The Role of Isopropyl Alcohol in the Properties of Sudanese Reformat Gasoline

Introduction

Additives and blending agents are added to the hydrocarbon mixture to improve the performance and stability of gasoline ^[1]. These compounds include anti-knock agents, anti-oxidants, metal deactivators, lead scavengers, anti-rust agents, anti-icing agents, upper-cylinder lubricants, detergents, and dyes ^[2].Gasoline anti – knock additives are compounds which, when added to a gasoline fuel for spark ignition engines, raise its antiknock quality, which is expressed by octane numbers. The classes of compounds from which antiknock additives are selected include  , Hydrocarbons of natural high octane number,  aromatic amines and organo metallic compounds^[3]. Other methods used to improve the quality of gasoline and increase its supply include polymerization, alkylation, isomerization, and reforming, using either heat or a catalyst to rearrange the molecular structure^[4][5]. Environmental Friendly additives such as diethylamine, di isopropyl ether, moringa oil, acetone and many others  are gasoline soluble chemicals that mixe with reformat gasoline to enhance octane number of gasoline, witch Ezeldin .etal,  found that the addition of  aniline  and  toluene improved the quality of Sudanese reformat gasoline through  increasing  its motor octane number (MON) (initially 88.5) to 93.8 and 95.5 in addition of aniline   (5 and 10% (v/v)) and to 91 and 94.2 in addition of toluene (5 and 10% (v/v))^[8]. Ezeldin .etal, also found that  whendimethylamine was added with different concentrations (5 and 10% (v/v)) to the Sudanese reformat  gasoline the (MON)  raised from 88.5 to 92.5and 94.9, respectively ^{[6][7][8] [9]}. Typically, they are derived from petroleum based raw materials and there. ON is a direct function of the molecular composition of the gasoline fuel, and any modeling effort should be explicitly acknowledge it^[6].

Materials and Methods

All chemicals used were of pure analytical reagent grade (AR). All solutions were prepared according to the usual analytical procedures.

Standard test Method for Distillation of Petroleum Products at Atmospheric Pressure

This test was carried out according to the method described by ASTM D86^[10] .Results are  shown in table (1).

Standard test Method for Determination of the Density of Petroleum Products

Density of marked reformate gasoline was characterized  according to the method described by ASTM D1293^[10]. Results are  shown in table (1).

Standard test Method for Vapor Pressure Determination of Petroleum Products

Vapour pressure test was carried out according to the method described by ASTM D323^[10]. Results are  shown in table (1).

Standard test Method for Determination of Gum Content in Fuels by Jet Evaporation

Gum existence  test was determined according to the method described by ASTM D381^[10]. Results are  shown in table (1).

Standard test Method for Copper Strip Corrosion

Copper strip corrosion test was carried out according to the method described by ASTM D93^[10]. Results are  shown in table (1).

Standard test Method for Determination of the Motor Octane Number (MON)

MON of used reformat gasoline was investigated according to the method described by ASTM D21900^[10]. Results are  shown in table (1).

Determination of Lead Concentration in Gasoline by Atomic Absorption Spectrophotometer Method

Preparation of Sample In a 100 mL volumetric flask 30 mL of methyl isoketone and 5 mL of a buffer solution were taken  ,then  0.1g of iodine and 5 mL of gasoline were transferred to the solution , finely the solution was  completed  to the mark with iso butyl ketone^[11]. Preparation of the standard lead (II) solution 0.5, 1.0 and 2.0 ppm of lead (II) solutions were prepared by dissolving known weight of Pb (II) in known volume of  deionized water. Blank of the instrument The device was blanked with deionized water and then the sample was injected into the device where a process of atomization of lead in gasoline  takes place (in the path of the light from the bulb short)and the device read the amount of lead directly^[12].Results are shown in table (1).

Standard test Method for Oxidation Stability of Fuels

Oxidation stability of used reformat gasoline was investigated according to the method described by ASTM D93^[10]. Results are  shown in table (1). Results are  shown in table (1).

Standard test Method for Determination of Sulfur Content in Gasoline by Energy Dispersive X-Ray Fluorescence Spectrometry

Sulfur content of used reformat gasoline was determined  according to the method described by ASTM D2624^[10]. Results are  shown in table (1).

The Effect of Adding Different Concentrations of Isopropyl Alcohol  to Sudanese Reformate Gasoline

Isopropyl alcohol as additive is gasoline soluble chemicals which mixed with reformat gasoline to enhance its octane number. iso propyl alcohol was added to the reformat gasoline at different concentrations 5% and 10% (v/v) as follow: A 1000 ml of reformat gasoline was prepared at refrigerator temp. and transferred to glass container had fitting cover. The octane number of gasoline was measured by CFR engine, and all physicochemical properties of gasoline were also detected before the addition of acetone. Two glass container were filled with 1000ml of reformat gasoline and by using a pipette iso propyl alcohol was added in different concentrations 5% and 10% (v/v) with shaking . The octane number of these blends was measured by CFR engine, and all physicochemical properties were also detected after the addition of isopropyl alcohol . Results are shown in table (1).

Table 1: Some physicochemical properties of Sudanese reformat gasoline before and after addition of  iso propyl alcohol

Test name	Reformat Gasoline (R.G)    before addition of		1000 ml .R.G + 50ml		1000 ml .R.G +100ml
	iso propyl alcohol		iso propyl alcohol		iso propyl alcohol
Distillation	37.9°C	Initial Boiling Point (IBP)	36.5°C	Initial Boiling Point (IBP)	33.7°C	Initial Boiling Point (IBP)
	58.5°C	10%	57°C	10%	55.6°C	10%
	97.2°C	50%	95°C	50%	93.5°C	50%
	159.0°C	90%	157.2°C	90%	157.6°C	90%
	190.5°C	Final Boiling Point (FBP)	185.2°C	Final Boiling Point (FBP)	182.1°C	Final Boiling Point (FBP)
Density	736.4 k/m3 (150°C)		729 k/m3 (150°C)		701 k/m3 (150°C)
Vapor pressure	52.5 KPa(37.8°C)		49KPa(37.8°C)		49.1KPa(37.8°C)
Gum content	0.8 mg/100ml		0.8 mg/100ml		0.95 mg/100ml
Copper corrosion	1a		1a		1a
Lead percentage	0.001 mg/L		0.001 mg/L		0.001 mg/L
Oxidation stability	494 min		452 min		403 min
Sulfur percentage	58.49 mg/L		58.49 mg/L		58.49 mg/L
Pressure reading in CFR engine	0.583KPa		0.502KPa		0.475KPa
Motor octane number	88.5		94.1		96

 

From the table it is obvious that, the distillation test of reformat gasoline before and after treatment showed a decrease in the final boiling points (FBP), which give a strong evidence, that the quality of the reformat gasoline has improved after two additions of (5, 10% v/v) of isopropyl alcohol . Also, the Initial Boiling Points (IBP) of the same reformat gasoline sample after treatment were decreased; this may be attributed to the conversion of some liquid petroleum gas (LPG) into fuel ^[13].The decrease in the initial boiling points (IBP) after all additions also indicated that, the quality of gasoline was improved. The addition of isopropyl alcohol with different concentrations raises the value of the octane number after the distillation and refining processes. Therefore, the distillation test gives an interpretation about the raising or lowering of the octane number only ^[10]. No limits had been assigned for the density and vapor pressure by ASTM, because they depend to a greater extent on the temperature of the country, but the refineries has assigned limits to these physical parameters as shown in table (2).

Table 2: Limits of physical parameters gasoline assigned by Khartoum refinery

Test	Summer	Winter
Density	>740 kg/m3	>740 kg/m3
Vapour pressure	40- 67 KPa	40 – 85KPa

 

According to the limits assigned for the density and vapor pressure, the results obtained in table (1)., appears to be in permissible range. The percent of gum in gasoline affect its stability, which can be a (+ve) or (–ve) effect on the octane number and the quality of the gasoline. the gum existence after first addition being stable at (0.8 mg/100ml) and after the second addition  increased to 0.95 mg/100ml and these results appears to be in permissible range assigned by ASTM as shown in table (3).

Table 3: The permissible range assigned by ASTM

Test name	Permissible range	ASTM
Distillation	FBP ≤250◦c	D86-99a
Gum content	0.5-2mg/100ml	D381-99
Copper corrosion	1a or 1b	D183-91
Oxidation stability	>240mints	D525-99a
Sulfur content	⊁250 ppm	D4294-89
Lead content	⊁ 0.001 ppm	D3341-91

 

Copper corrosion may take place in the gasoline tank  or the engine that use gasoline ,so the test of the copper strip corrosion  is very important to be carried out^[14]. ASTM stablished a color table from which it is possible to determine if corrosion of a copper plate when immersed in a gasoline sample takes place or not by comparison with ASTM copper strip corrosion standard. It is obvious that the result (1a) obtained after both additions is within permissible limits which indicates good quality of the Sudanese reformate gasoline. The lead content of the reformat gasoline before any addition of iso propyl alcohol was found (0.001mg/L) which it is within the permissible assigned by ASTM,this value was not altered after both additions of iso propyl alcohol. Oxidation stability considered as one of the most important property that used to assess the quality of gasoline, since it give clue on the circumstances of the product storing, and also the heat required to start the combustion of gasoline inside the engine ^[15].Results obtained from the oxidation stability test also lies within the permissible range of ASTM as shown in table (3). When adding isopropyl alcohol 5 and 10% (v/v) it was observed that the Sulfur percentage was stable and results obtained from sulfur content test was fond within the right permissible range assigned by ASTM, this means a high quality was occurred because high sulfur percentage (⊁250ppm) causes corrosion and lowers the octane number. Figure (1) shows the effect of adding isopropyl alcohol at different concentrations  to the Sudanese reformat gasoline.  The increase in the value of the motor octane number of the Sudanese reformat gasoline from 88.5 initially  to94.1 and 96  by the addition of 5 and 10% (v/v) isopropyl alcohol respectively,  indicates that isopropyl alcohol improve the quality of the Sudanese reformat gasoline  , this improvement is attributed to the ability of the material  to convert the hydrocarbon chains into cyclic compounds or increasing the branched chains in gasoline.

Figure 1: Effect of isopropyl alcohol concentration on the value of MON Click here to View figure

 

Conclusion

Motor Octane Number (MON) of reformat gasoline used in this project before improvement process was found to be 88.5. Isopropyl alcohol showed different abilities in improving MON of reformat gasoline produced at Khartoum Refinery. The density and vapour pressure properties for reformat gasoline after additions with different concentration were found to be within the range assigned by Khartoum refinery. Other properties for reformat gasoline after all additions with different concentration were found within the limits assigned by ASTM. MON was improved to 94.1 & 96 after adding isopropyl alcohol 5 & 10 (v/v) respectively.

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