Search

In this study, Ce1-xLaxNiO3 catalysts (x = 0.2, 0.4, 0.6, and 0.8) and Ce1-xLaxNiO3 on porous silica were prepared by co-precipitation. The effect of the La content on the catalytic activity in methane bi-reforming was investigated in the temperature range of 550 °C-750 °C. The physicochemical properties of the prepared catalysts were analysed by several methods, including X-ray diffraction, hydrogen temperature-programmed reduction, CO2 temperature-programmed desorption, N2 adsorption isotherm, energy-dispersive X-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy. From the research results, the suitable substitution rate of La in Ce1-xLaxNiO3 was found to be x = 0.4; its conversions of CH4 of 94% and CO2 of 92% were achieved at 700 °C and GHSV 30000 mL/(g.h). However, the intense coke accumulation on Ce0.6La0.4NiO3 limited its development. The porous silica carrier improved the structure and properties of the Ce0.6La0.4NiO3 catalyst. The SiO2-supported catalyst (Ce0.6La0.4NiO3/SiO2) showed excellent stability and coke resistance, which had stable activity for 100 h of time on stream, structure stability and low coke accumulation; 2.37 mgC/gcat formed after 100 h (coke formation rate of 0.02 mmolC/(gcat.h)), which demonstrated that it was one of the best coke-resistant perovskite catalysts for the BRM reaction. The large surface area of silica and strong interaction of Ni with metal oxide reduced the metal Ni particle size to the threshold size (2−4 nm), where the strongly reduced coke accumulation, high basicity, and vacancy oxygen content of CeO2 and La2O3 were considered major contributors to the high activity and exceptional coke resistance. The high structural stability, anti-sintering performance and high coke resistance all contributed to the excellent durability of the Ce0.6La0.4NiO3/SiO2 catalyst. This work provides a new resolution for the development of coke-resistant perovskite catalysts for methane reforming.

This work offered insights into the characteristics and performance of nickel nanocatalyst in situ synthesized through CeNiO3 perovskite for the bireforming of methane (BRM). Effects of calcination conditions on the characteristics of CeNiO3 structure and on the reduction regime of the as-prepared perovskite on the physicochemical properties and performance of nickel catalyst in BRM were assessed. The formation of high-crystallinity CeNiO3 at temperatures above 700 °C was confirmed. The synthesized CeNiO3 existed in the form of spherical particles 20–40 nm in size and uniformly distributed. Among the samples, one calcined at 700 °C for 2 h (C-700-2.0) had the smallest and the most uniform particle and the highest reducibility. This sample was found to be the optimum precursor for the in situ synthesis of a highly effective nano-Ni catalyst for BRM. The reduction mode significantly affected the catalytic performance of the C-700-2.0 precursor. The sample reduced at 750 °C for 1.5 h (R-750-1.5) possessed the optimum activity, with conversions of CH4 and CO2 reaching equilibrium (98% and 84%, respectively) and an ideal H2/CO ratio of 2 at the reaction temperature of 700 °C.

Hydroxyapatite (HA) derived from salmon bone byproducts is used as a green support for the nanostructured nickel catalysts applied in the methanation of carbon dioxide (CO 2 ). Undoped nickel catalysts and various ceria-doped nickel supported on hydroxyapatite (HA) were prepared by coimpregnation. Characteristics of the as-prepared catalysts were investigated by the various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), hydrogen temperature-programmed reduction (H 2 -TPR), carbon dioxide temperature-programmed desorption (CO 2 -TPD), and energy-dispersive X-ray spectroscopy (EDX). The catalyst activity was assessed throughout CO 2 methanation in the low-temperature range of 225-350 °C with the molar ratio of H 2 /CO 2 = 4/1. The function of HA and ceria provided a high dispersity of nickel particles over the catalyst surface with the size range of 24.5-25.8 nm, leading to improvement in the reduction and CO 2 adsorption capacity of the catalysts as well as enhancing the catalytic efficiency in CO 2 methanation. The 10Ni/HA catalyst reduced at suitable conditions of 400 °C for 2 h showed the highest catalytic performance among the tested catalysts. CO 2 conversion and CH 4 selectivity reached 76.6 and 100% at a reaction temperature of 350 °C, respectively. The results show that the Ni/HA sample doped with 6.0 wt % ceria was the best, with the CO 2 conversion and the CH 4 selectivity reaching 92.5% and 100%, respectively, at a reaction temperature of 325 °C., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)