Biomass-derived levulinic acid (LA) is an excellent substrate to obtain high-value esters that can be used as second-generation biofuels and biofuel additives. The present study focuses on the identification and definition of the key parameters crucial for the development of chemically and environmentally efficient protocols operating in continuous-flow for the preparation of structurally diverse alkyl levulinates via the esterification of LA. We have focused on the use of solid acid catalysts consisting of sulfonated cation exchange resins and considered different aliphatic alcohols to prepare levulinates 3 and 11-17 regioselectively, and in good to high yields (50-92%). Direct correlations between several reaction parameters and catalyst activity have been investigated and discussed to set proper flow reactors that allow minimal waste production during the workup procedure, enabling Environmental factor (E-factor) values as low as ca. 0.3, full recoverability and reusability of the catalysts, and the production of levulinates up to ca. 5 gxh −1 scale.
We report the use of biomass-derived furfuryl alcohol as an effective bidentate ligand able to promote the Ullmann-type copper-catalyzed coupling of aryl halides with heteroaromatic or aliphatic amines.
A pump-free, waste-minimized flow protocol exploiting the features of a specifically designed heterogeneous catalyst has been defined for a non-stop production of biomass-derived esters.
Green/Sustainable Chemistry is the scientific platform where chemists are contributing from different areas to develop modern and efficient processes aimed at minimizing the environmental impact of chemical production. To reach these goals scientists, from both academia and industry, need to strongly focus their fundamental and innovative research towards the application of modern principles of Green Chemistry. In this contribution a description of our efforts in this direction is presented.
The present work reports the preparation of 40MoAl200 and its full characterization using a number of analytical techniques (XRD, TEM, TGA, BET, EDX). Liquid‐assisted ball milling proved to be a key tool to achieve both the best efficiency of 40MoAl200 as a novel Keggin type catalyst in the selective sulfoxidation reaction and also for succeeding in its effective recovery and reuse. In addition, the liquid assisted grinding process was studied in detail evaluating the influence of different parameters such as frequency of rotation (rpm), number and size of the stainless steel balls used and reaction time. The use of aqueous hydrogen peroxide is essential as water proved to exert a crucial role to improve both yields and selectivity towards sulfoxide formation. The procedure was representatively extended to a number of substrates with the possibility to extend the scope of the system to produce sulfoxides in high yields (up to 95 %) and satisfactory selectivities (up to 80 %). The catalyst proved to be recoverable and reusable under the optimized reaction conditions.
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