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(1)

Chromatographic Study of Methanol Adsorption on

Activated Carbon

광운대학교 환경공학과

유 경 선

(2)

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

(3)

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,...

(4)

Concept of Chromatographic Study

pulse input Co

Elution Curve Ce(t)

Adsorbent Column

(5)

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

(6)

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

(7)

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

(8)

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

(9)

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]

(10)

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

(11)

Time (min)

.1 1 10

Detector Signal

dp = 0.2mm Temp = 100oC

Flowrate = 70ml/min

Fig. 1 Typical Gas Chromatogram

(12)

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

(13)

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

(14)

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

(15)

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

(16)

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

(17)

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)

(18)

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]

(19)

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

(20)

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

(21)

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

(22)

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

(23)

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

(24)

R2

x10-8 [m2

]

0 2e-7 4e-7 6e-7 8e-7 1e-6

15εδ 1/(1−ε p2

0 1000 2000 3000 4000 5000 6000 7000

open symbol : 500oC-2hr heat treatment closed symbol : 900oC-10hr heat treatment

: 70oC : 100oC

(25)

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

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