Note: Descriptions are shown in the official language in which they were submitted.
1136S66
FlELD OF THE INVENTION
The invention relates to a process for removing contaminants
from waste lubricating oil. More particularly the invention i`nvolves
clay contacting of waste lubricating oils.
BACKGROUND OF THE INVENTION
Waste lubricating oils include used motor oil, diesel oil,
crankcase oil, and transmission oil. These waste oils contain a number
of contaminants arising from both their use and from additives added
prior to their use. These contaminants for the most part include
calcium, barium, zinc, aluminum and phosphorus arising from detergent
dispersant agents, iron from engine wear, lead and light end hydrocarbons
from gasoline, and water. In order to reuse these oils, the contaminants
must be removed.
Due to the high viscosity of the oil, the fine colloidal or
dissolved form of the contaminants and the dispersing nature of the
additives, the contaminants cannot be removed by a simple filtration
procedure without some preliminary treatment.
Conventionally, waste oils are treated in a process which
includes metals removal steps, which steps involve coagulating or
precipitating the contaminants and thereafter either filtering the oil
or removing the metals in an aqueous phase. Often the oil is then clay
contacted to remove further color bodies or metals remaining after the
initial metals removal.
One of the most widely used metal removal steps is the acid-
clay process. Here the light ends are first removed from the oil by
steam stripping at a temperature in the range of about 500 - 650F. The
oil is then contacted with high strength sulphuric acid and the contaminants
removed in an acid sludge. The acidic oil product is thereafter contacted
with clay at a temperature in the range of about 300 - 600F to absorb
additional contaminants and color bodies. There are a number of problems
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associated with this process. Firstly, the process produces large amounts
of acid sludge which must be disposed of. Secondly, large volumes of
corrosive acid are consumed by the process. Thirdly, up to 20% of the
original waste oil is lost with the acid sludge.
Thus far, the standard practice in this art has been to acid
contact the oil, or otherwise remove the majority of the contaminants,
prior to clay contacting the oil, since it was commonly accepted that
detergents or other additives would render the clay-oil mixture unfilter-
able. Further, high temperature treatments have been avoided when re-
processing waste lubricating oil, to avoid undue cracking of the oil.
SUMMARY OF THE INVENTION
It is the inventor's discovery that, surprisingly, previously
untreated waste lubricating oil, when contacted at an elevated temperature
with a decolorizing clay, can be subsequently filtered to remove a consid-
erable portion of the contaminants. Apparently, the dispersing properties
of the detergents and other additives are destroyed by this treatment to
thereby render the waste oil filterable. While not being bound by the
same, it is believed that this high temperature clay contacting step
achieves selective cracking of the detergents and other additives
associated with the oil, without causing undue cracking of the oil. This
is in contrast to the teaching of the prior art which was to avoid high
temperature treatment of waste oil to limit cracking in the oil. The
filtered product is acceptable to further conventional upgrading processes
including hydrotreating, vacuum distillation and acid-clay contacting.
A temperature range in the order of about 650 - 725F has
been found to be preferable for the clay contacting step. The process
has been demonstrated with a number of known decolorizing clays. Pre-
ferably, light ends stripping is performed simultaneously with the clay
contacting step.
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1136S66
In accordance with a preferred version of the invention, the
clay contacting step is performed in a hydrogen atmosphere. Noticeable
improvements in the odour of the oil are obtained, no doubt due to the
hydrogenation of S-containing compounds.
Broadly stated, the invention is a process for the removal
of contaminants from untreated waste lubricating oil comprising the
steps of: contacting the untreated waste oil with a decolorizing clay
at a temperature in the range of about 650 - 725F for a time sufficient
to render the mixture readily filterable, whereby at least a portion of
the contaminants may be separated with the clay from the oil; and then
filtering the oil-clay mixture to obtain a filtrate product reduced in
contaminant content.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The process of the present invention is largely practiced
on waste lubricating oils which include motor oil, transmission oil,
hydraulic oil, crankcase oil, diesel oil and the like. Such oils
typically contain about 10% by weight contaminants, which contaminants
include both the additives added to the oil and the impurities arising
from use of the oil. The major contaminants to be removed include
calcium, barium, zinc, aluminum, phosphorous, lead, iron, water and hydro-
carbon light ends. The light end contaminants include light hydrocarbons
from fuel dilution of the waste oil and from thermal or oxidative de-
gradation of the original motor oil or additives.
To practice the process of the present invention, untreated
waste lubricating oil, which is generally a mixture of automobile drained
oils which has not been previously processed to remove the metal contaminants,
is contacted with a decolorizing clay and heated at a temperature suf-
ficient to volatilize water and light end contaminants for a time sufficient
to render at least a portion of the contaminants removeable by filtration.
Temperatures in the range of 650 - 725F are preferred. Temperatures below
about 650F can result in a clay-oil mixture which is not easily filtered
and generally increase the contacting time. Performing the clay contacting
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1136566
step above about 725F causes undue cracking in the oil. The time needed
is temperature dependent. For i`nstance~ at temperatures of 650F, 680F
and 700F, reaction times of about 4,~ and 1 hours respectively are
.
usually sufficient.
Decolorizing clays are well known in the art of reclaiming
waste lubricating oils. Those decolorizing clays normally used to
decolorize waste oil, for instance in the clay contacting step of the
conventional acid-clay process, are suitable for the process of the
present invention. The process has been demonstrated with Filtrol Clay
0 obtained fr~m Filtrol Corp., Los Angeles, California; Fullers Earth
from Fisher Laboratory Chemicals, Toronto, Ontario,
Attapulgus Clay from Engelhard Minerals & Chemicals, Appleton, Wisconsin;
and Pembina Clay obtained from Pembina Mountain Clays Ltd., Winnipeg,
Manitoba.
The quantity of clay used is preferably in the range of about
2 - 6% by weight. At less than about 2% clay, the color bodies removal is
poor; at greater than about 6% clay, the quantity of oil lost with the
clay is considerable.
The clay-oil mixture is then filtered by, for instance, gravity
or vacuum filtration, to produce a filtrate reduced in contaminant content.
This filtration step is preferably performed at a temperature in the range
of about 200 - 300F in order to reduce the oil viscosity and thus increase
the filtration rate. The amount of clay used in the clay contacting step
has been found to affect the filtration rate. Up to about 4% by weight
clay greatly improves the filtration rate. Further increasing the clay
content has no further beneficial effect on the filtration rate.
It may be desirable to perform the clay contacting step in
a hydrogen atmosphere. Significant improvements in both the odour and
filterability of the oil product are thereby obtained. A typical clay
contacting-hydrogenation step involves contacting the waste oil with
about 2 - 6% by weight decolorizing clay, in a hydrogen pressure in the
1136566
range of about 100 - 800 psig at a temperature in the range of about
650 - 675F for about 1 - 2 hours. Temperatures higher than 675F
generally cause an undue amount of hydrocracking in the oil. The hydrogen
pressure range is not critical to the reaction~ however pressures outside
these limits are more difficult to maintain.
Particularly good results have been obtained when diesel
oil is reprocessed by the above described clay contacting-hydrogenation
step. This oil is usually difficult to process by other methods since
the high molecular weight of the oil approaches the molecular weight
of the contaminants.
Since very high temperatures are used in the clay contacting
step, it is advantageous to conduct light ends stripping from the oil
simultaneously with this step. To that end the heated oil is purged
with a nitrogen or steam stream during the clay contacting step to remove
the volatile light ends~ which light ends are recovered by, for instance,
an o~erhead condensor system.
The filtrate product obtained from the clay contacting step
may be suitable for non-critical oil uses, that is those uses in which
color is not an important requirement. Otherwise, the filtrate product
may be further processed by conventional oil upgrading techniques in-
cluding hydrotreating, vacuum distillation and acid-clay contacting.
The invention is further illustrated by the following examples.
A number of oil samples were taken from a feedstock of
waste lubricating oil and subjected to the various treatrnents to be
described. The oil was a typical wet waste oil without preliminary
dehydration, light-ends removal or demetallization treatment. Prior
to each run the oil was air rolled to ensure sample uniformity. A typi-
cal metal analysis of the untreated waste oil is given in Table I. Three
litre samples of the waste oil were transferred to a 5 1., 3-necked
distillation flask equipped with either a steam or nitrogen purge and
an overhead condenser for light ends stripping. The desired amount of
1~36SS6
decolorizing clay was added to the oil and the clay-oil mixture heated to
650F. The decolorizing clays used are specified in Table I. This
temperature was maintained for a reaction time of about 4 hours and
the mixture was then cooled. Light ends stripping was maintained
throughout the heating, constant temperature and cooling phases. The
oil-clay mixture was allowed to cool and settle overnight. On the fol-
lowing day the mixture was reslurried, heated to about 200F and gravity
filtered.
The composition and amount of stripped overhead together with
the analysis of the filtered product are reported in Table I and II. The
metal contaminant content was determined by atomic absorption. The
filtered product is indicated in the columns headed "Before Hydrotreatment
(Hyd)".
To illustrate that the filtered product obtained from the clay
contacting process at an elevated temperature was acceptable to conventional
upgrading processes, the product was subjected to hydrotreating and
vacuum distillation techniques.
The filtered products were hydrotreated in a batch hydro-
treater at 650F and 650 psig for 4 hours using a Nalco DS 471 Co-Mo
catalyst (Alchem, Edmonton, Alberta~. After hydrotreatment the product
was filtered to remove catalyst fines and H2S and then analyzed. The
analyses are reported in Table II in the columns headed "After Hydro-
treatment (Hyd)".
From the product analyses after hydrotreatment it can be
seen that the preliminary clay contacting process of the present invention
produced an oil product sufficiently reduced in contaminants to be up-
graded by conventional hydrotreating. From the metal analyses in Table
I, it can be seen that the filtered oil product, prior to hydrotreating,
is suitable for non-critical oil uses.
1136566
The hydrotreated product was then vacuum distilled at 10 mm
Hg in a 5-tray column. Two 1,500 ml and two l,OOQ ml distillations
were made with the residue from the previous runs being left in the
distillation flask. Reflux ratios were varied from total take-off to 5:1.
Light ends, centre cut and residue amounts together with their analyses
are reported in Table III.
It is significant to note that the majority of the remaining
color bodies concentrate in the residue fraction leaving relatively
clean oil products.
To illustrate the effect of an acid-clay treatment subsequent
to the above described clay contacting process, the following example was
performed.
The waste lubricating oil was treated with 4% by weight clay
at 650F for 4 hours to yield a filtered pr-oduct having a viscosity of
162.4 SUS at 100F and of 44.14 SUS at 210F. The filtered product was
subsequently contacted with 0.5% vol/vol H2S04 and filtered. Further
clay contacting with 4% vol Pembina clay at 300F gave a filtered product
having a color of 4-1/2 - 5.
To obtain a similar color reduction by a straight forward
acid-clay treatment would require approximately 6% vol/vol H2S04 . Thus
the preliminary clay contacting step at an elevated temperature significantly
reduces the quantity of acid consumed.
While the present invention has been disclosed in connection
with the preferred embodiments thereof, it should be understood that there
may be other embodiments which fall within the spirit and scope of the
present invention as defined by the following claims.
11;~6566
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113~i566
TA~LF I II
PROPERTIES OF FEED AND VACUllM DISTILLATION CUTS
Color Flash Pt. Vis @ 100F Vis @ 210F A.P.I. Grav.
F SUS SUS @ 60F
Feed 4-4- 325 152.9 44.65 30.0
Forecut 1-1- 250 41.2 - 36.4
Centre Cut1-1- 405 140.1 42.29 31.1
Residue 8 560 1078.3 90.23 27.2
Residue 3- -4 550 990.9 87.20 28.0
(A.T.-C.C.)
