Commercial metals passivation systems

Maintenance of Proper Antimony Concentration. Close monitoring of the antimony concentration on the catalyst will assure that maximum benefits are derived from a metals passivation program. The antimony-to-nickel ratio on the equilibrium catalyst has been correlated with hydrogen production in commercial operations (Figure 5), The non-linear shape of the hydrogen production curve has been confirmed in pilot plant tests (Figure 1), The recommended antimony concentration corresponds to a point beyond the breakpoint of the curve, A "cushion" is desired to allow fluctuations in the system without major increases in the yields of hydrogen and coke. 

Metals passivation is an area of active research and development, and several passivation systems have been commercialized. Commercialized systems include addition of elements and combinations of elements to FCC catalysts, such as antimony, antimony plus phosphorus (6,. 14), antimony plus phosphorous plus tin, antimony plus tin, tin (19-21), and bismuth (22, 23). Other commercialized systems include process changes or catalyst changes such as the use of steam or light hydrocarbons as diluents in the reactor (24) and vanadium traps (25). Antimony has been used successfully in conjunction with these systems. Another metals passivation additive, containing ingredients that are proprietary, has also been introduced commercially (26) ... 

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