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Patented May 3, 1938 2,115,704 UNITED STATES PATENT oFFIcE 2,115,704 _ TREATMENT OF HYDROGARBON OILS ‘Eugene R. Browns'combe, Aidan, Pa., assignor to The Atlantic Re?ning Company, Philadelphia, * Pa., a corporation of Pennsylvania No Drawing. Application April 25, 1925, Serial No. 18,261 4 Claims. (Cl. 196-13) ‘The present‘ invention relates to the art of min— eral oil re?ning, and has particular reference to the separation of crude petroleum or petroleum gree of paraf?nicity or naphthenicity of an oil are the viscosity-gravity constant and the vis— cosity index. The viscosity-gravity constant is a products into fractions of different chemical com position while of approximately“ the‘same distil and is described in an article entitled “The vis- 5 lation range. ‘ ‘ cosity-gravity constant of petroleum lubricating ‘ In accordance with my invention, crude petro leum or'petroleum products, particularly oils of substantial viscosity, are separated into various 10 fractions by extraction with a mixture of solvents, and more particularly with selective solvents such as ‘nitrobenzene, nitrotoluene, benzaldehyde, di chloro ethyl ether, cresylic acid and furfural, to which has been added an organic acid anhydride ll such as, for example, acetic, succinic, maleic, phthalic anhydrides, and the homologues‘there of. ‘ constant relating viscosity and speci?c gravity , ‘It is recognized in the art that mineral oils, such as petroleum, comprise essentially a mixture 26 of hydrocarbons of various groups’ or homologous series of compounds, such for example, as paraf ?ns of‘ the'general formula CnH2n-I-2, olefines of the general formula CnHZn, hydroaromatics and polymethylenes of the same empirical formula, 25 and ‘various other series of compounds of chain oils” by J. B. Hill and H. B. Coates which will be found in vol. 20, page 641 et seq., of Industrial and Engineering Chemistry. Viscous oils result ing from the distillation of Pennsylvania type 10 crudes have viscosity-gravity constants ranging from about .805 to about .828 and in most in stances are below .820. Those resulting from the distillation of Mid-Continent crudes have viscos ity-gravity constants ranging from about .835 15 to about .855, whereas those from naphthenic crudes are generally higher than .860. The vis cosity index is a. coef?cient based on the change of viscosity with temperature and is described by ‘Dean and Davis in vol. 36, page 618 of Chemical 20 and Metallurgical Engineering. The more paraf ?nic oils are characterized by low viscosity-grew ity constants and high viscosity indices, whereas the more naphthenic oils are characterized by higher viscosity-gravity constants and lower vis- 25 and/or ring structures in which the hydrogen to cosity indices. carbon ratio is less than in the foregoing series. A large number of individual compounds of each My invention is based upon the discovery that oils containing both the para?inic series of hy drocarbons and the various naphthenic series series and of differing boiling points are present ‘ 30 in‘ petroleum. The various types of crude petroleum, which are generally classi?ed into three groups, namely, paraf?nicbase, naphthenic or asphaltic base, and mixed base,'contain the Various‘series of hydro ' may be fractionally extracted with a selective sol- 30 vent in admixture with an organic acid anhydride. The various series of hydrocarbons possess a dif ferential solubility in such solvent mixture, the naphethenic hydrocarbons being much more sol 35 carbons mentioned heretofore in different propor- ‘ uble therein than the paraf?nic hydrocarbons. By 35 tions. For example, in the‘para?inic base crude oils, such as those obtained ‘from the oil ?elds of Pennsylvania, there is a relatively high propor tion of hydrocarbons having a chain structure 40 means of extraction with such solvent mixture, it is therefore possible to effect a partial separa~ tion of the naphthenic hydrocarbons from the and a high hydrogen to ‘carbon ratio,v whereas in the, naphthenic or asphaltic base crude oils, para?inic, and to obtain from an oil containing both classes of hydrocarbons, an oil which is much more para?inic than the original oil and there is a relatively large proportion of hydrocar~ bons having ring structures and a low hydrogen one which is much more naphthetic. By my in vention, for example, it is possible to produce an to carbon‘ ratio. Mixed base crude oils, such as are obtained from the Mid-Continent oil ?elds, contain hydrocarbons in proportions intermediate between these two extremes. ‘ The paraflin base‘ oils and their distillates are said to be more para?inic than the mixed base 50 oils and their distillates and these in turn are more paraf?nic than the naphthene base oils and their distillates. Conversely the naphthene base oils ‘are more naphthenic‘ than the mixed base oils and these in turn more naphthenic than the‘ 55. paraffin base oils. ‘The usual criteria of the de oil of the quality normally obtained from Appa lachian crudes, from crudes of the mixed base 45 type from the Mid-Continent area or from those of the naphthenic base type and, conversely, to obtain oils from mixed base crudes or paraf?nic base crudes such as are normally obtained from the naphthenic oils of the Gulf coast area. In 50 general, from oils from any source there may be obtained by my process, oils which are respec tively more para?inic and more naphthenic than the oils normally obtained from such source by distillation. _ 55 2 2,115,704 It has been known heretofore to separate hy solvent, e. g., nitrobenzene, a suitable quantity of an organic acid anhydride, for example 5% or 10% of maleic anhydride, I am able to treat in a satisfactory manner, even the very asphaltic drocarbon oils into fractions by means of solvents such as sulfur dioxide, iurfural, and others. Such separation is accomplished by agitating the oil California oils. with the solvent and bringing the mixture to such a temperature, below the temperature of com In accordance with my invention, I ?rst mix the oil to be treated with a suitable-proportion of a mixture of a selective solvent and an organic acid plete miscibility of the oil and solvent, that the mixture separates into two layers, one of which is the undissolved and more para?inic portion of anhydride at a temperature such that complete solution is effected and a homogeneous liquid ob 10 tained. I then cool the solution to a temperature at which separation of the liquid into a two-layer 10 the oil containing some dissolved solvent and the other of which is solvent containing dissolved naphthenic constituents of the oil. These two layers are separated at this “separation tempera ture” and the solvent may subsequently be re 15 moved from each. I have found it highly advan tageous to eifect such separation by employing a system will take place. One layer will contain a relatively small amount of the solvent mixture dissolved in the paraf?nic portion of the oil, while the other layer Will contain the more naph thenic portion of the oil dissolved in the major quantity of the solvent mixture. Or, I may agitate the mixture of solvent and organic acid anhydride with the oil at temperatures at which mixture of a selective solvent and an organic acid anhydride. In particular‘, the aromatic nitro solvents, for example, nitrobenzene, are highly 20 selective but usually require a separation tem perature below, for example, 60° F., due to their relatively low miscibility temperature with the hydrocarbon oils. The separation temperatures employed are, in general, about 45° F. below the 25 miscibility temperature of the oil and solvent. the liquids are-only partially miscible, and thereby effect solution of the naphthenic portion of the oil in the solvent mixture. . In either of the above procedures I may take advantage of the prin ciples of countercurrent extraction. After the extraction proper, I effect separation of the two layers which form, by any suitable procedure, as for example, by decantation. I then remove from each of the separated layers, By employing a suitable mixture of a selective solvent and an organic acid anhydride, I am able to separate hydrocarbon oils into fractions at temperatures considerably above those which the portion of the solvent mixture which each . 30 could be employed with the selective solvent alone. For example, 100 parts by volume, of a medium viscosity lubricating oil distillate from Winkler (W. Texas) crude oil was mixed with 200 parts, contains, by suitable procedure, such as by vac uum distillation, thereby to obtain two oils of simi lar distillation ranges but of different chemical by volume, of nitrobenzene, and the miscibility composition and different physical characteristics. 35 temperature was found to be 79° F. In general, this would indicate that the extraction should be Before removing the solvent mixture from the _ undissolved or more paramnic layer, I may add a further quantity of the solvent mixture and re peat the extraction, thereby to remove additional carried out at temperatures not higher than about 35° F. When 109 parts of the same oil were ad naphthenic constituents from said layer. mixed with 200 parts of a solvent composed of of maleic anhydride, the miscibility temperature was found to be 104° F., indicating that an ex traction could be carried out satisfactorily at a temperature of the order of 60° F. When 100 45 parts, by volume, of the same oil were mixed with cosity-gravity constant. A countercurrent relationship in these succes sive extractions may be established in the conven tional manner by employing the partially spent solvent mixture containing dissolved naphthenic 200 parts, by volume, of solvent composed of 90% by volume of nitrobenzene and 10% by volume of maleic anhydride, the miscibility tem oil from the succeeding stages of the extraction system to extract additional quantities of oil in the preceding stages. In the event that the miscibility temperature of the oil with the se lective solvent in the latter stages of the system perature was found to be 129° R, which would 50 permit of extraction at temperatures as high as about 85° F. It will be understood, of course, that the quality of the undissolved or more par is sufficiently high, the organic acid anhydride a?inic oil fraction produced by means of the solvent mixture will frequently be somewhat lower than that of a similar fraction produced with nitrobenzene alone. In general, greater yields are obtained and higher operating temperatures may be introduced at any desired preceding stage, in order to lessen or eliminate the refrigeration required in the earlier stages. Where substantial quantities of waxy hydro carbons belonging to the true para?in series may be employed when a mixture of a selective (CnH2n+2) are present, such hydrocarbons re main in the undissolved or more para?inic layer 60 and may cause such layer to be solid or semi solid, after the removal of the solvent mixture therefrom. In some cases, the extraction and separation of the layers may be effected at tem solvent and an organic acid anhydride is utilized. 60 In any event, an economic balance must be struck between the yield and quality of the re ?ned oil, and the cost of producing the same. Furthermore, in accordance with my invention, I am able to separate hydrocarbon oils into frac 65 tions with my solvent mixture, which oils could not be economically treated with a selective solvent alone. For example, it is not practical to employ a solvent, such as nitrobenzene, in treat ing very asphaltic oil stocks such as those derived 70 from some California crude oils, for the reason that the miscibility temperature of the oil and solvent is very low, excessive refrigeration is re quired, and in certain cases the nitrobenzene may crystallize before separation of fractions can be effected. However, by adding to the selective The extraction step may be repeated any desired num 40 ber of times, each repetition producing an oil of higher para?inicity as evidenced by its lower vis 40 95% by volume of nitrobenzene and 5% by volume pertures above the melting point of the waxy hydrocarbons, so that substantial entrainment of oil in the molten or liquid wax is avoided. Such layer may be separated into solid and liquid hydrocarbons by any of the well-known dewax ing processes, such as by cold-settling, ?ltering, 70 or by centrifuging. In many instances, it may be advantageous to dewax the oil prior to ex traction. However, it is ‘to be understood that in accordance with my invention, dewaxing may be effected either prior or subsequent to extrac . tion. 2,115,704 My invention will be further understood from the following speci?c examples: I. 100 parts by volume of‘ a residuum from at Gulf Coast crude oil having a viscosity of 518 ,1 seconds Saybolt universal at 210° F., a speci?c gravity of 0.9759 at 60° FL, and a viscosity-gravity constant of 0.894 were mixed with 200 parts by volume of a solvent consisting of 90% by volume of nitrobenzene and 10% by volume of acetic 105 anhydride, and heated to slightly above the tem perature of complete miscibility, i. e., about 115° F. The homogeneous liquid which resulted was cooled, with agitation, to about 68° F,, and al lowed to settle, whereupon a two-layer“ system 16 was formed. After separation, the layers were each freed of solvent by vacuum distillation. The resulting undissolved oil fraction comprising 40.3% of the stock had a viscosity of 221 seconds Saybolt universal at 210° F., a speci?c gravity 20 of 0.9212, and a viscosity-gravity constant of 0.836. The initial Gulf Coast residuum had a miscibility temperature of 91° F., with nitroben zene alone, and would have required extraction at temperatures below 46° F., to effect a satis 25 factory separation of oil fractions. II. 100 parts by volume of a Barber’s Hill lubri cating oil distillate having a viscosity of 110 sec onds Saybolt universal at 210° F., a speci?c grav ity of 0.926 at 60° F., and a viscosity-gravity con 30 stant of 0.854, were mixed with 200 parts by vol ume of a solvent consisting of 90% by weight of nitrobenzene and 10% by weight of phthalic anhydride, and heated to slightly above the tem perature of complete miscibility, i. e., about 144° 35 F. The homogeneous liquid which resulted was cooled, with agitation, to about 95° F., and al lowed to settle, whereupon a two-layer system formed. After separation, the layers were each freed of solvent by vacuum distillation. The re sulting undissolved fraction comprising 56.0% of the stock had a viscosity of 91 seconds Say bolt universal at 210° F., a speci?c gravity of 0.9013, and a viscosity-gravity constant of 0.825. The initial lubricating oil distillate had a mis cibility temperature of 110° F., with nitrobenzene alone, and would have required extraction at temperatures below 65° F., to effect a satisfactory separation of oil fractions. 3, re?ned oil fraction had a viscosity of 84 seconds Saybolt universal at 210° F., a speci?c gravity of 0.8911, and a viscosity-gravity constant of 0.813. The initial lubricating oil stock had a‘ miscibility temperature of 110° F., with nitro benzene alone, and would have required extrac tion at temperatures below 65° F., to effect a satisfactory separation of the oil into fractions. From the above examples it will be noted that by extraction of an oil with a solvent mixture 10 comprising a selective solvent, such as nitroben zene, and an organic acid anhydride, there may be obtained‘oil fractions which are respectively more paraifinic and more naphthenic than the original oil. By repetition of the extraction proc ess upon the undissolved fraction, oils of even greater paraffinicity will result. The quantity of 1 organic acid anhydride to be employed in con junction with the selective solvent will vary, depending upon the character of the selective solvent, the temperature at which the extraction is to be carried out, and the quality of re?ned oil desired. In general, the quantity of organic acid anhydride employed will be of the order of from about 5% to about 10% of the selective 25 solvent. However, more or less of the organic acid anhydride may be employed, depending upon the temperature at which the extraction is to be carried out. While, in the above examples, I have shown 30 the use of a selective solvent such as nitrobenzene in admixture with various organic acid anhy drides, I do not intend to limit myself thereto, but may employ various selective solvents in con junction with the organic acid anhydrides. The 35 following table illustrates the effect upon the mis cibility temperature of oil with various selective solvents to which have been added small quan tities of an organic acid anhydride. The mis cibility temperatures were determined by heating 40 1 volume of lubricating oil stock with 2 volumes of selective solvent or solvent mixture, to a tem~ perature such that complete solution of oil and solvent was obtained, and thereafter cooling the 45 solution until the formation of a haze was noted, thus indicating the separation of two liquid phases. Selective solvent, percent by Acid anhydride, percent by volume volume Misci- ‘38511133’ mm increase °F. 55 77 60 90 Bcnzaldehyde ___________ __ D0 __________________ ~_ “B, 8 °F. 110 174 0 __________________ __ M-i-Sci' bility tempera ________ _ .. 64 ________ _ _ 147 70 100 103 ........ ._ 90 165 62 BB’ diChlOl'O ethyl ether“ 100 143 ________ __ D __________________ __ 197 54 293 ________ _. 313 25 163 225 ________ _. 62 90 Furt'ural - __ DO ________ _ .. Cresylic acid. . Do __________________ _ . III. The same Barber’s Hill lubricating oil dis tillate as shown in Example II was continuously extracted in a 3—stage countercurrent system with 200% by volume of a solvent comprising 90% by volume of nitrobenzene and 10% by volume of maleic anhydride, at a temperature of about 131° F., or about 43° below the temperature of miscibility, i. e., 174° F. The resulting undis solved oil fraction, after removal of solvent by vacuum distillation, comprised 45.2% of the oil 75 stock charged to the extraction system. This Maleic anhydride ..... ._ 10 (i i) My process is practically independent of the particular nature or source of the crude oil or oil fraction to be extracted. There may be produced by my process oil products of desired character istics from oil which by distillation will not pro duce such products. Moreover, it will be under 70 stood, that in accordance with my invention, an important aspect thereof is the increase of the miscibility temperature of the oil and naphthenic solvent by reason of the presence of the organic acid anhydride, regardless of any selective sol 75 4 2,115,704 vent action the anhydride itself may have upon the oil. When, in the appended claims, oil is referred to as being “viscous”, it is to be understood that 1 the oil is of substantial viscosity, i. e., of the order of 50 seconds Sayboit universal at 100° F., or more. What I claim is: 1. In the process of decreasing the viscosity gravity constant of a viscous mineral oil, the step substantially increase the miscibility temperature of said nitrobenzene with said oil. 3. In the process of decreasing the viscosity gravity constant of a viscous mineral oil, the step of extracting the oil with nitrobenzene containing acetic anhydride in suf?cient quantity to substan tially increase the miscibility temperature of said nitrobenzene with said oil. 4. In the process of decreasing the viscosity gravity constant of a viscous mineral oil, the step 10’ of extracting the oil with nitrobenzene containing of extracting the oil with nitrobenzene contain maleic anhydride in suf?cient quantity to sub ing an organic acid anhydride from the group stantially increase the miscibility temperature of consisting of acetic anhydride, maleic anhydride, and phthalic anhydride, said anhydride being said nitrobenzene with said oil. 2. In the process of decreasing the viscosity gravity constant of a'viscous mineral oil, the step of extracting the oil with nitrobenzene contain ing phthalio anhydride in sui?cient quantity to present in suf?cient quantity to substantially in— 151 crease the miscibility temperature of said nitro benzene with said oil. EUGENE R. BROWNSCOMBE.