Abstract

In this paper, carbonization of biomass in the presence of supercritical CO2 is investigated to obtain carbon solids with enhanced properties and potential to provide a sustainable pathway for high-value solid products which are currently resourced from expensive and carbon driven fossil-fuel routes. Carbonization of cellulose was carried out in supercritical CO2 at temperatures of 523 K and 623 K at ∼100 bar pressure in a stirred reactor for 1–8 h of residence times. The obtained solid residue was characterized for morphology using scanning electron microscopy (SEM), surface graphitization using Raman spectroscopy, thermal stability using thermogravimetric analysis (TGA), and crystallinity using powder X-ray diffraction (XRD). The solid chars were found to be dominated by clusters of microspheres (<5 μm), especially at temperatures of 623 K. Raman spectroscopy revealed the formation of graphitic crystallite units connected by sp3 carbons (i.e., aliphatic) suggesting significant graphitization. G-band peak ratio was found to be highest for a residence time of 5 h for both the temperatures. TGA data revealed that higher carbonization temperature led to higher thermal decomposition peaks of the chars. The peak value of thermal decomposition ranged between 700 and 800 K for char obtained at 523 K and between 750 and 900 K for char at 623 K. The values were significantly higher than the decomposition peak cellulose at ∼610 K. Proximate analysis results revealed significant increase of fixed carbon content compared with cellulose. Fixed carbon to volatile content ratios revealed increase from 0.052 in cellulose to values ranging from 1.4 to 4.3 making these chars similar in character to coal (with ranking of bituminous coal and petroleum coke). The net yield of solid chars from carbonization was around 50–66% depending upon the extent of carbonization. These results suggest this pathway to produce high yields of high-quality carbon solids with low volatile content, high thermal stability, and significant graphitization. The graphitized carbon offers potential applications in catalysis, electrode materials, pollutant absorption, and energy storage and solid fuels while avoiding drying to remove moisture unlike pyrolysis.

References

1.
EPA
,
2019
, “Advancing Sustainable Materials Management: Facts and Figures Report,” United States Environmental Protection Agency, https://www.epa.gov/sites/production/files/2021-01/documents/2018_ff_fact_sheet_dec_2020_fnl_508.pdf
2.
Burra
,
K. G.
, and
Gupta
,
A. K.
,
2018
, “Thermochemical Reforming of Wastes to Renewable Fuels,”
Energy for Propulsion: A Sustainable Technologies Approach
,
A. K.
Runchal
,
A. K.
Gupta
,
A.
Kushari
,
A.
De
, and
S. K.
Aggarwal
, eds.,
Springer
,
Singapore
, pp.
395
428
.
3.
Olah
,
G. A.
,
Prakash
,
G. K. S.
, and
Goeppert
,
A.
,
2011
, “
Anthropogenic Chemical Carbon Cycle for a Sustainable Future
,”
J. Am. Chem. Soc.
,
133
(
33
), pp.
12881
12898
.
4.
Zhang
,
H.
,
Cheng
,
Y.-T.
,
Vispute
,
T. P.
,
Xiao
,
R.
, and
Huber
,
G. W.
,
2011
, “
Catalytic Conversion of Biomass-Derived Feedstocks Into Olefins and Aromatics With ZSM-5: The Hydrogen to Carbon Effective Ratio
,”
Energy Environ. Sci.
,
4
(
6
), pp.
2297
2307
.
5.
Demirbas
,
A.
,
2004
, “
Pyrolysis of Municipal Plastic Wastes for Recovery of Gasoline-Range Hydrocarbons
,”
J. Anal. Appl. Pyrolysis
,
72
(
1
), pp.
97
102
.
6.
Libra
,
J. A.
,
Ro
,
K. S.
,
Kammann
,
C.
,
Funke
,
A.
,
Berge
,
N. D.
,
Neubauer
,
Y.
,
Titirici
,
M.-M.
,
Fühner
,
C.
,
Bens
,
O.
,
Kern
,
J.
, and
Emmerich
,
K.-H.
,
2011
, “
Hydrothermal Carbonization of Biomass Residuals: A Comparative Review of the Chemistry, Processes and Applications of Wet and Dry Pyrolysis
,”
Biofuels
,
2
(
1
), pp.
71
106
.
7.
Titirici
,
M.-M.
, and
Antonietti
,
M.
,
2010
, “
Chemistry and Materials Options of Sustainable Carbon Materials Made by Hydrothermal Carbonization
,”
Chem. Soc. Rev.
,
39
(
1
), pp.
103
116
.
8.
Jung
,
S. H.
,
Myung
,
Y.
,
Kim
,
B. N.
,
Kim
,
I. G.
,
You
,
I. K.
, and
Kim
,
T. Y.
,
2018
, “
Activated Biomass-Derived Graphene-Based Carbons for Supercapacitors With High Energy and Power Density
,”
Sci. Rep.
,
8
, pp.
1
8
.
9.
Xing
,
B.
,
Zhang
,
C.
,
Cao
,
Y.
,
Huang
,
G.
,
Liu
,
Q.
,
Zhang
,
C.
,
Chen
,
Z.
,
Yi
,
G.
,
Chen
,
L.
, and
Yu
,
J.
,
2018
, “
Preparation of Synthetic Graphite From Bituminous Coal as Anode Materials for High Performance Lithium-Ion Batteries
,”
Fuel Process. Technol.
,
172
, pp.
162
171
.
10.
Saikia
,
M.
,
Das
,
T.
,
Dihingia
,
N.
,
Fan
,
X.
,
Silva
,
L. F. O.
, and
Saikia
,
B. K.
,
2020
, “
Formation of Carbon Quantum Dots and Graphene Nanosheets From Different Abundant Carbonaceous Materials
,”
Diamond Relat. Mater.
,
106
, p.
107813
.
11.
Liu
,
P.
,
Si
,
Z.
,
Lv
,
W.
,
Wu
,
X.
,
Ran
,
R.
,
Weng
,
D.
, and
Kang
,
F.
,
2019
, “
Synthesizing Multilayer Graphene From Amorphous Activated Carbon via Ammonia-Assisted Hydrothermal Method
,”
Carbon
,
152
, pp.
24
32
.
12.
Li
,
S.
,
Li
,
F.
,
Wang
,
J.
,
Tian
,
L.
,
Zhang
,
H.
, and
Zhang
,
S.
,
2018
, “
Preparation of Hierarchically Porous Graphitic Carbon Spheres and Their Applications in Supercapacitors and Dye Adsorption
,”
Nanomaterials
,
8
(
8
), p.
625
.
13.
Chen
,
C.
,
Sun
,
K.
,
Wang
,
A.
,
Wang
,
S.
, and
Jiang
,
J.
,
2018
, “
Catalytic Graphitization of Cellulose Using Nickel as Catalyst
,”
Bioresources
,
13
, pp.
3165
3176
.
14.
Bazargan
,
A.
,
Yan
,
Y.
,
Hui
,
C. W.
, and
McKay
,
G.
,
2013
, “
A Review: Synthesis of Carbon-Based Nano and Micro Materials by High Temperature and High Pressure
,”
Ind. Eng. Chem. Res.
,
52
(
36
), pp.
12689
12702
.
15.
Goto
,
M.
,
2009
, “
Chemical Recycling of Plastics Using Sub- and Supercritical Fluids
,”
J. Supercrit. Fluids
,
47
(
3
), pp.
500
507
.
16.
Inagaki
,
M.
,
Park
,
K. C.
, and
Endo
,
M.
,
2010
, “
Carbonization Under Pressure
,”
Xinxing Tan Cailiao/New Carbon Mater.
,
25
(
6
), pp.
409
420
.
17.
Jain
,
A. A.
,
Mehra
,
A.
, and
Ranade V
,
V.
,
2016
, “
Processing of TGA Data: Analysis of Isoconversional and Model Fitting Methods
,”
Fuel
,
165
, pp.
490
498
.
18.
Simsir
,
H.
,
Eltugral
,
N.
, and
Karagoz
,
S.
,
2017
, “
Hydrothermal Carbonization for the Preparation of Hydrochars From Glucose, Cellulose, Chitin, Chitosan and Wood Chips via Low-Temperature and Their Characterization
,”
Bioresour. Technol.
,
246
, pp.
82
87
.
19.
Berge
,
N. D.
,
Ro
,
K. S.
,
Mao
,
J.
,
Flora
,
J. R. V.
,
Chappell
,
M. A.
, and
Bae
,
S.
,
2011
, “
Hydrothermal Carbonization of Municipal Waste Streams
,”
Environ. Sci. Technol.
,
45
(
13
), pp.
5696
5703
.
20.
Saqib
,
N. U.
,
Sharma
,
H. B.
,
Baroutian
,
S.
,
Dubey
,
B.
, and
Sarmah
,
A. K.
,
2019
, “
Valorisation of Food Waste via Hydrothermal Carbonisation and Techno-Economic Feasibility Assessment
,”
Sci. Total Environ.
,
690
, pp.
261
276
.
21.
Maniscalco
,
M. P.
,
Volpe
,
M.
, and
Messineo
,
A.
,
2020
, “
Hydrothermal Carbonization as a Valuable Tool for Energy and Environmental Applications: A Review
,”
Energies
,
13
(
16
), p.
4098
.
22.
Bevan
,
E.
,
Fu
,
J.
, and
Zheng
,
Y.
,
2020
, “
Challenges and Opportunities of Hydrothermal Carbonisation in the UK; Case Study in Chirnside
,”
RSC Adv.
,
10
(
52
), pp.
31586
31610
.
23.
Pawlak-Kruczek
,
H.
,
Urbanowska
,
A.
,
Yang
,
W.
,
Brem
,
G.
,
Magdziarz
,
A.
,
Seruga
,
P.
,
Niedzwiecki
,
L.
,
Pozarlik
,
A.
,
Mlonka-Mędrala
,
A.
,
Kabsch-Korbutowicz
,
M.
,
Bramer
,
E.
,
Baranowski
,
M.
,
Sieradzka
,
M.
, and
Tkaczuk-Serafin
,
M.
,
2020
, “
Industrial Process Description for the Recovery of Agricultural Water From Digestate
,”
ASME J. Energy Resour. Technol.
,
142
(
7
), p.
070917
.
24.
Faradilla
,
R. F.
,
Lucia
,
L.
, and
Hakovirta
,
M.
,
2020
, “
Remarkable Physical and Thermal Properties of Hydrothermal Carbonized Nanoscale Cellulose Observed From Citric Acid Catalysis and Acetone Rinsing
,”
Nanomaterials
,
10
(
6
), pp.
1
13
.
25.
Susanti
,
R. F.
,
Arie
,
A. A.
,
Kristianto
,
H.
,
Erico
,
M.
,
Kevin
,
G.
, and
Devianto
,
H.
,
2019
, “
Activated Carbon From Citric Acid Catalyzed Hydrothermal Carbonization and Chemical Activation of Salacca Peel as Potential Electrode for Lithium Ion Capacitor’s Cathode
,”
Ionics
,
25
(
8
), pp.
3915
3925
.
26.
Nizamuddin
,
S.
,
Baloch
,
H. A.
,
Griffin
,
G. J.
,
Mubarak
,
N. M.
,
Bhutto
,
A. W.
,
Abro
,
R.
,
Mazari
,
S. A.
, and
Ali
,
B. S.
,
2017
, “
An Overview of Effect of Process Parameters on Hydrothermal Carbonization of Biomass
,”
Renew. Sustain. Energy Rev.
,
73
, pp.
1289
1299
.
27.
Falco
,
C.
,
Perez Caballero
,
F.
,
Babonneau
,
F.
,
Gervais
,
C.
,
Laurent
,
G.
,
Titirici
,
M. M.
, and
Baccile
,
N.
,
2011
, “
Hydrothermal Carbon From Biomass: Structural Differences Between Hydrothermal and Pyrolyzed Carbons via 13C Solid State NMR
,”
Langmuir
,
27
(
23
), pp.
14460
14471
.
28.
He
,
C.
,
Giannis
,
A.
, and
Wang
,
J.-Y.
,
2013
, “
Conversion of Sewage Sludge to Clean Solid Fuel Using Hydrothermal Carbonization: Hydrochar Fuel Characteristics and Combustion Behavior
,”
Appl. Energy
,
111
, pp.
257
266
.
29.
Sevilla
,
M.
,
Maciá-Agulló
,
J. A.
, and
Fuertes
,
A. B.
,
2011
, “
Hydrothermal Carbonization of Biomass as a Route for the Sequestration of CO2: Chemical and Structural Properties of the Carbonized Products
,”
Biomass Bioenergy
,
35
(
7
), pp.
3152
3159
.
30.
Sevilla
,
M.
, and
Fuertes
,
A. B.
,
2009
, “
The Production of Carbon Materials by Hydrothermal Carbonization of Cellulose
,”
Carbon
,
47
(
9
), pp.
2281
2289
.
31.
Sheng
,
K.
,
Zhang
,
S.
,
Liu
,
J.
,
Shuang
,
E.
,
Jin
,
C.
, and
Xu
,
Z.
,
2019
, “
Hydrothermal Carbonization of Cellulose and Xylan Into Hydrochars and Application on Glucose Isomerization
,”
J. Cleaner Prod.
,
237
, p.
117831
.
32.
Guiotoku
,
M.
,
Hansel
,
F. A.
,
Novotny
,
E. H.
, and
de Freitas Maia
,
C. M. B.
,
2012
, “
Molecular and Morphological Characterization of Hydrochar Produced by Microwave-Assisted Hydrothermal Carbonization of Cellulose
,”
Pesqui. Agropecu. Bras.
,
47
(
5
), pp.
687
692
.
33.
Higgins
,
L. J. R.
,
Brown
,
A. P.
,
Harrington
,
J. P.
,
Ross
,
A. B.
,
Kaulich
,
B.
, and
Mishra
,
B.
,
2020
, “
Evidence for a Core-Shell Structure of Hydrothermal Carbon
,”
Carbon
,
161
, pp.
423
431
.
34.
Kambo
,
H. S.
, and
Dutta
,
A.
,
2015
, “
A Comparative Review of Biochar and Hydrochar in Terms of Production, Physico-Chemical Properties and Applications
,”
Renew. Sustain. Energy Rev.
,
45
, pp.
359
378
.
35.
Zhang
,
X.
,
Heinonen
,
S.
, and
Levänen
,
E.
,
2014
, “
Applications of Supercritical Carbon Dioxide in Materials Processing and Synthesis
,”
RSC Adv.
,
4
(
105
), pp.
61137
61152
.
36.
Sanli
,
D.
,
Bozbag
,
S. E.
, and
Erkey
,
C.
,
2012
, “
Synthesis of Nanostructured Materials Using Supercritical CO2: Part I. Physical Transformations
,”
J. Mater. Sci.
,
47
(
7
), pp.
2995
3025
.
37.
Kalina
,
J.
,
Skorek-Osikowska
,
A.
,
Bartela
,
Ł
,
Gładysz
,
P.
, and
Lampert
,
K.
,
2020
, “
Evaluation of Technological Options for Carbon Dioxide Utilization
,”
ASME J. Energy Resour. Technol.
,
142
(
9
), p.
090901
.
38.
Strakey
,
P. A.
,
2019
, “
Oxy-Combustion Modeling for Direct-Fired Supercritical CO2 Power Cycles
,”
ASME J. Energy Resour. Technol.
,
141
(
7
), p.
070706
.
39.
Hoffman
,
B. T.
, and
Shoaib
,
S.
,
2014
, “
CO2 Flooding to Increase Recovery for Unconventional Liquids-Rich Reservoirs
,”
ASME J. Energy Resour. Technol.
,
136
(
2
), p.
022801
.
40.
Jessop
,
P. G.
, and
Leitner
,
W.
,
1999
,
Chemical Synthesis Using Supercritical Fluids
,
Wiley-VCH Verlag
,
Weinheim, Germany
.
41.
Long
,
T. E.
,
Voit
,
B.
, and
Okay
,
O.
,
2015
,
Porous Carbons—Hyperbranched Polymers—Polymer Solvation
, Vol.
266
.
Springer-Verlag
,
Berlin/Heidelberg
.
42.
Gong
,
J.
,
Zhao
,
G.
,
Wang
,
G.
,
Zhang
,
L.
, and
Li
,
B.
,
2019
, “
Fabrication of Macroporous Carbon Monoliths With Controllable Structure via Supercritical CO2 Foaming of Polyacrylonitrile
,”
J. CO2 Util.
,
33
, pp.
330
340
.
43.
Cooper
,
A. I.
,
2001
, “
Recent Developments in Materials Synthesis and Processing Using Supercritical CO2
,”
Adv. Mater.
,
13
(
14
), pp.
1111
1114
.
44.
Li
,
L.
,
Zheng
,
X.
,
Wang
,
J.
,
Sun
,
Q.
, and
Xu
,
Q.
,
2013
, “
Solvent-Exfoliated and Functionalized Graphene With Assistance of Supercritical Carbon Dioxide
,”
ACS Sustain. Chem. Eng.
,
1
(
1
), pp.
144
151
.
45.
Gao
,
H.
,
Xue
,
C.
,
Hu
,
G.
, and
Zhu
,
K.
,
2017
, “
Production of Graphene Quantum Dots by Ultrasound-Assisted Exfoliation in Supercritical CO2/H2O Medium
,”
Ultrason. Sonochem.
,
37
, pp.
120
127
.
46.
Li
,
H.
,
Chang
,
Q.
,
Dai
,
Z.
,
Chen
,
X.
,
Yu
,
G.
, and
Wang
,
F.
,
2017
, “
Upgrading Effects of Supercritical Carbon Dioxide Extraction on Physicochemical Characteristics of Chinese Low-Rank Coals
,”
Energy Fuels
,
31
(
12
), pp.
13305
13316
.
47.
Putrino
,
F. M.
,
Tedesco
,
M.
,
Bodini
,
R. B.
, and
de Oliveira
,
A. L.
,
2020
, “
Study of Supercritical Carbon Dioxide Pretreatment Processes on Green Coconut Fiber to Enhance Enzymatic Hydrolysis of Cellulose
,”
Bioresour. Technol.
,
309
, p.
123387
.
48.
Kim
,
K. H.
, and
Hong
,
J.
,
2001
, “
Supercritical CO2 Pretreatment of Lignocellulose Enhances Enzymatic Cellulose Hydrolysis
,”
Bioresour. Technol.
,
77
(
2
), pp.
139
144
.
49.
Wei
,
L.
,
Yan
,
N.
, and
Chen
,
Q.
,
2011
, “
Converting Poly(Ethylene Terephthalate) Waste Into Carbon Microspheres in a Supercritical CO2 System
,”
Environ. Sci. Technol.
,
45
(
2
), pp.
534
539
.
50.
Pol
,
V. G.
,
Pol
,
S. V.
,
Calderon Moreno
,
J. M.
, and
Gedanken
,
A.
,
2006
, “
High Yield One-Step Synthesis of Carbon Spheres Produced by Dissociating Individual Hydrocarbons at Their Autogenic Pressure at Low Temperatures
,”
Carbon
,
44
(
15
), pp.
3285
3292
.
51.
Yu
,
B.
,
Kong
,
X.
,
Wei
,
L.
, and
Chen
,
Q.
,
2011
, “
Treatment of Discarded Oil in Supercritical Carbon Dioxide for Preparation of Carbon Microspheres
,”
J. Mater. Cycles Waste Manag.
,
13
(
4
), pp.
298
304
.
52.
Romero-Anaya
,
A. J.
,
Ouzzine
,
M.
,
Lillo-Ródenas
,
M. A.
, and
Linares-Solano
,
A.
,
2014
, “
Spherical Carbons: Synthesis, Characterization and Activation Processes
,”
Carbon
,
68
, pp.
296
307
.
53.
Álvarez-Murillo
,
A.
,
Sabio
,
E.
,
Ledesma
,
B.
,
Román
,
S.
, and
González-García
,
C. M.
,
2016
, “
Generation of Biofuel From Hydrothermal Carbonization of Cellulose. Kinetics Modelling
,”
Energy
,
94
, pp.
600
608
.
54.
Volpe
,
M.
,
Messineo
,
A.
,
Mäkelä
,
M.
,
Barr
,
M. R.
,
Volpe
,
R.
,
Corrado
,
C.
, and
Fiori
,
L.
,
2020
, “
Reactivity of Cellulose During Hydrothermal Carbonization of Lignocellulosic Biomass
,”
Fuel. Process. Technol.
,
206
, p.
106456
.
55.
Gao
,
Y.
,
Wang
,
X.
,
Yang
,
H.
, and
Chen
,
H.
,
2012
, “
Characterization of Products From Hydrothermal Treatments of Cellulose
,”
Energy
,
42
(
1
), pp.
457
465
.
56.
Cardea
,
S.
, and
De Marco
,
I.
,
2020
, “
Cellulose Acetate and Supercritical Carbon Dioxide: Membranes, Nanoparticles, Microparticles and Nanostructured Filaments
,”
Polymers
,
12
(
1
), p.
162
.
57.
Johnson
,
S.
,
Faradilla
,
R. F.
,
Venditti
,
R. A.
,
Lucia
,
L.
, and
Hakovirta
,
M.
,
2020
, “
Hydrothermal Carbonization of Nanofibrillated Cellulose: A Pioneering Model Study Demonstrating the Effect of Size on Final Material Qualities
,”
ACS Sustain. Chem. Eng.
,
8
(
4
), pp.
1823
1830
.
58.
Falco
,
C.
,
Baccile
,
N.
, and
Titirici
,
M. M.
,
2011
, “
Morphological and Structural Differences Between Glucose, Cellulose and Lignocellulosic Biomass Derived Hydrothermal Carbons
,”
Green Chem.
,
13
(
11
), pp.
3273
3281
.
59.
García-Bordejé
,
E.
,
Pires
,
E.
, and
Fraile
,
J. M.
,
2017
, “
Parametric Study of the Hydrothermal Carbonization of Cellulose and Effect of Acidic Conditions
,”
Carbon
,
123
, pp.
421
432
.
60.
Yang
,
G.
,
Jiang
,
Y.
,
Yang
,
X.
,
Xu
,
Y.
,
Miao
,
S.
, and
Li
,
F.
,
2017
, “
The Interaction of Cellulose and Montmorillonite in a Hydrothermal Process
,”
J. Sol-Gel Sci. Technol.
,
82
(
3
), pp.
846
854
.
61.
Roldán
,
L.
,
Santos
,
I.
,
Armenise
,
S.
,
Fraile
,
J. M.
, and
García-Bordejé
,
E.
,
2012
, “
The Formation of a Hydrothermal Carbon Coating on Graphite Microfiber Felts for Using as Structured Acid Catalyst
,”
Carbon
,
50
, pp.
1363
1372
.
62.
Liang
,
J.
,
Liu
,
Y.
, and
Zhang
,
J.
,
2011
, “
Effect of Solution pH on the Carbon Microsphere Synthesized by Hydrothermal Carbonization
,”
Procedia Environ. Sci.
,
11
, pp.
1322
1327
.
63.
2015
, Standard Test Methods for Proximate Analysis of Coal and Coke by Macro Thermogravimetric Analysis 1.
64.
Phyllis2, Database for Biomass and Waste. Energy Res Cent Netherlands 2018. https://www.ecn.nl/phyllis2/Biomass/View/3501, Accessed May 28, 2018.
65.
Jorio
,
A.
,
Ferreira
,
E. H. M.
,
Moutinho
,
M. V. O.
,
Stavale
,
F.
,
Achete
,
C. A.
, and
Capaz
,
R. B.
,
2010
, “
Measuring Disorder in Graphene With the G and D Bands
,”
Phys. Status Solidi B
,
247
(
11–12
), pp.
2980
2982
.
66.
Quirico
,
E.
,
Rouzaud
,
J. N.
,
Bonal
,
L.
, and
Montagnac
,
G.
,
2005
, “
Maturation Grade of Coals as Revealed by Raman Spectroscopy: Progress and Problems
,”
Spectrochim. Acta, Part A
,
61
(
10
), pp.
2368
2377
.
67.
Franklin
,
R. E.
,
1951
, “
Crystallite Growth in Graphitizing and Non-Graphitizing Carbons
,”
Proc. R. Soc. A
,
209
, pp.
196
218
.
68.
Zhang
,
H.
,
Zhang
,
F.
, and
Huang
,
Q.
,
2017
, “
Highly Effective Removal of Malachite Green From Aqueous Solution by Hydrochar Derived From Phycocyanin-Extracted Algal Bloom Residues Through Hydrothermal Carbonization
,”
RSC Adv.
,
7
(
10
), pp.
5790
5799
.
69.
Das
,
T.
,
Boruah
,
P. K.
,
Das
,
M. R.
, and
Saikia
,
B. K.
,
2016
, “
Formation of Onion-Like Fullerene and Chemically Converted Graphene-Like Nanosheets From Low-Quality Coals: Application in Photocatalytic Degradation of 2-Nitrophenol
,”
RSC Adv.
,
6
(
42
), pp.
35177
35190
.
70.
Sheng
,
C.
,
2007
, “
Char Structure Characterised by Raman Spectroscopy and Its Correlations With Combustion Reactivity
,”
Fuel
,
86
(
15
), pp.
2316
2324
.
71.
Ye
,
R.
,
Xiang
,
C.
,
Lin
,
J.
,
Peng
,
Z.
,
Huang
,
K.
,
Yan
,
Z.
,
Cook
,
N.
,
Samuel
,
E.
,
Hwang
,
C.
,
Ruan
,
G.
,
Ceriotti
,
G.
,
Raji
,
A.-R.
,
Martí
,
A.
, and
Tour
,
J.
,
2013
, “
Coal as an Abundant Source of Graphene Quantum Dots
,”
Nat. Commun.
,
4
, pp.
1
7
.
72.
Chowdhury
,
Z. Z.
,
Krishnan
,
B.
,
Sagadevan
,
S.
,
Rafique
,
R. F.
,
Hamizi
,
N. A. B.
,
Wahab
,
Y. A.
,
Khan
,
A.
,
Bin Johan
,
R.
,
Al-douri
,
Y.
,
Newaz Kazi
,
S.
, and
Tawab Shah
,
S.
,
2018
, “
Effect of Temperature on the Physical, Electro-Chemical and Adsorption Properties of Carbon Micro-Spheres Using Hydrothermal Carbonization Process
,”
Nanomaterials
,
8
(
8
), p.
597
.
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