Aug., 1914
T H E J O U R N A L O F I N D U S T R I A L A N D E-VGINEERING C H E M I S T R Y
a t o o C., N204 merely adds on t o ethylene bonds without oxidation.’ There is also t h e possibility t h a t such compounds a s picric acid a n d nitrobenzol form nonfluorescent addition products, or double compounds, such as is t h e case with pyrene a n d chrysene. However. t h e simple nitro paraffines are not known t o form such double compounds a n d “nitro kerosene” is fully as efficacious as nitrobenzol for neutralizingfluorescence. The following experiment is interesting in this connection: A sample of a highly fluorescent lubricating oil was “debloomed” b y t h e addition of nitrobenzol. This oil was t h e n shaken out six times with one-half i t s volume of 96 per cent alcohol, after which t r e a t m e n t t h e blue fluorescence h a d reappeared a n d exactly matched a sample of t h e same oil n o t treated with nitrobenzol, b u t shaken o u t with alcohol in t h e same way as t h e first sample. Refining such a “debloomed” oil with sulfuric acid yields a fluorescent oil identical in this respect with t h a t obtained by refining t h e original oil. T h e action of nitro compounds in neutralizing fluorescence must therefore be purely physical in character. T h e fact t h a t exposure t o t h e atmosphere for some time partially destroys a n d changes t h e character of t h e fluorescence suggeSted t h a t what took place during this process was slom autoxidation. S i t r o u s acid readily neutralized t h e fluorescence of lubricating oils, b u t t h e oils gradually became dark colored a n d resinous. Distillation of t h e latter d a r k colored oil in v a c u o or with superheated steam yielded oil having a bluish fluorescence. Repeated washing with alkali removes only a small p a r t of t h e coloring matter. Shaking a p a r t of a sample df pale engine oil with nitrous acid for three minutes, followed b y washing with water a n d filtering through Fuller’s earth, gave a less resinous, light colored oil, very similar t o t h a t obtained b y sun-bleaching. Oxides of nitrogen, generated b y t h e action of dilute nitric acid on a metal, were t h e n tried a n d i t was found t h a t t h e sun-bleached oil could be matched, with respect t o color a n d fluorescence. provided t h e temperature of t h e oil was not permitted t o rise above 10’C , before washing with dilute alkali. A t low temperatures addition of oxides of nitrogen t o unsaturated compounds probably results as shown b y Jegorow. Unless t h e oil is chilled before passing in t h e oxides of nitrogen, oxidation appears t o result, accompanied by rise in t e m perature, darkening in color a n d formation of resinous material. S o method of removing t h e resinous coloring m a t t e r without at least partially restoring t h e bluish fluorescence was found. T h e effect, on t h e color of t h e oil, of nitric acid in sulfuric acid when used for refining is well known a n d constitutes one of t h e advantages of acid made b y t h e contact process over t h a t made b y t h e chamber method. VC’e t h e n made a series of experime&s t o determine t h e chemical properties of t h e fluorescent substance. T h e efficiency of sulfuric acid, particularly fuming acid, in removing fluorescence is well known. It was found t h a t t h e wash water from freshly prepared acid sludge t a r , made b y refining lubricating stock, was highly fluorescent. This suggested t h a t t h e Jegorow, J prahl. C h e m , 86 (1912), 512.
625
fluorescent material formed water-soluble sulfonic acids, or t h a t t h e fluorescent substance was a base a n d removed a s a soluble sulfate. The latter hypothesis can hardly be t r u e since dilute acids do not extract t h e fluorescent material f r o m t h e oil. A quantity of such fluorescent aqueous solution was made alkaline a n d extracted with ether b u t no fluorescent material was obtained indicating t h a t t h e substance in question is not a base. A dilute acid solution of t h e fluorescent substance was nearly neutralized with lime t o remove t h e excess of sulfuric acid. T h e filtered aqueous solution was evaporated nearly t o dryness a n d t h e crystalline residue, containing sulfate of lime, extracted with alcohol. Twelve liters of lubricating distillate yielded, in this way, a b o u t I gram of a n impure crystalline residue which was intensely fluorescent when dissolved in t h e different solvents named above. The a m o u n t obtained was t o o small to be thoroughly investigated, b u t we hope t h a t we shall have a n opport u n i t y in t h e near future t o prepare a quantity of this highly interesting material sufficient for further work. The above results were enough t o show t h e general character of t h e substance. T h e crude fluorescent substance probably contains one or more compounds of t h e benzene series resembling or perhaps identical with chrysene, fluorene o r pyrene. Such compounds a r e known t o be formed b y t h e pyrogenic decomposition of many organic substames. Klaudy a n d Fink, in 1900. isolated a yellow crystalline substance, giving highly fluorescent solutions from t h e residuum of a cracking still. T h e y give i t t h e formula C2iH18. A large proportion of t h e fluorescent substance or substances is formed during t h e distillation of t h e crude. This was shown b y distilling a sample of Oklahoma crude a t atmospheric pressure a n d under a pressure of 5 mm. of mercury. The distillates in t h e first series were very much more fluorescent t h a n t h e latter. This is also t r u e of t h e distillates from coal when distilled a t atmospheric pressure a n d under a pressure of 5 m m . Parallel with this difference i t should be noted t h a t substances of t h e benzol series form a much greater proportion of t h e coal t a r obtained a t ordinary pressures, paraffines a n d olefines constituting over 8 0 per cent of t h e coal t a r obtained by distilling in vacu0.I It is also well known t h a t no fluorescent substances are known belonging t o t h e paraffin series. Halogenation destroys t h e fluorescence. as is t o be expected. Hydrogenation also destroys i t . MELLON INSTITUTE UNIVERSITY O F PITTSBURGH
PITTSBURGH
THE MANUFACTURE OF ETHYL ALCOHOL FROM WOOD WASTE-PRELIMINARY EXPERIMENTS ON THE HYDROLYSIS OF WHITE SPRUCE2 By F W. KRESSMAKN THE PRESENT VALUE
OF WOOD WASTE
T h e value for most of t h e wood waste produced t o d a y is limited t o its fuel value for t h e production of power a t t h e mill. I n some cases, methods of closer utilization have been worked out. b u t compared with t h e 1 Jones and Wheeler, J . Chem SOC. (London), 1914, 140. 2 Presented a t the 49th Meeting of the American Chemical Society, Cincinnati, April 6-10, 1914.
626
T H E J O U R N A L O F I L V D L ’ S T R I A L ALVD E N G I N E E R I N G C H E M I S T R Y
total amount of wood waste produced, t h e a m o u n t of material so utilized is almost negligible. Furthermore, most of t h e large lumber mills produce waste greatly in excess of t h e amount necessary for power production a n d t h e waste burners are still in use, involving not only a loss of large amounts of wood, b u t also a definite fixed charge t o get rid of it. The utilization of this material is limited, due t o a number of considerations which m a y be classified as follows: I-LARGE BuLK-The bulkiness of t h e waste material makes a minimum amount of handling imperative a n d almost prohibits its transportation. 2-MECHAKICAL COKDITION OR FORM-The mechanical condition or form of t h e waste is one of t h e greatest stumbling blocks t o i t s more complete utilization. Sawdust a n d shavings are t o o finely divided t o be of value for paper a n d pulp production or for destructive distillation. For t h e former: t h e fiber length has not only been reduced, b u t t h e fibers have also been t o r n a n d lacerated much as in t h e production of mechanical ground wood. T h e destructive distillation of sawdust a n d shavings is not practicable for t w o reasons: F i r s t , t h e small size of t h e material makes it such a poor conductor of heat t h a t i t is impossible t o char i t completely in t h e ordinary forms of retorts a n d kilns in use; s e c o n d , t h e charcoal produced is so finely divided t h a t i t is difficult t o cool a n d handle a n d there is n o ready market for it. I n addition, t h e waste, as it comes from t h e mill, is usually a mixt u r e of all t h e forms enumerated above a n d a n y a t t e m p t at a separation other, perhaps, t h a n a simple blowing or screening t o remove t h e very fine stuff will increase t h e cost of t h e raw material t o a prohibitive figure, as shown b y t h e experience of several pulp a n d paper mills in t h e yellow pine region of t h e south. A satisfactory process, therefore, for t h e utilization of wood waste should be able t o handle practically a n y a n d all forms of waste as t h e y happen t o come from t h e mill. 3-N
0 N- H 0 M 0 G E K E I T Y
AS D
K 0 S - U KIF 0 R MI T Y-
E X-
cept i n some cases, as i n factories using only one or t w o species of wood or in some mills manufacturing only a few species, as, for example, t h e “yellow pine’’ (longleaf, shortleaf, loblolly) mills of t h e south, t h e non-homogeneity of t h e waste has operated against i t s efficient utilization, for m a n y processes such as pulp a n d paper or destructive distillation require particular species t o give a yield a n d quality of product t h a t will make t h e processes commercially feasible. T H E V A L U E O F W O O D F O R A L C O H O L PRODUCTIOK
All woods, however, have one point in common a n d t h a t is t h e fact t h a t t h e y all contain more or less cellulose which makes u p t h e fibers of t h e wood along with a n incrusting substance called “lignin.” Any process which could chemically utilize this cellulose would, therefore, overcome t h e objections laid down above a s t h e form of t h e material, length of t h e fiber, species, etc., would not be a consideration since finely divided material would permit of a quicker a n d more complete reaction a n d coarse material could readily be reduced t o a finer condition. The production of sugars a n d ethyl alcohol from
Vol. 6 , NO. 8
cellulosic materials such as straw, linen, cotton, peat a n d wood, in fact. all plant fibers, has engaged t h e attention of chemists a n d technologists for nearly a century, although it is only within t h e last t w o decades t h a t serious a t t e m p t s have been made t o utilize wood waste b y this means. T h e principal sources of fermentable sugars from which alcohol is derived a t present are: I-Hydrolytic products of starch. 2-Sugars from fruits; sugar factory residues, such as molasses, etc. T h e cost of t h e raw material for alcohol derived from such sources, however, has been so high t h a t alcohol h a d not been able t o compete in certain fields where i t s properties a n d worth are recognized. T h e technical application in t h e arts a n d industries is gradually increasing, due t o a rather liberal denaturing policy which has permitted special denaturants for special industries, b u t its use in this country as a source of liquid fuel is comparatively limited a n d i t is this field t h a t offers greatest possibilities in t h e future. A s t u d y of t h e motor fuel problem will show t h a t t h e production of mineral fuels suc.h as gasoline, motor spirits, etc., is not keeping pace with modern automobile production, a n d alcohol appears t o be t h e only solution of t h e problem, for if alcohol can be produced from wood waste a t a reasonable figure a tremendous supply of raw material is not only available a t present b u t will continbe t o be so in t h e future from a natural growing raw material which is not a foodstuff. PROCESS
T h e process of producing ethyl alcohol from wood consists, in general, of digesting sawdust or hogged and shredded wood with a dilute mineral acid a t from 6 0 pounds a n d more of steam pressure. This converts p a r t of t h e wood into a mixture of pentose a n d hexose sugars. The latter are then fermented, producing alcohol. T h e processes using concentrated sulfuric acid, in which t h e wood is really attacked a n d dissolved b y t h e acid as i n t h e Ekstrom’ process, have not received commercial attention, notwithstanding t h e fact t h a t Flechsig,z many years ago, showed t h a t cotton cellulose could be converted into dextrose a n d alcohol almost’quantitatively thereby. . T h e more recent work of Willstatter3 and Feichmeister has ccnfirmed these results with fuming hydrochloric acid, b u t in all cases t h e amounts of acid have been so large compared t o t h e procesess in which t h e acid is used merely as a catalytic agent, t h a t t h e large initial a n d recovery costs for acid have prevented commercial development. T h e source of,the fermentable sugar, t h a t is, whether derived from t h e cellulose or lignin of t h e wood, has long been a mooted question a n d has been t h e occasion of considerable investigation, b u t t h e fact remains t h a t a wood cellulose like soda or sulfite pulp will produce about twice as much fermentable sugar a n d 1
French P a t e n t 380,358, German Patents 193,112, 207,354.
2
Z. p h y s . Chem., 1882.
3
Bey., 1913, 2401.
Aug., 1914
T H E J O C R S , - I L O F IAViD1-STRIzlL A N D E S GI LVE E RI 9G C H E M I S T R Y
alcohol as t h e original wood, t h e yields being proportional t o t h e cellulose content. H I ST OR Y
T h e earlier work in t h e field from t h e time of Braconnot in, 1819 until t h e work of Simonsenl in 1898, although exceedingly interesting historically, m a y almost be disregarded so far as its scientific value is concerned. It contains m a n y inaccurate a n d impossible statements, a n d many contradictions, a n d is in many cases very vague in regard to yields.
627
which hydrochloric acid was used as t h e catalytic agent instead of sulfuric. T h e d a t a t o be presented in this paper are t h e result of t h e first p a r t of a systematic s t u d y of t h e variables in this process carried on a t t h e Forest Products Laboratory a n d cover t h e first t w o of t h e following: I-The influence of pressure a n d temperatures of digestion. a-Length of time of digestion. 3-Ratio of water t o d r y sawdust. of catalyzing agent in t h e water. 4-Concentration j-Ratio of catalyzing agent t o d r y sawdust. 6-Size of t h e sawdust, hogged slabs, etc. of adding catalytic agent (acid) after 7-Effect preliminary heating of t h e wood. 8-Effect of varying amounts of bark in the sawdust, or, more specifically, tannins, etc. 9-Special chemical treatments other t h a n acid catalysis or in addition t o acid catalysis. IG---A s t u d y of t h e fermentation variables. I I-Steam consumption per t o n of sawdust inverted. I 2-Variations of yields from different species a n d mixtures. EXPERIMENTAL APPARATUS AND PROCEDURE
The apparatus used a n d method of procedure in each experiment were as follows: A rotary digester P L A T EI-EXPERIMENTAL ALCOHOL APPARATUS Showing digester with b o t h manhole covers o f f ,loaded with sawdust, and also tank T containing condensing coil a n d acid t a n k C.
Simonsen carried o u t t h e first systematic investigation of t h e subject in which t h e effect of different variables such as t h e a m o u n t of water, pressure, t e m perature, a m o u n t of acid, a n d time of inversion were studied in some detail. As shown later2 by Neumann, Simonsen's work is also contradictory in some cases: due mainly t o t h e fact t h a t only a single experiment under each set of conditions was made. I n his work on a large scale h e was in general unable t o duplicate t h e results obtained in t h e small autoclave cooks. The yields of alcohol varied considerably, although under t h e most favorable conditions he obtained in a few exceptional cases yields which were higher t h a n those obtained on t h e small scale (6 per cent of dry weight of sawdust). Since Simonsen published his work a n d took out patents on his process practically all over t h e world, t h e production of ethyl alcohol from sawdust has received considerable attention a n d a large a m o u n t of money has been spent in its technical development. Four plants have been built in this country, b u t none of t h e m u p t o t h e present are considered t o have achiel-ed commercial success. OUTLINE
OP EXPERIMEKTAL
WORK
Although other inrestigators have duplicated Simonsen's yield, which is a b o u t six per cent b y weight in alcohol of t h e d r y weight of t h e wood, no systematic s t u d y has been made reinvestigating t h e variables studied by Simonsen, except t h e work of Cohoe in See E. Simonsen, Zeitschrifl fur angewandfe Chemie. 1898, 195. 9 6 2 , 1007; Theor Khrner, I b i d . , 1908, 2353 ; N e u m a n n , Dissertation, Dresden, 1910. 2 h'eumann, Dissertation, Dresden, 1910. 1
P L A T E I I - E X P E R I M E K T AALCOHOL L APPARATUS ,I t h e settling t a n k s S a n d SI. t h e single effect Showing leaching t a n k , . vacuum evaporator E, a n d t h e hydroextractor H, in t h e foreground
consisting of thin cast-iron inner shell lined with acidproof enamel a n d a n outer shell of steel, t h e two being separated b y several inches from each other, was used for t h e digestions. The internal length of t h e inner
628
T H E JOURN.4L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
shell is about five feet, a n d t h e diameter about 2 l / 2 feet, making a total capacity of about 2 2 cubic feet. Steam is admitted t o t h e inner shell a n d space between t h e inner a n d outer shell simultaneously, t h e digester being similar t o a steam-jacketed apparatus except t h a t t h e inner shell is removable a n d can readily be taken o u t a n d replaced, After a cook has been completed t h e digester is blown off, t h e blow-off vapors being condensed in a quartz coil. A cast-iron t a n k also lined with acid-proof enamel is connected t o t h e digester so t h a t its contents may be introduced into t h e digester when t h e latter is under pressure. This t a n k is used for acid storage a n d mixing. The steam flows t o t h e inner shell a n d space between t h e two shells through separate pipes; t h e one leading t o t h e inner shell also connects with acid tank. All pipes in contact with acid liquor or acid vapor are enamel-lined a n d valves are of special bronze so as t o reduce corrosion t o a minimum a n d t o avoid complications in fermentations due t o t h e presence of iron, copper, and zinc salts. The pressure is t a k e n b y means of a gauge protected from t h e acid vapors a n d temperatures are taken on a recording thermometer, t h e bulb of which projects into t h e sawdust in the digester. The digester is filled a n d emptied through a pair of concentric manholes in t h e inner a n d outer shell. The usual procedure is t o load t h e digester with sufficient sawdust t o be equivalent t o about I O O pounds of d r y dust. T h e exact weight a n d moisture content are recorded. T h e diluted acid is then added, t h e manhole covers bolted on, steam admitted, a n d rotation begun. Before t h e temperature reaches 100' C., t h e air in t h e inner shell a n d space between the t w o shells is vented so as t o get a more accurate gauge reading. The admission of steam is continued until t h e desired pressure is reached, after which t h e steam is throttled t o maintain t h a t pressure for t h e desired length of time. At t h e completion of t h e latter (or, in cooks of I j minutes or more, t w o or three minutes before t h e time was up) t h e rotation was stopped a n d t h e vapors were t h e n blown, off a n d condensed as rapidly as possible. T h e time of blow-off varied somewhat, depending on t h e pressure at which t h e cook was made a n d t h e total a m o u n t of liquid a n d sawdust in t h e digester. T h e condensing a n d cooling capacity of t h e coil was n o t equal t o t h e demands placed upon i t so t h a t t h e blowing off of t h e digester took much longer t h a n i t should (about t w o hours from 7 t o 8 atmospheres t o atmospheric pressure). T h e condensed blow-off was weighed a n d analyzed. T h e steam which condensed between t h e t w o shells was drained out a n d weighed. It was also tested qualitatively for dextrose t o detect a n y leakage from t h e inner shell. T h e liquor in t h e inner shell was drained out. After as much of t h e liquor as would do SO h a d drained off t h e digester was rotated so t h a t t h e manholes were a t t h e bottom a n d t h e sawdust was raked out. I n t h e later experiments this sawdust was t h e n centrifuged. Both t h e digester liquor a n d treated sawdust were weighed a n d analyeed for acidity, total solids, dextrose, etc.
Vol. 6 , NO. 8
T h e treated sawdust was next placed in t h e leaching t a n k , where t h e remainder of t h e sugar was extracted from i t with warm water. T h e liquor from t h e digester a n d leaching t a n k was t h e n neutralized with calcium carbonate and allowed t o settle. The clear liquor was t h e n concentrated in a single effect vacuum evaporator t o a concentration of I O t o I j per cent sugar for fermentation. T h e liquors were usually saved until t h e concentrations from two or three runs were obtained. Where possible, these were divided into two or more parts a n d fermented with brewers' yeast under varying conditions. RESULTS
S U G A R YIELDS-Figs. I , 2 a n d 3 show t h e effect on yield of varying t h e pressure a n d time of cooking. The curves give the yields in total sugar instead of alcohol since t h e fermentation end of t h e work is being taken up in detail a t present and was not standardized a t t h e time these experiments were made so as t o give check results. T h e greatest variation on dupli-
)r FIG.
1--%IOWING
THE
TOTAL SUGAR ON D R Y WEIGHT OF WOOD VARIATION
P R E S S U R E OF DIGESTION.
OF
YIELD
OF
COOKING PERIOD,
TOTALSUGARWITH 15 MINUTES
cate digestions made with sawdust from t h e same batch was only 0 . 1 1 per cent of total sugar, so t h e sugar d a t a may be accepted as fairly accurate. I n each r u n the amount of sawdust used was very nearly equal t o 100 pounds d r y material; t h e amount of acid added was t h e same in all, 2 . 0 0 pounds of go t o g j per cent sulfuric; a n d t h e amount of water in all cases a t t h e end of t h e cook was equal t o four or more t h a n four times t h e dry weight of wood used. T h e ratio of acid t o dry wood was about 1.8 per cent, while t h a t of water t o dry wood was 400 per cent or more. Many of t h e charges were made u p so t h a t t h e initial amount of water present was exactly four times t h e dry weight of t h e material. These, however, showed no change from others in which t h e amount of water added was allowed t o v a r y within certain limits. Fig. I , with a cooking period of 1 5 minutes, shows a decided maximum i n yield a t a temperature equal t o 7 . 5 atmospheres steam pressure. A new lot of sawdust was used for part of t h e work which included t h e cooks a t 7. j atmospheres a n d which
T H E J O L ' R N A L O F I - V D L ' S T R I A L A S D ENGINEERI,VG C H E M I S T R Y
,lug., 1914
probably accounts for t h e increase in yields shown a t t h a t point and which has been indicated b y the dotted lines. O n comparing t h e yields shown in Fig. I with those of Simonsen a much greater decrease in yields a t pressures above 7 . j atmospheres was noted. F r o m t h e work of Neumann i t is known t h a t dextrose decomposition is very rapid above I ; j ' C., which corresponds
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tures, however, t h e rate of decomposition seems t o be decidedly greater t h a n the rate of formation which was shown in Figs. I and 2 . In Fig. I the curve crosses t h e abscissae corresponding t o 9 atmospheres a t a point showing a yield of 14 per cent of sugar, while in Fig. 2 the yield of 9 atmospheres was 2 1 . 2 9 per cent of sugar. This decided difference in sugar values shows clearly t h e injurious effect of increasing t h e time of cooking, especially a t pressures greater t h a n 7 . j atmospheres. T h e injurious effect of increased time of cooking is also shown in several other ways; the sawdust, of course, is rotated longer in the longer cooks a n d more fine stuff is formed which makes leaching and handling more difficult. The sawdust is also more friable and larger amounts of fine stuff were formed while being stirred in the leaching t a n k . ,4nd finally, as shown, b y t h e ratio between sugar a n d total water-soluble solids, more of the sawdust was attacked so t h a t the amount of extraneous water-soluble material other t h a n sugars was greater. Cohoel was the first one t o s t a t e t h a t given the
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24
3--sHOWING T H E V A R I A T I O N O F Y I E L D O F TOTAL S U G A R WITH C O O K I N G P R E S S U R E , 7 5 LiTMOSPIiERES V A R Y I N G P E R I O D S O F DIGESTION.
FIG
Figs. I a n d z ) and varying t h e time of cooking, as shown in Fig. 3 ) practically no increase or decrease in yield of sugar is shown; in other words, t h e rates of formation a n d decomposition of t h e sugars formed a t this temperature are the same a n d , therefore. maint a i n n constant yield of sugar. At higher tempera-
proper adjustment of t h e various phases t h e reaction is practically instantaneous and our work is in entire agreement with this statement. V O L A T I L E A C I D YIELDS-In addition t o the SLIgarS formed as a reiult of hydrolysis, acetic and formic acid are also produced, probably from a splitting off of acetyl and formyl groups in t h e lignin complex. T h e yield of acetic acid has been fairly constant over a wide range of cooking conditions averaging 1 . 4 2 per cent of the d r y weight of t h e wood. This is of particular interest not only because of its influence on t h e subsequent fermentation of t h e neutralized extract b u t also because i t is practically t h e same yield obtained b y destructive distillation of the wood. Numerous observers such as Klason, Buttner, and Wislicenus have shown t h a t this decomposition does not t a k e place until a temperature of 280' C . or more has been reached, whereas t h e temperatures of h y I
Jour Soc Cheni I n d , 1912, 5 1 3
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
630
drolysis in this work have averaged 100’ C. less t h a n t h a t . T h e yield obtained, however, is in very close agreement with t h e work of Bergstrom,’ although t h e latter used no acid, merely hydrolyzing with 4 parts b y weight of water a t 6 atmospheres pressure for t w o hours. T h e yield of formic acid, however, varies with t h e cooking conditions as shown by Fig. 4, t h e amount increasing with increasing cooking pressures. I n creasing t h e time of cooking also materially increases t h e yield, for as shown a t 7 1 / 2 atmospheres a n d a zerominute cook t h e yield is about 0 . 2 per cent, while a t t h e same pressure for a ~ j - m i n u t ecook t h e yield is about three times as great ( 0 . 5 8 per cent). This increase i n formic acid production also shows t h e rate of sugar decomposition since formic acid a n d levulinic acid are both products of such decomposition. T h e exact amount hydrolyzed from t h e wood is difficult t o determine since i t is also a product of sugar decomposition. Bergstrom obtained 0.19 per cent a t 6 atmospheres cooking for two hours with water alone, whereas we have obtained t h a t figure a t 7’/2 atmospheres in zero minutes b u t only 0.105 per cent a t 6.5 atmospheres in zero minutes. Technically, t h e yield of formic acid is of importance because of its influence on yeast growth. Numerous patents granted in this field have discussed t h e value a n d recovery of t h e volatile acids produced. To show t h e distribution of t h e various acids, t h e amqunts actually contained in t h e liquor drained from t h e inner shell, t h e condensed blow-off a n d moist sawdust, were calculated in percentages of t h e total amount of each acid produced. The results are given in t h e following table: Total amt. of
acid . involatile per cent of Moist digested dry weight of
OF TOTALVOLATILE ACID IN PERCENTAGE c
Cook number XV ...... ,
Inner shell liquor
Condensed blow-off
, d 7 -
..
XVI....... .
XVII . . . . . . . XVIII . . . . . , XIX . , . . , . . . XX... . .. ...
--
sawdust
original wood
Acetic Formic Acetic Formic Acetic Formic Acetic Formic 62.0 48.5 37.8 40.2 35.0 49.5
62.1 49.4 41.0 46.2 32.6 39.2
2.6 5.7 9.5 7.2 6.8 6.3
2.1 5.9 4.3 7.0 6.1 5.9
35.4 45.8 52.7 52.6 58.2 44.2
35.8 44.7 54.7 46.8 61.3 54.9
1.22 1.62 1.48 1.32 1.60 1.25
0.185 0,220 0,570 0,598 0,443 0.105
The average amount of acetic acid recovered in t h e blow-off wa.s 6.4 per cent of t h e total, a n d 5.2 per cent of t h e total amount of formic acid produced. With a n average yield of 1.42 per cent of acetic acid, this would be equivalent t o 1 . 8 1 pound: of acetic acid per dry t o n of wood a n d since t h e average concentration of acetic acid in t h e condensed blow-off was only 0 . 2 0 per cent, commercial recovery is obviously out of t h e question. A L C O H O L YIELDS-AS mentioned heretofore, t h e fermentation work on t h e experiments outlined in this paper h a d not been standardized. Ordinary brewers’ yeast, a bottom yeast, has been used without a t tempting t o acclimate i t t o t h e mashes used. The main difficulty encountered was t h e slowness of fermentation which, in some cases, permitted infection of t h e mashes with wild growth, It was found, however, t h a t t h e latter could be controlled a n d excluded b y judicious sulfiting a n d for this purpose potassium A
Der Papicrfabrikant, 2, 305.
Vol. 6 , S o . 8
metabisulfitel was used. Various forms of organic a n d inorganic nitrogen nutrients were used, of which freshly killed yeast (boiling for two minutes in p a r t of t h e mash) a n d ammonium nitrate seemed t o be t h e best. T h e following table gives p a r t of t h e results obtained: Yield of Yield of alcohol in Total realcohol U. S. gallons ducing sugars per cent of absolute per cent Per cent of Fermenta- by weight alcohol per tion of original dry ton of of original total sugars dry wood fermented efficiency dry wood original wood
Cook number I1. . . . . . . . .
21.50
X X . . . . , .. , X I I I . .. . . . . XIV . . . . . . . XII., .... .
20.29 11.58
v . . . . . . . . . 21.54 X V I I . ,. . . . 2 2 . 9 5 XVIII.. . . , 2 2 . 8 5
18.34
18.81
68.63 71.27 69.27 55.5 65.25 59.20 46.05 55.24
89.59 91.49 88.70 96.2 85.42 83.93 65.05 68.87
6.76 7.18 7.22 6.24 5.24 4.78 3.11 2.25
20.35 21.63 21.70 18.75 15.80 14.90 9.35 6.8
Some of t h e above results, however, do not represent t h e yields obtainable under ideal conditions since many of t h e fermentations were retarded or spoiled entirely due t o experimentation on fermentation conditions. Under improved conditions with a yeast specially propagated t h e yields undoubtedly could be materially increased. SUMMARY
I-The maximum yield of sugar was obtained a t a pressure of 7 . j atmospheres a n d above a n d below this point yields decreased very rapidly. 11-A cooking period of zero minutes, t h a t is, blowing off from 7 . j atmospheres as soon as t h a t pressure is attained, was t h e most advantageous for sawdust. 111-Increasing t h e time of cooking did not increase t h e yield a n d greatly influenced t h e mechanical condition of t h e sawdust wjth greater subsequent difficulty a n d cost of handling. Economically speaking, t h e yield decreased as t h e time of cooking increased. IV-Using white spruce sawdust as a raw material, from 2 2 t o 2 3 per cent of t h e dry weight of t h e wood was converted into sugar. About 7 0 per cent of this sugar was fermented with a n alcohol yield of over 9 1 per cent of t h e amount theoretically possible t o obtain from t h e fermentable sugars. Calculating these yields t o a tonnage basis, between 21.63 a n d 2 1 . 7 0 U. S. gallons of absolute alcohol were obtained per d r y ton. V-Under a rather wide range a n d variation of cooking conditions of hydrolysis, white spyuce yielded about 1.4 per cent acetic acid, showing, therefore, a parent substance (lignin?) of a comparatively definite acetyl content. VI-The yield of formic acid varied with t h e conditions of hydrolysis. I n cooks longer t h a n zero time, t h e formic acid yield was indicative of hexose decomposition rather t h a n increased formyl hydrolysis. FORESTPRODUCTS LABORATORY FOREST SERVICE, U S DEPARTMENT OF AGRICULTURE (In CoBperation with the University of Wisconsin) MADISON 1 See “Enological Investigations,” F. Bull. 230, Agr Expt. Sta., Berkeley, Cal.
T
Bioletti and W. V. Cruess,
