A simple Simulation Model for Oxidative Coupling of Methane over La0.6Sr0.4NiO3 Nanocatalyst.

Abstract

La_0.6Sr_0.4NiO₃ perovskite-type oxides were prepared by reverse microemulsion method aided by ultrasonic homogenizer. The mixed oxide precursors and the corresponding derived fresh catalysts were characterized by thermogravimetry and differential thermal analysis (TG/DTA), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area and high resolution transmission electron microscope (HRTEM). XRD results reveal that pure phase of perovskite-type crystalline structure was obtained for all samples and the electronic unbalance caused by the partial substitution for La³⁺ by Sr²⁺ is compensated by oxidation of a fraction of Ni³⁺ to Ni⁴⁺ and/or generation of oxygen vacancies in the perovskite lattice. There exist two kinds of oxygen species on the oxides: surface adsorption oxygen and bulk lattice oxygen. The surface oxygen contributed to oxidize methane completely to CO₂ and H₂O because of its higher reactivity, while the other one prone to oxidative coupling of methane into C₂H₆ and C₂H₂ (C₂₊).  In this study a mathematical model for the oxidative coupling of methane (OCM) over La_0.6Sr_0.4NiO₃ pervoskite is developed. From this simulation it can predict that the activity at temperature ? 925 ºC and methane partial pressure =0.3 and oxygen partial pressure =0.1 will be reach ~10% and selectivity ~50%.

Keywords: Oxidative coupling, Methane, Perovskite