Dilute Sulphuric Acid Hydrolysis Research Articles

Diluted Sulphuric Acid Hydrolysis of Destarched Sago Fibre assisted with Selected Pre-treatments for Glucose and Xylose Production

In Sarawak, Malaysia, approximately 7 t of sago fibre waste is produced daily from a single sago starch processing mill and it is currently disposed of either directly into a river nearby or in open spaces. On a dry basis, sago fibre contains 58% starch, 23% cellulose, 9.2% hemicellulose and 4% lignin. Our previous study used the trapped starch of sago fibre as a substrate for producing glucose through an enzymatic hydrolysis process in which the destarched fibre (DSF) remained unused. This study represents an attempt to utilise destarched sago fibre (DSF) as a raw material for glucose and xylose production. The DSF initially underwent a pre-treatment process via dilute sulphuric acid hydrolysis to liberate xylose for which four parameters were studied: the solid-to-liquid ratio (5:100-40:100), the dilute sulphuric acid concentration (0% (v/v) - 9% (v/v)), reaction time (30, 60 and 90 minutes) and the effects of steaming and microwave pre-treatment. Steaming pre-treatment led to the highest xylose (28.19 ± 0.78 g/L) and glucose (78.63 g/L ± 0.22 g/L) production, for which the dilute sulphuric acid concentration was set at 2% (v/v), reaction time was set at 60 minutes. The solid-to-liquid ratio was 30:100. Overall, this work indicates that the optimal pre-treatment of DSF can yield glucose and xylose which can be used to produce bioethanol and xylitol. The study also suggests that DSF can be an alternative raw material for xylitol production.

ZnCl2 Enhanced Acid Hydrolysis of Pretreated Corncob for Glucose Production: Kinetics, Thermodynamics and Optimization Analysis

The biomass of agricultural wastes as a source of fermentable sugars for biofuels production will address the food security and environmental preservation issues. These wastes are rich in lignocellulosic materials which can be hydrolyzed into fermentable sugars. However, low sugar yield and high energy consumption are some of the challenges faced in the process of hydrolization. This study investigated the low-cost corncob substrate for glucose production by dilute sulphuric acid hydrolysis in the presence of ZnCl2 at temperatures below 100°C after pretreatment with 10% NaOH.Time dependent hydrolysis data were analyzed by Saeman model, and thermodynamic parameters were obtained using Erying and Arrhenius equations while Box-Behnken model (Design Expert 6.0 version) was used for experimental design. As the substrate concentration increased from 50 mg/L to 150 mg/L, glucose yield increased from 10.4 mg/g to 14.6 mg/g for pretreated corncob while an increase from 3.4 mg/g to 8.6 mg/g was noted for untreated corncob. The hydrolysis rate constant was two orders of magnitude higher than the degradation rate constant. Thermodynamic parameters revealed endothermic process with positive Gibb’s free energy of hydrolysis having average values of 84.76 kJ/mol and 79.87 kJ/mol for pretreated and untreated samples respectively. The optimum yield from the model was found to be 177.44 mg/g with 3.94% H2SO4 and 0.43 mol/L ZnCl2 for 200 g/L compared with optimum yield of 46.37 mg/g obtainable without ZnCl2. The results of this study showed that the alkaline pretreatment of corncob increased the accessibility of cellulose from the solid fraction and increased glucose production.

Cellulase and acid-catalysed hydrolysis of Ulva fasciata, Hydropuntia dentata and Sargassum vulgare for bioethanol production

Hydrolysis in bioethanol production is one of the most limiting stages in the entire production process since it is the stage where the sugars to be converted to ethanol are obtained. Ulva fasciata, Hydropuntia dentata and Sargassum vulgare seaweeds were examined in this study to determine the most efficient pretreatment, optimal hydrolysis conditions and predictive models with dilute sulphuric acid and cellulase enzyme as catalysts. Dilute acid pretreatment was found to be the most efficient in maximizing the catalytic efficiency of enzymes applied on all the three selected seaweeds. Ulva fasciata, however, was found to be efficiently hydrolysable without any form of pretreatment. The study also found dilute sulphuric acid hydrolysis to be less effective since it released up to 52.4% of reducing sugars in the seaweeds as compared to the 90.9% from hydrolysis with cellulase enzyme. Also, the most efficient regression model between the seaweed species studied was obtained for the enzymatic hydrolysis of U. fasciata with a correlation coefficient of 99.4%. This indicates a high precision in predicting the reducing sugar yields from the species within boundary conditions. Overall, the optimal enzymatic hydrolysis process was influenced most by substrate concentration for all three seaweeds examined.

Hydrolysis of cellulosic bamboo biomass into reducing sugars via a combined alkaline solution and ionic liquid pretreament steps

Dilute acid hydrolysis of cellulosic biomass is not only controlled by the reaction conditions such as temperature, concentration of acidic catalyst and hydrolysis time but also by changing the physical aspects of the reaction media. Therefore, overcoming the insolubility of cellulose by the use of effective solvent without having to derivatize their basic functional groups is of tremendous advantage in the utilization of lignocellulosic biomass. Ionic liquids are considered as the most suitable solvents to dissolve cellulosic biomass and overcome the recalcitrant nature of lignocellulosic biomass. This study investigates the valorisation of bamboo biomass regenerated from alkaline solution and ionic liquid pretreament steps followed by dilute sulphuric acid hydrolysis. Lignin removal from the biomass as a result of pretreatment steps was analysed by crystallinity index determination, surface morphology and thermal stability analysis. The solid biomass materials were characterized using FTIR, XDR, SEM, TGA and Elemental analysis techniques to investigate the effect of the pretreatment steps on the properties of the original bamboo biomass. Alkaline treatment was found to be effective against lignin and hemicellulose removal. However, it did not remove the complexity of the cellulosic portion of the biomass with equal success. The crystallinity of the recovered cellulosic biomass could be effectively reduced by using the ionic liquid pretreatment. Investigation revealed that the yield of total reducing sugars increased to 64% after alkaline solution pre-treatment in comparison to only 30% yield of reducing sugar in the untreated biomass sample. After both pretreatment steps, the yield of reducing sugar further increased to 80%.

Artificial neural network modelling of xylose yield from water hyacinth by dilute sulphuric acid hydrolysis for ethanol production

Studies on dilute sulphuric acid pretreatment of water hyacinth for xylose yield was carried out with four independent parameters namely temperature, concentration, treatment time and residence time. Response surface methodology (RSM) was implemented to develop an experimental design matrix. Artificial neural network modelling was studied to develop and optimise the process based on the results obtained from the RSM design. The xylose yield under optimised condition obtained experimentally was 164.76 mg/g of dry water hyacinth biomass when hydrolysed with 4.89/ sulphuric acid, at 130°C operating temperature, residence time of 59.67 minutes and treatment time of ten minutes. Enzymatic saccharification was followed using a cocktail of cellulase and xylanase enzyme, which resulted in a total reducing sugar yield of 396.34 mg/g which followed fermentation. A substantial yield of 6.84 g/L of ethanol was obtained using P. stipitis the hydrolysate derived from hydrolysis.

Optimisation of Dilute Sulphuric Acid Hydrolysis of Waste Newspaper for High Yields of Fermentable Sugars

Dilute sulphuric acid hydrolysis of waste paper was investigated in this study. The effects of acid concentration, time, temperature and liquid to solid ratio on the total reducing sugar concentration were studied over three levels using a four variable Box-Behnken design (BBD). A statistical model was developed for the optimisation of the process variables using response surface methodology (RSM). The optimal hydrolysis conditions that resulted in the maximum total reducing sugar concentration were: acid concentration, 1.49 %w/w; temperature, 200°C; time, 20 min and liquid to solid ratio, 30 mL/g. Under these conditions, the total reducing sugar concentration was obtained to be 20 g/L. Validation of the model revealed no difference between predicted and experimental results.Keywords: Bioethanol, Waste paper, Response Surface Methodology, Pretreatment, Biomass

Influence of solid loading on D-xylose production through dilute sulphuric acid hydrolysis of olive stones

The selective hydrolysis of hemicellulose from olive stones was attempted in order to achieve a maximum D-xylose yield. For this aim, batch hydrolysis was conducted under different operating conditions of temperature, acid concentration and solid loading. Firstly, distilled water, sulphuric acid and nitric acid were assessed as hydrolytic agents at different temperatures (200, 205, 210 and 220 °C) and at a fixed acid concentration (0.025 M). Sulphuric acid and 200 °C were selected for the subsequent dilute acid hydrolysis optimization based on the obtained D-xylose yields. The combined influence of solid loading (from 29.3 to 170.7 g olive stones into 300 mL acid solution) and sulphuric acid concentration (0.006–0.034 M) on the release of D-xylose was then estimated by response surface methodology. According to a statistical analysis, both parameters had significant interaction effects on D-xylose production. The results illustrated that the higher the solid loading, the higher the required acid concentration. The decrease in the solid/liquid ratio in the reactor had a positive effect on D-xylose extraction and on the amount of acid used. The optimum solid loading and sulphuric acid concentration were determined to be 50 g (solid/liquid ratio 1/6) and 0.016 M, respectively. Under these conditions, the predicted D-xylose yield (expressed as g of sugar per 100 g of dry matter fed) was 20.4 (87.2% of maximum attainable).

Investigation of selective arabinose release from corn fibre by acid hydrolysis under mild conditions

AbstractBACKGROUNDThe high cost of pure arabinose has resulted in a growing demand to develop new cost‐effective methods of arabinose production from lignocellulosic and pectin‐rich materials. Corn fibre is an inexpensive by‐product of the corn wet‐milling process, and is a promising raw material for producing arabinose and other value‐added products. In this study fast dilute sulphuric acid hydrolysis of corn fibre was investigated for selective arabinose solubilization. Acid concentration and reaction time of hydrolysis of destarched ground corn fibre and raw corn fibre were 0.25–5 w/w% at 5–15 min and 0.25–1.25 w/w% at 25–75 min, respectively. Results were evaluated statistically and model equations were developed to predict the yields of sugars.RESULTSIn the case of raw corn fibre the most favourable conditions were 1.1 w/w% sulphuric acid concentration and 51 min reaction time at 90°C, where a total arabinose yield of 75.9% was achieved with satisfactory selectivity. In the case of destarched ground corn fibre at a sulphuric acid concentration of 4.6 w/w%, a reaction time of 5 min and a temperature of 90°C, a total arabinose yield of 80.5% could be achieved with satisfactory selectivity, according to the model equations.CONCLUSIONArabinose‐rich liquid fractions were produced by mild sulphuric acid treatments of corn fibre. Based on the models developed the mono‐ and oligosaccharide contents of the hydrolysates can be controlled under the conditions investigated. © 2014 Society of Chemical Industry

Effect of the Acid Hydrolysis Temperature on the Conversion of Birch Wood Hemicelluloses into Furfural

In this study, a new dilute sulphuric acid hydrolysis method was used for hemicelluloses secession from birch wood. The furfural extraction was investigated at different process temperatures (132°C ‑ 162°C, increasing it by 5°C) and at constant amount of catalyst 3.0%, calculated on oven‑dried wood. The greatest amount of furfural 11.09%, which is 75.6% from the theoretical possible yield, was formed at temperature 147°C after 90 min from the beginning of the birch wood pentoses monosaccharides dehydration process.

Application of Statistical Experimental Design for the Optimisation of Dilute Sulphuric Acid Hydrolysis of Cassava Bagasse

The dilute sulphuric acid hydrolysis of cassava bagasse was investigated in this study under the following conditions: acid concentration (0.5-2.5%w/w), temperature (100- 130⁰C), time (5-40 minutes) and liquid to solid ratio (10-30 mL/g). Results of chemical composition analysis of the bagasse showed that the major components of the cassava bagasse used in this study were cellulose, hemicellulose and lignin which accounted for 36.6, 21.3 and 17.3% of the weight of the material respectively. A statistical model was developed and validated to predict the yield of fermentable sugars during hydrolysis. Response Surface Methodology (RSM) was used to optimise the hydrolysis conditions. The maximum sugar yield of 81.63% was obtained at the optimum temperature, acid concentration, hydrolysis time and liquid to solid ratio (i.e. 122.5 o C, 2 %w/w, 20.5 minutes and 25 mL/g respectively).

Influence of Biomass Pretreatment Process Time on Furfural Extraction from Birch Wood

Abstract Furfural is a biomass derived-chemical that can be used to replace petrochemicals. In this study, dilute sulphuric acid hydrolysis was used for hemicelluloses secession from birch wood. The reaction was investigated at different biomass treatment times (10-90 min, increasing it by 10 min). We found that the greatest amount of furfural 1.4-2.6%, which is 9.7-17.7% from theoretical possible yield, was formed in the first 30 min of the beginning of birch wood pentoses monosaccharide dehydration, but the greatest yield of furfural 10.3%, which is 70.0% from the theoretical yield, can be obtained after 90 min. Given that furfural yield generally does not exceed 50% from the theoretical amount, the result can be considered as very good.

Low severity dilute-acid hydrolysis of sweet sorghum bagasse

Sweet sorghum is emerging as a promising energy crop in India, with potential for ethanol production both from the extracted juice and the bagasse residue. This work investigates the release of fermentable total sugars (TS) and formation of total degradation compounds (TDC) by dilute sulphuric acid hydrolysis of sweet sorghum bagasse from the genotype SSV 84. Hydrolysis was conducted at moderate temperatures (100°C and 121°C). The effect of pretreatment severity (measured by the combined severity factor, CS), particle size and substrate loading on the hydrolysate composition was examined. The kinetics of xylose, acetic acid and furfural formation was also studied. The maximum theoretical yield is 29.9g C5 sugars/100g bagasse on dry weight basis. Under the conditions of this study, 10% substrate loading in the CS range of 1.64–1.93 was optimal with C5 yield >22.3g/100g bagasse and efficiency (TS/TDC ratio) >8. Bagasse particle size reduction also resulted in a higher efficiency. SEM and FT-IR analysis of the solid residue confirmed disruption of the biomass structure and removal of functional groups associated with hemicelluloses and lignin. This study demonstrates that acid hydrolysis at moderate temperature has an advantage in terms of high sugars concentration vis-a-vis low degradation compounds formation.

Chemical characterisation and dilute-acid hydrolysis of rice hulls from an artisan mill

The chemical composition of rice hulls produced in an artisan mill and its conversion to fermentable sugars was investigated. The carbohydrate fraction represented 59.2% (w/w) of the dry hulls. Cellulose, with 36.6%, was the main component, followed by xylan with 13.9%. An important contribution of starch (8.7%) was also detected. The content of ash (19.6%) and lignin (15.5%) was comparable with that of rice hulls obtained in industrial mills. Dilute-sulphuric acid hydrolysis at different temperatures, from 160 to 210, was evaluated for production of fermentable sugars. Due to starch hydrolysis, the concentration of glucose in the hydrolysates produced at 160°C was higher than the values that have previously been reported for industrial sorts of rice hulls under comparable conditions. The xylan-to-xylose conversion increased steadily with increase of the temperature and reached a maximum (67.7%) at 190°C. Further increases of the hydrolysis temperature decreased the yield of sugars due to their dehydration to furfural and HMF.