January, 1945
INDUSTRIAL AND ENGINEERING CHEMISTRY
A series of three-cycle hydrolyses was made: rune 183, 184, and 185 at 1 8 5 O C., and 186 and 188 at 190'. The yield varied from 37.7 to 40.4 gallons per ton. I n rune 187 and 189 four 3minute cycles were used at 190° and 185' C., respectively. Yields of 41.5 and 44.0 gallons per ton were obtained, SUMMARY
Studies on the hydrolysis of wood in the rotary digester have resulted in several alternative methods of operation for the singlestage, multistage, and limited multistage hydrolysis of yields obtained' depending On technique Of in lo minutas to 6o vmfrom aPPro*kly 8o muons per gallons in 3 hours.
43
MRATURE CITED (1) Demuth, R, von, 2. angsro. C h m . , 26, Aufndrt., 786-92 (1913). (2) Foth, G., C h . - Z t g . , 37, 1221-2, 1297-8 (1913). (3) Harrk, E. E., Forest Products Lab., M i m w r u p h 81446, 1-68 (1Q-W. (4) Kresemen, F.W.,U.8.bept. Agr., BUU. 983, 1-100 (1922). (S) Neuman, J., diseertation, Polytech. Inat., Dresden, 1910. (6) Saeman, J. F,,IND.ENO.CRBIY., 37, 48 (1946). (7) Bsemm, J. F., Bubl, J. L.,and Harris,E. E.,IND.ENG.CHZDK.,
ANAL.ED.,to b published.
(8) Saeman, J. F., Harris, E.E.,Kline, A. A., Zbid., 1044. 10,869 (1918). (9) Tomlimn, C. H., J. IND.ENO.CHBIM., B A l l l D on rtudiea of the 0.8. Forest Products Laboratory in cooperation with the 0 5 0 s of Production Rbaearch and Development, War Production Board.
KINETICS of WOOD SACCHARIFICA TION Hydrolysis of Cellulose and Decomposition o f Sugars in Dilute Acid at High Temperature JEROME F. SAEMAN U. S.
F o r d Products Laboratory, Madison, Wir.
NUMBER of inveeti tors have made valusble contributions to the study of l rnetics of cellulose hydrolysisin strong
A
acid at low temperature. Most of this work was done with fuming hydrochloric acid or 60% or stronger sulfuric acid a t room temperature or below. The research of Freudenberg has been especially noteworthy in this field (1-4). Sherrard and Froehlke (16)studied the rate a t which dflerent cellulose preparations are hydrolyzed in fuming hydrochloric acid and found marked merenaes, depending on the cellulose used. Wolfrom and co-workers studied the depolymerization of cellulose in concentrated hydrochloric acid by a simultaneous hydrolysis-mercaptalation method. They used the increase in the sulfur content of the product as a measure of the free aldehyde group8 and, hence, of the amount of hydrolytic cleavage (17,18). I n 1922 and 1923 Meiler (8)and Scholler (13)working in the laboratory of Lflers a t Munich, studied the hydrolysis of a cellulose dextrin. On the basis of these findings the Scholler proceas (2.6) for wood hydrolysis was developed. After some plant-scale experimental work had been completed, Lflers (6,8)reported on the kinetics of the hydrolysis of cellulose dextrin. He stated that both the hydrolysis of the dextrin in dilute acid and the degradation of the resulting sugara are unimolecular reactions. He further reported that the speed of both reactions WES proportional to the acid concentrations and that both reactions were equally affected by temperature. He gave no experimental data to support such claims. There is much information in the literature on the hydrolysis of cellulose in strong acid a t low temperatures; but there is little quantitative work describing the hydrolysis of cellulose in dilute acid at high temperature-that is, hydrolyses using acid concentrations below 3% and temperatures above 150' C. This paper will describe recent research on the kinetics of the saccharification of wood in dilute acid a t high temperature. The work was a part of the program authorized by the War Production Board to develop a commercially practical method for the conversion of wood t o sugar and the subsequent fermentation of the sugar t o alcohol.
APPARATUS AND ANALYSES
The experiments on the hydrolysis of wood and the decomosition of sugars were carried out in sealed lass bombs heated gy direct steam in a rotating digester. A hoyder for the bombs was made by brazing together a number of length of &-inch streamline copper pi into a nest of such size as to t convenientl in a cylind%al sheet-iron container fitted with a lid held on i y win nuts. The assembly is shown in Fi Soft glaaa cukure tubes (10 X 150 mm.) were s e a E i k a blast lam in such a way as to give a smoothly rounded end, as shown in &gwe 1. The tubes could be opened by a hot wwe cutter. Breakage of these tubes in the di ester was rare. When tubes of 8 lsrger diameter and thinner waql (I9 X 150 mm. standard soft glass teat tubes) were used,breakage was more fre uent. When emere cooks were made, using sugar s&tions of high concentration, a significant amount of gas was formed, but at no time under the conditions of these experimenta was enough gas formed to be dangerous. About 1.5 minutes were required to reach the desired steam pressure in the digester and an equal time was required to drop it t o atmospheric pressure. If these operatiom had been carried out more rapidly, it is possible that breakage of the bombs would have been more frequent. Sugar anal ses were made by the Shaffer and Somogyi method (16), using tgeir reagent No. 50 and a 30-minute boiling time. Unhydrolyzed carbohydrate material was determined b sub'ecting the residue to a quantitative saccharification, followed by sugar analysis. This saccharification causes a small amount pf decomposition but the reducing-sugar yield from cellulose is in excess of 95% of the theoretical amount. The values are reproducible and can be corrected for the loss in sugar by an experimentally determined factor. I n this work, however, because the constant factor involved would have no effect on the determination of the rate constante, the values were used without correction. The fermentability of the su ars was determined by measuring the sugars sorbed by east in %igh concentration from the &luted sugar solutions. getailed descriptions of these methods are given in other reports (11, I d ) .
Y
DECOMPOSITION OF SUGARS
Early workers (9) on wood hydrolysis recognized that the sugars produced from cellulose were subject t o decomposition on continued exposure t o hot dilute acid, All sugara subjected to this treatment yield humic substances of indefinite composition.
U
INDUSTRfAL AND ENGINEERING CHEMISTRY
Data arc presented to &city the ,
