April, 1928
INDUSTRIAL AND ENGINEERING CHEMISTRY
371
Furfural and Carbon Dioxide from Wood before and after Chlorination‘ George J. Ritter and L. C. Fleck PRODUCTS LABORATORY, MADISON,WIS. U. S. FOREST
T IS generally believed that cellulose is modified to form oxycellulose during its isolation from wood by the Cross and Bevan method, The purpose of the study here reported was to secure, by means of furfural and carbon dioxide determinations, evidence for or against such oxycellulose formation. The determination of oxycellulose is based on the theory, confirmed by experimental data reported by HibbertZ and Heuser,3 that on treatment with boiling hydrochloric acid oxycellulose decomposes into furfural, carbon dioxide, and water in fixed proportions, in a manner similar to that of uronic acids. Under the same treatment pentosans decompose into furfural and water. Presumably, then, if oxycellulose is formed during the isolation of cellulose from wood it may be measured by determining the increase in either the furfural or the carbon dioxide from the chlorinated wood as compared with the amounts of the same materials obtained from the original wood. I n the present study, however, it was decided to determine both furfural and carbon dioxide in order to obtain a surer check on the nature of the reaction. Plan of Work
I
The material for study was air-dried catalpa sawdust passing an 80-mesh and retained on a 100-mesh standard sieve. The furfural from (1) the original sawdust, ( 2 ) the sawdust after extraction with alcohol-benzene solution, (3) the alcohol-benzene extracted sawdust in various stages of chlorination and extraction with sulfite, and (4)the sulfite extract itself was determined by boiling with 12 per cent hydrochloric acid and precipitation with phloroglucinol (Tollen’s method). Furfural yields were in all cases converted to pentosan equivalents and the results expressed as percentages of the oven-dry weight of the original sawdust sample. The carbon dioxide from materials (l), (2), and (3) was determined by absorption of the gas in an excess of standard barium hydroxide solution, and titration of the excess barium hydroxide. The comparison thus afforded would indicate whether furfural-yielding bodies additional to those in the original sawdust are formed or removed by the alcohol-benzene extraction, by the chlorination, or by the sulfite extraction. The apparatus used was a modification of that described by Heuser and S t i i ~ k i g tredesigned ,~ in such a manner that the furfural and carbon dioxide, from the same sample, could be determined a t the same time. Results Table I affords a comparison of the furfural (converted to pentosans) and carbon dioxide from the original and the extracted wood. It is clear that the alcohol-benzene extraction has no effect on either the furfural-yielding or the carbon-dioxide-yielding materials. A very large percentage, a t least, of the furfural (converted to pentosans) Presented under the title “Comparison of Furfural Yields from W o o d before and after Chlorination” before the 72nd Meeting of the American Chemical Society, Philadelphia, Pa., September 5 to 11, 1926. Received October 13, 1927. 2 J . SOC. Chem. I n d , 442, 475T (1925). 3 Ceiluloscchemie, 3, 61 (1922).
recorded in the table is the decomposition product of the pentosans in the original wood. Whether the material which yields carbon dioxide also yields some of the furfural was not determined in this study, but results recorded in a paper by O ’ D ~ y e rwho , ~ studied the decomposition products of wood from a different point of view, suggest that the carbon dioxide is a decomposition product of uronic-acid-like materials in the wood. If that be the case, approximately 3.4 per cent uronic acid (4 X 0.86), which is equivalent to 2.6 per cent pentosans (3 X 0.86), would be subtracted from the pentosan values shown in the table to obtain the true percentage of pentosans in the original wood. Table I-Carbon Dioxide C o n t e n t a n d Furfural Converted t o Pentos a n s in Wood before a n d after Chlorination (Percentages based on oven-dry weight of original wood) PENTOSANS CARBON DIOXIDE Per cent Per cent 22 6 0 86 Original sawdust 22 4 0 86 Alcohol-benzene extracted sawdust
The next step in the investigation was to complete the delignification of the wood by successive chlorinations and sulfite extractions and to compare the amounts of furfural and carbon dioxide from the residue a t the various stages. The results are recorded in Table 11. Carbon-Dioxide-Forming Material A material which liberates carbon dioxide as a decomposition product was formed by chlorination in a maximum amount during the first treatment and in decreasing amounts during subsequent treatments. (Table 11, column 7, samples 1, 3, and 5) The percentage of carbon dioxide liberated after each of the three treatments is recorded in column 8, which indicates that more than two-thirds of the material under consideration was formed during the first chlorination, when the total lignin was present in the sample. The material which liberates carbon dioxide as a decomposition product apparently exists in two forms: (a) a fraction soluble in sulfite, as indicated in column 9 by the difference in yields of carbon dioxide between samples 1 and 2, 3 and 4,5 and 6; and (b) a smaller fraction insoluble in sulfite as indicated in column 7 by the carbon dioxide yields of samples 2 , 6, 7 , and 8. (The zero value for sample 4 is believed to be an experimental error, since through oversight the carbon dioxide determination was not made in duplicate on that sample .) The soluble material removed from samples 2, 4, and 6 (refer to column 9) should not be considered oxycellulose, for, according to the arguments of oxycellulose is formed by the Cross and Bevan treatment only during the later stages after the lignin is removed. Moreover, it must be considered a material other than oxycellulose, for if oxycellulose exists a t all in the Cross and Bevan cellulose, as commonly maintained, it must be looked for in the cellulose residue proper, which is the part insoluble in the sulfite. INSOLUBLE CARBON-DIOXIDE-YIELDING MATERIAL-It is of interest to note that the total amount of the sulfitesoluble material indicated by the carbon dioxide in column 9 is greater than the total increase of the material due to 4
Biochem. J , 20, 656 (1926).
j
2. angew. C h e m , 26, 801 (1913)
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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Vol. 20, No. 4
Table 11-Carbon Dioxide a n d Furfural (Converted t o Pentosans) f r o m Untreated a n d Treated Wood (Percentages are based on oven-dry weight of the original wood unless otherwise specified) TREATMENT SAMPLE
NUMBER OF
residue From
~
(1)
Chlorinations (2)
Extractions
0 1
0 0 1
(3)
I Original wood 1 2 3 4 5 6
7 8
1 2 2
,
(4)
i
Per cent
1
3
I
Per cent
...
Per cent ...
1.4
16.86
1.7 0.5
20.48 6.02
+
Table 111-Furfural Converted t o P e n t o s a n s in Residue a n d Sulfite Extracts f r o m Three 5 - M i n u t e Chlorinations of Wood a n d Three Extractions w i t h Sulfite (Percentages based on oven-dry weight of original sawdust) ORIGINAL 1 SAMPLE 2 SAWDUST SAMPLE In 1st extract 4.7 5.3 .. In 2nd extract 1.8 1.9 In 3rd extract 1.0 0.9 In residue 14.8 14.6
-
--
22.3
22.7
22.5
Furfural from t h e Sulfite Extract I n the next phase of the work, then, a method (which will be described in a later paper) was developed for determining furfural in the sulfite extracts6 If appreciable amounts of oxycellulose were formed, the sum of the furfural in the extracts and residues should be greater than that in the original sawdust. Data showing the distribution of furfural in the various sulfite extracts and the insoluble cellulosic residue are presented in Table 111. The sum It is known that substances other than furfural are precipitated with phloroglucinol, as has been shown by Hagglund, Biochem. Z . , 179, 376 (1926). But, since in this study the total precipitate formed with phloroglucinol is considered as furfural, it is not necessary to identify the separate bodies. 8
Increase by chlorination
Soluble in sulfite
(7)
(8)
(9)
Per cent
Per cent
Pev cenl ..
0.86 2 00 0.30 0.60 0.00 0.20 0.10 0.06
0.07
1.14 0 : 30
1:io
0:so 0:io
.. ..
..
o:io ..
of the pentosans from both sources compares quite closely with that in the original sawdust. To obtain a check on this result by a simplified procedure, it was decided to use the several extracts from a given sample for a composite on which to determine the furfural (converted to pentosans). The sums of furfural as pentosans thus determined in the chlorinated residue and composite extract of four samples are recorded in Table IV. Converted to P e n t o s a n s in Residue a n d Sulfite Extracts of Wood (Percentages based on oven-dry weight of original sawdust)
Table IV-Furfural
N O . OF
K O . OF 5-MIN. EXTRAC- PENTOSANS PENTOSANS IN CHLORINATIONSTIONS I N RESIDUE EXTRACTS Per cent P e r cent
3 3 4 5
Furfural for t h e Insoluble Residue Column 4 of Table I1 indicates that the unstable pentosans are removed from the insoluble cellulose residue by four complete Cross and Bevan treatments. They constitute approximately one-third of the total pentosans in the wood. I n column 6 it will be noted that more than one-half the unstable pentosans are removed by the first chlorination and sulfite extraction. Since these treatments remove furfural-producing material, it is impossible to decide from Table I1 whether the same treatment may not also form oxycellulose, and increase the furfural yields. It is therefore necessary to determine furfural in the sulfite extract as well as in the insoluble residue in order to find whether the total furfural is increased by the treatments.
1
0.00 56.62
0.0 4.7
.. .. ..
r:i:Ee
On basis unstable pentosans” (6)
?:;lC
chlorination (column €9,which is explained on the assumption that the carbon-dioxide-yielding material in the original wood (line 1, column 7) is rendered soluble in sulfite gradually, by successive chlorinations. This explanation is further suggested and made more convincing by the fact that the total carbon dioxide in column 8 plus the carbon dioxide 0.86 = 2.50 per cent) is from the original wood (1.64 approximately equal to the total carbon dioxide in column 9 (2.40 per cent). Thus, the insoluble carbon-dioxideyielding material is accounted for as a decreasing residual of the material which yields carbon dioxide from the original wood, and not as some new compound resulting from the chlorination.
Total
CARBON DIOXIDE
LOSS B Y STEPS
22.5 22.5 17.8 16.9 16.4 15.6 14.7 14 2 14.2
2 2 3 4 5
3 4 5
1
PENTOSANS
3 3 4 4
15.0 15.0 14.8 14.7
7.8 7.3 7.6 7.6
TOTAL PENTOSANS Per cent 22.8 22.3 22 4 22.3
It will be noted that the sum of pentosans in the residue and composite extract agrees closely with the pentosans in the original wood. Judging from the pentosan yields, there is no indication that oxycellulose was formed by chlorination, The study, then, shows that the furfural yields from (1) original wood, (2) chlorinated wood, and (3) the insoluble residue plus its sulfite extract are the same, which indicates that no oxycellulose was formed by chlorination. An explanation that accounts for material which liberates carbon dioxide from the insoluble cellulose residue and that accords with the conclusions drawn from the furfural data has been given. Gortner’ has shown that some furfural is decomposed in the ordinary manner of distillation and that the furfural phloroglucide precipitate is not a true measure of the furfuralproducing material. I n this study a current of carbondioxide-free air was used to sweep the furfural and carbon dioxide from the distilling flask. Furthermore, the determinations of furfural from both the untreated and the chlorinated residues were made by the same method, and any increase in furfural from oxycellulose would be found. The conditions employed for isolating cellulose in this study were mild as compared with methods described by other workers for oxidizing cellulose. The study will be continued under more drastic conditions of chlorination accompanied by a search for the formation of oxycellulose. Further, an attempt will be made to isolate the material in the original wood which yields carbon dioxide and determine whether it yields furfural also. Summary of Results 1-No furfural-producing bodies are formed during the chlorination used for isolating cellulose from wood. 2-During chlorination there is formed a considerable amount of material which yields carbon dioxide but which 7
Ind. Eng. Chem., 15, 1167, 1255 (1923).
April, 1928
I N D U S T R I S L A S D EXGINEERISG CHEMISTRY
differs from oxycellulose in that it is soluble in sulfite and yields no furfural. 3-Most of the carbon-dioxide-yielding material is formed during the first chlorination, when 56.6 per cent of the unstable pentosans are rendered soluble in sodium sulfite.
373
4-Carbon dioxide equivalent to 0.86 per cent is liberated from the original wood by boiling hydrochloric acid. 5-There is no danger of forming oxycellulose during the analytical procedure for determining cellulose by the chlorination method.
Effect of pH on Lime Salts and Character of Colloids i n Filtered Juice from Cane Muds' J. C. Keane, M . A. McCalip, and H. S. Paine CARBOHYDRATE DIVISION,BUREAU OF CHEMISTRY AND
SOILS, WASHINGTON, D. C.
T
H E handling of the muds formed during cane-juice It is the usual practice to add lime to the diluted mud prior clarification presents a problem of importance in raw- to resettling, but this procedure was not followed because sugar manufacture. It has usually been approached lime did not increase the settling rate of the muds in question from the standpoint of expediting the disposition of the muds nor did it improve the quality of the mud-tank juice. Howwith as low a sucrose content as possible. One of two general ever, after resettling and decanting the supernatant liquid, procedures is followed, namely-filtration or return of the the mud was treated with a quantity of lime, heated, and muds to the mill. The former is the one more widely em- pumped to a separate filter press. A number of experiments ployed and with which this paper is concerned. The methods were made in which this procedure was repeated with the most frequently followed are thcse that permit rapid filtra- exception of varying the quantity of lime added to the mud. tion and yield a press cake of relatively low sucrose content, Composite samples of each lot of juice mere taken as follows a t the various stages of the but they give less consideraprocedure: (1) d e f e c a t e d tion to the effect that lime j u i c e , f r o m t h e draw-off may have on the filtered The filtration of muds formed by the defecation of valves of the four defecators; juice (which is r e t u r n e d cane juice is an important step in the manufacture of (2) resettled mud-tank juice, either to the raw or the raw sugar. In the effort to obtain a good filtration from the side ~ a l v eof the defecated juice). rate by the addition of excess quantities of milk of mud tanks; and (3) filtered The physical character of lime to the muds, the fact that the percentage of harmjuice, from the press during muds resulting from defecaful impurities-namely, lime salts and colloids-will be the period of filtration. tion varies greatly in pracincreased in the filtered juice by this practice is freThe following determinatice. For instance, some quently overlooked. Considering all factors, it was tions were made on each of muds are quite readily filterconcluded that the muds should be limed to a pH the above samples: Brix, able and form a firm press value not exceeding 7.8, and that the properly filtered purity, pH, CaO, and colcake with the addition of juice may be added to the clarified juice without de:loids by the dye test; in little or no lime, while others rimental effect and sent directly to the evaporators. some instances the quantity are gummy and difficult to of colloidal material was also f i l t e r unless considerable determined by ultra-filtralime or other filter aid is added. This difference in the character of the muds is depend- tion. A quinhydrone electrode, in conjunction with a saturated , ~ used for measent upon variation in certain characteristics of the juice as calomel half-cell as described by D a ~ s o nwas well as in procedure. Although addition of lime to the mud uring p H values. For estimating colloids the dye m e t h ~ d , ~ improves its filterability by altering the physical character specifying the basic dye night blue, was used. This method is of the press cake, it was suspected that certain 'adverse effects based upon the mutual neutralization of the electric charges on result, especially when addition of lime is not properly con- the colloid and dye particles, the end point being determined by trolled. The lack of information on this phase of factory means of an ultra-microscopic cataphoresis apparatus. The operation led the authors to conduct a series of laboratory quantity of dye required t o neutralize exactly the electric and factory experiments relative t o the effect produced on charge on the colloid particles is taken as a measure of the colthe filtered juice by treating the muds in various ways. Atten- loids present. CaO was determined in the ash from 100-cc. tion was also given to the two customary methods of return- portions of juice by the volumetric oxalate method, 0.1 N ing the filtered juice to the process for the purpose of deter- potassium permanganate solution being used for titration. In order to ascertain the relative proportions of the irremining which is the better procedure. versible and reversible types of colloids present in the liquors Methods of Analysis and Procedure a t different stages of the mud-treating process, some of the With the codperation of the factory staff2 four consecu- samples of defecated juice and the corresponding samples tively filled defecators were selected and so segregated that of filtered juice were subjected to ultra-filtration under careafter the defecated juice had been drawn off the muds were fully controlled conditions. The following procedure was dropped into two specially prepared mud tanks as a unit. used: A known weight of juice, containing approximately This mud was diluted with water, heated, and resettled. 200 grams of solids, was filtered with the aid of vacuum through standard collodion membranes. Toluene was used Presented before the Division of Sugar Chemistry a t the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 t o 10,
3
Sugav, 28, 211, 262, 310, 369 (1926).
1927.
4
Badollet and Paine, Intern. Sugar
The authors desire to express their appreciation of the hearty cooperation received from the officials and operating staff of Central Fajardo, Fajardo Sugar Company of Porto Rico, Fajardo, P. R.
J.,
28, 23, 97, 137, 497 (1926),
Planter Sugar M f r , 79, 121 (1927). 6 The technic of preparing these ultra-filters will be described in a forthcoming paper by .I E Dawson, formerly of this division.
