pona calculation and octane rating experiment … · pona calculation and octane rating experiment...

© March 2017 | IJIRT | Volume 3 Issue 10 | ISSN: 2349-6002

IJIRT 144266 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY 9

PONA CALCULATION AND OCTANE RATING

EXPERIMENT FOR MOTOR GASOLINE

Nadia Mahjabin1, Partha Das Chowdhury2 and Zayed bin Sultan3

1,2,3Department of Petroleum and Mining Engineering, Chittagong University of Engineering &

Technology,Super Refinery (Pvt.) Limited

Abstract—This paper has discussed the PONA analysis

and octane rating procedure for motor gasoline (MS).

PONA analysis is an indication of the paraffin, olefin,

napthenes and aromatic percentage in a petroleum

sample. And octane rating operation indicates the

research octane number (RON), motor octane number

(MON) for a fuel sample. Here both experiments are

performed for MS (regular). The sample was collected

from the condensate fractionation plant of Super

Refinery (Pvt.) Limited. For PONA calculation FIA

method was employed and for octane rating a octane

analyzer meter ( Zx 101C) was used.

Index Terms—FIA method, MS, MON, Napthenes,

octane rating, petroleum, PONA, RON.

I. INTRODUCTION

A petroleum stream is generally a complex mixture of

different hydrocarbon components. The mixture is

well defined when the composition and structure of all

componentss present in the mixture are known. The

various components present in the mixture are

generally identified by their carbon number or

molecular type [1]. The distillation of a petroleum

stream yields product like gasoline, diesel, liquefied

petroleum gas (LPG), residue etc. It is important to

have knowledge over molecular type composition of a

petroleum product is the most important

characteristics [1].

Gasoline is e refined petroleum product that is mainly

used as fuel in internal combustion engine. It is also

called by petrol that is it’s brand/market name. It

consists carbon from C5 to C10 [2]. High aromatic

percentage present in gasoline is an indicator of high

octane rating. The performance of gasoline is mainly

depended on it’s octane number since good octane

number means low knocking tendency.

There are several ways to express the composition of

a petroleum mixture among which the most important

types of composition are [1]:

PONA (paraffins, olefins, naphthenes, and

aromatics)

PNA (paraffins, naphthenes, and aromatics)

PIONA (paraffins, isoparaffins, olefins,

naphthenes, and aromatics)

SARA (saturates, aromatics, resins, and

asphalthenes)

Elemental analysis (Carbon, Hydrogen, Sulfer,

Nitrogen, Oxygen)

Normally most petroleum product contains a little

percentage of olefin. So a PNA analysis can be helpful.

But to have a better knowledge of the product type in

this paper the PONA analysis has been considered.

This type of analysis is normally useful for light and

narrow boiling range petroleum products (1).

II. PONA ANALYSIS (FIA METHOD)

The FIA method or ASTM D 1319 method,

determines saturates that is paraffin’s plus naphthenes,

non-aromatics, olefins, and aromatics up to 315°C in a

petroleum stream. But this method has shortcoming

because it does not provide information on naphthenes

content, carbon number distribution, or individual

component identification. The calculation of

naphthenes content in saturates requires few several

calculation [3].

A. Procedure:

A liquid petroleum sample, approximately 7.5 mL is

introduced into a special glass column. The column

has been packed with activated silica gel and a small

layer of fluorescent dyed gel [4]. After the sample has

been adsorbed on the gel, alcohol is added. Alcohol

acts to desorb the sample down the column to separate

the hydrocarbons. The fluorescent dyes are selectively



separated into aromatic, olefin, and saturate zones.

The separations are only visible under ultraviolet light.

Each boundary in the column is calculated by volume

percentage from the length of each zone in the column.

The upper limit of a portion is subtracted from it’s

lower limit and gives the percentage of a portion. This

procedure doesn’t give the actual percentage of

napthenes present rather presents the total percentage

of alkane and napthenes. Hence it is necessary to

perform several steps to get the actual percentage of

alkane and napthenes.

B. Steps for Napthenes Calculation:

7 steps for napthenes calculation are mentioned here.

1. 𝑉𝐴𝐵𝑃 = 10%+30%+50%+70%+90%

5 (1)

2. 𝑆𝑙𝑜𝑝𝑒(∆𝑇) =𝑇 @ 90 % 𝑉𝑜𝑙𝑢𝑚𝑒−𝑇 @ 10 % 𝑉𝑜𝑙𝑢𝑚𝑒

90%−10% (2)

Here T stands for Temperature.

3. Corrected ∆T from Fig.I.(Appendix) (3)

4. 𝐶𝐴𝐵𝑃 = 𝑉𝐴𝐵𝑃 − ∆𝑇 (4)

5. Cyclization Index (CI) from CABP

& Density curve (Fig.II).

(Appendix) (5)

6. ∆N calculation from Aromatics,% volume

& Density (Fig.II).

(Appendix) (6)

Napthenes,𝑊𝑇% = 𝐶𝐼 − ∆𝑁 (7)

III. OCTANE RATING

Octane number is an important characteristic of spark

engine fuels. The spark engine fuel may be mentioned

as gasoline, jet fuel or fractions that are used to

produce these fuels (i.e. naphthas). The octane number

of a fuel mainly represents the antiknock characteristic

of that fuel. Iso-octane (2,2,4- trimethylpentane) has

octane number of 100 and n-heptane has octane

number of 0. And these are same on both scales of

RON and MON [1].

Octane number of a mixture is determined by the

volume% of isooctane used. Iso-paraffins and

aromatics have high octane numbers while n-paraffins

and olefins have low octane numbers. That is presence

of high aromatic percentage can be taken as an

indication of high octane number. Therefore, octane

number of a fuel mainly depends on its molecular type

composition [1].

There are two types of octane number: research octane

number (RON) is measured under city conditions

while motor octane number (MON) is measured under

road conditions. The arithmetic average value of RON

and MON is known as posted octane number (PON)

[1].RON is generally greater than MON by 6-12

points,. But it is not always true. At low octane

numbers MON might be greater than RON by a few

points. The difference between RON and MON is

known as sensitivity of fuel that means it indicates the

sensitiveness of a fuel [1].

To calculate octane number in this paper an octane

meter is used. It is a Zx 101C brand octane meter. Here

the sample is placed in the meter and the values are

displayed on a paper coming out of the meter [5].

IV. DATA COLLECTION & CALCULATION

For performing the calculation at first some data are

needed to be collected. It includes the distillation

temperature of the sample at specified percentage.

Then this data are used to calculate the napthene

percentage.

To have the distillation temperature ASTM D86

method is employed. A distillation apparatus is used.

The distillation temperature at 10%, 30%, 50%, 70%

and 90% are collected,

Table I: ASTM D86 data for MS

Volume % Temperature

˚C

Temperature

˚F

10 72 161.6

30 88 190.4

50 100 212

70 112 233.6

90 136 276.8

The distillation temperatures are then used to calculate

napthene percentage from equations mentioned

earlier. At first the volume average boiling point

(VABP) is calculated. Then the slope is calculated

from equation (2). The correction factor is taken from

Fig.I. The cubic average boiling point (CABP) is

calculated next. Cyclization index is taken from Fig.II.

∆N is also taken from Fig.B. Finally napthenes wt%

is calculated from equation (7).



Table II: Napthenes Calculation

VABP 214.88

Slope 1.44

Correction Factor (Fig.I) 3.56

CABP ˚F 211.32

CABP ˚C 100 (rounding)

CI (Fig.II ) 69

∆ N 48

Wt % 21

V. RESULT AND DISCUSSION

The volume% of the hydrocarbon types present in the

sample involves two stapes. In the first step the upper

and lower limit values as visible from ultra-violated

light ate taken. In the second step the values are

subtracted to have the range of a particular

hydrocarbon type.

PONA calculation by weight%

a. Aromatics = 99-84.7 = 14.3

b. Olefin = 84.7-84 = 0.7

c. Alkane = 84-27 = 57

d. Total Weight % = (14.3+0.7+57) = 72

Conversion from Weight% to Volume%

a. Aromatics = 14.3

72× 100% = 19.86 %

b. Olefin = 0.7

72× 100% = 0.97 %

c. Alkene = 57

72× 100% = 79.17 %

The results obtained are tabulated below. It has shown

a higher percentage for saturates that is 57%. So it can

be assumed that the sample may have a lower octane

number.

Table III: PONA Result by Weight %

PONA

Observation for

Composition

Readin

g from

scale

Weigh

t %

Volum

e %

Aromatic 99-84.7 14.3 19.86

Olefin 84.7-84 0.7 0.97

Alkane ( Paraffin +

Napthene)

84-27 57 79.17

Alkan

e

Napthen

e

21 29.17

Paraffin 36 50

Finally the octane rating operation is performed for the

MS sample. The results are given in Table 4.

Table IV: Octane Rating for MS

Method Octane

Analyzer test

Comment

RON 78.8

Too low MON 72

(R+M)/2=PON 75.4

As expected from the PONA analysis, the sample has

a low RON value. Normally a good quality gasoline is

expected to have a RON of nearly 95. But this sample

has yielded a result that is too far from the standard

one. MON value is also low. One cannot expect to use

this fuel for running an engine without further

operations to improve the octane rating.

VI. CONCLUSION

To have knowledge over a particular petroleum type

the compositional analysis is very important. It may

be good one if the chromatographic analysis or the

PIANO analysis can be performed because these tests

yield the actual compositional type of a sample. But

this was not possible in this paper. Although the

results generated indicates a good approximation

with the calculated one. To have a good octane rating

the paraffinic portion is needed to be degrades. This

can be done by adding booster or by performing some

additional operation.

APEENDIX

Fig.I: CABP from VABP and distillation

(Engler) slope [6]



Fig.II: Napthenes calculation graph (source SRL)

ACKNOWLEDGEMENT

The authors are grateful to pay deep gratitude to the

almighty. The authors express special thanks to the

teachers of Petroleum and Mining Engineering

Department of Chittagong University of Engineering

& Technology and the officials of Super Refinery

(Pvt.) Limited for helping to complete the job in time.

REFERENCES

[1] Riazi, M. R., -Characterization and Properties

of Petroleum Fractions, 1st ed.. Philadelphia,

PA : ASTM, 2005. pp.131-135.

[2] Badrul Imam,-Energy Resources Of

Bangladesh 2nd ed., 2013, pp. 170.

[3] Nejat Kosal, Abdullatif Bhairi and Mohammed

Ashraf Ali,- Determination of hydrocarbon

types in naphthas, gasolines and kerosenes: a

review and comparative study of different

analytical procedures.‖ Vol.69, Dhahran

31261,Saudi Arabia:Butterworth-Heinemann

Ltd., 1990.

[4] Fluorescent Indicator Adsorption Analysis of

Petroleum Fuels Method, 2565 Plymouth Road,

Ann Arbor, MI 48105 : United States

Environmental Protection Agency, 2002.

[5] ZX-101C Portable Octane Analyzer, User's

Manual Version 6.0, Hagerstown, Maryland:

ZELTEX, INC., 2007, pp.7.

[6] Calculation of UOP Characterization Factor

and Estimation of Molecular Weight of

Petroleum Oils, West Conshohocken, PA

19428-2959,USA. : Honywell Company,1986.

pona calculation and octane rating experiment … · pona calculation and octane rating experiment...

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