Fast pyrolysis of glucose‐based carbohydrates with added NaCl part 1: Experiments and development of a mechanistic model

Abstract

Sodium ions, one of the natural inorganic constituents in lignocellulosic biomass, significantly alter pyrolysis behavior and resulting chemical speciation. Here, experiments were conducted using a micropyrolyzer to investigate the catalytic effects of NaCl on fast pyrolysis of glucose-based carbohydrates (glucose, cellobiose, maltohexaose, and cellulose), and on a major product of cellulose pyrolysis, levoglucosan (LVG). A mechanistic model that addressed the significant catalytic effects of NaCl on the product distribution was developed. The model incorporated interactions of Na 1 with cellulosic chains and low molecular weight species, reactions mediated by Na 1 including dehydration, cyclic/Grob fragmentation, ring-opening/closing, isomerization, and char formation, and a degradation network of LVG in the presence of Na

A Critical Review on Hemicellulose Pyrolysis

“…FTIR spectroscopy only detects characteristic functional groups and cannot identify all products, such as HMF and furfural, explicitly . Incomplete mass closure also poses a challenge to the quantification of products because mass loss cannot be avoided in the transfer line from the pyrolysis reactor to analytical equipment, such as the GC instrument, due to the condensation of products, such as oligomers . Moreover, there are unquantified minor peaks in the chromatograph and undetectable gases, such as hydrogen and light hydrocarbons (e.g., CH 4 , C 2 H 6 , and C 3 H 8 ) .…”

“…Incomplete mass closure also poses a challenge to the quantification of products because mass loss cannot be avoided in the transfer line from the pyrolysis reactor to analytical equipment, such as the GC instrument, due to the condensation of products, such as oligomers . Moreover, there are unquantified minor peaks in the chromatograph and undetectable gases, such as hydrogen and light hydrocarbons (e.g., CH 4 , C 2 H 6 , and C 3 H 8 ) . Future horizons in this area of research will require pushing the limits of analytical techniques to address these detection challenges.…”

“…All aldehyde species, such as formaldehyde and glycolaldehyde, can undergo decarbonylation to form CO to explain the increasing yield of CO with elevated temperature. However, the proposed thermal degradation of xylan through a radical mechanism is not likely because fast pyrolysis of carbohydrates has been increasingly recognized to follow a concerted mechanism . No detailed elementary reaction steps or information at the mechanistic level were reported in these studies.…”

“…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.…”