Kinetic modeling of propane selective oxidation to acrylic acid over Mo1V0.3Te0.23Nb0.12Ox in the presence and absence of water using genetic algorithm

Role of water vapor in propane selective oxidation to acrylic acid over Mo1V0.3Te0.23Nb0.12Ox has been investigated using kinetic study. The catalyst was produced by slurry method and two sets of experiments have been designed: reactions in the presence and absence of water vapor. Experimental data were obtained under different operating conditions in a tubular fixed bed reactor. Power law and Mars-Van Krevelen (MVK) models for the predictions the catalytic performance were employed using the genetic algorithm. The reaction orders obtained by the power law model determined that gas phase oxygen concentration has considerable effects on catalytic performance in wet condition. Contrary to dry ones which reveal that changing oxygen concentration has negligible effects on catalytic performance. MVK results indicate that in the presence of water vapor, lattice oxygen production is the rate determining step. Therefore dependency on gas phase oxygen concentration is expectable. While at dry conditions the activation energy of hydrocarbon is higher than that of oxygen. Therefore lattice oxygen is always available and independent of gas phase oxygen. Presence of water induces some structural modifications: improvement the crystallinity, decreasing production of non-selective sites (MoO3) and enhanced presence of the M1 phase. As a results, water vapor limits lattice oxygen availability through improvement of catalyst structure leading to better acrylic acid selectivity.