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7/27/2019 Anhydro Ethanol Bye Silica Gel
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4th BIOMASS-ASIA WORKSHOP
20 22, NOVEMBER 2007
ANHYDROUS ETHANOL PRODUCTION
SU SU HLAING
LECTURER
DEPARTMENT OF CHEMICAL ENGINEERING
MANDALAY TECHNOLOGICAL UNIVERSITY
MINISTRY OF SCIENCE AND TECHNOLOGY
UNION OF MYANMAR
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Objectives
To prepare anhydrous ethanol with liquid phase adsorption
process
To investigate the adsorption of water on blue silica gel and
to find the adsorption capacity of blue silica gel
To determine the operating parameters for liquid phase
adsorption process
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What is Ethanol?
product of the fermentation of starch and sugar
clear colorless liquid with a characteristic, agreeable odor
completely miscible with water and organic solventsapplications
fuel
chemical solvent
cosmetics and pharmaceutical
human consumption
commercial alcohol 96% ethanol + 4% water
anhydrous alcohol 99.5% ethanol + 0.5% water
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How is anhydrous ethanol produced?
by dehydration of commercial alcohol or industrial alcohol
Technologies
Extractive distillation
Adsorption of water
Azeotropic distillation
Molecular sieve technology
Pervaporation
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Adsorption Process
adsorption is essentially an attraction of adsorbate molecules to anadsorbent surface
silica gel selectively adsorbs water to give anhydrous ethanol
product (99.5% v/v) from commercial ethanol (96% v/v)the experimental technique is related to the various steps which
must take place:
preparation of blue silica gel packed columnoperating procedure
application of feed sample to the packed bed
flow of feed sample through the packed bed
collection of separated sample (effluent sample)
detection or identification of separated sample
regeneration of spent silica gel (pink color)
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Blue Silica Gel
Chemical molecular formula SiO2.nH2O
highly active adsorption material
inert and compatible with any kind of materials, except for strong
alkaline substances and hydrofluoric acid
turning from blue to pink after adsorping moisture
an infinite life in terms of the ability to adsorb or desorb moisture
silica gel can be reconditioned and reused indefinitelyit is not recommended that blue silica gel be heated above 120C
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Table 1. Properties of Blue Silica Gel
Apparent or bulk density, g/cm3 0.1 0.8
Specific gravity 2.1 2.3
Average porosity, % 50 65Specific surface, cm2/g 2x106 7x106
Average pore diameter, cm 4x10-7
Pore volume, cm3/g 0.43
Commercial gas velocity, cm/min 0.82 3.28
Weight adsorption of water at break
point, %
10 20
Weight of water at saturation, % 40
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Experimental Works
size reduction of blue silica gel
batch study (determination of isotherm)
column studies (dynamic method)
gravity flow separation process with one packed
columngravity flow separation process with two packed
column
separation processes with mobile phase pumping
unit
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Size Reduction of Blue Silica Gel
Grinding
the spherical silica gel was ground in a ball mill
Screening
screen analysis of the crushed particles was made
with the aid of a laboratory test sieve shakerDrying
the desired size of particleswas preconditioned in an oven
at 110C for 12 hr
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y = 2.6667x
R2 = 0.9996
0
0.01
0.02
0.03
0.04
0.05
0.06
0 0.005 0.01 0.015 0.02 0.025
C, g of adsorbate/ml of fluid
q,go
fadsorbate
/g
ofadsorben
Figure 1. Adsorption Isotherm Curve
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Feed Reservoir
Adsorption Column
Effluent Ethanol
Sample Collector
Figure 2. Gravity Flow Separation Process with One Packed Column
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Feed Reservoir
First Adsorption Column
Second Adsorption Column
Effluent Ethanol Sample Collector
Figure 3. Gravity Flow Separation Process with Two PackedColumn
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Feed Reservoir
Pump
Adsorption Column
Effluent Ethanol Sample Collector
Figure 4. Separation Process with Mobile Phase Pumping Unit by
using One Packed Column
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Conclusions
the adsorption isotherm curve on silica gel fit with the linear
isotherm
Separation of water using small particle size silica gel gave betterseparation, however, a high pressure pump is needed.
Water removal efficiency of the silica gel in this work is about 50%
of the 96% ethanol is removed for one pass operation.
In further work of separation with two columns in series is removed
75% on initial water present in 96% ethanol.
Separation process with mobile phase pumping unit by using three
column in series produces anhydrous ethanol (99.5% v/v) by
removing 87.5% of initial water present in commercial ethanol.
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