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Characteristics and precipitation of glucose oligomers in the fresh liquid products obtained from the hydrolysis of cellulose in hot-compressed water / Yun Yu in Industrial & engineering chemistry research, Vol. 48 N° 23 (Décembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 23 (Décembre 2009) . - pp. 10682–10690 Titre : Characteristics and precipitation of glucose oligomers in the fresh liquid products obtained from the hydrolysis of cellulose in hot-compressed water Type de document : texte imprimé Auteurs : Yun Yu, Auteur ; Hongwei Wu, Auteur Année de publication : 2010 Article en page(s) : pp. 10682–10690 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Characteristics--Precipitation--Glucose--Oligomers--Fresh  Liquid--Products--Obtained--Hydrolysis--Cellulose--Hot-Compressed--Water Résumé : Using a high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), this study shows the presence of a wide range of glucose oligomers with the degrees of polymerization (DPs) up to 30 and their derivatives in the fresh liquid products produced from cellulose hydrolysis in hot-compressed water (HCW) using a semicontinuous reactor system at 280 °C and 20 MPa. None of those oligomers can be detected by a high-performance liquid chromatography with evaporative light scattering detector (HPLC-ELSD) that however can detect glucose oligomers with DPs up to 6 after the liquid solutions are concentrated by 25 times via vacuum evaporation at 40 °C, during which a large amount of precipitate is formed. While quantitative analysis of the glucose oligomers with DPs > 5 cannot be done due to the lack of standards, that of the glucose oligomers from glucose (DP = 1) to cellopentaose (DP = 5) using both HPAEC-PAD and HPLC-ELSD are in good agreement, suggesting that these low-DP glucose oligomers do not contribute to the precipitate formation. Results from a set of purposely designed precipitation experiments indicate that the precipitation starts as the fresh liquid sample is collected and is fast during the initial 8 h, levels off as the precipitation time increases further, and completes after 120 h (5 days). On the basis of a new approach developed for the quantification of glucose oligomer retention during the precipitation process, it is found that the contribution of glucose oligomers to precipitate formation increases with DP. The higher the DP is, the lower the solubility of the glucose oligomer is. The glucose oligomers from glucose to cellopentaose and their derivatives (DPs = 1−5) contribute little to the precipitate formation, which explains why HPLC-ELSD can correctly analyze these glucose oligomers in the concentrated solutions prepared by vacuum evaporation. The glucose oligomers and their derivatives with DP > 5, which are soluble in HCW but become supersaturated in the solutions under ambient conditions, are responsible for precipitate formation. Most (but not all) of the glucose oligomers and their derivatives with DPs > 16 contribute to the precipitate formation as tiny peaks of these glucose oligomers are still shown in the chromatograms, suggesting that these glucose oligomers have very low (but nonzero) solubilities in ambient water. The retentions of glucose oligomers and their derivatives increase substantially with the DP decreasing from 16 to 6, indicating that less of these lower-DP oligomers contribute to the precipitate formation. To avoid the effect of precipitation on oligomer analysis, the fresh liquid products must be analyzed immediately after sample collection. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900768m [article] Characteristics and precipitation of glucose oligomers in the fresh liquid products obtained from the hydrolysis of cellulose in hot-compressed water [texte imprimé] / Yun Yu, Auteur ; Hongwei Wu, Auteur . - 2010 . - pp. 10682–10690. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 23 (Décembre 2009) . - pp. 10682–10690 Mots-clés : Characteristics--Precipitation--Glucose--Oligomers--Fresh  Liquid--Products--Obtained--Hydrolysis--Cellulose--Hot-Compressed--Water Résumé : Using a high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), this study shows the presence of a wide range of glucose oligomers with the degrees of polymerization (DPs) up to 30 and their derivatives in the fresh liquid products produced from cellulose hydrolysis in hot-compressed water (HCW) using a semicontinuous reactor system at 280 °C and 20 MPa. None of those oligomers can be detected by a high-performance liquid chromatography with evaporative light scattering detector (HPLC-ELSD) that however can detect glucose oligomers with DPs up to 6 after the liquid solutions are concentrated by 25 times via vacuum evaporation at 40 °C, during which a large amount of precipitate is formed. While quantitative analysis of the glucose oligomers with DPs > 5 cannot be done due to the lack of standards, that of the glucose oligomers from glucose (DP = 1) to cellopentaose (DP = 5) using both HPAEC-PAD and HPLC-ELSD are in good agreement, suggesting that these low-DP glucose oligomers do not contribute to the precipitate formation. Results from a set of purposely designed precipitation experiments indicate that the precipitation starts as the fresh liquid sample is collected and is fast during the initial 8 h, levels off as the precipitation time increases further, and completes after 120 h (5 days). On the basis of a new approach developed for the quantification of glucose oligomer retention during the precipitation process, it is found that the contribution of glucose oligomers to precipitate formation increases with DP. The higher the DP is, the lower the solubility of the glucose oligomer is. The glucose oligomers from glucose to cellopentaose and their derivatives (DPs = 1−5) contribute little to the precipitate formation, which explains why HPLC-ELSD can correctly analyze these glucose oligomers in the concentrated solutions prepared by vacuum evaporation. The glucose oligomers and their derivatives with DP > 5, which are soluble in HCW but become supersaturated in the solutions under ambient conditions, are responsible for precipitate formation. Most (but not all) of the glucose oligomers and their derivatives with DPs > 16 contribute to the precipitate formation as tiny peaks of these glucose oligomers are still shown in the chromatograms, suggesting that these glucose oligomers have very low (but nonzero) solubilities in ambient water. The retentions of glucose oligomers and their derivatives increase substantially with the DP decreasing from 16 to 6, indicating that less of these lower-DP oligomers contribute to the precipitate formation. To avoid the effect of precipitation on oligomer analysis, the fresh liquid products must be analyzed immediately after sample collection. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900768m

Effect of hydrodistillation on 1,8 - cineole extraction from mallee leal and the fuel properties of spent biomass / Hongwei Wu in Industrial & engineering chemistry research, Vol. 50 N° 19 (Octobre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 19 (Octobre 2011) . - pp. 11280-11287 Titre : Effect of hydrodistillation on 1,8 - cineole extraction from mallee leal and the fuel properties of spent biomass Type de document : texte imprimé Auteurs : Hongwei Wu, Auteur ; William Hendrawinata, Auteur ; Yun Yu, Auteur Année de publication : 2011 Article en page(s) : pp. 11280-11287 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Biomass  Fuel Résumé : Many mallee eucalyptus species have leaves that contain terpenoid oils commonly known as eucalyptus oil, of which 1,8-cineole is the major constituent. 1,8-Cineole is potentially a high-value product that might improve the economic viability of a mallee-based biomass industry. It can be extracted by hydrodistillation, but the extraction process may affect the fuel properties of spent biomass. It was found that extraction of 1,8-cineole from mallee biomass is fast initially and tapers off to completion after 30 min of hydrodistillation. The distillation process has little effect on the fuel chemistry or the mass energy density of the spent biomass. However, hydrodistillation can potentially extract a substantial proportion of the alkali and alkaline earth metallic species from the raw biomass, depending on the biomass component (leaf, wood, and bark). Typically, Na and K are easily extracted while Mg and Ca are hard to extract. After hydrodistillation, the spent leaf becomes more difficult to grind than the raw leaf, apparently because ofthe poorer grindiability ofthe oil gland enclosures and vascular bundles after hydrodistillation. However, hydrodistillation appears to have little effect on the grindability of spent wood and bark fractions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24573325 [article] Effect of hydrodistillation on 1,8 - cineole extraction from mallee leal and the fuel properties of spent biomass [texte imprimé] / Hongwei Wu, Auteur ; William Hendrawinata, Auteur ; Yun Yu, Auteur . - 2011 . - pp. 11280-11287. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 19 (Octobre 2011) . - pp. 11280-11287 Mots-clés : Biomass  Fuel Résumé : Many mallee eucalyptus species have leaves that contain terpenoid oils commonly known as eucalyptus oil, of which 1,8-cineole is the major constituent. 1,8-Cineole is potentially a high-value product that might improve the economic viability of a mallee-based biomass industry. It can be extracted by hydrodistillation, but the extraction process may affect the fuel properties of spent biomass. It was found that extraction of 1,8-cineole from mallee biomass is fast initially and tapers off to completion after 30 min of hydrodistillation. The distillation process has little effect on the fuel chemistry or the mass energy density of the spent biomass. However, hydrodistillation can potentially extract a substantial proportion of the alkali and alkaline earth metallic species from the raw biomass, depending on the biomass component (leaf, wood, and bark). Typically, Na and K are easily extracted while Mg and Ca are hard to extract. After hydrodistillation, the spent leaf becomes more difficult to grind than the raw leaf, apparently because ofthe poorer grindiability ofthe oil gland enclosures and vascular bundles after hydrodistillation. However, hydrodistillation appears to have little effect on the grindability of spent wood and bark fractions. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24573325

Evolution of primary liquid products and evidence of in situ structural changes in cellulose with conversion during hydrolysis in hot-compressed water / Yun Yu in Industrial & engineering chemistry research, Vol. 49 N° 8 (Avril 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp. 3919–3925 Titre : Evolution of primary liquid products and evidence of in situ structural changes in cellulose with conversion during hydrolysis in hot-compressed water Type de document : texte imprimé Auteurs : Yun Yu, Auteur ; Hongwei Wu, Auteur Année de publication : 2010 Article en page(s) : pp. 3919–3925 Note générale : Industrial Chemistry Langues : Anglais (eng) Mots-clés : Liquid  Evidence  Cellulose  Hydrolysis  Hot-Compressed  Water Résumé : This study shows the dynamic evolution of the primary liquid products with conversion during the hydrolysis of both amorphous and crystalline cellulose in hot-compressed water (HCW). The results suggest that the dynamic changes in cellulose structure occur during conversion and strongly depend on reaction temperature. Results from a set of purposely designed two-step experiments further confirm at least two mechanisms which may be responsible for such structural changes. One is the selective consumption of the reactive components within the intrinsically heterogeneous cellulose at early conversions. This mechanism dominates during the hydrolysis of at low temperatures, e.g., 180−200 °C for amorphous cellulose and 230 °C for microcrystalline cellulose. The other is the combined effects of various parallel reactions during hydrolysis in HCW, including cleavage of hydrogen bonds, degradation reactions, and cross-linking reactions. Enhanced hydrogen bond cleavage increases the production of glucose oligomers. However, parallel degradation reactions and cross-linking reactions decrease the selectivity of glucose oligomers. The effect of cross-linking of cellulose in HCW appears to increase with temperature and becomes significant at 270 °C, leading to a structural condensation and hence a reduction in the specific reactivity of cellulose and the selectivity of glucose oligomers in the primary liquid products. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902020t [article] Evolution of primary liquid products and evidence of in situ structural changes in cellulose with conversion during hydrolysis in hot-compressed water [texte imprimé] / Yun Yu, Auteur ; Hongwei Wu, Auteur . - 2010 . - pp. 3919–3925. Industrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp. 3919–3925 Mots-clés : Liquid  Evidence  Cellulose  Hydrolysis  Hot-Compressed  Water Résumé : This study shows the dynamic evolution of the primary liquid products with conversion during the hydrolysis of both amorphous and crystalline cellulose in hot-compressed water (HCW). The results suggest that the dynamic changes in cellulose structure occur during conversion and strongly depend on reaction temperature. Results from a set of purposely designed two-step experiments further confirm at least two mechanisms which may be responsible for such structural changes. One is the selective consumption of the reactive components within the intrinsically heterogeneous cellulose at early conversions. This mechanism dominates during the hydrolysis of at low temperatures, e.g., 180−200 °C for amorphous cellulose and 230 °C for microcrystalline cellulose. The other is the combined effects of various parallel reactions during hydrolysis in HCW, including cleavage of hydrogen bonds, degradation reactions, and cross-linking reactions. Enhanced hydrogen bond cleavage increases the production of glucose oligomers. However, parallel degradation reactions and cross-linking reactions decrease the selectivity of glucose oligomers. The effect of cross-linking of cellulose in HCW appears to increase with temperature and becomes significant at 270 °C, leading to a structural condensation and hence a reduction in the specific reactivity of cellulose and the selectivity of glucose oligomers in the primary liquid products. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie902020t

Kinetics and mechanism of glucose decomposition in hot-compressed water / Yun Yu in Industrial & engineering chemistry research, Vol. 50 N° 18 (Septembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 18 (Septembre 2011) . - pp. 10500-10508 Titre : Kinetics and mechanism of glucose decomposition in hot-compressed water : effect of initial glucose concentration Type de document : texte imprimé Auteurs : Yun Yu, Auteur ; Hongwei Wu, Auteur Année de publication : 2011 Article en page(s) : pp. 10500-10508 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Kinetics Résumé : At a given reaction temperature (175―275 °C), the reaction rate constant of glucose decomposition in hot-compressed water (HCW) is found to decrease by almost 1 order of magnitude with increasing the initial glucose concentration from 0.01 to 1000 mg L―1 (equivalent to 5.6 x 10―8―0.0056 M). The results demonstrate a clear shift in the glucose decomposition mechanism at various initial glucose concentrations. Fructose is always the dominant reaction product with a high selectivity at the early stage of glucose decomposition, suggesting that it is a key primary product from glucose decomposition in HCW. The initial glucose concentration also influences the selectivity of glucose decomposition products substantially. The hydroxyl ion appears to play a controlling role in catalyzing the isomerization and retro-aldol reactions under all conditions in this study. At an initial glucose concentration less than 10 mg L―1 (i.e., 5.6 x 10―5 M), particularly when it is close to or less than the molar concentration of the ion product in HCW, the hydroxyl ions play a dominant role in catalyzing the isomerization and retro-aldol condensation reactions to produce fructose, glyceraldehydes and/or glycolaldehyde, erythrose, etc. However, at an initial glucose concentration higher than 10 mg L―1 (i.e., 5.6 x 10―5 M), the selectivity of 5-hydroxymethylfurfural increases substantially, indicating that hydrogen ions play an enhanced role in catalyzing dehydration reactions under the conditions. The shift in glucose decomposition mechanism is also reflected in the change in apparent activation energy that increases with an increasing initial glucose concentration, mainly due to an increasing selectivity of acid-catalyzed dehydration reaction that has a higher activation energy. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24523872 [article] Kinetics and mechanism of glucose decomposition in hot-compressed water : effect of initial glucose concentration [texte imprimé] / Yun Yu, Auteur ; Hongwei Wu, Auteur . - 2011 . - pp. 10500-10508. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 18 (Septembre 2011) . - pp. 10500-10508 Mots-clés : Kinetics Résumé : At a given reaction temperature (175―275 °C), the reaction rate constant of glucose decomposition in hot-compressed water (HCW) is found to decrease by almost 1 order of magnitude with increasing the initial glucose concentration from 0.01 to 1000 mg L―1 (equivalent to 5.6 x 10―8―0.0056 M). The results demonstrate a clear shift in the glucose decomposition mechanism at various initial glucose concentrations. Fructose is always the dominant reaction product with a high selectivity at the early stage of glucose decomposition, suggesting that it is a key primary product from glucose decomposition in HCW. The initial glucose concentration also influences the selectivity of glucose decomposition products substantially. The hydroxyl ion appears to play a controlling role in catalyzing the isomerization and retro-aldol reactions under all conditions in this study. At an initial glucose concentration less than 10 mg L―1 (i.e., 5.6 x 10―5 M), particularly when it is close to or less than the molar concentration of the ion product in HCW, the hydroxyl ions play a dominant role in catalyzing the isomerization and retro-aldol condensation reactions to produce fructose, glyceraldehydes and/or glycolaldehyde, erythrose, etc. However, at an initial glucose concentration higher than 10 mg L―1 (i.e., 5.6 x 10―5 M), the selectivity of 5-hydroxymethylfurfural increases substantially, indicating that hydrogen ions play an enhanced role in catalyzing dehydration reactions under the conditions. The shift in glucose decomposition mechanism is also reflected in the change in apparent activation energy that increases with an increasing initial glucose concentration, mainly due to an increasing selectivity of acid-catalyzed dehydration reaction that has a higher activation energy. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24523872

Significant differences in the hydrolysis behavior of amorphous and crystalline portions within microcrystalline cellulose in hot-compressed water / Yun Yu in Industrial & engineering chemistry research, Vol. 49 N° 8 (Avril 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp. 3902–3909 Titre : Significant differences in the hydrolysis behavior of amorphous and crystalline portions within microcrystalline cellulose in hot-compressed water Type de document : texte imprimé Auteurs : Yun Yu, Auteur ; Hongwei Wu, Auteur Année de publication : 2010 Article en page(s) : pp. 3902–3909 Note générale : Idustrial Chemistry Langues : Anglais (eng) Mots-clés : Microcrystalline  Cellulose  Hot-Compressed  Water  Hydrolysis Résumé : Due to the presence of amorphous structure in microcrystalline cellulose, the reactivity of microcrystalline cellulose exhibits a considerable reduction in the initial stage during hydrolysis in hot-compressed water (HCW). Further analysis of the liquid products obtained at various temperatures suggests that the amorphous portion within microcrystalline cellulose contains some short glucose chain segments hinged with crystalline cellulose via weak bonds (e.g., hydrogen bonds). These short chain segments are reactive components responsible for the formation of C4−C13 oligomers in the primary liquid products during hydrolysis in HCW at temperatures as low as 100 °C. The minimal temperature for breaking the glycosidic bonds in those short chain segments to form glucose monomer from amorphous portion within microcrystalline cellulose is 150 °C. However, the minimal temperature at which glucose monomer starts to be produced from the crystalline portion within microcrystalline cellulose is around 180 °C, apparently due to the limited accessibility of the glycosidic bonds in the crystalline portion to HCW as a result of the strong intra- and intermolecular hydrogen bonding networks. The differences of chain length and hydrogen bonding pattern between amorphous and crystalline cellulose also greatly affect the distribution of glucose oligomers in their liquid products during hydrolysis in HCW. Generally, amorphous cellulose produces more glucose monomers and oligomers at the same hydrolysis temperature, but the selectivity ratios of glucose oligomers in the primary liquid products from amorphous and crystalline portions do not show a monotonic trend with the degree of polymerization, at least partly resulting from the presence of shorter glucose chain segments in the amorphous portion within the microcrystalline cellulose. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901925g [article] Significant differences in the hydrolysis behavior of amorphous and crystalline portions within microcrystalline cellulose in hot-compressed water [texte imprimé] / Yun Yu, Auteur ; Hongwei Wu, Auteur . - 2010 . - pp. 3902–3909. Idustrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 8 (Avril 2010) . - pp. 3902–3909 Mots-clés : Microcrystalline  Cellulose  Hot-Compressed  Water  Hydrolysis Résumé : Due to the presence of amorphous structure in microcrystalline cellulose, the reactivity of microcrystalline cellulose exhibits a considerable reduction in the initial stage during hydrolysis in hot-compressed water (HCW). Further analysis of the liquid products obtained at various temperatures suggests that the amorphous portion within microcrystalline cellulose contains some short glucose chain segments hinged with crystalline cellulose via weak bonds (e.g., hydrogen bonds). These short chain segments are reactive components responsible for the formation of C4−C13 oligomers in the primary liquid products during hydrolysis in HCW at temperatures as low as 100 °C. The minimal temperature for breaking the glycosidic bonds in those short chain segments to form glucose monomer from amorphous portion within microcrystalline cellulose is 150 °C. However, the minimal temperature at which glucose monomer starts to be produced from the crystalline portion within microcrystalline cellulose is around 180 °C, apparently due to the limited accessibility of the glycosidic bonds in the crystalline portion to HCW as a result of the strong intra- and intermolecular hydrogen bonding networks. The differences of chain length and hydrogen bonding pattern between amorphous and crystalline cellulose also greatly affect the distribution of glucose oligomers in their liquid products during hydrolysis in HCW. Generally, amorphous cellulose produces more glucose monomers and oligomers at the same hydrolysis temperature, but the selectivity ratios of glucose oligomers in the primary liquid products from amorphous and crystalline portions do not show a monotonic trend with the degree of polymerization, at least partly resulting from the presence of shorter glucose chain segments in the amorphous portion within the microcrystalline cellulose. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901925g