Effect of impregnation sequence of Mg on performance of mesoporous alumina supported Ni catalyst in dry reforming of methane

Abstract

In this study, effect of Mg impregnation sequence on the activity of the mesoporous alumina supported Ni catalysts was investigated in dry reforming of methane. Characterization and activity test results showed that Mg incorporation sequence significantly influenced the physicochemical properties and the activity of the catalyst as well as coke deposition during reforming reaction. The synthesized catalysts were characterized by x-ray diffraction, N2 adsorption, temperature programmed reduction, scanning electron microscopy, CO2-temperature programmed desorption, inductively coupled plasma optical emission spectrometry, x-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy (FTIR) and pyridine adsorbed diffuse reflectance FTIR spectroscopy techniques. Mg incorporation altered the reduction profile of the monometallic catalyst and increased the reduction temperature of the nickel particles. XRD diffraction peaks corresponding to γ-A2O3 and α-Al2O3, as well as nickel-magnesium spinels and metallic Ni were observed depending on Mg incorporation sequence. The monometallic Ni catalyst showed higher activity than the bimetallic NiMg catalysts. However, coke formation was significantly influenced as a result of synthesis route. Total organic carbon, thermogravimetric analysis and SEM images exhibited that the highest coke formation was obtained over the catalyst which was prepared by sequential impregnation of Mg and then Ni. Almost no coke formation was observed on the spent catalyst, which was synthesized by simultaneously impregnation of Mg and Ni, due to the high interaction between Ni and Mg with the formation of a NiOMgO solid solution during the high calcination temperature.