A successful transition towards a cleaner and more sustainable energy system in 2050 requires large-scale implementation of sustainable and renewable energy source. In contrast with conventional energy sources, the intermittency and fluctuation of renewable energy make difficult its integration into the existing energy grid [1]. Recently, the methanation of CO2 via the Sabatier process is gaining interest for power-to-gas (P2G) application [2]. It is a reaction of great technological and environmental potential, leading to (i) storage of excess H2 generated from renewable energy, (ii) reduction of CO2 emissions (greenhouse gas) from the atmosphere and (iii) production of SNG whose distribution infrastructures are readily available [3]. In this work, CO2 methanation activity and stability were investigated over Ni/GDC (gadolinium-doped-ceria) catalysts at atmospheric pressure varying reaction temperature (TSET = 300-600°C) and space velocity (GHSV = 10,000-50,000 h-1). Powder catalysts with different Ni content (15-50 wt.%) were synthesized by the solution combustion synthesis (SCS). The same method was adopted to in situ deposit the Ni/GDC (50 wt.%Ni) coating layer on the cordierite monolith (500 cpsi). The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), CO2 temperature programmed desorption (CO2-TPD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Temperature profiles along the structured catalytic bed were discussed to interpret the experimental results. Catalytic performance increased by increasing the Ni content due to enhanced metal-to-support interaction and basicity, as confirmed by H2-TPR and CO2-TPD analysis. In general, the activity increased by increasing the temperature while remaining well below the thermodynamic limits, due to the kinetic limitations at relative low temperatures (300-450°C). A slight decrease in activity was observed further increasing the temperature up to 600°C, due to thermodynamic limitation of methanation reaction and competing RWGS equilibrium. Very uniform, thin (10-40 ?m) and high-resistance catalytic layers were in-situ deposited on the cordierite monoliths by the SCS method [4]. Relative high activity of the structured catalysts was recognized, closely connected to the temperature profiles recorded on the catalytic bed. High surface-to-volume ratio, good interphase mass transfer and low pressure drops led to high methane productivity per unit weight of catalyst. The highest CH4 productivity of 10.7 LCH4·gcat -1·h-1 was obtained at 400°C and 50,000 h-1. Also, excellent long-term stability was observed over 200 h of time-on-stream. The results reported in this manuscript pinpointed on the important aspects of realizing CO2 methanation on structured catalysts, providing a platform for further optimization studies.
Monoliths supported Ni/GDC catalyst via in-situ combustion deposition for CO2 methanation
C Italiano;L Pino;M Ferraro;M Laganà;V Antonucci;A Vita
2018
Abstract
A successful transition towards a cleaner and more sustainable energy system in 2050 requires large-scale implementation of sustainable and renewable energy source. In contrast with conventional energy sources, the intermittency and fluctuation of renewable energy make difficult its integration into the existing energy grid [1]. Recently, the methanation of CO2 via the Sabatier process is gaining interest for power-to-gas (P2G) application [2]. It is a reaction of great technological and environmental potential, leading to (i) storage of excess H2 generated from renewable energy, (ii) reduction of CO2 emissions (greenhouse gas) from the atmosphere and (iii) production of SNG whose distribution infrastructures are readily available [3]. In this work, CO2 methanation activity and stability were investigated over Ni/GDC (gadolinium-doped-ceria) catalysts at atmospheric pressure varying reaction temperature (TSET = 300-600°C) and space velocity (GHSV = 10,000-50,000 h-1). Powder catalysts with different Ni content (15-50 wt.%) were synthesized by the solution combustion synthesis (SCS). The same method was adopted to in situ deposit the Ni/GDC (50 wt.%Ni) coating layer on the cordierite monolith (500 cpsi). The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), H2 temperature programmed reduction (H2-TPR), CO2 temperature programmed desorption (CO2-TPD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Temperature profiles along the structured catalytic bed were discussed to interpret the experimental results. Catalytic performance increased by increasing the Ni content due to enhanced metal-to-support interaction and basicity, as confirmed by H2-TPR and CO2-TPD analysis. In general, the activity increased by increasing the temperature while remaining well below the thermodynamic limits, due to the kinetic limitations at relative low temperatures (300-450°C). A slight decrease in activity was observed further increasing the temperature up to 600°C, due to thermodynamic limitation of methanation reaction and competing RWGS equilibrium. Very uniform, thin (10-40 ?m) and high-resistance catalytic layers were in-situ deposited on the cordierite monoliths by the SCS method [4]. Relative high activity of the structured catalysts was recognized, closely connected to the temperature profiles recorded on the catalytic bed. High surface-to-volume ratio, good interphase mass transfer and low pressure drops led to high methane productivity per unit weight of catalyst. The highest CH4 productivity of 10.7 LCH4·gcat -1·h-1 was obtained at 400°C and 50,000 h-1. Also, excellent long-term stability was observed over 200 h of time-on-stream. The results reported in this manuscript pinpointed on the important aspects of realizing CO2 methanation on structured catalysts, providing a platform for further optimization studies.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
