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| 2. |
- de Carvalho, Danila Morais, et al.
(author)
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Cold alkaline extraction as a pretreatment for bioethanol production from eucalyptus, sugarcane bagasse and sugarcane straw
- 2016
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In: Energy Conversion and Management. - : Elsevier. - 0196-8904 .- 1879-2227. ; 124, s. 315-324
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Journal article (peer-reviewed)abstract
- Optimal conditions for the cold alkaline extraction (CAE) pretreatment of eucalyptus, sugarcane bagasse and sugarcane straw are proposed in view of their subsequent bioconversion into ethanol through the semi -simultaneous saccharification and fermentation (SSSF) process (with presaccharification followed by simultaneous saccharification and fermentation, or SSF). The optimum conditions, which are identified based on an experiment with a factorial central composite design, resulted in the removal of 46%, 52% and 61% of the xylan and 15%, 37% and 45% of the lignin for eucalyptus, bagasse and straw, respectively. The formation of pseudo-extractives was observed during the CAE of eucalyptus. Despite the similar glucose concentration and yield for all biomasses after 12 h of presaccharification, the highest yield (0.065 g(ethanol)/g(biomass)), concentrations (5.74 g L-1) and volumetric productivity for ethanol (0.57 g L-1 h(-1)) were observed for the sugarcane straw. This finding was most likely related to the improved accessibility of cellulose that resulted from the removal of the largest amount of xylan and lignin.
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| 3. |
- de Carvalho, Danila Morais, et al.
(author)
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Comparative Study of Acid Hydrolysis of Lignin and Polysaccharides in Biomasses
- 2017
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In: BioResources. - : North Carolina State University. - 1930-2126. ; 12:4, s. 6907-6923
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Journal article (peer-reviewed)abstract
- Effects of different acid hydrolysis conditions were studied relative to the chemical transformations of lignin in eucalyptus, sugarcane bagasse, and sugarcane straw, and on the transformations of multiple polysaccharides in eucalyptus. The acid hydrolysis using 12 mol/L sulfuric acid followed by acid hydrolysis using approximately 0.41 mol/L sulfuric acid was used as the reference for the lignin and sugar analysis. During acid hydrolysis, the relative amount of lignin increased with longer reaction times and/or greater acid concentrations for all biomasses. The overestimation of lignin in harsher acidic conditions resulted from the summation of lignocellulosic-derivatives (pseudo- lignin) together with lignin itself. Lignin reactions (dissolution/deposition) for bagasse and straw occurred in a greater extent than for eucalyptus, considering similar conditions of acid hydrolysis. The sugar transformation during acid hydrolysis was also investigated for eucalyptus. The sugar content quantified in eucalyptus decreased as the acid concentration and/or reaction time in the second hydrolysis increased. Glucose, galactose, and mannose were more resistant to harsher acidic conditions than xylose and arabinose. However, the most severe conditions (121 degrees C, 90 min, and 6.15 mol/L H2SO4) caused complete sugar degradation.
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| 4. |
- de Carvalho, Danila Morais, et al.
(author)
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Hydrothermal and Acid Pretreatments Improve Ethanol Production from Lignocellulosic Biomasses
- 2017
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In: BioResources. - : NORTH CAROLINA STATE UNIV DEPT WOOD & PAPER SCI. - 1930-2126. ; 12:2, s. 3088-3107
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Journal article (peer-reviewed)abstract
- Hydrothermal and acid pretreatments using different acid charges (1.5%, 3.0%, and 4.5% H2SO4) were proposed for eucalyptus, sugarcane bagasse, and sugarcane straw prior to their bioconversion into ethanol using the semi-simultaneous saccharification and fermentation (SSSF) process. The hydrothermal and acid pretreatments were efficient for hemicelluloses removal from eucalyptus (63 to 96%), bagasse (25 to 98%), and straw (23 to 95%) and to remove a substantial amount of lignin from eucalyptus (10 to 34%) and bagasse (10 to 27%). During pretreatments, pseudo-extractives and pseudo-lignin were generated from biomasses. The SSSF was performed in pretreated biomasses using 24 h presaccharification followed by an additional 10 h of simultaneous saccharification and fermentation (SSF). With hydrothermal pretreatment, the eucalyptus presented the highest ethanol production, but only low values for SSSF parameters were obtained, as follows: ethanol yield (0.017 g(ethanol)/g(biomass)), volumetric productivity of ethanol (0.16 g L-1 h(-1)), and ethanol concentration (1.6 g L-1). On the other hand, using acid pretreatment, the straw (pretreated using 4.5% H2SO4) presented the highest ethanol production among the biomasses, assessed based on ethanol yield (0.056 g(ethanol)/g(biomass)), volumetric productivity of ethanol (0.51 g L-1 h(-1)), and ethanol concentration (5.1 g L-1).
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| 5. |
- de Souza, Gustavo B., et al.
(author)
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Enhancement of eucalypt pulp yield through extended impregnation cooking
- 2018
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In: Nordic Pulp & Paper Research Journal. - : AB SVENSK PAPPERSTIDNING. - 0283-2631 .- 2000-0669. ; 33:2, s. 175-185
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Journal article (peer-reviewed)abstract
- The improvement caused by eucalypt chip impregnation on kraft pulping performance was assessed for terminating the cook at kappa in the range of 15-27 and at controlled residual effective alkali (REA) of 6-8 g/L NaOH. Extended impregnation cooking of eucalypt chips (EIC) increased about 10/0 lignin- and HexA-free screen yield gains in relation to conventional cooking (CC), regardless of kappa number in the range of 15-27. The EIC technology allows for cooking eucalypt wood to kappa number up to 27, without rejects production, but without significant improvement in lignin- and HexA-free screen yield and with larger chlorine dioxide (ClO2) consume during bleaching. The optimum kappa number for both CC and EIC cooking was about 19 with similar refinability and strength properties for both technologies, CC and EIC. It was concluded that extended impregnation cooking is an attractive technique for enhancing bleached eucalypt Kraft pulp yield.
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| 6. |
- Moraisde Carvalho, Danila, et al.
(author)
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Assessment of chemical transformations in eucalyptus, sugarcane bagasse and straw during hydrothermal, dilute acid, and alkaline pretreatments
- 2015
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In: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 73, s. 118-126
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Journal article (peer-reviewed)abstract
- The impact of hydrothermal, dilute acid, and alkaline pretreatments on the chemical structure of eucalyptus, sugarcane bagasse, and straw were compared with a view to their subsequent bioconversion into ethanol. Sugarcane bagasse and straw contain high amounts of extractives (15.0% and 12.2%, respectively), ash (2.3% and 7.9%, respectively), and silica (1.4% and 5.8%, respectively). If not properly corrected, the presence of silica would lead to the overestimation of the lignin, while high amounts of extractives would cause the overestimation of the content of sugars in biomass. Applying a novel approach through the use of complete mass balance, bagasse and straw were proven to contain lower amounts of lignin (18.0% and 13.9%, respectively) than previously reported for these raw materials, and certainly a much lower amount of lignin than eucalyptus (27.4%). The syringyl to guaiacyl units ratio (SIG) for lignin in bagasse and straw (1.1 and 0.5, respectively) was lower than that for eucalyptus (2.7), indicating a different reactivity during chemical pretreatments. The xylan content in sugarcane bagasse and straw was much higher than that in eucalyptus, with a significantly lower degree of substitution for uronic acids and acetyl groups. The sugarcane straw showed the highest mass loss during the investigated pretreatments, especially under alkaline conditions, with a total biomass yield of only 37.3%. During the hydrothermal and dilute acid treatments, mostly hemicelluloses were removed, followed by the formation a significant amount of pseudo-lignin structures, while the alkaline pretreatment affected the lignin content. With eucalyptus, the formation of structures similar in their behavior to extractives (i.e., soluble in toluene and ethanol, subsequently referred to as "pseudo-extractives") was observed during all three pretreatments, with 12.4% for hydrothermal, 18.9% for dilute acid, and 8.7% for alkaline pretreatment. This information, combined with actual yields, should be taken into account when assessing the impact of pretreatments on the chemical composition and structure of biomass.
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