US2030870A - Hydrocarbon oil treatment - Google Patents

Description

- chemical compositions while of Patented F eb.- 1 8, 1936 PATENT OFFICE HYDROCARBQN OIL TREATMENT Lawrence M. Henderson, Narbertli, Pa., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania No Drawing. Application October 5, 1932,

Serial No. 636,352 1 18 Claims.

The present invention relates to the art of mineral oil refining, and has particular reference to the separation of crude petroleum or petroleum products into fractions of different approximately the same distillationrange.

In. accordance with my invention, crude petroleum or petroleum products, particularly oils of substantial viscosity, are separated into va- 10 rious fractions by means of fractional extraction with furoic compounds, and more particularly with furoic esters: methyl, ethyl, propyl, isopropyl, n-butyl, phenyl, and other furoates being exemplary of the furoic esters contemplated. The furoic radical, as the term is employed herein and in the appended claims has the structural formula HCCH The term "furoic acid as used herein refers to the acid sometimes called pyromucic acid. As well as the esters themselves, mixtures of the 25 esters with one another or mixtures of solvents containing substantialquantities of one or more furoic esters are contemplated within the scope of my. invention as selective solvents for the fractional extraction of hydrocarbon oils, particularly, viscous petroleum oils.

It is recognized in the art that mineral oils,

such as petroleum, comprise essentially a mixture of hydrocarbons of various groups or homologous series of compounds, such for example, as paraflins of the general formula CnH2n+2, olefines of the general formula CnHZn, hydroaromatics and polymethylenes of the same empirical formula, and various other series of compounds of chain and/or ring structures in which the-hydrogen to carbon ratio is less than in the foregoing series. A large number of individual compounds of each series and of differing boiling points is presentin petroleum.

The various types of crude petroleum, which are generally classified into three groups, namely, parafiinicvbase, naphthenic or asphaltic base, and mixed base, contain the various series of hydrocarbons mentioned heretofore, in difierent proportions For example, in the paraffln base crude oils, such' as those obtained from thecii fields of Pennsylvania, there is a relatively high proportion of hydrocarbons having a chain structure and a high hydrogen to carbon ratio, whereas in the naphthenic or asphaltic base crude oils,

there is a relatively large proportion of hydro-- carbons having ring structures and a low hydrogen to carbon ratio. Mixed base crude oils, such as are obtained from the mid-continent oil fields, contain hydrocarbons in proportions intermediate these two extremes.

As the use of practically all of the petroleum oils is almost entirely physical, the above described chemical nature of those oils is important in reflecting certain physical characteristics. The variance in the proportion of the different series of hydrocarbons in parafiinic, naphthenic, and mixed base oils is evidenced by the p y ical properties of the various oils, and particularly by the relationship of thespeciflc gravity to the viscosity of one oil as compared with another. For example, oils derived from a Pennsylvania crude and having a viscosity of 400 seconds Saybolt Universal at 100 R, will show a specific gravity at F., ofabout 0.878, whereas an oil of corresponding viscosity produced from a naphthenic crude, such as one from the Gulf Coast area, will show a specific gravity. of about 0.933 at 60" F. The relationship between the viscosity and gravity indicates the degree of the paraflim'c or naphthenic character of the oil.

If a given crude petroleum be distilled into. successive fractions and the specific gravities and visccsities of the several fractions determined,

it will be found that they conform to the general relationship:

G=a+ log.(V38) in which G is the specific gravity at 60 F., V" is Saybolt Universal viscosity at F., and a is a constant known asthe viscosity-gravity constant. Fractions from each of the different types of crude have different viscosity-gravity constants. Such constants are lower for fractions of the paraflinic crudes than are the constants for fractions of the naphthenic crudes. An article entitled The Viscosity-Gravity Constant of Petroleum Lubricating Oils by-J. B. Hill and H. B. Coats, whichwill be found in volume 20, page 641 et seq., Industrial and Engineering Chemistry for June 1928, explains the determination of such constant for several typical oils.

The viscosity-gravity constant is, therefore, an index of the paramnicity or naphthenicity of an oil, since when a given crude is distiiled and fractions thereof are collected, regardless of the fraction upon which the specific gravity and the viscosity are taken, when such specific gravity and viscosity are substituted in the formula and the viscosity-gravity constant of the fraction 02.1011:-

Milltown (Pennsylvania) 0.8067

Burbank (mid-continent) 0.8367 Guadalupe (Gulf Coast) 0.8635 Mirando (Gulf Coast) 1 0.9025

These oils are increasingly parafllnic as the viscosity-gravity constants decrease. My invention is'based upon thediscovery that oils containing both the paraffinic series of hy- .extraction'with furoic esters, for example, with drocarbons and the various naphthenic series may be fractionally extractedwith furoic compounds, particularly with furoic esters. The various series of hydrocarbons: possess a differential solubility in such solvents. The naphthenic hydrocarbons are much 'more soluble therein than a'rethe paraflinic hydrocarbons. By means of such'furoates as propyl furoateor butyl furoate, it'is therefore, possible to effect a partial separation of the naphthenic hydrocarbons from the paraflinic and to obtain from an oil containing both classes of hydrocarbons, an oil which is much more parafiinic than the original oil and one which is much more naphthenic. By my invention, for example, it is possible to produce an 011,01 the quality normally obtained from Appalachian crudes, from crudesfof the mixed base type of the mid-continent area, and conversely, to obtain, frommixed base crudes, oils such as are normally obtained from the naphthenic oils of the Gulf Coast area.

In practicing my invention, I prefer to mix the oil fraction withla suitable proportion of a furoic compound, or mixture of furoic compounds, and more particularly with furoic esters, such as the butyl'or propyl esters, at a temperature suinciently high so that complete solution is effected and a homogeneous liquid obtained. I then cool the mixture to'a temperature sufficiently low to cause a separation-of the liquid into a two-layer system, the upper layer being a solution of a relatively small amount of the furoic compound or compounds in' the more paraffinic portion of the oil and the lower layer comprising a solution of the more naphthe'nic portion of the oil in the furoic compound or compounds.

Instead of this heating and cooling to efiectextraction, I may simply agitate the mixture of liquids at normal temperatures. Where substantial quantities of solid hydrocarbons belonging to the true paraflin series (CnH2n+2) are presout, these solids or waxes remain in the upper layer and'may cause it to be solid or semi-solid. Separation of the two layers is then effected, for

example, by decantation, and the furoic esters 'removed from each of the separated oil layersby vacuum distillation or other suitable procedure, thereby obtaining twooils of similar distillation ranges but of otherwise widely difierent physical characteristics and correspondingly difierent chemical compositions. v Y

Before removing the furoic ester or esters from the upper and more paraflinic layer of oil ob-. tained in the above described process, I may add a further quantity of furoic ester or esters, or mixture thereof with other solvent where the furoic compound is present to substantial extent, and repeat the process for an extraction of additional naphthenic bodies from the oil. The extraction may be repeatedany desired number of times, thereby producing oils of progressively increasing paraflinicity as evidenced by a decreasing viscosity-gravity constant. In wax-bearing oils, the final undissolved product is a mixture of solid and liquid hydrocarbons. While the exact chemical compositions of these compounds are not known, it is probable that the liquid hydrocarbons are branched chain hydrocarbons of the paraffin series, whereas solid bodies are straight chainparaflin hydrocarbons. This product may be further separated into solid and liquid hydrocarbons by any of the well-known dewaxing processes, such as the cold settling process.

In many instances it will be foimd of advantage to dewax the oil ,prior to the extraction process, as this expedites handling the oil during such extraction.

My invention will be furtherillustrated from the following specific examples:

(1) parts of a previously untreated distillate obtained from a Gulf Coast crude oil and having a viscosity of 612 seconds Saybolt Universal at 100 F., a specific gravity of 0.9303, and a consequent viscosity gravity constant of 0.874 was mixed with 300 parts by volume of isopropyl furoate (C4H3OCOOC3H1) and heated to slightly above the temperature of complete miscibility, which in this particular case was approximately 17 C. The homogeneous liquid which resulted was cooled with agitation to 12 C., and allowed to settle, whereupon a two-layer system formed which consisted of an upper undissolved oil layer comprising 57.2 parts of mixture and a lower layer of oil dissolved in isopropyl furoate comprising approximately 342.8 parts of mixture. After separation, the layers were each freed from isopropyl furoate by vacuum distillation. The isopropyl furoate dissolved fraction yielded 285.6 parts of isopropyl furoate and 57.2 parts of oil having a viscosity of 914 seconds Saybolt Uni-- versal at 100 F., a specific gravity of 0.9606, and a viscosity-gravity constant of 0.914. The undissolved fraction yielded 14.4 parts of isopropyl furoate and 42.8 parts of an oil having a viscosity of 358 seconds Saybolt Universal at 100 F., a specific gravity of 0.8933, and a viscosity-gravity constant of 0.833.

(2) 100 parts of residual stock from a paraflln base crude having a viscosity of- 103v seconds Saybolt Universal at 210 F., aspecific gravity of 0.8905, and a consequent viscosity-gravity constant of 0.808 was mixed with 300 parts by volume of n-butyl furoate and heated to slightly above the temperature of complete miscibility, which in this case was-approximately 47 C. The homogeneous liquid which resulted was cooled with agitation to 20 C., and' allowed to settle, whereupon a two-layer system formed, which consisted of an upper undissolved oil layer comprising 81.5

parts of mixture and a lower layer dissolved in' n-butyl furoate comprising approximately 318.5 parts of mixture. After separation, thelayers were each freed from n-butyl furoate by vacuum distillation. The n-butyl furoate dissolved fraction yielded 285.9 parts of n-butyl furoate" and 32.6 parts of oil having an increased viscosity and specific gravity. The undissolved fraction yielded 14.1 parts of n-butyl furoate and 67.4 parts of an oil having a viscosity of 102 seconds Saybolt Universal at 210 F., a specific gravity of 0.8805, and a viscosity-gravity constant of 0.796.

From the above examples it will be seen that by extraction with furoic esters, there may be obtained oil fractions which are respectively higher in parafllnicity and naphthenicity than the origimay be obtained which are increasingly parafllnic, as evidenced by progressively decreasing viscositygravity constants.

It is evident that my process is practically independent oi' the particular nature or source of the crude oil, and'that there may be produced thereby oils of desired characteristics from oils which heretofor'ehave not been used .as a source of oils 01' such desired characteristics.

For example, my process may be employed to produce from petroleum of a mixed base type such as would, on normal batch distillation, give a residuum with a viscosity of 150 seconds Saybolt Universal at 210 F., with a specific gravity of 0.928 or more, a lubricating stock with a viscosity at 210 F. of 150 seconds Saybolt Universal, or more, and a specific gravity not higher than 0.910. This latter combination of properties is typical of cylinder stocks produced from Pennsylvania crudes.

In the extraction at ordinary temperatures of oils with iuroic esters, particularly in extraction of the more naphthenic oils, it is found that-some of the higher molecular weight furoic esters approach complete miscibility with the oil. A furoic ester oi low enough molecular weight must be used to obtain a two layer system with the oil sought to be separated. In general, a naphthenic oil will necessitate a lower ,molecular weight ester than a parafiinic oil. Allwl esters of furoic acid or mixtures thereof having an average molecular weight of the order of or lower than that of n-butyl furoate, viz., a molecular weight of 168. have a substantial selective action on hydrocarbon oils in general, excepting, possibly, some very naphthenic oils. A furoic ester or mixture of furoic esters having an averagemolecular weight of the order of that of ethyl furoate or propyl furoate is, in the case of many hydrocarbon oils, preferred. The very low molecular weight i'uroic esters, for example, methyl furoate, may be found,

in the case of very paraffinic oils, to be too immiscible to produce a substantial separation between the paraflinic and naphthenic components of the oil.

While furoic esters, including those formed by combination of alkyl and those formed by combination of aryl radicalswith the negative iuroic radical, are contemplated as selective solvents for oil, yet, due to the fact that the aryl, i. e., aromatic i'uroates are dimcultly obtainable commercially, the inmates formed with alkyl, 1. e., aliphatic radicals, are, from the point of practical operation, primarily contemplated. However, where aromatic furoates are employed, either alone or in mixture with other aromatic and/or aliphatic furoates, such aromatic i'uroates must be chosen, depending on'the parafinicity or naphthenicity of the oil to be se rated, so that such iuroates or mixture of imcates will be neither too immiscible nor uniformly miscible with components of the oil.

While the miscibility oi such esters with oils may be increased by increasing the. temperature oi the mixture and decreased by decreasing its temperature, yet practicability requires that the oil be not treated at too high a temperature,'or dinarily not at temperatures above 150 to 175 C., or of that order, nor at such low temperatures that the viscosity of the oil becomes great, for example, not below temperatures of the order of 15 C. This temperature range of 15 to 1*?5 Qis oniy exemplary of the genera-i range nai oil. By repetition of the extraction process upon the iuroic ester undissolved traction, oils practical, and I do not intend to hereby confine of temperature which is ordinarily found to be myself to this temperature range. The particular selective solvent and oil and also the presence conditions employed in any selective extraction process are factors which influence the choice of practical temperature conditions.

In extracting oils containing appreciable amounts of wax, such oils may be dewaxed, for example, by cold settling or centrifuging prior to carrying out the extraction. My process is operable, however, in the absence-of preliminary dewaxing.

Hereinabov'e, mixturesot solvents have been referred to. It is to be, understood that insuch mixtures the constituent solvents will not react with one another, nor with the oil upon which they are to be used, and that such mixtures will contain substantial amounts of furoic esters.

For brevity, in the appended claims, the term furoic esters is employed in a generic sense to include one or a mixture of esters of furoic acid, or a mixture of solvents which contains substantial quantities of such esters.

Also, where herein, or in the appended claims,'

an oil is specifically referred to as being viscous", it is to be understood that the oil is of substantial viscosity, i. e., of the order of 50 seconds Saybolt Universal at 100 F'., or more.

What I claim is: 1. In the art of refining mineral oils, the process which comprises separating an oil containing parafiinic and naphthenic hydrocarbons into fractions respectively richer in parafiinic and naphthenic compounds by extracting said oil with a furoic ester.

2. In the art of refining mineral oils, the process which comprises fractionally extracting an oil containing paraflinic and naphthenic hydrocarbons with a furoic ester to produce fractions of the oil respectively richer in parafiinic and naphthenic compounds.

3. In the art of refining mineral oils, the process which comprises adding a furoic ester to an oil containing parafiinic and naphthenic hydrocarbons, heating the mixture to such temperature as to eii'ect solution, cooling the solution to form a. two layer system, and separating the upper layer from the lower layer.

4. In the art of refining mineral oils, the process which comprises adding a furoic ester to an oil containing paramnic and naphthenic hydrocarbons, heating the mixture to such temperature as to efiect solution, cooling the solution to form a two layer system, removing the lower layer, and similarly'retreating the upper layer with a i'uroic ester.

5. In the art of refining mineral oils, the procas which comprises bringing a mineral'oil containing paraffinic and naphthenic hydrocarbons into contact with a furoic ester, thereby to eflect solution of a portion richer in naphthenic hydrocarbons in the furoic ester, separating the solution so formed from the remainder of the oil, and removing the furoic ester from both portions cf the, oil, thereby to obtain fractions of the oil respectively richer in paramnic and naphthenic hydrocarbons.'

6. The process for separating mineral oils containing parafinic and naphthenic hydrocarbons into fractions which comprises bringing the oil into contact with a iuroic ester, thereby to effect tion of 'a portion richer in naphthenic hydrocarbons in the Iuroic ester, separating the solution so formed from the remainder or; the oil, and retreating the oil remaining with amounts of iuroic ester.

8. A method of producing paraflinic lubricating oil from mixed base crude which comprises distilling the crude and bringing a portion thereof additional into contact with a selective solvent containing 1 a substantial proportion of an alkyl ester of furoic. acid, thereby partially dissolving the oil, separat-' ing the iuroic ester solution of oil so treated, and removing the furoic ester from-the treated oil.

9. The process of producing a lubricating stock of specific gravity less than 0.910 and of Saybolt Universal viscosity greater than 150 seconds at 210 F. from a crude petroleum which on normal distillation yields a residuum of 150 seconds viscosity at 210 F., and a specific gravity greater than 0.928, which comprises producing a residuum from the crude petroleum, and extracting said residuum from said crude petroleum with a selective solvent containing at least one alkyl'ester of furoic acid from the group consisting of propyl and butyl furoates.

10. In the art of refining mineral lubricating oil containing naphthenic and paraflinic hydrocarbons, the step of fractionally' extracting the oil with a selective solvent containing at least one alkyl ester of furoic acid from the group consisting ofpropyl and butyl inmates, to eflect a separation; of fractions respectively richer in paraflinic and-naphthenic compounds.

11. The process of producing a lubricating stock of specific gravity less than 0.910 and of a Saybolt Universal viscosity greater than 150 seconds at 210 F. from a crude petroleum which on normal distillation yields a residuum of 150 seconds Saybolt Universal viscosity at 210515. and a specific gravity greater than 0.928, which comprises separating a residuum from said crude petroleum and bringing such residuum into contact witha selective solvent containing a substantial amount of an' 12. In a process for separating a viscous mineral I oil containing paraflinic and naphthenic hydrocarbons into fractions which are respectively richer in naphthenic hydrocarbons and parafilnic iractions respectively richer in 'parafilnic and naphthenic hydrocarbons, the step which comprises extracting the oil with an alkyl ester of furoic acid.

14. In a process for separating a substantially wax free viscous mineral oil containing paraflinic and naphthenic hydrocarbons into fractions respectively richer in parafilnic and naphthenic hydrocarbons, the step which comprises extracting the oil with an alkyl ester of furoic acid.

15., The process of treating a viscous fraction of a'crude oil of one type' containing paraillnic and naphthenic hydrocarbons to procure a fraction having the quality of a corresponding fraction oi a crude oil of diiIerent type having a greater content of parafllnic hydrocarbons, which comprises extracting the viscous fraction with a selec-' tive solvent containing an alkyl ester of iuroic acid.- I I 16.; The'process of treating a viscous fraction of amixed base crude oil to procure a traction having the quality of a corresponding fraction of a paraflinic base crude, which comprises extractting the viscous fraction with a selective solvent containing an alkyl ester of furoic acid, and separating the oilso treated into portions respectively richer in paraflinic and naphthenic compounds.

7 '17. In the art oi-reflning mineral oils, the process which comprises adding to a viscous oil liquid at ordinary temperatures, containing parafiinic and naphthenic hydrocarbons, a selective solvent containing an alkyl ester of furoic acid, heating the mixture to'a temperature sufllcient to eflect solution, cooling the solution to a temperature sufilcient to form two layers respectively richer in naphthenic hydrocarbons and paraflinic hydrocarbons'other than wax, and separating the upper layer richer in paraflinic hydrocarbons from the lower layer richer in naphthenic hydrocarbons.

18. In the art of refining mineral oils, the process which comprises adding to a viscous oil liquid at ordinary temperatures, containing paraflinic and naphthenic hydrocarbons, a selective solvent containing an alkyl ester of i'uroic acid, heating the mixture to a temperature suflicient to effect solution, cooling the solution to a temperature suflicient to form two layers, separating the solvent and paraflin wax from the upper layer, and separating the solvent from the lower layer to produce one fraction richer in parafflnic and a second fraction richer in naphthenic hydrocarbons than said viscous oil.

M. HENDERSON.

CERTIFICATE OF CORRECTION.

Patent NO. 2,050,870. February 18, 1936.

LAWRENCE M. HENDERSON.

It is hereby certified that error appears in the printed specification of theabove numbered patent requiring correction as follows: Page 5, second column, line 4, for "presence" read pressure; and that the said Letters Patent should be read with this correction therein that the same may conform to the. record of the case in the Patent Office.

Signed and sealed this 7th day of April, A, I), 1.936, 7

Leslie Frazer (Seal) Acting Commissioner of Patents.