The invention pertains to a process for treating a mineral oil having a substantially large nitrogen content during which process at least some hydrocarbon molecules of the mineral oil are chemically altered to form a mineral oil having different properties. More particularly, the invention pertains to a process for hydrocracking hydrocarbon feedstocks containing a large amount of organic nitrogen compounds, which process employs two catalysts.
It is well known that a hydrocracking process may employ a catalyst containing a zeolitic molecular sieve component. In U.S. Pat. No. 3,159,564, Kelley, et al., disclose a hydrofining-hydrocracking process wherein the catalyst employed in the hydrocracking step of the process can contain partially dehydrated, zeolitic, crystalline molecular sieves, e.g., of the "X" or "Y" crystal types. In U.S. Pat. Nos. 3,894,930 and 4,054,539, Hensley discloses a hydrocracking process employing a catalyst comprising a hydrogenation component comprising a Group VI metal, preferably molybdenum, and a Group VIII metal, preferably cobalt, on a co-catalytic acidic cracking component comprising an ultrastable, large-pore crystalline aluminosilicate material and a silica-alumina cracking catalyst.
In U.S. Pat. No. 3,536,605, Kittrell discloses a hydrofining-hydrocracking process which comprises contacting a hydrocarbon feed containing substantial amounts of organic nitrogen with a catalyst comprising a gel matrix comprising silica and alumina and nickel and/or cobalt and molybdenum and/or tungsten and a crystalline zeolitic molecular sieve having a silica-to-alumina ratio above about 2.15, a unit cell size below about 24.65 Angstroms (A), and a sodium content below about 3 wt.%. Kittrell also discloses that the effluent from the reaction zone of the process may be hydrocracked in a second reaction zone in the presence of hydrogen and a hydrocracking catalyst at hydrocracking conditions.
In U.S. Pat. No. 3,558,471, Kittrell discloses a two-catalyt process wherein the hydrocarbon feedstock is first hydrotreated in the presence of a catalyst comprising a silica-alumina gel matrix containing nickel or cobalt, or both, and molybdenum or tungsten, or both, and a crystalline zeolitic molecular sieve substantially in the ammonia or hydrogen form, substantially free of any catalytic loading metal or metals, the sieve further having a silica-to-alumina ratio above about 2.15, a unit cell size below about 24.65 A, and a sodium content below about 3 wt.%, calculated as Na.sub.2 O, to produce a first effluent and contacting the first effluent in a second reaction zone in the presence of a hydrocracking catalyst. The catalyst in the second reaction zone may be the same catalyst as is used in the first reaction zone or it may be a conventional hydrocracking catalyst.
Buchmann, et al., in U.S. Pat. No. 3,788,974, disclose a two-catalyst hydrocracking process wherein a hydrocarbon oil feedstock containing from about 0.01 to 0.5 wt.% nitrogen compounds is contacted in a first hydrocracking zone with a crystalline aluminosilicate zeolite catalyst having hydrogen cations in at least a portion of its exchangeable cationic sites, the zeolite having uniform pore diameters, a crystal structure of faujasite, and a silica-to-alumina mole ratio greater than 3, and containing less than 2 wt.% sodium, the catalyst having associated therewith a hydrogenation component comprising nickel and tungsten, to provide an effluent which is contacted in a second separate hydrocracking zone with a hydrocracking catalyst. The catalyst in the first zone may have a silica-alumina binder, a content of 20% binder being shown in one of the examples, and the second hydrocracking catalyst can be the same as the first catalyst. The catalyst that is employed in the second stage can consist of any desired combination of a refractory cracking base with a suitable hydrogenation component. Suitable cracking bases include, for example, mixtures of two or more difficultly reducible oxides, such as silica-alumina, silica-magnesia, silica-zirconia, acid-treated clays, and the like. The preferred cracking bases comprise partially dehydrated zeolitic X- or Y- type crystalline molecular sieves.
Jaffe, in U.S. Pat. No. 3,536,604, discloses a hydrofining-hydrocracking process wherein a feed containing 300 to 10,000 ppm organic nitrogen is contacted with a hydrofining catalyst at a liquid hourly space velocity (LHSV) of 0.1 to 5 to reduce the organic nitrogen content to a level of 10 ppm to 200 ppm and a substantial portion of the resulting hydrofined hydrocarbon stream is contacted subsequently with a second catalyst comprising a gel matrix comprising at least 15 wt.% silica, alumina, nickel and/or cobalt, molybdenum and/or tungsten, and a crystalline zeolitic molecular sieve substantially in the ammonia or hydrogen form, substantially free of any loading metal, the second catalyst having an average pore diameter that is less than 100 A and a surface area that is greater than 200 m.sup.2 /gm. The hydrofining catalyst comprises a Group VI metal, a Group VIII metal, and a support selected from alumina and silica-alumina.
In U.S. Pat. No. 3,535,225, Jaffe discloses a two-catalyst hydrocracking process in which the hydrocarbon feedstock is contacted with a first catalyst comprising a hydrogenating component selected from the group consisting of Group VI metals and compounds thereof and Group VIII metals and compounds thereof and a component selected from the group consisting of alumina and silica-alumina and subsequently with a second catalyst, which second catalyst consists essentially of a gel matrix consisting essentially of a gel selected from silica-alumina, silica-alumina-titania, and silica-alumina-zirconia, at least one hydrogenating component selected from Group VIII metals and compounds thereof, and a crystalline zeolitic molecular sieve substantially in the ammonia or hydrogen form and substantially free of any loading metal or metals.
None of the above patents discloses a two-catalyst hydrocracking process which employs specifically as a first catalyst a catalyst comprising a specific hydrogenation component comprising nickel and molybdenum or tungsten and as the second catalyst a catalyst comprising a specific hydrogenation component comprising cobalt and molybdenum, each of the catalysts also comprising a co-catalytic acidic cracking component comprising an ultrastable, large-pore crystalline aluminosilicate material dispersed in and suspended throughout a silica-alumina matrix. Such a two-catalyst hydrocracking process is disclosed hereinafter.