Post hydrotreatment finishing of lubricant distillates

Abstract

A method wherein either crude oil or a used oil lubricant is processed to produce an intermediate lube distillate which is then hydrotreated to produce a hydrotreated base oil which is then processed by solvent treatment to produce a higher viscosity index base oil (such as Groups II+ and/or III) and a lower viscosity index base oil (such as Groups I and/or II), in each case as compared with the viscosity index of the hydrotreated base oil. In the solvent treatment, one or more solvents are utilized to selectively separate higher viscosity index components from lower viscosity index components found in the hydrotreated base oil, and after the separations have occurred, the solvent is preferably recovered for re-use in the process.

Claims

1. A method comprising a step of applying to a hydrotreated base oil a solvent treatment comprising at least one solvent utilized to extract naphthenic compounds to produce: a first base oil comprising a higher proportion of paraffinic compounds than occurred in said hydrotreated base oil, wherein said first base oil has a viscosity index of at least 112; and at least one additional base oil comprising a higher proportion of naphthenic compounds than occurred in said hydrotreated base oil.

2. The method of claim 1 wherein said hydrotreated base oil contains at least 90% saturates.

3. The method of claim 1 wherein said hydrotreated base oil contains less than 300 PPM of sulfur.

4. The method of claim 1 wherein said hydrotreated base oil contains a viscosity index of at least 80.

5. The method of claim 1 wherein said first base oil is a Group III base oil.

6. The method of claim 1 wherein said first base oil has a viscosity index of at least 120.

7. The method of claim 1 wherein at least 50% of said hydrotreated base oil has a boiling range between 550 degrees Fahrenheit and 1050 degrees Fahrenheit.

8. The method of claim 1 wherein said first base oil has a higher viscosity index than said hydrotreated base oil.

9. The method of claim 1 wherein the at least one solvent is at least one first solvent, and wherein the method further comprises a step of utilizing at least one second solvent to extract paraffinic compounds from at least of one of said first base oil and said at least one additional base oil.

10. The method of claim 1 wherein said hydrotreated base oil has been hydrotreated under a pressure of at least 800 psig.

11. The method of claim 1 further comprising a step of deriving said hydrotreated base oil from at least one of used oil and crude oil.

12. A method comprising steps of: applying to a hydrotreated base oil a solvent treatment comprising at least one first solvent utilized to extract naphthenic compounds to produce: a first base oil comprising a higher proportion of paraffinic compounds than occurred in said hydrotreated base oil; and at least one additional base oil comprising a higher proportion of naphthenic compounds than occurred in said hydrotreated base oil; and utilizing at least one second solvent to extract paraffinic compounds from at least of one of said first base oil and said at least one additional base oil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of an embodiment of the invention where solvent is preferentially selective to removal of aromatics, polars and naphthenes.

(2) FIG. 2 is a schematic diagram of an embodiment of the invention where the solvent is preferentially selective to removal of paraffinics.

(3) FIG. 3 is a simplified schematic diagram of an embodiment of the invention where two solvents are utilized in sequence, one being a solvent preferentially selective to the removal of aromatics, polars, and naphthenes and the other solvent being preferentially selective to removal of paraffinics.

(4) FIG. 4 is a schematic diagram of an embodiment of the invention where hydrotreatment is followed by clay treating.

DESCRIPTION OF THE INVENTION

(5) Turning to FIG. 1, used oil feedstock 100 is processed using any of several recycling technologies 110 to separate out an intermediate lube distillate 146 from each of an asphalt flux 135 of higher molecular weight and recycling technologies lighter materials 145 of lower molecular weight. In recycling technologies 110, the process equipment is preferably configured to generate the lighter materials 145 (which typically consist of water, glycols, diesel, and possibly a spindle oil) in several successive steps, all of which are intended to be included within recycling technologies 110. Intermediate lube distillate 146 is preferably created from used lubricating oils, and preferably by one or more distillation steps embodied within recycling technologies 110 to separate out lighter materials 145 via a line 140 and separate out asphalt flux 135 via a line 132. As denoted by broken line 141, optionally a portion of one or more of the lighter materials 145, such as diesel and spindle oil, may be re-combined via line 141 with Intermediate lube distillate 146 and then passed on to a hydrotreatment 151 via line 147. Certain lower boiling point overhead streams in line 140 may optionally be burned for heat generation or directly marketed as a type of burner fuel.

(6) Intermediate lube distillate 146, along with optionally some lighter materials 145 via line 141, such as diesel and spindle oil, preferably pass on to hydrotreatment 151 via line 147. Since intermediate lube distillate 146 may be stored in tankage which is at ambient temperature (not shown) and hydrotreatment 151 operates at elevated temperatures, preferably employed are heat exchangers HX-3 167 and HX-4 171 to heat intermediate lube distillate 146 even as these heat exchangers also cool a solvent recycle 166 and a solvent recycle 176. As is known in the industry, hydrotreatment 151 employs certain equipment to process the intermediate lube distillate 146 under conditions including: a) elevated temperatures, b) elevated pressures, c) residence times, d) a hydrogen stream 152 of a given purity and flow rate; all in e) the presence of one or more catalysts. Hydrotreatment 151 will preferentially achieve certain outcomes including: a) removal or conversion of aromatic and polar compounds, b) replacement of hetero-atoms (such as sulfur, nitrogen, oxygen) with hydrogen to create c) higher levels of saturates, and possibly d) opening of naphthene rings, and e) isomerization of paraffins to iso-paraffins, thereby all resulting in f) a higher quality base oil.

(7) As known in the industry, hydrotreatment 151 preferably utilizes equipment, including pumps, heat exchangers, compressors, guard beds, reactors, amine unit for purification of the hydrogen for recovery, a recycle loop for hydrogen, and stripping and fractionation equipment. Hydrotreatment 151 preferably includes stripping and fractionation of lighter materials, neutralization of acids created during hydrotreatment, and special metallurgies for equipment. Hydrotreatment 151, via a line 153, illustrates the separation of hydrotreatment lighter materials 154 which preferably include off-gases 155 and lighter materials (LM) liquids via a line 160, which may be either utilized as burner fuel or sold as products. The fractionation and/or stripping units in hydrotreatment 151 also separate out a heavier material designated as post HT base oil 156 which is then preferably passed to solvent extraction 161 at an entry point 159. Optionally, prior to passing to solvent extraction 161 is fractionation 157 in which post HT base oil 156 is separated into base oils of different viscosities (and possibly diesel). In optional fractionation step 157, preferably pressure is reduced to a vacuum but sufficient temperature is maintained to allow post HT base oil 156 to be divided into different viscosities as would satisfy, after applying solvent extraction 161, the viscosities for the products in the intended market applications. The above areas describe hydrotreatment, stripping, and fractionation processes that are generally known to industry process engineers and do not require further detail in this specification. As disclosed next below, the invention further includes innovations where it may be preferable for a portion of the elevated temperatures and/or pressures in hydrotreatment 151 to persist in post HT base oil 156 passed to Solvent Extraction 161. All temperatures referred to herein are at atmospheric pressures.

(8) Following hydrotreatment, post HT base oil 156 then passes to solvent extraction 161 as shown entering solvent extraction at 159. As noted previously, solvent extraction 161 is a known separations process. Separation is preferably implemented in a contactor and any of several non-limiting contactor types can be employed, such as rotating disc contactors, Karr columns, pulsed contactors, Podbielniak reactors, and counter current extraction columns (whether utilized, singly, in combination, or in series) and the like. An alternative embodiment for such a contactor in the instant invention is an atmospheric, vacuum, or flash distillation column (whether operated as normal, extractive, or azeotropic) which can utilize one or more solvents to create a higher relative volatility differential between the higher VI constituents (such as paraffinic or iso-paraffinic components) and the lower VI constituents (such as aromatic, polar or naphthenic components) of the feed stream. Such a column in this instance may have operating conditions, for example, which include a large temperature and/or pressure gradient between the upper and lower stages, and/or varied solvents may be introduced at different positions in the columns.

(9) In the instant invention, an elevated temperature for the post HT base oil 156 from hydrotreatment 151 is optionally utilized to: a) promote extraction results by enhancing solvent power above what would otherwise occur at the typical temperature of solvent extraction (which is generally below 250 F.); and b) provide for efficient recovery of the solvent by utilizing heat in the post HT base oil 156 to reduce or eliminate the need for adding heat to vaporize the solvent to be recovered in each of a raffinate 169 and an extract 179. In the instant invention, an elevated pressure for the post HT base oil 156 from hydrotreatment 151 is optionally utilized to: a) promote extraction results by enhancing solvent options and power above what would otherwise be available and occur at the typical pressure of solvent extraction (which is generally atmospheric or at a slight positive pressure); and b) enhance recovery efficiency of solvent from either or both of the raffinate 169 and extract 179. More efficient solvent recovery using pressure is achievable for example by reducing pressure in each of extract 179 and raffinate 169 which, when operated at a temperature differential sufficiently far above the boiling point of the solvent, will result in flash evaporation and re-capture of the solvent for recycling in the process with minimal or no additional heat. If flash evaporation is employed, it should preferably not vaporize either of the post SE lower VI material 180 or the post SE higher VI base oil 170, but only vaporize the solvent. When utilized, heat and pressure are thus preferably contributed from the elevated temperature and pressures contained in post HT base oil 156 as proceeding from hydrotreatment 151.

(10) Accordingly, disclosed in this invention is the aforementioned highly efficient means for achieving solvent recovery by separating out the solvent from the raffinate, leaving a higher VI base oil, and separating out the solvent from the extract, leaving a lower VI material (referred to as solute), with such separation optionally utilizing some or all of the elevated temperatures and/or pressures provided by hydrotreatment of the feed. The proposed innovations of elevated temperatures and pressures passed from hydrotreatment to aid in solvent recovery are not required to be utilized together and instead may be applied separately. For example, solvent extraction 161 could maintain an elevated pressure but operate below the typical temperature of 250 F., as may be used with a solvent of a low boiling temperature. Or solvent extraction 161 could be designed to maintain a temperature above 250 F., but below the boiling point of the solvent, and still operate in an atmospheric pressure range. Or a combination of the two may be utilized where some amount of elevated temperature and elevated pressure are both employed in solvent extraction 161, such as operating with a solvent extraction temperature above the boiling point of the solvent and also with sufficient elevated pressure to maintain the solvent in a liquid phase. However, to avoid excess operating cost and additional equipment cost and to promote or perhaps even enable effective separation, temperatures and pressures in solvent extraction 161 are preferably below temperatures and pressures utilized in hydrotreatment 151.

(11) One configuration is next discussed as to how the invention preferably employs both pressure and temperature between hydrotreatment 151 and solvent extraction 161 to increase efficiency. The effluent stream from hydrotreatment 151, which is post HT base oil 156, is cooled via heat exchangers HX-1 162 and HX-2 163 even as it then simultaneously heats extract at HX-1 162 and raffinate at HX-2 163 to assist or complete the heat required for vaporization of the solvent recovery in each. Under this configuration of the invention, post HT base oil 156 preferably supports an elevated pressure, but is preferably cooled down to a temperature for solvent extraction generally above the solvent's boiling point as charged to solvent extraction 161 at entry point 159. Then after solvent at entry point 178 and post HT base oil 156 at entry point 159 have been combined in the contactor, which is part of solvent extraction 161, and have moved counter currently, applying the above noted recuperative heat exchange using the heat from hydrotreatment 151 to each of raffinate and extract to elevate their temperatures sufficiently far above the boiling point of the solvent so that when the pressure is released at pressure control points PCP 165 and PCP 164, the solvent will flash off in overhead solvent recycle streams 166 and 176, respectively. To achieve this, post HT base oil 156 may require additional cooling capacity (not shown), which would be preferably positioned after HX-2 163 and before entry point 159 (not shown). Solvent distillation in raffinate 169 and extract 179 may require additional heating capacity which is shown in heating or cooling 177, but which may be alternatively or additionally employed after, as needed, PCP 164 as part of extract 179 (not shown) and after PCP 165 as part of raffinate 169 (not shown). However, the amount of extra cooling and heating required to operate according to the invention is far less than would be required in the absence of the recuperative heat exchange noted in the invention. This approach will preferably allow for solvent recycle 166 and solvent recycle 176 to be operated either without, or with a minimum of additional, heating, stripping, or vacuum distillation equipment, and thus capital and operating cost. Similarly, heating of the intermediate lube distillate 146 in each of HX-3 167 and HX-4 171 prior to entry point 148 into hydrotreatment 151 is provided by also cooling of solvent recovery streams 166 and 176, respectively, although additional heating equipment may be required (not shown) to attain the optimal operating temperature in hydrotreatment 151.

(12) An additional innovation that may be utilized is to control the pressure of each of raffinate 169 (such pressure control point shown illustratively at PCP 165) and extract 179 (such pressure control point shown illustratively at PCP 164) as to be sufficiently below that of solvent extraction 161 as a means of regulating the flow of material through solvent extraction 161 to a desired solvent to oil ratio, thus prospectively minimizing or eliminating use of pumps to solvent extraction 161. If the contactor in solvent extraction 161 is operated at a positive pressure (above atmospheric), there is preferably a pump 168 for re-pressurizing solvent recycle 166 and solvent recycle 176 for returning this as liquid at the proper pressure to solvent extraction 161 at point 178. Also prior to pump 168 equipment are heat exchangers HX-3 167 and HX-4 171 which are preferably employed to change the solvent's phase from gas to liquid state or to further cool the solvent if needed. As noted, heating or cooling 177 is also preferably employed after pump 168 to heat or cool the solvent as needed.

(13) For maximum operating and capital efficiency for solvent recovery, an alternative means of operating solvent extraction 161 is at a temperature that is sufficiently in excess of the boiling point of the solvent and at a pressure that maintains the solvent in a liquid state at the elevated temperature. (However, in seeking higher temperatures, considerations of solvent selection and excessive miscibility may prevent adequate separation as it may become difficult or impossible to achieve at elevated temperatures.) By way of example, a preferred solvent for this invention is N-methyl-2-pyrrollidone (or NMP) which has a boiling temperature of 395 F. In this mode, temperatures above 395 F. would require equipment to be operated at a high enough pressure to maintain both the solvent and oil in a liquid state within solvent extraction 161 and in each of HX-1 162 and HX-2 163. This state is referred to as supercritical, which is a temperature and pressure where the material is liquid until pressure is released whereupon it then becomes a gas. If solvent extraction 161 is maintained in a supercritical state, then this allows a subsequent release of pressure to vaporize the solvent in raffinate 169 and extract 179, with a minimum of added heat, stripping, or creation of a vacuum. The bottoms material that is not solvent (the base oil from the raffinate or the solute from the extract) thus preferably does not become a gas and is collected separately from the solvent. An additional advantage of operating at the higher temperatures and pressures is that the purity of the product that is created in post SE higher VI base oil 170 will be higher than if the solvent extraction 161 were to be operated at a traditional temperature of below 250 F. and at 1 atmosphere. However, associated with any higher temperature and pressure is a shift in yield from post SE higher VI base oil 170 to the post SE lower VI material 180 and is one factor to be optimized when selecting the optimum temperature to be used in solvent extraction 161. Considerations of elevated temperature should thus not only include thermal efficiency and desired product quality, but also reflect desired throughput and yields, as high levels of miscibility between the oil and solvent at higher temperatures can result in poor separation. To reduce this issue, a significant temperature gradient may preferably be employed across the contactor with the high temperature at the solvent entry point and the low temperature of the gradient at the extract exit point, or a recycle loop may be employed (not shown).

(14) To minimize capital and operating costs in solvent recovery, it may be preferable to avoid the need for: a) addition of separate heat or cooling; b) pressure below 1 atmosphere (e.g., some level of vacuum); or c) a stripping capability. The alternative operating conditions noted next will assist in specifying the operating parameters for solvent extraction 161 and prospectively minimize or eliminate the need for heat exchangers HX-1 and HX-2. To promote full solvent recovery in both of the raffinate 169 or extract 179 for the least cost, the loss of heat and drop in temperature resulting from solvent vaporization preferably shall not cool the remaining liquid to below the solvent's boiling point at atmospheric pressure. Since the amount of solvent to be vaporized relative to the bottoms (whether post SE higher VI base oil or post SE lower VI material) is generally largest in extract 179, to minimize capital and operating cost, the temperature of solvent extraction 161 may be determined to be that temperature needed to achieve full vaporization of the solvent recycle 176 in extract 179 after pressure is released downstream of PCP 164. This will logically be affected by the solvent selected and the dosage (that is, the ratio of the solvent introduced in 178 to the oil introduced in 159) with a higher solvent-to-oil ratio (dosage) necessitating higher heat in solvent Extraction 161 to provide for sufficient heat as needed to achieve full solvent vaporization in extract 179. The level of heating or cooling of the solvent to reach the optimum temperature in solvent extraction 161 is preferably controlled by heating or cooling 177.

(15) In solvent extraction 161, the solvent-to-oil ratio is one of several key variables with others, including choice of solvent, extraction contactor type(s), temperature, temperature gradient in the contactor, flow rate, and addition of a further polar solvent such as water to improve selectivity and the inclusion, or not, of a recycle loop. The solvent-to-oil ratio will be affected by a desired VI for post SE higher VI base oil 170, as well as desired product quality characteristics for post SE lower VI material 180. The higher the solvent-to-oil ratio, the higher will be the VI of post SE higher VI base oil 170. Additional factors include the quality of used oil feedstock 100, the choice of recycling technologies 110, and degree of severity of hydrotreatment 151. Generally speaking for the preferable solvent of NMP, the solvent-to-oil ratio is preferably in the range of about 0.2 to 10, usually in the range of 0.5 to 4, and most preferably in the range of 1 to 3.

(16) Economics and operability considerations should be generally weighed along with the desired base oil's yield, product quality, and performance characteristics. In addition to the elevated temperature and pressure and varied solvent-to-oil ratios, design of solvent extraction 161 will preferably include other factors such as extract equipment selection, solvent selection (preferably NMP), solvent recycle purity, and stripping, if preferred. Injection of water or an extract recycle loop to promote solvent selectivity may also be employed, although water addition would be adverse to performing solvent extraction at elevated temperatures (in the absence of higher pressures) due to water's 212 F. boiling point. Prospectively, a co-solvent may be used to enhance extraction efficiency and product quality. Design of solvent extraction 161 will also reflect factors such as operability (that is, controllability) of the process, capital cost, operating cost (including solvent loss and degradation), corrosion control, maintenance cost, capacity, up-time, operating safety and risk, and equipment availability.

(17) Solvent extraction 161 thus results in two streams, one leading to raffinate 169 and the other to extract 179. Raffinate contains a higher VI base oil rich stream that also contains solvent, which in raffinate 169 is distilled and recovered for re-use via solvent recycle 166, leaving then post SE higher VI base oil 170. Extract 179 contains a solvent rich extract stream that contains a lower VI material called solute. Extract 179 includes distillation to recover solvent for re-use via solvent recycle 176, leaving the solute which is post SE lower VI material 180 and which preferably contains a higher portion of naphthene, aromatic and polar compounds than is found in post SE higher VI base oil 170. In each of raffinate 169 and extract 169, the solvent is thus recycled for use in the process. The total of the naphthene, polar and aromatic compounds in post SE higher VI base oil 170 will then be lower than those found in post HT base oil 180 (and conversely the saturates will be higher). Since the naphthene, aromatic and polar compounds in post SE lower VI material 180 are low VI and were removed from post HT base oil 156, post SE higher VI base oil 170 is higher in VI than is post HT base oil 156, and benefits from the phenomenon known as VI Hop, as noted above, versus post SE lower VI material 180.

(18) Under certain combinations of used oil feedstock 100, recycling technologies 110, or process conditions of hydrotreatment 151 or solvent extraction 161, the post SE lower VI material 180 (as the aromatics and polar rich stream created from extract 179) may not be marketable as a base oil. However, depending on the quality of the used oil feedstock 100, hydrotreatment severity in hydrotreatment 151, and solvent selection and severity in solvent extraction 161, the post SE lower VI material 180 may be sufficiently low in poly nuclear aromatics (PNAs), which are known carcinogens, to be sold in market applications (such as, for example, in rubber or tire manufacturing) as shown in 187 where a solute from a solvent extraction process applied to a non-hydrotreated feed stream would otherwise be rejected. Optionally, post SE lower VI material 180 may be blended into the asphalt flux created in the distillation phase as shown in blended 185. Finally, it may be burned as fuel as shown in 186.

(19) A final determination of operating conditions for each of hydrotreatment 151 and solvent extraction 161 may be set by determining desired end product levels of saturation, sulfur, and VI, for the post SE higher VI base oil 170 and the post SE lower VI material 180 (which is preferably sold as a base oil as shown in 188) and then balancing between the operating parameters of each of hydrotreatment 151 and solvent extraction 161 to create the desired product qualities for the highest yield and least operating cost. For example hydrotreatment 151 is most suited for hydrogenating (and thus removing) sulfur, nitrogen, or oxygen hetero-atoms and also for naphthene ring opening, and in some circumstances, isomerization to create iso-paraffins.

(20) Solvent extraction 161 is well suited for separating aromatics and polars that are not removed by hydrotreatment 151 into a higher VI and lower VI stream, and it can also be used to preferentially separate paraffinic components from naphthenic components (both of which are saturates). A further example of a potentially improved outcome is where a type of aromatic can be converted into a saturate in hydrotreatment 151, but where that saturate is a low VI saturate (such as a naphthene), it may be preferable in hydrotreatment 151 not to convert all or some of the aromatics or polar compounds into the lower VI material but instead remove these later in solvent extraction 161 from the higher VI base oil stream. While the higher VI base oil would then have lower yield, the improvement in product quality in the higher VI base oil may more than offset the loss in its yield. These are optimizations by which the process conditions of hydrotreatment 151 and solvent extraction 161 may be altered to deliver one or more improved outcomes to create a better result versus than could be achieved by either hydrotreatment or solvent extraction alone.

(21) Next disclosed as shown in FIG. 2 is an alternative mode for implementing additional post hydrotreatment finishing of lubricating oils by means of using a solvent which preferentially removes paraffinic compounds. In FIG. 2 the process flows are the same as in FIG. 1, except that in this case the solvent used is less dense than the Post HT base oil 156 and is preferentially selective to removing paraffinic components versus removing aromatic, polar, and naphthenic components. Therefore in FIG. 2 the solvent is shown entering Solvent Extraction 161 at point 178 near the bottom of the contactor and the Post HT base oil 156 enters Solvent Extraction 161 at point 159 near the top of the contactor. In the case of use of a solvent (such as propane) that is a gas at the contactor's operating temperature, a compressor is preferentially used as Solvent Pump 168 to convert the (propane) gas into a liquid phase for re-use in the process.

(22) A further embodiment is shown in FIG. 3 in which Raffinate stream 169 from the solvent extraction process described above in FIG. 1 is then further processed via treatment with the paraffinic extraction process described above in FIG. 2. Assuming a preferentially selective aromatic/polar/naphthenic solvent that is more dense than the base oil field is used first in the solvent treatment processes, then turning to FIG. 3 the Post HT Base Oil stream 156 (as is created in FIGS. 1 and 2 and optionally either before or after Fractionation step 157) is charged to the lower area of Solvent Extraction 1 300 (a contactor) and Solvent Recycle 1 (303 and 304) is charged to the upper area of Solvent Extraction 1 300 at point 305. From Solvent Extraction 1 300 Raffinate 1 301 is generated above and Extract 1 302 is generated below. Raffinate 1 301 is the higher paraffinic, higher VI stream and Extract 1 302 is the higher naphthenic, lower VI stream. As noted, solvent is recovered from Raffinate 1 300 via Solvent Recycle 1 304 and solvent is recovered from Extract 1 via Solvent Recycle 1 303, each of which is charged back to Solvent Extraction 1 300 at point 305. Solute 1 304 is preferably sold as Base Oil 317, but if it should not achieve base oil specifications then it may be sold or blended in the asphalt stream as an Alternate Product 316 or burned as Fuel 315.

(23) After removal of the solvent in Raffinate 1 301, stream 306 is generated and charged to Solvent Extraction 2 320 at point 325. The preferentially selective paraffinic solvent that is less dense than the base oil is field is generated in Solvent Recycle 2 324 and Solvent Recycle 2 323 and charged to the Solvent Extraction 2 320 at point 327. From the bottom of contactor Solvent Extraction 2 320 is generated Extract 2 322, which after solvent removal, then becomes Post SE 2 Lower VI Base Oil 328. From the top of contactor Solvent Extraction 2 320 is generated Raffinate 2 321, which after solvent removal, then becomes Post SE 2 Higher VI Base Oil 329. In the order of the expected quality level from highest to lowest, Base Oil 329 will be higher quality than Base Oil 328, which will in turn be higher quality than Base Oil 317.

(24) Alternatively FIG. 3 could be altered quite easily in which a sequence configuration is employed where the paraffinic selective extraction process described above is applied first to the Post HT Base oil 156 stream and the aromatics, polars, napthenic selective solvent is applied second to the raffinate stream. This also will then create a higher paraffinic and higher VI raffinate stream than could be created by using either of the two solvents alone. Finally an alternative configuration is also disclosed wherein two solvents, one preferentially selective to aromatics/polars/naphthenes removal and one preferentially selective to paraffins removal may be applied in a single contactor. Such alternative embodiments of the instant invention in which solvent treatment is applied to a hydrotreated lube oil as are described herein are believed to be within the capabilities of one of ordinary skill in the art.

(25) Next disclosed is an alternative mode for implementing additional post hydrotreatment finishing of lubricating oils by means of Clay Treatment, as shown in FIG. 4. Used Oil Feedstock 100 is processed via Recycling Technologies 110 to generate Intermediate Lube Distillate 146, which is then charged to Hydrotreatment 151. Post HT Base Oil 156 is charged to Clay Treatment 400 using temperature, residence time and capacities as are appropriate to the clay utilized in the treating process. During Clay Treatment 400 polar impurities including nitrogen, oxygen, and sulfur containing compounds are adsorbed onto the clay and removed from the Post HT Base Oil 156. Periodically the clay is re-generated and re-used in the process based on the manufacturer's specifications for this process (regeneration and re-use cycles not shown). The resultant Post CT Base Oil 410 is thus further improved over the Post HT Base Oil 156.

(26) The instant invention as described herein preferably describes the intermediate lube distillate subject to hydrotreatment as derived from an intermediate lube distillate created from used lubricating oil which is then solvent treated or clay treated as per the instant invention. However an alternative embodiment, and thus an alternative application, is where the intermediate lube distillate may instead be derived from crude oil which has been processed as described herein to create hydrotreated base oil which is then solvent treated or clay treated as per the instant invention. A further alternate embodiment is to utilize hydrotreated base oil (say from the open market) and apply solvent treatment to this hydrotreated base oil, thus utilizing solvent treatment a period of time that is significantly later than when the original hydrotreated base oil was manufactured. Furthermore the subsequent solvent treatment (or clay treatment) may be undertaken at a separate, remote location from where the hydrotreated base oil was created, even prospectively in modular, or mobile, units. Applications of such alternative embodiments are believed to be well within the capabilities of one of ordinary skill in the art and, as such, are intended to lie within the scope of the instant invention.

(27) Suitable catalysts and operating conditions in hydrotreatment may be optimized as known to the art. Such catalysts typically comprise nickel molybdenum, cobalt molybdenum, platinum, palladium, and other catalysts as may be employed for de-sulfurization, de-nitrification, saturation, naphthene ring opening, and/or isomerization.

(28) Solvents are also known to the art for selectively separating aromatics, polars and other undesirable base lube oil constituents from desirable base lube oil constituents. Preferred solvents typically comprise N-methyl-2-pyrollidone, furfural, phenol, and the like. The optimum solvent may be selected based upon its effectiveness in the process as discussed.

(29) Other solvents are also known to the art for their preferential selectivity to paraffinic components. Preferred solvents typically comprise propane, acetone, hexane, heptane, isopropyl alcohol, and the like. The optimum solvent may be selected based upon its effectiveness in the process as discussed.

(30) The present invention is not limited to any particular solvent or catalyst since feedstocks and more detailed technology and process conditions may vary.

(31) While the present invention has been described by reference to certain of its preferred embodiments, the embodiments presented here are intended to be illustrative rather than limiting in nature and many variations and modifications are possible within the scope of the present invention. Many such variations may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of the preferred embodiments that are described in this specification.