US2339717A - Process for reclaiming used and partially oxidized lubricating oil - Google Patents

Description

Patented Jan. 18, 1944 PROCESS FOR RECLAIM'ING USED AND PAR- TIALLY OXIDIZED LUBRICAT N G OIL George G. Oberfell, Bartlesville, kla., assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Application April 28, 1942, Serial No. 440,855

2 Claims. (01. 196-16) This invention relates to the treatment of lubricating oils. More particularly it relates to the treatment of used lubricating oils, or fractions ing dehydration and condensation products from various oxygen-containing compounds.

thereof, which contain oxidized compounds to produce oils suitable as lubricating oils or stocks and containing minor amounts of desired oxygencontaining constituents.

Lubricating oils in common use in internal combustion engines are composed primarily of hydrocarbons. In general these are derived from natural sources of hydrocarbons and may contain residual hydrocarbons which remain after dis-.

tilling off hydrocarbons of lower boiling points or may comprise in large amount, or consist entirely of hydrocarbons which have been distilled from still heavier residues. In either case, the hydrocarbon fractions are generally subjected to additional chemical and/or physical treatments including treatment with sulfuric acid to precipitate and remove asphaltenes, and the like, selective solvent extraction, to remove similar compounds, and/or to remove highly aromatic hydrocarbon constituents, contacting in liquid phase with solid adsorbents, cracking, and hydrogenation, both destructive and nondestructive. Other lubricating oils stocks are the result of synthesis reactions, such as polymerization and/or alkylation. Generally lubricating oils, as the oils are found on the market, are produced by a final step of blending, so that a manufacturer produces, from stocks of low viscosity and stocks of high viscosity, commercial lubricating oils of different viscosities.

Such lubricating oils contain hydrocarbons predominantly; other constituents, which will be present only in small quantities if at all, comprise organic compounds containing nitrogen,

Isulfur and/or oxygen, etc. In addition to such compounds which will be present in stocks from natural sources, other nonhydrocarbon organic compounds containing nitrogen, sulfur, oxygen,

halogens and/or various metals, etc., may be added in small amounts as inhibitors for oxidation and/or corrosion and to enhance oiliness and/or film strength.

Under conditions of use, lubricating oils undergo numerous physical and chemical changes, chief among which are dilution with high boiling and with partially oxygenated materials from the fuels, partial decomposition by exposure to high piston and cylinder-wall temperatures, partial oxidation to aromatic, naphthenic and aliphatic aldehydes, ketoneaacids, and the like, and conversion to highly unsaturated compounds and tars and sums of high molecular weight, includ- 'I have now found that such used lubricating oils may be reclaimed and put into condition for reuse by a process ,which comprises a carefully controlled and limited catalytic hydrogenation. I have further found that when this hydrogenation step is so controlled and limited that not all of the oxygen-containing compounds are converted to hydrocarbons but are left in an intermediate stage of hydrogenation, such as phenols, naphthols, naphthenic alcohols, carbinols, and the like, the resulting lubricating 011 stock has improved characteristics, especially as regards resistance to subsequent oxidation, corrosion and gum formation during use. It appears that the oxygen-containing compounds which are formed by the controlled hydrogenation of the used lubricating oil contribute materially to these ends by acting to inhibit such oxidation and corrosion. The solvent properties of the processed oil are also improved in many cases, so that the rate of deposition of sludge and lacquer-like deposits in the engine is less as a result of those materials being present in the oil. In applying this.

process to the reclamation of used lubricating oil I prefer'to incorporate it with other steps includng apreliminary removal of water and other low-boiling constituents and also of suspended tars r 1d gums. Following the hydrogenation step, it is also desirable to remove water, hydro gen sulfide and/or ammonia formed therein, and also to include a, treatment to remove olefins and the like when the hydrogenation which forms the principal part of my process is conducted under conditions that such are present, even in minor amounts, in the efiluent.

It is an object of my invention to reclaim used lubricating oil.

It is a further object of my invention to treat used and partially oxygenated lubricating oil to produce a lubricating oil stock of improved characteristics.

A further object of my invention is to produce a lubricating oil'stock which contains oxidationinhibiting constituents.

Still another object of my invention'is to produce a lubricating oil stock which contains matcielrials improving the solvent properties of the o Further objects and advantages of my invention will become apparent to those skilled in the art from the accompanying disclosure and discussion.

As a preliminary treatment for the used lubricating oil, I prefer to include a distillation step which will remove as distillate, materials boiling below the lubricating oil range. Such materials will include water, low-boiling alcohols, organic acids and the like, resulting-from partial oxidation of constituents of the oil or materials from incomplete oxidation of the fuel which have found their way into the oil from the combustion chamber, and low-boiling hydrocarbons, such as those resulting from the decomposition of part of the lubricating oil and those taken up by the oil from the motor fuel as unvoiatilized constituents of the engine fuel. In this distillation it is necessary to avoid heating the: residual lubricating oil to temperatures so high that there is appreciable alteration or decomposition of materials contained therein, and a vacuum distillation and/or steam distillation is therefore to be preferred. It is intended that at least a large part of the material in the lubricating oil range will be left as a residue in this operation, but if a large amount of a low-boiling lubricating oil is present, as when a large amount of a light neutral oil has been used in the blend to form the original lubricatiing oil, and this material can be distilled without adversely affecting the residue, a substantial part may be recovered as distillate and subjected to a separate hydrogenation treatment, if desired.

The residue from this distillation will generally contain, in addition to compounds which are to be reacted in the hydrogenation step, high molecular weight compounds of a tarry or gummy character which, to a large extent, are suspended in the oil and which will not only not contribute to the desired characteristics of the oil after hydrogenation but will also adversely affect the course of the hydrogenation. When this is the case these should be removed, as by filtration, propane deasphalting, sulfuric acid deasphalting, etc. The deasphalting treatment should be such that substantially all of the coarse suspended 'asphaltic material is removed together with an appreciable proportion of the larger truly colloidal particles, but the specific treatment should be chosen with respect to the specific characteristics of the oil being treated so that the deasphalting treatment does not remove excessive quantities of the organic oxygencontaining compounds in solution in the oil. Filtration with a nonadsorptive filter aid, with or without dilution with a naphtha, or the like, to reduce the viscosity of the oil is often a satisfactory treatment forthis step.

'Following such preliminary treatments the oil is subjected to a relatively mild and limited catalytic hydrogenation, which step forms the essential part of my invention. In this hydrogenation the oil is contacted in liquid phase with a body of solid hydrogenation catalyst in the presence of a substantial amount of free hydrogen at a reaction temperature and pressure for a time such that an appreciable amount of the oxygencontaining organic compounds are not completely hydrogenated, so that the eiiluent contains an appreciable amount of organic oxygen-containand similar metals, are not in this group inasmuch as they form sulfides in the presence of sulfur which are not suificiently active to promote desired hydrogenations. Catalysts comprising oxides and sulfates of metals of the chromium subgroup of Group VI of the Periodic System are suitable for my process. particularly catalysts containing such-compounds'of chromium and/or molybdenum. These materials may be used by themselves but are preferably used on supports such as pumice, silica gel, alumina, etc. The use of such catalysts is preferred regardless of whether or not the oil to be hydrogenated contains sulfur.

With such catalysts it is necessary to conduct my hydrogenation process at somewhat elevated temperatures and with relatively high hydrogen pressures. The reaction temperature should be at least about 500 to 550 F., and most generally will be above 600 F. The upper limit.

for the reaction temperature should be about 750 to 800 F., but care should be exercised to insure that the reaction temperature, in combination with-other reaction conditions, is not so high as to cause any substantial destructive hydrogenation of the hydrocarbons into products unsuited for incorporation in lubricating oils. In order to obtain satisfactory hydrogenation of the oxygen-containing compounds some molecular decomposition of the hydrocarbon constituents may occur concomitantly, but in many instances this need not be greater than about 5%. The vapor pressure of the oil initially charged, even in the upper part of the temperature range just recited, will be very small-a matter of only a few pounds per square inch absolute-so that the total pressure in the hydrogenation apparatus will be substantially only the pressure of the hydrogen used, except that the presence of inert gases such as methane or nitrogen, or the like which may accompany the hydrogen charged to the process, may contribute to the total pressure. I prefer to conduct the hydrogenation under a relatively high pressure of at least several hundred pounds per square inch, although pressures in excess of 6,000 or 7,000 pounds will not give additional benefits. The most generally preferred pressure range isbetween about 3,500 and 5,000 pounds per square inch. Although it is intended that the oil shall be present in the reaction zone in liquid phase, it will be appreciated that with such a high hydrogen pressure a gas phase will also be present, and that inevitably some of the oil will be present in vapor form.

The reaction conditions of temperature, pressure, catalyst and reaction time are all interdependent and what will be an optimum correlation for one charge stock will not necessarily be an optimum, or even a satisfactory, correlation for a different charge stock. The reaction time should be sufliciently extended as to permit a major part of the oxygen present, as combined oxygen in organic oxygen-containing compounds as previously discussed, to be completely united with hydrogen to form water and should be limited so that not more than 90 per cent of the oxygen is so converted. Generally, when between 60 and per cent of the oxygen in the organic oxygen-containing compounds .of the charge to the hydrogenation has been converted to water the remainder of the oxygen-containing compounds will have been converted to the desired extent, forming products such as previously indicated.

After the hydrogenation treatment, and removal of water from the cflluent, the resulting material is often in condition for use as a lubrieating oil,.or at least for use as a lubricating oil stock. It small amounts of low-boiling hydrocarbons have been produced these should, of course, also be removed. Although the hydrogenation is conductedin the presence of substantial quantities of hydrogen the eflluent may' contain a small amount of oleflns, since temperatures in the upper part of the range will tend to promote production of olefins in spite of high hydrogen concentration. Such oleflns should be removed, as by a treatment with a few pounds of concentrated sulfuric acid per barrel of oil or by a mild, low temperature hydrogenation in ing than lubricating oil, filtering the'residue of said distillation to remove suspended tars and gums and to leave the major part of any true colloidal matter, subjecting the filtered oil to the presence of a nickel-catalyst. As a lubrieating oil stock, the oil may be blended with other stocks of diflerent viscosity to give a blend of a desired viscosity and/or may have added to it minor amounts of conventional additive agents. Inasmuch as one of the attendant results of the hydrogenation treatment will be to increase the amount of paraffin hydrocarbons present, the pour point of the oil will probably be higher than desired, and the oil may need to be subjected to a, dewaxing treatment and/or have added a pour-point depressor. .In' any event, it will be found that the organic oxygencontaining compounds which have been produced and remain in the oil contribute to the stability.

of the oil, as compared with a similar product which does not contain such compounds.

I claim:

1. An improved process for reclaiming used and partially oxidized lubricating oils, which the action of hydrogen under a pressure between 3,500 and 6,000 pounds per square men at a temperature between 600 and 800 F. in the presence of an oxide selected from the group consisting of theoxides of molybdenum, chromium, tungsten and uranium as a catalyst for a time such that between 60 and 80 per cent of the combined oxygen contained in said 011 is converted to water and concomitantly organic compounds of the phenol type are produced and'remain, and subsequently treatingthe resulting material to remove water.

2. An improved process for reclaiming used and partially oxidized lubricating oils, which comprises subjecting such an oil to low temperature distillation to remove materials lower boi1-. ing than lubricating oil, filtering the residue of said distillation to remove'suspended tars and gums and to leave the major part of any true colloidal matter, subjecting the filtered oil to the action of hydrogen under a pressure between 3,500 and 6,000 pounds per square inch at a temperature between 600 and 800 F. in the presence of an oxide selected from the group consisting of the oxides of chromium, molybdenum, tungsten and uranium supported on a carrier as a catalyst for a timesuch that between and of the combined oxygen contained in said oil is converted to water and concomitantly organic compounds of the phenol type are produced and remain, and subsequently treating the resulting material to remove the water.

GEORGE G. OBERFELL.