Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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28622
RECLAIMING USED MOTOR OIL VIA SUPERCRITIGAI
SO~VENT EXTRACTION AND HYDROTREATING
The inven~ion is concerned with a process for refining used
lubricating oil. The used oil is subjected to solvent extraction to obtain
a paraffin-rich phase, hydrogenation to eliminate unsaturated contaminants
therein, and separation of the solvent to yield a high quality stock.
Background
Motor oils are lubricants produced from petroleum by couventional
refi~ing techniques. They consis-t of a complex mixture of paraffinic
hydrocarbons whose structures and properties render the mixture effective
as a lubricant for internal combustion engines and the like. Besides
hydrocarbon mixtures, mo-tor oils often contain up to 30/O by weight of
additives such as detergents, pour point depressants, stabilizers, and
viscosi-ty modifiers. These oils break down during prolonged use,
particularly at high ~emperatures, leaving various contaminants.
During use in an engine, the motor oil becomes contaminated with
various impurities such as carbon, grit, ash, gasoline, water 9 metal
particles, particu]arly heavy metal residues, and other residues. Resins,
oxidation products and unsaturated impurities can also be formed.
In the past, most used motor oil has been discarded or directed
to low grade uses such as road oil or blending with heavy fuel oils. With
increasing interest in fuel conservation, greater use is being made of
motor oil reclaiming processes which can ofer means for recovery of most
of this premium hydrocarbon resource. Many of these processes have
disadvantages such as a multiplicity of steps, high capital investment,
waste disposal problems and low product recovery.
_jects of the In~ention
_
It is an object of this invention to provide a method for
treating oil which has been drained from the crankcase of an internal
combustion engine after residence therein during the engine's use.
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It is another object of this invention to provide a process Eor
reclaiming motor oil wherein used oil is subjected to solvent ex-trac-tion.
It is a further object of ~he invention to provide a method of
reclaiming mo-~or oil wherein the used oil is subjected to solvent
extraction and the hydrocarbon extract is then subjected to a
hydrogenation.
It is still another object of the invention to provide a process
of reclaiming used oils wherein the used oils are subjected to solvent
extraction, the hydrocarbon extract is hydrotreated, and the solvent from
the extraction step is recycled.
Description of the Inventi.on
In one embodiment of the invention motor oil is reclaimed by a
process which co~prises the steps of:
(a) contacting used motor oil with one or more organic solvents
under supercritical condi~ions of temperature and pressure so as to produce
an extrac-t phase;
(b) separatin~ some or all of the ex-tract phase from the other
products of step (a);
~c) hydrogenating the extract phase from step (b);
(d) removing organic solvent from the extract phase before or
after step ~c); and
(e) recovering a hydrogenated oil product. The extract phase can
usually also be characterized as an oil rich phase.
Optionally, the used oil feed may be processed through a flash
separation or other separation device to remove impurities such as metals,
wa-ter and/or gasoline components.
The oil feed may be combined with a portion or all of the
solven-t; preheated to extraction conditions; held for a suitable period of
time to effect dissolution of oil thereby producing a solvent-containing
extract which is relatively free of contaminants; passed through a
separation zone sllch as a cyclone~ filter, or phase separator to remove
solids, part or all of the solvent, and/or undissolved residue; and the
vapor phase introduced to a catalytic hydrotrea-ter along with hydrogen. If
desired, the temperature of the oil stream can be adjusted before
hydrotreatment.
~Iydrotreater effluent is expanded and optionally cooled to condense refined
oil which is removed from the sys-tem at the flash separator. Separator
vapor is cooled and condensed to recover liquid solvent which can be
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recycled to the extrac~ion s~ep and hydrogen gas which may be recompressed
and recycled to the hydrotreater.
The Eollowing ranges for process variables are suggested:
Range Preferred Ran&e
Extraction ~emperature C100-500 ~00-400
Extraction Pressure, psig. 200-2000 500-1500
Extraction Residence Time, min. 1-60 10
E~tract/Residue Split ~by weight)90/10-97/3 95/5
Feed/Solvent ~atio (by weight) 1~ 10 1:5-2:5
Solvents suitable for the supercritical extraction include single
ring aromatics having not more than 3 carbon atoms on substituent groups,
alicyclic hydrocarbons having at leas-t 5 but less than 10 carbon atoms and
acyclic hydrocarbon having at least 3 but not more than 10 carbon
atoms - preferably C3-C7n-alkanes. Mixed solvents can also be used.
By "hydrogenation" or "hydrotreating" i5 mean-t addition
hydrogenation, which is the reaction of hydrogen with non-aromatic
unsaturation to produce a saturated product. Well-known catalys-ts are
conv~ntionally employed. "~Iydrogenation" reactions are distinct from
"hydrogenolysis" or destructive hydrogenation reactions which cause the
rupture of -the bonds of organic compounds and the subsequent reaction of
hydrogen with the resultant fragments. A discussion oE -this distinction
may be found in _o densed Chemical Dic-tionary, 9th Edition ~1977).
The hydrogenation or hydrotreating step is conventional excep-t
for the presence of supercritical solvent which passes through unscathed
unless it is aromatic, in which evint a small Eraction may be hydrogenated.
Suitable catalysts useful in this step included those utilizing Group VI~
and Group VIII metals or combinations thereof using a refractory support.
Conventional hydrodesulfurizer conditions can be used. Suitable
hydrodesulfurization processes are disclosed in U.S. Patents 3,770,619,
issued November 6, 1973 by Derrien et al and 4,110,205, issued August 29,
1978 by Lee ~ilfman. It is preferred to operate the hydrodesulfurizer at
about the same pressure as the extraction step. In some cases, these two
operations can be carried out at about the same temperature7 but the
temperature can be adjusted for hydrotreating.
The oil product from the process is a quality hydrocarbon base
stock. It is believed to be equivalent to any virgin or unused hydrocarbon
stock. Accordingly, i-t can be mixed with conventional additives and
subjected to conventional treatment to render it more useful as a
lubricating oil.
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.Example 1
IJsed motor oil and n-heptane solvent were pumped into a
nitrogen-pressurized one liter extraction vessel maintained at abcut 30GC
and 750 psig (5.26 MPa). Pumping rate was about 10 ml/min For each Eluid,
and the fluids were preheated to about 300C before introduction into the
reactor. After approximately 15 minutes, product take-off commenced while
pumping of both fluies continued at the same rate until 550 ml of n-heptane
and 503 ml of oil had been added. Introduction of used oil was then
discontinued, but pumping of n-heptane solvent continued at 10 ml/min for
another 2~ hours to purge out the extracted oil. Product from the
extraction was condensed and recovered. An analysis is given in the -table
following Example II.
Example II
A similar run was made using n-pentane solvent at extraction
conditions of 225C and 750 psig (5.26 MPa). An analysis is given below.
Table
Example I Example II
(n-Heptane (n-Pentane
Extraction) Extraction)
Used
Motor Oil ~xtract Residue Extract Residue
-
Weight % Extracted 92.6 7.4 85.5 14.5
Analysis, W~. %
Carbon 79.66 84.51 22.25 85.05 55.73
Hydrogen 11.99 12.98 2.50 13.19 7.76
Sulfur 0.41 0.36 1.79 0.22 1.52
Iron 341 ppm 236 ppm 0.3 120 ppm 1.0
Magnesium 365 ppm 276 ppm 0.1 254 ppm 0.3
Lead 28,900 ppm 2,740 ppm 102,590 ppm 10
Calcium 6,290 ppm 29490 ppm 0.32,130 ppm1.0
Zinc 1,910 ppm 275 ppm 0.1829 ppm 0.3
Ash -~ - 1.04 26.840.91 21.6
~ ligh percentages of the feedstock's ash content remained in -the
residue. In Example l, for each 100 parts of Eeeds-tock, the total ash
content was (7.4 x .2684) = 1.99 plus (92.6 x .0104) - 0.96, or 2.95 parts
total ash. Since 1.99 parts ash was in -the residue the percen-tage in the
residue was
1 .99
~ - ) = 68%.
2.95
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Likewise, for Example II, each 100 parts of feedstock eontaine(1
(14.5 x .216) = 3.13 plus (85.5 x 0.91) = 0.78, or 3.91 parts -total ash.
Since 3.13 parts ash remained in the residue
3.~3
t - ) = BO/~
3.91
of the ash remained in the residue.
Both of the above examples demonstrate that high percen-tages of
ash remain in the residue.
Reasonable variations which will become apparent to those skilled
in the art can be made in the present invention without departing from its
spirit and scope.
