Nickel-containing cracking catalyst

Imaging SIMS has been used to locate the positions of trace amounts of metals such as vanadium and nickel on zeolite-containing cracking catalysts. This technique can be used ex-situ in a dynamic mode to determine the mobility of these poisons. The results... 

The equivalent nickel content of the feed to the FCCU can vary from <0.05 ppm for a weU-hydrotreated VGO to >20 ppm for a feed containing a high resid content. The nickel and vanadium deposit essentially quantitatively on the cracking catalyst and, depending on catalyst addition rates to the FCCU, result in total metals concentrations on the equiUbrium catalyst from 100 to 10,000 ppm. 

These metals permanently poison the FCC catalyst by lowering the catalyst activity, thereby reducing its ability to produce the desiretl products. Virtually all the metals in the FCC feed are deposited on the cracking catalyst. Paraffinic feeds tend to contain more nickel than vanadium. Each metal has negative effects. 

At very low surface areas (about 5 m /g) and constant conversion (70%), the contaminant selectivities are dominated by the matrix composition (Table I). Rare earth and magnesium-containing microspheres were prepared to examine the effects of these metal oxides on catalyst selectivities in the presence of nickel and vanadium. These oxides were chosen because the literature (3,5,10-15) has shown them to be effective at reducing the deleterious effects of vanadium in cracking catalysts. 

It is the purpose of this paper to review the progress made in understanding and designing zeolite-containing fluidized cracking catalysts capable of negating the deleterious effects of metals such as nickel and vanadium. 

The nickel concentration on this particle is extremely low with traces of the nickel impurity at the external surface. This low nickel concentration means that the particle in Figure 2 was in the refinery unit only a short time, otherwise more nickel would be present for the average particle (by bulk chemical analysis) contains 900ppm Ni and 4700 ppm V. The particle in this image contains a disproportionate amount of vanadium relative to nickel. If the nickel on the external skin of the catalyst accumulates by nickel porphyrin cracking at the first surface contacted, then vanadium must arrive not only by cracking vanadyl porphyrins but also by some other means like transfer from older catalyst particles in the FCC unit. The high vanadium concentration relative to nickel on new catalyst particles provides evidence that vanadium has interparticle mobility as well as intraparticle mobility. 

Nickel and vanadium are contained within the crude oil as their respective porphyrins and napthenates (2). As these large molecules are cracked, the metals are deposited on the catalyst. Nickel which possesses a high intrinsic dehydrogenation and hydrogenolysis activity drastically increases the production of coke and dry gas (particularly H2) at the expense of gasoline. Vanadium on the other hand interacts with the zeolitic component of a cracking catalyst and leads to destruction of its crystallinity. This results in reduced activity as well as an increase in non-selective amorphous silica-alumina type cracking. Supported vanadium also has an intrinsic... 

At temperatures above 250-300°C, nickel catalysts cause extensive d radation of hydrocarbons with the formation of methane and hydrogen and the deposition of carbonaceous materials on the catalyst surface. However, on combining a hydrogenation catalyst such as nickel with a cracking catalyst such as silica-alumina so that the final catalyst contains 4-6 per cent by weight of nickd, a complex catalyst results which is quite active and... 

When discussing the suitability of the ARCO pilot unit for cracking atmospheric residues, this cannot be done without touching on the question about how to prepare the catalysts for testing. An equilibrium catalyst used in a commercial residue FCCU contains significant amounts of metal contaminants, especially nickel and vanadium. Fresh catalysts must therefore be impregnated with these metals and deactivated before the catalysts can be nsed in the pilot unit. We have shown that this... 

A number of refinery processes require the use of a fixed-bed catalyst These processes include catalytic reforming, hydrodesulfurization, hydrotreating, hydro-cracking, and others. These catalysts become inactive in six months to three years and are eventually replaced in the reactors with fresh catalyst during a unit shutdown. Many of these catalysts contain valuable metals which can be recovered economically. Some of these metals, such as platinum and palladium, represent the active catalytic component other metals such as nickel and vanadium are contaminants in the feed which are deposited on the catalyst during use. After valuable metals are recovered (a service usually performed by the outside companies), the residuals are expected to be disposed of as solid waste. 

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