Synergistic Effect of Bimetallic Ni-Based Catalysts Derived from Hydrotalcite on Stability and Coke Resistance for Dry Reforming of Methane

Abstract

Bimetallic Ni–Al and Ni–Fe nanoparticles catalysts derived from hydrotalcite were synthesized by co-precipitation method and applied in dry reforming of methane. The samples were calcined at 800 °C and the crystalline phases were assessed by X-ray diffraction coupled with Rietveld refinement. Other analyzes were carried out to study their textural and structural properties including, Thermogravimetric Analysis (TG), Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), Brunauere-Emmette-Teller (BET), Scanning Electron Microscopy and Energy Dispersive-X-ray (SEM–EDX), Temperature Programmed Reduction (TPR), Transmission Electron Microscopy (TEM) and EDS mapping. The XRD Analyses confirmed the formation of the precursor’s layered double hydroxide structure, the formation of the γ-NiFe alloy confirmed by TEM-EDS Analysis. The specific surface area of the two samples increases after calcination, attributed to the destruction of the double-layered structure at high temperature, which produced cavities or crates resulting in larger surface areas. These catalysts were evaluated in CO2 reforming of methane under continuous flow with CH4/CO2 ratio equal to 1, at atmospheric pressure and a temperature range between 400 and 700 °C. At 700 °C, the NiAlHT catalyst displayed the best CH4 conversion (87.5%) and CO2 conversion (91.4%) compared to the conversion of CH4 (79.2%) and CO2 (84.1) for NiFeHT catalyst within 10 h stability test. The iron addition to the nickel showed improved resistance to coke deposition while a slight decrease in methane conversion was observed. The possible formation of γ-NiFe alloy observed during the study of reducibility by hydrogen was invoked to account for the catalytic behavior.