Hydrodesulfurization of residual oils

Three-phase reactors are widely used in hydroprocessing operations and for oxidation reactions. Trickle bed reactors have been widely used for hydrodesulfurization of residue oils, hydrodesulfurization, and hydrocracking of gas oils and in numerous oxidation reactions. Three-phase fluidized bed reactors are also used in coal liquefaction and in Fischer-Tropsch synthesis. It is in these and similar examples that the review presented in this monograph can most pertinently be applied. 

The model was basically developed for hydrodesulfurization of residual oil with a high level of catalyst contaminants causing pore mouth plugging of catalyst. 

Satori, H, and S, Nishizaki, "Studies on the Hydrodesulfurization of Residual Oil using a Test Apparatus of Larger Size. II, On the Theoretical Analysis of the Fixed Bed Reactor", Int, Chem, Eng. (1971) 339-344. 

A major problem in the catalytic hydrodesulfurization of residual oils is the deactivation of the catalyst by metal-containing asphaltenic species in the feed. As can be seen from the results of a typical desulfurization experiment presented in Fig. 1, the catalyst shows a rapid initial decline which is attended with a fast build-up of coke on the catalyst. At a relatively low catalyst age 0, as defined in Section IV, a stationary coke level is reached. In contrast, the deposition of the inorganic remnants of the hydro-cracked asphaltenes (mainly vanadium and nickel sulfides) continues and gradually clogs the pores in the outer zone of the catalyst particles, as confirmed by electron microprobe analyses of spent catalyst samples (see Fig. 2). This causes a slow further loss in desulfurization activity over a longer period of time. Ultimately, the catalyst becomes totally inactive for desulfurization because the - still active - inner core has become completely inaccessible to the sulfur-bearing molecules. 

The Shell residual oil hydrodesulfurization process is broadly defined as a process to improve the quality of residual oils by removing sulfur, metals, and asphaltenes... 

Figure 1. Conversion and chemical hydrogen consumption for hydrodesulfurization of residuals with H-Oil...

Simple conventional refining is based essentially on atmospheric distillation. The residue from the distillation constitutes heavy fuel, the quantity and qualities of which are mainly determined by the crude feedstock available without many ways to improve it. Manufacture of products like asphalt and lubricant bases requires supplementary operations, in particular separation operations and is possible only with a relatively narrow selection of crudes (crudes for lube oils, crudes for asphalts). The distillates are not normally directly usable processing must be done to improve them, either mild treatment such as hydrodesulfurization of middle distillates at low pressure, or deep treatment usually with partial conversion such as catalytic reforming. The conventional refinery thereby has rather limited flexibility and makes products the quality of which is closely linked to the nature of the crude oil used. 

No. 6 fuel oil contains from 10 to 500 ppm vanadium and nickel in complex organic molecules, principally porphyrins. These cannot be removed economically, except incidentally during severe hydrodesulfurization (Amero, Silver, and Yanik, Hydrode.suljurized Residual Oils as Gas Turbine Fuels, ASME Pap. 75-WA/GT-8). Salt, sand, rust, and dirt may also be present, giving No. 6 a typical ash content of 0.01 to 0.5 percent by weight. 

Flow diagram of the process for hydrogen and distillate fuel production from residual oil using iron oxides and steam. 1 = Cracking reactor, 2 = distillation column, 3 = hydrogen generator, and 4 = hydrodesulfurization reactor. 

Frost, C.M., and Cottingham, P.L. 1971. Hydrodesulfurization of Venezuelan Residual Fuel Oils. Report of Investigations RI 7557. U.S. Bureau of Mines, Washington, DC. 

Shah and Paraskos47 applied their analysis to evaluate the importance of axial dispersion on pilot scale (a) residue hydrodesulfurization, (b) gas-oil hydrocracking, and (c) shale-oil denitrogenation reactor performances. The calculations indicated that the axial dispersion effect is less important in case (c) than in cases (a) and (b). Under certain pilot-scale operations, axial dispersion effects could be significant in cases (a) and (b). 

A Catalyst Deactivation Model for Residual Oil Hydrodesulfiirization and Application to Deep Hydrodesulfurization of Diesel Fuel... 

Research. Assoc. Residual. Nichel Molybedenum Alumina Catalysts of Specified pore distribution used for combined hydrodesulfurization and hydrocaracking of Heavy Oil . US Patent No.4 732 886.(1988). 

Trickle bed reactors have grown rapidly in importance in recent years because of their application in hydrodesulfurization of naphtha, kerosene, gasoil, and heavier petroleum fractions hydrocracking of heavy gasoil and atmospheric residues hydrotreating of lube oils and hydrogenation processes. In trickle bed operation the flow rates are much lower than those in absorbers. To avoid too low effectiveness factors in the reaction, the catalyst size is much smaller than that of the packing used in absorbers, which also means that the overall void fraction is much smaller. 

Zn pzt/iotOJULm ndu t/u.2, hydrodesulfurization, hydrocracking of heavy or residual oil-stocks, hydrofinishing or hydrotreating of lubricating oils, demetallization, denitrification of gas-oils, isomerization of cyclopropane and hydrogenation of benzene and of naphthenic lube oil distillate (30, 31, 26, 6, 32). 

Elizalde, I., Ancheyta, J. 2012. Modeling the simultaneous hydrodesulfurization and hydrocracking of heavy residue oil by using the continuous kinetic lumping approach. Energy Fuels 26 1999-2004. 

Thermal Cracking. In addition to the gases obtained by distillation of cmde petroleum, further highly volatile products result from the subsequent processing of naphtha and middle distillate to produce gasoline, as well as from hydrodesulfurization processes involving treatment of naphthas, distillates, and residual fuels (5,61), and from the coking or similar thermal treatment of vacuum gas oils and residual fuel oils (5). 

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