A Method Of Reducing The Lead Content Of A Used Hydrocarbon Lubricating Oil By Adding Methylethyl Ketone To Separate The Resulting Mixture Into A Coagulated Insoluble Phase

Abstract

A method of reducing the lead content of a used hydrocarbon lubricating oil comprising mixing a used hydrocarbon lubricating oil having a lead content of at least about 0.5 wt. percent with methylethylketone, separating the resulting mixture into coagulated insoluble layer and a clarified hydrocarbon lubricating oil-methylethylketone layer, said mixing and said separating conducted under anhydrous conditions at a temperature between about 65.degree. and 95.degree.F.

Description

BACKGROUND OF INVENTION

Hydrocarbon lubricating oil compositions used as lubricants in internal combustion engines contain additives which serve as dispersants so that accumulated impurities such as metallic salts particularly lead salts remain dispersed in the oil rather than settling as a sludge in the crankcase. Although the function of the dispersants is a distinct advantage when the hydrocarbon oil composition is employed as a lubricating agent, it becomes a distinct hindrance in the disposal of the used oil composition or the reclaiming thereof, in that it prevents the ready separation of lead from the used oil.

Used oil such as that accumulated from the automobile service stations is sometimes disposed of by burning. The removal of lead prior to disposal is desirable for ecological reasons, for during burning, lead if not removed, is volatilized into the atmosphere in substantial quantities, the remainder entering the soil, both outlets being undesirable. In addition, if the oil is to be reused via a reclaiming process, lead must be removed therefrom in order to render it commercially saleable.

In the past, various materials have been employed to remove lead impurities such as reacting the impurities with N-phenyl alkylol amines as disclosed in U. S. Pat. No. 2,568,583. However, these materials are of relatively high cost, normally require the employment of elevated temperatures during separation, and are not reuseable.

SUMMARY OF INVENTION

We have discovered and this constitutes our invention a low cost method of readily separating lead from hydrocarbon lubricating oil compositions used in internal combustion engines which is conducted at moderate temperatures, preferably room temperature, utilizing a particular agent which is readily recoverable for reuse.

DETAILED DESCRIPTION OF THE INVENTION

Specifically, the invention comprises contacting a hydrocarbon lubricating oil having a dispersed lead content of at least about 0.5 wt. percent, normally between about 0.5 and 1.5 wt. percent with methylethylketone (MEK) under anhydrous and mixing conditions at a temperature between about 65.degree. and 95.degree.F. utilizing a volume ratio of methylethylketone to hydrocarbon oil of at least about 2:1, preferably between about 2:1 and 3:1, separating the resultant mixture into an upper layer of clarified lubricating oil and methylethylketone and a bottom coagulated, insoluble layer containing the bulk of the lead impurities under said anhydrous and temperature conditions. Separation can be effected, for example, by either gravity separation which is normally conducted for a period of between about 4 and 10 hours or centrifuging, either means followed by decanting or filtering to spatially separate the layers. The methylethylketone is readily recovered from the separated oil-methylethylketone layer by standard means such as distillation, leaving essentially a lead free (less than about 0.1 wt. percent) clarified dark oil. The recovered methylethylketone is either forwarded to storage for eventual reuse or recycled directly to the mixing stage for immediate reuse. Another means of separating the clarified oil-methylethylketone layer from the coagulated insoluble would be employing a high speed centrifuge and then upon the completion of centrifuging spatially separating the layers, and recycling the recovered methylethylketone for reuse or storage.

The separated lead containing sludge is normally deoiled by extraction with solvent, for example, additional methylethylketone, pentane or heptane to yield a dry powder of relatively high lead content, e.g., 20-40 wt. percent. The thus recovered lead can be containerized and the resultant lead filled container can be employed as land fill or the lead can be accumulated and reprocessed for industrial use.

Hereinbefore and hereinafter the term "anhydrous" denotes water content less than about 0.5 wt. percent.

In regard to mixing of the methylethylketone and used oil, this can be accomplished by standard means such as "in line" blending, paddle mixing, etc., and is normally conducted for only that period of time which is required to insure thorough contact of the oil and ketone, e.g., 0.5-10 minutes.

The process of the invention may be conducted on a batch or continuous basis. An example of a continuous operation would be to employ initial "in line" blending using adjustable proportioning pumps to provide the proper used oil-methylethylketone mix and introducing the mixture into a series of settling vessels. At least two separation vessels are employed in the continuous procedure with the flow of the mix, for example, being alternated between settling vessels, e.g., one being filled while recovering the separated layer from the other. Another approach would be to connect a number of settling vessels in series, introducing the mix into the first of the series and withdrawing the clarified oil-ketone layer from the last of the series. Still another approach would be to feed the used oil-methylethylketone mix directly into a number of high speed centrifuges and alternating such feed between the centrifuges.

In the method of the invention it is theorized the methylethylketone functions to solubilize a yet unidentified resin, said resin believed to provide a chemical bond between the lead impurity and lube oil dispersants, the latter maintaining the lead impurity in the dispersed state. Once this bond is broken via solubilization the lead and other metallic materials become desolubilized, coagulate and separate from the oil-methylethylketone layer.

In regard to the material and unexpected features of the invention, the ability of methylethylketone to function in desolubilizing lead impurities is surprising since many materials utilized in the solvent refining of virgin lubricating oils such as pentane, heptane, benzene and N-methyl-pyrrolidone were not effective in facilitating the removal of lead impurity from the used lubricating oil. Further, even closely related acetone is substantially unsatisfactory in lead impurity removal.

Another surprising material feature of the invention is that normally in purifying processes elevated temperatures of the order of 100.degree. to 300.degree.F., preferably above 150.degree.F., are employed. In contrast, our procedure preferably employs ambient temperatures, that is, of the order of 65.degree. to 95.degree.F., and therefore, affords a substantial saving in process costs since normally heat does not have to be supplied to the desolubilizing reaction. Temperatures above about 95.degree.F. in our procedure result in somewhat reduced lead removal.

Another feature of the invention is that a volume ratio of methylethylketone to used oil of at least about 2:1 is advantageous. Volume ratios substantially below 2:1 such as 1:1, except when high speed centrifuge separation is employed, result in a treated oil have an unsatisfactory high lead content, that is, above about 0.1 wt. percent.

Still another material feature is the requirement that the desolubilization be conducted under anhydrous conditions, i.e., the initial oil-ketone mixture have a water content below about 0.5 wt. percent. Higher water contents prevent separation of the lead impurity layer. If the oil to be treated has a water content which would bring the oil-ketone mixture above the aforementioned maximum value, it is subjected to a dehydration pretreatment. Such dehydration can be accomplished by standard means such as by passing used oil over a hot surface to flash off the water, by blowing with hot air or with steam above about 250.degree.F. or by vacuum treatment at ambient or elevated temperatures, preferably at about 150.degree.F.

Hereinbefore and hereinafter by the term "used hydrocarbon lubricating oil" it is intended to mean oils removed from the crankcases after extended use in operating internal combustion engines, wherein the lead therein has been "solubilized" by dispersant additive(s) in said oil and the initial lead content therein is at least about 0.5 wt. percent.

The used hydrocarbon lubricating oil compositions contemplated herein are derived from the hydrocarbon lubricating compositions, normally lead free, comprising between about 85 and 99 wt. percent hydrocarbon lubricating oil and between about 1 and 15 wt. percent additives. These additives in addition to the aforementioned dispersants normally comprise one or more of the following: pour depressors, anti thickening agents, antioxidants, corrosion inhibitors, VI improvers, and oiliness agents.

Examples of lube oil dispersants are overbased calcium alkylsulfonates, overbased sulfurized calcium alkyl-phenolates and polyisobutylene (e.g. 50 to 200 carbons) succinimide of tetraethylenepentamine.

The base oils employed in formulating the initial lubricating oil compositions from which the used oils are derived include a wide variety of hydrocarbon lubricating oils such as naphthenic base, paraffinic base and mixed base mineral oils or other hydrocarbon lubricating oils such as derived from coal products, synthetic oils, e.g., alkylene polymers such as polypropylene, polyisobutylene, of a molecular weight between 250 and 2500. Advantageously, the lubricating base oils employed have an SUS viscosity at 100.degree.F. between about 50 and 2000.

The following examples further illustrate the method of the invention but are not to be construed as limitations thereof.

EXAMPLE I

This example illustrates the method of the invention as practiced as a batch process.

The used crankcase lubricating oil employed in the following procedure was obtained from the waste oil disposal tank at a service station catering to automobiles. It was derived from motor oils which initially contained no lead. The used oil was introduced into a mixing kettle where it was stirred at ambient temperature to assure uniform distribution of materials therein and then stored in 1-gallon cans. Before use, the gallon cans were vigorously shaken on a mechanical shaker to redisperse any separated material and thereby assure uniform samples. The thus mixed and shaken used motor oil was subjected to analysis and the following was typically found:

Used crankcase oil results Lead as Pb, wt. % 1.25 Sulfated ash, wt. % 2.95 Viscosity at 100.degree.F., SUS 319 Viscosity at 210.degree.F., SUS 61.6 Viscosity Index 158 Pour, .degree.F. -35 Chlorine, wt. % 0.95 Bromine, wt. % 0.30 Water, wt. % 0.4 Fuel Dilution 0.8

The overall procedure employed was as follows:

To a cylinderical tank there was sequentially charged the used crankcase oil and methylethylketone. The resultant mixture was mixed to assure uniform contact between the used oil and ketone. The mixing was then ceased and the mixture was left undisturbed until coagulated insolubles settled to the bottom of the vessel leaving a clarified used oil MEK upper solution. The separated insolubles represented about 10 percent of the total volume and the used oil MEK solution about 90 percent. Coagulation was relatively rapid. It took no longer than six hours under laboratory conditions. This translated into commercial operating conditions would be expected to be about 24 hours. The clarified methylethylketone-oil solution was transferred to a distillation unit and methylethylketone was distilled off and returned to storage for reuse. The clarified oil residue was forwarded to storage for subsequent disposal. As an alternative, centrifuging was also employed.

Following Table I represents the procedure of the invention utilizing gravity separation and demonstrates in Run E the gravity separation of 1:1 volume ratio is ineffective. Table II represents the method of the invention utilizing centrifugal separation and gravity separation. Table II further demonstrates in comparative Run F the ineffectiveness of comparative known lube oil solvent materials. Table III shows the property difference between the untreated used oil and the clarified oil resulting from treatment of the used oil via the method of the invention.

TABLE I

METHYLETHYLKETONE TREATMENT OF USED CRANKCASE OIL

Run A B C D E Ingredients Methyl- ethyl- ketone, 45 40 34 1400 25 mls. Used Oil, mls. 5 10 17 600 25 (1.25 wt. % Pb) MEK/Waste Oil, wt. 9:1 4:1 2:1 2.3:1 1:1 ratio Treating Tempera- 70-80 70-80 70-80 70-80 70-80 ture, .degree.F. Sludge Separation yes yes yes yes no Tests on Clarified Oil Lead as Pb, wt. % 0.01 0.01 0.01 0.02 -- Sulfated Ash, wt. % -- -- -- 0.64 --

TABLE II

METHYLETHYLKETONE CLEAN-UP OF USED CRANKCASE OIL

Reference Run Used Oil F G H I Ingredients Methyl- ethyl- ketone, mls. -- -- 600 2800 800 Benzene, mls. -- 600 -- -- -- Used Oil, mls. -- 600 300 1400 800 Solvent:Oil, -- 1:1 2:1 2:1 1:1 wt. ratio Treating Temp., .degree.F. -- 70-80 70-80 70-80 70-80 Sludge Separation -- partial yes yes yes Method Sludge Sepa- -- gravity gravity gravity centri- ration fuge Tests on Recovered Oil Lead as Pb, wt. % 1.25 0.88 0.10 0.03 0.06 Sulfated Ash, wt. % 2.95 2.55 -- -- 0.81

TABLE III

EFFECT OF MEK TREATMENT (RUN D) ON OIL PROPERTIES

MEK treated Used Oil 2:1 MEK:used oil SUS Viscosity, 100.degree.F. 319 283 SUS Viscosity, 210.degree.F. 61.6 55.4 Viscosity Index 155 133 Pour, .degree.F. -35 -40 Sulfated Ash, wt. % 2.95 0.64 Lead as Pb, wt. % 1.25 0.02 Chlorine, wt. % 0.19 0.07 Bromine, wt. % 0.30 0.05

EXAMPLE II

This example illustrates the method of invention as practiced as a continuous process.

From two one-gallon storage vessels there was respectively drawn used crankcase oil and methylethylketone via proportioning pumps for inline blending of the materials at the desired ratio. The proportioning pumps were adjusted to provide the desired volume ratio of used oil to methylethylketone and also the desired flow rate. The mixture was then passed through 5 to 6 receiving vessels connected in series. The coagulation of the insoluble was accelerated by the inline blending and was completed in the receiving vessels. Rapid settling occurred providing a clear, dark brown used oil methylethylketone affluent equivalent to that obtained in the batch operation. The clearest fluid from the last vessel was continuously directed to a rotary evaporating distillation unit where the methylethylketone was distilled off leaving the treated used oil. The methylethylketone was returned to the methylethylketone storage vessel for reuse. The recovered oil was transferred to oil storage for subsequent disposal.

The test data and results are reported below in Table IV. The data further demonstrates the importance of maintaining a MEK:Used Oil volume ratio of at least about 2:1 under gravity separation conditions as can be seen from the high lead content in No. 5 and No. 6 Receivers of Run L.

TABLE IV

METHYLETHYLKETONE TREATMENT -- CONTINUOUS OPERATION

Run J K L MEK:Used Oil Ratio 2.2:1 2:1 1.1:1 liters/hr. (MEK+ 2.05 5.75 2.05 Used Oil) Total hours 4.25 6.0 8.5 Processed Volume, 13 34.5 16.3 liters Type Separation Gravity gravity gravity Temperature, .degree.F. 80-90 80-90 80-90 Lead as Pb., wt. % Original Used Oil 1.25 1.25 1.25 Receivers as Filled No. 1 (4liters) 0.039 0.040 0.043 No. 2 (2 liters) 0.069 0.040 0.068 No. 3 (2 liters) 0.065 0.040 0.094 No. 4 (2 liters) 0.057 0.035 0.093 No. 5 (2 liters) 0.043 0.035 0.163 No. 6 (2 liters) -- -- 0.200

EXAMPLE III

This example illustrates the ineffectiveness of closely related materials to methylethylketone in separating lead from used crankcase oil.

The procedure of Example I (gravity separation) was repeated utilizing pentane, heptane, N-methyl-1-pyrrolidone, N-methyl-2-pyrrolidone and acetone. These materials were substantially ineffective in coagulating and settling out the dispersed lead and other suspended materials.in the used crankcase oil.

EXAMPLE IV

This example illustrates the importance of conducting the reaction under essentially anhydrous conditions. The procedure of Example I was employed utilizing a 10 volume percent water content in a 1:2 volume ratio of used oil to methylethylketone. An emulsion was formed which was stable for several days with no significant sludge coagulation being evidenced.

Claims

We claim:

1. A method of reducing dispersed lead impurities in a used hydrocarbon lubricating oil composition having dispersed lead content of at least about 0.5 wt. percent consisting essentially of mixing under anhydrous conditions said composition with methylethylketone utilizing a methylethylketone to used oil composition volume ratio of at least about 2:1, forming a methylethylketone-clarified oil upper layer and a lead containing insoluble lower layer, separating the resultant methylethylketone-oil upper layer from said lead containing insoluble lower layer, and recovering from said methylethylketone-clarified oil upper layer, a lubricating oil composition of reduced lead content, said mixing, said forming, and said separating conducted at a temperature of between about 65.degree. and 95.degree.F.

2. A method in accordance with claim 1 wherein said forming comprises passing the used oil-methylethylketone mixture to a settling tank and maintaining said mixture in said tank until said methylethylketone-clarified oil layer is formed as an upper layer and said lead containing insoluble layer is formed as a lower layer, said separating comprising subsequently decanting from said tank said methylethylketone-clarified oil upper layer, and said recovering comprising passing the decanted methylethylketone-clarified oil upper layer to a distillation zone, recovering methylethylketone as distillation overhead, recovering a lubricating oil composition of reduced lead content as a distillation residue, and recycling the recovered methylethylketone to said mixing step.

3. A method in accordance with claim 1 wherein said forming comprises centrifuging the used oil-methylethylketone mixture to separate methylethylketone-clarified oil solution as an upper layer and lead containing coagulated insolubles as a lower layer, decanting said methylethylketone-clarified oil upper layer from the centrifuge, said recovering comprising passing the decanted methylethylketone-clarified oil upper layer to a distillation zone, recovering methylethylketone as distillation overhead, recovering a lubricating oil composition of reduced lead content as dis-tillation residue, and recycling the recovered methylethylketone to said mixing step.

4. A method in accordance with claim 1 wherein said mixing comprises in-line blending the methylethylketone and used oil composition, said forming and said separating comprising passing the resultant mixture into a series of settling vessels so that at least one of said vessels is continuously filling with said mixture while simultaneously continually removing from another vessel formed methylethylketone-clarified oil upper layer, and said recovering comprising passing to a distillation zone the removed methylethylketone-clarified oil upper layer, recovering methylethylketone as distillation overhead, recovering lubricating oil composition of reduced lead content as distillation residue, and recycling the recovered methylethylketone to said mixing step.