Kinetics of the thermal decomposition of coke formed on ZnO/H-BEA catalyst in the transformation of 2-methylthiophene in n-hexane stream.

Combustion kinetic data of the coke present in FCC catalysts and additives are important for developing industrial regenerator simulations. In this work, the Ozawa–Flynn–Wall kinetic model was applied to evaluate the impact of the modifications carried out with zinc oxide in a beta zeolite (BEA) on coke combustion activation energy values. The catalysts were coked by catalytic cracking of n-hexane, containing 2-methylthiophene at a temperature of 500 °C and mass hourly space velocity of 0.17 s⁻¹. The catalysts showed an average coke formation of 23% by mass. The activation energy in the coke combustion in the catalysts was 108.1 kJ mol⁻¹ (H-BEA), 114.7 kJ mol⁻¹ (ZnO/H-BEA2), and 122.3 kJ mol-1 (ZnO/H-BEA8). A directly proportional relationship was observed between the coke content formed, the activation energy of the combustion of this coke, and the type of coke formed (types I and II) with the zinc content in the catalysts. The incorporation of zinc at different levels in zeolite beta increased the adsorption capacity and the number of strong acid sites of the catalysts, increasing the interaction between the coke formed and the catalyst, favoring the formation of different types of coke under the reaction conditions studied. [ABSTRACT FROM AUTHOR]