Code:DB8976
Fractional Distillation
Objective: To observe the separation of an equal molar mixture of ethanol and nBuOH using fractional distillation. Additionally, noting temperature ranges at
which multiple vials were filled following fractional distillation.
Procedure: To start the experiment pack an air
condenser with stainless steel sponge and have
your partner weigh out several empty vials (in
this case 4). Then measure 2.5mL of ethanol and
2.5mL of n-butanol into a single flask. Next
assemble your apparatus by clamping the flask
to a ring stand and setting up a hot plate
underneath. Attach the air condenser along with
several columns to the flask hanging above the
hot plate. Turn on the hot plate and let the
mixture heat up long enough until you are able
to see vapors that rise and condense in the top
portion of the column where a drop off allows
the condensation to accumulate-known as the
HETP. After the HETP has a noticeable amount
of substance in the well, begin collecting in
Figure 1. Displays fractional distillation
vial number one. Repeat this process for at
on the micro- scale level.
least three times, or however many times it
takes to completely separate the ethanol from
the n-butanol. While collecting the substance in the HETP it is important to note
the particular temperature at which it was obtained. After acquiring enough
substance to fill up four vials, weigh each individual vial, and subtract it weight
from the original values you already obtained. Create a chart that displays the
temperature and weight acquired for each filled vial obtained.
Results and Discussion:
By using a micro sized distillation tower, and hot plate we were able to
separate the ethanol and n-BuOH hydrocarbons effectively. Through the use of
chromatography we were able to effectively see what was present in each
individual vial acquired.
1st Collection using Fractional Distillation
Figure 2. Displays pure ethanol and a
complete separation.
3rd
Collection
Distillation
using
Fractional
Figure 4. Displays ethanol completely
separated from n-BuOH.
2nd Collection using Fractional Distillation
Figure 3. Displays pure ethanol and complete
separation from n-BuOH.
4th Collection
Distillation
using
Fractional
Figure 5. Displays a mixture of ethanol
and n-BuOH.
Fractional Distillation-Temperatures and Weights
Temp. Range (C°)
Fraction #
65-73
78-80
78-80
79-82
1
2
3
4
Full-Empty Vial
(g)
5.78-5.45
5.83-5.56
5.98-5.68
6.66-5.65
Weight (g)
.33g
.27g
.30g
1.01g
Based off the acquired graphs by using chromatography, it is fair to conclude that
ethanol peaks in between the one to two minute mark. In addition, the peak
displayed within figures 2, 3, and 4 remains within the 1800-2000 mV range.
These three graphs display very good separation of the ethanol from the n-BuOH at
temperature ranges between 65-80°C. Figure 5, on the other hand, displays a
mixture of both ethanol and n-BuOH. This occurrence can be explained mainly
because of the increased temperature. Since ethanol has a boiling temperature of
78°C and n-BuOH has a boiling temperature of 116°C, a moderate change in
temperature during fractional distillation could potentially cause n-BuOH to
vaporize and condense in the HETP as well. Therefore, a mixture of both ethanol
and n-BuOH was seen in the final collection when the temperature of the hot plate
was at its highest point throughout the entirety of the experiment. Another notable
difference in the fourth vial acquired is the significant increase in weight compared
to the other three. This particular fact clearly hints that n-BuOH is most likely
present since it is a slightly heavier molecule than
ethanol.
However, how would fractional distillation stack
up against simple distillation results? Another test was
performed using equal molar mixtures of ethanol and nBuOH; this time using the method of simple distillation.
Although both methods attempt to separate
mixtures based off different boiling points, fractional
distillation requires fractional columns. Basically, a
fractional distillation is a more accurate method used
when dealing with a mixture in which both substances
have relatively close boiling points. Essentially the
fractional columns serve as an obstacle that the rising
Figure 6. Simple distillation
vapor must go through. Through this process the
apparatus.
rising vapor will condense on the packing material,
become reheated, and vaporize again until it reaches a
pure state. In contrast, simple distillation is a much quicker method in which
fractional columns are not used because the mixtures being separated have
significantly different boiling points. Below represents comparisons of simple
distillation vs. fractional distillation.
1st Collection
Distillation.
using
1st Collection
Distillation.
Simple
using
Fractional
VS.
Figure 7. Displays an unequal mixture
of ethanol and n-BuOH.
Figure 8. Displays pure ethanol and great
separation from n-BuOH.
Compilation using Simple Distillation
Figure 9. Displays the three trials ran using simple distillation.
The results obtained using fractional distillation stacked up against the
results obtained by simple distillation; clearly indicate that fractional distillation is
the better method. Since ethanol and n-BuOH have relatively close boiling points,
columns are necessary to help prevent “impure” vapor from rising to the collection
site (HETP). Taking a look at Figure 9 indicates that not one collected vial
contained a pure solution, as opposed to looking at the first vial collected in figure
8 and/or 2 using fractional distillation.
Conclusion: The experiments performed display a novel procedure of how
mixtures are separated from one another using boiling points as the key reference
point towards obtaining separation. Although there are various methods used when
attempting to separate hydrocarbons, it is important to note the different boiling
points of the molecules present in a given mixture. This distinct fact will allow you
to distinguish whether it is necessary to setup up a fractional distillation apparatus
or perform a quick and easy simple distillation apparatus.
Throughout the world many companies perform fractional distillation in
order to obtain pure solutions of a desired product. Oil companies for example
attempt to separate the impurities out of mixtures recently drilled out of the ground
by fractional distillation. Knowing how to perform fractional distillation is a key
experiment to have in one’s artillery of known experiments.