(2gi) Efficient Catalytic Synthesis of Adipic Acid Via Hydrogenation and Hydrogenolysis of Biomass Derived 2,5-Furandicarboxylic Acid

Adipic acid (AA) is one of the most important precursors for synthesizing nylon 6.6. Current adipic acid production continues to rely on the oxidation of KA oil (ketone-alcohol oil) with concentrated nitric acid, which leads to the formation of green house gas nitrous oxide (N₂O). Hence, catalytic synthesis of adipic acid from biomass-derived chemicals reduces the current dependence on the use of fossil-derived benzene as feedstocks and the generation of a substantial amount of N₂O.

In this study, a two-step pathway for synthesizing AA from 2,5-furan dicarboxylic acid (FDCA) is demonstrated via tetrahydrofuran-2,5-dicarboxylic acid (THFDCA) and 2-hydroxyadipic acid (HAA) using a recyclable Ru/Al₂O₃ and an ionic liquid system, [MIM(CH₂)₄SO₃H]I (MIM = methylimidazolium) to produce 99% of overall yield of AA. The hydrogenation and hydrogenolysis of FDCA to THFDCA and HAA were performed over Ru/Al₂O₃, where ruthenium is more economically viable than palladium or rhodium. The H₂ chemisorption, H₂ temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) results showed that the alumina phase strongly affected the interaction between Ru nanoparticles (NPs) and supports, resulting in materials with high dispersion and small size of Ru NPs, responsible for the high conversion of FDCA.

The hydrogenolysis of HAA-mediated THFDCA to AA was conducted over [MIM(CH₂)₄SO₃H]I without solvent. Hammett acidity analysis exhibited the strong Brønsted acidity of [MIM(CH₂)₄SO₃H]I along with high nucleophilicity of iodide, which contributes to the superior activity toward AA. Furthermore, [MIM(CH₂)₄SO₃H]I provides an internal hydrogen source via the dissociation and decomposition process, allowing the reaction occurs without external hydrogen. This catalytic system affords simple adipic acid isolation with high purity and reduces the severe corrosion problems caused by the conventional hydroiodic acid (HI) catalytic system.

Keywords: Adipic acid, 2,5-furan dicarboxylic acid, hydrodeoxygenation.

Figure: Adipic acid production via a two-step reaction from 2,5-furan dicarboxylic acid.

Research Interests

The dependent on fossil resources has placed significant emphasis on the environment, which has led to many critical challenges in climate change, global warming, fossil resources that are diminishing, etc. Due to those challenges, the conversion of biomass into high-value chemicals is a potential solution to minimize the dependence on unsustainable petroleum resources. Therefore, my research interest focuses on understanding and developing high selectivity catalysts for a more sustainable future.

My Ph.D. thesis focused on the production of urethanes (carbamates) and di-urethanes (di-carbamates) via the reductive carbonylation of nitroaromatic compounds over the supported CuSe₂ and FeSe₂ catalyst systems. These catalysts showed very high activity toward carbamate with over 98% yield. In the current postdoctoral research with Prof. Yong Jin Kim and Dr. Jayeon Baek in Korea Institute of Industrial Technology (KITECH), I am studying the use of the supported metal catalysts and ionic liquids for the two-step hydrodeoxygenation of 2,5-furan dicarboxylic acid (FDCA) toward adipic acid (AA). It is demonstrated that a Ru/Al₂O₃ was highly selective for FDCA hydrogenation to tetrahydrofuran-2,5-dicarboxylic acid (THFDCA) under mild conditions, while [MIM(CH₂)₄SO₃H]I (MIM = methylimidazolium) showed high activity toward adipic acid via a sequent ring-opening of THFDCA. Exciting recent results from these studies will be presented in this poster. Moreover, the one-pot pathway from FDCA to AA appears attractive and challenging because not many studies have mentioned this route. Motivated by those challenges, my research will expand to focus on developing new approaches and high-performing homogeneous and heterogeneous catalysts for the hydrodeoxygenation of bio-based platform molecules. It will aim to gain more understanding of ring-opening reactions, investigate catalyst’s stability and deactivation, and broaden the scope of the hydrodeoxygenation on different biomass-derived substrates such as HMF, furfural, furan derivatives toward high value-added chemicals. With the increasing environmental issues, biomass catalysis technology will aid the transition of our chemical industry to a more sustainable one and meet future needs in eco-friendly chemical manufacturing.