US3189540A - Production of lubricating oils by catalytic hydrogenation - Google Patents

Description

United States Patent 3,189,540 PRODUCTION OF LUBRICATING OILS BY CATALYTIC HYDROGENA'HGN Robert H. Kozlowski, Berkeley, and Robert L. Jacobson,

Pinole, Califi, assignors to California Research Corporation, San Francisco, Calif.," a corporation of Delaware No Drawing. Filed Jan. 2, 1962, Ser. No. 163,923

1 4 Claims. (Cl. 208-464) This application is a continuation-in-part of copending application SerialNo. 12,319, filed March 2, 1960, now US. Patent No. 3,114,701.

' This invention relates to the production of lubricating oils by catalytic hydrogenation, and in particular the invention relates to the production of lubricating oils of improved color by catalytic hydrogenation of petroleum oils rich in polycyclic hydrocarbons and containing nitrotion controlled to remove a specified fraction of the nitrogen compounds, using certain high metal content, sulfided, nickel-molybdenum-alumnia catalysts. Still more particularly, the invention relates to an improved process using relatively severe conditions of catalytic hydrogenagen content of a petroleum oil and thereby to obtain a lubricating oil product of improved properties.

The use of catalytic hydrogenation in the refining of lubricating oils is well known. Mild hydro-finishing has been employed as a substitute for acid treating or clay contacting of refined lube oils, using relatively mild conditions of low temperature, low pressure, and high space velocity. Destructive hydrogenation has also been proposed as a substitute for solvent extraction of crude lube molybdenum, on alumina, at 1000 p.s.i.g., 600

- content sulfided' catalysts;

tained at more'severe conditionsof elevated temperature "and pressure and'low'space velocity. v

oils, using severe conditions of high temperature and pressure. The catalysts employed in the prior art processes are usually either hydrofining catalysts such as molybdenum oxide, cobalt, molybdate, nickel-tungsten sulfide, etc., or hydrogenation catalysts, such as nickel or platinum. Usually the catalyst metals, oxides, or sulfides, are supported on -a carrier such as alumina, silica-alumina, or magnesia. The supported hydrofining catalysts have invariably a low metal content of less than by weight.

Ne have found that certain high metal content sulfided nickel-molybdenum-alumina catalysts give outstanding results in the cat-alytic'hydrogenation of petroleum oils rich in polycyclic hydrocarbons, particularly with respect to producing lube oils of improved color. Thus, for example, when a bright stock (187 SSU at 210 F.) was subjected to catalytic hydrogenation by contacting with a prior art hydrofining catalystcontaining 2.8% cobalt and 6.7% F., and 0.5 volume of oil per volume of catalyst per hour .(LHSV), with 2000 s.-c.f. of H per barrel of oil,the ASTM color was improved from 8 to 6.5. When a sulfided 6% nickelmolybdenum, on alumina, catalyst was used at the same conditions, the ASTM color wasimproved from 8 to 5.5. At greater severity, for example, 650 F. and with other conditions comparable, product color improved even more, from 8.0 to 3.5, with the sulfided Ni-Mo catalyst. Similar superior results are obtained in the catalytic hydrogenation of distillate lube oils with'the high metal Also, even better color is ob- The high metal content sulfided nickel-molybdenumalumina catalysts used in contain 340% by weight molybdenum, with the more active catalysts containing 4-l0% nickel and l5.5% molybdenum. ratio of nickel to molybdenum is in the range of 0.25 to 0.8, preferably about 0.6. A typical preferred catalyst will contain about 6 weight percent nickel and about 20 weight percent molybdenum. The catalysts may be prepared by alternate impreguation of a support consisting essentially of alumina, calcining titer each impregnation the process of this invention nickel and 1230% by Weight The atomic to convert the metal compounds to the metal oxides; or they may be prepared by simultaneous coprecipitation of aluminum, molybdenum, and nickel compounds; or by coprecipitation of aluminum and molybdenum compounds followed by impregnation with nickel, and with additional molybdenum, if desired. The catalysts are sulfided before use in the process. A special property of these catalysts when sulfided is their unusually high activity for the removal of nitrogen from petroleum oils containing nitrogen compounds by catalytic. hydrogenation of the Thus, for example, the

nitrogen compounds to ammonia. catalysts are found to be from two to five times as active as prior art hydroiining catalysts for the removal of nitrogen from neutral distillate lube oils. The catalysts, their preparation, and their use in processes for the substantially complete removal of nitrogen from distillable hydrocarbon oils are disclosed in our pending applications Serial Nos. 12,319, filed March 2, 1960, now US. Patent No. 3,114,701; 12,466, filed March 2, 1960, now abandoned; and 90,382, filed February 20, 1961, now abandoned,

in accordance with the catalytic hydrogenation process of this invention, a petroleum oil rich in polycyclic hydrocarbons and containing nitrogen compounds is hydrogenated by contacting with a high metal content, sulfided, nickel-molybdenum-alumina catalyst containing 3-l0 weight percent nickel and 1230 Weight percent molybdenum, in the presence of excess hydrogen at a partial pressure of over 800 p.s.i.a., at 600800 F., and 0.2-3 LHSV. The hydrogen partial pressure, temperature, and space velocity are controlled within the foregoing ranges to remove a specified fraction of the nitrogen content of the oil. When the conditions are so controlled, the degree, fraction or percent nitrogen removal from a petroleum oil is found to be a direct index ofthe degree of change in color and certain other properties of the oil which reflect the hydrogenation of unsaturated and unstable compounds therein. The lube oil properties found to be so related to the extent of hydrogenation in terms of nitrogen removal are-expressed in somewhat arbitrary measurements, in particular: color, viscosity, pour point, oxidation stability, and additive response. Improvement to a desired extent of at least one lube oil property, in addition to color, selected from the group consisting of viscosity, pour point, oxidation stability, and additive response, is achieved by controlling the conditions to obtain from 30 to percent nitrogen removal .in the catalytic hydrogenation process of this invention. 7

Preferred lubricating oils areessentially naphthenic in basic structure, and have alkyl substituents ofvarying complexity. Essentially parafiinic or waxy hydrocarbons are not desired, nor are essentially aromatic hydrocarbons, because of their poor lubricating properties. Hence, the petroleum oils from which lubricating oils are produced by this invention are petroleum oils rich in polycyclic hydrocarbons, and which contain nitrogen compounds. Predominantly parafiinic petroleum oils are not suitable feed stocks for the process because such compounds are not converted to the desired naphthenes by the catalysts at the conditions used in the process. In general, the suitability of a petroleum oil as feed declines as the parafiin content increases. Preferred petroleum oil feeds are partially refined lube oil stocks, such as bright stocks, neutrals, and rafiinates of naph- -thenic crude.

Crude lube cuts from highly naphthenic crude petroleum are also suitable, however, though the hydrogenated product may require mild dewaxing.

.The nitrogen content of petroleum oils rich in polycyclic hydrocarbons is present primarily as heterocyclic nitrogen compounds. Removal of the nitrogen improves the lube oil not only by eliminating the highly colored nitrogen compounds, but. also by converting such hetprior art where 0.5-2 LHSV,fto obtain the technical reliable index-of thedegree of color improvement is obtained The new concept of this denum-alumina catalysts are unusually active for hydro- V genation of nitrogen compounds, the conditions used in the process of this invention are peculiar to the catalysts, Although with these catalysts moremoderate conditions of temperature, pressure, and space velocity could be employed to remove a specified fraction or are'einployedin the invention, as compared to hydrofining processes ofthe only mild hydro-finishing was contemplated; V a

In .carrying out the catalytic hydrogenation of this invention any suitable equipment arrangement may be used for contacting the oil withthe catalyst in the presence of excess hydrogen. For example, the catalyst may be maintained as one or more fluidized beds, gravitating beds, or fixed beds of small the oil and hydrogen are passed, upflow or downfiow, concurrent or countercurrent.

oil may also be used. Usually, the catalyst is in the form of small pellets or rod-hke'extrusions contained in' a reactor as several fixed beds, and the oil and hydrogen are passed together downfiow through the beds at con trolled temperature, pressure, and flow rates. The efiluentis cooled to separate product oil from hydrogen-rich gas, while is recycled.

or more standard cubic feet per barrel ally 2,00O-6,000 s.c.f./bbl.

The total pressure depends on the purity of the hydro-v such pressures color improvement is accomplished over a broad range of.temperatures,,from 600 F; to 800 F., permitting maximum flexibility in control of the nitrogen removal. Preferred temperatures are between 600 and 750 F. for the limited nitrogen removal desired in this invention, especially temperatures of 650'700 F.

Space velocities of 0.23 LHSV are used, preferably and "economic advantages of adequate contacting time in equipment of 7 reasonable dimensions; At milder conditions of lower nitrogen'removal is a less hydrogenation of thetoil; the advantages [gained by using thehigh metal' content,

pressure, i.e., below 800 p.s.i.,

' sulfided, 'nickel-molybdeuum-alumina catalysts are less pronounced, and the range of temperatures at is narrower.; invention, the method of using it, and the advantages obtained, thereby may be best explained andunderstood by means of examples. In the following examples, where reference is made to a which particles, through which- A slurry. of catalyst in,

To maintain a high hydrogen partial pressure and to insure that excess hydrogen is present, the hydrogen-to-oil ratio is from 1,000 to 10,000

(s.c.f./bbl.), ususulfided nickel-molybdenum 'percent of the nitrogen content of an oil, 'in general higher pressures, above 800 psi,

Tab lel V V 1"? V Ralfinate yield Property Desired product 40% W Gravity, API 21. 7 19. 19. 3 Vlscosity, SSU at; 100 F- 1, 688 2, 525 2, 879 Viscosity, SSU at 210 IL -95- 86. 3 101 Color, A STM Less than 4 V 5 6.5 Pour point, F.-- Less than +10 10 +5 Natural oxidation Greater than 7 12 4. 9 3. 6 stability, hours. V Catalyzed oxidation Greater than 1.8.-. 1.9 0.8 0. 8

stability, hours. 7 Nitrogen, ppm 80D 1, 660 2, 400 AIQIJJ3-tl0$, percent 9 I I 15. 5

" bina'tion of mild solventextraction catalyst, the "catalyst employed was prepared by impregnating a high purity alumina base. with nickel nitrate, calcining, then impregnating with'ammonium molybdate, and calciniu'g, again impregnating with ammonium molybdate, and calcining. The oxide catalyst, which contained 6 nickel and 20% molybdenum, was sulfided by contactingwith hydrogen containingdimethylrlisulfide, equivalent 'on hydrogenation to 2% H 5, at about 500 F. to convert the, metal oxides substantially to the sulfides prior rouse in the catalytic hydrogenation process. The first exampleillustrates an embodiment of the invention in the production of low cold test lubricating oil of improved color and oxidation stability from a naphthenic cr'ude by acom followed by catalytic hydrogenation at controlled conditions. L

EXAMPLE I i A naphthenic California crude was distilledto obtain,

a'heavy crude lube distillate amounting to about 8 volume percent'ofthe crude, and boiling from about 500 F. to

about 700 F. at 10 mm. Hg. The distillate was solvent; extraction at varying solvent-to-oil;

treated by phenol ratios to obtain lube oil rafiina'tes' at volumetric yields of 40%, 60%, and 70%. Properties of therafiinates are listed in .Table'l. The 40% yield raflinate' representstlow cold test lube oil produced by the prior art without catalytic hydrogenation; The 60% of poor quality with respect.

and 70% rafiinates are The 60% and 70% nickel-molybdenum catalyst at conditions controlled-to treating conditions used and tained are listed inTable l1.

NoTn.Natural oxidation stability is the time required for a givenvolume of the oil, as is, to absorbfrom air bubbled through the oxidation inhibitor and the oxidation is This property Table II I ,7 l

Feed treated 60% Rattinate 70% Ratfiuate Congitions:

ressure, p.s.i.a. 112-; Temperature, F Space velocity, LHSV 1 40 Gas rate, s.c.f. Hz/bblu' 4 i300 Product properties:

Gravity, API 22 4 Viscosity, ssU at F 1 43s Viscosity, SSU at 210 F is 4 a Color, ASTM 1' 5 Pour point, F 5 Natural oxidation stability, hou.rs 3 8 Catalyzed oxidation stab ty, hours. 2 5 Nitrogen, p.p.m 905 Percent nitrogen removal to color and oxidation stability, and have higher than the dsiredviscosity; rafiinates were then subjected to, catalytic hydrog'enation by contacting with the sulfided oil, to absorb one liter of oxygen at the same conditions T The catalytic hydrogenation of Example I improved the color in every case and improved the oxidation stability of the rafiinates to the desired extent when the operating conditions were controlled to remove 30-60% of the nitrogen content, with an optimum apparently at about 40-50% removal. The viscosoity, however, dropped more than would be desired. In a novel embodiment of the present invention, product lube oil of the desired viscosity is produced at' greater over-all yield by starting with a crude lube distillate of higher than the desired boiling range, solvent treating the distillate to obtain a high yield of raflinate of higher than the desired viscosity and of poor quality with respect to color and oxidation stability, and then subjecting the rafiinate to catalytic hydrogenation by contact with a high metal content, sulfided, nickel-molybdenum catalyst at conditions of temperature, hydrogen partial pressure,

' and space velocity controlled in the ranges 650-750 F.,

at least 1500 p.s.i.a., and 0.5-3 LHSV, to remove 30- 60% of thenitrogen content and thereby to adjust the color, viscosity, and oxidation stability to the desired Values. That an increased yield of superior product is obtained thereby is illustrated by the following example.

EXAMPLE II The naphthenic crude of Example I was distilled to obtain a broader lube oil distillate amounting to about 9 volume percent of the crude by including higher boiling material. The distillate was solvent treated by phenol extraction to obtain a poor quality lube oil raffinate at 60% yield. The raifinate was then subjected to catalytic hydrogenation by contacting with the nickelmolybdenum catalyst at 2000 p.s.i.a. hydrogen partial pressure, 675 F., and 1.3 LHSV, with 6700 s.c.f. of H per barrel. Properties of the raflinate feed and the lube oil product are given in Table III. Processing in this way increases the yield of product lube oil from crude by 47.5% as compared to the solvent treating method formerly used.

Table 111 Property Ratr'mate Product Gravity, API 20. 2 22. 5 Viscosity, SSU at 100 F--- 2, 774 1, 715 Viscosity, SSU at 210 F 1 3. 6 (3. 3 Color, ASTM 8 1. 5 Pour point, F 0 Natural oxidation stability, hour 4. 6 12. Catalyzed oxidation stability, hours- 0. 8 2. 1 Nitrogen, ppm 1, 710 1, 050 Aromatics, percent 13. 5 Percent nitrogen removal 39 The conditions of temperature, pressure, and space velocity may be altered within limits to obtain the same fraction of nitrogen removal and thereby to obtain the same improved product. However, for the treatment of rafiinates, the pressure should be relatively high, i.e., above 1500 p.s.i.a. H preferably at least 2000 p.s.i.a. Lower temperatures may be used at lower space velocities, but we prefer for the best results to use a space velocity of at least 0.8. The temperature can then be in the preferred range of 650-750 F. Ordinarily, the temperature is increased over a period of time to compensate for catalyst deactivation. However, the conditions of Example II were maintained for over 1000 hours without any noticeable deactivation or catalyst fouling by coke deposits.

The invention may also be used to produce residual or non-distillate lube oils of improved color and oxidation stability, for example, bright stock. A high natural oxidation stability is a valuable property of bright stock because such oils are used to a great extent in uncompounded lubricants. The present invention produces bright stock of improved color and having maximum oxidation stability by catalytic hydrogenation of nitrogen-containing bright stock at conditions controlled with- 6 in the ranges 800-2000 p.s.i.a. hydrogen partial pressure, 600-7 00 F., and 0.5-3 LHSV, to remove 20-60% of the nitrogen content. This is illustrated by the following example.

EXAMPLE III A bright stock boiling entirely above 300 F. at one millimeter mercury absolute pressure was contacted with the sulfided nickel-molybdenum catalyst at 1000 p.s.i.a. H 650 F., 0.5 LHSV, and 6000 s.c.f. H bbl. Proper- Similar results were obtained by catalytic hydrogenation at 1000 p.s.i.a., 700 F., and 2.4 LHSV. At more severe-conditions the oxidation stability is adversely affected; at mild conditions the oxidation stability is not improved.

As shown, the invention can also be used to improve the additive response of bright stock, for example, to oxidation inhibitors. This is of particular value where the bright stock is to be used in compounded lubricating oils such as high viscosity turbine oils.

A turbine oil comprising 40% bright stock was prepared using the product of Example HI. With 0.25 weight percent of a commercial oxidation inhibitor added, the turbine oil had a life of 2,140 hours in a turbine oil standard test.

From the foregoing, it is seen that the exact conditions of temperature, pressure, and space velocity to be employed in a particular case depend on the properties of the particular feed stock and the properties of the lube oil desired. Thus, for example, in the case of two petroleum oils of similar boiling range but difierent nitrogen contents, the oil of higher nitrogen content will require somewhat more severe conditions to accomplish the same percent removal of nitrogen as the lower nitrogen content stock. However, these somewhat more severe conditions are found to be required also to obtain the desired improvement in the lube oil properties. This is illustrated by a comparison of the similar feeds of Examples I and 11. Thus, with the particular objective of this invention in mind, and having the examples herein before him, one skilled in the art will, with but minimal experimentation to verify the estimates, be able with reasonable accuracy to predict the appropriate conditions to use with the sulfided nickel-molybdenum catalysts to obtain a desired lube oil product. Hence, the examples themselves are not to be considered limiting, and the true scope of the invention is defined by the following claims.

We claim:

1. A process for producing lubricating oil of improved color and natural oxidation stability which comprises sol vent refining a heavy petroleum oil to obtain a solventrefined lubricating oil fraction rich in polycyclic hydrocarbons, containing heterocyclic nitrogen compounds and having poor color above 4.5 on the ASTM scale and poor natural oxidation stability,

hydrogenating said solvent refined fraction by contacting in the presence of excess hydrogen with a sulfided nickel-molybdenum-alumina catalyst containing between 4 and 10 weight percent nickel and between 12 and 30 weight percent molybdenum at reaction con ditions in the ranges 800-3000 p.s.i.a. hydrogen partial pressure, 600-750 F, and 0.2-3 LHSV, While controlling the reaction conditions in a narrow range j carrying out the solvent refining of said within said ranges appropriate for the particular sol- Vent-refined fraction to obtain only partial removal I amounting tobetween 30% and 60%- of the nitrogen from 'said'oil, i a

and recovering as the product hydrogenated lubricating oil having improved color below 4.5 on the ASTM scale and improved natural oxidation stability.

, 2. The processof claim 1 wherein said heavy petroleum 7 ''oil is a residual petroleum oil, which 'is solvent refined to obtain'as said solvent-refined lubricating oil fraction a bright stock, and the reaction conditions are controlled during contacting said brightrstock with said sulfided cata .lyst within the ranges 8002000 p.s.i.a. hydrogen partial pressure, 600700 F., and 0.5-3 LHSV.

i 3. A process in accordance with claim ,1 wherein said flheavy petroleum oil is a heavy vacuum distillate of naphthenic crude petroleum rfrom -which distillate there is recoverable by phenol extraction a raifinate of desired viscosity having acceptable color and oxidation stability only if limited to a rafiinate yield of less than 50% by virtue of said distillate having a higher average'boiling point than desired 'for said raflinate,

distillate to obtain as said solvent-refined lubricating oil fraction azrafiinate of poor'color and oxidation stability in greater than 50% yield and having higherthan desired viscosity, controlling the reaction conditions during said hydrogenating' in the ranges 1500-3000 750 F., and 0.5-3

p.s.i.a. hydrogen partial pressure, 650- LHSV, and recovering as said product which comprises '7 yield than is obtainable from the low cold test lubricating oilof the desired viscosity'having improved color and oxidation stability in a greater naphthenic crude by dis tillation and extraction. i I y a .4. The process of claim 3 wherein the reaction condi; tions during-said hydrogenating are controlled in the ranges 2000-3000 p.s.i.g., 650-750 F,. and O.8 3'LHSV to limit the removal of nitrogen compounds to between 40% and and thereis recovered as the production; cold test lubricating oil having a color below 4 on, the ASTM'scale and a natural oxidation stability greater. than 7hours. '7 r Pteterences Cited by the Examiner UNITED STATES PATENTS 2,706,167 7 4/ Harper et al. 208-264 2,905,625 9/59 Berger; 20s 254 2,905,636 9/59 Watkins et a1. 208-254 2,944,006 7/60' Scott 20889 2,983,676 5/61 Howland 20s 2s4 2,988,501 6/61 Inwood r 208-254 7 3,004,913 10/61 Tucker 208 544- 3,014,860 12/61 Douwe s et al. 208 254' 3,046,218 7/62 Henke et al. 208 14'4' 3,094,480 6/63 Richardson 208"143 3,105,813 10/63 Gtltberlet 208 254 3,114,701 12/63 Jacobson et al 200-254;

'ALPHoNso D. SULLIVAN, Primary Examiner. V

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,189,540 June 15, 1965 Robert H. Kozlowski et a1,

It is hereby certified that error appears in the above numbered patent reqliring correction and that the said Letters Patent should read as oorrected,below.

Column 1, line 17 for "alumnia" read -alumina column I5, line 30, for "while" read H which column 6, line 37, after "testq" insert With normal bright stock the life is 940 hours.

Signed and sealed this 7th day of December 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Altusting Officer Commissioner of Patents

Claims (1)

1. A PROCESS FOR PRODUCING LUBRICATING OIL OF IMPROVED COLOR AND NATURAL OXIDATION STABILITY WHICH COMPRISES SOLVENT REFINING A HEAVY PETROLEUM OIL TO OBTAIN A SOLVENTREFINED LUBRICATING OIL FRACTION RICH IN POLYCYCLIC HYDROCARBONS, CONTAINING HETEROCYCLIC NITROGEN COMPOUNDS AND HAVING POOR COLOR ABOVE 4.5 ON THE ASTM SCALE AND POOR NATURAL OXIDATION STABILITY, HYDROGENATING SAID SOLVENT REFINED FRACTION BY CONTACTING IN THE PRESENCE OF EXCESS HYDROGEN WITH A SULFIDED NICKEL-MOLYBDENUM-ALUMINA CATALYST CONTAINING BETWEEN 4 AND 10 WEIGHT PERCENT NICKEL AND BETWEEN 12 AND 30 WEIGHT PERCENT MOLYBDENUM AT REACTION CONDITIONS IN THE RANGES 800-300 P.S.I.A. HYDROGEN PARTIAL PRESSURE 600-750*F., AND 0.2-3 LHSV, WHILE CONTROLLING THE REACTION CONDITIONS IN A NARROW RANGE WITHIN SAID RANGES APPROPRIATE FOR THE PARTICULAR SOLVENT-REFINED FRACTION TO OBTAIN ONLY PARTIAL REMOVAL AMOUNTING TO BETWEEN 30% AND 60% OF THE NITROGEN FROM SAID OIL, AND RECOVERING AS THE PRODUCT HYDROGENATED LUBRICATING OIL HAVING IMPROVED COLOR BELOW 4.5 ON THE ASTM SCALE AND IMPROVED NATURAL OXIDATION STABILITY.