50
INDUSTRIAL AND ENGINEERING CHEMISTRY
p.p.m. turbidity a t 140-150" F. Saturated sodium chloride was used as regenerant, also at about 150' F. Although the unit gradually lost operating capacity to the extent of about 25% in 15 months because of resin fouling, no degradation of the resin occurred. Treatment with 1570 hydrochloric acid t o remove the accumulation of ferric hydroxide and complex silicates restored the original capacity. An unexpected result in all of these units has been a marked reduction in turbidity of the water being softened or demineralized. Water containing 5-10 p.p.m. turbidity which has passed through sand filters of 40-80 mesh will be reduced t o 1-2 p.p.m. turbidity in passing through a resin of 12-30 mesh. Surface water of 50-100 p.p.m. turbidity may be reduced to 15-20 p.p.m. The resin appears to coagulate the colloidal particles, possibly because of its high concentration of ionic charges. This clar5cation is advantageous for both boiler feed water and for municipal supplies. LITERATURE CITED
(1) Adams, B. A. [to Ocean Salts (Products) Ltd.], Brit. Patents 536,266 and 541,450 (1941) ; Johnsen, H. (to Norsk 1.iydro
Vol. 38, No. I
Electric), Norwegian Patent 59,035 (1938) ; Findlay, D. M. (to U.S.Rubber Co.), U. S. Patent 2,261,021 (1941). (2) Adams, B. A., and Holmes, E. L., J. SOC.Chem. Id., 54, 1-6T (1935); Brit. Patents 450,308-9 (1936) and 474,361 (1937); French Patents 796,796-7 (1936); U. S. Patents 2,104,501 (1938), 2,151,883 (1939), and 2,191,853 (1940). (3) Akeroyd, E. I., and Broughton, G., J . Phys. Chent., 42, 343 (1938).
Behrman, A. S., IND. EXG.CHEM.,1 9 , 4 4 6 (1927). Committee on Water Works Practice, J . Am. Water Worke ASSOC., 35, 721-50 (1943). 6)Furnas, C. C., and Beaton, R. H., IND.ENQ.CHEM.,33, 1500 (1941); Thomas, H. C., J. Am. Chem. SOC.,66, 1664 (1944). (7) Griessbach, R., Ueber die Herstallung und Anwendung neuerer Sustausch adsorbienten, inbesonders auf Rarzbasis", Verlag Chemie, Berlin, 1939; abstd. in Angcw. Chem., 52, 215-19 (4) (5)
(1939). (8) Myers, R. J., and Eastes, J. W., IND.ENG.CHEM.,33, 1204 (1941). (9) Thompson, J . Roy. A g r . SOC.Engl., 11, 313 (1850); 13, 123 (1852). (10) massenegger, H., and Jaeger, K. (to L G . Farbenindustrie), U S. Patent 2,204,539 (1940).
PRESENTED before the fall, 1945, Meeting-in-Miniature of the Midland Section. AMERICANCHEMICAL SOCIETY.
Kinetics of Sucrose Crystallization J
SUCROSE-NONSUCROSE SOLUTIONS ANDREW VAN HOOK Natural Resources Research Institute, University of W y o m i n g , Laramie, Wyo. The effects of the most commonly occurring nonsucrose constituents of cane and beet juices on the crystallieation velocity of sucrose were investigated. These materials invariably depress the rate of adjustment of sucrose solutions when conditions are similar to those encountered in sugar boiling and crystallizing. The activity interpretation previously proposed explains the effects of these contaminants in a qualitative way when they are present singly or in combinations which imitate real molasses.
A
QUAKTITATIVE understanding of the crystallizing behavior of massecuites should develop from a kinetic interpretation of the crystalliaation of sucrose from pure solutions and from synthetic sirups. Velocity data and mechanism for pure sucrose solutions have already been discussed in previous papers of this series (24, a5) as well as the effects of common electrolytes. The present paper supplements the list of salts already considered ($66)and presents additional data on the effects of various substances which are likely to be found in cane and beet juices. I n most cases the concentrations of impurities considered are greater than those usually found in ordinary final molasses. A static technique was used for most of the results presented. The procedure consists of seeding the sirup, which has previously been adjusted t o the proper conditions, and following the rate of adjustment refractometrically. It has already been demonstrated (24, 85) t h a t this method gives essentially the same values for pure sucrose as do methods involving the actual measurements of growing crystals, and the procedure is more convenient and rapid. With impure solutions the same agreement prevails out to the usual limit of impurity when single constituents are considered, but at extremely low velocities the usual procedure, in which the smear adjusts directly on the refractometer prism, gives velocities lower than methods in which stirring is involved.
This same difference is suggested by the observation that deviations from monomolecularity with unstirred solutions are more pronounced as the purity decreases. These variations, however, are all beyond the three-quarter life period of reaction and are therefore of little significance in the evaluation of rate constants; they may be important in ascertaining the mechanism of crystallization from impure solutions. It is well recognized that the p H of a sirup has a tremendous effect on the crystallization velocity of sucrose (6,10, 16). An acid condition causes a diminished rate t o a variable extent on account of inversion. From p H 6-8 the r&es are reproducibly constant; above 8 the values are again decreased variably. A development of color is associated with this change. A p H of 7-8 was therefore adopted as standard in these investigations, and was realized by the addition of acid or base when necessary, This was preferred to the use of buffered solutions in order t o avoid salt effects. VELOCITY OF CRYSTALLIZATION
The general behavior of synthetic sirups is demonstrated with the results for raffinose shown in Figure 1. The concave curvature is significantly maintained on a semilog plot, as discussed later in connection with Figure 5 . The same type of result was obtained when invert sugar and betaine were the impurities; in no case, at 30" C. or higher, was a n increase in velocity observed at small concentrations of nonelectrolytes (7, l a ) . However, a t 16' C. and an initial sucrose concentration equivalent t o sucrose/ (sucrose water) = 0.685, relative velocities of 1.30 in the presence of 0.4 gram of raffinose per 100 grams of water, 1.21 in the presence of 1.0 grams betaine per 100 grams water, and 1.11with 1.0 grams invert per 100 grams water, were obtained. At higher concentrations of impurities the relative velocities of crystallization were diminished and a t higher temperatures these maxima also disappeared. This general behavior is exactly what is ex-
+
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
January, 1946 1.2
z
0.61
c
0
\
.2 MOLALITY
.4 OF R A F F I N O S E
Figure 1. Effect of Raffinose on Crystallizatian Velocity of Sucrose
x 'O
2
Sucrose Source Sucroae Water 0.710 (8) This work 0.722 This work 0.722 This work 0.722
+
So 1.045 1.05
1.05 1.05
Temp., " C. 25
Stirring Gentle
30 30
Gentle Rapid
so
None
51
for calcium salts of some of the amino acids are noted ( 1 ) . Affermi also reports results of the free amino acids; and while his numerical values were fairly well duplicated in this work, they are not reported since the formation of invert sugar must have been extensive at the conditions used. NONELECTROLYTES. Invert sugar, one of the commonest nonsucrose constituents of cane juices, was investigated in some detail, and the results are summarized in Figure 3. The results for supersaturation coefficient 1.08 are composite of those already reported (86)and additional values. As already noted, these curves become still more concave upward at higher concentrations of impurities if agitation is employed during the adjustment. Betaine depresses the crystallization velocity of sucrose in the s i m e manner as other substances. The only comparable results available in the literature are those of Affermi (I), Figure 4. The purpose of industrial juice treatment is t o reduce the nonsucrose content t o a minimum previous t o boiling, and prominent among the undesirable constituents are various indefinite colloidal materials. Although the bulk of these materials is removed in the usual defecation and clarification processes, small amounts may concentrate in the sirups. Since practically their effects are serious, i t was considered significant t o ascertain their influence on the crystallization velocity of sucrose. Pectins (beet and citrus), albumen, lecithin, and dextrin were examined a t concentrations beyond what might be expected in normal practice. I n general, they restrain the rate of adjustment very little while increasing the viscosity tremendously. The results are summarized in Table I and a r e of the same nature as those previously reported (26) for gum-arabic and starch. Ingelman's data (9) for beet pectin show the same kind of effect but to a greater extent.
pected from the solubility relations in these polycomponent systems (6, 13, 14, $0'92,99,96),although there seems t o be no immediate quantitative connection between the two (8, $5). The TABLE I. EFFECT OF COLLOIDS ON CRYSTALLIZATION VELOCITY OF SUCROSE actual increases reported are small and would not have great 130" C.; sucrose/(sucrose water) 0.7221 practical consequence, since commercial boiling and crystallizing are carried out at purities and temperatures where the effect Crystn. Velocity Substance Relative to Pure of impurities upon the crystallization velodity of sucrose is invariSirup Substance Substance + Water pH ably a decelerating one. 0.057 6 0.92 0.012 7 0.97 ELECTROLYTES. The obvious naturally occurring salts of cane 0.057 7 1.02 and beet molasses (18),potassium sulfate, sodium sulfate, calcium 0.057 6 0.09 0.057 8 0.83 .salts, amino acid, and aconitic acid salts (9), were investigated t o Crude leoitgin Satd. 8 0.95 Egg albumen 0.01 8 0.98 supplement the general behavior already discussed ($6). The reDextrin British gum) 0.01 8 0.92 sults (Figure 2) fit fairly well into the linear semilog pattern alDextrin {British gum) 0.03 8 0.96 ready discussed, although the data for organic electrolytes suggest a steeper slope at intermediate concentration t h a n P t h a t for the inorganic substances. The values computed i n the usual way for both potassium .and sodium sulfates were abnormally high (9,%) at intermediate concentrations; but, .quite different from most of the other salts examined, the usual "24-48 hour end points were exb tremely variable and uncertain .4in these two cases. If a n e-: w P a b b trapolated end point was used I , I >inthe calculations, the agreeable results shown in Figure 2 were 2 4 6 >realized. I O N I C STRENGTH Calcium chloride and calcium hydroxide alone were too acid Figure 2. Effect of Electrolytes on Crystallization Velocity of Sucrose at 30' C . and pH 8 .and basic, respectively, to estabGenoralirsed from pnedoum results (15) lish a pH of 7-8, and therefore d Calicrum aspartate ( I ) 0 KrSOd mixtures were employed. LikeX NarSO4 So - 1.06, 20" C., p& unknown / \ 0 Sodium asparaginate A CaClrCa(0Hh wise, adjusted salts of amino V Sodium awnitate 0 Calcium asparaginate ( I ) 0 Glycine, sodium malt D Sodium succinate .acids and aconitic aoid {3)were 0 Glycine, calcium malt (1) Q Sodium glutamate rrequired. CorqpmM.athw results a Sodium aspartate ,O\ Tyrosine
+
4
-
-
INDUSTRIAL AND ENGINEERING CHEMISTRY
52
Vol. 38, No. 1
X
V
I
2
X
3
MOLALITY
Figure 4. Effect of Betaine on the Crystallization Velocity of Suerose
8 12 MOLAL1 T Y
4
Figure 3.
X
Q V
0
0.743
+
so
1.03 1.05
1.05(atirred during adjuatment) 1.08
EFFECTS OF NATURAL IMPURITIES
The salient features of the results obtained are assembled in Pigure 5 . Molalities are used exclusively and emphasize the valence effect as pointed out by Sandeia (19). The curves are approximately linear a t small concentrations of impurities, but a definite curvature is developed a t higher concentrations in all cases. This deviation is qualitatively of the nature demanded by the more complcte analysis of the situation according t o the artivity interpretation already suggested ( 2 4 ) . The formula, (velocity) impure = il (velocity) pure n h e r e z = aconstant I = concentration of impurity in terms of molalities is an approximation of the more accurate equktion. (velocity impure) ko asat,= log (velocity) pure ko asai.
Sucrose Sucrose Water
+
So
Affernii ( I )
0.711 0.722
1.06 1.05
0 This work
Effect of Invert Sugar on Crystallization Velocity o f Sucrose at 30' C. Sucrose Sucrose Water 0.709 0.722 0.722
0
16
Sourcc
"P'einp. G. pll j/
20
so
? 8
late actual sugar working conditions. The values are all of' thc order usually observed a t corresponding purities in actual juices ( 1 1 , 15, 17, 21). Lower purities than those represented were experimentally not feasible. The curves suggest the relative melassigenic values of the various juices ( 4 ) . In this case "molasses" means that product to which juice is economically exhausted rat.her than the equilibrium saturated solutioiis of the polycomponent systems involved. Thc slopes of tho curves in Figure 5 a t concentrations approaching those actually found in final molasses are significant for this purpose. If Figure 5 is converted t o a weight concentration basis and if potassium sulfate is considered as representative of ash, one finds that the relative impeding effects, or melassigenic values, of raffiiiosc, betaine, ash, and invert are in the order mentioned. This is, in part, the order observed from the exhaustibilities of different sirups (8, 2%). A quantitative expression of this relat,ion will bc attempted in subsequent consideration.
lo'
+
+
It is possible to evaluate the constant term / ~ from ~ the a data ~ for ~ pure ~ sucrose, and a t 30" C. in Kucharenko's dimensions ( I $ ) it is approximately - 1000. Tho correction needed to represent the data for invert sugar in a linear way over the complete range of concentration is of the order of -350 in these same units (and depends slightly on the sucrose concentration). The discrepancy is probably created by an accumulation of effects due to oversimplification of the theory. For qualitative and practical purposes the equation may be taken to represent the crystallizing behavior of impure sucrose solutions out to the usual ext,ent of these impurities. The validity of this semiempirical application is illustrated in Table 11, which compares calculated and observed results for several mixtures which simu-
b'igure 5 .
Sriinniary of Effects of Probable Natural Impurikies on C r j st.11lizaiion Yelocity o f Sucrose
(1,l) ctc. Corresponding valent typa salts A . gumrnary of psevious results (2s) for ammonia, phenol, aniline, and ethyl alcohol
Invert su-ar (Figure 3, 50 = 1.05) Raffinosc(Figure 1) D. Betaine (Figure 4)
B. C.
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
January, 1946
TABLE 11. RELATIVEVELOCITY OF CRYSTALLIZATION OF SYNTHETIC MOLASSES AT 30’ C. AND ~ € 1 8 Initial Purity, % Composition, % 2.9 NaC1, 8.8 invert, 63.8 sucrose, 24.5 water 84.5 2.1 NaC1, 32.6 invert, 47.2 sucrose, 18.1 water 57.5 1.8 NaC1, 43.6 invert, 39.4 sucrose, 15.2 water 46 5.0 raffinose. 5.8 betaine. 64.4 sucrose. 24.8 water 85.5 4.9 ra5nose, 5.6 betaine, 2.8 NaC1, 62.6 sucrose, 24.1 water 82.5
.
velocity of Crysg. Obsvd. Calcd. 0.27
0.38
0.09
0.09
0.01
0 03
0 20
0.13
0.08
0.11
ACKNOWLEDGMENT
The author acknowledges the support given this work by the Sugar Research Foundation and the assistance, through supplying samples of many of the contaminants used, of the Chemistry Department of the University of Wyoming (amino acids), E. K. Ventre of the Baton Rouge Station, U. S. Department of Agriculture (aconitic acid), and the Western Regional Research Laboratory (citrus pectins).
53
(4) Dahlberg, H. W., Proc. Am. Soo. Sugar Beet Tech., 3, 323 (1942). (5) Dubourg, J., and Saunier, R., Bull. SOC. chim., 6, 1196 (1939). (6) Grut, E. W., Listy Cukrovar., 5 6 , 3 7 (1938). (7) Hungerford, E. H., and Nees, A. R., IND. ENG.CHEM.,26, 462 (1934). (8) Hungerford, E. H., and Nees, A. R., Proc. Am. Soc. Sugar Beet Tech., 3,499 (1942); Intern. Sugbr J., 46, 323 (1944). (9) Ingelman, Bjarn, The Svedberg (Mem. Vol.), 1944, 156. (10) Kauznetzov, A. F., Sucr. belge, 45, 9 (1925). (11) Krasil’shchikov and Tsab, Khim. Referat. Zhur., 1940, No. 1011, 126. (12) Kucharenko, I. A., Planter Sugar Mfr., 75 (May-June, 1928). (13) Landolt-Biirnstein, Physikalisch-Chemische Tabellen, 1936. (14) Lebedeff, S., Z. Tier. deut. Zucker-Ind., 1908,599. (15) Nakhamovich and Zelekman, Nouch. Zapiski Sakharnol Prom., 6, 32, 109 (1928). (16) Naveau, G., Sucr. belga, 62, 310, 336 (1943). (17) Nees, A. R., and Hungerford, E. H., IND.ENG.CHEM.,28, 898 (1936). (18) Reich, G. T., Ibid., 37, 53G (1945). (19) Sandera, Chimie & Industrie, 1933, 1147. (20) Schukow,I., 2. V e r . deut. Zucker-Ind., 50, 291 (1900). (21) Smolenski, K., and Zelanzny, A., Gaz. Cukrownicza, 74, 303 (1934). (22) Spencer-Meade,Cane Sugar Handbooks, 8 t h ed., 1944. (23) Thieme, J. G., “Studies in Sugar Boiling”, tr. by 0. W. Willcox. New York. Facts About Sugar. 1928. (24) Van Hook, Andrew, IND.ENO.CHEM.,36, 1042 (1944); 37, 782 (1945). (25) Van Hook, Andrew, and Shields, D., Ibid., 36, 1048 (1944). (26) Verhaar, G.,Arch. Suikerind. Nederland en Ned. I n d i l , 1,324,464 (1940). I
LITERATURE CITED
(1) Affernii, E., Ind. snccar. ital., 27, 319 (1934). (2)
Amagasa and Nishizawa, J .
Soc. Chem. Ind. Japan, 39,
Suppl.
binding, 263 (1936)
(3) Ambler, J. A , , Turer, J., and Kennan, G. L., J . Am. Chem. Soc., 67, 1 (1945).
PRESENTED on the program of the Division of Sugar Chemistry and Technology of the 1945 Meeting-in-Print, &ERICAN CH~MICAL SOCIETY.
roduction of Isoprene from Turpentine Derivatives B. L. DAVIS’, L. A. GOLDBUTT, AND S. PALKIN2 Naval Stores Research Division U . S . Department of Agriculture, New Orleans, La.
I
SOPRENE, C,H8 (a homolog of butadiene), has been used
extensively as a copolymer in the production of syethetic elastomers. According to reports (9), it is utilized in the preparation of Butyl rubber. It constitutes a n essential monomer for certain neoprenes and is of value for the production of special Buna S type elastomers. Terpene hydrocarbons, C10H16 (dimers of isoprene), particularly terpenes derivable from turpentine, have long been regarded as a logical source for the production of pure isoprene, and figured prominently in early investigations and patent literature. Turpentine, consisting almost wholly of terpene hydrocarbons (over 98%), is an abundant commercial product, and the United States produces about two thirds of the world’s supply. Isoprene was first isolated in a reasonably pure state by Williams (2%) who applied the name “isoprene” t o a liquid fraction boiling between 37’ and 38’ C. (specific gravity 0.6823 at 20’ C.) which he obtained by distilling rubber. Tilden (21) first prepared isoprene from turpentine by passing the vapors through a red hot tube. H e obtained about a 2% yield of a fraction boiling between 37” and 40” C. The further discovery by Tilden (89) that isoprene polymerizes to rubber led to considerable experimental work on the production of isoprene from terpenes. Claims of isoprene yield up to 70% from various terpene frac1 2
Present address, Bureau of Animal Industry, Washington, D. C. Deceased May 2, 1943.
tions have been made in the patent literature (9, 4, 7 , 14, i 7 , 18, 20, 24). However, from other available literature (1, 6, 8, 10, 19, 13, 16, 19, 26)it is apparent that, in spite of occasional claims of high yields and purity (usually not confirmed by subsequent investigators), only small amounts of isoprene of doubtful purity can readily be obtained from turpentine or the terpenes by the methods so far described. I n 1942 Palmer (16) reported that isoprene was being produced commercially from terpenes, and that it was possible t o make isoprene of very high purity by this process. No details were given as to the process or the terpenes utilized. I n the investigation reported here the method of carrying out this depolymerization involved the use of a n electrically heated, glowing wire coil immersed in the liquid terpene itself; provision was made to allow low-boiling products, including the isoprene, to escape as rapidly as possible from the reacting medium. Although the wire coil is immersed in the liquid terpenes, the pyrolysis is actually that of a vapor phase system, since the coil is so hot (about 750’ C.) that liquid is not in actual contact with it. The products of pyrolysis are quickly removed from the hightemperature zone and cooled by the vigorously boiling liquid terpene. Further, the isoprene produced is only slightly soluble in the relatively high-boiling terpenes a t their boiling point, so there is comparatively little bpportunity for the isoprene t o be subjected to further pyrolysis. Figure 1is a diagram of the pyrolysis apparatus.
