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(266c) Stabilization of Carbohydrates with Formaldehyde during Integrated Biomass Depolymerization

Authors: 
Questell-Santiago, Y. M., Ecole polytechnique fédérale de Lausanne
Talebi Amiri, M., Ecole polytechnique fédérale de Lausanne
Shuai, L., Ecole polytechnique fédérale de Lausanne
Luterbacher, J. S., Ecole polytechnique fédérale de Lausanne

Stabilization of
Carbohydrates with Formaldehyde during Integrated Biomass Depolymerization

Biomass-derived carbohydrates are
important platform molecules for the production of renewable fuels and
chemicals. The production of carbohydrates from lignocellulosic biomass
requires the extraction of lignin and the cleavage of ether bonds in hemicellulose
(mostly xylan) and cellulose chains while minimizing further degradation of the
resulting carbohydrates.(1) Current methods lead to incomplete biomass
depolymerization (producing only polysaccharides) and high process costs due to
mineral acid recovery and enzyme production.(2) Lowering acid use to
improve process economics requires the use of higher temperatures and generally
leads to significant sugar degradation and low yields, which is why these
strategies have generally been difficult to implement.

             
   

Figure 1. (A) Xylose conversion to
diformylxylose and furfural during biomass pretreatment (B) Glucose conversion
to diformylglucose isomers and 5-hydroxymethylfurfural (5-HMF) during cellulose
acid depolymerization.

Recently, we have discovered that
formaldehyde (FA) could be used to stabilize lignin and facilitate the
conversion of extracted lignin to monomers at high yields (up to 97% of
theoretical yield).(3) This method could also
prevent xylan degradation by producing a stable xylose-derived molecule that we
refer to as diformylxylose. In the current work, we study the stabilization of
carbohydrates by the addition of FA during integrated biomass depolymerization.
The low water content and the acidic environment in the biomass pretreatment
allow FA to react with xylose, forming diformylxylose (Figure 1-A) at yields
above 90% and minimizing xylose degradation into furfural. In comparison,
reactions without formaldehyde lead to almost full xylose degradation into
furfural with only 16% xylose recovery. Diformylxylose could be used as is or
converted back to xylose at high yields in aqueous environments. A similar
process is observed with glucose during cellulose acid depolymerization,
forming diformylglucose (DG). The presence of FA led to the formation of two DG
isomers from glucose by forming 1,3-dioxolane and
1,3-dioxane structures (Figure 1-B). As with DX, these structures stabilize
glucose after depolymerization at conditions that were previously unfavorable
due to carbohydrate degradation. Future efforts include the characterization of
protected sugars and the removal of their protective groups. 

References:

1.    J. S. Luterbacher et al., Nonenzymatic Sugar Production from Biomass Using
Biomass-Derived γ-Valerolactone. Science.
343, 277–280 (2014).

2.    L. Shuai, Y.
M. Questell-Santiago, J. S. Luterbacher, A mild biomass pretreatment using
γ-valerolactone for concentrated sugar
production. Green Chem. 18, 937–943 (2016).

3.    L. Shuai et
al.
, Formaldehyde stabilization facilitates lignin monomer production
during biomass depolymerization. Science. 354, 329–333 (2016).

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