xiaoyue wang-characterization of biochars made from different
TRANSCRIPT
Characterization of biochars made from
different hydrothermal carbonization
techniques using advanced solid-state 13C NMR spectroscopy
Xiaoyan Cao, Kyoung S. Ro, Judy A. Libra, Claudia I.
Kammann, Mark Chappell, Yuan Li, Bo Sun, Xiaoyue
Wang, Jingdong Mao
Biochar Res Dev & appl Oct. 10-15, 2011, Nanjing
Biochar
Solid product from thermochemical processing of biomass
In the fields of soil and agricultural sciences
“Charred organic matter that is applied to
soil in a deliberate manner, with the intent
to improve soil properties”
Libra, J. A. et al. Biofuels 2011, 2, 71-106.
Motivation
• Role of char in sustained fertility in Amazonian
soils ‘Terra preta’
• Increase soil fertility
• Sequester carbon
Biochar production
Dry pyrolysis
Wet pyrolysis--- Hydrothermal carbonization (HTC)
temperatures above 100 °C (up to 250 °C);subcritical conditions of water.
Bridgwater, A. V. and Peacocke, G. V. C. Renewable Sustainable Energy Rev. 2000, 4, 1–73.
Brewer, C. E. et al. Environ. Prog. Sustainable Energy 2009, 28, 386–396.
Funke, A. and Ziegler, F. Biofuels, Bioprod. Biorefin. 2010, 4, 160–177.
Hydrothermal carbonization (HTC)
quite new in biomass conversion
Advantages
Process wet biomass
Nontraditional sources: wet animal manures,
human waste, sewage sludges
Libra, J. A. et al. Biofuels 2011, 2, 71-106.
Hydrochar (Biochar produced from HTC)
• The physical and chemical properties of biochars:
Feedstock type
Processing variables (temperature, duration of
heating, oxygen availability, moisture content)
Important to know chemical structure of hydrochar as a
function of production conditions in order to understand its
roles and utilize it beneficially
Solid-state NMR: ideal for its characterization
Nondestructive
Measure insoluble organic matter
Provide comprehensive structural information
Objectives
Characterization of biochars prepared from
hydrothermal carbonization (HTC) of bark mulch
and sugar beet, in steam and water media with
different temperatures and residence times using
advanced solid-state 13C NMR spectroscopy.
Biomass feedstock
Bark mulch and sugar beet
Water hydrochars (W-HTC) from water hydrocarbonization
W-HTC-bark/W-HTC-beet (200 ºC, 3 h)
W-HTC-bark/W-HTC-beet (250 ºC, 3 h)
W-HTC-bark/W-HTC-beet (250 ºC, 20 h)
Steam hydrochar (S-HTC) from steam hydrocarbonization
200 ºC, 16 bar, 3 h
S-HTC-bark/S-HTC-beet (200 ºC, 3 h)
Materials and Methods
Materials and Methods
呑 13C NMR spectroscopyBruker Avance III 300 spectrometer at 75 MHz (300 MHz 1H frequency)
1. Cross polarization/total sideband suppression (CP/TOSS)2. Dipolar dephasing3. 13C chemical-shift-anisotropy (CSA) filter4. 1H-13C long-range recoupled dipolar dephasing5. 13C direct polarization/magic-angle spinning (DP/MAS)
Results and Discussion
Bark vs. Sugar beetBark vs. Sugar beet
Bark:
Carbohydrates
Lignin, tannins, proteins
Sugar beet:
Carbohydrates
Proteins
Sugar beet and bark vs. HTC chars
Steam HTC chars vs. Water HTC chars
Sugar beet and bark vs. HTC chars
Steam HTC chars vs. Water HTC chars
Beet/bark vs. HTC
chars
Aromatic and alkyl
carbons increase;
Nonproton. aromatics
and arom. C-O increase;
Carbohydrates
decrease.
The increasing trends
of these functional
groups are more
prominent in water
hydrochars than steam
hydrochars.
Water HTC Chars
200 ºC˧˧˧˧ 250 ºCfurther enrichment of
aromatic C, and
nonpolar alkyl C;
depletion of signals from
carbohydrates.
3 h ˧˧˧˧ 20 hfurther enrichment of
nonprotonated aromatic
carbons and methyl
carbons
Fused aromatic rings revealed by 1H-13C recoupled
long-range dipolar dephasing
• The degree of aromatic ring
condensation is an important feature of
char structure, which determines its
degradability and sorption affinity
• Select fused aromatic rings
After 0.86 ms of recoupled dipolar
dephasing time, the signals of most
individual aromatic rings are dephased
Fused aromatic rings revealed by 1H-13C recoupled
long-range dipolar dephasing
Fused aromatic rings
Quantitative DP/MAS 13C NMR and DP/MAS after
recoupled dipolar dephasing
DP technique
provides reliable
quantification of
condensed aromatic
carbons.
DP/DD technique
allows quantitative
structural information on
nonprotonated carbons
and carbons of mobile
groups.
Sample
ppm220-190
190-165
165-150
150-112
112-68
68-48
48-0
CarboCarboCarboCarbonylnylnylnyl
COO/COO/COO/COO/NNNN----C=OC=OC=OC=O
AromAromAromArom. . . . CCCC----OOOO
NonprotonNonprotonNonprotonNonproton. . . . AromAromAromArom. C. C. C. C
Proton. Proton. Proton. Proton. AromAromAromArom. C. C. C. C
OOOO----alkyl Calkyl Calkyl Calkyl C
OOOO----CHCHCHCH3333
NCHNCHNCHNCH AlkylAlkylAlkylAlkyl
BeetBeetBeetBeet 0.0 0.8 0.0 0.5 0.2 59.3 0.8 25.4 13.0S-beetbeetbeetbeet (200 C/3 h) 8.6 11.4 7.0 12.1 8.5 20.0 0.2 9.0 23.2W-beetbeetbeetbeet (200 C/3 h) 5.3 8.7 7.2 20.5 8.6 13.6 1.3 6.5 28.3W-beet beet beet beet (250 C/3 h) 3.7 7.4 7.1 28.5 11.8 1.0 1.5 3.0 36.0W-beetbeetbeetbeet (250 C/20h) 4.9 7.0 8.7 32.8 10.8 0.3 0.2 3.6 31.6
BarkBarkBarkBark 0.0 2.7 9.9 8.6 3.6 38.6 1.0 19.5 16.0S-bark bark bark bark (200 C/3 h) 1.5 4.5 17.7 15.0 9.5 22.3 3.0 8.2 18.3W-bark bark bark bark (200 C/3 h) 3.6 5.9 19.7 14.6 10.0 19.6 2.1 5.7 18.8W-barkbarkbarkbark (250 C/3 h) 5.3 6.8 24.6 24.9 11.1 0.2 2.6 2.1 22.3W-barkbarkbarkbark (250 C/20 h) 4.1 6.7 25.2 27.5 11.3 0.4 1.1 2.4 21.4
Quantitative composition (in % of total C) of
biomass and biochars
Conclusion(1) chemical structures of hydrochars were closely related to the
structural characteristics of biomass feedstock;
(2) both bark and sugar beet were likely to undergo deeper
carbonization during water HTC process (200 ºC, 3 h) than
steam HTC process (200 ºC, 3 h);
(3) hydrothermal carbonization at higher temperatures (250 ºC)
produced hydrochars that were more aromatic and were
depleted of carbohydrates;
(4) increasing residence time from 3 h to 20 h at 250 ºC
generally resulted in the enrichment of nonpronated aromatic
carbons.
• National Science Foundation
• Petroleum Research Fund
Acknowledgements
