Process hydrocracking

In two stages with recycle to the second stage, the conversion per pass is approximately 50 wt. % and the selectivity to middle distillates is maximal 75 to 80 wt. %. However, the investment is clearly higher and is justified only when feedstocks are difficult to convert and that their content in nitrogen is high. Figure 10.11 represents two variants of the hydrocracking process. 

The hydrocracking process is characterized by a very low gas production and a low LPG yield especially when operated for maximum distillates. Byproducts in this operating mode are ... 

Table 10.18 presents some useful data on the mild hydrocracking process and resulting products. 

Hennico, A., A. Billon, P.-H. Bigeard and J.-P. Peries (1993), IFP s new flexible hydrocracking process combines maximum conversion with production of high viscosity, high VI lube stocks . Rev. Inst. Fran. du Petrole, Vol. 48, No. 2, p. 127. 

The following discussion of base metal catalyst regeneration uses the hydrocracking process and catalyst, specifically UOP HC Unibon, as an example. 

Products from hydrocracking processes lack olefinic hydrocarbons. The product slate ranges from light hydrocarbon gases to gasolines to residues. Depending on the operation variables, the process could... 

Analysis of feed and products from hydrocracking process ... 

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. 

Nikravech, M. et al., Plasma-fluidized bed hydrocracking process of heavy hydrocarbons, Proc. 9th Int. Symp. on Plasma Chemistry, Pugnochiuso, Italy, 209,1989. 

HC Unibon [Hydrocracking] A version of the hydrocracking process for simultaneously hydrogenating and cracking various liquid petroleum fractions to form branched-chain hydrocarbon mixtures of lower molecular weight. The catalyst is dual-functional, typically silica and alumina with a base metal, in a fixed bed. Developed by UOP. By 1988,46 licenses had been granted. Currently offered under the name Unicracking. 

Hy-C Cracking A hydrocracking process. The catalyst is nickel/tungsten on alumina. Developed by Cities Service Research and Development Company and Hydrocarbon Research. 

Isocracking A hydrocracking process developed and licensed by Chevron Research Company. The catalyst is nickel or cobalt sulfide on an aluminosilicate. First commercialized in 1962 more than 45 units had been built by 1994. See also Isomax. 

LC-Fining [Lummus Cities refining] A hydrocracking process using an ebullated catalyst bed. Developed by Lummus Crest and Cities Service Research and Development Company since the 1960s, initially for upgrading bitumen from tar sands. Three units were operating in 1996. 

Lomax An outdated name for a hydrocracking process now offered under the name Unicracking. 

LPG Unibon An outdated UOP version of the hydrocracking process for simultaneously hydrogenating and cracking a naphtha petroleum fraction to form C3 and C4 hydrocarbons. In 1992 the technology was offered under the umbrella of Unicracking. 

MHC Unibon [Mild hydrocracking] A mild hydrocracking process for desulfurizing gas oil and converting it to lower molecular weight hydrocarbons, suitable for further processing by catalytic cracking. Developed by UOP. 

MRH (2) A hydrocracking process for difficult petroleum residues, i. e., those containing high levels of metals, sulfur, and nitrogen compounds. It uses catalytic hydrogenation in a slurry bed. Developed by the MW Kellogg Company. 

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. 

Figure 4.16 Reactions occurring in hydrocracking process (M, metallic site A, acidic site).

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. 

Table 12.19 Zeolites used in hydrotreating or hydrocracking processes. 

Zeolite Beta with its three-dimensional channel system appears more suitable for conversion of gas oil feeds containing large molecules in FCC and hydrocracking processes and has indeed received much attention in the scientific and technical literature [38-40]. It exhibits very strong acidity which exceeds that of stabihzed Y zeolites. While the three dimensional pore system of this zeoHte with its 12-member pore mouth makes it suitable for use in processing heavier feedstocks, its more tortuous chaimel system appears to impart a tendency to selectively crack normal paraffins as compared to Y-zeolite. A close look as the channel geometry... 

In the hydrocracking process, this phenomenon is exploited to shift catalyst selectivity from the naphtha to the distillate products. Here the wide separation of sites is exploited to minimize the potential for secondary cracking in initial products and intermediates. This, along with the introduction of escape routes for the primary product tends to preserve the higher molecular weight hydrocarbons, thereby producing more dishllates [49, 61, 62]. 

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