US3026260A

US3026260A - Three-stage hydrocarbon hydrocracking process

Info

Publication number: US3026260A
Application number: US24594A
Authority: US
Inventors: Charles H Watkins
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1960-04-25
Filing date: 1960-04-25
Publication date: 1962-03-20
Anticipated expiration: 1979-03-20
Also published as: OA00529A; NL276096A

Description

March 20, 1962 c. H. WATKINS THREE-STAGE HYDROCARBON HYDROCRACKING PROCESS Filed April 25, 1960 QQQQ I @690 mm SE uev su IN VE/V TOR:

Char/es H. Watkins 4.. a QQQ A T TORNEXS United States Patent 3,026,260 THREE-STAGE HYDROCARBON HYDRO- CRACKING PROCESS Charles H. Watkins, Arlington Heights, 111., assignor to Universal Oil Products Company, Des Plaines, 111., a corporation of Delaware Filed Apr. 25, 1960, Ser. No. 24,594 17 Claims. (Cl. 208-68) The present invention relates to a process for the conversion of hydrocarbonaceous material into lower boiling hydrocarbon products, and, in one embodiment, is directed toward a process for producing hydrocarbons boiling within the gasoline and middle-distillate boiling ranges and substantially free from nitrogenous compounds, from hydrocarbons boiling at a temperature in excess of the middle-distillate boiling range, the latter being contaminated by substantial quantities of nitrogenous compounds.

Hydrocracking, or destructive hydrogenation, as distinguished from the relatively simple addition of hydrogen to unsaturated bonds between carbon atoms, efiects definite changes in the molecular structure of hydrocarbons. Hydrocracking may, therefore, be designated as cracking under hydrogenation conditions in such a manner that the lower-boiling hydrocarbon products resulting therefrom are substantially more saturated than when hydrogen, or material supplying the same, is not present. As presently practiced, hydrocracking processes are most commonly employed for the destructive conversion of various coals, tars and heavy residual oils for the purpose of producing substantial yields of low boiling, saturated products; to some extent, there exists at least partial conversion to intermediates which are suitable for utilization as domestic fuels. In many instances, heavier gas oil fractions, which find utilization as lubricating material, are also produced. Although many of these hydrocracking processes, or destructive hydrogenation reactions, may be, and are, conducted on a strictly thermal basis, either in the absence, or presence, of hydrogen, the preferred processing technique involves the utilization of a catalytic composite possessing a high degree of hydrocracking activity. To assure effective catalytic action over an extended period of time, and from the standpoint of producing an increased yield of liquid product having improved physical aud/or chemical characteristics, controlled or selective cracking is desirable in virtually all hydrocracking processes. For example, the lower molecular weight products, consisting essentially of those hydrocarbons boiling within the normal gasoline boiling 0 range, usually have an increased octane rating, and, as such, are extremely suitable for subsequent utilization in catalytic reforming processes to further increase the octane rating. Similarly, controlled or selective hydrocracking results in an increased yield of middle-distillate boiling range hydrocarbons which are substantially free from high molecular weight unsaturated hydrocarbons.

Selective hydrocracking is of particular importance when processing hydrocarbons, and mixtures of hydrocarbons, having a boiling range in excess of the gasoline and middle-distillate boiling ranges; that is, hydrocarbons and mixtures of hydrocarbons, a well as various hydrocarbon fractions, distillates and gas oils, having a boiling range indicating an initial boiling point of at least about 650 F. or 700 F., and an end boiling point as high as 1000 F., or more. The controlled, or selective hydrocracking of such hydrocarbon fractions results in greater yields of hydrocarbons boiling within the gasoline and middle-distillate boiling range; that is, those hydrocarbons and hydrocabon fractions having a boiling range indicating an end boiling point below about 650 F. to about 700 F. Furthermore, the selective hydrocracking of such 3,926,260 Patented Mar. 20, 1962 heavier hydrocarbon fractions results in a substantially increased yield of gasoline boiling range hydrocarbons; that is, those hydrocarbons and hydrocarbon fractions boiling within the range of from about F. to about 400 F. or 450 F., containing iso and normal butanes, as the particular case warrants. The necessity for hydrocracking selectivity exists in order to avoid the decomposition of normally liquid hydrocarbons substantially or completely into normally gaseous hydrocarbons, the latter being inclusive of methane, ethane and propane. The ultimate volumetric yield of normally liquid hydrocarbons, especially those boiling within the gasoline boiling range, as an inherent result of the excessive production of normally gaseous hydrocarbons, can be decreased to the extent Where the process is not economically feasible. Non-selective hydrocracking is distinguished from controlled or selective hydrocracking in that the latter involves the splitting of a higher-boiling hydrocarbon molecule into two hydrocarbon molecules, both of which are normally liquid hydrocarbons. To a somewhat lesser degree selective hydrocracking involves the controlled removal of methyl, ethyl and propyl groups, which, in the presence of hydrogen, are converted to methane, ethane and propane, the latter being referred to as light parafiinic hydrocarbons. In selective hydrocracking, the removal of the aforesaid radicals is controlled such that not more than one, or possibly two of such radicals are removed from a given molecule. For example, in the presence of hydrogen, and under selective hydrocracking conditions, normal decane may be reduced to two pentane molecules, normal heptane reduced to hexane, and nonane reduced to octane or heptane, etc. Conversely, uncontrolled or non-selective hydrocracking, will result in the decomposition of normally liquid hydrocarbons into the aforesaid normally gaseous hydrocarbons; for example, through the continuous demethylation of normal heptane to produce seven methyl groups which, in the presence of hydrogen, are converted to seven molecules of methane. Thus, hydrocracking reactions which are permitted to run rampant can be seen to effect seriously the economic considerations of a given process.

Another disadvantage of non-selective or uncontrolled hydrocracking is that such hydrocracking results in a more rapid formation of increased quantities of coke and other heavy carbonaceous material which becomes deposited upon the catalytic composite employed, and decreases, or even destroys, the activity thereof to catalyze the desired reactions in the desired manner. Such deactivation inherently results in a shorter processing cycle or period, with the attendant necessity of more frequent regeneration of the catalyst, or total replacement thereof with fresh catalyst. Gf further significance, in regard to the hydrocracking reaction, especially the economic considerations thereof, are the aspects of hydrogen production and consumption, the preservation of aromatic compounds which boil within the gasoline boiling range, and the production of a liquid product substantially free from low molecular weight, unsaturated hydrocarbons. The deactivation of the catalyst, through the deposition of coke and other heavy carbonaceous material, or other means, appears to inhibit the hydrogenation activity to the extent that a significant proportion of the gasoline boiling range hydrocarbons consists of unsaturated parafa'ins whereby the same is not highly suitable for subsequent direct processing by catalytic reforming. On the other hand, selective hydrocracking does not tend to effect substantial hydrogenation, or saturation, of the aromatic compounds boiling within the gasoline boiling range, or the destructive hydrogenation of low molecular weight, straight or branched-chain hydrocarbons into normally gaseous hydrocarbons. Aromatic hydrocarbons, boiling within the gasoline boiling range, possess a relatively high octane blending value, and are, therefore, utilized to great advantage in increasing the anti-knock characteristics of a given gasoline boiling range traction. In addition, selective hydrocracking, although inhibiting the saturation of aromatic compounds, does not necessarily result in the production of an excessive quantity of the lower molecular weight, unsaturated paratfinic hydrocarbons.

Investigations have indicated that the relatively rapid deactivation of a hydrocracking catalytic composite results from the presence of nitrogen-containing compounds within the hydrocracking charge stock. These nitrogenous compounds, such as naturally-occurring, organic nitrogenous compounds, examples of which include pyrroles, amines, indoles, and other classifications of organic compounds, result in the deactivation of the catalytically active metallic components, as well as the refractory inorganic oxide carrier material which acts as the acidic component of a great variety of hydrocracking catalysts. Such deactivation appears to result through the reaction of the nitrogenous compounds with the various catalytic components, the extent of such deactivation steadily increasing as the process continues, and as the nitrogencontaining feed stock continues to contaminate the catalyst through contact therewith. It is believed that neutraiization, occurring when the basicity of the nitrogenous compound reacts with the acidic catalyst, resulting in a neutralization of the latter, is a factor to be considered in the deactivation of the catalyst, but is not the predominating deactivating influence. The more predominating efiect, having the greatest influence in regard to catalyst deactivation, is believed to be the formation of a nitrogen-containing complex, through inter-reaction with the catalytically active metallic components, whereby the active centers of the catalyst, normally available to the hydrocarbon charge stock, are effectively shielded therefrom. Deactivation of this nature is not believed to be a simple reversible phenomenon which may be easily rectified by merely heating the catalyst in the presence of hydrogen for the purpose of decomposing the nitrogen-containing complexes.

The primary object of the present invention is to provide a hydrocracking process which produces substantially greater yields of hydrocarbons boiling within the gasoline and middle-distillate boiling ranges, without the attendant saturation of aromatic compounds and the uncontrolled cracking of the low molecular weight hydrocarbons. A related object is to provide a process which permits the utilization of petroleum hydrocarbon charge stocks having an initial boiling point as high as about 700 to about 800 F. or more, which charge stocks contain residual nitrogenous compounds in excessive quantities of the order of about 1000 ppm. to about 5000 p.p.rn., such concentrations otherwise resulting in the rapid deactivation of the catalytic composite employed.

In one embodiment, the present invention relates to a process for converting hydrocarbonaceous material, having a boiling range in excess of the gasoline boiling range, into lower boiling hydrocarbon products which comprises cracking said hydrocarbonaceous material in a first reaction zone, separating the resultant efliuent into a light fraction and a heavy fraction containing hydrocarbons having an initial boiling point in excess of a temperature of about 800 F.; reacting said light fraction with hydrogen in a second reaction zone, passing at least a portion of the effluent therefrom, along with additional hydrogen, into a third reaction zone maintained at hydrocracking conditions; separating the resultant normally liquid hydrocarbons into a first fraction having an end boiling point of about 400 F. to about 450 F., a second fraction having an end boiling point of about 650 F. to about 700 F., and a third fraction boiling at a temperature in excess of about 650 F. to about 700 F., and recycling at least a portion of said third fraction to combine with the efiiuent from said second reaction zone and hydrogen, prior to conversion thereof in said third reaction zone.

The present invention is directed toward a three-stage process for converting hydrocarbonaceous material having a boiling range of from about 700 F. to about 1000 F., and containing nitrogenous compounds, into lower boiling hydrocarbon products, which process comprises initially fractionating said hydrocarbonaceous material to produce a first light fraction containing those hydrocarbons boiling below about 800 F. and a first heavy fraction having an initial boiling point of about 800 F., cracking said first heavy fraction in a first reaction zone containing a catalyst comprising at least one metallic component selected from the metals of groups VIA and the iron-group of the periodic table, and mixtures thereof, separating the resultant efi'luent into a second light fraction and a second heavy fraction, the latter having an initial boiling point of about 800 F., recycling said second heavy fraction to combine with said first heavy fraction prior to conversion in said first reaction zone, and combining said second light fraction with said first light fraction; reacting the resultant light fraction mixture in a second reaction zone and in contact with a catalyst comprising from about 4% to about 45% by weight of molybdenum, removing ammonia and normally gaseou hydrocarbons from the resultant second zone eflluent, and passing the normally liquid hydrocarbons, along with additional hydrogen, into a third reaction zone maintained at hydrocracking conditions; removing normally gaseous hydrocarbons from the third reaction zone efiluent and separating the normally liquid hydrocarbons into a first fraction having an end boiling point of about 400 F. to about 450 F., a second fraction having an initial boiling point of about 400 F. to about 450 F. and an end boiling point of about 650 F. to about 700 F., and a third fraction boiling at a temperature in excess of about 650 F. to about 700 F., recycling at least a portion of said third fraction to combine with said hydrogen and the normally liquid hydrocarbons from said second reaction zone, prior to conversion thereof in said third reaction zone.

A more specific embodiment of the present invention involves a process for converting nitrogen-contaminated hydrocarbonaceous material, having a boiling range of from about 700 F. to about 1000 E, into lower boiling hydrocarbon products substantially free from nitrogenous compounds, which process comprises initially stabilizing said hydrocarbonaceous material to produce a first light fraction containing those hydrocarbons boiling below about 800 F., and a first heavy fraction having an initial boiling point of about 800 F.; cracking said first heavy fraction in a first reaction zone containing a cracking catalyst comprising at least one metallic component from the metals of groups VIA and the irongroup of the periodic table, and mixtures thereof, separating the resultant efiiuent into a second light fraction and a second heavy fraction containing hydrocarbons boiling in excess of a temperature of about 800 F., recycling the second heavy fraction to combine with said first heavy fraction prior to the conversion thereof in said first reaction zone, and combining said second light fraction with said first light fraction; reacting the resulting light fraction mixture with hydrogen in a second reaction zone containing a catalyst comprising from about 4% to about 45 by weight of molybdenum, removing ammonia and normally gaseous hydrocarbons from the resultant second zone efiluent, and passing the normally liquid hydrocarbons, along with additional hydrogen, into a third reaction zone maintained at hydrocracking conditions and containing a catalyst comprising from about 0.01% to about 5.0% by weight of palladium composited with silica and from about 10% to about by weight of alumina; removing normally gaseous hydrocarbons from the resultant third zone eifiuent and separating the normally liquid hydrocarbons into a first fraction having an end boiling point of about 400 F. to about 450 F., a second fraction having an initial boiling point of about 400 F. to about 450 F., and an end boiling point of about 650 F., to about 700 F., and a third fraction boiling at a temperature in excess of about 650 F. to about 700 F., recycling at least a portion of said third fraction to combine with the normally liquid hydrocarbons from said second reaction Zone and hydrogen, prior to conversion thereof in said third reaction zone.

The three-stage process of the present invention may be more clearly illustrated and understood by initially defining several of the terms and phrases as employed Within the present specification and the appended claims. The term, hydrocarbons, or hydrocarbonaceou material, is intended to connote saturated hydrocarbons, straightchain and branched-chain hydrocarbons, unsaturated hydrocarbons, aromatic and naphthenic hydrocarbons, as well as mixtures of various hydrocarbons such as hydrocarbon fractions and/ or hydrocarbon distillates, etc. The phrase, hydrocarbons boiling Within the gasoline boiling range, or gasoline boiling range hydrocarbons, is intended to connote those hydrocarbons boiling at a temperature of from about 100 F. to about 400 F. or 450 F.; that is, hydrocarbon fractions having an initial boiling points (as determined by Standard ASTM distillation methods) of about 100 F., and an end boiling point within the range of about 400 F. to about 450 F. Gasoline boiling range hydrocarbons i intended to include hydrocarbon mixtures having the aforesaid boiling range, and inclusive of iso and normal butanes. The term, light parafiinic hydrocarbons, is intended to con- .note those hydrocarbons containing three or less carbon atoms; that is, methane, ethane and propane. Therefore, hydrocarbons boiling at a temperature in excess of the gasoline boiling range is intended to connote those hydrocarbons and mixtures of hydrocarbons which possess an initial boiling point in excess of about 400 F. to about 450 F. The term, middle-distillate, or light gas oil, refers to those hydrocarbon fractions having an initial boiling point within the range of about 400 F. to about 450 F. and an end boiling point within the range of about 650 F. to about 700 F. Similarly, in regard to the various catalytic composites employed within the three individual reaction zones of the present process, and in one embodiment in two of the three reaction zones, the term, metallic component, or catalytically active metallic component," is intended to encompass those components which are employed for their hydrocracking activity, or for their propensity for the destructive removal of nitrogenous compounds, as the case may be. In this manner, the catalytically active metallic components are distinguished from those components which are employed as the solid support, or carrier material, or the acidic cracking component. As hereinafter set forth in greater detail, the process of the present invention consists of three integrated, but separate, stages. Each stage utilizes a distinct catalytic composite, difierent, in most applications of the present invention, from the catalytic composites employed in the other stages. The various catalytic composites will hereinafter be described in detail with reference to the particular stage in which employed, and also in regard to the function to be served.

The particular catalytically active metallic component, or components, regardless of the stage in which employed, are composited with a suitable, solid carrier material, which may be either naturally-occurring, or syntheticallyprepared. Naturally-occurring carrier materials, include various aluminum silicates, particularly when acid-treated to increase the activity thereof, various alumina-containing clays, earths, sand, and the like; synthetically-prepared carrier material generally includes at least a portion of both silica and alumina. Other suitable carrier material components which may, in particular instances, be combined in an integral portion of the synthetically-prepared carrier material, are zirconia, magnesia, thoria, boria, titania, etc. The preferred hydrocracking catalyst component, for use in the third stage, comprises a composite of silica and from about 10% to about 90% by weight of alumina, and still more preferably, a composite of silica and from about 25% to about by weight of alumina. As hereinabove stated, the process of the present invention involves the utilization of three separate, distinct reaction zones, each of which contains a catalyst Whose composition depends, at least in part, upon the function to be served within such reaction zone, and, therefore, these catalytic composites will hereinafter be described in greater detail.

As hereinbefore set forth, one embodiment of the present invention involves a process for producing hydrocarbons which boil within the gasoline and middle-distillate boiling range, from those hydrocarbons which boil at a temperature in excess of the middle-distillate boiling range. The three-stage process of the present invention encompasses at least one hydrocracking reaction zone, which, in and of itself, has been considered generally applicable to processing petroleum-derived feed stocks of the middle-distillate boiling range and above. Suitable charge stocks to hydrocracking processes are considered to include kerosine fractions, gas oil fractions, lubricating oil and white oil stocks, cycle stocks, fuel oil stocks, reduced crudes, the various high-boiling bottom recovered from the fractionating columns generally integrated within catalytic cracking operations, and referred to as heavy recycle stock, and other sources of hydrocarbons having a depreciated market demand due to the high boiling points of these hydrocarbons, accompanied by the usual presence of asphaltic and other heavy hydrocarbonaceous residues. The present invention is particularly directed toward processing the heavier of the aforementioned hydrocarbon feed stocks, namely, vacuum gas oil fractions, white oil stocks, heavy cycle stocks, fuel oil stocks, reduced crudes etc.; that is, those heavy hydrocarbons having an initial boiling point of at least about 650 F. to about 700 F. and an end boiling point of about 1000 F. or more. Generally, all of these sources of hydrocarbon feed stocks contain high-boiling nitrogenous compounds and sulfurous compounds as contaminants. Although the major proportion of such nitrogenous compounds may be removed by many known means, such as a hydrorefining pretreatment, it is very difiicult, if not virtually impossible, to remove the last few parts per million of nitrogen from the charge stock prior to subjecting the same to the hydrocracking process. For example, a hydrorefining pretreatment, in which the feed stock is subjected to the action of a catalyst, at reaction conditions, will result in the conversion of the nitrogenous, organically-bound components into ammonia and the corresponding hydrocarbon residue. Although the structure of the hydrocarbon components are not substantially altered, the resulting hydrocarbon charge stock will, in all probability, contain a relatively minor amount of nitrogenous compounds, as compared to the excessive quantity originally present. Notwithstanding such quantities, these organic nitrogen compounds will eventually result in the deactivation of hydrocracking catalyst, and particularly catalysts consisting of metals from groups VI and VIII of the periodic table. For example, I have found that a catalyst comprising at least one platinum-group metallic component, impregnated upon a silica-alumina carrier material, is a very effective catalyst for the hydrocracking of gas oils boiling below about 800 F. However, these catalysts are virtually immediately poisoned by either sulfurous or nitrogenous compounds, and particularly by the latter. The contaminants, and particularly organically-bound nitrogenous compounds, are very diflicult, if not impossible, to remove from hydrocarbon fractions boiling above about 800 F., whereas virtually complete removal may be effected from hydrocarbons boiling below about 800 F.

Through the utilization of the threestage process of the present invention, particularly when processing hydrocarbon charge stocks boiling above about 700 F, to about 1000 F. or more, it is possible to produce high volumetric yields of gasoline boiling range hydrocarbons while simultaneously maximizing the yield of middledistillate hydrocarbons which are substantially free from nitrogenous compounds. A substantial increase in the overall yield of gasoline boiling range hydrocarbons may then be obtained by further processing nitrogen-free, middle-distillate material simultaneously produced by the present process. The flexibility of the present process permits the withdrawal to storage of the middle-distillate hydrocarbon product for subsequent conversion to gasoline boiling range hydrocarbons when the marketability of the latter so requires.

The present three-stage process may be more clearly understood through reference to the accompanying drawing which illustrates one embodiment thereof. It is not intended, however, to unduly limit the present process to the particular embodiments indicated in the drawing. Various flow valves, control valves, coolers, condensers, overhead reflux condensers, pumps, compressors, heaters, knockout pots, etc., have been eliminated, or greatly reduced, as not being essential to the complete understanding of the present process. The utilization of these, and other miscellaneous appurtenances will immediately be recognized by one possessing skill in the art of petroleum processing; it is not intended that such modifications remove the process beyond the scope and spirit of the appended claims. Referring now to the drawing, the hydrocarbon change stock, contaminated by a substantial quantity of nitrogenous compounds, of the order of about 1000 p.p.m. to about 5000 p.p.m., and sulfurous compounds as high as about 3.0% to about 5.0% by weight, enters the process through line 1 into stabilizer 2. To illustrate a particularly preferred embodiment of the present invention, the charge stock in line 1 is indicated as having an initial boiling point of about 700 F. and an end boiling point of about 1000 F., as determined by standard ASTM distillation. However, it is understood that the charge stock may be any of the heavy hydrocarbonaceous material previously described; for exampie, a reduced crude consisting entirely of hydrocarbons boiling at a temperature in excess of 800 F. to 1000 F. or more. The total liquid charge stock entering stabilizer '2 is separated into a first light fraction having an end boiling point of about 800 F., shown as leaving stabilizer 2 via line 3, and a first heavy fraction having an initial boiling point of about 800 F., indicated as leaving sta- I bilizer 2 via line 4. This first heavy fraction is combined with a second heavy fraction, containing hydrocarbons boiling in excess of about 800 F., the mixture being passed through heater 6 and line 8 into cracking zone 9. The primary function, to be served by cracking zone 9, is the conversion of those hydrocarbons boiling in excess of a temperature of 800 F. into lower boiling hydrocarbon products which boil below about 800 F. Thus, cracking zone 9 may be a common thermal-cracking reaction zone of the single-coil or double-coil type, in which instance the total liquid charge thereto is raised to the desired thermal cracking temperature in heater 6, prior to entering cracking zone 9 through line 8. In another embodiment, cracking zone 9 may comprise a catalytic hydrocracking unit, in which event the total liquid charge in line 4 is admixed with the requisite quantity of hydrogen entering via line 5, the mixture being raised to the operating temperature in heater 6, passing through line 8 into cracking zone 9. In this latter instance, cracking zone 9 will contain a suitable hydrocracking catalyst which may be an iron-group metallic component composited with a siliceous carrier material such as alumina and silica. Or, the hydrocracking catalyst may comprise an iron-group metallic component promoted by a Group VIA metal such as molybdenum, chromium and/ or tungsten. The first reaction zone, cracking zone 9, may be, in particular processing schemes, a fluid catalytic cracking unit operating in the absence of added hydrogen. It is understood that the precise conversion means, illustrated in the drawing as cracking zone 9, by which those hydrocarbons boiling at a temperature in excess of about 800 F, are converted to hydrocarbons boiling below about 800 F., is not considered to be a limiting feature of the present invention. 1 have found that the nitrogenous compounds, contaminating the hydrocarbon charge stock entering line 1, are extremely diflicult to remove from the heavier hydrocarbons, that is, those hydrocarbons boiling in excess of 800 F whereas these nitrogenous compounds are readily susceptible to removal from those hydrocarbons boiling below about 800 F., especially through the utilization of a particular catalytic composite as hereinafter set forth. In any event, the total effluent from cracking zone 9 passes through line 10 into separator 11 from which the normally liquid hydrocarbons are removed via line 13 into fractionator 14.

Separator 11 serves to remove light parafiinic hydrocarbons, such as methahe, ethane and propane, and other various gaseous components from the total effiuent entering through line 10, providing thereby a normally liquid hydrocarbon stream in line 13. The light parafiinic hy drocarbons are indicated as leaving separator 11 via line 12. Other gaseous components are removed from the normally liquid hydrocarbons in separator 11, and include carbon monoxide, carbon dioxide, hydrogen sulfide, ammonia, sulfur dioxide, and various oxides of nitrogen. Various modifications may be made to the separating means illustrated by separator 11, whereby the overall flow pattern therein is changed, but the function to be served, as well as the end result, remains the same. For example, the total gaseous phase, illustrated as leaving via line 12, may be passed through a suitable absorbent material, whereby the light paraffinic hydrocarbons are recovered substantially free from hydrogen sulfide, ammonia, carbon dioxide, and the various oxides of nitrogen and sulfur. Similarly, water may be injected into line 10, the mixture entering a suitable liquid-liquid separating zone whereby the ammonia is adsorbed in, and removed with the water phase, the light parafiinic hydrocarbons and other gaseous components being removed as indicated by line 12, and the normally liquid hydrocarbons removed via line 13. Various other modifications, in regard to the separating means illustrated by separator 11, as well as those separating means hereinafter described, and illustrated by separators 21 and 30, will be immediately recognized by those possessing skill in the art of petroleum processing. It is not intended that these modifications, and those above set forth, remove the resulting flow from within the broad scope of the present invention. As illustrated, one of the essential features of the present invention is the initial preparation of a stream of normally liquid hydrocarbons boiling below about 800 F and which pass through line 13 into fractionator 14. Fractionator 14 is maintained under suitable operating conditions, of temperature and pressure, such that the normally liquid hydrocarbons entering via line 13 are separated into a second heavy fraction, containing those unreacted hydrocarbons boiling at a temperature in excess of 800 F. and a second light fraction containing those hydrocarbons having an end boiling point of about 800 F. The second heavy fraction is removed from fractionator 14 via line 7 and is combined With the first heavy fraction in line 4 leaving stabilizer 2. The second light fraction is removed from fractionator 14 via line 15, and is admixed with the first light fraction leaving stabilizer 2 in line 3. The resulting light fraction mixture is admixed with hydrogen, entering the system via line 16, and the total charge is raised to the desired operating temperature, within the range of about 500 F. to about 1000 F., in heater 17. The heated mixture of hydrogen and the light fractions from stabilizer 2 and fractionator 14 are passed via line 18 into clean-up reaction zone 19. Clean-up zone 19 has disposed therein a catalytic composite comprising from about 4% to about 45% by weight of molybdenum, calculated as the element. The reaction zone is maintained under operating conditions such that the substantially complete destruction of the nitrogenous compounds, as well as the sulfurous compounds, contained within the charge stock, the latter now consisting essentially of hydrocarbons boiling below about a temperature of 800 F., is effected. In addition, as hereinafter set forth, through the careful selection of both catalyst and operating conditions, there will be efiected, in clean-up zone 19, a substantial degree of hydrocarbon conversion whereby the heavier hydrocarbons, those boiling within the range of from about 650 F. to 800 F., are converted into hydrocarbons boiling below about 650 F., without experiencing the excessive production of light .paraifinic hydrocarbons, methane, ethane and propane. Furthermore, since the catalyst in clean-up zone 19 is selected for its nitrogeninsensitivity, the rapid deactivation of the catalyst, otherwise resulting when hydrocracking such nitrogen-containing charge stocks, is not experienced. The total eflluent from reaction zone 19 is passed via line 20 into separator 21. As previously described With reference to separator 11, separator 21 is employed to illustrate a separating means whereby the normally liquid hydrocarbons are recovered in line 23 substantially completely free from light parafiinic hydrocarbons and other gaseous material, indicated as leaving separator 21 through line 22. In addition, as a result of the catalyst and operating conditions of clean-up zone 19, substantial quantities of hydrogen sulfide and ammonia are removed in separator 21. The normally liquid hydrocarbons in line 23 enter line 24, are admixed with hydrogen entering the system via line 25, the entire mixture passing into heater 26, and thereafter through line 27 into hydrocra'cking zone 28. The total charge to hydrocracking zone 28 will be raised to a temperature, in heater 26, within the range of about 450 F. to about 950 F; that is, the operating temperature of hydrocracking zone 28 will be at least about 50 F. lower than the operating temperature of clean-up zone 19. The total effluent, including butanes, normally liquid hydrocarbons boiling within the range of from about 100 F. to about 800 F., carbon monoxide, carbon dioxide, light parafiinic hydrocarbons, etc., are passed through line 29 into separator 30. The normally liquid hydrocarbons, including butanes, are removed from separator 30" via line 32, and passed to side-cut fractionator 33 at a point below centerwell 34. The light paraflinic hydrocarbons entering separator 30 are removed via line 31, and, as hereinbefore described, various other gaseous components are removed therefrom, such that only normally liquid hydrocarbons, but including butanes, are passed into side-cut fractionator 33.

Fractionator 33 is maintained at suitable conditions of temperature and pressure whereby the butanes and normally liquid hydrocarbons having an initial boiling point of about 100 F. and an end boiling point of about 400 F., and containing less than about 0.1 'p.p.m. of nitrogen, are removed via line 36. A second fraction, containing less than about 3.0 ppm. of nitrogen, is removed from a point above centerwell 34, via line 35. This second fraction contains those hydrocarbons boiling within the middle-distillate boiling range, that is, having an initial boiling point of about 400 F. and an end boiling point of about 650 F. A third fraction, containing those unreacted hydrocarbons boiling within the range of from about 650 F. to about 800 F., are passed through line 24, combined, at least in part, Withth'e total normally liquid hydrocarbon effluent in line 23, further admixed with hydrogen in line 25, and recycled to the system through heater 26 and line 27 into hydrocracking zone 28.

From the foregoing description of the embodiment illustrated in the accompanying drawing, it is readily ascertained that the process is, in effect, a three-stage process for producing hydrocarbons boiling within the gasoline boiling range, and simultaneously for producing increased yields of middleistillate boiling range hydrocarbons, the latter being extremely suitable for direct processing to produce additional gasoline boiling range hydrocarbons. Various modifications may be made to the illustrated embodiment by those possessing skill within the art of petroleum processing, and it is not intended that such modifications remove the process from the scope and spirit of the appended claims. For example, as hereinabove stated in regard to separators 11, 21 and 30, changes may be made whereby a somewhat difierent flow pattern and apparatus setup results. It is evident, however, that such a flow pattern will merely accomplish the same object resulting from the flow pattern illustrated within the drawing. An essential feature of the process of the present invention involves the threestage reaction zone system, whereby each stage individually performs a particular function in a particular manner, the combinative effect being the production of gasoline and middle-distillate boiling range hydrocarbons from those hydrocarbons boiling in excess of a temperature of about 700 F., the latter contaminated by substantial quantities of nitrogenous compounds of the order of about 1000 ppm. to about 5000 ppm.

As hereinbefore set forth, the process of the present invention is particularly directed to the processing of hydrocarbons and mixtures of hydrocarbons boiling at temperatures in excess of the "gasoline boiling range. However, it is most advantageously applied to petroleumderived feed stocks, particularly those stocks commonly considered as being heavier than middle-distillate fractions. Such charge stocks include gas oil fractions, heavy vacuum gas oils, reduced cr'udes, lubricating oils, and white oil stocks, as well as high-boiling bottoms recovered from various catalytic cracking operations. Therefore, although the charge stock to the present three stage process may have an initial boiling point of about 400 F. to about 450 F., and an end boiling point of about 1000 F. or higher, the process affords additional benefits, and is particularly directed toward the processing of hydrocarbon charge stocks having significantly higher initial boiling points, that is, of the order of at least about 650 F. to about 700 F. In further describing the process of the present invention, and the various limitations imposed thereupon, the process will be divided, in the interest of simplicity, into its three separate, distinctly individual stages.

Essentially, the first stage comprises a stabilizing column, heater and reaction zone, suitable liquid-gas separating means, and a fractionator,'the latter employed for the purpose of separating the total normally liquid product efiluent into a light fraction having an end boiling point of about 800 F., and a heavy fraction having an initial boiling point of about 800 F. The various components of the first stage are utilized in such a manner, and under such conditions as to result in the substantially complete conversion of the charge stock into hydrocarbons boiling below 800 F. Although at least a portion of the charge stock is converted, in this first stage, to hydrocarbons boiling Within the gasoline boiling range, the greater proportion of the charge stock will be converted to hydrocarbons boiling within the range of from about 400 F. or 450 F. to about 800 F., the lighter fractions serving as the charge stock to the second stage of the entire process. Briefly, therefore, the heavy hydrocarbon charge stock, for example, a heavy vacuum gas oil having a boiling range of from about 700 F. to about 1000 F., or higher, and contaminated by nitrogenous compounds of the order of from about 1000 ppm.

'to about 5000 p.p.n1., and sulfurous compounds as high as about 3.0% to about 5.0% by weight, is introduced into a stabilizing column for the purpose of removing those hydrocarbons having an end boiling point of about 800 F. The remainder of the vacuum gas oil charge is admixed with hydrogen in an amount of from about 3000 to about 10,000 standard cubic feet per barrel of such hydrocarbon charge, in those instances wherein the first-stage of the process comprises a hydrocracking reaction zone. As hereinbefore set forth, the reaction zone comprising this first stage may be a thermal-cracking unit of the single-coil or double-coil type. It is preferred, however, in order to avoid the unnecessary, excessive production of light parafiinic hydrocarbons, normally resulting from a thermal cracking unit, or fluid catalytic cracking unit, to employ catalytic hydrocracking within the first stage of the process. In the latter instance, the mixture of hydrogen and those hydrocarbons boiling above about 800 F., is heated to the desired operating temperature, of from about 500 F. to about 1500 F., and thereafter passed into the first reaction zone. The reaction zone will be maintained under an imposed pressure within the range of from about pounds to about 3000 pounds per square inch, and at a temperature within the aforesaid range; the precise operating conditions will be dependent upon the various physical and/ or chemical characteristics of the particular heavy hydrocarbon charge being processed, and upon the type of cracking unit employed. Higher pressures appear to favor the destructive conversion of those hydrocarbons boiling in excess of about 800 F., and are, therefore, preferred; thus, the first reaction zone will preferably operate under an imposed pressure within the range of about 100 to about 3000 pounds per square inch. When utilized as a hydrocracking zone, as distinguished from a simple thermalcracking zone, the first reaction zone will contain a hydrocracking catalyst comprising at least one metallic component from the metals of groups VIA and the iron-group of the periodic table, and mixtures thereof. Thus, the catalyst will comprise one or more of the following: chromium, molybdenum, tungsten, iron, cobalt, and nickel. Regardless of the component, or components, they are composited with a suitable carrier material, and preferably one which contains substantial quantities of silica. Thus, the hydrocracking catalyst employed in the first reaction zone may comprise from about to about 50% by weight of nickel, and a composite of alumina and from about 65% to about 95% by weight of silica. Lesser quantities of the group VIA metallic components will be employed, and will lie within the range of from about 2.0% to about 20.0% by weight thereof. In any event, the hydrocarbon charge stock will contact the particular catalyst employed at a liquid hourly space velocity within the range of from about 0.3 to about 10.0; a relatively lower range of liquid hourly space velocity is preferred, that is, from about 0.3 to about 3.0. Although the first reaction zone is designed to serve a single function, that of converting those hydrocarbons boiling above about 800 F. into hydrocarbons boiling below about 800 F., there will be effected at least partial removal of the sulfurous and nitrogenous compounds. The resulting ammonia and hydrogen sulfide, in addition to light parafiinic hydrocarbons, carbon monoxide and carbon dioxide, and the normally liquid hydrocarbons including butanes, are passed into a suitable separating means whereby the bu-tanes and normally liquid hydrocarbons are recovered substantially free from the light parafiinic hydrocarbons and the aforementioned gaseous products. The normally liquid hydrocarbons are then subjected to fractionation to provide a light fraction comprising the material boiling below about 800 F., which light fraction is combined with the initial light fraction from the initial stabilizing procedure, thereby forming the charge to the second stage of the process. Those hydrocarbons which boil above a temperature of about 800 F. are recycled to combine with the heavy fraction from the 12 initial stabilizing step, thereby forming the total liquid charge to this first reaction zone.

Similarly, the second-stage of the present process comprises at least a heater, reaction zone, and separating means similar to that described in regard to the first stage of the process. The total liquid charge to the second stage of the process, now consisting essentially of hydrocarbons boiling below a temperature of about 800 F., is admixed with hydrogen in an amount of from about 1000 to about 8000 Standard cubic feet per barrel. The mixture of hydrogen and liquid hydrocarbons is raised to a temperature of from about 500 F. to about 1000 R, and passed into the second reaction zone, maintained under an imposed pressure of about 300 to about 3000 pounds per square inch, the catalyst in which second reaction zone serves a particular dual function. The liquid charge rate is equivalent to a liquid hourly space velocity of about 0.1 to about 10.0. Thas is, the catalyst is nonsensitive to the presence of substantial quantities of both nitrogenous compounds and sulfurous compounds, while effecting the destructive removal thereof, and also effects a significant degree of conversion of those hydrocarbons boiling at a temperature in excess of about 650 F. into those hydrocarbons boiling within the gasoline and middle-distillate boiling ranges. I have found that a catalyst comprising relatively large quantities of molybdenum, calculated as the element, and composited with a suitable carrier material such as alumina, is particularly eflicient in carrying out the desired dual operation of the second reaction zone. A particularly preferred catalytic composite, for utilization in this first reaction zone, comprises from about 4.0% to about 45.0% by weight of molybdenum, and utilizes alumina as the sole refractory inorganic oxide within the carrier material. It is preferred to utilize alumina in the absence of other refractory inorganic oxides, such as silica, zirconia, magnesia, titania, thoria, boria, etc. Although these refractory inorganic oxides may be employed in relatively minor quantities, with respect to the amount of alumina, they appear to impart additional cracking activity to the catalyst Within the second reaction zone, such that those hydrocarbons boiling in excess of about 650 F. are subjected to non-selective cracking whereby excessive quantities of light paraffinic hydrocarbons are produced therefrom. In addition to the aforementioned major proportion of molybdenum, minor quantities of nickel, iron and/or cobalt, from about 0.2% to about 6.0% may be employed. The precise composition of the catalytic composite employed in the second reaction zone will, of course, depend to a great extent upon the physical and chemical characteristics of the liquid charge therethrough.

The gaseous ammonia and hydrogen sulfide, resulting from the destructive removal of nitrogenous and sulfurous compound-s within the second reaction zone, are removed from the total efliuent in any suitable manner. For example, the total effluent may be admixed with Water, and thereafter subjected to separation such that the ammonia is adsorbed within the water-phase. Or, the total reaction zone efiluent may be passed into a separation zone, countercurrently to a liquid adsorbent, whereby the ammonia, hydrogen sulfide, and other gaseous components are efiectively completely removed therefrom. In addition to the removal of hydrogen sulfide and ammonia, it is desired that the few light parafiinic hydrocarbons, methane, ethane, and propane, resulting from the hydrocarbon conversion within the second reaction zone, are also removed from the total eflluent therefrom. Therefore, the separating zone may comprise a low-temperature flash chamber whereby the ammonia, hydrogen sulfide and light parafinic hydrocarbons are removed as a gas phase. In any event, the normally liquid hydrocarbons, which may or may not include butanes, substantially completely free from nitrogenous compounds, are utilized as the liquid charge to the third stage of the present process.

The third stage of the present process is designed to convert the now nitrogen and sulfur free hydrocarbons boiling within the range of from about 650 F. to about 800 F., into hydrocarbons boiling within the gasoline and middle-distillate boiling ranges. The charge to the third stage, being the total normally liquid hydrocarbons, including butanes, discharging from the second-stage separating means, is admixed with hydrogen in an amount of from about 1000 to about 6000 standard cubic feet per barrel of total liquid charge. The quantity of hydrogen, employed within the third reaction zone, may be less than that required in either of the two preceding zones. This is due to the physical and chemical characteristics of the charge stock, whereby such charge stock readily lends itself to comparatively mild hydrocracking conditions within the third stage of the process. Therefore, although the third stage may operate acceptably at an imposed pressure within the range of from about 1000 to about 3000 pounds per square inch, excellent results may be achieved through the utilization of lower pressures, within the range of from about 500 to about 1500 pounds per square inch. Similarly, the temperature at which the third reaction zone is maintained, may be significantly less than the temperature in either of the two preceding zones. For example, as hereinbefore stated, the second reaction zone is maintained at a temperature within the range of about 500 to about 1000 F. The third reaction zone operates at a temperature at least about 50 F. lower than the aforesaid range; it is not uncommon, in the process of the present invention, to permit the third reaction zone to operate at a temperature level as much as 100 F. to 200 F. lower than that in the second reaction zone. Thus, the third reaction zone may be maintained under the relatively mild hydrocracking conditions of from about 400 F. to about 800 F. Similarly, the liquid hourly space velocity through the third reaction zone may be significantly higher, within the range of from about 1.0 to about 10.0.

The catalyst employed within the third reaction zone compri es at least one metallic component selected from the metals of groups VIA and VHI of the periodic table. The metallic component of the catalyst utilized within the third stage of the present process may comprise mixtures of two or more of such metals. Thus, the catalyst employed in the third reaction zone may consist of chromium, molybdenum, tungsten, iron, cobalt, nickel, palladium, platinum, ruthenium, rhodium, osmium, iridium, and mixtures of two or more including nickel-molybdenum, nickel-chromium, molybdenum-platinum, cobaltnickel-molybdenum, molybdenum-palladium, chromiumplatinum, chromium-palladium, molybdenum-nickel-palladium, etc. The active metallic components are generally employed in an amount of from about 0.01% to about 20.0% by weight of the total catalyst. In those instances Where the hydrocracking catalytic composite in the third reaction zone comprises both a group VIII and a group VLA metallic component, these will be present in a weight ratio, of the group VIII metal to the group VIA metal, within the range of from about 0.05:1 to about 5.021. The total efiluent from the hydrocracking zone is passed into suitable separating means whereby the light paraflinic hydrocarbons, and other various gaseous products are removed. The resulting normally liquid hydrocarbons are subjected to distillation in a sidecut fractionator under such conditions as will yield a heart-cut having a boiling range of about 400 F. to about 650 F., which heart-cut fraction is substantially free from nitrogenous compounds, containing less than about 5.0 ppm. thereof. Those hydrocarbons boiling below about 400 F., including butanes, are removed from the upper portion of the side-cut fractionator, and may be transmitted to storage pending further use either as charge to a catalytic reforming unit, or as gasoline blending components. The comparatively minor quantity of those unreacted hydrocarbons boiling within the range of from about 650 F. to about 800 F. are removed from the bottom portion of the side-cut fractionator, and are recycled to combine with the normally liquid hydrocarbon effluent from the second reaction zone, thereby forming the total liquid charge to the third stage of the present process. The gasoline boiling range hydrocarbons, recovered from the present process as a liquid product, are virtually completely free from nitrogenous and sulfurous compounds, and, therefore, are extremely well suited for direct utilization as the charge to a catalytic reforming unit. The middle-distillate liquid product, those hydrocarbons boiling within the range of about 400 F. to about 650 F., contain less than about 5 .0 ppm. of nitrogen, and more often from about 1.0 to about 3.0 ppm. This middle-distillate fraction may be subjected to further processing, for example, in still another hydrocracking reaction zone, and due to the physical and chemical characteristics thereof, under extremely mild hydrocracking conditions whereby there is virtually total recovery therefrom of those hydrocarbons boiling within the gasoline boiling range. The middle-distillate hydrocarbon fraction is also well suited for subsequent utilization as fuel oil. During the operation of the three stage process of the present invention, it may be found that the middledistillate boiling range hydrocarbons are recovered containing more than about 5.0 ppm. of nitrogen. In this event, the heavier hydrocarbons recovered from the bottom portion of the side-cut fractionator, that is, those hydrocarbons boiling within the range of about 650 F. to about 800 F., may be recycled to combine with the charge to the second-stage, or clean-up reaction zone of the present process.

From the foregoing description, it is seen that the process of the present invention will utilize at least two catalytic composites, and three in those instances where the first reaction zone is designed to function as a hydrocracking reaction zone. In those instances where the heavy hydrocarbonaceous material, to be processed within the three stages of the present invention, possesses physical and/ or chemical characteristics which warrant the utilization of a severe hydrocracking reaction zone as the first stage, any suitable acidic-type cracking catalyst may be employed. Generally, suitable hydrocracking catalysts have been shown to consist essentially of substantially large quantities of chromium, tungsten, molybdenum, nickel, iron, cobalt, and mixtures thereof. For example, kieselguhr, composited with about 10% to about 50% by weight of nickel, and preferably, 30% to 50% by weight, is a suitable catalyst for utilization under severe hydrocracking conditions. On the other hand, an acidic carrier material, comprising about by weight of silica and 25% by Weight of alumina, may be composited with about 25% to about 50% by weight of chromium and/ or tungsten. In accordance with the process of the present invention, it is preferred that the first reaction zone contain a hydrocracking catalyst comprising at least one metallic component from the metals of group VIA and the iron-group of the periodic table, and mixtures thereof. Thus, a preferred catalytic composite of the present invention would comprise a carrier material of silica and alumina composited with about 10% to about 50% by weight of nickel, and promoted by lesser quantities of chromium, tungsten and molybdenum, within the range of about 2% to about 20% by weight. In any event, the catalytic composite, for utilization in the first reaction zone, may be manufactured by any suitable manner. A particularly advantageous procedure, from the standpoint of manufacturing, employs one or more impregnating techniques. Thus, where the catalyst is to contain both nickel and tungsten, the impregnation method of preparation involves first preparing the suitable carrier material, for example a composite of 75 by weight of silica and 25 by Weight of alumina, and subsequently forming an aqueous solution of watersoluble compounds of the desired metals, such as nickel nitrate, nickel carbonate, tungsten chloride hydrate, etc. The alumina-silica particles, serving as the acidic carrier material, are commingled with the aforementioned aqueous solutions, and subsequently dried at a temperature of about 200 F. The dried composite is then subsequently oxidized in an oxidizing atmosphere such as air, for the purpose of permanently affixing the metallic components Within and throughout the carrier material. The hightemperature oxidizing procedure is effected at an elevated temperature of about 1100 F. to about 1700 F., and for a period of from about 2 to about 8 hours or more. It is understood that the impregnating technique may be elfected in any suitable, desired manner; thus, the carrier material may be impregnated first with a nickel-containing solution, dried and oxidized, and thereafter impregnated with a tungsten-containing solution. The second impregnating step will then be followed by subsequent drying and high-temperature oxidation procedures. On the other hand, the two aqueous solutions may be intimately commingled with each other, and the carrier material impregnated in a single step. The particular means by which the catalyst, for utilization Within the first stage of the present process, is prepared, is not considered to be limiting upon the present invention. The primary function, or object, of the first stage of the present process, is to elfect the substantially complete conversion of those hydrocarbons boiling in excess of 800 E, into hydrocarbons boiling below about 800 F., and this is, in part, accomplished by means of intra-stage recycle of those unreacted hydrocarbons boiling in excess of about 800 F.

As hereinbefore set forth, virtually all heavy hydrocarbonaceous material boiling in excess of about 800 F. contains substantial quantities of nitrogenous and sulfurous compounds which are difiicult to remove from the higher boiling components. Therefore, as the function of the first stage of the present process is to convert the higher boiling components into material boiling below about 800 F., the function of the second stage of the present process is to efiiect the substantially complete destructive removal of those nitrogenous and sulfurous compounds now boiling below about 800 F. Therefore, the second stage of the present process, referred to as the clean-up zone, contains a nitrogen-insensitive catalyst comprising at least about 4.0% by Weight of molybdenum, calculated as the element thereof. The catalyst may be further promoted by including therein relatively minor quantities of iron-group metals, such as cobalt, nickel and iron. When these latter metals are utilized in conjunction with the large quantities of molybdenum, they will be employed in an amount within the range of about 0.2% to about 6.0% by weight thereof. In the presence of the molybdenum-containing catalyst, and under the operating conditions hereinbefore set forth, the organically-bound, nitrogen compounds are separated at the nitrogen-hydrogen bonds to form ammonia which is released in a free form from the reaction media. Similarly, any sulfurous compounds, such as mercaptans, thiophenes, etc., are converted into hydrogen sulfide and the corresponding sulfur free hydrocarbon. In addition to the effective clean-up of the hydrocarbon charge stock, a significant degree of hydrocarbon conversion occurs whereby the heavier molecular weight hydrocarbons, boiling at a temperature within the range of about 650 F. to about 800 F., are converted, via highly selective cracking reactions into hydrocarbons boiling below about 650 F. It is understood, however, that such selective hydrocracking reactions are not necessarily complete in the sense that all of the hydrocarbons boiling in excess of 650 are converted to lower boiling hydrocarbon products. In order to maintain the high degree of selec I tive cracking, in this second-stage of the present process, it is preferred that the previously mentioned catalytic components be composited with a carrier material comprising alumina without the addition thereto of other refractory' inorganic oxide material. The use of such material, for example, magnesia, Zirconia, thoria, boria, and especially silica, even in relatively minor quantities, has the tendency to increase the hydrocracking activity of the catalyst, whereby the conversion reactions result in the unnecessary production of light, straight-chain paraffinic hydrocarbons. Therefore, although the catalyst employed in the first stage of the process utilizes a composite of alumina and large quantities of silica, the catalyst within the second stage of the process preferably employs alumine. in a substantially pure state. The normally liquid hydrocarbons leaving the second-stage of the present process, will generally be contaminated with less than about 10.0 ppm. of nitrogen. Through careful selection of the operating conditions and catalyst within the second stage, the normally liquid hydrocarbons may be produced to contain less than about 5.0 parts per million of nitrogen. In any event, when compared to the quantity of nitrogen contained within the original heavy hydrocarbonaceous material, the charge stock to the third-stage of the present process may be considered substantially completely free from nitrogenous compounds. This is due, at least inpart, to the method of concentrating such nitrogenous compounds Within a hydrocarbon fraction boiling below about 800 F., and processing such fraction within the second stage of the present process.

The third stage of the present process is designed to convert the now substantially nitrogen-free hydrocarbon fraction boiling in excess of the middle-distillate boiling range, into hydrocarbons boiling within both the middledistillate and gasoline boiling ranges; in addition, the utilization of a selective catalyst within the third stage of the present process will effect substantial conversion of the middle-distillate boiling range hydrocarbons into gasoline boiling range hydrocarbons without the usual attendant conversion to light parafiinic hydrocarbons such as methane, ethane and propane. In view of the fact that the total hydrocarbon charge to this third reaction zone may contain from about 3.0 to about 5 .0 ppm. of nitrogen, it is to great advantage to utilize certain catalytic composites therein, and which composites are most effective for the mild hydrocracking of hydrocarbons boiling within the range of 650 to about 800 F., although containing these residual nitrogenous compounds. By the same token, as hereinabove described, the catalyst is selected to effect substantial conversion of middle-distillate hydrocarbons into gasoline boiling range hydrocarbons. To illustrate, alumina, containing relatively minor quantities of silica (approximately 12% by weight) possesses a high degree of activity in regard to the destructive removal of nitrogenous compounds. Likewise, silica is a good hydrocracking catalyst when containing a relatively minor quantity of alumina, while on the other hand, is not a good nitrogen remover. Similarly, the metallic components of the catalyst disposed within the third stage, or hydrocracking reaction zone, Will exhibit similar propensities. For example, as indicated in regard to the first reaction zone, when the latter contains a suitable hydrocracking catalyst, large quantities of nickel exhibit high activity in regard to hydrocracking, but do not possess a relatively high degree of activity in regard to the removal of nitrogenous compounds. On the other hand, molybdenum may be considered a good nitrogen remover, but is not relatively active as either a hydrocracking or hydrogenation catalyst. Similarly, metals selected from the platinum-group of the periodic table are considered excellent hydrogenation catalysts, and, although effecting hydrocracking to a certain degree, are not normally considered in the classification of hydrocracking catalysts. I have found that catalytic composites which comprise at least one metallic component selected from groups VIA and VIII of the periodic table, and mixtures thereof, including platinum, palladium, nickel and/or molybdenum, etc., and composited with silica and from about to about 90% by weight of alumina, constitute preferred hydrocracking catalysts for utilization within the third stage of the process of the present invention. Such catalysts have a relatively high degree of activity in regard to the conversion of hydrocarbons boiling Within the middle-distillate boiling range, and, more importantly, effect the substantially complete conversion of those hydrocarbons boiling Within the range of 650 F. to about 800 F. It is significant that such activity is substantially unaffected even by the relatively minor quantities of nitrogen, less than about 5.0 ppm. contained within the charge to the third-stage reaction zone.

The carrier material, for utilization within the catalyst employed in the first stage of the present process, unless of course such stage comprises a thermal cracking unit of the single-coil or double-coil type, may be alumina, magnesia, fullers earth, montmorillonite, silica, kieselguhr, etc. A suitable carrier material may consist, for example, of a major proportion of precipitated silica composited with one or more hydrated oxides such as hydrated alumina, hydrated zirconia, and hydrated thoria. When synthetically-produced, the solid carrier material may be made in any suitable manner including separate, successive or coprecipitation methods. For example, silica may be prepared by commingling Water glass and a mineral acid under such conditions as will precipitate a silica hydrogel. The silica hydrogel is subsequently washed with Water containing a small amount of a suitable electrolyte for the purpose of removing sodium ions. The oxides of other compounds, when desired, may be prepared by reacting a basic reagent such as ammonium hydroxide, ammonium carbonate, etc., with an acid salt solution of the metal, as for example, the chloride, sulfate, nitrate, etc., or by adding an acid to an alkaline salt of the metal such as, for example, commingling sulfuric acid with sodium aluminate, etc. When it is advantageous to prepare the carrier material in the form of particles of uniform size and shape, this may be readily accomplished by grinding the partially dried oxide cake, with a suitable lubricant such as stearic acid, resin, graphite, etc., subsequently forming the particles in any suitable pelleting or extrusion apparatus. The preferred carrier material, for utilization in the first stage of the present invention, comprises at least two refractory inorganic oxides, and such a composite may be prepared by the separate precipitation method, in which the oxides are precipitated separately, and then mixed, preferably in the wet state; when successive precipitation methods are employed, the first oxide is precipitated as previously set forth, and the wet slurry, either with or without prior washing, is composited with a salt of the other component. Thus, a precipitated, hydrated silica, substantially alkaline free, is suspended in an aqueous solution of aluminum chloride and zirconium chloride following which precipitated hydrated alumina and precipitated hydrated zirconia are deposited upon the silica gel by the addition of an alkaline precipitant, such as ammonium hydroxide. The resulting mass of hydrated oxide is water washed, dried and calcined at about 1400 F. Another possible method of manufacture consists of commingling an acid such as hydrochloric acid, sulfuric acid, etc., with commercial water glass under conditions to precipitate silica, washing the precipitate with acidulated water or other means to remove sodium ions, commingling with an aluminum salt such as aluminum chloride, and/or some suitable zirconium salt, etc., and either adding a basic precipitant such as ammonium hydroxide to precipitate alumina and/or zirconia, or forming the desired oxide or oxides through the thermal decomposition of the salt as the case may permit. The silica-alumina-zirconia cracking component may be formed by adding the aluminum and/or zirconium salts together or separately. It is understood that the particular means employed for the manufacture of the hydrocracking catalyst, utilized in the first reaction 18 zone, is not considered to be a limiting feature of the process of the present invention.

As hereinbefore set forth, the carrier material utilized within the second stage is preferred to be alumina. Since the primary function of this second stage is the destructive removal of nitrogenous and sulfurous compounds, it is considered advantageous to limit the conversion reactions in a manner such that little or no light parafiinic hydrocarbons are produced. The alumina may be prepared by adding a reagent such as ammonium hydroxide, ammonium carbonate, etc., to a salt of aluminum such as aluminum chloride, aluminum nitrate, aluminum acetate, etc., in an amount to form aluminum hydroxide. Aluminum chloride is generally preferred as the aluminum salt to be employed, not only for convenience in subsequent washing and filtering procedures, but also it appears to give the best results. The resulting precipitate is, upon drying, converted to alumina. The alumina particles may take the form of any desired shape such as spheres, pills, pellets, cakes, extrudates, powder, granules, etc. A particularly preferred form of alumina is the sphere, and these spheres may be continuously manufactured by passing droplets of an alumina hydrosol into an oil bath which is maintained at an elevated temperature, and retaining the droplets in said oil bath until the same set into firm hydrogel spheroids. This particular method, commonly referred to as the oil-drop method, is described in detail in U.S. Patent No. 2,620,314, issued to James Hoekstra.

With respect to the carrier material employed as a part of the catalyst disposed Within the [third reaction zone, it is preferred to utilize at least tWo refractory inorganic oxides, and preferably alumina and silica. When silica and alumina are employed in combination, the latter will be present within an amount of from about 10% to about by Weight. Thus, the carrier material within the third-stage of the present process may comprise the following: 88% by weight of silica and 12% by Weight of alumina, 75% by weight of silica and 25% by weight of alumina, 88% by weight of alumina and 12% by weight of silica. Following the formation of the carrier material, the catalytically active metallic components are composited therewith. The catalyst comprise at least one metallic component selected from the metals of groups VIA and VIII of the periodic table, and includes the platinum-group metals, the iron-group metals, molybdenum, tungsten, and chromium. These metallic components may be incorporated within the alumina-silica carrier material in any suitable manner. impregnating techniques may be advantageously employed by first forming an aqueous solution of a watersoluble compound of the desired metal such as platinum chloride, palladium chloride, chloroplatinic acid, chloropalladic acid, ammonia molybdate, nickel nitrate hexahydrate, tungsten chloride, dinitrito-diamino platinum, etc., and commingling the resulting solution with the alumina-silica in a steam drier. Other suitable metalcontaining solutions which may be employed are colloidal solutions or suspensions including the desired metal cyanides, metal hydrom'des, metal oxides, metal sulfides, etc. Where these solutions are not water-soluble at the temperature employed, other suitable solvents such as alcohols, ethers, etc., may be utilized. The final catalytic composite, after all of the catalytic components are present therein, is dried for a period of from about 2 to about 8 hour or more, and subsequently oxidized in an oxidizing atmosphere such as air, at an elevated temperature of about 1100 F. to about 1700 F., and for a period of from about one to about eight hours or more. Following the high-temperature oxidation procedure, the catalyst may be reduced for a period ranging from about /2 hour to about 1 hour in the presence of hydrogen, at a temperature within the range of about 700 F. to about 1000 F. Where convenient, the catalyst may be reduced in situ, that is, by placing the catalyst within the third reaction zone, subjecting the same to an imposed hydrogen purge of the system at a temperature of about 700 F.

The total quantity of metallic components of the catalyst disposed within the third reaction zone, is within the range of from about 0.01% to about 20.0% by weight of the total catalyst. The group VIA metal, such as chromium, molybdenum, or tungsten, is usually present within the range of from about 0.5% to about 10.0% by weight of the catalyst. The group VIII metals, which may be divided into two sub-groups, are present in an amount of from about 0.01% to about 10.0% by weight of the total catalyst. When an iron sub-group metal, such as iron, cobalt, or nickel, is employed, it is present in an amount of from about 0.2% to about 10.0% by weight, while, if a platinum-group metal such as platinum, palladium, iridium, etc., is employed, it is present in an amount within the range of from about 0.01% to about 5.0% by weight of the total catalyst. When the metallic component of the hydrocracking catalyst consists of both a group VIA metal and a group VIII metal, it will contain metals of the above groups in a ratio of from about 0.05:1 to about 5.0:1 of the group VIH metal component to the group VIA metallic component. Therefore suitable catalysts for utilization within the third reaction zone, include, but are not considered to be limited to, the following: 6.0% by weight of nickel and 0.2% by weight of molybdenum; 6.0% by weight of nickel and 0.2% by weight of platinum; 0.4% by weight of platinum; 6.0% by weight of nickel and 0.2% by weight of palladium; 0.4% by weight of palladium, etc.

The catalyst employed within the third stage of the process of the present invention is preferably disposed within the reaction zone as a fixed bed. As a result of the physical and chemical characteristics of the charge stock to the third stage, the operating conditions therein are relatively mild. For example, the operating temperature at which the catalyst is maintained may be at least about 50 F. less than the temperature employed within the second reaction zone. It is not unusual, in the process of the present invention, to operate the third reaction zone at a temperature which is as much as 150 F. lower than the temperature within the second reaction zone. Furthermore, there exists the requirement for a lesser quantity of hydrogen within the third stage, and the rate of liquid charge thereto may be substantially increased. The total efltluent from the hydrocracking reaction zone may be passed to a suitable high-pressure, low-temperature separation zone, from which a hydrogenrich gas stream is withdrawn and recycled to supply at least a portion of the hydrogen which is admixed with the liquid hydrocarbon charge stock. It is understood that the broad scope of the present invention is not to be unduly limited to a particular catalyst, or to a particular method of manufacturing the same. The utilization of any of the previously mentioned catalytic composites, whether in the first, second or third reaction zones, at operating conditions which vary within the limits hereinbefore set forth, do not necessarily yield results which are equivalent to those obtained through the utilization of other catalytic composites or other operating conditions. An essential feature of the present invention is the separate, distinctly integrated three stages within which the overall process is effected. Through the utilization of the process of the present invention, greater concentrations of hydrocarbons boiling within the gasoline and middle-distillate boiling ranges are produced from those hydrocarbons which boil in excess of the middle-distillate boiling range. Furthermore, greater concentrations of gasoline boiling range hydrocarbons may be produced from those middle-distillate boiling range hydrocarbons withdrawn as a product from the third stage pf the process. The overall picture results in a. substantial reduction in the quantity of light paraffinic hydrocarbons otherwise resulting from the non-selective singlestage hydrocracking of similar heavy hydro'carbonaceous material. Furthermore, the process of the present invention results in a gasoline boiling range hydrocarbon product substantially free from unsaturated paraffinic hydrocarbons; the gasoline boiling range product is, therefore, extremely well suited as charge stock to a catalytic reforming unit for the purpose of further increasing the octane rating thereof. Thus, through the utilization of the process of the present invention, a hydrocarbon charge stock, having a boiling range of from about 700 F. to about 1000 F. or higher, may be substantially completely converted into hydrocarbons boiling within the gasoline boiling range, notwithstanding the presence of exceedingly excessive quantities of nitrogenous and sulfurous compounds. Furthermore, these high volumetric yields are obtained Without the usual exceedingly high yield loss due to the formation of an excessive quantity of light paraffinic hydrocarbons, and without experiencing the rapid deactivation of the catalytic composite employed.

The process of the present invention may comprise either a batch or a continuous-type operation. When utilizing the continuous-type operation, which is the particularly preferred manner of efiecting the present in vention, the various catalytic composites may be disposed, in their respective reaction zones, as fixed beds, as illustrated in the accompanying drawing, and maintained under the desired operating conditions. The hydrocarbons, and hydrogen, are continuously charged to the re action zone, passing in downward flow through the catalyst, or, Where desired, either in upward flow or radialflow. The operation may be eifected as a moving-bed type, or a suspensoid-type of operation, in which the catalyst and hydrocarbons are passed as a slurry through the reaction zone.

The following examples are given to further illustrate the process of the present invention, and to indicate the benefits to be afforded through the utilization thereof. It is understood that the examples are given for the sole purpose of illustration, and are not intended to limit the generally broad scope and spirit of the appended claims.

EXAMPLE I A Mid-Continent vacuum gas oil, having a boiling range indicating an initial boiling point of about 600 F. and a distillation point (ASTM Method D-86) of 950 F., the latter indicating an end point of about 1000 F., was subjected to processing in accordance with the description of the second-stage of the present process. The gas oil was contaminated by 252 ppm. of nitrogen, and contained 0.35% by weight of sulfur. The catalyst employed consisted of an alumina-silica carrier material, comprising 88% by weight of alumina, impregnated with a single impregnating solution containing molybdic acid and nickel nitrate hexahydrate in amounts to yield a final catalyst containing 6.4% by weight of molybdenum and 2.4% by Weight of nickel. The catalyst was maintained at a temperature of 750 F., a pressure of 1500 pounds per square inch, and the liquid charge rate was equivalent to 0.3 liquid hourly space velocity, in the presence of 4500 standard cubic feet per barrel of hydrogen. Under these conditions, the normally liquid hydrocarbon product contained nitrogen in an amount of 21 ppm.

To illustrate the function of the first stage of the present process, whether utilizing a severe hydrocracking reaction zone, or a thermal cracking reaction zone, a Mid- Continent gas oil, containing no hydrocarbons boiling in excess of 800 F., was processed in a like manner, again simulating the second-stage of the present process. The gas oil was contaminated with total nitrogen in an amount of 252 ppm. and total sulfur in an amount of 0.35% by weight. These and other charge stock inspections are given in the following Table I.

Percent 650 F Total Nitrogen, wt. ppm 0.99 Total Sulfur, Wt. Percent Product Distribution:

Butanes- 180 R, ER, vol. percent 180 F.-400 F., E.P., vol. percent 400 F.650 F., E.P., vol. per

650 F. and Heavier, vol. percent Total Volumetric Yield 1 -0; Light Parafiinic Hydrocarbons=L80 wt. percent.

The total liquid product effluent, including butanes, had a nitrogen content of slightly less than 1.0 ppm. and a total sulfur content of 0.022 Wt. percent. These data indicate that the nitrogenous and sulfurous compounds may be effectively completely removed from those hydrocarbons boiling at a temperature less than about 800 F., whereas, these compounds, particularly the nitrogenous compounds, are difiicult to remove from those hydrocarbon fractions boiling in excess of 800 F. In addition to the rather effective clean-up of the charge to the second reaction zone, there is evidence of a considerable amount of selective hydrocracking taking place as shown by the shift in boiling range. The product distribution, as indicated in Table I, was obtained by precise laboratory fractionation in a 30-plate distillation column, and includes the butanes removed along with the light parafiinic hydrocarbons prior to the laboratory distillation. It is significant that the light parafiinic hydrocarbon yield was less than 2.0% by weight of the total charge, and that the total volumetric yield was in excess of 100%.

EXAMPLE H The charge stock employed in this example (illustrating the third stage), was the liquid hydrocarbon product resulting from the Mid-Continent gas oil utilized in Example I (illustrating the operation of the second-stage of the process). The catalyst employed in this example consisted of a carrier material of 88% by weight of silica and 12% by weight of alumina, impregnated with sutficient palladium chloride to result in a final composite containing 0.4% by weight of palladium. The operating conditions were, a pressure of 1500 pounds per square inch, a temperature of 575 F., a liquid hourly space velocity of 1.0 and a hydrogen rate of 3000 standard cubic feet per barrel of liquid charge. It should be noted Table II MILD HYDROCRACKING, MID-CONTINENT GAS OIL PRODUCT PROPERTIES Gravity, API 60 F. 49.1 ASTM, D-86 distillation, F.:

IBP 156 220 30% 305 50% 445 70% 560 22 650 End point 688 Percent 400 F 45.0 Percent 650 F. 90.0

Product distribution:

Butanes 180 F., E.P 11.8 180 F.-400 F., E.P. 46.1 400 F.-650 F., E.P. 40.3 650 F. and heavier 8.9

Total volumetric yield 107.1

1 C1-C3 light parafl'inic hydrocarbons:1.64 wt. percent.

As previously stated in regard to Example I, the indicated product distribution accounts for those butanes inadvertently removed from the total reaction zone efiluent while separating the light paraiiinic hydrocarbons therefrom. The product distribution is, however, based upon an overall material balance of 99.9%. It is again significant that the total light paraifinic hydrocarbon yield was less than about 2.0% by weight of the total liquid charge. In addition, the total volumetric yield was significantly in excess of Of greater significance, is the fact that only 8.9 volume percent of the total liquid charge to the third stage of the present process was unreacted. As indicated in the product distribution, there resulted 57.9% by weight of gasoline boiling range hydrocarbons and 40.3% by volume of middle-distillate boiling range hydrocarbons.

The foregoing examples clearly indicate the method of the present invention and the various benefits to be afforded through the utilization thereof. The three-stage process of the present invention has been shown to result in exceedingly large volumetric yields of gasoline boiling range hydrocarbons and middle-distillate hydrocarbons while processing heavy hydrocarbonaceous material sevcrly contaminated by excessive quantities of both nitrogenous and sulfurous compounds.

I claim as my invention:

1. A process for the conversion of hydrocarbon oil containing nitrogenous compounds and hydrocarbons boiling above about 800 R, which comprises cracking said oil to form hydrocarbons heavier than gasoline and boiling below about 800 F., reacting the last-named hydrocarbons with hydrogen to convert nitrogenous compounds therein to ammonia, separating the ammonia from normally liquid hydrocarbons, and hydrocracking at least a portion of the latter in the presence of hydrogen and a hydrocracking catalyst.

2. A process for converting hydrocarbonaceous material containing nitrogenous compounds and hydrocarbons boiling in the range of from about 700 F. to about 1000 E, into lower boiling hydrocarbon products, which comprises cracking said hydrocarbonaceous material in a first reaction zone, removing light paraffinic hydrocarbons from the resultant efiluent, and thereafter separating the remaining normally liquid hydrocarbons into a heavy fraction having an initial boiling point in excess of a temperature of about 800 F. and a light fraction heavier than gasoline and boiling below about 800 F., recycling said heavy fraction to combine with said hydrocarbonaceous material; reacting said light fraction with hydrogen in a second reaction zone to convert nitrogenous compounds therein to ammonia, removing ammonia and normally gaseous hydrocarbons from the resultant second zone efiiuent, and passing the normally liquid hydrocarbons, along with additional hydrogen, into a third reaction zone maintained at hydrocracking conditions; removing normally gaseous hydrocarbons from the resultant third zone efiluent and separating the normally liquid hydrocarbons into a first fraction having an end boiling point of about 400 F. to about 450 F., a second traction having an initial boiling point of about 400 F. to about 450 F. and an end boiling point of about 650 F. to about 700 F., and a third fraction boiling at a temperature in excess of about 650 F. to about 700 F., and recycling at least a portion of said third fraction to combine with said hydrogen and the normally liquid hydrocarbons from said second reaction zone, prior to conversion thereof in said third reaction zone.

3. The process of claim 2 further characterized in that said hydrocarbonaceous material is initially stabilized to produce a light fraction having an end boiling point below about 800 F., and a heavier fraction having an initial boiling point of about 800 F., said heavier fraction passing into said first reaction zone.

4. The process of claim 2 further characterized in that said first reaction zone is maintained at thermal cracking conditions.

5. The process of claim 2 further characterized in that said first reaction zone contains a hydrocracking catalyst comprising at least one metallic component from the metals of groups VIA and the iron-group of the periodic table, and mixtures thereof.

6. A process for converting hydrocarbonaceous mate rial having a boiling range of from about 700 F. to about 1000 F., and containing nitrogenous compounds, into lower boiling hydrocarbon products which comprises initially fractionating said hydrocarbonaceous material to produce a first light fraction containing those hydrocarbons boiling below about 800 F., and a first heavy fraction having an initial boiling point of about 800 F., cracking said first heavy fraction in a first reaction zone, separating the resultant efiluent into a second light fraction and a second heavy fraction, the former comprising hydrocarbons heavier than gasoline and boiling below about 800 F. and the latter having an initial boiling point of about 800 F., recycling said second heavy fraction to combine with said first heavy fraction prior to conversion in said first reaction zone, and combining said second light fraction with said first light fraction; reacting the resultant light fraction mixture with hydrogen in a second reaction zone to convert nitrogenous compounds therein to ammonia, removing ammonia and normally gaseous hydrocarbons from the resultant second zone efliuent, and passing the normally liquid hydrocarbons, along with additional hydrogen, into a third reaction zone maintained at hydrocracking conditions; removing normally gaseous hydrocarbons from the third reaction zone efiluent and separating the normally liquid hydrocarbons into a first fraction having an end boiling point of about 400 F. to about 450 F., a second fraction having an initial boiling point of about 400 F. to about 450 F. and an end boiling point of about 650 F. to about 700 F., and a third fraction boiling at a temperature in excess of about 650 F. to about 700 F., recycling at least a portion of said third fraction to combine with the normally liquid hydrocarbons from said second reaction zone and hydrogen, prior to conversion thereof in said third reaction zone.

7. The process of claim 6 further characterized in that said third reaction zone contains a catalyst comprising at least one metallic component selected from the metals of groups VIA and VIII of the periodic table, and mixtures thereof.

8. The process of claim 6 further characterized in that said third reaction zone contains a catalyst comprising a group VIA and a group VIII metallic component, the ratio of said group VIII metallic component to said group VIA metallic component being within the range of about 0.05:1 to about .021.

9. The process of claim 6 further characterized in that said third reaction zone contains a catalyst comprising at least one platinum-group metallic component composited with silica and from about to about 90% by weight of alumina.

10. The catalyst of claim 9 further characterized in '24 that said platinum-group metallic component is palladium.

11. The catalyst of claim 9 further characterized in that said platinum-group metallic component is platinum.

12. A process for converting nitrogen-contaminated hydrocarbonaceous material, having a boiling range of from about 700 F. to about 1000 F., into lower boiling hyrocarbon products substantially free from nitrogenous compounds, which comprises initially stabilizing said hydrocarbonaceous material to produce a first light fraction containing those hydrocarbons boiling below about 800 F., and a first heavy fraction having an initial boiling point of about 800 F; cracking said first heavy fraction in a first reaction zone containing a cracking catalyst comprising at least one metallic component from the metals of groups VIA and the iron-group of the periodic table, and mixtures thereof, separating the resultant etfiuent into a second light fraction comprising hydrocarbons heavier than gasoline and boiling below about 800 F. and a second heavy fraction containing hydrocarbons boiling in excess of a temperature of about 800 F., recycling the second heavy fraction to combine with said first heavy fraction prior to the conversion thereof in said first reaction zone, and combining said second light fraction with said first light fraction; reacting the resulting light fraction mixture with hydrogen in a second reaction zone containing a catalyst comprising from about 4% to about 45% by weight of molybdenum to convert nitrogenous compounds therein to ammonia, removing ammonia and normally gaseous hydrocarbons from the resultant second zone eflluent, and passing the normally liquid hydrocarbons, along with additional hydrogen, into a third reaction zone maintained at hydrocracking conditions and containing a catalyst comprising from about 0.01% to about 5.0% by weight of platinum composited with silica and from about 10% to about by weight of alumina; removing normally gaseous hydrocarbons from the resultant third zone efiluent and separating the normally liquid hydrocarbons into a first fraction having an end boiling point of about 400 F. to about 450 F., a second fraction having an initial boiling point of about 400 F. to about 450 F. and an end boiling point of about 650 F. to about 700 F., and a third fraction boiling at a temperature in excess of about 650 F. to about 700 F., recycling at least a portion of said third fraction to combine with the normally liquid hydrocarbons from said second reaction zone and hydrogen, prior to conversion thereof in said third reaction zone.

13. The process of claim 12 further characterized in that said second reaction zone is maintained at a temperature within the range of from about 500 F. to about 1000 F. and said third reaction zone is maintained at a temperature at least about 50 F. lower than the temperature in said second reaction zone.

14. A process for converting nitrogen-contaminated hydrocarbonaceous material, having a boiling range of from about 700 F. to about 1000 F., into lower boiling hydrocarbon products, substantially free from nitrogenous compounds, which comprises initially stabilizing said hydrocarbonaceous material to produce a first light fraction containing those hydrocarbons boiling below about 800 F., and a first heavy fraction having an initial boiling point of about 800 F.; cracking said first heavy fraction in a first reaction zone, separating the resultant effluent into a second light fraction comprising hydrocarbons heavier than gasoline and boiling below about 800 F. and a second heavy fraction containing hydrocarbons boiling in excess of a temperature of about 800 F., recycling the second heavy fraction to combine with said first heavy fraction prior to the cracking thereof in said first reaction zone, and combining said second light fraction with said first light fraction; reacting the resulting light fraction'mixture with hydro- 25 gen in a second reaction zone containing a catalyst comprising alumina, from about 4% to about 45% by weight of molybdenum to convert nitrogenous compounds therein to ammonia, and from about 0.2% to about 6% by weight of nickel; removing ammonia and normally gaseous hydrocarbons from the resultant second zone efliuent, and passing the normally liquid hydrocarbons, along with additional hydrogen, into a third reaction zone maintained at hydrocracking conditions and containing a catalyst comprising from about 0.01% to about 5.0% by weight of palladium composited with silica and from about 10% to about 90% by weight of alumina; removing normally gaseous hydrocarbons from the resultant third zone efiiuent and separating the normally liquid hydrocarbons into a first fraction having an end boiling point of about 400 F. to about 450 F., a second fraction having an initial boiling point of about 400 F. to about 450 F. and an end boiling point of about 650 F. to about 700 F., and a third fraction having an initial boiling point in excess of a temperature of about 650 F. to about 700 F., recycling at least a portion of said third fraction to combine with the normally liquid hydrocarbons from said second reaction zone and hydrogen, prior to conversion thereof in said third reaction zone; the process further characterized in that said second reaction zone is maintained at a temperature within the range of from about 500 F. to about 1000 F. and said third reaction zone is maintained at a temperature at least about 50 F. lower than the temperature in said second reaction zone.

15. The process of claim 1 further characterized in that said hydrocarbon oil has a boiling range of from about 700 F. to about 1000 F.

16. The process of claim 1 further characterized in that said oil is thermally cracked.

17. A process for the conversion of hydrocarbon oil containing nitrogenous compounds and hydrocarbons boiling above and below about 800 R, which comprises separating said oil into a light fraction boiling below about 800 F. and a heavy fraction boiling above about 800 F., cracking said heavy fraction to form additional hydrocarbons heavier than gasoline and boiling below about 800 R, combining the last-named hydrocarbons with said light fraction, reacting the resultant mixture with hydrogen to convert nitrogenous compounds therein to ammonia, separating the ammonia from normally liquid hydrocarbons, and hydrocracking at least a portion of the latter in the presence of hydrogen and a hydrocracking catalyst.

References Cited in the file of this patent UNITED STATES PATENTS 2,885,346 Kearby et a1. May 5, 1959

Claims

1. A PROCESS FOR THE CONVERSION OF HYDROCARBON OIL CONTAINING NITROGENOUS COMPOUNDS AND HYDROCARBONS BOILING ABOVE ABOUT 800*F., WHICH COMPRISES CRACKING SAID OIL TO FORM HYDROCARBONS HEAVIER THAN GASOLINE AND BOILING BELOW ABOUT 800*F., REACTING THE LAST-NAMED HYDROCARBONS WITH HYDROGEN TO CONVERT NITROGENOUS COMPOUNDS THEREIN TO AMMONIA, SEPARATING THE AMMONIA FROM NORMALLY LIQUID HYDROCARBONS, AND HYDROCRACKING AT LEAST A PORTION OF THE LATTER IN THE PRESENCE OF HYDROGEN AND A HYDROCRACKING CATALYST.