The Alpha–Bet(a) of Salty Glucose Pyrolysis: Computational Investigations Reveal Carbohydrate Pyrolysis Catalytic Action by Sodium Ions

Abstract

Biomass pyrolysis is a promising technology for the production of renewable fuels and chemicals from nonfood biomass. Given the potential of pyrolysis as a viable, costeffective biomass deconstruction method, there is active interest in understanding the chemical transformations at the heart of the technology. It has long been known that the presence of alkali-and alkaline-earth-metal ions in biomass, such as Na + , significantly alters product yields of biomass pyrolysis, but the mechanism behind this effect has not been elucidated. In this work, we employ density functional theory (DFT) to reveal the stereoelectronic basis of the effect of sodium ions on several key glucose thermal decomposition reactions, such as the formation of levoglucosan and 5-hydroxymethylfurfural (5-HMF). β-D-Glucose is of interest for pyrolysis, as it is the monomer of cellulose and a key intermediate in cellulose pyrolysis. α-D-Glucose is included in this study, as the two anomers can readily interconvert under pyrolysis conditions. The computational results are consistent with the experimental results for α-and β-D-glucose pyrolysis with NaCl, which demonstrate that the products are the same as those produced in neat pyrolysis, but with differing relative yields. We find that the sodium ion changes the reaction rate coefficients to varying degrees, with approximately 70% of the reactions in this study catalyzed by Na + , approximately 25% inhibited by Na + , and the remainder showing virtually no effect on the rate coefficient. The variations in how the ion modifies the rate coefficient reflect how the particular stereochemistry of the transition state interacts with the ion. The sodium ions have a more subtle effect on reactant electronic structure. The results of this study provide a molecular-level understanding of how naturally occurring salts act as catalysts in biomass pyrolysis.

Pyrolysis of the Cellulose Fraction of Biomass in the Presence of Solid Acid Catalysts: An Operando Spectroscopy and Theoretical Investigation

“…The nature and corresponding acidity of the supported AlO x nanostructures on SiO 2 were determined with 27 Al/ 1 HNMR and IR spectroscopy of chemisorbed CO, and DFT calculations. [29,30,33,35,53,54,[56][57][58] As imple acid wash can remove the majority of contaminants from biomass samples. The molecular transformations duringb iomass pyrolysis depended on both the domain size of the AlO x clustera nd molecular nature of the biomass feedstock.T hese new insights allowed the establishment of fundamental structure-activity/selectivityr elationshipsd uringb iomass pyrolysis.…”

“…[25] The presenceo fm ineral/inorganic contaminants in biomass has been shown to lead to ad ecrease in levoglucosan anda n increasei na cids, aldehydes,a nd phenols. [29,30,33,35,53,54,[56][57][58] As imple acid wash can remove the majority of contaminants from biomass samples. [29] The b (1)(2)(3)(4) glycosidicl inkage is crucial for the formation of levoglucosan, with ay ield correlating with the degree of polymerization of the (poly)saccharides as follows:p olysaccharides > oligosaccharides > disaccharides > monosaccharides.…”

Impact of combined acid washing and acid impregnation on the pyrolysis of Douglas fir wood

“…Many hypotheses have been presented to explain the impact of AAEMs on cellulose pyrolysis. The current understanding, based on molecular modeling techniques, explains that AAEMs alter the electronic structure of the carbohydrate by interacting with oxygen, affecting the stereochemistry of the molecules during reactions; because of that, rearrangement and dehydration reactions are enhanced, followed by fragmentation reactions [34,35]. It is thought that AAEMs can directly attack the cellulose chain before and during depolymerization reactions as well as catalyze reactions in the liquid intermediate phase [34,36].…”

Insights into the Hydrothermal Stability of ZSM-5 under Relevant Biomass Conversion Reaction Conditions

“…17, 35 We showed previously that Na + ions can interfere when pyrolyzing cellulose at high temperature. 35 Na + alters reaction pathways and modifies the product distribution.…”

“…17, 35 We showed previously that Na + ions can interfere when pyrolyzing cellulose at high temperature. 35 Na + alters reaction pathways and modifies the product distribution. Therefore, experiments were carried out to determine if NaCl also influences the conversion of glucose in the liquid phase (Entry 9).…”