US2029382A - Process for producing high molecular weight compounds from petroleum oil - Google Patents

Description

Patented Feb. 4, 1936 PATENT OFFICE PROCESS FOR PRODUCING HIGH MOLECU- LAB. WEIGHT COMPOUNDS FROM PETRO- LEUM OIL David R. Merrill, Long Beach, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application November 20, 1933, Serial No. 698,878

8 Claims.

The present invention relates to a process for producing lubricating oils of low pour point and green fluorescence. In particular, the invention relates to a process for producing pour point depressing agents adapted to be added to lubricating and other oils in order to lower the pour point of such oils.

It has been found that heavy asphaltic bodies from cracked residuum contain valuable materials which, when added to lubricating oils, impart a green bloom or fluorescence and depress the pour point of oils containingwax. As is Well known, 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 oils to remove the wax or parafiin from the oil to as great an extent as is feasible. This is usually accomplished by chilling the oil preferably in the presence of a solvent in order to precipitate the wax and then separating the precipitated wax from the oil solvent solution by settling, centrifuging or filtering.

The solvent is then removed from the dewaxed lubricating oil by distillation.

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 parafiin base crudes exhibit a low temperature viscosity susceptibility, whereas those produced from asphaltic base crudes as distillates exhibit a relatively high temperature viscosity susceptibility. I have observed that the removal of wax from oils containing the same increases the temperature viscosity susceptibility of the oil; in other words, waxes per so have especially low temperature viscosity susceptibility and impart to oils containing them a low temperature viscosity susceptibility. Consequently, their removal from oil is to be considered harmful from the standpoint of impairment of the temperature viscosity susceptibility of the oil.

In order to permit oils having high pour points to flow at the lower temperatures without eflEecting complete removal of the wax or paraffin or other substances in the oil which cause it to congeal under ordinary conditions of high temperatures, it has been, proposed to add to the lubricating oil, petroleum fractions containing highmolecular weight bodies which are very effective in depressing the pour point or congealing point of the oil and which also impart to lubricating oils produced from distillates or for other reasons deficient in green bloom, a rich green fluorescence characteristic of lubricating oils produced from parafiin base .crude oils.

One of the recent methods proposed for producing these petroleum fractions is to obtain a cracked residue such as the cracked residuum produced by cracking gas oil to produce gasoline in a Cross cracking process at a maximum pressure of 800 lbs. and a maximum temperature of 880 F. The residue obtained as the bottoms from the flashing drum in which gasoline and cycle stock are removed by distillation is then treated for the recovery of the high molecular weight and complex compounds comprising the pour point depressants. The recovery of these complex compounds from cracked residuum consists in first distilling the residue to remove the lighter constituents and to leave a high melting point cracked residuum pitch as a distillation bottom and then extracting the cracked residuum pitch with a suitable solvent in which the carbonaceous and coke-like bodies present in the cracked residuum pitch are not soluble but in which the desired pour point depressing agents and wax crystallization inhibitors are soluble. A solvent solution of pour point depressing agents is separated from the coke-like bodies by such methods as settling, centrifuging or filtering. One of these solvents comprises a lubricating oil or a lubricating oil stock, that is, an oil possessing physical characteristics similar to the oil to be treated for pour point depressing. A concentrated oil solution of the active pour point depressing agents is made which may be added to the oil to be treated for pour point depressing. The concentrated solution is then treated with concentrated sulphuric acid of say, 98% strength, neutralized with caustic alkali and clay treated with decolorizing clay by methods conventional in the art, or may be treated with clay alone, without a prior acid treatment.

The present invention relates in part to an improvement on the foregoing process for producing pour point depression agents adapted to be added to oils containing wax. I have discovered that when the concentrated solution of oil containing the pour point depressing agents is treated with concentrated sulphuric acid as aforesaid, a large proportion of the valuable components which impart a green bloom to lubricating oils and lower the pour point of waxy oils are lost to the acid sludge. The concentrated sulphuric acid appears not only to attack the undesirable and unstable components but also attacks the valuable high molecular weight compounds and yet it is entirely necessary to effect a treatment of the crude material in order to produce a product of satisfactory refinement as regards color and stability. 7

It is, therefore, an object of my invention to improve upon the aforesaid process for producing pour point depressing and green bloom compounds adapted to lower the pour point and impart a green fluorescence to lubricating oils and the like.

,Another object of my invention resides in providing a process wherein increased yields of pour point depressing agents may be recovered from cracked residuum pitches and the like containing such agents.

It is a particular object of my invention to restrict the activity of the acid employed to treat the pour point depressing agent and thus prevent a large proportion of the valuable pour point depressing agents present in the crude material from being attacked by the acid and thus lost to the acid sludge and yet to produce pour point depressing agents of satisfactory refinement.

Briefly stated, my invention relates to a process for producing high molecular weight compounds from cracked residuum which are capable of lowering the pour point of oils and imparting a green fluorescence to lubriating oils which comprises first extracting a crude pour point depressant from a cracked residuum pitch and then treating it in the presence of a solvent with acid, such as sulphuric acid. The invention includes the extraction of a crude pour point depressant and green bloom compounds from cracked residuum pitches and the like by means or a solvent capable of dissolving the pour point depressant and green bloom compounds but capable of dissolving only limited asphaltic, carbonaceous and coke-like materials, and subsequently treating th pour point depressant and green bloom compounds with sulphuric acid while the compounds are dissolved in a solvent.

One of the particular features of my invention comprises the treatment oi the extracted pour point depressing agents with acid in the presence of a highly aromatic solvent.

More particularly stated, my invention comprises a process for producing pour point depressants in which a cracked petroleum residuum is first reduced to a pitch-like consistency and then the pitch is mixed with a solvent capable of dissolving the pour point depressing agents-present in the cracked residuum pitch but to leave for the most part as undissolved fractions the asphaltie and coke-like materials resulting from the cracking operation, then separating the latter from the solvent solution and acid treating the dissolved fractions in the presence of a highly aromatic solvent such as benzene.

I have discovered that when the crude pour point depressing agent, such as the extract of a cracked residuum pitch, is acid treated in the presence of a highly aromatic solvent which has a high solvent power for the high molecular weight compounds present in cracked residuum pitches and which comprise the pour point depresmng agents, the action of the acid is restricted to the more reactive undesirable constituents present in the crude pour point depressing agent leaving unattacked the valuable pour point depressing agents. When the crude material is treated directly with sulphuric acid or in the presence of a solvent other than the highly aromatic solvent, a considerable amount of the valutime able constituents are lost to the acid sludge. The use of a highly aromatic solvent appears to take the high molecular weight compounds into a true solution rather than a colloidal solution and thus the action of the sulphuric acid is restricted to the more reactive bodies present in the solution but not the more colloidal hydrocarbons present in the cracked residuum extract.

The high molecular weight compounds comprisingthe valuable pour point depressing agents are preferably produced from asphaltic residues, particularly cracked residues, suchas those resulting from the cracking of kerosene, gas oil or other cracking stocks in the production of cracked gasoline, although they may be produced by cracking petroleum residues or heavy oils to reduce their viscosity. In general, the poor point depressants are preferably produced from stocks having a sufficient quantity of high molecular weight bodies and resinous 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 moderately viscous cracked residua are, in general, less eflective in depressing the pour point of oils than are the extracts which are produced from the cracked residuum pitches. Also, the lighter fractions of the cracked residua 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 residua often have high solvent properties for the asphaltic and coke-like material and may interfere with the precipitation of such impurities during extraction with oils as will be described. Therefore, I prefer to remove the light constituents present in the cracked residuum prior to the extraction step with the solvent.

The removal of the lower molecular weight hydrocarbons may be effected by steam distillation, preferably under vacuum, until a pitch remains as a distillation'bottom which has a high melting point, i. e. in excess of 200 F. Lubricating oil or lubricating oil stock is then added to the pitch while still hot in the still and the mass is quiescent state in the still until the black carbonaceous and coke-like bodies have settled out.

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 depressant ingredients is to be employed. Generally, 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 though other solvents may be employed which have a preferential solubility for the high molecular weight hydrocarbons presentin the cracked residuum pitch to leave as undissolved fractions the carbonaceous and solvents capable of dissolving the high molecular weight pour point depressants from the asphaltic carbonaceous and coke-like materials, I may employ in addition to the lubricating oil or lubripoint depression, al-

coke-like materials. As

eating oil stock mentioned, naphtha, gasoline,

kerosene, gas oil, fuel oil, alcohols,.such as butyl alcohol, ketones, such as acetone, .and esters, such as methyl formate. The amount of oil or solvent employed and the char-' such as carbon tetrachloride,

volumes of lubricating oil to one volume of the pitch gives very satisfactory results.

After settlement of the coke-like materials, the concentrated lubricating oil solution of active pour point depressant ingredients is decanted away and is ready for acid treatment. This solution is then dissolved in a highly aromatic solvent and treated with sulphuric acid of 93% or less strength. As solvent, I may employ benzene, toluene, xylene, heavy solvent naphtha from coal tar, highly aromatic solvents produced from the liquid sulphur dioxide treatment of light oils, such as Edeleanu extract, chlorinated solvents ethylene dichloride or trichloride, carbon disulphide and the like. The amount of solvent used for admixture with the pour point depressant is more or less elasticand will depend upon the type of aromatic sol vent added and the character of the pour point depressant. In general, a sufficient amount is employed to reduce the viscosity of the mass in order to permit acid sludge produced by the acid treatment to settle from solution. I may employ from one to three volumes of the solvent to one volume of the concentrated oil solution of pour point depressing ingredients. When solvents other than the lubricating oil or lubricating oil stock are employed for extracting the high molecular weight hydrocarbons or materials from the cracked residuum pitch and such solvents may interfere with the acid treatment in the presence of a highly aromatic solvent such solvents may be removed, as, for example, by distillation prior to the addition of the highly aromatic solvent to the pour point depressing agent. However, in the case of the lubricating oil, I prefer to add the aromatic solvent to the concentrated solution of pour point depressant and then acid treat The acid treated mixture may then be distilled to remove the aromatic solvent leaving as a distillation bottom a concentrated oil solution of acid treated pour point depressing ingredients which may be added to the oil to be treated for pour point depression.

The amount and concentration of acid should be carefully restricted in order to prevent removal as acid sludge, valuable components of pour point depressant character. The amount and concentration of acid will depend upon the character of the high molecular weight hydrocarbons of pour point depressants to be treated. I may employ acid of 93% or less strength in an amount of, for example, 30 lbs. per barrel based on the concentrated oil solution of the high molecular weight hydrocarbons, although I may use very-small proportions of the more concentrated acids. After the acid treatment, the solvent solution may be neutralized with aqueous alkali or by dry methods, such as treatment with fullers earth or other clays and I may further purify by clay treatment as by percolation of the solvent solution before recovering the product by evaporation of the solvent.

In producing my pour point depressing agent from recycled cracked gas oil residuum, I prefer to proceed as follows, although this is not to be considered as limiting my invention:

A cracked residuum, such as one obtained from cracking in recycling operations, a gas oil fraction distilled from a San Joaquin Valley crude to produce cracked gasoline, and steam until a hard pitch is produced having a melting point of approximately 300 to 400 F. The molten pitch in the still is then thoroughly mixed by steam agitation at a temperature of approximately 450 to 500 F. with lubricating oil in the proport on of one volume of pitch to five volumes of lubricating oil. The mixture is then allowed to settle for a period of ten to twelve hours with slow cooling after which the supernatant layer of oily solution, is decanted away from the black carbonaceous bodies. This concentrated solution of pour point depressing ingredients is then mixed with an aromatic solvent such as benzene in the proportion of one volume of the concentrated oil solution to two volumes of benzene. The mixture is then acid treated with about 25 lbs.of 93% sulphuric acid per barrel of the concentrated oil solution. The acid sludge is removed and the mixture is then neutralized with caustic soda and the benzene is removed by distillation, leaving as a distillation bottom a purified oil concentrate of pour point depressants. If a relatively light color is desired, the concentrate is then clay treated with about 5% of decolorizing clay. These materials may then be added to the oil having a high congealing temperature or pour point in an amount sufficient to lower the congealing temperature or pour point to the desired value.

The amount of this concentrated solution of pour point depressing agents or compounds which must be added to the waxy oil to lower its pour point to the desired value will vary; however, in most instances the addition of about 2% by volume of the concentrate to the oil will be suflicient. For example, by adding 2% of the agent to a waxy lubricating oil having a pour point of approximately 40 F., the pour point may be lowered to F. When the oil has a high congealing temperature due to large amounts of wax, it may be necessary to increase this amount to 3 to 5%.

While the cracked residua referred to in the above examples have been obtained by cracking distilled products, such as gas oil or cycle stock. the cracked residua obtained from the conversion of crude oils or fuel oils by the various cracking processes now known also contain large amounts of pour cracked residua which I employ as a source of pour point depressing agents are not limited to any particular type of cracking stock or to any method of operation of the cracking process because substantially all cracked residua, regardless of the source or method for their production, have been found to contain pour point reducing agents which appear to have been formed simultaneously with the gasoline or gas in the conversion process. The exact concentration of the pour point depressing agents, however, is dependent on the cracking conditions and in the charging stock with the more severe cracking conditions and highly aromatic or naphthenic charging stocks generally favoring a higher yield of pour point depressing agents.

If desired, the pour point depressing agent may be produced by distilling the cracking re: siduum with fire and steam until a pitch is left in the still having a melting point above 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 when acid treated in the presence of an aromatic solvent and the solvent removed, it may be employed to lower the congealing point of oil. However, such distillates obtained from cracked pitches are not as efiecpoint reducing agents. The

.40stoc carbon oil to cease to flow istic oi lubricating oil produced from paramn base aoaassa from the'pitches and aromatic solvent with acid and separating said aromatic solvent from said acid treated high molecular weight hydrocarbons.

hly satisfactory sources of these pour point 2. A process for the production of high molecweight hydrocarbons which comprises disa tiiling a cracked residuum to produce a pitch oi.

ling said Ditch with and separating said highly said acid treated high molecular weight hydrocarbons.

3. A process for the production 01' high molecular weight hydrocarbons which comprises distilling a cracked residum to produce a pitch of high melting point, commingling said pitch with an oil at an elevated temperature to dissolve high drocarbons from said pitch residue, separating the a.

2n by a rich green crude oil.

My invention is also ciety, Method D--36 26.

By the terms p'araflln" designate those substances or wax, I mean to which cause hydroupon the lowering oi the temperature.

subsequently separating said benzene from said acid treated oil and high molecular weight hydrocarbons.

6. A process for the production ular weight hydrocarbons which comprises com- 1 Weight mingling said mixture with a solvent having a high solvent power for desirable high molecular weight hydrocarbons so that subsequent action with acid is restricted to unstable reactive bodies contained in the high molecular weight hydrocarbons, treating said mixture with acid to remove the undesirable unstable reactive bodies and subsequently separating the solvent from the acid treated desirable high molecular weight hydrocarbons.

7. A process for the production of high molecular weight hydrocarbons which comprises commingling a cracked pitch with a lubricating oil to dissolve crude high molecular weight hydrocarbons contained in said pitch but to leave an insoluble residue, separating the solvent solution of high molecular weight hydrocarbons and oil from the insoluble residue, commingling said solution with a solvent selected irom the class consisting of benzene, toluene, xylene, heavy solvent naphtha obtained from coal tar, liquid sulphur dioxide soluble hydrocarbons, carbon tetrachloride, ethylene dichloride, ethylene trichloride and carbon disulphide, treating the solution of high molecular weight hydrocarbons, oil and, solvent with sulphuric acid to remove the undesirable unstable reactive bodies and separating the solvent from the acid treated high molecular weight hydrocarbons and oil.

8. A process as in claim 7 in which the strength of sulphuric acid employed does not exceed 93%.

DAVID R. MERRIIL.