From catalytic hydrocracking

Catalytic processes (finid catalytic cracking, catalytic hydrocracking, hydro-treating, isomerization, ether manufacture) also create some residuals in the form of spent catalysts and catalyst fines or particulates. The latter are sometimes separated from exiting gases by electrostatic precipitators or filters. These are collected and disposed of in landfills or may be recovered by off-site facilities. The potential for waste generation and hence leakage of emissions is discussed below for individual processes. 

Like catalytic cracking, hydrocracking processes generate toxic metal compounds, many of which are present in spent catalyst sludge and catalyst fines generated from catalytic cracking and hydrocracking. These include metals such as nickel, cobalt, and molybdenum. 

Butane Isomerization—C4 isomerization will be limited to smaller refineries which do not contain hydrocracking facilities. Since the i-C4/ n-C4 ratio for hydrocracking is about 2/1 to 3/1 sufficient isobutane should be available from this source to alkylate all of the available (C3-, C4-, and C5-) olefins from catalytic cracking. 

T-Star (2) A catalytic hydrocracking process using an ebullated bed reactor containing an extruded Ni/Mo-based catalyst. Developed by Axens North America, based on the H-Oil process. Planned to be used in a coal-to-liquids plant in Inner Mongolia from 2005. 

Modem analytical techniques, including HPLC with diode-array UV detection and spectrofluorometry, have been used to identify the large polycyclic aromatic hydrocarbons (PAHs) produced in catalytic hydrocracking. Several reaction pathways have been inferred from these structures. New simpler analytical methods can then be used to monitor PAH production. 

The use of modem analytical methods has led to the determination of the PAHs which are produced in catalytic hydrocrackers. A variety of HPLC-DAD, fluorescence, and UV absorbance methods were developed to determine the occurrence of the PAHs. These PAHs result from a small number of reactions. These are either a new ring forming through two-or four-carbon addition or the condensation of pyrene, coronene, or ovalene. The latter reactions result in very large PAHs which cause process problems because of their low solubilities. Their production rates (and eventual precipitation in the process streams) can be monitored through the use of UV absorbance and fluorescence spectrometries. A synchronous-scanning fluorescence method was developed to monitor the production of dicoronylene during process operation. The results of these analyses can then be used to determine process performance. 

Zmierczak et al.4 have investigated the catalytic hydrocracking of non-vulcanized rubber (SBR, styrene-butadiene copolymers) over superacid solids, consisting of sulfated Zr and Fe oxides. Figure 6.7 shows the GC-MS analysis of the liquids produced at 400 °C over sulfated Fe203, with assignments of the main peaks. Three types of product are observed C5-C9 paraffins produced from the butadiene blocks of the polymer, alkylbenzenes derived from the... 

Zeolitic catalysts are commonly used for such purposes however, the modification of the acidity of the perovskite by addition of a second acidic oxide such as silica or alumina yields materials with balanced hy-drogenating-cracking functions that may be effective for selective hydrocracking. Barium zirconates were found to be materials particularly suited for use in catalytic hydrocracking of residua, especially for their ability for removal of carbonaceous deposits from the coked catalysts... 

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