الفهرس 
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Abstract
Summary
In the internal combustion engines, lubricating oils suffer from auto-oxidation as a result of contact at elevated temperatures with air rate for long periods and metals that used in the manufacture of the engine such as iron, copper, aluminum, etc. these metals act as catalysts for the oxidation process resulting in the formation of oxygenated oil soluble and insoluble products which exert an adverse effect on the performance of the lube oils.
In our work, Hydro finished base stock oil (HBS) sample was obtained from Petroleum refinery (Elameria Company) on laboratory scale and subjected to our study. The physico-chemical properties of the base stock were carried out according to ASTM and/or IP standard test methods; these include density, viscosity, pour point, total acid number, flash point, water content and wax content. The oxidation test methods were carried according to the standard test method ASTM D- 943. The procedure was carried out at fixed temperature and at oxidation periods of 24, 48, 72 and 96 hours.
We aim to prepare three series of some heterocyclic compounds (Ia-c, IIa-c and IIIa-c), derived from 2-mercaptobenzothiazole (I), 2-mercaptobenzimidazole (II) and 2-mercapto-benzoxazole (III) respectively, and study their effect on the oxidation stability of the lubricating base stock. The selected heterocyclic compounds were added to the base stock with different concentrations, (200, 400, 500 and 1000ppm) We also study the relation between these concentrations of the prepared heterocyclic compounds to the base oil and their efficiency toward the base oil stability. The oxidation stability of all oxidized samples has been monitored, via the change in total acid number, viscosity, infrared spectroscopy.
The results obtainen in our work, indicate the following:
• The prepared compounds proved to be successful in controlling the oxidation stability of the base stock. The oxidation inhibition efficiency of these compounds depends on their structures.
• We noticed, in case of compounds (I) ,(II)and (III) the most effective compound is (II). In a contrary, compounds, Ib, Ic and IIIc are good inhibitors. In case of compounds (IIa-c) the orderof increasing oxidation stability is shown as follows, IIa > IIb >IIc.
• The data reveals that the most effective concentration in case of compounds (Ia-c) is 400 ppm and for (IIa-c) is 500ppm whereas for (IIIa-c) is 500 ppm and for IIIc the most effective one is 1000ppm.
• The results show that, by using the quantum chemical calculations (Ab initio {HF/3-21G} and the semiemperical gas phase AM1{Austin model 1}), the compounds with low energy gap (E) have good inhibition efficiencies which are in good agreement with the practical results.
Summary
In the internal combustion engines, lubricating oils suffer from auto-oxidation as a result of contact at elevated temperatures with air rate for long periods and metals that used in the manufacture of the engine such as iron, copper, aluminum, etc. these metals act as catalysts for the oxidation process resulting in the formation of oxygenated oil soluble and insoluble products which exert an adverse effect on the performance of the lube oils.
In our work, Hydro finished base stock oil (HBS) sample was obtained from Petroleum refinery (Elameria Company) on laboratory scale and subjected to our study. The physico-chemical properties of the base stock were carried out according to ASTM and/or IP standard test methods; these include density, viscosity, pour point, total acid number, flash point, water content and wax content. The oxidation test methods were carried according to the standard test method ASTM D- 943. The procedure was carried out at fixed temperature and at oxidation periods of 24, 48, 72 and 96 hours.
We aim to prepare three series of some heterocyclic compounds (Ia-c, IIa-c and IIIa-c), derived from 2-mercaptobenzothiazole (I), 2-mercaptobenzimidazole (II) and 2-mercapto-benzoxazole (III) respectively, and study their effect on the oxidation stability of the lubricating base stock. The selected heterocyclic compounds were added to the base stock with different concentrations, (200, 400, 500 and 1000ppm) We also study the relation between these concentrations of the prepared heterocyclic compounds to the base oil and their efficiency toward the base oil stability. The oxidation stability of all oxidized samples has been monitored, via the change in total acid number, viscosity, infrared spectroscopy.
The results obtainen in our work, indicate the following:
• The prepared compounds proved to be successful in controlling the oxidation stability of the base stock. The oxidation inhibition efficiency of these compounds depends on their structures.
• We noticed, in case of compounds (I) ,(II)and (III) the most effective compound is (II). In a contrary, compounds, Ib, Ic and IIIc are good inhibitors. In case of compounds (IIa-c) the orderof increasing oxidation stability is shown as follows, IIa > IIb >IIc.
• The data reveals that the most effective concentration in case of compounds (Ia-c) is 400 ppm and for (IIa-c) is 500ppm whereas for (IIIa-c) is 500 ppm and for IIIc the most effective one is 1000ppm.
• The results show that, by using the quantum chemical calculations (Ab initio {HF/3-21G} and the semiemperical gas phase AM1{Austin model 1}), the compounds with low energy gap (E) have good inhibition efficiencies which are in good agreement with the practical results.