Unmodified Maghemite from River Sand as a Selective Catalyst for Base-Free Transfer Hydrogenation of Furfural, Levulinic Acid, and o-Vanillin: A Pathway for Sustainable Biomass Conversions
2020
Vasanthakumar, Punitharaj | Karvembu, Ramasamy
Iron is one of the cheapest and abundant metals on the earth’s crust. Both its oxides and metallic form are highly active as oxidation and reduction catalysts. Its oxide forms such as Fe₂O₃ and Fe₃O₄ are magnetically active at room temperature, making them easy for separation and reuse. Fe₂O₃ exists in 14 different phases; among them, α, β, and γ are well known. We have separated phase-pure γ-Fe₂O₃ from the river sand and confirmed it by X-ray diffraction and selected area electron diffraction analyses. Its morphology was understood by scanning electron microscopy and high-resolution transmission electron microscopy analyses. The unmodified γ-Fe₂O₃ obtained from the natural source was employed as a catalyst for the transfer hydrogenation of carbonyl and nitro compounds and biomass derivatives such as levulinic acid, furfural, and vanillin, without using a base. Further, to understand the advantage of γ-Fe₂O₃ recovered from the natural source, phase-pure α-, β-, and γ-Fe₂O₃ were synthesized and characterized and their catalytic activity was studied under identical conditions. To our delight, γ-Fe₂O₃ recovered from the natural source exhibited superior activity under base-free conditions.
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