Component hydrocracking

The acidic function of hydrocracking catalysts can be provided by various solid acids such as amorphous silica-alumina, zeolites and doped alumina. The type of application dictates the nature of the acidic component. Hydrocracking catalysts designed for the production of naphtha require strong acidity, provided by zeolites (Y-zeolite). For special applications, such as dewaxing, where shape-selective reactions must be promoted, zeolites such as ZSM-5 and mordenite are used. 

Antimony trichloride is used as a catalyst or as a component of catalysts to effect polymerisation of hydrocarbons and to chlorinate olefins. It is also used in hydrocracking of coal (qv) and heavy hydrocarbons (qv), as an analytic reagent for chloral, aromatic hydrocarbons, and vitamin A, and in the microscopic identification of dmgs. Liquid SbCl is used as a nonaqueous solvent. 

Product separation for main fractionators is also often called black oil separation. Main fractionators are typically used for such operations as preflash separation, atmospheric crude, gas oil crude, vacuum preflash crude, vacuum crude, visbreaking, coking, and fluid catalytic cracking. In all these services the object is to recover clean, boiling range components from a black multicomponent mixture. But main fractionators are also used in hydrocracker downstream processing. This operation has a clean feed. Nevertheless, whenever you hear the term black oil, understand that what is really meant is main fractionator processing. 

Also in relumped form, single-event microkinetics account for all reactions at molecular level [2,3,13], This requires a molecular composition of the lumps considered. The definition of the lumps in hydrocracking is such that thermodynamic equilibrium can be assumed within the lumps. Per carbon number 12 lumps are considered, i.e., normal, mono-, di- and tribranched alkanes, mono-, di-, tri- and tetracycloalkanes and mono-, di-, tri- and tetra-aromatic components. 

Abramova, A. V., Slivinsky, Ye. V., Goldfarb, Y.Y., Kitaev, L. Ye., Kubasov A. A., Modeling of Nature and Strength of Acid Centres in Ultrastable Zeolites as a Component of Hydrocracker Catalysts, in Hydrotreatment and Hydrocracking of Oil Fractions. 1999, Elsevier Science B. V New York. pp. 377-380. 

Superficially the Oryx GTL refinery design has much in common with the SMDS process, but there are important differences. There is no separate hydrotreater, which limits production of chemicals, such as waxes. The hydrocracker employs the Chevron Isocracking technology, which is based on a sulfided supported base-metal catalyst that was designed for crude oil conversion. The operating conditions of the hydrocracker are also more severe (>350°C, 7 MPa) than those required by the SMDS process (300-350°C, 3-5 MPa). Only intermediate products are produced (Table 18.13),5 with the naphtha slated as cracker feed and the distillate as blending component for diesel fuel. 

The acid component of a hydrocracking catalyst can be an amorphous oxide, e.g., a silica-alumina ora zeolite, eg., USY. This component usually serves as a support for the metal compound responsible for the hydrogenation function. The metal compound can be a noble metal, e.g., Pt or Pd, or a mixture of sulfides, e.g., of Ni/Mo, NiAV, or Co/Mo. The relative amounts of the respective compounds have to be thoroughly balanced to achieve an optimum performance. 

The most imporant use of cobalt is in the manufacture of various wear-resistant and superalloys. Its alloys have shown high resistance to corrosion and oxidation at high temperatures. They are used in machine components. Also, certain alloys are used in desulfurization and hquefaction of coal and hydrocracking of crude oil shale. Cobalt catalysts are used in many industrial processes. Several cobalt salts have wide commercial apphcations (see individual salts). Cobalt oxide is used in glass to impart pink or blue color. Radioactive cobalt-60 is used in radiography and sterihzation of food. 

The hydrocracking unit is typically used to produce reformer feedstock, jet fuel plus gasoline, and distillate blend components. Feedstock consists of cycle oil, coker distillates, and gas oils. 

Much progress has been made in understanding the catalytic activity of zeolites for several type of reactions. The number of reactions catalyzed by zeolites has been extended, and new multi-component polyfunctional catalysts with specific properties have been developed. In addition to cracking and hydrocracking, reactions such as n-alkane isomerization, low temperature isomerization of aromatic C8 hydrocarbons, and disproportionation of toluene are industrially performed over zeolite-containing catalysts. Moreover, introduction of various compounds (C02, HCl) into reaction mixtures allows one to control the intensity and selectivity of the reactions. There are many reviews on the catalytic behavior of zeolites and even more original papers and patents. This review emphasizes the results, achievements, and trends which we consider to be most important. 

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