US3666657A

US3666657A - Oil stabilizing sequential hydrocracking and hydrogenation treatment

Info

Publication number: US3666657A
Application number: US90073A
Authority: US
Inventors: Sheldon L Thompson; Rene F Kress; Albert T Olenzak; Ib Steinmetz
Original assignee: Sun Oil Co
Current assignee: Sunoco Inc R&M; Sunoco Inc
Priority date: 1970-11-16
Filing date: 1970-11-16
Publication date: 1972-05-30
Anticipated expiration: 1989-05-30

Abstract

A process of improving the quality stability of hydrocracked oils by hydrogenating such oils subsequent to the hydrocracking treatment. The hydrocracking conditions comprise a temperature of from 700* to 900* F. and preferably from 700* to 800* F. and a pressure of at least about -500 psi and preferably at least about 1,500 psi over a sulfided mixture of Group VI B metal and Group VIII metal as a catalyst. The hydrogenation conditions comprise a temperature of from about 600* and preferably 625* to 675* F. a pressure of at least about 3,000 psi and the same catalysts as used for the hydrocracking operation.

Description

United States Patent Thompson et al.

Kress; Albert T. Olenzak, both of Media, all of Pa.; lb Steinmetz, Wilmington, Del.

[73] Assignee: Sun Oil Company of Pennsylvania,

Philadelphia, Pa.

[22] Filed: Nov. 16, 1970 [21] App1.No.: 90,073

Related US. Application Data [63] Continuation-impart of Ser. No. 694,096, Dec. 28,

1967, abandoned.

52 U.S.Cl ..208/58,208/18,208/97 [51] Int.Cl ..Cl0g37/06 5s FieldofSearch ..20s 15,1s,14,57,ss,59,

[56] References Cited UNITED STATES PATENTS 2,915,452 12/1959 Fear ..208/57 [451 May 30, 1972 Primary Examiner-Herbert Levine AttorneyGeorge L. Church, Donald R. Johnson, Wilmer E. McCorquodale, Jr. and Frank C Hilberg, Jr.

[57] ABSTRACT A process of improving the quality stability of hydrocracked oils by hydrogenating such oils subsequent to the hydrocracking treatment. The hydrocracking conditions comprise a temperature of from 700 to 900 F. and preferably from 700 to 800 F. and a pressure of at least about 500 psi and preferably at least about 1,500 psi over a sulfided mixture of Group VI 8 metal and Group VIII metal as a catalyst, The hydrogenation conditions comprise a temperature of from about 600 and preferably 625 to 675 F. a pressure of at least about 3,000 psi and the same catalysts as used for the hydrocracking operation.

7 Claims, No Drawings OIL STABILIZING SEQUENTIAL HYDROCRACKING AND HYDROGENATION TREATMENT CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending application Ser. No. 694,096 filed Dec. 28, 1967, by Sheldon L. Thompson, Rene F. Kress, Albert T. Olenzak and lb Steinmetz and now abandoned.

BACKGROUND OF THE INVENTION In the past various processes have been used for upgrading lubricating oil stocks. These generally have involved either solvent extraction or hydrogenation including hydrocracking. Recently there has been an increasing demand for lubricating oils having an increased viscosity index. Recent developments, and particularly in hydrocracking techniques has given birth to increased interest in commercial utilization of such techniques to upgrade lubricating oils particularly with respect to viscosity index. Briefly, this has involved catalytic hydrocracking of the lubricating oil stock at a temperature above about650 F. at high pressures. While such techniques have greatly enhanced the viscosity index of the stocks so treated, they have simultaneously caused said stocks to exhibit a marked increase in color degradation on exposure to ultraviolet light and also to form greater amounts of sludge in the presence of oxygen during such exposure.

It is the main object of the present invention to substantially reduce the extent of color degradation in hydrocracked lubricating oils which occur upon exposure of such oils to actinic radiation and oxygen. It is a further object of this invention to reduce the sludge-forming characteristics of such lube oils under such conditions. Other objects are to prepare lubricating oils in high yields, having a high viscosity index, and of improved stability. It is still a further object to accomplish each of the foregoing objects in an economical fashion.

SUMMARY OF THE INVENTION The present invention involves the discovery that the stability of a hydrocracked lubricating oil can be improved by further hydrogenation using high pressure but at a temperature below that used in the hydrocracking step.

The hydrogenation of this invention may advantageously be used with any lube hydrocracking process which employs temperatures above about 700 F. together with high pressures. Such processes are described in U.S. Pat. Nos. 2,9l7,448; 2,960,458; 3,046,218; 3,078,221; 3,078,238; and 3,088,908 the disclosures of which are hereby incorporated by references. A hydrocracking technique which is preferred for use in the present invention is described in U.S. Pat. No. 2,960,458 which generally involves subjecting a deasphalted residuum having a viscosity index between 75 and 100 and a viscosity at 210 F of between about 90 and 200 S.U.S. to treatment with hydrogen at a temperature of from about 735 to 825 F at a pressure above about 2,500 psi. up to 5,000 psi. or even 10,000 psi. A pressure of 3,600 to about 4,000 psi is preferred. A space velocity of from 0.4 to L5 is generally used. The hydrocracking reaction is carried out in the presence of a catalyst having both aromatic saturation and ring scission activity. Such catalysts are known in the art. For instance they may comprise a sulfide of any metal of Group V! left-hand column of the periodic system mixed with a sulfide of an iron group metal. Specifically the catalyst may be molybdenum sulfide, tungsten sulfide or chromium sulfide mixed with a sulfide of iron cobalt and/or nickel. A particularly desirable catalyst is a mixture of nickel sulfide and tungsten sulfide. Such a catalyst in a ratio of 1 to 4 mols of nickel to 1 mol of tungsten (determined as metals) has especially high activity and selectively. Other examples of satisfactory sulfide mixtures are cobalt sulfide-tungsten sulfide and nickel sulfidemolybdenum sulfide mixtures. The catalyst may be supported or unsupported. A mol ratio of 1:1 of these mixtures has been found satisfactory. The product is subjected to dewaxing when necessary in order to obtain yields of multi-grade oils of the desired viscosity it is essential to employ a residual type charge stock. The starting material may be any residuum obtained by vacuum or like distillation of any petroleum or residual fraction thereof which after deasphalting (if necessary), preferably with a low boiling hydrocarbon such as propane, propylene, or butane, has a viscosity index and a viscosity at 210 F. of to 200 S.U.S. Thus for instance, the resdiuum may be prepared by vacuum distillation of a Pennsylvania, Mid-Continent, West Texas, Kuwait, Ordovician, Lagomedio, etc. crude. It has been found that deasphalting with agents such as sulfuric acid, phenol, sulfur dioxide, etc. results in removal of components which upon hydrogenation have desirable properties for a multigrade oil product; and if these materials are employed for asphalt removal, the product produced will not be of as good quality, and the yield of multigrade oils will be lower. A high carbon residue will result in undesirable shortening of the life of the catalyst under the relatively sever hydrogen treatment conditions employed to produce the multi-grade oil. For this reason, it is usually preferred to employ charge stocks having a low carbon residue such as below about 2 (Conradson). However, higher carbon residue charge stock may be used if catalyst life is not of great importance or a rugged catalyst is used. The utilization of a charge stock having a viscosity index of 75 to is essential in obtaining a reasonable yield of a high viscosity index product i.e., a product having a viscosity index of over about 100 is produced in good yield only if a charge stock having a viscosity index of at least about 75 is employed. A charge stock viscosity of between about 90 and 200 S.U.S. at 210 F. is necessary so that the multi-grade oil product will have the proper viscosity after the hydrogen treatment.

The hydrogenation step which follows the above-described hydrocracking step serves to accomplish the desired results of reduced quality degradation as to both sludge and color. In this hydrogenation step it has been found that not only is the temperature important but that the employment of high pressure is particularly important. It has been found that sludge formation and quality stability in general is greatly increased by hydrogenating the hydrocracked lube stock at a temperature in the range of about 600 and preferably 625 to 675 F. and a pressure of at least about 3,000 psi.

Thepressure generally is in the range of 3,000 to 5,000 psi. Highly satisfactory results are obtained at from 3,000 to 3,500 psi. The pressures as used herein are the partial pressure of hydrogen. The hydrogen employed can be a refinery stream as long as it does not contain a significant'amount of a catalyst poisioning component. There is no theoretical upper limit on pressure, however, it is contemplated that the pressure'normally will not exceed about 10,000 psi. The partial pressure of hydrogen is important with respect to the hydrogenation aspect itself, however, total pressure is important with respect to the maximum temperature to be employed. Since cracking is to be essentially avoided, the temperature normally cannot exceed about 675 F, however, this limit has some upward flexibility if high enough pressures are employed to substantially prevent any cracking. Because the effect of increasing pressure is to increase the capital and operating cost, the pressure will preferably be kept at the minimum required to accomplish the desired results. The temperature should be kept in the range of about 600 to 675 F as indicated above in spite of pressure adjustments making higher temperatures possible because from an overall consideration such temperatures are No. 1,024,317 issued to that company on Mar. 30, 1966. Examples of other supports for such catalyst are activated.

The residence time expressed as liquid hourly space velocity (L.1-l.S.V.) will generally fall in the range of about 0.1 to 1.0. Best results are generally when the L.H.S.V. is about 0.5 volume of liquid feed per volume of catalyst.

The hydrogen recycle in the hydrocracking step generally is 2,500 to 10,000 S.C.F. per barrel of charge. In contrast to the hydrocracking step little or no hydrogen recycle is required in the hydrogenation step unless desired for quenching to control temperature. The hydrogen consumption in the hydrogenation step normally is in the range of from 150 to 200 S.C.F. of hydrogen per barrel of charge stock.

DESCRlPTION OF THE PREFERRED EMBODIMENTS Hydrocracking Refining Procedure 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 intial boiling point of 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 had initial boiling points of about 695 and 750 F respectively. The residual stock was deasphalted and extracted by the Duo-Sol process (i.e., which employs propane and a mixture of phenol-cresol as solvents) at approximately 130 F. The raft'mate from the deasphalter and the distillate stock from the vacuum still when combined had the following properties:

HYDRO CRACKER OHARGE PROPERTIES Gravity, AP1, Vacuum distillation range at 2 mm. adjusted to 760 mm. 30.5

int. 694 5% 760 784 30% 829 50% 881 70% 964 E.P. 1030 Recovery,% 83 Aniline Pt. 239.2 SSU/210 59.7 Avg. M.W. 505 Wt. Aromatics 22.4

The foregoing mixture was charged to a hydrocracker and said material was hydrocracked in the manner described in Us. Pat. No. 2,960,458. A hydrogen stream comprising gas and hydrogen, of which about 85 per cent 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 700 F. At this point, a product of about 105 viscosity index was obtained on a dewaxed basis. The quality stability is reported below.

Stabilizing Hydrogenation The foregoing hydrocracked lube fraction was charged to conventional high pressure hydrogenation equipment containing one bed of catalyst and it was hydrogenated therein. The catalyst and reaction conditions are set forth in Table I below. Product from the hydrogenation was charged to a dewaxer and dewaxed to a pour point of approximately 0 F. The product quality as to color, color stability and sludge formation of the hydrocracked product and the combination hydrocracked and mildly hydrogenated product are set forth also in Table l for comparison purposes.

TABLE 1 Hydrocracked Hydrocracked Oil Hydrofinished Hydrogenation Catalyst NiMo Hydrogen Partial Pressure, 3000 p.s.i.g. Temperature, F. -625 L.H.S.V. 0.5 initial D1500 1.5 1.5 D1500 Color after 45 hrs. 5.0 [.75 exposure to UV. light Heavy Nil Sludge Stability Test Procedure The stability test procedure employed was as follows: A 30 ml. sample of the material to be tested was placed in a ml. beaker. Two 275 watt ultraviolet sunlamps were placed approximately 12 inches away from the surface of the sample. The sample was placed in an air ventilated oven on a rotating table and heated to F The ultraviolet light was turned on when the sample was placed in the oven. After 45 hours, color of the test samples were determined using the ASTM-Dl 500 test. The sludge formed was determined qualitatively by visual observation.

For comparison purposes, tests were made on typical commercial fractions of commercial product, hydrocracked product and also the product of the combination of hydrocracking followed by mild hydrogenation (with the nickel-molybdenum catalyst) in accordance with the present invention. The products of each method were fractionated into both typical and comparative commercial fractions. The results of the color and sludge tests are reported in Table II as follows:

TABLE II [Comparison of UV stability of commercial product, liydrocracked product with and without mild hydrogenation] Typical 'Hydrocracked commercial Hydrocracked and hydroproduct oils I o finished oils Fraction #1 #2 #4 #1 #2 #4 #1 #2 #4 D1500 color,

initial 0. 5 l. 0 1. 75 0. 75 1. 25 2. 25 0. 25 0. 75 1. 25 D1500 color, after 45 hrs. exposure to UV light-.. 4. 5 4. 0 4. 5 5. 75 5. 75 5. 0 1. 00 1. 25 2. 0 D1500 color 4. 0 3. 0 2. 75 5.0 4. 5 2. 75 0.75 0. 50 0.75 Sludge Nil Nil 1 Heavy.

2 Medium.

3 Light.

4 Haze.

Similar results have been obtained when the product was carried out in a single reactor with two beds of the same catalyst, namely, nickel-tungsten sulfides. The temperature of the top bed was approximately 760 F. where hydrocracking occured and the temperature of the bottom bed as approxicatalyst bed. The hydrogen partial pressure was maintained at 3,000 psi in both beds.

We claim:

1. A process of improving the viscosity index and quality stability of lube oils which comprises first hydrocracking a lube oil fraction over a sulfided mixture of an iron group metal and a metal of Group VI left hand column of the periodic system at a temperature of about from 735 to 825F. at a hydrogen partial pressure above about 2,500 psi. to produce a hydrocracked lube oil fraction, and then hydrogenating said hydrocracked lube oil fraction over a sulfided mixture of an iron group metal and a metal of Group VI left hand column of the periodic system at a temperature of from 600 to 675 F. and a hydrogen partial pressure of at least 3,000 p.s.i.

2. The process of claim 1 wherein the hydrogenation step is carried out at from about 625 to 675 F.

3. The process of claim 2 wherein the hydrocracking catalyst composition is a nickel sulfide-tungsten sulfide com- 5 bination.

4. The process of claim 3 wherein the hydrogenation catalyst is a nickel sulfide-molybdenum sulfide combination.

5. The process of claim 4 wherein the hydrogenation catalyst is a nickel sulfide-tungsten sulfide combination.

6. The process of claim 4 wherein the liquid hourly space velocity in the hydrogenation step is about 0.5.

7. The process of claim 5 wherein the liquid hourly space velocity in the hydrogenating step is about 0.5.

- IF i

Claims

2. The process of claim 1 wherein the hydrogenation step is carried out at from about 625* to 675* F.
3. The process of claim 2 wherein the hydrocracking catalyst composition is a nickel sulfide-tungsten sulfide combination.
4. The process of claim 3 wherein the hydrogenation catalyst is a nickel sulfide-molybdenum sulfide combination.
5. The process of claim 4 wherein the hydrogenation catalyst is a nickel sulfide-tungsten sulfide combination.
6. The process of claim 4 wherein the liquid hourly space velocity in the hydrogenation step is about 0.5.
7. The process of claim 5 wherein the liquid hourly space velocity in the hydrogenating step is about 0.5.