Study on intrinsic kinetics of CO2 methanation on Ni/CeO2 catalyst
Hydrogenation of CO2 to synthesize CH4(CO2 methanation)is one of the crucial pathways for the efficient and clean conversion of CO2.Despite extensive researches on the catalytic system for CO2 methanation,the intrinsic kinetics of CO2 methanation under specific conditions have not been thoroughly investigated.Ni/CeO2 catalyst(Ni mass fraction of 10％)was prepared using the combustion method,and samples with varying m(α-Al2O3)∶m(Ni/CeO2)were produced by incorporating α-Al2O3 as the internal diluent.The intrinsic kinetics of CO2 methanation of sample A with m(α-Al2O3)∶m(Ni/CeO2)=25∶1 were examined under the conditions of temperature of 300 ℃,pressure of 1 MPa and gas hourly space velocity of 3 × 106 mL/(g·h).An in-depth analysis of the kinetic equations for the intrinsic CO2 methanation reaction was conducted through a combination of intrinsic kinetic tests,diffuse reflection infrared spectrum,H2-temperature programmed reaction and H2-temperature programmed desorption,etc.The results show that the CH4 generation rate under action of sample A can reach up to 41.4 mmol/(g·h)(H2 partial pressure is 400 kPa,and CO2 partial pressure is 120 kPa).When CO2 partial pressure is 30 kPa to 120 kPa,the CH4 generation rate exhibits linear increases with the rises of the H2 partial pressure,and is not affected by variation of the CO2 or CO partial pressure.Within this CO2 partial pressure range,the hydrogen-rich environment significantly enhances the catalytic activity of the catalyst for CO2 methanation.
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