US2035583A - Separation and purification of nitrogen bases - Google Patents

Description

J. R. BAILEY 2,035,583

SEPARATION AND PURIFICATION OF NITROGEN BASES Marek 31, 1936.

Filed Feb. 4, 1952 IY (An yatented 3i, 193

aun 2 st- "f: GEN pas James R. Bailey, Austin, Tex., Oil Company of California, i a coration cil California Application February 4, iosa, f (ci. aso-3s) i fr:

gible amounts of basic nitrogenous material. The

results .showed clearly that the crude oil itself does not contain any substantial amounts of basic nitrogen compounds.

-I have discovered that the process of ation generates basic organic nitrogen compounds not present in the original crude oil. The temperature's at which this conversion occurs are the usual distillation temperatures for the separation of crude oill into its fractions such as gasoline, kerosene', gas oil, lubricating oil and arey usually below the cracking temperatures used in the conversion of heavier hydrocarbons into` lighter hydrocarbons. While these higher crackingtemperatures are eicient for the generation oi basic nitrogen compounds, the lower noncracking temperatures also produce organic nitrogen bases from non-basic compounds in the oil. Undoubtedly the eiilcient agent is heat, and this conversion of non-basic into basic nitrogen compounds may be obtained as well` by merely heating without distillation to the temperatures usually employed. The above temperatures vary from 275 F. to, and including 740 F. while the cracking temperatures are much higher, varying from 800 F. to l200 F. In the process of distillation oilis heated to diil'erent temperatures to recover various fractions. These temperatures `vary depending on the distillation system employed. Representative temperatures are, however, as follows: For the removal of primary gasoline, oil is heated to about 275 F. For theA separate the crude bases into more simple mix-I 55 tures or individual compounds.

Another object is to septe the yb by fractional acid extraction.

Another object is to resolve the crude acid extract byiractional neutralization by repeated;

participation of the bases by z. f

In separating the bases from their oil content, I have found it desirable to first remove the hydrocarbon oil and to thus concentrate `the bases. 'I'here are several ways in which this canv be accomplished. Thus, the nitrogen b may be extracted from the oil by repeated washing with relatively dilute acid, preferably sulphurlc acid. Another method is to separate the bases from a major portion of the dilutingl hydrocarbon oil by extracting with a solvent in which the nitrogen bases are soluble but in which a large portion of the diluting hydrocarbon oil insoluble.

Among the solvents which y be used to extract the nitrogen bases, liquid sulphur dioxide is the most important and universally used. (See U. S. patent No. 911,553.)L Other solvents such as iuriural, aniline, nitrobenzene and isobutyl alcohol, accomplish the same purpose and may be substituted for the liquid sulphur diomde.

The portion oi the oil which is soluble in the solvent, which portion may be termed the x-l tract, contains the nitrogenous bodies, but -'=.f= contains a considerable` proportion of hydrocarbon oils, such as aromatic and oleiinic bodies which are soluble in these solvents to a considerable extent. I have found it desirable to remove as much oi the diluting oils as sible by extracting the bases with a dilute acid. The resulting solution m then be completely or fraction-l ally precipitated by an inorganic base such sodium hydroxide or ,nf-l t. onia to produce a '-1.' ture oi bases substantially i'ree oi contaminating hydrocarbon oil.

The so-called Edeleanu process described in the Patent 911,553 is particularly well adapted to this process. This invention will be better understood by reference to the drawing which shows one exemplication of this process in schematic form. The oil containing the organic nitrogen b is introduced from a source, not shown in the drawing, passes through line i, at a temperature of about F., and is pumped by a pump 2, at a pressure of about 25 pounds, through heat exchanger 3 in heat exchange with the rate r flowing from surge tank via pump i5, line i6,

valve i1, lines 2li and 2l and'valve i8 into heater 22. The ow of raiilnate may be controlled by proper manipulation of valves Il and i5. In case it is not desired to cool the incoming oil, valve it (which is closed when railinate is circulating through heat exchanger 3) may be opened and y by closing valves I1 and I8, theramnate from tank I4 may be passed directly into heater 22.

The oil, leaving exchanger 3, cooled to about 20 F., is forced into the bottom of the SO2 extractor 5 through jets 4 and meets a stream of liquid sulphur dioxide flowing through line 4| and jets 6. The SO2 in its passage downward through the oil dissolves therefrom the nitrogenous bodies together with the aromatic and oletlnic fractions.

The solution of these bodies in SO2 being heavier than the original hydrocarbon oil drops to the bottom of the extractor 5. The hydrocarbon oil (raffinate) being lighter than the sulphur dioxide extract rises to the top where it is removed throughline 1. The rafnate contains some SO2 in solution and some extract as entrained particles. The mixtureis discharged into the raflnate or continuous decanter 8. The SO2 extract which has settled in 8 is'removed through line4 I0 and joins the extract withdrawn through line 9. Lines 9 and I0 join to form line |I which carries the extract to the extract tank |2.

The raiilnate freed of extract ows into surge tank I4 from which it is withdrawn by pump I5 and forced through line I6 either through line 20 and/or valve I9 as previously described. The rafilnate then passes into heater 22 and then into an SO2 evaporator 23, operating at a` pressure of about 75 pounds and a temperature of about 150 F. The dissolved SO2 is removed through the top of evaporator 23 through line 24 and forced by means of compressor 28 into cooler 3| through line 30, and from this cooler through line 32 and into the SO2 storage tank 33. The ralnate leaving evaporator 23 is pumped through lheater 26 where itis heated to about 200 F., and introduced into rafllnate evaporator 26 operating at a pressure of about one-half pound absolute. The raiiinate freed ofSOz is withdrawn from evaporator 26 by pump |05 and introduced into the ramnate storage tank |06. y

The sulphur dioxide gas liberated in evaporator 26 flows through line 21 and vacuum pump 29 into the suction side of compressor 28 from where it goes into storage as previously described.

The extract collected in tank I2 passes by means of pump 42 through valve 43 into heat exchanger 31 where it is preheated by warm liquid sulphur dioxide coming from tank 33 via valve 36. The cooled liquid sulphur dioxide coming from heat exchanger 31 through valve 3 5 passes into' vaporizer 38, where the temperature of the SO2 is lowered to approximately 20 F. by vaporizing a portion of the SO2 under reduced pressure. The vaporized SO2 passes via valve |04 into line 39 and then through booster compressor ||0 to compressor 28 where it is re-compressed and passed by means of line 30 into cooler 3| where it is liquefied and passed by means of line 32 to sulphur dioxide storage tank 33.

The extract collected in tank I2 is pumped by pump 42, valve 44 being closed, through heat exchangers 31 and heater 45 into the extract evaporator 46. The temperature of the extract on reaching the evaporator 46 is about 100 F., and the pressure is about '15 pounds. 'I'he evaporated S02 is removed through line 41, and compressor |08 V into cooler 48 where it is liqueiled and then through lines 49 and 32 into the SO2 storage tank 33. The extract partially'ireed of SO2 discharges from the evaporator 46 through lines 5I and 52 into a cooler 5? I By controlling the temperature and pressure in to about atmospheric pressure. However any degree of pressure may be maintained in extractor 51 by controlling valve 54. It is preferable to operate at the elevated pressure to overcome the back pressure of the system. The extract passes through jets 56 into the bottom of the lead or ceramic lined extractor 51 where it is treated countercurrently with a stream of cold water, introduced through line andA jets 58,. The lighter hydrocarbon oil freed of organic nitrogen bases i flows through line 59 into the separator 60 where the oil is removed through line 6| and the aqueous layer through line 63. The water extract from the SO2 extract contains small amounts of SO2 and all the nitrogen bases in the .form of acid sulfites in solution. This water solution is discharged through line 62 and joins line 63 also carrying dissolved acid` sultes of the. nitrogen bases withdrawn from the bottom of 60. Lines 62 and 63 join to form line 64 through which the aqueous solution of the bases passes through heater 65 into evaporator 66. The water is heated sufficiently to drive oil' any SO2 dissolved therein.

The remaining SO2 is removed through rectifyingv column 61. which is operated to reflux water and permit substantially dry SO2 to pass. TheSOz gas ows through line 68 into the salt dryer 69 where remaining water vapor is removed, through line 10, into the suction side of compressor 29. The evaporator 66 may be operated at an elevated or sub-atmospheric pressure as desired.

The SO: freed solution of the nitrogen bases ows from evaporator 66, pump through heater 1| into line 12 where it meets a stream of caustic solution introduced from tank 13 by means of pump 14. The solution passes through agitator 15 into separator 16 where the nitrogen bases freed by the addition of caustic, are removed at the top through line 11 and subsequently pass through heater 18 into a fractionating column '19. Conventional reilux condenser 84 may be provided and steam may be introduced at the bottom through jets 80.'

The nitrogen bases entering the fractionatin column 19 are fractionated into various cuts which may be removed as side cuts 82, 83 and as a bottom fraction through 8|.l The vapors discharge through line |03 into condenser 85 and separator 86. In separator 96 the nitrogen base vapors arelcondensed and removed via 81 wlile the water vapor` passes uncondensed through line 86. The water vapors emerging from separator 86 through line 88 are introduced into the suction side of a conventionalvacuum steam jet 89 and is introduced into a barometric condenser 90 where they meet a stream of water at about Gil-'10 F. entering through line |I2. The uncondensed vapors which may include fixed gases pass through line 9| into the suction` side of vacuum pump 92 and subsequently are liquefied by owing through cooler 93.

The sodium sulte solution formed by the addition of sodium hydroxide to the nitrogen bases in solution is discharged from separator 16 through line S4, into concentrator 95. The solution is heated suiilciently by steam coil SS to drive onthe major portion of the water which is removed by means of line 91. 7 sulte solution passes through line S8 into the y lead lined treater S9 into which a stream of dilute desired degree of pressure but it is preferred to operate at as low a pressure as possible in order to avoid the decomposition or cracking of the nitrogen bases. Pressures as low as 1-25 mm. of mercury absolute pressure may be used and are obtainable in the above apparatus. The use of a vacuum steam jet and barometric condenser 9@ permits of condensation of steam by ordinary cooling water.

It is well known that liquid sulphur dioxide extracts from petroleum distillates contain a large number of compounds such as unsaturated, aromatic and sulphur bodies. Experimentsconvducted on kerosene and heavier fractions indicate that the resulting product afterSOz extraction is practically nitrogen free.. These nitrogen bodies are'found in the SO2 soluble fraction. The exact condition in which the nitrogen bases are present in the liquid SO2 extract is not known. I believe, however, that there is strong evidence that these nitrogen bases are present partly combined with sulphur dioxide as sulphur dioxide addition products and partly as free bases dissolved in the extract.

The extract from the liquid sulphur dioxideV treatment is forced under pressure into a separating chamber where some of the sulphur dioxide is distilled ofi. The remaining extract containing only small amounts oi SO2 is pumped into a contact chamber where it is washed with water. The SO2 is converted into HzSOa which reacts with the organic nitrogen bases to form soluble suliites. A subsequent heating of this layer after separation from the petroleum fractions may liberate additional SO2 which may be dried and recovered. The bases present in the aqueous layer may be liberated by treatment with caustic. The caustic solution is steam distilled and the bases recovered. It should be noted that this processmay operate in a continuous manner and that the amount of basic materials required is reduced to a minimum as no acid is added to extract the bases.

This mixture of crude bases may be fractionated as shown and these fractions or` the crude mixture itself may be further resolved by chemical methods into purer and simpler mixtures and even into pure compounds.

As was stated previously, the bases may be extracted either from the petroleum oil or from the extract or other concentrate of these basesV by means of dilute acids such as sulphurousl acid,

.- sulphuric, nitric or other inorganic acids or by means of relatively strong organic acids such as acetic, chloracetic, oxalic acids or acidic substances such as picric acid, etc.

The result of the acid or solventextraction is a complex mixture of aromatic and naphthenic nitrogen compounds, partly of the pyrrole type and partly of the pyridine and piperidine type. The number of the bases isolated from any fraction in which they occur is undoubtedly very' large. Their nature depends, to a large extent,

The concentrated sodium' upon the source from which they are isolated. They range from low boiling liquids to comparatively high melting solids. As a rule, a. mixture' of the aforementioned bases has a rather pungent odor and tends to darken on standing.

These crude mixtures may be purified and re- Y,

operation advantage istaken-of the diierent basicity oi these bases and their relative reactivity with various acids or salts.

A. complex mixture of bases may be separated into several more simple ones, or pure compounds, by the `addition of various reagents capable of forming salts with the nitrogen bases present. Some of `the bases form easily separable salts with the common inorganic or organic acids.

Various salts. are capable of forming salts or double salts with some oi the bases present in a crude mixture, so that on separation of the prod-v ucts formed a simpler aggregate of bases is obtained or abase is removed from its impurities in pure form.

For instance, sodium ferrocyanide in dilute hydrochloric acid solution combines with some of the bases to form nicely crystallizing, well dened precipitates. These precipitates may be removed from the mixture leaving a more simple num, palladium, gold, cadmium, iron (ferrous and ferrie), potassium dichromate, etc. Thus, with the 2.3.8 trimethylquinoline base, which .may be isolated from the nitrogen bases present in kerosene distillate, -gold chloride forms a salt of yellow color resembling the picrate of said base and recrystallizing from water in long, slender rods; platinum chloride forms a granular light orange colored salt, difllcultly soluble in Water and alcohol; potassium dichromate gives an orange yellow salt, but crystallized from water in a `fine granulated condition; potassium ferrocyanide precipitates the diilicultly soluble hydroferrocyanide of a light cream color which in boiling water decomposes with the evolution of prussic acid; zinc chloride gives a salt recrystallizing from alcohol in long slender prisms; the mercurio chloride salt' is readily soluble in hot water and hot alcohol and separates from either solvent in long, slender rods; the stannous chloride salt has solubilities similar to the mercurio chloride )salt and is best crystallized from glacial acetic acid in the formoi rods.

It has been established that some of the bases form insoluble salts with some vof the salts previously mentioned'while' others do not react at all. By successive'addition of small amounts of these salts, the original mixture is more and more completely broken up into simpler ones. Whenthis procedure is carried out on a narrow cut of nitrogen bases obtained by fractional dis- ,be carried out by fractional acid extraction and fractional caustic precipitation. I havefound that the bases in the individual fractions show a considerable difference in their pH values and that by partial acid extraction followed by fractional caustic precipitation, the distillate fractions or the crude' bases themselves can be separated into much simpler mixtures. I have also found that through fractional distillation followed by fractional acid extraction, a large number of bases can be brought to a state of purity whereby final recrystallization of the appropriate salts will effect their complete purification.

In carrying out this fractional extraction, the base is treated with successive amounts of dilute acid such as sulphurlc acid or 'picrlc acid or any of the acids previouslymentioned. The unreacted base is separated from the acid solution of the bases. The unreacted base is again extracted with additional amounts of acid and the extrac- Ation and separation is repeated until all of the bases are removed by the Iacid. By regulating the strengthof the acid, the bases may be extracted so that the relatively strong bases are separated from the relatively weak ones. Thus, the partition of acid between a number of bases of varying pH value will be such that the acid will be taken up by the strong bases in a greater degree than by the weakr cries.I The weaker the base, the less the formation of its salt. In this manner, we may resolve the bases into those of varying degrees of basicity. It will be recognized that by extracting, with increasing or decreasing acid strengths, a further segregation according to the above principle into varying strength bases is possible.

The various salt ferent fractions. may be further resolved into free bases by fractional precipitation by alkali. This operation is identical in principle to acid extraction since it also depends on the relative pH value of the bases. It operates oppositely to the acid extraction. Whereas with acid extraction, the stronger bases are preferentially removed, it lis the weaker bases which are preferentially precipitated by the alkali. By regulating the strength of the alkali, a classification of the bases may be obtained. Thus, if we made .three extractions with acidsto obtain three classes of bases in three different salt solutions, then precipltate the bases by treating each salt solution with three different treatments with alkali, we will have then resolved the original mixture of bases into nine fractions of varying basicity and purity.

The fractional extraction with acids and bases tends to resolve the bases'into varying basic strengths, also acts to separate the b'ases of pyridine type from the naphthenic bases, i. e. those of piperldine type. The pyridine bases being strong, will be preferentially dissolved by the acid and the piperidines will be preferentially liberated from the mixture of salts of these bases.

solutions, each containing dif.

'I'he above methods may be employed ,for the separation of pure components from the crude mixture of4 bases.

-A kerosene boiling between 35o-,550 F., obtained from a California McKittrick asphaltic crude, was extracted with liquid SO2. The SO: extract was freed of SO: and washed with dilute sulphuric acid. The acid solutions were neutralized with sodium hydroxide and the freed base was separatedfrom the sodium sulphate solu tion. The crude bases were fractionally distilled, and distillates re-distilled to produce narrow cuts. The distillation was carried out under very high vacuum to minimize decomposition.l The fraction boiling at atmospheric pressure at 276- 277 C. was isolated. This fraction contains approximately 18% of a pure base which is 2,3,8, trimethylquinoline. A very. satisfactory method for isolation of this base from the other bases in this fraction is to separate it in the form of the picrate admixed with the picrate of the base 'Cisl-MN, another base present in this fraction,

by the addition of successive portions of 20 grams of picrlc acid in 50 c. c. of 50% acetic acid to 100 c. c. of the above distillation fraction dissolved in 350 c. c. of 50% acetic acid. The picrate of the latter base in contrast with that of the former is' readily soluble in both benzene and alcohol and, therefore, a mixture of these salts is easily separated.

A second method of isolation of 2,3,8, tri methylquinoline is offered through its acid sul--` phate. APreliminary tests are made to indicate the amount of 50% sulphuric acid to be used as -well as the concentration of this base in diil'erent fractions. Through the sulphate test fractions boiling from 274 to 280 C. (748 m. m.) inclusive, were found to contain 2,3,8, trimethylquinonllne with the maximum amount of around 20% in the 276 to 277 C. fraction. Since the sulphate of the base CmHzsN is very soluble, it is not precipitated but can be subsequently separated as picrate. However, admixed with this sulphate there occurs in small amount the sulphate of a second base having the formula CnHiaN. This latter base is an odorless solid melting at 43 and boiling at 278.9 C. (748 m. m.) It reacts with formaldehyde and with methyl iodide forms the cor- -CHx CH: N

Characteristic of this substance is its faint fecal odor. It is readily soluble in the common organic solvents, very diilcultly soluble in water even at aosaoas tions of the kerosene bases. Dissolved in hot gla j cial acetic acid,it separates on cooling in arborescent canary'yeilow crystals which blacken and decompose with. gas evolution. at 242=245 C. 0n heating in ammonium hydroxide solution the base is liberated.

The resolution of the bases into mixtures of varying degrees of basic strength is especially useful in the preparation of strong organic bases which are oil soluble. All of these bases are, of course, oil soluble. The stronger bases are useful as emulsiers for oil. Thus, the fatty acid salts of these bases may be useful to form oil soluble soaps which may be used in making emulsiable oil. Obviously, the stronger the base, the more emoient it will be for this purpose and the separation of the weaker bases from the stronger bases results in a purer, stronger and more emcient oil soluble base. y

In like manner, the removal of the hydroaromatic bases from the aromatic base, i. e. the piperidine type bases from the pyridine type base resuits in a purer compound to be used as onintermediate in the preparation of phthalone dyes of the methyl quinoline type.

The 2,3,S trimethylquinoiine condenses on fusion with phthalic anhydride to form a phthalone dye intermediate which when sulphonated, forms a beautiful yellow dye. The reaction may be carried out by simply fusing the intermediate at a temperature of 200 C. for a period of four hours. The resulting dye is extremely stable.

In like manner, the crude mixture of pyridine type bases obtained preferably by fractional extraction-to separate it from the hydroaromatic bases may be used instead of the pure 2,33, trimethyiquinoiine. The crude mixture of these bases contain a large number of quinolines which have the methyl group in proper position for condensation with phthalic anhydride. For example, 2L3 dimethylquinoline and 2,4 dimethylquinollne are present in the crude mixture. The quinolines methylated at the 2 position are capable of condensation with phthalic anhydride. Where such a condensation reaction is carried out with phthalic anhydride, the quinolines metbylated in the above mentioned positions` react. Thus, where we have a mixture containing other quinolines besides the ones methylated in the proper position, others not so constituted, addition of phthalic anhydride will cause a selective condensation, i. e. only the quinolines methylated in the proper positions react. By fractional acid extraction and caustic precipitation, a particular cut may be narrowed down to a point where the particular methylated quinolines predominate. Addition of phthalic anhydride will cause the formation of phthalone dyes. Thus by fractional acid extraction and caustic precipitation, a complex mixture of bases may be narrowed down to a point where phthalone dye formation is materially facilitated. The same results may of course, be obtained by fractional precipitation of the various bases as salts.

The various examples set forth herein are not to be considered as limitations upon .my invention. As to the scope thereof, reference is made to the appended claims.

I claim:

1. A method of separating organic nitrogen bases from petroleum fractions which comprises extracting said fractions with liquid sulphur dioxide to form an extract containing said organic nitrogen bases, hydrocarbon oil and liquid suls phur diomde. removing a portion of the sulphur .x s dioxide from said` extract and contacting the extract with water, septing an containing nitrogen bases from an and liberating the nitrogen bases from said aqueous phase by addition thereto of an inorganic hydroxide. i 2. A method of uw ting organic nitrogen bases from petroleum fractions which comps extracting said fractions with liguid sulphur dloxide to forni an extract containing said organic nitrogen bases, hydrccarbonoil andvliquid sulphur dioxide, removing a portion of the sulphur dioxide from said extract and contacting the remaining extract with water, separating an aqueous phase containing nitrogen bases from au oil phase, liberating the nitrogen bases from said aqueous phase by addition thereto of a solution of'an alkali metal hydroxide and separating the liberated nitrogen :c

3. A method of' separating organic nitrogen bases from petroleum fractions which comprises extracting said fractions with liquid sulphur dioxide to form an extract containing said organic nitrogen bases, hydrocarbonv oil and liquid sulphur dioxide, removing a portion' of the sulphur dioxide from said extract4 and contacting the remaining extract with water, separating an aqueousphase containing nitrogen bases from an oil phase, liberating the nitrogen bases from said Y aqueous phase by contacting said aqueous phase with an alkali metal hydroxide, separating the liberated nitrogen bases and fractionally distilling the liberated basesat pressures lessthan atmospheric.

d. A method of separating nitrogen bases from kerosene produced from asphalt base crude oil, which comprises extracting said kerosene with liquid sulphur dioxide, separating the sulphur dioxide extrnct from the portion of the kerosene insoluble in liquid sulphur dioxide, separating the sulphur dioxide from the extract to produce a crude mixture of bases, distilling said crude mixture to obtain a fraction containing components having a boiling range of 276-277 C. and adding picric acid to said fraction to precipitate the vpicrate of 2.3.3 trimethylquinoline, separating the piorate from. the remainder of the fraction and liberating the 2.3.8 trimethylquinoline from the picrate by reaction with an hydroxide.V

5. d method of separating nitrogen bases from kerosene produced from asphalt base crude oil which comprises extracting said kkerosene with liquid sulphur dioxide, separating a sulphur diox- -ide extract from the portion of the kerosene in? soluble in liquid sulphur dioxide, removing the sulphur dioxide from the extractfto produce a crude mixture of nitrogen bases, extracting said crude mixture with an inorganic acid to form an aqueous solution of salts of the nitrogen bases, liberating the bas from said aqueous solution by means of an inorganic hydroxide, separating the nitrogen bases, fractionally distilling said separated bases to obtain a fraction containing components having a boiling point range of approxinitrogen bases, hydrocarbon oil and liquid sulphur dioxide, removing a portion of the sulphur dioxide from the said extract, contacting the remaining mixture with water and separating an aqueous solution containing acid sulphites of the nitrogen bases.

7. A method of separating organic nitrogen bases from petroleum fractions which comprises extracting said fractions with liquid sulphur dioxide to form an extract containing saidorganic nitrogen bases, lhydrocarbon oil and Aliquid sulphur dioxide, removing a portion of the sulphur dioxide from the saidextract, contacting the remaining mixture with water, separating an aqueous solution containing acid sulphites of the nitrogen bases and separating the nitrogen bases from said aqueous solution.

JAMES R. BAILEY.

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