Selective and Robust Ru Catalyst for the Aqueous Phase Aerobic Oxidation of Furfural to 2-Furoic Acid

Abstract

Synthesis of 2-furoic acid (FURA) via oxidation of furfural (FAL) is vital in evolving the biorefinery concept as FURA has numerous important applications in the pharmaceuticals and optic areas. Though few works on this reaction are done, those are marred with shortcomings such as the nonrecyclability of catalyst, dilute solutions, lower yields, or use of H 2 O 2 as an oxidizing agent. Herein, we report catalytic aqueous phase oxidation of FAL to FURA using molecular oxygen as an oxidizing agent. For the synthesis of FURA, various catalysts with a combination of metal (Pt, Pd, Ru) and supports (carbon, Al 2 O 3 ) were prepared and characterized by multiple techniques (X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer−Emmett−Teller (BET), X-ray photoelectron spectroscopy (XPS)). Oxidation of FAL carried out over 5 wt % Ru/C catalyst in the presence of Na 2 CO 3 yielded 83% of FURA at 120 °C and 15 bar oxygen pressure. The catalyst could show potential for reusability as similar activity was achieved after subjecting the spent catalyst to mild reduction treatment (150 °C). Studies on the effects of temperature, pressure, and time could help accomplish enhanced yields of FURA. Additionally, learning about the effect of base (weak/strong/solid) revealed that due to the weak basicity of Na 2 CO 3 , higher yields could be achieved by maintaining approximately a pH of 11, which is optimal for suppressing side reactions. Under the given conditions, FURA is stable (>90%) and also adsorption studies divulge that it is immediately removed from the catalyst surface, and hence higher yields could be achieved in our catalytic system. Using the initial rates methodology, an activation energy of 21.91 kJ mol −1 was derived and also a high turn over frequency (TOF) (85.9 h −1 ) was observed under optimized conditions.

Bioconversion of Furanic Compounds by Chlorella vulgaris—Unveiling Biotechnological Potentials

“…2-Furoic Acid and 5-Hydroxymethyl-2-Furoic Acid have been studied for their potential in industrial applications. 2-Furoic Acid has been used in optical applications [ 46 ], as resin materials and coatings [ 47 ] and in flavor and fragrance industries [ 48 ]. Whereas 5-Hydroxymethyl-2-Furoic Acid has been utilized as building blocks for bio-based polymers substituting for petrol-based polyethylene terephthalate [ 17 , 49 , 50 , 51 , 52 ].…”