Comparing Combustion
Energies of Petroleum
Diesel and Biodiesel Fuels
By Bomb Calorimetry
Penn State University, Department of Chemistry, CHEM 457, Section 1, Fall 2013
By: Tim Haggerty, Arjun Plakkat, Kelly Helfrich, Kristen Woznick
Motivation
Holmes, Frank. "World Running Low on Its "Energy Drink" - U.S. Global Investors - September 21, 2011." World Running Low on Its "Energy
Drink" - U.S. Global Investors - September 21, 2011. US Global Investors, 2013. Web. 10 Dec. 2013.
Matt. "Half of Oil Burnable in 2000-2050 to Keep Us within 2 Degrees Warming Has Been Used up as We Hit 400 Ppm." Half of Oil Burnable in
2000-2050 to Keep Us within 2 Degrees Warming Has Been Used up as We Hit 400 Ppm. Crude Oil Peak, 16 May 2013. Web. 10 Dec. 2013.
Introduction
Combustion for Average Diesel Molecule
Combustion for Average Biodiesel Molecule
Ciolkosz, Daniel, Joseph Perez, Dennis Buffington, and Glen Cauffman. "Renewable and Alternate Energy Fact Sheet." Penn State College of Agricultural Science, 2009. Web. 1 Dec. 2013. <http://
pubs.cas.psu.edu/FreePubs/pdfs/uc205.pdf>.
Krol, Walter J. "Comparative Fuel Characteristics." Biodiesel Fuel. The Connecticut Agricultural Experiment Station, n.d. Web. 4 Dec. 2013. <http://www.ct.gov/caes/lib/caes/documents/>.
Graboski, Michael S., and Robert L. McCormick. "Combustion of Fat and Vegetable Oil Derived Fuels in Diesel Engines." Progress in Energy and Combustion Science 24.2 (1998):
12564. ScienceDirect. Web. 30 Nov. 2013. <http://www.sciencedirect.com/science/article/pii/S0360128597000348>.
Patzek, Tad. "A First Law Thermodynamic Analysis of Biodiesel Production From Soybean." Texas A&M Department of Petroleum and Geosystems Engineering, 13 Apr. 2009. Web. 29 Nov. 2013.
<http://gaia.pge.utexas.edu/papers/Biodiesel.pdf>.
Biodiesel Labs. "Combustion of a Renewable and Fossil Fuel: Teacher Manual." Loyola University of Chicago, n.d. Web. 7 Dec. 2013.
Dunn, Bruce. "Liquid Fuels." Liquid Fuels. NASA, n.d. Web. 07 Dec. 2013.
Parr Bomb
Calorimetry
∆U = Q + W
First Law of Thermodynamics
Milosavljevic, Bratoljub H. Lab Packet for CHEM 457 Experimental Physical Chemistry.
Chem 345. "Bomb Calorimetry." Bomb Calorimetry. Hope University, n.d. Web. 09 Dec. 2013.
∆Hv =∆U + ∆n(g)RT
Parr Bomb
Calorimetry
Milosavljevic, Bratoljub H. Lab Packet for CHEM 457 Experimental Physical Chemistry.
Chem 345. "Bomb Calorimetry." Bomb Calorimetry. Hope University, n.d. Web. 09 Dec. 2013.
EXPERIMENTAL
Calorimeter
Motor For Stirrer
Bomb
Ignition Box
EXPERIMENTAL
Specifications:
•5 Diesel Samples
•5 Biodiesel Samples
•10 cm of Wire
•30 atm Oxygen
•2 L Water Bath
Bomb: Samples Placed In Here
Milosavljevic, Bratoljub H. Lab Packet for CHEM 457 Experimental Physical Chemistry.
Results
Trial Parameters
Trial parameters- Day 1
Benzoic Acid
Biodiesel 1
Diesel 1
Biodiesel 2
Diesel 2
Biodiesel 3
Δ Wire Mass (±0.0008 g)
Sample Mass (±0.0004 g)
0.0102
0.0084
0.0049
0.0061
0.0104
0.0092
1.0044
0.5877
0.5768
0.6039
0.5467
0.5741
Δ T (oC)
2.577 ± 0.007
2.39 ± 0.01
1.981 ± 0.002
2.497 ± 0.004
2.5947±0.0009
2.389 ± 0.005
Trial parameters- Day 2
Benzoic Acid
Diesel 3
Biodiesel 4
Diesel 4
Biodiesel 5
Diesel 5
Δ Wire Mass ( ± 0.0008 g)
Sample Mass ( ± 0.0004 g)
0.1457
0.0079
0.0053
0.0102
0.0045
0.008
0.9701
0.5259
0.5126
0.5625
0.5379
0.5728
Δ T (oC)
2.470
2.156
2.395
2.579
2.397
2.492
±
±
±
±
±
±
0.020
0.002
0.008
0.001
0.001
0.001
Results
Bomb Calorimetry DataAverage Temperature Profiles
T60%=24.33 °C
t60%=6.62 min.
Data Analysis

Instantaneous Tf and Ti determined
from T60% and t60%

Regression slopes of pre-/postignition lines due to stirrer work and
heat transfer to surroundings

Calorimeter heat capacity determined
from benzoic acid combustion

First diesel run excluded as per Qtest
Milosavljevic, Bratoljub H. Lab Packet for CHEM 457 Experimental Physical Chemistry.
T60%=23.23 °C
t60%=6.89 min.
T60%=24.56 °C
t60%=6.81 min.
Results
Bomb Calorimetry DataΔHcomb
Final Results
Δn
(mol)
(kJ/mol)
Biodiesel
-15
-11,700 ± 60
Experimental
ΔHcomb
(kJ/g)
-43.3 ± 0.2
-47.9 ± 0.4
(kJ/L)
-36,600 ± 200
-39,900 ± 300
-10963
-7202
7%
12%
-11616
-7538
0.72%
11.51%
Literature
ΔHcomb
(kJ/mol)
Deviation between Exp. and Lit.
Values
Theoretical
(kJ/mol)
ΔHcomb
Deviation between Exp. and
Theo. Values
Diesel
-6
-8,070 ± 60
Krol, Walter J. "Comparative Fuel Characteristics." Biodiesel Fuel. The Connecticut Agricultural Experiment Station, n.d. Web. 4 Dec. 2013.
<http://www.ct.gov/caes/lib/caes/documents/>.
Graboski, Michael S., and Robert L. McCormick. "Combustion of Fat and Vegetable Oil Derived Fuels in Diesel Engines." Progress in Energy and Combustion Science 24.2 (1998):
125-64. ScienceDirect. Web. 30 Nov. 2013. <http://www.sciencedirect.com/science/article/pii/S0360128597000348>.
Discussion
Controlling for accurate data

Measured temperature difference
largest source
◦ Same calorimeter used each day
◦ Same volume of water used in each trial
◦ Increasing by 0.01 K -> 4% change in ΔHcomb

Purged bomb with 30 atm O2 to prevent
NOx formation
Milosavljevic, Bratoljub H. Lab Packet for CHEM 457 Experimental Physical Chemistry.
Why is biodiesel’s value higher?
◦
Biodiesel structure has more C-C bonds
(C17)
◦
Diesel structure has no ester group
(C12)

Biodiesel Labs. "Combustion of a Renewable and Fossil Fuel: Teacher Manual." Loyola University of Chicago, n.d. Web. 7 Dec. 2013.
Sources of error

Ideal gas behavior assumed
◦ Assumption holds best at 1 atm
◦ SRK or PR EOS better choice to model
thermodynamics

Puncturing capsule with fuse wire
◦ Contained liquid sample beforehand
◦ Might be mitigated with larger capsules

Uncertainty change in temperature
Conclusion
Experimental objective achieved

Liquid biodiesel
◦ ΔHcomb=- 11700 ± 60 kJ/mol
 7% difference from lit. value
◦ ΔHcomb=-36,600±200 kJ/L
◦ ΔHcomb=-43.3±0.2 kJ/g

Liquid diesel
◦ Δhcomb=- 8070 ± 60 kJ/mol
 12% difference from lit. value
◦ ΔHcomb=-39,900 ± 300 kJ/L
◦ ΔHcomb=-47.9 ± 0.4 kJ/g
Questions?