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STUDIES IN EXTRACTIVE AND AZEOTROPIC DISTILLATION SERIES

Study Number 4 - SEPARATION OF ALCOHOLS FROM THE ACETATE/ALCOHOL/WATER TERNARY BY EXTRACTIVE DISTILLATION

A summary of experimental results (in outline format) from a series of investigations of hard-to-separate acetate/alcohol/water ternary mixtures

 

Dr. Lloyd Berg,

Chairman and Director of Research, Brix-Berg Company PLLC
Emeritus Department Head and Professor, Chemical Engineering Department, Montana State University
and

A. Terry Brix, President, Brix-Berg Company PLLC

 

Separations Studied:

Acetate/alcohol/water ternary mixtures are found in the manufacture of acetates, in some waste solvent or process streams, and in laboratory preparations. Specific ternary systems studied by Brix-Berg include:

Ethyl acetate/ethanol/water (Table 1)

n-propyl acetate/n-propanol/water (Table 2)

Isopropyl acetate/isopropanol/water (Tables 3 and 4)

n-butyl acetate/n-butanol/water (Table 5)

2-butyl acetate/2-butanol/water (Table 6)

iso-butyl acetate/iso-butanol/water (Table 7)

n-amyl acetate/n-amyl alcohol/water (Table 8)

n-hexyl acetate/n-hexanol/water (Tables 9 and 10)

 

Typically, these acetate/alcohol/water ternary systems are complex mixtures in that they often contain combinations of binary and ternary azeotropes. To illustrate this complexity, Table 1. provides boiling point and azeotrope compositional data for the ethyl acetate/ethanol/water system.

Table 1 - Azeotropes in the Ethyl Acetate/Ethanol/Water System

 

Compound(s) BP - oC

Azeotrope Composition ( %)

   

Ethanol

Ethyl Acetate

Water

Ethanol

78.3

     
Ethyl acetate

77.1

     
Water

100

     
Ethanol/water

78.2

95.4

 

4.6

Ethyl acetate/water

70.4

 

91.9

8.1 (2 phases)

Ethanol/ethyl acetate

71.8

31

69

 
Ethanol/ethyl acetate/water

70.2

8.4

82.6

9.0

We have found that many of these acetate/alcohol/water ternary mixtures can be separated by extractive distillation. In general, the acetate/water component goes overhead, but we have found agents that do bring the alcohol overhead for some systems.

Experimental:

For each ternary system studied, typically 100 to 200 different organic solvents were evaluated for potential as agents in extractive distillation. Tests consisted of determination of relative volatility - with and without agent - in an Othmer vapor-liquid equilibrium still.

In a number of cases (but not all), where favorable relative volatility was found in the Othmer still, a batch distillation test was conducted in a 3" diameter - 5.5 theoretical plate glass distillation column. All testing was conducted at atmospheric pressure at Bozeman MT.

Analyses were conducted by the author or his assistants using a Varian Gas Chromatograph.

Results:

Following are a series of Tables summarizing the test series for each organic hydrocarbon separation studied in this work.

 

Table 1 - Ethyl acetate/ethanol/water Separation

Separation

Ethyl acetate from ethanol/water

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

~50, including combinations

Range of Relative Volatilities found with agents

1.6 to >3

Effective agent classes

Glycols, oxygenated, sulfur-containing or nitrogenous organic compounds, and mixtures thereof

Agent Performance Examples

 

Agent

Relative Volatility

Notes

1:1:1 Glycerin/ethylene glycol/1,4-butanediol

3.7

Ethyl acetate overhead

VLE and 3" col. tests

1:1 Glycerin/diethylene glycol

3.4

Ethyl acetate overhead

VLE and 3" col. tests

1,4-Butanediol

3.2

Ethyl acetate overhead

VLE and 3" col. tests

1:1:1:1 Glycerin/ethylene glycol/tetraethylene glycol/1,5-pentanediol

2.9

Ethyl acetate overhead
1:1 Ethylene glycol/dimethylformamide

2.6

Ethyl acetate overhead
1:1 Diisooctyl phthalate/dimethylsulfoxide

2.4

Ethyl acetate overhead
Propylene glycol

2.4

Ethyl acetate overhead
1:1:1 Glycerin/ethylene glycol/adiponitrile

2.1

Ethyl acetate overhead

Table 2 - n-propyl acetate/n-propanol/water Separation

Separation

n-propyl acetate/water from n-propanol

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

~100, including combinations

Range of Relative Volatilities found with agents

1.2 to >2.9

Effective agent classes

Glycols, oxygenated, sulfur-containing or nitrogenous organic compounds, and mixtures thereof

Agent Performance Examples

 

Agent

Relative Volatility

Notes

acetamide

2.9

n-propyl acetate/water overhead (2-phase binary)
1:1/4 Ethylene glycol/acetamide

2.2

Acetate/water overhead, VLE and 3" col.
Dimethylsulfoxide

1.9

Acetate/water overhead, VLE and 3" col.
Ethylene glycol

1.9

Acetate/water overhead, VLE and 3" col.
1,4-Butanediol

1.8

Acetate/water overhead, VLE and 3" col.
1:1 N-Methyl pyrrolidone/ethylene glycol

1.7

Acetate/water overhead, VLE and 3" col.
Dimethylformamide

1.6

Acetate/water overhead, VLE and 3" col.
Triethanolamine

1.5

Acetate/water overhead, VLE and 3" col.

Table 3- isopropyl acetate/isopropanol/water separation - acetate overhead

Separation

isopropyl acetate from isopropanol/water

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

20, including combinations

Range of Relative Volatilities found with agents

1.3 to 3.4

Effective agent classes

Alcohol amines, amides

Agent Performance Examples

 

Agent

Relative Volatility

Notes

Ethanolamine

3.4

isopropyl acetate overhead, VLE and 3" col.
1:1 Ethanolamine/N-Methylpyrrolidone

3.2

Acetate overhead
Diethanolamine

2.7

Acetate overhead
Isopropanolamine

2.5

Acetate overhead
N-Methyl ethanolamine

2.3

Acetate overhead
3/5 mix Acetamide/triethanolamine

1.8

Acetate overhead

 

Table 4- isopropyl acetate/isopropanol/water separation - alcohol overhead

Separation

isopropanol from isopropyl acetate/water

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

>100, including combinations

Range of Relative Volatilities found with agents

1.4 to 2.9

Effective agent classes

Nitroparaffins, phthalates, benzoates

Agent Performance Examples

Agent

Relative Volatility

Notes

Methyl benzoate

2.9

Isopropanol overhead
2-Nitropropane

2.2

Isopropanol overhead
Di-isononyl phthalate

2.2

Isopropanol overhead
Nitromethane

2.1

Isopropanol overhead
Dimethyl phthalate

1.8

Isopropanol overhead
1:1 Benzyl benzoate/propylene carbonate

1.7

Isopropanol overhead
1:1 Methyl benzoate/diisooctyl phthalate

1.4

Isopropanol overhead,

VLE and 3" col. tests

Table 5 - n-butyl acetate/n-butanol/water separation

Separation

n-butyl acetate from n-butanol and water

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

>100, including combinations

Range of Relative Volatilities found with agents

1.2 to 2.1

Effective agent classes

DMSO, DMFA, glycols, mixtures with DMSO

Agent Performance Examples

 

Agent

Relative Volatility

Notes

Dimethylsulfoxide

2.1

Acetate overhead, VLE and 3" col. tests
Dimethylformamide

1.8

Acetate overhead, VLE and 3" col. tests
1,4-Butanediol

1.7

Acetate overhead, VLE and 3" col. tests
Diethylene glycol

1.6

Acetate overhead, VLE and 3" col. tests
1:1 1,4-Butanediol/DMSO

1.6

Acetate overhead, VLE and 3" col. tests
Triethylene glycol

1.4

Acetate overhead, VLE and 3" col. tests

Table 6 - isobutyl acetate/isobutanol/water separation

Separation

isobutyl acetate from isobutanol and water

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

70, including combinations

Range of Relative Volatilities found with agents

1.2 to 2.8

Effective agent classes

DMSO, DMFA, glycols, polyols

Agent Performance Examples

 

Agent

Relative Volatility

Notes

Ethylene glycol

2.8

Acetate overhead, VLE and 3" col. tests
Dimethylsulfoxide

2.6

Acetate overhead, VLE and 3" col. tests
Dimethylformamide

2.3

Acetate overhead, VLE and 3" col. tests
Propylene glycol

2.2

Acetate overhead, VLE and 3" col. tests
1,4-Butanediol

1.8

Acetate overhead, VLE and 3" col. tests
Diethylene glycol

1.5

Acetate overhead, VLE and 3" col. tests
Tetraethylene glycol

1.4

Acetate overhead, VLE and 3" col. tests

Table 7 - 2-butyl acetate/2-butanol/water separation

Separation

2-butyl acetate from 2-butanol and water

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

26, including combinations

Range of Relative Volatilities found with agents

1.2 to 2.2

Effective agent classes

DMSO, DMFA, amides, polyols

Agent Performance Examples

 

Agent

Relative Volatility

Notes

1:1:1 Acetamide/DMFA/1,2,6-hexanetriol

2.2

Acetate overhead
80/20 DMSO/acetamide

2.0

Acetate overhead, VLE and 3" col. tests
1:1 DMFA/DMSO

1.9

Acetate overhead
1:1:1 DMFA/DMSO/dipropylene glycol

1.9

Acetate overhead
Acetamide

1.8

Acetate overhead
N,N-Dimethylacetamide

1.7

Acetate overhead

Table 8 - n-amyl acetate/n-amyl alcohol/water separation

Separation

n-amyl acetate from n-amyl alcohol and water

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

84, including combinations

Range of Relative Volatilities found with agents

1.2 to 2.6

Effective agent classes

DMSO, DMFA, glycols, polyols

Agent Performance Examples

 

Agent

Relative Volatility

Notes

1:1:1 DMSO/DMFA/Polyethylene glycol

2.6

Acetate overhead
1:1 Polyethylene glycol/DMSO

2.4

Acetate overhead
Ethylene glycol

2.4

Acetate overhead, VLE and 3" col. tests
Ethylene glycol/DMFA/DMSO

2.2

Acetate overhead
1,4-Butanediol

2.1

Acetate overhead
Diethylene glycol

1.8

Acetate overhead

Table 9 - n-hexyl acetate/n-hexyl alcohol/water separation - alcohol/water overhead

Separation

n-hexyl alcohol and water from n-hexyl acetate

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

18, including combinations

Range of Relative Volatilities found with agents

1.1 to 2.4

Effective agent classes

Benzoates, salicylates

Agent Performance Examples

 

Agent

Relative Volatility

Notes

1:1:1 Methyl benzoate/ethyl benzoate/methyl salicylate

2.4

Alcohol and water overhead
Methyl salicylate

2.4

Alcohol and water overhead
Ethyl benzoate

2.2

Alcohol and water overhead,
Benzyl benzoate

2.1

Alcohol and water overhead
Methyl benzoate

1.6

Alcohol and water overhead, VLE and 3" col. tests

Table 10 - n-hexyl acetate/n-hexyl alcohol/water separation - acetate/water overhead

Separation

n-hexyl acetate and water from n-hexyl alcohol

Method

Extractive Distillation

Relative Volatility - no agent

1.00 (azeotrope)

Effective Extractive agents found

20, including combinations

Range of Relative Volatilities found with agents

1.1 to 2.2

Effective agent classes

DMSO, glycols, polyols

Agent Performance Examples

 

Agent

Relative Volatility

Notes

1:1 DMSO/1,4-Butanediol

2.2

Acetate and water overhead
1:1:1 DMSO/DMFA/1,3-Butanediol

2.2

Acetate and water overhead
1:1 DMSO/Ethylene glycol

1.8

Acetate and water overhead,
DMSO

1.8

Acetate and water overhead, VLE and 3" col. tests
1:1 DMSO/1,5-pentanediol

1.6

Acetate and water overhead,

STUDIES IN EXTRACTIVE AND AZEOTROPIC DISTILLATION SERIES

 


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