Adsorptive properties of carbon molecular sieve from Saran

470

Letters to the Editor

The characteristics of the I-zone LTPC prepared under the standard conditions were: Specific gravity, 1.50; specific resistance, 3.7 x 10-2R-cm; X-ray parameters, c& = 3.88 A, L, = 10A; Cl content, 4.3 atom%.

Gunma Technical College Toriba-cho, Maebashi-shi 371 Japan

AKIRAKOJMA

Faculty of Technology Gunma University Tenjin-cho, Kiryu-shi 376 Japan

SUGIO OTANI

REFERENCE 1. J. C. Bokros, In Chemistryand Physics of Carbon (Edited by :%?I Walker, Jr), Vol. 5, p.1. Marcel Dekker, New York

Carbon Vol.19.No.6.pp.470-472, 1981 Printed inGreat Britain.

ciu-6223/81/060470-03suz.aJ/0 @ 1981 Per@mon PressLrd.

Adsorptive properties of carbon molecular sieve from Saran (Received 18 March 1981) It is well known that carbon from Saran, a copolymer of viny lidene chloride and vinyl chloride, exhibits molecular sieve properties. Lamond et al.[l] have shown that a 6 A type molecular sieve can be prepared from Saran. Metcalfe[2] has found that Saran 489 carbon pelletized with methyl cellulose produces a pellet which exhibits SA type molecular sieve properties. Recently, we have found that carbon exhibiting 5 A type molecular sieve properties can be prepared from waste products of Saran without necessitating any activating treatment, by subjecting a mixture of carbonized Saran, coal tar pitch and sulfite pulp waste liquor to a HTT of 600 - 900°C[3]. In this paper we present data on the adsorptive properties of carbon molecular sieve obtained from Saran waste. The waste product of Saran (manufactured by Asahi Dow Co., Japan) was carbonized at 800°C for 1.5 hr and then pulverized to a particle size smaller than 100 mesh size giving Carbon A. Then 15.7 wt% coal tar pitch and 13.0 wt% sulfite pulp waste liquor were added to Carbon A. Properties of coal tar pitch and sulfite pulp waste liquor are presented in Tables I and 2. The mixture was granulated into spherical pellets of I -2mm in diameter using a disc-type pelletizer. The spherical pellets were heat-treated at 800°C for I hr in flowing N, to give carbon B. Adsorption isotherms on the carbons were determined gravimetrically using a quartz spring for adsorbates of different molecular size, such as carbon dioxide (3.3 A), butane (4.3 A). isobutane (5.0 A). neopentane (6.2 A), benzene (3.7 A. 7.Oh) and cyclohexane (4.8 A. 6.8 A)[2].

a negligible capacity for isobutane, and a significant capacity for butane. This carbon molecular sieve from Saran waste exhibits molecular sieve properties similar to zeolite 5 A.

‘Table 2. Properties of sulfite pulp waste liquor Specific

1.26

gravity

5.4

PH Solid,

46.8

%

5.1

Ash. %

200

1 Butane

Isobutane

160 --& 0-l

Table I. Properties of coal tar pitch c,

%

91.9

“,

%

4.7

N,%

ul

E D

120

2

1.4

S, I

0.5

Ash, %

0.3

c

1.30

E

3

Specific

gravity OC

Softening

point*

Quinoline

insoluble

Benzene

insoluble,

76.5

s % 3.5 %

a

40 Neopentane

16.1

Adsorption isotherms of carbon dioxide, butane. isobutane and neopentane on Carbon A are shown in Fig. I. Carbon A has significant capacities for butane and isobulane and has rather a small capacity for neopentane. Adsorption isotherms on Carbon B are shown in Fig. 2. Carbon B does not adsorb neopentane. has

0

200 Pressure

LOO

600

( mmHg 1

Fig. I. Adsorption isotherms of carbon dioxide. butane. isobutane and neopentane on Carbon A at 25°C.

471

Letters to the Editor Table 3. Limiting adsorption volumes determined from Dubuun-Astakhov

Sample

dioxide

Butane

lsobutane

NeOpentane

Carbon A

0.336

0.319

0.306

0.031

Carbon

0.240

0.209

0.024

nil

0.186

0.174

0.012

nil

Zeolite

^,

Carbon

plots

B

5A

‘60i I

Butane

120

160

80

120

40

80

; w

p” L :: u d c

0’ E

4

0 0

200

40

LOO

Pressure

( mmHg

600

f

Cyclohexane

Fig. 2. Adsorption isotherms of carbon dioxide, isobutane on Carbon B at ZS’C.

butane and

a 0

20 Pressure

Fig. 3. Absorption The foliow~ng Dubinin-Astakhov these adsorption data W W=exp 0

eq~tion[4]

A-RTlnb

A” i2 P

(mmHg

60

1

isotherms of benzene and cyclohexane Carbon B at 25°C.

on

was applied to

[Ol -

40

(2)

where W is the volume of adsorption space, W, is the limiting volume of adsorption space, A is the adsorption potential, E is the characteristic energy. R is the gas constant, p. is the saturated vapor pressure, p is the equilibrium vapor pressure and n is the integer constant. The adsorption data were well corre!ated by eqn (1) with n = 2 for Carbon B and n = 3 for zeolite 5 A. The limiting volume of adsorption space W, was calculated from the intercept of (log W vs A”) plots. Values of W, for four gases of different moiecuiar size are presented in Table 3.

Adsorption isotherms of benzene and cyclohexane are shown in Fig. 3. Carbon B adsorbs negligible amounts of cyclohexane: however, it adsorbs significant amounts of benzene. The value of W, for benzene was calculated as 0.188 ml/g. The pores of Carbon B are considered to be spit-shaped from the result that it adsorbs benzene. a Rat molecuie with a molecular size of 3.7 A in thickness and 7.0 a in width, whereas it does not adsorb neopentane. a spherical molecule with a diameter of 6.2 /5.

rational Researrh Institute for Poliutio~ and Resources Yatnbe-cho. Tsukuba-gun Ibaraki. Japan

H.

KITAGAWA

N. YUKI

412

Letters to the Editor ~~~NC~

1. T. G. Lamond, J. E. Metcalfe, III and P. L. Walker, Jr., Carbon 3, 59 (1965). 2. J. E. Metcalfe, III, Ph.D. Thesis. Pennsylvania State Uni-

versity, p. 35 11965).

3. U.S. Pat. ~67~ (1977). 4. V. A. Astakhov, M. M. Dubinin and P. G. Romankov, Theor. Osn. Khim. Tekhn. 3, 292 (1969).