Exploring the impact of Nickel on ceria doped Cobalt catalysts for low-temperature catalytic combustion of methane

Abstract

Reducing methane emissions through complete catalytic oxidation at lower temperatures, using efficient and cost-effective catalysts, holds an importance in various industrial and environmental applications. In this study, we developed a series of bimetallic catalysts by incorporating nickel into ceria-doped cobalt oxide at varying loadings. These catalysts were thoroughly characterized to understand the impact of nickel incorporation on the catalytic performance, and subsequently tested for their efficiency in methane oxidation. To gain a comprehensive understanding of the catalysts' properties, a range of characterization techniques was employed, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), nitrogen adsorption-desorption (BET), Raman spectroscopy, hydrogen temperature-programmed reduction (H₂-TPR), and oxygen temperature-programmed desorption (O₂-TPD). These methods provided insights into the physicochemical properties of the catalysts and the influence of nickel on their catalytic activity. The catalysts' performance in complete methane oxidation was evaluated in the range of 200–600°C. Water vapour (1.5 vol%) was introduced into the feed stream to study the impact of water vapour on the catalytic performance. Among the catalysts tested, the 15Co15NiCe catalyst exhibited the highest activity, achieving a T₅₀ value at 389°C. The characterization results revealed that the optimal incorporation of nickel led to an increase in active surface oxygen species, the creation of lattice defects, an enlarged surface area, and enhanced reducibility, all of which contributed to an improved catalytic performance. Kinetic analysis showed that the calculated activation energy aligned with the observed methane oxidation activity trends. Furthermore, the best-performing catalyst demonstrated an exceptional stability over extended reaction times, with stability tests conducted over 12 hours revealing minimal variation in conversion efficiency. Post-reaction characterization of the spent catalyst using thermogravimetric analysis (TGA) and temperature-programmed oxidation (TPO) provided insights into the slight variations observed during the stability tests. The findings from this study pave the way for the development of low-temperature catalytic processes pretinent to catalytic oxidation of methane.