Abstract
Eucalyptus globulus wood samples were subjected to preliminary aqueous processing to remove water-soluble extractives and hemicelluloses, and the resulting solid (mainly made up of cellulose and lignin) was employed as a substrate for converting the cellulosic fraction into mixtures of levulinic and formic acid through a sulfuric acid-catalyzed reaction. These runs were carried out in a microwave-heated reactor at different temperatures and reaction times, operating in single-batch or cross-flow modes, in order to identify the most favorable operational conditions. Selected liquid phases deriving from these experiments, which resulted in concentrated levulinic acid up to 408 mmol/L, were then employed for γ-valerolactone production by levulinc acid hydrogenation in the presence of the commercial 5% Ru/C catalyst. In order to assess the effects of the main reaction parameters, hydrogenation experiments were performed at different temperatures, reaction times, amounts of ruthenium catalyst and hydrogen pressure. Yields of γ-valerolactone in the range of 85–90 mol % were obtained from the hydrogenation of the wood-derived solutions containing levulinic acid, obtained by single-batch operation or by the cross-flow process. The negative effect of co-produced formic acid present in crude levulinic acid solutions was evidenced and counteracted efficiently by allowing the preliminary thermal decomposition of formic acid itself.
Highlights
Fossil resources are currently employed as feedstocks for manufacturing a wide range of building blocks for further conversion into polymers, plastics, fuels and a number of fine and specialty chemicals [1,2]
Aqueous processing caused an extensive removal of extractives and hemicelluloses, resulting in 61.1% yield of autohydrolyzed wood (AW), measured on an oven-dry basis with respect to the initial amount of solid
As reported in the literature [6], the liquid phase was largely composed of hemicellulose-derived saccharides; whereas acetic acid and minor amounts of furans, furfural (F) and HMF, were present in these solutions
Summary
Fossil resources are currently employed as feedstocks for manufacturing a wide range of building blocks for further conversion into polymers, plastics, fuels and a number of fine and specialty chemicals [1,2]. Replacing the fossil resources by renewable materials (for example, lignocellulosic materials) contributes to the sustainable development of the chemical industry, fostering the development of a new bio-economy with favourable socio-economic and environmental implications. Lignocellulosic biomass is expected to play a key role in the future development of the chemical industry, as it is a major source of organic carbon that does not compete with the food. The conversion of raw lignocellulosic materials into chemicals, fuels and products can be conveniently achieved following the biorefinery concept: the feedstocks can be subjected to different consecutive physico-chemical treatments to obtain separate streams containing “fractions” that can be valorized separately, in order to maximize the overall added-value of the starting substrate [3].
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