US2741578A

US2741578A - Recovery of nitrogen bases from mineral oils

Info

Publication number: US2741578A
Application number: US283429A
Authority: US
Inventors: Art C Mckinnis
Original assignee: Union Oil Company of California
Current assignee: Union Oil Company of California
Priority date: 1952-04-21
Filing date: 1952-04-21
Publication date: 1956-04-10
Anticipated expiration: 1973-04-10

Description

April 10, 1956 A. c. M KINNIS 2,741,578

RECOVERY OF NITROGEN BASES FROM MINERAL OILS Filed April 21, 1952 s Sheets-Sheet 1 (WA 01 M/E April 10, 1956 A. c. MOKINNIS RECOVERY OF NITROGEN BASES FROM MINERAL OILS 3 Sheets-Sheet 2 Filed April 21, 1952 A. c. MCKINNIS 2,741,578

RECOVERY OF NITROGEN BASES FROM MINERAL OILS 5 Sheets-Sheet 3 April 10, 1956 Filed April 21, 1952 United States Patent RECOVERY OF NITROGEN BASES FROBA MINERALOILS Art C. McKinnis, Long Beach, (Ialifi, assignor to Union Oil'Compan'y of California, Los Angeles, Calirl, a corporation of California Application April 21,1952, Serial No. 283,429 17 Claims. (Cl. 196-144) This invention relates to the refining of mineral oils and is particularly'concerned with the separation and recovery of nitrogen-base compounds from hydrocarbon feedmixtures containing the same. In accordance with thepr'esent process mineral oils or treated fractions thereof such as Would'be obtained in the processing of petroleum fractions, shale oils, or in the coking of soft coals are treated by selective solvent extraction in order to segregate the nitrogen-"base compounds in a useful form. This extraction process utilizes a particularly desirable cla'ssi'of solvents which consists broadly of neutral, organic hydroxy compounds.

It is well known'that hydrocarbon oils of mineral origing'e. 'g., petroleum oils, shale oils, coal tars and their "fractions or other distillates, as well as the products obt'ained by the pyrolysis of certain vegetable materials, contain varying amounts of nitrogen-base compounds of the nature of quinoline, methyl quinolines, pyridine, "picolines, lutidines, collidines, and the like. Theseni trogenfcompounds 'are'often troublesome in the hydrocarbon distillates becauseof their "gum-forming potentialities and other undesirable properties, and are hence often removed therefrom. The conventional method for removing these compounds involves the treating of the hydrocarbon oil With a relatively strong aqueous acid such as sulfuric acid, whereby an aqueous acid sludge is obtained inwh'ich the nitrogen bases are contained as "salts. This sludge cannot-be readily disposed of assuch byreason of-its high acid content andconsequently it must be neutralized with an alkali before it can be dis 'carded. Thisprocedure obviously involves the' waste both ofacid and basic materials, as Wellas the nitrogen bases themselves, which are intrinsically valuable as chemibalsj 'The' expense involved in recovering such nitrogenbases from theaqueous extracts' has heretofore proliibitecl their" commercial recovery. 'This acid treatment 'ishence carried out almost exclusively for the purpose bf removing nitrogen bases from the desired hydrocarbon fractions in order to improve their stability, and also to render them more amenable to subsequent cracking operations in which the presence of nitrogen" compounds is known tobe very deleterious. 'lhe present processaccomplishes all the objectives of the previous acid treatmentJ-and inaddition provides for theeconomical recovof the nitrogen 'b'ases.

The materials employed herein as s elective solvents consistprimarily of organic'hydroxy compounds-such as ethylene glycol, ethyl alcohol, methyl alcohol and 'similar materials which have been heretofore employed in tltierfining of petroleum oils for extractingaromatichy- 'dro'ca'rb'ons therefrom. Inasmuch as themineral oil frac- "tions treated herein also generally contain appreciable quantities of aromatic hydrocarbons, e. g., *between 70%, it is necessary 'to render the solvents as selective as possible I for nitro'gen-base compounds as opposed to aromatic hydrocarbons. It is a a surprising 'idiscovery that these hydroxy compounds area more selective l-fori the. exttractioneofnitrogen bases-' than'for aromatics, t inasmuch be extracted are highly aromatic. :droxy organic compounds are of .valueiiin this type :of

,ture: of the extraction. show-.21 decreasing. solvent: capacity for aromatic hydro- '2 as some other widely used solvents for aromatics, e. g., nitrobenzene or ethylenedicyanide were found to .be relatively more selective for aromatic hydrocarbons. v.

In view of the above it will be seen that the broad object of this invention is to provide an improved method for the separation and recovery of nitrogen-base .compounds from hydrocarbon oils; 1

A more specific object is toprovidie methods for the removal of nitrogen bases by a process comprising ,ex} traction of mineral oil fractions with a nonacidic selective solvent. The realization of this object resultsin the elimination of the cost of chemicals consumed in the non-reversible chemical removal processes, and at the same time permits theme of less costly metals in thecon struction of plant equipment. 7

A further object is to provide optimum ratios of sol vent to oil, reflux ratios and temperatures whereby the extraction of aromatic hydrocarbons is repressed in favor of nitrogen-base extraction.

A further object is to provide extraction procedures which may be effected economically in a continuous man- 'ner.

Afurther object is to provide efiicient means for resolving the solvent-nitrogen base extracts into their component parts.

A st'illfurther object is to provide'means forrecovering the nitrogen bases normally contained in mineral oil fractions in a torrn suitable for further use in the chemical arts.

Other objects will be apparent from the-following detailed description ofthe invention, and various advantages not specifically referred to herein will occur to those skilled in the art.

The above and related objects may be realized in the practice of this inventiom'which consists essentially in contacting a hydrocarbon oil containing n-itrogen base compounds with certain organic hydroxy compounds, whereby a solventphase richlin nitrogen bases is formed, and a raffinate phase lean in nitrogen base is produced. Although anumber'of nonacidic comparatively nonreactive compounds are operative in this process when a large number ofzextraction stagesnare. used, it has been foundthat vcompounds containing one or more :hydroxy i groups per :molecule are far superior in their selective-action. Experimentation: has shown thatwmany hydroxy compounds: are capable .of extracting nitrogen bases from hydrocarbons of .aisimilar boilingrangeeven under the most unfavorable conditions, such as where the nitrogen bases are completelyeaturated with respect to hydrogen and the hydrocarbons from which the bases are to Although manyahyextraction it :is preferred tousepure compounds or Ll'l'llX- tures-whichrhave thethighest ratio of hydroxy groups to carbon atoms perxmoleculeuwhich is compatible with sufficientsolvent power. 'Prirne examples ofsuchcompounds are the ;.glycols. and -polyglycols.

The selection of a particular hydroxy compound or mixture of hydroxy compounds for use as a-selective solvent in anygiven case will depend on the hydrocarbon fraction being treated, thatt-is on its boiling range, gravity, degree of saturation, aromatic content, and .the like. Other determining factors aretthe operatiir temperature, amount ofasolvenhnumber -of extraction stages,-the;desired purity ofthe extra'ctednitrogen bases, andthe, completeness of: removal of nitrogen compounds from =the hydrocarbon fraction.

Optimum solubility.(relationships betweenthe solvent SJJdwSOlllt may be attained by .controllingthetempera- The solvents employed herein carbons -Withdecreasing,temperatures,v but surprisingly thioethers.

they exhibit an increasing solvent power for nitrogen bases with decreasing temperatures. Theoretically, the the greatest selectivity for nitrogen bases would be attained at the temperature where the ratio of the solubility of 'nitrogen bases to that of aromatic hydrocarbons in the solvent is at a maximum. In the present case this maximum selectivity may be reached at very low temperatures, e. g., 65 C.'-O C. Ethylene glycol, for example, is completely miscible with most nitrogen bases at 64 C., while complete miscibility with toluene is not reached even at 120 C. However, at these low tempera tures, the solvent viscosity is generally very high, and diffusion rates are low. It is therefore preferred to perform the extraction at as low a temperature as may be consistent with the rapid formation of equilibrium concentrations in rafilnate and extract, and economical separa tion of the phases. This temperature range generally varies between about C. to about 50 C., depending to some extent upon the viscosity of the solvent and feed mixture. For the glycol type solvents, the preferred temperature range between about 050 C.

The selectivity and capacity of the solvent may also be varied to suit particular conditions by controlling its composition. For example, a composition can be obtained by mixing two or more compounds from a group comprising ethylene glycol, polyethylene glycols, water, glycerol, and monohydroxy derivatives of paraflin hydrocarbons such as methanol, which will be suitable for extracting any nitrogen compound-hydrocarbon mixture at hand. In this way a solvent may be composed for the purpose of efiiciently extracting nitrogen bases from naturally occurring mineral oils such as shale oil or petroleum and the various fractions thereof. As the degree of saturation or molecular weight of the nitrogen bases to be extracted increases, hydroxy compounds showing greater solvent power should be employed. The following hydroxy compounds, for example, show increasing solvency for nitrogen bases in the order listed: water, glycerol, ethylene glycol, diethylene glycol, methanol and ethanol.

The solvents which may be employed herein include monohydroxy and polyhydroxy derivatives of paraflinic, olefinic, naphthenic, and aromatic hydrocarbons and mixtures thereof. The solvent may also consist of hydroxyl derivatives of halogenated hydrocarbons or ethers and Any organic hydroxy compound may be of use in this process provided its aqueous solution does not redden blue litmus paper or have a pH less than 6.5, and would therefore not form salts with the nitrogen bases. More specifically, solvents which may be employed include the lower molecular weight monohydroxy alcohols such as methanol, ethanol, and isopropanol, the polyhydroxy alcohols such as glycols, for example, ethylene glycol, propylene glycol, butylene glycol, and tetramethylene glycol, the diglycols, such as diethylene glycol, dipropylene glycol, and triethylene gycol, the esters and ethers of the above compounds which have one or more hydroxy groups unreacted, such as diethylene glycol, monomethyl ether and glycerol diacetate, the alkanol amines, such as diethanol amine and tributanol amine, the halogenated alcohols, such as ethylene chlorohydrin, propylene chlorohydrin, and para chloro phenyl carbinol, the hydroxy derivatives of ethers, .such as furfuryl alcohol, and the hydrated aldehydes and ketones and derivatives thereof, such as an aqueous formaldehyde solution, methyl hemiacetal and ethyl hemiformal. If desired, any mixture of hydroxy compounds may be employed to suit the particular requirements of a given extraction problem. The selectivity and capacity of such solvents may be varied by the addition of other materials such as water.

A particularly valuable group of solvents consists of the water-soluble alkylene glycols, and especially the polyalkylene glycols. These materials are found to have the highest selectivity for nitrogen bases as opposed to aromatic hydrocarbons, and a relatively high capacity. Solvents such as methanol generally have a higher capacity but a lower selectivity. In employing glycols for the extraction of nitrogen bases from mineral oil fractions containing between 10-70% aromatic hydrocarbons, solvent-to-oil ratios of between 0.4-3,0 are preferable, assuming a reasonable number, e. g., 2-4, theoretical extraction stages and no reflux.

The extraction efficiency may be further increased by suitable reflux procedures. For example, the extract may be freed of solvent and partly recycled to the extraction column, at a point below the feed inlet. In this manner the hydrocarbon content of the extract may be further reduced.

One method for studying the type of separations possible with a given solvent is to prepare binary mixtures of representative members of the two types of constituents being considered, and determine equilibrium relationships between the binary mixtures and the solvent. These equilibrium data can then be plotted on triangular graphs, from which calculations of the solvent-to-oil ratio and number of theoretical stages necessary for a given separation can be made. (The properties of triangular graphs are covered thoroughly by Roozeboom, Die Heterogenerr Gleichgewichte. They are summarized by Hunter and Nash, J. Soc. Chem. Ind. 53, 9ST (1934). The latter article and one by Vartcressian and Fenske, Ind. Eng. Chem. 29, 270 (1937) summarize methods of calculations.) In the triangular graphs each apex of the triangle represents a component of the mixture which components are the solvent and the two hydrocarbons involved. A perpendicular from each apex to the opposite side is divided into equal parts. Lines which pass through these points, parallel to the opposite side, represent lines of constant percentage of the particular component represented by the opposite vertex. Any liquid mixture of three components can be represented by a point on the graph. The perpendicular distance from this point to any side is proportional to the percentage of the component represented by the opposite vertex. If two liquid solutions are mixed, the compositions of the resultant solution will be represented by a point on a straight line between the composition points of the two original solutions, and the proportion of each original solution will be inversely proportional to the distance between its composition point and the final composition point.

Referring specifically to Fig. 1 herein, this equilibrium diagram shows the solubility relationships at 25 C. of ternary mixtures of quinoline, tetralin and diethylene glycol. This diagram is a representative illustration of the solubility relationships of a typical nitrogen base and a typical aromatic hydrocarbon when mixed with various proportions of diethylene glycol. To construct such a diagram various two-phase mixtures of the three components are prepared, the phases of which are in equilibrium with each other. The composition of the solvent phase and the raffinate phase of each equilibrium system is then determined and plotted on the graph, and tie lines are drawn connecting each raffinate composition point with its respective extract composition point. The ends of the tie lines are then connected to give a continuous binoidal curve A. Any mixture whose composition falls below the binoidal curve will resolve into a two-phase system, and by drawing a tie line through the composition point of the original mixture, which tie line is in geometrically interpolated relationship to the other tie lines, the composition of extract and rafiinate will be indicated by the points where the tie line intersects the binoidal curve A. It will be noted that the composition of rafiinate and extract become more nearly identical as each approaches the plait point P at the top of the curve. A further characteristic of this diagram is that the relative volumes of extract and raflinate in an equilibrium system may also be determined by the length of the tie "lineone'ither side of the original compositionpoint. For

example, an original mixture having a composition corresponding to point C "on "the diagram will form two This selectivity factorfbeta is analogous 'to the alpha factor employed in "distillation and "may be represented by the following formula:

1E1; Rb

Beta- R in which the terms'E and R are used to denote concentrations in the extractand rafiiuate respectively, while a and b denote, respectively, the more soluble and less soluble components of the material being extracted. Through the beta concept the limiting conditions 'for any separation can bedetermined as described by Varteressian and Fenske above mentioned. Beta is a numerical measure Of the ,solvents selectivity, or its ability to dissolve preferentially one particular type of constituent to the exclusion of other types of constituents. However, the selectivity or beta factor of a solvent is not the only measure 'ofits utility in this process. Other factors must be considered such as the solvents capacity, its specific gravity and the ease with which it may be separated from the extract components.

The data contained in Fig. 1 may also be. employed to determine the solvent-to-oil ratios, reflux ratios and minimum number of extraction stages necessary for a given separation. Such data, however, would apply only to mixtures of quino'line, tetral'in and diethylene glycol. Inasmuch as this invention is concerned primarily with the extraction of more complex mixtures, the data derivable from Fig. 1 will nothe strictly applicable. Fig. 1 should therefore be considered primarily as a graphical illustration showing the remarkable selectivity of hydroxy compounds for nitrogen bases in preference to aromatic hydrocarbons. lf nitrobenzene, for example, were substituted for diethylene glycol in Fig. l a curve would be obtained showing a greater selectivity for the tetralin and a lesser selectivity for the quinoline.

Fig. 1 indicates that the highest concentration of quinoline obtainable in the solvent-free extract is about 55%. Even when the rafiinate phase contains only quinoline on a solvent-free basis the equilibrium extract phase will contain about 49% quinoline on a solvent-free basis. When mineral oil fractions are substituted for the tetralin of the diagram, a more favorable nitrogen-base content in the extract is obtainable, e. g., between 658'5%, due to the presence of the more insoluble paratfinsand naphthenes in the feed. Considering that the feed materials normally contain only about 36% nitrogen bases, it will be seen that very small amounts of hydrocarbons, relative to the total feed volume, e. g. between 1-2%, are lost to the extract phase. High rafiinate yields are thus obtained.

in extracting a mineralo'il fraction containing originally say 5% of nitrogen bases, the equilibrium raflinate obtained in a single stage may contain about 1% nitrogen bases. The corresponding equilibrium extract phase will contain about -25% nitrogen bases on a solvent-free basis, the remainder thereof being hydrocarbons. in order thereforeto preventexcessive loss of aromatics and other hydrocarbons to the extract phase, it is necessary asa practicalmatter to perform the extraction in a number of stages, preferably between 2-5 theoretical or actual stages In this manner the portion of raflinat'e which is "in equilibrium with the final extractphase will appfoach the "raw feed material in composition, there providing a final equilibriume'xtract "z:ontaining;6585% of nitrogen bases and onlyabout 15-35% -hydrocarbons. Sine the 65-85% nitrogen bases inth'e extract represents only about 1-4.5 of the original fee'd (the fee'dhavin'gbe'en reduced-to 'about 0i5l.0'% nitrogen bases),the 15-35% hydrocarbons in the extract represents only about 0.6% to 133 %et the feecl. y

it is clear tlier'e'fore 'th'at in "order to achieve relatively complete removal of nitrogen bas'es, and at 1 the same time attain high rafiinate yields, it is necessary -to balance the interrelated factor's, extraction temperature, *solvent/ oil ratio, extraction sta'ges ahd solvent composition to 'fit e'ach particular ease.

Aside from the-intrinsic sae'cuvnyand capacity of a 'solvent for a given feed 'inixture,' the choice bf a pr'ac tical solvent m'ay'depend upon the type of recovery system to be employed. The u'sualnitrogen bases encountered in hydrocarbon fractions are ofthe highmolecular w'eight, Water-insoluble types such as quinoline and quinaldine. An extract containing such materials together'with a water-soluble solvent may be separated by adding water to form a two-phase system, and removing the solvent in the Water phase and the nitrogen bases in the organic Iphase. For this type of separation substantially any of the hydroxy compounds heretofore listed maybe employed. I

Referring now more particularly to Figure 2, this diagram illustrates a suitable extraction and recovery system utilizingthe above procedure. The solvent is passed through line linto anextractioncolumn 2, which is prefer'ablylpacked with glass beads or other supporting material, and flows downwardly in countercurreht relationship to the feed material which enters through line 3. l hc nitrogen 'base-depleted'rafiinate is withdrawn from the top of extractor 2 through line 4, and is agitated with water in mixer 5 to wash out traces of solvent. The railihatewater mixture then passes through line i? to decanter 7 wherein the lowerrsolvent-water layer is removed through line and mixed with the extract in line '9 as will be subsequently described. The purified rafiinate from decanter'l'is withdrawn through line 10.

The extract from extraction column 2 is withdrawn as bottoms'through line 9 and is mixed with the solvent-water layer from decanter 7. The mixtureis-passedinto amixing vessel 11 to which a small proportion of a light naphtha is also admitted through line 12. The naphtha serves "the purpose of breaking the emulsions which are usually formed when water, glycol and nitrogen bases are agitated together. The mixture from mixer 11 is then passed through line 13 to a decanter 14 wherein an upper organic phase and a lower aqueous phase are formed. The aqueous phase is withdrawn through line 15 and transferred to a distillation column 16 where water is removed overhead through line 17, and the dehydrated solvent, in the case of high boiling materials such as glycols, is removed through line 18 and recycled to the solvent feed line 1. Obviously of'course, in the event that low boiling solvents are employed the solvent may form the overhead fraction and the Water will form the bottoms. In some cases the overhead aqueous fraction removed through line 17 may contain small quantities of water-soluble nitrogen bases such as pyridine and picolines. These materials may be separated by conventional methods if desired.

The organic phasefrom decanter 141's passed overhead through line 19 to a second distillation column 20. in this column the light naphtha fraction is removed overhead through line 21 and is recycled to the mixer 11. The bottoms fraction from distillation column 20 consists primarily of the nitrogen bases, which are removed through line 22 and may befurther purified by conventional methods if desired.

The above separation scheme is relatively simple but isfapplicable only in cases where the extracted nitrogen currently through an extraction column 30, as previously described. The extract is withdrawn near the bottom through line 4 and is passed to an azeotropic distillation column 5. In this column an azeotrope former is introduced through line 6 which is selected to form an azeotrope with the solvent but not with the nitrogen bases. Suitable azeotrope formers include, for example, toluene, xylene, octane, 2,7-dimethyloctane, cymene, indene and other hydrocarbons, esters, ethers, amines, halogenides, ketones, alcohols, nitro compounds, etc. The practical choice of an azeotroping agent is determined primarily by the nature of the solvent employed, and the type of nitrogenbases present. Advantage is taken of the fact that the solvents employed herein are generally more ready azeotrope formers than the nitrogen bases. The glycols, for example, form azeotropes with hydrocarbons which generally boil very close to the boiling point of the hydrocarbon. If the solvent is a polyhydric alcohol such as glycol the hydrocarbon azeotrope former should be selected to boil Within 100 C. of the boiling point of the glycol. In the case of monohydric alcohols such as butanol, the azeotrope forming hydrocarbon should boil in the range of 40 C. below the boiling point of the solvent. Any azeotrope former may be employed which forms an azeotrope with the solvent, which azeotrope boils at a temperature lower than the boiling point of the nitrogen bases, or of any azeotrope formed between the nitrogen bases and the azeotrope former. Solvents boiling below 100 C. such as methanol or ethanol may sometimes be distilled overhead without an azeotrope former.

The nitrogen bases are removed as bottoms from distillation column through line 7 and are transferred to a second distillation column 8 wherein the residual entrainer is stripped and taken overhead through line 9 to be recycled through line 10 to azeotroping column 5. The bottoms from distillation column 8 are drawn off through line 11, and consist of nitrogen bases, together with varying proportions of hydrocarbons from the feed material. If further purification of the nitrogen basis is desired, this may be accomplished by conventional procedures, as fractional distillation or azeotropic distillation.

The azeotrope removed overhead from azeotroping column 5 passes through line 12 to a mixer 13 to which water is admitted through line 14. The mixture is agitated for a short period of time and then transferred through line 35 to a decanter 16. The organic phase which separates, consisting predominantly of the entrainer, is removed through line 17 and recycled to azeotroping column 5. The aqueous phase is removed through line 18 and is passed to a solvent recovery system to be subsequently described.

The rafiinate from extractor 3 is removed through line 19 and transferred to a mixer 20 to which water is admitted through line 21. The mixture is agitated for a sufiicient period of time to remove residual solvent from the raffinate to the water phase, and the mixture is then transferred through line 22 to a decanter 23. The organic phase in decanter 23 consists of the purified raffinate and is removed through line 24?. The aqueous phase in decanter 23 is removed through line 25 and is passed to distillation column 26, together with the aqueous phase in line 13 from the previously described solvent-azeotrope decanter 16. In this column the Water is stripped from the solvent and removed overhead through line 27. Solvent is removed as bottoms through line 28 and is recycled to extraction column 3.

Various other recovery systems may be employed for separating the solvent from the extract, without departing from the primary inventive concept of extracting nitrogen bases from hydrocarbon oils with organic hydroxy compounds. In order to further illustrate the invention the following specific examples are cited, but should not be interpreted as limitative.

EXAMPLE I A shale oil gasoline fraction boiling between ZOO-400 F. and containing about 5% of total nitrogen bases is passed upwardly through a glass bead packed extraction coiumn countercurrently to a downfiowing stream of dicthyiene glycol. The extraction column is of a height corresponding to 3.5 theoretical extraction stages, and the solvent-to-oil ratio is 1.3. At an extraction temperature of about 28 C., the ralfinate is found to contain only about 0.3% nitrogen bases, and the extract contains 70% nitrogen bases, on a solvent-free basis. The raifiuate yield is about 92% by volume.

The nitrogen bases are recovered by first mixing the total extract with its own volume of water and about /5 its volume of a light naphtha fraction boiling between 150 C. and agitating the mixture. The naphtha acts as an emulsion breaker, permitting the ready formation of two liquid phases. The upper organic phase is removed by decantation, and is fractionally distilled to recover the naphtha overhead. The still bottoms consist of mixed nitrogen bases together with about 25-30% of heavier hydrocarbons, including aromatic and nonaromatic constituents. It is generally not feasible to further purify this mixture by solvent extraction inasmuch as its total solubility is too high, and little selectivity is obtained. it is therefore further purified by fractional distillation. The bases thus obtained are about 95% pure, boiling between 220-250 C. The mixture may be further resolved into its chemical constituents e. g., quinoline and quinaldine by conventional methods.

The aqueous solvent phase from the above decantation is distilled to obtain overhead a water phase, containing a very small proportion of low-boiling, water-soluble nitrogen bases including principally picolines and lutidines. The still bottoms consists of the dehydrated solvent which is recycled to the extraction column.

EXAMPLE II By employing methanol in the procedure of Example I, and reducing the solvent/ oil ratio to 0.5, the raffinate contains about 0.5% nitrogen bases and the extract, on a solvent-free basis contains about 40% nitrogen bases. This latter figure reflects the higher capacity, but lower selectivity of the lower alcohols for nitrogen bases, as compared to the glycols. The raffinate yield is about 87%.

EXAMPLE III- A petroleum gas oil fraction boiling from 250600 F. and containing 3.5% of total nitrogen bases is passed through a packed extraction column countercurrently to a downfiowing stream of ethylene glycol. The extraction column is of a height corresponding to 3 theoretical extraction stages and the solvent-to-oil ratio is 2.0. The extraction temperature is about 28 C. The raffinate is found to contain about 0.2% nitrogen bases and the extract contains about 60% nitrogen bases on a solventfree basis. The rafiinate yield is about 94% by volume.

The extract is then passed to an azeotroping column and distilled with added toluene. The overhead contains the toluene-glycol azeotrope boiling at C. and containing 6.5% glycol, and also small proportions of low-boiling hydrocarbons contained in the extract. The overhead is condensed, mixed with about 3 times its volume of water and run into a decanter. The toluene and other hydrocarbons form a top layer which is recycled to the azeotroping column. The lower phase, consisting of glycol and water is distilled to drive off the water overhead, and recover the glycol as bottoms which is re cycled to the extraction column.

EXAMPLE IV By substituting triethylene glycol for the ethylene glycol of Example 111, and substituting a mixture of C-9 aromatic hydrocarbons boiling between 1 60-170" C. for the toluene in the azeotroping column, an even more efiicient separation is obtained. In this case the rafiinate oil contains about 0.2% nitrogen bases, while the extract contains, on a solvent-free basis, about 72% nitrogen bases. This latter figure shows that triethylene glycol has a higher selectivity for the particular fractions treated, than any of the other solvents employed.

The above examples are illustrative of suitable continuous extraction procedures for commercial adaptation. In order to further illustrate the invention the following examples are given to illustrate the eifectof batch type operations.

EXAMPLE V A 1 ml. sample of a shale oil fraction containing 3.2 volume .per cent of nitrogen bases, and having a gravity of 44.6 A. P. I. and boiling from 250600 F. was agitated for several minutes with 90 ml. diethylene glycol and .10 ml. triethanolamine. The phases were allowed to separate, the lower phase withdrawn, and the upperrafih nate phase re-extracted in the same manner with a second 100 ml. portion of the same hydroxy compound mixture. At ,the conclusion of the first extraction the nitrogen base content of the oil fraction had been reduced to 1.8 volume per cent, while the second extraction further reduced the nitrogen base content to 0.9 volume per cent.

EXAMPLE VI Three batchwise extractions A, B, and C .were performed serially on 'a synthetic mixture comprising 10 grams quinoline and 90 grams tetralin (l,2,3,4-.tetr a'hydronaphthalene). The solvent in each extraction was an equal weight of anhydrous diethylene glycol. The solvent-free extract was readily recovered from each of the three extracts by diluting them each :with 100 ml. water, shaking the emulsions with 20 ml. pentane, separating the aqueous solvent phases from the oil phasesiib decantation, and distilling the pentane *from the residual oil phases. The three :oil phases obtained were then analyzed for tetralin and quinoline. The results .of the experiment are summarized in the .table.

Table Extraction A B 0 Weight of solvent, percent of weight of oil 100 100 100 Weight percent yield of solvent-free raffinate 90 96 98 Weight percent nitrogen bases in solvent-tree raffinate 2. 0. 75 0. 18 Weight percent nitrogen bases in solvent-free extract 44 18 5 10 EXA'MPLEWI Fifty ml. of a solvent consisting of 10 volumes per cent water, 9 volumes per cent methanol, and Si volumes Pm cent ethanol was agitated with .50 ml. ofa kerosene extract containing 20% by volume of nitrogen bases and about 40% aromatics. The kerosene extract had a gravity of 15 .7 A. P. I., and a boiling range of 400-5 -50 F. After the two phases had separated, a determination showed the extract layer contained 47.6 volumes per cent nitrogen bases while the rafiinate layer contained 13.4 volumes percent nitrogen bases, both on a solventfree basis. I

From the above description ;1t w ll be seen that the processes and solvents described herein prov de remarkably effective means forlseparating and recovering nitrogen bases from mineral oil fractions containing aromatic hydrocarbons.

The foregoing disclosure is not to be considered as limiting since many variations may be made by those skilled in the art without departing from the scope or spirit of the following claims.

Iclaim:

l. Aprocess for separating organic nitrogen basesfrom a feed mixture comprising (1) a major proportion of hydrocarbons (2) at least about 10% by volume of aromatic hydrocarbons and .(3)'a minor proportion above about 0.2% by volume of organic nitrogen bases, which comprises extracting said mixture with a quantity of a sub tantially neutralsolvent comprising a major proportion of an aliphatic ghydroxy compound, said quantity of solvent being sufficient to extract an appreciable, signiticantproportion of said nitrogen bases but insufiicient to extract ,more than a minor proportion ofsaid aromatic hydrocarbons, the proportion oft original nitrogen bases extracted being larger than the proportion. of original aromatic hydrocarbons extracted, thereby forming a nitrogen-base-rich extract, and a laffinate having a reduced nitrogen base content but still containing a major proportion of the original aromatic hydrocarbons, and recovering nitrogen bases trom said extract.

.2. A process as defined in claim .1 wherein the volume ratio of said solventto said .feed mixture is between about 0.4.and 3.0.

3. A process as defined in claim 1 wherein said feed mixtureis a mineral oil distillate.

.4. ,A ,process according to claim iincluding the steps of .azeotropically distilling said extract with :a relatively water-insoluble .entrainer which .forms a constant boiling mixture with said solvent,.mixing the resulting azeotrope with water, thereby forming a t o phase system, one .of said phases consisting esesntially of .cn trainer, the other of said phases consisting essentially of solvent and water, and separating said two phases by decantation.

,5. A processas.definedinclaim 1 wherein said solvent is a water-solublecompound, and including the steps of treating saidextract with water to term a two-phasesya tern, one phase consisting essentially of water and solvent, the other of said phases consisting essentially of nitrogen bases, and separating said two phases by decantation.

6. A process for separating organic nitrogen bases from a feed mixture comprising (1) a major proportion of hydrocarbons (2) between about 10% and by volume of aromatic hydrocarbons and (3) a minor proportion above about 0.2% by volume of organic nitrogen bases, which comprises extracting said mixture with a quantity of a solvent comprising a major proportion of an aliphatic polyhydroxy compound, said quantity of solvent being sufficient to extract a major proportion of said nitrogen bases but insufficient to extract: more than a minor proportion of said aromatic hydrocarbons, the proportion of original nitrogen bases extracted being larger than the proportion of original aromatic hydrocarbons extracted, thereby forming a nitrogen-base-rich extract, and a rafiinate having a reduced nitrogen base content but still containing a major proportion of the original aromatic hydrocarbons, and recovering nitrogen bases from said extract.

7. A process as defined in claim 6 wherein the volume ratio of said solvent to said feed mixture is between about 0.4 and 3.0, and said extraction is carried out at a temperature between about and 50 C.

8. A process as defined in claim 6 wherein said feed mixture is a mineral oil distillate.

9. A process as defined in claim 6 wherein said feed mixture is a shale-oil distillate.

10. A process according to claim 6 wherein said solvent is ethylene glycol.

11. A process according to claim 6 wherein said solvent is diethylene glycol.

12. A process according to claim 6 wherein said solvent is triethylene glycol.

13. A process according to claim 6 incuuding the steps of azeotropically distilling said extract with a relatively water-insoluble entrainer which forms a constant boiling mixture with said solvent, mixing the resulting azeotrope with water, thereby forming a two-phase system, one of said phases consisting essentially of entrainer, the other of said phases consisting essentially of solvent and water, and separating said two phases by decantation.

14. A process for separating organic nitrogen bases from a mineral oil distillate containing a substantial proportion of aromatic hydrocarbons and a lesser but appreciable, extractable proportion of nitrogen base compounds which comprises extracting said distillate at between about 0 and 50 C. with a solvent selected from the group consisting of lower alkylene glycols, dialltylene 'glycols and trialkylene glycols, the volume of said solvent employed being between about 0.4 and 3.0 times the volume of said mineral oil distillate, thereby selectively dissolving said nitrogen bases in preference to said aromatic hydrocarbons and forming an extract relatively rich in said nitrogen base compounds and a hydrocarbon raflinate having a reduced nitrogen base content but still containing most of the original aromatic hydrocarbons, separating said extract from said rafiinate, azeotropically distilling said solvent extract with a relatively Water-insoluble entrainer which forms a constant boiling mixture with said solvent, mixing the overhead azeotrope with water thereby forming a two-phase system, one of said phases consisting essentially of entrainer, the other of said phases consisting essentially of a solvent-water phase, separating said two phases by decantation and recovering solvent from said solvent-water phase, removing a bottoms product from said azeotroping step consisting essentially of nitrogen base compounds and said entrainer, and fractionating said bottoms product to separate entrainer from said nitrogen base compounds.

15. In a process for separating organic nitrogen bases from a mineral oil distillate containing an appreciable, extractable proportion of nitrogen bases wherein said distillate is extracted with a solvent comprising a water soluble aliphatic polyhydroxy compound to form a solvent extract of said nitrogen bases, the improved method of separating nitrogen bases from said solvent which comprises azeotropically distilling said solvent extract with a relatively water-insoluble entrainer which forms a constant boiling mixture with said solvent, mixing the overhead azeotrope with water thereby forming a two-phase system, one of said phases consisting essentially of entrainer, the other of said phases consisting essentially of a solvent-water phase, separating said two phases by decantation and recovering solvent from said solvent-water phase, removing a bottoms product from said azeotroping step consisting essentially'of nitrogen compounds and said entrainer, and fractionating said bottoms product to separate entrainer from said nitrogen compounds.

16. A process according to claim 15 wherein said en trainer is a hydrocarbon boiling between about and 200 C.

17. In a process for separating substantially waterinsoluble organic nitrogen bases from a mineral oil distillate containing an appreciable, extractable proportion of nitrogen bases wherein said distillate is extracted with a solvent comprising a water soluble aliphatic polyhydroxy compound to form hydrocarbon raffinate having a reduced nitrogen base content and a solvent extract of said nitrogen base compound, the improved method of recovering said solvent and said nitrogen bases from said extract which comprises washing said hydrocarbon raffinate with water to form a Water-solvent phase and a second ratfinate phase, separating said water-solvent phase from said second raffinate, agitating said water-solvent phase with said solvent extract in the presence of an added minor proportion of a light hydrocarbon emulsion breaker thereby forming two liquid phases, one phase consisting essentially of nitrogen compounds and light hydrocarbon, the other of said phases consisting essentially of water and solvent, separating said two phases by decantation, and separating each of said phases into its said two components by distillation.

377, 380 and 381. Pub. by Reinhold iublishing Corporation (1945), New York, New York.

Claims

1. A PROCESS FOR SEPARATING ORGANIC NITROGEN BASES FROM A FEED MIXTURE COMPRISING (1) A MAJOR PROPORTION OF HYDROCARBONS (2) AT LEAST ABOUT 10% BY VOLUME OF AROMATIC HYDROCARBONS AND (3) A MINOR PROPORTION ABOVE ABOUT 0.2% BY VOLUME OF ORGANIC NITROGEN BASES, WHICH COMPRISES EXTRACTING SAID MIXTURE WITH A QUANTITY OF A SUBSTANTIALLY NEUTRAL SOLVENT COMPRISING A MAJOR PROPORTION OF AN ALIPAHTIC HYDROXY COMPOUND, SAID QUANTITY OF SOLVENT BEING SUFFICIENT TO EXTRACT AN APPRECIABLE, SIGNIFICANT PROPORTION OF SAID NITROGEN BASES BUT INSUFFICIENT TO EXTRACT MORE THAN A MINOR PROPORTION OF SAID AROMATIC HYDROCARBONS, THE PROPORTION OF ORIGINAL NITROGEN BASES EXTRACTED BEING LARGER THAN THE PROPORTION OF ORIGINAL AROMATIC HYDROCARBONS EXTRACTED, THEREBY FORMING A NITROGEN-BASE-RICH EXTRACT, AND A RAFFINATE HAVING A REDUCED NITROGEN BASE CONTENT BUT STILL CONTAINING A MAJOR PROPORTION OF THE ORIGINAL AROMATIC HYDROCARBONS, AND RECOVERING NITROGEN BASES FROM SAID EXTRACT.