Chemistry from Waste Products Fractional Distillation of Used Engine Oil Peter M. Mashava', llori E. Alonge, and Francis Mlenga Department of Curriculum Studies, University of Zimbabwe, P. 0. Box MP 167, Mt. Pleasant, Harare, Zimbabwe Major issues in the teaching of chemistry a t every level continue to include the need to relate the subject to the environment. In particular, i t is often stressed that this be Chemistry teaching a t the done through e~perimentation.~~3 tertiary level is perhaps better endowed for meeting these challenees because i t is usuallv better e a u i ~ ~ with e d manpower &d requisite teaching resource; The situation in most high schools is less so. Indeed i t is much more difficult in the high schools of the developing countries. In many of these countries used engine oil is drained from automobiles and thrown in open drains as waste products. The experiment described below teaches some chemist^. " . content and process, provides avenues for acquiring techniques, and poses suitable questions for future learning. Experlment Results All glassware used in the experiment was thoronghly washed and dried in the ovm at 1W 'C. Used cngine oil was ohtsined from a local auumobile service station. Fiftv mlllilitera of the used oil was put in a round-bottomed flask and a few antibumpinggranules were added. The distillation apparatus should be set up in a h o d or vented outside. A fractional distillation column fitted with a Vigreux Was set up. Heating was provided by a heating mantle to avoid use of open flames. Caution: The oil and distillates are quite flammable. The first fraction was collected after about 1'12 h in the temperature range of I S 1 4 0 OC. Four other fractions were collected at about l-h intervals. Precautionary Measures
1. The experiment was carried out in a well-ventilated fume h o d
behind protective glass shield.
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2. A water-cooled ail (Graham-be). condenser was used. 3. The experimenter must wear safety goggles.
The table below shows qualitative information about the fractions collected. Fractions from Fractional Dlrtlllationr of Used Englne 011
Fraction Label A B
C D
E
Range P C )
Volume (mL)
crude yellow yellow yellow yellow vellow
78-140 140-200 200-240 240-280 280340
0.3 0.9 1.3 2.5
Journal of Chemical Education
Dlscusslon Engine oil is prepared and sold by oil companies. I t is a special kind of lubricating oil suitable for engines that function modestly a t high temperatures (e.g., 100 OC in petroldriven cars and about 200 OC in diesel-engine vehicles). The oil is characterized bv varvine viscosities and is sold under trade names with differen; coknercial descriptions such as SAF: 10. SAE40. and SAE 10-50. each of these being suitable for par&ular engine types as specififed by vehicle manufacturers. Although prepared and sold under different trade names, i t is initially obtained from t h e same source-petroleum refineries. I t is a nonvolatile liquid fraction in the lower part of the distillation tower containing hydrocarbons in the This component is then treated and blended range C2@&. t o the specific quality of the engine type for which i t is desired. In order to make the engine oil serve well, some additives and rust inhibitors are added in the course of bleudine and treatment. The additives are to minimize oxidation, control foaming, and resting or improving viscosity of the oil. An example of a viscosity improver is the polymer of 2-methyl propeie. Alkyl benzene sulfonate is also used as a rust i n h i b i t ~ r . ~ The oil churns when the engine is running. The reaction that takes place is complex. A simplified account suggests that the long-chain hydrocarbons are degraded. Oxidation also takes place. Thus, the oil that circulates around the eneine chanees in structure and becomes less viscous. The chemical reactions that take place yield new products that are oresent in the oil that is remlarlv drained and replaced by "fresh" engine oil when theiehicfe is being serviced. The oil that is thus drained is a mixture of different compounds with much lower numhersof carbon atoms than were in the oriainal nonvolatile fractions from crude oil. It is expected include products of combustion and petrol additives. The process illustrated in this experiment is the basis of recycling used engine oil in some developed countries. This experiment is considered a valuahle learning experience for high school students, particularly those who may never be ahle to see fractional distillation in one of chemistry's most pronounced examples of its use-distillation of crude oil.
to
Temperature Color
3.2
This experiment was repeated three times with samples of used oil from the same source. There were no obvious differences in the qualitative results. Qualitative tests were carried out on samples of each fraction. Each of the samoles was readilv flammable in air with increasine amounts of soot from sample A to E. Each of the samples decnlorized hromine in tetrachlorimelhane ( T E i as well analkaline parnasium permanganate. This test ,how5 the presence of cnrbon-rarbon double bonds in the sample of the fractions. Spectral analysis (IR) of each of the samples was undertaken. Sample A showed signals for OH groups (3200 em-' to 3600 cm-'), CH2group (1450 cm-I to 1500 cm-I), and CH8group (1360 c n - I to 1400 em-'). In addition to the above, sample B showed signals of
1042
C=C bond (1640 c n - I to 1680 cm-1). Samples C, D, and E showed signals similar to one another and differed from A and B mainly in that they did not give OH group signals.
Acknowledgment The authors thank the Chemistry Department a t the University of Zimbabwe for providing the facilities to camy out his work.
' Author to whom cwesoondence should be addressed.
~rizer.M. J. "~esolutldnsand Recommendations in Proceedlngs of the Sixty International Conference on Cherntcal Education": MD 1981; pp 15-20. Zoller, U. J. Cham. Educ. 1982.59.401-403. Sellnger, 6. Chemistry in the Market Place; Austral., Nat. Unlv. Canberra: 1978: pp 276-277.
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