Analysis of light-off during oxidation of reactant mixtures on Pt/Al2O3 using micro-kinetic models

作者：Kota Arun S; Dadi Rama Krishna; Luss Dan; Balakotaiah Vemuri^*

来源：Chemical Engineering Science, 2017, 166: 320-333.

DOI：10.1016/j.ces.2017.02.050

• Micro-kinetic model
• Steady-state hysteresis
• Dynamic hysteresis
• Co-oxidation

An elementary step mechanism, which accounts for adsorption, desorption and surface reaction steps is proposed for co-oxidation of CO, propylene, hydrogen and ethane on Pt/Al2O3. Parameter estimation is used to determine the kinetic parameters for these steps, which depend on platinum loading and dispersion. A micro-kinetic model is proposed for water-gas shift reaction that captures the experimental trend observed during co-oxidation of CO/H-2. This mechanism is used to predict hysteresis features during oxidation and co-oxidation reactions. The oxidation of all the individual reactants exhibits regular hysteresis and the model predicts the experimentally observed inverse hysteresis during co-oxidation of CO and C3H6. The inverse hysteresis is caused by surface intermediates formed during C3H6 oxidation. These surface intermediates block the active sites, decreasing the light-off activity of CO during ramp down. The developed micro-kinetic model can also explain steam reforming of propylene and ethane on Pt/Al2O3\. Finally, we compare the predicted hysteresis during CO oxidation by global and micro-kinetic models. The predicted ignition temperature by both global and micro-kinetic models is almost same. However, the predicted extinction temperature by the global and micro-kinetic models is rather different. This behavior is due to different rate determining step during ramp down period.

• 出版日期2017-7-20