regeneration of granular activated carbon (gac) exhausted by model diesel fuel
DESCRIPTION
2010 Annual ChE Graduate Student Conference , Head Hall, UNB Fredericton, May 14 th. Regeneration of granular activated carbon (GAC) exhausted by model diesel fuel. --Characterization of the spent GACs. Xue Han Supervisor: Dr. Ying Zheng. Hydroprocessing Laboratory - PowerPoint PPT PresentationTRANSCRIPT
Regeneration of granular activated carbon (GAC) exhausted by model diesel fuel
Xue HanSupervisor: Dr. Ying Zheng
Hydroprocessing Laboratory Department of Chemical Engineering
University of New Brunswick
2010 Annual ChE Graduate Student Conference, Head Hall, UNB Fredericton, May 14th
--Characterization of the spent GACs
• Composition of model diesel fuel:
• Regeneration method: Thermal regeneration (450 oC for 2 h in nitrogen)Ultrasound regeneration in dimethylfomamide (US-DMF, at room temperature for 1 h) Solvent extraction by dimethylfomamide in Soxhlet (Sol-DMF)Solvent extraction by toluene in Soxhlet (Sol-Tol)
Dibenzothiophene (DBT, 761.6 ppmw S) , indole (333.33 ppmw N) , carbazole (333.33 ppmw N) , 0.31 wt% naphthalene and 26.5 wt% ethyl acetate in dodecane.
• Adsorbent:Granular activated carbon (GAC)
2
Textural data of the spent GACs
Regeneration cycle
Regeneration method SBET (m2/g)
Total pore volume (cm3/g)
Micropore volume (cm3/g)
Average pore diameter (nm)
original Original 2323 1.675 0.8349 2.884
1
Thermal 1492 1.078 0.6181 2.889US-DMF 1637 1.160 0.6963 2.835Sol-DMF 1837 1.270 0.7931 2.765Sol-Tol 1648 1.163 0.6995 2.823
3
Thermal 1166 0.8493 0.4877 2.913US-DMF 1401 0.9922 0.5944 2.832Sol-DMF 1582 1.119 0.6746 2.829Sol-Tol 1317 0.9280 0.4733 2.819
9
Thermal 783.6 0.6159 0.3237 3.144US-DMF 906.7 0.6784 0.3776 2.993Sol-DMF 882.9 0.6141 0.3792 2.782Sol-Tol 1111 0.8008 0.4657 2.883
(1)The SBET, total volume and micropore volume of GAC samples decrease with the increase of regeneration cycle.
(2)More micropores of GAC are lost in thermal regeneration.
3
4
600 800 1000 1200 1400 1600 1800 200020
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
SBET (m2/g)
Reg
ener
atio
n ef
ficie
ncy
of
N in
car
bazo
le (%
)
600 800 1000 1200 1400 1600 1800 200020
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
SBET (m2/g)
Reg
ener
atio
n ef
ficie
ncy
of
N in
indo
le (%
)
600 800 1000 1200 1400 1600 1800 200020
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
SBET (m2/g)
Reg
ener
atio
n ef
ficie
ncy
of
S in
DB
T (%
)Effect of specific surface area on regeneration efficiency
For the other two cases, surface area seems to play a key role in the regeneration of adsorptive sites occupied by S and N species. Linear relationship is found between regeneration efficiency and SBET, indicating regeneration is governed by surface area.
When Sol-DMF is used for regeneration, the slopes of the trendlines are smaller than those in the other regeneration processes in both cases. Considering the higher regeneration efficiency, it is likely that this method is fit for long run operation.
For the regeneration of adsorptive sites taken by N in indole, the regeneration efficiency changed randomly with SBET, which means surface area is not the dominant effect on the regeneration.
The effect of micropore volume and total pore volume on the regeneration efficiency are similar to that of specific surface area.
5Figueiredo JL, Pereira MFR, Freitas MMA, et al. Carbon, 1999, 37(9): 1379-1389.
Surface groups on carbon and their decomposition by TPD
The peaks in TPD spectrum are divided into two parts:
(1) the peaks at low temperature (below 300 oC) can be mainly ascribed to CO2 release from the decomposition of carboxylic and lactonic groups (strong acidity);
(2) the peaks at high temperature (above 400 oC) can be mostly attributed to CO from the decomposition of phenolic and carbonylic groups (weak acidity).
Peak attribution in TPD spectrum
6
TPD results of GACs in Cycle 9
200 400 600 800
Original C9-Thermal C9-US-DMF C9-Sol-DMF C9-Sol-Tol
In
tens
ity
Temperature (oC)
For the GAC regenerated by Thermal method, an additional peak shows up at 760 oC, which can be attributed to the decomposition of carboxylic anhydrides groups.
The carboxylic anhydrides groups come from the dehydration of carboxylic acids under the conditions of Thermal regeneration, which can be verified by the significant decrease of peak area of the peak at low temperature and the FTIR results.
Thermal US-DMF Sol-DMF Sol-Tol
100
200
300
400
500
Area of peak at low temperature Regeneration efficiency
Regeneration method
Are
a of
pea
k at
low
tem
pera
ture
(a.u
.)
30
40
50
60
70
80
Regeneration efficiency (%
)
Indole
Thermal US-DMF Sol-DMF Sol-Tol
100
200
300
400
500
Area of peak at low temperature Regeneration efficiency
Regeneration method
Are
a of
pea
k at
low
tem
pera
ture
(a.u
.)
30
40
50
60
70
80
Regeneration efficiency (%
)
Carbazole
Thermal US-DMF Sol-DMF Sol-Tol
100
200
300
400
500
Area of peak at low temperature Regeneration efficiency
Regeneration method
Are
a of
pea
k at
low
tem
pera
ture
(a.u
.)
30
40
50
60
70
80
Regeneration efficiency (%
)
DBT
In Cycle 9, the amount of strong acidic groups increase in the order of Thermal<US-DMF<Sol-DMF<Sol-Tol in terms of regeneration method, which is more or less accordant to that of regeneration efficiency.
Thermal regeneration results in the least strong acidic groups, which is benefit to the adsorption. This might be another reason to the lowest regeneration efficiency.
Effect of regeneration method on the strong acidic groups
7
8
TPD results of GACs regenerated by Sol-Tol
100 200 300 400 500 600 700 800
Original Cycle 1 Cycle 3 Cycle 9
Inte
nsity
Temperature (oC)
With the increase of the regeneration cycle, the center temperature of the peak attributed to both CO2 from strong acidic groups and CO from weak acidic groups shift to lower temperature, which indicates the decrease of the stability of the oxygen surface functional groups.
This shift may be resulted from the change of the kinds of strong/weak acidic surface functional groups, which happens in the solvent extraction process.
9
FT-IR spectrums of GACs after different cycle’s regeneration by different methods in S and N adsorption
Peak attribution: 1457 cm-1--skeletal C=C vibrations in aromatic rings [1] 746 cm-1--ortho-aromatics [2]; C-S bond in DBT [3]
1 Wang CT, Chen SH, Ma HY, et al. JOURNAL OF APPLIED ELECTROCHEMISTRY, 2003(33): 179-186. 2 Masson JF, Gagne M. ENERGY & FUELS, 2008 (22): 3402-3406.3 Castillo K, Parsons JG, Chavez D, et al. JOURNAL OF CATALYSIS, 2009 (268): 329-334.
The adsorbates left on the GAC since the first cycle’s regeneration, especially for the samples regenerated by ultrasound and thermal methods.The amount of accumulated adsorbates increased with the regeneration cycle.
2000 1600 1200 800 400
Cycle 1
Original Thermal US-DMF Sol-DMF Sol-Tol
Inte
nsity
Wavenumbers / cm-1
2000 1600 1200 800 400
Original Thermal US-DMF Sol-DMF Sol-Tol
Inte
nsity
Wavenumbers / cm-1
Cycle 3
2000 1600 1200 800 400
Cycle 9
Original Thermal US-DMF Sol-DMF Sol-Tol
Inte
nsity
Wavenumbers / cm-1
1457746
1457
746
1457 746
Conclusion• The structure of GACs can be better maintained when the
ultrasound and solvent method is used for regeneration.• The texture of the GACs has little influence on the
regeneration of the adsorptive sites taken by N in indole.• The regeneration of the adsorptive sites occupied by N in
carbazole and S in DBT is governed by the structure of GACs.
• Loss of strong acidic surface functional groups takes a negative effect on the regeneration of GACs.
10
• FTIR results indicate that the adsorbates left on the GAC since the first cycle’s regeneration, and the amount of adsorbates increased with the regeneration cycle.
Future work
• Finish TPD tests of the other GAC samples
• Nitrogen and sulfur analysis in the spent GAC samples
• TGA characterization of the spent GAC samples
11
Acknowledgement
12
Thank my supervisor Dr. Ying Zheng for her guidance and support!
Thank Dr. Hongfei Lin for his helpful suggestion and discussion about my experiment!
Thank the planning committee of this conference!
13
Content
14
• BET analysis of the spent GAC samples• TPD analysis of the spent GAC samples• FTIR analysis of the spent GAC samples• Accumulated sulfur and nitrogen content
on the spent GAC samples• Conclusion• Future work• Acknowledgement
15
0.2 0.4 0.6 0.820
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
Micropore volume (cm3/g)
Reg
ener
atio
n ef
ficie
ncy
of
N in
car
bazo
le (%
)
0.2 0.4 0.6 0.8 1.020
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
Micropore volume (cm3/g)
Reg
ener
atio
n ef
ficie
ncy
of
N in
indo
le (%
)
0.2 0.4 0.6 0.8 1.020
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
Micropore volume (cm3/g)
Reg
ener
atio
n ef
ficie
ncy
of
S in
DB
T (%
)
Effect of micropore volume on regeneration efficiency
Similar conclusions are obtained on the relationship between micropore volume and regeneration efficiency, as shown in the previous slide.
When Sol-Tol is taken as the regeneration method, the micropore volume decreases little since the third cycle, which demonstrates that this approach can maintain most of the micropores of the adsorbent.
16
0.4 0.6 0.8 1.0 1.2 1.420
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
Total pore volume (cm3/g)
Reg
ener
atio
n ef
ficie
ncy
of
N in
car
bazo
le (%
)
0.4 0.6 0.8 1.0 1.2 1.420
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
Total pore volume (cm3/g)
Reg
ener
atio
n ef
ficie
ncy
of
N in
indo
le (%
)
0.4 0.6 0.8 1.0 1.2 1.420
40
60
80
100
Thermal US-DMF Sol-DMF Sol-Tol
Total pore volume (cm3/g)
Reg
ener
atio
n ef
ficie
ncy
of
S in
DB
T (%
)
Effect of total pore volume on regeneration efficiency
The effect of total pore volume on the regeneration efficiency is similar to that of micropore volume.
The higher pore recovery is, the higher regeneration efficiency for sulfur and nitrogen compounds is obtained.
17
Effect of specific surface area on the capacity of nitrogen and sulfur
600 800 1000 1200 1400 1600 1800 2000
0.1
0.2
0.3
Thermal US-DMF Sol-DMF Sol-Tol
SBET (m2/g)
Cap
acity
of N
in in
dole
(m
mol
N/g
GA
C)
600 800 1000 1200 1400 1600 1800 2000
0.3
0.4
0.5
0.6
0.7
0.8
Thermal US-DMF Sol-DMF Sol-Tol
SBET (m2/g)
Cap
acity
of S
in D
BT
(mm
ol S
/g G
AC
)
600 800 1000 1200 1400 1600 1800 2000
0.2
0.3
0.4
Thermal US-DMF Sol-DMF Sol-Tol
SBET (m2/g)
Cap
acity
of N
in c
arba
zole
(mm
ol N
/g G
AC
)
In the case of regeneration of nitrogen in indole,
18
0.2 0.4 0.6 0.8
0.2
0.3
0.4
Thermal US-DMF Sol-DMF Sol-Tol
Micropore volume (cm3/g)
Cap
acity
of N
in c
arba
zole
(mm
ol N
/g G
AC
)
0.2 0.4 0.6 0.8 1.0
0.1
0.2
0.3
Thermal US-DMF Sol-DMF Sol-Tol
Micropore volume (cm3/g)
Cap
acity
of N
in in
dole
(m
mol
N/g
GA
C)
0.2 0.4 0.6 0.8 1.0
0.3
0.4
0.5
0.6
0.7
0.8
Thermal US-DMF Sol-DMF Sol-Tol
Micropore volume (cm3/g)
Cap
acity
of S
in D
BT
(mm
ol S
/g G
AC
)
Effect of micropore volume on the capacity of nitrogen and sulfur
19
0.4 0.6 0.8 1.0 1.2 1.4
0.3
0.4
0.5
0.6
0.7
0.8
Thermal US-DMF Sol-DMF Sol-Tol
Total pore volume (cm3/g)
Cap
acity
of S
in D
BT
(mm
ol S
/g G
AC
)
0.4 0.6 0.8 1.0 1.2 1.4
0.2
0.3
0.4
Thermal US-DMF Sol-DMF Sol-Tol
Total pore volume (cm3/g)
Cap
acity
of N
in c
arba
zole
(mm
ol N
/g G
AC
)
0.4 0.6 0.8 1.0 1.2 1.4
0.1
0.2
0.3
Thermal US-DMF Sol-DMF Sol-Tol
Total pore volume (cm3/g)
Cap
acity
of N
in in
dole
(m
mol
N/g
GA
C)
Effect of total pore volume on the capacity of nitrogen and sulfur
20
Area of the peaks in TPD spectra
Sample name Area of peak(s) at low temperature
Area of peak(s) at high temperature Total area of peaks
Original 803.7C1-Sol-DMF 1335.7C1- Sol-Tol 320.2 2594.0 2914.2
C3- Sol-DMF 588.9 2709.9 3298.8C3- Sol-Tol 540.1 3289.7 3975.5C9-Thermal 93.9 2478.4 2572.3C9-US-DMF 278.4 3991.1 4269.5C9- Sol-DMF 372.3 4226.3 4598.6
C9-Sol-Tol 476.5 4608.0 5084.5
(1) With the increase of regeneration cycle, the area of peaks at low temperature decrease, which means the consumption of strong acidic sites; while the area of peaks at low temperature increase, suggesting the introduction of weak acidic groups during the regeneration under atmosphere, especially when solvents are used.
(2) In the same cycle, e.g. Cycle 9, the amount of both strong and weak acidic groups increase in the order of Thermal<US-DMF<Sol-DMF<Sol-Tol, which is same as that of regeneration efficiency.
100 200 300 400 500 600 700 800
In
tens
ity
Temperature (oC)
Original C1-Thermal C1-US-DMF C1-Sol-DMF C1-Sol-Tol
21
22
Area of the peaks in TPD spectra
Sample name Area of peak(s) at low temperature
Area of peak(s) at high temperature Total area of peaks
C1- Sol-Tol 320.2 2594.0 2914.2C3- Sol-DMF 588.9 2709.9 3298.8C3- Sol-Tol 540.1 3289.7 3975.5C9-Thermal 93.9 2478.4 2572.3C9-US-DMF 278.4 3991.1 4269.5C9- Sol-DMF 372.3 4226.3 4598.6
C9-Sol-Tol 476.5 4608.0 5084.5
With the increase of regeneration cycle, the area of peaks at low temperature decrease, which means the consumption of strong acidic sites; while the area of peaks at high temperature increase, suggesting the introduction of weak acidic groups or conversion of the strong acidic groups to the weak ones during the regeneration processes and the desorption of the adsorbates.
In the same cycle, e.g. Cycle 9, the amount of both strong and weak acidic groups increase in the order of Thermal<US-DMF<Sol-DMF<Sol-Tol, which is same as that of regeneration efficiency.
23
Effect of acidic groups on regeneration efficiency
Relationship between strong acidic groups and regeneration efficiency. Regeneration method: Sol-DMF.
The more strong acidic groups, the higher regeneration efficiency.
A linear relationship exists between the amount of strong acidic groups and regeneration efficiency of adsorptive sites occupied by N in carbazole, which means the carboxylic groups may play a dominant role in this regeneration process.
400 500 600 700
70
80
90
100
Indole Carbazole DBT
Reg
ener
atio
n ef
ficie
ncy
(%)
Peak area (a.u.)
24
Relationship between acidic groups and regeneration efficiency: (1) strong acidic groups (2) weak acidic groups and (3) total acidic groups. Regeneration method: Sol-Tol.
When the GAC samples are regenerated by Sol-Tol, the strong acidic groups take little effect on the regeneration of GACs exhausted by either S or N compounds.
Weak acidic groups, such as phenolic groups seem to influence the recovery of the adsorptive sites taken by S in DBT and N in carbazole when Sol-Tol method is used.
The effect of total acidic groups is similar to that of weak acidic groups.
2500 3000 3500 4000 4500 500060
70
80
90
100
Indole Carbazole DBT
Reg
ener
atio
n ef
ficie
ncy
(%)
Peak area (a.u.)500 600 700
60
70
80
90
100
Indole Carbazole DBT
Reg
ener
atio
n ef
ficie
ncy
(%)
Peak area (a.u.)
2500 3000 3500 4000 4500 5000 550060
70
80
90
100
Indole Carbazole DBT
Reg
ener
atio
n ef
ficie
ncy
(%)
Peak area (a.u.)
(1) (2)
(3)