This study investigated the fractionation of biomass using a decomposing mixture of hydrogen peroxide-formic acid as a pretreatment for the biorefining of Miscanthus × giganteus and of sugarcane bagasse. The main parameters investigated were the hydrogen peroxide concentration (2.5, 5.0 and 7.5 wt%) and biomass loading (5.0 and 10.0 wt%). At the highest hydrogen peroxide concentration used (7.5 wt%), the energy released by the decomposition of the H2O2 could heat the reaction mixture up to 180 °C in a short time (6-16 min). As a result, highly delignified pulps, with lignin removal as high as 92 wt%, were obtained. This delignification process also solubilised a significant amount of pentosan (82-98 wt%) from the initial biomass feedstock, and the resulting pulp had a high cellulosic content (92 wt%). The biomass loading only affected the reaction rate of hydrogen peroxide decomposition. Various analytical methods, including Fourier transform infrared spectroscopy, and thermogravimetric and elemental analyses, characterized the lignin obtained.

This study investigated the kinetics of acid hydrolysis of the cellulose and hemicellulose in Miscanthus to produce levulinic acid and furfural under mild temperature and high acid concentration. Experiments were carried out in an 8 L-batch reactor with 9%-wt. biomass loading, acid concentrations between 0.10 and 0.53 M H2SO4, and at temperatures between 150 and 200 C. The concentrations of xylose, glucose, furfural, 5-hydroxymethylfurfural and levulinic acid were used in two mechanistic kinetic models for the prediction of the performance of ideal continuous reactors for the optimisation of levulinic acid and the concurrent production of furfural. A two-stage arrangement was found to maximise furfural in the first reactor (PFR - 185 degrees C, 0.5 M H2SO4, 27.3%-mol). A second stage leads to levulinic acid yields between 58% and 72%-mol at temperatures between 160 and 200 degrees C. (C) 2013 Elsevier Ltd. All rights reserved.

There is a significant research effort worldwide to identify attractive chemical conversion routes for lignocellulosic biomass to organic (bulk-)chemicals. This study has focussed on the acid-catalysed hydrolysis of sugar cane bagasse for the production of levulinic acid (LA), a platform chemical used for the synthesis of a variety of materials for applications such as fuel additives and polymer and resin precursors. The objectives of this study were to develop a broadly applicable kinetic model for the acid-catalysed hydrolysis of sugar cane bagasse to LA and to determine the optimum reaction conditions for its production. Systematic kinetic experiments were carried out by varying the reaction temperature between 150 and 200 °C, and the sulphuric acid concentration between 0.11 and 0.55 M. The highest LA yield was obtained at 150 °C and 0.55 M H2SO4 at 63 mol%, which equates to the production of 194 kg of LA from 1 dry tonne of sugar cane bagasse. The kinetic model developed was in good agreement with the experimental data and also with the previous kinetic models developed for cellulose and sugar cane bagasse. Our kinetic model, though developed for the sugar cane bagasse, can be applied over a wide range of hydrolysis reaction conditions for lignocellulosic biomass. Based on the optimisation study carried out using our kinetic model, an empirical equation is proposed to predict the LA yield at a particular temperature and acid concentration.

The application of reactive extraction to isolate organic acids, particularly acetic acid, from the aqueous stream of phase splitted pyrolysis oil using a long chain aliphatic tertiary amine is reported. Acetic acid recovery was optimized by selecting the proper amine and diluent combination and adjustment of the process conditions. The best results were obtained with tri-n-octylamine (TOA) in 2-ethyl-hexanol (40wt%) with 84% acetic acid recovery at equilibrium conditions (room temperature). Other organic acids present in the feed (formic acid and glycolic acid) were also co-extracted (92% and 69% extraction efficiencies), as well as relatively non-polar compounds like substituted phenolics and ketones. The continuous reactive extraction process was successfully demonstrated in a centrifugal contactor separator (CCS) device, and acetic acid recoveries of 51% and 71% were obtained in a single CCS device and a two stage cross currently operated cascade, respectively.

A comprehensive experimental and modelling study on the acid-catalysed hydrolysis of the water hyacinth plant (Eichhornia crassipes) to optimise the yield of levulinic acid (LA) is reported (T=150–175°C, CH2SO4=0.1–1M, water hyacinth intake=1–5wt%). At high acid concentrations (>0.5M), LA was the major organic acid whereas at low acid concentrations (<0.1M) and high initial intakes of water hyacinth, the formation of propionic acid instead of LA was favoured. The highest yield of LA was 53mol% (35wt%) based on the amount of C6-sugars in the water hyacinth (T=175°C, CH2SO4=1M, water hyacinth intake=1wt%). The LA yield as a function of the process conditions was modelled using a kinetic model originally developed for the acid-catalysed hydrolysis of cellulose and good agreement between the experimental and modelled data was obtained.

A variety of interesting bulk chemicals is accessible by the acid-catalyzed hydrolysis of cellulose. An interesting example is levulinic acid, a versatile precursor for fuel additives, polymers, and resins. A detailed kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid is reported in this paper. The kinetic experiments were performed in a temperature window of 150-200 degrees C, sulfuric acid concentrations between 0.05 and 1 M, and initial cellulose intakes between 1.7 and 14 wt %. The highest yield of levulinic was 60 mol %, obtained at a temperature of 150 degrees C, an initial cellulose intake of 1.7 wt %, and a sulfuric acid concentration of 1 M. A full kinetic model covering a broad range of reaction conditions was developed using the power-law approach. Agreement between the experimental data and the kinetic model is good. The kinetic expressions were used to gain insights into the optimum process conditions for the conversion of cellulose to levulinic acid in continuous-reactor configurations. The model predicts that the highest obtainable levulinic acid yield in continuous-reactor configurations is about 76 mol %, which was obtained when using reactors with a large extent of backmixing.

Levulinic acid (LA), accessible by the acid catalyzed degradation of biomass, is potentially a very versatile green intermediate chemical for the synthesis of various (bulk) chemicals for applications like fuel additives, polymers, and resin precursors. We report here a kinetic study on one of the key steps in the conversion of biomass to levulinic acid, i.e. the reaction of 5-hydroxymethylfurfural (HMF) to levulinic acid. The kinetic experiments were performed in a temperature window of 98–181 °C, acid concentrations between 0.05–1 M, and initial HMF concentrations between 0.1 and 1 M. The highest LA yield was 94% (mol/mol), obtained at an initial HMF concentration of 0.1 M and a sulfuric acid concentration of 1 M. The yield at full HMF conversion is independent of the temperature. An empirical rate expression for the main reaction as well as the side reaction to undesired humins was developed using the power law approach. Agreement between experimental and model data is good. The rate expressions were applied to gain insights into optimum process conditions for batch processing.

Levulinic acid has been identified as a promising green, biomass derived platform chemical. A kinetic study on one of the key steps in the conversion of biomass to levulinic acid, i.e., the acid catalysed decomposition of glucose to levulinic acid has been performed. The experiments were performed in a broad temperature window (140–200°C), using sulphuric acid as the catalyst (0.05–1 M) and a initial glucose concentration between 0.1 and 1 M. A kinetic model of the reaction sequence was developed including the kinetics for the intermediate 5-hydroxymethyl-2-furaldehyde (HMF) and humins byproducts using a power-law approach. The yield of levulinic acid is favoured in dilute glucose solution at high acid concentration. On the basis of the kinetic results, continuous reactor configurations with a high extent of back-mixing are preferred to achieve high levulinic acid yields.

Levulinic acid has been identified as a promising green. biomass derived platform chemical. A kinetic study oil one of the key steps in the conversion of biomass to levulinic acid, i.e., the acid catalysed decomposition of glucose to levulinic acid has been performed. The experiments were Performed in a broad temperature window (140-200 degrees C), using sulphuric acid as the catalyst (0.05-1 M) and a initial glucose concentration between 0.1 and 1 M. A kinetic model of the reaction sequence was developed including the kinetics for the intermediate 5-hydroxymethyl-2-furaldehyde (HMF) and humins byproducts using a power-law approach. The yield of levulinic acid is favoured in dilute glucose solution at high acid concentration. On the basis of the kinetic results, continuous reactor configurations with a high extent of back-mixing are preferred to achieve high levulinic acid yields.