Fast pyrolysis of glucose‐based carbohydrates with added NaCl part 2: Validation and evaluation of the mechanistic model

Abstract

A mechanistic model considering the significant catalytic effects of Na+ on fast pyrolysis of glucose-based carbohydrates was developed in Part 1 of this study. A computational framework based on continuous distribution kinetics and mass action kinetics was constructed to solve the mechanistic model. Agreement between model yields of various pyrolysis products with experimental data from fast pyrolysis of glucose-based carbohydrates dosed with NaCl ranging from 0-0.34 mmol/g at 500 °C validated the model and demonstrated the robustness and extendibility of the mechanistic model. The model was able to capture the yields of major and minor products as well as their trends across NaCl concentrations. Modeling results showed that Na+ accelerated the rate of decomposition and reduced the time for complete thermoconversion of carbohydrates. The sharp reduction in the yield of levoglucosan (LVG) from fast pyrolysis of cellulose in the presence of NaCl was mainly caused by reduced decomposition of cellulose chains via end-chain initiation and depropagation due to Na+ favoring competing dehydration reactions. Analysis of the contributions of reaction pathways showed that the decomposition of LVG made a minor contribution to its yield reduction and contributed less than 0.5% to the final yield of glycolaldehyde from fast pyrolysis of glucose-based carbohydrates in the presence of NaCl.

A Critical Review on Hemicellulose Pyrolysis

“…More recently, the group of Broadbelt has developed a mechanistic model for fast pyrolysis of hemicellulose, specifically hemicellulose extracted from corn stover (with a dominant polysaccharide component of arabinoxylan), to bridge these gaps . The model was built based on the reaction family approach applied to build mechanistic models for fast pyrolysis of glucose‐based carbohydrates, including cellulose –. The model describes the detailed reaction pathways and mechanisms for the decomposition of hemicellulose chain species (through initiation, end‐chain initiation, dehydration, mid‐chain dehydration, hydrolysis, etc.…”

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.…”

Catalytic fast pyrolysis of lignocellulosic biomass for aromatic production: chemistry, catalyst and process

“…The rank order of the effects of AAEMs on the reduction in levoglucosan yield was K + > Na + > Ca 2+ > Mg 2+ . Furthermore, AAEMs also strongly catalyzed the secondary degradation reactions of Levoglucosan . As shown in Figure (b), levoglucosan bound to metal ions (e.g., Na + ) to form a complex of levolgucosan–Na + .…”

“…(a) Primary pyrolysis reactions of cellulose (b) secondary degradation reaction of levoglucosan. Adapted with permission from Ref . Copyright 2010 Elsevier and Copyright 2015 John Wiley and Sons)…”

“…36 Furthermore, AAEMs also strongly catalyzed the secondary degradation reactions of Levoglucosan. 36,37 As shown in Figure 3(b), levoglucosan bound to metal ions (e.g., Na + ) to form a complex of levolgucosan-Na + . The complex then underwent retro-aldol reactions to yield aldehydes and ketones.…”