Synthetic natural gas production in a 1 kW reactor using Ni–Ce/Al2O3 and Ru–Ce/Al2O3: Kinetics, catalyst degradation and process design

Abstract

Nickel and ruthenium promoted by ceria were compared as catalyst active phase for the production of synthetic natural gas in a 1 kW fixed-bed reactor (49 cm in length and 3 cm in diameter). Both catalysts were tested in a broad range of conditions: 250–450 °C, 8000–16000 h−1 GHSV, 3.5–5.5H2/CO2 ratio, and atmospheric pressure. The Ni-based catalyst presented higher CO2 conversion and lower reduction of BET area and metal dispersion after utilization. Two kinetic models were elaborated according to the performance of the catalysts in this reactor. The minimum mean squared error between the kinetic model and experiments was 3.0% for the Ru-based catalyst and 1.4% for the Ni-based catalyst. The kinetic model of the Ni-based catalyst was implemented in Aspen Plus to evaluate potential methanation plant designs. The simulation minimized the amount of catalyst required to reach 95 vol% of CH4, within proper technical limits (GHSV ≤ 5000 h−1 and temperature ≥ 300 °C). The 3-reactor plant was the most adequate configuration. The total catalyst mass was 3.26 kg per kg/h of SNG, the heat removed from the reactors was 10.8 MJ/kgSNG, and the preheating necessity was 4.90 MJ/kgSNG. The electrolysis energy consumption was 86.4 MJ/kgSNG.