US2200534A - Low pour point lubricating oil - Google Patents

Description

'dewaxing methods.

Patented May 14, 1940 LOW POUR POINT LUBBIOATING OIL Ulric B. Bray, Palos Verdes Estates, Calif.I asslgnor to Union Oil Company of California, Lon. Angeles, Calii'., a corporation of California No Drawing. Application April 19, 1932;

Serial No. 606.278

1 claim." (or. 196-151) The present invention relates to the production of low pour point oil. More specifically, it relates to a new product and the process of pro, ducing the same.

Lubricating oils are desirable which possess ,a low pour point, i. e., do not congeal at the lower temperatures. Oils which contain paraflin or wax solidify at the lower temperatures and will not flow. To overcome this undesirable characteristic of waxy oil it has been customary in the art of producing lubricating oil to remove asubstantial quantity of the wax or paraflln from the oil.

Another desirable characteristic of lubricating oil is a low temperature viscosity susceptibility, i. e.', a minimum change in viscosity with a given change in temperature. Lubricating oils produced from paraflin base crudes exhibit a-"low temperature viscosity susceptibility whereas lubricating oils produced from asphalt base crudes as distillates exhibit a relatively high temperature viscosity susceptibility.

It is well known that many parafflns or waxes have temperature viscosity susceptibilities which are lower than the best paramn base lubricating oils. Furthermore, it has been shown that an oil which contains paraffin or wax has a lower temperature viscosity susceptibility than the same oil possesses after the removal of the wax. Therefore, removal of wax from oil is to be considered harmful from the standpoint of impairment of the viscosity temperature susceptibility of the oil.

I have discovered a method wherein lubricating oils possessing a high pour point may be made to flowat the lower temperatures without the complete removal of the wax or paraflin or other substances in the oil which cause it to congeal under ordinary conditions at high temperatures. Furthermore, the method which I employ to lower the pour point of waxy oil is simple and does not require the expensive and elaborate apparatus as is ordinarily employed in the production of low pour p int lubricants by present day My invention is also useful in conjunction with the production of low pour point fuels of either the distillate or residual type. Fuel oils which congeal at moderate temperatures and which cannot be transported through pipe lines or withdrawn from storage during cold weather without heating to maintain a temperature well above the congealing point of the oil can be made to flow at much lower temperatures by my novel discovery. Thus the utility of certain Diesel fuel oils of high wax content is ordinarily reduced because of their tendency to solidity when stored' in double bottom tanks next to the ship's hull, with consequent difliculty from stoppage oi suction lines and screens, and this'is overcome by the application of my invention. Furthermore; the invention may also be applied to certain crude oils which also exhibit the property of congealing at moderate temperatures and which must be heated more or less during their transportation.

, I have discovered that certain petroleum fractions contain high molecular weight bodies which are very eflective in depressing the pour point or congealing point of oil. The effect is probably the result of crystallization inhibition; however, I do not propose to limit myself by any such theory. These high molecular weight bodies are found associated with residual oil and especially residual oil resulting from hydrocarbon conversion processes and which is commonly known as "cracked residuum.

Such an oil residue is produced when gas oil of approximately 29.0 A. P. I. gravity at F. having a. viscosity of 40 seconds (Saybolt Universal at F.) and a pour point below 0 F. is subjected to recycle cracking operation in a Cross cracking process at a maximum pressure of 800 pounds and a maximum temperature of 880 F. The residuum obtained as the bottoms from the flashing drum in which the gasoline and cycle stock are removed by distillation has a specific gravity at 60 F. of 1.061 and a viscosity of 87 seconds (Saybolt Furol at 122 F.). As other examples of cracked residues, 32 A. P. I. gravity mixed base gas oil of 20 F. pour point, parafin base lubricating distillate of seconds (Saybolt Universal at'100" F.) viscosity and 31 A. P. I.- gravity at 60 F. and paraihnscale wax have all been cracked at temperatures of 900 to 950- F. to give cracked residua containing pour point lowering materials.

It is, therefore, an object of myinvention to produce an agent from certain petroleum fractions which is .efiective in lowering the pour point or congealing temperature of oil.

It is another object of my invention to produce oils which exhibit a low pour point or congealing The bodies which are present in cracked residuum and which'are'active in depressing the pour.

point of oil are of high molecular weight and probably possess a very complex structure. The recovery of these complex compounds from cracked residuum consists in extracting the residuum with a suitable solvent in which the carbonaceous, coke-like bodies present in the cracked residuum are not soluble but in which the desired pour point depressing agents, or wax crystallization inhibitors, are soluble and then separating the solvent solution of pour point depressing agents from the coke-like bodies by such methods as settling, centrifuging or filtering. The solvent which I may employ to separate these active pour point agents from the cracked residuum is dependent more or less upon the characteristics of the cracked residuum which I extract. I have found that cracked resldua which are only moderately viscous in character can be extracted to advantage with a solvent, such as naphtha or gasoline for the separation of the coke-like bodies from the active pour point depressing agents. Such a solvent would have a boiling point range within the limits of 75 and 500 F. The solvent may be removed entirely or in part by distillation from the fractions extracted from the cracked residuum. When the cracked residuum is highly viscous in character or is substantially solid at ordinary temperatures I find that heavier solvents may be employed to obtain a satisfactory separation of the coke-like bodies from the active pour point depressing agents. Where the cracked residuum has been distilled to a high melting point pitch I find it highly desirable to employ a gas oil or lubricating oil for the extraction step, because the temperature at which the extraction is carried out should be well above the melting point of the residue. The extraction of the high melting pitches, however, may be carried out with the lighter solvents, such as gasoline, by pulverizing the pitch and/or operating under pressure to permit the use of high temperatures without substantial loss of solvent.

Solvent oils which are highly aromatic in character are to be avoided for the extraction of the pour point depressing agents from the residuum or pitch because of their high solvent power for asphaltic bodies. Furthermore, oils which are highly parafilnic in character and are substantially free from aromatic constituents are also to be avoided as such oils are capable of forming relatively concentrated solutions of the pour point depressing agents at the extraction temperature MOO-450 F.) but upon cooling there is a separation of these agents in solid form due to the lessened solvent power of the paramnic oil which causes a reduction in the potency of the extract. It is, therefore, desirable to employ an oil of balanced solvent power in order to avoid the subsequent separation of the pour point depressing agents upon cooling and at the same time not dissolve excessive amounts of the asphaltic materials.

The lower molecular weight hydrocarbons present in the cracked residuum are of little value in depressing the pour point of wax containing oil, therefore, the extracts which are produced from the moderately viscous cracked residua are in general less effective in depressing the pour point of oil than are the extracts which are produced from the cracked pitches. Also, the lighter fractions of the cracked residues are generally less stable in character than the lubricating oil to which it is desired to add the pour point depressing agents. Moreover, the lighter constituents of the cracked residua often have high solvent properties for the asphaltic and cokelike material and may interfere with the precipitation of such impurities during the extraction with oils as described. Therefore, I often prefer to remove the light constituents present in the cracked residuum prior to the extraction step. The cracked residuum is preferably distilled until a residual pitch is obtained which has a melting point in excess of 300 F. Lubricating oil or lubricating oil stock is then added to the pitch while still hot in the still and the mass is thoroughly agitated with steam. After thorough agitation the mass is allowed to remain in a quiescent state in the still until the black carbonaceous bodies have settled out. This usually requires about 10 to 12 hours, although a shorter time can be employed. After settlement, the concentrated lubricating oil solution of active pour point depressing ingredients is decanted away and is ready for use. The type of oil used for the extraction step will be governed by the use to which the concentrated oil solution of active pour point depressing ingredients is to be employed. In general, it will be preferable to use an oil for the extraction step which has physical characteristics similar to the oil to be treated for pour point depression. The amount of oil used in the extraction step is more or less elastic; however, I find that about five to seven volumes of lubricating oil to one volume of the pitch gives very satisfactory results.

Where further refinement is necessary the oil solution of pour point depressing agents may be treated with about 10 pounds of 98% sulphuric acid per barrel of oil, neutralized and claytreated with 10% of decolorizing clay by methods conventional in the art.

When it is desired to lower the pour points of such products as gas oil or Diesel fuel oil I find it desirable to employ a light solvent oil having characteristics similar to the gas oil or Diesel fuel oil itself. In such cases, it is unnecessary to reduce the cracked residue to a pitch before the extraction, but it is then generally advisable to remove the precipitated coke-like particles by filtration rather than by decantation. The extract so obtained is then added to the gas oil or Diesel fuel oil in an amount suflicient to produce the desired depression of the pour point.

In the case of crude oil or residual fuel oil where color is no consideration, I find that I may obtain the desired pour point depression by adding the cracked residuum or pitch directly to the oil without removing the black carbonaceous bodies which are present in the cracked oil or pitch. If a fuel oil of very low sediment content is desired, the sediment may be separated by decantation, filtration or other suitable means.

In producing my new pour point depressing agent from recycled cracked gas oil residuum, I prefer to proceed as follows: The cracked residuum is reduced by fire and steam until a hard pitch is produced having a melting point of from 300 to 400 F. The molten pitch inthe still is then thoroughly mixed by steam agitation at a temperature of approximately 450 to 500 F. with lubricating oil in the proportion of one volume of pitch to eight volumes of lubricating oil. The mixture is then allowed to settle for a period of 10 to 12 hours with slow cooling after which the supernatant layer of oily solution is decanted away from the black carbonaceous bottoms.

This concentrated solution of pour point depressing ingredients is then acid treated with about pounds of 98% sulphuric acid per barrel of oil, neutralized and clay treated with 10% of decolorizing clay after which it is added to the oil having a high congealing temperature or pour point in an amount sufiicient to lower the congealing temperature or pour point to the desired value. 1

The amount of this concentrated solution of pour point depressing agents orcompounds which must be addedto waxy oil to lower its pour point to the desired value will vary; however, in most instances about 2% by volume of this agent added to the oil will be sufficient. In some cases when the oil has a high'con'gealing temperature dueto large amounts of wax this aniount may have to be increased to 35%. I The following table is illustrative of the -depressing effect which the lubricating oil solution of heavy hydrocarbons produced from the pitch having a melting point of 372 F. in the manner described above, has upon typical commercial samples of Pennsylvania lubricating oil:

Pergentfllublri Pour point, F

as g 0 so u- 1 essr a or. w

point depres- Before treat- After treatsant added ment I ment 2. 0 Below 0 2. 0 Below 0 a 0 25 10 4.0 80 i5 If further concentration point depressing agents is desired, I may treat the oil solution of these agents with such solvents as sulphur dioxide, aniline, nitrobenzene or furfural and recover the extract which is soluble in the foregoing solvents as a concentrated solution of the active agent. Such treatment, however, is unnecessary in most instances as the heavy hydrocarbon bodies obtained from the cracked residuum or cracked pitch are sufllciently concentrated to produce the necessary lowering influence upon the pour point of oil without any further concentration.

' As an example of the application of my invention to gas oil or Diesel fuel oil, it was desired to lower the pour point of a heavy gas oil obtained by distilling approximately 40% overhead from a Los Angeles basin residuum of 180 A. P. I. gravity from which the 720? F; end point gas oil and lighter fractions had already been removed. The heavy gas oil had 27 A. P. I. gravity at 60 F., approximately '70 seconds viscosity (Saybolt'Universal) at 100 F. and a pour point of 75 F. Four volumes of this heavy gas oil were added to one volume of 8.5 A. "P. I. cracked residuum as obtained from the bottom of the evaporator in a Cross. cracking plant and agitated at a temperature of 210 F. 1 After two hours the mixture was then filtered to remove the precipitated coke-like sediment. The filtrate was then added to a portion of the original heavy gas oil in the ratio of one part of filtrate to two parts of the high pour point gas oil. The resulting gas oil had a pour point of 10 F.

As an example of cracked residuum produced from other. charging stocks, paramn scale wax of appoximately125 F. melting point was cracked. V

at 950? E'under ,800pounds pressure to give 40% gasoline boiling under 425 F. The cracked wax of the active pour ten' volumes of lubricating oil of 350 seconds (Saybolt Unisersallviscosity at l00-F. at a temperature of 400 F. The lubricating oil phase was decanted from the coke-like phase and it was found that three parts of this extract were capable of reducing the pour point of '100 parts of commercial Pennsylvania from 30 to 0 F.

While the cracked residua. referred to in the above examples have been obtained by crackme distilled products, the cracked residua'obtained from the conversion of .crude oils or fuel oils by the various cracking processes also contains large amounts of pour point reducing agents. The cracked residues which I agents are not limited to any particular type of cracking stock or to any method of op 'eration of the cracking process. because every oil of s. A. E. 40 grade employ as-a source of pour point reducing point-reducing agents which appear to have been formed simultaneously with the gasoline or gas in the conversion process. The exact concentration of pour point depressing agents, however, is dependent on the cracking conditions and in the charging stock, with the more severe cracking conditions generally favoring a higher yield of pour point depressing agents.

As a further modification of the method of producing my new pour point depressing agent, I

' may first distill the cracked residuum with fire and steam until a pitch is left in the still which has a melting point in excess of 300- F. and then collect the heavy distillate produced upon further distillation of the pitch in the still. The distillate so produced possesses pour point depressing characteristics and may be employed as produced or in solution in oil to lower the congealing point of oil. It is my experience, however, that the distillates obtained from the pitches are not as. effective as the material extracted from the pitches by suitable solvents.

While cracked residua have been found to highly satisfactory sources of these pour point depressing agents I have found that these agents may also be produced from crude oil residues. For example, asphalt base crude oil which is relatively'free from wax may be distilled until a residue is obtained having a melting point between 200 and 350 F. (Ball. and Ring) and then extracted in the same manner as previously described for the production of agents which are efiective in lowering the pour point of oil.

When these heavy hydrocarbons recovered from cracked residuum or cracked pitch by the methods described above, are blended with oil, and especially lubricating oil, the resultant pour point is depressed and the blended oil is characterized by a rich green fluorescence which is characteristic of lubricating oils produced from paraffin base crude oil.

By "pour point is meant the temperature 5 F. above the test temperature at which an oil ceases to flow as determined by American Society of Testing Materials Method D 97-30.

By the terms paraflin or "wax I mean to designate those substances which cause oil to cease to flow upon'the lowering of the temperature. Y

It is to be understood that the foregoing examples are merely illustrative and must not be construed as limiting the invention which I claim,

as many modifications of the invention will appear to those skilled in the art.

I claim:

A lubricating oil having a relatively low pour 5 point comprising a lubricating oil having a relatively higher pour point blended with a small ULRIC B. BRAY.