US3004913A

US3004913A - Process for removing nitrogen compounds from hydrocarbon oil

Info

Publication number: US3004913A
Application number: US779728A
Authority: US
Inventors: Tucker Stanley
Original assignee: Socony Mobil Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1958-12-11
Filing date: 1958-12-11
Publication date: 1961-10-17
Anticipated expiration: 1978-10-17

Description

Oct. 17, 1961 PPM NITROGEN IN NAPHTHA FRACTION Filed Dec. 11, 1958 cATA Lxe'r-A I CATALYST-'5 4-00 v 1 l \oo l 1 0 .oz .0 4- .06 .05 .lo .12 .14 .la .\a 10 S. TUCKER PROCESS FOR REMOVING NITROGEN COMPOUNDS FROM HYDROCARBON OIL y w-r NITROGEN \N TOTAL LlQUlD vRooucT INVENTOR ATTORNEY United States Patent 3,004,913 PROCESS FOR REMOVING NITROGEN COM- POUNDS FROM HYDROCARBON OIL Stanley Tucker, Collingdale, Pa., assignor to' Socony Mobil Oil Company, Inc., a corporation of New York Filed Dec. 11, 1958, Ser. No. 779,728 Claims. (Cl. 208-254) This'invention relates to a process for removing nitrogen compounds from hydrocarbon oils. More particularly, the invention is concerned with a process for treating nitrogen-containing petroleum oils and various liquid fractions obtainable therefrom in the presence of a catalytic composite which has been found to be usually effective in selectively removing nitrogen.

In the reforming of petroleum and fractions thereof, the presence of nitrogen compounds has heretofore been recognized as undesirable. Petroleum hydrocarbons generally contain varying amounts of nitrogen compounds as impurities, which are distributed in the various fractions and products obtained from the crude hydrocarbon stocks according to their boiling points or to their relative volatility in hydrocarbon mixtures. Also, the particular kind and amounts of nitrogen compounds present in a petroleum hydrocarbon vary with the previous manufacturing and processing operation to which said petroleum hydrocarbon has been subjected.

The presence of nitrogen compounds in hydrocarbon oils is objectionable for various reasons. For example, certain petroleum distillates may be marketed under specifications which recite a maximum nitrogen content. In other cases, nitrogen compounds in hydrocarbon oils tend to destroy the activity of hydrocarbon conversion catalysts with which the oil may be brought into contact during various processing operations. Thus, in catalytic cracking of a hydrocarbon oil containing an appreciable amount of nitrogen compounds, the catalyst prematurely loses activity due to the poisoning effects of the nitrogen compounds. Commercial cracking catalysts generally consist of natural or synthetic composites of silica and alumina. During the cracking reaction, nitrogen compounds undergo conversion to basic ammonia which combines with the active acid sites on the silica-alumina catalyst. This combination or poisoning inhibits the cracking reaction and reduces the conversion and gasoline yield.

The presence of nitrogen in naphtha feed to catalytic reformers has been shown to be similarly deleterious. The catalysts commercially employed in reforming generally contain a noble metal and particularly platinum deposited on silica-alumina or on alumina which may have halogen combined therewith. When effecting reforming in the presence of these catalysts, there results a certain degree of selective poisoning of the catalyst and a decrease in the activity thereof. The nitrogen compounds of the gasoline fractions become converted under the catalytic reforming conditions and it is believed that the resulting ammonia adversely poisons and deactivates the catalyst.

Numerous hydrogenation processes have heretofore been proposed to reduce the nitrogen content of hydrocarbon oils and various liquid fractions thereof, particularly those stocks intended for use as charge to cracking and reforming units. In these processes, the gas oil and naphtha charge stocks are sometimes hydrogen treated separately to effect removal of nitrogen. In other cases, the heavy gas oil is hydroprocessed in a single unit, the naphtha is distilled out and subsequently charged to a reformer pretreating unit to further reduce the nitrogen content of the naphtha charge before the same is brought into contact with the platinum or other noble metal-containing catalyst in the reforming unit.

The above hydrogenation processes for denitrifying nitrogen-containing hydrocarbon oils have been carried 3,004,913 Patented Oct. 17, 1961 ice out in the presence of various reagents and composites intended to catalytically promote the desired removal of nitrogen. Thus, various catalysts of metals and metal oxides have heretofore been proposed for such purposes including composites of chromia-alumina, chromia-molybdena-alumina, cobalt oxide-molybdenum oxide-alumina, nickel on alumina, cobalt on alumina and iron on alumina. While some of these catalysts have been found to be more effective for nitrogen removal than others, each of the aforementioned composites has certain operational disadvantages and none has proved to be exceptional when employed on a commercial basis.

It is accordingly a major object of the present invention to provide an improved, commercially attractive catalytic method for removing objectionable nitrogen compounds from hydrocarbon oils containing the same. A further object is the provision of a process for effecting selective denitrogenation of particular petroleum fractions wherein the nitrogen content thereof is efiectively reduced without adversely influencing the yield and quality of the resulting denitrized product. A still further object is the provision of a catalytic hydrogenation process for removing nitrogen from hydrocarbon oils and fractions thereof carried out in the presence of a catalyst characterized by the ability to effect an unusual reduction in nitrogen content of the charge.

The above and other objects which will be apparent to those skilled in the art are achieved in accordance with the present invention; Broadly, the process described herein involves treating hydrocarbon oils containing nitrogen compounds With hydrogen under specified conditions of reaction in the presence of a catalyst consisting essentially of 15 to 40 percent by weight of silica, 1 to 8 percent by weight of cobalt oxide, 3 to 20' percent by weight molybdenum trioxide and remainder alumina.

It has been discovered, in accordance with the present invention, that catalysts of the above recited composition, under particularly defined hydrogenation reaction conditions hereinafter set forth, provide a highly efiicient and selective means for effecting removal of nitrogen from hydrocarbon oils containing the same. It is contemplated that hydrocarbon oils which contain nitrogen compounds may generally be treated in accordance with the present process. Thus, petroleum crudes, shale oils, gas oils, gasoline, naphtha, aromatic solvent, kerosene, diesel fuel, transformer oil, lubricating oil, and other liquid petroleum fractions may be effectively treated with resulting denitrification thereof. While the process described herein is particularly applicable to the treatment of petroleum distillates, it is understood that it may be utilized with other organic compounds containing nitrogen impurities and may thus be utilized for the treatment of liquids comprising alcohols, aldehydes, ketones and acids.

In one embodiment, the present invention relates to an improvement in the removal of nitrogen from a nitrogen-containing gas oil by treating the same with hydrogen in a separte zone in the presence of a catalyst consisting essentially of 15 to 40 percent by weight silica, l to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina under conditions of hydrogen concentration, temperature and pressure such that nitrogen is substantially removed from the gas oil, and thereafter charging the substantially denitn'zed gas oil .to a catalytic cracking unit utilizing a silica-alumina cracking catalyst and maintained under con.- ventional conditions for effecting the cracking of gas oils to lighter materials boiling in the rangeof gasoline.

, In another embodiment, the invention comprises a process for effecting removal of nitrogen from a high nitrogen content naphtha, particularly one having an initial boiling point within the approximate range of from 50 F. to F. and an end boiling point within the range containing vhydroca'rbon'oil.

of from about 325 -F. to about 425 F. or a selected fraction thereof, for example, having an initial boiling point Within the range of from 125 F. to 250 F. and an end boiling point within the range of from about 350 F. to 425 F. Such nitrogen-containing naphtha stocks are, in accordance with the present invention, treated in-a separate zone with hydrogen in the presence-of a catalyst maintained under conventional conditionsfor eifecting' reforming of naphtha charge stocks to improve the-octane number thereof. In the reforming reaction, hydrogen is produced and the hydrogen thus produced maybe utilized, at least in part, in the aforementioned zone for accomplishing denitrogenation.

The catalyst used in thepresent process for removing nitrogen from nitrogen-containing hydrocarbon oils contains predominant proportions of alumina'and'specified minor proportions of molybdenum trioxide, silica, and cobalt oxide combined in a particular manner such that the resulting composite is characterized'by a silica content of about 15 to about 40 percent by weight, a molybdenum trioxide content of about 3 to about 20 percent by weight, a cobaltoxide content of about 1. to'about 8 percent "by weight and theremainder alumina. Pref- 'erably, the catalyst has a composition of about 15 to about 25 weight percent silica, about 7 to about 16 Weight percent molybdenum trioxide, about 2 to about 4.5-cobalt oxide and the remainder-alumina. Such catalyst employed in the process of the invention has been found to be highly effective in denitrifying the charge of nitrogen- The catalyst components of silica, alumina, cobalt oxide and molybdenum trioxide may be combined in any suitable'manner. It has-been discovered, however, that it 'is preferable to produce the catalyst by mechanical admixture of the silica and'alumina-containing components, rather than by chemical compositing of these oxides such as, for example, by cogelation. Either the silica or alumina-containing component may prior to admixture with the other have depositedthereon one or'both of the other catalyst components, i.e. cobalt oxide and/ or molyb- Alternatively, the catalyst may result from mechanical admixture of alumina with silica which has previously been impregnated with the oxides of molybdenum and cobalt. Another method of combining the catalyst components ,in-volves admixture of silica impregnated with either molybdenum triox'ide' or cobalt oxide with'aluruina impregnated'with the other of such metal oxides. It is'also feasible, and insome'a'spects preferable, to initially intimately'admix the silica'andalumina'components and thereafterto impregnate the resulting silica-alumina com posite'with the oxides of molybdenum and cobalt. The composite obtained, in accordance with any of the above techniques, is dried and calcined to obtain'the finished catalyst. While the alumina component is the predominating'constituent of the present catalyst and has, of itself, no dc nitrogenation activity, its careful preparation is essential to the production of the catalyst affording the'fdesired activity in the contemplated denitrogenation of the hydrocarbon, charge. The alumina'when properly prepared exerts ofsynergistic eflect with the other catalyst com.- ponents. I V

"Thealumina component of the catalyst utilized'herein V 4 a r I is a porous alumina, not adversely affected by the tem* perature conditions of the instant process, having a surface area greater than 100 square meters per gram and which may extend up to 500 square meters. per gram or more. Catalyst prepared from alumina having a surface area of 100 square meters per. gram or'less 'have a considerably higher aging rate when employed in the instant denitrogenation process in comparison "to catalysts in which the alumina component initially is characterized by a surface area in substantial excess of 100 square meters per gram. The term surface area as used herein designates the surface area as determined by the adsorption of nitrogen 'according-tothemethod of Brunnauer et al., Journal American Chem. Soc, 6 0, 309 et seq. -.(193' 8). As noted aboVe the-alumina itself isdevoidof or exerts negligible catalytic activityunder reaction=conditions at which thepresent denitrogenation process-is carried out. The density of the alumina employedie, the density thereof, usuallybe within the range of 0.2 to 2.0 -g./ cc. and moreparticularly-between about 0.4 and about 1.2 g./cc.

The alumina component-ofthe catalyst used in the .pre'sentproc'ess for efiectingremoval of nitrogen from a-hydrocarbon-oil may bepreparedbycommingling a suitable basic compound including ammonium hydroxide, ammonium carbonate, etc. with an acidic compound of aluminum including chloride, bromide, iodide, fluoride,

I sulfate, phosphate, nitrate, acetate,--etc. or by the addidenum trioxide. Thus, the catalyst utilized in the process tion of a suitable acidiccompound'includinghydrogen chloride, sulfuric acid, phosphoric 'acid etc. to analkaline compound of the metal as for example, alkali metal aluminate' such as sodium alurninate. -The resultant aluminum hydroxide is'usually washed to remove soluble impurities and then is dried at atemperature of about '200 to 600 F.-for aperiod of from Ito 24 hours or more. 'ln onemethod, the driedalumina is formed into particles of definite size. and shape in any suitable manner such as casting,.pelleting, extruding, etc. and then is subjected-to calcination at atemperature of from about 600 to about 1600 F. 'In another method, the alumina'may beformedintoparticlesof spheroidalshape by dropping a suitable aluminasol into a suitable-medium which'may comprise an, an inert atmosphere asfor example, nitro gen, carbon monoxide, etc. or into an oil orot-her suitable immiscible liquid; The resultantspheroids :are then washed, dried and calcined in the manner- 'hereinbefore 's'etforth. Alternatively, the alumina-may beprepared in the form of a precipitate'by eontrolledreaction of aluminum metal with water in thejpresenceof a mercury compound whereby'the aluminum undergoes amalgamation and the resulting amalgamatedaluminum reacts with the water to form alumina.

The silica component is initially prepared in the form of-a hydrogel or-gelatinous precipitate. .zPreferably, the silicacomponent is prepared in the" form of athydrogel by reaction between sodium-silicate and an acid such :as sulfuricacid While "maintaining-the pH-ofthe'reaction mixture generally below about d-and'preferably "in the'approx- :imate range of 3.5 to 5. 'The-initiallyiformedihydrosol of silica undergoes gelation afterlapse ofa suitable period of time to silica hydrogel. The" time ofgelationcan be control-led Within desired limits by well-known me'ans such "as adjustment in the temperature or solids concentration of the reaction mixture or hydrosol produced :therefrom. The resulting 'hydrogel is thereafter-waterwashed,baseexchanged to remove zeolitic-sodiumand-dried. :If it is desired to prepare silica initially free of alka'li metal ions, such may be accomplished by effecting hydrolysis of alkyl silicates, i.e. ethyl silicate. 'The silica'hydrogel may be produced in the form of granules'or -in the form of 'a "mass which is thereafter-broken'up'intwpieces or particles of desired size; Alternatively, silica" hydrogel may be produced in theform of spheroidal'bead particles by methods such as those described bY MafiSic in US. 384,946 or in the'fornr' ofuriifornilyshapdparticles prepared by casting or extrusion methods; Itis alsofeasi-- ble to initially produce silica in the form of finely divided,

particles of requisite particle size by employing techniques used in the preparation of fluid catalyst particles for example by spraying or rapid agitation of a hydrosol to form minute particles of hydrosol that set to particles of hydrogel which upon drying yield discrete particles of silica The alumina and silica prepared as above may be com-.

posited by mechanically admixing and thereafter impregnated with cobalt oxide and molybdenum trioxide or either of these components prior to admixture with the other may be impregnated with suitable compounds of molybdenum and cobalt to etfect deposition thereon of cobalt oxide and molybdenum trioxide.

admixture of silica and alumina is contacted with an impregnating solution of a cobalt compound such as cobalt nitrate and of a molybdenum compound such as a ammonium molybdate.

the pores thereof and while maintaining the vacuum, the above-described impregnating solution i brought into contact with the particles of base material. Alternatively; the base material for example, alumina in the form of an aqueous slurry may be impregnated with the solution of molybdenum compound and cobalt compound. It is understood that any other suitable method of commingling particles of the base material with the impregnating solution may be employed.

In another method for preparing a catalyst used in the present process, separate impregnating solutions of the;

molybdenum compound and of the cobalt compound are prepared and are composited successively with the base material with or without intervening heating .of the support. In general, using this technique, it is preferred to composite the molybdenum component first and then the.

cobalt component although the reverse procedure may be employed. After the impregnation, the base material is dried and then calcined to convert the metal compoundsv to the oxides.

Other suitable cobalt compounds for effecting deposition of cobalt oxide on the base material may be employed including for example, cobalt ammonium nitrate,

cobaltammonium chloride, cobalt ammonium sulfate,.

cobalt bromide, cobalt bromate, cobalt chloride, cobalt chlorate, cobalt fluoride and cobalt fluorate. In similar. manner, other suitable compounds of molybdenum may: be employed. Suitable soluble molybdenum compounds include molybdenum tetrabromide, molybdenum oxydibromide, molybdenum tetrachloride, molybdenum dichloride, molybdenum oxypentachloride, and molybdenum oxytetrafiuoride.

The silica-containing component, preferably in finely divided form, is intimately mixed with the aluminacontaining component which likewise is in finely divided state, preferably having a particle size Within the ap proximate range of 60 to 200 mesh (Tyler). After thorough mixing of the components, the resulting mixture is formed by pelleting, casting, molding or other suitable means into pieces of desired size and shape such as rods, spheres, pellets, etc. After forming into particles of desired size, the resulting particles are dried and thereafter calcined at an elevated temperature in the approximate range of 600 to 1200 F. It is understood that either of the silica and alumina-containing components may, prior to admixture, impregnated with The base material, i.e. alumina, silica, or composite resulting from The particles of base material may initially be subjected to a vacuum to remove air from molybdenum trioxide and cobalt oxide or that the mixed composite of silica and alumina may subsequently. be impregnated with the oxides of molybdenum and cobalt.

The impregnating solution used oridinarily contains the cobalt and molybdenum compounds in the portions desired in the final catalyst and the impregnation is controlled to produce a final catalyst containing these components in the desired concentrations. The concentrations of the cobalt and molybdenum oxides in the catalyst employed in the present process may respectively range from about 1 to about 8 percent by weight and from about 3 to about 20 percent by weight of the final catalyst. The preferred catalyst for use in the present denitrogenation process contain cobalt oxide (C00) in a concentration of from about 2.0 to about 4.5 percent and molybdenum trioxide (M00 in a concentration of from about 7 to 16 percent by weight of thefinal catalyst. After impregnation, the final composite generally is dried at a temperature of from about 200 to about 600 F. for a period of from about 2 to 24 hours or more and thereafter calcining at a temperature of from about 600 to about 1200 F. for a period of from about 1 to 12 hours or more.

It is an essential feature of the process described herein that the catalyst employed contain at least about 15 percent by weight of silica. Composites containing amounts of silica less than about 15 percent by weight do not possess the requisite denitrogenation activity observed in the case of the hereinabove described catalyst.

The cobalt oxide content of the catalyst, as noted above,.

is preferably between about 2 and about 4.5 percent by weight. The molybdenum trioxide content of the catalyst used in the present process is preferably between about 7 and about 16 percent by weight. Catalysts having cobalt oxide and molybdenum trioxide contents outside the foregoing ranges resulted in substantially less effective removal of nitrogen compounds from the hydrocarbon stocks undergoing treatment.

. The catalyst used in the process of the invention desirably has a surface area within the approximate range of 200 to 450 square meters per gram. Composites having surface area of less than about 200 square meters per gram were found to have considerably higher aging rates in the denitrogenation process and accordingly are less preferred than catalysts characterized by surface areas within the aforementioned range.

The process of this invention may be carried out in any suitable equipment for catalytic operations. The process may be operated batchwise. It is preferable, however, and generally more feasible to operate continuously. Accordingly, the process is adapted to operations using a fixed bed of catalyst through which the charge is passed at the desired temperature and pressure in either upward or downward flow. Also, the process can be operated using a moving bed of catalyst wherein the hydrocarbon flow may be concurrent or countercurrent to the catalyst charge are transported as a slurry into the reaction zone,

may feasibly be employed in carrying out the present.

process.

As previously noted, hydrocarbon oils which contain nitrogen compounds may generally be treated with the hereinabove described catalyst. The particular conditions under which treatment is elfected may vary depending on the charge stock employed. Broadly, the removal I of nitrogen from hydrocarbon oils in accordance with the present process is carried out at a temperature between about 650 F. and about 950 F., utilizing a hydro-. gen partial pressure of between about and about 5000 pounds per square inch gauge. The liquid hourly space velocity of fresh feed, i.e. the liquid volume of hydrocarbons per hour per volume of catalyst is between 0.1.

and '10. The amount of fresh hydrogen charged is generally between about 200 and about 10,000 standard cubic "feet per barrel ('42 gallons at 60 F.) of hydrocarbon fee'd. 'When the charge stock is a'nitrogen-containing *gas oil, the conditions ot-"treatment ordinarily involve =a temperature between about 700 -F. and about 900 'F., a hydrogen partial pressuref between about 500 {and -2000 pounds per square inch gauge, a liquid hourly 'space 1 velocity of between 05 and "4,: and a i fresh hydrogen charge of b'etween-ab'out 2500 to 3500 standard cubic feet perbarrel -of gas oilfeed. When, the charge stock is a nitrogen-containing naphtha, the conditions of treatment ordinarily involve. a temperature' between about 650 and about-800 1 a hydrogen partial pressure of-between about 100 and about 1000 poundsper'square inch-gauge, a liquid hourly "space velocityof between '1 and and thepresence of between-about 350" to 2500 standardcubic feet of hydrogen :per barrel of feed.

Generally, the hydrocarbonoils-undergoing treatment 7 in accordance with the process described herein will. have a nitrogen contentin excessof 1 part Der million which may extend, 1 particularly for -certain shale =oils,'up tof2 percent by weight-or more. Naphtha charge stocksem- V ployed generally will contain between about 5 and about 1500parts'per million ofnitrogen. 'It is generally-idesired v to reduce such nitrogen content'to less:than lpart per million, particularly in instances where; the'naphtha charge after treatment 'is to be subjected to reforming -in'the presence of a platinum 'orother'noble metalacontaining catalyst. -Gas oil: stocks employed generally will contain between about .02 and 1 percent by weight'of nitrogen.

The following examples will serve toillustrate the process of this invention without limiting the same:

' Example .1

A composite of cobalt and molybdenum oxides on alumina in-the form of s":x- /s=.pellets and prepared by impregnation of alumina gel with approximately 3 pep cent by weight C00 and approximately 9.5 percent by weight M00 was crushed to arparticle size of less than 100 meshtTyler). Approximately 85 parts by Weighto-f the crushed material were. mixed with approximately 43 parts by weight of silica hydrogel containing about .35 weight percent ISiO and 65 weight percent waterand having a particle size of less than 60 mesh (Tyler). The resulting compositewas-intimately mixed by ball milling the components for about 24'hours at which time the 'particles'were of 14 to.l5- micronsaveragesize. 'The ball milled material -was then pelleted to A5" diameter by A v thickpellets. The pellets'so obtainedwere then tempered for '3 hours -.-at I000 dry air. The resultingproduct contained on -.-aweight basis, about 2.5 percent C00, about 8 percent Mo0 ,-a bout.15,percent SiO iand about 74.5 percent A1 0 and possessed a surface-area of approximately220 square meterspergram.

Example 2 A hydrocarbon oil charge stock characterized "by a contentof 0.25 percent by weight was passed over a bed of the catalystcf Example 1 at a temperature of 750 F., apressure of 1500'p.s.i.g. in the presence of Example 3 A hydrocarbon oil rcharge 1 stock such as used in Example 2 was passed over abedofthe catalyst of Example 1 ate temperature of 820 F., a pressure of 1500 p.s.i.g. :in the presence .ofhydrogen circulating at a rate of about3100 standard cubic feetperbarrel of charge utilizing aliquid hourly space velocity of -.2. The product obtained from such operation, upon analysis, 'was found to contain-0.018 weight percent :nitrogen, corresponding to a removal .of 92.8 weight percent of the nitrogen contained in the original charge.

For purposes of-comparison, asilica-free catalyst of cobalt oxide and :molybdenum oxide composited with alumina of the type heretoforeemployed for .denitrogenation andcontaining 3.1 percent-by weight cobalt oxide, 9.3 .percent .by-weight molybdenum oxide and'remainder substantially alumina was employed-in treating the'above stock under identical reaction conditions. :Thenitrogen content of theproduct obtained with the use .of this catalyst was 0.047 weight percent, corresponding to a removal 'of 81.2 Weight percent .of the nitrogen .contained in the original charge.

'It will -be evident" from the comparative data o'f .the above Example 3 rthatthe additionof .15 weight percent silica to the cobalt oxide-molybdenum oxide-alumina catalyst resulted in an 11.6 weight percent more efiective removal ofnitrogen from the .nitrogenecontaiuing charge.

' Example 4 A hydrocarbon oil charge characterized by a gravity of 23.8 A.P.I., a boiling range'of 404 Fxto 732 F.,

hydrogen .circulating at a rate .of 3000 standard' cubic cobalt ;oxide and molyb'denumoxide 'composite'd vwith aluminaof' the type heretofore employed for denitrogenation-and containing 3.1 percent by weightcobaltoxide,

'923 percent'by-weight molybdenurn oxideandmemainder substantially: alumina was employed' in treatingitheabove stock under: identicahreaction conditions. Thenitrogen content of ftheproduct obtained with-use of thisycatalyst was 0.10 weight percent, corresponding to a removal feet per barrel of charge utilizing a liquid hourly space an aniline number of 131 Rand a nitrogen content of 0.25 percent by weight was passed over a bed of the catalyst of Example 1 at a temperature of 830-865 F., a pressure of .1640 p.s.i.g. in the presence of hydrogen circulating at a rate of 2500-3000 standard cubic feet of hydrogen per barrel of charge utilizing a liquid hourly space velocity of 2 and a liquid recycle to fresh:feed ratio of 3/1. The product obtained was treated under theforegoing conditions until the nitrogen content thereof was reduced to 0.043 percent by weight. Theproduct was then distilled to remove a naphtha fraction boiling in the approximate range of 180 to 390 F. This fraction, upon analysis, was found to contain .69.parts per million'of nitrogen.

For purposes of comparison, a silica-freecatalyst of cobalt oxide and molybdenum oxide composited with alumina of the type heretofore employedfor denitrogenation and containing 3.1 percent by weight cobalt oxide,

9.3 percent by-weight molybdenum oxide and remainder,

substantially alumina was employed in treatingv the above stock under identical reaction conditions untilthenitrogen content thereof was likewise reduced to 0.043 percent by weight. The product was then distilled to remove a naphtha fraction boiling intheapproximate range of 180 to 390 F. This fraction, upon analysis, was found to contain 160 parts per million ofnitrogen.

It will be 'evident from the comparative data of the above Example 4 that the addition of 15 weight percent;

silica to the cobalt oxide-molybdenum oxide-alumina catalyst results in a marked selective denitrogenationof the .naphtha contained in the total processed product treated to the same total denitrogenationlevely Example 5 to reduce the nitrogen content to 0.06 percent by weight. The product was then distilled to remove a naphtha fraction boiling in the approximate range of 180 to 390 F. This fraction, upon analysis, was found to contain 83 parts per million of nitrogen.

For purposes of comparison, a silica-free catalyst of cobalt oxide, molybdenum oxide composited with alumina of the type described in Example 4 was employed in treating the same stock under identical reaction conditions until the nitrogen content thereof was likewise reduced to 0.06 percentby weight. The product was then distilled as above to remove a naphtha fraction boiling in the approximate range of 180 to 390 F. This fraction, upon analysis, was found to contain 200 parts per million of nitrogen.

The comparative data of the above Example further establishes that the addition of silica to the cobalt oxidernolybdenum oxide-alumina catalyst resulted in a marked selective denitrogeuation of the naphtha contained in the total processed product treated to the same total denitrogenation level.

The selective denitrogenation of naphtha utilizing a catalyst containing, on a weight basis, about 2.5 percent CoO, about 8 percent M00 about 15 percent SiO and about 74.5 percent A1 0 designated as catalyst A as compared with a silica-free catalyst containing, on a weight basis, about 3.1 percent C00, about 9.3 percent M00 and remainder A1 0 designated as catalyst B is shown in the attached figure. The data were obtained by treating a hydrocarbon oil charge of the type and under the conditions described in Example 4 with each of the above catalyst until the nitrogen content of said charge had been reduced to a predetermined extent corresponding to the abscissa of the figure. The product in each instance was then distilled to remove a naphtha fraction boiling in the 180-390 F. range. The fraction obtained in each case was analyzed for nitrogen. The nitrogen content of the naphtha fraction obtained in each instance expressed in parts per million was plotted, as will be seen from the attached figure, against the percent weight nitrogen in the corresponding total liquid product, i.e. the product obtained after treating but before removal therefrom of the above-indicated naphtha fraction. It will be evident from the data of the figure that in every instance a more selective denitrogenation of the naphtha fraction was achieved with catalyst A, i.e. cobalt oxidemolybdenum oxide-alumina composite containing silica than was obtainable with catalyst B, i.e. the silica-free cobalt oxide-molybdenum oxide-alumina composite.

It will be understood that the above description is merely illustrative of preferred embodiments of the invention of which many variations may be made within the scope of the following claims by those skilled in the art without departing from the spirit thereof.

I claim:

1. A process for removing nitrogen from a nitrogencontaining hydrocarbon oil which comprises contacting said oil in the presence of hydrogen with a catalyst consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide and remainder alumina, at a temperature between about 650 F. and about 950 F., a liquid hourly space velocity between about 0.1 and about 10 and a hydrogen partial pressure between about 100 and about 5000 pounds per square inch gauge employing between about 200 and about 10,000 standard cubic feet of hydrogen per barrel of oil.

2. A process for removing nitrogen from a nitrogencontaining hydrocarbon oil which comprises contacting said oil in the presence of hydrogen with a catalyst consisting essentially of to 25 percent by weight of silica, 2 to 4.5 percent by weight cobalt oxide, 7 to 16 percent by weight of molybdenum trioxide and remainder alumina, at a temperature between about 650 F. and about 10 950 F., at a liquid hourly space velocity between about 0.1 and about 10, a hydrogen partial pressure between about and about 5000 pounds per square inch gauge employing between about 200 and about 10,000 standard cubic feet of hydrogen per barrel of oil.

3. A process for effecting selective denitrogenation of the naphtha fraction of a hydrocarbon oil made up of said fraction and components boiling outside the naphtha range which comprises contacting said oil with a catalyst consisting essentially of 15 to 40 percent by weight silica, l to 8 percent by weight cobalt oxide, 3 to 20 percent by weight molybdenum trioxide, and remainder alumina at a temperature between about 650 F. and about 950 F., at a liquid hourly space velocity between about 0.1 and about 10, a hydrogen partial pressure between about 100 and about 5000 pounds per square inch gauge employing between about 200 and about 10,000 standard cubic feet of hydrogen per barrel of oil, and thereafter separating from the treated hydrocarbon oil a naphtha fraction substantially free of nitrogen.

4. A process for effecting selective denitrogenation of the naphtha fraction of a hydrocarbon oil made up of said fraction and components boiling outside the naphtha range which comprises contacting said oil with a catalyst consisting essentially of 15 to 25 percent by weight silica,

2 to 4.5 percent by weight cobalt oxide, 7 to 16 percent by weight molybdenum trioxide and remainder alumina at a temperature between about 650 F. and about 950- F., at a liquid hourly space velocity between about 0.1- and about 10, a hydrogen partial pressure between about 100 and about 5000 pounds per square inch gauge employing between about 200 and a about 10,0000 standard cubic feet of hydrogen per barrel of oil, and thereafter separating from the treated hydrocarbon oil a naphtha fraction substantially free of nitrogen.

5. In a process for reforming a naphtha originally having a nitrogen content in excess of 1 part per million by contacting said naphtha under catalytic reforming conditions with a reforming catalyst adversely affected by the presence of nitrogen, the improvement which comprises treating said naphtha, prior to contact with said reforming catalyst, to reduce the nitrogen content thereof below 1 part per million by contacting with a catalyst consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent by weight cobalt oxide, and 3 to 20 percent by weight molybdenum trioxide and remainder alumina, in the presence of hydrogen at a temperature between about 650 and about 800 F; at a liquid hourly space velocity between about 1 and about 10, a hydrogen partial pressure between about 100 and about 1000 pounds per square inch gauge, employing between about 350 and about 2500 standard cubic feet of hydrogen per barrel of naphtha.

6. In a process for cracking a nitrogen-containing gas oil by contacting said gas oil under catalytic cracking conditions with a cracking catalyst adversely alfected by the presence of nitrogen, the improvement which comprises treating said gas oil prior to contact with said cracking catalyst to reduce the nitrogen content thereof below the minimum which adversely affects said cracking catalyst by contacting with a catalyst consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent by weight cobalt oxide, and 3 to 20 percent by weight molybdenum trioxide and remainder alumina, in the presence of hydrogen at a temperature between about 700 F and about 900 F. at a liquid hourly space velocity between about 0.5 and about 4, a hydrogen partial pressure between about 500 and about 2000 pounds per square inch gauge, employing between about 2500 and about 3500 standard cubic feet of hydrogen per barrel of gas oil.

7. A process for removing nitrogen from a nitrogencontaining hydrocarbon oil which comprises contacting said oil in the presence of hydrogen with a catalyst consisting essentially of 15 to 40 percent by weight silica, 1 to 8 percent-by weightrcobaltroxidqito 20. percent by weight molybdenum trioxide and ;remaiuder alumina, prepared byimpregnating the valumina component with the cobalt oxideand molybdenum trioxide. components, mechanically mixing the resulting impregnatedmroduct with the silica component, t drying and ,calciningthe resulting composite atanelevated temperature, said contacting beingalfected at alemperat-ure between about .650 and. about 9501K, a liquidhourlyepacevelocity between about 0.1 and about 10, a;hydrogen partial pressure-between about 1Q0and about 500,-p'ounds per-square inchgauge, employing betweeniabout 20,0;andrabout10,000standard cubic feet of hydrogen per .barrel of :oil.

. .8. :A-process for removing-nitrogen' fromzanitrogencontaining hydrocarbon -oil which comprises contacting said oil'in the presence of-hydrogenwith-a catalyst consisting essentiallyiof 1510' 40 percent by weight silica, 1 to 8 percent by weight cobalt oxide, '3- to .20 percent'by-weight molybdenum trioxide .aridremainder-alumina prepared by mechanically mixingthe :aluminasand .silica components and impregnating the resulting composite with the cobalt oride and molybdenumtrioxide components, drying and calcining the resulting product at an elevated temperature, said vcontacting being effected -.at a temperature between about 650 and about 950 R, a liquid hourly space velocity betweenabout- 0.1 and about 10, a hydrogen-partial pressure between about 100 and about 5000 pounds per square inch gauge, employing between about 200 and about 10,000 standardicubic feetof hydrogen .per barrel of oil.

ing silica hydrogel with alumina having a surface area greater than 100 square meters per gram, impregnatingthe resulting composite with ;the colablt oxide and molyb- 9. A process for removing nitrogen from a nitrogen- 3 denum I oxide components, I d yin and calcin n he resulting mroduet at an elevated tempe a r said contac ing being xefieeted at a tempera re between ;about .650 and about. 950 ,F., .a liquidrhourly-space velocity between about 0.1 and about 10, a hydrogen ;partial pressure between about and about v5000 -pounds per square inch gauge, employing between about 200 and "about 10,000 standardcubic feetof-hydrogenrperbarrel of oil.

10. A process zfQl removing nitrogen from. a nitrogenconiaining hydrocarbon oil which comprises contacting said oil with a catalyst characterized by a surface area within theapproximaterangeof 2.00 to 450 square meters per gram consisting essentially of v15 to 40 percent by weight silica, .1 to r8 pcrcentaby weight cobalt oxide, and 3 to 20 percent by weight molybdenum.:trioxide, and remainder aluminaprepared byimpregnating alumina having a surface area. greater;- than 1100; square meters ;per 7 gram with the cobalt oxide and ,molybdenum trioxide components, 'mechanicallymixing s-the resulting impregnated product with silicathydrogehdrying and calcining-the re sulting composite at an elevated temperature, saidlcontactingbeing elfectedat :a temperature between about ,650 and about 950 F., 'a liquidzhourly space velocity between about 0.1 and about 10, ahydrogenpartialpressure between about100 and about 500 pounds per square inch gauge, employing between about 200 and about 10,000 standard cubic feet ofbydrogen per barrel of oil.

'ReferenceszCited in the tile of this patent UNITED STATES PATENT S 2,687,381 Hendricks Aug. 24, 1954 2,691,623 .Hartley v Oct. 12, 1954 2,728,710 Hendricks Dec.,27,, 1955 2,760,907 Attane et al .Aug. 28, .1956 2,767,121 Watkins, Oct. 16, 1956 2,790,751 Gerald Apr. 30, 1957 2,799,661 DeRosset -July 16, 1957 72,894,903 McGrath:et a1. July, 14, 1959 2,905,636 Watkins et a1 Sept..22, 1,959 2,921,023 Holrn.., Jan. 12, 1960 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No 3 O04 9 13 00 1961 3133101 531 Tucker the sald Letters Patent should read as corrected below.

Column 2, line 4, for "purposes" read purpose line 56, for "separte" read separate'-; column 4, line 14 for "60" read 6O column 11, line 10, for "500" read 5000 Signed and sealed this 3rd day of April 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

Claims

1. A PROCESS FOR REMOVING NITROGEN FROM A NITROGENCONTAINING HYDROCARBON OIL WHICH COMPRISES CONTACTING SAID OIL IN THE PRESENCE OF HYDROGEN WITH A CATALYST CONSISTING ESSENTIALLY OF 15 TO 40 PERCENT BY WEIGHT SILICA, 1 TO 8 PERCENT BY WEIGHT COBALT OXIDE, 3 TO 20 PERCENT BY WEIGHT MOLYBDENUM TRIOXIDE AND REMAINDER ALUMINA, AT A TEMPERATURE BETWEEN ABOUT 650*F. AND ABOUT 950*F., A LIQUID HOURLY SPACE VELOCITY BETWEEN ABOUT 0.1 AND ABOUT 10 AND A HYDROGEN PARTIAL PRESSURE BETWEEN ABOUT 100 AND ABOUT 5000 POUNDS PER SQUARE INCH GAUGE EMPLOYING BETWEEN ABOUT 200 AND ABOUT 10,000 STANDARD CUBIC FEET OF HYDROGEN PER BARREL OF OIL.