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Improvement of Octane Number of Naphtha Cut of Taq-Taq Crude Oil and Khormala Crude Oil Wells by Using Additives.

Abdulsalam R. Karim1

Abstract— Gas condensate from khor-Mhor field and Naphtha cuts from Taq-Taq crude oil and Khormala crude oil have been fully analyzed and evaluated using ASTM standard test methods.

Two Types of additives and pyrolysis gasoline have been blended with naphtha samples in different volumetric ratios. Octane number of each blend has been measured using three different octane analyzers.

Index Terms—Additive , ASTM , Gasoline , Gas condensate , Naphtha, Octane analyzer , Octane number .

——————————  ——————————

1 INTRODUCTION

Gasoline is a complex mixture of hundreds of volatile and combustible compounds derived from petroleum, with 5-12 carbon atoms and boiling points in the range of 30-220 °C[1] . The properties of commercial gasoline are influenced by the origin of the crude oil, the refinery processes and the presence
of additives, which are added with the purpose of improving the
environmental performance , fast , easy and accurate determination of octane numbers is important for refiners and quality inspectors as optimization of refining process and quality control at a reasonable cost is ever – increasing requirement , very soon scientists began to look for a correlation between the tendency of hydrocarbon – based fuels to knock and the composition of these fuels to calculate the octane numbers indirectly and rapidly , such as using gas

[13]

performance and reducing the emissions of automotive vehicles

[2],[3],[4],[5]. The addition of oxygenates to gasoline became

chromatography and FTIR spectroscopy
curves and partial least squares regression

[15]

, by distillation

[14], and methods

widespread after the elimination of the tetra ethyl lead compounds [6].
Specifications for gasoline properties were re – evaluated when a major change accured in the oil – automobile industry system. For example , the "oil crisis " in the 1970 s and the planned phase – out of tetra ethyl lead prompted studies of the optimum octane rating new unleaded - gasoline in the united states and Europe [7],[8],[9],[10] .
Octane number is one of the main parameters used in quality control of gasoline and provides information about the resistance to auto – ignition - this phenomenon occurs when the temperature of the fuel – air mixture under the effect of compression , leading to sufficiently increased self – detonation of the mixture without the help of a spark [11] .
Octane rating is measured at two different operational conditions, the rating measured at the more severe operating conditions (inlet temp. and RPM) is called Motor octane number (MON) and the rating measured at the mild conditions is called the research octane number, (RON), the spread between the two numbers (MON & RON) is known as the fuel sensitivity and pump octane number (PON) or Anti Nock index
(AKI) is the arithmetic average of RON and MON [12].
Currently both RON and MON are still measured in a standardized single cylinder, internal combustion engine (cooperation research fuel – CFR engine), following the standard methods ASTM D2699 (RON) and ASTM D2700 (MON), respectively. As all the standard methods are time
consuming , complicated , relatively expensive and of poor
depend on dielectric spectroscopy .
This work describes the use of automatic analyzer based on mid
– infrared spectroscopy ( zeltex 101C), and (shatox SX –
100M) which operates by measuring. The sample's dielectric properties, as well as the Ukrainian device called octane meter OKM - 2.

2 Experimental:

2.1 Materials used:

(i) Gas condensate from khor – mhor field, near Kirkuk with properties and specifications shown in table (1)
(ii) Naphtha produced from taq – taq crude and khormalla crude oil with specifications and properties shown in table (2) (iii) Additive (A): EPT octane Enhancer from: Enviro petro technologies pty LTD, Sydney, NSW, Australia.
Composition: Xylene, toluene, vegetable oil fatty acid, Diethyl malonate, trimethyl benzene, N- Methyl aniline, and Dimethyl carbonate.
(iv) Additive (B): octane Enhancer from: UKRZEMRESOURCE, Kyiv, Ukraine.
Composition: N – methyl aniline, MTBE, Toluene and unknown composition component.
2.2 Motor and research octane numbers of prepared samples
were measured by the following devices:-
(i) octane Meter type OKM – 2 : equivalent to motor ( EN ISO
5163 : 2005 ) and research ( EN ISO 5164 : 2005 ) methods :
from Ukraine ,
(ii) octane meter – type Zeltex 101 C : portable , battery

1 Chemistry Dept., School of Science, University of Sulaimani. E-mail: abdulsalam_doctor@hotmail.com

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powered octane analyzer for gasoline from : (Zeltex , Inc , Hagerstown , MD .USA ) provides accuracy and repeatability equivalent to ASTM – approved CFR engines .
(iii) Octane meter type shatox Sx – 100 M: portable octane / cetane Analyzer for gasoline, diesel fuel and other petroleum products; from: SHATOX research organization for developing and manufacting of instrument in cooperation with the Petroleum chemisorptions institute of Siberian Branch of Russian Academy of science. Equivalent to ASTM D 2699 –
86, ASTM D 2700 – 86 Methods.

2.3 procedures and Methods:

The physical and chemical properties of gas condensate, and both Naphtha sample have been determined according to specific ASTM and IP standard methods. Specific gravity and API gravity by hydrometer methods (ASTM D 1298) , sulfur- total ( ASTM D 4294 ) , sulfur mercaptan (ASTM D 3227 ) ,
Reid vapor pressure (ASTM D 323 ) , salt content (ASTM D
3230) , Kinematic viscosity (ASTM D 445) , wax content (
UOP 46) , pour point (ASTM D 97) , Ash content (ASTM D
482) , Total acid number (ASTM D 664) , Water content (
ASTM D 4928) , Total nitrogen (ASTM D 3228) , metals ( IP
470) .
PIONA (ASTM D 6293), Distillation (ASTM D 86), asphaltenes (IP 143).

3 Results and Discussion:

Some of physical and chemical properties of both Naphtha samples and gas condensate measured according to specific ASTM methods are illustrated in Table (1) (naphtha from khormala), table (2) (naphtha from taq – taq), and table (3) (gas condensate from khor – mhor)
Table (1) some physical and chemical properties of naphtha produced from khormala crude.

(*) with compliments of NRG – GLOBAL LLC.
Table (2) some physical and chemical properties of naphtha produced from Taq – Taq crude.

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(**) with compliments of intertek, Fujairah.
Table (3) some physical and chemical properties of gas condensate produced in khor – mhor field.

As it is very clear from the tables above , naphtha produced from Taq-Taq crude oil is more paraffinic and lighter than naphtha produced from khormala crude oil , also its sulfur content is much less while nitrogen content of both naphtha samples are identical . The sulfur content of gas condensate is also low (0.06%) and it is very light (API = 68.6), and highly

paraffinic (KRwR = 12.2). Table (4) lists the general properties of

full range naphtha samples and gas condensate, octane numbers (clear) are low and close to each other , RON of the two naphtha samples are little bit higher than RON of gas condensate sample, (77.5 for khormala, 74.5 for Taq-Taq , and
65.6 for gas condensate). Fractionation of gas condensate
shows that it contains some kerosene and gas oil fractions, these amounts differ depending on the boiling range of the

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chosen condensate fraction, for example if these two different break downs were chosen ; [16],[17] then different amounts of
kerosene & gas oil will be obtained as shown below :-

Table (4) general properties of full range naphthas and gas condensate samples.

Enhancements of octane number:

The RON , MON, and AKI (𝑅+𝑀 ) Values for both naphtha's

2

and gas condensate measured by zeltex 101C , shatox , and
OKM -2 instruments without additives are shown in table (5).
Table (5) octane number of naphtha's and gas condensate by zeltex 101C, shatox, and OKM – 2 instruments.

Addition of additive (A): EPT octane Enhancer:

According to data shown in table (6) and fig (1) the addition of additive (A) (EPT octane Enhancer) is not suitable for naphtha
by measuring octane number with zeltex 101C, but by
measuring shatox, the ONS increased suitably for naphtha samples.

Table (6) EPT octane Enhance effect on the ONS value of naphtha sample from Taq-Taq crude oil by using zeltex 101C and shatox instruments.
Additive %V Measuring by zeltex Measuring by shatox

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According
Enhance
pyrolysis gasoline to meet national fuel determination therefore we blended our naphtha with pyrolysis gasoline of (RON = 98)
and general properties shown in table (7), in deferent ratios,
erent volume ratios and two instruments zeltex
101C, and shatox. These results are shown in tables (8 – 14)
and figs. (2 - 9).
Table (7) general properties of pyrolysis gasoline

Table (8) octane number of blended naphtha and pyrolysis gasoline (P.G) using zeltex 101C instrument.

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Table (9) octane number of blended naphtha and pyrolysis gasoline (P.G) using shatox instrument.

Table (10) ONS of blended naphtha (80%) and P.G 20% with different doses of EPT octane Enhancer by zeltex 101C , and shatox
instrument.

Table (11) ONS of bended naphtha 78% and P.G 22% with different doses of EPT octane Enhancer by zeltex 101C and shatox instruments.

Table (12) ONS of bended naphtha 75% and P.G 25% with different doses of EPT octane Enhancer by zeltex 101C and shatox
instruments.

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Table (13) ONS of bended naphtha 70% and P.G 30% with different doses of EPT octane Enhancer by zeltex 101C and shatox instruments.

Table (14) ONS of bended naphtha 60% and P.G 40% with different doses of EPT octane Enhancer by zeltex 101C and shatox instruments.

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320

100

80

-

"' "'

94

_.,

-

60 ...

z

88 - -

0 so

a::

20

10

0

a::

. RON by shatox 84

82

80

78

...............

-- .......

RON by zeltex

. RON by shatox

0 0.5 1 LS 2 2.5

additive%

0 0.5 LS

additive%

2 2.5

Fig. (4) Effect ofEPT Octane Enhancer on the RON s of the blend

(22%) P.G plus (78%) naphtha using Zeltex and shatox instruments.

94

92

90

Fig. (5) Effect of EPT Octane Enhancer on the RON s of the blend

(25%) P.G plus (75%) naphtha using Zeltex and shatox instruments.

96

94

92

z88

0

a: 86

84

82

RON by zeltex

_._RON by shatox

z90

0

a: 88

86

84

RON by zeltex

_._RON by shatox

80

0 0.5 1 1.5 2 2.5

additive%

Fig. (6) Effect of EPI Octane Enhancer on the RON s of the blend

(30%) P.G plus (70%) naphtha using Zeltex and shatox instruments.

82

0 0.5 1 1.5 2 2.5

additive%

Fig. (7) Effect of EPT Octane Enha ncer on the RON s of the blend

(40%) P.G plus (60%) naphtha using Zeltex a.nd shatox instrument.

98

97.5

97

96.5

96

z

Naphtha from

85

84

83

82

81

z 80

Naphtha from

a0:: 95.5

95

94.5

94

93.5

93

0

2 4 6 additive% (B)

Khormala

-+-Naphtha from TaqT·aq

8

79

78

77

76

75

74

0 2 4 6

additive% (BI

khormala

-+-Naphtha from Taq-Taq

8

Fig. (8) Effect of additove (B) on the RON s of both naphtha samples using OKM:- 2 instruments.

Fig. (9) Effect of additive (B) on the RON s of both naphtha samples using Zeltex 101 C instruments.

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Addition of additive (B):

Six blends from additive (B) components prepared with
different motor octane number as shown below:

Then these blends added to both naphtha samples with the
using OKM – 2 instruments. The results are show in table (15).
specified percentages, and octane number measured for all
using OKM – 2 instruments. The results are show in table (15).
Table (15) effect of additive (B) on ONS of both naphtha samples using 0 KM – 2 instruments.

While addition of additive (B) and measuring ONS using zeltex are shown in table (16).
Table (16) effect of additive (B) on ONS of naphtha samples using zeltex instrument.

Zeltex 101C instrument measures octane number via near –
infrared (NIR) transmission spectroscopy , the instrument contains a patented sold – state optical system comprising 14 near – infrared emitting diodes with narrow band pass filters, a silicon detector system, and fully integrated micro processor , this instrument operates in the short NIR, from 800 to 1100 nm wave , the instrument is factory calibrated to predict octane number from the absorption spectra of the fuels being tested , this prediction is accomplished through the use of a
multivariate regression of the form : [18],[19]
Octane number = K° + K1 ( OD1) + K2 (OD2) ……..…. + K14 (OD14) + K15 (Ta ) where K° is a bias term, K1 through K15 are slope coefficients, OD1 through OD14 are the absorbencies measured at each of the 14 wave length , and Ta is the ambient temperature .
The instrument can store up to 10 calibration equations and is factory calibrated for RON, MON, and AKI of blended gasoline. The results obtained by zeltex 101C measurements in this research have no significant differences between
measurements before and after additive addition this means that
the existing calibration mode of the instrument is not suitable
for these additives (A) and (B) and it needs factory calibration to predict octane numbers from the absorption spectra of the fuels being tested, because the empirical rules of octane number dependence on the structure of alkenes are amended [20]. ON decreases with the number of CH2 groups and increases with the number of CH3 groups, the number of adjacent CH2 groups has the highest influence; ON decreases with the separation between branches; it increases with the more central position of branches and with their bulkiness, Ethyl group causes apparently contradictory effects: if it increases the number of CH2 groups, ON decreases; if not, ON increases.
The use of structured features of alkanes i.e. the size of the
molecule, the number of branches , the position of branches , the separation between them, the type of branches , and the type of the branched structure enables a more thorough understanding of the relation between the structure of alkane and their physicochemical properties (20).
The composition of each additive package used in this research
is different from the other, so it is necessary to factory

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calibration of this zeltex 101C instrument to be suitable to predict octane number from the absorption spectra of the blends being tested.
While the principle of the operation of OMK – 2 instruments is based on the test of hydrocarbon fuel under high temperature, which causes the oxidation reaction (combustion), followed by
the release of heat. As a result of the measurement of the
temperature characteristic of the oxidation reaction we establish an unambiguous relationship with the parameters of the oxidation reaction with knock resistance of the tested gasoline. The low octane number is indicated also by higher reaction temperature and lower time of reaction period as show in the figures below.

Shatox instrument operates by measuring the sample's dielectric properties and comparing the results to stored parameters in its internal program of typical known chemical compounds widely used in fuel production Extremely sensitive to changes in these dielectric properties , the octane meter is able to detect subtle differences in the chemical makeup of the fuel sample and therefore become valuable tool for determining the octane , cetane as well as many other parameters for typical gasoline , diesel fuel and other petroleum products.
Since different fuel blends react differently, all shatox octane meters employ additional modes providing the ability to make corrections quickly and easily.
The disadvantage is that the octane meter is not compatible with Bio – fuels and ethanol fuel blends.

4 Conclusions: From the results of this work it has been concluded that:

1- Fractionation of gas condensate showed that it contains some kerosene and gas oil fractions, which must be removed prior to blend with additives.
2- The instruments must be factory calibrated for RON, MON, and AKI of blended gasoline samples with additives.

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3- The instrument OMK - 2 is based on the oxidation reactions following by the release of heat, so it gives better results.
4- The additive EPT alone can raise RON only 3-4 numbers up to 2.5% dosage and it is better to use it with higher octane number gasoline to reach the premium grade gasoline.
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