsted acid sites (Figure 18h), while the Pt@Na-ZSM-5 only possesses the former (Figure 18f).…”

“…i,j) Product distribution in the conversion of furfural on i) Pt@Na-ZSM-5 and j) Pt@H-ZSM-5. Reproduced with permission [185]. Copyright 2020, American Chemical Society.…”

Understanding the geometric and electronic factors of PtNi bimetallic surfaces for efficient and selective catalytic hydrogenation of biomass-derived oxygenates

“…The overexploitation and depletion of non-renewable fossil source are causing aggravating energy crisis and severe environmental pollution [1][2][3][4]. Upgrading of various renewable biomassderived platform chemicals is a sustainable approach to provide valuable biofuels and high value-added chemicals for human society [5][6][7][8]. Furfural (FAL) is a crucial versatile intermediate to manufacture biofuels and high value products, which was directly obtained from enormous potential supply of lignocellulose [9][10][11][12][13].…”

One-step upgrading of bio-based furfural to γ-valerolactone via HfCl4-mediated bifunctional catalysis

“…[21][22][23] The main barrier could be that the selective transformation of FF into GVL requires multiple steps (Scheme 1), including hydrogenation, hydrolysis ring-opening, partial hydrogenation, cyclization, and other steps (e.g., etherication, esterication, and lactonization), in which a specic active site is needed for each step of the reaction. 9,24,25 In addition, the reaction process is oen accompanied by the formation of humin, [26][27][28] making it far from ideal for commercialization.…”

“…33 In addition, the Brønsted acid site is also essential for the ring-opening reaction. 31 In the reported studies, the non-noble metals that catalyze the cascade transformation of FF into GVL are mostly Zr-based catalysts, [26][27][28] while there are few reports on Hf-based catalysts. 30 Although these prepared catalysts show good catalytic activity for the conversion of FF to GVL, they have some disadvantages too that cannot be ignored.…”