Molybdenum recovery from spent Mo-based dispersed catalyst accumulated in heavy oil steam cracking coke

Recovery of molybdenum has been studied from coke formed as a by-product of catalytic steam cracking of heavy oil containing a Mo-based nanodispersed unsupported catalyst, and from mixtures of industrial coke with Mo-based compounds - as model systems, via combustion in the fluidized bed of deep oxidation catalyst and the fixed bed of coke (without a catalyst). Quantitative carbon removal was found to be impossible even for several cycles of combustion in fluidized catalyst bed, most probably due to a drop of size of the coke particles to those of too small in order to have a sufficient contact time for the complete burning off. Non-catalytic combustion in the fixed bed mode showed best efficacy resulting in complete carbon removal without any Mo losses in the range of 450-750 degrees C.