Enhancing the selective catalytic oxidation of lignocellulosic biomass to formic acid using hydrogen peroxide and a reusable MgAl hydrotalcite-derived as a catalyst in a green solvent

Abstract

Biofuels or liquid fuels derived from natural matter, are one of the most intriguing yet divisive alternatives for petroleum-based fuels. The most common approach to produce biofuels is to transform plant sugars and other carbohydrates into oxygen-deficient chemicals. A growing relevance has been devoted in the direct synthesis of platform molecules from biomass resources, using one-pot or cascade techniques via adequate catalytic system tuning and improvement of the reaction conditions which have merged as a beneficial strategy from an economic and ecological standpoint. In a similar vein, the major objective of this contribution was to investigate and enhance the conditions for a selective oxidation of lignocellulosic biomass-derived cellulose to yield formic acid (FA), the latter is one of the most coveted liquid hydrogen carriers and among the key compounds used in the pharmaceutical, cosmetic, and leather industries. Both oxidizing aqueous hydrogen peroxide and calcined heterogeneous hydrotalcite catalyst have been employed at an atmospheric pressure for this purpose. The effect of reaction time, temperature, amount of catalyst and oxidant on the product's yield and selectivity have been investigated. The oxidation of a plant-derived cellulosic fiber at 70 °C using an H2O2 excess (7 mmol) provided an impressive result with a high yield and TON of 61.0 %, 12.30 respectively, the latter was confirmed to be relatively close to the one from the oxidation of pure cellulose. Furthermore, the reusability of the catalyst has also been studied which was demonstrated to result in the same yields for one reuse and 3 recycles.