Application of the generalized Jaroniec-Choma isotherm equation for describing benzene adsorption on acttvated carbons

Application of the generalized Jaroniec-Choma isotherm equation for describing benzene adsorption on acttvated carbons

Materials Chemistry and Phy~~ks~25 (1990) SHORT 323 C~ICA~ON APPLICATION OF FOR DESCRIBING Y. 323-330 THE GENERALIZED BENZENE JARONIEC-CHOM...

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Materials Chemistry and Phy~~ks~25 (1990) SHORT

323

C~ICA~ON

APPLICATION

OF

FOR DESCRIBING

Y.

323-330

THE

GENERALIZED

BENZENE

JARONIEC-CHOMA

ADSORPTION

ISOTHERM

ON ACTI VATED

EQUATION

CARBONS

CHOMA

Institute 00908

of

Warsaw

Chemistry,

Military

Technical

Academy,

C Pol and3

M. JARONIEC Faculty 20031

of Chemistry,

Lublin

M. Curie-Sklodowska

University,

CPoland1

s. ZIETEK Military 00910

Institute

of Chemistry

Warsaw-Rembertow

Received

November

In 1988 equation


6. 1989;

Jaroniec

to describe

by assuming

the gamma-type

heterogeneities

C2-81 showed

for characterizing

of microporous

description

microporous

solids

was

of gas proposed,

equation

micropores,

and by

to represent

to

the

theoretical utility

the structural

which

was

CDR>

the great

adsorption

on

equation

Extensive

activated

isotherm

and vapours

This

function

of micropores.

studies

theoretical

0x4-0584/90/$3.50

in uniform

distribution

heterogeneity

equation

a simple

the Dubinin-Radushkevich

applying

isotherm

23. 1989

of gases

micropo~~~~s solids.

the gas adsorption

and experimental

December

Cl1 proposed

the adsorption

describe

structural

accepted

and Choma

strongly-heterogeneous derived

and Radiometry,

carbons.

of this

and energetic In CQ3 a

on heterogeneous led to a general

0 Elsevier Sequoia/Printed

form of

in The Netherlands

324

the Jaroniec-Choma the JC equation CDA3

isotherm

micropores.

CJC3

was obtained

equation

Stoeckli

calorimetric

isotherm

equation.

by assuming

to represent

et al.

experiments

n = 3 describes

well the adsorption

these

solids.

These

describing

JC equation measured

form

gas adsorption

this communication

that

careful

on molecular DA

equation

provide

commercial

samples

sieves

micropores arguments

microporous

adsorption

and

the exponent

equation

the utility

the benzene

of

in uniform

adsorption

with

additional

of the JC isotherm

we will demonstrate

form

carbon

in the uniform

on heterogeneous

for describing

on three

the

experiments

the use of the general

the gas adsorption

for benzene

and showed

general

the Dubinin-Astakhov

I91 performed

t&SC-S and MSC-7

This

of for

for solids.

In

of the general isotherms

of microporous

activated

carbons.

The

general

following

=a ami

JC isotherm

form

O&Cl

+

equation

may be written

in the

C43:

cAq3pP3-v’n

Cl3

where

A = RT lnCpO/p>

Here

ca>

ati denotes

equilibrium maximum

pressure

amount

potential.

the amount

adsorbed

p and the absolute

adsorbed

coefficient

adsorbate

ClOl. p. is the saturation

universal

gas constant.

equation,

which

vapour

A is the adsorption that characterizes pressure,

p and v are the parameters

function.

and n is the exponent

has the following

form:

at the

0 T, ami is the

temperature

in the micropores,

/3 is the similarity

type distribution

in the micropores

the

R is the

of the gammain the

DA

325

8=

exp

The

symbol

respect

like

is

to

energy the

of

that

in

this

a limited

structural

of

gamma-type

= n&

This

distribution

z"-'

isotherm

eqn.

assuming

n

exp

Cl].

= 2

was

Here

we

= 3.

which

adsorption

on

benzene

and

DA

form

verify

may

the

was

slit-

Stoeckli

et -

z and

x

therefore,

a

the

C12.131.

In

C41

used:

of

eqn.

for

C31 Cl1

microporous

JC

by

gas solids

the

with

a moderate

will

be

three

the

obtained

describing

description

verification on

generate

a good

solids

isotherms

eqn.

experimentally

give

microporous

adsorption

the

heterogeneous

will

This

of

describe

solids FCz>

successfully

strongly

heterogeneity.

x of

c43

special

used

Cl-3.581. n

microporous function

characteristic

sizes;

to

with

between

micropore

preferred

the

C-Coz>"l

The

on

with

of

function

adsorption

Cl>

region

is

solid

studies

proportionality

of

EQ

half-width

simple

distribution

FCz1

the

inverse

experimental

z is

heterogeneity

The

to

and

microporous

adsorbate.

Recent

function

adsorption,

a homogeneous

proportional

Clll.

showed

distribution

the

is

micropores

observed

relative

reference

= l/E0

z

CQI

al. -

the

8 denotes

characteristic

energy

c32

[-CA/13E01nl

isotherm of

gas

structural

performed

different

eqn.

for

the

activated

carbons.

The

benzene

RIB

and

the

Norft

RIC

designed The

vapour

adsorption

activated

Company for

use

benzene

carbons.

CThe in

isotherms

were

which

are

Netherlands>.

both

vapour

adsorption

and

measured commercial

These liquid

isotherms

on

on

activated phases these

the

RIAA,

products

from

carbons

were

applications. microporous

326

activated

carbons

Presented

in Fidl

were

range

relative

pressures,

of relative

is a simple

is plotted

against

against

isotherms

show

In the region

pressures. they differ respect

to benzene

is lower

is highest

microporous specific

parameters

structure

surface

the as-method standard

to extract

at. The procedure the total

isotherm

of

adsorbed

extraction

The pressure-dependent

from

the benzene

in Table

I; this Table

specific

surface

highest

value

of

area =me

carbon.

the mesopore

areas

the total

contains

also

was obtained

adsorbed

the values carbons

of

Cl!51

amount

amt from

E143.

a mi was analysed

isotherms

for the activated

carbon

amount

elsewhere

amount

by means

and the

reference

of the adsorbed

adsorption

it

the

carbons

surface

amt from

adsorbed

with

for the RIC carbon.

activated

is described

pressures

capacity

activated

eqn. Cl:,. The parameters

of the isotherm

evaluated

adsorption

on a nonporous

amount

amount

of low relative

relative

we evaluated

these

is

benzene

p and v that characterize

Sme for these

the adsorbed

and high

and lowest

C143, and we used

adsorption

in the region

for the RIAA

of a solid.

area

this quantity

The measured

the maximum

for the RIB carbon

To calculate

means

pressure.

surface)

of the relative

pressures.

of moderate

significantly;

in the

on the mesopore

logarithm

behaviour

for the

at of benzene

ati adsorbed

relative

the relative a similar

amount

ame adsorbed

for high

however.

adsorbed

the natural

isotherms

method.

For low and moderate

sum of the amount

and the amount

plotted

pressures.

the total

micropores

pressure;

at 2Q3 K by a gravimetric

are the above-mentioned

complete

Cwhich

measured

a:.

by

p and v

amiCpD

are listed

of the mesopore studied.

for the RIB carbon.

The

whereas

327

P/P

0.2

10

0.4 ' 0.6 I

I

0.8

I

1.0

1

6

Fig.

1. The amount

of benzene

and RIC CA> activated

carbons

the natural

of

logarithm

of low and moderate pressure

p/p,

the RIAA

activated

micropore

in the region

adsorption

RIC carbons.

for RIAA

pressure

possesses a:

C.3,

RIB CO1

as a function

of

p/p, in the region

and as a function

of high

capacity

Cat)

at 293 K plotted

the relative

prwssurws.

carbon

adsorbed

of the relative

pressures.

the highest in comparison

value

of the

to the RIB and

328

Table

I. The mesopore

parameters

specific

n = 3 for the RIAA.

Carbon

S

RIAA

area

Sne and the micropore

according

RIB and RIC activated

to eqn.

Cl1 with

carbons.

0 ami

me

Cm2/gD

V

P

CmmoleYg3

CkJ/mole>

84

8.78

11.9

2.32

RIB

149

4.84

17.1

2.82

RIC

49

4.27

18.3

2.81

Figure

2 presents

the distribution

according

to eqn.

functions

characterize

micropores. Fig.

surface

p and v calculated

as.

C41 for the activated

RI8 activated

that

carbons

observed

for the RIAA

stronger

structural

RIC carbons.

value

For a strongly larger

studied.

with

heterogeneity.

The higher

the width

heterogeneous

than that obtained

about

value

micropore

with

in Table

values

of ; relates

to the

x. The dispersion

solid

a

heterogeneities

of the distribution

for a solid

shows

we listed

us; these

size

microporous

that

to the RIB and

statement

structural

in

of the RIC and

The RIAA carbon

2 and the dispersion

information

shown

from

in comparison

the above

of the average

is associated

heterogeneity

carbon.

These

of the

curves

and it differs

heterogeneity

value

valuable

of the carbons higher

activated

studied.

heterogeneities

the,structural is similar

FCz> calculated

carbons

of the distribution

To illustrate

II the average provide

structural

A comparison

2 indicates

functions

function the value

small

0s

FCz>. of oz is

structural

329

Fig.

2. Distribution

C4> for RIAA

functions

Cdotted

line1

activated

Table

II.

line].

calculated

RIB Cdashed

function

Carbon

F(z)

5 and os associated shown

in Fig.

z

66

28

RIB

31

19

RIC

47

18

*The quantities

2 and a z were

and

to equations

The experimental that

for describing activated

illustration

adsorption that

with

the

2*.

calculated given

the generalized

carbons

heterogeneities.

and RIC Csolid

Cmmole/kJJ

RIAA

indicates

to eqn.

,Y z

Cmmole/kJ1

according

line1

according

carbons.

The quantities

distribution

FCz3

presented JC eqn.

of gases

possess

from the parameters

in [41.

in this

Cl1 with

and vapours

moderate

paper

n = 3 is useful on microporous

structural

330

ACKNOWLEDGEMENT This

work

Research

was

supported We

RP-I-08.

samples

of

the

in

thank

RIAA.

RIB

part

the and

by

Norit

RIC

the

Polish

Company

activated

Program

for

of

providing

Basic free

carbons.

REFERENCES 1

M.

Jaroniec

and

J.

Choma,

Mater.

Chem.

2

M.

Jaroniec

and

J. Choma,

Chem.

and

R.

Physical

Phys.

Phys..

12

ClQ86>

Carbon.

28

Cl9893

821.

197. 3

M.

Jaroniec

Heteroaeneous

4

M.

Madey.

Solids.

Jaroniec,

Elsevier.

Adsorption

Amsterdam.

X. Lu and R. Madey.

on chap.

Chem.

Scripta,

Chem.

Phys.,

8.

5

1988.

Cl9883

389. and M. Jaroniec,

Mater.

5

J. Choma

8

M.

Jaroniec,

Langmuir,

3 Cl9872

7

M.

Jaroniec.

R.

X.

Madey,

Lu

2C -

C1988>

179.

7QS.

and

J.

Choma.

Langmuir.

4 cl9883

911.

8

J. Choma.

9

H.F.

M. Jaroniec

Stoeckli,

Bernardini,

and J. Piotrowska.

F. Kraehenbuehl.

Carbon, --

27 Cl9891

IO

M.M.

Dubinin,

Progress

11

M.M.

Dubinin.

Carbon, --

Carbon.

L. Ballerini

28 - Cl987>

and S. de

128.

Surface

Membrane

23 Cl985

373;

Sci..

2 Cl9782

25 Cl9873 -

893;

1.

27 - Cl9891

487. 12

M.M.

Dubinin

13

M. Jaroniec

14

M. Jaroniec. Carbon. --

15

and

R.

press.

M.

Madey.

R. Madey.

27 Cl9891

J. Choma, in

and 0. Kadlec.

Carbon,

25

-_ J.

Phys.

J. Choma.

Cl9871

Chem..

E

B. McEnaney

321.

C198Q>

5225.

and T. Mays.

77.

Jaroniec

1.

and S. Zietek.

Biuletyn

WAT CWarsaw3,