Hydrodesulfurizers and Hydrocrackers

For materials selection, hydrocrackers are treated the same as hydrodesulfurizers, particularly in the first stage. From a materials standpoint, the demarcation between low-pressure units (hydrodesulfurizers) and high-pressure units (usually hydrocrackers) is 650 psia (4,480 kPa). 

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The trickle-bed reactor can be operated as a partially or completely vapor-phase reactor. It minimizes the energy costs associated with reactant vaporization. Mixed flow conditions at the catalyst surface exist in hydrocracking reactions, hydrogenation of crotonaldehyde and isomerization of cyclopropane. When the temperature rise in a trickle-bed reactor is significant (e.g., hydrodesulfurization and hydrocracking reactions), it can be conveniently controlled by the addition... 

The commercial trickle-bed reactors, such as hydrodesulfurization and hydrocracking reactors, are often operated adiabatically. The temperature rise in such reactors is often controlled by the additions of a quench fluid (normally hydrogen) at one or more positions along the length of the reactor. A schematic of an adiabatic trickle-bed HDS reactor with a single quench is shown in Fig. 4-7. 

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. 

Thermal processes such as coking, cat cracking, hydrodesulfurization, and hydrocracking ail produce both NF 3 and H2S. The resulting aqueous-phase ammonium hydrosulfide is antagonistic to carbon steel heat-exchanger tubes. Most of the ammonium hydrosulfide winds up in sour-water streams. Before disposal, the sour water must be steam stripped. The overhead condenser used for this stripper has an extremely corrosive environment. Titanium is preferred for this service. 

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. 

Gulf HDS A process for hydrorefining and hydrocracking petroleum residues in order to make fuels and feeds for catalytic cracking. Developed by the Gulf Research Development Company. See also hydrodesulfurization. 

Trickle-bed reactors usually consist of a fixed bed of catalyst particles, contacted by a gas liquid two-phase flow, with co-current downflow as the most common mode of operation. Such reactors are particularly important in the petroleum industry, where they are used primarily for hydrocracking, hydrodesulfurization, and hydrodenitrogenation other commercial applications are found in the petrochemical industry, involving mainly hydrogenation and oxidation of organic compounds. Two important quantities used to characterize a trickle-bed reactor are... 

The wide ranges of temperature and pressure employed for the hydrodesulfurization process virtually dictate that many other reactions will proceed concurrently with the desulfurization reaction. Thus, the isomerization of paraffins and naphthenes may occur and hydrocracking will increase as the temperature and pressure increase. Furthermore, at the higher temperatures (but low pressures) naphthenes may dehydrogenate to aromatics and paraffins dehydrocyclize to naphthenes, while at lower temperature (high pressures) some of the aromatics may be hydrogenated. 

The Demex process is a solvent extraction demetallizing process that separates high metal vacuum residuum into demetallized oil of relatively low metal content and asphaltene of high metal content (Table 8-5) (Houde, 1997). The asphaltene and condensed aromatic contents of the demetallized oil are very low. The demetallized oil is a desirable feedstock for fixed-bed hydrodesulfurization and, in cases where the metals and carbon residues are sufficiently low, is a desirable feedstock for fluid catalytic cracking and hydrocracking units. 

Combined with hydrodesulfurization, the process is fully applicable to the feed preparation for fluid catalytic cracking and hydrocracking. The process is capable of using a variety of feedstocks including atmospheric and vacuum residues derived from various crude oils, oil sand, visbroken tar and so on. 

In a number of petrochemical processes, a gas (hydrogen) is present as reactant. In hydrodesulfurization (HDS), hydrocracking (HC), and hydrodenitrogenation (HDN), the reaction products H2S and ammonia, respectively, are known to decrease the catalyst activity, but are partly transferred to the gas phase. Therefore, also these processes profit from reactive stripping. 

To remove sulfur, the kerosene and diesel sidecuts are fed to hydrotreaters or hydrodesulfurizers (HDSs). Light gas-oil is fed to a hydrocracker to convert it to diesel and lighter products. The HDS units and hydrocracker consume hydrogen supplied by the catalytic reformer and a hydrogen manufacturing plant. 

Hydrogenation of a-methylstyrene to cumene in 0.5% and 1% Pd-on-alumina Petroleum hydrocracking, hydrodenit rogenation, hydrodesulfurization, and hydrogenation... 

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