WO2005056729A1

WO2005056729A1 - Method for upgrading lube oil boiling range raffinates by treatment with a sulfuric acid solution

Info

Publication number: WO2005056729A1
Application number: PCT/US2004/040089
Authority: WO
Inventors: Mark A. Greaney; Daniel P. Leta; Richard F. Socha; Chris A. Wright; Lei Zhang
Original assignee: Exxonmobil Research And Engineering Company
Priority date: 2003-12-05
Filing date: 2004-12-01
Publication date: 2005-06-23

Abstract

The instant invention relates to an improved hydroprocessing method for lube boiling range feedstreams involving contacting a lube oil boiling range raffinate with an acidic solution to remove heterocyclic nitrogen-containing compounds prior to hydroprocessing.

Description

METHOD FOR UPGRADING LUBE OIL BOILING RANGE RAFFINATES BY TREATMENT WITH A SULFURIC ACID SOLUTION

FIELD OF THE INVENTION

[0001] The instant invention relates to a method for upgrading nitrogen- containing hydrocarbon streams. More particularly, the present invention relates to an improved hydroprocessing method for lube boiling range feedsteams involving contacting a lube oil boiling range raffinate with an acidic solution to remove heterocyclic nitrogen-containing compounds prior to hydroprocessing.

BACKGROUND OF THE INVENTION

[0002] Currently, there exists a need to reduce the heterocyclic nitrogen content of feedstreams used in the lube oil processes because heterocyclic nitrogen-containing compounds, especially basic heterocyclic nitrogen- containing compounds, contained in lube oil boiling range feedstreams act as competitive inhibitors on the catalytic sites of catalysts. These nitrogen- containing compounds are indigenous to crude oils, and are typically concentrated in the higher boiling fractions, such as lube oil fractions. The presence of these heterocyclic nitrogen-containing compounds typically prevents lube oil hydroprocesses from operating as effectively and/or efficiently as possible. For example, the presence of these heterocyclic nitrogen-containing compounds in lube oil boiling range feedstreams used in hydrodewaxing operations requires that the hydrodewaxing be performed at high temperatures that impart a higher degree of cracking than isomerization when compared to dewaxing processes that run at a lower temperature.

[0003] Also, the removal of nitrogen species from lube oil boiling range feedstreams allow cracking operations to operate more efficiently because these heterocyclic nitrogen-containing compounds, especially basic heterocyclic nitrogen-containing compounds, act as competitive inhibitors on the acidic cracking sites of cracking catalysts. Thus, many methods for reducing the nitrogen content in feedstreams have been proposed.

[0004] For example, United States Statutory Invention Registration H1368, Fraytet, teaches the use of concentrated sulfuric acid, i.e. at least 95 wt.% sulfuric acid, to treat straight run jet fuel boiling range streams. The process requires that the sulfuric acid-containing stream be dispersed in the jet fuel in the form of droplets smaller than about 300 microns. The Fraytet process discloses that 90% or more of the nitrogen can be removed from the jet fuel boiling range stream.

[0005] United States Patent Number 4,392,948, Debande, teaches the use of acidic treatments for straight run distillates boiling in the range of 150°C to about 290°C. The acidic solution used in Debande has an acid concentration from about 0.01 to about 2.5 vol.%. This acid is contacted with the straight run distillate feedstream for a short period of time, i.e. not to exceed two seconds.

[0006] However, there still exists a need in the art for a more effective nitrogen removal method to be used in hydroprocessing schemes for lube oil boiling range feedstreams because with their removal, lube hydroprocessing operations could be improved. SUMMARY OF THE INVENTION

[0007] One embodiment of the instant invention is directed at an improved method for the hydroprocessing of a nitrogen-containing lube oil boiling range raffinate. The method comprises: a) solvent extracting at least one nitrogen-containing lube oil boiling range feedstream under conditions effective for producing at least a nitrogen- containing raffinate having a boiling point in the lube oil range; b) providing a sulfuric acid solution having a sulfuric acid concentration of at least about 75 vol.%, based on the sulfuric acid solution; c) contacting the nitrogen-containing lube oil boiling range raffinate with the sulfuric acid solution under conditions effective at removing at least about 80 wt.% of the nitrogen compounds contained in said lube oil boiling range raffinate thereby producing at least a mixture comprising a raffinate effluent and a used sulfuric acid solution, wherein the volumetric treat rate of the sulfuric acid solution is greater than about 0.1 vol.%, based on the lube oil boiling range raffinate; d) processing said raffinate effluent by a process selected from solvent dewaxing, hydrotreating, hydrodewaxing, and hydrofinishing thereby producing a lube oil boiling range product.

[0008] In one embodiment of the instant invention the sulfuric acid solution is a spent sulfuric acid solution obtained from an alkylation process unit.

[0009] In another embodiment of the instant invention, the nitrogen- containing raffinate is solvent dewaxed to produce a dewaxed nitrogen- containing raffinate that is subsequently contacted with the sulfuric acid solution described above. [0010] In yet another embodiment, the raffinate effluent is solvent dewaxed after being treated with the sulfuric acid solution to produce at least a dewaxed raffinate effluent. The dewaxed raffinate effluent is subsequently treated by a process selected from hydrotreating, hydrofmishing, hydrodewaxing to produce a lube oil boiling range product.

DETAILED DESCRIPTION OF THE INSTANT INVENTION

[0011] Catalytic processes are typically impeded by the presence of nitrogen, among other things. These nitrogen-containing heterocyclic molecules act as competitive inhibitors of catalytic sites. In lubes processing, the nitrogen-containing heterocyclic molecules force refiners to operate hydrodewaxing processes at temperatures higher than desired. This increased operating temperature increases the relative amount of cracking in relation to isomerization when compared to a process operated at lower temperatures. Thus, by reducing the content of nitrogen-containing heterocyclic species in a feedstream, catalytic dewaxing processes can operate at a lower temperature that favors isomerization over cracking thereby increasing both lube oil product yield and viscosity index ("VI"). The removal of heterocyclic nitrogen species also pennits the practitioner of catalytic dewaxing processes to utilize hydrogen pressures lower than processes utilizing nitrogen feedstreams having higher nitrogen concentrations. The reduction in nitrogen-containing heterocyclic molecules also benefits other lube oil processes such as, for example, hydrotreating and hydrofmishing.

[0012] Therefore, the instant invention is directed at an improved method for the hydroprocessing of a nitrogen-containing lube oil boiling range raffinate. This embodiment involves solvent extraction of a nitrogen- containing lube oil boiling range feedstream to produce at least one nitrogen- containing lube oil boiling range raffinate. The nitrogen-containing lube oil boiling range raffinate is then contacted with a sulfuric acid solution, thus reducing the nitrogen content of the lube oil boiling range feedstream by at least 80 wt.%. The contacting of the nitrogen-containing lube oil boiling range raffinate with the sulfuric acid solution produces at a mixture comprising a raffinate effluent and a used sulfuric acid solution. The raffinate effluent is subsequently processed with a process selected from hydrotreating, hydrodewaxing, and hydrofinishing to produce a lube oil boiling range product.

[0013] Lube oil boiling range feedstreams suitable for treatment in the present methods include any conventional feedstreams used in lube oil processing. Such feedstreams typically include wax-containing feedstreams such as feeds derived from crude oils, shale oils and tar sands as well as synthetic feeds such as those derived from the Fischer-Tropsch process. Typical wax-containing feedstocks for the preparation of lubricating base oils have initial boiling points of about 315°C or higher, and include feeds such as reduced crudes, hydrocrackates, raffinates, hydrotreated oils, atmospheric gas oils, vacuum gas oils, coker gas oils, atmospheric and vacuum resids, deasphalted oils, slack waxes and Fischer-Tropsch wax. Such feeds may be derived from distillation towers (atmospheric and vacuum), hydrocrackers, hydrotreaters and solvent extraction units, and may have wax contents of up to 50% or more. Preferred lube oil boiling range feedstreams boil above about 650°F (343°C). [0014] The at least one lube oil boiling range raffinate used herein is produced by solvent extracting a lube oil boiling range feedstream, such as those described above. In this embodiment, the lube oil raffinates so produced boil within the range described above and prefened lube oil boiling range raffinates boil above about 650°F (343°C). The lube oil boiling raffinate may also comprise mixtures of lube oil raffinates boiling within the above-defined parameters. Thus, more than one lube oil boiling range feedstream can be solvent extracted, and the resulting lube oil boiling range raffinates combined, or treated separately, to form one lube oil boiling range raffinate that is contacted with the sulfuric acid solution. The lube oil raffinates may be either fully or partially extracted, i.e. under-extracted. By under- extracted it is meant that, the extraction is earned out under conditions such that the raffinate yield is maximized while still removing most of the lowest quality molecules from the feed. Raffinate yield may be maximized by controlling extraction conditions, for example, by lowering the solvent to oil treat ratio and/or decreasing the extraction temperature.

[0015] Lube oil raffinates used herein can be produced under standard solvent extracting conditions, and the conditions chosen are not critical as long as the raffinate so produced meets the above-described boiling range criteria. Typically, the solvent extracting process involves contacting a lube oil boiling range stream with an extraction solvent. The extraction solvent can be any solvent known that has an affinity for aromatic hydrocarbons in preference to non-aromatic hydrocarbons. Non-limiting examples of such solvents include sulfolane, furfural, phenol, and N-methyl pynolidone ("NMP"). Furfural, phenol, and NMP are prefened. [0016] The lube boiling range stream can be contacted with the extraction solvent by any suitable solvent extraction method. Non-limiting examples of such include batch, semi-batch, or continuous. It is prefened that the extraction process be a continuous process, and it is more prefened that the continuous process be operated in a counter-cunent fashion. In a counter- cunent configuration, it is prefened that the lube oil boiling range feedstream be introduced into the bottom of an elongated contacting zone or tower and caused to flow in an upward direction while the first extraction solvent is introduced at the top of the tower and allowed to flow in a downward direction, counter-cunent to the upflowing lube oil boiling range feedstream. In this configuration, the lube oil boiling range feedstream is forced to pass counter- cunently to the extraction solvent resulting in the intimate contact between the extraction solvent and the lube oil boiling range feedstream. The extraction solvent and the light lube stream migrate to opposite ends of the contacting zone.

[0017] The conditions under which the extraction solvent is contacted with the lube oil boiling range feedstream can be any conditions known to be effective in the solvent extraction of lube oil boiling range feedstreams. In a prefened embodiment, the temperature and pressure are selected to prevent complete miscibility of lube oil boiling range feedstream in the extraction solvent.

[0018] The contacting of the lube oil boiling range feedstream with the extraction solvent produces at least a first aromatics-rich extract solution and a first aromatics-lean raffinate solution. It should be noted that as used herein, aromatics-lean is meant to refer to the concentration of aromatics present in the raffinate phase produced by solvent extraction in relation to the concentration of aromatics present in the extract phase produced by solvent extraction. The first aromatics-lean raffinate solution is then treated to remove at least a portion of the extraction solvent contained therein, thus producing the lube oil boiling range raffinate used herein. The removal of at least a portion of the extraction solvent can be done by any means known in the art effective at separating at least a portion of an extraction solvent from an aromatics lean raffinate solution. Preferably the lube oil boiling range raffinate is produced by separating at least a portion of the first extraction solvent from the first aromatics-rich extract solution in a stripping or distillation tower. By at least a portion, it is meant that at least about 80 vol%, preferably about 90 vol%, more preferably 95 vol%, based on the first aromatics-lean raffinate solution, of the extraction solvent is removed from the aromatics-lean raffinate solution. Most preferably substantially all of the extraction solvent is removed from the aromatics-lean raffinate solution. It should be noted that when the solvent extracting method that produces the lube oil boiling range raffinate is referenced herein, it is meant to encompass this separation step.

[0019] The lube oil boiling range feedstreams suitable for treatment by the present method contain, among other things, heterocyclic nitrogen-containing compounds. Typically, the total nitrogen content of such streams is greater than about 10 wppm. Thus, these streams are sometimes refened to herein as nitrogen-containing lube oil boiling range feedstreams and raffinates. The nitrogen compounds appears as both basic and non-basic nitrogen species. Non-limiting examples of basic nitrogen species may include quinolines and substituted quinolines, and non-limiting examples of non-basic nitrogen species may include carbazoles and substituted carbazoles. [0020] In practicing the embodiments of the instant invention, the above- defined lube oil boiling range raffinates are intimately contacted with a sulfuric acid solution to remove at least about 80 vol.% of the nitrogen species, both basic and non-basic. The sulfuric acid solution used herein contains at least about 75 wt.% sulfuric acid, based on the sulfuric acid solution, preferably greater than about 85 wt.%, more preferably about 92 wt.% to about 98 wt.%. The sulfuric acid solution may be obtained through any means known. However, in one embodiment the sulfuric acid solution is the spent sulfuric acid obtained or recycled from an alkylation process unit having a sulfuric acid concentration within the above-defined ranges.

[0021] A typical alkylation process involves combining an olefinic hydrocarbon feedstream containing C₄ olefins with isobutane to produce a hydrocarbonaceous mixture. This hydrocarbonaceous mixture is subsequently contacted with sulfuric acid. The sulfuric acid used for contacting the hydrocarbonaceous mixture is typically reagent grade sulfuric acid having an acid concentration of at least about 95 wt.%. Preferably the sulfuric acid has a sulfuric acid concentration of greater than about 95 wt.%. The hydrocarbonaceous mixture is contacted with the sulfuric acid under conditions effective at producing at least an alkylate and a sulfuric acid solution. The sulfuric acid solution so produced comprises at least about 75 wt.% sulfuric acid, based on the sulfuric acid solution, preferably greater than about 80 wt.% sulfuric acid, more preferably about 80 vol.% to about 95 wt.% sulfuric acid. The sulfuric acid solution also typically contains about 0.5 to about 5 wt.% water, with the remaining balance being acid suspended hydrocarbons. It is more prefened that the effective conditions be selected such that the sulfuric acid solution so produced comprises between about 82 and 92 wt.% sulfuric acid, about 1 to about 4 wt.% water, with the remaining balance being suspended hydrocarbons. However, it is most prefened that the effective conditions be selected such that the sulfuric acid solution so produced comprises between about 92 and 98 wt.% sulfuric acid, about 1.5 to about 4 wt.% water, with the remaining balance being suspended hydrocarbons.

[0022] It should be noted that it is within the scope of the present invention to dilute the sulfuric acid obtained from the alkylation unit, or otherwise, with a suitable diluent, preferably water, in order to provide a sulfuric acid solution having the above-described concentration of sulfuric acid, i.e. at least about 75 wt.% sulfuric acid, based on the sulfuric acid solution, preferably greater than about 80 wt.%), more preferably about 80 wt.% to about 95 wt.%. In order to determine the sulfuric acid concentration once the diluent has been added to the sulfuric acid solution, the sulfuric acid content and water content are measured by standard analytical techniques. The equivalent acid strength can then be calculated with the following formula: equivalent wt% sulfuric acid = wt% sulfuric acid / (wt% sulfuric acid + wt% water).

[0023] As discussed above, the lube oil boiling range raffinate is contacted with the sulfuric acid solution at an acid volumetric treat rate of greater than about 0.1 vol.%, based on the lube oil boiling range raffinate, preferably greater than about 0.5 vol.% more preferably about 0.5 vol.% to about 2.0 vol.%. The contacting can be achieved by any method known to be effective at remove nitrogen compounds from a lube oil boiling range raffinate by contacting it with a sulfuric acid solution. Non-limiting examples of suitable contacting methods include passing the sulfuric acid solution and the lube oil boiling range raffinate through a mixing valve, mixing the sulfuric acid solution and the lube oil boiling range raffinate in a mixing tank or vessel, and, passing the sulfuric acid solution and the lube oil boiling range raffinate through a packed bed of inert particles, and other comparable methods. In a prefened embodiment, a mixing tank or mixing valve is used to contact the lube oil boiling range raffinate and the sulfuric acid solution.

[0024] The contacting of the lube oil boiling range raffinate with the sulfuric acid solution occurs under effective conditions. By effective conditions, it is to be considered those conditions that allow the present method to achieve a reduction of nitrogen of at least about 80 wt.%, preferably greater than about 85 wt.%, more preferably greater than 90 wt.%. Effective conditions include contact times of at least about 1.0 second, preferably about 10 to about 120 seconds, more preferably about 30 to about 90 seconds, and treat rates as defined above.

[0025] The contacting of the lube oil boiling range raffinate with the sulfuric acid solution produces at least a mixture comprising a raffinate effluent and a used sulfuric acid solution. The mixture is preferably separated into a raffinate effluent and a used sulfuric acid solution. The used sulfuric acid solution, which now contains the removed nitrogen species, and the raffinate effluent can be separated by any means known to be effective at separating an acid from a hydrocarbon stream. Non-limiting examples of suitable separation methods include gravity settling, electric field induced settling, centrifugation, microwave induced settling and settling enhanced with coalescing surfaces. However, it is prefened that the raffinate effluent and the used sulfuric acid solution be separated, or allowed to separate, into layers in a separation device such as a settling tank or drum, coalescer, electrostatic precipitator, or other similar device.

[0026] The raffinate effluent thus obtained by the present method will contain substantially less nitrogen, both basic and non-basic, than the initial lube oil boiling range raffinate. By substantially less, it is meant that the nitrogen content of the lube oil boiling range raffinate is reduced by at least about 80 wt.%, preferably greater than about 85 wt.%, more preferably at least 90 wt. This will typically result in a raffinate effluent having a nitrogen level of less than about 20 wppm, preferably less than about 15 wppm, more preferably less than about 10 wppm, and most preferably less than about 5 wppm.

[0027] The raffinate effluent is preferably withdrawn from the separation device and passed to a suitable lube oil process such as, for example, hydrodewaxing, hydrotreating and hydrofinishing. In this embodiment, any suitable hydrodewaxing, hydrotreating or hydrofmishing catalyst can be used under any conditions effective at achieving the results sought by the practitioner, i.e. converting a certain percentage of the feed in hydrodewaxing operations, removing a certain amount of sulfur impurities in hydrotreating operations, etc.

[0028] As stated above, in one embodiment, the nitrogen-containing raffinate described above is solvent dewaxed to produce a dewaxed nitrogen- containing raffinate that is subsequently contacted with the sulfuric acid solution described above. The nitrogen-containing raffinate can be dewaxed under standard solvent dewaxing conditions. [0029] The dewaxing solvent used may include the C₃-C₆ ketones such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), mixtures of MEK and MIBK, aromatic hydrocarbons like toluene, mixtures of ketones and aromatics like MEK/toluene, ethers such as methyl t-butyl ethers and mixtures of same with ketones or aromatics. Similarly, liquefied, normally gaseous hydrocarbons like propane, propylene, butane, butylene, and combinations thereof may be used as the solvent. Preferably the solvent employed will be an equal volume mixture of methyl ethyl ketone and methyl isobutyl ketone. Typically the isomerate to solvent ratio will range between 1 to 10 and preferably will be about 1:3. The dewaxed lube oil boiling range feedstream is then subjected to treatment with a sulfuric acid solution to remove at least a portion of the nitrogen heterocyclic compounds contained therein as described herein.

[0030] In yet another embodiment, the raffinate effluent is solvent dewaxed after being treated with the sulfuric acid solution to produce at least a dewaxed raffinate effluent. The dewaxed raffinate effluent is subsequently treated with a process selected from hydrotreating, hydrodewaxing, and hydrofinishing to produce a lube oil boiling range product.

[0031] The above description is directed to several embodiments of the present invention. Those skilled in the art will recognize that other embodiments that are equally effective could be devised for carrying out the spirit of this invention. [0032] The following examples will illustrate the improved effectiveness of the present invention, but is not meant to limit the present invention in any fashion.

EXAMPLES EXAMPLE 1

[0033] Two lube raffinate samples were separately combined in glass vials with a spent alkylation unit sulfuric acid solution at various treat rates. The sulfuric acid solution had an acid concentration of 96.1 vol.%. The first lube raffinate is refened to herein as feed #1 and the second as feed #2. Feed #1 was a 100N lube raffinate, and feed #2 was a 150N raffinate.

[0034] 10ml of Feed #1 was separately combined with 0.025ml (0.25 vol.% treat rate), 0.050ml (0.50 vol.% treat rate), 0.10ml (1.0vol.% treat rate), and 0.20ml (2.0 vol.% treat rate) of the sulfuric acid solution, respectively. Two 10ml samples of Feed #2 were separately combined with 0.050ml (0.50 vol.% treat rate), 0.10ml (1.0vol.% treat rate) of the sulfuric acid solution, respectively. The mixtures were shaken by hand for 60 seconds and then allowed to separate at room temperature. The two phases, i.e. the lube oil boiling range effluent and the sulfuric acid solution, separated and the lube oil effluent layer was removed. The lube oil effluent thus removed was weighed and analyzed by ANTEK for nitrogen and sulfur contents. The results of this experiment along with the various treat rates are contained in Table 1 below.

[0035] As can be seen in Table 1, both feeds responded well to treatment with the acidic solution, with nearly quantitative nitrogen removal. Low feed losses were also observed. The feed recovered was calculated by dividing the weight of lube oil effluent recovered by the weight of the lube oil feedstream and then multiplying by 100. Reductions in sulfur were also observed. Feed#l contained 6350wppm sulfur but contained only 5150wppm after treatment with the spent sulfuric acid solution at lvol.% treat rate. Likewise, feed #2 initially contained 1290wppm sulfur but contained 577wppm after treatment with the spent sulfuric acid solution at lvol.% treat rate.

EXAMPLE 2 [0036] The effects of nitrogen removal on hydrodewaxing were also tested. A MSDW-2 commercial dewaxing catalyst was obtained from ExxonMobil. 5 cc of catalyst was loaded into a 3/8 inch stainless steel tube. Sand was added to fill the tube above and below the catalyst, separated from the catalyst by quartz wool. A nickel plated copper jacket was employed around the reactor to ensure even heat distribution. [0037] The catalyst was dried in the reactor with nitrogen using a temperature ramp of 2°C per minute until a temperature of 350°C was reached. The reactor was then cooled to 200°C, and the nitrogen was replaced with hydrogen. The reactor was pressurized to 600psig (4240kPa), hexadecane (nC16) was introduced at a liquid hourly space velocity of 2.0, and the temperature was increased to 270°C after the catalyst was wetted. The conversion, selectivity, and reactor temperature were measured.

[0038] Two more experiments were conducted in which quinoline, a 2-ring aromatic compound containing nitrogen in one ring, was added in various amounts to the feed as reactor temperature was increased to achieve conversion similar to those achieved on the hexadecane feed without quinoline. The amount of quinoline added was enough to provide a feed having a nitrogen concentration as described in Table 2 below, which shows the results of all three of these experiments.

[0039] Table 2 illustrates that as the nitrogen content of the feed increases, the temperature required to achieve the same conversion increases also. This increase in reactor temperature is well known in the art to lower the yield of lube oil boiling range products. Thus, if nitrogen could be removed from a paraffmic feedstream, the reactor temperature used in dewaxing the paraffmic feed would decrease and yield would increase. EXAMPLE 3 [0040] A MSDW-2 commercial dewaxing catalyst was obtained from ExxonMobil. 5 cc of catalyst was loaded into a 3/8 inch stainless steel tube. Sand was added to fill the tube above and below the catalyst, separated from the catalyst by quartz wool. A nickel plated copper jacket was employed around the reactor to ensure even heat distribution.

[0041] The catalyst was dried in the reactor with nitrogen using a temperature ramp of 2°C per minute until a temperature of 350°C was reached. The catalyst was sulfided using 2% H₂S in hydrogen for 1 hour at 350°C. The reactor was then cooled to 200°C, and the 2% H₂S in hydrogen was replaced with substantially pure hydrogen. The reactor was pressurized to 600psig (4240kPa), hexadecane (nC16) was introduced at a liquid hourly space velocity of 1.0, and the temperature was increased to 270°C after the catalyst was wetted. The conversion, selectivity, and reactor temperature were measured. 40 wppm of nitrogen as 7,8-benzonquinoline, a 3-ring aromatic having nitrogen in one ring, was added, and the reactor temperature was increased to achieve conversions similar to those achieved without the presence of nitrogen. The liquid hourly space velocity was also increased to 2.0. The results of these experiments are contained in Table 3 below.

[0042] Again, the results contained in Table 3 illustrate that the temperature needed to achieve similar conversions of hexadecane increased with the presence of nitrogen.

EXAMPLE 4

[0043] A 13 ON lube oil boiling range raffinate was obtained by solvent extracting a lube oil boiling range feedstream with NMP solvent. The lube oil boiling range raffinate had a boiling range above 370°C, a nitrogen concentration of 33 wppm and also contained 7270wppm sulfur.

[0044] A commercial MSDW-2 catalyst was obtained from ExxonMobil and a commercial KF-840 hydrotreating catalyst was obtained from Akzo Nobel. 100 cc of the MSDW-2 catalyst was placed in a 250cc reactor and 100 cc of the KF-840 hydrotreating catalyst was placed in a 250 reactor. The remainder of each reactor was filled with inert materials. The two reactors were placed in series such that the effluent produced from the reactor containing the MSDW-2 ("Reactor 1 ") catalyst was conducted to the reactor containing the KF-848 catalyst ("Reactor 2") without interstage gas separation. The lube oil boiling range raffinate described above was hydroprocessed through the reactor system. The processing conditions in Reactor 1 included hydrogen pressures of 400psig, liquid hourly space velocities of 0.47hr^"1, hydrogen treat gas rates of 2700scf/bbl H₂, and temperatures from 370°C to 381°C. The processing conditions in Reactor 2 included hydrogen pressures of 400psig, liquid hourly space velocities of 0.47hr^"1, hydrogen treat gas rates of 2700scf/bbl H2, and temperatures of 290°C. [0045] The product obtained through processing the 13 ON lube oil boiling range raffinate was fractionated into a lube oil boiling range product boiling above 370°C and one boiling below 370°C. The pour point of the fraction boiling above 370°C was measured according to ASTM D5985, and the temperature in Reactor 1 was increased to try and lower the pour point. The results of this example are contained in Table 4 below.

[0046] As can be seen from the results in Table 4, a lube oil boiling range product having a pour point lower than -19°C could not be produced by processing the lube oil boiling range raffinate containing 33wppm even by raising the reactor temperature to over 380°C.

EXAMPLE 5

[0047] The same 13 ON lube oil boiling range raffinate as used in Example 4 was treated by contacting it with a sulfuric acid solution having a sulfuric acid concentration of 96 wt.% at a treat rate of 1.0 vol.%. The resulting raffinate had a nitrogen content reduced to 4 wppm and a sulfur content of 6020 wppm. The sulfuric acid treated raffinate was hydroprocessed in a 250cc continuous flow reactor at 400 psig H2, and a space velocity of 0.5 LHSV/hr., and 5100 scf/bbl H2, over one bed containing 100 cc MSDW-2 commercial Pt containing dewaxing catalyst. The remainder of the reactor was filled with inert material. Table 5 below shows the results of this Example, i.e. the pour points obtained on the 370°C+ fraction of the oil as a function of the reactor temperature.

[0048] Example 5 illustrates that it was possible to lower the pour point of the lube oil product as low as -47°C at reactor temperatures of 350°C or less by first treating the raffinate with a sulfuric acid solution to reduce the nitrogen concentration therein. This demonstrates a significant increase in dewaxing catalyst activity as compared to Example 4 by using the reduced nitrogen content feed.

Claims

CLAIMS:

1. An improved method for hydroprocessing a nitrogen-containing lube oil boiling range feedstream comprising: a) solvent extracting at least one nitrogen-containing lube oil boiling range feedstream under conditions effective for producing at least a nitrogen-containing raffinate having a boiling point in the lube oil range; b) providing a sulfuric acid solution having a sulfuric acid concentration of at least about 75 vol.%, based on the sulfuric acid solution; c) contacting the nitrogen-containing lube oil boiling range raffinate with the sulfuric acid solution under conditions effective at removing at least about 80 wt.% of the nitrogen compounds contained in said lube oil boiling range raffinate thereby producing at least a mixture comprising a raffinate effluent and a used sulfuric acid solution, wherein the volumetric treat rate of the sulfuric acid solution is greater than about 0.1 vol.%, based on the lube oil boiling range raffinate; and d) processing said raffinate effluent by a process selected from solvent dewaxing, hydrotreating, hydrodewaxing, and hydrofinishing.

2. The method according to claim 1 wherein the nitrogen-containing lube oil boiling range feedstream has an initial boiling point of about 315° C.

3. The method according to any preceding claim wherein nitrogen- containing lube oil boiling range feedstream contains about 50% wax.

4. The method according to any preceding claim wherein the at least one nitrogen-containing lube oil boiling range raffinate has an initial boiling point of about 315° C.

5. The method according to any preceding claim wherein more than one lube oil boiling range feedstream is solvent extracted to produce more than one lube oil boiling range raffinate, and the more than one lube oil boiling range raffinates are combined to form one lube oil boiling range raffinate that is contacted with the sulfuric acid solution.

6. The method according to any preceding claim wherein said sulfuric acid solution is a spent sulfuric acid solution obtained from an alkylation process unit.

7. The method according to any preceding claim wherein the at least one lube oil boiling range raffinate is fully extracted.

8. The method according to any preceding claim wherein the at least one lube oil boiling range raffinate is partially extracted or under extracted.

9. The method according to any preceding claim wherein the nitrogen- containing raffinate is solvent dewaxed to produce a dewaxed nitrogen- containing raffinate that is subsequently contacted with the sulfuric acid solution described above.

10. The method according to any preceding claim wherein the raffinate effluent is solvent dewaxed after being treated with the sulfuric acid solution to produce at least a dewaxed lube oil boiling range effluent.

11. The method according to any preceding claim wherein the sulfuric acid obtained from the alkylation unit is diluted with a suitable diluent.

12. The method according to any preceding claim wherein the volumetric treat rate of the sulfuric acid solution is greater than about 0.5 vol.%.

13. The method according to any preceding claim wherein the volumetric treat rate of the sulfuric acid solution is about 0.5 vol.%> to about 2.0 vol.%>.

14. The method according to any preceding claim wherein the nitrogen- containing lube oil boiling range raffinate and the sulfuric acid solution are intimately contacted by any method known to be effective in contacting a lube oil boiling range raffinate and a sulfuric acid solution to reduce the nitrogen content of the lube oil boiling range raffinate.

15. The method according to any preceding claim wherein the contacting method is selected from mixing valves, mixing tanks, mixing vessels, passing the sulfuric acid solution and the lube oil boiling range raffinate through a packed bed of inert particles, and other comparable devices.

16. The method according to any preceding claim wherein said method further comprises separating said raffinate effluent and said used sulfuric acid solution.

17. The method according to any preceding claim wherein the raffinate effluent and the sulfuric acid solution are separated by any means known to be effective at separating an acid from a hydrocarbon stream.

18. The method according to any preceding claim wherein the raffinate effluent and the sulfuric acid solution are separated by a separation device selected from settling tanks or drums, coalescers, electrostatic precipitators, or other similar device.

19. The method according to any preceding claim wherein the process selected from solvent dewaxing, hydrocracking, hydrotreating, hydrodewaxing, and hydrofinishing is operated under effective conditions.