Optimization of the partial oxidation of methane on Ni-MgO/a-alumina monolith catalyst in a reverse flow reactor using the method of steepest ascent

Catalytic partial oxidation of methane (CPOM) has been recognized as a suitable method to produce synthesis gas for production of liquid fuel and hydrogen. CPOM, which is a mildly exothermic reaction, can be conducted autothermally in a reverse flow reactor (RFR) wherein the direction of flow is reversed cyclically. Implementation of real RFR is complicated. Recent published studies have focused mainly on numerical simulation and control strategy, but there have been few published experimental studies. This study describes a systematic experimental optimization of a laboratory scale RFR for CPOM on Ni-MgO/a-Al2O3 monolith catalyst using the response surface methodology. The effect of initial temperature (Tini), switching time (), total flowrate (F), molar feed ratio between methane and oxygen (M), and catalyst length were investigated. Hydrogen yield and methane conversion are used as the experimental responses. The steepest ascent path was established based on the first experimental design to determine the stationary point whose nature was confirmed by the second experimental design. The iteration of establishing the steepest ascent path and experimental design was done until the maximum point was specified. In this study, the optimum operating conditions were determined in the second experimental design. The analysis of reactor operation proved to be challenging due to the complex interplay of the different experimental factors. The following interactions were found to be significant for methane conversion: M*, F* and M*F. The interaction of F* also affected the hydrogen yield. The third order interaction of F**M was also found to be statistically significant. The optimum methane conversion value of 56.38% could be obtained by setting switching time, total flowrate and molar ratio of 4.24 minutes, 543ml/min and 1.575, respectively. The optimum value of hydrogen yield of 35.91% was reached by setting total flowrate, molar feed ratio and switching time of 540ml/min, 1.442 and 4.15 minutes, respectively