CA1136566A - Clay contacting process for removing contaminants from waste lubricating oil - Google Patents

Abstract

"CLAY CONTACTING PROCESS FOR REMOVING
CONTAMINANTS FROM WASTE LUBRICATING OIL"
ABSTRACT OF THE DISCLOSURE
A process is provided for removing contaminants from waste lubricating oil. The previously untreated waste oil is contacted with decolorizing clay at a temperature in the range of about 650 - 725°F
and the clay-oil mixture filtered to produce a filtrate product re-duced in contaminants. The clay contacting step may optionally be performed in a hydrogen atmosphere. The filtered product can be used for non-critical uses or further upgraded by conventional methods.

Description

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

- 2 -` -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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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 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 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.

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.

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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.)

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. 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 - 725°F 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.

2. The process as set forth in claim 1 which further comprises:
stripping the light ends simultaneously with the clay contacting step.

3. The process as set forth in claim 1 wherein:
the decolorizing clay is selected from the group consisting of Filtrol clay, Pembina clay, attapulgus clay and Fullers Earth.

4. The process as set forth in claim 3 wherein:
the amount of clay used is in the range of about 2 - 6 weight percent.

5. The process as set forth in claim 4 wherein:
the filtration step is performed at a temperature in the range of about 200 - 300°F.

6. The process as set forth in claim 1 wherein:
the clay contacting step is performed in a hydrogen atmosphere, at a temperature in the range of about 650 - 675°F.

7. The process as set forth in claim 6 wherein:
the decolorizing clay is selected from the group consisting of Filtrol clay, Pembina clay, attapulgus clay and Fullers Earth.

8. The process as set forth in claim 7 wherein:
the amount of clay used in the oil is in the range of about 2 - 6 weight percent.

9. The process as set forth in claim 8 wherein:
the filtration step is performed at a temperature in the range of about 200 - 300°F.

10. The process as set forth in claim 9 wherein:
a hydrogen pressure in the range of about 100 - 800 psig is used.

11. The process as set forth in claims 3 or 7 which further comprises the step of:
subsequent to the filtration step, hydrotreating the filtrate product to remove additional contaminants.

12. The process as set forth in claims 3 or 7 which further comprises the step of:
subsequent to the filtration step, vacuum distilling the filtrate product to remove additional contaminants.

13. The process as set forth in claims 3 or 7 which further comprises the step of:
subsequent to the filtration step, contacting the filtrate product with sulphuric acid and removing additional contaminants in an acid sludge.