Characterization of polymer carbons derived from porous sulfonated polystyrene

Carbon Vol. 19. pp. 21-36 @ Pergamon Press Ltd.. 1981.

W3-4223/81/010027-I0$02.lWl

Printed in Great Britain

CHARACTERIZATION OF POLYMER CARBONS DERIVED FROM POROUS SULFONATED POLYSTYRENE JAMESW. NEELY Rohm and Haas Company, Spring House, PA 19477,U.S.A. (Received 30 June 1980)

Abstract-The chemical and physical properties of carbonaceous adsorbents produced from macroreticular sulfonated styreneldivinylbenzene copolymers have been studied over the temperature range 30&1200°C.The beads char upon heating but retain the macroporous structure of the original coplymer. Chemical structures are presented which are consistent with chemical analysis of the solid and the volatiles. Microporosity is created during heat treatment. As the temperature rises the volume of micropores increases and the effective size of the micropores decreases. The microporevolume increases linearly as the skeletal volume decreases with half the volume lost by the skeleton creating new micropores and the other half appearing as shrinkage of the bead.

copolymers are pyrolyzed to various temperatures in an inert atmosphere.

1. INTRODUCTION

Linear polystyrene produces no carbonaceous residue when thermalized making it an unsuitable starting material for carbon production. The thermal decomposition of polystyrene has been shown to proceed by a combination of depolymerization (unzipping) and chain scission reactions[l]. The first observable weight loss occurs at 260°C in air and 350°C in nitrogen [lc] with complete volatilization occuring by 440°C. Degradation products vary with temperature and polymer tacticity and consist primarily of monomer (cu. 45%) dimer and trimer units of styrene. Crosslinked polystyrenes convert readily to carbonaceous residues between 300 and 500°C indicating condensation processes competing with chain scission[2]. The yield of carbonaceous solid increases as the crosslinking level increases[3-91 with 50% divinylbenzene giving a residue equivalent to 6% of the original polymer skeleton[3] and 100% trivinylbenzene giving about a 55% weight yield[2]. The weight yield of 100% DVB is increased from 8% to about 80% by carbonization at high pressure[4]. The composition of the volatile products changes with temperature and crosslinker level. Below 50% DVB the first volatile product is mainly styrene but methane, ethylene, benzene, toluene and hydrogen are produced at higher temperatures. In higher network density materials hydrogen and alaphatic hydrocarbons predominate [5]. Reaction of polystyrene with oxidants has been shown to increase the yield of carbonaceous product and change the character of the resulting solid. Most commonly sulfonation has been used[lO-151 but oxygenation[3] and chlorination[3,16] have also been reported. Useful adsorbents from porous styrene precursors were first reported in 1975[17] and are currently marketed by Rohm and Haas Company under the trade name “Ambersorb”.t This report will describe the changes in chemical composition and pore structure which occur as sulfonated macroreticular styrene/divinylbenzene

2. RESULTS

2.1 Pyrolysis When macroreticular sulfonated styrene/DVB is heated in an inert atmosphere, a series of chemical reactions occurs which transforms the porous starting material into a carbon replica of the original plastic. The original macroreticular structure as shown in the micrographs in Fig. 1 is retained in the resulting carbonaceous solids. As the temperature is raised (see Fig. 2) a series of endothermic reactions occurs beginning with the loss between 100and 200°C of the last water of hydration from each sulfonate group followed by desulfonation and finally carbonization. Reactions occurring in various temperature ranges have been studied in some detail. 2.1.1. Room temperature up to 300°C. The nature of the volatiles produced up to 300°C was investigated by passing the nitrogenlvolatiles stream exiting the pyrolysis tube (see Experimental Section) through a water bubbler containing either I&arch solution or NaOH solution. In two successive experiments one using I&arch and the second using NaOH the per cent of total sulfur in the starting material recovered in the traps was 83% (21%) for I2 and 82.8% (?l%) for NaOH. The caustic will react with any of the volatile forms of sulfur (SO,, SO1, H2S). Iodine will react with SO2 and H,S but not with SO,. The I&arch reaction produced a clear solution with no evidence of colloidal sulfur formed by reaction of It with H,S. Since the I2 and NaOH reacted with the same amount of sulfur, we conclude that the volatile sulfur produced up to 300°C is exclusively SO*. The resin used in these experiments was sulfonated by a similar but not identical procedure as that used in all other experiments reported here. The elemental analyses and weight yields given in Figs. 4 and 5 indicate that only 74.9% of the sulfur is lost up to 300°C for this material. The only other volatile material recovered was water. The amount of water recovered was consistent with the amount expected based on the measured water content of the starting material and the assumption of the for-

tFor product information, contact Rohm and Haas Co., Independence Mall West, Philadelphia, PA, U.S.A. 27

28

J. W. NEELY

Fig. 1. Scanning electron micrographs of (a) macroreticular copolymer used throughout this work, (b) the copolymer after su~onation, (c) the copolymer after sulfonation and pyrolysis to 800°Cin nitrogen.

Thermal gr~ime~ic

anaiysls

Differential scanrung calorimetry

15

0

100

200

300

400

600

600

Tempemture,

Kx)

600

900

.I000

ilo

1200

‘C

2. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) of sulfonated porous styrene/DVB beads showing a series of endothermic reactions (a) 100-200°Closs of the last water of hydration (b) 225-300°Cdesuffonation (c) above 300°Closs of 28.8%of the carbon as volatile orpanics.

Fii.

mation of 1 water moleculefor each SO2 molecule. Of the sulfur remainingin the adsorbent, 50% is still in the form of sulfonate groups as measured by the remaining ion exchange capacity of the 3OtW material. The rernai~~ sulfur is likely presentas suifone groups. Aryl sulfones are known to be stable to temperatures in excess of 3oo”C[181.

Presented in Fig. 3(a)is a proposed chemicalstructure of the 300°Cmaterial.A representative 10 monomerunit is shown undergoingradical desulfonationI191followed by hydrogen abstraction predominantlyfrom the backbone by the resulting HSO, radical. A series of radical recombinationand cyclization reactions was assumed in order to produce the structure pictured in Fig. 3(a).This

Characterization of polymer carbons

29

30

J. W. NEELY

presumablyfollowed by dehydrochlo~nationto produce structures of the type shown in Fig. 3(c). 2.1.3.5OO”C up to 1200°C.At temperaturesabove 500°C the aromatizationreactions can proceed thermallyby the direct loss of hydrogen to produce new carbon-carbon bonds. As shown in Figs. 4 and 5 the majority of the weightlost above 500°Cis hydrogen.The heliumdensity of these materials increases above 500°Cas shown in Fig. 6. By lOOO-1200°C the densities are nearly those of graphite (2.25g/cc). The helium densities are consistent 300 400 500 600 700 600 900 1000 1100 120% with the formation of polynuclear aromatic structures. Temperature, “C As shown in Table 1 the extent of the polynuclear Fig.4. EIement~com~sitionof the c~~naceous adsorb&s produced by pyrolysis from 300to 1200°CThe wt.% hydrogen~) is aromatic character of the pyrolyzed st~ctures can be estimated both from the density and the C/H ratio of plotted on the right hand scale. knownpolynucleararomatic structures.As the degree of polynuclear aromatic character increases both the denVolume yield - 0 sity and the C/H atomic ratio increase(see Table 1).The density and C/H ratio for coronene are similar to the Q 70 values found for the 500°Cproduct shown in Fig. 6 “60 which lends additionalcredibility to the 500°Cstructure E50 2 given in Fig. 3(b). $40 Increasing polynuclear aromatic character would be expected to result in increasingelectrical conductivity. As shown in Fig. 7 the electrical resistance decreases Zol 1 ’ * s ( g 2 1 1 300 400 530 600 700 fxJ0 900 loo0 1100 1200 over 5 orders of ma~itude between 600and 800°C. Temperature, DC X-Ray analysis of the 8WC material showed no evidence of graphite crystallite structures larger than the Fig. 5. Weight and volume yields of sulfonated styrene/DVB experimentallimit of 50A. copolymers heated to the indicated maximum temperatures. st~ct~e is consistent with the weight loss and the elementalanalyses given in Figs. 4 and 5. 2.1.2. 300°Cup to 500°C.As the temperatureis raised from 300 to SWC, 70% of the remainingsulfur is volatilized predominantly as SO,. However, smaller quantities of H2Sand elementalsulfur are also present in the off-gases.Of the carbon in the originalpolymer 28.8%is lost as volatile hydrocar~ns, predominancy as styrene and toluene by GC analysis. A reddish oil is produced which consists of a very large number of unidentified compounds. The structure proposed for the 500°C material shown in Fig. 3(b) is consistent with the elementalanalysesand weightyields shownin Figs.4 and 5. The carbon was assumed to have been volatilize by unzipping reactions producing styrene and ethylvinylbenzene. The remaining sulfur was assumed to have been lost as S and H,S and this loss was followed by alicyclic rearrangementsto produce a maximumamount of polynucleararomatic structures. The originaldivinylbenzene rings are marked with asterisks to assist in following&is transfo~ation. No ion exchangecapacity remains in the 500°Cmaterial so the small amount of sulfur remainingis likely present as sulfone. The 500°Cmaterialis reactive towards chlorine. Reaction with gaseous Cl, is a vigorous exothermic reaction producing one mole of HCl for each Cl, reacted. Depending on the temperat~e at which the reaction takes place, the 500°Cmaterialcan increase in weightby as much as 3E40% by reaction with chlorine. Addition of chlorine to the low energy double bonds in the conjugated aromatic systems present in the 500”material is

2.2. Pore structure The pore structure has been studied using three separate measurements: (a) Bead Volume-using low pressure mercury to determine the volume occupied by the beads excluding the voids between beads (measures no pores less than about 100,000A dia.). (b) Skeletal Volume-using helium at room temperature to determine the solid volume (measures all pores larger than 2.5A dia.). (c) Macropore Volume-using high pressure mercury (up to 60,OOOpsi) to measure the volume of pores from 100,000A down to 35A dia. Results of these experiments are given in Fig. 8. To simplify the present discussion,we will call those pores measured by the mercury intrusion technique macropores even though this range includes both macropores and transitional pores as traditionally defined[20].The -ci

“.

22. -2.1

40

ozoyis-

* 0

>l6il.7. .z 16-

0

E l5-14El3-2 1.2 I”ir. 0

300

n fJ

0

-3og

-20

o

0

8 e Y

IO

6 $ ii P > i

fl; 400

500

600

Pyrolysis

700

800

900

temperature,

Km0

1100 1200

OU

OC

Fig. 6. Skeletal density and carbon/hydrogen atomic ratio of the pyrolysis products vs pyrolysis temperature.

31

Characterizationof polymer carbons Table I. Structure, density and C/H atomic ratio for various polynuclear aromatic compounds[28] C/H

Density

Structure

NalE

AtomiS

Benzene

0.879

1

Biphenyl

0.866

1.25

1.025

1.25

1.4

.YSO

Phenanthrene

1.283

Anthraoene

Ratio

1.4

(25’C)

1.271

1.6

Perylene

1.35

1.5

Corcnene

1.377

2

Mfmapafevolume

0’

3co

4 400

1’ 500

Heat

600

treatment

0 700

‘1 aca

1 900 mco

temperature,

t 1100 12oc

“C

Fig. 8. Results of the measurement of the bead volume (cckJg), skeletal volume (cc,tclew./g)and macropore volume (cc,,-,Jg) for several different pyrolysis temperatures.

oso0

700

800

SW

TEMPERATURE

1000

1100

1

0

(‘C)

Fii. 7. Logarithm of the electrical resistance measured by a standard voltmeter across 0.385+0.03 mm dia. beads (-40+ 45 mesh). Results are the average of IO determinations.

mercury intrusion measurements are particularly useful for the resent work because the pore size range (100,OMlIg-35 A dia.) includes nearly all the pores which originated in the copolymer and none of the pores created during heat treatment. Those ores smaller than 35 A which will admit helium (2.5 1 ) will be called micropores even though this range includes both micropores and supermicropores [20]. This definition includes

all the pores created during heat treatment and none of the pores present in the original copolymer. 2.2.1 Macropores. The pore structure of the pyrolyzed product appears in Fig. 1 as a somewhat shrunken replica of that in the original copolymer. The pores in the copolymer used in this study fall largely in the range lOO-3OOAdia. A typical mercury intrusion pore size distrubution for the sulfonated precursor and the 800°C pyrolyzed product are given in Fig. 9. The pore size has shrunken somewhat from an average pore size of 243 A in the sulfonated material to 223 A in the pyrolyzed product. Assuming a spherical model, the pore diameter based on the volume yield would have been about 170A. The difference is likely due to limitation in the assumptions used in the pore size distribution calculations. The weakest assumption is that the mercury contact angle (assumed to be 140”)is the same for both materials.

32

J. W. NEELY

c

400°Cas shown in Fig. 10. The 300°Cmaterial has a porosity very similar to that of the copolymer and the PYRolYZEO 2.4 2.4 400°C material has a porosity in line with that of all the TO 800% t higher temperatureproducts. 2.2 a = 24d A partial collapse of the macropore structure occurs YACROPORI 2.0 ii = 2231 between 300and 400°C.Above 400°Cthe nearly constant 1.8 MACROPORE macroporosity is consistent with a uniformly shrinking VOLUME l.6 .0.2scc/g macropore structure. I.4 A useful model for the macroporous s~cture is a packed bed of beads. The packed bed void fraction for these samples was measured and is shown in Fig. 11 plotted as a function of the bead volume. Though the size and volume of the voids in the bed decrease as the beads shrink, the porosity of the packed bed does not change as the bead size changes. In a similar way between 400 and 1200°Cthe macro~res shrink propor0 100200 300400500 0 100200300400SOO tionately as the microspheresshrink (see Fig. 8). 2.2.2.Micropore volume. The volume of pores created DIAMETER (i, during heat treatment is calculatedfrom measuredquanFii. 9. High pressure mercury pore size distributions for the sulfonated copolymers and the same material pyrolyzed to 800°C tities as follows: 2.6

SUt.FONATtD CDPOLVMER

in nitrogen. Vmicropores =

Kun and Kunin[Zl]have describedthe structure of the macroreticularcopolymer as agglomeratesof randomly packed microspheres with a continuous pore structure consistingof the spaces between microspheres,As seen in Fig. 1 the microspheresin the copolymer are roughly 5008, in dia. As the temperature is raised and the beads shrink the fraction of the bead volume which is due to macropores remains roughly constant over the range 400-1200°C.A small trend toward loss of porosity at higher temperatures is indicated by the slope of the least squares line shown in Fig. 10 though the magnitudeof the trend is within experimentaluncertainty. A loss in macropore void fraction (macroporosity) occurs between 300 and 0.4

COPoLYMER---r, 300‘C

c

Vbead - Vmacropores

-

Vskeleton.

A similaranalysis to that conducted for the macropores is shown in Fig. 12 with the microsphere void fraction plotted vs the skeletal volume. ( Vmicropom /V,,,icrosphhcrcr) Unlike the macropores, the void fraction due to micropores increases as the heat treatment temperatu~ rises. As the skeleton shrinks in volume the porosity of the microspheresincreases markedly. The micropore volume is shown in Fig. 13 plotted vs the skeletal volume. Within experimental error the micropore volume increases linearly as the skeletaf volume decreases with a slope of one half. Of the volume created as the skeleton becomes more dense at higher temperatures,one half creates microporesand the other half appears as shrinkageof the microspheres.The line plotted in Fig. 12 was calculatedfrom 0.498- 0.533v&&ton MicrosphereVoid Fraction = o,498+ o-45, VBkckton

-0

00 B

_

oq

I

t 28 0 5

400% -

0.1

-

f 0. 0.7

’

’

’

’

’ 0.3

’

’

’

’

’

WCROSPHERE VOLUME

Fii. 10. Macropore void fraction (~rosity~ vs the

volume

microsphere

Vol. macropores macropore void fraction Vol. bead mic~sphere

volume= Vol. bead-vol. macropores.

Thestraight line is the result of a linear least squares best fit with a slope of 0.20 and R = 0.55.

Bead volume, cc/g Fig. 11.Packed bed void fraction vs bead volume. The packedbed void fraction is calculated from measured quantities as follows: Vol. beads (cc/ Packed bed void fraction = 1- vol_bedtcc,t. Thelineistheresultofalinearleastsquaresbstfitanaiysisandhasa slope of -0.004 and R = 0.04.

~haracteri~tion of polymercarbons

c 1.4 SKELETAL

VOLUME

(cc/g)

Fig. 12. Microsphere void fraction (MVF) vs skeletal volume. The MVF is calculated from measured quantities as follows: MVF = bead volume-macropore volume-skeletal volume bead volume-macropore volume ’ The line is calculated assuming the linear relationship between the micropore volume and the skeletal volume shown in Fig. 13. As the skeletal volume approaches zero the MVF approaches 1.

Skekml

votumc, cc/g

Fig. 13. The micropore volumeisplotted vs the skeletal volume.The solid line is the result of a linear lest squares bestfit to the data and is calculated from the following equation (R =O.%) micropore volume = 0.49lLO.533skeletal volume.

assuming Vmicmp*re = 0.498 - 0.533 Vskcleton

(2)

eqn (1) predicts the physically reasonable result that the microsphere void fraction approaches one as the skeletal volume approaches zero. In addition the skeletal volume calculated from eqn (2) assuming no micropore volume is 0.92 cc/g which is equal to the skeletal volume of the copolymer. Based only on the data, assumption of a linear relationship between the ,microsphere porosity and the skeletal volume (Fig. 12) could equally well be made. However, this assumption leads to the physically unreasonable prediction that the microsphere void fraction approaches 0.73 as the skeletal volume approaches zero.

Kritical dimension is defined as the diameter of the circumscribed circle of the cross section of minimum area[22el. CAR Vol. 19. No. I-C

33

2.2.3. Total pore size distribution, An estimate of the effective micropore size was obtained by measurement of the amount of adsorption for different sized molecules under conditions which fill the micropores [6,10,22]. The results are given in Table 2. Carbon tetrachloride (critical dimensions 6.0 A) [29]t and hexane (critical dimension 4.3 A)[301 adsorbed at P/PO = 0.36 were measured for each of the materials pyrolyzed from 500 to 1200°C. As described in Table 2 corrections have been made for the amount of adsorption on the macropore surface and dissolution into the solid phase. Assuming monolayer coverage and normal liquid density, the volume of solvent adsorbed on the macropore surface can be calculated from the surface area occupied by each molecule (40 A’ for CC& and 57.7 A’ for hexane)[24] and the macropore surface area measured by mercury intrusion. An additions correction must be made because some of the adsorbents swell in hexane and carbon tetrachloride. An estimate of the amount of solvent dissolved into the solid phase was obtained by measurement of the swelling of the adsorbent in the liquid. This has been subtracted from the total to obtain an estimate of the amount condensed in the micropores. The volume of carbon tetrachloride adsorbed in the micropores indicates the volume of pores between 35 and 6.0A. The volume of hexane minus the volume of Ccl, adsorbed gives the volume of pores in the ranges 4.3-6.0 A. The total pore size distribution is given in Fig. 14. When the sum of the pore volumes measured by mercury intrusion and vapor adsorption was less than the total pore volume measured with helium, the difference was assigned the size range 2.5-4.3 A. It is assumed that helium can enter all pores larger than 2.5 A diameter [29c]. This pore volume is the least accurate value in Fig. 14 because the sum of all the experimental errors in each of the pore volume measurements is included in the result. Within the limits of the assumptions made, this pore size distribution is an indication of the volume of pores accessible from the exterior of the beads. It is not an estimate of the size of the pores actually present in the adsorbents if constrictions are present. The volume of a particular pore will be measured by these techniques to be the size of the smallest constriction allowing access to the pore from the exterior of the bead. Many investigators have shown that such constrictions exist in polymer derived carbons[23]. The pore size distributions given in Fig. 14 should be interpreted to indicate the volume of pores accessible through constrictions of the indicated size range. The micropore (and/or constriction) size decreases as the heat treatment temperature rises. Above 600°C the micropores are sufficiently small to act as carbon molecular sieves-capable of separating molecules by size and shape. The micropores (and/or cons~ictions) are slit shaped as demonstrate by the fact that the same volume of benzene is adsorbed as hexane [25] suggesting a structure of slit shaped pores and/or pore constrictions less than -3.7 8, thick and more than 7.0A wide[lO]. The volume of 4.3-6.0A pores reaches a maximum between

34

J. W. NEELY

0.5

ey 0.4 go.3 ZO2 e (f 01 0 500

600 Heat

625

650

700

treatment

750

800

temperature,

900

1OOOI2OO

“C

Fig. 14. Histo~m of tbe total pore size dist~butjons including the results given in Table 2. Table 2. micropore size distribution calculations

(5) (1) Heat treatment tem~ratu~

(2)

(3)

Macropore surface area m2fg

CCL

500 600 625 650 700 750

adso~tion (cck)

Per cent swel(4) Ccl, adsorbed ling on macro~res in Ccl, (Vol %) @c/g)

0.166 0.097 0.066 0.054 0.049 0.043 0.039 0.040 0.039 0.039

Z 1000 1200

0.034 0.031 0.030 0.026 0.025 0.023 0.021 0.021 0.019 0.016

7.3 : 1:s 0.5 0

(6) CC& in solid Wg) 0.053 0.013 0.015 0.009 0.003 :

It 0 0

: 0

(7)

(12)

micropores W/g) Vol. of pores 6.0-35 8,

(8) Hexane adsorption W/g)

(9) Hexane on macropores (cc/g)

(10) Hexane % swelling (Vol. %)

(11) Hexane in solid (cc/g)

Hexane in Micropores (cc/g) Vol. of pores 4.3-35 A

0.079 0.053 0.021 0.019 0.021 0.020 0,018 0.019 0.020 0.023

0.190 0.184 OS81 0.181 0.180 0.175 0.162 0.130 0.081 0.051

0.032 0.030 0.028 0.025 0.023 0.022 0.019 0.019 0.018 0.015

12.8 6.7 3.8 2.9 2.6 4.3 2.0 3.3 0 3.5

0.093

0.065

CC&in

:g 0:018 0.015 0.023 0.010 0.017 0.:16

0.110 0.129 0.138 0.142 0.130 0.133 0‘094 0.063 0.020

(13) Volume of pores 4.3-6.0 8, -0.014 0.057 0.108 0.119 0.121 0.110 0.115 0.075 0.043 -0.003

(2) Calculated from Mercury Intrusion experiments. (4) Calculated assuming 40 AZ/moleculeand monolayer coverage-and liquid density for adsorbed layer. (10)and (5) Measured as per cent swelling = [(Vol in liquid - Vol drylVol dry)]. (11)and (6) Calculated from (5) x skeletal volume or (10)x skeletal volume. (7) Calculated from (9, (4)-@)= volume of pores 6.&35 A. (9) Calculated assuming 57.7A/molecule, monolayer coverage and liquid density for adsorbed layer. (12) Calculated from (8), (9x11) = volume of pores 4.3-35 A. (8) and (3) Meas~d ~avimetrically at P/PO= 0.36 and 20°C assuming liquid density. (13) Calculated from (12)-Q).

700and 800% By 1200°Cthe micropores are nearly all in the range of 4.3-2.58, and are sufficiently small to exclude Nz as shownin Fig. 15.In spite of the increasing microporevolumeand decreasingpore size whichshould result in increasing surface area, the surface area measured by nitrogen adsorption at liquid nitrogen temperatures decreases at higher heat treatment temperatures consistent with lack of access of the nitrogen to a large fraction of the micropore volume.

3. EXPERIMJINTAL

3.1 Synthesis The starting material in all experiments was a macroreticular styrene~2~ DVB copolymer insisting of spherical particles 0.85-0.25mm in dia. (20-60mesh). Synthesisand characterizationof the materialhave been reported previously[21,26]. The copolymer was sulfonated by exposure to 96% H2S04 for 3 hr at 122°C followed by slow dilution with water at 100°C over 3 hr.

35

Characterization of polymer carbons Table 3. Physical properties of copolymer and sulfonated copolymer cqxdyner

beads

1.07

Skeletal Density (g/ccl

Fore Voluim kc/g) Void Fraction (cc/cc) Bulk Density (g/cc) N BET Surface Area (m2/g) Analysis %C Ezem&A %-I %O $s

0.55 0.37 0.43 145 91.3 8.44 1.04 0.37

loo -

I

8

,000

1100

0 500

600

700

800

tIEAT TREATMENT

no0

TEMPERATURE

(‘C)

Fig. 15. Nitrogen surface area measured by the one point BET method. product was washed free of excess acid with water and vacuum dried at 110°C.This was the starting material for all the pyroiyses reported here. The residual water content was 7.5% as determined by weight change following column treatment with methanol, toluene and iso-octane followed by vacuum drying at 110°C. The physical properties of the copolymer and the sulfonated product are given in Table 3. Pyrolysis was performed in a horizontal 2.45 cm dia. quartz tube in a Blue M tube furnace (Model TF-242OC4) modified for temperature programming with a Research Inc. Model 5310 card reader and temperature controller. All temperature programs included a I hr hold at 2OO”C,a 0.50 hr heat-up to the indicated maximum temperature and a 1 hr hold at the maximum heat treatment temperature. After the 1 hr hold the furnace was turned off and allowed to cool which required about 2.5 hr to reach 100°C. Approximately 27g (49 cc) of sulfonated beads were contained between quartz wool plugs and spread evenly over -4Ocm of the 63 cm heated zone. Nitrogen at 2 llmin was passed through the tube during the entire heat-up and cool down procedure. All samples were cooled below lOOY!before exposure to air, immediately placed in screw cap jars and stored in a dessicator confining anhydrous CaS04 (Dririte). Unless otherwise indicated samples were placed in a 110°C air oven for at least 1 hr prior to analysis. Skeletal volumes were measured using the technique of Scumb and Ritner[27]. Bead volumes were determined by measuring in an evacuated dilatometer the volume of a mixture of accurately weighed amounts of mercury and sample. Mercury column heights never exceeded 30 cm and therefore could not have penetrated The sulfonated

Sulfonatsd Beads 1.37 0.42 0.36 0.59 70 55.15 5.24 23.88 15.67

into pores less than about 500,OOOAdia. Identically the same beads used for the skeletal volume measurement were used in the bead volume measurements. Mercury int~sion measurements were done using a Micromeretics Model 90.5~2 High Pressure Mercury Porosimeter, Macropore volume measurements were made at a starting pressure equal to that on the sample in the dilatometer to maintain consistency. Maximum pressure was 60,000 psi. Carbon tretrachloride and hexane vapor adsorptions were determined ~avimetrically by placing approx. 1 g of each sample in a weighing bottle into a vacuum dessicator containing approx. 250 ml of a 0.36 mole fraction solution of the solvent in hexadecane. The dessicator was evacuated and allowed to equilibrate for 24 hr at 20°C. A constant weight was obtained in about 2 hr. Surface areas were measured using a ~icromeretics Model 2200 high speed surface area Analyzer.

Acknorvledgemenrs-The author is indebted to Dr. P. Cartier and Dr. P. Klugherz for developing the micropore size analysis, to Mr. 1. J. Maikner for expert technical assistance and to Dr. 8. Chong for numerous helpful discussions.

REFERENCES

l(a) G. G. Cameron and J. R. MacCallum, .I Mucromol. Sci.

-Rem. Mucrotnof. Chem. C1(2), 327 (1%7) and references therein. (b) K. Murata and T. Makino, J. C/rem. SOC.of Japan 7, 1248(1975).(c) R. H. Still, P. B. Jones and A, L. Nansell, .I Appf. Polymer Sci. 10, 193(1966);13,4Of (1%9). 2. F. H. Winslow and W. Matreyek, .I Poly. Sci. XXII, 315 (1956). 3. F. H. Winslow,W. 0. Baker,N. R. Pape and W. Matreyek, J. PO/Y.Sci. XVI, 101(1955). 4. S. Hirano, F. Dachille and P. L. Walker, Jr., High Temperature-~fgh Pressures 5,207 (1973). 5. 0. Hirasa, ~uffetfn for Research insiitu~e for Polymers and Textifes 112, 11 (1976). 6. P. L. Walker,Jr., T. G. Lamondand J. E. Metcalfe, III Proc. 2nd Conf, on Industrial Carbon and Graphite,p, I. Published SC1 (1966). 7. H. Marshand W. F. K. Wynne-Jones,Carbon 1,269 (1964). 8. JapaneseKokai patent pub~cationNo. 49-53594(1974). 9. J. J. Kipling. J. N. Sherwood, P, V. Shooter and N. R. Thompson, Carbon I, 315 (1964). 10. J. J. Kipling and R. B. Wilson, Trans. Faruduy Sot. 56, 557 (1960). 11. S. Kawasumi, M. Egashira and K. Uno, J; Chem. Sot. Japan 3,403 (1979). 12. Japanese lyokai 74 106,491 A. Tasaka, S. Horikiri S. Munemiya, Y. Murakami, C. Kawai, Sumitomo Chemical Co., Ltd. (1974). 13. Japanese Kokai 77 86,986 H. Nishio and T. Tokumaru, Sumitomo Chemical Co., Ltd.

36

J. W. NEELY

14. East German Patent 27,022F. Wolf, R. Bachmann and H.

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