US2903426A - Lubricants containing comminuted fluid coke - Google Patents

Description

United States Patent Oifice 2,903,426 Patented Sept. 8, 1959 2,903,426 LUBRICANTS CONTAINING COMMINUTED FLUID COKE Arnold J. Morway, Clark, and William J. Sweeney,

Summit, N..l., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application March 13, 1957 Serial No. 645,681 3 Claims. (Cl. 252--22) This invention relates to improved liquid or solid lubricants containing a novel solid carbonaceous material. It is more particularly concerned with a lubricant having added thereto a comminuted fluid coke to improve its extreme pressure, anti-friction, and other properties. Fluid coke is a unique form of carbon produced from petroleum residua by carbonization in a fluidized solidssystem, as hereinafter described in more detail;

In brief compass, this invention proposes a lubricant comprising a major proportion of a lubricating oil and 4 to 40 wt. percent of a comminuted fluid coke having a size under 200 mesh (approximately 75 microns). Normally the particle size of the fluid coke will not be below 75 microns.

Without the use of other suspending and/or bodying agents, the lubricant is a fluid or a semi-fluid. Surprisingly, however, the fluid coke does not aggregate and does not settle out as is the case of some other carbonaceous materials such as graphite or furnace blacks, which have an equally small particle size. Also, when used in amounts in the upper portion of the above range, i.e., 25 to 40 wt. percent, the fluid coke is not so absorbent as to result in a dry powdery material, as is the case with some reticulate materials such as acetylene blacks. Thus, fluid coke unexpectedly permits the attainance of non-settling fluid lubricants containing a high concentration of carbon.

A stable lubricant or grease containing a suspending and/or bodying agent in addition to the fluid coke is a much preferred embodiment of this invention. The contribution of the suspending agent and its coaction with the fluid coke varies to some extent. There are certain suspending and/ or bodying agents that are preferred. Particularly preferred are fatty acid soaps and especially preferred are what are known as soap-salt complexes, conventionally used to thicken lubricants.

More definitely stated, a preferred embodiment of this invention is a grease comprising a major proportion of an oleaginous lubricant, 10 to 30 wt'. percent of fluid coke having a maximum particle size of about 80 microns and a median particle size in the range of 40 to 60 microns, and 3 to 8 wt. percent of a soap of a fatty acid having 8 through 22 carbon atoms which soap is preferably in the form of a complex with 5 to '8 wt. percent of salts of lower fatty acids having 1 through 6 carbon atoms. The grease obtained in this preferred embodiment has exceptionally good properties. Dropping points are above 500 F., unworked penetrations are less than 350, and the grease remains unctuous at temperatures below 0 F.

The grease can, of course, contain other conventional materials, for example, bodying, thickening, or suspending agents such as polyethylene and bentonite, antioxidants, dyes, etc., and other lubricating oils besides the primary base stock.

By fluid coke is meant the product or modification thereof, obtained from the fluid coking process used, in petroleum refining operations. In this fluid coking proc ess, an oil, usually a low value heavy residual oil, is converted by pyrolysis to relatively lighter hydrocarbons and coke by contact with finely divided heat carrying solid coke so heated is then maintained as a gravitating bed in 1 particles maintained at a temperature in the range of 850 to 1500 F. or above. The heat carrying solids are preferably maintained as a fluid bed in a coking zone, but the process can be carried out in a transfer line coking zone. The coke produced by the pyrolysis deposits on the fluidized solids, layer by layer, and becomes a part thereof. Although some of the coke produced by the cracking may be consumed by burning to supply heat in the coking process, a substantial amount is removed as by-product. The heat carrying solids normally used are coke particles produced by the process such that the byproduct coke is of uniform composition. The by-product. fluid coke produced has a high percentage of carbon with an ash and sulfur content characteristic of the oil feed stock. Fluid coke as removed from the fluid coking process, when coking the customary residual oil feed stocks, normally will have a sulfur content of about 7 wt. percent or above.

The particle size of the heat carrying solid used in the coking process is in the range of about 18 to 400 US. sieve number, with the median particle size normally being in the range of 45 to 70. The by-product coke recovered usually has a somewhat smaller average size. This unique by-product coke is characterized by its spherical or ovoid shape, laminar structure, high density and hardness, and diflers substantially from the cokes produced by the pyrolysis of hydrocarbonaceous solids and oils by other processes. The term fluid coke is intended to include the solid product of the fluid coking process, i.e., the by-product coke or raw fluid coke, besides the treated forms of the raw fluid coke described below.

The raw fluid coke received from the coking process can be pretreated by calcination and/ or desulfurization to decrease its volatile matter and sulfur content and to increase its density. The product so obtained by this pretreatment is referred to as calcined fluid coke. Although desulfurization treatment of raw fluid coke normally results in calcination of the coke, it is not necessarily always true. The term calcined fluid coke herein used, includes fluid coke that has only been desulfurized. Calcined fluid coke gives many superior and unexpected results over raw fluid coke.

Generally speaking, calcination of fluid coke normally having a sulfur content of l-12 wt. percent, will reduce. its volatile matter content below about 1 wt. percent and. sulfur content by 520%, and increase its true density' above 1.7 g./cc. Desulfurization usually will reduce sulfor content to below 3 wt. percent.

. Calcination of the raw fluid coke to primarily increase perature zone fromwhich the by-product coke can be withdrawn. The calcination or heat soaking may becarried out while the fluid coke is in the form of a fixed, gravitating or fluid bed. A preferred method of calcination is to quickly heat the raw fluid coke up to about 2400 to 2800 F. by direct contact with high temperature flue gases or products of combustion, and then'to quickly separate the heated coke from the gases. The

a refractory lined soaking chamber for about one hourto complete the calcination.

ways. One preferred method is to oxidizethe cokeby fiuidizing it with an oxygen containing gas at a temperature in the range of 600 to 1500" F. for a time suflicient to consume over 3 wt. percent of the fluid coke. An especially preferred method of desulfurization comprises this oxidation treatment followed by hydrogenation with a free hydrogen containing gas at temperatures above 1100" F. In some cases the fluid coke may be desulfurized without preliminary heat coaking, by contact With'a desulfurizing gas such as hydrogen, ammonia, sulfur dioxide,zetc. When using hydrogen it is preferred to maintain the temperature above 1100 F.; when using sulfur dioxide, the temperature is preferably maintained above 18.00" F. Also, pressures of about 35 to 1000 p.s.i. or above are useful during desulfurization.

Instead of treatment with a desulfurizing gas, the coke can be desulfurized simply by a high-temperature thermal treatment. Thus, attemperatures of about 24002800 F., the sulfur compounds in fluid coke can be broken down and driven off. At the lower temperature, several hours ofheat soaking may be required to remove the sulfur.

In some uses it may be preferred, besides calcining the fluidcoke, to further pretreat it as by treatment with a solvent or by impregnating it with a suitable material such as water glass or finely divided graphite to decrease its porosity.

Because of inherent limitations in the fluid coking process, the fluid coke product obtained at times has some particles of a size too large to be useful in greases. The fluid coke, therefore, must be reduced in size in some manner. This is preferably done after the calcination and/or desulfurization steps, if the coke is so treated. The comminuation can be carried out in any convenient manner as by grinding, jet impact attrition, etc.

In general, the present lubricant compositions will contain a major proportion of a lubricating oil which may be either a mineral, synthetic, animal or vegetable oil or mixtures thereof in any combinations and proportions. Generally, the lubricating oil will represent about 60m 99% by weight of the total composition. The mineral oils may be mineral oils obtained from petroleum crude oils and they may be paraflinic, naphthenic or the like and may be refined by conventional mineral lubricating oil processes,.such as acid treating, solvent extracting, solvent dewaxing, filtering and clay treating.

The synthetic oils include esters of monobasic acids, esters ofxdibasic acids (e.g., di-Z-ethyl hexyl sebacate), and esters of glycols. Complex esters can be used such as the complex ester formed by reacting one mole of sebacic acid with two moles of tetraethylene glycoland two moles of 2-ethy1 hexanoic acid, complex ester formed by reacting one mole of tetraethylene glycol with two moles of sebacic acidand two moles of 2-ethyl liexanol. Quite generally, the base oils should have a viscosity within the range of about 35 to 200 SSU at 210 F.

and flash points of about 350 to 600 F. Lubricating oils having a viscosity index of 100 or higher may be employed. However, oils of lower viscosity index such as below 60 V.I., give better yields.

The fluid compositions of this invention can include other additives in minor proportions, i.e., 0.1 to wt. percent. Examples of such materials are detergents, e.g., calcium petroleum sulfonate; oxidation inhibitors, e.g., phenyl-alpha-naphthylamine; thickeners, e.g., polyisobutylene; pour depressants, e.g.', chlorowax-naphthalene condensation products, dyes, and the like.

By suspending, thickening and/or bodying agent is meant high molecular weight carboxylic acid soaps, low

molecular .Weight carboxylic acid salts, mixtures or complexes thereof, inorganic thickeners such as bentonite', clays, acetylene blacks, channel blacks, silicas, silicas treated with surface active agents to prevent preferential welting of the silica with water, mono-olefin polymers such as polyethylene, polypropylene, isobutylene and copolymers of the above.

The high molecular weight carboxylic acids contemplated in this invention are the saturated and unsaturated hour at-this temperature.

grease-making fatty acids that are commonly known in the art. Suitable fatty acids include caprylic, myristic acid, palmitic acid, stearic acid, the various hydroxy stearic acids, oleic acid, arachidic acid, behenic acid and the like. Naturally occurirng fatty acids such as fish oil acids, tallow acids, coconut oil acids, etc., may also be utilized directly or after hydrogenation to decrease any undesirably high degree of unsaturation. Mixtures of these high molecular weight fatty acids, e.g., hydrogenated fish oil acids with oleic acid, in any proportions are also operable.

The low molecular weight acids are exemplified by acetic, propionic, butyric, isobutyric, and valeric acids, acetic acid being especially preferred.

The metal component of the soaps or salts can be any conventional grease-forming metal, such as the alkali metals, e.g., sodium and lithium, but is preferably an alkaline earth metal such as calcium, strontium, barium or magnesium, the preferred alkaline earth metal being calcium. Mixtures of the metals, of course, can be used and a lithium-calcium mixture is especially preferred.

As previously indicated, a soap-salt complex is an especially preferred thickener. This soap-salt complex may exist with the ratio of salt to soap above 3, but it is preferred to maintain a ratio in the range of 7:1 to 40:1. When using a soap/salt complex, it is preferred to maintain the grease in a substantially anhydrous state and this can be done by dehydrating the grease at a temperature in the range of 400 to 500 F. during its preparation.

The fluid coke can be added to the lubricating oil in any convenient manner. Simple mixing, perhaps at elevated temperatures in the range of 100 to 300 F., is usually suflicient, although homogenization can be used if desired. In making a grease, the fluid coke can be added at any time during the manufacture of the grease. It can be added before, during, or after saponification of the fatty materials if they be used; it can be added during and after dehydration, if this is carried out; or it can be added during or after cooling of the grease. While homogenization of the grease is not necessary, the greases are in many instances substantially improved by homogenization.

It is preferred'to homogenize the greases in order to obtain more intimate dispersion and to impart better structure. This can be carried out by subjecting the greases to high rates of shear in the range of 50,000 to 500,000 reciprocal seconds at a temperature in the range of 100 to 200 F. Homogenization is well known to the art and is carried out using such apparatus as the Gaulin homogenizer, wherein the greases pass through a restricted orifice; or the Morehouse or Charlotte Mills wherein the grease is passed through an adjustable annular opening against a. revolving surface rolling on a stationary surface.

To make a grease containing a salt/ soap complex, the preferred method of manufacture consists of charging the alkaline earth hydroxide (e.g., hydrated lime) and min- 'eral oil to a steam heated grease kettle equipped with efficient means of agitation. To the intimate mixture of the lime and mineral oil is added a blend of the low molecular weight acid (e.g., acetic acid), and higher molecular weight acid (e.g., low molecular weight coconut fatty acids). Mixing is continued for /2 to 1 hour with no external heating. The temperature rises to l200 F. After this, external heating is initiated and the temperature is raised to 300-320" F. over a period of 3 to 4 hours.- Heating is continued for an additional /2 to l The grease is then rapidly cooled by passing cold water through the kettle jacket to 200 F. for l to 2 hours. The base material so obtained is then homogenized by passage through suitable milling equipment at a rate of shear approximating 100,000 reciprocal seconds. Additional mineral oil'is then added along with the pulverized fluid coke, to give a consistency of about grade. The materials are intimately mixed for about 1 hour in a grease kettle and packaged.

The following examples will serve to make this invention clear. All compositions are expressed as weight percentages unless otherwise specified.

The fluid coke used in the examples was obtained by the coking in a fluid bed of heavy Elk Basin vacuum bottoms having a Conradson carbon of about 30 wt. percent, sulfur of about 4.1 wt. percent, I.B.P. of 925950 F., and an A.P.I. gravity of 0-2. The coking temperature was 960-980 F. at a conversion of 34-36% coke make, based on fresh feed.

The raw fluid coke had the following typical inspection:

Carbon percent 89.1 Sulfur 6.1 Ash 1742 F. do 0.11 Volatile matter 1100 F. do 0.44 Moisture do 0.24 Real density 1.45

The fluid coke was pulverized and screened. The material passing through a 200 mesh screen (Tyler) was used in the examples.

Electron photomicrographs showed the screened fluid coke to have an amorphous particulate structure, somewhat similar to graphite, as compared to the extremely small size particulate channel blacks and the somewhat larger sized reticulate acetylene blacks.

Graphite is amorphous and has no structure imparting properties, as is also true of carbon black. Channel black is particulate and has fair structure imparting properties. Acetylene black is reticulate and has excellent structure imparting properties, which approach those of metallic soaps. Fluid coke has poor structure and is particulate. Structure is defined as the ability to impart a solid structure when dispersed in an oil. For instance, 20% channel black is equivalent to 5% acetylene black in that they both give a 300 mm./ work penetration in the same oil. Graphite at 30% concentration imparts no structure and settles out of the dispersion. Fluid coke at about 30% concentration gives a semi-fluid structure but the structure is stable and no settling occurs even after long storage.

EXAMPLE I This example compares the properties of apparently similar carbonaceous materials to the properties of the fluid coke of this invention, this comparison being done in the absence of any other materials except the base oils. The base oil, here called mineral oil A, was a lubricating oil base stock obtained by hydrofining a naphthenic type low cold test crude and had a SSU viscosity in the range of 500 to 600 at 100 F. and a V1. of 50. The carbonaceous materials were simply admixed into the oil in the concentrations indicated. Table I gives wear test results obtained with these compositions:

Table 1 Product Type of Structure Diameter, mm.

Oil alone 30% Common Amorphous Graphite.

30% Acetylene Black 5% Acetylene Black 30% Channel Black Channel Black 30% Fluid Coke tration. Semi-fluid stable grease dispersion.

The wear test used in these examples and the following examples is the four ball wear test wherein a central steel ball is rotated against three supporting steel balls at 1800 r.p.m. with 10 kg. loadingat 75 C. for one hour.

EXAMPLE II This example shows the use of other thickening and suspending agents in the fluid coke dispersion. Grease A was formulated, having the following composition.

10.0% imal fat 1.4% hydrated lime 0.8% water 5.0% fluid coke 82.8% mineral oil A The animal fat and one half the mineral oil were charged to a steam jacketed kettle and While mixing, the hydrated lime was added. The temperature was raised to 300 F. p.s.i.g. steam) and the fat completely saponified. The temperature was lowered to 210 F., the water added, and the grease formed. The balance of the oil was added followed by the fluid colke. The grease was filtered and packaged. No homogenization was necessary.

Properties:

Appearance Excellent, smooth uniform glossy black grease.

Penetrations, 77 F. mm./10

Unworked 290. Worked 60 strokes 29S. Wear test scar diameter, mm. 0.65. Same grease without fluid coke-Wear test scar diameter, mm 0.85.

These results indicate that fluid coke is an antiwear agent when used in greases, and does not contribute to wear and abrasiveness which is somewhat surprising. Fluid coke in appearance looks a good bit like beach sand, and it would be expected to be detrimental to a lubricant rather than beneficial.

EXAMPLE III Fluid coke and graphite were admixed with a conventional lithium soap grease. The lithium soap grease containing 12% of lithium stearate suspended in a naphthenic oil from a low cold test coastal crude having a 300 SSU viscosity at 210 F. (mineral oil B). The greases were prepared simply by intimately admixing the carbonaceous materials into the grease. Grease B contained 5% fluid coke, grease C contained 5% graphite (a common flake graphite containing a minimum quantity of clay), and grease D was the lithium grease per se. Table II gives the inspections and performance of these greases.

Table II B on DIV Penetrations, 77 I mmJlO:

Unworked 275 278 280 Worked 60 strokes 285 284 298 Wear test; sear diameter, mm 0.57 0.73 0. 72

These data clearly indicate the superior anti-wear properties of the fluid coke containing grease.

EXAMPLE IV 7 containedr10% Estersil, fluid coke, and 85% of a mineral oil C, which was a naphthenic type lubricating oil obtained by hydrofining a typical low test coastal crude, and liada viscosity of 1200 SSU at 100 F. and a V.I. of 40. The properties of the grease were as follows:

Appearance Excellent, smooth, glossy black grease. Penetrations, 77 F. mm./-

Unworked 290.

Worked 60 strokes 292. Dropping point, F None. Water solubility None.

Wear test scar diameter, mm 0.75. Estersil grease without fluid cokeWear test scar diameter, mm. 0.89.

EXAMPLE V This example also shows the use of another thickener that is not derived from carboxylic acids. Mineral oil A above described was used to formulate the greases. 10% acetylene carbon black and 5% fluid coke were mixed in the cold oil, and then the mixture was passed through a Manton-Gaulin homogenizer at 5,000 p.s.i. The grease had the following properties:

Appearance Excellent, smooth, uniform product.

This example illustrates the preferred embodiment of this invention wherein a soap-salt thickener is used. Mineral oil D, used as the base oil in this example, was a hydrofined naphthenic type mineral oil from a selected low cold test crude and had a SSU viscosity of 1200 seeonds at 100 F. and a V1. of 40. The grease was made up as follows:

Ingredients: Percent Fluid coke 30.00 Glacial acetic acid 3.15 Mixed carboxylic acids A 1 1.58 Hydrated lime 2.59 Phenyl alpha naphthylamine 0.14

Mineral oil D 62.54 Low molecular weight coconut fatty acids (Wecoline AAC 2 6 caprylic acid 57% capric acid 17% lauric acid The grease was prepared by blending the mineral oil, acids and fluid coke to a smooth, uniform, homogeneous mixture. During the addition of the acids, the temperature rose to l65l75 F., and the mixing was continued until the temperature subsided. The antioxidant was blended into the mixture at its hottest temperature. After cooling somewhat, the product was filtered through a 100 mesh filter. Homogenization of the product was not necessary. The product grease had the following properties:

Appearance Excellent, smooth, glossy product. Dropping point, F. 500+. Penetration, 77 F. mm./10

Unworked 340. Worked 60 strokes 322.

Worked 100,000 strokes 310. Water solubility Nil (boiling water),

8 EXAMPLE v11 A grease similar to that of Example VI was prepared, except the water of reaction from the saponification of the acids was removed by external heating. When the temperature due to the saponification reaction was at a maximum, external heating was initiated and the temperature was raised to 320 F. until the product was dehydrated. The phenyl alpha naphthylamine antioxidant was added at this point, and the product was cooled rapidly and filtered. The grease had the following properties:

Appearance Smooth, uniform,

glossy. Dropping point, F 500+. Penetrations, 77 F. mm./ 10- Unworked 325. Worked 60 strokes 327. Worked 100,000 strokes 318. Wear test, scar spot diameter, mm. 0.40. Norman-Hoifmann oxidation hours to 5 p.s.i. drop 362. Lubrication life hours (250 F 10,000 rpm.) 1300.

The lubrication life test was carried out by method described in Tentative Method for Determination of Performance of Lubricating Greases in Anti-Friction Bearings at Elevated Temperatures, Technical Bulletin #5, ABEC-NLGI Cooperative Committee.

EXAMPLE VIII This example shows the preparation of a grease extremely useful as a forging compound and containing another type of suspending agent, hydrated lime. This example shows that the combination of fluid coke and lime is unexpectedly better than the use of either medium alone. Three greases were prepared:

Grease E comprised 30% fluid coke and 20% hydrated lime carried in mineral oil D. Grease E was prepared simply by mixing to a smooth slurry and then filtering through a mesh screen. It had the following properties:

Penetrations, 77 F. mm./ l0

Unworked 325 Worked 60 strokes 340 Worked 100,000 strokes 355 Wear test, scar spot diameter, mm. 0.45

Penetrations, 77 F. mm./10

Unworked 230 Worked 60 strokes 245 Worked 100,000 strokes 246 Dropping point, F. 500+ Water solubility Nil Wear test scar spot diameter, mm. 0.50

Grease G was prepared by adding 15% fluid coke and 20% hydrated lime to a base grease. This was carried out by simple mixing. The base grease had the following composition:

Percent Glacial acetic acid 4.50 Mixed acids A 2.25 Hydrated lime 3.70 Phenyl alpha napththylamine .20

Mineral oil D 89.35

The grease was formed in a conventional manner as described in Example VI. The grease had the following properties:

Penetration, 77 F. mm./-

Unworked 320 Worked 60 strokes 340 Wear test scar diameter, mm. 0.35

Comparison of the wear test results of greases E, F and G, and also of the results of other examples, shows that while the fluid coke enhances the wear properties of the greases, exceptionally good results are obtained when the fluid coke is in admixture with the hydrated lime and a complex salt thickener is used, as illustrated by grease G which has a scar diameter of Mineral oil D 88.722 Mol ratio acetic/mixed acids 12.1

To make a base grease, the mineral oil and lime were charged to a steam heated kettle and mixed to an intimate slurry. The acids were then added with no external heating. The temperature rose and a grease structure was formed. Steam heating was then used to dehydrate the base grease to less than 0.3% water. This was followed by cooling and homogenization. 20% fluid coke was then intimately mixed into the base grease to obtain composition H.

Grease H was used in the hot forging of automotive combustion engine valves. This entails heating metal in the form of approximately 1" x 1 cylindrical alloy steel billets to red heat and forging under pressure in dies into the proper shapes. Two steps are involved, a rough forge and a finishing step. The products of this invention gave over 500 pieces before the dies were worn out. The consistencies of the lubricant were satisfactory for this application. The stay-putness of the lubricant even at the high forging temperature was extremely good. The finished pieces had sharp corners and only a light flufiy powder remained on the Work, and it was easily removed. When a graphite lubricant was employed, shorter die life was obtained. The finished pieces were coated with a lubricant residue which could only be removed by an expensive burning step before further grinding and finishing steps could be carried out.

Having described this invention, what is sought to be protected by Letters Patent is succinctly set forth in the following claims.

What is claimed is:

1. A lubricant consisting essentially of a major proportion of a mineral lubricating oil and 4 to wt. percent of fluid coke having a maximum particle size under 200 mesh (Tyler).

2. A grease consisting essentially of a major proportion of a mineral lubricating oil, 10 to 30 wt. percent of fluid coke having a maximum particle size of about 80 microns and a median particle size in the range of 40 to microns, and 3 to 8 wt. percent of a soap of a carboxylic acid having in the range of 8 through 22 carbon atoms per molecule.

3. The grease of claim 2 wherein said soap is in admixture with 5 to 8 wt. percent of a salt of a carboxylic acid having from 1 to 6 carbon atoms per molecule.

References Cited in the file of this patent UNITED STATES PATENTS 1,754,297 Ackerman Apr. 15, 1930 2,467,147 Morway et a1. Apr. 12, 1949 2,653,131 OHalloran Sept. 22, 1953 2,696,469 OHalloran Dec. 7, 1954

Claims (1)

1. A LUBRICANT CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF A MINERAL LUBRICATING OIL AND 4 TO 40 WT. PERCENT OF "FLUID COKE" HAVING A MAXIMUM PARTICLE SIZE UNDER 200 MESH (TYLER).