Mass hydrocracking

Rhenium is used in tungsten and molybdenum-based alloys. It is used for filaments for ion gages in mass spectrometers. Rhenium-tungsten alloys are used in thermocouples to measure temperatures up to 2,200°C. Rhenium wire is used in flash bulbs for photography. Rhenium compounds also are used as catalysts in hydrogenation and hydrocracking reactions in petroleum refining. 

It is well known that the accessibility of the mesoporous materials would play an important role in catalysis, and catalytic activity depends on the free diffusion of the reactants, intermediates and products [5], Thus, a mesoporous molecular sieve with better mass transport pore would be a more suitable candidate for some industrial catalytic reactions of the largesized hydrocarbons in dehydrogenation, hydrocracking or hydrodesulfurization. 

High amounts of asphaltenes and resins require high hydrogen partial pressures and may actually limit the maximum level of hydrodesulfurization, or final traces of sulfur in the residuum may only be eliminated under extremely severe reaction conditions where hydrocracking is the predominant reaction in the process. High asphaltene and resin contents are also responsible for high viscosity (Figure 6-7) which may increase the resistance to mass transfer of the reactants... 

Many processes of gas absorption with chemical reaction are set up at high pressures, result of technical and/or economical requirements. That is, for example, processes of hydrocracking and hydrorefining of heavy oils and processes of oxydation of liquid effluents. However, if many chemical systems are found to determine the mass transfer parameters in an industrial reactor at atmospheric pressure by using the chemical method, they become scarce at elevated pressures. Several physical and chemical methods have been proposed chemical methods present some severe drawbacks, since one has to replace the gas-liquid system of interest by another one, presenting different physical properties (specially a different coalescence behaviour). 

Estimation of gas-liquid mass-transfer rates also requires the knowledge of solubilities of absorbing and/or desorbing species and their variations with temperature (i.e., knowledge of heats of solution). In some reactions, such as hydrocracking, significant evaporation of the liquid occurs. The heat balance in a hydrocracker would thus require an estimation of the heat of vaporization of the oil as a function of temperature and pressure. The data for the solubility, heat of solution, and heat of vaporization for a given reaction system should be obtained experimentally if not available in the literature. 

The compositions of progressively processed naphtha were also determined by mass spectrographic analysis and are summarized in Table VI. These show the expected shifts from paraffins in the straight-run naphtha as well as naphtha from hydrocracking LGO to aromatics, especially benzenes in the reformate. 

The residue from dichloromethane extraction of hydrocracker deposits is a reddish powder. This material was found to be sparingly soluble in 1,2,4-trichlorobenzene (TCB). A mass spectrum of the TCB extract showed a major ion at 596 daltons, with peaks at 610, 624, and 638 daltons due to alkylation of this first species. Smaller peaks were seen at 620,... 

Finally, it should be possible to calculate Vis in the relatively near future from composition, although it will always be quicker to simply measure viscosities and calculate. Gatto et al.40 employed compositions obtained from mass spectral analyses on some 15 hydrocracked and polyolefin base stocks to develop a correlation that predicted VI. While this one used only one component, the... 

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