The Cooking Process V. Cooking Wood with Sodium Sulfite S. I. AIIONOVSKY AND Ross AIKEN GORTNER,Minnesota Agricultural Experiment Station, St. Paul, iV' inn. REVIOUS reports h a v e shown that water alone (I), and a q u e o u s solutions ofsodium c a r b o n a t e (S), sodium sulfate (5), and sodium t h i o s u l f a t e (4), w h e n used as cooking agents, affect the various c o m p o n e n t s Of t h e wood i n a d r a s t i c m a n n e r . S o d i u m s u l f i t e , used in the here renortea. is ...... of .. ... ~. .-.. ..=. ~...~, . . the main cooking i n g r e d i e n t ~
~
Aspen sawdasl is cooked ut 170° and 186" C. for 2 and 12 hours With 23.8 and 47.6 per cent sodium su&te (based on the own-dry wood), equivalent, on the sodium basis, to 20 and 40 per cent sodium curbonate, respectiuely. More tola1 organic matkr. volatile oroanic acids [a " " acetic acid), pentosans, and reducing sugars are foun,d in these residual liquors than in those from the Correwonding water cooks. No lignin is found in the sodium sulfite residual 1iquor.s.
by the factor 2.0. The calculation of total organic matter by the method used in previous reports-i, e,, the suhtrsction of total soda as s o d i u m sulfate from the total dry matter in the liquors-wasnot suitable for the residual liquors from the sodium sulfite cooks. This was due t o the that a large portion of t,hn . ~sodiim .~ ~ . w. ... aomhind .. -....-wi61, the organicmatter in theliquors. ~~
~1
ess. It is also p r e s e n t , in
partially to compk,ely pulped, These residual woods contain less lignin (72 per cent sulfuric ucid method) but more pentosuns and cross and Renan cellulose than do those of the correspond;ng water cooks. TIE &stru&n of alpha-~ellulose at the higher kmperuture and longer duration. is hindered by the sodirm sulfite. Sadium sulflle is u strong pulping agent.
sodium combined as s o d i u m , sodium oxide, or sodium sulfite were unlinown, The organic was determinediy the "wet comhustion" or chromic acid method as o u t l i n e d b y Gortner (6). €le s h o w e d t h a t the ratio of humus matter to its carbon content was 2 to 1, and the same ratio waa approximately correct for peat and unchanged vegetable materials. The ratio of aspen sawdust to its carbon was found to be 2.04 to 1 (Table IV). The ratios of the sums of the lignin (basis C,&On), pentosans, volatile acids (as acetic), and reducing sugam of the rosidual liquors of the sodium sulfite cooks, to the sums of their organic carbon contents averaged about 2.3 to 1. The sums of these components, however, account for only about 50 per cent of the total organic matter present. It was therefore considered that the factor 2.0 was probably RESIDUAL LiQuons the more accurate figure to use in calculating the total organic The residual liquors from the sodium sulfite cooks were matter of the residual liquors from thcir organic carbon conclear, orange-red to dark red when hot, and reddish brown to tents. The quantities of total orgaiiie matter (as calculated from brown-black and turbid when cold. Small quantities of light colored solid matter separated out upon standing. This the total organic carbon) found in the residual liquors of the solid matter was readily and uniformly dispermd in the sodium sulfite cooks are given in Table I and shown graphiliquor upon shaking. a l l y in Figure 1. The a d d i t i o n of 23.8 per T h e liquors f o a m e d cent of the salt to the readily, but t h e foam disappeared q u i c k l y water caused large in911 of the liquors were creases in the amounts alkaline t o litmus of o r g a n i c m a t t e r paper with the excepfound, these increases tion of ttint from cook being greater for the 74 (12 hours, 180" C., longer d u r a t i o n s of 23.8 per cent sodium moking. Doubling the s u l f i t e ) w h i c h >>as a m o u n t s o f sodium neutral to litmus. sulfite yielded l a r g e r T O T A LO R G A N I C quantities of o r g a n i c MATTER. The t o t a l matter, but these inorganic matter in the creases were not twice residual liquors of the those o b t a i n e d with s o d i u m sulfite cooks the lower salt concentrations. The increase was d e t e r m i n e d by in cooking temperature multiplying the t o t a l o r g a n i c carbon confrom 170" to 186' C. tents of these liquors PAPER MACHINE(204-1~CR), NonTHwEST PAPER COMPANY, CLOQUET, Ml". also caused increases in varying a m o u n t s , i n liquorb used in the m a n u f a c t u r e nf sulfate or Kraft rtolu. E i g h t c o o k s w e r e run at 170" or 186' C. f o r 2 o r 12 hours c o o k i n g duration; c. P. crystalline sodium sulfite, containing 07.0 per cent sodium sulfite and 2.7 per cent sodium sulfate, was used. The sodium sulfite was used in quantities equal to 23.8 and 47.6 per cent of the weight of ovendry wood, equivalcnt, on the sodium basis, to 20 and 40 per cent sodium carbonate, respectively. The wood used (100.0gramsair-dfyequals90.0grams oven-dry) was aspen sarddust from t.he same batch described in the previous reports. The analytical results given are the means of a t least two determinations.
.
1349
1350
IKDUSTRIAL AND ENGINEERING CHEMISTRY
1'01. 23, No. 12
TABLEI. YIELDSOF RESIDCALWOODSAND TOTAL ORGANICMATTERI N RESIDUAL LIQUORS~ TOTALORG.4NIC MATTERIN RESIDUAL LIQUOR RESIDEAL WOOD (ORGANIC CARBONX 2) On basis On basis original original NazS03 ADDED oven-dry oven-dry COOK TIME TEMP. TO DIGESTER Keight wood Weight wood Hours Grams Grams % % Grams 13 2 170 H20 onlyb 63.7 70.94 19.21e 21.39 2 170 70 21.4.: 62.0 68.89 25.24f 28.04 72 2 170 42.W 60.5 67.22 28.32/ 31.47 16 12 170 HzO onlyb 61.8 68.82 14.98 16.68 71 12 170 21.4 54.3 60.33 31.56 35.07 73 12 170 42.8 50.8 56.44 33 34 37.04 17 2 186 HzO onlyb 61.6 68.60 16.31 18.16 76 2 186 21.4 55.2 61.33 28.40 31.56 77 2 186 42.8 52.6 58.44 31.80 35.33 21 12 186 H20 onlyb 54.5 60.69 15.90 17.71 74 12 186 21.4 46.0 51.11 34.48 38.31 75 12 186 42.8 40.2 44.67 45.18 40.66 a 90.0 grams oven-dry wood (100.0 grams air-dry) were used in each cook. b 89.8 grams oven-dry wood (100.0 grams air-dry) were used in cooking with water only. c 23.78 of wejght of oven-dry wood used and equivalent, on sodium basis, to 20% Na2SOs (Hz0 3350 grams). d 4 7 . 5 6 F of weight of oven-dry wood used and equivalent. on sodium basis. to 40% NazC03 (Hd. 3350 erams). o Total.organic matter in water cooks includes furfural from digester condensate. . ' - ' !Total organic matter in sulfite cooks was determined by multiplying total organic carbon content of liquors by 2.
c.
t
-
MATERIAL UNACCOUNTED FORB Y a4NALYSIS On basis original oven-dry Weight wood Grams % 6.9 7.67 2.8 3.07 1.2 1.31 13.0 14.50 4.1 4.60 5.9 6.52 11.9 13.24 6.4 7.11 5.6 6.23 19.4 21.60 9.5 10.58 9.1 10.15
I -
~
TABLE
11. DISTRIBUTIOS OF SALTS
-CHEMICALS
Coox 70 72 71 73 76 77 74 75
TIM& Hours 2 2 12 12 2 2 12 12
TEMP. a C. 170 170 170 170 186 186 186 186
NatS03 Grams 21.4 42.8 21.4 42.8 21.4 42.8 21.4 42.8
ADDEDTotal aa NazO (1) Grams 10.84 21.63 10.84 21.63 10.84 21.63 10.84 21.63
NazSOt Grams 0.7 1.3 0.7 1.3 0.7 1.3 0.7 1.3
IN ORIGINAL AND RESIDU.4L
SALTSAS SUCHFOUNDI N RESIDUAL LIQUOR NazSz03 NazSOr Grams Grams Grams 3.02 0.95 3.66 3.10 3.61 19.97 0.50 1.26 2.39 11.88 1.53 3.31 1.80 0.64 1.88 18.07 2.86 1.01 0.46 0.77 1.29 4.16 3.21 2.32
NazsO3
the yields of organic matter, these increases being more pronounced for the 12-hour cooks. Table I shows that cook 75 (12 hours, 186" C., 47.6 per cent sodium sulfite) yielded a quantity of organic matter equal to 45 per cent of the original dry wood and larger than the yield of pulp obtained. DISTRIBUTION OF SALTS. The residual liquors were analyzed for the sulfite, thiosulfate, sulfide, and sulfate radicals; results are given in Table 11. It is apparent from these data that the amounts of sodium sulfite, used up or converted into other compounds in the cooking process, increased with the quantity of this salt added, and with the temperature and duration of cooking. When the sodium sulfite was increased from 23.8 to 47.6 per cent of the dry wood, larger quantities of the salt were used up, but the relative proportion used was smaller. An increase in the quantity of sodium sulfite in the white liquor caused an increase in the sodium thiosulfate formed, the other cooking conditions being the same. The total amounts of the thiosulfate formed were small, however, except in the case of cook 7 2 ( 2 hours, 170" C., 47.6 per cent sodium sulfite). The quantities of sodium sulfate found in the residual liquors were fairly small. They decreased somewhat with increased time of cooking, but increased when the temperature was raised from 170" to 186" C., the other cooking conditions being held constant. No sodium sulfide was found in these liquors. The quantities of sodium combined with organic matter were rather high, generally, and increased with time and temperature of cooking and with increased concentration of sodium sulfite. It appears from these data that a large proportion of the sodium sulfite, as such, was removed from the solution very rapidly in the first part of the cooking process by the wood itself, and that the remainder was removed or changed, as needed, by the products formed during the process. IRON REMOVED FROM THE DIGESTER WALLS. Owing t o the alkalinity of the liquor and the excellent circulation obtained
LIQUORS
TOT.4L SALTSAS NatO (2) Grams 3.46 12.63 1.78 7.89 1.96 10.54 1.09 4.36
Nag0 COMBINED XITH ORQANIC MATTER. .~ ...~ ~. (1) MINUS (2) On basis original Weight Nad3 % Q&i* 7.38 68.1 9.00 41.6 9.06 83.6 13.74 63.5 8.88 81.9 11.09 51.3 9.75 89.9 17.27 79.8
Fez03 FOUNDI N LIQUOR Gram 0.13 0.14 0.08 0.15 0.05 Trace 0.11 Trace
by rotating the autoclave during the cooking period, the amounts of iron found in the liquors were very small, as shown in Table 11. LIGNIN. As shown in Table I11 and Figure 1, surprisingly low quantities of lignin (72 per cent sulfuric acid-insoluble) were found in the residual liquors of the sulfite cooks. These quantities are nearly within the experimental errors of the lignin determination. In order to find whether or not these results came about through some error in the analytical procedure, these determinations were repeated and yielded like results. Furthermore, lignin determinations run a t the same time on the residual liquors obtained by cooking with sodium sulfide, hydroxide, and phosphate yielded copious quantities of lignin, showing that the low lignin content of the sodium sulfite liquors is peculiar to these liquors. The sodium sulfite apparently combined with the lignin in solution to form compounds soluble in 72 per cent sulfuric acid. The pentoses and pentosans PENTOSES AKD PESTOSANS. (calculated together as pentosans) in the residual liquors of this series of cooks were larger in quantity than those found in the liquors of the cooks made with water only, under similar cooking conditions, with the exception of the 2-hour, 170" cooks (cooks 70 and 72), which yielded somewhat lower quantities of pentosans than the corresponding water cooks. These data are shown in Table I11 and Figure 1. Changing the quantity of sodium sulfite from 23.8 to 47.6 per cent had but little effect on the pentosans in the liquors. The increased time and temperature of cooking caused a decrease in the pentosans. The quantities under consideration, as shown in Table 111, were relatively small. TOTAL REDUCIKG SUGARS.Before analysis for reducing sugars, these residual liquors were hydrolyzed by boiling 2 hours in a 2 per cent hydrochloric acid solution in order to remove the sulfite and thiosulfate ions. The hydrolyzed liquors were then neutralized with calcium carbonate, clarified in the usual manner, and analyzed for reducing sugars by
December, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
the picric acid method. The clarified liquors contained none of the above ions. The quantities of total reducing sugars found in these liquors were greater, with the exception of those of cooks 3 70 and 72, than those found in the liquors of the corresponding water cooks. The addition of sodium sulfite apparently caused a decrease in the hydrolysis of pentosans and hexosans " and also prevented to some extent the destrurtion or degradation of the reducing sugars after they were formed. ! z Doubling the amounts of sodium sulfite used caused a slight decrease in the reducing sugars, except in cook 7 5 , in which * case the increase TTas probably due to the large quantity of organic matter present in the liquor. An increase in the / time of cooking caused a slight lowering in the yields of reducing sugars. The temperature increase from 170" to 186' C. had little effect upon the reducing sugars in the liquors from the 2-hour cooks and caused a slight decrease in the 9 Ne. SOJ reducing sugars obtained in the 12-hour cooks. Coohinp Z-*-2 Hn Coohog 5-p VOLATILE ORGANICACIDS. As shown in Table 111 and 40 Figure 1, the yields of volatile organic acids (calculated as acetic) obtained in these cooks were three to five times as 35 large as those obtained in the corresponding water cooks. .4n increase in sodium sulfite from 23.8 to 47.6 per cent re- 3o sulted in increased yields of volatile acids, but the increases zs were not proportional to the salt increase. In regard to the 5 time and temperature of cooking, these acid yields showed zo remarkably little fluctuation, with the exception of the 2- i hour, 170" C. cooks. The curves in Figure I show that, as in I the case of sodium carbonate, the mechanism of the formation of volatile organic acids is mainly one of saponification. 10
1331
- LjJ"!" - pe,,'cse"s
'
Ac
"d"f,/C
9No2 SO, -170'C
C 0 o k " 9 ~ r n .- / 2 H r ~ C.-o&n,
Trmp -17o'C
90
3s
M /
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, IO
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1
DIGESTER COXDENSATES The digester condensate liquors were neutral to litmus paper and varied in color from almost water-white to light orange. Thev were all turbid. and thev all had a slight mercaDtan odor. Littie or no free sulfur was found in these-liquors. Tests for furfural gave negative results. A
RESIDUAL WOODS The residual woods from the sodium sulfite cooks were lighter in color than any of the residues previously obtained in this series of cooks. The pliancy of the reeidual woods was similar to that of the sodium thiosulfate pulps. The residues from cooks 70 and 76 were softened considerably but not pulped. Cooks 72 and 77 yielded residues which were still in sawdust form, but they could be easily pulped, when moist, by rubbing between the fingers. The residues from cooks 73-75 were completely pulped while that from cook 71 was semi-pulped. TABLE111.
Coos
TIME
1,
TEMP.
",rm. FIGURE TOS.4NS,
+Ne,
cwl( "p
Grams 5.77 0.08 0.23 4.29 0.19 0.33 4.95 0.15 0.39 5.10 0.19 0.11
- /86'c
a cl.i
V* Ne, 50, Co.4,.p Trr
476 "~Fc,
,s,.c
1. YIELDS OF TOTAL ORGANICMATTER,LIGNN, P E N REDUCING SUGARS, AND VOLATILE ORGANIC ACIDS(AS ACETIC)IN RESIDUAL LIQUORS
All data based on original charge of 100.0 grams sir-dry (90.0grams ovendry) aspen sa,wdust: zero per cent sodium sulfite represents results obtained by cooking with wateronly.
The yields of residual woods and pulps from the sodium sulfite cooks are shown in Tables I and IV and Figure 2. These yields were, in all cases, lower than those obtained by cooking with water only. The addition of 23.8 per cent sodium sulfite caused lower yields than those obtained with water only and doubling the salt quantity caused a further decrease in yield, but this decrease was not double that obtained with the lower salt concentration. An increase in the
TOTAL LIQNINI N ORQANIC RESIDUAL LiauoR MATTER On basis (ORGANIC original NazSOs ADDED CARBON oven-dry TO DIGESTER Weight wood x 2)
Grams 19.21 25.24 28.32 14.98 31.56 33.34 16.31 28.40 31.80 15.90 34.48 40.66
z3
50,
TOTAL ORGANIC MATTER,LIGNIN,PENTOSANS, VOLATILE SUGARS IN RESIDUAL LIQUORS
c. Grams 13 170 H20 only 70 2 170 21.4 72 2 170 42.8 16 12 170 HzO only 71 12 170 21.4 73 12 170 42.8 17 2 186 HzO only 76 2 186 21.4 77 2 186 42.8 21 12 186 Hz0 only 74 12 21.4 186 75 12 42.8 186 Calculated together a8 pentosans. Calculated a8 glucose. Hours 2
a
YIELDS OF
,,
% 6.43 0.09 0.26 4.78 0.21 0.37 5.51 0.17 0.43 5.68 0.21 0.12
ORGANIC
ACIDS,.4ND
TOTAL
REDWING
PENTOSES AND VOLATILE ORQANIC TOTALREDUCING PENTOIANBa I N ACIDS(AS ACETIC)IN SUGARSb I N RESIDUAL LIQUOR RESIDEALLIQUOR RESIDUAL LIQUOR On basis On basis On basis original original original oven-dry oven-dry oven-drg Weight wood Weight wood Weight wood
Grams 5.12 4.02 4.12 0.60 3.68 3.28 0.75 4.88 3.74 0.54 1.26 2.63
% 5,io 4.47 4.58 0.67 4.09 3.64 0.83 5.42 4.16 0.60 1.40 2.92
Grams 1.77 4.54 5.36 1.58 5.02 6.52 1.34 5.80 6.55 1.60 5.06 6.57
% 1.97 5.04 5.96 1.76 5.58 7.24 1.49 6.44 7.28 1.78 6.62 7.30
Gams 11.33 5.28 4.38 2.35 4.78 3.72 4.47 5.38 5.24 2.83 2.80 3.49
% 12.62 5.87 4.87 2.62 5.31 4.13 4.98 5.9s 5.82 3.15 3.11 3.88
I N 0 U S T R I A I,
1352
A N D
OF LIGNIN,PENTOSANS, CELLULOSE, AND ALPWA-CELLULOSE AND TABLX~ IV. YEELDB IN
Coo=
Tim Houri
Original wood 13 70 72
.. 2 2
16
71 73
2 12 12 12
17
2
76 77 21 74 75
2 2 I2
TEIIP. ' C.
...
170 170 170 170 170 170 186 186
12
IS6 186 IS6
12
IS6
REslnunL
....
21.4 42.8
w*oOnly 21.4 42.8 Ha0 only 21.4 42.8
REsmrnr.
WOODTO CARBON RATIO,
WOODS
Ne,SOs Aooeo R m s i o a ~ Rstio ~ residual TO D ~ S S T B R WOOD wood t o osrbun Gr0"kS Grama 80.0 2.04 H,O ooly 63.7 2:is 21.4 62.0 60.6 2.30 42.8 €110 0"lY
Vol. 25, No. 12
E N C I V E :F K I N G C I1 E M I S T 11 Y
61.8
54.3 50.8 61.6 55.2 52.6 54.5 46.0 40.2
2:33 2.33
IN R n s i o a ~WOOD ~ Lignin
2:29 2.27
Alpha-
GVZrnS
GTWI8
GIOM
cellulose Grams
22.80 17.79 9.1s 7.69 17.97 4.95
15.29 2.75 s.63 8.64 1.40 7.15 6.69 1.56 7.37 7.22 0.21 3.77 4.50
56.39 44.23 51.65 51.69 42.40 48.92 47.53 42.68 49.80 47.68 34.87 42.73 39.23
41.90 37.68 36.42 38.13 34.11 33.10 31.15 35.40 32.62 30. so 22.49 30.83 30.10
3.22 17.70 5.08 3.93 18.66 3.30
2:31 2.29
Cross and Pentossns Bevan oellulose
0.86
time arid temperature of cooking caused further decreases in to carbon ratio of 2.02 to I, while the w e t cornbustion proresidual wood yields. The yield of pulp obtained in cook 75 cedure gave a ratio of 2.04 to 1. v a s lower t,han the amount of organic matter dissolved in the liquor, and it is lower than the yields obtained by cooking TABLE V, MA,N CoMPoNENTs aspen chips with 40 per cent sodium sulfite on a commercial DEBTEOYED IN COOKING PROCESS, NOT AC~OUNTED Fox IN ANALVSISOF RESIDUAL WOODS AND LIQUORS scale. However, the cooking conditions employed for this particular cook were too drastic to warrant a good yield of (All figureson bsaia of these oomgnnenta in original wood) P%RCENTI(IBOF O m o r K * L CorrsTlTusnTB pulp. NOTA c c o n r ~ ~Fom DI ANAIZBTB CIOSS In this series of cooks, with the concentration of sodium and sulfite held constant, cooking for 12 hours at 170' C. yielded Revan AlphaNmSOa Aooao TO aellu- eenupractically the same quantity of pulp as that obtained hy T,MH TEMP. DIoaapEa Wood I,sntonsns cooking for 2 hours a t 186" C . In other words, increasing the rruura c. Grama % % % % % temperature of cooking from 170" to 186' C. is equivalent 13 2 170 w,Ooniy 7.67 1.01 50.06 20.62 S.75 to a saving of 10 hours in cooking time at the lower tempera;:: ::: :!E i::! ture. 170 LIsOonIy 14.60 6.47 87.31 23.90 17.35 16 12 The percentage losses of wood in the cooking process arc 71 12 170 21.4 4.60 77.26 29.17 13.26 21.00 42.8 6.62 84.89 34.79 16.73 25.66 73 12 170 given in Tables I and T', and shown graphically in Figure 3. These values were obtained by subtracting the sums of the $: wa$p;'y ;!:$! residual w6ods plus the total organic matter in the liquors 77 2 186 42.8 6.23 80.88 28.32 16.46 26.49 from the quantities of the original wood charged into the 21 12 186 H , o ~ 21.60 ~ ~ 0.59 ~ 96.24 37.42 46.61 autoclave. These l o w s were, in all the cooks of this aeries, zi :g:Z :$:; :$:$ the sole lower than t,hose suffered when water was used cooking agent. In fact, these losses were lower than any found in the whole series of cooks which had been reported to The ratios of wood to carbon (Table IV) are somewhat date. An increase in the time and temperature of cooking larger in the residual woods than in the original wood, but tended to increase the loss of material in the cooking process, they are practically constant for all the residual woods. The larger v a l u e s b u t d o u b l i n g the f o u n d for the requantity of sodiuni s u l f i t e h a d , apsidual woods a r e mainly due to their parently, very little lower l i g n i n coneffect. TOTAL ORGAXIC t e n t s , since t h e CARBON. T h e ratio of l i g n i n to its c a r b o n (using total organic carbon c o n t e n t s of t h e C,oHioO,, coniferyl a l d e h y d e , as the original a n d reb a s i c l i g n i n subsidual woods were stance) is 1.48 to 1. determined by the chromic acid The ratios of cellumethod, previously lose (CaHIoOs)and described. The acpentosans (C&O,) to their carbon concuracy of the methtents arc 2.25 to 1 ads for this purpose and 2.20 to 1, rewas checked by determining the total spectively, l o w e r organic carbon than those f o n n d content of t h e for t h e r e s i d u a l woods from the sooriginal w o o d , by dium sulfite cooks. m e a n s of the Parr pe r oxi d e combusSmall amounts tion procedure. Courrcw ol Norfhwest Paper Cornpaw of o x y c e l l u l o s c The l a t t e r method kn"rIAL BOOKANI) WRITlNG PAPEn [CloH,X). or Cl0HsO6 (6)l having a wood laom in right baokground i i oonneoted to the mill proper by B chip oonveyoz. y i e l d e d a wood 0
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December, 1933
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1353
0 -Ly.* %, - h h d ratio of 2.47-2.44 to 1 may, h o w e v e r , be @ - o(-C e / / u / o s r 0 -P.of~s."r 0 -cJf"l.ase present in the residual woods and would thus ;100 tend to raise the wood to carbon ratio of these B ;eo woods above that of cellulose. LIGNIN.Cooking with sodium sulfite re$. 60 sulted in pulps with much lower lignin con2. z> 40 tents than was the case in cooking with water only. Increases in the concentration of the 2 salt from 23.8 to 47.6 per cent of the wood, 34 20 and in time and temperature of cooking, de* creased the quantities of lignin in the residual 3 -/.NO~V,sO3 NOJO, pulps. These data are shown in Table IV Cookmy & e - 2 tfn. Cooh:,?p 7imp -170-C. C w & y 7;n. 4.2 Hrs. Ceolmy Gmp. -17O.C. and Figure 2. There is, apparently, a good 2 100 correlation between the pliabilities of the ret sidual woods and their lignin c o n t e n t s , the Y 80 better pulps containing less lignin. The above -? : data also show that, keeping the cooking time 2 60 and temperature constant, the decreases in 5 the yields of residual woods, with increasing salt concentration, were due largely to t h e d -8 PO loss of lignin. In comparing the lignin contents of these residual woods (Table IV) with h 3 the amounts of hydrochloric acid formed dur./.No250, +Na.50, ing chlorination of the woods (Table VI) it C a o l m y Tmc 2 H.3. Cooht-9 T;-p.- 186.C. COO!..^^ i h C a d t F p GmP -186'C. is interesting to note the high correlation beFIGURE 2. YIELDS OF RESIDU.4L W O O D AND ITS COMPONENTS tween these values. All data based on original charge of 100.0 grams air-dr (900 grams oven-dry) aspen The sodium sulfite has, apparently, a more sawdust; zero per cent sodium sulfite represents results ottained by cooking with water only. selective solvent or peptizing action upon the lignin than any of the chemicals used in the previous series of cooks. The quantities of lignin destroyed, the wood, varying from about 2 to 14 per cent of the weight or rendered soluble in 72 per cent sulfuric acid, in these sulfite of wood. This substance was shown to be insoluble in 72 cooks were considerably higher than any found heretofore. per cent sulfuric acid and was therefore considered to be a part The losses of lignin increased with increasing concentration of the lignin fraction. It was assumed, owing to its solubility of sodium sulfite used for cooking and with increasing time in alcohol, acetone, and glacial acetic acid and to its acidic and temperature of c,ooking. nature, to be composed of partially depolymerized lignin or The extraction of the residual woods with the benzene-alco- lignin acids. This substance was not present in the sodium hol mixture throws further light upon the reaction between sulfite residual woods, for these woods, instead of suffering a sodium sulfite and lignin (Table VI). I n all the previous loss in weight upon extraction, showed a slight but definite cooks, extracting the residual woods with the benzene-alcohol gain in weight. The sodium sulfite, therefore, either dismixture resulted in a dark substance being removed from solved or peptized the lignin out of the wood prior to breaking it down k rendering it soluble in 72 per cent sulfuric acid, or, what is more likely, it reacted with the depolymerization products formed by the action of water on the lignin. The gain in weight of the residual woods upon extraction with the benzene-alcohol mixture may be due to adsorption of the alcohol or adsorption and subsequent polymerization of the acetaldehyde formed from the alcohol. Extraction of S. and S. KO.595 filter paper resulted in a gain in weight of 0.71 per cent. PENTOSANS. More of the pentosans were retained by the residual woods of the sodium sulfite cooks than by those of the water cooks, I00 as shown in Table IV and Figure 2. In the IW case of this constituent the effects of sodium 2 80 80 sulfite and sodium carbonate were about the same, except in the 12-hour, 186' C. cooks (74 em 60 and 75), the residual woods of which contained 6 less pentosans than those of the correspond40 40 ing cooks of the sodium carbonate series. The 2 quantities of pentosans remaining in the so20 20 dium sulfite residual woods decreased slightly ct with the increase in temperature and somewhat 0 23.8 426 more with the longer time of cooking, but doubling the quantity of the salt had very FIGURE3. PERCENTAGE OF ORIGINAL COMPONEVTS OF WOOD DESTROYED little effect. (NOTACCOUNTED FORBY ANALYSIS)IN COOKINQ PROCESS The amounts of pentosans destroyed were Zero per cent sodium sulfite represents results obtained by cooking with water only. considerably less for this series of cooks than c/o
%
.
:
. .
"T.l-i;l-1-.i
I S U li
I 3 2
S T II 1 A I. h N D E N G 1 N E
~i-lreirwater or the . d f a t eur thiosulfate oi sodium were used :is t h e c o o k i n g :agents. These data lire g i v e n in Table 1' arid F i g u r e 3 . T h e losses of pentrisans increased \vitli iucreased time and t e i n p e r a t itre o f cooking. T h e i n c r e a s e in sodiuni sulfite froin 23.8 to 47.0 prr cent of tlre wood c a u s e d i n creased destruction of pentosans except in the c a s e of the? 12-liour, 186" r. c o o k s . The compar a t i r e 1 y I (in :amounts of n e n tosans destroyed are prohal>ly due, in this series of cooks, to the inliihiting itct,ion of the alkaline -odium sulfite upon the hydrolytic effectsof the water. CELLULOSE.The Cross and I k r m celluluses in these residual woods are given in Tahle I V and Figure 2. Milch more cellulose remained in t,he residual woods of tire sodium sulfite cooks tlian in those ohlained hy cooking with water (~nly. Increasing tlie time and teoqmatlsre of cooking caused lower yields of Cross and Bevan cellulase. 1)ouhling the salt concentration cawed a small decrease in cellulose yield in the cooks made at 170' C. and a larger one in tlie 18V C . cooks. Tile sums oi the cellulose and lignin in the residual woods of these cooks comprise practically 100 per cent of these woods, showing that the pentosans remaining i n the pulp,? are held in 11stable associatioil with the cellulose.
vrood
..
.,.
....
1.87
2J.97
18.!17
l2.iY.l
I:J
2 2
170 170
tiiOoi~ly
8.82
lS.25 9.71 7.87
6.84 7.50 6.511
11.4!1 1.93
6.90 4.80
8.1111
4.88
4.11
13.7s 20.48 1.31 7.18 42.8 t0.22 3.29 pain i n weight """0 oxirilrti',,,
s:in7
7.30
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170
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42.8
+(La2
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2
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tlsOririly
2
2
180 186
21.4 42.8
11.48 t0.211
18.39 10.73
Pi
12
74
12 1%
180 180
70 72
17
!p
75 '8
PLUS
2
180 sigma i,,dica,e
112Ooniy 21.4
h
f0.18
The losses of Cross and Bevan celliilose suffered in t,he cooking process are given in Tahle V and Figure 3. It is apparent that sodium sulfite had less effect on tlie cellolose than any of the cooking age& discussed in the earlier report,s. Here, too, an increase in temperature of 16' above 170" C. is eqnivaleiit to 10 hoors of cooking tinre at the lower teniperatiire. AL~'HI-C~I,I,L'L~SF:.The quantities tif alpha-cclluloaa reirlaining in the residnal woods are given in Tahle IV and
I C II 1 N
ti C ti E hl 1 S T R
Vol. 25, No. 12
\t
Icigiire 2. The add i t i o n of 23.8 per cent sodiuiir sulfite to tlic water resulted in bot little change in the alplia-cellulose y i e l d s of the l i 0 " C. cooks or of the !&hour, 186' C. cooks, showing only a slight decrease in y i e l d s Ironi those olrdained hy c o o k ing with water only. In the case of tlie l z - h o u r , 186" C. cooks, however, tlie s o d i u in s u ISi t e caused a d e c r e a s e i n t h e destructive action of water on the aluha-cellulose.
resulted in sliRlrtly siiinller quantities of alpha-cellulose remaining in tlie residual woods. The increase in time opcookins decreased the alplra-cellulose yields a t 170" C . but showed no apprecialrle effect. a t 186" C. The higher cooking tcmperatores resulted in nornewhat lower alpha-cellulose yields. The percentage losses of alpha-cello lo^ in cooking with aqueous solutions of sodium sulfite arc shown in Table V and Figure 3. It is apparent Sroin the above data that sodiuni sulfite had less destructive effects upon t.he alpha-cellulose than any of the salts previously used in the earlier studies of this series. The values found for cooks 74 and 75 indicate that tlie sodium sulfite liad an inhibitive action upon the conversion, by water, oi allha-cellulose into cclhloses soluble in 17.5 per cent sodiiini Irydrotiide, the so-called beta- and gamma-cellulases, l~urtlierrnore,i n tlie cooks run a t 186' (:. with 4 i . 6 per cent sodiuni sulfite, the increase in cooking time froin 2 to 12 Irours had no appreciable effect on the alpha-cellulose. The data indicate that, under the cooking conditions employed in this investigation, the maximum destruction or oonversion of alplia-cellulose, using aqueous solutions OS sodium sulfite as the pulping agcnts, was about 28 per cent of the alphacellu1o.e present in t,lie original wood. LITERATURE CITED (1) Armovaky arid Gortncr. Iva. ENS CH~M.. 22, 261 (1830) ('2) Ibid.. 22, !].+I (1'330).
(6) Scliorsor. "Cheiilidry o I Collulose anJ Wood," p. 233. McGrawHill, 1'326. l t s ~ e i v ~July o 20. 1035. Presented before the Diviaion 01 Celluioee CliernIstry nt tlio 84th Meeliox 0 1 Lhe American Chemical Sooiety. Denver, Colo.. August 22 l o 26. 193% Publinlmd riLh the s p ~ m v a lof the director as Paper No. 1187, Journal serios. MiiineJoth Agricultursl Experinlent StsLi"". S . I. hmnovsky is Lhe Cloqiiet Wood Priiducta Foiiow, Uniwrsity of M i n n e ~ iotr: 1 . i ~ iellorship was established by tho Noit,hreat Paper Cornoniiy d l:l"lueL, Mi,>,>. ~~~~
Correction tha irrtieie "Tlir Drying of Solids. VI" [INu. I k + . CHEM., 25, 1134 (1933)1,the lirnit,s on the first iritegrnl sign of Equation 2 should be 0 to 2 R irisread of 0 to I?. !,I
