Effect of Crystallinity and Additives on the Thermal Degradation of

Chapter 22

Effect of Crystallinity and Additives on the Thermal Degradation of Cellulose Tor P. Schultz, Gary D. McGinnis, and Darrel D. Nicholas

Downloaded by GEORGE MASON UNIV on February 29, 2016 | http://pubs.acs.org Publication Date: May 9, 1990 | doi: 10.1021/bk-1990-0425.ch022

Mississippi Forest Products Laboratory, Mississippi State University, Mississippi State, MS 39762

Thermogravimetric analysis (TGA) measures cellulose pyrolytic mass loss rates and activation parameters. The technique i s relatively simple, straightforward and fast, butitdoes have disadvantages. One disadvantage i s that determination of the kinetic rate constants from TGA data i s dependent on the interpretation/analysis technique used. Another disadvantage of TGA i s that the rate of mass loss i s probably not equivalent to the cellulose pyrolysis rate. In this study five cellulose samples of different c r y s t a l l i n i t i e s (10, 41, 63, 67, and 74%) were treated to 10% by weight with H PO , H BO , and AlCl ·6H O. These treated samples and untreated (control) samples were isothermally pyrolyzed under N at selected temperatures and the TGA data analyzed by four methods (0-, 1st-, and 2nd-order; and Wilkinson's approximation) to obtain rates of mass loss. From these rates, activation energy (E ), activation entropy (ΔS‡) and enthalpy (ΔΗ‡) values were obtained. E was also determined by the integral conversion method. Both 1st- and 2nd-order rate expressions gave s t a t i s t i c a l l y good f i t s for the control samples, while the treated samples were s t a t i s t i c a l l y best analyzed by 2nd-order kinetics. The rate constants, 1st-order activation parameters, and char/residue yields for the untreated samples were related to cellulose c r y s t a l l i n i t y . In addition, ΔS‡ values for the control samples suggested that the pyrolytic reaction proceeds through an ordered transition state. The mass loss rates and activation parameters for the phosphoric acid-treated samples implied that the mass loss mechanism was different from that for the control untreated samples. The higher rates of mass loss and 3

4

3

3

3

2

2

a

a

0097-6156/90/0425-0335$07.50/0 © 1990 American Chemical Society

In Fire and Polymers; Nelson, Gordon L.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

336

FIRE AND POLYMERS

low E 's of the phosphoric acid samples also suggest that wood products treated with fire retardants which contain ammonium phosphates and then exposed to moderate temperatures over long times may undergo extensive degradation. Under the conditions studied boric acid appeared to be the best fire retardant. This conclusion is based on a high char yield and similar rates of mass loss at 300°C for untreated and boric acid treated samples. Boric acid samples also had much higher ΔH 's and, consequently, higher E 's. Our results suggest that certain thermally-stable, weak polybasic acids which can complex with polysaccharides may provide fire-resistant properties to lignocellulosics. The results and conclusions were strongly influenced by the technique used to analyze the TGA data. a

‡


a

In

order

to

convert

cellulose area

fireproof

biomass

and

wood a n d c o t t o n

into

chemicals,

pyrolysis.

Extensive

several

reviews

Thermogravimetric determine

pyrolysis

technique

is

cellulose, extremely separate mass

with

complex and

loss

kinetic

variables

as

different

mass

losses

Analysis is

(Mc),

is

be

M is

kinetic

technique

dimensionless, to

the

mass a t

initial

rates

of

complex

(8,18-20)

or

these

(4,6).

rate,

order

is

E

reported

the

the

rate

rate

to

of

pyrolysis which

result

values a

in

obtained

analyze

obtaining for

be

the

data.

corrected

residual

char

and

Mr (1)

t;

Mr

(4,10).

mass l o s s

is

E

f l

from

the

reactions

also

crystallinity

has

(2,26,27).

The

to

occur

in

the

(11 ) , have

(18,21-23)

been

initial

residual

multiple

available

isothermal

's

or

Mc v a l u e s

(17)

include

and

for

TGA d a t a

assumptions necessary

first

char

From t h e

reported

Techniques are or

Mr

b a s e d on 0 - o r d e r

and 2 n d - o r d e r

and/or

f l

Also,

can

needed

=

consecutive reactions

Cellulose and

time

mass

reactions

interpretation rates

for

often

to

account

many

are

used to

involves

and

mass l o s s

reactions

kinetic

to

by:

(2-4,7,8,10-16) Other

related

Finally,

on the

this

The

f l

of

(9^).

competing

used

(E ). However

experiments

Mo -

Mo t h e

kinetics

effects

M -

and

been

examined.

the

assumed t o

M c

where

often

convenient,

and

isothermal

thermally

conducted i n

simple

c e l l u l o s e TGA d a t a

which

calculated

been

energies

polymers,

dependent

of

has

quickly

occur.

has

to

understand

(1-7).

(TGA)

temperature be

and

must

activation

(k) s i n c e m u l t i p l e

f r o m TGA c a n be mass

fast,

(8) a n d

should not

rate

and

c a n be

most

identify

research

available

analysis

rates

relatively

experimental

are

products

researchers

over

material; time,

lst-order been

examined.

competitive combinations

determination with

of of

no

(17,24,25).

shown t o low

amorphous

affect

temperature region

pyrolysis decomposition

(5,26,27).


Also,

22. SCHULTZETAL. levoglucosan regions place

is

while

in

the

believed

direct

the

on E

order

give

for

treated


analysis The

of

crystallinity,

This

data

pyrolysis results

is of

is

of

The

used to

by

are

and

and

The

reported

as

commonly u s e d r a t e

lst-order expression

cellulose. to

examine

analysis

the

technique

effect

pn

activation

enthalpy

( Δ Η * ) and

from

mass l o s s

the

an u n d e r s t a n d i n g

crystallinity the

and

of

how

additives

data

of

isothermally

determined

on

effect

reaction

,

dependent

a

salts

were

f l

as

(1,3,7). little

(12,18).

f l

by

char

its

has

on

to

work

more

compounds

generally

most

untreated

develop

affected

obtained

E

r e s e a r c h was E

form

chloride

the

takes

effect

shown

retardants to

volatile

been

and d a t a

(AS?)

fire

a major

been

phosphoric acid

the

this

can have

ash have

aluminum

crystalline derivatives

(2,6,28).

rate

increases

also

additives

entropy was

that

acid

cellulose.

activation

reaction

flammable

TGA d a t a

objective

pyrolyzed

Generally,

samples has

which

of

from

furan

cellulose

(6).

noted

and

retardants,

(13,18,22,29),

f l

mainly

char

amounts

and b o r i c

f l

of

fire

fewer

have

E

(12,13,18,29) for

as

formed

form

trace

dehydration

papers

decrease (22)

the

result

Several

such even

pyrolysis

increasing

be

to

amorphous a r e a s

and

influence

to

dehydration

Additives, pyrolysis,

337

Thermal Degradation of Cellulose

rates.

cellulose a n d how

analysis

the

technique.

Experimental Cotton

linter

s a m p l e s were

various

times

and

(27,30).

74%

solutions 10%

by

of

weight

and

The System

to

desired

the

initial

four

reached

was

temperature was

pyrolysis Instead

infinity,

Mr

that

the

and/or give

14

set

once the

held

at

110

then

by

the

calculate

heated

rate

calculate

Mr

by

determined method

was

by h e a t i n g

infinity

s h o u l d be A few

plots

be

per

rate

in The

the

the

run.

were

of

minutes of

order

to

150°C/min from

the

was to

avoid

remained actual

activation of

with

TGA d a t a

calculated each

steady

observed

parameters.

using Equation isothermal

sample/additive

1.

plot to

to

550°C

have

(4,8,10-12,15,16,19,23,26,31).

same r e g a r d l e s s

duplicate

reproducible

Mc v a l u e s

points

molecular would

u s e d b e c a u s e c e l l u l o s e TGA r a t e s

Arrhenius

were

Mc was

extrapolation

follow

temperature.

data

to

not

a N £ flow 10

temperature

used to

The

of

we

the

temperature

constants

was

calculating

a

controller. pyrolysis

Reaction

"weight/mass"

C for at

temperature

results

was

regions

4 mgs w i t h

temperature.

mass.

67

prior

TGS-2 thermobalance

desired

at

affect

to

target

complications.

This

pyrolysis

air,

used to

shown t o

Thus,

residual

lag

was

CI

2

the

under been

initially

not

Mr

retentions

samples because

2 ° C of

of

63,

aqueous

frozen

on the

amorphous

a Perkin-Elmer

temperature

dimensionless

and

further

and

S a m p l e m a s s was

minutes

within

the

with

for

41,

extents.

Samples were and

from

10,

provide

wetting

ash would

crystalline

TGA s y s t e m was

moisture

of

milling of

treated to

3

ball (CI)

vacuum d r i e d

effect

the

then

A1C1 *6H20 then

removed

of

4 controller.

remove

The

not

removal

different

cc/min.

and

The

because the

to

or

solute,

by

indices

samples were

HgBO^,

the

A s h was

that

altered

These

of

decrystallized

crystallinity

experiments.

determined. believed

give

HgPO^,

weight

pyrolysis

30

to

runs

and n o t

calculated

These values

were

of

affected at were

the

made by

4-minute then

to

isothermal insure

sample

size

intervals

used

to


to

338

FIRE AND POLYMERS

c a l c u l a t e 0-order ( 1 1 ) , l s t - o r d e r (2-4,8,14,15) and 2nd-order (17) r a t e c o n s t a n t s . W i l k i n s o n ' s a p p r o x i m a t i o n method (24,25) was a l s o used t o o b t a i n r a t e s and r e a c t i o n o r d e r s . Because o f the d i m e n s i o n l e s s v a l u e of Mc and t h e way i n which a l l r a t e c o n s t a n t s were determined, a l l r a t e s had u n i t s o f see"* and can be d i r e c t l y compared. E and t h e r a t e c o n s t a n t s a t 300°C were determined by the A r r h e n i u s e q u a t i o n , and ΔΗ* and àS% were c a l c u l a t e d by t h e E y r i n g e q u a t i o n . Ε was a l s o c a l c u l a t e d by the i n t e g r a l c o n v e r s i o n method · fl


R e s u l t s and D i s c u s s i o n T a b l e s I , I I I , V, and V I I g i v e the k i n e t i c mass l o s s r a t e c o n s t a n t s . T a b l e s I I , I V , V I , and V I I I p r e s e n t the a c t i v a t i o n parameters. In a d d i t i o n t o the a c t i v a t i o n parameters, the r a t e s were n o r m a l i z e d t o 300°C by the A r r h e n i u s e q u a t i o n i n o r d e r t o e l i m i n a t e any temperature e f f e c t s . Table IX shows the c h a r / r e s i d u e ( M r ) , as measured a t 550°C under N . 2

C o n t r o l Samples. The 0-, 1 s t - and 2nd-order mass l o s s r a t e c o n s t a n t s (Table I ) g e n e r a l l y gave s t a t i s t i c a l l y good f i t s , w i t h most r ^ > 99%. Thus, no k i n e t i c e x p r e s s i o n seems " b e s t " f o r e x p r e s s i n g mass l o s s . T h i s i s p a r t i a l l y because o n l y s m a l l mass changes o c c u r r e d a t the lower t e m p e r a t u r e s , e s p e c i a l l y f o r the more c r y s t a l l i n e samples. With s m a l l mass l o s s e s , an e s s e n t i a l l y s t r a i g h t and almost h o r i z o n t a l l i n e i s o b t a i n e d r e g a r d l e s s of t h e method used. These i n c l u d e a normal p l o t f o r 0-order, l o g Mc f o r l s t - o r d e r , and i n v e r s e Mc f o r 2nd-order. The 1 s t - and 2nd-order r a t e e x p r e s s i o n s both appeared t o g i v e s l i g h t l y b e t t e r f i t s than 0-order. Researchers i n p r e v i o u s s t u d i e s g e n e r a l l y used l s t - o r d e r k i n e t i c s t o d e s c r i b e c e l l u l o s e p y r o l y s i s , but r a r e l y have they examined 2nd-order k i n e t i c s . Thus, d i s c u s s i o n of our r e s u l t s f o r u n t r e a t e d samples w i l l c o n c e n t r a t e on l s t - o r d e r r a t e c o n s t a n t s so t h a t our r e s u l t s can be d i r e c t l y compared w i t h r e s u l t s from p r i o r s t u d i e s . A t r u e r e a c t i o n o r d e r o f c e l l u l o s e p y r o l y s i s based on TGA d a t a i s e s s e n t i a l l y meaningless, however, s i n c e mass l o s s i n v o l v e s complex competing m u l t i p l e r e a c t i o n s ( 2 , 4 , 8 ) . I n a d d i t i o n , r e a c t i o n o r d e r was c a l c u l a t e d on a d i m e n s i o n l e s s mass v a l u e r a t h e r than on the c o r r e c t but u n c a l c u l a b l e molar c o n c e n t r a t i o n term. For a l l samples, i n c l u d i n g t h e t r e a t e d c e l l u l o s e s , W i l k i n s o n ' s a p p r o x i m a t i o n g e n e r a l l y gave u n r e a l i s t i c r a t e c o n s t a n t s , r e a c t i o n o r d e r s , and e s p e c i a l l y E 's. Although t h i s method i s easy and r e q u i r e s no assumption of o r d e r , v a l u e s o b t a i n e d by t h i s t e c h n i q u e should be viewed c a u t i o u s l y . The l s t - o r d e r r a t e c o n s t a n t s , and a l s o the 0- and 2nd-order r a t e s , appeared t o be r e l a t e d t o c r y s t a l l i n i t y , w i t h the more c r y s t a l l i n e samples h a v i n g s m a l l e r r a t e c o n s t a n t s . The l o g of t h e 300°C l s t - o r d e r r a t e c o n s t a n t s (Table I I ) , as measured by the A r r h e n i u s e q u a t i o n t o a v o i d s l i g h t temperature e r r o r s , gave a good c o r r e l a t i o n ( r = 0.94) when r e g r e s s e d a g a i n s t c r y s t a l l i n i t y . As mentioned e a r l i e r , c r y s t a l l i n i t y has been p r e v i o u s l y r e c o g n i z e d t o a f f e c t p y r o l y s i s (2,6,26-28). The l s t - o r d e r Ε 's (Table I I ) and t h e A r r h e n i u s p l o t o f the l s t - o r d e r r a t e s ( F i g u r e l ) a l s o show a fl


22.

SCHULTZETAL


339

c r y s t a l l i n e e f f e c t , which i s i n agreement w i t h p r e v i o u s s t u d i e s ( 5 , 2 6 ) . S p e c i f i c a l l y , the amorphous sample had a s i g n i f i c a n t l y lower E (13 k c a l ) than the o t h e r samples (33-40 k c a l ) . The 0-order but not the 2nd-order Ε 's a l s o i n d i c a t e a c r y s t a l l i n e i n f l u e n c e (Table I I ) . F i n a l l y , the char y i e l d (Table IX) i s a l s o r e l a t e d t o c r y s t a l l i n i t y which agrees w i t h p r e v i o u s s t u d i e s (2,6,28) t h a t the amorphous r e g i o n s form more char and c r y s t a l l i n e c e l l u l o s e more v o l a t i l e s . We found an e x c e l l e n t f i t ( r = 0.96) when the l o g of the char y i e l d was r e g r e s s e d a g a i n s t c r y s t a l l i n i t y . The c e l l u l o s e p y r o l y t i c mechanism has been g e n e r a l l y proposed to be e i t h e r a thermal h o m o l y t i c ( r a d i c a l ) bond c l e a v a g e or a h e t e r o l y t i c ( i o n i c ) i n t e r n a l n u c l e o p h i l i c d i s p l a c e m e n t of the g l u c o s i d i c group by an a d j a c e n t h y d r o x y l t o g i v e an anhydro-sugar (4,6,7,21,31,32). The h i g h l y n e g a t i v e AS* v a l u e s which we o b t a i n e d suggest t h a t the r e a c t i o n may proceed through a v e r y o r d e r e d t r a n s i t i o n s t a t e ( 3 3 ) . An ordered t r a n s i t i o n i n d i c a t e s a n u c l e o p h i l i c d i s p l a c e m e n t r a t h e r than a r a d i c a l mechanism. T h i s i s i n agreement w i t h r e c e n t work (6^) which r e p o r t s t h a t r a d i c a l s are a s s o c i a t e d w i t h char f o r m a t i o n (minimal mass l o s s ) and t h a t l e v o g l u c o s a n f o r m a t i o n w i t h a c o r r e s p o n d i n g h i g h mass l o s s proceeds v i a the n u c l e o p h i l i c displacement pathway. I f the mechanism does proceed through an i n t e r n a l n u c l e o p h i l i c pathway and i f the r a t e of mass l o s s i s e q u i v a l e n t t o the p y r o l y s i s r a t e , the ΔΗ+ and ASr v a l u e s should be a f f e c t e d by c r y s t a l l i n i t y . S p e c i f i c a l l y , the n u c l e o p h i l i c h y d r o x y l i n an amorphous sample would break r e l a t i v e l y few hydrogen bonds (low ΔΗ?) (26) i n o r d e r t o o b t a i n the c y l i c t r a n s i t i o n s t a t e . However, the amorphous sample would e x p e r i e n c e a l a r g e l y n e g a t i v e AS+ v a l u e , s i n c e the t r a n s i t i o n s t a t e i s o r d e r e d w h i l e the amorphous " r e a c t a n t " i s r e l a t i v e l y d i s o r d e r e d . C o n v e r s e l y , a h y d r o x y l group i n a c r y s t a l l i n e r e g i o n would r e q u i r e e x t e n s i v e hydrogen bond c l e a v a g e and c o n s e q u e n t l y a large I n a d d i t i o n , the AS+ of c r y s t a l l i n e c e l l u l o s e should be more p o s i t i v e than t h a t f o r amorphous c e l l u l o s e s i n c e the " r e a c t a n t " i s more o r d e r e d . I n Table I I the l s t - o r d e r a c t i v a t i o n parameters but not the 2nd-order a c t i v a t i o n parameters appear t o f o l l o w t h i s trend. E ' s were a l s o determined by the i n t e g r a l c o n v e r s i o n method ( 1 7 ) . T h i s method does not r e q u i r e assumption of o r d e r or d e t e r m i n a t i o n of r a t e c o n s t a n t s . The i n t e g r a l c o n v e r s i o n method may have l i m i t e d u s e f u l n e s s s i n c e the v a l u e s o b t a i n e d d i d not always agree w i t h the E v a l u e s o b t a i n e d by the A r r h e n i u s e q u a t i o n of the 0-, 1 s t - or 2nd-order c o n s t a n t s .


fl

a

fl

B o r i c A c i d . The s t a t i s t i c a l f i t s f o r the d i f f e r e n t r a t e e x p r e s s i o n s ( T a b l e I I I ) c o n t i n u e d t o g i v e h i g h r v a l u e s f o r the c e l l u l o s e / H B 0 samples. U n l i k e the c o n t r o l samples, the 2nd-order e q u a t i o n g e n e r a l l y gave the s t a t i s t i c a l l y best f i t . W i l k i n s o n ' s a p p r o x i m a t i o n method f o r a n a l y z i n g TGA data gave h i g h r a t e s and r e a c t i o n o r d e r s , and sometimes gave i m p o s s i b l y n e g a t i v e E ' s and ΔΗ + 's (Table I I I , I V ) . E v a l u e s o b t a i n e d by i n t e g r a l c o n v e r s i o n were not always s i m i l a r t o the v a l u e o b t a i n e d by the A r r h e n i u s e q u a t i o n of the 2nd-order r a t e s . 2

3

a

a


3


Table I.

*

(2)

(1)

1 2 6. 7 0 1 2 25.6 0 1 2 26. 7

(0.986) (0.988) (0.990) (0.825) (0.981) (0.983) (0.984) (0.958) (0.989) (0.989) (0.990) (0.940)

0.01 0.00 0.01 0.09 0.01 0.01 0.01 0.06 0.00 0.00 0.00 0.04

+

0.13 0.13 0.14 0.59 0.12 0.13 0.13 0.45

Η Β C D

R Β C D

67

74

0

* » » #

* » * *

0 1 2 9.,6 0 1 2 10..5

(0.999) (0.999) (0.999) (0.830) (0.999) (0.999) (0.999) (0.807)

1 o.,00

1 o.,00 ± 0.,00 t o..05 ± o..00 t 0..00 ± 0..00 ± 0..04

0.30 0.32 0.35 0.64 0.26 0.28 0.30 0.54

1 2 9. 5

(0.994) (0.996) (0.998) (0.927)

0

0 1 2 6. 8

0 1 2 2. 3

o. 01 o. 01 0. 01 o., 15

(0.993) (0.996) (0.999) (0.934)

(0.920) (0.973) (0.999) (0.995)

η

± ± ± ±

± o. 01 ± 0. 00 t o. 01 1 o. 11

± o. 11 ± o. 14 • 0. 09 t o. 65

(r*2)

0.34 0.37 0.41 0.93

0.48 0.54 0.62 1.46

» 1.34 » 2.94 * 6.78 «11.47

Rate ± S.D.

310

Indicates a sample which was run in duplicate.

Continued Oft next page

R = zero-order; Β = first-order; C = second-order; D = Wilkinson's Approximation, where slope is equal to n/2 and the intercept is the inverse of the rate. Indicates target temperature. The actual temperature differed ± 2 deg.C but remained fairly constant The actual temperature was used to calculate activation parameters.

•

•

±

•

•

•

•

•

•

10. 3

0 1

0.22 0.23 0.24 0.31

(0.982) (0.985) (0.989) (0.964)

A θ C 0

Β C D

63

0 1 2 2. 8

(0.958) (0.987) (0.999) (0.987)

0.07 0.07 0.02 0.62 0.01 0.01 0.01 0.07

41

10

0.32 0.35 • 0.38 1.10 t

±

η

A

(r 2)

S.D.

fl

Rate 1.17 2.08 3.78 8.06

hod (1)

300

R θ C 0

Crystal 1inity Index, '/.

Reaction Te mperature (2),, ° c

A

Comparison of Cellulose Pyrolysis Rates (Rates of Weight Loss) Analyzed by Differential Methods for Control (Untreated) Samples. fill Rates are in Units of lO -4 / Sec


^ 3 M £

Q

W §

In Fire and Polymers; Nelson, Gordon L.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990. (0.996) (0.998) (0.999) (0.912) (0.995) (0.997) (0.998) (0.919)

0.53 0.01 0.61 + 0.01 0.70 0.01 1.24 + 0.08 •

fl

74

67

63

0.73 0.01 0.88 + 0.00 1.08 ± 0.02 1.75 ± 0. 13

fl

41

0.34 0.37 0.40 0.74

fl

Β C D

0.01 0.01 0.01 0. 11

0.40 0.01 0.44 + 0.01 0.49 0.01 0.96 + 0.06

Β C D

fl

Β C D

Β C D

(0.992) (0.992) (0.992) (0.878)

(0.998) (0.999) (0.997) (0.885)

(0.884) (0.934) (0.959) (0.999)

1.26 0. 16 3.58 0.27 ± 11.40 0.68 ± 19.57 0.71

θ C D

fl

±

0..05 0..06 0..07 1..47

0..05 0..06 0..07 1..07

Wilkinson's Approximation.

5..7

->

0 1

0 1 2 5.,5

•

(0..934) CO..957) CO..975) CO..994)

(0. 941) (0.,961) (0..977) (0.,994)

CO. 921) (0. 942) CO. 960) CO. 996)

l

0..05 0..06 0..08 1..27

•

0.,55 0..85 1..33 12..84

0 1 2 4..0

0 1 2 4.. 1

0 1 2 4. 3

0 1 2 3. 6

0 1 2 4. 4

η

0..74 1.,35 2..50 15..79

0. 67 1.06 1.,70 10. 73

0. 60 1.05 1.85 17. 04

0. 77 1.67 3. 69 21. 59

0. 67 1. 13 1.92 13. 73

± +

±

+

±

± ± +

0..06 0..09 0.. 12 1..41

0. 04 0.,07 0.,06 1..20

0. 05 0. 07 0. 10 !• 75

0. 07 0. 12 0. 18 84

0. 05 0. 07 0. 08 *· 43

Rate ± S.O.

(0..916) (0..948) (0..973) (0..997)

(0. 953) (0. 972) (0. 986) (0. 992)

(0. 920) (0. 946) (0. 967) (0. 997)

(0. 900) (0. 941) (0. 973) (0. 973)

(0. 937) (0. 960) (0. 978) (0. 995)

A

(r 2)

0 1 2 3..3

0 1 2 3.,9

0 1 2 3. 6

0 1 2 2. 9

0 1 2 3. 7

η

Continued on next page

Indicates a sample uhich was run in duplicate.

second-order;

± ± ± •

± ± ± ±

0 1 2 5. 1

(0. 928) (0. 945) (0.,959) (0.,995)

(0. 946) (0. 962) (0. 976) CO. 994) -ζ


63

10

Crystal 1ιηιty Index, V.

270

(0. 878) (0.,923) (0..957) (0.,999) (0..892) (0..935) (0..967) (0. 998)

0..71 ± 0.08 1..55 ± 0.13 3..45 ± 0.21 24..73 ± 1.95 0..75 • 0.08 1..59 ± 0.12 3..43 0. 18 21..53 1.88

fl

θ C 0

8 C 0

(0. 898) (0. 937) (0. 967) (0. 998)

(0.860) (0. 911) (0. 950) (0.999)

fl

0.08 0.15 0.27 2.30

0.,65 0.06 1.42 • 0. 11 3..16 ± 0. 17 26..33 • 2.62

8 C 0

+

•

fl

8 C 0

•

(0.901) (0. 938) (0.967) (0.998)

A

(r 2)

0.68 1.64 4.,05 30.72

0.07 • 0.73 » 1.48 ± 0. 11 • 3.05 • 0. 16 1.72 «20.26

Rate ± S.D.

fl

8 C 0

fl

hod (1)

0 1 2 3..0

0 1 2 2..9

0 1 2 3..0

0 1 2 2.8

0 1 2 3.0

η

C 280

0.08 0.17 0.36 2.75

+

•

0..08 0..16 0..32 3..00 0..61 ± 0..08 1..58 ± 0..17 4..21 • 0..36 39..62 2..47

0..64 1..76 4..95 38..08

0..60 ± 0.,07 1..69 ± 0., 14 4..84 ± 0..28 40..49 • 3..69

0..51 + 0.07 1.,57 0.17 4.,97 ± 0.41 56..45 4.24

0.,57 1.,46 • 3.,96 43.,35 ±

Rate ± S.O.

Reaction Temperature (2),

Table V. Continued


(0.814) (0.873) (0.921) (0.999)

(0.848) (0.907) (0.951) (0.999)

(0.874) (0.924) (0.961) (0.999)

(0.821) (0.879) (0.926) (0.999)

(0.806) (0.861) (0.908) (0.999)

A

(r 2)

0 1 2 2..7

0 1 2 2..6

0 1 2 2..6

0 1 2 2.6

0 1 2 2.8

η

350

FIRE AND POLYMERS


Table VI. Activation Parameters for Pyrolysis (Rate of Weight Loss) for Cellulose Samples Treated with 10% Phosphoric Acid, Based on Data in Table I

Crysta11iηιty Index, V. 10

Method (1)

Ea (kcal/Mole) ± S.O.

fl

θ C D Ε 41

fl Β C •

Ε 63

fl θ C 0 Ε

67

fl θ C D Ε

74

fl θ C D Ε

6 15 25 21 64

±3 ±2 ±1 ±4

- 1 θ 18 22 56

±3 ±3 ±3 t4 ±4

4 13 23 20 65

t1 t1 ±2 ±2 ± 10

4 14 24 21 68

t 2 ±2 ±2 ±4 ±9

4 13 23 22 47

±3 ±3 ±3 ±2 ±9

± 7

fl - zero-order; Β = first-order; C = second-order; D = Wilkinson's Approximation; Ε = Integral Conversion Method. (2)

Determined using the Arrhenius equation. Continued on next page


22.

SCHULTZETAL.

351



Table VI. Continued Activation Parameters A

k (10 -4/sec) 300

(

2

)

Δ Η * (kcal/Mole) ± S.O.

0.86 2.70 8.83 59.34

5 14 24 20

0.58 2.25 9.09 90.71

- 3 7 17 21

0.71 2.46 8.77 64.85

12 22 19

0.80 2.69 9.31 59.51

3 13 23 20

0.81 2.66 9.01 65.27

3 12 22 21

A S * ( e . u . ) ± S.O.

•

3 2 1 4

-69 -51 -32 -36

± 6 ± 4 ±2 ± 7

+ +

3 3 3 5

-83 -64 -44 -33

±6 ± 5 ± 5 ± 5

1 1 2 2

-74 -55 -35 -37

± 4 + 1 ±3 -»· 3

+ ±

2 1 2 4

-73 -54 -33 -34

± 4 ±3 ± 5 ± 8

± +

3 3 3 2

-73 -55 -36 -33

± 6 ± 5 ± 5 ±3

• •

2

•



A

*

(1) (2)

A Β C

41

±

•

0 1 2 6. 6 0 1 2 6.,7

(0.,982) (0..985) (0.,988) (0..996) (0..982) (0..986) (0..989) (0..996)

0. 01 0. 01 0. 01 2. 08 0. 01 0. 01 0. 01 2. 04

±

•

0.01 0.02 0.02 1.53

0.02 0.02 0.02 1.56

0.03 0.03 0.02 1.34

0..45 • 0.01 0..66 0.01 0.,98 + 0.01 11..43 1.77

0..39 0.,55 0..78 0.,90

0.,51 0. 76 1., 14 10.,56

« 0..71 * 1., 14 • * 1..86 • «10.,08 ±

0..37 ± 0.02 0..60 + 0.03 0..99 ± 0.04 21..39 ± 2.99

(0.989) (0.994) (0.997) (0.991)

(0.984) (0.990) (0.994) (0.993)

(0.987) (0.993) (0.996) (0.989)

(0.984) (0.994) (0.999) (0.986)

(0.959) (0.969) (0.978) (0.997)

A

(r 2)

0 1 2 4. 8

0 1 2 5. 4

0 1 2 4. 6

0 1 2 3. 7

0 1 2 4. 3

>

W

0.24 0.32 0.43 12.96

•

± ±

0 1 2 5. 8

(0. 985) (0. 989) (0. 993) (0. 994)

0. 01 0. 01 0. 02 1. 96

290 Rate ± S.O.

Continued on next page

A Β C 0

74

0.25 0.33 0.45 12.73

0 1 2 5. 3

0. 01 0. 01 0. 01 1. 69

(0..988) (0.,993) (0.,996) (0. 991)

η 0 1 2 5. 0

A

(r 2) (0..953) (0..961) (0..969) (0..998)

0.,02 0. 03 0. 03 3. 29

280

^ ^ £ 2*

A 8 C 0

67

•

±

±

•

±

0.34 0.47 ± 0.66 11.19 t

0.40 0.56 0.80 0.67

0.28 0.43 0.67 22.80

Rate ± S.O.

A = zero-order; Β = first-order; C = second-order; D = Wilkinson's Approximation. Indicates target temperature. The actual temperature differed • 2 deg.C but remained fairly constant (± Q.2 deg.C) during the run. The actual temperature was used to calculate activation parameters. Indicates a sample which was run in duplicate.

A 8 C 0

63

•

A 8 C 0

Method (1)

10

Crystallinity Index, '/.

Reaction Temperature (2), C

Table VII. Comparison of Cellulose Pyrolysis Rates (Rates of Weight Loss) Analyzed by Differential Methods for Cellulose Treated with 10'/. Aluminum Chloride Hexahydrate. All Rates are in Units of 10 -4 / Sec


In Fire and Polymers; Nelson, Gordon L.; ACS Symposium Series; American Chemical Society: Washington, DC, 1990. 0.90 1.65 3.07 11.57 0.76 1.26 2.10 10.24 0.64 1.00 1.5Θ 10.18 0.58 0.89 1.35 9.76

Η θ C 0

fl

H Β C

fl

41

63

74

67

0.4Θ 0.Θ9 1.65 22. Θ6

Β C 0

•

Β C 0

θ C 0

fl

10

300

+

± ± ±

±

± ±

•

±

•

+

±

±

0.02 0.01 0.01 1.45

0.02 0.02 0.02 1.40

0.03 0.03 0.02 1.35

0.04 0.04 0.02 1.36

0.03 0.04 0.05 3.30

Rate ± S.D.

Method (1)

Crystal 1inity Index, '/.

(0..991) (0..997) (0..999) (0..986)

(0.,984) (0..993) (0..998) (0..987)

(0. 984) (0. 995) (0.,999) (0.,985)

(0. 974) (0.992) (0.999) (0. 988)

(0.965)

Effect of Crystallinity and Additives on the Thermal Degradation of

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