Chromatographic Study of Methanol Adsorption on
Activated Carbon
광운대학교 환경공학과
유 경 선
Introduction
Importnace of Adsorption Reaction
Experimental Method for Adsorption
• Packed bed experiment
• TGA experiment
• Measuring the partial pressure
• Chromatographic study
• Air pollution control
• Catalytic reaction
• Lots of gas-solid reaction in industrial processes
Some Features of Chromatographic Study
Advantage
• Little Time to Experiment
• Easyness of Experimental Apparatus
• Quantitative Determination of Reaction Parameters
• Small Amount of Adsorbent
• Reusable of Adsorbent Disadvantage
• Limitation to the Region of Linear Adsorption
• Requirement of Physical Properties Surface area, Pore volume, Porosity,...
Concept of Chromatographic Study
pulse input Co
Elution Curve Ce(t)
Adsorbent Column
Assumptions for the Chromatographic Study
Isothermal Condition of Column
Constant Void Fraction and Interstitial Velocity
Linear Adsorption of Adsorbate
Constant Size of Spherical Particle
One Dimensional Dispersed Flow
Governing Equations of Packed Column
R i b
b e
Z r
c R
D x
u C x
E C t
C 3 1 ( )
2
2
∂
∂
− −
∂
− ∂
∂
= ∂
∂
∂
ε ε
) ) ( (
)
( i R f i R
e k C c
t
D c = −
∂
∂
) (
A a i
a a
K c c
t k
c = −
∂
∂
t c r
r c r
D c t
c a
P i
i e
i
p ∂
− ∂
∂ + ∂
∂
= ∂
∂
∂ ρ
ε ( 2 2 (2/ ) )
Column
Particle
Diffusion rate Adsorption rate
현재 이 이미지를 표시할 수 없습니다.
= 0
=
= ci ca
C at t=0 C = 0 at
x = ∞
= 0 r
)
1(t
C = C at x=0 = 0 at
∂
∂ r ci
Definition of Moment
dt t t C
mn = 0∞ e( )⋅ n
Definition of n-th Moment
dt C
dt t m C
m
e n e
n n ∞
∞
⋅
=
=
0 0
/ 0
μ
n-th Absolute Moment
n-th Central Moment
( )
dt C
dt t t
C
e n n e
n ∞
∞
⋅
−
=
0
' 0 μ1
μ
Moment Analysis of Elution Curve of Pulse Input
pulse
u
z / )[1 ] ( )
( 0 1
1 δ μ
μ = + +
] )[
/ 2
2 (
1 2
'
2 μ μ z u δax δ f δd δad
μ = − = + + +
) ](
/ ) 1
0 =[( −ε ε ε p + ppka
δ
2 2 (1 δ0)
δ = +
u Ez
ax
)2
3 ( 1
a p p
f
f K
k
R ε ρ ε
δ = −ε +
)2
15 ( 1
a p p
e
d K
D
R ε ρ
ε
δ = −ε +
a a p
ad k
K 2
1 ρ
ε δ = −ε
Table 1. Properties of Activated Carbon (Calgon, BPL 4×10 granule)
True Density 2.0 x 103 [kg/m3] Particle Density 0.85 x 103 [kg/m3] Particle Porosity 0.63
Surface Area(BET) 992 [m2/g]
Particle Size 0.20 mm, 0.34mm, 0.93mm Total Pore volume 0.75 x 10-3 [m3/kg]
Table 2. Characteristics of Packed Column and Operating Conditions
Packed Length [m] 0.07
Column I.D. [m] 4.37 x 10-3
Particle Size[m] 0.20, 0.34, 0.93
Sample Weight [g] 0.50, 0.43 0.43 Column Porosity [-] 0.48 0.52 0.51 Gas Flow Rate [ml/min] 30, 50, 70, 90
Temperature [oC] 70, 100, 130
Time (min)
.1 1 10
Detector Signal
dp = 0.2mm Temp = 100oC
Flowrate = 70ml/min
Fig. 1 Typical Gas Chromatogram
MeOH injection (μl)
0 1 2 3 4
1st absolute moment
0 2 4 6 8 10
: 250-425μm, 70oC : 150-250μm, 100oC : 850-1000μm, 100oC
Fig. 2 Effect of the Injection Amount of CH3OH on the Fisrt Absolute Moment
z/u [min]
0.00 .01 .02 .03 .04
1st absolute moment [μ ]
0 2 4 6 8 10 12
: 250-425μm : 150-250μm : 850-1000μm
70 oC
100 oC
130 oC
Fig. 3 Fisrt Absolute Moment of Methanol on Activated Carbon
1/T
.0024 .0025 .0026 .0027 .0028 .0029 .0030
ln K A
-4 -3 -2 -1 0
ΔH = -9.5 Kcal/mol
Fig. 4 Van’t Hoff Plot of Adsorption Equilibrium Constant
106/u2 [min/cm]2
0 3 6 9 12 15 18 21
μ 2/[2 z/u]
1 10 100 1000
70oC
100oC
130oC particle size : 0.2mm
Fig. 5 Second Moment Plot of Methanol on Activated Carbon
106/u2 [min/cm]2
0 3 6 9 12 15 18 21
μ 2/[2 z/u]
20 40 60 80 100 120 140 160 180 200
0.2mm
0.337mm
0.93mm adsorption temperature : 70oC
Fig. 6 Second Moment Plot of Methanol on Activated Carbon
Table 3. Adsorption Equilibrium Constant For Methanol On Activated Carbon (BPL 4×10)
Temperature [oC] 70 100 130
Equilibrium
Constant [m3/kg] 0.407 0.124 0.048 (Moment)
Equilibrium
Constant [m3/kg] 0.715 0.220 0.082 (Packed)
Table 4. Axial Dispersion Coefficient of MeOH On Activated Carbon (BPL 4×10)
0.2mm 0.34mm 0.93mm
70oC 100oC 130oC
1.77 2.55 1.91
1.62 2.72 3.17
1.12 0.99 -
× 10-5 [cm2/min]
Time (min)
0 5 10 15 20 25 30 35
C/C o
0.0 .2 .4 .6 .8 1.0
: 70 oC : 100 oC : 130 oC
Fig. 6 Breakthrough Curves of MeOH over Activated Carbon
z/u [m in]
0.00 0.01 0.02 0.03 0.04
1st absolute moment [μ ]
0 2 4 6 8 10 12
500 oC 2hr 900 oC 10hr
Temperature [oC]
0 150 300 450 600 750 900 1050 1200
Arbitrary unit
0 20000 40000 60000 80000
CO CO2
Temperature [oC]
0 150 300 450 600 750 900 1050 1200
Arbitrary unit
0 500 1000 1500 2000
CO CO2
1/T
0.0024 0.0025 0.0026 0.0027 0.0028 0.0029 0.0030 ln K A
-4 -3 -2 -1
ΔH = -9.8 Kcal/mol
ΔH = -9.1 Kcal/mol
106 /u2
[min/cm]2
0 3 6 9 12 15 18 21
μ 2/[2 z/u]
1 10 100
70oC
100oC particle size : 0.34mm
70oC
100oC
R2
x10-8 [m2
]
0 2e-7 4e-7 6e-7 8e-7 1e-6
15εδ 1/(1−ε)ε p2
0 1000 2000 3000 4000 5000 6000 7000
open symbol : 500oC-2hr heat treatment closed symbol : 900oC-10hr heat treatment
: 70oC : 100oC
Condition Di/a2 [s-1] Da[m2/s] DAB [cm2/s]
70 oC
500 – 2hr 0.0106 1.152e-6
0.77 900 – 10hr 0.0102 3.288e-6
100 oC
500 – 2hr 0.0198 5.224e-6
0.88 900 –10hr 0.0286 4.182e-6
Summary of Diffusivities