Senior Design Project Final Report

Determination of Thermodynamic Properties of Organic Compounds

Logan Williamson | Owen Perlowski | Kristen Webster | Nick Kasper

University of Rochester Department of Chemical Engineering

December 16, 2016

Abstract

Molecular Glasses, a Rochester, NY based start-up company, develops non-crystallizable OLED compounds to be sold to companies that manufacture consumer electronics. One of the inefficiencies in their developmental process is in the determination of the thermodynamic properties of their materials. In order to improve the current method, Team Serval was assigned the task of developing a way to measure the vapor pressure and heat of vaporization of organic compounds. Two different methods were pursued: thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) with a pressure reduction modification. The TGA method was able to estimate the vapor pressure of the model compounds, naphthalene and anthracene, to within 21% of the literature values and the heats of vaporization to within 30% of literature values. The DSC method yielded no evidence of reducing the boiling point of our samples when using a pressure reduction modification. All sealed pan trials produced boiling points above literature values. DSC trials performed in pans without a sealed lid seemed to be a viable option for measuring the heat of sublimation. Measurement for these trials were within 5% of the literature values.

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Table of Contents

1. Introduction 1.1. Background and Motivation 3

2. Experimental Approach 2.1. Thermogravimetric Analysis (TGA) 3 2.2. Differential Scanning Calorimetry (DSC) 4 2.3. Vacuum Bagging System 5 2.4. Model Compounds 5

3. Experimental Procedure 3.1. Thermogravimetric Analysis (TGA) 6 3.2. Differential Scanning Calorimetry (DSC) 6 3.3. Vacuum Bagging System 7

4. Results and Discussion 4.1. Thermogravimetric Analysis (TGA)

4.1.1. Determination of the Calibration Constant and 8 Percent Error in Vapor Pressure 4.1.2. Calculating Heats of Vaporization 8 4.1.3. Determination of Vapor Pressures and Heat of 9 Vaporization of TTA

4.2. Differential Scanning Calorimetry (DSC) 9 4.2.1. Non-Hermetically Sealed Pans 10 4.2.2. Hermetically Sealed Pans, 1 atm 11 4.2.3. Hermetically Sealed Pans, Vacuum 11

5. Final Recommendations and Conclusion 12 6. Acknowledgements 13 7. References 14 Appendix A. Figures 15 Appendix B. Tables 27

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1. Introduction

1.1. Background and Motivation Molecular Glasses, a start-up company in Rochester, NY, develops novel organic

light-emitting diode (OLED) compounds to be sold to companies that manufacture consumer electronics such as smartphones and televisions. In order to purify their materials, the company currently uses a separation technique called train sublimation. Train sublimation requires a specific combination of temperatures and pressures to successfully separate impurities, which means the properties of the compound must be well-known.

Molecular Glasses’ current problem lies in determining the thermodynamic properties of their new compounds. Each time a new compound is synthesized, the company makes an educated guess about its properties. A trial train sublimation is then performed on an unpurified sample to see how well the impurities are separated. This is an iterative process that costs the company a lot of material, time, and money.

Team Serval was approached by Molecular Glasses with the task of developing a method to experimentally determine the thermodynamic properties, namely vapor pressure and heat of vaporization, of organic compounds. Furthermore, since many of the OLED materials developed by Molecular Glasses begin to degrade near their normal boiling point, Team Serval had to choose experimental methods that would allow measurement of a compound’s heat of vaporization without heating the compound to its atmospheric boiling point.

2. Experimental Approach

After conducting substantial research, Team Serval decided to pursue two different analytical approaches to determine heat of vaporization and vapor pressure - thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). 2.1. Thermogravimetric Analysis (TGA)

Thermogravimetric analysis (TGA) is an analytical tool that measures mass change as a function of time and temperature. TGA is primarily used to measure thermal stability and characterize materials that undergo oxidation, dehydration, and decomposition. It is a versatile technique, with most instruments being able to reach temperatures of at least 1000°C.

A basic TGA schematic is shown in Figure 1. An open pan, usually made of platinum or ceramic, is filled with a sample. The pan is then placed on a balance in an airtight furnace. A purge gas flows across the sample and exits the furnace through an exhaust. The furnace heats the sample in the presence of the purge gas while the balance measures mass loss as a function of time and temperature.

The theory behind using TGA to measure vapor pressure and heat of vaporization comes from a paper by Duncan Price entitled “Vapor Pressure Determination by Thermogravimetry”

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(Price). The theory is based on two assumptions. Since sublimation and evaporation are zeroth-order processes, the rate of mass loss of a sample under isothermal conditions must be constant, and the surface area of the sample must not change as mass leaves the system. These assumptions lead to the Langmuir equation for free evaporation:

(Equation 1)

where -dm/dt is the rate of mass loss per unit area, p is the vapor pressure, M is the molecular weight of the compound, R is the gas constant, T is the absolute temperature, and 𝛼 is the vaporization coefficient. If the sample is vaporized in a vacuum, 𝛼 is assumed to be 1. If this were the case, vapor pressure could be solved directly from a TGA test using the equation above. In the case of a material being vaporized into a flowing purge gas at 1 atm, 𝛼 cannot be assumed to be 1. Rearranging Equation 1 and letting k = and v = gives:/α√2πR dm/dt)( * √T /M

(Equation 2)

The calibration constant, k , can be determined by plotting known literature vapor pressure values for a compound vs v . The values of v are determined experimentally. The slope of this linear relationship is k , which is assumed to be the same for any compound. Once k is calculated, vapor pressure can be determined for an unknown compound using Equation 2.

Once vapor pressure is known, heat of vaporization can then be calculated using one of two forms of the Clausius-Clapeyron equation:

(Equation 3)

(Equation 4)

with the enthalpy of vaporization coming from the slope of a plot of ln p (or ln v ) vs. reciprocal absolute temperature. 2.2. Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry measures the difference between the rate of heat flow to a sample pan and reference pan as a function of temperature. DSC is used to measure several

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properties of substances, such as enthalpies of phase change, temperatures of fusion and crystallization, and chemical reactions. A pan, usually made of aluminum, is loaded with a sample. The pan may also be sealed to form a closed system at ambient pressure. An identical empty pan is used as a reference. The masses of both pans are measured and recorded. The two pans are heated together through a user-defined temperature profile, maintaining a constant increase in temperature. The heat required to change the temperature of each pan is measured throughout the trial.

Most DSC devices operate at atmospheric pressure. As mentioned earlier, the thermodynamic properties of our compounds needed to be measured below their atmospheric boiling point. Our solution was to seal the pans under vacuum, in hopes of reducing the pressure inside the sealed pan and therefore the boiling point of the compound. To do this, we built a vacuum bagging system that would allow DSC pans containing sample to be hermetically sealed below atmospheric pressure. Theoretically, the lower pressure would reduce the temperature at which samples vaporized within the DSC device.

2.3. Vacuum Bagging System

The design for our vacuum bagging system was modeled after the vacuum bagging systems utilized in the resin composites industry. Several of the materials, including the bagging film, sealant tape, and the thru-bag connector are the same materials used in that industry. As shown in Figure 3, the design was relatively simple. The vacuum pump was connected to a glass pressurization chamber with air tubing. A ball valve was installed between the pump and the chamber as a means of controlling the airflow to the chamber. In addition, the top of the air chamber was sealed with a rubber cork and gorilla glue to prevent air leakage. Coming off from the side of the chamber was another section of air tubing with a ball valve on the end. This served as a relief valve to prevent the buildup of excessive pressure within the system. The chamber was also enclosed by a cardboard blast shield as a further safety precaution if implosion were to occur while running the system.

The chamber was connected to the thru-bag connector with air hose. The thru-bag connector had a removable base that allowed it to be connected to a bag. Two pressure gauges were installed. One was right after the chamber and allowed us to read the pressure inside the chamber. The other was after the ball valve between the chamber and bag. This gauge was liquid filled to offset the effects of the vibrating pump and increase readability. The ball valve allowed us to slowly remove air from the bag.

2.4. Model Compounds

The model compounds chosen for our experiments were naphthalene and anthracene. Both compounds are organic, aromatic substances that have an established knowledge base in literature. We chose two model compounds to give us a greater variety of data as well as to help

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us determine the TGA calibration constant mentioned earlier. For TGA, we also tested a third compound, tri-p-tolylamine, an OLED material whose properties haven’t yet been documented in literature.

3. Experimental Procedure

3.1. Thermogravimetric Analysis (TGA) A TA Instruments Discovery Series 5500 TGA with 100 μL platinum pans were used for

all experiments. The experimental process for TGA was relatively simple as it was largely automated. Each trial required an experimental procedure to be programmed into the instrument software, TA Trios. This procedure consisted of an automated balance tare followed by a temperature profile for each sample.

Mass loss rates were measured at several temperatures for each trial. Each temperature was held isothermally for three minutes, and the ramp rate between temperatures was 20°C/min, which was chosen as an arbitrary heating rate. Data for naphthalene was collected at 80°C, 93°C, 98°C, 103°C, and 115°C. For anthracene, the isothermal temperatures were 227°C, 237°C, 247°C, and 257°C. The temperature values for each trial were selected with two factors in mind: existence of literature vapor pressure data for the compound at that temperature, and assurance that there would be sufficient sample in the pan to collect data throughout the experiment. At higher temperatures, the sample vaporized very quickly and therefore many more trials would have been needed to be conducted to collect information over a sufficient temperature range. Due to time constraints, tests had to be optimized to measure rates of mass loss at multiple temperatures in each trial.

Aside from programming the temperature profile for each test, minimal setup was required. The purge gas (nitrogen) was turned on, experiments were programmed and run, and the gas was turned off after the tests were complete. 3.2. Differential Scanning Calorimetry (DSC)

Experiments were run using a TA Instruments Q2000 DSC. Three different pan configurations were tested using the DSC: non-hermetically sealed pans, pans hermetically sealed at 1 atm, and pans hermetically sealed under vacuum. The non-hermetically sealed pans for this experiment were supplied by Mark Juba, and the hermetically sealed pans were provided by Dr. Anthamatten’s lab. The non-hermetic pans were used as a control to examine how model compounds reacted in a constant atmospheric pressure environment. The sealed pans configurations were used to measure the effects of pressure reduction on the boiling points of model compounds.

The experimental procedure for the DSC was also largely automated, but required some manual preparation. First, the purge gas (nitrogen) was turned on and the DSC was programmed

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to begin cooling the flange, the unit that ensures adequate heat dissipation during trials. Usually, pan sealing or other pan preparation was carried out while the flange was cooling. Once the flange temperature reached around –80°C, the machine was safe to operate.

Similar to the TGA, a temperature profile for each experiment was programmed into the DSC software, TA Universal Analysis. Our tests consisted of ramping the temperature at 10°C/min from room temperature to an upper limit that was chosen based on the compound’s boiling point. For naphthalene, the upper limit was 230°C, just above the atmospheric boiling point. As it became apparent that there might be pressurization happening within the pans, the upper limit was increased to 250°C for the remaining trials to ensure a boiling point peak would be observed. For anthracene, the upper limit was 400°C, well above the boiling point, to ensure complete vaporization.

After all trials were complete, the DSC was programmed to turn off the cooler and begin re-heating the flange. Once the flange was sufficiently re-heated to around 40°C, the purge gas was turned off.

3.3.Vacuum Bagging System

The procedure for constructing the bags and sealing the pans is described below.

Bag Construction (See Figure 5): 1. Cut bagging film into two 3”x 8” sheets. 2. Place one sheet onto a flat surface. On top of the sheet, place the base of the thru bag

connector and the DSC pan loaded with sample and placed inside the blue pan holder. 3. Apply sealant tape around the edges of the sheet. 4. Place a second sheet of film on top of the first. Press firmly around the edges to seal. 5. Use an exacto knife to cut a slit into the bag where the connector base will attach to the

vacuum bagging system. 6. Attach base of connector to system.

Vacuum Sealing (See Figure 4):

1. Make sure valve B is closed, valve A is open, and that the relief valve is half-way open. 2. Turn on pump and monitor the pressure gauge closest to chamber. 3. Once the pressure within the chamber reaches –30 inHg, close valve A and slowly open

valve B. Hold the lid of the DSC pan slightly off center as the air is removed from the bag to ensure the maximum amount of air is removed from within the pan.

4. After all air has been removed from the bag, slide the lid back onto the pan. 5. Clamp the lid onto the pan using the TA Tzero press. 6. Turn off system and remove pan from bag. The sample is now sealed and ready to be run

in the DSC.

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This process ran best with three operators: one to hold the lid over the pan, one to operate

the ball valves on the system, and one to work the pump and press. Slightly opening the relief valve to allow small amounts of air to enter the system reduced the risk of chamber implosion.

4. Results and Discussion

4.1. Thermogravimetric Analysis (TGA) 4.1.1. Determination of the Calibration Constant and Percent Error in Vapor Pressure

Results from the TGA tests on our model compounds are shown in Table 1. From this mass loss data, v was calculated for each trial. A plot of literature vapor pressure values vs. v produced a linear relationship with a slope of k , the calibration constant. These results can be seen in Figure 6 and Figure 7 for naphthalene and anthracene, respectively. For naphthalene, the value of k was found to be 1,503,009 and for anthracene it was 887,652.

As shown in Figures 6 and 7, there is significantly more noise in the anthracene data. One possible explanation for this is that there is a positive correlation between temperature and noise. To visualize the variation in the data, box and whisker plots were constructed for each compound. These plots, shown in Figure 8, do lend some plausibility to this hypothesis, but further testing on other compounds would be necessary for any confident conclusions to be drawn. OLED materials tend to be more non-volatile than our model compounds and therefore require higher temperatures to test via TGA: this noise-temperature correlation should be taken into account when applying this method to those compounds.

Since the calibration constants for the two compounds were different, a linear least-squares regression was performed with the objective of minimizing the error between the back-calculated vapor pressures (using k and v ) and the literature values to calculate a more representative value of k . This resulted in a calibration constant of 1,183,875. Table 2 shows the average error in the vapor pressure calculations at each of the temperatures using this optimized value of k for naphthalene and anthracene, respectively. Using only two model compounds and a regressed calibration constant, vapor pressures were able to be calculated to within 21% error, with an mean error of 13%. 4.1.2. Calculating Heats of Vaporization

Once the calibration constant and vapor pressures had been determined, the Clausius-Clapeyron equation was then used to calculate the heat of vaporization of the model compounds. The natural log of the calculated vapor pressures was plotted against reciprocal absolute temperature for both compounds in accordance with Equation 3. This produced a linear relationship as can be seen in Figure 9. Using the slope of these lines, the heat of vaporization of

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naphthalene was found to be 49.3 kJ/mol, resulting in a 12.1% error compared to the literature value of 56.1 kJ/mol (Webbook.nist.gov) . The heat of vaporization of anthracene was calculated to be 41.2 kJ/mol, resulting in a 30.1% error compared to the literature value of 59.2 kJ/mol (Webbook.nist.gov) .

One result to note is that the calculated values of heat of vaporization are less than the literature values. This is expected because the Clausius-Clapeyron equation assumes that heat of vaporization is independent of temperature, which provides a reasonable estimate but is still a simplification. Neglecting the effect of temperature on heat of vaporization could result in error. Also, the larger error in the anthracene result is presumably due to the more pronounced noise in that data.

Another interesting takeaway from this analysis was the fact that the calculated heats of vaporization were independent of the calibration constant. As long is k is chosen to be greater than zero, the same value will be calculated for ΔH vap . The only thing that changes when k is altered is the y-intercept of the line. The slope remains constant, and therefore so does ΔH vap .

Therefore, if the only value of interest is the heat of vaporization, there is no need to determine a calibration constant.

4.1.3. Determination of Vapor Pressures and Heat of Vaporization of Tri-p-tolylamine

After successful tests with model compounds, tests were run on the OLED compound tri-p-tolylamine (TTA), which has no established literature data for vapor pressure or heat of vaporization. Due to time constraints, the only temperatures tested were 250°C and 280°C. Using the optimized calibration constant, vapor pressure and heat of vaporization data were calculated. The heat of vaporization of TTA was estimated to be 52.2 kJ/mol. Vapor pressure results are shown in Table 3. In order to improve the accuracy of these results, tests at a greater range of temperatures would need to be performed.

4.2. Differential Scanning Calorimetry (DSC) Figure 12 shows a sample calculation from the DSC, analyzed using TA Universal

Analysis software. The green line represents the amount of heat required to maintain an increase in temperature (dT/dt ) at a given temperature (T ). Integrating over the length of the curve gives the total heat absorbed by the phase changes that the sample underwent throughout the test. The red lines show the integration bounds which the user has the ability to change for integration over a more precise region. Figure 11 shows a sample result of integration. Shown below the red line is the total heat per gram for the whole process. A simple unit conversion reveals:

(Equation 5) gJ * g

mol * kJ1000 J = kJ

mol

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with kJ/mol being the appropriate literature units for heats of phase change. Taking the integration result above this calculation can be performed, with the molecular weight of naphthalene being equal to 128.174 g/mol (Webbook.nist.gov) .

(Equation 6) 49.7 28.17 0.455 5 g

J * 1 gmol * kJ

1000 J = 7 kJmol

This result has a 2.58% error when compared to the literature value of 72.320 kJ/mol

(Torres-Gomez). Peak shapes vary by trial. This selected trial yielded a combined peak, which indicated rapid evaporation post-melting. For trials with a combined peak like the one shown in Figure 12, only the heat of sublimation can be calculated, which is mathematically equivalent to the heat of fusion added to the heat of vaporization.

Below is the breakdown of collected data, with discussion related to each.

4.2.1. Non-Hermetically Sealed Pans (See Figures 12 & 13) For these trials, the moment at which all material was lost from the system (the moment

of heat drop off, or when the graph flatlined) was very clear, which aided in selecting the integration boundaries for heats of phase change calculations. Figures 12 and 13 show a peak close to the melting point of each substance. The melting point is 80.2°C for naphthalene and 218°C for anthracene (O’Neil). Measurements for the melting point of naphthalene and anthracene were calculated within 1% of literature values.

Despite obtaining good results for the melting point, peaks near the boiling point of either substance were not observed. One possible explanation for this occurrence is the constant-pressure configuration of these tests. Since the pressure of the system is maintained at 1 atm for these trials, the sample began to exist in vapor-liquid equilibrium as soon as the melting point was surpassed. Our results show that the entire sample evaporated into the gas phase and left the system prior to reaching literature boiling points.

It was impossible to integrate over individual phase change peaks because the melting and boiling peaks were combined, so only the heat of sublimation was calculated for these trials. The measured heats of sublimation were within 5% of the literature values, suggesting that this method is viable.

Figure 12(R) shows a drastic increase in energy required for the phase change of naphthalene. A very large heat of sublimation was calculated (116 , with an error of roughlykJ

mol 61.312%). An attempt was also made to measure the heat of fusion separately, as seen by the red line under the first peak (38.861 , with an error of 106.59%). Both values were determined tokJ

mol be outliers.

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4.2.2. Hermetically Sealed Pans, 1 atm (See Figures 14, 15, & 18) These tests were conducted with sealed pans under 1 atm. Figure 14 shows no obvious

signs of phase change near naphthalene’s boiling point of 218oC (O’Neil). This is because initial naphthalene tests were run only up to 230oC. The next set of tests, seen in Figure 15, show that ramping the temperature 30oC higher allowed peak formation at higher temperatures. Figures 15 and 18 are the only graphs that have representative spikes close to the literature boiling points of either compound.

As shown in Figure 16, a peak slightly higher than literature values was observed, but the data is noisy. It was determined that qualitative conclusions could not be made from this trial, since the temperature appears to be going backwards.

A boiling point approximately 20°C higher than the literature value is significant qualitatively and quantitatively. One plausible explanation for the trend of absence of a boiling point peak near literature values could be the pressurization of air inside the pan. When the air that is sealed to atmosphere in the pan begins to heat up under constant volume, the increasing pressure of the air and the evaporation of the sample will increase the ambient pressure inside the pan. This increasing pressure may limit the sample from vaporizing further until higher temperatures are reached. Inspecting the pans after testing further confirmed this hypothesis. Figure 20 shows an image of a hermetically sealed pan that underwent significant deformation during testing, likely due to the hypothesized pressure buildup.

It is worth noting the accuracy of the measured melting points compared to that of the boiling points for all trials. This comparison is consistent with our hypothesis regarding pressure increase in the pan, since the melting point is not dependent on ambient pressure.

4.2.3. Hermetically Sealed Pans, Vacuum (See Figures 17 & 19)

Similar to the previous trials, melting point peaks were observed to be close to literature values. Increased boiling points were also observed for all trials. Therefore, no clear conclusions can be made to support the initial hypothesis that the vacuum bagging system would reduce the boiling points. One observation that can be seen is in Figure 17(R), where the beginnings of a potential boiling point peak are shown. Unfortunately, this trial was only heated to 220°C. If it had been heated to a higher final temperature, it is possible that a boiling point peak at a temperature closer to the boiling point than the previous 1 atm hermetic trials could have been shown. At first glance, Figure 19(R) appears to indicate a reduced boiling point, but the presence of a third peak and temperature decline (on the peak itself) mean that this trial cannot be qualitatively interpreted.

Even under reduced pressure, the measured boiling points were above literature values. Similar to 1 atm hermetic trials, this is likely due to the internal pressure buildup that occurs as the sample vaporizes. The sample takes up a significant volume of the pan as a solid and as a vapor, its presence likely counteracts any pressure reducing effects that previous air removal

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could have had. From these trials, it appears the vacuum bagging system had no effect on the boiling points of the compounds. The condensed data for all DSC trials are shown in Tables 4 and 5.

5. Final Recommendations and Conclusion

Thermogravimetric analysis appears to be a promising method for Molecular Glasses to

pursue when analyzing their materials. TGA has been shown to be an effective way to determine how long it will take to completely vaporize a compound at any given temperature. This could allow the company to save time during their purification process. Vapor pressures of naphthalene and anthracene were able to be estimated within 20% of their literature values with an average error of 13%, and heats of vaporization were able to be estimated within 12% and 30% of the literature values for naphthalene and anthracene, respectively. These error percentages are within the predetermined range of error set by the company. It was also determined that heats of vaporization are independent of the calibration constant and therefore can be calculated simply using the results of various TGA trials and the molecular weight of the compound. To improve the accuracy of the estimates, more model compounds could be tested over a wider temperature range to decrease the uncertainty in the data.

The use of the DSC proved useful for some applications. If Molecular Glasses is interested purely in the heat of sublimation, a non-hermetically sealed, constant-pressure system approach is suggested. This yielded results within 5% of literature values. For determining heat of fusion, data from any pan/lid combination proved accurate to less than 25% error. Heats of vaporization can be determined using any sealed pan with decent error, but the observed boiling point will be higher than literature values if working under these conditions. For this reason, we recommend calculating heats of vaporization using a two-step process. First, calculate the heat of fusion from a sealed pan trial. Next, calculate the heat of sublimation using a non-hermetically sealed trial. Subtracting this heat of fusion from the heat of sublimation will yield the heat of vaporization. This quick backwards calculation should provide smaller error than was achieved by attempting to measure heat of vaporization directly.

No decrease in boiling point was observed when vacuum sealing our pans before placing them in the DSC. Future projects could focus on these types of trials, and potentially determine the pressure inside the pans when they are heated. Upon examination of the DSC pans post-trial, it is clear that there was pressure buildup occurring within the pans during experimentation. In the future, experiments with larger volume chambers in vacuum could be conducted so that the evaporation of the sample would not affect the reaction vessel. The pressure that causes this vessel expansion could potentially be used to calculate some pan offset, as proposed by Mark Juba.

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6. Acknowledgements

Lab group serval would like to thank everyone in the chemical engineering department

for allowing us this opportunity with a special thanks to Professor Kelley, Mark Juba, Dave Weiss, Larry Kuntz, Cindy Fitzgerald, Rachel Monfredo, Thor Olsen, Ken Marshall, our TA Robbie Harding, Professor Tenhaeff, and Dawei Chen from the Anthamatten Lab.

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7. References

"Anthracene". Webbook.nist.gov . N.p., 2016. Web. 16 Dec. 2016. "Naphthalene". Webbook.nist.gov . N.p., 2016. Web. 16 Dec. 2016. O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals.

Cambridge, UK: Royal Society of Chemistry, 2013., p. 1187 O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals.

Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 111

Price, Duncan M. "Vapor Pressure Determination by Thermogravimetry." Thermochimica Acta 367-368 (2001): 253-62.

Torres-Gomez, L.A.; Barreiro-Rodriguez, G.; Galarza-Mondragon, A., A new method for the

measurement of enthalpies of sublimation using differential scanning calorimetry, Thermochim. Acta, 1988, 124, 229-233.

Ying Duan Lei, Raymond Chankalal, Anita Chan and Frank Wania. “Supercooled Liquid Vapor

Pressures of the Polycyclic Aromatic Hydrocarbons.” J. Chem. Eng 47 (2002): 801-806.

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Appendix A. Figures

Figure 1: TGA schematic

Figure 2: DSC schematic

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Figure 3: Vacuum bagging system concept drawing

Figure 4: Vacuum bagging system

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Figure 5: Bag construction

Figure 6: Determination of k for naphthalene

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Figure 7: Determination of k for anthracene

Figure 8: Variance in rate of mass loss as a function of temperature for naphthalene (left) and

anthracene (right)

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Figure 9: Heat of vaporization calculation for naphthalene (top) and anthracene (bottom)

Figure 10: Sample data output for DSC

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Figure 11: Manual integration of DSC output curve

Figure 12: Trials 7 (left) and 8 (right) for naphthalene in non-hermetically sealed pans

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Figure 13: Trials 6 (left) and 7 (right) for anthracene in non-hermetically sealed pans

Figure 14: Trials 1 (left) and 2 (right) for naphthalene hermetically sealed at 1 atm.

Only the 140.1 J/g value was used for (left)

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Figure 15: Trials 3 (left) and 4 (right) for naphthalene hermetically sealed at 1 atm

Figure 16: Detail of figure 15(left)

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Figure 17: Trials 5 (left) and 6 (right,R) for naphthalene sealed under vacuum

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Figure 18: Trials 1 (top), 2 (left), and 3(right) for anthracene sealed at 1 atm

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Figure 19: Trials 4 (left) and 5 (right) for anthracene sealed under vacuum

Figure 20: Hermetically sealed pan after being run through DSC

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Figure 21: Non-hermetically sealed pan after being run through DSC

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Appendix B. Tables Table 1: Rate of vaporization of naphthalene and anthracene

Table 2: Average error in the vapor pressure calculations at each of the temperatures using the optimized value of k for naphthalene and anthracene

Naphthalene

Temp (℃ ) Literature Vapor Pressure (Pa)

Avg. Calculated Vapor Pressure (Pa)

Percent Error

80 1000 828 17.2

93 1811 1672 7.7

98 2357 2036 13.6

103 2833 2418 14.7

115 4752 3754 21.0

Anthracene

Temp (℃ ) Literature Vapor Pressure (Pa)

Avg. Calculated Vapor Pressure (Pa)

Percent Error

227 7000 7898 12.8

237 9000 10,227 13.6

247 12000 12,051 0.4

257 16000 13,330 16.7

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Table 3: Vapor pressure calculations for tri-p-tolylamine

Temperature (℃) Avg. Calculated Vapor Pressure (Pa)

250 2692

280 5157

Table 4: DSC data for Anthracene

Trial Mass (mg)

Lid Type Calculated HFus (kJ/mol)

Error % Calculated HVap (kJ/mol)

Error % Calculated HSub (kJ/mol)

Error %

1 7.9 Hermetic 1atm 27.96 6.176 None None None None

2 9 Hermetic 1atm 24.96 16.222 47.241 29.174 72.207 26.244

3 17.3 Hermetic 1atm 27.55 7.551 45.797 31.338 73.347 25.08

4 7.2 Hermetic Vacuum

27.55 7.551 46.778 29.869 74.327 24.08


25.25 15.265 47.793 28.346 73.044 25.389

6 13.4 Non-Hermetic None None None None 98.188 0.294


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Table 5: DSC data for Naphthalene Trial Mass

(mg) Lid Type Calculated HFus

(kJ/mol)

Error % Calculated HVap (kJ/mol)

Error % Calculated HSub (kJ/mol)

Error %




4 16.4 Hermetic 1atm 19.35 2.885 9.56 82.954 28.92 60.02


None None None None 67.12 7.19


17.83 5.22 None None None None


8 9.6 Non-Hermetic None None None None None None

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Senior Design Project Final Report

Engineering

Transcript of Senior Design Project Final Report