Stage hydrocracking

Hydrocracking reaction conditions vary widely, depending on the feed and the required products. Temperature and pressure range from 400 to 480°C and 35 to 170 atmospheres. Space velocities in the range of 0.5 to 2.0 hr" are applied. Figure 3-8 shows the Chevron two-stage hydrocracking process. 

Paragon A two-stage hydrocracking process, based on the zeolite ZSM-5, claimed to increase the yield and quality of the gasoline produced. Developed by Chevron Research Company, but not commercialized by 1991. 

Residuum which is less refractory and thus amenable to upgrading in a conventional second-stage hydrocracker... 

FIRST-STAGE HYDROCRACKER WITH ICR 106 CATALYST FEED - PARTIALLY HYDROTREATED SRC-II... 

Silica-alumina and zeolites are used commercially in hydrocracking catalysts. Ni-Mo on silica-alumina is a better HDN catalyst than Ni-Mo/Al203 and is used in the first reactor of a two-stage hydrocracking process (/). 

Finally, it would be worth to mention that ordered mesoporous aluminosilicates like MCM-41 have also been studied as the acidic component of hydrocracking catalysts. Thus, NiMo/MCM-41 catalysts showed higher activity than NiMo/ASA and NiMo/USY for the one-stage hydrocracking of a vacuum gas oil feed containing 2.5 wt% sulfur and 2900 ppm nitrogen, despite the Bronsted acidity of MCM-41 was much lower than that of USY and similar to that of ASA [199], In addition, catalysts based on MCM-41 provided better... 

One-stage hydrocracking of vacuum gas oil over NiMo catalysis supported on MCM-41, USY and amorphous silica-alumina (ASA)... 

Further evidence for the desirability of removing aromatics and polyaromatics in hydrocracked base stocks came from a Mobil35 study in 1994 which found that ASTM D943 times increased as aromatics and polyaromatics levels were reduced by hydrotreating. In this study, which was one of the first to focus on hydrocracked stocks, ASTM D943 tests were run on a number of first- and second-stage hydrocracked oils and several solvent refined reference stocks. 

IFP s paper on their Spanish plant described their hydrocracked stocks as having about the same stability to oxidative storage conditions as those from solvent refining. This has generally not been industry experience elsewhere. In fact, unfinished first-stage hydrocracked base oils, waxy or dewaxed, have been found to darken in color over relatively short times and form haze or insoluble deposits, and these effects are accelerated when samples are exposed to high (about 100°C) temperatures or sunlight in so-called window tests, which were later replaced by more specific exposure to ultraviolet (UV) sunlamps. This was... 

As an example, noble metal catalysts are effective only when sulphur levels are below approximately 500 ppm. Hence, such catalysts are only applicable in two-stage hydrocracking processes with interstage removal of H2S - they are not appropriate to single-stage hydrocrackers or two-stage units without intermediate H2S removal [3]. Such limitations will not apply to F-T wax processing. 

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