CA1174630A - Reclaiming used lubricating oil - Google Patents

Abstract

Abstract of the Disclosure A novel method for purifying used oil comprising removing ash forming components and then vacuum fractionating the oil.

Description

30195C~

~ECLAI~IING ~SED LUBRICATING OI~
This invention relates to a method for reducing the ash-content of lubricating oil containing ash-~orming components. In another aspect this invention r~lates to a method for the treatment of used lubricating oils to obtain purified oil suitable for use as fuel oil, in grease formu-lations, or in the preparation oE lubricating oil formulations.
Background of Invention Used motor oil has been estimated as being generated in the United States at a rate of about l.l billion gallons per year. Some of this used oil has been used as furnace oil and some has been used on rural dirt roads for d~st control. Much of the oil has been merely dis-carded in sewers, dumps, and back alleys. With the ever decreasing petroleum reserves, it becomes more and more essential that this used oil be saved and u.sed as long as possible.
One major obstacle to re-use of used oil in many applications involves the presence of various ash-formi.ng impurities that remain dis-persed in the oil due to the very effective dispersant characteristics of the additives in modern day lubricant systems.
~ laterials contained in a typical used crankcase oil that are considered to contribute to the ash content of the oil include sub-micron size carbon particles, inorganic materials such as atmospheric dust, metal particles, lead and other metal compounds originating from fuel combustion. Besides lead, which is generally present at concentrations of l.O to ~.5 weight percent, appreciable amounts of zinc, barium, cal-cium, phosphorus and iron are also present in the used crankcase oil.

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1~74630 Examination of the used oil under an optical microscope at 600 magnifica-tions reveals the very effective dispersant characteristics of modern day lube oils. The particle size of the particulates is estimated from this microscopic examination to be 0.1-1.0 microns with virtually no occurrence of agglomerates in the oil.
The presence of the ash-forming components in used oil puts limits on the extent to which the material can be used economically with-out ecological damage. For example, reuse of the used oil as fuel oil can give rise to serious atmospheric pollution when the oil contains in excess of one percent lead. Also, such fuel oil often results in burner and refractory maintenance costs that offset the purchase price differ-ential between used oil and regular furnace oil.
Clearly, it is in the national interest to provide economical ways of removing the impurities from used oil so that it can be reused practically.
Recently, a technique of purifying used oil has been developed in which the used oil is reacted with an aqueous solution of an ammonium salt treating agent, then the water phase is removed, and the resulting oil phase-containing mass is separated by filtration. Such a technique is described in U. S. Patent No. 4,151,072.
It is an object of this invention to provide an improvement on the method disclosed in U. S. Patent No. 4,151,072.
In another aspect it is an object of the present invention to provide a means of obtaining from used motor oil a plurality of oil frac-tions suitable for reuse in forming blended oil formulations.
One embodiment of this invention provides a means of obtaining such useable fractions without the use of hydrotreating.
Another embodiment of this invention provides a means of reduc-ing the severity of the conditions to which a hydrotreating catalyst mustbe exposed to produce the desired fractions.
Still another object of the present invention is to increase the catalyst life of the employed hydrotreating catalyst.
Still yet another object of the present invention is to reduce the amount of hydrogen needed in the reclaiming process.

1:174630 Summary o the Invention In accordallce with the present invelltioll, a process is provided for the production of an essentially ash free oil slock from a lubricating oil containing ash-forming components comprising;
(1) contacting said lubricatillg oil with an a~ueous solution of a treating agent comprising an ammonium salt capable of reacting with the ash forming components and rerldering tbem removable under conditions sufficient to disperse said agent in said lubricating oil and react said agent with ash-forming components of said lubricating oil;

(2) removing a major portion of the water from the mixture resulting from combining said aqueous solution and said lubricating oil;

(3) separating so]ids from the oil resulting from st~p (2) to obtain a partially purified oil;

(4) vacuum distilling the partially purified oil with steam dilution to obtain a plurality of boiling range oil fractions; and

(5) decolorizing and deodorizing at least one of said plurality of different boiling range oil fractions using at least one step selected from the group consisting of hydrotreating and clay treating.
Des,cription of the Drawing FIGURE 1 is a schematic representation of a specific process employing the present invention.
Detailed Descriytion of the Inven~ion The present invention is applicab'le to the de-ashing of oil in which ash forming components can be rendered removable by the treating age~t. The invention is particularly applicable to the purification of oils that have been used for internal combustion engine lubrication purposes such as crankcase oils, e.g., in gasoline engines or diesel ; engines. Other sources of used oils include steam-turbine oils, trans-mission and gear oils, steam-engine oils, hydraulic oils, heat-transfer oils and the like.
The oils generally used for preparing internal combustion engine lubricants are the refinery lubricating cuts from paraffin-base, mixed-,.: . ,- . . . .

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- ` 1174630 base, or naphth~l1ic crudes. Tileir v:iscoSj ties are generally in the range of from about 100 to about 1,800 SUS at 100F. The oils also contain various additives such as oxidation il1hibitors (e.g., barium, calcium and 7inc alkyl thiophosphates, di-t-butyl-p-cresol, etc.), antiwear agents (e.g., organic lead compounds such as ~ead diorganophosphorodithioates, zinc dialkylditlliophosphates, etc.), rust inhibitors (e.g., calcium and sodium su]fonates, etc.) disp^rsants (e.g., calcium and barium sulfonates and phenoxides, etc.), viscosity index improvers ~e.g., polyisobutylenes, poly-(alkylstyrenes), etc.), detergents (e.g., calcium and barium salts of alkyl benzene sulfonic acids) and ashless-type detergents such as alkyl-substituted succinimides, etc.
If desired, water entrained in the untreated used lubricating oil can be removed before use of same in the process of this invention.
Such a separation can be readily achieved by removal of the water phase which may occur in the storage tanks for the used lubricating oil.
- The ammonium salt treating agents which are useful in the process of the present invention are tllose selected from the group con-sisting of ammonium sulfate, ammonium bisulfate, ammonium phosphate, diammonium hydrogen phospXate, ammonium dihydrogen phosphate, ammonium thiosulfate, ammonium polyphosphates such as ammonium metaphosphate, urea sulfate, guanidine sulfate, urea phosphate, and guanidine phosphate, and mixtures thereof. Said treating agents can be formed in situ if desired as, for example, by combining ammonia and/or ammonium hydroxide with sulfuric acid and/or phosphoric acid and/or an ammonium hydrogen sulfate or phosphate, i.e., ammonium bisulfate, diammonium hydrogen phos-phate, and/or ammonium dihydrogen phosphate. When the treating agent is formed in situ, the reactants empioyed can be introduced at the same time, or one after the other.
Although the concentration of treating agent in the aqueous solution of treating agent is not critical and more dilute solutions can be used, the economics of the process are enhanced by the use of rela-tively concentrated solutions in order that the amount of water to be removed subsequently will not be great. Generally, the concentration of . .

` 117463~
treating agent in the aq-leous so]ution will be ~ithin t~le range of about 30 to about 95 weight percent, typically about ~0 ~eight percent7 of that in an aqueous solution that is saturated with the treating agent at 25C.
Frequcntly some water will be found in uscd oil, and in these instances tbe conccntration of the treating agent can be adjusted accordingly.
In the process oE this invention, the treatin~ agent should pre-ferably be employed in an amount at least suEficient to react with essen-tially all of the metal constituents in the used oil. Although the weight : ratio of the treating agent to the oil can vary greatly, depending in part upon the nature and concentration of metal-containing components in the oil and on the particular treating agent employed, generally it will be within the range of about 0.002:1 to about 0.05:1, most often being within - the range of about 0.005:1 to about 0.015:1, and typically being about0.01:1. Although larger amounts of treating agent can be used, in most instances this would be wasteful of treating agent.
Water can be removed from the mixture resulting from the com-bination of the aqueous solution and the oil by any suitable means. Dis-tillation is the preferred method of removing water. Generally, the dis-tillation is carried out at a temperature in the range of about 100 to 20 about 140C and a pressure in the range of about 5 to about 25 psig for a period of time sufficient to effect removal of a major portion of the water. Light hydrocarbons contained in the oil that boil under the dis-tillation conditions, e.g. gasoline, will be, of course, separated from the oil along with the water.
The solids are separated from the treated oil in any suitable -manner. Currently filtering is the preferred technique. Generally, it is desirable to use a filter aid in the iiltration process. Filter aids which are useful in the practice of the invention include those selected from the group consisting of diatomaceous earth, perlite, and cellulose fibers. The presently preferred filter aid is diatomaceous earth.
It is further currently preferred to expose the oil to a heat soak at a temperature in the range of about 320C to about 420C prior to the filtration step. Such a procedure is disclosed in U. S. 4,247,389, ,, .

~17~;30 Typically, such a heat soak is conducted at pressures in the range of about atmospheric to about 400 psig.
The partially purified oil is next vacuum distilled to produce a plurality of different boiling range oil fractions. The vacuum distil-lation should be carried out under conditions which mini~ize cracking and coking of the oil.
An especially preferred technique for achieving that end is to provide high dilution with superheated steam in the vacuum fractional distillation column. The temperature in the fractionation column is kept below 700F. Preferably, the maximum temperature is no greater than 650F
and the pressure is in the range of about 90 to 200 mm Hg, most preferably about 93 to 103 mm ~g (1.8-2.0 psia). The steam added to the bottom of the column below the point of introduction of the oil feed is generally used in amounts equal to about 0.05 to 0.2 weight percent of the oil feed, preferably about 0.1.
In an especially preferred embodiment superheated steam is also added to the oil feed prior to the passage of the oil feed through the heater where it is heated for transfer into the fractionator. The use of steam in this fashion adds dilution and helps minimize decomposition of the oil in the heat exchanger coils of the heater.
The various fractions obtained can be collected in storage vessels and further processed separately or in a combined fashion as desired. If processed separately, the fractions needing additional pur-ification can be passed through a single decolorizing and deodorizing zone in a blocked out fashion, i.e., one after the other as desired.
Alternatively, the separate fractions can be passed through decolorizing and deodorizing zones especially adapted for that specific fraction.
Even if the various lubricating oil fractions are recombined and passed through a single decolorizing and deodorizing zone, the products obtained are generally of a much better quality than those obtained in the prior art processes in which the heavies were not removed before the final purification.
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The bottoms from thc fract:ionation column ~hile being heavier than wllat would generslly be used in blending lu~ricating oils are rela-tively metal free and can be further processed for other uses, such as heavy gear oils or asphalt additives. If desired the heavies can be sent to a cracking zone to prod~lce fuel ~ractions.
The dccoloriæing and deodorizing step or steps can be carried out by any of severa] processcs useful for that purpose, for example, clay treating or mild hydrogenation. Altllough the hydrogenation method is pre-ferred, it is more expensive and satisfactory products can be obtained by using only clay treating.
In clay-contacting, excellent results are attainable by mixing the oil with from 0.2 to about 1 lb of clay per gallon oil, preferably 0.3 to 0.5 lbs/gallon, and heating the resultant slurry to from 300 to 700F, preferably about 500 to 650F for periods of 30 minutes to 3 hours. Times longer than about 3 hours encourage oxidation of khe oil, while larger ouantities of clay merely incrcase the amount of waste which must be disposed of. Oxidation may also be controlled by introducing an inert atmospllere SUC}I as H2 or N2 into the tank. Alternatively, a steam sparge will also provide excellent results, since, in addition to con-trolling oxidation, it helps to sweep impurities from the oil. It is pre-$erred that the oil and clay be separated as soon as possible after the contact time is met to obtain a better product. Separation can be accom-plished by any well-known separation method such as filtering. Any acid-activated bleachin~ clay such as Filtrol grade 2 ~, Superfiltrol~ or Tonsil~ was found to provide satisfactory results.
Mild hydrogenation as an alternative process to effect odor and color improvement of the reprocessed lubricating oil is preferred if ade-quate quantities of hydrogen are available at practical prices. Typical conditions of hydrogenation to produce a satisfactory finished lubricating oil with neutral odor and light color include an operating temperature oE
about 600-700F with a temperature in the range of 650F preferred. The hydrogen partial pressure may range between about 400 and 900 psig, with a preferred level near 650 psig. Space velocities may vary between about 0.5 and 2.5 vol/vol/hr with a preferred value of 1. Hydrogen rates of from 250-2000 Standard Cubic Foot/Barrel (SCFB) have been found satis-' 11746~30 factory, with a rate of 1500 SCFB bcirlg pre~erred. The catalyst employedmay be substan~ially any of t~le kno~n hydrofinisllillg catalysts which pro-mote desired reactions whicll result in the removal of undesirable unsatu-rated materials and polar compounds. ~ mctal of.Groups II-A, II-B, VI-B, or VIII of the Periodic Table of ~lements, an oxide of a metal of Groups II-A, II-B, VI-B, or VIII, or a stllfide of a metal of Groups II-A, II-B, VI-B, or VIII is satisfactory as catalyst material. Typical catalysts are cobalt molybdate and nickel molybdate on an inert substrate such as alumina.
A further understanding of the present invention will be pro-vided by the following description of a preferred embodiment of the present invention as illustrated in ~IGURE 1.
Referring now to FIGURE 1j used oil from storage tank 101 is passed via line 102 to heater 103 and contactor 106. Aqueous treating agent such as diammonium hydrogen phosphate from makeup tank 105 is introduced via line 104. If desired, agent precursors ammonia, phos-phoric acid, and water can be introduced into the heated oil downstream of heater 103, thereby forming the treating agent in situ in line 102 and contactor 106. The oil from heater 103 is passed in admixture with treating agent into the first agitated contactor 106 wherein the mixture is maintained under agitation for a time sufficient to react with at least a portion of the ash-forming components in the oil. Preferably, a recycle stream is passed tkrough conduit 152 to pump 153 and then through heater 154 before its return to contactor 106, thereby providing heat and agitation to the contents of the contactor. Stirring means also can be employed.
Thereafter the mixture is passed via conduit 107 t0 second con-tactor 109, which is maintained at a temperature in the range of about 110 to about 140C, for a time sufficient to effect distillation of a major portion of the water and at least some of the light hydrocarbons present therein. Thus, while retained in contactor 109, essentially all of the water and at least a portion of the light hydrogen components of the mixture are removed via line 110 and passed to separator 111 wherein ; a hydrocarbon layer and a water layer are allowed to form. The hydro-carbon phase can then be transferred via line 112 to storage ll3. The , .

---` 1174630 water layer can be ren-oved and discarded or employed for any desired purpose. Preferably, a recycle str~am is passed through conduit 155 to pump 156 and then through heater 108 beforc its return to contactor 109, thereby providing hcat and agitation to the contents of the reactor.
Stirring means also can be employed.
The resulting mixture comprising a hot oil phase which is essentially free of water is passcd via conduit 114 to a third contactor whercin it is subjected to agitation and a temperature in the range of about 140 to about 200C to remove additional water and lighter compo-nents. Preferably, a recycle stream is passed through conduit 157 topump 158 and then through heater 115 before its return to contactor 116, thereby providing heat and agitation to the contents of the contactor.
Any residual water and light hydrocarbons are removed from contactor 116 via line 159.
If desired, any one or two or all of contactors 106, 109 and 116 can be provided with jackets heated by steam or other source of heat to aid in maintaining the contents of the contactors at the desired temperatures. Any one or t~o or all of contactors 106, 109 and 116 can be equipped with stirrers to provide additional agitation. In an oper-able but presently less preferred arrangement, a stirrer in any one or more of the three contactors can be used instead of the recycle system employed with the corresponding one or more of the three contactors, any additional heating being provided by heaters in the line ahead of the contactors and/or by heated jackets around the contactors. Also, if desired, any one or two or all of conduits 103, 107 and 114 can feed into the recycle stream for contactors 106, 109 and 116, respectively, i.e., into conduits 152, 155 and 157, respectively, instead of directly into the respective contactor as shown. In one preferred technique the feed in conduit 102, rather than being passed directly into contactor 106, is passed into conduit 152 at the inlet side of pump 153. In a still more preferred technique, pump 153 is a high-volume pump that will cause the oil to flow in the turbulent flow range so as to promote heat transfer and decrease scaling in the conduit 152.
The heated oil from contactor 116 is passed via conduit 117 through heater 163 to a fourth contactor 164 wherein the mixture is sub-- ~ lo li74~30 jectcd to agitation at a temperature in ~hc range of about 320 to about 420~C for a period of time su:Eficient to result in a product which when later filtered will contain less ash than it would contain if it had not been so heated. Prefcrably, a recycle stream is passed through conduit 165 to pump 166 and then through heater 167 before its return to contactor 164, thereby providing heat and agitation to the contents o~ contactor 164.
Any residual water or light ccmponellts can be removed from contactor 164 via line 168.
Treated oil from contactor 164 is passed through conduit 169 through a cooler 170 wherein the oil is cooled to a temperature in the range of about 150 to about 180C and then passed into a fifth contactor 171 wherein it is admixed with filter aid provided via conduit 118, prefer-ably as a slurry in light hydrocarbons provided from makeup tank 119. In a presently, preferred embodiment, not illustrated, the oil from contactor 164 is cooled at least in part as a result of passing in indirect heat - exchange with the feed passing through line 102 whereby the heat in the oil in line 120 is used to heat the feed oil in line 102.
Following admixture of filter aid, the resulting mixture is passed via line 172 to firter 121, which optionally can be precoated with filter aid. The use of the heat soak step of the present invention can in many cases result in a reduction in the amount of filter aid required for a suitable filtration rate.
Filter cake from filter 121 is removed via line 147 and option- ;
ally passed to furnace 148 from which, following burning or calcination, at least a portion of the resulting ash containing filter aid can be passed to waste via line 149 or recycled via conduits 120 and 160 to slurry makeup tank 119 for further use in the system. Fresh filter aid is added through conduit 160. Light hydrocarbons for use in preparing the slurry can be recovered from the integrated process and can be passed to tank 1.19 via conduit 151.
The filtered oil, being essentially free of ash-forming constit-uents is then combined with superheated stcam and passed through a heater 200. The steam diluted oil feed is then passed into the 1.ower portion of a vacuum fractionation column 201. Superheated steam is passed into an even lower portion of the vacuum fractionator via line 203. Distillation r `

-- ~174630 in the prcscllce of this ste~m pcrmits the vaporization and distillation of lube oil at moderate vaCIIUm and at ~emI)erature conditions sufficiently low to avoid thermal decomposition of the oil fractions.
The preferred fractiona~ing column illustrated in FIGURE 1 comprises five staggered 50% cut baffle pla~es 202, i.e., plates extend-ing halfway across the column, located beneath the point of entry of the oil feed and above the point of entry of thc operating steam provided via line 203. The oil feed combined with mixing steam is introduced into the column by way of a fced distributor 204 comprising a channel formed by a plate with weirs extending around approximately a third of the cir-cumference of the column. The column 201 is divided into three main zones by total drawoff plate 205 and partial drawoff plate 206. Both plates 205 and 206 are provided with liquid overflow chimneys. Partial drawoff plate 206 is provided with a second liquid overflow chimney having an upper height between the upper height of the first chimney of that plate and the intermediate height of the partial drawoff plate. Four areas of static mixing packing material 207-210 are provided. Any suitable low pressure drop static mixing packing can be used. Examples include intalox saddles, sulzer, pall rings, and the like. Preferably, area 210 comprises a layer of KOCH Sulzer above a layer of intalox saddles such as Norton 40 Intalox.
The layer of Intalox servés to protect the Sulzer from gum~ning and plugging.
The illustrated column allows for the withdrawal of two side-stream fractions via lines 211 and 212, an overhead fraction via line 213, and a bottoms fraction via line 214.
Portions of the fraction removed via line 212 are returned as liquid to liquid distributors in the column via lines 215 and 216. The overhead fraction is passed via line 213 to a condenser 217 where steam and lighter hydrocarbons are separated from the oil to provide an over-head oil fraction. A portion of the overhead fraction is recycled via line 218 to a liquid distributor placed above packing 207.
The recycle provided via line 216 provides additional reflux to the system. The recycle provided via line 215 is employed to assure that the tray 205 does not run dry.

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1:174630 In a prcferred elllbodiillel-lt, the ste.~m Erom accumul;1tor 217 along with thc light hydrocarbons is cooled alld passed to a phase separator where the hydrocarbons and water are separated. The recovered water is then recycled to provide at least part of tbe wa~er used for producing operating steam for the frac~ionatiotl column.
In a preferred embodiment, the fractionaLor is shaped as illus-trated in FIGURE l. The section of the fractiona~or containing the trays and the packing is about 5 feet in diameter and about 40 feet in length.
The section containing the 50% cut baffle plates is about 27 inches in diameter and about 6 feet in length. The section for bottoms accumulation beneath the operating steam inlet is about 18 inches in diarneter and 3 feet in length.
The plate of the feed distributor extends inwardly to a point defined by an arc which at all points lies 18 inches from the adjoining wall of the column. The plate extends outward from about a third of the - circumference of the column wall. Weirs extend upwardly from the interior edges of the plate about 18 inches high.
The first layer of packing 210 is located about 42 inches from the bottom of the 5 foot diameter portion of the column. That layer of packing preferably comprises a l foot layer of Norton 40 Intalox below a 2 foot layer of KOCH Sulzer.
The next layer of packing 209 is located about 72 inches above the top of packing 210 and comprises a 4 foot layer of KOCH Sulzer. The packing 208 is a 4 foot bed of KOCH Sulzer in turn located about 42 inches above the top of packing 209. And finally packing 207 is a 6 foot bed of KOCH Sulzer located about 69 inches above the top of packing 208.
This particular fractionator design allows for s~eady operation under a wide range of operating conditions. For example, it can be readily operated so that the overhead can be as much as 40 weight percent of the oil feed. Alternatively, it can be operated so that either cut #2 or cut #3 can be as much as 50 weight percent of the oil feed. Further, the column can be operated when as much as 15 weight percent of the oil feed is removed as bottoms. Typical examples calculated for the amounts of various streams under those extremes of operation is presented in Table I.

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~1~4~;30 The typical and preferred operating ranges for the demetalizing and filtering steps of the preferred oil purification process are as set forth in the table on the page of U. S. 4,247,389 that contains columns 9 and 10.
The cuts resulting from the vacuum fractionation can be sub-jected to decolorization and deodorization as deemed necessary. The present invention is particularly useful since in many cases the oil cuts that will be used in a blending operation will not require the decolori-zation and deodorization step. The present invention is further advanta-geous in that the fractionation results in fractions which have been sufficiently devolatilized that they will generally meet flash point standards without further treatment.
A particularly preferred technique of purifying fractions from the vacuum fractionator, especially for the bottoms fraction, involves passing the fraction through a bed of adsorbent and then through a hydro-treater. The adsorbent can be bauxite, activated carbon, silica gel, clay, activated alumina, combinations thereof, and the like. The adsor-bent serves to effect breakdown and decomposition of the ammonium salts of sulfonic acids and the ashless detergents contained in the oil. The adsorbent further serves to collect a small portion of the resulting products and thus precludes passage of such undesirable decomposition products to the hydrotreater. Such adsorbents can be regenerated by conventional means and reused.
Preferably, the adsorbent contains about 0.2 to about 20 weight percent of at least one metal selected from the group consisting of Group VIB and Group VIII metals, this weight percent being based on the total weight of modified adsorbent. This modified adsorbent can be prepared by impregnation of the adsorbent with an aqueous solution of a water-soluble compound of a Group VIB or Group VIII metal, followed by evaporation of water. Water-soluble compounds presently preferred for this use are iron compounds such as ferric ammonium oxalate, ferric ammonium ci-trate, ferric sulfate, and ferrous ammonium sulfate.
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From ~he foregoing it should be apparent that the present inven-tion provides an improved method of purifyirlg ui-ied lubricating oil.
Reasonable variations and modifications can obviously be made without departing from the spirit and scope of the presently disclosed invention.

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Claims (9)

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

1. A process for the production of an essentially ash free oil stock from a lubricating oil containing ash-forming components comprising:
(1) contacting said lubricating oil with an aqueous solution of a treating agent comprising an ammonium salt capable of reacting with the ash forming components and rendering them removable under conditions sufficient to disperse said agent in said lubricating oil and react said agent with ash-forming components of said lubricating oil;
(2) removing a major portion of the water from the mixture resulting from combining said aqueous solution and said lubricating oil;
(3) separating solids from the oil resulting from step (2) to obtain a partially purified oil;
(4) vacuum distilling the partially purified oil with steam dilution to obtain a plurality of boiling range oil fractions; and (5) decolorizing and deodorizing at least one of said plurality of different boiling range oil fractions using at least one step selected from the group consisting of hydrotreating and clay treating.

2. A process according to claim 1 wherein all said decolorizing and deodorizing is achieved by clay treating.

3. A process according to claim 2 wherein only the bottoms from the fractionating column are subjected to decolorizing and deodorizing.

4. A process according to claim 1 wherein at least one of the oil,fractions from step (4) is not subjected to decolorizing and deodor-izing.

5. A process according to claim 1 wherein said ammonium salt is diammonium hydrogen phosphate.

6. A process according to claim 5 wherein the product of step (2) is subjected to a heat soak step prior to carrying out step (3), said heat soak step comprising heating said oil at a temperature in the range of about 320°C to about 420°C for a period of time sufficient to decompose at least a major portion of any ammonium salts of sulfonic acid or dialkyl-dithiophosphoric acid contained therein.

7. A process according to claim 6 wherein the bottoms from said vacnum distillation are passed through an adsorbent and then through a hydrotreater.

8. A process according to claim 7 wherein said adsorbent comprises clay.

9. A process according to claim 1 wherein various fractions are collected and individually subjected to hydrotreatment by being passed through the same hydrotreating zone in succession.