US2704758A - Pyrolytic hydrogemnolysis of nitrogen bases - Google Patents

Description

J. W. WETZEL.

PYROLYTIC HYDROGENOLYSIS OF' NITROGEN BASES Filed Nov. 22, 1949 March 22, 1955 United States PYuoLYrrc Hrnnoourrorrsrs or NrrnoouN casas The present invention relates to pyrolytic hydrogenolysis of heterocyclic nitrogen bases and or crude oil fractions and concentrates rich in nitrogen bases, to produce desired conversion products including lower molecular weight heterocyclic N-compounds. There can be recovered from the reaction mixture when starting from natural oil distillates or extracts, in addition to heterocyclic N-bases, valuable non-nitrogenous cyclic cornpounds formed by the reaction or otherwise present in the reaction mixture.

Many crude petroleum oils and distillate fractions thereof contain heterocyclic nitrogen compounds such as higher homologues of pyridine, quinoline and isoquinoline, which have been found to interfere with the catalytic cracking of these oils. These nitrogen compounds when present even in relatively small amounts in a hydrocarbon charge stock subjected to catalytic cracking, act either as transitary poisons or deactivants for the catalyst, and/or demonstrate an inhibitory eect on the cracking reactions, resulting in lower conversion rates and in reduced yields of desired conversion products. The presence of these nitrogenous compounds in oil fractions or distillates which are not ordinarily employed as cracking stocks, also may be undesirable in certain particular uses of these oils; for instance in lubricants, fuel oils, medicinal oils, transformer oils, etc. Nitrogenous compounds of the type described are found not only in petroleum oil fractions and distillates, but also in shale oils, coal tar oils, and distiilates therefrom.

Lower molecular weight heterocyclic N-compounds such as pyridine, picolines, lutidines and to a lesser extent leucolines, if present, can be separated comparatively easily from hydrocarbon oils, such as by simple aqueous extraction. The higher homologues are removable to greater or less extent depending upon the nature of the oil, by selective adsorption as with silica gel or by treatment with strong mineral acids, or with selective reactants such as sulfur dioxide or furfural. Such processes of treating nin'ogenous oils have not been economically attractive and have been utilized commercially only to limited extent, not only because of the initial cost of reagents, but also because of the simultaneous removal, of other non-nitrogenous constituents of the oil, with consequent loss of valuable and desirable products therefrom. Recovery of useful nitrogen compounds from the concentrated extracts thus obtained, becomes complicated and costly.

In accordance with the present invention hcterocyclic N-bases boiling above about 260 in selected hydrocarbon oil fractions comparatively rich in such bases, particularly such hydrocarbon oil fractions boiling above the gasoline range, are subjected to pyrolytic hydrogenolysis at temperatures of about 800l200 F. and under selected conditions hereinafter described, including high pressures and large excess of hydrogen, resulting in dealkylation and perhaps other carbon-carbon scission of these higher molecular weight bases without excessive destruction of the N-hetero ring structure. The obtained reaction mixture is separated for separate treatment into basic and non-basic fractions. rThe basic fractions can be further fractionated to recover desirable simpler N-hetero bases present therein, such as pyridine, quinolines, and monoor di-methyl and ethyl homologues of these, such as picolines, lutidines, quinaldines, etc., while the non-basic fractions particularly when starting from a hydrocarbon oil fraction may contain laromatic and other carbocyclic compounds often atent together with iveand/ or six-membered ring compounds containing a hetero sulfur atom, and may also include hydroxy compounds such as phenols and cresols. From the non-basic fractions there can be separated, depending upon the boiling range of the starting material, such compounds as benzene, toluene, xylene, naphthalene, anthracene, thiophene, etc.

The recovered nitrogen bases as Well as the compounds recovered from the non-basic fraction have extensive and important uses as solvents, pharmaceutical agents, and as intermediates in organic synthesis for the preparation of dyes and medicinals.

Although a Whole crude oil such as petroleum or shale oil, or a selected distillate fraction thereof, may be directly subjected to hydrogenolysis under the described conditions, it is preferred in practice of the invention to treat an extract therefrom more concentrated in nitrogen compounds. By acid extraction, as with sulfuric or formic acid of below concentration, comparatively smaller quantities of aromatics including benzene ring and condensed benzene ring compounds are extracted Vthan in the case of SO2 extraction, for instance according to the known Edeleanu process. Furfural extraction may also be used, particularly in refining heavier or more viscous oils, as those in the lube oil range.

ln the treatment of a hydrocarbon charge stock such as a reduced petroleum crude to improve the crackability of the stock by removal of interfering nitrogen com-` pounds therefrom, such removal of the nitrogen com,-`

'pounds is best carried out with concentrated acid or even with anhydrous acid, such as sulfuric, forrnic or acetic acid. The existingobjections to the use of highly con-V centrated acids based on economic considerations because of the simultaneous removal of aromatic and certain naphthenic components of the stock are more than overcome, by the subsequent recovery of valuable components from the extract/ln cases in which the produc.- tion of a rainate for cracking is not among the primary objectives, aqueous acid solution such as those of sulfurie or formicacid of 2O to 30% concentration or higher may be employed. As the concentration and/or proportion of acid is increased and with elevation of treat.- ing temperature, larger quantities of hydrocarbon and other non-nitrogenous components go into the extract,

while more reactive oleiinic constituents may thus be` polymerized to tarry residues.

Separation of the nitrogenous extract from the acid or solvent treated crude oil may be eected in known man.-V ner, for instance by neutralization of the acid extract and water washing. formic acid to form an acid extract containing nitrogen addition compounds. On distillation of the formic acid extract the addition compounds are split to form therfreel nitrogen bases with the release of the acid, which acid can then be recycled to the extraction step.

There is thus obtained a nitrogen base-free hydrocarbon fraction and a concentrate rich in nitrogenous com pounds. The hydrocarbon fraction may beV cracked or otherwise treated or stored for use as such, depending upon the boiling range of the starting material. The nitrogen-rich concentrate is subjected to pyrolytic hydrogenolysis under the selected conditions hereinafter'more fully described.

The reaction products from hydrogenolysis are then.

condensed, and fixed gases including saturated lower molecular weight hydrocarbon gases such as methane and ethane, and unreacted hydrogen are thus separated. FromA the condensates the nrtrogenous compounds can be separated, as by water washing, or dilute acid extraction, leaving a substantially nitrogen-free oil. The gaseous fraction may be recycled to the hydrogenation reactor, after at least a simple treatment to roughly separate out a portion of the hydrocarbons therein, and with the be further fractionated and purified to recoverthe desired aromatic hydrocarbons. Thus, there may be separated concentrates of benzene, toluenes, xylenea; llaphthalene,

Preferably the oil is extracted withk anthracene, etc., and in some instances sulfur-containing ring compounds such as thiophenes.

The addition salts in the acidic nitrogenous extract from hydrogenolysis areV readily hydrolized toreform the free nitrogen bases. The mixture of nitrogen bases from such hydrolysis may then be separated into its various components by known fractionation procedures, and individual fractions concentrated; or these may be furtherV lfractionated and puriiied, if desired, to isolate the various simpler heterocyclic nitrogen bases, such as pyridine, picoline, quinolines, quinaldines, ethyl pyridines, dimethyl-pyridines, etc. The residual heavier nitrogen bases in the bottom fraction may be returnedV to the hydrogenolysis step for further reaction therein, or may be separately subjected rto further fractionation and recovery o f valuable products therein.

'I'he invention will be best understood by reference to the accompanying drawings showing schematically a method of operation that can be employed in practice of the invention. In these drawings:

VFigure l is a schematic flow diagram of the hydrogenolysis reactor section of the process with which the present invention is more particularly concerned, showing certain of the adjacent associated and auxiliary portions of the system; and y Figure 2 is an illustrative flow diagram showing the relation and position of the hydrogenolysis reaction step in a preferred sequence of operations, starting from a suitable raw material and recovering ultimate desired valuable compounds.

It will be understood that the illustrated ow diagramsk are merely representative and are not to be construed as limiting the scope of the operation. The reference characters on the drawings refer to various steps of the process as identified or explained at the corresponding numbers iu the description which follows.

' In vthe operation illustrated in Figure 2, a nitrogenous oil is initially extracted with formic acid 1, as for instance with 85% formic acid employing 10 volumes of the 85% acid' per 100 volumes of the oil. The acid-oil mixture is run to a settling tank 2 wherein it is permitted to stratify and thejoil layer separated from the aqueous layer. The oil layer is sent to a flasher 3 operating at about 300 F. wherein the formic acid inthe oil is iiashed 0E to return to storage 4. The oil fraction thus freed from formic acid is returned to separate storage for any desired use.

The `aqueous acid extract from the settling `tank 2 is sent to a decomposition still 5, wherein it is heated to a temperature effecting decomposition of the formic acid addition compounds of the nitrogen bases; for instance the still may be operated at an initial temperature of about 200 F. and over a distillation range up to a maximum of Vabout 400 to 500 F. The overhead from the decomposition still including light hydrocarbons and reconsti-V tuted formie acid is condensed and sent to a settling tank 6 wherein the materials which steam distill with formic acid are separated into an aqueous layer and an oil layer. The aqueous layer comprising chiefly formic acid is returned to the formic acid supply reservoir, with intermediate purification or fortication, if desired. The oil layer from settling tank 6 is added to the oil from settling tank 2 and sent together therewith to flasher 3.

Y There is thus obtained a nitrogen base-free hydrocar bon fraction from the asher 3 and a concentrate rich in nitrogeneous compounds. The latter is sent to a suitable furnace or heat exchanger (not shown) ,to be heatedV to reaction temperature and then to a pressure reactor 8, while the hydrocarbon fraction may be cracked or otherwise treated or stored for use without further treatment, depending upon the boiling range of ,the starting'material and the use to be made of that fraction. In the pressure reactor 8 the nitrogen rich concentrate is subjected to pyrolytic hydrogenolysis under selected conditions. Thus, the nitrogen-base concentrate is heated to a temperature in the range of about SOO-1200* F., preferablyV above 900 F., and hydrogen run in, maintaining a pressure in the range of 500-3000 pounds per Vsquare inch gauge or somewhat above during the reaction, preferably above 1500 poundsV perY -square inch. Pressures above 1500 pounds per square inch are generally preferred, and if the recovery of light heterocyclic bases such as pyridine is a controlling objective, the total pressure should not be permitted to exceed about 2500 pounds per square inch gauge; l It is important that hydrogen be maintained in considerable excess of its stoichiometric requirements, since it was found that coke formation could thereby be reduced to very low levels. As a rule, in practical operation of the process, 5 to 20 or more mols of hydrogen per mol (average molecular weight) of the charge is advised, corresponding to a partial pressure of not less than about 1250 pounds per square inch in the preferred operating range, but short of that causing such high partial pressure of hydrogen at the temperatures and pressures of the reaction to hydrogenate the heterocyclic nucleus with consequent breaking down of the ring structure. At high temperatures in the order of about 1025 F. a'partial pressure of hydrogen may be used up to about 2700-2800 pounds per square inch. The reaction may be carried out under conditions of throughput rates affording a residence time of reactants corresponding to a liquid hourly space velocity (based on reactor volume) of the oil in the range of about 0.1 to 3.0. VLower space rates, as that corresponding to a residence time of 15 minutes or more, are not recommended, since abnormally high yields of gas result with concomitant increased losses of nitrogen as ammonia and volatile amines.

'Ihe operation of the hydrogenolysis step will be better understood from Figure 1 of the accompanying drawings. The net result of the reactions taking place in reactor 8 is exothermic so that it may be desirable to provide means for controlling the temperature of the reaction not to exceed a set maximum. This may be accomplished in known manner by the provision of a temperature controlling jacket surrounding the reactor or better by the provision of coils in the reactor circulating an indirect heat exchangemedium 9; the temperature being Vreadily controlled by the rate of ow of the medium responsive to a temperatureV sensitive flow control means such as a thermostat, .as indicated at TC. The addition of unheated hydrogen assists in keeping the reaction temperature down, reducing'cooling requirements in the reactor to a minimum; in some instances indirect cooling may be omitted entirely. The vaporous reaction eiuent from the reactor is withdrawn 10 at a iixed pressure under control of pressure controller (PC), and is sent to a pressure cooler 12. The liquid products from pressure reactor 8 are separately withdrawn 13 and sent to an expansion chamber for the separation of gases evolved as a result of depressuring of the liquid. Instead of bringing the reaction liquid from its initial pressure as discharged from the reactor to atmospheric pressure in a single expansion chamber, it is preferred to employ a series of such chambers operating at consecutvely decreased pressures, as diagrammatically indicated for instance at 14 and 15, the final chamber being at atmospheric pressure. The gas evolved in the initial expansion chamber 14 will contain any unreacted hydrogen accompanying the liquid oil together with some dissolved low molecular weight hydrocarbon gases.

18, and added to the liquid product 13 discharged direct-- ly from the reactor. The uncondensed gas from the cooler 12 is sent to a pressure scrubber A19 wherein'the same may be contacted with oil for the removal of hydrocarbon gases 20, the undissolved hydrogen-rich gas being withdrawn overhead 21. The latter gas may be'recycled directly to the line supplying hydrogen to the reactor 8 or may be returned to the hydrogen supply reservoir with or Without further purification. In order to maintain the desired ratio of hydrogen and nitrogenous oil concentrate supplied to the reactor 8 these may be automatically controlled in known manner by suitable proportionating control devices 22. l

The liquid product 17 is separated into desired fractions of different boiling range for appropriate individual treatment to break each of these fractions down into desired recoverable concentrates or componentsrof required crude distillation separating the same into three cuts: (I)

an initial cut 24 boiling at atmospheric pressure say up to 150 C.; (l1) a fraction 25 obtained by reducing the pressure say to 1 to 3 mm. of mercury, and collecting the eluent boiling up to about 115 C.; and (III) a residual fraction 26 boiling at the reduced pressure between about 115 C. to 150 C. The crude distillation may be eiected in a reflux column equipped for evacuation and employing about l or 2 theoretical plates. The above fractions correspond roughly to a pyridine fraction containing monomethyl and some dimethyl pyridines; an intermediate quinoline fraction containing also alkyl quinolines and higher alkyl pyridines; and a heavy fraction containing polycyclic bases and substituted quinolines boiling above that of the intermediate Jiraction. The residue may be recycled to hydrogenolysis for further splitting.

The first fraction (l), containing the products boiling up to 150 C. at atmospheric pressure, is subjected to acid extraction 27. In this step there may be employed a hydrochloric acid solution of the concentration obtained by diluting reagent grade hydrochloric acid (38% HCl) with equal parts water by volume, which acid solution may be used in the proportions of 2-3 volumes of oil distillate per volume of acid. The acid-oil mixture separates on standing to form an aqueous layer (A) and an oil layer (B) which are separately treated as follows. The aqueous layer is neutralized with sodium hydroxide solution 28, eiecting the release of free nitrogen bases from the acid addition salts present, and the formation of a sodium chloride salt solution, which assists in salting out the otherwise Water soluble pyridine and methyl pyridine compounds. The salt solution is separated from the free nitrogen bases 29 and the latter subjected to fractional distillation 30 to separate the same into desired cuts. Thus, the cuts may be taken at boiling ranges predominating in (a) pyridine, (b) alphapicoline and (c) a cut comprising chieiiy gamma and beta picoline and 2-6 lutidine, which latter cut nds important uses as a mixed fraction as such, or may be further treated to eiect additional separation of components.

The oil layer (B) comprising chiey hydrocarbons is washed with a dilute alkaline solution 31, which may be for example a solution of sodium hydroxide, causing separation of the product into an aqueous layer 32 and an oil layer 33.` The aqueous layer is neutralized with acid 34 effecting separation of low boiling phenols. The oil layer is subjected to vacuum fractionation to recover aromatic hydrocarbon fractions therein which may comprise benzene, toluene and C-2 alkyl benzenes.

The intermediate fraction (Il) is collected 36 and is treated with solid KOH to form a fusion melt 37, the solid 38 being readily separated from the liquid oil layer 39 by decantation, ltration or centrifuging. The melt is extracted with water and benzene 40, the benzene solution being withdrawn and treated to drive oi the benzene 41, leaving a residue of weak acids, such as carbazoles and indoles. The aqueous layer is neutralized with acid 42, recovering cresols and other alkyl phenols.

The liquid oil layer from which the KOH melt was separated is extracted with hydrochloric acid 43 forming an aqueous layer and an oil layer. The aqueous layer is then treated 44 similarly to the aqueous layer (A) from the light fraction as by neutralization with alkaline solution with the resulting separation of a mixture of free bases including quinolines and higher alkyl pyridines, which may be recovered as concentrates or components of desired purity, for instance by vacuum fractionation.

The oil layer from acid extraction is washed in alkaline solution and otherwise treated 45 similarly to the oil layer B in the initial light fraction, except for the step of separation of phenolic compounds (compare step 42), the washed oil comprising hydrocarbons boiling in the range of C3 alkyl benzenes, naphthalenes, mono and dimethylnaphthalenes, which may include some acenaphthenes. The oil may be further fractionated into concentrates or components, as desired.

Fraction III, is fused with solid potassium hydroxide 45 in the same manner as the middle cut was treated under step 37 above, the melt being separated and extracted with water and benzene, and the oil separated from the melt extracted with acid. Further treatment of the separated portions may follow the same procedure as in fraction II, and resulting in the ultimate separation of a neutral fraction comprising higher polycyclic hydrocarbons, a basic fraction consisting largely of nitrogen bases of the type of acridine and benzoquinoline, and an acid fraction sepa- 6 rable into` weak acids of the` carbazole type on the one hand and stronger acidic materials among which higher alkyl phenols are typical.

Example I An Edeleanu extract of 0.3% N content (15.6 API gravity) from a diesel cut of a nitrogenous gas oil `fraction (about 20% byvolume boiling Vin theI range up to 500 F.) was charged to a copper lined reactor together with 7.1 moles o hydrogen per mol of oil at a liquid hourly space velocity of 0.7 liter of oil per liter ofA reactor capacity per hour, at an average temperature of 970? F. and an average pressure of 1925 lbs. per square inch gauge, the run being continued for 9,0 minutes. Condensation of the eiuent yielded a liquid product constituting 78.5 b y weight of the charge of which 49% distilled in the range of 'up to 500 P.

Example 1I (a) An Edeleanu extract of a diesel cut of the saine m'trogenous gas oil as in the preceding example was'extracted with formic acid employing 0.10 part by volume of the acid to the oil, to provide an extracthighly concentrated in nitrogen bases. The acid layery thereby formed was separated from the oil layer and distilled to split off formic acid from the addition salts formed. This gave a nitrogenous oil product of 4.4% N content which was subjected to hydrogenolysis in a copper lined reactor under conditions and withthe'yields reportedbelow.

(b) The individual fractions of the several rans were then composited and the initial and intermediate fractions extracted with reagent grade concentrated hydrochloric acid (38% HC1) diluted with` an equal volume of water. The free bases'were regenerated from the aqueous hydrochloric acid solution by solid sodium hydroxide. The free bases were ether extracted from the excess caustic and salt solution. The ether extract was dried over solid` caustic and vacuum fractionated in a high temperature Podbielniak column. The approximate analysisbased on distillation characteristics is given below:

Wt. percent of liquid product Pyridine 1 Alpha-picoline 0.7 Beta-picoline 1.0 Gamma-picoline 0.1 2,6-lutidine i 0.5 Bases b. r. 146/1 atm.83/150 mm 8.2 Quinoline Y Y 9.9 Isoquinoline 3.4 Quinaldine 2.3 Bases b. r.:

93-109" F./4 mm 3.7

(c) The non-basic middle oil fraction from (b) above was extracted with 10% NaOH solution to remove phenolic materials which were recovered by acidication and ether extraction. They amounted to 1.1 weight per cent of liquid product.

(d) The remaining oil of the neutral middle oil from (c) yabove was extracted repeatedly with concentrated sulfuric acid diluted with water (2:1); a reddish tany acid layer'was obtained'which amounted to 4.5 Weight per cent of liquid product.

(e) The oil remaining afterl acid extraction in (d) above was then treated at 1407"-150" C. with solid potas- 'siumhydroxide and the resulting precipitate was removed by ltratio'n and washed'with ether. The weak acids so removed vamountedto 0.9 weight per cent of the liquid product. t

(f) The filtrate separatedfrom the potash precipitate above (e) was'dried overanhydrous sodium sulfate and vacuum fractionated in a high temperature Podbielniak column. Ihe approximate analysis based on the dis- :tillation is as follows:

(g) A qualitative examination of the heavy oil boiling above 115/ 1 mm. (24.5 weight per cent of liquid product) showed the presence of carbazole, phenanhrene, anthracene, andV acridine.

Example III 'Y A Los Angeles basin gas oil of 21.1EL A. P. I. gravity {and boiling in the range of (vacuum assay) 615 F.

' initial to 90% at ,910 F. was distilled, and the lower boilinghalf up to aboutr 850 F. was'collected. This light boiling `fraction ywas extracted with 85% formic acid, employing one part of the acid to parts of the oil by volume, giving a nitrogenous oil concentrate of 22.5 A. P. I. comprising about 2.25% of the crude Y Y oil subjected to extraction, and having a 4.1% N content.

dAfter removal of formic acid as in the preceding example, the Vnitrogenous oil concentrate was subjected to hydrogenolysis at an average temperature 'of 1040 F. and an average pressure of about 3000 p. s. i. g., at a liquid hourly space Velocity of 0.20, employing 12.8 mols per hydrogen per mol of oil.

The liquid products condensed Vfrom-the reactor eluent were combined with the liquid product from another 'run at approximately the same conditions, and theV mixture dividedinto av light oil .fraction boiling up to 150 C. under atmosphericpressure, a middle oil fraction (plus traps) Vcollected under'a vacuum of Vl mm. mercury boiling at this'reduced` pressure up to .115. C., and afresidual oil fraction. The Ylightrto middle oil frac'-Y tions were Vseparated into acidic, basic and yneutral portions using the techniques described in the preceding example. The composition of eac/h of these portions is given in the following table.

Light oil (to 150 0.); .l Y Y Per eem;

Neutral 4compounds 8.8 Bases 3.2

AcidsVv 'H .05 Water 1.2

Losses .5`

Totals Y Y, 13.8

Middle Ol'(i` Traps) V(to`115/1 mJ:n.): 1

Neutral compounds 12.2 Bases, approx- 20.1 Phenols and acids, ether so1 v 1.3 f Acids; insol. in ether (ca.) ".1

Veryweak'acids (K-salt completely' decomposed by water) 1.8 Losses, approx 0.9

Totals Y i 36.4

Y Heavy oil 49.7

K i Grand total "i 99.9

Y Basic portion:

sol

. s The basic and non-basic portions were distilled separatelyV and by using a combination of the chemical and distillation characteristics, the following approximate analysis of the liquid product was made: f

Weight percent crude l liquid product Basic portion, light and middle oil: I Pyridine ,Y

Alpha-picoline Beta and gamma-picoline, 2,6 lutdine Bases, B. P. 150-225. C Quinoline, isoquinoline, quinaldine Higher bases and loss Total bases, light and.midd1e.oi1s

Nerves Total, nonfbasic portion, light and mid-Y dieV oil '27.4

Heavy oil residue Total Example I V The whole Los Angeles Basin gas oil of 21.1 API gravity was subjected to'formic acid extraction and the extract subjected to hydrogenolysis at 104 F., 2980 p. s. i. g., liquid hourly space velocity of 0.2 and hydrogen to oil ratio molar ratio of 15.3.Y A liquid recovery of over 63% was obtained. In this reaction the product obtained was somewhat higher boiling than in the hydrogenolysis of the lower boiling fraction in the preceding example. The main diierences were found in the pyridine-picoline fraction.

The liquid portion from this run was combined with the liquid portions from several other runs at approxi-'1 mately the same. conditions, and the mixture fractionated into cuts, as follows:

I. Initial to 150 C./at111.,V II; 150 C. atm. to 115 C./1 mm. III. C./l mm. to 150 C./1 mm.

Cuts I and II were then individually treated as in the preceding example to separate the same into acidic, basic and non-basic portions which were further Vextracted similarlI to the corresponding portions in the previous examp e. f

Based on the chemical and distillation characteristics, the liquid product was found to have the following ap proximate analysis:

Weight perV cent liquid product Pyridine l( 0 5 Alpha-picoline Beta,gammapicoline Y Q 05 2,6-lutidine Bases, b. r.,150225 C `2.6 Y Quinoline, isoquinoline} 40 Quinaldine Higher bases 1.6

Total bases .9.2

'mulooomox'm 'Anfahrt-bo Weight per cent Non-basic portion: liquid product Benzene 7.1 Toluene 1.9 Neutral, b. r. 112-210 C 3.4 Naphthalene 3.2 Methylnaphthaline 1.5 Higher boiling neutral 9.3 Acidic compounds 4.8

Total non-basic 31.2

Fraction 1l5150/1 mm 8.6 Heavy oil bottoms 51.9

Total 100.9

Example V The basic charge described in Example IV was subjected to hydrogenolysis at 1055 F., 2010 p. s. i. g., liquid hourly space velocity of 0.1 and a hydrogen to oil mol ratio of 12.6. The liquid product was treated as described in the above example except that the KOH fusion was omitted. The approximate analysis is given below:

Weight per cent Basic portion: liquid product Pyridne 0.9 Picolines and 2,6-lutidine 1.2 Bases, b. r. 15G-225 C 2.5 Quinoline 3.0 Iso-quinoline 1.2 Quinaldine 1.1 Higher bases 2.1

Total bases 12.0

Non-basic portions:

Benzene 8.7 Toluene 3.9 Neutral, b. r. 112-210 C 4.5 Naphthalenes 5.9 Methylnaphthalenes 2.8 Higher boiling neutral 5.9 Acidic compounds 0.3

Total non-basic 32.0

I-lzO--dist. losses 1.6

Frac. 115-150/1 mm 12.1 Heavy oil bottoms 42.6

Total 100.3

The described conditions of hydrogenolysis are also generally applicable for the conversion of individual higher molecular weight heterocyclic nitrogen bases as such and mixtures thereof to simpler heterocyclic compounds.

Obviously many modiications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim as my invention:

1. The method which comprises subjecting a hydrocarbon oil fraction rich in nitrogen content and containing heterocyclic nitrogen compounds including higher homologues of quinoline and pyridine, -to pyrolytic hydrogenolysis in the absence of catalyst in a reaction zone under selected conditions favoring carbon-carbon scission without excessive destruction of the N-hetero ring structures present in such fraction, said selected conditions including temperatures in the range of 800-1200 F., a total pressure of about 500-3000 pounds per square inch gauge, relatively high throughput rates of the oil corresponding to a residence time in the reaction zone of less than 15 minutes, and the addition of hydrogen in an amount corresponding to 5-20 moles per mole of oil fraction charged.

2. The method as dened in claim 1 wherein said relatively high throughput rates correspond to a liquid hourly space velocity of said oil based on volume capacity of reaction zone between 0.1 and 3.0.

3. The method as dened in claim 1 wherein said selected conditions include a partial pressure of the added hydlrogen of not less than about 1250 pounds per square mc 4. The method of converting to lower boiling heterocyclic nitrogen bases those higher boiling heterocyclic nitrogen bases boiling above about 260 F. and normally present in nitrogenous petroleum oils, which comprises subjecting a nitrogenous petroleum oil containing such higher boiling bases to pyrolytic hydrogenolysis in the absence of catalysts in a reaction zone at a temperature in the range of 900-l200 F. at a total pressure of 1500 to 2500 pounds per square inch gauge and in the presence of added hydrogen present during the reaction at a partial pressure of hydrogen of at least 1250 pounds per square inch, the residence time of said bases in said reaction zone corresponding to a liquid hourly space velocity based on volume capacity of said reaction zone between 0.1 and 3.0.

5. The method of pyrolytic hydrogenolysis of nitrogenous oils containing higher homologues of pyridine and quinoline for recovery of monocyclic hetero nitrogen compounds therefrom which comprises heating such an oil in the absence of catalysts to a temperature of 900- 1200 F. and a pressure of 1500-2500 pounds per square inch gauge, in the presence of at least 5 moles hydrogen per mole of oil, recovering the normally liquid products of hydrogenolysis, and separating from such liquid products the desired monocyclic hetero nitrogen compounds.

6. The method of claim 5 wherein said liquid products of hydrogenolysis are fractionated to recover products of desired boiling range, leaving a higher boiling residual oil containing nitrogenous compounds, which oil is recycled to pyrolytic hydrogenolysis.

7. The method of treating naturally nitrogenous petroleum oils, including components boiling above the range of gasoline and including heterocyclic nitrogen bases, which method comprises contacting such an oil with formic acid to form therein addition compounds of nitrogen bases present in the oil, stratifying the obtained mixture into an oil fraction and an aqueous acid fraction, the latter containing said addition compounds, separating the recited fractions, heating the aqueous acid fraction to a temperature above the decomposition tempera-ture of said addition compounds to split off the formic acid as vapors which are separated from the remaining oil concentrated in thus reconstituted nitrogen bases, and subjecting the said remaining oil to pyrolytic hydrogenolysis in the absence of catalysts at a temperature of 800- 1200 F. in the presence of hydrogen at a partial hydrogen pressure of at least 1250 pounds per square inch.

8. The method of treating naturally nitrogenous petroleum oils boiling above the range of gasoline, and containing heterocyclic basic nitrogen materials boiling above the range of gasoline, which comprises extracting such an oil with concentrated acid to obtain an oil fraction rich in nitrogen compounds, removing acid from said oil fraction, subjecting the nitrogen-rich oil fraction to pyrolytic hydrogenolysis in the absence of catalyst, at a temperature of 900-1200 F. and at a to-tal pressure of 1500 to 3000 pounds per square inch, in the presence of hydrogen added at the rate of 5 to 20 mols per mol of the oil charged, collecting the normally liquid eliuent from hydrogenolysis step, separating the liquid etluent into basic and non-basic portions by acid extraction, removing acid from the non-basic portion, thereby causing such portion to separate into an aqueous layer containing phenolic compounds and an oil layer, separating 4the oil layer, and fractionating the oil rainate to recover aromatic hydrocarbons therein of desired boiling range.

References Cited in the tile of this patent UNITED STATES PATENTS 1,965,828 Fox July 10, 1934 2,035,583 Bailey Mar. 31, 1936 2,237,541 Bailey et al. Apr. 8, 1941 2,302,655 Rutherford Nov. 17, 1942 2,410,906 Stewart Nov. 12, 1946 2,432,644 Alther Dec. 16, 1947 OTHER REFERENCES Chem. Abst., vol. 40, p. 5073 (1946).

Chem. Abst., vol. 41, pp. 950-1 (1947).

Groggins: Unit Processes in Organic Synthesis (NcGraW-Hill; N. Y.; 1947), 3rd ed., pp. 508, 524 and 52

Claims (1)

1. THE METHOD WHICH COMPRISES SUBJECTING A HYDROCARBON OIL FRACTION RICH IN NITROGEN CONTENT AND CONTAINING HETEROCYCLIC- NITROGEN COMPOUNDS INCLUDING HIGHER HOMOLOGUES OF QUINOLINE AND PYRIDINE, TO PYROLYTIC HYDROGENOLYSIS IN THE ABSENCE OF CATALYST IN A REACTION ZONE UNDER SELECTED CONDITIONS FAVOURING CARBON-CARBON SCISSION WITHOUT EXCESSIVE DESTRUCTION OF THE N-HETERO RING STRUCTURES PRESENT IN SUCH FRACTION, SAID SELECTED CONDITIONS INCLUDING TEMPERATURES IN THE RANGE OF 800-1200*F., A TOTAL PRESSURE OF ABOUT 500-3000 POUNDS PER SQUARE INCH GAUGE, RELATIVELY HIGH THROUGHOUT RATES OF THE OIL CORRESPONDING TO A RESIDENCE TIME IN THE REACTION ZONE OF LESS THAN 15 MINUTES, AND THE ADDITION OF HYDROGEN IN AN AMOUNT CORRESPONDING TO 5-20 MOLES PER MOLE OF OIL FRACTION CHARGED.

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