Carbon dioxide reforming of methane over La 2NiO 4 as catalyst precursor—Characterization of carbon deposition

Abstract

La 2NiO 4-type perovskites were prepared by the “self-combustion” method and were used as catalyst precursor for the CO 2 reforming of CH 4 reaction at 700 °C. The catalysts were used in reduced and non-reduced form. High CH 4 and CO 2 conversions were obtained with a H 2/CO ratio lower than 1. This result was explained by the occurrence of the RWGS (reverse water gas shift) reaction. The reduction of the perovskite La 2NiO 4 leads to the formation of small nickel particles (average diameter: 7 nm), consequently the catalytic activity is higher than that obtained with 5% Ni/La 2O 3 (average diameter: 11 nm). The use of the perovskite La 2NiO 4 without reductive treatment prior to the reaction shows that the catalyst is composed of a mixture of Ni, La 2O 2CO 3 and La 2NiO 4 during the first hours of the reaction. The catalytic activity is thus lower than that obtained with the reduced perovskite. The reaction performed using the non-reduced perovskite is accompanied by carbon deposition. TEM and Raman analysis showed that multiwalled carbon nanotubes are formed under those experimental conditions.