US2072104A - Hydrocarbon oil treatment - Google Patents

Description

Patented Mar. 2, 1937 UNITED STATES PATENT OFFICE HYDEOCARBON OIL TREATIWENT No Drawing. Application April 1, 1933, Serial No. 664,030

4 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 chemical com- 5 position while of approximately the same distillation range.

In accordance with my invention, crude petroleum or petroleum products, particularly oils of substantial viscosity, are separated into various fractions by means of fractional extraction with an aliphatic chlorhydrin, or a mixture of solvents containing substantial amounts of aliphatic chlorhydrins. Specific examples of such compounds as may be employed in my process are ethylene chlorhydrin, epichlorhydrin and propylene chlorhydrin.

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 parafiins of the general formula CnHZn-l-2, olefins 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 individualcompounds of each series and of difiering boiling points are present in petroleum.

The various types of crude petroleum, which are generally classified into three groups, namely, parafiinic base, naphthenic or asphaltic base, and mixed base, contain the various series of hydrocarbons mentioned heretofore in different pro- 5 portions. For example, in the parafiin base crude oils, such as those obtained from the oil 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 hydrocarbons 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.

The variance in the proportion of the different series of hydrocarbons in paraffinic, naphthenic, and mixed base oils is evidenced by the physical properties of the various oils and particularly by the relationship of the specific 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., of about 0.878, whereas an oil of corresponding viscosity produced from a naphthenic I 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 grav- 5 ity indicates the degree of paraflinicity or naphthenicity of the oil, and such relationship may be expressed by the viscosity-gravity constant as hereinafter described.

If a given crude petroleum be distilled into ,10 successive fractions and the specific gravities and viscosities of the several viscous fractions be determined, it will be found that they conform to the general relationship expressed by the formulae- 15 G=0.24+0.'755a+0.022 log (V'35.5) in, which G is the specific gravity at 60 F., V and V' are respectively Saybolt universal viscosities at F. and 210 F., and a is a constant known as the viscosity-gravity constant. Viscous fractions from each of the different types of crude have difierent viscosity-gravity constants. While, $725 in, general, viscous fractions from a single crude have substantially the same viscosity-gravity constant, such constant is lower for fractions of the parafiinic crudes than is the constant 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, which will be found in volume 20, page 641 et seq., Industrial and Engineering Chemistry for June, 1928, explains the determination of such constant 3 for several typical oils.

The viscosity-gravity constant is, therefore, an index of the paraffinicity or naphthenicity of viscous oils, since when a given crude is distilled, the fractions thereof collected, and the specific gravity and the viscosity of each of the viscous fractions .50 Milltown (Pennsylvania) 0.8067' Burbank (Mid-Continent) 0.8367 Guadalupe (Gulf Coast) 0.8635 Mirando (Gulf Coast); 0.9025

While the above figures indicate the viscosity- ,55

um into a two-layer system will take place.

gravity constants of specific oils from several types of crudes, it is to be understood that for any particular type of crude such constant may be within a range between values above and below the constant of the typical crude given. For example, viscous oils resulting from the distillation of Mid-Continent crudes have viscositygravity constants ranging from about 0.835 to about .855, whereas the viscous fractions resulting from the distillation of Pennsylvania type crudes range from about .805 to about .828, and in most instances, are below .820. Oils are increasingly paraffinic as their viscosity-gravity constants decrease.

My invention is based upon the discovery that oils containing both the paraffinic series of hydrocarbons and the various naphthenic series may be fractionally extracted with an aliphatic chlorhydrin. The various series of hydrocarbons possess a differential solubility in such solvent,

the naphthenic hydrocarbons being much more soluble therein than the paraflinic hydrocarbons. By means of extraction with such solvent, 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, anoilwhich is much more paraffinic than the original oil and one which is much more naphthenic. By my invention, for example, it is possible to produce an oil of the quality normally obtained from Appalachian crudes, from crudes of the mixed base type from the Mid-Continent area, and, conversely, to obtain oils from mixed base crudes such as are normally obtained from the naphthenic oils of the Gulf Coast area. In general, from oils fror'n'any source there may be obtained by my process, oils which are respectively more paraffinic and more naphthenic than the oils normally obtained from such source by distillation.

In accordance with my invention, Ifirst mix the oil to be treated with a suitable proportion of an aliphatic chlorhydrin at a temperature such that complete solution is effected and a homogeneous liquid obtained. I then cool the mixture to a temperature at which separation of the liq- The upper layer will contain a relatively small amount of the solvent dissolved in the parafiinic portion of the oil while the lower layer will contain the more naphthenic portion of the oil dissolved in the solvent. Or, I may agitate the mixture of solvent and oil at temperatures at which the liquids are only partially miscible, andthereby effect solution of the naphthenic portion of the oil in the solvent. In either of the above procedures I may take advantage of the principles of countercurrent extraction. a

After the extraction proper, I efiect 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, the portion or" solvent which each contains by suitable procedure, such as by vacuum distillation, thereby to obtain two oils of similar distillation ranges but of difierent chemical compositions and different physical characteristics.

Before removing the solvent from the upper and more parafiinic layer, I may add a further quantity of solvent and repeat the extraction, thereby to remove additional naphthenic constituents from said layer. The extraction step may be repeated any desired number of times, each repetition producing an oil of higher paraflinicity as evidenced by its lower viscosity-gravity constant.

Where substantial quantities of waxy hydrocarbons belonging to the true paraffin series (CnHZn-l-2) are present, such hydrocarbons remain in the upper or more paraffinic layer and may cause such layer to be solid or semi-solid. Such layer may be separated into solid liquid hydrocarbons by any of the well-known dewaxing processes such as by cold-settling or by centrifuging. In many instances it may be advantageous to dewax the oil prior to extraction. However, it is to be understood that in accordance with my invention, dewaxing may be effected either prior or subsequent to extraction.

My invention will be further understood from the following specific examples:

parts of a Mid-Continent distillate having a viscosity of'305 seconds Saybolt universal at 100 F., a specific gravity of 0.909 at 60 F., and a viscosity-gravity constant of 0.853 was mixed with 500 parts of ethylene chlorhydrin and heated to slightly above thetemperature of complete miscibility. The homogeneous liquid which resulted was cooled with agitation to 100 C.', and allowed to settle, whereupon a two-layer system formed. After separation, the layers were each freed of solvent by vacuum distillation. The undissolved oil fraction comprising 67.7% of the stock had a viscosity of 198 seconds Saybolt universal at 100 F., a specific'gravity of 0.883, and a viscosity-gravity constant of 0.828. The dissolved oil fraction comprising 32.3% of the stock had a viscosity of 686 seconds Saybolt universal at 100 F., a specific gravity or" 0.947 and a viscosity-gravity constant of 0.898. V

100 parts of the same Mid-Continent distillate having a viscosity of 305 seconds Saybolt universal at 100 F., a specific gravity of 0.909 at 60? F.,

and a viscosity-gravity constant of 0.853, was extracted in the above described manner with 300 parts of epichlorhydrin. The resulting undissolved oil fraction comprising 60.0% of the stock had a viscosity of 218 seconds Saybolt universal at 100 F., a specific gravity of 0.881 and a viscosity-gravity constant of 0.825, while the dissolved oil fraction comprising 40.0% of the stock had a viscosity of 572 secondsSaybolt universal at 100 F., a specific gravity of 0.947 and a viscosity-gr'avity constant of 0.900.

From the above examples it will be noted that hydrin, there may be obtained oil fractions which are respectively more paraifinic and more naphthenic than the original oil. By repetition of the extraction process upon the undissolved fraction,

oils of even greater parafilnicity will result.

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 characteristics from oils which by distillation will not produce such products.

Hereinabove, mixtures of solvents have been referred to. It is to be understood that in such mixtures the constituents 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 an aliphatic chlorhydrin.

For brevity, herein and in the appended claims aliphatic chlorhydrin is employed in a generic sense to include one or a mixtureof aliphatic chlorhydrins. or a mixture of solvents containing substantial amounts of aliphatic chlorhydrins.

Also, when herein and in the appended claims,

oil is specifically referred to as being viscous, it.

is to be understood that the oil is of substantial by extraction of an oil with an aliphatic chlor 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 5 which comprises bringing an aliphatic chlorhydrin into intimate contact with a viscous hydrocarbon oil of a quality other than that of a Pennsylvania type viscous oil, and containing paraffinic and naphthenic components, thereby to dissolve from the oil substantial amounts of its naphthenic components, thereafter removing the solvent and oil dissolved therein from that portion of the oil which remains undissolved, thereby to produce an oil such as is normally obtained from Pennsylvania type crude by distillation.

2. The process of treating a viscous mineral oil of viscosity-gravity constant between substantially 0.850 and 0.875 to reduce the viscosity-gravity constant by at least 0.015, which comprises i'ractionally extracting said viscous oil with an allphatic chlorhydrin.

3. The process of treating a viscous mineral oil of viscosity-gravity constant higher than 0.850 to produce an oil having a viscosity-gravity constant less than 0.830 which comprises fractionally extracting said viscous oil with an aliphatic chlorhydrin.

4. The process of treating a viscous mineral oil of viscosity-gravity constant higher than 0.835 to produce an oil having a viscosity-gravity constant of less than 0.828 which comprises fractionally extracting said viscous oil with an aliphatic chlorhydrin.

SEYMOUR W. FERRIS.