Separation of 2-butanol from tert.amyl alcohol by azeotropic distillation

2-Butanol cannot be separated from t-amyl alcohol by distillation or rectification because of the closeness of their boiling points. 2-Butanol is readily separated from t-amyl alcohol by azeotropic distillation. Effective agents are methyl acetate, ethyl propionate and octane.

FIELD OF THE INVENTION 
This invention relates to a method of separating 2-butanol from tert.amyl 
alcohol by azeotropic distillation. 
DESCRIPTION OF PRIOR ART 
Azeotropic distillation is the method of separating close boiling compounds 
or azeotropes from each other by carrying out the distillation in a 
multiplate rectification column in the presence of an added liquid, said 
liquid forming an azeotrope with one or more of the compounds to be 
separated. 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 azeotrope forming agent is introduced with the feed 
to a continuous column. The azeotrope forming agent and the more volatile 
component are taken off as overhead product and the less volatile 
component comes off as bottoms product. The usual methods of separating 
the azeotrope former from the more volatile component are cooling and 
phase separation or solvent extraction. 
The usual method of evaluating the effectiveness of azeotropic distillation 
agents is the change in relative volatility of the compounds to be 
separated. Table 1 shows the degree of separation or purity obtainable by 
theoretical plates at several relative volatilities. Table 1 shows that a 
relative volatility of at least 1.2 is required to get an effective 
separation by rectification. 
TABLE 1 
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Effect of Relative Volatility on Theoretical stage 
Requirements. 
Separation Purity, 
Relative Volatility 
Both Products 
1.02 1.1 1.2 1.3 1.4 1.5 2.0 3.0 
(Mole Fraction) 
Theoretical Stages at Total Reflux 
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0.999 697 144 75 52 40 33 19 12 
0.995 534 110 57 39 30 25 14 9 
0.990 463 95 49 34 26 22 12 7 
0.98 392 81 42 29 22 18 10 6 
0.95 296 61 31 21 16 14 8 4 
0.90 221 45 23 16 12 10 5 3 
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2-Butanol and t-amyl alcohol boil two degrees apart and have a relative 
volatility of 1.2 which makes it difficult to separate them by 
conventional distillation or rectification. Table 2 shows that with an 
agent giving a relative volatility of 1.7, only twenty-four actual plates 
are required to get 99% purity compared to 61 plates for straight 
rectification. 
TABLE 2 
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Theoretical and Actual Plates Required vs. Relative 
Volatility for 2-Butanol and t. Amyl Alcohol Separation 
Relative 
Theoretical Plates Required 
Actual Plates 
Volatility 
At Total Reflux, 99% Purity 
Required, 75% Efficiency 
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1.22 46 61 
1.4 26 35 
1.5 22 30 
1.7 18 24 
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OBJECTIVE OF THE INVENTION 
The object of this invention is to provide a process or method of 
azeotropic distillation, that will enhance the relative volatility of 
2-butanol and t.-amyl alcohol in their separation in a rectification 
column. It is a further object of this invention to identify effective 
azeotropic distillation agents that are stable and can be recycled. 
SUMMARY OF THE INVENTION 
The objects of this invention are provided by a process for the separation 
of 2-butanol and t.-amyl alcohol which entails the use of certain organic 
compounds when employed as the agent in azeotropic distillation. 
DETAILED DESCRIPTION OF THE INVENTION 
I have discovered that certain organic compounds will effectively increase 
the relative volatility between 2-butanol and tert. amyl alcohol during 
rectification when employed as the agent in azeotropic distillation. They 
are methyl acetate, dimethyl carbonate, 2-butanone, ethyl propionate, 
octane, isooctane and 1-octene. 
TABLE 3 
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Effective Azeotropic Distillation Agents Fo 
Separating 2-Butanol From tert. Amyl Alcohol 
Relative 
Compounds Volatility 
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Methyl acetate 1.8* 
Dimethyl carbonate 
1.4 
2-Butanone 1.8* 
Ethyl propionate 1.35 
Octane 1.45 
Isooctane 1.3 
I-Octene 1.45 
None 1.2 
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*Reverses the volatility. 
THE USEFULNESS OF THE INVENTION 
The usefulness of this invention can be demonstrated by referring to the 
data presented in Tables 1,2 and 3. All of the successful agents show that 
2-butanol can be separated from t-amyl alcohol by means of azeotropic 
distillation in a rectification column and that the ease of separation as 
measured by relative volatility is considerable.

WORKING EXAMPLES 
1. Fifty grams of 2-butanol--t.amyl alcohol mixture and fifty grams of 
1-octene were charged to a vapor-liquid equilibrium still and refluxed for 
two hours. The vapor composition was 74.4% 2-butanol and 25.6% t-amyl 
alcohol; the liquid composition was 66.7% 2-butanol and 33.3% t-amyl 
alcohol. This is a relative volatility 2-butanol to t.amyl alcohol of 
1.45. 
2. Fifty grams of 2-butanol--t-amyl alcohol mixture and fifty grams of 
methyl acetate were charged to a vapor-liquid equilibrium still and 
refluxed for two hours. The vapor composition was 26.3% 2-butanol and 
73.7% t-amyl alcohol; the liquid composition was 40% 2-butanol and 60% 
t-amyl alcohol. This is a relative volatility of t-amyl alcohol to 
2-butanol of 1.8.