Effects of pretreatments of Napier Grass with deionized water, sulfuric acid and sodium hydroxide on pyrolysis oil characteristics

MOHAMMED, Isah Yakub, ABAKR, Yousif, KABIR, Feroz <http://orcid.org/0000-0002-3121-9086> and YUSUF, Suzana

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MOHAMMED, Isah Yakub, ABAKR, Yousif, KABIR, Feroz and YUSUF, Suzana (2017). Effects of pretreatments of Napier Grass with deionized water, sulfuric acid and sodium hydroxide on pyrolysis oil characteristics. Waste and Biomass Valorization, 8 (3), 755-773.

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Raw biomass

Proximate, ultimate thermogravimetric and

FTIR analyses Pyrolysis

Leachate

Pretreated biomass

1

2

4

3

5

Filtration

Liquid/solid ratio: 5Agitation speed:

100 rpm

Field Code Changed

Figure 1: Pretreatment process flow diagram. (RNGS) raw NGS, (WTNGS) water treated NGS,

(ACTNGS) acid treated NGS, (ALTNGS) alkaline treated NGS, (WL) water leachate,

(ACL) acid leachate and (ALL) alkaline leachate.

Figure 2. Pyrolysis system with a fixed bed reactor

Reactor

N2 (30mL/min)

Thermocouple

Data logger

Chiller

Con

den

ser

Out

In

Water (4oC)

Bio-oil collectorGas scrubber

Bio-oil samples

Venting

Gas sampling

Pyrolysis temperature: 600oC

Heating rate: 30oC/min

Biomass: 30g

Figure 2. Pyrolysis system with a fixed bed reactor

Field Code Changed

Figure 3. Mass and energy yield of pretreated samples. (YM) mass yield and (YE) energy yield

40

50

60

70

80

90

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Mass

, E

ner

gy

Yie

ld (

%)

H2SO4, NaOH (%w/w); H2O (Ro)

Yield-M (H2SO4) Yield-E (H2SO4)

Yield-M(NaOH) Yield-E (NaOH)

Yield-M (H2O) Yield-E (H2O)

Figure 4. Effect of pretreatment solvents on ash removal and extractives from NGS.

0

20

40

60

80

0.3 0.8 1.3 1.8 2.3 2.8

Ash

rem

ov

al,

Extr

act

ives

(%

)

NaOH, H2SO4 (%w/w); H2O (Ro)

Ash (H2SO4) Ash (NaOH)

Ash(H2O) Extve (H2SO4)

Extve (NaOH) Extve ( H2O)

Figure 5. SEM images of raw and pretreated samples. Scanning conditions: HV (20kV), Mag

(1200x). (RNGS) raw NGS, (WTNGS) water treated-Ro: 0.9, (ACTNGS) acid treated-1.5

w/w% H2SO4 and (ALTNGS) alkaline treated 1.5 w/w% NaOH

Figure 6. Van Krevelen plot raw and pretreated samples

0.10

0.11

0.12

0.13

0.14

0.83 0.85 0.87 0.89 0.91

H/C

ato

mic

ra

tio

O/C atomic ratio

Raw Biomass H2O H2SO4 NaOH

Figure 7. Averaged FTIR spectra (auto-smoothed and auto-baseline corrected) of Napier grass

samples (RNGS, WTNG-0.9, ALTNGS-1.5% and ACTNGS-1.5%)

40080012001600200024002800320036004000

Tra

nsm

itta

nce

(A

.U)

Wave number (cm-1)

RNGS WTNGS ALTNGS ACTNGS

O-H

C-H

C=C -CH3-

O-H

C-O

, C

-C-O

C-H

Figure 8. DTG of RNGS, ACTNGS and ALTNGS on dry basis. (e) Extractives; (h)

Hemicellulose; (c) Cellulose; and (l) lignin decompositions. Condition: nitrogen

atmosphere (20 mL/min), heating rate (10 K/min).

0

3

6

9

12

373 523 673 823 973

DT

G (

%/K

)

Temperature (K)

RNGS

WTNGS

ALTNGS

ACTNGS

e

h

h

c

c c

c

l

Figure 9. Pyrolysis products distribution from the raw and pretreated Napier grass samples.

Biomass condition: bone dry, 0.2 to 2 mm particle size; heating rate: 30 °C/min,

nitrogen flow rate: 30 mL/min; pyrolysis temperature: 600oC

0

10

20

30

40

50

RNGS WTNGS ACTNGS ALTNGS

Py

roly

sis

pro

du

ct y

ield

(%

)

Biomass type

Bio-oil Bio-char Non-condensable

Figure 10. Averaged FTIR spectra (auto-smoothed and auto-baseline corrected) of bio-oil from

raw and pretreated samples

40080012001600200024002800320036004000

Tra

nsm

itta

nce

(A

.U)

Wave number (cm-1)

Bio-oil (RNGS) Bio-oil (WTNGS)

Bio-oil (ALTNGS) Bio-oil (ACTNGS)

O-H

C-H

C=

O

C-O

-C=

C-

C-H

C-O

C-H

Figure 11. GC-MS chromatogram of bio-oil samples from raw and pretreated Napier grass

Figure 11. GC-MS chromatogram of bio-oil samples Napier grass. (a) RNGS, (b) WTNGS, (c) ALTNGS, (d) ACTNGS

2 5 8 11 14 17 20 23

GC

MS

Sig

na

l (A

.U)

Retention time (min)

(a)

2 5 8 11 14 17 20 23

GC

MS

Sig

na

l (A

.U)

Retention time (min)

(b)

2 5 8 11 14 17 20 23

GC

MS

Sig

na

l (A

.U)

Retention time (min)

(c)

2 5 8 11 14 17 20 23G

CM

S S

ign

al

(A.U

) Retention time (min)

(d)

Figure 12. Classification of organic in the bio-oil from raw and pretreated NGS samples

0

20

40

60

80

HC VAC AAK NS EOC

GC

-MS

pea

k a

rea

(%

)

Group of organic compound

RNGS WTNGS ALTNGS ACTNGS