Abstract
AbstractBACKGROUNDModern day scientific endeavour strives towards global sustainability through the smart utilisation of renewable resources as base materials for chemicals. Until now, the most common commercial process to produce levulinic acid (a mass‐produced platform chemical) depends on a two‐stage mineral acid‐catalysed reaction, which generates harmful environmental waste. In this work, an environmentally friendly levulinic acid production route using less harmful organic acids assisted by microwave heating from biomass feedstocks is reported for the first time.RESULTSUsing aluminum sulfate as a green Lewis acid catalyst and seven organic acids, levulinic acid was successfully produced from barley straw under microwave heating, with maleic acid giving the highest catalytic conversion. A Response Surface Methodology (RSM) approach was used to rapidly and effectively examine the effect of five reaction variables on the productivity of the levulinic acid. A wide range of different biomass wastes (barley straw, brewery waste, olive cake, spent tea leaves and potato, tomato, and mandarin peels) were subsequently screened to produce the levulinic acid. The highest yield of 86 wt% based on cellulose content from mandarin peel (a value comparable to a lengthier ‘non‐green’ route) was achieved under the following optimized reaction conditions: 180 °C, 38 min, 2 M maleic acid concentration, 0.1 g Al2(SO4)3 and 1:22 biomass: maleic acid ratio (g mL−1).CONCLUSIONSThe proposed method is a promising new route towards the green, high yield production of levulinic acid from a variety of agricultural and household lignocellulosic biomass wastes, without the need for pre‐treatment. © 2020 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Highlights
The world is witnessing great economic advances in both the chemical and polymer industries to meet the requirements of modern society
Out of the seven different biomass feedstocks tested in this work
Production of levulinic acid (LA) from barley straw using different organic acids To date, most studies aimed to produce LA have depended upon strong homogenous acid catalysts, such as HCl and H2SO4.2 In an attempt to replace these environmentally harmful reagents with greener alternatives, strong organic acids were chosen to catalyse the synthesis of LA from barley straw
Summary
The world is witnessing great economic advances in both the chemical and polymer industries to meet the requirements of modern society. The best candidate (barley straw) was subsequently treated with seven different organic acids in the presence of aluminium chloride catalyst These acids were chosen due to their low pKa values, as most reported studies depend on strong homogenous acid catalysts, such as HCl and H2SO4 to produce LA.[2] The most effective organic acid in converting cellulose to LA (i.e. maleic acid) was employed in a carefully designed optimization study using Response Surface Methodology (RSM). All purchased chemicals were of analytical grade and used without further purification (unless stated otherwise) Prior to determining their cellulose content by Thermogravimetric Analysis (TGA), the feedstocks (barley straw, brewery waste, olive cake, spent tea leaves, tomato peel, potato peel and mandarin peel) underwent pre-treatment to remove compounds that may interfere with the results. Results are discussed in detail in the ESI (see Figs S15 and S16)
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