Levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) have been identified as promising biomass-derived platform chemicals. A kinetic study on the conversion of D-fructose to HMF and LA in water using sulfuric acid as the catalyst has been performed in batch setups. The experiments were carried out in a temperature window of 140−180 °C, using sulfuric acid as the catalyst (0.005−1 M) and an initial D-fructose concentration between 0.1 and 1 M. A kinetic model for the conversion of D-fructose to HMF and the subsequent reaction of HMF to LA was developed including the kinetics for the formation of solid byproducts (humins) using a power-law approach. According to the model, the maximum attainable HMF yield in the experimental window is 56 mol % (C fruc = 0.1 M; C acid = 0.005 M; 166 °C), which is close to the highest experimental value within the range (53 mol %) and considerably higher than that reported for D-glucose. The highest modeled LA yield was 70 mol % (C fruc = 0.1 M; C acid = 1 M; 140 °C), close to the experimental value of 74 mol %. This LA yield is considerably higher than that found for D-glucose within the range of experimental conditions. The model was used to determine the optimum reactor configuration for highest HMF and LA yields, and it is shown that highest HMF yields are attainable in a PFR reactor, whereas a large extent of backmixing is favorable when aiming for a high LA yield.

We herein present a study on the application of homogeneous catalysts in the form of metal salts on the conversion of trioses, such as dihydroxyacetone (DHA), and glyceraldehyde (GLY) to lactic acid (LA) in water. A wide range of metal salts (26 in total) were examined. Al(III) salts were identified as the most promising and essentially quantitative LA yields (>90 mol%) were obtained at 140 °C and a reaction time of 90 min. A reaction pathway is proposed and a kinetic model using the power law approach was developed for the conversion of DHA to LA with pyruvaldehyde (PRV) as the intermediate. Good agreement between experimental data and the model was obtained. Model predictions, supported by experiments, indicate that a high yield of LA is favoured in dilute solutions of DHA (0.1 M) at elevated temperatures (180 °C) and reaction times less than 10 min.

Inulin, a plant polysaccharide consisting of mainly D-fructose units, is considered an interesting feed for 5-hydroxymethylfurfural (HMF), a top 12 bio-based chemical. We here report an exploratory experimental study on the use of a wide range of homogeneous metal salts as catalysts for the conversion of inulin to HMF in water. Best results were obtained using CuCl2. Activity-pH relations indicate that the catalyst activity of CuCl2 is likely related to Lewis acidity and not to Brönsted acidity. The effects of process conditions on HMF yield for CuCl2 were systematically investigated and quantified using a central composite design (160-180 °C, an inulin loading between 0.05 and 0.15 g/mL, CuCl2 concentration in range of 0.005-0.015 M, and a reaction time between 10 and 120 min). The highest experimental HMF yield in the process window was 30.3 wt. % (39 mol %, 180 °C, 0.05 g/mL inulin, 0.005 M CuCl2 and a reaction time of 10 min). The HMF yields were modelled using non-linear, multi variable regression and good agreement between experimental data and model were obtained.

Background: 5-Hydroxymethylfurfural (HMF), an important biobased platform chemical, is accessible by the acid catalysed conversion of biopolymers containing hexoses (cellulose, starch, inulin) and monomeric sugars derived thereof. We here report an experimental study on the uncatalysed, thermal conversion of inulin to HMF in aqueous solutions in a batch set-up. Results:The reactions were conducted in a temperature range of 153-187°C, an inulin loading between 0.03 and 0.12 g/mL and batch times between 18 and 74 min using a central composite experimental design. The highest experimental HMF yield in the process window was 35 wt% (45 mol%), which is 45% of the theoretical maximum (78 wt%). The HMF yields were modeled using a statistical approach and good agreement between experiment data and model was obtained. The possible autocatalytic role of formic acid (FA) and levulinic acid, two main byproducts, was probed by performing reactions in the presence of these acids and it was shown that particularly FA acts as a catalyst. Conclusions:Inulin is an interesting feed for the synthesis of HMF in water. A catalyst is not required, though autocatalytic effects of FA play a major role and also affect reaction rates and product yields. Graphical abstract:Chicory 5-hydroxymethylfurfural No catalystInulin

In this study, the optimization of microwave-assisted alkaline (MAA) pretreatment is performed to attain the optimal operating parameters for the delignification of cocoa pod husk (CPH). The MAA performance was examined by heating the CPH solid with different particle sizes (60–120 mesh) and NaOH solution with a different sample to a solvent (SS) ratio (0.02–0.05 g/L), for short irradiation time (1–4 min). Box-Behnken Design (BBD) was utilized to optimize the percentage of lignocellulose composition changes. The results show that by enlarging particle size, the content of lignin and cellulose decreased while hemicellulose increased. By prolong irradiation time, the content of lignin and hemicellulose decreased while cellulose elevated. On the other hand, increasing the SS ratio was not significant for hemicellulose content changes. From FTIR and SEM characterization, the MAA drove the removal of lignin and hemicellulose of CPH and increased cellulose slightly. Supported by kinetic study which conducted in this work, it was exhibited that MAA pretreatment technology is an effective delignification method of CPH which can tackle the bottleneck of its commercial biofuel production. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA   License (https://creativecommons.org/licenses/by-sa/4.0).

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Anthocyanins are present in high concentration in cocoa peels. A microwave-assisted extraction was used to extract the anthocyanins from cocoa peel by using aqueous ethanol solvent. Extraction process conditions such as particle size, material/solvent ratio (w/v), optimum extraction time, and microwave power in the extraction process will affect the obtained concentration of anthocyanin. The purpose of this study is to identify the relationship between each input variables and to develop predictive models used in optimizing the conditions of the anthocyanin extraction process. The Design Expert vs11 program with Response Surface Methodology (RSM) Box-Behnken Design was used for research and select process conditions from a combination of factors producing the optimal responses. Based on the Box-Behnken RSM Design, particle size, material/solvent ratio, extraction time, and microwave power in the extraction process are factors which mainly affect the response of produced anthocyanin concentration. Relationship between variables and the response of anthocyanin concentration was modeled by Y = 0.000178-4.17412E-07A + 0.012205B + 0.000022C + 7.75551R-08D + 0.000060AB - 2.96236E-08AC + 1.20818E-09AD − 0.001314BC − 0.000029BD + 1.84413E-07CD (A is particle size; B is the ratio of cocoa peel/ethanol; C is extraction time; and D is the power of microwave). The optimal response value of anthocyanin concentration is 1,435 mM, with the condition of the particle size at the extraction process of 60 mesh; the ratio of cocoa peel/ethanol of 0.0625 w/v; extraction time of 10 minutes; and the microwave of 450 watts.

Spent coffee ground-based magnetic activated carbon (MSC) was prepared using hydrothermal synthesis and utilized for the adsorption of methylene blue (MB). The MSC was made using the following conditions: the molar ratio of ferrous/ferric ions was 1:1.5, the hydrothermal treatment at 126°C for 2 h. The prepared MSC was investigated for surface morphology and chemical structure using FTIR and SEM. Batch adsorption studies were performed at 308 K; 318 K and MB concentration of 50-400 mg L−1 to evaluate the adsorption behaviour. The results showed as follows: there were C=O, C=C, C-O, Fe-O groups on the MSC surface and magnetite existed in the pores and surfaces of the MSC. Sorption behaviour at different temperatures were evaluated using the Langmuir, Freundlich, Temkin models, confirming Freundlich model was fitted on MSC. First and second order kinetic models were tested and the data fitted the first order behaviour. The adsorption process was a spontaneous, endothermic, and more reactive upon raising the temperature. After adsorption, MSC could be separated by applying magnetic field. Magnetic removal would allow convenient tool for adsorbent separation from contaminated water.