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البحـث الأول
مجلة النفط والتعاون العربي
161
العدد
- 2017
أربعون
المجلد الثالث و ال
2016
أوابك العلمية لعام
�
ص لبحوث العلمية الفائزة بجائزة
�
عدد خا
41
31
than Group I. They cost reasonably more but are increasingly demanded over
Group I.
Group-III: base stocks contain greater than or equal to 90% saturates and less than
or equal to 0.03% sulpher and have a viscosity index greater than or equal to 120.
They are more refined than Group II by more sever hydro-treating to yield purer
base oils. Some Group III manufacturers were able to produce base stocks
equivalent in performance to Group IV below. The recent availability of gas-to-
liquids (GTL)
28
base stocks have emerged as viable alternatives for the
conventional Group III and Group IV lubricants
28
.
Group IV: Base stocks composed of polyalfa-olefins (PAO). These are synthetic
base oils which are suitable for more sever temperature applications and extreme
cold conditions. Synthetic oils here are hydrocarbons molecules reengineered by
certain processes and they do not contain contaminants such as sulpher and wax,
which enables them to flow better at cold temperature
82
. PAO is mostly
synthesised from the products of naphtha or condensate steam cracking in
petrochemical plants
104
.
Group-V: Base stocks excluding all components from the above groups but
include base oils produced from silicone polymers, phosphate ester, poly alkylene
glycol, polyol-ester, and oils made from biomass sources. They may be blended
with other base stocks to enhance the properties of the base oil. They are more
applicable to higher temperatures and will provide superior detergency compared
with PAO synthetic base oil.
Table (5) summarizes the above groups.
Table (5)
Summary of API Lubricating Oil Groups
Group
Process
Saturates
%
Aromatics
%
Sulpher
%
Viscosity
Index
I
Solvent Extraction
>
90
01<
1010 <
80 -
>
120
II
Hydro-processed
<
90
01>
>
0.03 80 -
>
120
III
Hydrocracked
<
90
01>
>
0.03
120+
IV
PAO
100
0
0
V
Other synthetics
Source: 1 based on API 1509 - 2012