SP_Final_Report

Chemical Engineering
To: Professor Doug Kelley
Distillation and Characterization
of Methacrylic Acid
Megan Johnson, Tom Ignaczak, Vito Martino and Daisy Jin
Supervised by:
Mark Juba
Robert Harding
December 16, 2016

Distillation and Characterization of
Methacrylic Acid
Megan Johnson, Tom Ignaczak, Vito Martino and Daisy Jin
December 16, 2016
Abstract
Methacrylic acid (MAA) is a common monomer used for industrial
processes. For many of these processes to succeed methacrylic acid must
be separated from it’s inhibitor and polymer. This project consisted of
the construction of a simple vacuum distillation apparatus in order to
separate methacrylic acid from the mono methyl ether of hydroquinone
(MEHQ) inhibitor and poly-MAA. Simultaneously the team developed a
characterization method for the distillate.
1 Introduction
Methacrylic acid (MAA) is a common monomer used in many industrial poly-
merization processes. As such, many large chemical manufactures produce this
very useful monomer in mass quantities and ship it far and wide. However, those
looking to use this monomer in an industrial or lab setting may run into a few
problems. The company sponsoring this project, Acuity Polymers, had this to
say, “In the production of contact and IOL lenses, [MAA and other] hydrophilic
monomers are used to provide a wettable, biocompatible surface. One issue
is that vendors frequently supply these monomers containing inhibitors which
must be removed prior to use in the polymerization process. Another complica-
tion is that there may also be present polymer contamination which will cause
the final lens to be cloudy in appearance.“ It is the goal of this project to develop
a simple process for separating MAA from both its inhibitor and polymer. In
order that the product produced may be tested for purity, a standard procedure
by which the purified distillate may be characterized is also presented.
Per Acuity Polymers request, the process should be able to be performed
with basic lab equipment, have a production rate of 125g per hour, and produce
a purified product with an polymer/inhibitor content of less than 100 ppm. If
this sounds fairly straightforward, here are a few things to consider. There exist
only two commonly used procedures for separating inhibitor compounds from
MAA and monomers like it. The first procedure consists of simply running the
monomer solution through an activated alumina filter. While activated alumina
columns are very effective at removing inhibitor, they are also very effective at
1

absorbing MAA and thus would lead to low yields and need to be replaced or
regenerated frequently [3]. The second process consists of distilling the monomer
solution, but here too there are problems. MAAs polymerization reaction’s
activation energy is low enough that it can occur spontaneously at standard
temperature and pressure. Manufacturers also realize that the individuals and
companies seeking to use their MAA product would like it as pure as possible
and as a result they add just enough inhibitor to prevent polymerization under
a reasonable range of temperatures. The final wrench in the process, the longer
a solution of MAA is heated the higher its boiling point becomes (likely due to
the solutions polymer concentration increasing). The result is an unfortunate
downward spiral into a less and less efficient process. Heating MAA to distill
it can quickly result in the MAA polymerizing, which in turn results in the
solution having a higher boiling point, which reduces the rate of evaporation
unless the solution is heated further. Then, once a purified product is formed,
MAA without inhibitor will polymerize independently at standard temperature
and pressure. In addition to the obstacles with the design, Acuity‘s desire for
an analytical technique that can detect 100 ppm polymer in MAA is limited
by budget constraints. Equipment with the sensitivity to detect such a small
amount of polymer can very expensive so balance needs to be found between
cost and sensitivity.
With all of this in mind, a gradual-feed, simple vacuum distillation appa-
ratus was constructed using mainly pyrex glassware. Operating at pressures of
between -28.8 and -29.5 inHg gauge, allows the MAA to distill at temperatures
as low as 51 C. Gradual feed of MAA solution into the distillation flask reduces
the length of heating time per unit volume of solution. Both of these methods
taken together reduce the effect of polymerization on the process and result in a
process which is able to deliver a high yield, high purity product in a reasonable
amount of time. Purified MAA is then frozen for storage to prevent spontaneous
polymerization before use.
Taking into account expenses, sensitivity, and feasibility of various analyt-
ical techniques, a list of 11 tests was compiled to be researched and utilized
for characterizing the distilled product. Each of the 11 tests falls into one of
2 categories based on whether it was used to detect MEHQ or detect polymer.
For the MEHQ it was assumed based on the design parameters that there was
very little chance of it boiling and ending up in the collection flask. This was
not verified by UV spectroscopy due to conflicting results and since it was un-
successful. The test should be run each time distillate is created until it can be
assured the process is operating correctly and then tested randomly for proper
operation in the future. The technique to detect 100 ppm polymer contami-
nation proved more difficult to identify. In the end two tests were selected: a
solubility test using hexane and liquid chromatography with mass spectrometry
(LC/MS). The solubility test works for polymer presence between 200-300 ppm
whereas the LC/MS can give an exact breakdown of all the components in a
possible mixture. The solubility test can act as an initial pass/fail test as to
whether the product should be run in the LC/MS.
2

2 Design and Experimental
Simple distillation of a binary mixture is a procedure which separates compo-
nents according to their relative volatilities by evaporating off the more volatile
component and condensing the resulting vapor directly without any intermedi-
ate stages. If, at a given temperature and pressure, a binary mixture is composed
of one compound which exists almost entirely in the vapor phase and one com-
pound which exists almost entirely in the liquid phase, then this component can
easily be separated using simple distillation. The following calculations quantifi-
ably show that simple distillation should theoretically satisfy the requirements
of this project. All calculations are performed with well known thermodynamic
equations [5][11].
A common way to mathematically represent the volatility of a component is
with K-Values.
Ki =
Mole Fraction of i in Vapor
Mole Fraction of i in Liquid
=
xi
yi
(1)
Logically then, the relative volatility of the components of a mixture can be
defined as:
αij =
Ki
Kj
(2)
For a quick ”back of the envelope” calculation let’s examine an ideal system.
In an ideal system the vapor phase will obey Dalton’s Law while the liquid phase
will obey Raoult’s Law:
Dalton’s Law
yi =
pi
P
(3)
Raoult’s Law
yi =
pi
po
i
(4)
The Result of this Ideal analysis:
Ki =
yi
xi
=
pi
P
(5)
αij =
Ki
Kj
=
po
i
po
j
(6)
What this means is that if the vapor pressure of both of the components of
the binary mixture at a given temperature and pressure are known then their
relative volatility at these conditions are also known.
This exact analysis was performed for a mixture of methacrylic acid and hy-
droquionone mono methyl ether and at atmospheric pressure and a temperature
of 20 o
C, and a relative volatility of 144 resulted.
xbulk methacrylix acid = 0.9991[2] (7)
αij = 144 (8)
3

From these two numbers, a distillate purity for simple distillation can easily
be calculated.
yi =
αijxi
1 + xi(αij − 1)
= 0.99999 (9)
This purity will more than likely suﬃce for Acuity’s purposes [1][2][7][8].
Now comes the question, what operating temperature and pressure were pre-
dicted and how were these numbers calculated? Approximate operating condi-
tions can be found using the boiling points and critical temperatures [1][6][8]
of our components in conjunction with three equations: Trouton’s Rule, the
Clausius-Claperyron equation, and Watson’s equation.
Trouton’s Rule
∆Hn
RTn
∼ 10 (10)
Watson’s Equation
∆H2
∆H1
= (
1 − Tr2
1 − Tr1
)0.38
(11)
Watson’s Equation allows for the generation of a set of ∆Hn corresponding
to any range of temperatures from a single known temperature and ∆Hn pair
which was generated using Trouton’s Rule.
Clausius-Claperyron Equation
Psat
T 2 =
Psat
T 1
e
∆H
R ( 1
T2
− 1
T1
)
(12)
Figure 1: Trial 2 of MEHQ Absorbance vs. Wavlength
According to Figure 1, MAA and MEHQ can be eﬀectively separated using
vacuum distillation over a wide range of operating temperatures and pressures
(again it is safely assumed that this technique also works for separating MAA
from its polymer).
4

To reach meaningful conclusions one has to consider the relationship be-
tween operating temperature, yield, and production rate. Lower the operating
temperatures result in MAA being exposed to less heat and less polymer being
formed during the process. This in turn will result in a high yield. However,
runtime has the opposite relationship with operating temperature. The higher
the operating temperature, the faster MAA will transfer from the liquid phase
into the vapor phase, and the more pure MAA will be able to be produced in
a given period of time. Taking all this into account, this theoretical analysis
hints at effective operating conditions ranging from the likely slow and high
yield -29.5 inHg and 42 C, to the likely fast and low yeild values of -27.5 inHg
and 80 C, with the best process likely being somewhere in the middle.
Figure 2: Effect of MEHQ accumulation on vapor pressure at various production
level runs
A final point of consideration is the effect of impurity build up during dis-
tillation. The dashed line at the bottom of Figure 2 is the MEHQ inhibitor
and the top dotted line is the pure MAA. As more MAA is evaporated off the
mole fraction of MEHQ in the distilling solution will increase and a correspond-
ing decrease in vapor pressure will be seen. What this means for the vacuum
distillation process is that the larger the batch size is, the larger boiling point
elevation will be over the course of the process. This is depicted in Figure 3
below, the trend is perfectly linear and any non-linear behavior is due simply
to rounding. Small amounts of polymer will also be formed over the course of
the distillation and will also contribute to this boiling point elevation.
In the end, a gradual-feed, simple vacuum distillation apparatus was con-
structed. Low operating pressures allow the MAA to distill at low temperatures
and gradual feed of the MAA solution into the distillation flask reduces the
length of heating time per unit volume of solution. Both of these methods
5

Figure 3: Effect of Batch Size on Boiling Point of MEHQ
taken together reduce the effects of polymerization on the process and result
in a process which is able to deliver a high yield, high purity product in a
reasonable amount of time. Purified MAA can then be frozen for storage.
3 Design
Figure 6 is a PID for the vacuum distillation unit and Figure 5 shows a photo-
graph of the constructed distillation unit.
Figure 4: Front panel of the LabVIEW program built to monitor temperature
6

Figure 5: Actual apparatus built for prototyping
All glassware used in the design was PYREX(R), except a specialized feed
flask, and used a 24/40 ground glass joint size, and all connective tubing was
1/4 in outer diameter 1/8 inch inner diameter latex plastic. The distillation
flask was a 1 liter, round-bottom, three-neck flask, condensers with different
geometries were chosen (differences will be compared in results section), and
the collection flask was a 250 mL erlenmeyer flask but any flask with the correct
joint size would work. A 250 mL constant addition funnel made by Kimble(R)
Kontes(R) was attached to the first neck of the distillation flask, which allowed
for a controlled feed of bulk MAA into the distillation flask while the whole
system was evacuated. The second neck was attached to the condenser, and the
third neck was left open (plugged with PYREX(R) stopper during production)
for directly loading bulk monomer if desired.
On the other side of the condenser, a 105o
bent vacuum adaptor connected
the collection flask and the rest of the apparatus to a length of latex plastic
tubing. This tubing then connected the following in order: a 4-1/2 mechanical
contractors vacuum gauge ranging from -30 to 0 inHg made by Grainger, a bleed
valve, an on/off ball valve, a liquid trap (made out of tubing, a 1L erlenmeyer
flask, and a ice bath), and finally a 2.5 CFM vacuum pump made by Pittsburgh
Automobile(R)
. The valves served to help control the pressure in the system,
and the liquid trap prevented any vapor that went through the tubes from
reaching the vacuum pump and ruining it. All the glassware and valves were
obtained from the University of Rochester Chemical Engineering departments
store room.
System pressure was controlled by running the vacuum pump during the
whole process to obtain a constant pressure. A steady pressure of around -29.5
inHg was easily achieved once all leaks in the system had been sealed with either
Dow Corning(R)
vacuum grease, for the glass joints, or Gorilla Glue(R)
, for the
joints between valves. Unfortunately, vapor entered the vacuum pump at some
7

point during trial testing and the pumps performance gradually degraded over
the course of the project, leading to the range of pressures seen in testing.
To achieve the process goals there are three areas where temperature needed
to be controlled carefully: the distillation flask where the MAA was boiled off,
the condenser where the MAA reformed into a liquid state, and the collection
flask where the distillate was collected and frozen. The distillation flask tem-
perature was controlled by submerging the flask in a near constant temperature
water bath controlled with a stirring hot plate made by Corning(R) and simple
on off control. A type K thermocouple made by OMEGA Engineering(R) was
used to measure the water temperature. The thermocouple was obtained from
the department. The thermocouple was wired to a 8-channel USB-TC board
made by Measurement Computing(R) also acquired from the department and a
LabVIEW program was made to monitor and record any temperature changes
in the water bath (included in appendix). The front panel of LabVIEW program
was shown in Figure 4.
Figure 6: PID of the prototype apparatus
To prevent unnecessary polymerization, the temperature of the collection
flask needs to be kept fairly low. To achieve this an ice water bath was em-
ployed to bring the temperature of the collection down to a steady 0C. This is
low enough to freeze MAA and prevent any polymerization. Finally, the cold
water circulated through the condenser was produced using a constant temper-
ature circulating pump acquired from the department, which supplies water at
a constant temperature (normally 20C), in order to condense but not freeze the
monomer.
8

4 Experiments
In preparation for each experiment, all glassware was cleaned (described below),
dried, and attached appropriately as described above. The collection flask was
tarred in order to eventually compute the yield. Then the temperature sensor,
vacuum pump, and and hot plate were tested to make sure they were working
properly. After this the hot plate was turned on until the hot water bath reached
3C less than the desired operating temperature. Then the hot plate was turned
off and the system was allowed to reach a stable temperature. Normally the
system leveled off at the desired operating temperature, but sometimes the
system would overshoot or undershoot and have to be corrected for by either
turning the hot plate back on briefly or adding a few pieces of ice to the hot water
bath. Finally, the feed flask was filled with bulk MAA and set to the desired
feed rate, the hot plate was turned back on, the vacuum pump was turned on
once again, the bleed-valve was slowly oped to re-pressurize the system, and
production was allowed to begin.
After noticing distillate ceases to accumulate in the collection flask in appre-
ciable amounts, the distillation unit was slowly re-pressurized and the hot plate
turned off to end the production. The collection flask was removed, and, after
weighing to obtain yield, the flask was stored in a refrigerator at temperatures
less than 16C to prevent further polymerization.
Glassware Cleaning Procedure:
• Detached the feed flask, condenser, vacuum adaptor, and collection flask
from the system then rinse them with DI water
• Filled distillation flask with DI water and carefully rinsed the necks, mak-
ing sure there is no residual left on the inner surface of the flask (NOTE:
did not move the hot water bath or detach the distillation flask in order
to not have to reposition temperature sensors between production runs)
• Syringed out the water in distillation flask
• Rinsed the feed flask, condenser, vacuum adaptor, and collection flask
with acetone
• Rinsed the distillation flask with acetone and syringed out
• Leave the parts to dry in fume hood for no less than an hour and put
them back together once all the glassware is fully dry
• To save time, often the product was stored directly in a stoppered dis-
tillation flask and a new distillation flask was simply used for the next
production run
Several small scale tests were conducted to identify optimal operating con-
ditions, and then two larger large scale production runs were conducted under
the identified optimal conditions. All experiments are listed below:
9

4.1 Verifying Boiling Point of MAA vs. Pressure Curve
This experiment was conducted to experimentally verify the theoretically gen-
erated boiling point of MAA versus pressure curve shown earlier in the report.
The original plan was to measure the boiling point of MAA 10 different pressures
and plot them next to the theoretical curve to measure their correspondence.
However, a phenomena known as boiling point elevation was encountered when
performing the experiment [3]. Boiling point elevation in this circumstance is
the process by which when MAA is heated, PMAA is formed, which raises the
boiling point of the now MAA / PMAA solution. This made experimentally
verifying our calculated curve far too costly in terms of the amount of MAA that
would have had to been used. However, throughout our remaining experiments
this plot proved to be very successful at predicting the initial boiling point of
MAA under various pressures.
4.2 Identification of Most Favorable Operating Conditions
For this experiment, different distillation temperature settings were tested in
order to find the optimal operating condition which would give high yield, high
purity along with a relatively short runtime. 20C was identified as an effective
temp for our condenser as MAAs normal freezing point is 16C and the collection
flask was kept at a constant 0C by employing a simple ice bath to freeze the
purified MAA product. Also, it was realized that there was really no harm
in keeping the system pressure as low as possible as long as the distillation
temperature was kept low enough such that the process would not be vaporizing
any appreciable amount of inhibitor. These three variables were kept constant
for every test in order to find the most effective distillation flask temperature.
10g samples of MAA were run through the system with different distillation
temperature set points (51C, 55C and 65C) and the results of these tests were
compared on the basis of their yields, runtimes, and purities. Runtime and
distillation temperature were recorded by a LabVIEW program, yield can be
easily computed using a scale, and purity was tested using a solubility test
described later in this report.
4.3 Mid-Scale MAA Experiment With Slow Feed
This experiment aimed to verify the optimal conditions found from small scale
testing. These conditions were: distillation flask temperature 65C, condenser
20C, collection flask 0C, pressure -29 inHg. 44g bulk MAA was added to the
feed, and the flow rate was carefully monitored so that only around 10 mL of
MAA solution was present in the distillation flask at any point in time. Process
runtime and distillation temperature were again recorded using LabVIEW, yield
was computed, and solubility test was used to test if theres any polymer left in
distillate.
10

4.4 System Capacity Production
This experiment was conducted to test how the system would perform during
a large scale production. A 210g, maximum capacity for the system, test run
was performed. Unfortunately, the vacuum pump being used had started to
decline in performance, and thus the experiment was run at a gauge pressure
of -28.75inHg, which meant the distillation temperature had to be increased
correspondingly in an attempt to achieve an acceptable runtime. The distilla-
tion temperature was varied over the course of the experiment, but the highest
temperature reached was 77C. As before, the condenser temperature was set to
20C, and the collection ﬂask temperature 0C. Process runtime and distillation
temperature were again recorded using LabVIEW, yield was computed, and
solubility test was used to test if theres any polymer left in distillate.
5 Methods
Before researching tests for polymer detection, it was important to understand
the behavior of MAA polymer in MAA monomer. As it turns out the polymer
is very insoluble in the monomer [8] so certain levels of polymer in the monomer
can be detected with the naked eye. Below are three images of 10,000 ppm,
1,000 ppm and 100 ppm polymer in monomer.
Figure 7: Decreasing concentrations of PMAA in MAA from left to right
At 10,000 ppm there is a distinct line of separation between the polymer and
the monomer. Then at 1,000 ppm there is a white haziness where the polymer is
insoluble. Unfortunately at 100 ppm the solution is completely clear and there
is no visual indication that any polymer if present. A list of possible tests to
look for polymer detection was created and then narrowed done by feasibility
and cost.
11

5.1 NMR
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spec-
troscopy, is a research technique that exploits the magnetic properties of certain
atomic nuclei. This type of spectroscopy determines the physical and chemical
properties of atoms or the molecules in which they are contained. This test was
our last resort. The reasoning behind this is that Acuity doesn’t have access to
an NMR machine for testing and it would be too expensive to purchase it.
5.2 TLC
Thin layer chromatography, or TLC, is a method for analyzing mixtures by
separating the compounds in the mixture. TLC can be used to help deter-
mine the number of components in a mixture, the identity of compounds, and
the purity of a compound. The premise for our use of this test was to check
for polymer chains based on the rate through which they ran down the TLC
plate. TLC would have been utilized as a quick qualitative test for polymer
presence, but was deemed irrelevant once solubility testing was conﬁrmed as a
quick qualitative test for polymer presence.
5.3 HPLC
An idea proposed by Acuity when detecting polymer formation in the methacrylic
acid was size exclusion chromatography. The general idea of size exclusion chro-
matography is that a column packed with a porous material that allows for
solution to pass through. When a mixture of solutions with varying molecu-
lar weight passes through, the components with less molecular weight will pass
through faster and separate the solution into its many parts. One such version
of this technique is High Performance Liquid Chromatography (HPLC)
5.4 MALDI
A popular detection method for polymers is Matrix-assisted Laser Desorp-
tion/Ionization (MALDI) in which a solution is placed on a MALDI tray and
then irradiated with lasers prompting desorption. Then the molecules are ion-
ized and run through a mass spectrometer to detect the presence of polymers.
This test works best for molecules with molecular weights in the thousand range
but methacrylic acid has a molecular weight of 86. 06 g/mol [Reference]. Since
the MALDI equipment is expensive and results for methacrylic acid were not
guaranteed, it was decided not to run the test.
5.5 FTIR
In the search for a polymer detection technique, Professor Tenhaeﬀ was con-
sulted due to his work with polymers. He most often uses Fourier Transform
Infrared Spectroscopy (FTIR) to detect polymers. This technique looks at the
absorption of molecules for the infrared spectrum and plots them over a wide
12

range for a visual breakdown of the sample. Although effective in detecting
a large amount of polymer, since ACuity was looking for a sensitivity of 100
ppm, Professor Tenhaeff believed that the test would not be sensitive enough.
Once again weighing the uncertainty of the results against Acuitys budget, it
was decided not to run the test.
5.6 Refractive Indexing
Another technique for analyzing the distillate product was measuring its re-
fractive index. A refractometer looks at how light passes through a medium by
measuring the angle at which light reflects off the medium. Once a refractometer
has been calibrated to a solution, even slight impurities will change this angle
of refraction and therefore indicate the presence of other molecules. While this
test was promising, the contacts in the chemistry department were unable to
find a refractometer to run the test.
5.7 LC/MS
Liquid Chromatography with Mass Spectrometry combines two common de-
tection techniques to provide a highly sensitive test for mixtures. The liquid
chromatograph separates the individual components based on their different
masses which the mass spectrometer then measures in order to identify them.
Although a more expensive procedure, as a qualitative test it allows for an exact
detection of polymers in solution. For this method both a Shimadzu LC/MS
2010 and a Thermo Scientific LTQ Velos were used. The machines showed a
lack of polymer presence up to a molecular weight of 500 g/mol.
5.8 GC
Gas chromatography (GC) is a common type of chromatography used in ana-
lytical chemistry for separating and analyzing compounds that can be vaporized
without decomposition. The gaseous compounds being analyzed interact with
the walls of the column, which is coated with a stationary phase. Our use of GC
was limited to an attempt to detect MEHQ. After running a few tests we failed
to find any peak that may have correspond to MEHQ. However, upon realiza-
tion that the boiling point of MEHQ is too high to be run in our instrument
the results made sense and the test was discarded.
5.9 Viscosity
Viscosity is a principal parameter when any flow measurements of fluids, such
as liquids, semi-solids, gases and even solids are made. Viscosity measurements
are made in conjunction with product quality and efficiency. Formation of
polymer was thought to lead to an increase in viscosity and could be used as a
way to test for polymer presence in our distillate product. The initial testing
produced mixed results eventually leading to the removal of this test from our
13

procedure. A thorough statistical analysis was done to figure out the test fails
to differentiate between products that do or do not contain any polymer.
5.10 Solubility
Acuitys current test for polymer detection is a solubility test using trifluoroethyl
methacrylate (TFEMA). Methacrylic acid monomer is soluble in TFEMA but
the presence of polymers presents as haze. Unfortunately TFEMA is a very
volatile chemical and wasnt safe to store in Gavett. Instead Professor Tenhaeff
suggested contacting Scientific Polymers, a company that specializes in polymer
detection. They too use a solubility test for methacrylic acid, but their solvent
is hexane. After testing multiple variables including amount of solvent and
solute, temperature and using heptane as a solvent, a procedure was created
that tests with a sensitivity up to 200-300 ppm of polymer in solution. At
room temperature a test tube is filled with 2 mL of hexane which is colorless
in appearance. Then 1 mL of colorless distillate is added. If a white/yellow
precipitate forms, this indicates the presence of polymer. Solutions of aqueous
polymer of varying concentration were tested to create a maximum sensitivity
within the range of 200-300 ppm polymer present in solution. As water does
not form precipitate in hexane, any precipitate formation can be attributed to
the presence of polymer. Although Acuity is looking for an analytical technique
that has a sensitivity of 100 ppm, this solubility procedure can act as an initial
pass/fail test before the distillate is tested using more expensive methods.
5.11 UV Spectroscopy
Since the starting amount of MEHQ in methacrylic is only 250 ppm, a more
sensitive test is needed for MEHQ detection. Based on the certificate of analysis
that Sigma Aldrich sent with the bulk methacrylic acid, the presence of MEHQ
is measured via UV spectroscopy. Since methacrylic acid doesnt absorb wave-
lengths above 300 nm the samples were placed in 1 mm quartz cuvettes and
run in a Perkin-Elmer Lambda 900 spectrophotometer that runs as low as 200
nm. The results were inconclusive but there are two options for Acuity going
forward: continue testing by creating a standard via multiple experiments or
send our their samples to other companies for analysis.
6 Results and Discussion
In Table 1, it is clear to see that the yield and production rate improved iter-
atively. There was a big improvement from test two to test three in terms of
runtime as a result of a change in condenser geometry from Figure 8 to Figure 9
which captured much more vapor and allowed less to drip back into the distilla-
tion flask. In hindsight, insulation could have been placed around the glass up
until the condenser in order to capture as much vapor as possible. Significant
improvements were also seen in yield and production rate between trials 4 and
14

Table 1: Results Overview
Trial
Number
Distillation
Temperature
Set Point [C]
MAA
Used [g]
Yield
[%]
Runtime
[min]
Production
Rate [g/hr]
Product
Solubility
in Hexanes
1 51
Not
Recorded
Not
Recorded
Not
Recorded
N/A YES
2 51 9.91 72.15 51.4 8.35 YES
3 55 9.97 79.34 15.4 30.86 YES
4 65 9.66 80.75 6.1 76.92 YES
5 65 44.03 95.30 16.7 156.25 YES
6 65-77 210 91.30 176.6 71.43 YES
5. These improvements can be attributed mainly to the system being able to
operate at steady state for a longer period of time during the larger trial. Trial
5 achieved all process goals with a production rate greater than 125g/hour and
a polymer content of at most 300 ppm and likely less.
Figure 8: Original vacuum adapter
15

Figure 9: Optimized vacuum adapter
The capacity trial was able to achieve high purity product, but production
rate suffered due mainly to being run at a higher pressure. Production of purified
MAA completely stopped twice during this trial and the temperature of the
distillation flask had to be increased to get production started again. Had the
vacuum been working properly the production rate would have been better for
this test. However, it is likely that the production rate for this test would have
still been lower than that of trial 5 do to boiling point elevation.
6.1 Solubililty
The use of hexanes for solubility testing provided a quick and cheap way to test
for the presence of polymer in our product solution. After optimization the test
was able to detect down to 300 ppm contamination level. Various temperatures
were used ranging from 18 to 23 degrees Celsius. Other solvents such as heptanes
were used to test for optimal detection levels. When testing the 6 production
run products it was seen that all passed the test, meaning each had at most 300
ppm contamination of polymer. A test with more than 300 ppm polymer would
turn the solution hazy as seen in Figure 10.
16

6.2 UV Spectroscopy
In using UV spectroscopy for the detection of MEHQ the expected result was
that any MEHQ present in solution would increase the absorbance of light.
There the absorbances of the products would be noticeably different if the dis-
tillation successfully removed the inhibitor. The wavelength to look for this
trend at was around 290 nm according to research done on MEHQ in acryloni-
trile where the concentration of MEHQ in parts per million was increased and
each absorbance was measured in Figure 11.
Looking at the results, by changing the concentration about 20 ppm, the
absorbance went from around 0.7 to 1.7. Since the bulk MAA had about 250
ppm MEHQ, the expected results should have been quite noticeable. Two trials
were done in which the bulk MAA with inhibitor was run along with the prod-
ucts from the fifth and sixth trials. Looking at the results plotted from 250-300
nm it is immediately obvious that something was wrong with trial one as the
MAA with inhibitor is significantly lower than the two products.
However, trial 2 was much more in line with the expected results. The bulk
MAA starts with a higher absorbance, as is to be expected with the presence
of MEHQ. Looking specifically at 290 nm however there is an issue. Although
the absorbance of product 6 is lower than that of the bulk MAA, product 5
is higher. Due to this the results are inconclusive for this test. Although it
is still safe to assume that the MEHQ would have been completely separated
due its significantly higher boiling point, there was no quantitative evidence of
this result. Further testing may have shown positive results but due to lack of
resources and time this was not possible. Since a UV spectrophotometer and
the specialized quartz cuvettes are both expensive pieces of equipment Acuity
will most likely not purchase them. Under the current design parameters it
17

is highly unlikely that MEHQ will be present in the collection flask due to its
much higher boiling point compared to that of methacrylic acid. Although these
results were inconclusive, this is the general standard for testing for the presence
of MEHQ. To avoid expensive purchases, Acuity might want to consider to send
their distillate products for occasional testing to confirm that it is still operating
as it should.
6.3 LC/MS
Although the solubility test was successful in showing a passing concentration
of less than 200-300 ppm polymers in MAA for all the products, in order to fully
analyze the distillates, they were run through an LC/MS. Due to expenses only
the bulk MAA and products from the fifth and sixth trials were tested. This
test was able to separate the bulk MAA as well as products 5 and 6 by molecular
weight and plot those values by intensity. The higher peaks indicate a higher
presence of a particular molecular weight. The expected peaks were around 86
g/mol for MAA and 124 g/mol for MEHQ as those are their molecular weights.
First the bulk MAA and was run in Shimadzu LC/MS 2010 and is results can
be shown in Figure 14.
Figure 11: Absorbance Spectrum of MeHQ in Acrylontrile
18

Figure 14: LC/MS of Dilute MAA
19

Figure 15: Dilute Bulk MAA LC/MS
Although the technician forgot to make the scale span low enough to include
values under 100 g/mol, there were still distinct peaks at 171 and 257 g/mol.
These are the dimer and trimer of MAA respectively. Since these samples were
not diluted it was likely that the machine was unable to distinguish between
the monomer and its first two polymer structures. To confirm this the bulk
MAA was then run through the Thermo Scientific LTQ Velos and the results
are shown below.
Here there is a distinct peak at 85.2 showing the presence of mainly monomer
in the solution. The other peak at 193 is the dimer with a sodium ion which
is not uncommon for mass spectroscopy. Most importantly though is the value
saying that the average molecular weight of the compound is 86.18. The other
peak of notice for bulk MAA through the Shimadzu LC/MS 2010 [14] is one
at 285 g/mol. The current conclusion is that it is 2 MEHQ molecules with a
potassium ion. Although not as common as sodium ions, potassium ions are
found to attach during ionization in mass spectroscopy. The evidence to support
this comes when looking at the LC/MS results for the products. When running
both products through the Shimadzu LC/MS 2010, the scale was adjusted to
go down to 50 g/mol; however once again the solutions were not diluted and
therefore there were peaks at 173 and 257-259 in Figure 15 and Figure 16.
What is important is the noticeable absence of the 285 g/mol peak. Since
20

Figure 16: Product 5
Figure 17: Product 6
21

the only potential change between the bulk MAA and the two products is the
loss of MEHQ, this does give merit to the theory of the peak at 285 g/mol
containing MEHQ. Instead the results for products 5 and 6 show that aside
from the same dimer and trimer that can be explained by the solution being
too concentrated, there arent any peaks of large mass up to 500 g/mol. These
results in combination with those of the solubility test show that this process
will not produce any polymers up to 500 g/mol with a sensitivity of 200-300 ppm
for anything longer. Due to insolubility of poly-MAA in the monomer MAA it
is likely that heavy polymers would form in the solution unnoticed. This more
technical equipment is more expensive to use and although it was accessible for
these trials, Acuity will most likely not want to purchase the equipment for their
own lab. This test was meant to show more quantitatively what the solubility
test showed qualitatively.
7 Analysis of Precision and Error
When considering error introduced by the experimental aspect of this project, of
course the glassware could have always been cleaner. However, great precaution
was taken when cleaning. The only unavoidable source of imprecision was the
low cost pressure gauge used which was accurate to within around plus or minus
.1 inHg.
Looking at sources of error for the analysis there was a possibility of polymer
forming outside of the distillation process. When the bulk MAA was left in the
hood outside of its tinted container or not wrapped in aluminum foil, polymer
formed even with the inhibitor. Additionally the product needed to be in liquid
form for testing, meaning it needed to be melted from the frozen form it was
collected in. Although the temperature was increased gradually, its possible
that if it melted too quickly, polymer formation would occur.
Looking at the UV results ideally it would have been better to run more
trials. There were two limiting factors there: time and money. Since the focus
was on polymer most of our energy went into that rather than MEHQ. Given
more time the best procedure would be to ﬁnd the absorbances of MAA with
varying concentrations of MEHQ. Although reagent grade MEHQ is relatively
inexpensive, the equipment to run these trials is. As an alternative to buying
this equipment and creating a standard, companies like Sigma Aldrich, where
the the bulk MAA was ordered from, already have a test in place. If it appears
that MEHQ may be present in the distillate, Acuity could send their products to
these companies for a higher chance of successful analysis. Paying for this service
would be a safer “investment“ than buying all the equipment and materials to
make this standard themselves.
22

8 Conclusion
At the end of the day, it was the goal of this project to deliver a prototype
process to prove this purification methods feasibility. Included in this report
is a vacuum distillation apparatus build description and a PID. Also included,
procedures for cleaning, solubility testing for polymer, UV testing for MEHQ
inhibitor, and controlling for both temperature and pressure. The list here,
along with the guide below, constitutes the prototype process.
8.1 Guide for Process Implementation
• Distillation flask temperature to be controlled to within 1 of 65
• Condenser temperature to be controlled to within 1 of 20
• Collection flask temperature to be 0 - exact temperature easy to achieve
with ice bath
• System pressure to be controlled to within .1 inHg of -29 inHg gauge, .45
.05 psi absolute
• Condenser geometry should be such that as much vapor is captured as pos-
sible without reflux into the distillation flask. Insulation of glass leading
to condenser will also aid in vapor capture.
• Analysis of MAA solutions:
– A simple hexane solubility test will determine if polymer content has
exceeded 300 ppm
– UV spectrum analysis is industry standard for detecting MEHQ in
solution
8.2 Future Work
Ideas for future work include both material characterization tests and process
improvement recommendations. Further testing to validate vapor pressure vs
temperature trends for both MAA and MEHQ would be valuable to anyone
seeking to improve MAA purification methods. Modification of the process to
account for changes in vapor pressure of the distilling solution over the course
of production would greatly increase the production rate of the process. Possi-
ble methods of accounting for this vapor pressure change include: automation
of distillation temperature control to follow the increasing boiling point over
the course of production, introduction of a mechanism for flushing out concen-
trated MEHQ solution from the distillation flask mid-production, use of multiple
distillation flasks simultaneously in order to distribute the buildup of MEHQ
inhibitor such that its effects are mitigated. If extensive process improvement is
desired then it will become financially advantageous to obtain the necessary UV
spectroscopy equipment in order to test for the presence of MEHQ inhibitor.
23

ACKNOWLEDGMENT
Team Lynx would like to extend thanks to all those who have helped make this
project possible. Robbie Harding for insight into group development and equip-
ment usage; Mark Juba for invaluable knowledge into the processes involved
throughout the experiment; Acuity Polymers for the opportunity to work on a
real life problem; and the faculty and professors in the Chemical Engineering
department.
24

References
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[3] Deichert, William G., Kai C. Su, Martin F. VAN Buren, and Bausch Lomb
Incorporated. ”Patent US4195030 - Preparation of monomeric organosilicon
esters.” Google Books. N.p., n.d. Web. 16 Dec. 2016.
[4] Joﬀe, Joseph. ”Boiling-point elevation.” Boiling-point elevation - Journal
of Chemical Education (ACS Publications). N.p., June 1945. Web. 12 Dec.
2016.
[5] Kister, Henry Z. Distillation Design. New York: McGraw-Hill, 1992. Print.
[6] Measuring MEHQ (Polymerization Inhibitor). 1st ed. Applied Analytics.
2013. Web.
25

[7] Methacrylate Producers Association, Inc, and Methacrylates Sector Group
of the European Chemical Industry Council.Methacrylic Acid: Safe Han-
dling Manual. 1st ed. 2007. Web.
[8] ”Methacrylic Acid.” Hanhong Group. Hanhong Group, 1999. Web. 19 Sept.
2016.
[9] ”Methacrylic Acid”.Pubchem.ncbi.nlm.nih.gov. N.p., 2016. Web.
[10] Rhodia,.Paramethoxyphenol Safety Summary. 1st ed. Solvay Group, 2011.
Web.
[11] Smith, J. M., Van C. Ness H., and Michael Abbott M. Introduction
to Chemical Engineering Thermodynamics. Boston: McGraw-Hill, 2005.
Print.
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