Mechanism of Esters Formation during Cellulose Liquefaction in Sub- and Supercritical Ethanol

Tang, Cheng-zheng; Tao, Hong-Xiu; Zhan, Xuejia; Xie, Xianmei

doi:10.15376/biores.9.3.4946-4957

Cited by 9 publications

(4 citation statements)

References 19 publications

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“…In recent years, significant progress has been made in the preparation of levulinic acid and its esters by catalytic liquefaction of woody fiber biomass. − In this experiment, by analyzing the liquid products of glucose, cellobiose and cellulose, we found that in the process of preparing ethyl levulinate by acid catalytic liquefaction of lignocellulosic biomass in ethanol, ethyl levulinate mainly came from cellulose liquefaction. Moreover, we found that ethyl levulinate can be generated not only by glucose, fructose, 1,6-anhydro-beta- d -glucopyranose (AGP), levoglucosenone (LGO), and 5-HMF as reported in previous studies ,− (as shown in Figure S10), but also by the other pathways shown in Figure .…”

Section: Resultssupporting

confidence: 73%

Qualitative Analysis of Liquid Products Generated from Lignocellulosic Biomass Using Post-Target and Nontarget Analysis Methods and Liquefaction Mechanism Research

Guo

Cheng

Jiang

et al. 2020

ACS Sustainable Chem. Eng.

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Significant progress has been made in the preparation of levulinic acid and its esters, furfural, 5-HMF, and other small molecular platform compounds by catalytic liquefaction of lignocellulosic biomass. However, the components of the lignocellulosic biomass’s liquefaction products are complex, in particular, the liquid phase products. This makes product separation difficult and presents challenges for the full composition of liquefied products. In this study, gas chromatography coupled with quadrupole time-of-flight mass spectrometry (GC/Q-TOF MS), combined with post-target and nontarget analysis methods, was used to analyze the liquid phase products generated from lignocellulosic biomass liquefaction, such as poplar wood, pine wood, cellulose model compounds, including glucose, cellobiose and microcrystalline cellulose, hemicellulose model compounds, including xylose, xylan, glucose and xylose mixture, and microcrystalline cellulose and xylan mixture, liquefied in ethanol catalyzed by sulfuric acid. A total of 72 compounds were identified from nine samples. Fifty-four compounds were identified by post-target analysis, and 18 unknown compounds were identified for the first time by nontarget analysis. Among the 18 unknown compounds, five were intermediates of lignocellulosic biomass liquefaction, and 13 were byproducts. The reaction mechanism of ethyl levulinate by catalytic liquefaction of lignocellulosic biomass acid was further clarified based on the intermediate compound ethyl 2-hydroxy-4-oxopentanoate (EHO), which was first reported. The mechanism was as follows: (i) cellulose is hydrolyzed to generate glucose, from which 1,6-anhydro-beta-d-glucopyranose (AGP), 1,6-anhydro-beta-d-glucofuranose (AGF), 3-hydroxy-4-oxopentanoic acid (HOA), and EHO are gradually generated, and finally ethyl levulinate is produced; and (ii) cellulose was hydrolyzed into glucose, which was gradually generated into 1,4:3,6-dianhydro-alpha-d-glucopyranose (DGP), HOA, and EHO, and finally into ethyl levulinate.

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Section: Resultssupporting

confidence: 73%

Qualitative Analysis of Liquid Products Generated from Lignocellulosic Biomass Using Post-Target and Nontarget Analysis Methods and Liquefaction Mechanism Research

Guo

Cheng

Jiang

et al. 2020

ACS Sustainable Chem. Eng.

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“…Recently, alcohols have been utilized as an alternative solvent in the liquefaction of various types of biomass, including cellulose, lignin, sewage sludge, and microalgae, due to their advantages with better solubility of organic intermediates, hydrogen donor properties, and easier separation due to their low boiling points [50][51][52][53][54][55][56][57][58][59]. Compared to water, alcohols such as methanol and ethanol have much lower critical temperatures and pressures.…”

Section: Mesoporous Silicate Materials Containing Zirconium Have Highmentioning

confidence: 99%

Mechanistic insights into the production of methyl lactate by catalytic conversion of carbohydrates on mesoporous Zr-SBA-15

Yang

Tian

et al. 2016

Journal of Catalysis

114

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The as-synthesized Zr-SBA-15 catalysts with tunable mesoporous structures showed excellent catalytic performance for the conversion of carbohydrates to methyl lactate in a "onepot" process using near-critical methanol or methanol-water mixture as the solvents. The effects of reaction conditions, including temperature, reaction time, and catalyst loading amount, on the conversions of carbohydrates and the yields of methyl lactate were investigated. The high yields of methyl lactate, up to 41 % and 44%, were produced from pentose and hexose, respectively, in the near-critical methanol at 240°C. Moreover, the Si/Zr ratio of the Zr-SBA-15 catalysts profoundly affected the Lewis acidity and therefore the catalytic activity and selectivity to methyl lactate in the conversion of carbohydrates. The pore size of the Zr-SBA-15 catalysts, tuned by the synthesis temperature, strongly affected the formation of solid residues. The key intermediates such as glyceraldehyde, glycolaldehyde, and pyruvaldehyde were used as probe reactants to understand the mechanism. The role of the Zr-SBA-15 catalyst in the aldol-and retro-aldol condensation, isomerization, and Cannizzaro reactions of carbohydrates and their derivatives was discussed. Furthermore, 28% and 27% yields of methyl lactate were obtained from cellulose and starch, respectively, in methanol-water mixture (5 wt% water and 95 wt% methanol) at 240°C. The Zr-SBA-15 catalyst was relatively stable in short term without regeneration.

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“…Table 1 shows that ketones (Carbon numbers C 5 ∼C 20 ), esters (Carbon numbers C 7 ∼C 30 ), alkanes (Carbon numbers C 10 ∼C 30 ) have a higher content in BO, and alcohols, acids, aldehydes and phenols were lower. Acetates and methyl esters were the dominant compounds of esters, this indicated that CH 3 • and CH 3 C = O• radicals were produced from supercritical acetone, the addition and condensation among these methyl and acetyl radicals and cellulose active fragments produced a lot of esters, on the other hand, the esterification between acids and alcohols also have a contribution on esters formation (34). Ketones were composed of aliphatic ketones (4-Hydroxy-4-methyl-2pentanone, etc.…”

Section: Gc-ms Analysis For Bo Obtained From Various Acetone Dosagesmentioning

confidence: 97%

“…According to 3.5.1 and 3.5.2(above), the formation pathways and networks of dominant chemicals (ketones, esters, acids, alcohols, alkanes, aldehydes, glucosides, etc.) during cellulose liquefaction in supercritical acetone were developed (21,29,34,37,38). It is shown in Figure 8.…”

Section: Chemicals Distribution In Bo and The Formation Pathwaysmentioning

confidence: 99%

Investigation of cornstalk cellulose liquefaction in supercritical acetone by FT-TR and GC-MS methods

Xie

Sun

et al. 2019

Green Chemistry Letters and Reviews

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Cornstalk cellulose was liquefied in supercritical acetone at various temperature by a high-pressure autoclave, where the maximum yield of bio-oil was 43.79% and the highest conversion rate of cellulose was 72.13%. FT-TR spectrums showed that the CO -C and CC bonds in cellulose were cleaved under the attack of supercritical acetone, then active fragments were produced and transformed into liquefaction products. GC-MS results showed that the dominant components in bio-oil were ketones, esters, alkanes, etc. As the acetone dosage increased, ketones and glucosides increased while esters and alkanes decreased. A higher temperature was suitable for ketones and esters formation, which had an inhibition on alkanes formation. Finally, the formation of pathways and networks of dominant chemicals during cellulose liquefaction in supercritical acetone were developed. This investigation contributes to the knowledge of cellulose liquefaction in supercritical solvents for bio-oil and platform chemicals, which can provide an alternative method for biomass resources utility.

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Mechanism of Esters Formation during Cellulose Liquefaction in Sub- and Supercritical Ethanol

Cited by 9 publications

References 19 publications

Qualitative Analysis of Liquid Products Generated from Lignocellulosic Biomass Using Post-Target and Nontarget Analysis Methods and Liquefaction Mechanism Research

Qualitative Analysis of Liquid Products Generated from Lignocellulosic Biomass Using Post-Target and Nontarget Analysis Methods and Liquefaction Mechanism Research

Mechanistic insights into the production of methyl lactate by catalytic conversion of carbohydrates on mesoporous Zr-SBA-15

Investigation of cornstalk cellulose liquefaction in supercritical acetone by FT-TR and GC-MS methods

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