Pyrolytic Sugars from Cellulosic Biomass

Depolymerization of cellulose offers the prospect of inexpensive sugars from biomass. Breaking the glycosidic bonds of cellulose to liberate glucose has usually been pursued by acid or enzymatic hydrolysis although a purely thermal depolymerization route to sugars is also possible. Fast pyrolysis of...

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Bibliographic Details
Published in:ChemSusChem 2012-11, Vol.5 (11), p.2228-2236
Main Authors: Kuzhiyil, Najeeb, Dalluge, Dustin, Bai, Xianglan, Kim, Kwang Ho, Brown, Robert C.
Format: Article
Language:English
Subjects:
acids
Biomass
Catalysis
Cellulose - chemistry
heterogeneous catalysis
pyrolysis
Salts - chemistry
sugars
Temperature
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Summary:Depolymerization of cellulose offers the prospect of inexpensive sugars from biomass. Breaking the glycosidic bonds of cellulose to liberate glucose has usually been pursued by acid or enzymatic hydrolysis although a purely thermal depolymerization route to sugars is also possible. Fast pyrolysis of pure cellulose yields primarily the anhydrosugar levoglucosan (LG) whereas the presence of naturally occurring alkali and alkaline earth metals (AAEMs) in biomass strongly catalyzes ring‐breaking reactions that favor formation of light oxygenates. Here, we show a method of significantly increasing the yield of sugars from biomass by purely thermal means through infusion of certain mineral acids (phosphoric and sulfuric acid) into the biomass to convert the AAEMs into thermally stable salts (particularly potassium sulfates and phosphates). These salts not only passivate AAEMs that normally catalyze fragmentation of pyranose rings, but also buffer the system at pH levels that favor glycosidic bond breakage. It appears that AAEM passivation contributes to 80 % of the enhancement in LG yield while the buffering effect of the acid salts contributes to the balance of the enhancement. Thermolytic sugars from biomass: Using a simple acid pretreatment, the catalytic activity of naturally occurring alkali and alkaline earth metals in lignocellulosic biomass is dramatically reduced, allowing the purely thermal production of sugars from biomass. The optimal amount of acid for the thermal depolymerization of biomass to sugars is proportional to the amount of alkali and alkaline earth metals inherently contained in the biomass feedstock.
ISSN:1864-5631
1864-564X
DOI:10.1002/cssc.201200341