Aalborg Universitet
Reaction mechanisms and kinetics of processing glucose, xylose and glucose-xylose
mixtures under hot compressed water conditions for predicting bio-crude composition
Grigoras, Ionela; Toor, Saqib Sohail; Rosendahl, Lasse Aistrup
Publication date:
2015
Document Version
Publisher's PDF, also known as Version of record
Link to publication from Aalborg University
Citation for published version (APA):
Grigoras, I., Toor, S. S., & Rosendahl, L. A. (2015). Reaction mechanisms and kinetics of processing glucose,
xylose and glucose-xylose mixtures under hot compressed water conditions for predicting bio-crude
composition. Poster session presented at 4th International Conference on Thermochemical Conversion Science
(TcBiomass 2015), Chicago, IL, United States.
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Reaction mechanisms and kinetics of processing glucose,
xylose and glucose-xylose mixtures under hot compressed
water conditions for predicting bio-crude composition
Ionela F. Grigoras*, Saqib S. Toor, Lasse A. Rosendahl
Aalborg University, Department of Energy Technology, Pontoppidanstræde 101, 9220 Aalborg, Denmark
*[email protected]
Mechanisms for bio-crude formation during the conversion of glucose, xylose and glucose-xylose mixtures as biomass model compounds under
hot compressed water conditions are investigated. Studies in literature have shown that the diverse products formed at the early stages of glucose
or xylose conversion are 5-HMF, erythrose, glyceraldehyde, dihydroxyacetone, pyruvaldehyde, and saccharinic acids resulted through reactions
such as dehydration, retro-aldol condensation and isomerization. However, these compounds are mostly water soluble compounds and lack the
final steps towards formation of water insoluble components at longer reaction times. The effects of pressure, pH, catalyst and reaction time on
the main products are examined thoroughly. The possible routes for the formation of oil compounds are developed.
HTL process
Separation process
400 °C
250 – 350 bar
0 – 20 min
0 – 4 % catalyst
Glucose
CO₂ CO CH₄
C₃H₈ C₄H₁₀
H₂
Xylose
Water
phase
Solids
Oil
Mixture of
Glucose - Xylose
Centrifugation
Vacuum
Filtration
Solvent Evaporation
Parametric study – Glucose case
Solids
Water ph.
Gas
Biocrude
Solids
Water ph.
Gas
Biocrude
Solids
Water ph.
80
Gas
60
70
40
50
50
60
40
50
30
20
10
0
40
30
20
10
0
250
275
300
325
350
0
1
Pressure (bar)
2
3
Vol. %
60
Yield (wt.% DM)
50
Yield (wt.% DM)
Yield (wt.% DM)
Biocrude
30
20
20
0
10
0
Catalyst conc. (wt.% DM)
5
10
15
Reaction time (min)
20
CH4
30
10
4
CO2
40
C4H10
C3H8
0
0
10
Reaction time (min)
20
Conclusions
Reaction mechanism
o Pressure and reaction time did not influence the final pH of
the product significantly; Catalyst concentration was found
to be the only factor affecting the final pH of the product.
Gases
CO₂, CO, H₂, CH₄, C₃H₈,
C₄H₁₀
Ketones
roge
nati
on
- 3 H₂ O
Hyd
Dehydration
Glucose
o Reaction time influences gas composition; longer reaction
time increased the concentration of CH₄, C₃H₈ and C₄H₁₀ in
the gas phase, whereas the CO₂ decreased for glucose and
mixtures of glucose-xylose, but increased in the case of
xylose.
Formic acid
HMF
Dehydration
Condensation
Hydrogenation
Phenolics & Aromatics
- 3 H₂ O
Xylofuranose
Furfural
Tetrahydro-furan
0°
40
Glycolaldehyde
C
Acetic acid
Furan
H⁺
H₂ O
Acids
Polymerization
Coke
C3BO
Center for BioOil
grant #: 1205-00030B
o At short reaction times furan based compounds such as
furfurals, furanones, tetrahydrofuranols will be kept in the
biocrude composition. At longer reaction times, the furan
ring opens under the water attack. The ring opening leads
to production of ketones and aldehydes. Analysis of water
soluble products and biocrude showed a decrease in the
furan-methanol concentration as the reaction time was
increased during the HTLprocess. At the same time, the
concentration
of
4-hydroxy-4-methyl-2-pentanone
increased. Long reaction times also favor formation of
carboxylic acids.
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