distillation of_crude_oil

1. PET 321E – Petroleum and Natural Gas Lab. 1 | 1 1
Distillation of Crude Oil
Distillation of Crude Oil
CRUDE OIL is a liquid mixture of organic compounds called hydrocarbon consisting of hydrogen and
carbon elements. Hydrocarbons differ depending upon their molecular structures. Hydrocarbons
exhibiting similar structural and physical properties can be classified into two different groups such as
aliphatics and aromatics. These two main groups are divided into subgroups such as alkanes,
cycloparaffins, heteroaromatics, etc.
Crude oils exhibit different physical properties due to having different hydrocarbon groups in different
proportions. Hydrocarbon gases and light oils are the mixtures of mainly normal paraffins. As the
specific gravity of oils increases, the proportions of other hydrocarbon groups (paraffinic isomers,
cycloparaffins [naphthenes (asphalt base)], aromatics, etc.) change in oil composition.
The complexity of the molecular structure of crude oils makes it hardly possible to separate crude oil
into its components by means of chemical analysis. Therefore, separation of crude oil by heating it in a
process called as distillation is a commonly used method. Since the crude oil is a mixture of lots of
different hydrocarbons having different boiling points, it is easy to separate and estimate the
hydrocarbon compounds in crude oil, based on the physical properties of oil compounds such as boiling
point, density, etc.
Distillation most refers to the process of vaporizing crude oil by heating in one vessel and then
condensing it in another vessel. Depending on the boiling temperatures and gravities of distilled
condensates, the composition and some physical properties of crude oil can be predicted.
NAPHTHA: is a colorless, volatile petroleum distillate which is usually an intermediate product
between gasoline and benzene.
ASPHALT: is a residue of crude oil distillation and that consists of heavy hydrocarbons having high
molecular weights.
PARAFFIN: is a residue of paraffin-based crude oil distillation and that consists of heavy hydrocarbons
having high molecular weights.
CHARACTERIZATION FACTOR, K: is a qualification number to determine the types of unknown
hydrocarbon components of crude oil based on distillation results. It is defined as a
function of boiling point and specific gravity as follows:
𝐾 =
𝑇𝑏
1/3
𝛾60/60℉
where;
𝑇𝑏 : average boiling temperature, °R (°F+460)
𝛾60/60℉ : specific gravity compared with water at 60°F

2. PET 321E – Petroleum and Natural Gas Lab. 2 | 1 1
Distillation of Crude Oil
APPARATUS used in the Experiment:
• Distillation flask
• Heater
• Thermometer
• Condenser
• Graduated cylinder
• Pycnometer
METHODS used for the Experiment:
Section A: Distillation of Crude Oil
1. Take a sample of crude oil that its properties are not known. Record the identity of this in the
raw data sheet.
2. Determine the specific gravity of sample by using pycnometer and record in the raw data sheet.
3. Pour 150 ml crude oil sample into the distillation flask and then place 10-12 ceramic boiling
chips.
4. Set up distillation apparatus and ensure that all the connections in Fig. 1, are tighten securely.
Especially, pay attention to the sealing of the snug-fitting cork which holds the thermometer.
Moreover, be sure that the bulb of the thermometer is aligned below the side arm of the
condenser.
5. Provide water input and output for the condenser.
6. Apply heat to the distillation flask. Heat the sample at the highest rate until the first drop of
distillate is obtained. When the first droplet is formed, record the observed temperature as the
first boiling point.
7. Then regulate the heating to collect 1-2 ml distillate per minute into the graduated cylinder.
8. Record the observed temperature after every collection of 1 ml of distillate.
9. When the distillate volume reaches 11 ml, replace the graduated cylinder with an empty one.
Record the temperature of each 11 ml distillate and determine the specific density of each of
them by using a pycnometer.

3. PET 321E – Petroleum and Natural Gas Lab. 3 | 1 1
Distillation of Crude Oil
10. Distill until 77 ml (7 graduated cylinder is filled) distillate is collected or temperature value
reaches to the end limit of the thermometer.
11. Turn off the heater and let the apparatus to cool down. After the distillation flask is cooled
(about 30 minutes later), measure the temperature and specific gravity of the residual
hydrocarbon in the distillation flask.
12. If any cracks in the distillation flask are observed, notify the situation to your lab coordinator.
13. Pour all the collected distillates and residue hydrocarbon into waste hydrocarbon container.
14. Clean and dry the distillation apparatus and all glassware before leaving the lab.
Figure 1: Distillation apparatus.
condenser
water inlet
water outlet
thermometer
distillation flask
graduated cylinder

4. PET 321E – Petroleum and Natural Gas Lab. 4 | 1 1
Distillation of Crude Oil
CALCULATIONS and RESULTS:
Section A: Generation of Boiling Point Curve
1. Plot the observed boiling point temperature of each distillate as a function of the percentage of
distillate volume (Fig. 2).
2. Percentage of distillate volume (%) can be calculated as follows:
𝑉% = 100 ×
𝑉𝑑𝑖𝑠𝑡𝑖𝑙𝑙𝑎𝑡𝑒
𝑉𝑖𝑛𝑖𝑡𝑖𝑎𝑙
where; 𝑉𝑑𝑖𝑠𝑡𝑖𝑙𝑙𝑎𝑡𝑒 represents the cumulative distillate volume, 𝑉𝑖𝑛𝑖𝑡𝑖𝑎𝑙 is the initial hydrocarbon volume
to be distillate (150 ml), and 𝑉% is the percentage of distillate volume.
3. An example of the graph of boiling point-temperature percentage of distillate volume is given in
Fig. 3.
Section B: Generation of API-SPECIFIC GRAVITY Curve
1. Plot the API gravity of each distillate volume as a function of the percentage of distillate volume as
described in Fig. 2. Consider API gravities corresponding to the half volume of each distillate
volume. For example; API gravity of the first distillate (1. graduated cylinder) corresponds to 6 ml
or 4% ([6/150)x100) of the total distillate volume. On the other hand, the API gravity of the second
distillate (2. graduated cylinder) will correspond to 17 ml or 11.3% ([(6+11)/150)x100) of the total
distillate volume.
Section C: Determination of the First Distillated Hydrocarbon Component
1. Based on the knowledge of the first boiling point temperature, determine the first
evaporated/condensed hydrocarbon component by selecting an appropriate one given in Table 1.
2. Related to this selection, determine the API gravity of the first distillate by using same table
(Table 1), and record this value to the API gravity plot obtained in Fig. 2.

5. PET 321E – Petroleum and Natural Gas Lab. 5 | 1 1
Distillation of Crude Oil
Section D: Characterization Factor, K
1. Calculate the characterization factor of each distillate volume by the equation. In calculations,
use the corresponding temperature of 50% of distillate volume as the average boiling point
temperature.
2. Calculate the characterization factor and molecular weight of each distillate volume by using Fig.
4.
3. Compare the characterization factors that calculated and determined graphically.
4. Estimate the average boiling point temperature of the distilled crude oil sample by using the
plot of boiling point temperature vs. percentage of distillate volume (Fig. 2).
5. Determine the characterization factor and molecular weight of the distilled crude oil sample by
using Fig. 4.
6. Determine the type of distilled crude oil by using the characterization factor in Fig. 5.
Table 1: Boiling temperatures and specific gravities of light hydrocarbons.
Hydrocarbon Boiling Temperature, F 𝛾60/60℉
n-Pentane 96.9 0.631
Toluene 110.8 0.866
n-Hexane 155.7 0.664
n-Heptane 209.1 0.688
Ethylene 154.6 0.993
Benzene 176.1 0.929

6. PET 321E – Petroleum and Natural Gas Lab. 6 | 1 1
Distillation of Crude Oil
Figure 2: Supplementary graphic sheet for the plot of boiling point curve.
BoilingPointTemperatureat760
mmHg,F
API60/60F
Percentage of Distillate Volume, %

7. PET 321E – Petroleum and Natural Gas Lab. 7 | 1 1
Distillation of Crude Oil
Figure 3: Boiling Point Curve as a function of the percentage of distillate volume.

8. PET 321E – Petroleum and Natural Gas Lab. 8 | 1 1
Distillation of Crude Oil
Figure 4: Relationship between boiling point temperature, characterization factor, and molecular
weight.
CHARACTERIZATIONFACTOR,K
BOILING POINT TEMPERATURE, °F

9. PET 321E – Petroleum and Natural Gas Lab. 9 | 1 1
Distillation of Crude Oil
Figure 5: Characterization of oils.
BoilingPointTemperatureat760
mmHg,F

10. PET 321E – Petroleum and Natural Gas Lab. 10 | 1 1
Distillation of Crude Oil
Name, Surname : .....................................................................
Faculty ID Number : .....................................................................
Group : .....................................................................
Date : .....................................................................
RAW DATA SHEET
Distillation of Crude Oil
Ambient Temperature, °C (°F) : --------------------- Ambient Pressure, mmHg : ----------------------
CRUDE OIL TEMPERATURE, C 𝜸 𝑻/𝟔𝟎℉ API@T API@60F
Original (Undistilled)
Residue/remaining part
in the distillation flask
FIRST BOILING POINT TEMPERATURE: ________C
Temperature,
C
Distilled
Volume, ml
Temperature,
C
Distilled
Volume, ml
Temperature,
C
Distilled
Volumes, ml

11. PET 321E – Petroleum and Natural Gas Lab. 11 | 1 1
Distillation of Crude Oil
Specific Gravity Measurement (Pycnometer Volume: _______ ml)
Sample
No
Distilled
Volume,%
Empty
Weight, g
Total
Weight, g
Sample
Weight, g
Temperature,
C
𝜸 𝑻/𝟔𝟎℉ API
Lab. Coordinator Name, Surname:
Date:
Signature: