013132 1
U. S. Department of Agriculture, Forest Servic e
FOREST PRODUCTS LABORATORY
In cooperation with the University of Wisconsin
- "'-rn r
I
MADISON, WISCONSIN
'e-G‘-79
By L . F. HAWLE Y
Principal Chemist
an d
E . E . HARRI S
Associate Chemist
I
ti p •
'L
-!
v. .1 :
:it*
1= .
1
-1 c..''
t
11
_
Published in
1
[INDUSTRIAL
&
ENGINEERING
CHEMISTRY
_ 1
111 1 1
August, 1932
1 L
. .
.
r
[L
-I
1
I T
111
.4
I,
I
SYNTHETIC LIGGI N
By
L . F, Hawley, Principal Chemist
and
A . .~ Harris, Associate Chemis t
In 1931 Hawley and Niertelak (1) reported the chemical . ana1 W
of wood that had been subjected to a temperature of 135° C, for severa J
periods of time up to 8 days . The analysis showed a par.'-i.al decompoe ti.o n
of carbohydrates in the wood and the formation of a material (rough1 r
equivalent in amount) that was iso1ated along with the lignin . In orde r
to investigate this lignin-like material farther, it was prepared fro m
Cross and Bevan cellulose and was thus obtained unmixed with the lignin o f
the original wood . The results of that inveatigation i confirming and
extending the previous work, were presented t-t .t the Spring, 1931, meeting;
of the American Chemical Sodidty j but thdy were not publi .shod bedaus e
meanwhile Sherrard and harris (5) and Ritter, Seborg, and Mitchell (3) ha d
shown the possibility of serious error in the standard method used fo r
lignin determination . Instead of publishing, the researchers decided t o
repeat the experimental work, using the improved method for determinin g
lignin . Only the parts of the data from the first experiments that are
required for comparison will be presented here .
Heat Treatment of Cellulos e
In the present experiments large quantities of Cross and Beva n
cellulose were prepared from white spruce and sugar maple by the metho d
used in isolating the cellulose for its quantitative determination .
Fifteen-gram samples were sealed in glass tubes and heated in a pressure steam retort for 1, 2, and 8 days at 135° C . Duplicate runs were made ,
and, except in the few instances where a tube was broken accidentally, th e
figures in the table are the averages of two closely agreeing determinations ;
one from each duplicate tube . The slight gas pressure remaining in the
tubes after cooling was relieved by breaking an end of each tube unde r
water, and an approximate determination of the gas evolved was made . Thi s
gas was largely carbon dioxide, but under the conditions of the experiment
no significant quantitative figure could be obtained . The amount of wate r
formed during the heating can be calculated approximately from the differen . F
in moisture content of the samples before and after heati
The data in Table 1, when considered alone, indicate that th e
rate of the reaction with the spruce was much faster than with the mapl e
celluloses . This difference, however, is probably caused by something els e
than inherent differences between the species . In the previous work a
maple cellulose, prepared and treated in as nearly as possible the same way ,
gave 18 .8 per cant lignin in 8 days, while the softwood cellulose (loblolly
pine in this case) gave only 11,2 per cent . With any one lot of cellulose
the rate seems to be the same in all rtgi as is shown by the relation
bwWwwom p ipmriod of heat '
■rOmmi gr reaction, and the close checks i n
d.rplioateh Tae ; bite
OMOPOW46WW4JIf cellulose the rates may be vary
d fferc bs Lnall amo
probably exert a considerable
catalytic effect .
The later wo7is Moi confirhed the general conclusions of Hawle y
Wiertelak 1 regard
4#composition of the carbohydrates in wood .
The carbohydratlti are de•grO°with the formation of water-soluble an d
a cohol-b
do np1
,$dli tkmlt' 010-0414V are intermediate product s
l b 'm
t
. la 06 1[
dwood cellulose ,
l
t?~
. siOpsrst atiabbumarta
i ~rrr ie j L r
i to driummOm whether ul
other
rates msmOrd
stacker :41 t softwood
, hexosans wer e
4m
ed a
s eqQ rblil rlien.
ems.
%
IMNOMei.,ofe
, '+•' ,
agai
0;rp%ipt
carbo te s
ligni sola t MWqlp
-ti-tit-5,11.y i a'
by the hear reat
oaf
. Ntttt
one of
SNP-tile
ven .
obtain 11Wlwith wood
ainations of the
lignin is baser*.
core_
h the lignin
}'chose
by
AiM
in produced
alreac.
4i■`; 'tfU '
.01lulosel
i ►, 1s-violet absorption
..r
.. 'j
icular sample examined
ere for
Wt 401 , 104agibed in
i M
ea
per cent
erive d
uses ,,:
r
l
thod o thei r
les, af
i
thei r
e similar
c acid. Furtherm
p lated lignin s
s aft °~ tion in the same way
i= _ ..r' ~tly
wood
.
44
r-,k',g
e%
a
resis t
dissol
as ].i• ~+ . Bch is
■
Ritter, M 'c, 'f`
(2) have reeaf'tly shown that spruc e
lignin, put into solution by chlor' ,
on and sulfites, has a reducing
value which is 29 .5 per cent of that
n equal amount of glucose, and
that maple lignin had a reducing value
34 .5 per cent, Tr=y lignin isolated .
t1
R979
-2-
f~ O
O
150 M • O
LrM
N
N
N
150
'CO
N
150
N
~-
Ol
~9
\O
0
150
PEI
LLl 150
\.O
H
. -Ol
LO
O
Ol
Ol
LC")
N
Ol
Lfl M
N H r-I r- I
rn
H
R ,-A"
IFtk
I`
N
E
H
I
&.p
I
•
I
rn
tt
it
I
H O 0 LO
`O O
0
us,
r-I
I
k
O
F~
tt
•• •T
N
I t tt T T *} ft tt t• e•
t? tt t t t t
.•
VP
tt
tt
tt t ?
O O N O M
0
H Ol '60 O
O
O
C\
ro
N
O LCl N Ltl
N I~
O
N- LC! M LC\
H H H H 'O H
M
N
150
▪
ti
N
M N•
v
LCl H
M N
L`0
O
O
rl
In O
t.
..
O CO LO LC1
0 H H 150
t . •e
O
M•
N
Mt
1- 1
a)
24
i
F
•I-.I
1 7 +)
a) RH
a)
H
O
00
OF-1
C_)cd
F-10
-N
cd
1
+'
oP, o
rd
o
I
-d
0
cd
r-t
o
.O
to
O
0
O FaO F
l
Cl.!
,
0
▪
H
H
U
' ,r
1
II
;iu C
ti l.
11
-
.!
a
•p
0
~
1
-
I
l_
y
=
rr
6r ~,
"
I
.
from the -'
treatment, •c ,, ruce cellulose, when treated in the sam e
nner, , had a glucose eq•' tint, in reducing value, of 20 per cent ; t
411day maple lignin had q~e.. walent of 31 .0 per cent.. .
'f ; ,
can 'baoduc
L
}
'The material ptepar'ed at described contains no methoxyl but it
hvlated. Two methylations at 500 C . for 2 hours each gave a
7 .0 per cant of methoxyl, which is faD 1044
vale ' 10'
ha$ been obtained with natural lioni~n•t j), i. emptt f
+Obtain a higher degree of mc•thylatidn .
D37' lmtr 4i ree methods of charactecization,, the >rm a
¢tt
obtained in these experiments' has shown a close stmilaoitl to tile ii
obtained directly from wood, and the authors believe they atr--e justified
in calling it tt synthetic lignin.' At least they have PV -esd a .oiigct ,
that, in its basi_: chemical characteristics, •corx;esrpo rnds 0o ]tnin . Irk,
certain quantitat . : a respects the- corresponc-ence may no =t -be cc m,plete, ,
but this should be expected, not only from the va 'iabi]a.ty of
al'
lignins but also ~~- account of probable im ;:-urities, suck as iant.>s~meaia .t0 - r
or by-proms., in the synthetic product .
nattkI
c
It is intereSt4ng to note ow closely these exdp rimenta l
•
- 6fauth (4) on the constitti'on
{ hetical intermediate product between glucos e
to 5-hydroxymethyl fiirfural, 3 molecules of which
5imination df b molecules of Water to form a compound o f
r±ngs This bompoiknd contains three hydroxyl groups i n
antral six-carbon ring that require hydrogenation for their removal
has for the completion of the formation of a compound that account s
he chhe c . p w-sffteristics of lignin The ti',w ,ter•- pL e Anc Alcohol _
formed by the heat 4 compmg,ition
the
Schrauth.'s
hypothetical
n
ermedia
,
product
,
to
he
:„oughly
tea
Quo6
rrasponds
'•
ti no indi~ In the present pat$
s' pe'
tfiie~>1̀
s except :ithat carbon dioxide may be Po
' the
e amount of carbon dioxide, how+ -, l scient
Mira small part of this oxygen .
ell
. xeat interest ,
a li ;i3
.
It
y exardination
a trace o f
blysis with dilute
On acidification
tial precipitation takes pl e and a part of the
to chlorination and subsequent treatment wit h
asistant to chlorination may then be completely
L
dissolved in 72 per cant sulfuric acid . No conclusions are drawn fro m
such fragmentary data, but it is merely suggested that further study o f
I ;'PW this water-soluble material seems to offer an important new field fo r
research in the chemistry of both cellulose and lignin .
'aa
Although there are many slight qualitative differences to b e
noted between hardwood and softwood lignins, there are few well-define d
quantitative differences . Perhaps the most characteristic are in th e
ultra-violet absorption spectra and in the reducing number . It ha s
already been sho w " that the synthetic lignin made from hardwood cellulose ,
and evidently foracd largely by the decomposition of pentosan r-iits, ha s
an absorption spa, 7 -um and a reducing value that correspond closely to a
typical hardwood gnin, while the synthet c lignin made from a soft pl,)o d
cellulose, and ev? .ently formed largely from. hexo :an units, has a re racin g
value corresponding closely to a typical softwood lignin . (The author s
have not yet had opportunity to measure) the absorption spectrum of suc h
a sample .) This information leads directly to the hypothesis that th e
differences between natural hardwood and softwood lignins are due to th e
relative proportions of hexose and pentose units that have entered int o
their formation . This hypothesis will be developed further as the nex t
step in the reseaach on synthetic lignins . It should be readily possibl e
to prepare lignins from pure pentosans, pure hexosans, and known varyin g
proportions of the two, and thus to establish the relation between the
source and the characteristics of the product .
Literature_
Cite d
1. Hawley and Wiertelak, Ind . Eng . Chem . D. , 184 (1931) .
2 . R4 ter-, 11PI'V'im2l, and Seborg, paper presented before the Division o f
Cellulose Chemistry at the 83rd meeting of the American Chemica l
Society, New Orleans, La ., March 28 to April 1, 1932 .
3. Ritter, Soborg, and Mitchell, Ind . ng . Chem ., Anal . Ed., 1, 2
4. Schrauth, Z . angew . Chem .
36,
149 (1923) .
5. Sherrard and Harris, Ind . ring . Chem, 24, 103 (1932) .
6. Stare, Samib, and Harris, J . Phys . Chem .
R979
-5 -
36,
1574 ( 1932 ) .
(1932) .