It has been observed that the deposition of nickel on FCC catalysts, whilst producing small changes on conversion (defined as the sum of the yields of gasoline + total gas + coke) produces a significant decrease in bottoms conversion. The influence of the sulphur plus phosphorus and the nature of other organic ligands in antimony complexes, on the nickel passivation ability during gas-oil cracking has been studied by comparing the results obtained using O,O,diethyldithiophosphate-, O,O,didecyldithiophosphate-, and ethyl-xanthate-Sb complexes, at two Sb/Ni ratios. The influence of the passivator on nickel on the surface has been discussed using results from X-ray photoelectron spectroscopy measurements. Finally, on unsupported samples, the different Ni-Sb phases formed have been studied by X-ray diffraction.
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