@article {48691, title = {Industry-oriented method for the aqueous phase oxidation of crude 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxylic acid (FDCA)}, journal = {New Journal of Chemistry}, volume = {47}, year = {2023}, month = {AUG }, pages = {15325-15335}, type = {Article}, abstract = {

Valorization of cellulose, hemicellulose, and lignin into value-added industrially relevant chemicals is important to achieve sustainability goals that various governments and industries have set. In view of this, the oxidative synthesis of 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethyl furfural (HMF) as an analogous compound to terephthalic acid in the synthesis of PEF is interesting to researchers. Though advancements in the oxidation of HMF have been made, the efficient synthesis of HMF, its storage, and isolation are great challenges due to its instability under normal conditions. While purified HMF can be used to synthesize FDCA, it is imperative to use crude HMF for the synthesis of FDCA since several techno-economical studies reveal that the purification of HMF is the most cost-intensive step. Herein, we demonstrate the oxidation of crude HMF, synthesized in the laboratory to FDCA, using nonprecious-based mixed metal oxides in the aqueous medium in the presence of oxygen/air. Among various catalysts, Cu-Mn catalyst at 120 \& DEG;C within 8 h in the presence of oxygen (10 bar) could yield 90\% FDCA. This activity was comparable with that of the commercially available and well-studied Ru/C (5 wt\%) catalyst (93\% yield). In addition, the role of HMF purity, air as an oxidant, and the influence of temperature, pressure, and time is systematically studied. It is also demonstrated that FDCA formation proceeds via HMFCA and FFCA formation. The isolation of FDCA and its purity (\>99\%) is corroborated with various techniques such as NMR, IR, and HRMS.

}, issn = {1144-0546}, doi = {10.1039/d3nj01834b}, author = {Lokhande, Priya and Sonone, Kalyani and Dhepe, Paresh L.} } @article {48674, title = {Selective and robust Ru catalyst for the aqueous phase aerobic oxidation of furfural to 2-furoic acid}, journal = {ACS Applied Materials \& Interfaces}, volume = {15}, year = {2023}, month = {SEP }, pages = {47004-47015}, type = {Article}, 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 H2O2 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, Al2O3) 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 Na2CO3 yielded 83\% of FURA at 120 degrees 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 degrees 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 Na2CO3, 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.

}, keywords = {2-furoic acid (FURA), Biomass conversion, furfural (FAL), heterogeneous catalyst, Oxidation, ruthenium on carbon etc}, issn = {1944-8244}, doi = {10.1021/acsami.3c09965}, author = {Lokhande, Priya and Dhepe, Paresh L.} } @article {49645, title = {Ru/MgO-catalysed selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid}, journal = {Australian Journal of Chemistry - an International Journal for Chemical Science}, volume = {77}, year = {2024}, month = {SEP}, type = {Article}, abstract = {

Biomass valorisation through the selective oxidation of carbohydrate and lipid derivatives offers access to an array of platform chemicals through energy- and atom-efficient catalytic processes. Supported metal nanoparticles are promising catalysts for the aerobic selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), but typically require strong liquid base to achieve high selectivity. Here, we explore the utility of MgO as a solid base support for the Ru-catalysed aerobic oxidation of HMF, obtaining 68\% FDCA yield at 160{\textdegree}C and 1.5\ MPa of O2\ using \<1\ mol-\% metal.

}, doi = {https://doi.org/10.1071/CH24082}, author = {Lokhande, Priya and Dhepe, Paresh L. and Wilson, Karen and Lee, Adam F.} }