US3617484A

US3617484A - Increasing the v.i. of hydrocracked light lubes

Info

Publication number: US3617484A
Application number: US780241A
Authority: US
Inventors: Sheldon L Thompson; Albert T Olenzak; Rene F Kress; Ib Steinmetz
Original assignee: Sun Oil Co
Current assignee: Sunoco Inc
Priority date: 1968-11-29
Filing date: 1968-11-29
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02
Also published as: FR2024536B1; NL6916947A; GB1270439A; BR6914224D0; NL160870B; FR2024536A1; DE1959869B2; JPS4949006B1; DE1959869A1; DE1959869C3; BE742422A; NL160870C

Abstract

A process for increasing the V.I. of a light lube fraction approximating the viscosity range of a 100 Neutral oil which has been hydrocracked as part of a relatively wide-range lube fraction wherein the light lube fraction is isolated and rehydrocracked in the absence of heavier fractions.

Description

United States Patent Inventors Sheldon L. Thompson Glen Mills;

Albert T. Olenzak; Rene F. Kress, Media, Pa.; Ib Steinmetz, Wilmington, Del. 780,241

Nov. 29, 1968 Nov. 2, 1971 Sun Oil Company Philadelphia, Pa.

INCREASING THE V.l. OF HYDROCRACKED LIGHT LUBES 5 Claims, No Drawings Int. Cl C 10g 37/02 Field of Search 208/19, 59, 264, 18

Primary Examiner-Herbert Levine Attorneys-George L. Church, Donald R. Johnson, Wilmer E.

McCorquodale, Jr. and Harold M. Dixon ABSTRACT: A process for increasing the V.l. ofa light lube fraction approximating the viscosity range of a 100 Neutral oil which has been hydrocracked as part of a relatively widerange lube fraction wherein the light lube fraction is isolated and rehydrocracked in the absence of heavier fractions.

Neutral oil, derived from hydrocracked lubricating oil product by subjecting said isolated fraction to a second hydrocracking treatment.

BACKGROUND OF THE INVENTION Various processes have been used from time to time for upgrading lubricating oil stocks. These have generally involved either solvent extraction or hydrogenation including hydrocracking treatment. In more recent times, there has been a demand for lubricating oils having an increased viscosity index. Recent developments, particularly in hydrocracking techniques, or hydrotreating techniques, as some prefer to call it, have given birth to an increased interest in commercial utilization of such hydrogenation processes as a lubricatingoil-stock-upgrading method to obtain lubricating oils with an increased viscosity index. Briefly, this has involved catalytic hydrocracking of the lubricating oil stock at a temperature on the order of about 650 F. and above at high partial pressures of hydrogen. The lube stocks that are hydrocracked are also subjected before and after the hydrocracking to many of the conventional refining operations. Among these is the substantially final step of fractionating or distilling the lube stock into various fractions according to viscosity which can then be blended to obtain a particular desired viscosity. The first fraction typically has an S.U.S. viscosity of about 100 and 100 F. and a boiling range of about 700 to 800 F. This is usually referred to in the industry as 100 Neutral. While hydrocracking processes have greatly enhanced the viscosity index of the lubricating oil stocks so treated, on occasion at least certain fractions and especially the lighter fractions (e.g., 100 Neutral) are somewhat lower in viscosity index than the heavier fractions. It is desirable that the lighter fractions be of substantially the same V.I. as the heavier fractions. Typically, the lighter and first fractions comprise about one-third of the total finished lube product. Therefore, it is quite important that it have a fully satisfactory character such as viscosity index. It would be highly advantageous to provide a method for enhancing the viscosity index of the lighter fractions of hydrocracked lube oil product. It is therefore a primary object to prepare lubricating oils in high yields and having a high V.I. and particularly the lighter fractions or 100 Neutral product of a finished lube stock. It is another object to accomplish the V.I. enhancement without undue adverse effects on the other properties of the oil. It is still a further object to accomplish the objects of this invention in a relatively economical fashion. Other objectives will become apparent from the comments found herein.

SUMMARY OF THE INVENTION To the accomplishment of the foregoing and related ends a paraffinic-base lube oil stock which has been hydrocracked over a hydrocracking catalyst at a temperature above about 650 F. under high pressure is fractionated into a first cut boiling in the range of about 700to 800 F. and a viscosity of about I at 100F., and said hydrocracked fraction boiling in the range of about 700to 800 F. is then separately rehydrocracked under substantially the same conditions as the total charge in the first step, and finally the rehydrocracked product fraction is recovered. When recovered, the rehydrocracked fraction has an enhanced V.I.

The results obtained by this invention are unexpected since the same viscosity index enhancement of the lighter fraction or I00 Neutral is not realized if it is recycled in contrast to the present inventive procedure of the isolation and the separate rehydrocracking of the 100 Neutral fraction in the absence of substantial amounts of heavier fractions.

The broad and preferred conditions of the hydrocracking operation, some of the soluble feedstocks, conventional operations which are to be carried out, and equally important, which conventional operations can or are to be omitted are described in great detail in U.S. Pat. No. 2,960,458. The teachings of that patent are incorporated here in entirety but with certain important variations that will be found hereinafter. As a matter of convenience to the reader, a relatively brief summary of certain of the teachings of that patent are set forth hereinbelow.

These teachings of the patent comprise the following: A deasphalted residuum having a V.I. in the range of about 75 and 100 and a viscosity at 210 F. in the range of about to 200 S.U.S. is treated with hydrogen at a temperature between about 650and 825 F. but preferably between about 735and 825 F. at a pressure of at least about 1,500 p.s.i. but more usually and preferably above about 2,500 and at a space velocity between about 0.2 and 4.0 but more usually about 0.4 and 1.5. The treatment with hydrogen is carried out in the presence of a catalyst having both aromatic saturation and ring-scission activity, which broadly comprises a sulfide of any metal of Group VI, left-hand column, of the periodic system mixed with an iron group metal, for example, a nickel sulfide and tungsten sulfide catalyst in about a l:l to 4:] metal ratio. The product from the hydrogen treatment is subjected to dewaxing (when necessary) and is then distilled to yield components most of which directly, or upon blending with each other, meet the SAE specifications for a multigrade lubricating oil and have a V.I. of about and preferably or above.

U.S. Pat. No. 2,960,548 teaches that in order to obtain suitable yields of multigrade oils having the desired viscosity it is essential to employ as the charge to the hydrocracking reactor residual-type charge stocks; however, in the present invention at least, vacuum distillates, Duo-sol extracted residuum, residuums extracted with a solvent having preferential solubility for aromatics such as furfural and phenol, or blends of the foregoing are also suitable. The procedures for carrying out the extraction can be found in copending application Ser. No. 743,915 filed July 3, 1968, by Rene F. Kress. The charge should have an initial boiling point at above about 650 F. and preferably about above 700 F. The residuum starting material, however, can be any residuum obtained by atmospheric or vacuum distillation, or the like, of any petroleum or residual fraction thereof which after deasphalting, preferably with a low-boiling hydrocarbon such as propane, propylene, or butane, has a V.I. of 75 to 100 and a viscosity at 210 F. of about 45 to 200 S.U.S. but is preferably above 50 S.U.S and still more preferably at least about 90 S.U.S. Thus, for instance, the residuum may be prepared by vacuum distillation of a Pennsylvania, Mid-Continent, West Texas, Kuwait. etc., crude. Unlike U.S. Pat. No. 2,960,458, deasphalting with agents such as sulfuric acid, phenol, sulfur dioxide, etc., in the present invention does not necessarily result in removal of components which upon hydrogenation have desirable properties for a multigrade oil product. In this invention if these materials are employed for asphalt removal, the product produced in some cases is of as good or better quality; and the yield of multigrade oils is the same or even better in some cases. A higher carbon residue will result in undesirable shortening of the life of the catalyst under the relatively severe hydrogen treatment conditions employed to produce the multigrade oil. For this reason, it is usually preferred to employ charge stocks having a low-carbon 2 such as below about 2 (Conradson). However, higher carbon residue charge stock may be used if catalyst life is not of great importance or if a rugged catalyst is used. The utilization of charge stock having a V.I. of 75 to 100 is essential in obtaining a reasonable yield ofa multigrade lubricating oil; i.e., a V.I. of above about 100 is produced in good yield only if a charging material of at least about 75 V.I. is employed. It will result in drastically lower yields if a lower than 75 V.I. charge stock is used. Unlike U.S. No. 2,960,458, a viscosity of between about 90 and 200 S.U.S.

at 210 F. is not absolutely required as the viscositymay be as low as about 45 S.U.S. but preferably is above about 50 S.U.S. at,2 F. The only important difference in using a feed having a viscosity below about 90 S.U.S. at 210 F. is the product viscosity and product distribution. When a feed having a viscosity below about 90 S.U.S., for example, about 60 S.U.S., is charged, a full range of the conventionally desired blend stocks will not be obtained. Unless the feed has a viscosity of at least about 45 S.U.S., there will be little if any lube fraction produced having a viscosity in the range of a 200 Neutral oil; and the problem of adjusting reaction conditions to produce a 100 Neutral oil with a satisfactory V.l. will not be encountered. At viscosities below about 45 S.U.S. the only lube oil product is essentially one that is in the viscosity range of a 100 Neutral oil. A substantial amount of lighter material is, of course, simultaneously produced. As the viscosity increases above about 45 S.U.S., the problem of producing a 100 Neutral becomes more difficult; and as a consequence thereof, the need for this invention increases. To the extent that it is most frequently desired to produce a lube product containing the full range of conventional blending stocks for maximum flexibility in blended product viscosities, this invention is most advantageously and preferably employed with feeds having a viscosity of about 90 to 200 S.U.S. at 210F.

In many cases the lighter or l00 Neutral fraction obtained from the foregoing hydrocracking procedure does not exceed about I00 V.l. or is even less. Where the lighter fractions V.l. is desirably higher, according to the present invention, it alone is rehydrocracked at the foregoing conditions employed in the first hydrocracking step. The preferred conditions in the initial hydrocracking treatment are especially preferred in rehydrocracking the 100 Neutral fraction. in order to provide fullness of disclosure, the conditions for the rehydrocracking of the No. l distillate fraction will now be set forth although they are the same as the initial hydrocracking conditions employed for the total original feedstock.

ln brief, the procedure comprises charging the No. l distillate with hydrogen at a temperature between about 650and 825 F., preferably between 700and 800 F., and most preferably in the range of about 735to 775 F., a pressure above 1,500 psi. but more usually and preferably about 2,500, and a space velocity between about 0.2 and 4.0 but more usually about 0.4 and 1.5. The treatment with hydrogen is carried out in the presence of a catalyst having both aromatic saturation and ring-scission activity, which broadly comprises a sulfide of any metal of Group Vl, left-hand column, of the periodic system mixed with an iron group metal, for example, a nickel sulfide and tungsten sulfide catalyst, in about a 1:1 to 4:1 metal ratio. Other variations of the hydrocracking process are well known or suggested in the art and are to be considered included within the scope of this invention. Examples of such are those described in U.S. Pat. No. 2,917, 448 to Beuther et al.; U.S. Pat. No. 3,046,218 to Henke et al., U.S. 3,222,272 to Bercik et al. Especially important variations are the improved catalysts described in U.S. Pat. No. 3,078,221 to Beuther et al. and U.S. Pat. No 3,078,238 to Beuther et al. In addition, other variations are known and of catalysts in particular. An example is the suitability of catalysts which are not sulfactive by a proper pretreatment of the feed to remove or convert sulfur and nitrogen compounds to the harmless form. Such catalysts include platinum and palladium metals. Preferably, these and all suitable catalyst metals are employed in the sulfided form.

ILLUSTRATIVE EXAMPLES A charge stock of grade B solvent lube crude mix was charged to a crude still and fractionated into approximately 70 percent and 30 percent of overhead and bottoms, respectively. The bottoms had an initial boiling point at 650 F. at atmospheric pressure. The bottoms were charged to a vacuum still and fractionated to produce a gas oil, a distillate stock, and a residual asphalt stock, the latter two having initial boiling points of about 695 F. and 750 F., respectively. The residual stock was deasphalted and extracted by the Duo-Sol process (which employs propane'and a mixture of phenalcresol as solvents) at approximately 130F. The raffinate from the deasphalter and the distillate'stock from the vacuum still when combined had the following properties:

TABLE 1 Gravity, API 30.5 Vacuum Distillation Range at 2 mm. Adjusted to 760 mm.

Initial 694 70% 964 E.P. 1,030 Recovery, 83 Aniline Point 239.2 SUS/2l0F. 59.7 Average M. W. 505 Wt. Aromatics 22.4

Viscosity index The foregoing mixture was charged to a hydrocracker, and said material was hydrocracked in the preferred manner described in U.S. Pat. No. 2,960,458, i.e., at the preferred conditions and using a preferred nickel-tungsten sulfide catalyst set therein. A hydrogen stream comprising gas and hydrogen, of which about 85 percent was hydrogen, was used in the hydrocracking reaction.

The crude hydrocracked product was charged to a stripper or atmospheric still and fractionated to produce gas, naphtha, and fuel oil, and a waxy lube of initial boiling point of approximately 700F.

At this point a total product of about 105 average V.l. was obtained (on a dewaxed basis), However, the V.l.'s of the separate lube fractions (on a dewaxed basis) were:

Neutral I00 200 Neutral I08 500 Neutral I05 Brightstock l06 The total fraction was dewaxed, and a 100 Neutral fraction was separated and passed through a second hydrocracking reactor.

The product from the second hydrocracking was charged to a stripper or still and light ends removed to produce a 100 Neutral fraction. The yield based on 100 Neutral charged was 75 percent. The details of the hydrocracking conditions in each of the hydrocracking steps as well as the resulting V.l. were as follows:

l. A process comprising hydrocracking a lube oil charge stock boiling above about 650 F., at from about 735 to 825 F and a hydrogen partial pressure of at least 1,500 p.s.i. to produce a hydrocrackate, separating a fraction boiling at from about 700 to 800 F. from said hydrocrackate and separately secondly, hydrocracking said fraction substantially by itself at from about 735 to 775 F. and a hydrogen partial pressure of at least about 1,500 p.s.i. and recovering from said second step recovering a lube oil having an enhanced viscosity index and boiling in the range of about 700 to 800 F., wherein the space velocity in both hydrocracking steps is from 0.4 to 1.5.

2. The process of claim 1 wherein both hydrocracking steps are carried out in the presence of a catalyst which is a sulfactive metal of at least one member of the group consisting of Group Vl b and Group VIII b of the periodic table.

3. The process of claim 2 wherein the oil boiling in the range of from about 700 to 800 F. is recovered from the second hydrocracking step in about a 75 percent yield as based on the oil charge to said second hydrocracking step.

4. The process of claim 3 wherein the catalyst in both hydrocracking steps is a combination of at least two members of the group consisting of nickel sulfide, tungsten sulfide, cobalt sulfide, and molybdenum sulfide,

5. The process of claim 4 wherein the catalyst in both hydrocracking steps is a combination of nickel sulfide and tungsten sulfide in a metal ratio of from 1:1 to 4:1 nickel:tungsten supported on an alumina carrier.

Claims

2. The process of claim 1 wherein both hydrocracking steps are carried out in the presence of a catalyst which is a sulfactive metal of at least one member of the group consisting of Group VI b and Group VIII b of the periodic table.
3. The process of claim 2 wherein the oil boiling in the range of from about 700* to 800* F. is recovered from the second hydrocracking step in about a 75 percent yield as based on the oil charge to said second hydrocracking step.
4. The process of claim 3 wherein the catalyst in both hydrocracking steps is a combination of at least two members of the group consisting of nickel sulfide, tungsten sulfide, cobalt sulfide, and molybdenum sulfide.
5. The process of claim 4 wherein the catalyst in both hydrocracking steps is a combination of nickel sulfide and tungsten sulfide in a metal ratio of from 1:1 to 4:1 nickel: tungsten supported on an alumina carrier.