Recovery of Used Lubricating Oils - A Brief Review_Crimson Publishers

José Carlos Oliveira Santos*
Department of Biology and Chemistry, University of Campina Grande, Brazil
*Corresponding author : José Carlos Oliveira Santos, Laboratory of Bio-fuels and Environmental Chemistry, Department of Biology and Chemistry,
Federal University of Campina Grande, Brazil.
Submission: February 28, 2018; Published: April 10, 2018
Recovery of Used Lubricating Oils - A Brief Review
Introduction
Synthetic or non-synthetic lubricating oils are petroleum
derivatives, used for automotive or industrial purposes, which after
the recommended period of use recommended by the equipment
manufacturers deteriorate in part, forming oxygenated compounds
(organic acids and ketones), polynuclear aromatic compounds of
high viscosity (and potentially carcinogenic), resins and lacquers
[1]. In addition to the basic oil degradation products, there are
present in the used oil the additives which have been added in the
process of formulating these lubricants and which have not yet
been consumed, wear metals of lubricated engines and engines and
various contaminants such as water, fuel, dust and other impurities.
The lubricating oil used may still contain chemicals which are
sometimes unscrupulously added to the oil and its characteristic
contaminants [2]. In this way, when waste oils are released directly
into the environment (in water, sewage and soil networks) or
when uncontrolled burning, they cause serious soil, water and air
pollution problems. When released into the soil, the waste oils seep
into the ground with the rainwater contaminating the soil they
pass through, and when they reach underground groundwater,
they also pollute the water from fountains and wells [3,4]. When
discharged into wastewater drainage systems, they pollute water
receiving facilities and also cause significant damage to wastewater
treatment plants. The used oil contains high levels of hydrocarbons
andmetals[4],beingthemostrepresentativeiron,lead,zinc,copper,
chromium, nickel and cadmium. The indiscriminate burning of the
lubricating oil used, without prior treatment of demetallation,
generates significant emissions of metallic oxides in addition to
other toxic gases, such as dioxins and sulfur oxides.
Lubricating oils are among the few petroleum derivatives that
are not fully consumed during use. Manufacturers of additives
and formulators of this type of oil have been working on the
development of products with longer life, which tends to reduce the
production of waste oils. However, with the increase in additivation
and the useful life of the oil, the difficulties in the regeneration
process of the basic oil after use increase. On the other hand, if we
look at the dangers that used oil can cause to the environment, a
solution to the difficulties encountered would be easily justified. In
addition, re-refining restores the conditions of the basic lubricating
oil, whose quality is as good, as or even better than the basics
of first refining. The refined oils would return to the market,
generating jobs, saving foreign exchange and avoiding the increase
of environmental pollution [5]. The introduction of the additives to
the lubricants is intended to add to these important characteristics,
such as dispersion or dispersivity, detergency inhibitor, anti-
wear, antioxidant, anticorrosive, antifoam, viscosity modifying,
emulsifying, lowering pour point, tackiness etc. The amount of
additives recommended by suppliers varies, on average, from 0.5 to
28% by volume. To formulate these additives, various chemicals are
added to the base oil for the lubricant to perform well. In addition,
the lubricating oil carries all kinds of impurities generated by the
wear of the internal components. In this way, it is necessary to
monitor the physicochemical properties of the lubricants used to
determine the appropriate time to change them. Motor wear can be
monitored through this characterization in waste oils. To achieve
these goals, some techniques have been widely used to characterize
lubricating oils and also in other petroleum derivatives [3,6,7].
Mini Review
79
Copyright © All rights are reserved by José Carlos Oliveira Santos.
Volume 1 - Issue - 4
Abstract
Lubricating oils are substances of mineral or synthetic base responsible for forming a protective film, which prevents direct contact between two
surfaces that move with each other. The lubricant mixture is formed by the addition of additives to the base oil obtained in the distillation of petroleum.
When used oils are released directly into the environment or when uncontrolled burning causes serious soil, water and air pollution problems. Recycling
the lubricant means applying physical-chemical processes on the used oil, making it possible to obtain base oil, a raw material that can be reused to
obtain lubricants. The objective of the present work is to evaluate the recent processes of recovery of used automotive lubricating oils.
Keywords: Lubricating oils; Environment; Recycling
Progress in Petrochemical Science
C CRIMSON PUBLISHERS
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Progress Petrochem Sci
80
How to cite this article: José C O S. Recovery of Used Lubricating Oils - A Brief Review. Progress Petrochem Sci .1(4). PPS.000516.2018.
DOI: 10.31031/PPS.2018.01.000516
Copyright © José Carlos Oliveira Santos
Used oils, if disposed of in the soil, burned or discarded in
water bodies, will cause strong environmental damage due to the
high polluting potential [3]. Another great risk is when it reaches
the ground; it becomes a kind of reservoir that will severely affect
the subsoil and the water table, forming a plume of contamination,
limiting the circulation of air through the soil particles, inhibiting
the action of microorganisms and prevents access of plants to
nutrients. The oils contain toxic metals from the additives as well
as the wear of the engines, and contain in their composition poly-
aromatic hydrocarbons, such as benzopyrene, phenanthrene,
fluorene, which are formed by oxidation processes during their
useful life. Through the above we see how important it is to recycle
this material that can be reused several times reducing the pollution
of the environment [8].
Recycling the lubricant means applying physical-chemical
processes on the used oil, making it possible to obtain base oil, a
raw material that can be reused to obtain lubricants. The reuse of
the oil is conditioned to the degree and type of contamination. The
most common contaminants found in oils are: mild compounds
(low boiling point), soluble compounds and insoluble compounds.
Within the light compounds the most common are: water, gasoline
and diesel. In the case of the soluble compounds all oxidized
compounds and additives previously incorporated (antioxidants,
detergents, dispersants) are highlighted, while the insoluble
compounds comprise the oxidized hydrocarbons, particles and
metal oxides [5,8,9].
In the case of lubricants, an alternative to their use after
incineration is due to their high calorific value, however, since it
is a material of non-renewable origin (base oils), it should not be
used because it is highly polluting. Taking into account the fact that
during its use the lubricant is not consumed, but its additives is that
it loses its efficiency, recycling can be the most viable alternative
not only technologically as well as economic and ecological. Some
of the processes used in the recycling are of a physical nature, that
is, they use only the different physical properties of the components
to separate them. Others exist that employ chemical reactions to
obtain products and the purification of the same ones [10-19].The
processes employed can thus be described:
i. Sedimentation: It consists of leaving the used oil in a
cuneiform bottom tank, without agitation, for a sufficient and
adequate period of time. This method depends on the density
of water, solid impurities and oil. Oxidized products that have
the same oil density are not removed. Fluid oils separate from
suspended matter more easily than viscous ones.
ii. Filtration: Consists of passing the oil through certain
materials that retain the solid particles. Filtering devices
are largely based on the principle of operation, cost and
performance. Lately a lot of adsorbent filters have been used;
the activated bauxite being widely used. The great problem of
filtration efficiency is the presence of water in considerable
quantities. Efficiency depends on the type of oil and the service.
iii. Centrifugation: Centrifugal purification is a mechanical
process by which the separation of impurities from liquids
is accelerated, spinning at high peripheral speeds. It is an
economical process for large volumes of oil. It does not remove
additives and takes up small space. It is used successfully in the
purification of the oils of air filters, hydraulic oils, motor oils.
iv. Degasification: It consists of a high vacuum chamber
with an inlay containing small metal rings or ceramic pieces to
obtain a large surface. This process is widely used in the drying
of insulating oils. In this process, dissolved gases, as well as
water and mixtures of solvents which may be present in the
lubricant are withdrawn.
v. Thermal dehydration: Consists of passing the lubricating
oil through a two-stage column operating independently. The
first stage consists of heating the oil in the range of 160 ̊C to
200 ̊C under normal pressure. The oil circulates in a continuous
stream through a heat exchanger where a certain amount of
dehydrated oil is removed to the second stage at the top of
the column and cooled. The water and the light fractions are
removed.
vi. Solvent extraction: It is a very useful process as it can be
used for any type of paraffinic oil. It consists in separating, by
solubility difference, paraffinic and naphthenic compounds
from undesirable compounds such as sludge, resins and asphalt
compounds. The process is capable of removing about 10-14%
of the contaminants, which corresponds to approximately
the amount of additives and impurities normally found in the
lubricating oil used. In this process, two parameters are critical
to the success of the recovery, the ratio (solvent: lubricant used)
and the extraction temperature, where these must be chosen
to be able to remove impurities and additives and decrease the
base oil loss.
vii. Acid treatment: The use of sulfuric acid in the treatment
of waste oils. The acid attacks the unsaturated hydrocarbons
producing esters, alcohols, polymers and oxidized products.
This treatment allows the deposition of sludge after a decanting
step.
viii. Neutralization:Aprocessthataimstoneutralizetheexcess
of acid or base present in the medium converting into salts. At
this stage the pH of the solution is adjusted to approximately
7. It consists of adding caustic soda or potash to the oil. This
treatment is done in a bottom tank equipped with a reactor.
ix. Hydrofination: consists of hydrogenolysis, where
hydrogen acts under high pressure on unstable hydrocarbons.
Hydrogen acts to saturate unstable hydrocarbons. In addition
to improving the color, a better oxidation resistance and a
reduction of the carbon residue is obtained.
x. Fractional distillation: it consists of separating by strip
of distillation the mixture that constitutes the used oil. Steam
extraction is used to increase the flash point of most heavy

81
Progress Petrochem Sci Copyright © José Carlos Oliveira Santos
DOI: 10.31031/PPS.2018.01.000516
oils where hot oil is placed in contact with the steam in an
extraction tower. Vacuum distillation is indicated to reduce a
residual stock of asphalt and by-products, in the distillation
of crude oil, in the production of low-carbon oils. Some work
has been done on the determination of metals and other
contaminants in lubricating oils [14,16,20]. However, works
that recovers used lubricating oils and make their chemical and
physicochemical characterization relating these properties to
those found in new lubricating oils has been poorly reported
[21-23]. From the above, it is highly relevant that this raw
material is regenerated through cleaner technology, providing
protection to the environment, avoiding waste and promoting
an intelligent use of natural resources.
4. Conclusion
The indiscriminate disposal of the lubricating oil harms the
environment and misses a promising source of resources and,
therefore, it is necessary to develop technologies for its recovery.
Recycling becomes the proper treatment of the used oil, through
specific processes, thus allowing the reuse of the same. Various
recycling alternatives have been used around the world for recovery
of used lubricating oil, each with its advantages and disadvantages.
Recycled engine oil can be burned as fuel, usually in boilers, plant
heaters or for industrial heating applications such as furnaces and
cement kilns. Recycled oil is distilled in diesel fuel or marine fuel, in
a process similar to refining. The lubricating property of the engine
oil persists even with used and can be recycled indefinitely. Thus,
the recycling of used lubricating oils can gain more and more space
in the context of environmental conservation.
Regeneration or re-treatment treatments are processes to
produce basic oils. There are several technologies on the market,
but in common are pre-treatment, cleaning, fractionation and
final treatment of waste oils. In general, the different processes
of regeneration of lubricating oils are applied as a function of the
level of degradation suffered by the oil, where it passes through the
processes of fluid withdrawal, viscosity correction, filtering and
separation of particulates, chemical additives specified according
to standards established by law.
References
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(2004) Thermoanalytical and rheological characterization of automotive
mineral lubricants after thermal degradation. Fuel 83(17-18): 2393-
2399.
2. Santos JCO, Santos IMG, Souza AG (2015) Thermal degradation process
of synthetic lubricating oils: Part I - Spectroscopic Study. Petrol Sci
Technol 33(11): 1238-1245.
3. ParkSW,LeeJY,YangJS,KimKJ,BaekK(2009)Electrokineticremediation
of contaminated soil with waste-lubricant oils and zinc. J Hazard Mater
169(1-3): 1168-1176.
4. Santos JCO, Souza AG, Oliveira AD, Lima LN, Silva CC, et al. (2007) Kinetic
and activation thermodynamic parameters on thermal decomposition of
synthetic lubricant oils. J Therm Anal Calorim 87(3): 823-829.
5. Al Ghouti MA, Al Atoum L (2009) Virgin and recycled engine oil
differentiation: A spectroscopic study. J Environ Manag 90(1): 187-195.
6. Tsai WT (2011) An analysis of used lubricant recycling, energy utilization
and its environmental benefit in Taiwan. Energy 36(7): 4333-4339.
7. Santos JCO, Souza AG (2006) Liquid specific heat capacity of motor
lubricant oils after thermal degradation. J Eng Applied Sci 1(3): 495-499.
8. Santos JCO, Almeida RA, Carvalho MWNC, Conceição MM, Souza AG
(2014) Avaliação da estabilidade térmica e oxidativa de óleo lubrificante
automotivo recuperado usando o solvente metiletilcetona. Química No
Brasil 8(2): 49-56.
9. Lima AEA, Conceição MM, Santos JCO,Rosenhaim R, Santos IMG, et al.
(2016) Otimização do processo de recuperação de lubrificante usado
por extração com solventes polares. Rev Quím Ind 84: 57-66.
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using hydrocarbon solvents. J Environ Manag 74(2): 153-159.
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322.
12. Lam SS, Russel AD, Chase HA (2010) Microwave pyrolysis, a novel
process for recycling waste automotive engine oil. Energy 35(7): 2985-
2991.
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molecular sieves as sorbents. Chemosphere 78(5): 591-598.
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and lubricant contamination from viscous oil by high-gradient magnetic
separation technique.Sep Purif Technol 92(18): 122-128.
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various solvent extraction techniques. J Ind Eng Chem 19(2): 536-539.
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Natural clay applied to the clarification of used automotive lubricating
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18. Santos JCO, Santos IMG, Souza AG (2017) Thermal degradation of
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21. Santos JCO, Santos IMG, Souza AG, Sinfrônio FSM, Silva MA, et al. (2005)
Thermodynamic and kinetic parameters on thermal degradation of
automotive mineral lubricant oils determined using thermogravimetry. J
Thermal Anal Calorim 79(2): 461-467.
22. Santos JCO, Santos IMG, Souza AG (2006) Kinetic on thermal
decomposition reactions of mineral lubricant oils by thermogravimetry.
Res J Applied Sci 1(1): 7-10.
23. Santos JCO, Santos IMG, Souza AG, Lima LN (2007) Thermal,
spectroscopic and rheological study of mineral base lubricating oils. J
Therm Anal Calorim 87(3): 639-643.

Progress Petrochem Sci
82
DOI: 10.31031/PPS.2018.01.000516
Copyright © José Carlos Oliveira Santos
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