Hydroprocessing Approaches

Finally, a hydrofinishing step is often used to improve color and stability by saturation of trace multiring species and by removing some residual polar hydrocarbons, e.g. those containing nitrogen. Basestocks from typical crudes have VI ranging from 95 to 105, with saturates contents 65 to 85% and sulfur levels usually above 0.1 wt%. 

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A new illustration of this approach is given in this paper with the hydroprocessing of chloronitrobenzenes over the sulfided industrial hydro-treating catalysts, CoO-MoOj/y-Al 203 HR 306 and NiO-MoOj/y-AlHR 348 from Procatalyse. These catalysts have been shown to differ in their hydrogeno-lysis rather than in their hydrogenation properties (ref.2). 

Previous reference has been made to the benefits of removing an asphaltene fraction from the feedstock prior to hydroprocessing and prior to the application of a hydroconversion process. Chemically, this approach may be sound but an economic benefit must also be realized. This will be determined on a case by case basis. 

The commercial hydroprocessing reactors operate under near-plug-flow conditions. Nearly complete wetting of catalyst particles should be obtained as mass velocities typical of commercial reactors are approached. At Acff > 0.6, the experimental Aerr falls below the one predicted by Eq. (4-8), suggesting an asymptotic approach to complete wetting. Mears suggested that Eq. (4-9) cannot be used as a precise basis for scaleup above a mass velocity of approximately 500 g h 1 cm 2. For scaleup purposes, Mears indicated the use of the correlation of Onda et al.33 for Acff, namely,... 

Transportation fuel. For mixed post-consumer plastic (PCP) that contains significant amounts of paper, inorganics, and chlorine, the best approach appears to be pyrolysis followed by hydroprocessing. Batch mode pyrolysis at 600°C, followed by thermal or... 

The information on carbon-supported catalysts has been dominated by cata-lytically active metals that are part of the conventional hydroprocessing catalysts, i.e. Co(Ni)Mo(W). In a sulfided form, the structure of the Co(Ni)-Mo(W)-S active phase in these catalysts should approach that of Type-II phase observed on the y-Al203-supported catalysts after a high-temperature sulfidation. " Apparently, there is a sufficient driving force for a direct interaction of carbon with either Mo or sulfur leading to the formation of the Mo-C(S) bonds. Then, in carbon-supported catalysts, the presence of another active phase, i.e. Co-Mo C(S), appears to be plausible. The formation of metal carbides may take place if the supply of sulfur to maintain the catalyst surface in a sulfided form becomes limited, particularly if such a state persists for an extended period. ... 

Recent books by Magee and Dolbear and by Scherzer and Gruia are superb sources of technical information on hydroprocessing catalysts, which are also discussed in Chapters 9-12. The hydroprocessing catalyst business is big, with annual sales approaching US 800 million per year. The materials most commonly used to make these catalysts are shown in Table 7 and Table 8. 

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