Exfoliated Layered Metal Oxide-Supported Ruthenium Catalysts for Base-Free Oxidation of 5-Hydroxymethylfurfural into a Renewable Bioplastic Precursor

Thedeveloped Ru-based nanocomposites are potential catalystsfor sustainable production of a high-purity FDCA biopolymer precursorin a homogeneous base-free aqueous system. 2,5-Furandicarboxylic acid (FDCA) is a potential biopolymerprecursorfor polyethylene furanoate production. This study focused on synthesizingFDCA via catalytic oxidation of 5-hydroxymethylfurfural (HMF) overRu-based catalysts supported on exfoliated MgAl-double oxides (LDO)for the first time in a homogeneous base-free system. Effects of theexfoliation solvent, preparation method, and Ru loading level on thephysicochemical and catalytic properties of the resulting catalystswere investigated. The exfoliated LDO-supported Ru catalysts exhibitedenhanced textural properties, RuO x dispersion,and basicity, resulting in better catalytic activity (at least 6 timeshigher FDCA yield) than conventional LDO-supported Ru catalysts inthe conversion into FDCA. The Ru-based catalyst supported on an exfoliatedLDO/carbon nanocomposite, Ru(3)/ESV-LDC, revealed the nearly completeHMF conversion (99.2%) at an FDCA selectivity of >98%. This wasattributedto the synergistic effect derived from good RuO x dispersion, providing a high proportion of lattice oxygenfor boosting surface oxygen mobility, and high basicity, in termsof both strength and number of basic sites. Moreover, Ru(3)/ESV-LDCexhibited good reusability without a significant loss of HMF conversionand FDCA yield, suggesting strong chemical robustness of RuO x species and a stable interaction between the activemetal and support.