Metals feed hydrotreating

Problems sulfur and nitrogen transferred to the products (and coke) Solutions feed hydrotreating, reduction of S, N, Conradson carbon, metals Results higher quality products reduction in pollution better yields of valuable products reduced post-treatment... 

The FCC process is the most common conversion unit in use today. As such, it is important to determine the performance of an FCC when feeding hydrotreated shale oil. The two 650° F+ feeds shown in Table VI were evaluated in an FCC pilot plant operating in a fixed fluidized-bed mode. The catalyst was withdrawn from an operating commercial FCC unit. It is a zeolite catalyst, CBZ-1, produced by Davison Chemical Division of W. R. Grace and Company and is moderately active as well as contaminated with metals. 

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. 

Hydrotreating is a hydrogen-consuming process primarily used to reduce or remove impurities such as sulfur, nitrogen, and some trace metals from the feeds. It also stabilizes the feed hy saturating olefrnic compounds. 

Among the classes of feedstock processed in the hydrocracker the most highly aromatics feed are light cycle oils produced in the FCC unit Once formed by cyclization and the hydrogen transfer mechanism discussed above, they accumulate in the product due to the absence of a metal function in the FCC catalyst and adequate hydrogen in the process environment. They are typically sold as low-value fuel oil, or hydrotreated to reduce sulfur content and improve their quality as diesel blend stocks. Another approach to upgrade their value even further... 

The hydrogen sulfide and ammonia can be removed by amine extraction and acid washes respectively. Hydrotreating also removes metals from the feed that would otherwise poison the reforming and cracking catalysts. 

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. 

Hydrotreating processes have two definite roles (1) desulfurization to supply low-sulfur fuel oils and (2) pretreatment of feed residua for residuum fluid catalytic cracking processes. The main goal is to remove sulfur, metal, and asphaltene contents from residua and other heavy feedstocks to a desired level. 

A recapitulation of the catalyst stability data reported indicates that within the time scale of the hydrotreating runs, the UOP-filtered SRC filter feed gave relatively stable performance. SRC itself caused substantial catalyst deactivation Synthoil gave stable performance after an initial deactivation. Since dissolved metals and particulate matter are known to have an adverse effect on catalysts, a correlation was sought based on an analysis for these components. 

More irreversible deactivation (hydrothermal, metals), if the feed is not hydrotreated. 

All licensors agree on the necessity of hydrotreating the feed to lower the level of poisons for the platinum-based reforming catalyst. Temporary poisons are sulfur and nitrogen, while As, Pb, and other metals are permanent poisons. Proper conditions of hydrogen, pressure, temperature, and space velocities are able to reduce these poisons to the acceptably low levels of modern catalysts. Numerous process design modifications and catalyst improvements have been made in recent years. 

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