Production of Food J
J
NUTRIENT REQUIRE ELWIK E. HARRIS, hIARTHA L. " W A N , AND RALPH R. IPIAEQGARDT Forest Products Laboratory, Madison, W i s .
the air supply of increasing the depth of the propagator, of sugar concentration, and of wood species upon the growth of yeast.
Wood hydrolyzates from Douglas fir contain very few of the requirements for yeast production except the sugar. Experiments were conducted at the Forest Products Laboratory in which various levels of nitrogen phosphate, potassium, and magnesium were present. With an excess of nitrogen present, nitrogen utilization was found to be 3.2 pounds per 100 pounds of reducing sugar. With less than that amount, ihe )ield of yeast decreased. Phosphate requirements for maximum yeast yields were 1.5 pounds of phosphoric pentoxide for 3 00 pounds of reducing sugar. Potassium requirements were 1 pound of potassium chloride for each 100 pounds of reducing sugar. The addition of magnesium sulfate did not change the yield or rate of grow-th of yeast. §oIutions to which had been added 3.4 pounds of nitrogen in the form of urea, 1.6 pounds of phosphoric pentoxide as phosphate salts, and 1.1 pounds of potassium chloride for each 100 pounds of reducing sugar gave, by continuous propagation in a throughput time of 3 to 4 hours, yeast yields of about 42% of the fermentable sugar.
PRODUCTION AND PROPERTlES OF WOOD HYDROLYZATE
HE production of food yeast on nood hydrolyzates has been shown by several investigators to be retarded by the presence of inhibiting substances. Fink and Lechner (W, 5,4) reported yeast growth was improved by diluting the sugar solution to 1.5Yc concentration. It is desirable to avoid such a procedure, hon-ever, in order to keep to a minimum the amount of liquor that must be fermented and centrifuged. Leonard and Hajny ( l a ) found that the presence of malt extract and the application of elevated temperatures to the sugar solution after neutralization aided in yeast growth. Peterson, Snell, and Frazier (16) found that it was necessary to dilute wood hydrolysates to 1% concentration to obtain maximum yields of yeast. Several special investigators (1, 11, 13, 14, 15, 19, 22) have reported interviews with various companies engaged in the production of yeast in Germany. Because many of these interviews were made when the plants were closed, when the technical staffs of the plants were not present a t the conferences and technical data upon which plant operation was based were not available, it is necessary to verify some of their work. In work a t the Forest Products Laboratory several modifications were made on the German procedure (2'1) for the production and neutralization of wood sugars (5, 6, 7') that alter the biological character of the wood hydrolyzates; therefore, the conditions used in Germany may not apply to present work and tests should be made on the new material. The use of mechanical means of controlling foam conditions ( l O , l 7 ) has made possible continuous production of food yeast from higher concentrations of sugar with more efficient air utilization and without the use of antifottm agents. This also indicates that previous work should be repeated. This report describes experiments performed at the Forest Products Laboratory to determine the amount of nitrogen, phosphate, potash, magnmium, and sulfite that must be added to the wood-sugar solutions to obtain the niaximum growth of yeast, the amount of air required, and thp effects of adding oxygen to
The wood hydrolyzate used for these experiments was produced by methods that have been described recently (6, 7 ) . The process consisted of continuously pumping 0.5 7, sulfuric acid solution through a charge of chipped mood waste in w stationary digester a t temperatures increasing progressively from 150' to 185' C . for a period of about 3 hours. The acid n-as neut'ralized with lime to about pH 4.2 and the precipitate removed at 130" to 138' C. The resulting sugar solution WBB passed to a flash tank to permit the removal of furfural, met'hanol, and other volatile producm. The solution obtained in this manner in the pilot plant contained 4.5 to 6'3, reducing materia! calculated as glucose, about 0.1% calcium sulfate, 0.5 to 1.0%, other salts, and about l.Oy$ nonsugar orgaiiic products, which nzay consist of bark and wood extracts, soluble lignin, and suga) deconiposit>ionproducts. The material indicated as reducing sugar and calculated at4 glucose consisted of a mixture of hexoscs and pentoses plus nonsugar-reducing materials. The amounts difi'cred with each species of wood, sugar from softwoods being lox- in pentosee
A'R CAP *ic
Figure 1.
2068
8CJ70V SEA RjiMS
5CL'LF
, -o
SCALE
tu o
r i m
5,4AFJ E(/~H!?~'G SGALh 10 -
,tic*
Laboratory-Scale Experimental Propagator. with Mechanical Aerater
November 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
(about 10%) and the hardwoods high (about 30%). This material also included matter that had reducing properties but was not sugar. For example, wood sugar from the hydrolysis of Douglas fir wood waste was 83y0 fermentable to ethyl alcohol by yeast and therefore concluded to be 83% hexoses. When the total wood sugar was subjected to yeast production until there was no further drop in reducing properties, there still remained 6% of reducing material calculated as glucose. A test of this jolution for sugars by the osazone test indicated no sugars to be present. This would indicate the presence of 11% pentoses. In work with Douglas fir hydrolyzates, when the reducing material had been 94% utilized, it was cpncluded t h a t the sugars were completely utilized. The nonsugar organic products as determined by analysis of the residue, which in Douglas fir hydrolyzate are present in about 1yo concentration, have some tannin-like properties in that neutral or slightly alkaline solutions in contact with iron and air turn exceptionally dark. For t h a t reason, if a light colored yeast is desired, unprotected iron should not be used for the construction of the propagator. Aeration also caused the precipitation of some of the dark material if the pII of the propagator was 6 or above. Evaporation of the hjrdrolyzate to a molasses having 50% reducing sugar changed the nature of this material so that a large portion of the nonsugar organic material settled out of the Jolution on standing. Solutions that had been evaporated and allowed t o stand until this material had settled out were less Inhibitory to the growth of yeast. Wood-sugar solutions contained very little nitrogen or phosphate and therefore both of these elements had t o be added for the growing of yeast. EQUIPMENT
The propagator used for this work has a working capacity of L1.2 liters of liquid. It is shown in Figures 1 and 2 and has been described previously in a report by Saeman (17). Sugar solutions with nutrients were introduced continuously by a proportioning pump from a feed tank. Because of the tendency of‘the solutions to become alkaline as the yeast used the organic acids in solution, a n automatic p H controller was installed for introducing sulfuric acid solution to maintain the desired pH. The feed was maintained a t a low p H (approximately 4.1) so as to
2069
decrease the acid required. Under satisfactory operating conditions very little acid was required t o maintain the propagator at a p H of 5.0 to 5.5. If a higher p H was desired, the p H of the feed could be raised. Air was measured by a household dry gas meter INOCULUM
The inoculum used for these experiments was prepared ac described in previous reports (9, 10). The yeast used for all tests, except those involving baker’s yeast, was a strain of Torulo utilis isolated at the University of Wisconsin and designated a8 Torula utilis No. 3 in their collection. This strain has been acclimatized for use on wood hydrolyzates at the Forest Producte Laboratory. The CeTeviseae yeast used in one portion of thip work was a commercial baker’s yeast purchased at a local grocerv store and acclimatized for use on wood sugars. METHODS OF SAMPLING AND ANALYSIS
Reducing sugar was determined by the method of Schaffer and Somogyi (18, 20). Samples for yield of yeast were obtained by placing 10 ml of the substrate with the yeast in a 5 X inch weighed culture tube and then centrifuging. The supernatant liquor was decanted. I n order t o wavh the yeast, water was added to the remaining contents of the tube and mixed with the yeast, after which the tube was again centrifuged. The washing was repeated and then, after the free liquid was decanted, the tube with the yeast residue was dried for 24 hours at 100” C. and then weighed. Nitrogen determinations were made by the usual Kjeldahl method on the sample used for yeast yield. OPERATION OF T H E YEAST PROPAGATOR
For each set of experiments on nutrient requirements, the propagator was operated with a “normal” feed containing the experimentally determined normal requirements of nutrient salts between each test until the yeast was growing normally with sugar and nutrients flowing in and yeast and spent liquor Rowing out, so as to make each test as independent of other teste as possible in a continuous propagator. T h e temperature used was 29 ’ to 30 O C. The propagator was started by placing approximately 2 liters of yeast inoculum produced in shake flasks into the tank and then starting the motor for the aerator, the air, and the pump for introducing the sugar solution. I n the start it was found to be advisable t o use a diluted sugar solution until the quantity of yeast had been built up. Yeast was removed from the overflow and returned to the propagator t o hasten the establishment of equilibrium conditions. After the propagator had operated on full-strength sugar throughout 2 or 3 days and was utilizing the sugar continuously in a throughput time of 3 hours it was then ready for the tests. Yeast yields were obtained after operating continuously at equilibrium conditions of the test for 24 t o 36 hours and were determined by sampling.
Figure 2. Temperature-Control Equipment of Laboratory- Scale Propagator
NITROGENREQUIR~MENTS. Reports (19) of nitrogen for yeast production in Germany gave 3.5 kg. of nitrogen per 100 kg. of sugar for solutions containing approximately 373 reducing sugar, but there was no indication as t o the reason for choosing this value. A series of experiments was made, using amounts of nitrogen from 2.5 t o 12 pounds of nitrogen in the form of urea per 100 pounds of sugar in t h e feed liquor. T h e nitrogen content of the yeast was slightly higher with the higher concentrations of nitrogen, but recovery was low. Maximum recovery of nitrogen with maximum sugar utilization was obtained when there were 3.2 pounds of nitrogen per 100 pounds of sugar in the feed. Table I gives the average values for the series of experiments. PHOSPHATE, POTASH, AND MAGNESIUMREQUIREMENTS. A series of experiments was made t o determine t h e phosphate, potash, and magnesium requirements for satisfactory yeast
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
2070 TABLE
I.
Kitrogenb per 100 Pounds of Reducing Sugar in Feedc, Lb.
REQUIREMEXTS FOR Y E A S T GROTTR~
A-ITROGER'
Nitrogen Content
of Yeast,
70
Nitrogen Recovered in Yeast,
%
- PH Feed
Propagator
Reducing Sugai Utilized,
70
Other nutrients were held constant as follows: phosphoric pentoxide [ a s (NHI)ZHPO~], 2 pounds; potassium chloride, 1.6 pounds: and magnesium sulfate as 1 pound per 100 pounds of sugar in feed. b S i t r o en i n addition t o that contained in the ammonium phosphate was introfuced as urea. Douglas fir hydrolyzate reducing-sugar content, 4.6%.
TABLE 11. PHOSPHATE REQUJREMENT FOR YEASTGROXTH" Phosphateb (P~OS) per 100 Pounds of Duration Reducing Sugar of Test, in Feedc, Lb. Hours 2.0 1.5 1.0 0.5
48 24 24 25 25
Yeast Yield Based on Sugar Used,
70
Protein Content of Yeast, %
Reducing Sugar Utilized, %
44.1 43.0 36.4 35.5 27.8
51.9 52.8 60.9 49,8 38.3
93.7 93.8 22.5 (6.9
33.5 0.0 Other nutrients were held constant as follows: nitrogen, 3.4 pounds; potassium chloride, 1.6 pounds; magnesium sulfate, 1.5 pounds pcr 100 pounds of sugar in feed. 6 Phosphate (PzOi)wa3 added as (KHdzHPO4. C Douglas fir hydrolyzate with reducing sugar content 4.57,. Feed rate was 3 liters per hour into a tank with 11.2 litera operating capacity. a
TABLE 111.
POT-4sSIUM
Potassium Chloride per 100 Pounds of Duration Reducing Sugar of Test, in Feedb, Lb. Hours 2.0 1.5 1.0 0.5 0.0 1.1
24 24 22 22 33 24
REQGIREYENTS FOR Yeast Yield Based on Sugar Csed,
%
42.0 42.1 40.2 41.0 37.2 42.0
YEAST
GROWTH'
Protein Content of Yeast, c/o
Reducing Sugar Utilized, %
52.0 53.0 50.4 54.0 49.9
93.8 93.0 90.0 80. t 42.2 93.0
50.9 Other nutrients were held at: nitrogen, 3.4 pounds. magnesium sulfate, 1.5 pounds; phosphoric pentoxide, 1.6 pounds per l o b pounds of sugar in feed. b Douglas fir hydrolyzate with reducing-sugar content 4.5%. Feed rate was 3 liters per hour into a tank with 11.2 liters operating capacity. Air was introduced a t 0.5 cubic foot per hour. a
Vol. 40, No. 11
determine if the same benefit iesultcd. The sugar solution was fed into the propagator at 3 and 5 liters per hour in order to provide conditions that usually permit good yeast production and also limit the good utilization. At both feed rates the addition of sulfite improved yeast growth. Table W gives the values for yeast growth under the two conditions. EFFECT OF ADDIXGOXYGENTO THE AIR SUPPLY. The addition of oxygen to the air supply may have the samr effect as adding more air or of increasing the ratio of oxygen in the air supply. The quantity of oxygen was increased by about 25 and 50Yc in the experiments. Yeast growth was determined at different pH's. The results of the experiments are shown in Table V. Utilization of sugars was improved by about the sanie degree as increasing the amount of air would have cauqed. T h e yicld of yeast, however, was higher when oxygen was added than would have resulted by an increase of air. EFFECT OF INCREASIXG THE HEIGHTOF THE DRAFT TUBE. An increase in the height of the draft tube (Figure 1) results in a n inciease in the capacity of the propagator without changing anything except the depth of the liquid. This increase in height extends the throughput time without changing the feed rate. I n these experiments the depth was increased by 25y0by attaching ail extension to the top of the draft tube and increasing t h e height of the overflow tube. This increased the operating liquid capacity from 11 2 to 14 liters. The results of t,hese experiments are shown in Table VI. At a feed rate of 3 liters per hour, very little improvenient was noted with the increased depth. Yeast yield, air required per pound of yeast, and sugar utilization were within the limits of experimental error. At a feed rate of 4 and 5 liters per hour, the increased depth gave higher yields of yeast and better sugar utilization. At a feed rate of 6 liters per hour, however, the yeast was mashed out so rapidly that it was difficult to maintain equilibrium conditions.
EFFECTOF SCGARCOXCEKTRATION o s YEAST GROWTH. Much of the previous work on yeast growth has been with dilute sugar solutions. Peterson, Snell, and Frazier (16) used solutions containing 170 reducing sugar, and the German yeast production (19)was with solutions Containing 2.5 to 3% sugar concentrations. Table VI1 gives the results of a serieq of experiments in which the
TABLE 11'. EFFECT ON YEAST GROWTH O F ADDIXGSULFITE SUGAR SOLUTIONS growth. Table I1 shows that 1.0 to 1.5 pounds of phosphoric pentoxide per 100 pounds of sugar in the feed provide sufficient phosphate for good yeast production and sugar utilization. The data in Table I11 indicate that 1.1 pounds of potassium chloride per 100 pounds of wood sugar provide sufficient potassium. Experiments with and without magnesium sulfate gave no change in yeast yield or in sugar utilization, indicating that sufficient magnesium was present already. or that its presence was not a requirement. EFFECTON YEAST GROWTHO F -4DDIh-G SULFITE TO SL*GAR SOLUTIONS. Several investigators (2,1%,16) have found t h a t the addition of small amounts of sodium sulfite improve the yeast growth on wood hydrolyzate. The most beneficial results in previous work (8) at the Forest Products Laboratory were obtained if the sulfite was added with the lime when the solutions were neutralized. This treatment appeared to provide a reducing medium while the solutions were being neutralized. Bpcause of its insolubility, calcium sulfite was not present in the neutralized solution. One pound of commercial sodium sulfite was added for each 200 pounds of reducing sugar. The same effect was obtained with about one tenth that amount of sulfur dioxide if introduced into the unneutralized sugar solution just before the addition of lime. The use of the improved propagator had a favorable effect upon so many of the growth characteristics of yeast t h a t the tests on the addition of sulfite were repeated to
Duration Feeda Rate of Test, per Hour, Hours Liters
Dry Yeast Based on Sugar Used,
%
PH
Protein Content,
TO
Sugar Utilized,
%
%
53.7 54 4
94.1 65.7
With Sulfite 69 24
3 5
$5, 0
40.0
5,O 32.5 Without Sulfite
3 5.0 27.0 53.7 84.7 5 5.0 20.0 55.3 76.0 The feed was Douglas fir hydrolyzate containing 4.5% reducing sugar plus the required amounts of nitrogen, phosphate, and potadi. .4ir wae introduced a t a rate of 0.5 cubic foot per minute. 73 31
Q
TABLE v. EFFECTON Oxygen Added per Minute Cu. Ft.' 0.000 0,000 0.025 0.028 0.028 0.025 0.05 0.05 0.05
YEAST THE
Air Supplied Rate of per Feeda Minute, per Hour, Cu. Ft. Liters 0.500 0.500 0.475 0.475 0.475 0.476 0.480 0.450 0.450
GROWTH OF
ADDING OXYGEN T O
SUPPLY
pH p.0 J .0 5,8 5 5 4.;
6.7 4.7
5.5
Dry Yeast on Sugar Used, %
Protein Content,
Sugar Utilized,
43.5 35.0 43.8 43 0 31.7 49.1 43.8 47.9
53.0 54.0 50.9 53.0 55.1 5 1 .o 54.9 50 2 46.8
94.3 90.3 94.2 90.8 85.0 94.9 90.4 91.1 94.4
70
%
6.0 53.0 Feed was Douglas fir hydrolyzate containing 4.5% reducing sugar and the usual supply of nutrients. 4
INDUSTRIAL AND ENGINEERING CHEMISTRY
November 1948
TABLE VI. EFFECTON Rate of Feed b Der Hour, Liters pH 3 4
5.9 5.0 5.8 5.4 5.2 5.2 6.3 5.2 6.2
YEAST GROWTHO F INCREASING THE HEIGHT OF THE DRAFT TUBE& DuraDry Air per rlir per tion of Yeast on Protein Pound of Sugar Sugar Content, Yeast, Utilized, Minute Test 7% Cu. Ft. % Cu. Ft.’ HouA Used, % N o Extension
22 43.: 22 35.0 With Extension 14 43.8 32 39.0 20 38.1 26.4 20 14 37.6 18 29.0 8 29.5
0.5
0.5
0.5 0.75 0.5
0.5 0.5 0.5
0.5
52 4 54.0
241 233
94.3 90.3
52.7 50.7 e4.0 OB. 1 49.2
240 399 210 249 193 218 232
94.1 94,s 91.8 89.9 81.6 77.4 72.6
..
..
2071
peared to be the maximum yeast growth for the air supplied. This represented 1pound of dry yeast for 200 cubic feet of air. GROWTH OF YEAST ON VARlOUS HYDROLYZATES
Species of wood may vary in respect t o the inhibiting properties and also in the amount of nonsugar reducing material that may be produced when hydrolyzed. Table VI11 gives the values for yeast yields and sugar utilization with four species of wood. The yield of yeast was highest from oak and lodgepole pine, but the highest utilization of reducing substances resulted with Douglas fir and lodgepole pine. Oak hydrolyzate is high in acetic acid, which is utilized for the production of yeast. Oak wood is also high in extractives, which would explain the lower utilization of the reducing substances. GROWTH OF BAKER’S YEAST (CEREVISEAE) ON WOOD HYDROLYZATES
The success attained in the growing of Torula yeast in the specialized propagator used for these experiments has resulted in Concentrainterest in the possibility of growing a commercial baker’s yeast Sugar Dry Yeast on Protein tion of Sugar on wood hydrolysates in this propagator. A sample of baker’s Utilized, 9% pH Sugar Used, % Content, 7% in Feeda, 7% yeast was purchased a t a local store and used to inoculate a 95.1 63.3 39.1 1 5.3 42.1 94.5 49.9 2 5.2 sample of wood sugar in the propagator. There was a delay of a 95.1 42.6 45.3 4 5 1 93.4 40.6 55.3 6 5.3 few hours before the yeast began t o develop, but after the initial 55.1 90.9 26.6 8 5.0 period, acclimatization was complete and the yeast grew readily ‘l’he sugar in the feed was Douglas fir hydrolyzate, which had been on Douglas fir hydrolyzate. When the pumping rate was 3 ooncentrated t o 20% and then diluted for use and fed a t a rate of 3 liters per hour. Air was introduced a t a rate of 0.5 oubic foot per minute. liters of feed per hour and the air rate 0.5 cubic foot per minute, yeast yields were 44.6 t o 49.9% of the sugar utilized and the reducing material was 93 to 94% utilized (Table IX). As with OF YEASTON VARIOUS HYDROLYZATES~ TABLEVIII. GROWTH Torula, yields and utilization were lower a t higher feed rates. Rate of Feed per Dry Yeast Protein Sugar Oak hydrolyzate appeared to contain inhibiting substances t h a t Hour, on Sugar Content, Utilized, did not permit the growth of baker’s yeast on that hydrolyzate. Hydrolyzate Liters PH Used, % % %
TABLEVII. EFFECTO F
SUGAR CONCENTRATION ON YE.4sT
GROWTH
(I
Laroh
3 3 5
5.3 6.3 4.5
45.9 49.0 91.2 47.4 47.4 91.7 33.0 52.4 49.3 5 6.3 37.6 42.4 50.6 3 5.0 42.6 45.3 95.1 Douglas fir 3 5.9 51.7 53.8 94.0 Lodgepole pitic Southern red oak 3 5.5 49.3 54.0 83.8 5 The hydrolyaates from these species of wood were concentrated to 20% eugar concentration and later diluted to 5”1, for yeast growth. Nutrients used were 3.4 pounds of nitrogen in the form of urea, 1.6 pounds of PzO6 as phosphate salts, and 1.1 pounds of potassium chloride or each 100 pounds of sugar in the feed liquor. Air was introduced a t 0.5 cubic foot per minute.
TABLE IX. GROWTH OF BAKER’S YEAST(Cereviseae) ON WOOD HYDROLYZATE Rate of Peed per Hour, Hydrolyzate Liters Red oak 3 Douglas fir 3 3 4 5
Dry Yeast Based on Protein Sugar Used, Content, pH 5.2 5.5 6.2 5.0 5.9
%
15.3 44.6 49.9 41.0 26.7
%
44:7 44.7 44.8 52.5
Air Requirement per Pound Sugar of Dry Yeast Utilized,
Cu. Ft’.
%
...
24.8 93.1 94.0 88.8 57.0
235 210 291
...
sugar concentration ranged from 1 to 8%. I n order to produce Bolutions t h a t would differ only by the effect of dilution, wood hydrolyzate from Douglas fir was evaporated t o 20% sugar concentration and then diluted t o the various concentrations used in these experiments. This evaporation precipitated some of the inhibiting materials and, as a consequence, the values In this table may not be compared with solutions that were not so evaporated. The air rate was the same in all experiments and, therefore, the ratio of air to yeast produced was much greater with dilute solutions. When 8% sugar solutions were fed, the air supplied was insufficient to grow yeast, and alcohol was also produced. The high sugar utilization and also high yeast yield, when 6% sugar solutions were introduced, represented what ap-
SUMMARY
Wood-sugar solutions to which had been added 3.4 pounds of nitrogen in the form of urea, 1.6 pounds of phosphoric pentoxide as phosphate salts, and 1.1 pounds of potassium chloride for each 100 pounds of sugar gave yeast yields of 40 t o 50% of the fermentable sugar. The use of a special fermentor for mechanical control of foam to increase the contact of air with the solution resulted in complete utilization of the sugars in 3 to 4 hours’ time in a continuous fermentor. The presence of sulfite during the neutralization of the sugar prior t o yeast production improved the yeast yield. Adding oxygen to the air supply increased the yield of yeast. Increasing the depth of the propagator gave slightly higher efficiency in the use of the air used for yeast growth. I n the equipment used, sugar in concentrations over 6% was not efficiently utilized. Species of wood differ in respect to the yield of yeast given as compared to the sugar utilization. Baker’s yeast may also be propagated continuously on Douglas fir hydrolyzate, giving good yeast yield and good sugar utilization. ACKNOWLEDGMENT
The authors wish to acknowledge the assistance given them by Jean Koehler of the Forest Products Laboratory staff and the counsel given by W. H. Peterson of the University of Wisconsin. LITERATURE CITED
David, Lt. Col. B. D., Technical Intelligence Industrial Committee Report, “Manufacture of Torula Food Yeast from Sulfite Liquor,” May 23, 1945. (2) Fink, H., and Lechner, R., Biochenz. Z . , 286,83(1936). (3) Fink, H., Lechner, R., and Heinesch, E., Zbid., 278,23(1935). (4) Ibid., 283,71 (1935). (5) Harris, E.E.,“Saccharification of Wood,” Forest Products Laboratory Mimeograph, R1475 (March 1945). (1)
2072
INDUSTRIAL AND ENGINEERING CHEMISTRY
(6) Harris, E. E., a n d Beglinger, E., IND.ENG.C H E M . , 38, 890 (1946). (7) Harris, E. E . , Beglinger, E., I l a j n y , G. J., a n d Sherrard, E. C., I N D . ENG.CREM., 37, 12 (1945). (8) Harris, E. E., H a j n y , G. J., H a n n a n , M. L., Rogers, S. C., I b i d . , 38, 896 (1946). (9) H a r r i s , E. E., H a n n a n , If.L., Llarquardt, R. Ii.,a n d B u b l . J. L., I b i d . , 40, 1216 (1948). (10) H a r r i s , E. E., S a e m a n , J. F., M a r q u a r d t , R. R., H a n n a n , 11.L., a n d Rogers, 8.C., I b i d . , 40, 1220 (1948). (11) Holderby, J. M., “Waldhof Process for Production of Food Y e a s t , ” F I A T Report 619, U. 8.D e p t . Commerce, (May 2 2 , 1946). (12) Leonard, R. IT., a n d Hajny, G. J.,IKD.ENG.(:REM., 37, 390 (1945). (13) Pavcek, P. L., Technical Intelligence I n d u s t r i a l C o m m i t t e e Report, “Wood Sugar Yeast M a n u f a c t u r e , ” May 28, 1945. (14) I b i d . , “Wulf Hefa-Fabrik-Dessau,” May 29, 1945. (15) Pavcek, P. L., “Wood Sugar Yeast M a n u f a c t u r e , ” IJ. S. Depr,. Commerce, P B Report 4292 11945).
Vol. 40, No. 11
W.H., Snell, J. F., a n d E’razier, W. C . , IND.ENQ. CHEM.,37, 30 (1925). (17) Saenian, J. F., Anal. Chem., 19, 913 (1947). (18) S a e m a n , J. F.,Harris, E. E., and Kiine, A. A , , INr). E N U
(16) Peterson,
CHEM., AIT.41,. ED., 17, 95 (1945). (19) S a e m a n , J. F., Locke, E. G., a n d D i c k e r m a n , G. K., “Produw tion of Wood Sugar in G e r m a n y and I t s Conversion t o Yeas? a n d Alcohol,” F I d T Report 499, C . 5 . Dept. Commerce (Nov 14, 1945). (20) Schaffer, R . A , , a n d Somogyi, N., J . B i d . Chem., 100, 695 ( 1 933) (21) Scholler, H., F r e n c h P a t e n t 706,678 ( N o v . 28, 1 9 3 0 ) ; Spiritusin& 55, 94 (1932); Zellsfoff-Faser, 32, 64 (1938); Chcm. Ztg., 60, 293 (1936); 63, 737, 752, (1939). ( 2 2 ) Skoog, F. K., “Food Yeast Production a n d Utilization in ( h r . many,” U. 6 . Dept. Commerce, P B Report 2041 (1945).
RBCBIVED -May 9, 1947. Presented before tho Division of Agricultural and Food Chemistry at the 111th Meeting of the A h i E R I c A n CHEMICAL Socraru. Atlantic City, N. J.
k Catalysts f o r
rocarbon
LOUIS SCHRIERLING (j.,iversal Oil Products Company, Riverside, I l l . Anhydrous aluminum chloride dissolves readily in nitromethane, nitroethane, and the two nitropropanes yielding solutions which, i n contrast to those in alcohols, ethers, and ketones, are catalytically active. The active component of the solution is the addition complex, AlCd3.RN02. The nitroparaan solutions of aluminum chloride are miscible with benzene; the nitroparaffins thus are solubilizers for the metal chloride in the hydroaarbon. Homogeneous phase alkylation may be accomplished by contacting the clear solution with a n olefin or alkyl halide. [n a two phase system, to permit the recycling of the catalyst, the catalyst l a ~ e m ~ a. y be salted out by adding sodium chloride. The solutions of aluminum chloride in the nitroparaffins may be used also for the alkylation of
isoparaffins with olefins. The solutions are not soluble iu paraffins and are available for recj cling. Higher reaction temperatures are necessary. than those that are used witb unmodified aluminum chloride. Data for the alkylation of isabutane with propene are disctissed. When isopropyl chloride is brought into contact with isobutane in the presence of unniodifiied aluniinunr chloride, the principal reaction is reduction of the alkyl chloride to propane. If, on the other hand, a solution of aluminum chloride in nitromethane is used as catalyst, reduction of the isopropyl chloride is markedly decreased and alkylation of isobutane to heptane occurs. The nitroparaffin solutions of aluminmn chloride effected virt-caally no isomerization of n-pentane or methjlcy clopentame.
ERTAIK properties of anhydrous aluminum chloride lessen its usefulness as a catalyst for hydrocarbon conversions. [t is often excessively active initially and catalvzes undesirable side reactions such as cracking or autodestructive alkylation. I t forms addition compounds (lower layer sludge) with aromatic and olefinic hydrocarbons (present as reactants or formed during the reaction) which usually result in a decrease in the activity and Life of the catalyst. Frequently it is advantageous, both in industrial processes and in laboratory syntheses, to use a catalyst which has uniform activity and a constant physical state. Fluid aluminum chloride catalysts become the logical choice because Loss of the original crystalline form is apparently inherent in all but a few reactions. Furthermore, the liquid catalyst permits more efficient utilization of the aluminum chloride; there is no loss in activity because of the coating of catalyst particles with sludge. The fluid aluminum chloride catalysts which have been described previously have usually been addition compounds, such as make up the lower layer complex, and uncombined aluminum chloride. Mixtures of aluminum chloride and certain metal &lorides-e.g., antimony trichloride-in the liquid state a190
are active catalystg. Kitrobenxene has been used as solvent for aluminum chloride in a few isolated cases. Other organic compounds such as chloroparaffins (methyl chloride and tetrachloroethane) and carbon disulfide also have been uhed but have the disadvantage that they dissolve only a small amount of the metal halide; thus the use of large proportions of the solvent is necessary. On the other hand, aluminum chloride is highly soluble in ethers, ketones, and alcoho!s, but the resulting solutions are catalytically inactive, a t least for the alkylation of hydrocarbons. h’itroparaffins also have high solvent power for anhydrous aluminum chloride; solutions containing more than SOY0 by weight of the metal halide are obtainable. I n the present investigation it was discovered t h a t unlike the ether, ketone, and alcohol solutions, these nitroparaffin solutions are excellent catalysts, particularly for alkylation reactions. This paper describes the results obtained with nitromethane, nitroethane. and the two nitropropanes as solvents. CATALYST SOLUTIONS
The active component of the solutions of aluminum chloride iD the nitroparaffins is not aluminum chloride as such but rather the
