US2943049A - Denitrogenation of hydrocarbon mixtures - Google Patents

Description

June 28, 1960 P. G. NAHIN ETAL DENITROGENATION oF HYDRocARBoN MIXTURES Filed Jan. 25, 1957 f. l d, MW L a a M. zg m j ww, 2RM ,M M n; ,c mi. www m uw M M United States. O

DENITROGENATION OF HYDROCARBON MIXTURES Paul G. Nahin, Brea, and John E. Sherborne, Whittier,

Calif., assignors to Union Oil Company of California,

. This invention relates to the-purification of contaminated hydrocarbon mixtures and particularly tothe removal of hydrocarbon compounds of nitrogen from such mixtures. This invention specically relates to the `denitrogenation of such hydrocarbons by contacting them with a synthetic or natural siliceous mineral 'with base exchange properties in the hydrogen form, such Ias hydrogen bentonite forming what is apparently a solid salt which is readily and rapidly separable -by physical means from the substantially nitrogen-free hydrocarbon.

Many crude petroleum streams are produced from'the ground and are` found to contain considerable quantities of hydrocarbon derivatives Kof nitrogen in addition to the principal hydrocarbon constituents. In some cases the incidence of these nitrogen compounds is sutiicient that the nitrogen analysis runs as high as 1.0% byweight.

.i 2 Y the feed. In -a platinum catalyzed 4gasoline reforming system using a halide promoted catalyst, the nitrogen compounds appear to react with the catalyst or the promoter forming ammonium halides which deposit as solids in the apparatus. This deactivates the catalyst and lowers the yield unless the halide is continuously replenished, and eventually plugs the reactor.

Because of these adverse effects,` repeated attempts have been made to remove the nitrogen compounds from. hydrocarbon feedstocks in refining processes and from the products produced. For example, acid treating with dilute sulfuric acid forms readily removable water soluble salts with the fbasic nitrogen compounds, i.e. the nitrogen bases or amines. It is otherwise ineffective with respect to the nonbasic nitrogen Catalytic hydrogenation is effective to remove much of the nitrogen compounds, but in order to reduce their incidence in the hydrogenated product to a levelwhich does not adversely affect a platinum catalyzed reforming process for'gasoline, hydrogenation pressures of the order of5000'p.s.i. and higher are required.V Treatment of such materials with fullers earth tends to reduce thequantity of nitrogen compounds, but this involves a relatively high liquid yield loss through retention of hydrocarbons on the adsorbent. The nitrogen compounds are lost through dis- Y posal of the spent adsorbent, and seldom if'everV is the California crude oils in many cases average 0.5% by weight nitrogenv analysis. Mexican -`and* Venezuelan crudes have nitrogen analysis ranging from about 0.2% to about 0.35% by lweight. Extensive-analysis of these nitrogen-containing crudes indicate that much of the nitrogen occurs in the form of amines or the so-called nitrogen bases.- These include pyridine, quinoline, and the mono, di, tri, and tetra-alkylated derivatives of these materials. For example, in California kerosene distillate the di, tri, and tetra-alkylated quinolines vand alkylated pyridines are found. There is however considerable nonbasic nitrogen present in these materia1s. Coal tar oils produced in the coking of coal contain extensive quantities of nitrogen bases and these are principally aromatic amines and heterocyclic nitrogen compounds. ShaleV oil produced by the heating and retorting of shale rock such as that which is found in Coloradoand elsewhere, resembles waxy crude but isA characterized particularly in that it contains such extensive quantities of hydrocarbon derivatives of nitrogen that the nitrogen analysis runs as high as about 2.5% by weight. j A ,l

Crude petroleum, coal tar oils,and shale oils are principal or potential sources of liquid fuelsv and solvents. The presence of nitrogen compounds in the fuel orv solvent product imparts a very bad odor to these materials. `Their presence in theoriginal oil very adversely alfects f hydrocarbon refining techniques by which the fuels and solvents or other materials are produced. They have, for example, well defined adverse effects on such processes yas catalytic cracking, catalytic isomerization, catalytic reforming, and particularly platinum catalyzed halide promoted reforming. The nitrogen compounds appear to be adsorbed on a cracking catalyst and selectively deactivate its active cracking centers. The cracked gasoline yield may be reduced as much as 50%,through the presence of sufficient hydrocarbon derivatives of nitrogen to give the feed a nitrogen analysis of about0.3% by Weight,;and reducedby 75% when the nitrogen lanalysis reaches about 0.45%. Platinum catalyzed reforming and other reforming processes in general are also nitrogen analysis reduced suiciently to avoid the abovementioned problems in platinum catalyzed reforming.

The present invention is directed to a process for the removal of basic hydrocarbon derivatives of nitrogen from the hydrocarbon fractions associated therewith and derived from virtually any source. Y

i It is a primary objectfofthis invention to provideY an improved process -for hydrocarbon denitrogenation.

It is a further object of this invention to contact nitrogen-contaminated 'hydrocarbons with hydrogen bentonite,

or more specifically hydrogen montmorillonite, or hydrogen illite, or hydrogen kaolinite to produce a solid salt of nitrogen bases present in the hydrocarbon.`

It is a further object of this invention to provide in such denitrogenation processes a regeneration of the solid contact material by high temperatureoxidation if the nitrogen bases are of no substantial value, or 4by extraction and recovery of these nitrogen bases if they constitute a valuable commodity.' f

vOther objects and advantages of the present invention will ibecome apparent to those skilled in the art as the Y description and illustration thereof proceed.

4The present invention comprises an improved process for the separation of basic hydrocarbon compounds of nitrogen, more generally known as nitrogen bases, from 'adversely affected bypresence ofi nitrogen compounds in hydrarbon mixtures. The process employs a solid` contacting material which appears to react' directly in some way as an acid with the nitrogen bases forming aV stable product which is a solid. This solid material is very rapidly and completely separable from the liquid hydrocarbon phase. The solid contact material employed in this invention is a natural or synthetic siliceous mineral having base exchange properties converted into the acid or hydrogen ion condition. Hydrogen illite, .hydrogen kaolinite, and hydrogen bentonite, whichcontains a relatively high concentration of hydrogen montmorillonite, are examples of suitable materials. For purposes of the process, these materials appearY to behave as a solid acid either' in theY presence' or in the absence of liquid water. They further appear to react directly with nitrogen basesto form a solid salt. The process can be conducted using the solid'contacting material in the formrof a relatively dilute dispersion in liquid water,`

or in the dry state with the solid either in the form of solid granules 0r as a dry finely divided powder. Y-With Y the water dispersion, Ithe process partakes of a solvent extraction in which solvent is the aqueous dispersion, the rainate consists of the substantially nitrogen-free hydfoarborl, and the extract Campuses. au asm-1011s phase containing the solid vreacticn product of 'thejnit'rogen bases and the solid Vmaterial. fWith the granular form of solid contact material, the.process may bei conducted in a manner analogous to the'welllknown hydrocarbon cracking process in which the hydrocarbon, :in either the liquid or vapor phase, is ypassed 'through either astatic or moving bed of the granules. With the powdered form of solid materiah'the feed hydrocarbon may be slurried with the powder in the liquid phase ormay `be uidized with the powder in the vapor phase according to well known chemical engineering principles. 'In any of these process modifications, thehydrocarbon after contact with the solid materiall is freed of the basically reacting hydrocarbon compounds of nitrogen. The spent-solid material is then regenerated for reuse in denitrogenating'additional feed hydrocarbon and this regeneration may be such as to either recover the nitrogen bases as such or to destroy themas by oxidation as indicated in greater detail below. Y' n The following discussion will 'refer to 'hydrogen bentonite or montmorillonite by way offexample, it being understood that illite Vor kaolinite may be treated similarly.

The preferred process for preparing hydrogen montmorillonite and several modifications of the process for using it according to the present invention will be more clearly understood by reference to the accompanying drawing in which:

Figure 1 is a schematic dow, diagram of the preferred process for preparing hydrogen montmorillonite,

Figure 2 is a schematic flow diagram illustrating the process of this invention which employs an Yaqueous dispersion of hydrogen montmorillonite, and

Figure 3 is a highly schematic flow diagram in which the hydrogen montmorillonite is recirculated in the dry state.

Referring now more particularly to Figure l, bentonite clay, such as commercially available Wyoming bentonite and having a high concentration of montmorillonite, is introduced through line into mixer l2. Water is introduced through line 14 and agitator 16 thoroughly mixes these two materials. Suitable proportions are about one pound of clay per 5 gallons of Water. The Wyoming bentonite used in the process is Vpowdered material, 99% of which `will pass a 200 mesh screen. These materials are thoroughly mixed in mixer 12 and then passed through line 18 into settler 20. The material is allowed to stand for about 2 hours, or for sufiicient time whereby approximately 25% of `the` original bentonite settles leaving an aqueous dispersion contain; ing 75% of the original clay and including those particles which are less than about 2 microns in size. The settling time is of course a function of the settler geometry and the time necessary to settle out particles above 2 microns varies.

Wyoming bentonite and other naturally occurring montmorillonite clays contain on their crystal surfaces or in the crystalline structure exchangeable cations which may include sodium, calcium, magnesium, and iron. These clays also containI adsorbed salts, principally sodium and calcium chloride, derived from waters which have been originally associated with the clay. In the process of this invention it is necessary to remove not only the adsorbed salts but also the exchangeable cations present in the mineral. ln the preferred form for preparing hydrogen montmorillonite this is accomplished in a manner which prevents theconversion of the anions contained in the adsorbed salts into free acids. Thus the preparation of hydrogen montmorillonite may be eected in mild steel equipment.

The :settled bentonite .dispersion is pumped through line 22 fthroughrst- .ion exchange column 24 in which it contacts a synthetic cationic exchange resin previously treated with ammonium chloride so that the resin is in the ammonium condition. During the contact 'of the dispersion with this exchange resin, the adsorbed salts on the bentonite are converted to ammonium salts and the sodium and calcium and any other cations accumulate on the resin. Simultaneously the exchangeable cations presentin the ,clay structure are exchanged for ammonium cations producing an ammonium bentonite and the exchangeable cations accumulate on the resin. Since the adsorbed salts are principally chlorides, the adsorbed salts originally on the dry clay are converted to ammonium chloride'now principally in the 'aqueous phase.

The eluent from first column 24 thus consists of ammonium bentonite dispersed in-a diluent ammonium chloride solution. It is pumped through line 26 into second ion exchange column 28 containing a synthetic anionic exchange resin previously treated with ajstrong hydroxide such as caustic soda and is-thus in thehydroxyl condition. During contact of the dispersion with this resin, the ammonium chloride solution is converted to an ammonium hydroxide solution, the chloride anions being exchanged -for hydroxyl ions. The `chloride is of course accumulated on the resin. The euent from exchange column -28 thus consists of a dispersion of arnmonium bentonite in a dilute lammonium hydroxide.

This eiuent is pumped through line 30 into third ion exchange column 32 and contacts therein a synthetic cationic exchange :resin previously treated with strong acid and is thus in the hydrogen condition. During this third contact the-ammonium bentonite is converted by base exchange with the hydrogen resin to produce hydrogen bentonite. VSimultaneously the dilute solution of ammonium'hydroxide is converted to water by exA change of the ammonium ion in the solution for hydrogen ion on the resin. The Aammonium ion thus accumulates on the resin and the effluent from the third base exchange column comprises a dilute dispersion ofhydrogen bentonite in pure water.

For Wyoming bentonite the base exchange capacity is about milliequivalents per lOO-grams. This capacity may be entirely exchanged for hydrogen ions. This is the preferable form for denitrogenation of light oilsfcontaining relatively `low molecular weight nitrogen bases such as methyl and ethyl amine.` For heavier oils-containing pyridine and' quinoline and their alkylated derivatives, arsmallerfdegree offexchange to t-he hydrogen form can be used because thelarge hydrocarbon radical of one nitrogen Vbase retainedatone-active lsite on the hydrogen bentonite appears toblockadjacent sites in a 100% hydrogen bentonite. At least a 20%' exchange is re quired, that is, at least20%' of the base exchange ions areexchanged'for hydrogen andthe bentonite-softreated has a reactive hydrogen ion contentofatleast about '20 `milliequivalents per 100 grams. Because illite-"and kaolinite havetcapacitiesof'ZO milliequivalents or less, 4100% exchange for hydrogen is 'highly desirable and the resulting solids are best applied to removal of high molecular weight nitrogen bases from high boiling oils, e.g. boiling above about 500 P. These siliceous'minerals are-thus not equivalent.

Depending upon the physical form inwhich the'hydrogen bentonite is to be used in the process of this'invention, the dispersion is Veither produced through line 34 through valve 36 inthe aqueous form and is sent'to storage =facilities notshown, or if the hydrogen bentonite is to be used in the-dryzstate, valve 36 isclosed and the dilute dispersion is passed through Vline 38 into separator 40. This may'comprisea tilter or a centrifuge or .other means capable fof separating ne solids from liquids. The liquidphase is removed-through line 42zand the solid hydrogen `bentonite..phaseis removed through line 44.

Referring poumon particularly vtofignre 2,. a schematic diagram is shown of the process for denitrogenation of hydrocarbons using the aqueous'dispersion of hydrogen bentonite. .In this process mixer-contactor 50 is provided with a motor driven propeller agitator 52. The

contaminated oil is introduced through line 54 at a rate controlled by valve 56 and simultaneously the aqueous dispersion of hydrogen bentonite is introduced through line 58 at a rate controlled by valve 60. This is combined with a recirculated stream of regenerated hydrogen bentonite flowing through line 62. The materials are thoroughly agitated in mixer 50 in proportions sufficient to reduce the nitrogen combination of the hydrocarbon to the desired value. at least about 1.0 pound of hydrogen bentonite (dry basis) per barrel of oil must be used for each 0.1% by weight of basic nitrogen present in the feed.

The mixed stream of aqueous dispersion and treated oil is removed from mixer 50 through line 64 and pumped by means of pump 66 through. line. 68 into separator 70. The rate of removal is controlled by valve 72 n accordance with liquid level controller 74. In settler 70 the aqueous and oil phases are allowed to separate and the free oil product is produced through line 76 at a rate controlled by valve 78. If desired, the aqueous dispersion of the bentonite-nitrogen base salt is passed through line 80 into regenerator 82. A regenerating agent is introduced through line 84 at a rate controlled by valve 86 and the eiiuent removed through line 88. The regenerated hydrogen bentonite is recirculated in the process through line 62.

This regeneration may be a solvent extraction-with an aromatic hydrocarbon and an aliphatic alcohol. Thus the nitrogen base is extracted from the salt by solvents such as approximately equal parts of benzene-methyl alcohol, benzene-ethyl alcohol yand the like, the extract is separated and the nitrogen Y base is produced in its original form through line 88 as a product. The regenerating agent may also comprise a strong mineral acid in which case a water soluble nitrogen base salt is produced through line 88. 'Typically sulfuric or hydrochloric acids are used.

The regenerating agent may also comprise an oxygencontaining gas in which case the nitrogen base-bentonite salt is chemically decomposed and the nitrogen base radical is burned forming nitrogen oxides, carbon oxldes, and Water.

Referring finally to Figure 3, a highly schematic illustration of a continuous process modification of this 1nvention is shown including extraction zone 90 and regeneration zone 92. Conveyor zones 94 and 96 are provided to maintain a continuous circulation of dry solid hydrogen bentonite. The oil to be purified is introduced in either the liquid or vapor phase through line 98 and the purified oil is removed through line 100. The bentonite-nitrogen base "sal passes through conveyor 94 to regenerator 92. An oxygen-containting ygas such as For complete removal of nitrogen bases 6 V from the spirit and scope of this invention as set 'forth "f in the appended claims.

We claim:

1. A process for denitrogenation of hydrocarbons contaminated with nitrogen bases which comprises contacting said hydrocarbons with a siliceous solid having base exchange properties and which has been converted to .the hydrogen ion form, vand separating hydrocarbon of substantially reduced nitrogen analysis therefrom.

2. A process according to claim 1 wherein said siliceous solid is in .the form of an aqueous dispersion.

3. A process according to claim 1 in combination with the steps of regenerating lthe* spent siliceous solid to remove the nitrogen bases therefrom and returning the regenerated siliceous solid to contact further quantities of hydrocarbon.

4. A process according to claim 3 wherein said spent siliceous solid is regenerated by contacting it with an oxygen-containing gas, and controlling the regeneration air, or other, and recirculated cooled flue gas is introv duced through line 102. The regeneration is effected at temperatures of 40G-800 F. and part ofvthe resulting ue gas is discharged to the atmosphere through line 104. The remaining pant may be recycled and cooled to dilute .the incoming air through line 102 and to control the regeneration temperature. The regenerated hydrogen bentonite is returned to extraction zone through conveyance zone 96.

A particular embodiment of the present invention has been hereinabove described in considerable detail by way of illustra-tion. It should be understood that various other modications and adaptations thereof may be made by those vrskilled in this particular art without departing v7 temperature at between about 400 F. and about 800 F. whereby said nitrogen bases are burned.

5. A process according to claim 3 wherein said spent siliceous solid is regenerated .by contacting it with an ex- .tractive solvent to dissolve the -nitrogen bases, separating the extract from the regenerated siliceous solid, and separating the solvent from said hydrocarbon compounds of nitrogen in said extract.

6. A process according to claim 1 wherein said siliceous solid comprises hydrogen bentonite.

7. A process according to claim 1 wherein said siliceous solid comprises hydrogen illite.

8. A process according to claim 1 wherein said siliceous solid comprises hydrogen kaolinite.

9. A process for denitrogenation of hydrocarbons contaminated with nitrogen bases .which comprises contacting the contaminated hydrocarbon with solid hydrogen bentonite having at least about 20 milliequivalents of exchangeable hydrogen ion per grams forming spent hydrogen bentonite and a hydrocarbon product having a substantially reduced nitrogen analysis, regenerating said I spent hydrogen bentonite, and contacting additional quantitles of hydrocarbons therewith.

10. A process according to claim 9 wherein the solid to hydrocarbon ratio is at least about 1.0 pound of hydrogen bentonite per barrel of hydrocarbon per 0.1% by weigh-t of basic nitrogen in said hydrocarbon.

11. A process according to claim 9 wherein said re-V generation is effected by extracting said spent hydrogen bentonite with a solvent mixture of an aromatic hydro-V carbon and a water soluble aliphatic alcohol to remove the nitrogen bases therefrom, then separating the nitrogen :bases as a product from the solvent mixture, and

lrecirculating said solvent mixture.

12. A process according to claim 11 wherein said solvent mixture comprises an approximately 50-50 mixture of benzene and an .alcohol selected from the group l* 'consisting of methyl, ethyl, and propyl alcohols.

References Cited in the le of this patent UNITED STATES PATENTS OTHER REFERENCES Adsorption by Mameli, 2nd edition, 1951, unschw-Y (pages -201). Y v

Mitra et a1.: J. Phys., Chem., v01. 56, pagana-6,37, Y

May 1952.

Cross Dec. l5, 1931 n UNITED STATES PATENT OFFICE CERTIFICATE OE CORRECTION Patent No. 2,943,049 June 28, 1960 Paul G. Nahn et a1.,

It is hereby certified that error appears in the printed lspecification of thev above numbered patent requiring correction and that the said Letters .Patent should read as corrected below.

Column lines '26 and 27, strike outJ "hydrocarbon compounds of'"; line 27, after "nitrogen". insert bases Signed and sealed this 4th day of April 1961.,

(SEAL) y Auen: ERNEST W. SWIDER ttestlg l cer Acting Commissioner of 'Patents

Claims (1)

1. A PROCESS FOR DENITROGENATION OF HYDROCARBONS CONTAMINATED WITH NITROGEN BASES WHICH COMPRISES CONTACTING SAID HYDROCARBONS WITH A SILICEOUS SOLID HAVING BASE EXCHANGE PROPERTIES AND WHICH HAS BEEN CONVERTED TO THE HYDROGEN ION FORM, AND SEPARATING HYDROCARBON OF SUBSTANTIALLY REDUCED NITROGEN ANALYSIS THEREFROM.

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