CA1209512A - Used oil re-refining - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Used oils, especially used lubricating oils which are normally considered waste and are discarded or burned, are reclaimed for reuse by a re-refining procedure involving the steps of:

(a) heat soaking the used oil;

(b) optionally stripping the heat soaked oil under conditions sufficient to remove the low boiling conversion products from the heat soaker, (c) distilling the heat soaked oil;

(d) passing the distillate through a guard bed of activated materials;

(e) hydrotreating the guard bed treated dis-tillate under standard hydrotreating conditions.

If the used oil to be rerefined contains a quantity of water and/or fuel fraction which the prac-titioner considers sufficiently large to be detrimen-tal, the used oil may be subjected to a dewatering/defueling step prior to being heat soaked.

Description

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DESCRIPTION OF THE INVENTION

2 Used oils, especiall~ used lubricating oils

3 which are normally discarded or burned as waste, are

4 reclaimed for reuse by a re-refining procedure com-prising the steps of~

6 (a) heat soaking the used oil;

7 (b) stripping the heat soaked oil under 8 conditions and employing procedures sufficient to g remove the low boiling conversion products from the heat soaker, so as to reduce the Total Acid Number 11 (TAN), Toluene Insolubles (T.I~) and halides content of 12 the oil;

13 (c) distilling the heat soaked, stripped 14 used oil to produce a distillate and a residue;

(d~ passing the distillate through a guard 16 bed of activated material;

17 (e) hydrotreating the guard bed treated 18 distillate to produce a refined oil product suitable 19 for use as lube oil base stock.

Alternatively, the rerefining process can be 21 practiced effectively even when the stripping step (b) 22 recited above i5 omitted. In such a case a greater 23 burden is imposed on the guard bed/ but the overall 24 process still produces a rerefined oil which closely matches virgin base oils in physical properties and 26 chemical composition.

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1 If the used oil to be rerefined contains a 2 quantity of water and/or fuel fraction which the prac-3 ti~;oner considers sufficiently large to affect the 4 heat soaking operations (by requiring higher pressures than desirable) the used oil may be subjected to a 6 dewatering/defueling step prior to being heat soaked.

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8 Used oils, particularly those used as lubri-g cating oils, are normally considered waste once they have been used for their intended purpose, (e.g., 11 crankcase oils etc.) as lubricants and are normally 12 either discarded or burned, either disposal method 13 having deleterious environmental ramifications asso-14 ciated therewith.

Consequently, as an alternative, methods for 16 reclaiming the used oil molecules have been developed 17 to reduce the environmental hazard associated with 18 either disposal or burning of the oil, and to conserve 19 valuable oil molecules which can be refined into base stock having a quality equivalent to virgin base 21 stocks. Acid~clay treating is of diminishing appli-22 cability due to the complexity of the additives 23 employed in modern lubr;cating oils, as well as in 24 light of the sludge disposal problem associated with acid/clay treatment.

26 The Phillips (PROP) process combines 27 chemical demetallization with clay/hydrotreating as 28 finishing steps. Used oil is mixed with an aqueous 29 solution of, for example, diammonium phosphate which reacts with metal contaminants to form metallic phos-31 phates which separate from both water and oil due to 32 low solubility, The demetallized oil, after filtration ~f~ 2 1 using a filter aid and heating, is con~acted with a 2 guard bed of clay and hydrotreated over a catalyst, for 3 example Ni/Mo and stripped. (See USP 4,151,072).

4 The chief disadvantage of the PROP tech-nology is the disposal of the large amount of solid 6 wastes associated with the ilter cake and spent clay7 7 In addition, a large amount of waste water, origînated 8 from the chemical solution, is generated by this tech-g nology.

Vacuum distillation followed by hydrotreat-11 ing has been proposed in the litera~ure for used oil 12 rerefiningr The process is characterized by pollution-13 free operation without incurring sludge and oily-clay 14 wastes. However, the drawback of this process is that contaminants in the distillate, originated from lube 16 additives and/or degraded oil, cannot be removed to a 17 low enough level during the distillation step. As a 18 result, hydrotreater fouling becomes a serious problem.

19 Dewatering/defueling extraction/distilla-tion/clay contacting and/or hydrofinishing has also 21 been suggested ~See USP 3,919,076, USP 4,073,719 and 22 USP 4,073,720. In these processes, various kinds of 23 extraction solvent are used, e.g., propane or a mixture 24 of alcohol and ketonel to reduce coking and fouling precursors in the dewatered/defueled used oil prior to 26 the vacuum distillation. The resulting distillate is 27 further upgraded by clay contacting and/or hydrofinish-28 ing. The chief disadvantage of this approach is the 29 complexity of the solvent recovery systems which require high energy consumption, and generate waste 31 chemicals via lealcage from the unit and waste/solvent 32 separations.

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1 In addition to the above-mentioned waste oil 2 re-refining technologies, distillation of used oil in a 3 thin-film or wiped film evaporator (TFE or WFE) to 4 recover lube dis~illate is also known in the art.
"Recent Technology Development in Evaporation 6 Re-Refinery of Waste Oil" r Bishop and Arlidge;
7 "Thin-Film Distillation as a Tool in Re-Refining Used 8 Oil" Pauley; both of these articles in Third Inter-g national Conference on Waste Oil Recovery and Reuse, 1978. However, the distillate has to be further pro-11 cessed in order to make an end-product equivalent to 12 the virgin basestock in quality performance. Heat 13 soaking is also known in the industry as a method for 14 breaking up additive molecules and precipitating ~5 polymers. (See USP 4,033,859). Predistilling a used oil 16 preferably by steam stripping said oil, within the 17 temperature range of between 480F and 650F (about 18 249-345C) for at least 4 hours to remove NOX, light 19 oil components and residual water from the stock prior to distilling the oil in a thin-film evaporator as 21 described in USP 4,101,414.

23 Figure 1 is a schematic of the processing 24 step sequence of the present invention.

Figure 2 is a schematic of the processing 26 step sequence of the present invention including the 27 stripping of the heat soaked oil. For the sake of 28 simplicityt the pumps, heaterst piping, etc. which 29 would be employed in the process, and whose location and mode of operation would be within the scope of the 31 ability of those skilled in the art, have been omitted, 32 as have the subsequent down stream processing steps ~z~c~

1 which would be or could be practiced o~ the various 2 effluent streamsA

3 In Figure 1 used oil would be fed via line 1 4 to an optional dewatering/defueling uni~ (2) operating under appropriate conditions (to be recited in detail 6 below)~ Dewatering~defueling can be omitted if the 7 water/fuel concentration in the used oil is determined 8 to be low enough so as not to be detrimental to the 9 overall process, e.g., when the used oil is a trans-former oil already of low water and fuel fraction 11 content; however, in most instances, used lube oils of 12 the crankcase oil type, will require a 13 dewatering/defueling step. This dewatering/defueling 14 unit can be a single unit or a number of units, each one designed to handle a separate aspect of the 16 dewatering and defuelingO Water and fuel overheads are 17 carried off via lines (3) and 14). The 18 dewatering/defueling operation may be preceded by a 19 filter unit (OPT-2) to remove any grit, solids, metal filings, etc. which may be present in the used oil. The 21 dewatered/defueled used oil is passed via line (5) to 22 a heat soaker (6) and thence via line (7) to a dis-23 tillation unit (8) which will not coke up under the 24 conditions employed (explained in detail below).
Residue from unit (8) is removed via line (8~). The 26 distillate from this unit is sent via line (9) to a 27 guard bed (10) wherein the sludge and halide content is 28 reduced. Optionally, a second heat soaker (lO(A)) may 29 precede the guard bed. Effluent from the guard bed (10) is sent via line (11) to a hydrotreater unit (12) 31 wherein the oil is processed to produce an oil product 32 stream (13) which is equivalent to a virgin oil and can 33 be employed as a base oil for the production of oil 34 products such as lube oil, transformer oil, refriger-ator oil, turbine oil, white oil, etc.

~C~5~2 1 In Figure 2 used oil would be fed via line 1 2 to an optional dewatering/defueling unit (2) operating 3 under appropriate conditions (to be recited in detail 4 later). Dewatering/defueling can be omitted if the water/fuel concentration in the used oil is determined 6 to be low enough so as to be not detrimental to the 7 overall process, (e.g., when the used oil is a trans-8 former oil already of low water and fuel fraction g content); however, in most instances, using used lube oil of the crankcase oil type, dewateriny/defueling 11 will be needed. This dewatering/defueling unit (2) can 12 be a single unit or a number of units each one designed 13 to handle a separate aspect of the dewatering and 14 defueling. Water and fuel overheads are carried off via lines (3) and (4). The dewatering/defueling unit (2) 16 may be preceded by a filter unit (OPT-2) to remove any 17 grit, solids, metal filings, etc. which may be present 18 in the used oil. The dewatered/defueled used oil from 19 unit (2) is passed via line (5) to a heat soaker ~6) and thence via line (7) to the light ends stripper 21 tower (8) wherein the i-10, preferably i-5, most 22 preferably i-3 wt.% fraction of the used oil is removed 23 via line (9). Although the heat soaking ~6) and light 24 ends stripper tower (8) are represented by two separate units it is entirely within the scope of this invention 26 that a single integrated unit can be used to accomplish 27 both the heat soaking and light ends removal. The 28 effluent from this step is sent via line (10) to a 29 distillation unit (11) which will not coke up under the conditions employed (explained in detail below).
31 Residue from unit (11) is recovered via line (ll(a)).
32 The distillate from the unit is sent via line (12) to a 33 guard bed (13) wherein the sludge and halides content 34 is reduced. Optionally, a second heat soaker (13(a)) may precede the guard bed. Effluent from the guard bed ~iLZ~5~LZ
~ 7 --1 (13) is sent via line ~14) to a hydrodreating unit 15 2 wherein the oil is processed to produce an oil product 3 stream (16) which is equivalent to a virgin oil and can 4 be employed as a base oil for the production of oil product such as lube oil, transformer oil, refrigerator 6 oil, turbine oil, white oil, etc. Each processing step 7 in the above-identified sequence is treated in depth 8 helow.

g THE PRESENT INVENTION
.

A used oil re-refining process has been dis-11 covered which produces a re-refined oil which is com-12 parable to virgin and can be processed into lube, 13 transformer, refrigerator, white oil or other 14 speciality oil. The process is not marked by the operational or environmental drawbacks of prior used 16 oil reprocessing procedures.

17 The re-refining process of the present 18 invention comprises:

19 (a) heat soaking the used oil;

(b) stripping the heat soaked oil at atmo-21 spheric or reduced pressure to remove the low boiling 22 conversion products;

23 (c) distilling the heat soaked, stripped 24 oil;

(d) passing the distilled oil through a 26 guard bed of activated material;

27 (e) hydrotreating the guard bed treated 28 oil.

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1 If necessary the used oil can be dewatered/defueled 2 prior to the heat soaking step.

3 Alternatively, the rerefining process can be 4 practiced effectively even when the stripping step (b) recited above is omittedO In such a case a greater 6 burden is imposed on the guard bed, but the overall 7 process s~ill produces a rerefined oil which closely 8 matches virgin base oils in physical properties and 9 chemical composition.

USED OIL FEEDSTOCKS

11 Basically, any used oil which in the past 12 has been recovered for burning or for reclamation or 13 has been discarded after use can be the subject feed-14 stream for the present invention. The used oil stream which will be rè-refined is predominantly a lube oil 16 (e.g. crankcase oil, etc) but may contain minor quan-17 tities of other specialty oils, transformer oil, white 18 oil, refrigerator oil, etc. and mixtures thereof, but 19 is preferably used lube oils. The used oils subjected to the rerefining procedure of the present invention 21 are preferably relatively free of PCB's for envion-22 mental reasons. Representative of feedstreams which can 23 be employed are the two streams A and B below (Table 1) 24 which are recovered Canadian lubricating oil (motor oil) and are offered merely as illustrations and not by 26 way of limitation. The compositional slate is reported 27 for a target l0 grade lube oil. The compositional slate 28 will, of course9 be different if the target product is 29 other than a 10 grade lube oil, for example a 5 or 30 grade oil.

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g 3 Feedstock A Feedstock B
4 June 1980 API 25.0 25.7

6 Density, kg/dm3 @ 15C 0.9037 0.8996

7 Viscosity, cSt @ 40C - 50.4

8 Composition g Water (LV~) 5 12 Fuels (LV%) 12 15 11 10-grade distillate (LV%) 68 57 12 Residue 15 16 13 Sulphur, Wt.% 0.49 0 39 14 Nitrogen, wppm n.a. 550 Halogen (Cl/Br), ppm 770/n.a. 2500/340 16 PCB, ppm <0.1 0.4 17 Metals ppm , 19 Zn 1229 1025 Ca 13~6 1010 21 Mg 295 166 23 DEWATERING AND DEFUELING T~E USED OIL

24 Removal of water, fuel fraction light hydrocarbons and light vacuum gas oil from used oils is 26 a procedure well known in the industry. Typically, such 27 dewatering and defueling is performed by atmospheric 28 and/or vacuum distillation, although other procedures 29 such as settling, decantation or passage through molecular sieves or treatment with drying agents or ~;~Q$5~Z

1 selective absorbents or extractants can also be 2 employed. However, for economical and environmental 3 reasons, distillation, be it atmospheric and/or vacuum, 4 is preferred. As an option and depending on the quality of the used oil being processed, the used oil feed 6 stream can be passed through a filter or other 7 separation means to reduce the level of entrained 8 solids (i.e., dirt, metal filings, sand, etc.) which g may be present in the oil prior to the dewatering-defueling step so as to reduce the potential for damage 11 to processing equipment and therefore eventually 12 produce a higher quality re-refined basestock oil.

13 In performing such atmospheric and/or vacuum 14 distillation dewatering and defueling of used oils standard state of-the-art procedures, techniques and 16 operating conditions may be employe~. ~s is readily 17 apparant this dewatering/defueling step will be prac-18 ticed only when necessary, i.e., only when the used oil 19 to be rerefined, possesses water or light hydrocarbon or light vacuum gas oil fraction which the practitioner 21 is desirous of removing. In some instances the water 22 content and/or fuel fraction content of the used oil 23 can already be low enough so that this step can be 2~ omitted (when the used oil is, e.g., a transformer oil). This step will, therefor, be most usually prac-26 ticed. Typical dewatering/defueling process parameters 27 are distillation temperature, (in the range of 80C to 28 300C) distillation pressure, (in the range of 0.5 kPa 29 to atmospheric) reflux ratio (from 0.5/1 to 5/1) and unit throughput presently employed in industry.
31 Dewatering is practiced under conditions, and to the 32 extent necessary to remove as much of the water 33 present, if any, as possible from the used oil, 34 preferably about 90~, more preferably about 95%, most preferably about 100% of the water present in the used 5~2 1 oil stream being processed~ During defueling the amount 2 Of "fuel fraction" removed, if any, from the used oil 3 and the combination of condi~ions employed are set by 4 the final characteristics~ i~e., the grade of the lube oil distillate which is desired to be recovered after 6 the subsequent distillation step (covered in detail 7 below). For example, a larger fuel fraction, i.e., a 8 high fuel concentration, can be tolerated in the oil

9 when the target is a light oil distillate Conversely, if a heavier grade oil is sought a lower concentration 11 of fuel can be tolerated. The exLent and severity of 12 the defueling step is left to the discretion of the 13 practitioner to be set in response to the oil charac-14 teristics (gradel target of the product to be recovered. In short, the topping severity, i.e., 16 atmospheric equivalent tempera~ure (AET) is regulated 17 by the volatility target i.e., the grade of the lube 18 oil to be recovered. In addition to~ or as an altern-19 ative to conventional distilla~ion in standard distil-lation towers, thin ilm evaporators (TFE), or wiped 21 film evaporators (WFE~ may be employed. These pieces of 22 equipment, TFE or WFE, have been patented by many 23 inventorsO Their principles of operation and typical 24 operating conditions are described in detail in "Recent Technology Development in Evaporative Re-Refining of 26 Waste Oil" by J. Bishop and D. Arlidge and in 27 "Thin-Film Distillation as a Tool in Re-Refining Used 28 Oil" by J. F. Pauley, both articles appearing in Third 29 International Conference on Waste Oil Recovery and Reuse, 1978. See also USP 4,073,719, USP 3,348,600 and 31 USP 4,160,692 inc~p~ b~ b~_~f~4~

32 As an example, dewatering and defueling of a 33 typical Canadian used oil by a batch distillation 34 (atmospheric followed by vacuum) is presented in Table 2. In this example, a 390C atmospheric equivalent ~LZ~5~
- ~2 -1 temperature (AET) is required to meet an SAE 10-grade 2 oil volatility target. It is, of course, clear that 3 different temperature (AET~ will be required when 4 different grades of oil are the target products, 6 DEWATERING/DEFUELING OF USED OIL(l) BY BATCH DISTILLATION

7 Dewatering Defueling(2) 8 Distillation Temperature g (Vapour), oC 100 228

10 Distillation Pressure~ kPa 101 0.887 (atmospheric)

11 Atmospheric Equivalent

12 Temperature, oC 100 390

13 Yield Range on Raw

14 (Whole) Used Oil

15 LV% (Material Removed) i-5 5-17

16 (1) Feedstock A in Table 1

17 (2) The dewatered oil was used as the feed for

18 defueling operation.

19 Table 3 shows the results obtained on dewatering/defueling of a Canadian used oil feedstock B
21 (Table 1) using a continuous pilot atmospheric and 22 vacuum (A&V) distillation unit. In many instances 23 vacuum distillation alone will be adequate~

$ 5 12 2DEWATERING/DEFUELING OF USED OIL (1) 3BY CONTINUOUS A&V DISTILLATION

4 ~ Defueling 5 Throughput, m3/d 2~2 1.1 6 Temperature~ C ~bottom)250 270 7 Pressure, kPaatmospheric 3.3 8 Reflux Ratio No 3/1 g Yield of Overhead13.8 12.4 (Wt.% on Feed) 11 ~1) Feestock B in Table 1 12 (2) It contained 83 wt.% water, 17 wt.% fuels.

13 Dewatering and defueling of the used oil 14 feedstock A using Luwa TFE and Pfaudler WFE are presented in Table 4. In both TFE and WFE
16 distillations, water and fuel streams were obtained as 17 overheads in a single pass operation.

19 DEWATERING/DEFUELING OF RAW USED OIL (13

20 Equipment Lu~a TFE Pfaudler WFE

21 Throughput (feed), kg/m2-hr 344-402 180-288

22 Distillation Temperature

23 (hot oil), C 276 264

24 Distillation Pressure, kPa 1.33-2.0 ~2) 4

25 Overhead Yield on Feed, LV% 17.0 1609

26 (1) Feedstock A in Table 1

27 (2) Pressure measured at the exit of an external con-

28 denser ?5~2 :L4 -3 It has been discovered that for the 4 successful practice of the instant used oil re-refining process scheme, dewatering and defueling is best 6 followed by a heat soaking step. Further, this heat 7 soaking is best conducted at a temperature range of 8 from about 250C to 340C, preferably 280C to 320C, g most preferably 300C to 320C for a time sufficient to maximize halide (chloride), phosphorus and sludge 11 precursor removal, such times typically being in the 12 range of from about 15~120 minutes, preferably about 3D
13 to 120 minutes.

14 The heat soaked dewatered/defueled oil is then optionally treated so as to reduce Total Acid 16 Number (TAN), toluene insolubles (T.I.) and halides 17 content of the oil prior to its being distilled. This 18 treatment may take any of the commonly practiced forms 19 for the removal of materials contributing to TAN, T.I.
and for the removal of halides from oil. Preferably, 21 however, the treatmen~ practiced involves stripping the 22 oil so as to remove the relatively low boiling com-23 ponents produced after the heat soaking step. This 24 stripping may be conducted under atmospheric pressure or vacuum. A stripping gas may also be used. Stripping 26 conditions used should be such that the about i-10 wt.%
27 fraction preferably the i-5 wtr% fraction, most pre-28 ferably the i-3 wt.% fraction of low boiling point

29 conversion product materials generated during ~he heat soaking step is removed.

31 The stripped material is then subjected to a 32 coke formation resistant distillation step. The dis-33 tillation is conducted in a manner such that coking in ~ZQ~5~2 1 the unit employed is kept to a minimum under the con-2 ditions of residence time, temperature and pressure 3 selected to give a distillate having the desired end 4 pointO Distillate end point at this step is set by determining whether a light, medium or heavy grade oil 6 is the final material desired upon completion of the 7 overall process. Selection of distillate end point as 8 well as the distillation conditions employed are Ieft 9 to the practitioner to set in response to the final product requirements and the particular distillation 11 apparatus employed in light of the prior recited con-12 straint that coke formation be kept to a minimum. This 13 distillation step is preferably carried out in a coke 14 formation resistant unit such as the cyclonic distil-lation tower for waste oil re-refining described in 16 U. S. Patent No. 4,140,212, or in a thin film 17 evaporator (TFE) or a wiped film evapora~or (WFE) due 18 to their higher efficiencies.

19 The key advantage of the preferred TFE (or WFE) distillation is its ability to fract;onate 21 unstable material under high temperature/short resi-22 dence time conditions with minimal degradation or 23 coking. Thus, a unit such as this is ideally suited and 24 preferred for distillation of used lube oil~

Although the majority of foreign materials 26 in the dewatered/defueled used oil, i.e., additives~
27 ash, sludge and wear metals, go to the bo~toms during 28 the distillation step, a certain amount of the lube 29 additives (original or decomposed) having a boiling range similar to that of the lube distillate tends to 31 distil over along with the distillate. In addition, a 32 small fraction of these materials which boils outside 33 of the distillate boiling range may get entrained in 34 the distillate during the distillation stage. As a ~2~5~Z

1 result of these effects, the distillate is contaminated 2 with a high concentration of phosphorus (50-300 ppm3 3 and sludge precursors. The latter tend to form a sludge 4 (1,000~3,000 ppm) during high temperature processing (i.e., hydrotreating). Because of the presence of these 6 materials, process problems such as hydrotreater 7 catalyst deactivation and reactor plugging are 8 encountered when contaminated distillate is hydro-g treated over conventional catalystsO These phosphorus compounds and æludge precursors are identified as the 11 major causes of catalyst deactivation and bed plugging~
12 respectively. These deficiencies associated with the 13 processing sequence comprised of dewatering, defueling, 14 distillation and hydrotreating can be overcome by heat soaking and stripping the dewatered/defueled used oil 16 prior to distillation. Heat soaking causes the majority 17 of the phosphorus compounds and sludge precursors to 18 form high boiling point materials which essentially all 19 go with the residue during the distillation step. This is possible because the dispersant and antifoulant 21 materials in the original lube additive package keep 22 the sludge suspended in the oil which, in turn, 23 prevents equipment fouling. The optional stripping step 24 removes low boiling point conversion products from the heat soaker which conversion products are themselves 26 converted into sludge during the distillation step.

27The beneficial effects of heat soaking prior 28to distillation on distillate quality, in terms of 29phosphorus and sludge contents, is shown in Table 5.
30Dewatered/defueled used oil from a Luwa TFE (Table 3) 31was continuously heat soaked in a pilot plant set-up at 32atmospheric pressure, at two temperatures (280C and 33320C) and three residence times (1/~, 1 and 2 hours) 34 to define the optimum heat-soaking conditions. The tests were carried out with a 0.95 cm I.D. stainless ~L2a~s~

1 steel tube coil (located in a high temperature sand 2 bath) in a once-through mode. No pressure drop across 3 the heat soaking coil was observed after about 369 4 hours of smooth operation at 320C. Distillations of used oils, both raw and heat soaked, were carried out 6 with a lab size Pope WFE (1,100 cm2 evaporation area) 7 to define the effect of heat soaking on distillate 8 quality. Results indicated that relative to the non g heat soaked distillate (base case), the distillate derived from the heat~soaked oil (320C, 1/2 hour resi-11 dence time) threw down about 75% less sludge and con-12 tained only 3-8 ppm of phosphorus (versus 240 ppm for 13 the base case). Phosphorus removal increased with 14 increasing heat soaking temperature. At 320C, the distillate quality in terms of phosphorus and sludge 16 lay-down improved slightly with increasing residence 17 time.

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2 distillation were further demonstrated in a Pfaudler 3 WFE (Table 6). The Pfaudler WFE with its internal de-4 entrainment device produced a much better quality dis-tillate from the (pilot plant) heat soaked used oil 6 than the lab Pope WFE. A comparison of Tables 5 and 6 7 indicates that at comparable phosphorus levels~ the 8 Pfaudler distillate had a significantly lower sludge g content. However, it must still be noted that either piece of equipment, after the heat soaking of the 11 dewatered/defueled used oil, gave a distillate product 12 of significantly reduced phosphorus and sludge content 13 when compared with the non-heat soaked material and 1~ that the heat soaked material from either unit is fully acceptable for use in the present process.

19Dewatered/Defueled Used Oils (1) .
20 Heat Soaking NO ~2) YES (3) 21 Temperatur~, C - 320 22 Residence Time, Hr. - 0.5 23 WFE Distillation .
24 Temperature, C 278 . 288 25 Pressure, kPa 0.19 0.28 26 Phosphorus, ppm 337 3 27 Sludge, ppm @ 310C 2860 113 28 (1) Derived from feedstock A in Table 1~
29 (2) This feed was dewatered/defueled in the Pfaudler WFE (See Table 4).
31 (3) This feed was dewatered/defueled in a batch dis-32tillation unit (See Table 2 for conditions).

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1 Another example illustrating the benefits of 2 high temperature heat soaking prior to WFE distilla~ion 3 is shown in Table 7. A large scale pilot plant heat 4 soaking ~0,62 m3/D) oE A&V dewatered/defueled oil (from Table 3) was carried out over a wide temperature range 6 using a heating coil in connection with a heat soaker.
7 After heat soaking, the oil was pumped to the WFE where 8 it was fractionated into a lube distillate and a g residue. Results obtained on the lab (Pope) WFE dis-tillation of heat soaker feed (non-heat soaked) are 11 also shown in the same table for comparison purposes.
12 As shown in Table 7 r distillate phosphorus content 13 decreased with increasing heat soaking temperature. A
14 low heat soaking temperature ~i~e. <280C) resulted in high phosphorus content in the WFE distillate which 16 would give a high rate of catalyst deactivation in the 17 downstream Hydrotreating operation, ~n the other hand, 18 too high a heat soaking temperature (340C or above) 19 resulted in a complete decomposition of dispersant type additives (they boil at 340C with decomposition). As a 21 result, sludge suspended in oil (about 2 vol.%) started 22 to settle. A non-agitated horizontal heat soaker, while 23 it did function, eventually plugged with settled sludge 24 due to areas of liquid stagnation. This potential operating problem can be effectively avoided by the use 26 of a preferred vertical heat soaker or a horizontal 27 unit augmented with agitationO In addition, excess 28 amount of light-ends was formed and on-spec viscosity 29 distillate (29-31 cSt @ 40C) could not be produced as heat soaking temperature exceeded 340C~ From this it 31 is seen that the optimum heat soaking temperature is 32 between about 300C-320C.

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:) ~ ." ~ ; >. .,~
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u~ h O ,1 ~ ~ ~:: a) C E M C:l Ci 3:: ~n a~ ~ ~ ~ ~ ~ ~ ~ ~ o U~
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O Q) ~ E4 O ~ ELI .~ 1 O ~ ~1 ~1 ~ ~ ~
3 ~ ~n E~ ____ 5~2 1 Some inspections of the residue made from 2 th~ Pfaudler WFE using heat-soaked used oil feed is 3 given in Table 8. A study indicated that this residue 4 could be disposed of by blending (until about 8 LV% of the blend is residue) with 85/100 penetration paving 6 asphalt without adversely affecting the asphalt product 7 quality ~Table 9). From this it is seen that the pro-8 cess of the present invention does not have the serious g hazardous waste disposal/environmental problem asso-ciated with it as do typical clay/acid used oil 11 refining techniques.

13 INSPECTIONS OF WFE ~EAT SOAKED) RESIDUE ~1) 14 Penetration @ 25C, dmm >400 15 Flash point tCOC), C 278 15 Viscosity @ 100C, cS~ 127 17 135C, cSt 48 18 Solubility in Trichloroethylene, Wt.~ 98.55 19 Acid No., mg RO~/g 3.8 Metals,_ppm 21 Pb 9000 22 Mg 1100 23 Ca 4700 24 Zn 4100 26 Ba 256 27 ~1) Derived from feedstock A in Table 1 5~2 - :23 -1TABL~ 9 2QUALITY OF ASPHALT/USED OIL RESIDUE BLEND tl) 3Target 5Blend Min. Max, 6 85/100 Penetration Asphalt (Vol %) 91.6 7 Used ~il Residue (Vol %) 8.4 8 Penetration ~ 25C, dmm 166 150 200 g Viscosity @ 135C, cSt 254 200 Flash tCOC)~ C 312 260 11 Ductility @ 40C, cm >50 10 12 Solubility in Trichloroethylene, 99.5 99.5 13 wt.%
14 Acid No. mg KOH/g 0.5 0.8 Thin-film Oven Test .
16 Change in Weight, % +0.03 1.3 17 Retained Penetration @ 25C 62.7 42 1~ Ductility @ 25C, cm >150 100 -19 (1) See Table 8 Light Ends Removal 21 The amount of contaminants such as residual 22 sludge tor toluene insolubles) and halides which are 23 present in the distillate produced in the distillation 24 step (explained in detail above) can be reduced even more by removing, prior to the distillation step, the 26 low boiling point conversion products formed during the 27 heat soaking ~previously described) of the 28 dewatered/defueled used oil. This removal of the low 29 boiling point conversion products can be accomplished by any procedure known to remove such material but 31 preferably by strippîng either under atmospheric 5~2 1 cond;tions or under reduc,ed pressure. Steam or other 2 conventional stripping streams such as helium, 3 nitrogen, hydrogen, light hydrocarbon gases or flue 4 gases, etc., can be used as the stripping gas for light ends removal. The about i-10 etc. wt.% fraction 6 preferably the i-5 wt.% fraction most preferably the 7 i-3 wt.% fraction of the heat soaked dewatered/defueled 8 used oil is removed by this stripping step prior to 9 distillation. This light end removal procedure may be practiced either integrated into the heat soaking step 11 or as a separate, subsequent procedural step. Light 12 ends stripping conditions of temperature ranging from 13 150C to 320C, pressure ranging from 0.2 kPa to 14 atomspheric, and/or stripping stream ranging from 0.5 kmol/m3 to 5 kmol/m3 can be used.

16 Data in Table 9-A show that by removing the 17 about i-3 wt. % fraction of a laboratory ~batch) heat 18 soaked dewatered/defueled Canadian used oil, the 19 toluene insoluables content of the WFE (laboratory unit designed by Pope Scientific) distillate was reduced to 21 about 100 ppm, Total Acid Number (TAN), toluene 22 insolubles ~TI) and ha~ides were also significantly 23 reduced. While mild topping slightly increased the 24 distillate viscosity, the distillate volatility (by GCD) was significantly improved (decreased) by removing 26 the about i-3 wt. % of the heat soaked oil.

~2~5 ~

Heat Soaking 5 Conditions (2) Dewate ed/defueled Used Oil (1) 6 Temperature, C 304 311 330 7 Residence Time (hrs) 8 Pressure, kPa Atmospheric 63 68 g Light-ends Treatment RefluxedRemovedRemoved Light-Ends 11 Wt.% Removed - 3 3 12 TAN, mg KOH/g - 7.1 11.5 13 WFE (Lab) Distillate (3) 14 Toluene Insolubles, ppm 328 103 91 TAN, mgKOH/g 0.60 0.38 0~32 16 Chloride/Bromine, ppm 110/7771jS8 60/37 17 Viscosity~ cSt @ 40C 31.2931.88 18 Volatility, % off @ 368C 9~5 5,5 19 (1) Produced in Luwa TFE (See Table 4) (Feed stock A) (2) 1 hour on temperature with N2 agitation ~batch 21 operation) 22 (3) Feed to WFE is heat-soaked, dewatered/defueled 23 used oil, with or without light end removal.

24 The beneficial effect of heat soaking with light-ends removal (i-3 wt.%) was further demonstrated 26 in a continuous pilot heat soaker connected in series 27 with a packed stripping unit. The oil from the heat 28 soaker passed through the stripper countercurrently to a flow of nitrogen stripping gas. Heat soaked oils, with and without light-ends removal, were subsequently ~ 26 -1 fractionated in the lab using the Pope WFE to produce 2 10-grade distillate. Some inspections of the resulting 3 distillates are shown in Table 9-B.

= _ 7 Heat Soaking 8 Conditions (2) Dewatered/defueled Used Oil (1) 9 Temperature, C --------------320-------------Pressure ~ -----Atmospheric-----~---11 Residence Time, hr --------------1~2-------~-----12 Light-Ends Treatment Unstripped Stripped(3) 13 Wt. % Removed - i-3 14 WFE Distillate Toluene Insolubles, ppm 312 127 16 TAN, mgKOH/g 0~82 0.39 17 Phosphorus, ppm 7 5 .
18 (1) Produced in Luwa TFE (See Table 4) (Feed stock ~).
19 (2) Carried out in a 0.95 cm I~D. stainless steel coiled tubing.
21 (3) Stripping gas (N2) to oil ratio = 2.2 kmol/m3;
22 pressure = 0.3 kPa, average stripping temperatu~e 23 = 160C.

24 Results indicate that heat soaking with 25 lightends removal reduced the contaminant level in the 26 subsequent distillate. This is in agreement with 27 results obtained from the batch operation (Table 9-A).

1 Dewatered/defuelled Canadian used oil, prior 2 to and after pilot plant heat soaking (unstripped see 3 Table 9-B), was fractionated into 1 LV% cuts up to 10 4 LV% under reduced pressure to evaluate the effect of heat soaking on front-ends composition. Results in 6 Table 9-C for the first three cuts indicate that heat 7 soaking significantly increased the halides content, 8 the bromine number, and the acid number of the front-9 ends, but the increases decreased with increasing cut point.

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~, g 1 These data are in agreement with the results 2 given in Tables 9-A and 9-B which show that the WFE
3 distillate derived from feed from which light-ends were removed had lower halide content and lower acid number than the distillate obtained from the unstripped feed.
6 The preferred i-3 wt.~ fraction is about all that need 7 be removed and still show any improvement in the dis-tillate quality and not significantly adversely affect g the light distillate yield. It should be mentioned that the reduction of the halide content in the distillate 11 should benefit the downstream hydrotreating operation -12 problems associated with corrosion and plugging due to 13 formation of compounds such as hydrogen halides and 14 ammonium halides can be minimized. The high acid and bromine numbers of the heat-soaked front-ends suggest 16 that polymeric additives are decomposing into monomers 17 or larger fractions during the high temperature heat 18 soaking. It is believed that these highly acidic and 19 olefinic monomers, etc. form toluene insolubles during the distillation via some mechanism and eventually end 2~ up in the distillate. Removing these low boiling 22 materials prior to distillation should minimize this 23 effect.

24 Steam is preferred as the stripping gas because it is better than nitrogen, light hydrocarbon 26 gases, etc. for preventing lay-down of ammonium halides 27 on the top section of the heat soaker and in the vent 28 lines (which would cause plugging of the vent line).
29 The ammonium halides are formed as a result of additive decomposition during the heat soaking.

31 The severity of the defueling operation can 32 be monitored by a flash point measured on the 33 dewatered/defueled product. The Elash point was set to 34 take into account the v;scosity cut out across the heat ~L2l~$S~

- 30 l soaking (and stripping) steps, and thus to ensur0 that 2 the distillate (in the example WFE) is within the 3 viscosity specification range of the target oil 4 product.

Consequently, stripping may be conducted 6 under a wide variety of conditions of pressure and 7 temperature and stripping atmospheres, the only 8 requirement being that the conditions employed be such 9 that a sufficient fraction of low boiling point con-version products from the heat soaker be removed, 11 preferably the i~3 wt.% fraction.

12 The benefits ~o be derived from the practice 13 of the reduction in TAN, TI and halide content of the 14 oil, preferably by the employment of a stripping pro-cedure which removes the preferably about i-3 wto%
16 fraction of low boiling point conversion products from 17 the heat soaker treated used oil, is seen by reference 18 to the following process seguences which form part of 19 the present application, but which sequences were practiced on oils which had not had its TAN or halide 21 content reduced in accordance with the present inven-22 tion i.e., were not light ends stripped. From this data 23 it is seen that although a used oil re-refining process 24 which does not include a TAN, TI and halide reduction step (i.e., removal of the preferred i-3 wt.% fraction 26 of low boiling point conversion products from the heat 27 soaker treated oil) is a viable and extremely valuable 28 process yielding a quality product, the process is 29 marked by a number of operational drawbacks, i.e.
sludge formation (related to the presence of TI and a

31 high TAN) in the distillation units (defueling over-

32 head), WFE vacuum system and alumina bed/hydrotreater,

33 and generation of ammonium chloride etc., in the heat

34 soaker overheads vent lines and in the hydrotreater.

~2~ 5~;~

1 The proce~s of the present invention, therefore 2 includes a step, the express purpose of which is the 3 reduction in TAN, TI and halides by the removal of the 4 low boiling point conversion products from the heat soaker, preferably the i-3 wt.% fraction preferably by 6 stripping.

8 Distillate coming from the distillation step g but without light ends stripping was subjected to passage through a guard bed of material suitable for 11 removing various contaminants from the distillate.
12 These contaminants include halides, trace phosphorus, 13 and residual sludge remaining in the distillate after 14 distillation.

lS Various adsorbents, (Fullerls earth, 16 charcoal, lime and activated alumina) were evaluated 17 for removing contaminants from the distillate. In 18 general, solid adsorbents capable of removing phos-19 phorus, halides and residual sludge from the distil-late, having high surface area (such as those used in 21 the prior art in clay treating or which are typically 22 used in guard beds in front of hydrotreaters) can be 23 used for this purpose. (See e.g., USP 4,151,072, USP
24 3,919,076, USP 4,073,719, and USP 4,073,720) Results shown in Table 10 indicate that the most effective 26 adsorbent for the guard bed is activa~ed alumina and 27 for this reason a guard bed of activated alumina is 28 preferred. However, while activated alumina is pre-29 ferred, it must be noted that all the materials tested demonstrated some ability to remove phosphorus and 31 halides from the distillate.

5~Z
- ~2 -1 T E l 2 BATCH GUARD BED TREATING OF USED OIL DISTILLATE (1) (2) 3 Fuller's Activated 4 Feed Earth Charcoal Lime ~lumina Phosphorus, 100 6 18 30 6 ppm 7 Halogens, ppm 110 12 35 59 9 8 Surface Area, - 98 3474.5 245 9 ~3/g (13 Norske Esso 130N TFE distillate (not stripped)~
11 (2) Batch treating conditions: 250C, 1 h, 12 oil/adsorbent weight ratio 4~1, using nitrogen as 13 blanket.

14 ~oth continuous flow and static batch bed contacting can be used. However, the former is pre-16 ferred since it can be integrated with the downstream 17 hydrotreating operation. Operating conditions for the 18 guard bed which can be employed include a pressure 19 ranging from about atmospheric to about 5 MPa, (700 psi), temperature ranging from about 180 to about 21 340C preferably about 280-320C, LHSV ranging from 22 about 0.5 to about 2 v/v/hr preferably about .5-1.0 23 v/v/hr. Any inert gas can be used. However, the use of 2~ hydrogen as treat gas is preferred because of the pre-ferred integration with the downstream hydrotreater.
26 The use of hydrogen could prevent coke formation in the 27 guard bed, preferably the alumina guard bed.

28 Some sludge was observed at the top of the29 bed. The amount of sludge formed could have been reduced by light ends strippingl The removal of halides 31 (chlorides, bromides~ by light ends stripping would 32 augment the capacity of the guard bed, especially the 33 alumina guard bed.

~Z~5~Z

1 The use of activated alumina i5 preferred 2 since, in addition to adsorbing residual sludge from 3 the distillate, the alumina can also remove residual 4 phosphorus as well as high concentrations of halides (chlorides and bromides)O It is desirable to remove the 6 halides prior to hydrotreating to avoid the formation 7 of corrosive compounds such as hydrogen chloride and 8 hydrogen bromide in the hydrotreater reactor. Removal g of halides prior to hydrotreating would also minimize ammonium halide deposits in the hydrotreater exit line.
11 The effectiveness of activated alumina for removing 12 phosphorus and halides from a used oil distillate, 13 i.e., Norske Esso 130N distillate (77 ppm phosphorus, 14 90 ppm halogens) was further studied in the pilot plant~ This sample of Norske Esso 130N distillate had 16 been vacuum distilled and filtered. Adsorption was 17 carried out by passing the distillate mixed with 18 hydrogen in a continuous flow over a fixed bed of acti-19 vated alumina at ~rom 180 to 320C, 3.4 MPa H2, 1.0 LHSV and 1.5 kmol/m3 gas rate. The results shown in 21 T3ble 11 indicate that both the phosphorus and halide 22 contents of the alumina treated oil decreased with in-23 creasing temperature. At 320C, the product phosphorus 24 and the halogen content was 1 ppm and 17 ppm, respec-tively.

l fl;dQ~ , 2 3(PILOT PLANT RESULTS) 4Luwa TFE Distillate (1) 5Temperature, C (2) Feed 180 280 300 320 6 Phosphorus, ppm 77 55 6 3 7 Halogens, ppm 90 80 60 30 17 8 (1) Norske Esso 130N TFE distillate, vacuum frac-g tionated (i-95% blend) and filtered with 3 micron filter (not heat soaked, not stripped)~ This 11 pretreatment reduced the phosphorus and halogen 12 levels of the feed to the reported levels before 13 guard bed treatmen~.
14 (2) Other conditions: 3.4 MPa H2, 1.0 L~SV, 1.5 kmol/m3 gas rate.

16 The effectiveness of alumina treating a heat 17 soaked WFE distillate was also studied in the pilot 18 plant. Results shown in Table 12 indicate that once 19 again the major changes across alumina treating are removal of phosphorus, halogens and trace metals from 21 the WFE distillate.

~2~S~;~

- 35 -2 ALUMINA TREATING WFE (HEAT SOAKED) DISTILLATE

3 Conditions Feed(l) 4 LHSV - 1.0 Gas Rate, kmol/m - 7.5 6 Temperature, C - 320 7 Pressure, MPa H2 ~ 3.5 8 Inspections .
g Density kg/dm3 @ 15C 0.8703 0.8703 Viscosity, cSt @ 40C 3~.46 30.71 11 Viscosity, cST @ 100C5.17 5020 13 Total Nitxogen, wppm150 160 14 Basic Nitrogen, wppm 36 41 Sulfur, Wt% 0.25 0.23 16 Color, ASTM D8 D8 17 Phosphorus, wppm 20 <3 18 Halogens, wppm 140 61 19 Metals, ppm Pb 12 <1 21 Si 11 <1 22 Ca 7 <2 23 Zn 5 2 24 (1) Derived from used oil feedstock B. Results of ~5 dewatering/defueling and heat soaking/WFE dis-26 tilling of this feed are shown in Table 3 and 7, 27 respectively.

~z~s~

- 36 -HYDROTREATING

2 The final processing step is hydrotreating 3 the alumina treated oil over a conventional hydro-4 treating catalyst to produce the finished re~-refined base oil. The conditions used are quite similar to 6 those used in conventional raffinate hydrotreating, 7 i.e., about 260-400C preferably about 260-320C, about 8 3-11 MPa, preferably about 3-5 MPa hydrogen pressure, g about 0.5-4 LHSV, preferably about 0~5-2.0 LHSV and about 1.5-15 k mol/m3, preferably about 1.5-5.0 k 11 mol/m3 gas rate. Suitable catalysts for this hydrotr-12 eating are the elemental metals and the oxygen or 13 sulfur-containing compounds of metals of the sixth and 1~ eighth groups of the Periodic Table of the Element, preferably the metals and the oxides and sulfides of 16 these metals and mixtures thereof. Preference is given 17 to a catalyst which contains both a metal of the sixth 18 group or a compound of this metal and a metal of the 19 eighth group of the Periodic Table or a compound of this metal. They can be supported on a carrier, such as 21 silica, bauxi~e, clay or alumina. Preference is given 22 to a carrier consisting, at least substantially, of 23 alumina. Preferred catalysts include Co~Mo on alumina, 24 Ni/Mo on alumina wherein the cobalt, nickel and ~5 molybdenum are in the elemental, oxide or sulfide form, 26 preferably the sulfide form.

27 As a result of the improvements on the 28 hydrotreater feedstock quality as a result of the 29 practice of the previously recited steps which are part of the present invention, (i.e., phosphorus, sludge and 31 halide removal), smooth hydrotreater operations and 32 good quality base oils are secured. While operating on 33 the clean distillate resulting from the previously 34 identified process sequence, (but omitting light ends ~2~3~5~

- 37 -1 stripping) about 1,500 hours of continuous pilot plant 2 hydrotreating were logged with no noticeable catalyst 3 (Ni/Mo) deac~ivation.

4 Base oils were made for quality evaluation (base oil target in the example was a 10-grade oil) by 6 hydrotreating oils prepared by the above processing 7 steps (i.e., the feed for each step was the product 8 obtained from the proceding step in sequence) except g that the oil which was hydrotreated in this example had not been subjected to the stripping step. The oil was 11 hydrotreated over Ni/Mo catalyst (Co/Mo catalyst can 12 also be used) at the conditions shown in Table 12.
13 Inspections of a virgin SAE 10-grade oil made from 14 Western Canadian crude are also shown in the same table for comparison purposes. Results indicated that the 16 re-refined (280-300C)oils derived from a Canadian 17 waste oil closely matched the virgin base oil in 18 physical properties and chemical compositions.

~Z,~$5~

- 38 -3 Conditions Fe~d---1 0~ 10 ~A~de 5 Sas Rate, kmol/m3 -----7.5-----6 Temperature, C 290 284 7 Pressure, MPa ~2 3.5 5.6 8 Inspections g Density, kg/dm3 0.8703 0.8682 0.8682 0.8741 @ 15C
11 Viscosity, cST 30.71 29.46 29.55 29.50 12 ~ 40C
13 Viscosity, cST 5.20 5.09 5~10 4.97 14 @ 1~0C

1~ Total Nitrogen, 160 43 47 17 wppm 18 Basic Nitrogen, 41 23 24 19 wppm Sulphur, Wt% 0.23 0.09 0.10 0.07-OolO
21 Colour, ASTM D8 <1.0 <1.0 <1.0 22 Halogens, ppm 61 <2 <2 23 Phosphorus, ppm <3 <1 <1 24 TAN, mgKOH/g - 0.02 0.01 0.02 typ 25 Aromatics, Wt~ - 14.7 1408 26 Saturates, wt% ~ 83.3 83.2 80 min 27 Polars, Wt~ - 1.7 1.8 28 G.C. Distillation (D2387) 30 5% 359 359 31 10~ 371 372 32 Volatility ~ off 268C 8 8.5 10 max 33 (1) Derived from used oil feedstock B (Table 1).
34 Results on dewatering/defueling, heat soaking/WFE
distillation and alumina treating are shown in 36 Table 3, 7 and 12, respectively.
37 The beneficial effects of feed treatment in 38 accordance with the present invention on hydrotreating

39 operation is shown in the following examples. Untreated TFE distillate (phosphorus ~ 77 ppm), which had not 41 been heat soaked or alumina treated, was hydrotreated 42 with conventional catalysts (Ni/Mo or Co/Mo) at 290C
43 to 330C, 3.4 to 4~8 MPa pressure. The catalyst was 44 quickly deactivated (the product color dropped from 0.5 to 2.0 ASTM, product sulfur increased from 0~2 to 0.6 ~2,~5~;2 1 wt.% within 180 hours of operation). Alumina guard bed 2 treating is effective for removing phosphorus and 3 halide compounds from the TFE (or WFE) distillate (see 4 Tables 11 and 12). However, when the feed had not been first subjected to a heat soaking step the adsorbent 6 bed plugged after about 200 hours of operation due to 7 the presence of excess amount of sludge precursors in 8 the non-heat soaked TFE (or WFE) distillate. Heat 9 soaking prior to TFE or WFE distillation significantly reduces both phosphorus and sludge precursors in the 11 TFE (or WFE) distillate (see Tables 5, 6 and 7). From 12 this it can be seen that each of the reci~ed steps is 13 necessary for the successful practice of the present 14 invention.

As an optional step, the distillate coming 16 from the distillation unit (TFE or WFE for example~ may 17 be subjected to a second heat soaking and settling 18 prior to being fed to the guard bed and subsequently 19 into the hydrotreater. This step should be practiced in the event the sludge content cf the distillate is high 21 (see, for example, the sludge content of the material 22 obtained in Table 5). This optional second heat 23 soaking/settling should be considered if the sludge 24 con~ent (toluene insolubles) of the distillate is greater than about 100 to 300 ppm~

26 Heat soaking (e.g., at preferably 320C, 1/2 27 hour) prior to WFE distillation precipitated the 28 majority of the phosphorus compounds and sludge pre-29 cursors, but the distillate could still contain about 150-403 ppm of residual sludge at about 310Co This 31 sludge material is comprised of about 100-300 ppm of 32 toluene insolubles (as measured at room temperature) 33 which are usually present in the freshly made distil-34 late, and about 50-100 ppm of sludge that can form at i3L2 -- ~10 --1 the high temperature of 300-320C (from the sludge 2 precursors). This sludge material, especially the 3 toluene insolubles, should be removed from the dis-4 tillate prior to adsorbent treating in order to avoid plugging of the guard reactor bed.

6 By allowing the distillate to stand for a 7 period of time (48-72 hours) at a moderate temperature 8 (125-150C~ under quiescent conditions, these parti g culates tend to settle out of the oil. Results shown in Table 14 indicated that the settling rate of toluene 11 insolubles was enhanced with increasing temperature.
12 After standing at 150C for 72 hours the distillate 13 toluene insolubles dropped from an initial value of 14 about 200 ppm to about 15 ppm. The sludge from the sludge precursors was also reduced from about 300 ppm 16 to less than lS0 ppm, which is at the ].ower limit of 17 accurate measurement by the sludge test.

21Toluene Insolubles,_ppm (1) 22 Post-Heat Soaking 0 24 40 72 120 .3 tResidence Time Hrs~) 24 Temperature, C (Fresh Distillate) .

26 150 298 92 ~4 15 7 27 (1) Distillate was made from pre-heat soaked oil (at 28 320C, 1/2 hour residence time) and subsequently 29 distilled using the lab Pope WFE. The distillate was allowed to settle for different time periods 31 at 25C and 150C.

Claims (22)

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

1. A process for rerefining used oils so as to produce a base stock oil essentially equivalent in quality to virgin base stock which process comprises the steps of:
(a) heat soaking the used oil at a temperature of from about 250° to 340°C for a time sufficient to maximize the removal of phosphorus, halides and sludge precursors;
(b) distilling the heat soaked used oil to produce a distillate and a residue:
(c) passing the distillate through a guard bed of activated material;
(d) hydrotreating the guard bed treated distillate under hydrotreating conditions:
thereby producing a rerefined base stock.

2. The process of claim 1 comprising the additional step of stripping the heat soaked oil from step (a) under conditions and employing procedures sufficient to remove the low boiling conversion products from the heat soaked oil prior to distillation step (b).

3. The process of claim 1 wherein the used oil subjected to the rerefining process is a used lube oil.

4. The process of claim 1 wherein the heat soaking step is preceded by a dewatering-defueling step.

5. The process of claim 1 wherein the heat soaking step is conducted at a temperature of from about 280°C to 320°C for from about 15-120 minutes.

6. The process of claim 2 wherein the stripping step removes the about 1-10 wt% fraction of low boiling point conversion product materials generated during the heat soaking step.

7. The process of claim 1 wherein the distillation step is conducted using a coke formation resistant apparatus under the conditions of residence time, temperature and pressure selected to give a distillate whose end point is essentially that of the target base oil product.

8. The process of claim 1 wherein the distillation step employs a thin film evaporator, a wiped film evaporator or a cyclonic distillation tower so as to keep coke formation to a minimum.

9. The process of claim 1 wherein the distillate of step (c) is passed through a guard bed of Fuller's Earth, charcoal, lime or activated alumina.

10. The process of claim 1 wherein the guard bed is operated at a pressure ranging from about atmospheric to about 5 MPa, a temperature of about 180° to about 340°C, a LHSV of about 0.5 to about 2 v/v/hr.

11. The process of claim 1 wherein the hydrotreating is conducted at a temperature of about 260-400°C, a hydrogen pressure of about 3 to 11 MPa, a flow rate of about 0.5 to 4 LHSV and a gas rate of about 1.5 to 15.0 kmol/m3.

12. A process for rerefining used oils so as to produce a base stock oil essentially equivalent in quality to base stock produced from virgin crude oil which process comprises the steps of:
(a) heat soaking the used oil at from 250°C-340°C for a time sufficient to maximize halide, phosphorus and sludge precursors removal by conversion of these materials into materials which go with the residue during the distillation step:
(b) passing the entire contents of the heat soaker directly to coke resistant distillation means:
(c) distilling the contents from the heat soaker under conditions of residence time, temperature and pressure selected to produce a distillate whose end point is essentially that of the target stock product and a residue:
(d) passing the distillate through a guard bed of activated material capable of removing residual phosphorus, halides and sludge from the distillate; and (e) hydrotreating the guard bed treated distillate under standard hydrotreating conditions, thereby producing a rerefined base stock.

13. The process of claim 12 wherein the used oil subjected to the rerefining process is a used lube oil.

14. The process of claim 12 wherein the heat soaking step is preceded by a dewatering and defueling step.

15. The process of claim 12 wherein the dewatering and defueling step is practiced using distillation.

16. The process of claim 12 wherein the heat soaking step is conducted at a temperature of about 280° to 320°C for from about 15-120 minutes.

17. The process of claim 12 wherein the heat soaking is conducted for from about 30 to 120 minutes.

18. The process of claim 17 wherein the distillation is conducted in a thin film evaporator, a wiped film evaporator or a cyclonic distillation tower.

19. The process of claim 12 wherein the guard bed is a bed of Fuller's Earth, charcoal, lime or activated alumina.

20. The process of claim 18 wherein the guard bed is a bed of activated alumina.

21. The process of claim 18 wherein the guard bed is run at a temperature of about 180° to 340°C, a pressure of about atmospheric to 5 MPa, a LSHV of about 0.5 to 2 v/v/hr.

22. The process of claim 21 wherein the hydrotreating is conducted at a temperature of from about 260°-400°C, a hydrogen pressure of about 3-11 MPa, a LSHV of about 0.5-4, and a gas rate of about 1.5-15 kmol/m3.