چكيده به لاتين
The catalytic conversion of carbon dioxide, a potent greenhouse gas, into valuable chemicals such as methane, a clean and storable fuel, has garnered significant attention. Nickel catalysts, owing to their high activity, selectivity, and low cost, are prime candidates for the methanation process. However, these catalysts exhibit insufficient activity at low temperatures and undergo degradation over extended periods. In this research, bimetallic catalysts containing nickel and iron were investigated. Throughout the study, magnesium oxide was employed as a support, synthesized using a novel mechanochemical method, while other metals were introduced via wet impregnation. The catalytic performance of these materials in the CO2 methanation process was evaluated under operating conditions of 18,000 h⁻¹ GHSV and a H2/CO2 ratio of 4, after reduction at 650°C for 2 hours. Initially, catalysts with varying nickel loadings (5-25 wt%) supported on magnesium oxide were synthesized and evaluated. The catalyst containing 20 wt% nickel, with a specific surface area of 59.52 m²/g, exhibited the best performance, achieving a CO2 conversion of 59.94% and a methane selectivity of 87.61% at 450°C. In the second phase, iron was added to this optimized catalyst at loadings ranging from 1-5 wt% to enhance the properties of the nickel metal. The catalyst containing 3 wt% iron, with a specific surface area of 90.98 m²/g, demonstrated the best performance, achieving a CO2 conversion of 66.73% and a methane selectivity of 93.91% at 400°C. In both parts of this study, the effects of various process parameters, such as reduction temperature, calcination temperature, feed ratio, gas hourly space velocity, and long-term stability, were investigated on the selected catalyst. The physicochemical properties of the synthesized catalysts were evaluated using XRD, BET, TPR, and FE-SEM analyses.
