The ideal coke mitigation catalyst technology prevents both heterogeneous coke formation and homogeneous coke deposition on reactor wall surfaces. The catalyst can be applied as a coating to passivate and isolate wall metal surfaces in order to circumvent the metal surface-catalyzed nucleation and growth of coke deposits. An effective catalyst coating would eliminate the heterogeneously catalyzed dissociative adsorption of hydrocarbons (HC)s at metal surfaces, which could lead to carbon (C) solubilization and saturation (1). The nucleation of heterogeneous coke originates from the reemergence of the saturated C at the wall surface to form metal carbide catalytic particles and/or graphitic precursor structures (2). The catalyst coating would also resist the adsorption and condensation of homogeneous coke precursor species formed in the gas phase. It is advantageous for low molecular weight free radical species to be quenched at the surface, either by adsorption, neutralization, or saturation, to prevent their involvement in gas-phase radical cascade reactions leading to coke precursor formation. However, the coating must resist the adsorption of electron-rich higher molecular weight unsaturated and/or polycyclic species that are believed to contribute to amorphous coke formation on the wall. Even after adsorption, these species typically contain multiple sites which can participate in condensation and cyclization reactions with new species arriving continuously at the surface (3). Thus, to prevent the accumulation of homogeneous coke, the coating not only needs to resist the binding of coke precursors, but it must also actively catalyze their decomposition. In the cases where coke is still able to accumulate, the coating also serves to catalyze decomposition of the coke deposits.
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