Separation of ketone isomers by extractive distillation

The higher boiling ketone isomers are difficult to separate one from another by conventional distillation or rectification because of the close proximity of their boiling points. Ketone isomers can be readily separated from each other by extractive distillation. Typical examples of effective agents are: for 3-pentanone from 2-pentanone, dipropylene glycol; 3-hexanone from 2-hexanone, butoxypropanol; 3-heptanone from 2-heptanone, 50% ethylene glycol--50% butoxypropanol; 3-octanone from 2-octanone, ethylene glycol diacetate.

FIELD OF THE INVENTION 
This invention relates to a method for separating ketone isomers one from 
another using certain higher boiling liquids as the agent in extractive 
distillation. 
DESCRIPTION OF PRIOR ART 
Extractive distillation is the method of separating close boiling compounds 
from each other by carrying out the distillation in a multiple 
rectification column in the presence of an added liquid or liquid mixture, 
said liquid(s) having a boiling point higher than the compounds being 
separated. The extractive agent is introduced near the top of the column 
and flows downward until it reaches the stillpot or reboiler. Its presence 
on each plate of the rectification column alters the relative volatility 
in a direction to make the separation on each plate greater and thus 
require either fewer plates to effect the same separation or make possible 
a greater degree of separation with the same number of plates. The 
extractive agent should boil higher than any of the close boiling liquids 
being separated and not form minimum azeotropes with them. Usually the 
extractive agent is introduced a few plates from the top of the column to 
insure that none of the extractive agent is carried over with the lowest 
boiling compound. This usually requires that the extractive agent boil 
twenty Centrigrade degrees or more above the lowest boiling component. 
At the bottom of a continuous column, the less volatile components of the 
close boiling mixture and the extractive agent are continuously removed 
from the column. The usual methods of separation of these two components 
are the use of another rectification column, cooling and phase separation 
or solvent extraction. 
Extractive distillation typically requires the addition of an equal amount 
to twice as much extractive agent as the ketone isomer mixture on each 
plate of the rectification column. The extractive agent should be heated 
to about the same temperature as the plate into which it is introduced. 
Thus extractive distillation imposes an additional heat requirement on the 
column as well as somewhat larger plates. However this is less than the 
increase caused by the additional agents requires if the separation is 
done by azeotropic distillation. Another consideration in the selection of 
the extractive distillation agent is its recovery from the bottoms 
product. The usual method is by rectification in another column. In order 
to keep the cost of this operation to a minimum, an appreciable boiling 
point difference between the compound being separated and the extractive 
agent is desirable. It is also desirable that the extractive agent be 
miscible with the extracted ketone otherwise it will form a two-phase 
azeotrope with the extracted ketone in the recovery column and some other 
method of separation will have to be employed. 
In the manufacture of the higher ketones, the process frequently yields a 
mixture of isomers. Depending upon the number of isomers and the 
difference in their molecular structure, the boiling points of some 
isomers can be very close together. The closest boilers in a series of 
isomeric ketones are listed as follows for their boiling points and 
relative volatilities: 2-pentanone, B.P.=100.degree. C., 3-pentanone, 
B.F.=102.degree. C., rel. vol.=1.02; 3-hexanone, B.P.=123.degree. C., 
2-hexanone, B.P.=127.degree. C., rel. vol.=1.15; 3-heptanone, 
B.P.=146.degree. C., 2-heptanone, B.P.+146.degree. C., rel. vol.=1.17; 
3-octanone, B.P.=168.degree. C., 2-octanone, B.P.=173.degree. C., rel. 
vol.=1.15. 
TABLE 1 
______________________________________ 
Plates Required To Effect Separation Of 99% Purity 
Relative Theoretical 
Actual Plates, 
Volatility Plates 75% Efficiency 
______________________________________ 
1.02 465 620 
1.15 66 88 
1.17 59 79 
1.25 41 55 
1.30 35 47 
1.35 31 41 
1.40 27 36 
______________________________________ 
Table 1 shows that to separate a mixture having a relative volatility of 
1.15, 66 theoretical or 88 actual plates would be required to separate in 
99% purity. If the relative volatility could be improved to 1.3, only 47 
actual plates would be required and with a relative volatility of 1.4, 
only 36 actual plates are needed. 
Extractive distillation would be an attractive method of effecting the 
separation of ketone isomers one from another, if agents can be found that 
(1) will increase the relative volatility of one isomer to the other and 
(2) are easy to recover from the ketone being extracted, that is, form no 
azeotrope with ketone and boil sufficiently above it to make separation by 
rectification possible with only a few plates. 
Pacoud & Dallemagne, U.S. Pat. No. 3,013,954 described the use of an 
auxiliary substance to separate the ketone acetone from acetic acid, 
formic acid, formaldehyde and water. The auxiliary substance used was 
isopropyl ether. 
Carpenter, Taylor & McNair, U.S. Pat. No. 3,228,985 described the use of 
aqueous sodium carbonate in a solvent extraction process to recover methyl 
ethyl ketone from a complex mixture of water, acids, alcohols, ketone and 
esters. Van Melsen & Langedijk, U.S. Pat. No. 2,010,384 described a 
process for separating isomeric pentanones using a water soluble bisulfite 
as the agent in a solvent extraction method. 
OBJECTIVE OF THE INVENTION 
The object of this invention is to provide a process or method of 
extractive distillation that will enhance the relative volatility of 
ketone isomers one from another in their separation in a rectification 
column. It is a further object of this invention to identify organic 
compounds which in addition to the above constraints, are stable, can be 
separated from the ketone being extracted by rectification with relatively 
few plates and can be recycled to the extractive distillation column and 
reused with little decomposition. 
SUMMARY OF THE INVENTION 
The objects of the invention are provided by a process for separating 
ketone isomers one from another which entails the use of certain glycols, 
either alone or admixed with certain high boiling organic compounds in an 
extractive distillation. 
DETAILED DESCRIPTION OF THE INVENTION 
3-Pentanone From 2-Pentanone: 
We have discovered that certain glycols, either alone or admixed with 
certain high boiling organic compounds will effectively enhance the 
relative volatility of 3-pentanone to 2-pentanone by rectification when 
employed as the agent in extractive distillation. Table 2 lists the 
glycols and certain high boiling organic compounds that we have found to 
be effective. 
The glycols and mixtures which are effective in the separation of 
3-pentanone from 2-pentanone are propylene glycol, 1,3-butanediol, 
1,2-butanediol, triethylene glycol, tetraethylene glycol, dipropylene 
glycol, hexylene glycol, 1,4-butanediol, polyethylene glycol 200, 
2-methyl-1,3-propanediol, 50% ethylene glycol, 50% propoxypropanol, 67% 
ethylene glycol, 33% dipropylene glycol and 67% ethylene glycol, 33% 
polyethylene glycol 200. 
Three compounds, namely triethylene glycol, 1,4-butanediol and dipropylene 
glycol, whose relative volatility had been determined in a vapor-liquid 
equilibrium still and reported in Table 2, were then evaluated in a glass 
perforated plate rectification column possessing 7.3 theoretical plates. 
The results are listed in Table 4 and show that triethylene glycol gave a 
relative volatility of 1.167, 1,4-butanediol gave 1.25 and dipropylene 
gave 1.63. 
Table 3 lists several glycols that might have been expected to be effective 
but which were not. 
TABLE 2 
______________________________________ 
Effective Agents For Separating 3-Pentanone From 2-Pentanone 
Relative 
Compounds Volatility 
______________________________________ 
None 1.02 
50% Ethylene glycol, 50% Propoxypropanol 
1.14 
Propylene glycol 1.18 
1,3-Butanediol 1.31 
1,2-Butanediol 1.29 
Triethylene glycol 1.22 
tetraethylene glycol 1.19 
Dipropylene glycol 1.30 
hexylene glycol 1.15 
1,4-Butanediol 1.25 
Polyethylene glycol 200 1.30 
67% Ethylene glycol, 33% Dipropylene glycol 
1.17 
67% Ethylene glycol, 33% polyethylene glycol 200 
1.30 
2-Methyl-1,3-propanediol 1.30 
______________________________________ 
TABLE 3 
______________________________________ 
Ineffective Agents For Separating 3-Pentanone From 2-Pentanone 
Relative 
Compounds Volatility 
______________________________________ 
1,5-Pentanediol 1.02 
1,6-Hexanediol 1.08 
Diethylene glycol 1.06 
Tripropylene glycol 
1.03 
Polyethylene glycol 300 
1.04 
______________________________________ 
TABLE 4 
______________________________________ 
Data From Runs Made in Rectification Column - 
3-Pentanone From 2-Pentanone 
Weight Weight 
Time % 3-Pen- 
% 2-Pen- 
Relative 
Agent Column hrs. tanone tanone Volatility 
______________________________________ 
Triethylene 
Overhead 1.5 58.7 41.3 1.167 
glycol Bottoms 31.4 68.6 
1,4- Overhead 2 72.1 27.9 1.25 
Butanediol 
Bottoms 33.5 66.5 
Dipropylene 
Overhead 1 98.7 1.3 1.63 
glycol Bottoms 67.3 32.7 
______________________________________ 
3-Hexanone From 2-Hexanone: 
We have discovered that certain oxygenated organic compounds will 
effectively enhance the relative volatility of 3-hexanone to 2-hexanone 
when employed as the agent in extractive distillation. Table 5 lists the 
compounds that we have found to be effective. The relative volatilities 
shown in Table 5 were obtained in an Othmer type vapor-liquid equilibrium 
still. The compounds and mixture which are effective in the separation of 
3-hexanone from 2-hexanone are triethylene glycol, dipropylene glycol 
methyl ether, n-octanol, ethylene glycol diacetate, diethylene glycol 
hexyl ether, benzyl alcohol, tripropylene glycol methyl ether, 
butoxypropanol, propoxypropanol, sulfolane, benzonotrile and 50% ethylene 
glycol--50% butoxypropanol. 
TABLE 5 
______________________________________ 
Effective Agents For Separating 3-Hexanone From 2-Hexanone 
Relative 
Compounds Volatility 
______________________________________ 
None 1.15 
Ethylene glycol, Butoxypropanol 
1.27 
Triethylene glycol 1.22 
Dipropylene glycol methyl ether 
1.25 
Ethylene glycol diacetate 
1.20 
Diethylene glycol hexyl ether 
1.23 
n-Octanol 1.23 
Tripropylene glycol methyl ether 
1.27 
Butoxypropanol 1.28 
Propoxypropanol 1.33 
Sulfolane 1.22 
Benzyl alcohol 1.23 
Benzonitrile 1.28 
______________________________________ 
TABLE 6 
______________________________________ 
Ineffective Agents For Separating 3-Hexanone From 2-Hexanone 
Relative 
Compounds Volatility 
______________________________________ 
Propylene glycol 1.16 
Ethylene glycol hexyl ether 
1.10 
Diethylene glycol methyl ether 
1.16 
Glycerol triacetate 1.19 
Diethylene glycol butyl ether 
1.19 
Isononyl alcohol 1.17 
Dodecanol 1.18 
Nitrobenzene 1.13 
2-Nitrotoluene 1.01 
3-Nitrotoluene 1.14 
2-Methylpyrrolidone 1.13 
o-tert. Butyl phenol 1.12 
Phenol 1.19 
Ethyl acetoacetate 1.17 
______________________________________ 
TABLE 7 
______________________________________ 
Data From Run Made In Rectification Column - 
3-Hexanone From 2-Hexanone 
Weight Weight 
Time % 3-Hex- 
% 2-Hex- 
Relative 
Agent Column hrs. anone anone Volatility 
______________________________________ 
Butoxypro- 
Overhead 1 71.5 28.5 1.32 
panol Bottoms 25.8 74.2 
Butoxypro- 
Overhead 2 70.2 29.8 1.31 
panol Bottoms 24.4 75.6 
______________________________________ 
Table 6 lists several compounds that might have been expected to be 
effective but which were not. 
One compound, butoxypropanol, whose relative volatility had been determined 
in the vapor-liquid equilibrium still and reported in Table 5, was then 
evaluated in a glass perforated plate rectification column possessing 7.3 
theoretical plates. The results are listed in Table 7 and show that 
butoxypropanol gave a relative volatility of 1.31. 
3-Heptanone From 2-Heptanone: 
We have discovered that certain oxygenated organic compounds will 
effectively enhance the relative volatility of 3-heptanone to 2-heptanone 
when employed as the agent in extractive distillation. Table 8 lists the 
compounds that we have found to be effective. The relative volatilities 
shown in Table 8 were obtained in an Othmer type vapor-liquid equilibrium 
still. The compounds and mixtures which are effective in the separation of 
3-heptanone from 2-heptanone are propylene glycol, triethylene glycol, 
hexylene glycol, 1,2-butanediol ethylene glycol-butoxypropanol, diethylene 
glycol-butoxypropanol, propylene glycol-butoxypropanol, 
1,4-butanediol-butoxypropanol and nitrobenzene-butoxypropanol. Table 9 
lists several compounds and mixtures that might have been expected to be 
effective but which were not. One mixture, 50% ethylene glycol, 50% 
butoxypropanol, whose relative volatility had been determined in the 
vapor-liquid equilibrium still and reported in Table 8, was then evaluated 
in a glass perforated plate rectification column possessing 7.3 
theoretical plates. The results are listed in Table 10 and show that 50% 
ethylene glycol--50% butoxypropanol gave a relative volatility of 1.28. 
3-Octanone From 2-Octanone: 
We have discovered that certain oxygenated organic compounds will 
effectively enhance the relative volatility of 3-octanone to 2-octanone 
when employed as the agent in extractive distillation. Table 11 lists the 
compounds and mixtures that we have found to be effective. The relative 
volatilities shown in Table 11 were obtained in an Othmer type 
vapor-liquid equilibrium still. The compounds and mixtures which are 
effective are ethylene carbonate, propylene carbonate, sulfolane, 
2-hydroxyacetophenone, tripropylene glycol methyl ether, ethylene glycol 
hexyl ether, ethylene glycol diacetate, dipropylene glycol methyl ether, 
benzonitrole, n-(2-hydroxyethyl-2-pyrrolidone, butoxyethoxy-2-propanol, 
diethylene glycol hexyl ether, triethylene glycol-diethylene glycol butyl 
ether and polyethylene glycol 200--tripropylene glycol methyl ether. 
TABLE 8 
______________________________________ 
Effective Agents For Separating 3-Heptanone From 2-Heptanone 
Relative 
Compounds Volatility 
______________________________________ 
None 1.17 
Propylene glycol 1.29 
Triethylene glycol 1.28 
Hexylene glycol 1.23 
1,2-Butanediol 1.24 
Ethylene glycol, Butoxypropanol 
1.28 
Diethylene glycol, Butoxypropanol 
1.26 
Propylene glycol, Butoxypropanol 
1.25 
1,4-Butanediol, Butoxypropanol 
1.27 
Nitrobenzene, Butoxypropanol 
1.28 
______________________________________ 
TABLE 9 
______________________________________ 
Ineffective Agents For Separating 
3-Heptanone From 2-Heptanone 
Relative 
Compounds Volatility 
______________________________________ 
Dimethylsulfoxide 1.18 
Dimethylacetamide 1.10 
Adiponitrile 1.12 
1,2-Butanediol, Butoxypropanol 
1.16 
1,3-Butanediol, Butoxypropanol 
1.10 
1,5-Pentanediol, Butoxypropanol 
1.12 
1,6-Hexanediol 1.20 
Dipropylene glycol 1.05 
Tripropylene glycol 1.19 
Polyethylene glycol 200 
1.21 
Polyethylene glycol 300 
1.18 
Butoxypropanol 1.14 
Tetraethylene glycol 1.18 
2-Methoxymethyl ether 1.00 
2-Nitrotoluene, Butoxypropanol 
1.18 
3-Nitrotoluene 1.15 
4-Nitrotoluene 1.13 
______________________________________ 
TABLE 10 
______________________________________ 
Data From Run Made In Rectification Column - 
3-Heptanone From 2-Heptanone 
Weight Weight 
time % 3-Hep- 
% 2-Hep- 
Relative 
Agent Column hrs. tanone tanone Volatility 
______________________________________ 
50% Ethyl- 
Overhead 1 74 26 1.262 
ene glycol, 
Bottoms 33.9 66.1 
50% Butoxy- 
propanol 
50% Ethyl- 
Overhead 1.7 73.8 26.2 1.28 
ene glycol, 
Bottoms 32 68 
50% Butoxy- 
propanol 
______________________________________ 
TABLE 11 
______________________________________ 
Effective Agents For Separating 3-Octanone From 2-Octanone 
Relative 
Compounds Volatility 
______________________________________ 
None 1.15 
Ethylene carbonate 1.25 
Propylene carbonate 1.23 
2-Hydroxyacetophenone 1.22 
Sulfolane 1.23 
Tripropylene glycol methyl ether 
1.25 
Ethylene glycol hexyl ether 
1.24 
Ethylene glycol diacetate 
1.28 
Dipropylene glycol methyl ether 
1.21 
Benzonitrile 1.20 
N-(2-Hydroxyethyl-2-Pyrrolidone) 
1.21 
Triethylene glycol, Diethylene glycol 
1.20 
butyl ether 
Polyethylene glycol 200, Tripropylene 
1.23 
glycol methyl ether 
Butoxyethoxy-2-propanol 
1.24 
Diethylene glycol hexyl ether 
1.28 
______________________________________ 
TABLE 12 
______________________________________ 
Ineffective Agents For Separating 3-Octanone From 2-Octanone 
Relative 
Compounds Volatility 
______________________________________ 
Adiponitrile 1.14 
Butyl benzoate 1.11 
Dihexyl phthalate 1.03 
Methyl salicylate 1.09 
Pelargonic acid 1.16 
Polyethylene glycol 200 
1.19 
Polyethylene glycol 300 
1.15 
Diethylene glycol butyl ether 
1.18 
Glycerol triacetate 1.08 
Diethylene glycol diethyl ether 
1.06 
Ethyl acetoacetate 1.15 
Diethylene glycol methyl ether 
1.14 
Diethyl malonate 1.10 
Triisononyl trimellitate 
1.13 
N-Methyl-2-pyrrolidone 
1.16 
N-Cyclohexyl-2-pyrrolidone 
1.02 
Diisononyl adipate 1.19 
Tridecyl phthalate 1.10 
Tributyl phosphate 1.16 
Tri-2-Ethyl hexyl trimellitate 
1.09 
Ethylene glycol phenyl ether 
1.19 
2-Ethyl hexyl acetate 1.17 
Diisodecyl phthalate 1.15 
Tetraethylene glycol, Tripropylene 
1.16 
glycol methyl ether 
Propylene carbonate, n-Methyl-2- 
1.13 
pyrrolidone 
______________________________________ 
TABLE 13 
______________________________________ 
Data From Runs Made In Rectification Column - 
3-Octanone From 2-Octanone 
Weight Weight 
Time % 3- % 2- Relative 
Agent Column hrs. Octanone 
Octanone 
Volatility 
______________________________________ 
Dipropylene 
Overhead 2 38.6 61.4 1.20 
glycol methyl 
Bottoms 14.1 85.9 
ether 
Dipropylene 
Overhead 3 39.6 60.4 1.21 
glycol methyl 
Bottoms 14.4 85.6 
ether 
Ethylene gly- 
Overhead 1 54.4 45.6 1.36 
col diacetate 
Bottoms 11.1 88.9 
Ethylene gly- 
Overhead 2 57.6 42.4 1.39 
col diacetate 
Bottoms 10.7 89.3 
______________________________________ 
Table 12 lists several compounds and mixtures that might have been expected 
to be effective but which were not. 
Two compounds, dipropylene glycol methyl ether and ethylene glycol 
diacetate, whose relative volatilities had been determined in the 
vapor-liquid equilibrium still and reported in Table 11, were then 
evaluated in a glass perforated plate rectification column possessing 7.3 
theoretical plates. The results are listed in Table 13 and show that 
dipropylene glycol methyl ether gave a relative volatility of 1.21 and 
ethylene glycol diacetate gave a relative volatility of 1.39. 
THE USEFULNESS OF THE INVENTION 
The usefulness or utility of this invention can be demonstrated by 
referring to the data presented in Tables 1-13. All of the successful 
extractive agents show that ketone isomers can be separated one from 
another by means of distillation in a rectification column and that the 
ease of separation as measured by relative volatility is considerable. 
Without these extractive distillation agents, only slight improvement will 
occur in a rectification column. The data also show that the most 
attractive agents will operate at a boilup rate low enough to make this a 
useful and efficient method of recovering high purity ketone from any 
mixture of ketone isomers. The stability of the compounds used and the 
boiling point difference is such that complete recovery and recycle is 
obtainable by a simple distillation and the amount required for make-up is 
small.

WORKING EXAMPLES 
EXAMPLE 1 
Ten grams of 3-pentanone, 40 grams of 2-pentanone and 20 grams of 
1,3-butanediol were charged to an Othmer type vapor-liquid still and 
refluxed for six hours. Analysis by gas chromatography gave a vapor 
composition of 19.2% 3-pentanone, 80.8% 2-pentanone; a liquid composition 
of 15.4% 3-pentanone, 84.6% 2-pentanone which is a relative volatility of 
1.31. 
EXAMPLE 2 
A glass perforated plate rectification column was calibrated with m-xylene 
and o-xylene which possesses a relative volatility of 1.11 and found to 
have 7.3 theoretical plates. A solution comprising 250 grams 3-pentanone 
and 50 grams of 2-pentanone was placed in the stillpot and heated. When 
refluxing began, an extractive agent comprising dipropylene glycol was 
pumped into the column at a rate of 15 ml/min. The boil-up rate was 20 
ml/min. and the temperature of the extractive agent as it entered the 
column was 85.degree. C. After establishing the feed rate of the 
extractive agent, the heat input to the m-xylene and o-xylene in the 
stillpot was adjusted to give a total reflux rate of 30-40 ml/min. After 
one hour of operation, the overhead and bottoms samples of approximately 
two ml. were collected and analysed by gas chromatography. The overhead 
analysis was 98.7% 3-pentanone, 1.3% 2-pentanone. The bottoms analysis was 
67.3% 3-pentanone, 32.7% 2-pentanone. Using these compositions in the 
Fenske equation with the number of theoretical plates in the column being 
7.3, gave an average relative volatility of 1.63. for each theoretical 
plate. This run is presented in Table 4. 
EXAMPLE 3 
Ten grams of 3-hexanone, 30 grams of 2-hexanone and 20 grams of 
tripropylene glycol methyl ether were charged to an Othmer type 
vapor-liquid equilibrium still and refluxed for 12 hours. Analysis by gas 
chromatography gave a vapor composition of 21.25 3-hexanone, 78.8% 
2-hexanone; a liquid composition of 17.4% 3-hexanone, 82.6% 2-hexanone 
which is a relative volatility of 1.27. 
EXAMPLE 4 
A glass perforated plate rectification column was calibrated with m-xylene 
and o-xylene which possesses a relative volatility of 1.11 and found to 
have 7.3 theoretical plates. A solution comprising 200 grams of 3-hexanone 
and 100 grams of 2-hexanone was placed in the stillpot and heated. When 
refluxing began, an extractive agent comprising butoxypropanol was pumped 
into the column at a rate of 15 ml/min. The boil-up rate was 20 ml/min. 
and the temperature of the extractive agent as it entered the column was 
85.degree. C. After establishing the feed rate of the extractive agent, 
the heat input to the m-xylene and o-xylene in the stillpot was adjusted 
to give a total reflux rate of 30-40 ml/min. After one hour of operation, 
the overhead and bottoms samples of approximately two ml. were collected 
and analysed by gas chromatography. The overhead analysis was 71.5% 
3-hexanone, 28.5% 2-hexanone. The bottoms analysis was 25.8% 3-hexanone, 
74.2% 2-hexanone. Using these compositions in the Fenske equation with the 
number of theoretical plates in the column being 7.3, gave an average 
relative volatility of 1.32 for each theoretical plate. This run is 
presented in Table 7. 
EXAMPLE 5 
Ten grams of 3-heptanone, 30 grams of 2-heptanone and 20 grams of 
triethylene glycol were charged to an Othmer type vapor-liquid equilibrium 
still and refluxed for five hours. Analysis by gas chromatography gave a 
vapor composition of 18.4% 3-heptanone, 81.6% 2-heptanone; a liquid 
composition of 15% 3-heptanone, 85% 2-heptanone which is a relative 
volatility of 1.28. 
EXAMPLE 6 
A glass perforated plate rectification column was calibrated with m-xylene 
and o-xylene which possesses a relative volatility of 1.11 and found to 
have 7.3 theoretical plates. A solution comprising 100 grams of 
3-heptanone and 200 grams of 2-heptanone was placed in the stillpot and 
heated. When refluxing began, an extractive agent comprising 50% ethylene 
glycol, 50% butoxypropanol was pumped into the column at a rate of 15 
ml/min. The boil-up rate was 20 ml/min. and the temperature of the 
extractive agent as it entered the column was 85.degree. C. After 
establishing the feed rate of the extractive agent, the heat input to the 
m-xylene and o-xylene in the stillpot was adjusted to give a total reflux 
rate of 30-40 ml/min. After one hour of operation, the overhead and 
bottoms samples of approximately two ml. were collected and analysed by 
gas chromatography. The overhead analysis was 74% 3-heptanone, 26% 
2-heptanone. The bottoms analysis was 33.9% 3-heptanone, 66.1% 
2-heptanone. Using these compositions in the Fenske equation with the 
number of theoretical plates in the column being 7.3, gave an average 
relative volatility of 1.26 for each theoretical plate. This run is 
presented in Table 10. 
EXAMPLE 7 
Ten grams of 3-octanone, 30 grams of 2-octanone and 20 grams of diethylene 
glycol hexyl ether were charged to an Othmer type vapor-liquid equilibrium 
still and refluxed for four hours. Analysis by gas chromatography gave a 
vapor composition of 13.15 3-octanone, 86.9% 2-octanone; a liquid 
composition of 10.5% 3-octanone, 89.5% 2-octanone which is a relative 
volatility of 1.28. 
EXAMPLE 8 
A glass perforated plate rectification column was calibrated with m-xylene 
and o-xylene which possesses a relative volatility of 1.11 and found to 
have 7.3 theoretical plates. A solution comprising 50 grams of 3-octanone 
and 250 grams of 2-octanone was placed in the stillpot and heated. When 
refluxing began, an extractive agent comprising ethylene glycol diacetate 
was pumped into the column at a rate of 15 ml/min. The boil-up rate was 20 
ml/min. and the temperature of the extractive agent as it entered the 
column was 85.degree. C. After establishing the feed rate of the 
extractive agent, the heat input to the m-xylene and o-xylene in the 
stillpot was adjusted to give a total reflux rate of 30-40 ml/min. After 
two hour of operation, the overhead and bottoms samples of approximately 
two ml. were collected and analysed by gas chromatography. The overhead 
analysis was 57.6% 3-octanone, 42.4% 2-octanone. The bottoms analysis was 
10.7% 3-octanone, 89.3% 2-octanone. Using these compositions in the Fenske 
equation with the number of theoretical plates in the column being 7.3, 
gave an average relative volatility of 1.39 for each theoretical plate. 
This run is presented in Table 13.