chloride. The nitrogen was present as a result of the proteinaceous material in the wheat, and presumably, there would be a small amount of sulfur i n the char also. The granular carbon from the whole wheat mas not as hard or abrasion-resistant as the laboratory grade of coconut charcoal. Hoivever, the wheat char can be handled and poured without a significant amount of breakage or dusting. T h e attrition of the wheat char from abrasion is greater than tlie maximum allowed for commercial carbons. T h e yields ranged from 20-30y0 of the starting weights of the wheat after washirig and drying the carbon. Much fine carbon wis lost because of the need to break u p the cake of char.
literature Cited
Conclusions
College of Engineering Research Division T T-ashington State C7niversity Pullman, TT7ash. 99163 To whom correspondence should be addiessed. RECEIVI:D for review lIay Yl 1972 ACCEPTED August 23, 1972 Presented ;at the Seventh Sational Conference on Wheat Utiliz;ition ltesearch, Manhattan, Kan., Xovember 3, 1‘371. Thi.5 stiiJy was funded in part by the Washington Wheat Commisbioii.
Granular-activated carbon can be produced by heating whole d i e a t in the presence of zinc chloride to decompose the carbonaceous material and then continuing the heating up to 600°C to activate the char. The resulting carbon has activity comparable to that of a commercial activated carbon but lacks the cohesive strength characteristic of coconut char.
Iloyirig, E. G. in “Encyclopedia of Chemical Tech.,” 1-01 4, 2nd ed., pp 149-38, Interscience, Kew York, N.Y., 1964. Koppelmaii, E., Chem. Eng. .Yews,48 (43), X (October 12, 1Y70). llaggs, F. A. 1) in“l1anufactured Carbon,”pp81-101, Pergainon, Kew York, S . Y . j 1968. Riley, T. I{., “Carbonized Wheat Composite-,” R t . Louis Sympo+m on Advanced Composites, St. Louis, l I o . , April 6-7, 19il.
Sasaki, K., Kanagawa Daz‘gaku Kogakubu Kenkyic Hokokic ( 8 j, 44-56 (1970); CA, 73, 3449 (1970).
Shindo, A,, Souina I., U.S.Patent 3,55i,020 (Janiiarj- 19, lYi1). Smisek, ll.,Cerny, S.,“Active Carbon,” pp 10-4>, Elrevier, X e x York, N.Y., 1970. I3RUC’E 1 7 . ETTLISGl K I R K F. AII).ilIS DOROTHY J. SCHECTEK
Separation of Trimethylpentanes by Extractive Crystallization with Thiourea Multistage extractive crystallization with thiourea i s used as an effective method for the enrichment of the isomeric trimethylpentanes. Data are presented on the separation of 2,2,4-TMP from mixtures with the 2,3,3- and 2,3,4-TMP isomers and on the separation of the 2,3,3,-TMP from mixtures with 2,3,4-TMP.
R e c e n t work a t this laboratory has shown that mixtures of certain close boiling hydrocarbons can be separated by multistage adduction ivith thiourea. This includes the separation of hydrogenated monoterpenes (XcCandless, 1 9 i l ) and the selective separation of p-phellandrene from dipentene and p-cymene (Handl, 1971). As a n ext,ension t,o these studies, we have recently investigated the separation of the trimethylpentanes with this t.echnique. Experimental
in the previous studies, adducts ivere formed by mixing the hydrocarbon mixture wit’li a near-saturat’ed solution of thiourea in methanol and then cooling. The following conditioiis apply for all runs: Thiourea solution-feed 1\Iethanol-thiourea
10 cc/cc 8 . 0 cc/gram
hdductioii began immediately upoii contact of the feed and thiourea solution a t room temperature, but the adduct was allowed to form for 24 h r in a chest freezer a t -1iOC before filtering. For the t,est in ivhicli 2,2,4-TMP was separat,ed, feeds of varying composition were prepared by adding appropriat’e amounts of 99 mol yo 2,2,4-T1\1P to a mixture coiitainiiig about i9.4y0 2,3,4-TMI’, 20.6y02,3,3-TMPJ arid a negligible
amount of the 2,2,3-T1\IP isomer. The starting feed material for the experiments 011 the selmatioii of the 2,3,Y-’TM1’ : i l l t i 2,3,4-T1\IP isomers contained about ilyc 2,3.4-TSI1’ : i l l t i 297, 2,3,3-T11P, except for two test. which u-ed tlie niixtuw containing 20.670 2,3,3-TlIP. -111 were obtniiiecl from l’liill1~~> Petroleum Co. Following adduction the t,als \yere filteretl from tile rero\.ereil methanol and residue, and the li~-drocarboii~ : i > from t’lie adduct by steani distillation. R e d u e 1 i y ~ r i ) c ~ ~ i ~ l ~ ) i i ~ !!-ere liberated bl- wat,er waaliiiig. 111each ?aye a~)~iuijxin~:il +*I\. 1,’2 of tlie original feed was recovered in the ntltluc t , 1 The niaterial liberated from the adducat \ w s u-ell :Ifor the next adductioii run iii the 2J.3- a i i t l 2,:3)4-‘1’11i ) separatioii test- (+) 1
y1
where y1 = fraction of species enriched in adduct (either 2,2,4- or
2,3,3-T;\I P) ZI = fraction of same species in residue
2 4 .B FRACTION 2 2 4 - OR 23,3-TMP IN RE’SIDUE
10
Figure 1. Adduct and residue compositions for 2,2,4-TMP in mixtures with 2,3,3-and 2,3,4-TMP and for 2,3,3-TMP in mixtures with 2,3,4-TMP
Table I. Comparison of Extractive Crystallization Separation Factor with Relative Volatility AV
~ 2 , 2 , 4 - ,(2,3,32,3,4-) c~2,3,3-,2,3,4-
+
Adduction
Distillation
5.1
1.6
1.4
0.97
Literature Cited
Results and Discussion
The results of the experiments are presented in Figure 1 which shon s the equilibrium distribution between the adduct and the residue of the species enriched in the adduct. This is analogous to the more familiar vapor-liquid equilibrium. The adduction tenciency was 2,2,4-T;\1P > 2,3,3,-TMP > 2,3,4-T1\IP. The selectivity was greatly in favor of the 2,2,4-T1\IP when the feed contained the three isomers, and in these tests there ‘il.as no discernible separation of the 2,2,3- and 2,3,4-TMP isomers This may have been because the feed for each of these tests was made by the additlon of the 2,2,4-TLIP to the same mixture of the other ti\o, and as a result the feed for each run contained the same relative amounts of the 2,3,3and 2,3,4-TlIP isomers I n the tests 151th the 2,3,3- and 2,3,4-TXP mixtures, the 2,3,3-T3IP was the species enriched in the adduct, but the selectir ity \vas much leis than for the 2,2,4-T1\IP.
464
Ind. Eng. Chern. Prod. Res. Develop., Vol. 1 1 , No.
The average values of t’he experimental separation factors are shown in Table I compared with the ideal vapor-liquid relative volatility. The extractive crystallization separation factor is significantly higher than the relative volatility. 2,3,3-TMP has a higher boiling point than 2,3,4-TJIP; therefore, the relative volat’ilitg is less than 1 which means the 2,3,4-TMP would be enriched in distillation. Although pure 2,2,4-T11P is readily obtained by distillation, it’ is not practical to obtain the other isomers in pure form by dist’illation of mixed trimethylpentanes. However, it is evident from this study that 2,2,4-, 2,3,3-, and 2,3,4TblP could readily be separated by multist’age extractive crystallization, whereas the same separation would require a greater number of stages by distillation. The effects that 2,2,3-TMP would have on the separation is not known, but this compound is apparent.ly oiily present in minor amounts in alkylate (Kirk and Othmer, 1947).
4, 1972
Handl, E . L., AIS thesis, Montana State University, Bozeman, Mont., 1971. R. E. Kirk and D. F. Othmer, Eds., “Encyclopedia of Chemical Technology,” 1st ed., 1‘01 1, p 546, Interscience, New York, K.Y., 1947. McCandless, F. P., Ind. Eng. C h e w . Prod. Res. Develop., 10 ( 4 ) , 406 (1971).
F. P. lIcCAINDLESS1 RICH-IRD D. XIOUKTAIN ROBERT D. OLSOX STEVEN P. ROTH LXWRESCE J. VATU‘ D Y K E Department of Chemical Engineering Montana State University Bozeman, Jlont. 69715 1
To whom correspondence should be addressed.
RECEIVED for review June 12, 1972 A C C E P T E D September 11, 1972
