Kinetic Modeling of Methane Oxidation Over Βcyclodextrin-Cu/Hydroxyapatite (Βcd-Cu/HAP) Using Power-Law Model

In recent years, industrialization and urbanization have increased the emissions of volatile organic compounds (VOCs). The term "VOCs" refers to carbon-based chemicals exhibiting a significant vapor pressure at ambient conditions. In addition to causing air pollution, VOCs can also threaten human health. Among the available technologies for mitigating VOC emissions, catalytic oxidation stands out as a promising solution.
A deep understanding of oxidation mechanism via fundamental kinetic modeling will allow exploiting the synergies between the catalytic material and operating conditions, aiming to develop optimal technologies for the abatement of VOCs. In general, deep catalytic oxidations of VOCs are explained by three models, namely the Langmuir− Hinshelwood (L-H), Eley−Rideal (E-R), and Mars−van Krevelen (MVK) models. In addition, a power law kinetic model can be employed as the first approach for further selection among the mentioned mechanistic models.
In this work, methane was chosen as a VOC model compound to investigate its kinetic behavior over βcyclodextrin-Cu/hydroxyapatite (βCd-Cu/HAP), applying a power-low approach. The temperature (350 – 450 °C), inlet partial pressures (CH4:2.9 – 8 kPa, O2: 16 – 48 kPa), and spacetime (150 – 550 kgcat s molCH4,0) were varied to investigate the impact of operating conditions on reaction performance. The kinetic parameters were obtained using the power law model as a first step to finding the best mechanism for the deep oxidation of methane over the tested conditions. The optimized reaction orders for methane (0.6) and oxygen (0.1) showed that methane oxidation depends less on gas-phase oxygen, meaning that oxygen contained inside the catalyst plays a larger role. The power-law model parameters also helped to eliminate 27 models (out of 69) and identify LH and MVK as possible mechanisms.