Production of Syngas by CO2 Reforming on MxLa1−xNi0.3Al0.7O3−d (M = Li, Na, K) Catalysts

Abstract

This paper deals with the effect of modification with alkali metals (Li, Na, K) in MxLa1−xNi0.3Al0.7O3−d (x = 0, 0.2, 0.5, 0.8, and 1.0) mixed-oxide perovskites as catalysts for the dry reforming of methane to produce syngas. The perovskite-type oxides have been synthesized by a sol−gel method using propionic acid as solvent and have been characterized by techniques such as Fourier-transform infrared (FT-IR), Bruner Emmet Teller surface area (BET), spectroscopy, X-ray diffraction (XRD), temperature programmed reduction (TPR), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and carbon analysis (CA). Characterization of the MxLa1−xNi0.3Al0.7O3−d samples has shown that by applying this synthetic method it is possible to obtain highly crystalline, homogeneous, and pure solids with well-defined structures. However, when lanthanum was replaced by potassium or lithium, the reduction temperature was increased and the reaction temperature had to be increased to obtain good activity. After establishment of the optimal catalytic and experimental conditions, the selected catalysts did not show significant deactivation even after 15 h on stream, maintaining their activity and selectivity in the production of synthesis gas. Among all catalysts, Li0.2La0.8Ni0.3Al0.7O2.8 showed less coke formation; Na0.5La0.5Ni0.3Al0.7O2.5 showed high yield; and K0.5La0.5Ni0.3Al0.7O2.5 produced an H2/CO ratio close to 1 over a wide temperature range. These catalysts showed the best activities in lithium-, sodium-, and potassium-promoted series, respectively. In reactivity tests, methane conversions in excess of 90% and selectivities for H2 up to 80% at 850 °C under 1 atm have been achieved.