Key Takeaways & Executive Findings
- •• • Ni2Al-LDO catalyst achieves 91.42% yield of furfuryl alcohol (FOL) at 160 °C and 1.4 MPa H2, demonstrating high selectivity for partial hydrogenation of furfural, which is critical for producing resin and pharmaceutical intermediates. • • After reduction at 700 °C for 2 h, the catalyst (Ni2Al-LDO-700) yields 93.95% tetrahydrofurfuryl alcohol (HFOL) under identical conditions, showcasing a complete switch in selectivity from FOL to HFOL via reduction-degree engineering. • • The selectivity switch is governed by the NiO/Ni0 ratio: NiO-rich surfaces adsorb only the carbonyl group, promoting MPV hydrogenation with isopropanol, while metallic Ni0 surfaces adsorb both furan ring and carbonyl, enabling full hydrogenation with H2 as the primary hydrogen source. • • The reduction-degree engineering strategy offers a general approach for designing non-precious metal catalysts with tunable selectivity, addressing the bottleneck of controlling hydrogenation pathways in biomass upgrading.
Abstract
The selective hydrogenation of biomass-derived furfural (FAL) to high-value chemicals such as furfuryl alcohol (FOL) or tetrahydrofurfuryl alcohol (HFOL) is pivotal yet challenging due to the need for precise control over reaction pathways. In this study, a Ni2Al-LDO (layered double oxide) catalyst with highly dispersed surface NiO was synthesized via structural topological transformation of layered double hydroxides. The catalyst exhibited excellent performance in furfural hydrogenation, achieving a 91.42% yield of FOL at 160 °C and 1.4 MPa H2. Gradual reduction of Ni2Al-LDO produced Ni/NiO mixtures, enabling a tunable shift from FOL to HFOL as NiO content decreased and metallic Ni content increased. After reduction at 700 °C for 2 hours, the HFOL yield reached 93.95% under identical conditions. CO2-TPD, NH3-TPD, and FT-IR analyses revealed that variations in reduction degree influenced furfural adsorption behavior. NiO species selectively adsorb the C=O group of furfural, with isopropanol serving as the hydrogen source via the Meerwein-Ponndorf-Verley (MPV) pathway, yielding FOL. In contrast, metallic Ni0 surfaces facilitate flat adsorption, enabling simultaneous activation of both the furan ring and carbonyl group, and can activate both H2 and isopropanol, with H2 as the primary hydrogen source, leading to complete hydrogenation to HFOL. This work elucidates a clear structure-activity relationship centered on the metal oxidation state and provides a practical reduction-engineering approach for designing adaptable catalysts in biomass upgrading.
1. Introduction
The catalytic hydrogenation of biomass-derived furfural (FAL) is a cornerstone reaction for producing renewable chemicals, yet achieving selective conversion to either furfuryl alcohol (FOL) or tetrahydrofurfuryl alcohol (HFOL) remains a significant challenge. Conventional catalysts often suffer from poor selectivity due to uncontrolled adsorption modes, leading to over-hydrogenation or ring-opening side reactions. The industrial demand for high-purity FOL (used in resins, lysine, and vitamins) and HFOL (a green solvent and intermediate) necessitates precise control over the hydrogenation pathway, but existing noble-metal catalysts are costly and exhibit limited tunability.
This study addresses this bottleneck by employing a Ni-based catalyst derived from layered double hydroxides (LDHs), where the reduction degree of nickel (NiO vs. Ni0) is systematically engineered. The authors demonstrate that NiO-rich surfaces selectively hydrogenate the carbonyl group via the MPV mechanism, yielding FOL, while metallic Ni0 surfaces enable flat adsorption and complete hydrogenation to HFOL. This reduction-degree engineering provides a cost-effective, non-precious metal alternative with switchable selectivity, offering a practical solution for biomass upgrading.
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CHANG Xiaoqing, JIA Lingyu, DANG Shanshan, LU Tianliang, WANG Peng, TU Weifeng, ZHANG Zhenzhou (2026). Switching Hydrogenation Pathways of Furfural via Reduction-Degree Engineering of Ni-Based Catalysts. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60664-0
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Frequently Asked Questions
What is the exact reduction temperature and time required to achieve the highest HFOL yield, and how does this affect the NiO/Ni0 ratio?
The highest HFOL yield of 93.95% is achieved after reducing the Ni2Al-LDO catalyst at 700 °C for 2 hours. This reduction transforms the catalyst into a Ni0-dominant state, as evidenced by the shift in selectivity from FOL to HFOL. The NiO content decreases while metallic Ni increases, enabling complete hydrogenation of furfural.
How does the catalyst's adsorption mode change with reduction degree, and what are the mechanistic implications for hydrogenation?
On NiO-rich surfaces, furfural adsorbs only via the carbonyl group, activating isopropanol as a hydride donor via the MPV mechanism, yielding FOL. On metallic Ni0 surfaces, furfural adopts a flat adsorption mode, allowing simultaneous interaction with both the furan ring and carbonyl group. This, coupled with efficient H2 dissociation on Ni0, drives complete hydrogenation to HFOL.
What are the optimal reaction conditions for achieving high FOL yield, and how do they compare to typical industrial processes?
The Ni2Al-LDO catalyst achieves 91.42% FOL yield at 160 °C and 1.4 MPa H2. These conditions are relatively mild compared to some industrial processes that may require higher pressures or temperatures. The use of isopropanol as a hydrogen donor in the MPV pathway also offers an alternative to high-pressure H2, potentially reducing operational costs.
What is the role of isopropanol in the reaction, and can H2 be used as a sole hydrogen source for FOL production?
Isopropanol serves as the hydrogen source for the NiO-rich catalyst via the MPV mechanism, where it donates a hydride to the carbonyl group. The Ni2Al-LDO catalyst is only capable of activating isopropanol, not H2. In contrast, the reduced Ni2Al-LDO-700 can activate both H2 and isopropanol, but H2 becomes the primary hydrogen source for HFOL production. For FOL production, isopropanol is essential; H2 alone would not yield FOL on the NiO-rich catalyst.
How does the catalyst's stability and recyclability perform under repeated reaction cycles?
The paper does not explicitly report recyclability data. However, the catalyst is derived from layered double hydroxides, which are known for thermal stability. The reduction process at 700 °C suggests robustness, but further studies are needed to assess long-term stability and potential deactivation mechanisms such as sintering or coke formation.
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