Pyrolytic Sugars from Cellulosic Biomass

Abstract

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.

Impact of Nonthermal Atmospheric Plasma on the Structure of Cellulose: Access to Soluble Branched Glucans

“…To determine whether or not NTAP-promoted oxidation is propagated to deeper regions in the cellulose material, aP -MCC < 10 sample was next analyzed by solid state 13 CC P/MAS NMR spectroscopy ( Figure S4). No peak ascribable to carbonyl groups was detected, suggesting that oxidation remained restricted to the surfaceo fp articles only and did not occur to as ignificant extent in the bulk.…”

The Influence of Alkali and Alkaline Earth Metals and the Role of Acid Pretreatments in Production of Sugars from Switchgrass Based on Solvent Liquefaction

“…This value is comparable to the yield of levoglucosan during the pyrolysis of the AI switchgrass in a micropyrolyzer. 20 It should also be noted that only about 1/100th of the mass of the AI switchgrass used in the present study was pyrolyzed. 20 It is known that the levoglucosan yield decreases as the mass of the sample increases during cellulose pyrolysis, due to the polymerization of levoglucosan.…”

“…20 It should also be noted that only about 1/100th of the mass of the AI switchgrass used in the present study was pyrolyzed. 20 It is known that the levoglucosan yield decreases as the mass of the sample increases during cellulose pyrolysis, due to the polymerization of levoglucosan. 22 Therefore, the comparison results suggest that the solvent liquefaction of the AI switchgrass could potentially produce more levoglucosan than fast pyrolysis at lower temperatures.…”

“…15,19 Recently, we reported that direct acid infusion of biomass can also increase sugar yield, mainly by converting AAEM into thermally stable salts that are catalytically inactive. 20 Furthermore, the weak acid salts buffer acid-catalyzed depolymerization of cellulose, thereby increasing levoglucosan yield.…”

“…The concentration of sulfuric acid in switchgrass was 2 wt %, since switchgrass at this concentration of the acid should produce the maximum yield of levoglucosan based on previous pyrolysis research conducted by our group. 20 ■ EXPERIMENTAL SECTION Material. Switchgrass was used as the feedstock in all experiments.…”