US2261866A - Refining hydrocarbon distillates - Google Patents

Description

Patented Nov. 4, 1941 2,261,866 7 REFINING HYDROCARBON DISTILLATES, Meyer S. Agruss and George W. Ayers, Jr., Chicago, Ill., assignors to Chicago, 111., a corpora The Pure Oil Company, tion of Ohio No Drawing. Application October 2, 1939, Serial No. 297,436

Claims.

This invention relates to a process of refining hydrocarbon oil and especially light petroleum distillates such as gasoline, kerosene and furnace oils. More particularly, the invention relates to a process by which reduction of the sulfur content may be effected; or by means of which separation of distillate into fractions differing as to octane rating, solvency or other characteristics may be effected; or by means of which the two may be simultaneously effected.

It is well known that mineral oils such as petroleum oil comprise essentially a mixture of various groups or homologous series of compounds such, for example, as paraffins, olefins, aromatics, hydro-aromatics, polymethylenes and other series of compounds of chain and/or ring structure, in which the hydrogen to carbon ratio is less than in the aforementioned series. Crude petroleum oils are generally classified into three types, namely, parafinic, naphthenic and mixed base which contain the various series of hydrocarbons mentioned heretofore in varying proportions.

It is also well known that most light mineral oil distillates such as gasoline, kerosene and furnace oils, contain undesirable sulfur compounds which render them corrosive and of disagreeable odor as well as adversely affecting other properties such as knock rating, and which therefore detract from their market value. tion of these sulfur compounds are mercaptans or thio alcohols and it is generally agreed that they are the principal cause of most of theunpleasant odor associated with unrefined distillates. The method most generally used to convert such compounds to innocuous substances is the well known sodium plumbite treatment.

It is an object of this invention to reduce the sulfur content of light hydrocarbon distillates.

It is a further object of this invention to improve the odor of light hydrocarbon distillates.

Another object of this invention is to separate light mineral oil into fractions differing as to octane rating, solvency or other characteristics.

It is another object of this invention to provide a method for separating light mineral oils into fractions by means of solvents simultaneously with a reduction in sulfur content.

A still further object is to provide a method whereby with a single operation mercaptanbearing light mineral oil may be separated into fractions that are respectively more paraifinic and less paraflinic than the original oil, and the mercaptan content-of both fractions substantially reduced.

At least a por- Other objects and advantages will be apparent from the following detailed description.

It has been found that oils containing both paraflinic and various naphthenic and other types of hydrocarbons may be fractionally extracted or treated with a selective'solvent such as morpholine and derivatives thereof, suchas those derivatives in which one or more hydrogen atoms in the morpholine molecule are substituted by alkyl groups. As examples of such derivatives may be mentioned ethyl tetrahydro-' paroxazine, l-methyl tetrahydroparox-azine and l-butyl tetrahydroparoxazine. The various series of hydrocarbons possess a different solubility in such solvents, the non-parafiinic hydrocarbons being much more soluble therein than the parafiinic hydrocarbons. When mineral oil containing various series of hydrocarbons is extracted with a solvent of the class above set forth, it is possible to effect at least a partial separation of the parafiinic from the non-paraffinic hydrocarbons and to obtain a fraction which is more paraffinic than the original .oil and one which is less paraffinic. For example, from an oil of the mixed base type such as is frequently found in the Mid-Continent area, it is possible to produce an oil of a more paraffinic type such as is generally found in the Pennsylvania oil fields. source, it is possible to obtain by our process oils which are respectively more parafiinic and less parafiinic than the oils normally obtained from such source by distillation. At the same time both the fraction which is respectively more parafiinic and the fraction which is respectively less paralfim'c than the original oil may be simultaneously rendered sweet to the doctor test.

' Generally speaking, when oil such as light petroleum distillate is to be treated with solvents such as those herein described, the solvent and oil are mixed at a temperature at which substantially complete miscibility is effected. When the temperature of the mixture is reduced, a separation into a two-layer system occurs, one layer containing a relatively small amount of the solvent dissolved in the more parafiinic portion of the oil. This is called the raffinate. The other layer contains the less paraffinic portion of the oil dissolved in a major quantity of the solvent. This is called the extract. This procedure may be conducted batchwise or continuously. Furthermore, such is the nature of the treating reagents contemplated by this invention that by means of a single reagent sulfur compounds such as mercaptans are removed and However, regardless of the plished, the two layers formed as a result of the extraction operation are, of course, separated prior to the removal of solvent. Where the purpose of the treatment is to desulfurize only, sep-' aration of the fractions prior to removal of the solvent is not necessary. This separationmay be accomplished by any suitable procedure, for example, by decantation. The extraction of either rafilnate or extract may be repeated any number of times. Each successive extraction of the extract produces an extract of higher aromaticity and of lower sulfur content, as may be evidenced by analyses of the oil for sulfur and aromatic hydrocarbon content. Each successive extraction of the raffinate also reduces the sulfur content and increases the paraffinicity thereof. Solvent separated from the raflinate and from the extract may be treated to separate sulfur compound from the solvent and to restore the solvent to a condition suitable for further extraction operations. Separation of the sulfur compound, water and solvent may be accomplished by a number of methods but is preferably efiected by distillation. When such a mixture comprising morpholine or morpholine derivatives, mercaptans and water is subjected to ordinary distillation, the mercaptan-morpholine reaction product decomposes into mercaptans and morpholine, the mercaptans distilling overhead together with water, leaving a residue of morpholine. Since the mercaptans are substantially insoluble in water, they may be separated from i r the distilled water by simple decantation. The invention will be more clearly understood from the following specific examples:

Table I were obtained by extracting 100 parts by volume of cracked gasoline obtained from Gulf Coast crude with 100 parts by volume of commercial morpholine. The gasoline and morpholine were mixed at room temperature (approximately 70 F.) at which temperature they were completely miscible, and. then cooled to 12 F. whereupon a two-layer system was formed. The two layers were separated by decantation. The rafiinate, without. any separation of solvent, was re-extracted with 100 parts by volume of morpholine and the fractions again separated. The solvent was removed from both the raifinate and extract by washing with water, approximately 40% by volume of water, based on the volume of morpholine pres- The results shown in ent, being required to cause the morpholine to be substantially completely insoluble in the gasoline. 18 parts of finished extract were obtained from the first extraction step and 60 parts of finished extract from the second extraction step. 20 parts of finished rafiinate were obtained.

Table II Mercap- Unsatu- A.S.T.M. Sample tan rates and octane sulfur aromatics number Percent Percent Original gasolnie 0. 025 Positive... 10. 7 63. 5 Raifinate 0. 0007 Negative. 7. 4 58. 3 Extract 0. 0009 N egatwe. 25. 4 66. 0

The results given in Table II were obtained by line obtained from Van-Schuler crude oil with 300 parts by volume of commercial morpholine. Extraction of the extract was repeated five additional times using three volumes of morpholine to each volume of extract in each extraction. The gasoline and morpholine were mixed at room temperature and then cooled to 12 F. and a twolayer system formed. As in the previous example, the morpholine was removed from the separated phases by the addition of water. 83 parts of raftinate and 16 parts of extract were obtained. Reference to Tables I and 11 clearly shows the reduction in mercaptan sulfur content and concentration of unsaturates and aromatics effected by the treatment with morpholine. The octane rating of the extract was appreciably higher than that of the original gasoline. After separation of the solvent from the rafiinate and extract by the addition of water, the water solution of the mercaptan-morpholine reaction product was distilled, the mercaptans and water being recovered overhead as separate layers of condensate and morpholine containing a small amount of water obtained as a bottom product. The bottoms are suitable without further treatment, for subsequent extraction of distillate, or if it is desired to obtain the morpholine in a more pure state, the morpholine may be precipitated from the small amount of water present by addition of suitable reagents, such as by the addition of carbon dioxide, the morpholine precipitating as morpholine carbamate. After filtration the precipitate is readily decomposed to morpholine and carbon dioxide at approximately F. and the morpholine recovered in a substantially pure .state. The temperature at which the treatment is most advantageously carried out, the quantity of treating agent used and the method of separating the solvent from the oil may vary considerably depending upon the stock being treated and the equipment available with which to carry out the process as well as the characteristics desired in the final product. In general, the ratio of solvent to oil will range from 1 to 10 parts of solvent by volume to 1 part of oil and the temperature of mixing from room temperature to 200 F. The temperature of separation of the solvent and distillate into two distinct phases will vary over a wide range depending upon the distillate treated and upon whether or not water or other substances are used as anti-solvents, but temperatures between 0 to 32 F. have been found satisfactory.

While the foregoing example shows the use of morpholine as a selective treating agent for hydrocarbon distillate, derivatives of morpholineparticularly those in which the hydrogen is replaced by an alkyl group-may also be suitably employed either alone or mixed with each other or with morpholine or with other known solvents. Although the process is applicable to petroleum distillates of all types, it is obviously of most advantage as applied to those distillates that contain appreciable quantities of sulfur compounds such as mercaptans, carbon disulfide and possibly others which will be removed by the solvent at the same time that solvent fractionation is effected.

The process is especially useful in providing, from a single treating operation, distillates having several particularly desirable characteristics. For example, that portion of a crude oil boiling up to approximately 600 F. may be separated from the crude oil by fractionation in a conventional manner and subjected to treatment with morpholine, whereby a rafiinate of relatively high paraflinic character and an extract of relatively high non-parafiinic character may be produced. After separation of the solvent from the raifinate, the rafiinate may be fractionally distilled to produce a highly paraffinic low sulfur, doctor sweet extraction naphtha such as is required in the rosin industry or a reforming naphtha, of approximately 320 F. end point, a high-grade kerosene of approximately 320 F. to 500 F. boiling range and a high-grade Diesel fuel of-approximately 350 F. to 600 F. boiling range. In each case the highly paraflinic nature, low sulfur and greatly improved odor permits more effective and profitable utilization of the products produced. Similarly, the extract, after separation of the solvent, may be fractionated into solvent naphtha of, for example, about 400 F. end point, having a high Kauri-butanol value, low sulfur and of good odor. Such naphthas command a distinct premium in the paint and varnish industry. The remaining extract, boiling over about 400 F. may be fractionated into portions particularly suitable in some horticultural spray compositions or the entire portion boiling over 400 F. may be utilized as high quality cracking stock. Many advantageous variations of the foregoing procedure will be obvious to those skilled in the ar The foregoing discussion has been limited to treating operations in which the paraflinic and non-parafiinic constituents were separated simultaneously with a doctor sweetening and desulfurizing operation. It has been found, however,

that with but a slight modification of the aforementioned procedure, desulfurizing and doctor sweetening maybe accomplished with little or no solvent fractionation effect. This may be accomplished by adding to morpholine or a derivative of morpholine, sufficient water to cause the resulting solution to have substantially no solvent fractionation effect and to be only slightly soluble or insoluble in the hydrocarbon distillate. The greater the proportion of water or other anti-solvent used, the lower becomes the solubility of the water-morpholine mixture in a given hydrocarbon'distillate, but at the same time the ease with which the morpholine removes sulfur compounds from hydrocarbon distillate diminishes. For example, morpholine containing 40% of water was found to be substantially completely insoluble in a sample of cracked gasoline and when 3.86 parts of the Water-morpholine reagent were contacted at room temperature with 1 part of the gasoline eight successive times, the mercaptan content of the gasoline was reduced from 0.0294% to 0.0109% and complete separation of gasoline and treating reagent readily occurred.

It is apparentthat by increasing the amount of spent treating reagent may be recovered for furmg operations and other variables.

ther use by various methods, as for example, by heating to a sufficient temperature to cause decomposition of the mercaptan-morpholine reaction product, followed by separation of the mercaptans by fractional distillation. Instead of treating with morpholine containing a, substantial quantity of water, anhydrous morpholine or morpholine containing less than 5% of water may be used for mercaptan removal. In this case after the morpholine has been contacted with light hydrocarbon distillate, water may be added in suiiicient quantity, for example 40%, based on the amount of morpholine present, to cause the water-morpholine mixture to become substantially completely insoluble in the distillate, whereupon a two-layer system is formed. The morpholine-mercaptan reaction product remains in the water-morpholine layer. The foregoing method of reducing the mercaptan content of motor fuel is relatively easily accomplished although when morpholine containing 40% of water is contacted with the same motor fuel under the same conditions, it has been found to be more difiicult to effect a similar reduction of mercaptan content.

Other methods of recovering the partially spent treating reagent may be employed such, for example, as the use of mildly acidic reagents such as carbon dioxide, or even strongly acidic reagents such as sulfuric acid. Since the treating reagent after dilution with water or other antisolvent 'is substantially insoluble in the hydrocarbon distillate being treated, the loss of treating reagent through solution in the hydrocarbon is negligible. The amount of water required to cause the treating reagents to be substantially insoluble in the hydrocarbon being treated may vary within rather wide limits, depending upon such factors as the characteristics of the distillate being treated, the temperature of the treat- For example, more water isrequired to make morpholine substantially insoluble in a highly aromatic distillate than in the caseof a highly parafiinic distillate. In general, however, it has been found that the addition of 5% of water to commercial morpholine materially reduces the solubility. of the morpholine, while 40% Water renders. the morpholine substantially completely insoluble.

While procedure for the purpose of carrying out the invention has been particularly described, it is to be understood that this is by way of illustration only and that changes, omissions, ad'- ditions, substitutions and modifications may be made without departing from the spirit of the invention which is intended to be limited only as required by the prior art and in view of the following claims.

We claim:

1. A process of treating sulfur bearing hydrocarbon oil containing paraffinic and non-paraffinic hydrocarbons comprising contacting the oil with a reagent selected from the group consisting of morpholine and its derivatives, subjecting the mixture to such conditions as to produce two liquid phases, separating said phases to obtain fractions of said'oil respectively more parafiinic and less parafiinic and of reduced sulfur content and separating the reagent from the fractions.

2. A process of treating sulfur bearing hydrocarbon distillate containing paraffinic and nonparaffinic hydrocarbons wherein at least a portion of the sulfur is in the form of mercaptan sulfur comprising contacting the distillate with one or more compounds selected from the group consisting of morpholine and'its derivatives, subjecting the mixture to such conditions asv to produce two liquid phases, separating said phases to obtain fractions of said distillate respectively more paraffinic and less parafiinic and of reduced sulfur content and separating the reagent from the fractions.

3. Process in accordance with claim 2 where the distillate is contacted with morpholine.

4. Process of treating doctor sour hydrocarbon distillate containing paraffinic and non-parafiinic hydrocarbons comprising contacting the distillate with a treating reagent selected from the group consisting of morpholine and its derivatives, subjecting the mixture to such conditions as to produce two liquid phases, separating said phases to obtain doctor sweet fractions of said H distillat respectively more paramnic and less paraflinic and separating treating reagent from both phases.

5. Process in accordance with claim 4 where water is added to the phases subsequent to separation to facilitate separation of treating reagent and the separated treating reagent is recovered for further treating operations by heating sufficiently to remove water and to decompose reaction products.

6. Process of improving octane rating of hydrocarbon motor fuel comprising contacting the motor fuel with a compound selected from the group consisting of morpholine and its derivatives, subjecting the mixture to such conditions as to produce two liquid phases, separating said phases to obtain fractions of respectively higher and lower octane rating and. separating the compound from the fractions.

'7. The method of producing gasoline of improved anti-knock value from gasoline distillate containing components having relatively higher and lower anti-knock values, which comprises commingling said distillate with a solvent comprising morpholine, forming a phase comprising morpholine and the higher anti-knock value components, and a second phase comprising the lower anti-knock value components, separating the phases so formed, and removing morpholine from the phase first mentioned.

8. The method of producing gasoline of improved anti-knock value from gasoline distillate containing components having relatively higher and lower anti-knock values, which comprises contacting said distillate with a solvent comprising morpholine to extract from said distillate the higher anti-knock value components, separating the solution of morpholine and higher antiknockvalue components from the undissolved portion of the distillate, and removing morpholine from the higher anti-knock value components so extracted.

9. The method according to claim 7 wherein the morpholine is removed from the solution of morpholine and higher anti-knock value components by water washing.

10. Method in accordance with claim 2, wherein the conditions to which the mixture is subjected to produce two liquid phases includes chilling said mixture to temperatures below about 32 F.

11. The method of producing gasoline of improved anti-knock value from gasoline distillate containing components having relatively higher and lower anti-knock values which comprises commingling said distillat with a solvent comprising morpholine at temperatures sufficiently high to produce complete miscibility, chilling said commingled materials to a temperature below approximately 32 F., whereby to form a phase containing morpholine and a portion of said distillate richer in higher anti-knock value components than said distillate and a second phase containing a portion of said distillate richer in lower anti-knock value components than said distillate, separating the phases so formed and removing morpholine therefrom.

12. Method in accordance with claim 11 in which the commingled materials are chilled to temperature between approximately 0 and 32 F.

13. Method in accordance with claim 11 wherein the distillate and solvent are commingled at temperatures of about to 200 F.

14. Process of reducing the mercaptan sulfur content of mercaptan-containing distillate comprising mixing said distillate with a reagent se lected from the group consisting of morpholine and its derivatives, adding sufficient water to the mixture to cause substantially complete separation between th distillate and reagent, removing the reagent together with mercaptans as a liquid from the distillate, reconditioning the reagent for further treating operations by heating sufficiently to decompose reaction products, separating the mercaptans from the reagent and reusing the reagent.

15. Process in accordance with claim 14 in which the reagent is morpholine.

MEYER S. AGRUSS. GEORGE W. AYERS, JR.