Effect of calcination temperature and reaction conditions on methane partial oxidation using lanthanum-based perovskite as oxygen donor

Abstract

Abstract:We investigated the effect of calcination temperature, reaction temperature, and different amounts of replenished lattice oxygen on the partial oxidation of methane (POM) to synthesis gas using perovskite-type LaFeO 3 oxide as oxygen donor instead of gaseous oxygen, which was prepared by the sol-gel method, and the oxides were characterized by XRD, TG/DTA, and BET. The results indicated that the particle size increased with the calcination temperature increasing, while BET and CH 4 conversion declined with the calcination temperature increasing using LaFeO 3 oxide as oxygen donor in the absence of gaseous oxygen. CO selectivity remained at a high level such as above 92%, and increased slightly as the calcination temperature increased. Exposure of LaFeO 3 oxides to methane atmosphere enhanced the oxygen migration of in the bulk with time online owing to the loss of lattice oxygen and reduction of the oxidative stated Fe ion simultaneously. The high reaction temperature was favorable to the migration of oxygen species from the bulk toward the surface for the synthesis gas production with high CO selectivity. The product distribution and evolution for POM by sequential redox reaction was determined by amounts of replenished lattice oxygen with gaseous oxygen. The optimal process should decline the total oxidation of methane, and increase the selectivity of partial oxidation of methane.Keywords: perovskite LaFeO 3 ; lattice oxygen; synthesis gas; redox reaction; rare earths Renewed interest in methane conversion to synthesis gas, which can be used to produce a variety of chemicals by the Fischer-Tropsch and methanol synthesis, has arisen. Currently, large-scale industrial route for synthesis gas production was based on steam reforming of methane, which was a capital-and energy-intensive process owing to the highly endothermic nature of the reaction and also a large H 2 /CO ratio. The catalytic partial oxidation (CPO) offered the greatest potential for an efficient and economical conversion of methane to synthesis gas, owing to the high selectivity and suitable H 2 /CO ratio, but the Ni-based catalyst exhibited a rapid deactivation because of carbon deposition that has been reported [1] . Recently, a novel method for synthesis gas production by the direct use of lattice oxygen of perovskite has been proposed by our group [2][3][4] . This new route was superior to general partial oxidation of methane (POM) in stability (resistance to carbonaceous deposition), safety (avoiding effectively the accidental explosion), easy operation and optimization, and low cost (making use of air not oxygen) [4] . The present study aimed to explore the effect of calcination temperature and reaction temperature on catalytic activity for POM over perovskite-type LaFeO 3 oxide using lattice oxygen, and the product distribution was investigated by controlling the amount of replenished lattice oxygen with gaseous oxygen.

LaFeO3 Perovskite as New and Performant Catalyst for the Wet Peroxide Oxidation of Organic Pollutants in Ambient Conditions

“…Depending on the glycine/NO 3 -molar ratio, the mean crystal domain size was shown to vary from 25 (LaFe-1.33 sample) to more than 100 nm (for LaFe-0.55 sample). This phenomenon is consistent with previously reported data for oxides and perovskites, namely that larger crystal domain sizes are usually observed when increasing the calcination temperature [27]. The reaction temperature reached during a self-combustion synthesis is mainly related to the fuel/oxidant ratio (s), leading either to an oxidant enriched (s \ 0.55) or to a fuel enriched (s [ 0.55) mixture.…”

Perovskite-type oxide catalysts for low temperature, anaerobic catalytic partial oxidation of methane to syngas

“…Several literature reports had been published, where the use of framework oxygen of reducible oxides in direct contact with methane was presented as an option. 21,[54][55][56][57][58][59]61,62,68,69,[71][72][73][74] .…”

“…The partial substitution of La 3+ with Sr 2+ decreases the global charge present on the A site and forces the metal cation in the B site to an oxidation state higher than 3+ and may at the same time create oxygen vacancies in the structure 47,48 The reversible oxygen uptake and release associated with the specific nonstoichiometry range, δ, that the perovskite experiences has inspired several practical applications. One of these, and the most relevant for this PhD work, has been the reaction of this available oxygen with methane to form mixtures of CO 2 , H 2 O, CO and H 2 21,[54][55][56][57][58][59][60][61][62][63] . Most of these works report the presence of two "types of oxygen" that respectively give rise to total…”

Lanthanum Ferrite Ceramic Powders: Synthesis, Characterization and Electrochemical Detection Application

“…Thus, a depolarization effect toward the oxygen evolution reaction and a polarization effect on the hydrogen evolution reaction were manifested through LaFeO3 on the BDD electrode surface. The electrocatalytic activity of the LaFeO3 sample is relevant with the crystalline size and the rate of oxygen migration from bulk towards the surface [57,58], which relates to the applied potential range. Both unmodified and LaFeO3/BDD electrodes were tested in the presence of 5 µM CCB and no signal was found at an unmodified BDD electrode (the results are not shown here).…”