Separation of the C,, to
C,,Fraction
of Petroleum
BEVERIDGE J. MAIR, WILLIAM J. MARCULAITIS, and FREDERICK D. ROSSlNl Petroleum Research laboratory, Carnegie Institute o f Technology, Pittsburgh, Pa.
b The heavy gas oil and light lubricating oil fraction, Cle to CZj, of the representative Mid-continent petroleum of the API Research Project 6 was separated into an aromatic portion and a paraffin-cycloparaffin portion b y adsorption with silica gel. The aromatic portion was further separated b y adsorption with alumina into portions containing mononuclear, dinuclear, and trinuclear aromatics. The paraffincycloparaffin portion was further separated b y treatment with urea into a concentrate of n-paraffins and a concentrate of branched paraffins plus cycloparaffins. The portion containing the n-paraffins was fractionated b y distillation at very low pressure to give concentrates of the individual nparaffin hydrocarbons. These latter were separately subjected to crystallization to yield purified samples of the individual n-paraffins, C18 to C24. Taking the C18to Cz6fraction as 1 OO%, the relative amounts o f the several types of hydrocarbons separated from this fraction of this petroleum are, in percentage b y volume: total aromatics, 25.2; mononuclear aromatics, 12.2; dinuclear aromatics, 7.9; trinuclear aromatics, 5.1 ; n-paraffins, 17.1; branched paraffins plus cycloparaffins, 56.3; residue, 1.4.
A
of the work of the . h e l i e a n Petroleum Institute Research Project G on the composition of petroleum, a n investigation involving the separation of the CISto CZsfraction of petroleum, heavy gas oil, and light lubricating oil, into several types of hydrocarbons has been completed. I n this n-ork, the following types of hydrocarbons were separated and determined in this fraction: n-paraffins, branched paraffins plus cycloparaffins, mononuclear aromatics, dinuclear aromatics, and trinuclear aromatics. The individual nparaffins, Cis to C24,were separated. S PART
OUTLINE
OF
INVESTIGATION
Portion. The separation of the c18 to C25 fraction into a paraffin-cycloparaffin portion and a n aromatic portion was effected b y adsorption n-ith silica gel (Davison Chemical, grade 912, 28-200 mesh) in stainless steel columns, 4.5 cm. (1-3, -I inches) in inside diameter and 19.3 nieteis (63.3 feet) in length (5, 6). I n a typical experiment, 16 liters of an equivolume mixture of the GIBto Cog fraction and 2,2,4-tiimethylpentane was charged to the column. This mas followed in order, with 16 liters of 2,2,4-trimeth-lpentane, 16 liters of benzene, and 24 liters of 2-propanol, respectively. The pressure of inert gas a t the head of the column varied from 0 to 15 pounds per q u a r e inch gage and the rate of collection of filtrate was between 0.4 and 1.5 liters per hour. The results of a typical experiment are shown in Figures 2, 3 and 4. Figure 2 s h o w the refractive index of the filtrate v i t h respect to its volume. The initial high refractive index portion, d.of the curve corresponds to the palaffin-cycloparaffin material which n as eluted n i t h 2,2,4 - trimethylpentane. The removal of the paraffins and cycloparaffins is indicated by the drop in refractive index to the value foi 2.2.4-
The steps involved in this inrestigation are shonn in Figure 1, as follows: ( a ) The CISto C25 portion of the original petroleum was separated by adsorption with silica gel to give a paraffin-cycloparaffin portion, a n aromatic portion, and a smal! residue portion, the latter comprising the nonhydrocarbon components; (b) an aliquot part of the aromatic material m s fractionated by adsorption with alumina to give mononuclear, dinuclear. and trinuclear aromatic portions; (c) an aliquot part of the paraffin-cycloparaffin portion was fractionated by treatment with urea to give a portion containing n-paraffins and a portion containing branched parafins pluq cycloparaffins; ( d ) an aliquot part of the n-paraffin portion Tyas separated by distillation a t low pressures into concentrates of the individual n-paraffins, c18 to C24; and ( e ) the concentrates of the individual n-paraffins were puiified by crystallization to give samples of the individual n-paraffine, C18to C24. SEPARATION
C1, to Cr5 Fraction into a ParaffinCycloparaffin Portion and an Aromatic
j
C,9
10
Cz5
;SACTION
OF
PETROLELIM
loo%
ADS3RPTION. WIT?
1
SILICA GEL
7
MATERIAL ANALYZED
The CISto CZ6fraction of petroleum, heavy gas oil, and light lubricating oil, examined in the present n-ork was from the representative Mid-continent petroleum which has been under investigation since 1928 by the American Petroleum Institute Research Project G (6). The material comprised 139 liters and constituted 15.6% by volume of the original crude petroleum. 92
ANALYTICAL CHEMISTRY
Figure 1. Schematic diagram showing separation of CIS to C2b fraction of petroleum
trimethylpentme. The peak a t R corresponds to the aromatic portion n-hich )vas eluted with benzene. The remwal of the aromatic portion is indicated ljy the gradual drop in refractive index to t'lie value for pure benzene. The peak a t C corresponds t o the residual portion which was desorbed by 2propanol and consists of nonhydrocarbon components. Figure 3 shows the percentage by rolwne of oil contained in the filtrate with respect to the volume of filtrate. This plot further emphasizes t'lie quantitative nature of the separation of the niaterial into the three portions. Figure 4 shon-s the refractivc index o f t'lie hydrocarbon part of the filtrate ivitli xspect to its volume, after the i,cxioT-al of the solvent by distillation from the hydrocarbon. The gradual inwcnse in the refractive indes of the ai,omatic portion indicates some sellaration according to type of :iromatic hydrocarbon (mononuclear, dinuclearj and tr,inuclear). The composition of the Cis to c ' 2 1 fraction, coniputed from similar adsorption esperiments on 139 liters of niat,erial, \vas found to he as follon-s in pciwntage by volume : paraffin-cycloparafin port,ion, 73.47,; aromatic portion, 25.2%; and residue portion. 1.4%. Aromatic Material into Mononuclear, Dinuclear, and Trinuclear Aromatic Portions. Experiments ivere conducted with several adsorbents antl eluents to find t h e combiiiation of adsorbent antl eluent, best atiited for t h e separation of tlie aronistic material into mononuclear, dinuclear, a n d trinuclear aromatic portions. Stainless steel adsorption columns 19.3 met,ers (63.3 feet) in lcngtli and 1.93 em. ("4 inch) in diameter were used (6, 6). The rate of n-itlitdrnival of filtrate was about 0.4 liter per hour, with 50-ml. fractions normally being collected. The solvent was removed from each fraction, or from a blend of adjacent fractions! by simple distillation, followed by sweeping the oil a t 180" C. with a stream of nitrogen to remove the last trsces of solvent. As shown in Figure 1, the aromatic material was blended into four lots according to refractive index: Lot A greater than 1.580, Lot 13 from 1.580 to 1.555, TJot C from 1.555 to 1.520, mid Lot I> from 1.520 to 1.500. The first series of experiments was performcd with aromatic material from each of Lots A , B, C, and D, using silica gel (Davison Chemical, grade 912, 28-200 mesh) and alumina (Aluminum Co. of America, grade F-20, 80-200 mesh) as adsorbents and benzene as tlie eluent. I n addition, one experiment \vas performed with aromatic material from Lot T) using activated carbon
152-
d 1 5 o r
0
0
BENZENE
LY
I-
'm-
Q 0 C
.
146-
X W C
l
a E
140
=
c II
138-
I L
I
I
0
10
20
I 30
2 .2 . 4 - TRIMETHYLPE F NTA ANE NE 2- PROPANOL PANOL I
I
40
50
VOLUNE IN L I T E R S
Figure 2.
Fractionation of original material of Cia to Czj fraction by adsorption
The charge was a mixture of 8 liters of the Cla to C25 fraction plus 8 liters of 2,2,4trimethglpentane. The adsorbent R as silica gel. The material charged was eluted with 2,2,4trimethylpentane, benzene, and 2-propanol, in that order. A , B , and C are, respectivel>-.the paraffin-cycloparaffin, aromatic, and residue portions.
w L 5
I
80
PARAFFINS PLUS C Y C LO PAR AFF I N S
AROMATIC S
-T-
7
0
i',
40
VOLUME I N L I T E R S
Figure 3.
Fractionation of original material of
CIS to
C26
fraction by adsorption
This experiment is the same as that shown in Figure 2, but with a different presentation. The scale of ordinates gives the percentage of the C18 t o CZSmaterial in the filtrate, and the scale of abscissas gives the volume of the filtrate.
(Columbia Carbon, grade F, 60-200 mesh) as the adsorbent and benzene as the eluent. The columns were packed t o a height of 52 feet with the respective adsorbents (7.8 pounds of silica gel, 10 pounds of alumina, or 5 pounds of carbon). Each charge consisted of 200 ml. of aromatic material mixed with 100 ml. of benzene. The results are shown in Figures 5, 6, and 7 . Figure 5 s h o w the refractive index of the filtrate Ivith respect to its volume, for two experiments with aromatic material from Lot B, one using silica
gel (curve I) the other alumina (curve 11). The other evperiments in ahich the original charge consisted of material from Lots A, C, and D yielded results similar to those shown in Figure 5. Figure 6 shows the refractive index of the hydrocarbon part of the filtrate with respect to its percentage by volume, after recovery from experiments with silica gel. Curves A . R , C, and D show the separations obtained with these lots of material. Figure 7 shows the refractive index of the hydiocarbon part of the filtrate with respect to its percentage by volume, after Iecoveiy froiii experiments n i t h VOL. 29, NO. 1 , JANUARY 1957
93
PERCENTAGE BY VOLUME cc
2c
,E$
I
6C
80
I
I
100
-
Figure 4. Fractionation of original material of Cl*to C25 fraction by adsorption
This experiment is the same as that shown in Figures 2 and 3, but with a different presentation. The scale of ordinates gives the refractive index, and the scale of abscissas the volume, of the CIS to Czs material recovered from the filtrate.
C
-
1.52
1
I
1
u' e v)
N
f-
U
Figure 5. Fractionation of aromatic portion (Lot B)s by adsorption
c0
Results of two experiments are shown: I, with silica gel, and 11, with alumina. For each experiment, the charge was 200 ml. of the aromatic portion, Lot B, plus 100 ml. of benzene. The eluent was benzene.
n
-
1.50-
z
W
2 V
a a LL W
a
1.48
0
1
1
I
I
2
3
VOLUME IN LITERS I
7
O
7
-
Figure 6. Fractionation of aromatic portions (Lots A, B, C, and D) by adsorption
1 I45
0
25
50 PERCENTAGE
94
ANALYTICAL CHEMISTRY
75
BY
VOLUME
100
The scale of ordinates gives the refractive index and the scale of abscissas the percentage by volume of the aromatic material recovered from the filtrate. The adsorbent was silica gel. For each experiment, the charge was a mixture of 200 ml. of the given aromatic portion plus 200 ml. of benzene. The eluent was benzene. The dashed line near the middle of each curve indicates the refractive index of the original lot.
4
Figure 7. Fractionation of aromatic portions (Lots A, B, C, and D) by adsorption
The scale of ordinates gives the refractive index and the scale of abscissas the percentage by volume of the aromatic material recovered from the filtrate. The adsorbent was alumina. For each experiment, the charge was a mixture of 200 ml. of the given aromatic portion plus 200 ml. of benzene. The eluent was benzene. The dashed line near the middle of each curve indicates the refractive index of the original lot.
r
1 I
I
' I
W
-
"
IS
I
oocTEN E s
"
W
1.39
t '371 0
I
\ \
5
< (
2- P R O P A N O L + I 25
-. 1
I
1
30
VOLUME IN L I T E R S
Figure 8. Fractionation of aromatic portion (Lot A) by adsorption
The scale of ordinates gives the refractive index and the scale of abscissas the volume of the filtrate. The adsorbent was alumina. The charge was a mixture of 200 ml. of the aromatic portion, Lot -4;plus 200 ml. of iso-octenes. The material charged was eluted with iso-octenes, benzene, and 2-propanol, in that order. X, Y , and 2 refer to mononuclear, dinuclear, and trinuclear aromatic portions, respectively.
0
25
PERCENTAGE
50
BY
75 VOLUME
100
Figure 9. Fractionation of aromatic portion (Lot B) by adsorption
The scale of ordinates gives the refractive index and the scale of abscissas the volume of the filtrate. The adsorbent was alumina. The charge was a mixture of 200 ml. of the aromatic portion, Lot B, plus 200 ml. of iso-octenes. The material charged was eluted with iso-octenes, benzene, and 2-propanol, in that order. X, Y , and 2 refer to mononuclear, dinuclear, and trinuclear aromatic portions, respectively.
i -
--4
2-PROPANOL I
I
-
I
VOL. 29, NO. 1 , JANUARY 1957
95
alumina. Curves A , B , C, and D show the separations obtained with these lots of material. The experiment in which activated carbon was used as the adsorbent and Lot D aromatic material as the charge was abandoned after 242 liters of filtrate had issued from the column. The oil content of the filtrate had decreased from about 2% a t the beginning of the experiment to less than 0.02% a t the time the experiment was halted, when 70% of the original charge had been recovered. It was apparent that some of the aromatics were so strongly adsorbed as to render further use of this adsorbent impractical. The second series of experiments was performed [Tith aromatic material from each of Lots A, B, C, and D, and a blend prepared from these four lots to have the same composition as the total aromatic portion. illuniina rvas used as the adsorbent and a commercial mixture of “isooctenes” as the principal eluent. Each column was packed to a height of 63 feet with 12 pounds of alumina. Each charge consisted of a mixture of 200 ml. of aromatic material and 200 ml. of isooctenes. I n the first experiment, the charge contained aromatic material from Lot A. It was eluted with 25 liters of iso-octenes, 4 liters of benzene, and 4 liters of 2-propanol. I n subsequent experiments, the charges consisted of aromatic material from Lots R,C, D, and the blend. Each was eluted with 12 liters of iso-octenes, 4 liters of benzene, and 4 liters of 2-propanol. The results are shoivn in Figures 8 to 14. Figures 8 to 11 shon. the refractive index of the filtrate with respect to its volume, for experiments in which aromatic material of Lots -4,B, C, and D, respectively, xere fractionated. Peaks X , I‘, and 2 correspond to the mononuclear, dinuclear, and trinuclear aromatic portions, respectively. The mononuclear and dinuclear aromatics ivere eluted with the iso-octcnes and the trinuclear aromatics ii-ith benzene. Figure 12 shons the refractive index of the hydrocarbon part of the filtrate with respect to its percentage by volume. Curves -4. B , C, and D correspond to the experiments shov n in Figures 8, 9, 10, and 11, respectively. Figure 13 shows the refractive index of the filtrate with respect to its volume, for the experiment with the blend corresponding to the total aromatic portion. Peaks X , Y . and 2 havc the same significance as in Figures 8 to 11. Figure 14 shows the refractive index of the hydrocarbon part of the filtrate with respect to its percentage, after recovery from the experiment with the blend. For an ideal sepalation of the aromatic portion into the three constituent types of hydrocarbons by the elution piocedure, a plot of refractive index with respect to the volume of filtrate would be expected to show three peaks, each peak containing components corresponding to the different degrees of aromaticity (mononuclear aromatics, dinuclear aromatics, and trinuclear aromatics). Also, a plot of refractive index mith respect to the volume of recovered oil may be expected t o show three plateaus of increasing refractive index. coiresponding, respectively, to the niononuclear, dinuclear, and trinuclear aromatic portions. I n the experiments with silica gel and alumina as the adsorhents and benzene as the eluent, only one peak was obtained (for each adsorbent
96
ANALYTICAL CHEMISTRY
I51
I
I
1
I
I\
i
I
I 5
10
15
20
VOLUME IN L I T E R S
Figure 10. adsorption
Fractionation of aromatic portion (Lot C) by
The scale of ordinates gives the refractive index and the scale of abscissas the volume of the filtrate. The adsorbent was alumina. The charge was a mixture of 200 ml. of the aromatic portion, Lot C, plus 200 ml. of iso-octenes. The material charged
was eluted with iso-octenes, benzene, and 2-propanol, in that order. X, Y,and 2 refer to mononuclear, dinuclear, and trinuclear aromatic portions, respectively.
2- P R 0PA N 0 L I37
I
1
5
IO
+
-L
I 15
7 20
V O L U M E IN L I T E R S
Figure 1 1 . adsorption
Fractionation of aromatic portion (Lot
D) by
The scale of ordinates gives the refractive index and the scale of abscissas the volume of the filtrate. The adsorbent was alumina. The charge was a mixture of 200 ml. of the aromatic portion, Lot D, plus 200 ml. of iso-octenes. The material charged was eluted pith iso-octenes, benzene, and 2-propanol, in that order. X and Z refer to mononuclear and trinuclear aromatic portions, respectivelv.
I .70
I45 0
I
I
I
25
50 PERCENTAGE BY
100
75 VOLUME
Figure 12.
Fractionation of aromatic portions (Lots A, B, D) by adsorption These experiments are the same as those shown in Figures 8 to 11, but with a different presentation. The scale of ordinates gives the refractive index and the scale of abscissas the percentage by volume of the aromatic material recovered from the filtrate.
C, and
-1
I
I
1
I
I
149;-
'1 A
'ISOGGTENES'
i i
0 cl
1
iI
1
I
I
I
instead of the t l i i ~ cn-hich n'ere espected (Figure 5 ) . Also, (Figures G and 7 ) definite plateaus were not obtained in the plot of refractive index with respect to the per cent by volume of recovered oil. The range of refractive index is larger in the experiments with alumina (Figure 7 ) than in those with silica gel (Figure G), indicating a slightly better separ~itionn-ith the alumina. This is in accord with published reports that alumina is better for tlie separation of aroniatics from aromatics ( 2 ) . For these reasons. alumina was used in thc subsequcmt esperimcnts. I t is apparent from Figures 8 to 11 that a reasonably satisfactory separation of Lots A, B, C,and D into monoiiuclear, dinuclear, and trinuclear aromatics \vas obtained with alumina as the adsorbent and with iso-octeiies as the principal eluent. I%ch figure shorn three peaks. Peak X bec~omes progressively larger in going from Lot A to Lot D, indicating. as expected, a higher content of mononuclear aromatics in the lower refractive index portion, Lot D. Peaks I.? and Z become progressively smaller in going from Lot A to Lot 11, indicating smaller amounts of dinuclear arid trinuclear aromatics in the lots of loner refractive index. An exception is peak Z of Figure 8. which is smaller than peak Z in Figure 9. This is explained by the fact that a larger volume of iso-octenes was used in t'he esperiment corresponding to Figure 8, so that some of the trinuc4lear aromatics were eluted with the isooctenes. The relatively rapid increase in refractive indes at values 11~ar1.55 and 1.62 for each curve in Figure 12 corresponds to the valleys between peaks X and I.', and 1' and Z3 respectively, of Figures 8 t o 11. These valur~srepresent approximately the I)omidai,it~sbetnwii the t h e e types of aromatics. The last fraction from eac'li experiment contained some high mclting rrystalline solid (indicated by the dottcd lilies in Figwe 12), possibly some tetranuclear aromatic material. The results given in Figures 13 and 14 show a satisfactory separation of the blend comprising the total aromatic portion and indicate that notliing is gained by processing t h p aromatic niatc~ial in the scparatc lots. Table I g i v e t,he composition of the aromatic portion computed from tlie results of the separate experiments on Lots A, B, C, and D, and from the results of the experiment on the whole blend. Paraffin-Cycloparaffin Portion into Concentrate of n-Paraffins and Concentrate of Branched Paraffins plus Cycloparaffins. TWO lots of n-paraffins were separated from t h e paraffin-cycloparaffin portion by treatment with urea. For t h e first lot, two processings with urea were used. T h e second lot was prepared using four processings with urea, as fo1lon.s: I n the first p r o c e s h g , 450 grams of urea was a d d d slonly to a mixture of 2 liters of acetone and 0.5 liter of the paraffin-cycloparaffin material. T h e mi\ture ma'. stirrid vigorously for 1 hour. The solid niol(~cu1ar compound IT hich the nparaffins form nith urca was separated by centrifuging (in a Flctclier 1abor:itory centrifuge, 12inch size. 2000 r.p.m.), transferred to a 4-liter beakcr containing 2 litrrs of acetone saturated n i t h urea, and stirred into a slurry. The solid material IT-asagain separated by centrifuging and decomposed with hot water, nnd tlic n-paraffin VOL. 29, NO. 1 , JANUARY 1 9 5 7
97
I70
-
I
I
I
Figure 14.
1.65-
Fractionation of total aromatic portion of
Cle to C25 fraction by adsorption
ci
*
This experiment is the same as that shown in Figure The scale of ordinates gives the refractive index, and the scale of abscissas
v)
13 but with a different presentation.
(u
t
a
0 C
xW
0
5 U
1
t 0
a
a LL U
a
I
/ M I N I
98
I
I
0
ANALYTICAL CHEMISTRY
I
P
I
I
I
For the entire C.8 to CZs fraction, this leads to the following values for the composition in percentage by volume:
lower and the refractive indices higher than those of the corresponding nparaffins. It is apparent that pure nparaffins were not obtained even rvith the four processings used in the treatment with urea. I n the high molecular w i g h t range (greater than 18 carbon
atoms per molecule), both cyclic and branched paraffins form solid molecular compounds with urea where the branching or cyclic ring is near the end of a long chain (8). I n this case i t is supposed t h a t only the chain part of the molecule enters the channel in the urea
\ X
W
H
'.
X
2 -J
'2,
X
0
>
4 2 Figure 16. n-paraffin
16 A
1'4
2;
i?lP
:4
21
N U M B E R OF C A R B O N ATOMS Percentage of total crude constituted b y each
The scale of ordinates gives the percentage by volume of the total crude and the scale of abscissas the number of carbon atoms per hydrocarbon molecule. 0 Previously reported values (6). X Values of this investigation.
Table I.
Amounts of Aromatics in
C18
to Ct5 Fraction of this Petroleum
ilmount in Aromatic Portion, Vol. yo Type Of From Lots A, Aromatic From blend B, C, and D Xononuclear 48.2 48.0 Dinuclear 31.5 27.8 Trinuclear" 20.3 24.2 Total 100 100
-
a
-
Amount in Entire CISto CZ6 Fraction, Vol. yo From Lots A, From blend B, C, and D 12.2 12.1 7.9 7.0 5.1 6.1 25 2 25.2
-
Probably includes small amount of tetranuclear aromatics.
Table II.
-
frameir oik R ith the branched or cyclic portion remaining outside. Also, certain branched chain hydrocarbons, which do not form solid molecular compounds n ith urea by themselves. are capable of entering into such compounds when mixed with n-paraffins. Examples are 3-methylheptane, 2-methylnonane, and 7-methyltridecane in the presence of n-decane ( 9 ) . These facts provide some explanation for the failure t o obtain a pure normal paraffin portion from the paraffin-cycloparaffin part of this material. I n Figure 15, portions M to T , respectively, were taken to represent the relative volumes of the individual n-paraffins, CI7 to C211 respectively, in this distillate. The percentage of each n-paraffin in the n-paraffin portion and in the total CI8to C25fraction was computed from these volumes. The amount in the total crude v,as then computed, assuming that no part of the n-paraffin material. Cli t o Cz4,was contained in fractions distilling above or below the portion investigated. These results are plotted in Figure 16, together n i t h results from earlier investigations (6) for the C i 2 to (2x7 n-paraffins. It is apparent from this figure that some of the C17 to C20 n-paraffins TT ere contained in the lowerboiling light gas oil and some of the C p 4 and Cs5 n-paraffins were present in the higher boiling material. For this reason the final curve in Figure 16 Tws drawn through what as considered to be the best data-that is, the previous data for the n-paraffins CI2 to C l ~and , the ne\$-data for the n-paraffins, Czl to (223. This curve leads to the following amounts of the individual n-paraffins in the total crude petroleum, in percentage by volume: n-octadecane, 0.50, n-nonadecane, 0.43; n-eicosane. 0.37; n-heneicosane. 0.32: n-docosane, 0.28; n-tricosane, 0.24; n-tetrscosane. 0.21. PURIFICATION
OF
n-PARAFFIN HYDROCARBONS
A to G in Figure 15 designate the portions of distillate which were selected for purification by crystallization. The procedure is described herewith.
Results of Processing with Urea of Paraffin-Cycloparaffin Portion to Obtain n-Paraffin Concentrate
Branched Paraffins plus n-Paraffins Cycloparaffins Loss in N o . of Freezing Refractive Freezing RefractiG Processing Volume, Process- Volume, pooint, index, Volume, point, index, Volume, Material Processed ml. ings ml. c. n 8z ml . c. n8z ml. 70 Paraffin-cycloparaffin portion 13 500 1 4100 30.9 1.4224 8693 Glass 1.4382 707 5.2 n-Paraffin concentrate from first processing 4,100 2 3438 33.3 1.4210 446 G1:iss 1.4382 216 5.3 From second processing 3,438 3 3080 34.4 1.4204 115 2 1.4247 243 7.1 From third processing 3,080 4 2830 35.0 1.4200 4-1 J 1.4218 20G 6.7 ~
____~
VOL. 29, NO. 1, JANUARY 1957
99
LITERATURE CITED
Table 111.
Summary of Crystallization Procedure and Results
Starting Material Portion Freezingfrom Volume, point, ml. C. Compound Fig. 15 n-Octadecane -4 112 26 0 n-Nonadecane B 157 30 9 n-Eicosane C 155 34.6 n-Heneicosane D 157 38.2 n-Docosane E 151 41.2 n-Tricosane F 141 43.9 n-Tetracosane G 92 46.9 Table IV.
(1) American Petroleum Institute Re-
Crystallization Procedure Final Sample No. of Vol. of Vol- Freezine crystal- Temp., solvent, ume, point, lizations O C. ml. ml. “C. 6 10 125 50 27.15 7 15 100 44 31.89 7 15 125 44 36.15 6 28 100 40 40.33 7 28 125 46 43.92 c 28 125 47 47.42 28 150 45 50.93
-
i
Freezing Points of
C18
to
C24
n-Paraffins
Freezing Point in Air a t 1 Atni., O C. Hydrocarbon n-Octadecane n-Sonadecane n-Eicosane n-Heneicosane n-Docosane n-Tricosane n-Tetracosane
This investigation 27.15 31.89 36.15 40.33 13.92 47.42 50.93
,4solution of the ?I--paraffinin methyl ethyl ketone was cooled to the desired temperature. The crystals were separated from the mother liquor by centrifuging (in an International Centrifuge Co. centrifuge, S o . 418, %inch basket. 3600 r.p.m.), and were melted and washed n i t h hot water. This procedure was repeated. ilfter each crystallization the freezing point was determined for processing purposes with a mercury-in-glass thermometer to the nearest 0.1’ C. 1J7hen there was no perceptible change in freezing point for three successive crystallizations, the n-
(1)
(10)
(0
28.184
28.10 31.75 36.35
28.2 32.0 36.6 40.2
31
no
3G.44 40.5 44.4 4i.G 50.9
44.0
47.5 50.6
paraffin material was passed through silica gel in order to remove water and any possible trace of methyl ethyl ketone. An accurate freezing point was determined (under the supervision of ii. J. Streiff) on each purified sample, using the standard procpdure of the .%PIResearch Project 6 ( 3 ) . The results of the purification of the individual n-paraffins are summarized in Table 111. The freezing points of the n-paraffins obtained in this investigation are compared with values from the literature in Table IV.
search Project 44, “Selected Values of Properties of Hydrocarbons,” Carnegie Institute of Technology, Pittsburgh, Pa. (2) Charlet, E. RI., Lanneau, K. P., Johnson. F. B., ANAL.CHEM.26, 861 (1954). ’ (3) Glasgow, A. R., Jr., StreifF, A. J., Rossini, F. D., J. Research iVatl. Bur. Standards 35,219 (1945). (4) Mair, B. J.,Pignocco, A. J., Rossini, F. D.. ASAL. CHEV. 27, 190 (1955).’ ( 5 ) Montjar, Ill. J., “Fractionation of Hydrocarbons by Adsorption,” thesis, Carnegie Institute of Technology, Pittsburgh, Pa., October 1954. (6) Rossini, F. D., Mair, B. J., Streiff, il. J., “Hydrocarbons in Petroleum,” Reinhold, New York, 1953. (7)Schaerer, A. A,, Busso, C. J., Smith, A. E., Skinner, L. B., J . Am. Chem. SOC.77, 2017 (1955). (8) Schiessler, R. W., Flitter, D. J., Ibid., 74, 1720 (1952). (9) Schlenk, W.,Jr., Ann. 565, 204 (1949). (10) Tilicheev, M. D., Peshkov, V. P., Yuganova, S. A., J . Gen. Chem. ( U . 8. S. R.) 21, 1229 (1951). RECEIVEDfor review April 19, 1956. Accepted October 22,1956. Investigation performed under the American Petroleum Institute Research Project 6 in the Petroleum Research Laboratory, Carnegie Institute of Technology. The material in this report is taken from a dissertation submitted to the Carnegie Institute of Technology in partial fulfillment of the requirements for the degree of doctor of philosophy by W. J. Marculaitis, holder of a fellowship of the American Petroleum Research Institute Research Project 6, 1953-55, and of E. I. du Pont de Kemours I%Co., Inc., 1955-56.
Qua nti tut ive Se pa rati o n a nd Determina ti o n
of Glycol Mixtures by Azeotropic Distillation HELEN M. ROSENBERGER and CLARENCE J. SHOEMAKER Chemical Research and Engineering Department, A. 6. Dick Co., 5700 W. Touhy Ave., Chicago 31, 111.
A method for separating and quantitatively determining the per cent by volume of the constituents in an aqueous polyhydric alcohol mixture is based on the well-established principle of azeotropic distillation of the components from an immiscible solvent. Benzene, tetrachloroethylene, and d-limonene were selected as entrainers. This investigation was undertaken primarily as a mode of analysis for mixtures containing water-soluble tinctorial agents and water-soluble resins.
F
of aqueous polyhydric alcohol mixtures, containing water-soluble tinctorial agents and REQUEXT ANALYSIS
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ANALYTICAL CHEMISTRY
water-soluble resins, has led to the utilization of azeotrope formation for separation and subsequent identification of the constituents. The widely used analytical methods have had certain undesirable characteristics. Standard oxidation methods involving periodic acid (1) or potassium dichromate are critically dependent upon sample size and are limited by specificity. The presence of tinctorial agents seriously impairs the colorimetric procedures, such as formation of the sodium cupriglycerol complex (12, 13) with glycerol or colored complexes of the hydroxyl compound with ammonium hexanitrato cerate ( 3 ) . The
use of ethyl alcohol as a diluent in the former test causes precipitation of the water-soluble resins present in the sample. Previous publications have cited the separation of water from glycols (7) and the determination of certain polyhydroxy compounds b y selective entrainment with cyclohexane, turpentine, toluene, xylene, chloroform, methylcyclohexane, Decalin, and benzene. Ethylene glycol, propylene glycol, and trimethylene glycol were entrained in cyclohexane, and water and glycerol were entrained in Decalin (8-11). Experimental results in this laboratory have shonwi that ethylene glycol-
